processdesign - User contributions [en]

Design S2

2014-03-15T05:30:04Z

Karetstik: /* Discussion */

Title: Production of 1,4-butanediol

Authors: Nick Pinkerton, Karen Schmidt, and James Xamplas

Date Presented: March 14, 2014

==Introduction==
1,4-butanediol (BDO) is traditionally made from petroleum-derived feedstocks in a variety of processes such as the Reppe (acetylene-based), Mitsubishi (butadiene-based), and Davy (maleic acid-based) processes [1]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, BDO [1]. It is this process that Team S2Kool4Skool has chosen to develop for a new bio-butanediol plant, because the Davy method is mature and requires no new innovations, and because an appropriate feedstock of bio-succinic acid is now available. The plant will be located in East Carroll Parish, Louisiana. This county is also home to Myriant; located in Lake Providence, they are the largest domestic provider of bio-succinic acid [2]. Furthermore, Lake Providence is conveniently located on the Mississippi River, which will allow for affordable transportation of our bio-based butanediol product. The intent of this project is to produce 45,000 metric tonnes of 99.5 wt% 1,4-butanediol per year in a new plant in Lake Providence, LA. The plant will run 24 hours per day for 350 days out of the year, allowing approximately two weeks for a maintenance shutdown.

As there are several techniques for producing 1,4 butanediol in industry, the first step was to determine a synthesis path. Based on the chosen path, reaction kinetics, and required production rate of the process, a reactor system was then designed. Next, the process was designed to deliver the reactants to the reactor at the proper operating conditions, and the separations, purification, and waste management steps were designed. Cost estimates were made using costing software and hand calculations. Finally, the process was iterated and optimized to reduce costs.

==Background==
===General information===
BDO is an organic chemical with the molecular formula <math>C_4H_{10}O_2</math>. It is also a diol with its two hydroxyl groups located at the terminal carbons. BDO has a boiling point of 235 degrees C and is therefore a colorless liquid at standard temperatures and pressures [3].

There are many precursors that petrochemical synthesis of BDO uses. The commonality between all of the precursor acids is that they are hydrogenatable. In replacement of one of these petrochemical precursors, our team has been tasked with the challenge of deriving BDO from the bio-based precursor succinic acid. This catalyzed reaction will take place in the presence of hydrogen as the hydrogenating component shown below:

<math>C_4H_6O_4 + 4H_2 = C_4H_{10}O_2 + 2H_2O</math>

As described in the above reaction, there will need to be at least 4:1 stoichiometric ratio of hydrogen gas to succinic acid. Two moles of water will also be produced along with each mole of BDO. This reaction is exothermic, which requires the reactor to be continuously cooled to maintain our reactor temperature. There are also side products that are produced which include tetrahydrofuran (THF) and γ-butyrolactone (GBL); however, thanks to catalyst selectivity these byproducts are produced in small quantities.

===Market analysis===
Butanediol has a quickly expanding market due to new technological evolutions and its growing use as a chemical intermediary in advanced materials. With biological routes being optimized, the potential of biomass-derived chemicals is tremendous. The global demand of BDO was estimated at 1.5 million metric tons in 2011 and is projected to grow at an annual rate of 4.5% for the next several years [1]. Unlike other chemical products, BDO’s profitability and attractiveness to producers lies in its downstream potential. Figure 1 below demonstrates several potential downstream products that can be directly or indirectly synthesized from BDO. The largest of these contributors include THF and GBL.

[[File:BioButanediol_Downstream.JPG|center|frame|Figure 1. BDO downstream potential flow chart]]

The current market demand of BDO is being supplemented by several global chemical companies. These companies include BASF, BioAmber, Purac, Myriant, DSM, Mitsubishi Chemical, Roquette, and OPXBIO. The market shares of these companies were not available for this product; however, with the consistent growth of the BDO market our team feels that the market is not saturated or impenetrable. The current market price of BDO fluctuates between $3.06 and $3.31 per kg for US-made products [4]. These prices correlate to a nearly 7 billion dollar industry.

===Process alternatives===
1,4-butanediol is traditionally made from petroleum-derived feedstocks in a variety of processes [5]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Several companies are currently implementing bio-routes of producing butanediol. Genomatica is using a bioengineered microorganism to convert sugar feedstocks directly to BDO via fermentation [6], but most companies are instead using microorganisms to convert sugar to succinic acid. The bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, which is the path that most are choosing, although research is being conducted on alternative pathways [7].

==Process overview==
The newly proposed plant can be divided into four stages: pre-reactor, reactor, post-reactor and distillation. Each section is an integral part to the overall process and demands close attention. See the complete process flow diagram in Figure 2.

[[File:PFD.JPG|center|frame|Figure 2. Process flow diagram]]

===Pre-reactor===
This chemical process begins with two feedstocks: hydrogen gas and bio-succinic acid. The hydrogen gas will be obtained from a pipeline at 150 atm and will be used in molar excess inside the reactor. The bio-succinic acid will be purchased by Myriant Corporation which is located near the planned plant site. The pricing for this feedstock is approximately $2.12 per kg. The plant will require 63,000 metric tonnes of bio-succinic acid per year to meet the proposed plant capacity. First the bio-succinic acid feed is pumped up to 150 atm to match the hydrogen gas feed, and then it is mixed with the hydrogen gas prior to being sent into heat exchanger E-101 for heating. The heat exchanger brings the two feeds up to 110oC and sends them to the jacketed packed bed reactor.

===Reactor===
The hydrogenation reaction occurs inside of the reactor thanks to the packed catalyst bed. The catalyst used is 0.4% Fe, 1.9% Na, 2.66% Ag, 2.66% Pd, 10.0% Re on 1.5mm carbon support. With this catalyst, BDO is produced with over 90% selectivity and minimal side reactions of THF and GBL [8]. The reaction has an operating pressure of 2000-4000 psi and internal reactor temperature of 165°C. This temperature allows for about 99.7% conversion of succinic acid [8]. Due to the exothermic nature of the reaction, a cooling jacket is required which utilizes downstream cold streams to cool the internal bed to maintain the desired reaction temperature.

===Post-reactor===
The effluent of the reactor is sent back to E-101 as the hot stream. After exiting E-101, the reactor product stream is sent to a secondary exchanger, E-102, where utility cooling water is used to reduce the temperature to an acceptable temperature prior to sending it to a pressure let-down valve. At this point the pressure of the stream is taken from 150 atm to 1 atm. This large pressure drop allows for the stream to split into its vapor and liquid portions in a gas-liquid separator. The vapor stream of the gas liquid separator is primarily hydrogen gas and sent to a flare for disposal. The liquid effluent is at approximately 45oC leaving the separator and is therefore pumped to the reactor jacket for the reaction cooling mentioned previously. After running through the reactor jacket, the stream enters the separation processes.

===Distillation===
The first distillation column, T-101, is a 10 stage column whose primary purpose is separating the THF from the product feed. Due to THF’s lower boiling point, the byproduct comes off of the top of the column with mostly water. This distillate is sent to the plant's THF waste storage tank that has the capacity of two weeks. The bottoms of the column is sent to the subsequent distillation column that separates the BDO from the GBL and water. The relatively close boiling points of BDO and GBL, 235oC and 204oC, respectively, create a difficult separation that requires a 15 stage column. The distillate of the column is approximately 23% GBL with balance water. This stream is sent to a storage tank with similar sizing parameters as the THF storage tank. The bottom stream is the final 99.5wt% BDO product. This stream is sent to the final product tank, S-104. Depending on our customer demands and the plant location we have the ability to barge, rail or pipe our product to its final destination. Due to low purity of the byproducts, future iterations are needed to optimize either purifying byproducts or selling impure byproducts. There is definitely an available market for these byproducts that should be researched more extensively to increase profit.

===Mass and energy balances===
Using an Aspen HYSYS simulation we were able to record the material and energy streams going in and out of the process system. As expected, the material and energy totals for the inlet and outlet streams add together to equal 0. This proves that our system is mathematically prudent and thermodynamically feasible. The total mass flow of the system is 15,639 kg/h and the total energy in and out of the system is 1.41e8 kJ/h.

===HYSYS simulation===
The HYSYS simulation was performed using the NRTL ideal fluid package. After using AspenPlus to verify that the HYSYS package had the appropriate vapor-liquid equilibrium information between THF and water, and between GBL and water, we concluded it was feasible to proceed with that fluid package. The simulation consists of a reactor, a gas-liquid separator, 2 pumps, 3 heaters, a valve, and 2 distillation columns (see Figure 3). The simulation successfully converted the succinic acid feed into the desired products. Also, the combination of the two distillation columns was able to effectively separate the BDO to obtain a 99.5% pure product with 99.5% recovery. In addition, a set was made between the energy required to heat stream 12 and the energy required to cool the reactor so that these values were made equal. Lastly, the condenser and reboiler duties were used in four heat exchangers in order to determine the appropriate size of this equipment as well as the necessary utility flow rates.

[[File:S2_HYSYS_Simulation.JPG|center|frame|Figure 3. HYSYS simulation]]

==Health and safety==
===Chemical properties===
Inherent to this process are a number of toxic chemicals. Table 1 summarizes the important safety data including hazard type, odor, color, and exposure limits.

[[File:Chem_properties.JPG|center|]]

As shown in the above table, the chemicals that this facility will be dealing with will be relatively mild and non-life threatening. Regardless of their perceived threat, chemicals should always be handled with care especially when they are at high temperatures and pressures.

===Safety procedures===

'''Fire'''. There are many flammable materials that will be included in this process; therefore, fire safety is imperative for all employees. There are countless possible causes of ignition and care should be taken while handling any flammable material whether in the lab or in the field.

In case a fire is present on, the following protocol should be implemented:

* Small fire: Use DRY chemical powder.
* Large fire: Use alcohol foam, water spray, or fog.
* Call for backup if unable to control.
* Immediately contact supervisor and emergency personnel on site.
* Evacuate to safe distance in case of fires around any hazardous materials or pressure vessels.

'''Spills'''. Process chemical spills will eventually occur in a plant of this scale. Small spills are likely to occur in a laboratory setting. Large spills could be a result of loss of containment in the system. We must ensure that all personnel are aware of proper spill mitigation protocol.

* Small spill: Dilute with water and mop or absorb with inert dry material. Dispose of in proper receptacle.
* Large spill: Keep away from sources of ignition and heat. Prevent rundown to any drains or sewers. Call for assistance on disposal. Absorb material with DRY earth or other non-combustible materials.
* If spill is due to a loss of containment in the system, quickly consult the PLC and shut any valves to prevent further loss.

'''Exposure'''. We must ensure that our employees are aware of the possible toxicity levels of each substance and how to handle exposure. The chemicals that are being used in this process are known chemical irritants to the eyes, skin, and throat. Safety measures must be in place to acknowledge this hazard. Due to the possibility of high pressure releases, we will have 2-minute emergency oxygen masks placed strategically throughout the plant to ensure the safety of any operator in the presence of a large release.

If exposed to the process chemicals, find nearest eye wash station or safety shower immediately and flush exposed skin for at least 15 minutes. Remove any contaminated clothing. Seek medical attention immediately.

'''Storage'''. Store chemicals in segregated and approved areas. Any closed containers for laboratory purposes should be placed in cool, well-ventilated areas.

==Economics==
===Equipment costing===
The calculated capital costs from Aspen Economic Analyzer are reported in Table 2 for all process equipment. The size of the reactor was calculated from the liquid hourly space velocity given in the 2011 ISP patent [8] and a void fraction estimate of 0.4. Storage tanks were sized to contain up to two continuous weeks of material. The number of distillation trays in each tower and the flow rates through pumps, vessels, and the flare were calculated in HYSYS. Heat exchange areas were given in Aspen Energy Analyzer or from HYSYS.

[[File:Equipment_cost.JPG|center|]]

In addition to the above equipment, our plant will require an ion exchanger to produce deionized process water from the municipal water. This is estimated to cost $42,000 in capital cost.

===Cash flow analysis===
Summarizing the important takeaways from the economic analysis, this process will return a revenue of 144 MM$ annually. Offset by production costs, the yearly cash flow is approximately 2.7 MM$, except for in the years in which the catalyst must be reinstalled (approximately every 5 years). At a cost of 2.5 MM$, the cash flows in those years decrease to approximately 0.2 MM$. This analysis assumes the plant will take 2 years to construct, and will operate at 50% in its first year. Furthermore, an interest rate of 10% was assumed with a tax rate of 38% (the maximum for corporate gains taxes). Using the 7-year MACRS depreciation method, the 20 year NPV for the project is 4.3 MM$. With an IRR of 15.1%, which is greater than the assumed interest rate, this project looks to be profitable. Further optimization techniques should be used in future iterations to further increase profitability. See Tables 3 and 4 for key economic information.

[[File:Econ_summaries.JPG|center|]]

===Sensitivity analysis===
As seen in Figure 4, the economic evaluation of this process is influenced the most by changes in the sales price and feed cost. A 20% increase in sales price will result in an approximate 120 MM$ increase in NPV whereas a decrease of the same percentage will result in over a 120 MM$ decrease in NPV. Inversely, a 20% increase in feed cost will result in a 115 MM$ decrease in NPV and a 20% decrease in feed cost will result in a 60 MM$ increase in NPV.

[[File:S2_Sensitivity.JPG|center|frame|Figure 4. Sensitivity analysis]]

To alleviate the risk associated with feed price, the team researched the price forecasting of bio-succinic acid. We compared the bio-succinic acid price to the adipic acid price over the six years between 2006 and 2012. The price of bio-succinic has remained relatively stable over this time period. Adipic acid, which is a common petrochemical precursor for BDO production, has had large fluctuations in price that result in unstable cash flows and uncertainty from shareholders. Thankfully, the stability of bio-succinic acid is a good sign that this process has a huge potential to be profitable especially if the demand for BDO continues to rise as projected.

==Discussion==
As described previously, the Davy process was selected as the most promising process of BDO production. The modified Davy process involves the hydrogenation of bio-succinicic acid with a Pa,Ag,Re catalyst and hydrogen gas. This process has many advantages, one being that it has mature technology that has been improved over the last 20 years. Additionally, the conversion to of succinic acid is virtually complete. Finally, overall plant yields can reach as high as 94 mol%.

Streams ahead of the pressure valve (PRV-101) are at approximately 1.51e4 kPa, and streams after the pressure valve are between 100 and 450 kPa. Furthermore, operating temperatures do not exceed 200°C, including safety factors. These operating conditions contribute to the feasibility of the process, as all the components can be designed with reasonable dimensions (wall thickness, cap type, etc.).

Of particular interest are the large costs of the reactor and pump P-101. The reactor costs nearly 2 MM$ because it has a moderate size with a liquid volume of 16.7 m3, and it operates at 150 atm, which requires a strong stainless steel shell for safety purposes. Pump P-101 has such a large capital cost because it is a centrifugal multistage pump that also needs to be made of stainless steel to withstand pressuring the succinic acid feed to 150 atm.

Financial indicators for the proposed plant suggest that it will be moderately profitable, and additional optimization should be performed before making the capital investment. There is a fair amount of risk associated with the implementation of this production facility, and the return at this juncture may not justify the risk.

The process design and simulation in HYSYS has relied on several key assumptions, which are cause for certain limitations to the results. First, the conversions and selectivity of the catalyst, while taken from literature sources, are assumed to be true. Furthermore, the assumption of negligible side reactions and products was made. It is possible that small waste products in the form of succinates also form in the reactor. Therefore, the main limitation of this model is generally due to reaction specifications.

There are certain safety concerns that go along with the proposed process. First, there are many pipes and vessels that will be at a pressure of approximately 150 atm. Extra insulation and protection must be applied to the piping that contains highly pressurized fluids, to prevent operator injury. Furthermore, the PFR is at a slight risk for runaway reactions due to the exothermic nature of the reaction. The temperature of the reactor must always be monitored by an operator, and the jacket cooling system requires a backup system as well. A benefit of this process is that there are no toxic or severely hazardous components in the process. Additionally, there are no instances of temperature greater than 200°C.

The process design will be fitted with instrumentation and controls to ensure stable operation. These controls, including sensors and valves, minimize potential damage to components due to variation in plant conditions, as well as optimizing the overall performance. For example, the piping entering the tower will be fitted with a control loop. In the direction of flow, a sensing instrument first detects the pressure of the fluid, and then sends a signal to the controller. If the pressure is not within the operating limits, the actuator is signaled to close or open a control valve which is located farther down the stream.

==Conclusion==
The Evanston Chemical Engineering Division suggests a process that produces 45,000 tonnes/year of 99.5 wt% 1,4-butandeiol to enter the market with an appropriate market share. The feasibility of producing BDO as a significant process was investigated. A wide range of BDO production processes were researched, with a modified Davy process being identified as having the most potential. Using a Pa,Ag,Re catalyst on carbon support, this process converts bio-succinic acid to BDO with approximately 94% conversion. This process was designed in Aspen HYSYS, and economic analysis was conducted in Aspen Economic Analyzer. Total capital costs of the project are 12.2 MM$, with a simple payback period of 5.2 years. Total operational costs annually are 139.7 MM$. The process design was successful, with the capability of producing the desired production of BDO.

==Recommendations==
Given the moderate profitability of this process design, it is recommended that Evanston Chemicals explores further optimization techniques to increase the profitability of this process. This includes investigating sales of the γ-butyrolactone byproduct, recycling process water, and further optimizing utility streams for the distillation tower.

Second, we would like to investigate recycling the 2300 kg/h of water produced in the reaction. Our succinic acid enters the reactor as a 50 wt% solution in water, so we should look into replacing some of this with the product water. Not only will this decrease our water bill, but it will also lower the cost of ion exchange.

==References==
# Nexant.''Is Bio-Butanediol Here to Stay?'' White Plains, NY: ChemSystems Products; 2012.
# De Guzman D. Chemical industry awaits for bio-succinic acid potential. ICIS. Available at: http://www.icis.com/resources/news/2012/01/30/9527521/chemical-industry-awaits-for-bio-succinic-acid-potential/. Accessed January 24, 2014.
# Australian Government: Department of Health. 1,4-butanediol factsheet. National Industrial Chemicals Notification and Assessment Scheme. Available at: http://www.nicnas.gov.au/communications/publications/information-sheets/existing-chemical-info-sheets/other-information-sheets. Accessed January 24, 2014.
# TecnonOrbiChem. Chem-net facts: 1,4-butanediol. TecnonOrbiChem. Available at: http://www.orbichem.com/userfiles/CNF%20Samples/bdo_13_11.pdf. Accessed January 23, 2014.
# Nexant. 1,4-butanediol/tetrahydrofuran (BDO/THF). ChemSystems. Available at: http://www.chemsystems.com/about/cs/news/items/ PERP2012_3_BDO_THF.cfm. Accessed February 6, 2014.
# Burk MJ, Van Dien SJ, Burgard AP, inventors; Genomatica, Inc., assignee. Compositions and methods for the biosynthesis of 1,4-butanediol and its precursors. US patent 8,067,214. Nov. 29, 2011.
# Chung S-H, Kim M-S, Eom H-H, Lee K-Y. Catalytic hydrogenation of bio-based succinic acid for the production of 1,4-butanediol through the indirect pathway. AIChE. Available at: https://aiche.confex.com/aiche/2013/webprogram/Paper327470.html. Accessed January 23, 2014.
# Bhattacharyya A, Manila MD, inventors; ISP Investments Inc., assignee. Catalysts for maleic acid hydrogenation to 1,4-Butanediol. US patent 7,935,834 B2. May 3, 2011.

Design S2

2014-03-15T05:29:46Z

Karetstik: /* Mass and energy balances */

Title: Production of 1,4-butanediol

Authors: Nick Pinkerton, Karen Schmidt, and James Xamplas

Date Presented: March 14, 2014

==Introduction==
1,4-butanediol (BDO) is traditionally made from petroleum-derived feedstocks in a variety of processes such as the Reppe (acetylene-based), Mitsubishi (butadiene-based), and Davy (maleic acid-based) processes [1]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, BDO [1]. It is this process that Team S2Kool4Skool has chosen to develop for a new bio-butanediol plant, because the Davy method is mature and requires no new innovations, and because an appropriate feedstock of bio-succinic acid is now available. The plant will be located in East Carroll Parish, Louisiana. This county is also home to Myriant; located in Lake Providence, they are the largest domestic provider of bio-succinic acid [2]. Furthermore, Lake Providence is conveniently located on the Mississippi River, which will allow for affordable transportation of our bio-based butanediol product. The intent of this project is to produce 45,000 metric tonnes of 99.5 wt% 1,4-butanediol per year in a new plant in Lake Providence, LA. The plant will run 24 hours per day for 350 days out of the year, allowing approximately two weeks for a maintenance shutdown.

As there are several techniques for producing 1,4 butanediol in industry, the first step was to determine a synthesis path. Based on the chosen path, reaction kinetics, and required production rate of the process, a reactor system was then designed. Next, the process was designed to deliver the reactants to the reactor at the proper operating conditions, and the separations, purification, and waste management steps were designed. Cost estimates were made using costing software and hand calculations. Finally, the process was iterated and optimized to reduce costs.

==Background==
===General information===
BDO is an organic chemical with the molecular formula <math>C_4H_{10}O_2</math>. It is also a diol with its two hydroxyl groups located at the terminal carbons. BDO has a boiling point of 235 degrees C and is therefore a colorless liquid at standard temperatures and pressures [3].

There are many precursors that petrochemical synthesis of BDO uses. The commonality between all of the precursor acids is that they are hydrogenatable. In replacement of one of these petrochemical precursors, our team has been tasked with the challenge of deriving BDO from the bio-based precursor succinic acid. This catalyzed reaction will take place in the presence of hydrogen as the hydrogenating component shown below:

<math>C_4H_6O_4 + 4H_2 = C_4H_{10}O_2 + 2H_2O</math>

As described in the above reaction, there will need to be at least 4:1 stoichiometric ratio of hydrogen gas to succinic acid. Two moles of water will also be produced along with each mole of BDO. This reaction is exothermic, which requires the reactor to be continuously cooled to maintain our reactor temperature. There are also side products that are produced which include tetrahydrofuran (THF) and γ-butyrolactone (GBL); however, thanks to catalyst selectivity these byproducts are produced in small quantities.

===Market analysis===
Butanediol has a quickly expanding market due to new technological evolutions and its growing use as a chemical intermediary in advanced materials. With biological routes being optimized, the potential of biomass-derived chemicals is tremendous. The global demand of BDO was estimated at 1.5 million metric tons in 2011 and is projected to grow at an annual rate of 4.5% for the next several years [1]. Unlike other chemical products, BDO’s profitability and attractiveness to producers lies in its downstream potential. Figure 1 below demonstrates several potential downstream products that can be directly or indirectly synthesized from BDO. The largest of these contributors include THF and GBL.

[[File:BioButanediol_Downstream.JPG|center|frame|Figure 1. BDO downstream potential flow chart]]

The current market demand of BDO is being supplemented by several global chemical companies. These companies include BASF, BioAmber, Purac, Myriant, DSM, Mitsubishi Chemical, Roquette, and OPXBIO. The market shares of these companies were not available for this product; however, with the consistent growth of the BDO market our team feels that the market is not saturated or impenetrable. The current market price of BDO fluctuates between $3.06 and $3.31 per kg for US-made products [4]. These prices correlate to a nearly 7 billion dollar industry.

===Process alternatives===
1,4-butanediol is traditionally made from petroleum-derived feedstocks in a variety of processes [5]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Several companies are currently implementing bio-routes of producing butanediol. Genomatica is using a bioengineered microorganism to convert sugar feedstocks directly to BDO via fermentation [6], but most companies are instead using microorganisms to convert sugar to succinic acid. The bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, which is the path that most are choosing, although research is being conducted on alternative pathways [7].

==Process overview==
The newly proposed plant can be divided into four stages: pre-reactor, reactor, post-reactor and distillation. Each section is an integral part to the overall process and demands close attention. See the complete process flow diagram in Figure 2.

[[File:PFD.JPG|center|frame|Figure 2. Process flow diagram]]

===Pre-reactor===
This chemical process begins with two feedstocks: hydrogen gas and bio-succinic acid. The hydrogen gas will be obtained from a pipeline at 150 atm and will be used in molar excess inside the reactor. The bio-succinic acid will be purchased by Myriant Corporation which is located near the planned plant site. The pricing for this feedstock is approximately $2.12 per kg. The plant will require 63,000 metric tonnes of bio-succinic acid per year to meet the proposed plant capacity. First the bio-succinic acid feed is pumped up to 150 atm to match the hydrogen gas feed, and then it is mixed with the hydrogen gas prior to being sent into heat exchanger E-101 for heating. The heat exchanger brings the two feeds up to 110oC and sends them to the jacketed packed bed reactor.

===Reactor===
The hydrogenation reaction occurs inside of the reactor thanks to the packed catalyst bed. The catalyst used is 0.4% Fe, 1.9% Na, 2.66% Ag, 2.66% Pd, 10.0% Re on 1.5mm carbon support. With this catalyst, BDO is produced with over 90% selectivity and minimal side reactions of THF and GBL [8]. The reaction has an operating pressure of 2000-4000 psi and internal reactor temperature of 165°C. This temperature allows for about 99.7% conversion of succinic acid [8]. Due to the exothermic nature of the reaction, a cooling jacket is required which utilizes downstream cold streams to cool the internal bed to maintain the desired reaction temperature.

===Post-reactor===
The effluent of the reactor is sent back to E-101 as the hot stream. After exiting E-101, the reactor product stream is sent to a secondary exchanger, E-102, where utility cooling water is used to reduce the temperature to an acceptable temperature prior to sending it to a pressure let-down valve. At this point the pressure of the stream is taken from 150 atm to 1 atm. This large pressure drop allows for the stream to split into its vapor and liquid portions in a gas-liquid separator. The vapor stream of the gas liquid separator is primarily hydrogen gas and sent to a flare for disposal. The liquid effluent is at approximately 45oC leaving the separator and is therefore pumped to the reactor jacket for the reaction cooling mentioned previously. After running through the reactor jacket, the stream enters the separation processes.

===Distillation===
The first distillation column, T-101, is a 10 stage column whose primary purpose is separating the THF from the product feed. Due to THF’s lower boiling point, the byproduct comes off of the top of the column with mostly water. This distillate is sent to the plant's THF waste storage tank that has the capacity of two weeks. The bottoms of the column is sent to the subsequent distillation column that separates the BDO from the GBL and water. The relatively close boiling points of BDO and GBL, 235oC and 204oC, respectively, create a difficult separation that requires a 15 stage column. The distillate of the column is approximately 23% GBL with balance water. This stream is sent to a storage tank with similar sizing parameters as the THF storage tank. The bottom stream is the final 99.5wt% BDO product. This stream is sent to the final product tank, S-104. Depending on our customer demands and the plant location we have the ability to barge, rail or pipe our product to its final destination. Due to low purity of the byproducts, future iterations are needed to optimize either purifying byproducts or selling impure byproducts. There is definitely an available market for these byproducts that should be researched more extensively to increase profit.

===Mass and energy balances===
Using an Aspen HYSYS simulation we were able to record the material and energy streams going in and out of the process system. As expected, the material and energy totals for the inlet and outlet streams add together to equal 0. This proves that our system is mathematically prudent and thermodynamically feasible. The total mass flow of the system is 15,639 kg/h and the total energy in and out of the system is 1.41e8 kJ/h.

===HYSYS simulation===
The HYSYS simulation was performed using the NRTL ideal fluid package. After using AspenPlus to verify that the HYSYS package had the appropriate vapor-liquid equilibrium information between THF and water, and between GBL and water, we concluded it was feasible to proceed with that fluid package. The simulation consists of a reactor, a gas-liquid separator, 2 pumps, 3 heaters, a valve, and 2 distillation columns (see Figure 3). The simulation successfully converted the succinic acid feed into the desired products. Also, the combination of the two distillation columns was able to effectively separate the BDO to obtain a 99.5% pure product with 99.5% recovery. In addition, a set was made between the energy required to heat stream 12 and the energy required to cool the reactor so that these values were made equal. Lastly, the condenser and reboiler duties were used in four heat exchangers in order to determine the appropriate size of this equipment as well as the necessary utility flow rates.

[[File:S2_HYSYS_Simulation.JPG|center|frame|Figure 3. HYSYS simulation]]

==Health and safety==
===Chemical properties===
Inherent to this process are a number of toxic chemicals. Table 1 summarizes the important safety data including hazard type, odor, color, and exposure limits.

[[File:Chem_properties.JPG|center|]]

As shown in the above table, the chemicals that this facility will be dealing with will be relatively mild and non-life threatening. Regardless of their perceived threat, chemicals should always be handled with care especially when they are at high temperatures and pressures.

===Safety procedures===

'''Fire'''. There are many flammable materials that will be included in this process; therefore, fire safety is imperative for all employees. There are countless possible causes of ignition and care should be taken while handling any flammable material whether in the lab or in the field.

In case a fire is present on, the following protocol should be implemented:

* Small fire: Use DRY chemical powder.
* Large fire: Use alcohol foam, water spray, or fog.
* Call for backup if unable to control.
* Immediately contact supervisor and emergency personnel on site.
* Evacuate to safe distance in case of fires around any hazardous materials or pressure vessels.

'''Spills'''. Process chemical spills will eventually occur in a plant of this scale. Small spills are likely to occur in a laboratory setting. Large spills could be a result of loss of containment in the system. We must ensure that all personnel are aware of proper spill mitigation protocol.

* Small spill: Dilute with water and mop or absorb with inert dry material. Dispose of in proper receptacle.
* Large spill: Keep away from sources of ignition and heat. Prevent rundown to any drains or sewers. Call for assistance on disposal. Absorb material with DRY earth or other non-combustible materials.
* If spill is due to a loss of containment in the system, quickly consult the PLC and shut any valves to prevent further loss.

'''Exposure'''. We must ensure that our employees are aware of the possible toxicity levels of each substance and how to handle exposure. The chemicals that are being used in this process are known chemical irritants to the eyes, skin, and throat. Safety measures must be in place to acknowledge this hazard. Due to the possibility of high pressure releases, we will have 2-minute emergency oxygen masks placed strategically throughout the plant to ensure the safety of any operator in the presence of a large release.

If exposed to the process chemicals, find nearest eye wash station or safety shower immediately and flush exposed skin for at least 15 minutes. Remove any contaminated clothing. Seek medical attention immediately.

'''Storage'''. Store chemicals in segregated and approved areas. Any closed containers for laboratory purposes should be placed in cool, well-ventilated areas.

==Economics==
===Equipment costing===
The calculated capital costs from Aspen Economic Analyzer are reported in Table 2 for all process equipment. The size of the reactor was calculated from the liquid hourly space velocity given in the 2011 ISP patent [8] and a void fraction estimate of 0.4. Storage tanks were sized to contain up to two continuous weeks of material. The number of distillation trays in each tower and the flow rates through pumps, vessels, and the flare were calculated in HYSYS. Heat exchange areas were given in Aspen Energy Analyzer or from HYSYS.

[[File:Equipment_cost.JPG|center|]]

In addition to the above equipment, our plant will require an ion exchanger to produce deionized process water from the municipal water. This is estimated to cost $42,000 in capital cost.

===Cash flow analysis===
Summarizing the important takeaways from the economic analysis, this process will return a revenue of 144 MM$ annually. Offset by production costs, the yearly cash flow is approximately 2.7 MM$, except for in the years in which the catalyst must be reinstalled (approximately every 5 years). At a cost of 2.5 MM$, the cash flows in those years decrease to approximately 0.2 MM$. This analysis assumes the plant will take 2 years to construct, and will operate at 50% in its first year. Furthermore, an interest rate of 10% was assumed with a tax rate of 38% (the maximum for corporate gains taxes). Using the 7-year MACRS depreciation method, the 20 year NPV for the project is 4.3 MM$. With an IRR of 15.1%, which is greater than the assumed interest rate, this project looks to be profitable. Further optimization techniques should be used in future iterations to further increase profitability. See Tables 3 and 4 for key economic information.

[[File:Econ_summaries.JPG|center|]]

===Sensitivity analysis===
As seen in Figure 4, the economic evaluation of this process is influenced the most by changes in the sales price and feed cost. A 20% increase in sales price will result in an approximate 120 MM$ increase in NPV whereas a decrease of the same percentage will result in over a 120 MM$ decrease in NPV. Inversely, a 20% increase in feed cost will result in a 115 MM$ decrease in NPV and a 20% decrease in feed cost will result in a 60 MM$ increase in NPV.

[[File:S2_Sensitivity.JPG|center|frame|Figure 4. Sensitivity analysis]]

To alleviate the risk associated with feed price, the team researched the price forecasting of bio-succinic acid. We compared the bio-succinic acid price to the adipic acid price over the six years between 2006 and 2012. The price of bio-succinic has remained relatively stable over this time period. Adipic acid, which is a common petrochemical precursor for BDO production, has had large fluctuations in price that result in unstable cash flows and uncertainty from shareholders. Thankfully, the stability of bio-succinic acid is a good sign that this process has a huge potential to be profitable especially if the demand for BDO continues to rise as projected.

==Discussion==
As described previously, the Davy process was selected as the most promising process of BDO production. The modified Davy process involves the hydrogenation of bio-succinicic acid with a Pa,Ag,Re catalyst and hydrogen gas. This process has many advantages, one being that it has mature technology that has been improved over the last 20 years. Additionally, the conversion to of succinic acid is virtually complete. Finally, overall plant yields can reach as high as 94 mol%.
As shown in Appendix B, streams ahead of the pressure valve (PRV-101) are at approximately 1.51e4 kPa, and streams after the pressure valve are between 100 and 450 kPa. Furthermore, operating temperatures do not exceed 200°C, including safety factors. These operating conditions contribute to the feasibility of the process, as all the components can be designed with reasonable dimensions (wall thickness, cap type, etc.).

Of particular interest are the large costs of the reactor and pump P-101. The reactor costs nearly 2 MM$ because it has a moderate size with a liquid volume of 16.7 m3, and it operates at 150 atm, which requires a strong stainless steel shell for safety purposes. Pump P-101 has such a large capital cost because it is a centrifugal multistage pump that also needs to be made of stainless steel to withstand pressuring the succinic acid feed to 150 atm.

Financial indicators for the proposed plant suggest that it will be moderately profitable, and additional optimization should be performed before making the capital investment. There is a fair amount of risk associated with the implementation of this production facility, and the return at this juncture may not justify the risk.

The process design and simulation in HYSYS has relied on several key assumptions, which are cause for certain limitations to the results. First, the conversions and selectivity of the catalyst, while taken from literature sources, are assumed to be true. Furthermore, the assumption of negligible side reactions and products was made. It is possible that small waste products in the form of succinates also form in the reactor. Therefore, the main limitation of this model is generally due to reaction specifications.

There are certain safety concerns that go along with the proposed process. First, there are many pipes and vessels that will be at a pressure of approximately 150 atm. Extra insulation and protection must be applied to the piping that contains highly pressurized fluids, to prevent operator injury. Furthermore, the PFR is at a slight risk for runaway reactions due to the exothermic nature of the reaction. The temperature of the reactor must always be monitored by an operator, and the jacket cooling system requires a backup system as well. A benefit of this process is that there are no toxic or severely hazardous components in the process. Additionally, there are no instances of temperature greater than 200°C.

The process design will be fitted with instrumentation and controls to ensure stable operation. These controls, including sensors and valves, minimize potential damage to components due to variation in plant conditions, as well as optimizing the overall performance. For example, the piping entering the tower will be fitted with a control loop. In the direction of flow, a sensing instrument first detects the pressure of the fluid, and then sends a signal to the controller. If the pressure is not within the operating limits, the actuator is signaled to close or open a control valve which is located farther down the stream.

==Conclusion==
The Evanston Chemical Engineering Division suggests a process that produces 45,000 tonnes/year of 99.5 wt% 1,4-butandeiol to enter the market with an appropriate market share. The feasibility of producing BDO as a significant process was investigated. A wide range of BDO production processes were researched, with a modified Davy process being identified as having the most potential. Using a Pa,Ag,Re catalyst on carbon support, this process converts bio-succinic acid to BDO with approximately 94% conversion. This process was designed in Aspen HYSYS, and economic analysis was conducted in Aspen Economic Analyzer. Total capital costs of the project are 12.2 MM$, with a simple payback period of 5.2 years. Total operational costs annually are 139.7 MM$. The process design was successful, with the capability of producing the desired production of BDO.

==Recommendations==
Given the moderate profitability of this process design, it is recommended that Evanston Chemicals explores further optimization techniques to increase the profitability of this process. This includes investigating sales of the γ-butyrolactone byproduct, recycling process water, and further optimizing utility streams for the distillation tower.

Second, we would like to investigate recycling the 2300 kg/h of water produced in the reaction. Our succinic acid enters the reactor as a 50 wt% solution in water, so we should look into replacing some of this with the product water. Not only will this decrease our water bill, but it will also lower the cost of ion exchange.

==References==
# Nexant.''Is Bio-Butanediol Here to Stay?'' White Plains, NY: ChemSystems Products; 2012.
# De Guzman D. Chemical industry awaits for bio-succinic acid potential. ICIS. Available at: http://www.icis.com/resources/news/2012/01/30/9527521/chemical-industry-awaits-for-bio-succinic-acid-potential/. Accessed January 24, 2014.
# Australian Government: Department of Health. 1,4-butanediol factsheet. National Industrial Chemicals Notification and Assessment Scheme. Available at: http://www.nicnas.gov.au/communications/publications/information-sheets/existing-chemical-info-sheets/other-information-sheets. Accessed January 24, 2014.
# TecnonOrbiChem. Chem-net facts: 1,4-butanediol. TecnonOrbiChem. Available at: http://www.orbichem.com/userfiles/CNF%20Samples/bdo_13_11.pdf. Accessed January 23, 2014.
# Nexant. 1,4-butanediol/tetrahydrofuran (BDO/THF). ChemSystems. Available at: http://www.chemsystems.com/about/cs/news/items/ PERP2012_3_BDO_THF.cfm. Accessed February 6, 2014.
# Burk MJ, Van Dien SJ, Burgard AP, inventors; Genomatica, Inc., assignee. Compositions and methods for the biosynthesis of 1,4-butanediol and its precursors. US patent 8,067,214. Nov. 29, 2011.
# Chung S-H, Kim M-S, Eom H-H, Lee K-Y. Catalytic hydrogenation of bio-based succinic acid for the production of 1,4-butanediol through the indirect pathway. AIChE. Available at: https://aiche.confex.com/aiche/2013/webprogram/Paper327470.html. Accessed January 23, 2014.
# Bhattacharyya A, Manila MD, inventors; ISP Investments Inc., assignee. Catalysts for maleic acid hydrogenation to 1,4-Butanediol. US patent 7,935,834 B2. May 3, 2011.

Design S2

2014-03-15T05:29:20Z

Karetstik: /* Distillation */

Title: Production of 1,4-butanediol

Authors: Nick Pinkerton, Karen Schmidt, and James Xamplas

Date Presented: March 14, 2014

==Introduction==
1,4-butanediol (BDO) is traditionally made from petroleum-derived feedstocks in a variety of processes such as the Reppe (acetylene-based), Mitsubishi (butadiene-based), and Davy (maleic acid-based) processes [1]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, BDO [1]. It is this process that Team S2Kool4Skool has chosen to develop for a new bio-butanediol plant, because the Davy method is mature and requires no new innovations, and because an appropriate feedstock of bio-succinic acid is now available. The plant will be located in East Carroll Parish, Louisiana. This county is also home to Myriant; located in Lake Providence, they are the largest domestic provider of bio-succinic acid [2]. Furthermore, Lake Providence is conveniently located on the Mississippi River, which will allow for affordable transportation of our bio-based butanediol product. The intent of this project is to produce 45,000 metric tonnes of 99.5 wt% 1,4-butanediol per year in a new plant in Lake Providence, LA. The plant will run 24 hours per day for 350 days out of the year, allowing approximately two weeks for a maintenance shutdown.

As there are several techniques for producing 1,4 butanediol in industry, the first step was to determine a synthesis path. Based on the chosen path, reaction kinetics, and required production rate of the process, a reactor system was then designed. Next, the process was designed to deliver the reactants to the reactor at the proper operating conditions, and the separations, purification, and waste management steps were designed. Cost estimates were made using costing software and hand calculations. Finally, the process was iterated and optimized to reduce costs.

==Background==
===General information===
BDO is an organic chemical with the molecular formula <math>C_4H_{10}O_2</math>. It is also a diol with its two hydroxyl groups located at the terminal carbons. BDO has a boiling point of 235 degrees C and is therefore a colorless liquid at standard temperatures and pressures [3].

There are many precursors that petrochemical synthesis of BDO uses. The commonality between all of the precursor acids is that they are hydrogenatable. In replacement of one of these petrochemical precursors, our team has been tasked with the challenge of deriving BDO from the bio-based precursor succinic acid. This catalyzed reaction will take place in the presence of hydrogen as the hydrogenating component shown below:

<math>C_4H_6O_4 + 4H_2 = C_4H_{10}O_2 + 2H_2O</math>

As described in the above reaction, there will need to be at least 4:1 stoichiometric ratio of hydrogen gas to succinic acid. Two moles of water will also be produced along with each mole of BDO. This reaction is exothermic, which requires the reactor to be continuously cooled to maintain our reactor temperature. There are also side products that are produced which include tetrahydrofuran (THF) and γ-butyrolactone (GBL); however, thanks to catalyst selectivity these byproducts are produced in small quantities.

===Market analysis===
Butanediol has a quickly expanding market due to new technological evolutions and its growing use as a chemical intermediary in advanced materials. With biological routes being optimized, the potential of biomass-derived chemicals is tremendous. The global demand of BDO was estimated at 1.5 million metric tons in 2011 and is projected to grow at an annual rate of 4.5% for the next several years [1]. Unlike other chemical products, BDO’s profitability and attractiveness to producers lies in its downstream potential. Figure 1 below demonstrates several potential downstream products that can be directly or indirectly synthesized from BDO. The largest of these contributors include THF and GBL.

[[File:BioButanediol_Downstream.JPG|center|frame|Figure 1. BDO downstream potential flow chart]]

The current market demand of BDO is being supplemented by several global chemical companies. These companies include BASF, BioAmber, Purac, Myriant, DSM, Mitsubishi Chemical, Roquette, and OPXBIO. The market shares of these companies were not available for this product; however, with the consistent growth of the BDO market our team feels that the market is not saturated or impenetrable. The current market price of BDO fluctuates between $3.06 and $3.31 per kg for US-made products [4]. These prices correlate to a nearly 7 billion dollar industry.

===Process alternatives===
1,4-butanediol is traditionally made from petroleum-derived feedstocks in a variety of processes [5]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Several companies are currently implementing bio-routes of producing butanediol. Genomatica is using a bioengineered microorganism to convert sugar feedstocks directly to BDO via fermentation [6], but most companies are instead using microorganisms to convert sugar to succinic acid. The bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, which is the path that most are choosing, although research is being conducted on alternative pathways [7].

==Process overview==
The newly proposed plant can be divided into four stages: pre-reactor, reactor, post-reactor and distillation. Each section is an integral part to the overall process and demands close attention. See the complete process flow diagram in Figure 2.

[[File:PFD.JPG|center|frame|Figure 2. Process flow diagram]]

===Pre-reactor===
This chemical process begins with two feedstocks: hydrogen gas and bio-succinic acid. The hydrogen gas will be obtained from a pipeline at 150 atm and will be used in molar excess inside the reactor. The bio-succinic acid will be purchased by Myriant Corporation which is located near the planned plant site. The pricing for this feedstock is approximately $2.12 per kg. The plant will require 63,000 metric tonnes of bio-succinic acid per year to meet the proposed plant capacity. First the bio-succinic acid feed is pumped up to 150 atm to match the hydrogen gas feed, and then it is mixed with the hydrogen gas prior to being sent into heat exchanger E-101 for heating. The heat exchanger brings the two feeds up to 110oC and sends them to the jacketed packed bed reactor.

===Reactor===
The hydrogenation reaction occurs inside of the reactor thanks to the packed catalyst bed. The catalyst used is 0.4% Fe, 1.9% Na, 2.66% Ag, 2.66% Pd, 10.0% Re on 1.5mm carbon support. With this catalyst, BDO is produced with over 90% selectivity and minimal side reactions of THF and GBL [8]. The reaction has an operating pressure of 2000-4000 psi and internal reactor temperature of 165°C. This temperature allows for about 99.7% conversion of succinic acid [8]. Due to the exothermic nature of the reaction, a cooling jacket is required which utilizes downstream cold streams to cool the internal bed to maintain the desired reaction temperature.

===Post-reactor===
The effluent of the reactor is sent back to E-101 as the hot stream. After exiting E-101, the reactor product stream is sent to a secondary exchanger, E-102, where utility cooling water is used to reduce the temperature to an acceptable temperature prior to sending it to a pressure let-down valve. At this point the pressure of the stream is taken from 150 atm to 1 atm. This large pressure drop allows for the stream to split into its vapor and liquid portions in a gas-liquid separator. The vapor stream of the gas liquid separator is primarily hydrogen gas and sent to a flare for disposal. The liquid effluent is at approximately 45oC leaving the separator and is therefore pumped to the reactor jacket for the reaction cooling mentioned previously. After running through the reactor jacket, the stream enters the separation processes.

===Distillation===
The first distillation column, T-101, is a 10 stage column whose primary purpose is separating the THF from the product feed. Due to THF’s lower boiling point, the byproduct comes off of the top of the column with mostly water. This distillate is sent to the plant's THF waste storage tank that has the capacity of two weeks. The bottoms of the column is sent to the subsequent distillation column that separates the BDO from the GBL and water. The relatively close boiling points of BDO and GBL, 235oC and 204oC, respectively, create a difficult separation that requires a 15 stage column. The distillate of the column is approximately 23% GBL with balance water. This stream is sent to a storage tank with similar sizing parameters as the THF storage tank. The bottom stream is the final 99.5wt% BDO product. This stream is sent to the final product tank, S-104. Depending on our customer demands and the plant location we have the ability to barge, rail or pipe our product to its final destination. Due to low purity of the byproducts, future iterations are needed to optimize either purifying byproducts or selling impure byproducts. There is definitely an available market for these byproducts that should be researched more extensively to increase profit.

===Mass and energy balances===
Using an Aspen HYSYS simulation we were able to record the material and energy streams going in and out of the process system. Mass and energy balances are provided Appendix D where each inlet and outlet stream is described and quantified. As expected, the material and energy totals for the inlet and outlet streams add together to equal 0. This proves that our system is mathematically prudent and thermodynamically feasible. The total mass flow of the system is 15,639 kg/h and the total energy in and out of the system is 1.41e8 kJ/h.

===HYSYS simulation===
The HYSYS simulation was performed using the NRTL ideal fluid package. After using AspenPlus to verify that the HYSYS package had the appropriate vapor-liquid equilibrium information between THF and water, and between GBL and water, we concluded it was feasible to proceed with that fluid package. The simulation consists of a reactor, a gas-liquid separator, 2 pumps, 3 heaters, a valve, and 2 distillation columns (see Figure 3). The simulation successfully converted the succinic acid feed into the desired products. Also, the combination of the two distillation columns was able to effectively separate the BDO to obtain a 99.5% pure product with 99.5% recovery. In addition, a set was made between the energy required to heat stream 12 and the energy required to cool the reactor so that these values were made equal. Lastly, the condenser and reboiler duties were used in four heat exchangers in order to determine the appropriate size of this equipment as well as the necessary utility flow rates.

[[File:S2_HYSYS_Simulation.JPG|center|frame|Figure 3. HYSYS simulation]]

==Health and safety==
===Chemical properties===
Inherent to this process are a number of toxic chemicals. Table 1 summarizes the important safety data including hazard type, odor, color, and exposure limits.

[[File:Chem_properties.JPG|center|]]

As shown in the above table, the chemicals that this facility will be dealing with will be relatively mild and non-life threatening. Regardless of their perceived threat, chemicals should always be handled with care especially when they are at high temperatures and pressures.

===Safety procedures===

'''Fire'''. There are many flammable materials that will be included in this process; therefore, fire safety is imperative for all employees. There are countless possible causes of ignition and care should be taken while handling any flammable material whether in the lab or in the field.

In case a fire is present on, the following protocol should be implemented:

* Small fire: Use DRY chemical powder.
* Large fire: Use alcohol foam, water spray, or fog.
* Call for backup if unable to control.
* Immediately contact supervisor and emergency personnel on site.
* Evacuate to safe distance in case of fires around any hazardous materials or pressure vessels.

'''Spills'''. Process chemical spills will eventually occur in a plant of this scale. Small spills are likely to occur in a laboratory setting. Large spills could be a result of loss of containment in the system. We must ensure that all personnel are aware of proper spill mitigation protocol.

* Small spill: Dilute with water and mop or absorb with inert dry material. Dispose of in proper receptacle.
* Large spill: Keep away from sources of ignition and heat. Prevent rundown to any drains or sewers. Call for assistance on disposal. Absorb material with DRY earth or other non-combustible materials.
* If spill is due to a loss of containment in the system, quickly consult the PLC and shut any valves to prevent further loss.

'''Exposure'''. We must ensure that our employees are aware of the possible toxicity levels of each substance and how to handle exposure. The chemicals that are being used in this process are known chemical irritants to the eyes, skin, and throat. Safety measures must be in place to acknowledge this hazard. Due to the possibility of high pressure releases, we will have 2-minute emergency oxygen masks placed strategically throughout the plant to ensure the safety of any operator in the presence of a large release.

If exposed to the process chemicals, find nearest eye wash station or safety shower immediately and flush exposed skin for at least 15 minutes. Remove any contaminated clothing. Seek medical attention immediately.

'''Storage'''. Store chemicals in segregated and approved areas. Any closed containers for laboratory purposes should be placed in cool, well-ventilated areas.

==Economics==
===Equipment costing===
The calculated capital costs from Aspen Economic Analyzer are reported in Table 2 for all process equipment. The size of the reactor was calculated from the liquid hourly space velocity given in the 2011 ISP patent [8] and a void fraction estimate of 0.4. Storage tanks were sized to contain up to two continuous weeks of material. The number of distillation trays in each tower and the flow rates through pumps, vessels, and the flare were calculated in HYSYS. Heat exchange areas were given in Aspen Energy Analyzer or from HYSYS.

[[File:Equipment_cost.JPG|center|]]

In addition to the above equipment, our plant will require an ion exchanger to produce deionized process water from the municipal water. This is estimated to cost $42,000 in capital cost.

===Cash flow analysis===
Summarizing the important takeaways from the economic analysis, this process will return a revenue of 144 MM$ annually. Offset by production costs, the yearly cash flow is approximately 2.7 MM$, except for in the years in which the catalyst must be reinstalled (approximately every 5 years). At a cost of 2.5 MM$, the cash flows in those years decrease to approximately 0.2 MM$. This analysis assumes the plant will take 2 years to construct, and will operate at 50% in its first year. Furthermore, an interest rate of 10% was assumed with a tax rate of 38% (the maximum for corporate gains taxes). Using the 7-year MACRS depreciation method, the 20 year NPV for the project is 4.3 MM$. With an IRR of 15.1%, which is greater than the assumed interest rate, this project looks to be profitable. Further optimization techniques should be used in future iterations to further increase profitability. See Tables 3 and 4 for key economic information.

[[File:Econ_summaries.JPG|center|]]

===Sensitivity analysis===
As seen in Figure 4, the economic evaluation of this process is influenced the most by changes in the sales price and feed cost. A 20% increase in sales price will result in an approximate 120 MM$ increase in NPV whereas a decrease of the same percentage will result in over a 120 MM$ decrease in NPV. Inversely, a 20% increase in feed cost will result in a 115 MM$ decrease in NPV and a 20% decrease in feed cost will result in a 60 MM$ increase in NPV.

[[File:S2_Sensitivity.JPG|center|frame|Figure 4. Sensitivity analysis]]

To alleviate the risk associated with feed price, the team researched the price forecasting of bio-succinic acid. We compared the bio-succinic acid price to the adipic acid price over the six years between 2006 and 2012. The price of bio-succinic has remained relatively stable over this time period. Adipic acid, which is a common petrochemical precursor for BDO production, has had large fluctuations in price that result in unstable cash flows and uncertainty from shareholders. Thankfully, the stability of bio-succinic acid is a good sign that this process has a huge potential to be profitable especially if the demand for BDO continues to rise as projected.

==Discussion==
As described previously, the Davy process was selected as the most promising process of BDO production. The modified Davy process involves the hydrogenation of bio-succinicic acid with a Pa,Ag,Re catalyst and hydrogen gas. This process has many advantages, one being that it has mature technology that has been improved over the last 20 years. Additionally, the conversion to of succinic acid is virtually complete. Finally, overall plant yields can reach as high as 94 mol%.
As shown in Appendix B, streams ahead of the pressure valve (PRV-101) are at approximately 1.51e4 kPa, and streams after the pressure valve are between 100 and 450 kPa. Furthermore, operating temperatures do not exceed 200°C, including safety factors. These operating conditions contribute to the feasibility of the process, as all the components can be designed with reasonable dimensions (wall thickness, cap type, etc.).

Of particular interest are the large costs of the reactor and pump P-101. The reactor costs nearly 2 MM$ because it has a moderate size with a liquid volume of 16.7 m3, and it operates at 150 atm, which requires a strong stainless steel shell for safety purposes. Pump P-101 has such a large capital cost because it is a centrifugal multistage pump that also needs to be made of stainless steel to withstand pressuring the succinic acid feed to 150 atm.

Financial indicators for the proposed plant suggest that it will be moderately profitable, and additional optimization should be performed before making the capital investment. There is a fair amount of risk associated with the implementation of this production facility, and the return at this juncture may not justify the risk.

The process design and simulation in HYSYS has relied on several key assumptions, which are cause for certain limitations to the results. First, the conversions and selectivity of the catalyst, while taken from literature sources, are assumed to be true. Furthermore, the assumption of negligible side reactions and products was made. It is possible that small waste products in the form of succinates also form in the reactor. Therefore, the main limitation of this model is generally due to reaction specifications.

There are certain safety concerns that go along with the proposed process. First, there are many pipes and vessels that will be at a pressure of approximately 150 atm. Extra insulation and protection must be applied to the piping that contains highly pressurized fluids, to prevent operator injury. Furthermore, the PFR is at a slight risk for runaway reactions due to the exothermic nature of the reaction. The temperature of the reactor must always be monitored by an operator, and the jacket cooling system requires a backup system as well. A benefit of this process is that there are no toxic or severely hazardous components in the process. Additionally, there are no instances of temperature greater than 200°C.

The process design will be fitted with instrumentation and controls to ensure stable operation. These controls, including sensors and valves, minimize potential damage to components due to variation in plant conditions, as well as optimizing the overall performance. For example, the piping entering the tower will be fitted with a control loop. In the direction of flow, a sensing instrument first detects the pressure of the fluid, and then sends a signal to the controller. If the pressure is not within the operating limits, the actuator is signaled to close or open a control valve which is located farther down the stream.

==Conclusion==
The Evanston Chemical Engineering Division suggests a process that produces 45,000 tonnes/year of 99.5 wt% 1,4-butandeiol to enter the market with an appropriate market share. The feasibility of producing BDO as a significant process was investigated. A wide range of BDO production processes were researched, with a modified Davy process being identified as having the most potential. Using a Pa,Ag,Re catalyst on carbon support, this process converts bio-succinic acid to BDO with approximately 94% conversion. This process was designed in Aspen HYSYS, and economic analysis was conducted in Aspen Economic Analyzer. Total capital costs of the project are 12.2 MM$, with a simple payback period of 5.2 years. Total operational costs annually are 139.7 MM$. The process design was successful, with the capability of producing the desired production of BDO.

==Recommendations==
Given the moderate profitability of this process design, it is recommended that Evanston Chemicals explores further optimization techniques to increase the profitability of this process. This includes investigating sales of the γ-butyrolactone byproduct, recycling process water, and further optimizing utility streams for the distillation tower.

Second, we would like to investigate recycling the 2300 kg/h of water produced in the reaction. Our succinic acid enters the reactor as a 50 wt% solution in water, so we should look into replacing some of this with the product water. Not only will this decrease our water bill, but it will also lower the cost of ion exchange.

==References==
# Nexant.''Is Bio-Butanediol Here to Stay?'' White Plains, NY: ChemSystems Products; 2012.
# De Guzman D. Chemical industry awaits for bio-succinic acid potential. ICIS. Available at: http://www.icis.com/resources/news/2012/01/30/9527521/chemical-industry-awaits-for-bio-succinic-acid-potential/. Accessed January 24, 2014.
# Australian Government: Department of Health. 1,4-butanediol factsheet. National Industrial Chemicals Notification and Assessment Scheme. Available at: http://www.nicnas.gov.au/communications/publications/information-sheets/existing-chemical-info-sheets/other-information-sheets. Accessed January 24, 2014.
# TecnonOrbiChem. Chem-net facts: 1,4-butanediol. TecnonOrbiChem. Available at: http://www.orbichem.com/userfiles/CNF%20Samples/bdo_13_11.pdf. Accessed January 23, 2014.
# Nexant. 1,4-butanediol/tetrahydrofuran (BDO/THF). ChemSystems. Available at: http://www.chemsystems.com/about/cs/news/items/ PERP2012_3_BDO_THF.cfm. Accessed February 6, 2014.
# Burk MJ, Van Dien SJ, Burgard AP, inventors; Genomatica, Inc., assignee. Compositions and methods for the biosynthesis of 1,4-butanediol and its precursors. US patent 8,067,214. Nov. 29, 2011.
# Chung S-H, Kim M-S, Eom H-H, Lee K-Y. Catalytic hydrogenation of bio-based succinic acid for the production of 1,4-butanediol through the indirect pathway. AIChE. Available at: https://aiche.confex.com/aiche/2013/webprogram/Paper327470.html. Accessed January 23, 2014.
# Bhattacharyya A, Manila MD, inventors; ISP Investments Inc., assignee. Catalysts for maleic acid hydrogenation to 1,4-Butanediol. US patent 7,935,834 B2. May 3, 2011.

Design S2

2014-03-15T05:28:23Z

Karetstik: /* Sensitivity analysis */

Title: Production of 1,4-butanediol

Authors: Nick Pinkerton, Karen Schmidt, and James Xamplas

Date Presented: March 14, 2014

==Introduction==
1,4-butanediol (BDO) is traditionally made from petroleum-derived feedstocks in a variety of processes such as the Reppe (acetylene-based), Mitsubishi (butadiene-based), and Davy (maleic acid-based) processes [1]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, BDO [1]. It is this process that Team S2Kool4Skool has chosen to develop for a new bio-butanediol plant, because the Davy method is mature and requires no new innovations, and because an appropriate feedstock of bio-succinic acid is now available. The plant will be located in East Carroll Parish, Louisiana. This county is also home to Myriant; located in Lake Providence, they are the largest domestic provider of bio-succinic acid [2]. Furthermore, Lake Providence is conveniently located on the Mississippi River, which will allow for affordable transportation of our bio-based butanediol product. The intent of this project is to produce 45,000 metric tonnes of 99.5 wt% 1,4-butanediol per year in a new plant in Lake Providence, LA. The plant will run 24 hours per day for 350 days out of the year, allowing approximately two weeks for a maintenance shutdown.

As there are several techniques for producing 1,4 butanediol in industry, the first step was to determine a synthesis path. Based on the chosen path, reaction kinetics, and required production rate of the process, a reactor system was then designed. Next, the process was designed to deliver the reactants to the reactor at the proper operating conditions, and the separations, purification, and waste management steps were designed. Cost estimates were made using costing software and hand calculations. Finally, the process was iterated and optimized to reduce costs.

==Background==
===General information===
BDO is an organic chemical with the molecular formula <math>C_4H_{10}O_2</math>. It is also a diol with its two hydroxyl groups located at the terminal carbons. BDO has a boiling point of 235 degrees C and is therefore a colorless liquid at standard temperatures and pressures [3].

There are many precursors that petrochemical synthesis of BDO uses. The commonality between all of the precursor acids is that they are hydrogenatable. In replacement of one of these petrochemical precursors, our team has been tasked with the challenge of deriving BDO from the bio-based precursor succinic acid. This catalyzed reaction will take place in the presence of hydrogen as the hydrogenating component shown below:

<math>C_4H_6O_4 + 4H_2 = C_4H_{10}O_2 + 2H_2O</math>

As described in the above reaction, there will need to be at least 4:1 stoichiometric ratio of hydrogen gas to succinic acid. Two moles of water will also be produced along with each mole of BDO. This reaction is exothermic, which requires the reactor to be continuously cooled to maintain our reactor temperature. There are also side products that are produced which include tetrahydrofuran (THF) and γ-butyrolactone (GBL); however, thanks to catalyst selectivity these byproducts are produced in small quantities.

===Market analysis===
Butanediol has a quickly expanding market due to new technological evolutions and its growing use as a chemical intermediary in advanced materials. With biological routes being optimized, the potential of biomass-derived chemicals is tremendous. The global demand of BDO was estimated at 1.5 million metric tons in 2011 and is projected to grow at an annual rate of 4.5% for the next several years [1]. Unlike other chemical products, BDO’s profitability and attractiveness to producers lies in its downstream potential. Figure 1 below demonstrates several potential downstream products that can be directly or indirectly synthesized from BDO. The largest of these contributors include THF and GBL.

[[File:BioButanediol_Downstream.JPG|center|frame|Figure 1. BDO downstream potential flow chart]]

The current market demand of BDO is being supplemented by several global chemical companies. These companies include BASF, BioAmber, Purac, Myriant, DSM, Mitsubishi Chemical, Roquette, and OPXBIO. The market shares of these companies were not available for this product; however, with the consistent growth of the BDO market our team feels that the market is not saturated or impenetrable. The current market price of BDO fluctuates between $3.06 and $3.31 per kg for US-made products [4]. These prices correlate to a nearly 7 billion dollar industry.

===Process alternatives===
1,4-butanediol is traditionally made from petroleum-derived feedstocks in a variety of processes [5]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Several companies are currently implementing bio-routes of producing butanediol. Genomatica is using a bioengineered microorganism to convert sugar feedstocks directly to BDO via fermentation [6], but most companies are instead using microorganisms to convert sugar to succinic acid. The bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, which is the path that most are choosing, although research is being conducted on alternative pathways [7].

==Process overview==
The newly proposed plant can be divided into four stages: pre-reactor, reactor, post-reactor and distillation. Each section is an integral part to the overall process and demands close attention. See the complete process flow diagram in Figure 2.

[[File:PFD.JPG|center|frame|Figure 2. Process flow diagram]]

===Pre-reactor===
This chemical process begins with two feedstocks: hydrogen gas and bio-succinic acid. The hydrogen gas will be obtained from a pipeline at 150 atm and will be used in molar excess inside the reactor. The bio-succinic acid will be purchased by Myriant Corporation which is located near the planned plant site. The pricing for this feedstock is approximately $2.12 per kg. The plant will require 63,000 metric tonnes of bio-succinic acid per year to meet the proposed plant capacity. First the bio-succinic acid feed is pumped up to 150 atm to match the hydrogen gas feed, and then it is mixed with the hydrogen gas prior to being sent into heat exchanger E-101 for heating. The heat exchanger brings the two feeds up to 110oC and sends them to the jacketed packed bed reactor.

===Reactor===
The hydrogenation reaction occurs inside of the reactor thanks to the packed catalyst bed. The catalyst used is 0.4% Fe, 1.9% Na, 2.66% Ag, 2.66% Pd, 10.0% Re on 1.5mm carbon support. With this catalyst, BDO is produced with over 90% selectivity and minimal side reactions of THF and GBL [8]. The reaction has an operating pressure of 2000-4000 psi and internal reactor temperature of 165°C. This temperature allows for about 99.7% conversion of succinic acid [8]. Due to the exothermic nature of the reaction, a cooling jacket is required which utilizes downstream cold streams to cool the internal bed to maintain the desired reaction temperature.

===Post-reactor===
The effluent of the reactor is sent back to E-101 as the hot stream. After exiting E-101, the reactor product stream is sent to a secondary exchanger, E-102, where utility cooling water is used to reduce the temperature to an acceptable temperature prior to sending it to a pressure let-down valve. At this point the pressure of the stream is taken from 150 atm to 1 atm. This large pressure drop allows for the stream to split into its vapor and liquid portions in a gas-liquid separator. The vapor stream of the gas liquid separator is primarily hydrogen gas and sent to a flare for disposal. The liquid effluent is at approximately 45oC leaving the separator and is therefore pumped to the reactor jacket for the reaction cooling mentioned previously. After running through the reactor jacket, the stream enters the separation processes.

===Distillation===
The first distillation column, T-101, is a 10 stage column whose primary purpose is separating the THF from the product feed. Due to THF’s lower boiling point, the byproduct comes off of the top of the column with mostly water. This distillate is sent to the plant's THF waste storage tank that has the capacity of two weeks. The bottoms of the column is sent to the subsequent distillation column that separates the BDO from the GBL and water. The relatively close boiling points of BDO and GBL, 235oC and 204oC, respectively, create a difficult separation that requires a 15 stage column. The distillate of the column is approximately 23% GBL with balance water. This stream is sent to a storage tank with similar sizing parameters as the THF storage tank. The bottom stream is the final 99.5wt% BDO product. This stream is sent to the final product tank, S-104. Depending on our customer demands and the plant location we have the ability to barge, rail or pipe our product to its final destination. Due to low purity of the byproducts, future iterations are needed to optimize either purifying byproducts or selling impure byproducts. There is definitely an available market for these byproducts that should be researched more extensively to increase profit. A detailed description of the equipment from the PFD can be found in Appendix C, in addition to sizing specifications and purpose of equipment.

===Mass and energy balances===
Using an Aspen HYSYS simulation we were able to record the material and energy streams going in and out of the process system. Mass and energy balances are provided Appendix D where each inlet and outlet stream is described and quantified. As expected, the material and energy totals for the inlet and outlet streams add together to equal 0. This proves that our system is mathematically prudent and thermodynamically feasible. The total mass flow of the system is 15,639 kg/h and the total energy in and out of the system is 1.41e8 kJ/h.

===HYSYS simulation===
The HYSYS simulation was performed using the NRTL ideal fluid package. After using AspenPlus to verify that the HYSYS package had the appropriate vapor-liquid equilibrium information between THF and water, and between GBL and water, we concluded it was feasible to proceed with that fluid package. The simulation consists of a reactor, a gas-liquid separator, 2 pumps, 3 heaters, a valve, and 2 distillation columns (see Figure 3). The simulation successfully converted the succinic acid feed into the desired products. Also, the combination of the two distillation columns was able to effectively separate the BDO to obtain a 99.5% pure product with 99.5% recovery. In addition, a set was made between the energy required to heat stream 12 and the energy required to cool the reactor so that these values were made equal. Lastly, the condenser and reboiler duties were used in four heat exchangers in order to determine the appropriate size of this equipment as well as the necessary utility flow rates.

[[File:S2_HYSYS_Simulation.JPG|center|frame|Figure 3. HYSYS simulation]]

==Health and safety==
===Chemical properties===
Inherent to this process are a number of toxic chemicals. Table 1 summarizes the important safety data including hazard type, odor, color, and exposure limits.

[[File:Chem_properties.JPG|center|]]

As shown in the above table, the chemicals that this facility will be dealing with will be relatively mild and non-life threatening. Regardless of their perceived threat, chemicals should always be handled with care especially when they are at high temperatures and pressures.

===Safety procedures===

'''Fire'''. There are many flammable materials that will be included in this process; therefore, fire safety is imperative for all employees. There are countless possible causes of ignition and care should be taken while handling any flammable material whether in the lab or in the field.

In case a fire is present on, the following protocol should be implemented:

* Small fire: Use DRY chemical powder.
* Large fire: Use alcohol foam, water spray, or fog.
* Call for backup if unable to control.
* Immediately contact supervisor and emergency personnel on site.
* Evacuate to safe distance in case of fires around any hazardous materials or pressure vessels.

'''Spills'''. Process chemical spills will eventually occur in a plant of this scale. Small spills are likely to occur in a laboratory setting. Large spills could be a result of loss of containment in the system. We must ensure that all personnel are aware of proper spill mitigation protocol.

* Small spill: Dilute with water and mop or absorb with inert dry material. Dispose of in proper receptacle.
* Large spill: Keep away from sources of ignition and heat. Prevent rundown to any drains or sewers. Call for assistance on disposal. Absorb material with DRY earth or other non-combustible materials.
* If spill is due to a loss of containment in the system, quickly consult the PLC and shut any valves to prevent further loss.

'''Exposure'''. We must ensure that our employees are aware of the possible toxicity levels of each substance and how to handle exposure. The chemicals that are being used in this process are known chemical irritants to the eyes, skin, and throat. Safety measures must be in place to acknowledge this hazard. Due to the possibility of high pressure releases, we will have 2-minute emergency oxygen masks placed strategically throughout the plant to ensure the safety of any operator in the presence of a large release.

If exposed to the process chemicals, find nearest eye wash station or safety shower immediately and flush exposed skin for at least 15 minutes. Remove any contaminated clothing. Seek medical attention immediately.

'''Storage'''. Store chemicals in segregated and approved areas. Any closed containers for laboratory purposes should be placed in cool, well-ventilated areas.

==Economics==
===Equipment costing===
The calculated capital costs from Aspen Economic Analyzer are reported in Table 2 for all process equipment. The size of the reactor was calculated from the liquid hourly space velocity given in the 2011 ISP patent [8] and a void fraction estimate of 0.4. Storage tanks were sized to contain up to two continuous weeks of material. The number of distillation trays in each tower and the flow rates through pumps, vessels, and the flare were calculated in HYSYS. Heat exchange areas were given in Aspen Energy Analyzer or from HYSYS.

[[File:Equipment_cost.JPG|center|]]

In addition to the above equipment, our plant will require an ion exchanger to produce deionized process water from the municipal water. This is estimated to cost $42,000 in capital cost.

===Cash flow analysis===
Summarizing the important takeaways from the economic analysis, this process will return a revenue of 144 MM$ annually. Offset by production costs, the yearly cash flow is approximately 2.7 MM$, except for in the years in which the catalyst must be reinstalled (approximately every 5 years). At a cost of 2.5 MM$, the cash flows in those years decrease to approximately 0.2 MM$. This analysis assumes the plant will take 2 years to construct, and will operate at 50% in its first year. Furthermore, an interest rate of 10% was assumed with a tax rate of 38% (the maximum for corporate gains taxes). Using the 7-year MACRS depreciation method, the 20 year NPV for the project is 4.3 MM$. With an IRR of 15.1%, which is greater than the assumed interest rate, this project looks to be profitable. Further optimization techniques should be used in future iterations to further increase profitability. See Tables 3 and 4 for key economic information.

[[File:Econ_summaries.JPG|center|]]

===Sensitivity analysis===
As seen in Figure 4, the economic evaluation of this process is influenced the most by changes in the sales price and feed cost. A 20% increase in sales price will result in an approximate 120 MM$ increase in NPV whereas a decrease of the same percentage will result in over a 120 MM$ decrease in NPV. Inversely, a 20% increase in feed cost will result in a 115 MM$ decrease in NPV and a 20% decrease in feed cost will result in a 60 MM$ increase in NPV.

[[File:S2_Sensitivity.JPG|center|frame|Figure 4. Sensitivity analysis]]

To alleviate the risk associated with feed price, the team researched the price forecasting of bio-succinic acid. We compared the bio-succinic acid price to the adipic acid price over the six years between 2006 and 2012. The price of bio-succinic has remained relatively stable over this time period. Adipic acid, which is a common petrochemical precursor for BDO production, has had large fluctuations in price that result in unstable cash flows and uncertainty from shareholders. Thankfully, the stability of bio-succinic acid is a good sign that this process has a huge potential to be profitable especially if the demand for BDO continues to rise as projected.

==Discussion==
As described previously, the Davy process was selected as the most promising process of BDO production. The modified Davy process involves the hydrogenation of bio-succinicic acid with a Pa,Ag,Re catalyst and hydrogen gas. This process has many advantages, one being that it has mature technology that has been improved over the last 20 years. Additionally, the conversion to of succinic acid is virtually complete. Finally, overall plant yields can reach as high as 94 mol%.
As shown in Appendix B, streams ahead of the pressure valve (PRV-101) are at approximately 1.51e4 kPa, and streams after the pressure valve are between 100 and 450 kPa. Furthermore, operating temperatures do not exceed 200°C, including safety factors. These operating conditions contribute to the feasibility of the process, as all the components can be designed with reasonable dimensions (wall thickness, cap type, etc.).

Of particular interest are the large costs of the reactor and pump P-101. The reactor costs nearly 2 MM$ because it has a moderate size with a liquid volume of 16.7 m3, and it operates at 150 atm, which requires a strong stainless steel shell for safety purposes. Pump P-101 has such a large capital cost because it is a centrifugal multistage pump that also needs to be made of stainless steel to withstand pressuring the succinic acid feed to 150 atm.

Financial indicators for the proposed plant suggest that it will be moderately profitable, and additional optimization should be performed before making the capital investment. There is a fair amount of risk associated with the implementation of this production facility, and the return at this juncture may not justify the risk.

The process design and simulation in HYSYS has relied on several key assumptions, which are cause for certain limitations to the results. First, the conversions and selectivity of the catalyst, while taken from literature sources, are assumed to be true. Furthermore, the assumption of negligible side reactions and products was made. It is possible that small waste products in the form of succinates also form in the reactor. Therefore, the main limitation of this model is generally due to reaction specifications.

There are certain safety concerns that go along with the proposed process. First, there are many pipes and vessels that will be at a pressure of approximately 150 atm. Extra insulation and protection must be applied to the piping that contains highly pressurized fluids, to prevent operator injury. Furthermore, the PFR is at a slight risk for runaway reactions due to the exothermic nature of the reaction. The temperature of the reactor must always be monitored by an operator, and the jacket cooling system requires a backup system as well. A benefit of this process is that there are no toxic or severely hazardous components in the process. Additionally, there are no instances of temperature greater than 200°C.

The process design will be fitted with instrumentation and controls to ensure stable operation. These controls, including sensors and valves, minimize potential damage to components due to variation in plant conditions, as well as optimizing the overall performance. For example, the piping entering the tower will be fitted with a control loop. In the direction of flow, a sensing instrument first detects the pressure of the fluid, and then sends a signal to the controller. If the pressure is not within the operating limits, the actuator is signaled to close or open a control valve which is located farther down the stream.

==Conclusion==
The Evanston Chemical Engineering Division suggests a process that produces 45,000 tonnes/year of 99.5 wt% 1,4-butandeiol to enter the market with an appropriate market share. The feasibility of producing BDO as a significant process was investigated. A wide range of BDO production processes were researched, with a modified Davy process being identified as having the most potential. Using a Pa,Ag,Re catalyst on carbon support, this process converts bio-succinic acid to BDO with approximately 94% conversion. This process was designed in Aspen HYSYS, and economic analysis was conducted in Aspen Economic Analyzer. Total capital costs of the project are 12.2 MM$, with a simple payback period of 5.2 years. Total operational costs annually are 139.7 MM$. The process design was successful, with the capability of producing the desired production of BDO.

==Recommendations==
Given the moderate profitability of this process design, it is recommended that Evanston Chemicals explores further optimization techniques to increase the profitability of this process. This includes investigating sales of the γ-butyrolactone byproduct, recycling process water, and further optimizing utility streams for the distillation tower.

Second, we would like to investigate recycling the 2300 kg/h of water produced in the reaction. Our succinic acid enters the reactor as a 50 wt% solution in water, so we should look into replacing some of this with the product water. Not only will this decrease our water bill, but it will also lower the cost of ion exchange.

==References==
# Nexant.''Is Bio-Butanediol Here to Stay?'' White Plains, NY: ChemSystems Products; 2012.
# De Guzman D. Chemical industry awaits for bio-succinic acid potential. ICIS. Available at: http://www.icis.com/resources/news/2012/01/30/9527521/chemical-industry-awaits-for-bio-succinic-acid-potential/. Accessed January 24, 2014.
# Australian Government: Department of Health. 1,4-butanediol factsheet. National Industrial Chemicals Notification and Assessment Scheme. Available at: http://www.nicnas.gov.au/communications/publications/information-sheets/existing-chemical-info-sheets/other-information-sheets. Accessed January 24, 2014.
# TecnonOrbiChem. Chem-net facts: 1,4-butanediol. TecnonOrbiChem. Available at: http://www.orbichem.com/userfiles/CNF%20Samples/bdo_13_11.pdf. Accessed January 23, 2014.
# Nexant. 1,4-butanediol/tetrahydrofuran (BDO/THF). ChemSystems. Available at: http://www.chemsystems.com/about/cs/news/items/ PERP2012_3_BDO_THF.cfm. Accessed February 6, 2014.
# Burk MJ, Van Dien SJ, Burgard AP, inventors; Genomatica, Inc., assignee. Compositions and methods for the biosynthesis of 1,4-butanediol and its precursors. US patent 8,067,214. Nov. 29, 2011.
# Chung S-H, Kim M-S, Eom H-H, Lee K-Y. Catalytic hydrogenation of bio-based succinic acid for the production of 1,4-butanediol through the indirect pathway. AIChE. Available at: https://aiche.confex.com/aiche/2013/webprogram/Paper327470.html. Accessed January 23, 2014.
# Bhattacharyya A, Manila MD, inventors; ISP Investments Inc., assignee. Catalysts for maleic acid hydrogenation to 1,4-Butanediol. US patent 7,935,834 B2. May 3, 2011.

Design S2

2014-03-15T05:26:36Z

Karetstik: /* Sensitivity analysis */

Title: Production of 1,4-butanediol

Authors: Nick Pinkerton, Karen Schmidt, and James Xamplas

Date Presented: March 14, 2014

==Introduction==
1,4-butanediol (BDO) is traditionally made from petroleum-derived feedstocks in a variety of processes such as the Reppe (acetylene-based), Mitsubishi (butadiene-based), and Davy (maleic acid-based) processes [1]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, BDO [1]. It is this process that Team S2Kool4Skool has chosen to develop for a new bio-butanediol plant, because the Davy method is mature and requires no new innovations, and because an appropriate feedstock of bio-succinic acid is now available. The plant will be located in East Carroll Parish, Louisiana. This county is also home to Myriant; located in Lake Providence, they are the largest domestic provider of bio-succinic acid [2]. Furthermore, Lake Providence is conveniently located on the Mississippi River, which will allow for affordable transportation of our bio-based butanediol product. The intent of this project is to produce 45,000 metric tonnes of 99.5 wt% 1,4-butanediol per year in a new plant in Lake Providence, LA. The plant will run 24 hours per day for 350 days out of the year, allowing approximately two weeks for a maintenance shutdown.

As there are several techniques for producing 1,4 butanediol in industry, the first step was to determine a synthesis path. Based on the chosen path, reaction kinetics, and required production rate of the process, a reactor system was then designed. Next, the process was designed to deliver the reactants to the reactor at the proper operating conditions, and the separations, purification, and waste management steps were designed. Cost estimates were made using costing software and hand calculations. Finally, the process was iterated and optimized to reduce costs.

==Background==
===General information===
BDO is an organic chemical with the molecular formula <math>C_4H_{10}O_2</math>. It is also a diol with its two hydroxyl groups located at the terminal carbons. BDO has a boiling point of 235 degrees C and is therefore a colorless liquid at standard temperatures and pressures [3].

There are many precursors that petrochemical synthesis of BDO uses. The commonality between all of the precursor acids is that they are hydrogenatable. In replacement of one of these petrochemical precursors, our team has been tasked with the challenge of deriving BDO from the bio-based precursor succinic acid. This catalyzed reaction will take place in the presence of hydrogen as the hydrogenating component shown below:

<math>C_4H_6O_4 + 4H_2 = C_4H_{10}O_2 + 2H_2O</math>

As described in the above reaction, there will need to be at least 4:1 stoichiometric ratio of hydrogen gas to succinic acid. Two moles of water will also be produced along with each mole of BDO. This reaction is exothermic, which requires the reactor to be continuously cooled to maintain our reactor temperature. There are also side products that are produced which include tetrahydrofuran (THF) and γ-butyrolactone (GBL); however, thanks to catalyst selectivity these byproducts are produced in small quantities.

===Market analysis===
Butanediol has a quickly expanding market due to new technological evolutions and its growing use as a chemical intermediary in advanced materials. With biological routes being optimized, the potential of biomass-derived chemicals is tremendous. The global demand of BDO was estimated at 1.5 million metric tons in 2011 and is projected to grow at an annual rate of 4.5% for the next several years [1]. Unlike other chemical products, BDO’s profitability and attractiveness to producers lies in its downstream potential. Figure 1 below demonstrates several potential downstream products that can be directly or indirectly synthesized from BDO. The largest of these contributors include THF and GBL.

[[File:BioButanediol_Downstream.JPG|center|frame|Figure 1. BDO downstream potential flow chart]]

The current market demand of BDO is being supplemented by several global chemical companies. These companies include BASF, BioAmber, Purac, Myriant, DSM, Mitsubishi Chemical, Roquette, and OPXBIO. The market shares of these companies were not available for this product; however, with the consistent growth of the BDO market our team feels that the market is not saturated or impenetrable. The current market price of BDO fluctuates between $3.06 and $3.31 per kg for US-made products [4]. These prices correlate to a nearly 7 billion dollar industry.

===Process alternatives===
1,4-butanediol is traditionally made from petroleum-derived feedstocks in a variety of processes [5]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Several companies are currently implementing bio-routes of producing butanediol. Genomatica is using a bioengineered microorganism to convert sugar feedstocks directly to BDO via fermentation [6], but most companies are instead using microorganisms to convert sugar to succinic acid. The bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, which is the path that most are choosing, although research is being conducted on alternative pathways [7].

==Process overview==
The newly proposed plant can be divided into four stages: pre-reactor, reactor, post-reactor and distillation. Each section is an integral part to the overall process and demands close attention. See the complete process flow diagram in Figure 2.

[[File:PFD.JPG|center|frame|Figure 2. Process flow diagram]]

===Pre-reactor===
This chemical process begins with two feedstocks: hydrogen gas and bio-succinic acid. The hydrogen gas will be obtained from a pipeline at 150 atm and will be used in molar excess inside the reactor. The bio-succinic acid will be purchased by Myriant Corporation which is located near the planned plant site. The pricing for this feedstock is approximately $2.12 per kg. The plant will require 63,000 metric tonnes of bio-succinic acid per year to meet the proposed plant capacity. First the bio-succinic acid feed is pumped up to 150 atm to match the hydrogen gas feed, and then it is mixed with the hydrogen gas prior to being sent into heat exchanger E-101 for heating. The heat exchanger brings the two feeds up to 110oC and sends them to the jacketed packed bed reactor.

===Reactor===
The hydrogenation reaction occurs inside of the reactor thanks to the packed catalyst bed. The catalyst used is 0.4% Fe, 1.9% Na, 2.66% Ag, 2.66% Pd, 10.0% Re on 1.5mm carbon support. With this catalyst, BDO is produced with over 90% selectivity and minimal side reactions of THF and GBL [8]. The reaction has an operating pressure of 2000-4000 psi and internal reactor temperature of 165°C. This temperature allows for about 99.7% conversion of succinic acid [8]. Due to the exothermic nature of the reaction, a cooling jacket is required which utilizes downstream cold streams to cool the internal bed to maintain the desired reaction temperature.

===Post-reactor===
The effluent of the reactor is sent back to E-101 as the hot stream. After exiting E-101, the reactor product stream is sent to a secondary exchanger, E-102, where utility cooling water is used to reduce the temperature to an acceptable temperature prior to sending it to a pressure let-down valve. At this point the pressure of the stream is taken from 150 atm to 1 atm. This large pressure drop allows for the stream to split into its vapor and liquid portions in a gas-liquid separator. The vapor stream of the gas liquid separator is primarily hydrogen gas and sent to a flare for disposal. The liquid effluent is at approximately 45oC leaving the separator and is therefore pumped to the reactor jacket for the reaction cooling mentioned previously. After running through the reactor jacket, the stream enters the separation processes.

===Distillation===
The first distillation column, T-101, is a 10 stage column whose primary purpose is separating the THF from the product feed. Due to THF’s lower boiling point, the byproduct comes off of the top of the column with mostly water. This distillate is sent to the plant's THF waste storage tank that has the capacity of two weeks. The bottoms of the column is sent to the subsequent distillation column that separates the BDO from the GBL and water. The relatively close boiling points of BDO and GBL, 235oC and 204oC, respectively, create a difficult separation that requires a 15 stage column. The distillate of the column is approximately 23% GBL with balance water. This stream is sent to a storage tank with similar sizing parameters as the THF storage tank. The bottom stream is the final 99.5wt% BDO product. This stream is sent to the final product tank, S-104. Depending on our customer demands and the plant location we have the ability to barge, rail or pipe our product to its final destination. Due to low purity of the byproducts, future iterations are needed to optimize either purifying byproducts or selling impure byproducts. There is definitely an available market for these byproducts that should be researched more extensively to increase profit. A detailed description of the equipment from the PFD can be found in Appendix C, in addition to sizing specifications and purpose of equipment.

===Mass and energy balances===
Using an Aspen HYSYS simulation we were able to record the material and energy streams going in and out of the process system. Mass and energy balances are provided Appendix D where each inlet and outlet stream is described and quantified. As expected, the material and energy totals for the inlet and outlet streams add together to equal 0. This proves that our system is mathematically prudent and thermodynamically feasible. The total mass flow of the system is 15,639 kg/h and the total energy in and out of the system is 1.41e8 kJ/h.

===HYSYS simulation===
The HYSYS simulation was performed using the NRTL ideal fluid package. After using AspenPlus to verify that the HYSYS package had the appropriate vapor-liquid equilibrium information between THF and water, and between GBL and water, we concluded it was feasible to proceed with that fluid package. The simulation consists of a reactor, a gas-liquid separator, 2 pumps, 3 heaters, a valve, and 2 distillation columns (see Figure 3). The simulation successfully converted the succinic acid feed into the desired products. Also, the combination of the two distillation columns was able to effectively separate the BDO to obtain a 99.5% pure product with 99.5% recovery. In addition, a set was made between the energy required to heat stream 12 and the energy required to cool the reactor so that these values were made equal. Lastly, the condenser and reboiler duties were used in four heat exchangers in order to determine the appropriate size of this equipment as well as the necessary utility flow rates.

[[File:S2_HYSYS_Simulation.JPG|center|frame|Figure 3. HYSYS simulation]]

==Health and safety==
===Chemical properties===
Inherent to this process are a number of toxic chemicals. Table 1 summarizes the important safety data including hazard type, odor, color, and exposure limits.

[[File:Chem_properties.JPG|center|]]

As shown in the above table, the chemicals that this facility will be dealing with will be relatively mild and non-life threatening. Regardless of their perceived threat, chemicals should always be handled with care especially when they are at high temperatures and pressures.

===Safety procedures===

'''Fire'''. There are many flammable materials that will be included in this process; therefore, fire safety is imperative for all employees. There are countless possible causes of ignition and care should be taken while handling any flammable material whether in the lab or in the field.

In case a fire is present on, the following protocol should be implemented:

* Small fire: Use DRY chemical powder.
* Large fire: Use alcohol foam, water spray, or fog.
* Call for backup if unable to control.
* Immediately contact supervisor and emergency personnel on site.
* Evacuate to safe distance in case of fires around any hazardous materials or pressure vessels.

'''Spills'''. Process chemical spills will eventually occur in a plant of this scale. Small spills are likely to occur in a laboratory setting. Large spills could be a result of loss of containment in the system. We must ensure that all personnel are aware of proper spill mitigation protocol.

* Small spill: Dilute with water and mop or absorb with inert dry material. Dispose of in proper receptacle.
* Large spill: Keep away from sources of ignition and heat. Prevent rundown to any drains or sewers. Call for assistance on disposal. Absorb material with DRY earth or other non-combustible materials.
* If spill is due to a loss of containment in the system, quickly consult the PLC and shut any valves to prevent further loss.

'''Exposure'''. We must ensure that our employees are aware of the possible toxicity levels of each substance and how to handle exposure. The chemicals that are being used in this process are known chemical irritants to the eyes, skin, and throat. Safety measures must be in place to acknowledge this hazard. Due to the possibility of high pressure releases, we will have 2-minute emergency oxygen masks placed strategically throughout the plant to ensure the safety of any operator in the presence of a large release.

If exposed to the process chemicals, find nearest eye wash station or safety shower immediately and flush exposed skin for at least 15 minutes. Remove any contaminated clothing. Seek medical attention immediately.

'''Storage'''. Store chemicals in segregated and approved areas. Any closed containers for laboratory purposes should be placed in cool, well-ventilated areas.

==Economics==
===Equipment costing===
The calculated capital costs from Aspen Economic Analyzer are reported in Table 2 for all process equipment. The size of the reactor was calculated from the liquid hourly space velocity given in the 2011 ISP patent [8] and a void fraction estimate of 0.4. Storage tanks were sized to contain up to two continuous weeks of material. The number of distillation trays in each tower and the flow rates through pumps, vessels, and the flare were calculated in HYSYS. Heat exchange areas were given in Aspen Energy Analyzer or from HYSYS.

[[File:Equipment_cost.JPG|center|]]

In addition to the above equipment, our plant will require an ion exchanger to produce deionized process water from the municipal water. This is estimated to cost $42,000 in capital cost.

===Cash flow analysis===
Summarizing the important takeaways from the economic analysis, this process will return a revenue of 144 MM$ annually. Offset by production costs, the yearly cash flow is approximately 2.7 MM$, except for in the years in which the catalyst must be reinstalled (approximately every 5 years). At a cost of 2.5 MM$, the cash flows in those years decrease to approximately 0.2 MM$. This analysis assumes the plant will take 2 years to construct, and will operate at 50% in its first year. Furthermore, an interest rate of 10% was assumed with a tax rate of 38% (the maximum for corporate gains taxes). Using the 7-year MACRS depreciation method, the 20 year NPV for the project is 4.3 MM$. With an IRR of 15.1%, which is greater than the assumed interest rate, this project looks to be profitable. Further optimization techniques should be used in future iterations to further increase profitability. See Tables 3 and 4 for key economic information.

[[File:Econ_summaries.JPG|center|]]

===Sensitivity analysis===
As seen in Figure 4, the economic evaluation of this process is influenced the most by changes in the sales price and feed cost. A 20% increase in sales price will result in an approximate 120 MM$ increase in NPV whereas a decrease of the same percentage will result in over a 120 MM$ decrease in NPV. Inversely, a 20% increase in feed cost will result in a 115 MM$ decrease in NPV and a 20% decrease in feed cost will result in a 60 MM$ increase in NPV.

[[File:S2_Sensitivity.JPG|center|frame|Figure 4. Sensitivity analysis]]

To alleviate the risk associated with feed price, the team researched the price forecasting of bio-succinic acid. Figure 5 provides the bio-succinic acid price over the six years between 2006 and 2012. The price of bio-succinic, shown by the blue line, has remained relatively stable over this time period. This price history can be compared to adipic acid, the green line, which is a common petrochemical precursor for BDO production. Adipic acid as shown has had large fluctuations in price that result in unstable cash flows and uncertainty from shareholders. Thankfully, the stability of bio-succinic acid is a good sign that this process has a huge potential to be profitable especially if the demand for BDO continues to rise as projected.

==Discussion==
As described previously, the Davy process was selected as the most promising process of BDO production. The modified Davy process involves the hydrogenation of bio-succinicic acid with a Pa,Ag,Re catalyst and hydrogen gas. This process has many advantages, one being that it has mature technology that has been improved over the last 20 years. Additionally, the conversion to of succinic acid is virtually complete. Finally, overall plant yields can reach as high as 94 mol%.
As shown in Appendix B, streams ahead of the pressure valve (PRV-101) are at approximately 1.51e4 kPa, and streams after the pressure valve are between 100 and 450 kPa. Furthermore, operating temperatures do not exceed 200°C, including safety factors. These operating conditions contribute to the feasibility of the process, as all the components can be designed with reasonable dimensions (wall thickness, cap type, etc.).

Of particular interest are the large costs of the reactor and pump P-101. The reactor costs nearly 2 MM$ because it has a moderate size with a liquid volume of 16.7 m3, and it operates at 150 atm, which requires a strong stainless steel shell for safety purposes. Pump P-101 has such a large capital cost because it is a centrifugal multistage pump that also needs to be made of stainless steel to withstand pressuring the succinic acid feed to 150 atm.

Financial indicators for the proposed plant suggest that it will be moderately profitable, and additional optimization should be performed before making the capital investment. There is a fair amount of risk associated with the implementation of this production facility, and the return at this juncture may not justify the risk.

The process design and simulation in HYSYS has relied on several key assumptions, which are cause for certain limitations to the results. First, the conversions and selectivity of the catalyst, while taken from literature sources, are assumed to be true. Furthermore, the assumption of negligible side reactions and products was made. It is possible that small waste products in the form of succinates also form in the reactor. Therefore, the main limitation of this model is generally due to reaction specifications.

There are certain safety concerns that go along with the proposed process. First, there are many pipes and vessels that will be at a pressure of approximately 150 atm. Extra insulation and protection must be applied to the piping that contains highly pressurized fluids, to prevent operator injury. Furthermore, the PFR is at a slight risk for runaway reactions due to the exothermic nature of the reaction. The temperature of the reactor must always be monitored by an operator, and the jacket cooling system requires a backup system as well. A benefit of this process is that there are no toxic or severely hazardous components in the process. Additionally, there are no instances of temperature greater than 200°C.

The process design will be fitted with instrumentation and controls to ensure stable operation. These controls, including sensors and valves, minimize potential damage to components due to variation in plant conditions, as well as optimizing the overall performance. For example, the piping entering the tower will be fitted with a control loop. In the direction of flow, a sensing instrument first detects the pressure of the fluid, and then sends a signal to the controller. If the pressure is not within the operating limits, the actuator is signaled to close or open a control valve which is located farther down the stream.

==Conclusion==
The Evanston Chemical Engineering Division suggests a process that produces 45,000 tonnes/year of 99.5 wt% 1,4-butandeiol to enter the market with an appropriate market share. The feasibility of producing BDO as a significant process was investigated. A wide range of BDO production processes were researched, with a modified Davy process being identified as having the most potential. Using a Pa,Ag,Re catalyst on carbon support, this process converts bio-succinic acid to BDO with approximately 94% conversion. This process was designed in Aspen HYSYS, and economic analysis was conducted in Aspen Economic Analyzer. Total capital costs of the project are 12.2 MM$, with a simple payback period of 5.2 years. Total operational costs annually are 139.7 MM$. The process design was successful, with the capability of producing the desired production of BDO.

==Recommendations==
Given the moderate profitability of this process design, it is recommended that Evanston Chemicals explores further optimization techniques to increase the profitability of this process. This includes investigating sales of the γ-butyrolactone byproduct, recycling process water, and further optimizing utility streams for the distillation tower.

Second, we would like to investigate recycling the 2300 kg/h of water produced in the reaction. Our succinic acid enters the reactor as a 50 wt% solution in water, so we should look into replacing some of this with the product water. Not only will this decrease our water bill, but it will also lower the cost of ion exchange.

==References==
# Nexant.''Is Bio-Butanediol Here to Stay?'' White Plains, NY: ChemSystems Products; 2012.
# De Guzman D. Chemical industry awaits for bio-succinic acid potential. ICIS. Available at: http://www.icis.com/resources/news/2012/01/30/9527521/chemical-industry-awaits-for-bio-succinic-acid-potential/. Accessed January 24, 2014.
# Australian Government: Department of Health. 1,4-butanediol factsheet. National Industrial Chemicals Notification and Assessment Scheme. Available at: http://www.nicnas.gov.au/communications/publications/information-sheets/existing-chemical-info-sheets/other-information-sheets. Accessed January 24, 2014.
# TecnonOrbiChem. Chem-net facts: 1,4-butanediol. TecnonOrbiChem. Available at: http://www.orbichem.com/userfiles/CNF%20Samples/bdo_13_11.pdf. Accessed January 23, 2014.
# Nexant. 1,4-butanediol/tetrahydrofuran (BDO/THF). ChemSystems. Available at: http://www.chemsystems.com/about/cs/news/items/ PERP2012_3_BDO_THF.cfm. Accessed February 6, 2014.
# Burk MJ, Van Dien SJ, Burgard AP, inventors; Genomatica, Inc., assignee. Compositions and methods for the biosynthesis of 1,4-butanediol and its precursors. US patent 8,067,214. Nov. 29, 2011.
# Chung S-H, Kim M-S, Eom H-H, Lee K-Y. Catalytic hydrogenation of bio-based succinic acid for the production of 1,4-butanediol through the indirect pathway. AIChE. Available at: https://aiche.confex.com/aiche/2013/webprogram/Paper327470.html. Accessed January 23, 2014.
# Bhattacharyya A, Manila MD, inventors; ISP Investments Inc., assignee. Catalysts for maleic acid hydrogenation to 1,4-Butanediol. US patent 7,935,834 B2. May 3, 2011.

File:S2 Sensitivity.JPG

2014-03-15T05:25:41Z

Karetstik:

Design S2

2014-03-15T05:24:39Z

Karetstik: /* Cash flow analysis */

Title: Production of 1,4-butanediol

Authors: Nick Pinkerton, Karen Schmidt, and James Xamplas

Date Presented: March 14, 2014

==Introduction==
1,4-butanediol (BDO) is traditionally made from petroleum-derived feedstocks in a variety of processes such as the Reppe (acetylene-based), Mitsubishi (butadiene-based), and Davy (maleic acid-based) processes [1]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, BDO [1]. It is this process that Team S2Kool4Skool has chosen to develop for a new bio-butanediol plant, because the Davy method is mature and requires no new innovations, and because an appropriate feedstock of bio-succinic acid is now available. The plant will be located in East Carroll Parish, Louisiana. This county is also home to Myriant; located in Lake Providence, they are the largest domestic provider of bio-succinic acid [2]. Furthermore, Lake Providence is conveniently located on the Mississippi River, which will allow for affordable transportation of our bio-based butanediol product. The intent of this project is to produce 45,000 metric tonnes of 99.5 wt% 1,4-butanediol per year in a new plant in Lake Providence, LA. The plant will run 24 hours per day for 350 days out of the year, allowing approximately two weeks for a maintenance shutdown.

As there are several techniques for producing 1,4 butanediol in industry, the first step was to determine a synthesis path. Based on the chosen path, reaction kinetics, and required production rate of the process, a reactor system was then designed. Next, the process was designed to deliver the reactants to the reactor at the proper operating conditions, and the separations, purification, and waste management steps were designed. Cost estimates were made using costing software and hand calculations. Finally, the process was iterated and optimized to reduce costs.

==Background==
===General information===
BDO is an organic chemical with the molecular formula <math>C_4H_{10}O_2</math>. It is also a diol with its two hydroxyl groups located at the terminal carbons. BDO has a boiling point of 235 degrees C and is therefore a colorless liquid at standard temperatures and pressures [3].

There are many precursors that petrochemical synthesis of BDO uses. The commonality between all of the precursor acids is that they are hydrogenatable. In replacement of one of these petrochemical precursors, our team has been tasked with the challenge of deriving BDO from the bio-based precursor succinic acid. This catalyzed reaction will take place in the presence of hydrogen as the hydrogenating component shown below:

<math>C_4H_6O_4 + 4H_2 = C_4H_{10}O_2 + 2H_2O</math>

As described in the above reaction, there will need to be at least 4:1 stoichiometric ratio of hydrogen gas to succinic acid. Two moles of water will also be produced along with each mole of BDO. This reaction is exothermic, which requires the reactor to be continuously cooled to maintain our reactor temperature. There are also side products that are produced which include tetrahydrofuran (THF) and γ-butyrolactone (GBL); however, thanks to catalyst selectivity these byproducts are produced in small quantities.

===Market analysis===
Butanediol has a quickly expanding market due to new technological evolutions and its growing use as a chemical intermediary in advanced materials. With biological routes being optimized, the potential of biomass-derived chemicals is tremendous. The global demand of BDO was estimated at 1.5 million metric tons in 2011 and is projected to grow at an annual rate of 4.5% for the next several years [1]. Unlike other chemical products, BDO’s profitability and attractiveness to producers lies in its downstream potential. Figure 1 below demonstrates several potential downstream products that can be directly or indirectly synthesized from BDO. The largest of these contributors include THF and GBL.

[[File:BioButanediol_Downstream.JPG|center|frame|Figure 1. BDO downstream potential flow chart]]

The current market demand of BDO is being supplemented by several global chemical companies. These companies include BASF, BioAmber, Purac, Myriant, DSM, Mitsubishi Chemical, Roquette, and OPXBIO. The market shares of these companies were not available for this product; however, with the consistent growth of the BDO market our team feels that the market is not saturated or impenetrable. The current market price of BDO fluctuates between $3.06 and $3.31 per kg for US-made products [4]. These prices correlate to a nearly 7 billion dollar industry.

===Process alternatives===
1,4-butanediol is traditionally made from petroleum-derived feedstocks in a variety of processes [5]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Several companies are currently implementing bio-routes of producing butanediol. Genomatica is using a bioengineered microorganism to convert sugar feedstocks directly to BDO via fermentation [6], but most companies are instead using microorganisms to convert sugar to succinic acid. The bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, which is the path that most are choosing, although research is being conducted on alternative pathways [7].

==Process overview==
The newly proposed plant can be divided into four stages: pre-reactor, reactor, post-reactor and distillation. Each section is an integral part to the overall process and demands close attention. See the complete process flow diagram in Figure 2.

[[File:PFD.JPG|center|frame|Figure 2. Process flow diagram]]

===Pre-reactor===
This chemical process begins with two feedstocks: hydrogen gas and bio-succinic acid. The hydrogen gas will be obtained from a pipeline at 150 atm and will be used in molar excess inside the reactor. The bio-succinic acid will be purchased by Myriant Corporation which is located near the planned plant site. The pricing for this feedstock is approximately $2.12 per kg. The plant will require 63,000 metric tonnes of bio-succinic acid per year to meet the proposed plant capacity. First the bio-succinic acid feed is pumped up to 150 atm to match the hydrogen gas feed, and then it is mixed with the hydrogen gas prior to being sent into heat exchanger E-101 for heating. The heat exchanger brings the two feeds up to 110oC and sends them to the jacketed packed bed reactor.

===Reactor===
The hydrogenation reaction occurs inside of the reactor thanks to the packed catalyst bed. The catalyst used is 0.4% Fe, 1.9% Na, 2.66% Ag, 2.66% Pd, 10.0% Re on 1.5mm carbon support. With this catalyst, BDO is produced with over 90% selectivity and minimal side reactions of THF and GBL [8]. The reaction has an operating pressure of 2000-4000 psi and internal reactor temperature of 165°C. This temperature allows for about 99.7% conversion of succinic acid [8]. Due to the exothermic nature of the reaction, a cooling jacket is required which utilizes downstream cold streams to cool the internal bed to maintain the desired reaction temperature.

===Post-reactor===
The effluent of the reactor is sent back to E-101 as the hot stream. After exiting E-101, the reactor product stream is sent to a secondary exchanger, E-102, where utility cooling water is used to reduce the temperature to an acceptable temperature prior to sending it to a pressure let-down valve. At this point the pressure of the stream is taken from 150 atm to 1 atm. This large pressure drop allows for the stream to split into its vapor and liquid portions in a gas-liquid separator. The vapor stream of the gas liquid separator is primarily hydrogen gas and sent to a flare for disposal. The liquid effluent is at approximately 45oC leaving the separator and is therefore pumped to the reactor jacket for the reaction cooling mentioned previously. After running through the reactor jacket, the stream enters the separation processes.

===Distillation===
The first distillation column, T-101, is a 10 stage column whose primary purpose is separating the THF from the product feed. Due to THF’s lower boiling point, the byproduct comes off of the top of the column with mostly water. This distillate is sent to the plant's THF waste storage tank that has the capacity of two weeks. The bottoms of the column is sent to the subsequent distillation column that separates the BDO from the GBL and water. The relatively close boiling points of BDO and GBL, 235oC and 204oC, respectively, create a difficult separation that requires a 15 stage column. The distillate of the column is approximately 23% GBL with balance water. This stream is sent to a storage tank with similar sizing parameters as the THF storage tank. The bottom stream is the final 99.5wt% BDO product. This stream is sent to the final product tank, S-104. Depending on our customer demands and the plant location we have the ability to barge, rail or pipe our product to its final destination. Due to low purity of the byproducts, future iterations are needed to optimize either purifying byproducts or selling impure byproducts. There is definitely an available market for these byproducts that should be researched more extensively to increase profit. A detailed description of the equipment from the PFD can be found in Appendix C, in addition to sizing specifications and purpose of equipment.

===Mass and energy balances===
Using an Aspen HYSYS simulation we were able to record the material and energy streams going in and out of the process system. Mass and energy balances are provided Appendix D where each inlet and outlet stream is described and quantified. As expected, the material and energy totals for the inlet and outlet streams add together to equal 0. This proves that our system is mathematically prudent and thermodynamically feasible. The total mass flow of the system is 15,639 kg/h and the total energy in and out of the system is 1.41e8 kJ/h.

===HYSYS simulation===
The HYSYS simulation was performed using the NRTL ideal fluid package. After using AspenPlus to verify that the HYSYS package had the appropriate vapor-liquid equilibrium information between THF and water, and between GBL and water, we concluded it was feasible to proceed with that fluid package. The simulation consists of a reactor, a gas-liquid separator, 2 pumps, 3 heaters, a valve, and 2 distillation columns (see Figure 3). The simulation successfully converted the succinic acid feed into the desired products. Also, the combination of the two distillation columns was able to effectively separate the BDO to obtain a 99.5% pure product with 99.5% recovery. In addition, a set was made between the energy required to heat stream 12 and the energy required to cool the reactor so that these values were made equal. Lastly, the condenser and reboiler duties were used in four heat exchangers in order to determine the appropriate size of this equipment as well as the necessary utility flow rates.

[[File:S2_HYSYS_Simulation.JPG|center|frame|Figure 3. HYSYS simulation]]

==Health and safety==
===Chemical properties===
Inherent to this process are a number of toxic chemicals. Table 1 summarizes the important safety data including hazard type, odor, color, and exposure limits.

[[File:Chem_properties.JPG|center|]]

As shown in the above table, the chemicals that this facility will be dealing with will be relatively mild and non-life threatening. Regardless of their perceived threat, chemicals should always be handled with care especially when they are at high temperatures and pressures.

===Safety procedures===

'''Fire'''. There are many flammable materials that will be included in this process; therefore, fire safety is imperative for all employees. There are countless possible causes of ignition and care should be taken while handling any flammable material whether in the lab or in the field.

In case a fire is present on, the following protocol should be implemented:

* Small fire: Use DRY chemical powder.
* Large fire: Use alcohol foam, water spray, or fog.
* Call for backup if unable to control.
* Immediately contact supervisor and emergency personnel on site.
* Evacuate to safe distance in case of fires around any hazardous materials or pressure vessels.

'''Spills'''. Process chemical spills will eventually occur in a plant of this scale. Small spills are likely to occur in a laboratory setting. Large spills could be a result of loss of containment in the system. We must ensure that all personnel are aware of proper spill mitigation protocol.

* Small spill: Dilute with water and mop or absorb with inert dry material. Dispose of in proper receptacle.
* Large spill: Keep away from sources of ignition and heat. Prevent rundown to any drains or sewers. Call for assistance on disposal. Absorb material with DRY earth or other non-combustible materials.
* If spill is due to a loss of containment in the system, quickly consult the PLC and shut any valves to prevent further loss.

'''Exposure'''. We must ensure that our employees are aware of the possible toxicity levels of each substance and how to handle exposure. The chemicals that are being used in this process are known chemical irritants to the eyes, skin, and throat. Safety measures must be in place to acknowledge this hazard. Due to the possibility of high pressure releases, we will have 2-minute emergency oxygen masks placed strategically throughout the plant to ensure the safety of any operator in the presence of a large release.

If exposed to the process chemicals, find nearest eye wash station or safety shower immediately and flush exposed skin for at least 15 minutes. Remove any contaminated clothing. Seek medical attention immediately.

'''Storage'''. Store chemicals in segregated and approved areas. Any closed containers for laboratory purposes should be placed in cool, well-ventilated areas.

==Economics==
===Equipment costing===
The calculated capital costs from Aspen Economic Analyzer are reported in Table 2 for all process equipment. The size of the reactor was calculated from the liquid hourly space velocity given in the 2011 ISP patent [8] and a void fraction estimate of 0.4. Storage tanks were sized to contain up to two continuous weeks of material. The number of distillation trays in each tower and the flow rates through pumps, vessels, and the flare were calculated in HYSYS. Heat exchange areas were given in Aspen Energy Analyzer or from HYSYS.

[[File:Equipment_cost.JPG|center|]]

In addition to the above equipment, our plant will require an ion exchanger to produce deionized process water from the municipal water. This is estimated to cost $42,000 in capital cost.

===Cash flow analysis===
Summarizing the important takeaways from the economic analysis, this process will return a revenue of 144 MM$ annually. Offset by production costs, the yearly cash flow is approximately 2.7 MM$, except for in the years in which the catalyst must be reinstalled (approximately every 5 years). At a cost of 2.5 MM$, the cash flows in those years decrease to approximately 0.2 MM$. This analysis assumes the plant will take 2 years to construct, and will operate at 50% in its first year. Furthermore, an interest rate of 10% was assumed with a tax rate of 38% (the maximum for corporate gains taxes). Using the 7-year MACRS depreciation method, the 20 year NPV for the project is 4.3 MM$. With an IRR of 15.1%, which is greater than the assumed interest rate, this project looks to be profitable. Further optimization techniques should be used in future iterations to further increase profitability. See Tables 3 and 4 for key economic information.

[[File:Econ_summaries.JPG|center|]]

===Sensitivity analysis===
As seen in Figure 3, the economic evaluation of this process is influenced the most by changes in the sales price and feed cost. A 20% increase in sales price will result in an approximate 120 MM$ increase in NPV whereas a decrease of the same percentage will result in over a 120 MM$ decrease in NPV. Inversely, a 20% increase in feed cost will result in a 115 MM$ decrease in NPV and a 20% decrease in feed cost will result in a 60 MM$ increase in NPV.

To alleviate the risk associated with feed price, the team researched the price forecasting of bio-succinic acid. Figure 4 provides the bio-succinic acid price over the six years between 2006 and 2012. The price of bio-succinic, shown by the blue line, has remained relatively stable over this time period. This price history can be compared to adipic acid, the green line, which is a common petrochemical precursor for BDO production. Adipic acid as shown has had large fluctuations in price that result in unstable cash flows and uncertainty from shareholders. Thankfully, the stability of bio-succinic acid is a good sign that this process has a huge potential to be profitable especially if the demand for BDO continues to rise as projected.

==Discussion==
As described previously, the Davy process was selected as the most promising process of BDO production. The modified Davy process involves the hydrogenation of bio-succinicic acid with a Pa,Ag,Re catalyst and hydrogen gas. This process has many advantages, one being that it has mature technology that has been improved over the last 20 years. Additionally, the conversion to of succinic acid is virtually complete. Finally, overall plant yields can reach as high as 94 mol%.
As shown in Appendix B, streams ahead of the pressure valve (PRV-101) are at approximately 1.51e4 kPa, and streams after the pressure valve are between 100 and 450 kPa. Furthermore, operating temperatures do not exceed 200°C, including safety factors. These operating conditions contribute to the feasibility of the process, as all the components can be designed with reasonable dimensions (wall thickness, cap type, etc.).

Of particular interest are the large costs of the reactor and pump P-101. The reactor costs nearly 2 MM$ because it has a moderate size with a liquid volume of 16.7 m3, and it operates at 150 atm, which requires a strong stainless steel shell for safety purposes. Pump P-101 has such a large capital cost because it is a centrifugal multistage pump that also needs to be made of stainless steel to withstand pressuring the succinic acid feed to 150 atm.

Financial indicators for the proposed plant suggest that it will be moderately profitable, and additional optimization should be performed before making the capital investment. There is a fair amount of risk associated with the implementation of this production facility, and the return at this juncture may not justify the risk.

The process design and simulation in HYSYS has relied on several key assumptions, which are cause for certain limitations to the results. First, the conversions and selectivity of the catalyst, while taken from literature sources, are assumed to be true. Furthermore, the assumption of negligible side reactions and products was made. It is possible that small waste products in the form of succinates also form in the reactor. Therefore, the main limitation of this model is generally due to reaction specifications.

There are certain safety concerns that go along with the proposed process. First, there are many pipes and vessels that will be at a pressure of approximately 150 atm. Extra insulation and protection must be applied to the piping that contains highly pressurized fluids, to prevent operator injury. Furthermore, the PFR is at a slight risk for runaway reactions due to the exothermic nature of the reaction. The temperature of the reactor must always be monitored by an operator, and the jacket cooling system requires a backup system as well. A benefit of this process is that there are no toxic or severely hazardous components in the process. Additionally, there are no instances of temperature greater than 200°C.

The process design will be fitted with instrumentation and controls to ensure stable operation. These controls, including sensors and valves, minimize potential damage to components due to variation in plant conditions, as well as optimizing the overall performance. For example, the piping entering the tower will be fitted with a control loop. In the direction of flow, a sensing instrument first detects the pressure of the fluid, and then sends a signal to the controller. If the pressure is not within the operating limits, the actuator is signaled to close or open a control valve which is located farther down the stream.

==Conclusion==
The Evanston Chemical Engineering Division suggests a process that produces 45,000 tonnes/year of 99.5 wt% 1,4-butandeiol to enter the market with an appropriate market share. The feasibility of producing BDO as a significant process was investigated. A wide range of BDO production processes were researched, with a modified Davy process being identified as having the most potential. Using a Pa,Ag,Re catalyst on carbon support, this process converts bio-succinic acid to BDO with approximately 94% conversion. This process was designed in Aspen HYSYS, and economic analysis was conducted in Aspen Economic Analyzer. Total capital costs of the project are 12.2 MM$, with a simple payback period of 5.2 years. Total operational costs annually are 139.7 MM$. The process design was successful, with the capability of producing the desired production of BDO.

==Recommendations==
Given the moderate profitability of this process design, it is recommended that Evanston Chemicals explores further optimization techniques to increase the profitability of this process. This includes investigating sales of the γ-butyrolactone byproduct, recycling process water, and further optimizing utility streams for the distillation tower.

Second, we would like to investigate recycling the 2300 kg/h of water produced in the reaction. Our succinic acid enters the reactor as a 50 wt% solution in water, so we should look into replacing some of this with the product water. Not only will this decrease our water bill, but it will also lower the cost of ion exchange.

==References==
# Nexant.''Is Bio-Butanediol Here to Stay?'' White Plains, NY: ChemSystems Products; 2012.
# De Guzman D. Chemical industry awaits for bio-succinic acid potential. ICIS. Available at: http://www.icis.com/resources/news/2012/01/30/9527521/chemical-industry-awaits-for-bio-succinic-acid-potential/. Accessed January 24, 2014.
# Australian Government: Department of Health. 1,4-butanediol factsheet. National Industrial Chemicals Notification and Assessment Scheme. Available at: http://www.nicnas.gov.au/communications/publications/information-sheets/existing-chemical-info-sheets/other-information-sheets. Accessed January 24, 2014.
# TecnonOrbiChem. Chem-net facts: 1,4-butanediol. TecnonOrbiChem. Available at: http://www.orbichem.com/userfiles/CNF%20Samples/bdo_13_11.pdf. Accessed January 23, 2014.
# Nexant. 1,4-butanediol/tetrahydrofuran (BDO/THF). ChemSystems. Available at: http://www.chemsystems.com/about/cs/news/items/ PERP2012_3_BDO_THF.cfm. Accessed February 6, 2014.
# Burk MJ, Van Dien SJ, Burgard AP, inventors; Genomatica, Inc., assignee. Compositions and methods for the biosynthesis of 1,4-butanediol and its precursors. US patent 8,067,214. Nov. 29, 2011.
# Chung S-H, Kim M-S, Eom H-H, Lee K-Y. Catalytic hydrogenation of bio-based succinic acid for the production of 1,4-butanediol through the indirect pathway. AIChE. Available at: https://aiche.confex.com/aiche/2013/webprogram/Paper327470.html. Accessed January 23, 2014.
# Bhattacharyya A, Manila MD, inventors; ISP Investments Inc., assignee. Catalysts for maleic acid hydrogenation to 1,4-Butanediol. US patent 7,935,834 B2. May 3, 2011.

Design S2

2014-03-15T05:24:18Z

Karetstik: /* Cash flow analysis */

Title: Production of 1,4-butanediol

Authors: Nick Pinkerton, Karen Schmidt, and James Xamplas

Date Presented: March 14, 2014

==Introduction==
1,4-butanediol (BDO) is traditionally made from petroleum-derived feedstocks in a variety of processes such as the Reppe (acetylene-based), Mitsubishi (butadiene-based), and Davy (maleic acid-based) processes [1]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, BDO [1]. It is this process that Team S2Kool4Skool has chosen to develop for a new bio-butanediol plant, because the Davy method is mature and requires no new innovations, and because an appropriate feedstock of bio-succinic acid is now available. The plant will be located in East Carroll Parish, Louisiana. This county is also home to Myriant; located in Lake Providence, they are the largest domestic provider of bio-succinic acid [2]. Furthermore, Lake Providence is conveniently located on the Mississippi River, which will allow for affordable transportation of our bio-based butanediol product. The intent of this project is to produce 45,000 metric tonnes of 99.5 wt% 1,4-butanediol per year in a new plant in Lake Providence, LA. The plant will run 24 hours per day for 350 days out of the year, allowing approximately two weeks for a maintenance shutdown.

As there are several techniques for producing 1,4 butanediol in industry, the first step was to determine a synthesis path. Based on the chosen path, reaction kinetics, and required production rate of the process, a reactor system was then designed. Next, the process was designed to deliver the reactants to the reactor at the proper operating conditions, and the separations, purification, and waste management steps were designed. Cost estimates were made using costing software and hand calculations. Finally, the process was iterated and optimized to reduce costs.

==Background==
===General information===
BDO is an organic chemical with the molecular formula <math>C_4H_{10}O_2</math>. It is also a diol with its two hydroxyl groups located at the terminal carbons. BDO has a boiling point of 235 degrees C and is therefore a colorless liquid at standard temperatures and pressures [3].

There are many precursors that petrochemical synthesis of BDO uses. The commonality between all of the precursor acids is that they are hydrogenatable. In replacement of one of these petrochemical precursors, our team has been tasked with the challenge of deriving BDO from the bio-based precursor succinic acid. This catalyzed reaction will take place in the presence of hydrogen as the hydrogenating component shown below:

<math>C_4H_6O_4 + 4H_2 = C_4H_{10}O_2 + 2H_2O</math>

As described in the above reaction, there will need to be at least 4:1 stoichiometric ratio of hydrogen gas to succinic acid. Two moles of water will also be produced along with each mole of BDO. This reaction is exothermic, which requires the reactor to be continuously cooled to maintain our reactor temperature. There are also side products that are produced which include tetrahydrofuran (THF) and γ-butyrolactone (GBL); however, thanks to catalyst selectivity these byproducts are produced in small quantities.

===Market analysis===
Butanediol has a quickly expanding market due to new technological evolutions and its growing use as a chemical intermediary in advanced materials. With biological routes being optimized, the potential of biomass-derived chemicals is tremendous. The global demand of BDO was estimated at 1.5 million metric tons in 2011 and is projected to grow at an annual rate of 4.5% for the next several years [1]. Unlike other chemical products, BDO’s profitability and attractiveness to producers lies in its downstream potential. Figure 1 below demonstrates several potential downstream products that can be directly or indirectly synthesized from BDO. The largest of these contributors include THF and GBL.

[[File:BioButanediol_Downstream.JPG|center|frame|Figure 1. BDO downstream potential flow chart]]

The current market demand of BDO is being supplemented by several global chemical companies. These companies include BASF, BioAmber, Purac, Myriant, DSM, Mitsubishi Chemical, Roquette, and OPXBIO. The market shares of these companies were not available for this product; however, with the consistent growth of the BDO market our team feels that the market is not saturated or impenetrable. The current market price of BDO fluctuates between $3.06 and $3.31 per kg for US-made products [4]. These prices correlate to a nearly 7 billion dollar industry.

===Process alternatives===
1,4-butanediol is traditionally made from petroleum-derived feedstocks in a variety of processes [5]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Several companies are currently implementing bio-routes of producing butanediol. Genomatica is using a bioengineered microorganism to convert sugar feedstocks directly to BDO via fermentation [6], but most companies are instead using microorganisms to convert sugar to succinic acid. The bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, which is the path that most are choosing, although research is being conducted on alternative pathways [7].

==Process overview==
The newly proposed plant can be divided into four stages: pre-reactor, reactor, post-reactor and distillation. Each section is an integral part to the overall process and demands close attention. See the complete process flow diagram in Figure 2.

[[File:PFD.JPG|center|frame|Figure 2. Process flow diagram]]

===Pre-reactor===
This chemical process begins with two feedstocks: hydrogen gas and bio-succinic acid. The hydrogen gas will be obtained from a pipeline at 150 atm and will be used in molar excess inside the reactor. The bio-succinic acid will be purchased by Myriant Corporation which is located near the planned plant site. The pricing for this feedstock is approximately $2.12 per kg. The plant will require 63,000 metric tonnes of bio-succinic acid per year to meet the proposed plant capacity. First the bio-succinic acid feed is pumped up to 150 atm to match the hydrogen gas feed, and then it is mixed with the hydrogen gas prior to being sent into heat exchanger E-101 for heating. The heat exchanger brings the two feeds up to 110oC and sends them to the jacketed packed bed reactor.

===Reactor===
The hydrogenation reaction occurs inside of the reactor thanks to the packed catalyst bed. The catalyst used is 0.4% Fe, 1.9% Na, 2.66% Ag, 2.66% Pd, 10.0% Re on 1.5mm carbon support. With this catalyst, BDO is produced with over 90% selectivity and minimal side reactions of THF and GBL [8]. The reaction has an operating pressure of 2000-4000 psi and internal reactor temperature of 165°C. This temperature allows for about 99.7% conversion of succinic acid [8]. Due to the exothermic nature of the reaction, a cooling jacket is required which utilizes downstream cold streams to cool the internal bed to maintain the desired reaction temperature.

===Post-reactor===
The effluent of the reactor is sent back to E-101 as the hot stream. After exiting E-101, the reactor product stream is sent to a secondary exchanger, E-102, where utility cooling water is used to reduce the temperature to an acceptable temperature prior to sending it to a pressure let-down valve. At this point the pressure of the stream is taken from 150 atm to 1 atm. This large pressure drop allows for the stream to split into its vapor and liquid portions in a gas-liquid separator. The vapor stream of the gas liquid separator is primarily hydrogen gas and sent to a flare for disposal. The liquid effluent is at approximately 45oC leaving the separator and is therefore pumped to the reactor jacket for the reaction cooling mentioned previously. After running through the reactor jacket, the stream enters the separation processes.

===Distillation===
The first distillation column, T-101, is a 10 stage column whose primary purpose is separating the THF from the product feed. Due to THF’s lower boiling point, the byproduct comes off of the top of the column with mostly water. This distillate is sent to the plant's THF waste storage tank that has the capacity of two weeks. The bottoms of the column is sent to the subsequent distillation column that separates the BDO from the GBL and water. The relatively close boiling points of BDO and GBL, 235oC and 204oC, respectively, create a difficult separation that requires a 15 stage column. The distillate of the column is approximately 23% GBL with balance water. This stream is sent to a storage tank with similar sizing parameters as the THF storage tank. The bottom stream is the final 99.5wt% BDO product. This stream is sent to the final product tank, S-104. Depending on our customer demands and the plant location we have the ability to barge, rail or pipe our product to its final destination. Due to low purity of the byproducts, future iterations are needed to optimize either purifying byproducts or selling impure byproducts. There is definitely an available market for these byproducts that should be researched more extensively to increase profit. A detailed description of the equipment from the PFD can be found in Appendix C, in addition to sizing specifications and purpose of equipment.

===Mass and energy balances===
Using an Aspen HYSYS simulation we were able to record the material and energy streams going in and out of the process system. Mass and energy balances are provided Appendix D where each inlet and outlet stream is described and quantified. As expected, the material and energy totals for the inlet and outlet streams add together to equal 0. This proves that our system is mathematically prudent and thermodynamically feasible. The total mass flow of the system is 15,639 kg/h and the total energy in and out of the system is 1.41e8 kJ/h.

===HYSYS simulation===
The HYSYS simulation was performed using the NRTL ideal fluid package. After using AspenPlus to verify that the HYSYS package had the appropriate vapor-liquid equilibrium information between THF and water, and between GBL and water, we concluded it was feasible to proceed with that fluid package. The simulation consists of a reactor, a gas-liquid separator, 2 pumps, 3 heaters, a valve, and 2 distillation columns (see Figure 3). The simulation successfully converted the succinic acid feed into the desired products. Also, the combination of the two distillation columns was able to effectively separate the BDO to obtain a 99.5% pure product with 99.5% recovery. In addition, a set was made between the energy required to heat stream 12 and the energy required to cool the reactor so that these values were made equal. Lastly, the condenser and reboiler duties were used in four heat exchangers in order to determine the appropriate size of this equipment as well as the necessary utility flow rates.

[[File:S2_HYSYS_Simulation.JPG|center|frame|Figure 3. HYSYS simulation]]

==Health and safety==
===Chemical properties===
Inherent to this process are a number of toxic chemicals. Table 1 summarizes the important safety data including hazard type, odor, color, and exposure limits.

[[File:Chem_properties.JPG|center|]]

As shown in the above table, the chemicals that this facility will be dealing with will be relatively mild and non-life threatening. Regardless of their perceived threat, chemicals should always be handled with care especially when they are at high temperatures and pressures.

===Safety procedures===

'''Fire'''. There are many flammable materials that will be included in this process; therefore, fire safety is imperative for all employees. There are countless possible causes of ignition and care should be taken while handling any flammable material whether in the lab or in the field.

In case a fire is present on, the following protocol should be implemented:

* Small fire: Use DRY chemical powder.
* Large fire: Use alcohol foam, water spray, or fog.
* Call for backup if unable to control.
* Immediately contact supervisor and emergency personnel on site.
* Evacuate to safe distance in case of fires around any hazardous materials or pressure vessels.

'''Spills'''. Process chemical spills will eventually occur in a plant of this scale. Small spills are likely to occur in a laboratory setting. Large spills could be a result of loss of containment in the system. We must ensure that all personnel are aware of proper spill mitigation protocol.

* Small spill: Dilute with water and mop or absorb with inert dry material. Dispose of in proper receptacle.
* Large spill: Keep away from sources of ignition and heat. Prevent rundown to any drains or sewers. Call for assistance on disposal. Absorb material with DRY earth or other non-combustible materials.
* If spill is due to a loss of containment in the system, quickly consult the PLC and shut any valves to prevent further loss.

'''Exposure'''. We must ensure that our employees are aware of the possible toxicity levels of each substance and how to handle exposure. The chemicals that are being used in this process are known chemical irritants to the eyes, skin, and throat. Safety measures must be in place to acknowledge this hazard. Due to the possibility of high pressure releases, we will have 2-minute emergency oxygen masks placed strategically throughout the plant to ensure the safety of any operator in the presence of a large release.

If exposed to the process chemicals, find nearest eye wash station or safety shower immediately and flush exposed skin for at least 15 minutes. Remove any contaminated clothing. Seek medical attention immediately.

'''Storage'''. Store chemicals in segregated and approved areas. Any closed containers for laboratory purposes should be placed in cool, well-ventilated areas.

==Economics==
===Equipment costing===
The calculated capital costs from Aspen Economic Analyzer are reported in Table 2 for all process equipment. The size of the reactor was calculated from the liquid hourly space velocity given in the 2011 ISP patent [8] and a void fraction estimate of 0.4. Storage tanks were sized to contain up to two continuous weeks of material. The number of distillation trays in each tower and the flow rates through pumps, vessels, and the flare were calculated in HYSYS. Heat exchange areas were given in Aspen Energy Analyzer or from HYSYS.

[[File:Equipment_cost.JPG|center|]]

In addition to the above equipment, our plant will require an ion exchanger to produce deionized process water from the municipal water. This is estimated to cost $42,000 in capital cost.

===Cash flow analysis===
Summarizing the important takeaways from the economic analysis, this process will return a revenue of 144 MM$ annually. Offset by production costs, the yearly cash flow is approximately 2.7 MM$, except for in the years in which the catalyst must be reinstalled (approximately every 5 years). At a cost of 2.5 MM$, the cash flows in those years decrease to approximately 0.2 MM$. This analysis assumes the plant will take 2 years to construct, and will operate at 50% in its first year. Furthermore, an interest rate of 10% was assumed with a tax rate of 38% (the maximum for corporate gains taxes). Using the 7-year MACRS depreciation method, the 20 year NPV for the project is 4.3 MM$. With an IRR of 15.1%, which is greater than the assumed interest rate, this project looks to be profitable. Further optimization techniques should be used in future iterations to further increase profitability. See Tables 3 and 4 for key economic information.

[[File:Econ_summaries_JPG|center|]]

===Sensitivity analysis===
As seen in Figure 3, the economic evaluation of this process is influenced the most by changes in the sales price and feed cost. A 20% increase in sales price will result in an approximate 120 MM$ increase in NPV whereas a decrease of the same percentage will result in over a 120 MM$ decrease in NPV. Inversely, a 20% increase in feed cost will result in a 115 MM$ decrease in NPV and a 20% decrease in feed cost will result in a 60 MM$ increase in NPV.

To alleviate the risk associated with feed price, the team researched the price forecasting of bio-succinic acid. Figure 4 provides the bio-succinic acid price over the six years between 2006 and 2012. The price of bio-succinic, shown by the blue line, has remained relatively stable over this time period. This price history can be compared to adipic acid, the green line, which is a common petrochemical precursor for BDO production. Adipic acid as shown has had large fluctuations in price that result in unstable cash flows and uncertainty from shareholders. Thankfully, the stability of bio-succinic acid is a good sign that this process has a huge potential to be profitable especially if the demand for BDO continues to rise as projected.

==Discussion==
As described previously, the Davy process was selected as the most promising process of BDO production. The modified Davy process involves the hydrogenation of bio-succinicic acid with a Pa,Ag,Re catalyst and hydrogen gas. This process has many advantages, one being that it has mature technology that has been improved over the last 20 years. Additionally, the conversion to of succinic acid is virtually complete. Finally, overall plant yields can reach as high as 94 mol%.
As shown in Appendix B, streams ahead of the pressure valve (PRV-101) are at approximately 1.51e4 kPa, and streams after the pressure valve are between 100 and 450 kPa. Furthermore, operating temperatures do not exceed 200°C, including safety factors. These operating conditions contribute to the feasibility of the process, as all the components can be designed with reasonable dimensions (wall thickness, cap type, etc.).

Of particular interest are the large costs of the reactor and pump P-101. The reactor costs nearly 2 MM$ because it has a moderate size with a liquid volume of 16.7 m3, and it operates at 150 atm, which requires a strong stainless steel shell for safety purposes. Pump P-101 has such a large capital cost because it is a centrifugal multistage pump that also needs to be made of stainless steel to withstand pressuring the succinic acid feed to 150 atm.

Financial indicators for the proposed plant suggest that it will be moderately profitable, and additional optimization should be performed before making the capital investment. There is a fair amount of risk associated with the implementation of this production facility, and the return at this juncture may not justify the risk.

The process design and simulation in HYSYS has relied on several key assumptions, which are cause for certain limitations to the results. First, the conversions and selectivity of the catalyst, while taken from literature sources, are assumed to be true. Furthermore, the assumption of negligible side reactions and products was made. It is possible that small waste products in the form of succinates also form in the reactor. Therefore, the main limitation of this model is generally due to reaction specifications.

There are certain safety concerns that go along with the proposed process. First, there are many pipes and vessels that will be at a pressure of approximately 150 atm. Extra insulation and protection must be applied to the piping that contains highly pressurized fluids, to prevent operator injury. Furthermore, the PFR is at a slight risk for runaway reactions due to the exothermic nature of the reaction. The temperature of the reactor must always be monitored by an operator, and the jacket cooling system requires a backup system as well. A benefit of this process is that there are no toxic or severely hazardous components in the process. Additionally, there are no instances of temperature greater than 200°C.

The process design will be fitted with instrumentation and controls to ensure stable operation. These controls, including sensors and valves, minimize potential damage to components due to variation in plant conditions, as well as optimizing the overall performance. For example, the piping entering the tower will be fitted with a control loop. In the direction of flow, a sensing instrument first detects the pressure of the fluid, and then sends a signal to the controller. If the pressure is not within the operating limits, the actuator is signaled to close or open a control valve which is located farther down the stream.

==Conclusion==
The Evanston Chemical Engineering Division suggests a process that produces 45,000 tonnes/year of 99.5 wt% 1,4-butandeiol to enter the market with an appropriate market share. The feasibility of producing BDO as a significant process was investigated. A wide range of BDO production processes were researched, with a modified Davy process being identified as having the most potential. Using a Pa,Ag,Re catalyst on carbon support, this process converts bio-succinic acid to BDO with approximately 94% conversion. This process was designed in Aspen HYSYS, and economic analysis was conducted in Aspen Economic Analyzer. Total capital costs of the project are 12.2 MM$, with a simple payback period of 5.2 years. Total operational costs annually are 139.7 MM$. The process design was successful, with the capability of producing the desired production of BDO.

==Recommendations==
Given the moderate profitability of this process design, it is recommended that Evanston Chemicals explores further optimization techniques to increase the profitability of this process. This includes investigating sales of the γ-butyrolactone byproduct, recycling process water, and further optimizing utility streams for the distillation tower.

Second, we would like to investigate recycling the 2300 kg/h of water produced in the reaction. Our succinic acid enters the reactor as a 50 wt% solution in water, so we should look into replacing some of this with the product water. Not only will this decrease our water bill, but it will also lower the cost of ion exchange.

==References==
# Nexant.''Is Bio-Butanediol Here to Stay?'' White Plains, NY: ChemSystems Products; 2012.
# De Guzman D. Chemical industry awaits for bio-succinic acid potential. ICIS. Available at: http://www.icis.com/resources/news/2012/01/30/9527521/chemical-industry-awaits-for-bio-succinic-acid-potential/. Accessed January 24, 2014.
# Australian Government: Department of Health. 1,4-butanediol factsheet. National Industrial Chemicals Notification and Assessment Scheme. Available at: http://www.nicnas.gov.au/communications/publications/information-sheets/existing-chemical-info-sheets/other-information-sheets. Accessed January 24, 2014.
# TecnonOrbiChem. Chem-net facts: 1,4-butanediol. TecnonOrbiChem. Available at: http://www.orbichem.com/userfiles/CNF%20Samples/bdo_13_11.pdf. Accessed January 23, 2014.
# Nexant. 1,4-butanediol/tetrahydrofuran (BDO/THF). ChemSystems. Available at: http://www.chemsystems.com/about/cs/news/items/ PERP2012_3_BDO_THF.cfm. Accessed February 6, 2014.
# Burk MJ, Van Dien SJ, Burgard AP, inventors; Genomatica, Inc., assignee. Compositions and methods for the biosynthesis of 1,4-butanediol and its precursors. US patent 8,067,214. Nov. 29, 2011.
# Chung S-H, Kim M-S, Eom H-H, Lee K-Y. Catalytic hydrogenation of bio-based succinic acid for the production of 1,4-butanediol through the indirect pathway. AIChE. Available at: https://aiche.confex.com/aiche/2013/webprogram/Paper327470.html. Accessed January 23, 2014.
# Bhattacharyya A, Manila MD, inventors; ISP Investments Inc., assignee. Catalysts for maleic acid hydrogenation to 1,4-Butanediol. US patent 7,935,834 B2. May 3, 2011.

File:Econ summaries.JPG

2014-03-15T05:23:46Z

Karetstik:

Design S2

2014-03-15T05:23:00Z

Karetstik: /* Equipment costing */

Title: Production of 1,4-butanediol

Authors: Nick Pinkerton, Karen Schmidt, and James Xamplas

Date Presented: March 14, 2014

==Introduction==
1,4-butanediol (BDO) is traditionally made from petroleum-derived feedstocks in a variety of processes such as the Reppe (acetylene-based), Mitsubishi (butadiene-based), and Davy (maleic acid-based) processes [1]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, BDO [1]. It is this process that Team S2Kool4Skool has chosen to develop for a new bio-butanediol plant, because the Davy method is mature and requires no new innovations, and because an appropriate feedstock of bio-succinic acid is now available. The plant will be located in East Carroll Parish, Louisiana. This county is also home to Myriant; located in Lake Providence, they are the largest domestic provider of bio-succinic acid [2]. Furthermore, Lake Providence is conveniently located on the Mississippi River, which will allow for affordable transportation of our bio-based butanediol product. The intent of this project is to produce 45,000 metric tonnes of 99.5 wt% 1,4-butanediol per year in a new plant in Lake Providence, LA. The plant will run 24 hours per day for 350 days out of the year, allowing approximately two weeks for a maintenance shutdown.

As there are several techniques for producing 1,4 butanediol in industry, the first step was to determine a synthesis path. Based on the chosen path, reaction kinetics, and required production rate of the process, a reactor system was then designed. Next, the process was designed to deliver the reactants to the reactor at the proper operating conditions, and the separations, purification, and waste management steps were designed. Cost estimates were made using costing software and hand calculations. Finally, the process was iterated and optimized to reduce costs.

==Background==
===General information===
BDO is an organic chemical with the molecular formula <math>C_4H_{10}O_2</math>. It is also a diol with its two hydroxyl groups located at the terminal carbons. BDO has a boiling point of 235 degrees C and is therefore a colorless liquid at standard temperatures and pressures [3].

There are many precursors that petrochemical synthesis of BDO uses. The commonality between all of the precursor acids is that they are hydrogenatable. In replacement of one of these petrochemical precursors, our team has been tasked with the challenge of deriving BDO from the bio-based precursor succinic acid. This catalyzed reaction will take place in the presence of hydrogen as the hydrogenating component shown below:

<math>C_4H_6O_4 + 4H_2 = C_4H_{10}O_2 + 2H_2O</math>

As described in the above reaction, there will need to be at least 4:1 stoichiometric ratio of hydrogen gas to succinic acid. Two moles of water will also be produced along with each mole of BDO. This reaction is exothermic, which requires the reactor to be continuously cooled to maintain our reactor temperature. There are also side products that are produced which include tetrahydrofuran (THF) and γ-butyrolactone (GBL); however, thanks to catalyst selectivity these byproducts are produced in small quantities.

===Market analysis===
Butanediol has a quickly expanding market due to new technological evolutions and its growing use as a chemical intermediary in advanced materials. With biological routes being optimized, the potential of biomass-derived chemicals is tremendous. The global demand of BDO was estimated at 1.5 million metric tons in 2011 and is projected to grow at an annual rate of 4.5% for the next several years [1]. Unlike other chemical products, BDO’s profitability and attractiveness to producers lies in its downstream potential. Figure 1 below demonstrates several potential downstream products that can be directly or indirectly synthesized from BDO. The largest of these contributors include THF and GBL.

[[File:BioButanediol_Downstream.JPG|center|frame|Figure 1. BDO downstream potential flow chart]]

The current market demand of BDO is being supplemented by several global chemical companies. These companies include BASF, BioAmber, Purac, Myriant, DSM, Mitsubishi Chemical, Roquette, and OPXBIO. The market shares of these companies were not available for this product; however, with the consistent growth of the BDO market our team feels that the market is not saturated or impenetrable. The current market price of BDO fluctuates between $3.06 and $3.31 per kg for US-made products [4]. These prices correlate to a nearly 7 billion dollar industry.

===Process alternatives===
1,4-butanediol is traditionally made from petroleum-derived feedstocks in a variety of processes [5]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Several companies are currently implementing bio-routes of producing butanediol. Genomatica is using a bioengineered microorganism to convert sugar feedstocks directly to BDO via fermentation [6], but most companies are instead using microorganisms to convert sugar to succinic acid. The bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, which is the path that most are choosing, although research is being conducted on alternative pathways [7].

==Process overview==
The newly proposed plant can be divided into four stages: pre-reactor, reactor, post-reactor and distillation. Each section is an integral part to the overall process and demands close attention. See the complete process flow diagram in Figure 2.

[[File:PFD.JPG|center|frame|Figure 2. Process flow diagram]]

===Pre-reactor===
This chemical process begins with two feedstocks: hydrogen gas and bio-succinic acid. The hydrogen gas will be obtained from a pipeline at 150 atm and will be used in molar excess inside the reactor. The bio-succinic acid will be purchased by Myriant Corporation which is located near the planned plant site. The pricing for this feedstock is approximately $2.12 per kg. The plant will require 63,000 metric tonnes of bio-succinic acid per year to meet the proposed plant capacity. First the bio-succinic acid feed is pumped up to 150 atm to match the hydrogen gas feed, and then it is mixed with the hydrogen gas prior to being sent into heat exchanger E-101 for heating. The heat exchanger brings the two feeds up to 110oC and sends them to the jacketed packed bed reactor.

===Reactor===
The hydrogenation reaction occurs inside of the reactor thanks to the packed catalyst bed. The catalyst used is 0.4% Fe, 1.9% Na, 2.66% Ag, 2.66% Pd, 10.0% Re on 1.5mm carbon support. With this catalyst, BDO is produced with over 90% selectivity and minimal side reactions of THF and GBL [8]. The reaction has an operating pressure of 2000-4000 psi and internal reactor temperature of 165°C. This temperature allows for about 99.7% conversion of succinic acid [8]. Due to the exothermic nature of the reaction, a cooling jacket is required which utilizes downstream cold streams to cool the internal bed to maintain the desired reaction temperature.

===Post-reactor===
The effluent of the reactor is sent back to E-101 as the hot stream. After exiting E-101, the reactor product stream is sent to a secondary exchanger, E-102, where utility cooling water is used to reduce the temperature to an acceptable temperature prior to sending it to a pressure let-down valve. At this point the pressure of the stream is taken from 150 atm to 1 atm. This large pressure drop allows for the stream to split into its vapor and liquid portions in a gas-liquid separator. The vapor stream of the gas liquid separator is primarily hydrogen gas and sent to a flare for disposal. The liquid effluent is at approximately 45oC leaving the separator and is therefore pumped to the reactor jacket for the reaction cooling mentioned previously. After running through the reactor jacket, the stream enters the separation processes.

===Distillation===
The first distillation column, T-101, is a 10 stage column whose primary purpose is separating the THF from the product feed. Due to THF’s lower boiling point, the byproduct comes off of the top of the column with mostly water. This distillate is sent to the plant's THF waste storage tank that has the capacity of two weeks. The bottoms of the column is sent to the subsequent distillation column that separates the BDO from the GBL and water. The relatively close boiling points of BDO and GBL, 235oC and 204oC, respectively, create a difficult separation that requires a 15 stage column. The distillate of the column is approximately 23% GBL with balance water. This stream is sent to a storage tank with similar sizing parameters as the THF storage tank. The bottom stream is the final 99.5wt% BDO product. This stream is sent to the final product tank, S-104. Depending on our customer demands and the plant location we have the ability to barge, rail or pipe our product to its final destination. Due to low purity of the byproducts, future iterations are needed to optimize either purifying byproducts or selling impure byproducts. There is definitely an available market for these byproducts that should be researched more extensively to increase profit. A detailed description of the equipment from the PFD can be found in Appendix C, in addition to sizing specifications and purpose of equipment.

===Mass and energy balances===
Using an Aspen HYSYS simulation we were able to record the material and energy streams going in and out of the process system. Mass and energy balances are provided Appendix D where each inlet and outlet stream is described and quantified. As expected, the material and energy totals for the inlet and outlet streams add together to equal 0. This proves that our system is mathematically prudent and thermodynamically feasible. The total mass flow of the system is 15,639 kg/h and the total energy in and out of the system is 1.41e8 kJ/h.

===HYSYS simulation===
The HYSYS simulation was performed using the NRTL ideal fluid package. After using AspenPlus to verify that the HYSYS package had the appropriate vapor-liquid equilibrium information between THF and water, and between GBL and water, we concluded it was feasible to proceed with that fluid package. The simulation consists of a reactor, a gas-liquid separator, 2 pumps, 3 heaters, a valve, and 2 distillation columns (see Figure 3). The simulation successfully converted the succinic acid feed into the desired products. Also, the combination of the two distillation columns was able to effectively separate the BDO to obtain a 99.5% pure product with 99.5% recovery. In addition, a set was made between the energy required to heat stream 12 and the energy required to cool the reactor so that these values were made equal. Lastly, the condenser and reboiler duties were used in four heat exchangers in order to determine the appropriate size of this equipment as well as the necessary utility flow rates.

[[File:S2_HYSYS_Simulation.JPG|center|frame|Figure 3. HYSYS simulation]]

==Health and safety==
===Chemical properties===
Inherent to this process are a number of toxic chemicals. Table 1 summarizes the important safety data including hazard type, odor, color, and exposure limits.

[[File:Chem_properties.JPG|center|]]

As shown in the above table, the chemicals that this facility will be dealing with will be relatively mild and non-life threatening. Regardless of their perceived threat, chemicals should always be handled with care especially when they are at high temperatures and pressures.

===Safety procedures===

'''Fire'''. There are many flammable materials that will be included in this process; therefore, fire safety is imperative for all employees. There are countless possible causes of ignition and care should be taken while handling any flammable material whether in the lab or in the field.

In case a fire is present on, the following protocol should be implemented:

* Small fire: Use DRY chemical powder.
* Large fire: Use alcohol foam, water spray, or fog.
* Call for backup if unable to control.
* Immediately contact supervisor and emergency personnel on site.
* Evacuate to safe distance in case of fires around any hazardous materials or pressure vessels.

'''Spills'''. Process chemical spills will eventually occur in a plant of this scale. Small spills are likely to occur in a laboratory setting. Large spills could be a result of loss of containment in the system. We must ensure that all personnel are aware of proper spill mitigation protocol.

* Small spill: Dilute with water and mop or absorb with inert dry material. Dispose of in proper receptacle.
* Large spill: Keep away from sources of ignition and heat. Prevent rundown to any drains or sewers. Call for assistance on disposal. Absorb material with DRY earth or other non-combustible materials.
* If spill is due to a loss of containment in the system, quickly consult the PLC and shut any valves to prevent further loss.

'''Exposure'''. We must ensure that our employees are aware of the possible toxicity levels of each substance and how to handle exposure. The chemicals that are being used in this process are known chemical irritants to the eyes, skin, and throat. Safety measures must be in place to acknowledge this hazard. Due to the possibility of high pressure releases, we will have 2-minute emergency oxygen masks placed strategically throughout the plant to ensure the safety of any operator in the presence of a large release.

If exposed to the process chemicals, find nearest eye wash station or safety shower immediately and flush exposed skin for at least 15 minutes. Remove any contaminated clothing. Seek medical attention immediately.

'''Storage'''. Store chemicals in segregated and approved areas. Any closed containers for laboratory purposes should be placed in cool, well-ventilated areas.

==Economics==
===Equipment costing===
The calculated capital costs from Aspen Economic Analyzer are reported in Table 2 for all process equipment. The size of the reactor was calculated from the liquid hourly space velocity given in the 2011 ISP patent [8] and a void fraction estimate of 0.4. Storage tanks were sized to contain up to two continuous weeks of material. The number of distillation trays in each tower and the flow rates through pumps, vessels, and the flare were calculated in HYSYS. Heat exchange areas were given in Aspen Energy Analyzer or from HYSYS.

[[File:Equipment_cost.JPG|center|]]

In addition to the above equipment, our plant will require an ion exchanger to produce deionized process water from the municipal water. This is estimated to cost $42,000 in capital cost.

===Cash flow analysis===
Summarizing the important takeaways from the economic analysis, this process will return a revenue of 144 MM$ annually. Offset by production costs, the yearly cash flow is approximately 2.7 MM$, except for in the years in which the catalyst must be reinstalled (approximately every 5 years). At a cost of 2.5 MM$, the cash flows in those years decrease to approximately 0.2 MM$. This analysis assumes the plant will take 2 years to construct, and will operate at 50% in its first year. Furthermore, an interest rate of 10% was assumed with a tax rate of 38% (the maximum for corporate gains taxes). Using the 7-year MACRS depreciation method, the 20 year NPV for the project is 4.3 MM$. With an IRR of 15.1%, which is greater than the assumed interest rate, this project looks to be profitable. Further optimization techniques should be used in future iterations to further increase profitability. See Tables 3 and 4 for key economic information.

===Sensitivity analysis===
As seen in Figure 3, the economic evaluation of this process is influenced the most by changes in the sales price and feed cost. A 20% increase in sales price will result in an approximate 120 MM$ increase in NPV whereas a decrease of the same percentage will result in over a 120 MM$ decrease in NPV. Inversely, a 20% increase in feed cost will result in a 115 MM$ decrease in NPV and a 20% decrease in feed cost will result in a 60 MM$ increase in NPV.

To alleviate the risk associated with feed price, the team researched the price forecasting of bio-succinic acid. Figure 4 provides the bio-succinic acid price over the six years between 2006 and 2012. The price of bio-succinic, shown by the blue line, has remained relatively stable over this time period. This price history can be compared to adipic acid, the green line, which is a common petrochemical precursor for BDO production. Adipic acid as shown has had large fluctuations in price that result in unstable cash flows and uncertainty from shareholders. Thankfully, the stability of bio-succinic acid is a good sign that this process has a huge potential to be profitable especially if the demand for BDO continues to rise as projected.

==Discussion==
As described previously, the Davy process was selected as the most promising process of BDO production. The modified Davy process involves the hydrogenation of bio-succinicic acid with a Pa,Ag,Re catalyst and hydrogen gas. This process has many advantages, one being that it has mature technology that has been improved over the last 20 years. Additionally, the conversion to of succinic acid is virtually complete. Finally, overall plant yields can reach as high as 94 mol%.
As shown in Appendix B, streams ahead of the pressure valve (PRV-101) are at approximately 1.51e4 kPa, and streams after the pressure valve are between 100 and 450 kPa. Furthermore, operating temperatures do not exceed 200°C, including safety factors. These operating conditions contribute to the feasibility of the process, as all the components can be designed with reasonable dimensions (wall thickness, cap type, etc.).

Of particular interest are the large costs of the reactor and pump P-101. The reactor costs nearly 2 MM$ because it has a moderate size with a liquid volume of 16.7 m3, and it operates at 150 atm, which requires a strong stainless steel shell for safety purposes. Pump P-101 has such a large capital cost because it is a centrifugal multistage pump that also needs to be made of stainless steel to withstand pressuring the succinic acid feed to 150 atm.

Financial indicators for the proposed plant suggest that it will be moderately profitable, and additional optimization should be performed before making the capital investment. There is a fair amount of risk associated with the implementation of this production facility, and the return at this juncture may not justify the risk.

The process design and simulation in HYSYS has relied on several key assumptions, which are cause for certain limitations to the results. First, the conversions and selectivity of the catalyst, while taken from literature sources, are assumed to be true. Furthermore, the assumption of negligible side reactions and products was made. It is possible that small waste products in the form of succinates also form in the reactor. Therefore, the main limitation of this model is generally due to reaction specifications.

There are certain safety concerns that go along with the proposed process. First, there are many pipes and vessels that will be at a pressure of approximately 150 atm. Extra insulation and protection must be applied to the piping that contains highly pressurized fluids, to prevent operator injury. Furthermore, the PFR is at a slight risk for runaway reactions due to the exothermic nature of the reaction. The temperature of the reactor must always be monitored by an operator, and the jacket cooling system requires a backup system as well. A benefit of this process is that there are no toxic or severely hazardous components in the process. Additionally, there are no instances of temperature greater than 200°C.

The process design will be fitted with instrumentation and controls to ensure stable operation. These controls, including sensors and valves, minimize potential damage to components due to variation in plant conditions, as well as optimizing the overall performance. For example, the piping entering the tower will be fitted with a control loop. In the direction of flow, a sensing instrument first detects the pressure of the fluid, and then sends a signal to the controller. If the pressure is not within the operating limits, the actuator is signaled to close or open a control valve which is located farther down the stream.

==Conclusion==
The Evanston Chemical Engineering Division suggests a process that produces 45,000 tonnes/year of 99.5 wt% 1,4-butandeiol to enter the market with an appropriate market share. The feasibility of producing BDO as a significant process was investigated. A wide range of BDO production processes were researched, with a modified Davy process being identified as having the most potential. Using a Pa,Ag,Re catalyst on carbon support, this process converts bio-succinic acid to BDO with approximately 94% conversion. This process was designed in Aspen HYSYS, and economic analysis was conducted in Aspen Economic Analyzer. Total capital costs of the project are 12.2 MM$, with a simple payback period of 5.2 years. Total operational costs annually are 139.7 MM$. The process design was successful, with the capability of producing the desired production of BDO.

==Recommendations==
Given the moderate profitability of this process design, it is recommended that Evanston Chemicals explores further optimization techniques to increase the profitability of this process. This includes investigating sales of the γ-butyrolactone byproduct, recycling process water, and further optimizing utility streams for the distillation tower.

Second, we would like to investigate recycling the 2300 kg/h of water produced in the reaction. Our succinic acid enters the reactor as a 50 wt% solution in water, so we should look into replacing some of this with the product water. Not only will this decrease our water bill, but it will also lower the cost of ion exchange.

==References==
# Nexant.''Is Bio-Butanediol Here to Stay?'' White Plains, NY: ChemSystems Products; 2012.
# De Guzman D. Chemical industry awaits for bio-succinic acid potential. ICIS. Available at: http://www.icis.com/resources/news/2012/01/30/9527521/chemical-industry-awaits-for-bio-succinic-acid-potential/. Accessed January 24, 2014.
# Australian Government: Department of Health. 1,4-butanediol factsheet. National Industrial Chemicals Notification and Assessment Scheme. Available at: http://www.nicnas.gov.au/communications/publications/information-sheets/existing-chemical-info-sheets/other-information-sheets. Accessed January 24, 2014.
# TecnonOrbiChem. Chem-net facts: 1,4-butanediol. TecnonOrbiChem. Available at: http://www.orbichem.com/userfiles/CNF%20Samples/bdo_13_11.pdf. Accessed January 23, 2014.
# Nexant. 1,4-butanediol/tetrahydrofuran (BDO/THF). ChemSystems. Available at: http://www.chemsystems.com/about/cs/news/items/ PERP2012_3_BDO_THF.cfm. Accessed February 6, 2014.
# Burk MJ, Van Dien SJ, Burgard AP, inventors; Genomatica, Inc., assignee. Compositions and methods for the biosynthesis of 1,4-butanediol and its precursors. US patent 8,067,214. Nov. 29, 2011.
# Chung S-H, Kim M-S, Eom H-H, Lee K-Y. Catalytic hydrogenation of bio-based succinic acid for the production of 1,4-butanediol through the indirect pathway. AIChE. Available at: https://aiche.confex.com/aiche/2013/webprogram/Paper327470.html. Accessed January 23, 2014.
# Bhattacharyya A, Manila MD, inventors; ISP Investments Inc., assignee. Catalysts for maleic acid hydrogenation to 1,4-Butanediol. US patent 7,935,834 B2. May 3, 2011.

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Design S2

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Title: Production of 1,4-butanediol

Authors: Nick Pinkerton, Karen Schmidt, and James Xamplas

Date Presented: March 14, 2014

==Introduction==
1,4-butanediol (BDO) is traditionally made from petroleum-derived feedstocks in a variety of processes such as the Reppe (acetylene-based), Mitsubishi (butadiene-based), and Davy (maleic acid-based) processes [1]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, BDO [1]. It is this process that Team S2Kool4Skool has chosen to develop for a new bio-butanediol plant, because the Davy method is mature and requires no new innovations, and because an appropriate feedstock of bio-succinic acid is now available. The plant will be located in East Carroll Parish, Louisiana. This county is also home to Myriant; located in Lake Providence, they are the largest domestic provider of bio-succinic acid [2]. Furthermore, Lake Providence is conveniently located on the Mississippi River, which will allow for affordable transportation of our bio-based butanediol product. The intent of this project is to produce 45,000 metric tonnes of 99.5 wt% 1,4-butanediol per year in a new plant in Lake Providence, LA. The plant will run 24 hours per day for 350 days out of the year, allowing approximately two weeks for a maintenance shutdown.

As there are several techniques for producing 1,4 butanediol in industry, the first step was to determine a synthesis path. Based on the chosen path, reaction kinetics, and required production rate of the process, a reactor system was then designed. Next, the process was designed to deliver the reactants to the reactor at the proper operating conditions, and the separations, purification, and waste management steps were designed. Cost estimates were made using costing software and hand calculations. Finally, the process was iterated and optimized to reduce costs.

==Background==
===General information===
BDO is an organic chemical with the molecular formula <math>C_4H_{10}O_2</math>. It is also a diol with its two hydroxyl groups located at the terminal carbons. BDO has a boiling point of 235 degrees C and is therefore a colorless liquid at standard temperatures and pressures [3].

There are many precursors that petrochemical synthesis of BDO uses. The commonality between all of the precursor acids is that they are hydrogenatable. In replacement of one of these petrochemical precursors, our team has been tasked with the challenge of deriving BDO from the bio-based precursor succinic acid. This catalyzed reaction will take place in the presence of hydrogen as the hydrogenating component shown below:

<math>C_4H_6O_4 + 4H_2 = C_4H_{10}O_2 + 2H_2O</math>

As described in the above reaction, there will need to be at least 4:1 stoichiometric ratio of hydrogen gas to succinic acid. Two moles of water will also be produced along with each mole of BDO. This reaction is exothermic, which requires the reactor to be continuously cooled to maintain our reactor temperature. There are also side products that are produced which include tetrahydrofuran (THF) and γ-butyrolactone (GBL); however, thanks to catalyst selectivity these byproducts are produced in small quantities.

===Market analysis===
Butanediol has a quickly expanding market due to new technological evolutions and its growing use as a chemical intermediary in advanced materials. With biological routes being optimized, the potential of biomass-derived chemicals is tremendous. The global demand of BDO was estimated at 1.5 million metric tons in 2011 and is projected to grow at an annual rate of 4.5% for the next several years [1]. Unlike other chemical products, BDO’s profitability and attractiveness to producers lies in its downstream potential. Figure 1 below demonstrates several potential downstream products that can be directly or indirectly synthesized from BDO. The largest of these contributors include THF and GBL.

[[File:BioButanediol_Downstream.JPG|center|frame|Figure 1. BDO downstream potential flow chart]]

The current market demand of BDO is being supplemented by several global chemical companies. These companies include BASF, BioAmber, Purac, Myriant, DSM, Mitsubishi Chemical, Roquette, and OPXBIO. The market shares of these companies were not available for this product; however, with the consistent growth of the BDO market our team feels that the market is not saturated or impenetrable. The current market price of BDO fluctuates between $3.06 and $3.31 per kg for US-made products [4]. These prices correlate to a nearly 7 billion dollar industry.

===Process alternatives===
1,4-butanediol is traditionally made from petroleum-derived feedstocks in a variety of processes [5]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Several companies are currently implementing bio-routes of producing butanediol. Genomatica is using a bioengineered microorganism to convert sugar feedstocks directly to BDO via fermentation [6], but most companies are instead using microorganisms to convert sugar to succinic acid. The bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, which is the path that most are choosing, although research is being conducted on alternative pathways [7].

==Process overview==
The newly proposed plant can be divided into four stages: pre-reactor, reactor, post-reactor and distillation. Each section is an integral part to the overall process and demands close attention. See the complete process flow diagram in Figure 2.

[[File:PFD.JPG|center|frame|Figure 2. Process flow diagram]]

===Pre-reactor===
This chemical process begins with two feedstocks: hydrogen gas and bio-succinic acid. The hydrogen gas will be obtained from a pipeline at 150 atm and will be used in molar excess inside the reactor. The bio-succinic acid will be purchased by Myriant Corporation which is located near the planned plant site. The pricing for this feedstock is approximately $2.12 per kg. The plant will require 63,000 metric tonnes of bio-succinic acid per year to meet the proposed plant capacity. First the bio-succinic acid feed is pumped up to 150 atm to match the hydrogen gas feed, and then it is mixed with the hydrogen gas prior to being sent into heat exchanger E-101 for heating. The heat exchanger brings the two feeds up to 110oC and sends them to the jacketed packed bed reactor.

===Reactor===
The hydrogenation reaction occurs inside of the reactor thanks to the packed catalyst bed. The catalyst used is 0.4% Fe, 1.9% Na, 2.66% Ag, 2.66% Pd, 10.0% Re on 1.5mm carbon support. With this catalyst, BDO is produced with over 90% selectivity and minimal side reactions of THF and GBL [8]. The reaction has an operating pressure of 2000-4000 psi and internal reactor temperature of 165°C. This temperature allows for about 99.7% conversion of succinic acid [8]. Due to the exothermic nature of the reaction, a cooling jacket is required which utilizes downstream cold streams to cool the internal bed to maintain the desired reaction temperature.

===Post-reactor===
The effluent of the reactor is sent back to E-101 as the hot stream. After exiting E-101, the reactor product stream is sent to a secondary exchanger, E-102, where utility cooling water is used to reduce the temperature to an acceptable temperature prior to sending it to a pressure let-down valve. At this point the pressure of the stream is taken from 150 atm to 1 atm. This large pressure drop allows for the stream to split into its vapor and liquid portions in a gas-liquid separator. The vapor stream of the gas liquid separator is primarily hydrogen gas and sent to a flare for disposal. The liquid effluent is at approximately 45oC leaving the separator and is therefore pumped to the reactor jacket for the reaction cooling mentioned previously. After running through the reactor jacket, the stream enters the separation processes.

===Distillation===
The first distillation column, T-101, is a 10 stage column whose primary purpose is separating the THF from the product feed. Due to THF’s lower boiling point, the byproduct comes off of the top of the column with mostly water. This distillate is sent to the plant's THF waste storage tank that has the capacity of two weeks. The bottoms of the column is sent to the subsequent distillation column that separates the BDO from the GBL and water. The relatively close boiling points of BDO and GBL, 235oC and 204oC, respectively, create a difficult separation that requires a 15 stage column. The distillate of the column is approximately 23% GBL with balance water. This stream is sent to a storage tank with similar sizing parameters as the THF storage tank. The bottom stream is the final 99.5wt% BDO product. This stream is sent to the final product tank, S-104. Depending on our customer demands and the plant location we have the ability to barge, rail or pipe our product to its final destination. Due to low purity of the byproducts, future iterations are needed to optimize either purifying byproducts or selling impure byproducts. There is definitely an available market for these byproducts that should be researched more extensively to increase profit. A detailed description of the equipment from the PFD can be found in Appendix C, in addition to sizing specifications and purpose of equipment.

===Mass and energy balances===
Using an Aspen HYSYS simulation we were able to record the material and energy streams going in and out of the process system. Mass and energy balances are provided Appendix D where each inlet and outlet stream is described and quantified. As expected, the material and energy totals for the inlet and outlet streams add together to equal 0. This proves that our system is mathematically prudent and thermodynamically feasible. The total mass flow of the system is 15,639 kg/h and the total energy in and out of the system is 1.41e8 kJ/h.

===HYSYS simulation===
The HYSYS simulation was performed using the NRTL ideal fluid package. After using AspenPlus to verify that the HYSYS package had the appropriate vapor-liquid equilibrium information between THF and water, and between GBL and water, we concluded it was feasible to proceed with that fluid package. The simulation consists of a reactor, a gas-liquid separator, 2 pumps, 3 heaters, a valve, and 2 distillation columns (see Figure 3). The simulation successfully converted the succinic acid feed into the desired products. Also, the combination of the two distillation columns was able to effectively separate the BDO to obtain a 99.5% pure product with 99.5% recovery. In addition, a set was made between the energy required to heat stream 12 and the energy required to cool the reactor so that these values were made equal. Lastly, the condenser and reboiler duties were used in four heat exchangers in order to determine the appropriate size of this equipment as well as the necessary utility flow rates.

[[File:S2_HYSYS_Simulation.JPG|center|frame|Figure 3. HYSYS simulation]]

==Health and safety==
===Chemical properties===
Inherent to this process are a number of toxic chemicals. Table 1 summarizes the important safety data including hazard type, odor, color, and exposure limits.

[[File:Chem_properties.JPG|center|]]

As shown in the above table, the chemicals that this facility will be dealing with will be relatively mild and non-life threatening. Regardless of their perceived threat, chemicals should always be handled with care especially when they are at high temperatures and pressures.

===Safety procedures===

'''Fire'''. There are many flammable materials that will be included in this process; therefore, fire safety is imperative for all employees. There are countless possible causes of ignition and care should be taken while handling any flammable material whether in the lab or in the field.

In case a fire is present on, the following protocol should be implemented:

* Small fire: Use DRY chemical powder.
* Large fire: Use alcohol foam, water spray, or fog.
* Call for backup if unable to control.
* Immediately contact supervisor and emergency personnel on site.
* Evacuate to safe distance in case of fires around any hazardous materials or pressure vessels.

'''Spills'''. Process chemical spills will eventually occur in a plant of this scale. Small spills are likely to occur in a laboratory setting. Large spills could be a result of loss of containment in the system. We must ensure that all personnel are aware of proper spill mitigation protocol.

* Small spill: Dilute with water and mop or absorb with inert dry material. Dispose of in proper receptacle.
* Large spill: Keep away from sources of ignition and heat. Prevent rundown to any drains or sewers. Call for assistance on disposal. Absorb material with DRY earth or other non-combustible materials.
* If spill is due to a loss of containment in the system, quickly consult the PLC and shut any valves to prevent further loss.

'''Exposure'''. We must ensure that our employees are aware of the possible toxicity levels of each substance and how to handle exposure. The chemicals that are being used in this process are known chemical irritants to the eyes, skin, and throat. Safety measures must be in place to acknowledge this hazard. Due to the possibility of high pressure releases, we will have 2-minute emergency oxygen masks placed strategically throughout the plant to ensure the safety of any operator in the presence of a large release.

If exposed to the process chemicals, find nearest eye wash station or safety shower immediately and flush exposed skin for at least 15 minutes. Remove any contaminated clothing. Seek medical attention immediately.

'''Storage'''. Store chemicals in segregated and approved areas. Any closed containers for laboratory purposes should be placed in cool, well-ventilated areas.

==Economics==
===Equipment costing===
The calculated capital costs from Aspen Economic Analyzer are reported in Table 2 for all process equipment. The size of the reactor was calculated from the liquid hourly space velocity given in the 2011 ISP patent [8] and a void fraction estimate of 0.4. Storage tanks were sized to contain up to two continuous weeks of material. The number of distillation trays in each tower and the flow rates through pumps, vessels, and the flare were calculated in HYSYS. Heat exchange areas were given in Aspen Energy Analyzer or from HYSYS.

In addition to the above equipment, our plant will require an ion exchanger to produce deionized process water from the municipal water. This is estimated to cost $42,000 in capital cost.

===Cash flow analysis===
Summarizing the important takeaways from the economic analysis, this process will return a revenue of 144 MM$ annually. Offset by production costs, the yearly cash flow is approximately 2.7 MM$, except for in the years in which the catalyst must be reinstalled (approximately every 5 years). At a cost of 2.5 MM$, the cash flows in those years decrease to approximately 0.2 MM$. This analysis assumes the plant will take 2 years to construct, and will operate at 50% in its first year. Furthermore, an interest rate of 10% was assumed with a tax rate of 38% (the maximum for corporate gains taxes). Using the 7-year MACRS depreciation method, the 20 year NPV for the project is 4.3 MM$. With an IRR of 15.1%, which is greater than the assumed interest rate, this project looks to be profitable. Further optimization techniques should be used in future iterations to further increase profitability. See Tables 3 and 4 for key economic information.

===Sensitivity analysis===
As seen in Figure 3, the economic evaluation of this process is influenced the most by changes in the sales price and feed cost. A 20% increase in sales price will result in an approximate 120 MM$ increase in NPV whereas a decrease of the same percentage will result in over a 120 MM$ decrease in NPV. Inversely, a 20% increase in feed cost will result in a 115 MM$ decrease in NPV and a 20% decrease in feed cost will result in a 60 MM$ increase in NPV.

To alleviate the risk associated with feed price, the team researched the price forecasting of bio-succinic acid. Figure 4 provides the bio-succinic acid price over the six years between 2006 and 2012. The price of bio-succinic, shown by the blue line, has remained relatively stable over this time period. This price history can be compared to adipic acid, the green line, which is a common petrochemical precursor for BDO production. Adipic acid as shown has had large fluctuations in price that result in unstable cash flows and uncertainty from shareholders. Thankfully, the stability of bio-succinic acid is a good sign that this process has a huge potential to be profitable especially if the demand for BDO continues to rise as projected.

==Discussion==
As described previously, the Davy process was selected as the most promising process of BDO production. The modified Davy process involves the hydrogenation of bio-succinicic acid with a Pa,Ag,Re catalyst and hydrogen gas. This process has many advantages, one being that it has mature technology that has been improved over the last 20 years. Additionally, the conversion to of succinic acid is virtually complete. Finally, overall plant yields can reach as high as 94 mol%.
As shown in Appendix B, streams ahead of the pressure valve (PRV-101) are at approximately 1.51e4 kPa, and streams after the pressure valve are between 100 and 450 kPa. Furthermore, operating temperatures do not exceed 200°C, including safety factors. These operating conditions contribute to the feasibility of the process, as all the components can be designed with reasonable dimensions (wall thickness, cap type, etc.).

Of particular interest are the large costs of the reactor and pump P-101. The reactor costs nearly 2 MM$ because it has a moderate size with a liquid volume of 16.7 m3, and it operates at 150 atm, which requires a strong stainless steel shell for safety purposes. Pump P-101 has such a large capital cost because it is a centrifugal multistage pump that also needs to be made of stainless steel to withstand pressuring the succinic acid feed to 150 atm.

Financial indicators for the proposed plant suggest that it will be moderately profitable, and additional optimization should be performed before making the capital investment. There is a fair amount of risk associated with the implementation of this production facility, and the return at this juncture may not justify the risk.

The process design and simulation in HYSYS has relied on several key assumptions, which are cause for certain limitations to the results. First, the conversions and selectivity of the catalyst, while taken from literature sources, are assumed to be true. Furthermore, the assumption of negligible side reactions and products was made. It is possible that small waste products in the form of succinates also form in the reactor. Therefore, the main limitation of this model is generally due to reaction specifications.

There are certain safety concerns that go along with the proposed process. First, there are many pipes and vessels that will be at a pressure of approximately 150 atm. Extra insulation and protection must be applied to the piping that contains highly pressurized fluids, to prevent operator injury. Furthermore, the PFR is at a slight risk for runaway reactions due to the exothermic nature of the reaction. The temperature of the reactor must always be monitored by an operator, and the jacket cooling system requires a backup system as well. A benefit of this process is that there are no toxic or severely hazardous components in the process. Additionally, there are no instances of temperature greater than 200°C.

The process design will be fitted with instrumentation and controls to ensure stable operation. These controls, including sensors and valves, minimize potential damage to components due to variation in plant conditions, as well as optimizing the overall performance. For example, the piping entering the tower will be fitted with a control loop. In the direction of flow, a sensing instrument first detects the pressure of the fluid, and then sends a signal to the controller. If the pressure is not within the operating limits, the actuator is signaled to close or open a control valve which is located farther down the stream.

==Conclusion==
The Evanston Chemical Engineering Division suggests a process that produces 45,000 tonnes/year of 99.5 wt% 1,4-butandeiol to enter the market with an appropriate market share. The feasibility of producing BDO as a significant process was investigated. A wide range of BDO production processes were researched, with a modified Davy process being identified as having the most potential. Using a Pa,Ag,Re catalyst on carbon support, this process converts bio-succinic acid to BDO with approximately 94% conversion. This process was designed in Aspen HYSYS, and economic analysis was conducted in Aspen Economic Analyzer. Total capital costs of the project are 12.2 MM$, with a simple payback period of 5.2 years. Total operational costs annually are 139.7 MM$. The process design was successful, with the capability of producing the desired production of BDO.

==Recommendations==
Given the moderate profitability of this process design, it is recommended that Evanston Chemicals explores further optimization techniques to increase the profitability of this process. This includes investigating sales of the γ-butyrolactone byproduct, recycling process water, and further optimizing utility streams for the distillation tower.

Second, we would like to investigate recycling the 2300 kg/h of water produced in the reaction. Our succinic acid enters the reactor as a 50 wt% solution in water, so we should look into replacing some of this with the product water. Not only will this decrease our water bill, but it will also lower the cost of ion exchange.

==References==
# Nexant.''Is Bio-Butanediol Here to Stay?'' White Plains, NY: ChemSystems Products; 2012.
# De Guzman D. Chemical industry awaits for bio-succinic acid potential. ICIS. Available at: http://www.icis.com/resources/news/2012/01/30/9527521/chemical-industry-awaits-for-bio-succinic-acid-potential/. Accessed January 24, 2014.
# Australian Government: Department of Health. 1,4-butanediol factsheet. National Industrial Chemicals Notification and Assessment Scheme. Available at: http://www.nicnas.gov.au/communications/publications/information-sheets/existing-chemical-info-sheets/other-information-sheets. Accessed January 24, 2014.
# TecnonOrbiChem. Chem-net facts: 1,4-butanediol. TecnonOrbiChem. Available at: http://www.orbichem.com/userfiles/CNF%20Samples/bdo_13_11.pdf. Accessed January 23, 2014.
# Nexant. 1,4-butanediol/tetrahydrofuran (BDO/THF). ChemSystems. Available at: http://www.chemsystems.com/about/cs/news/items/ PERP2012_3_BDO_THF.cfm. Accessed February 6, 2014.
# Burk MJ, Van Dien SJ, Burgard AP, inventors; Genomatica, Inc., assignee. Compositions and methods for the biosynthesis of 1,4-butanediol and its precursors. US patent 8,067,214. Nov. 29, 2011.
# Chung S-H, Kim M-S, Eom H-H, Lee K-Y. Catalytic hydrogenation of bio-based succinic acid for the production of 1,4-butanediol through the indirect pathway. AIChE. Available at: https://aiche.confex.com/aiche/2013/webprogram/Paper327470.html. Accessed January 23, 2014.
# Bhattacharyya A, Manila MD, inventors; ISP Investments Inc., assignee. Catalysts for maleic acid hydrogenation to 1,4-Butanediol. US patent 7,935,834 B2. May 3, 2011.

File:Chem properties.JPG

2014-03-15T05:19:07Z

Karetstik:

Design S2

2014-03-15T05:17:53Z

Karetstik: /* HYSYS simulation */

Title: Production of 1,4-butanediol

Authors: Nick Pinkerton, Karen Schmidt, and James Xamplas

Date Presented: March 14, 2014

==Introduction==
1,4-butanediol (BDO) is traditionally made from petroleum-derived feedstocks in a variety of processes such as the Reppe (acetylene-based), Mitsubishi (butadiene-based), and Davy (maleic acid-based) processes [1]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, BDO [1]. It is this process that Team S2Kool4Skool has chosen to develop for a new bio-butanediol plant, because the Davy method is mature and requires no new innovations, and because an appropriate feedstock of bio-succinic acid is now available. The plant will be located in East Carroll Parish, Louisiana. This county is also home to Myriant; located in Lake Providence, they are the largest domestic provider of bio-succinic acid [2]. Furthermore, Lake Providence is conveniently located on the Mississippi River, which will allow for affordable transportation of our bio-based butanediol product. The intent of this project is to produce 45,000 metric tonnes of 99.5 wt% 1,4-butanediol per year in a new plant in Lake Providence, LA. The plant will run 24 hours per day for 350 days out of the year, allowing approximately two weeks for a maintenance shutdown.

As there are several techniques for producing 1,4 butanediol in industry, the first step was to determine a synthesis path. Based on the chosen path, reaction kinetics, and required production rate of the process, a reactor system was then designed. Next, the process was designed to deliver the reactants to the reactor at the proper operating conditions, and the separations, purification, and waste management steps were designed. Cost estimates were made using costing software and hand calculations. Finally, the process was iterated and optimized to reduce costs.

==Background==
===General information===
BDO is an organic chemical with the molecular formula <math>C_4H_{10}O_2</math>. It is also a diol with its two hydroxyl groups located at the terminal carbons. BDO has a boiling point of 235 degrees C and is therefore a colorless liquid at standard temperatures and pressures [3].

There are many precursors that petrochemical synthesis of BDO uses. The commonality between all of the precursor acids is that they are hydrogenatable. In replacement of one of these petrochemical precursors, our team has been tasked with the challenge of deriving BDO from the bio-based precursor succinic acid. This catalyzed reaction will take place in the presence of hydrogen as the hydrogenating component shown below:

<math>C_4H_6O_4 + 4H_2 = C_4H_{10}O_2 + 2H_2O</math>

As described in the above reaction, there will need to be at least 4:1 stoichiometric ratio of hydrogen gas to succinic acid. Two moles of water will also be produced along with each mole of BDO. This reaction is exothermic, which requires the reactor to be continuously cooled to maintain our reactor temperature. There are also side products that are produced which include tetrahydrofuran (THF) and γ-butyrolactone (GBL); however, thanks to catalyst selectivity these byproducts are produced in small quantities.

===Market analysis===
Butanediol has a quickly expanding market due to new technological evolutions and its growing use as a chemical intermediary in advanced materials. With biological routes being optimized, the potential of biomass-derived chemicals is tremendous. The global demand of BDO was estimated at 1.5 million metric tons in 2011 and is projected to grow at an annual rate of 4.5% for the next several years [1]. Unlike other chemical products, BDO’s profitability and attractiveness to producers lies in its downstream potential. Figure 1 below demonstrates several potential downstream products that can be directly or indirectly synthesized from BDO. The largest of these contributors include THF and GBL.

[[File:BioButanediol_Downstream.JPG|center|frame|Figure 1. BDO downstream potential flow chart]]

The current market demand of BDO is being supplemented by several global chemical companies. These companies include BASF, BioAmber, Purac, Myriant, DSM, Mitsubishi Chemical, Roquette, and OPXBIO. The market shares of these companies were not available for this product; however, with the consistent growth of the BDO market our team feels that the market is not saturated or impenetrable. The current market price of BDO fluctuates between $3.06 and $3.31 per kg for US-made products [4]. These prices correlate to a nearly 7 billion dollar industry.

===Process alternatives===
1,4-butanediol is traditionally made from petroleum-derived feedstocks in a variety of processes [5]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Several companies are currently implementing bio-routes of producing butanediol. Genomatica is using a bioengineered microorganism to convert sugar feedstocks directly to BDO via fermentation [6], but most companies are instead using microorganisms to convert sugar to succinic acid. The bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, which is the path that most are choosing, although research is being conducted on alternative pathways [7].

==Process overview==
The newly proposed plant can be divided into four stages: pre-reactor, reactor, post-reactor and distillation. Each section is an integral part to the overall process and demands close attention. See the complete process flow diagram in Figure 2.

[[File:PFD.JPG|center|frame|Figure 2. Process flow diagram]]

===Pre-reactor===
This chemical process begins with two feedstocks: hydrogen gas and bio-succinic acid. The hydrogen gas will be obtained from a pipeline at 150 atm and will be used in molar excess inside the reactor. The bio-succinic acid will be purchased by Myriant Corporation which is located near the planned plant site. The pricing for this feedstock is approximately $2.12 per kg. The plant will require 63,000 metric tonnes of bio-succinic acid per year to meet the proposed plant capacity. First the bio-succinic acid feed is pumped up to 150 atm to match the hydrogen gas feed, and then it is mixed with the hydrogen gas prior to being sent into heat exchanger E-101 for heating. The heat exchanger brings the two feeds up to 110oC and sends them to the jacketed packed bed reactor.

===Reactor===
The hydrogenation reaction occurs inside of the reactor thanks to the packed catalyst bed. The catalyst used is 0.4% Fe, 1.9% Na, 2.66% Ag, 2.66% Pd, 10.0% Re on 1.5mm carbon support. With this catalyst, BDO is produced with over 90% selectivity and minimal side reactions of THF and GBL [8]. The reaction has an operating pressure of 2000-4000 psi and internal reactor temperature of 165°C. This temperature allows for about 99.7% conversion of succinic acid [8]. Due to the exothermic nature of the reaction, a cooling jacket is required which utilizes downstream cold streams to cool the internal bed to maintain the desired reaction temperature.

===Post-reactor===
The effluent of the reactor is sent back to E-101 as the hot stream. After exiting E-101, the reactor product stream is sent to a secondary exchanger, E-102, where utility cooling water is used to reduce the temperature to an acceptable temperature prior to sending it to a pressure let-down valve. At this point the pressure of the stream is taken from 150 atm to 1 atm. This large pressure drop allows for the stream to split into its vapor and liquid portions in a gas-liquid separator. The vapor stream of the gas liquid separator is primarily hydrogen gas and sent to a flare for disposal. The liquid effluent is at approximately 45oC leaving the separator and is therefore pumped to the reactor jacket for the reaction cooling mentioned previously. After running through the reactor jacket, the stream enters the separation processes.

===Distillation===
The first distillation column, T-101, is a 10 stage column whose primary purpose is separating the THF from the product feed. Due to THF’s lower boiling point, the byproduct comes off of the top of the column with mostly water. This distillate is sent to the plant's THF waste storage tank that has the capacity of two weeks. The bottoms of the column is sent to the subsequent distillation column that separates the BDO from the GBL and water. The relatively close boiling points of BDO and GBL, 235oC and 204oC, respectively, create a difficult separation that requires a 15 stage column. The distillate of the column is approximately 23% GBL with balance water. This stream is sent to a storage tank with similar sizing parameters as the THF storage tank. The bottom stream is the final 99.5wt% BDO product. This stream is sent to the final product tank, S-104. Depending on our customer demands and the plant location we have the ability to barge, rail or pipe our product to its final destination. Due to low purity of the byproducts, future iterations are needed to optimize either purifying byproducts or selling impure byproducts. There is definitely an available market for these byproducts that should be researched more extensively to increase profit. A detailed description of the equipment from the PFD can be found in Appendix C, in addition to sizing specifications and purpose of equipment.

===Mass and energy balances===
Using an Aspen HYSYS simulation we were able to record the material and energy streams going in and out of the process system. Mass and energy balances are provided Appendix D where each inlet and outlet stream is described and quantified. As expected, the material and energy totals for the inlet and outlet streams add together to equal 0. This proves that our system is mathematically prudent and thermodynamically feasible. The total mass flow of the system is 15,639 kg/h and the total energy in and out of the system is 1.41e8 kJ/h.

===HYSYS simulation===
The HYSYS simulation was performed using the NRTL ideal fluid package. After using AspenPlus to verify that the HYSYS package had the appropriate vapor-liquid equilibrium information between THF and water, and between GBL and water, we concluded it was feasible to proceed with that fluid package. The simulation consists of a reactor, a gas-liquid separator, 2 pumps, 3 heaters, a valve, and 2 distillation columns (see Figure 3). The simulation successfully converted the succinic acid feed into the desired products. Also, the combination of the two distillation columns was able to effectively separate the BDO to obtain a 99.5% pure product with 99.5% recovery. In addition, a set was made between the energy required to heat stream 12 and the energy required to cool the reactor so that these values were made equal. Lastly, the condenser and reboiler duties were used in four heat exchangers in order to determine the appropriate size of this equipment as well as the necessary utility flow rates.

[[File:S2_HYSYS_Simulation.JPG|center|frame|Figure 3. HYSYS simulation]]

==Health and safety==
===Chemical properties===
Inherent to this process are a number of toxic chemicals. Table 1 summarizes the important safety data including hazard type, odor, color, and exposure limits.

As shown in the above table, the chemicals that this facility will be dealing with will be relatively mild and non-life threatening. Regardless of their perceived threat, chemicals should always be handled with care especially when they are at high temperatures and pressures.

===Safety procedures===

'''Fire'''. There are many flammable materials that will be included in this process; therefore, fire safety is imperative for all employees. There are countless possible causes of ignition and care should be taken while handling any flammable material whether in the lab or in the field.

In case a fire is present on, the following protocol should be implemented:

* Small fire: Use DRY chemical powder.
* Large fire: Use alcohol foam, water spray, or fog.
* Call for backup if unable to control.
* Immediately contact supervisor and emergency personnel on site.
* Evacuate to safe distance in case of fires around any hazardous materials or pressure vessels.

'''Spills'''. Process chemical spills will eventually occur in a plant of this scale. Small spills are likely to occur in a laboratory setting. Large spills could be a result of loss of containment in the system. We must ensure that all personnel are aware of proper spill mitigation protocol.

* Small spill: Dilute with water and mop or absorb with inert dry material. Dispose of in proper receptacle.
* Large spill: Keep away from sources of ignition and heat. Prevent rundown to any drains or sewers. Call for assistance on disposal. Absorb material with DRY earth or other non-combustible materials.
* If spill is due to a loss of containment in the system, quickly consult the PLC and shut any valves to prevent further loss.

'''Exposure'''. We must ensure that our employees are aware of the possible toxicity levels of each substance and how to handle exposure. The chemicals that are being used in this process are known chemical irritants to the eyes, skin, and throat. Safety measures must be in place to acknowledge this hazard. Due to the possibility of high pressure releases, we will have 2-minute emergency oxygen masks placed strategically throughout the plant to ensure the safety of any operator in the presence of a large release.

If exposed to the process chemicals, find nearest eye wash station or safety shower immediately and flush exposed skin for at least 15 minutes. Remove any contaminated clothing. Seek medical attention immediately.

'''Storage'''. Store chemicals in segregated and approved areas. Any closed containers for laboratory purposes should be placed in cool, well-ventilated areas.

==Economics==
===Equipment costing===
The calculated capital costs from Aspen Economic Analyzer are reported in Table 2 for all process equipment. The size of the reactor was calculated from the liquid hourly space velocity given in the 2011 ISP patent [8] and a void fraction estimate of 0.4. Storage tanks were sized to contain up to two continuous weeks of material. The number of distillation trays in each tower and the flow rates through pumps, vessels, and the flare were calculated in HYSYS. Heat exchange areas were given in Aspen Energy Analyzer or from HYSYS.

In addition to the above equipment, our plant will require an ion exchanger to produce deionized process water from the municipal water. This is estimated to cost $42,000 in capital cost.

===Cash flow analysis===
Summarizing the important takeaways from the economic analysis, this process will return a revenue of 144 MM$ annually. Offset by production costs, the yearly cash flow is approximately 2.7 MM$, except for in the years in which the catalyst must be reinstalled (approximately every 5 years). At a cost of 2.5 MM$, the cash flows in those years decrease to approximately 0.2 MM$. This analysis assumes the plant will take 2 years to construct, and will operate at 50% in its first year. Furthermore, an interest rate of 10% was assumed with a tax rate of 38% (the maximum for corporate gains taxes). Using the 7-year MACRS depreciation method, the 20 year NPV for the project is 4.3 MM$. With an IRR of 15.1%, which is greater than the assumed interest rate, this project looks to be profitable. Further optimization techniques should be used in future iterations to further increase profitability. See Tables 3 and 4 for key economic information.

===Sensitivity analysis===
As seen in Figure 3, the economic evaluation of this process is influenced the most by changes in the sales price and feed cost. A 20% increase in sales price will result in an approximate 120 MM$ increase in NPV whereas a decrease of the same percentage will result in over a 120 MM$ decrease in NPV. Inversely, a 20% increase in feed cost will result in a 115 MM$ decrease in NPV and a 20% decrease in feed cost will result in a 60 MM$ increase in NPV.

To alleviate the risk associated with feed price, the team researched the price forecasting of bio-succinic acid. Figure 4 provides the bio-succinic acid price over the six years between 2006 and 2012. The price of bio-succinic, shown by the blue line, has remained relatively stable over this time period. This price history can be compared to adipic acid, the green line, which is a common petrochemical precursor for BDO production. Adipic acid as shown has had large fluctuations in price that result in unstable cash flows and uncertainty from shareholders. Thankfully, the stability of bio-succinic acid is a good sign that this process has a huge potential to be profitable especially if the demand for BDO continues to rise as projected.

==Discussion==
As described previously, the Davy process was selected as the most promising process of BDO production. The modified Davy process involves the hydrogenation of bio-succinicic acid with a Pa,Ag,Re catalyst and hydrogen gas. This process has many advantages, one being that it has mature technology that has been improved over the last 20 years. Additionally, the conversion to of succinic acid is virtually complete. Finally, overall plant yields can reach as high as 94 mol%.
As shown in Appendix B, streams ahead of the pressure valve (PRV-101) are at approximately 1.51e4 kPa, and streams after the pressure valve are between 100 and 450 kPa. Furthermore, operating temperatures do not exceed 200°C, including safety factors. These operating conditions contribute to the feasibility of the process, as all the components can be designed with reasonable dimensions (wall thickness, cap type, etc.).

Of particular interest are the large costs of the reactor and pump P-101. The reactor costs nearly 2 MM$ because it has a moderate size with a liquid volume of 16.7 m3, and it operates at 150 atm, which requires a strong stainless steel shell for safety purposes. Pump P-101 has such a large capital cost because it is a centrifugal multistage pump that also needs to be made of stainless steel to withstand pressuring the succinic acid feed to 150 atm.

Financial indicators for the proposed plant suggest that it will be moderately profitable, and additional optimization should be performed before making the capital investment. There is a fair amount of risk associated with the implementation of this production facility, and the return at this juncture may not justify the risk.

The process design and simulation in HYSYS has relied on several key assumptions, which are cause for certain limitations to the results. First, the conversions and selectivity of the catalyst, while taken from literature sources, are assumed to be true. Furthermore, the assumption of negligible side reactions and products was made. It is possible that small waste products in the form of succinates also form in the reactor. Therefore, the main limitation of this model is generally due to reaction specifications.

There are certain safety concerns that go along with the proposed process. First, there are many pipes and vessels that will be at a pressure of approximately 150 atm. Extra insulation and protection must be applied to the piping that contains highly pressurized fluids, to prevent operator injury. Furthermore, the PFR is at a slight risk for runaway reactions due to the exothermic nature of the reaction. The temperature of the reactor must always be monitored by an operator, and the jacket cooling system requires a backup system as well. A benefit of this process is that there are no toxic or severely hazardous components in the process. Additionally, there are no instances of temperature greater than 200°C.

The process design will be fitted with instrumentation and controls to ensure stable operation. These controls, including sensors and valves, minimize potential damage to components due to variation in plant conditions, as well as optimizing the overall performance. For example, the piping entering the tower will be fitted with a control loop. In the direction of flow, a sensing instrument first detects the pressure of the fluid, and then sends a signal to the controller. If the pressure is not within the operating limits, the actuator is signaled to close or open a control valve which is located farther down the stream.

==Conclusion==
The Evanston Chemical Engineering Division suggests a process that produces 45,000 tonnes/year of 99.5 wt% 1,4-butandeiol to enter the market with an appropriate market share. The feasibility of producing BDO as a significant process was investigated. A wide range of BDO production processes were researched, with a modified Davy process being identified as having the most potential. Using a Pa,Ag,Re catalyst on carbon support, this process converts bio-succinic acid to BDO with approximately 94% conversion. This process was designed in Aspen HYSYS, and economic analysis was conducted in Aspen Economic Analyzer. Total capital costs of the project are 12.2 MM$, with a simple payback period of 5.2 years. Total operational costs annually are 139.7 MM$. The process design was successful, with the capability of producing the desired production of BDO.

==Recommendations==
Given the moderate profitability of this process design, it is recommended that Evanston Chemicals explores further optimization techniques to increase the profitability of this process. This includes investigating sales of the γ-butyrolactone byproduct, recycling process water, and further optimizing utility streams for the distillation tower.

Second, we would like to investigate recycling the 2300 kg/h of water produced in the reaction. Our succinic acid enters the reactor as a 50 wt% solution in water, so we should look into replacing some of this with the product water. Not only will this decrease our water bill, but it will also lower the cost of ion exchange.

==References==
# Nexant.''Is Bio-Butanediol Here to Stay?'' White Plains, NY: ChemSystems Products; 2012.
# De Guzman D. Chemical industry awaits for bio-succinic acid potential. ICIS. Available at: http://www.icis.com/resources/news/2012/01/30/9527521/chemical-industry-awaits-for-bio-succinic-acid-potential/. Accessed January 24, 2014.
# Australian Government: Department of Health. 1,4-butanediol factsheet. National Industrial Chemicals Notification and Assessment Scheme. Available at: http://www.nicnas.gov.au/communications/publications/information-sheets/existing-chemical-info-sheets/other-information-sheets. Accessed January 24, 2014.
# TecnonOrbiChem. Chem-net facts: 1,4-butanediol. TecnonOrbiChem. Available at: http://www.orbichem.com/userfiles/CNF%20Samples/bdo_13_11.pdf. Accessed January 23, 2014.
# Nexant. 1,4-butanediol/tetrahydrofuran (BDO/THF). ChemSystems. Available at: http://www.chemsystems.com/about/cs/news/items/ PERP2012_3_BDO_THF.cfm. Accessed February 6, 2014.
# Burk MJ, Van Dien SJ, Burgard AP, inventors; Genomatica, Inc., assignee. Compositions and methods for the biosynthesis of 1,4-butanediol and its precursors. US patent 8,067,214. Nov. 29, 2011.
# Chung S-H, Kim M-S, Eom H-H, Lee K-Y. Catalytic hydrogenation of bio-based succinic acid for the production of 1,4-butanediol through the indirect pathway. AIChE. Available at: https://aiche.confex.com/aiche/2013/webprogram/Paper327470.html. Accessed January 23, 2014.
# Bhattacharyya A, Manila MD, inventors; ISP Investments Inc., assignee. Catalysts for maleic acid hydrogenation to 1,4-Butanediol. US patent 7,935,834 B2. May 3, 2011.

Design S2

2014-03-15T05:17:00Z

Karetstik: /* Mass and energy balances */

Title: Production of 1,4-butanediol

Authors: Nick Pinkerton, Karen Schmidt, and James Xamplas

Date Presented: March 14, 2014

==Introduction==
1,4-butanediol (BDO) is traditionally made from petroleum-derived feedstocks in a variety of processes such as the Reppe (acetylene-based), Mitsubishi (butadiene-based), and Davy (maleic acid-based) processes [1]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, BDO [1]. It is this process that Team S2Kool4Skool has chosen to develop for a new bio-butanediol plant, because the Davy method is mature and requires no new innovations, and because an appropriate feedstock of bio-succinic acid is now available. The plant will be located in East Carroll Parish, Louisiana. This county is also home to Myriant; located in Lake Providence, they are the largest domestic provider of bio-succinic acid [2]. Furthermore, Lake Providence is conveniently located on the Mississippi River, which will allow for affordable transportation of our bio-based butanediol product. The intent of this project is to produce 45,000 metric tonnes of 99.5 wt% 1,4-butanediol per year in a new plant in Lake Providence, LA. The plant will run 24 hours per day for 350 days out of the year, allowing approximately two weeks for a maintenance shutdown.

As there are several techniques for producing 1,4 butanediol in industry, the first step was to determine a synthesis path. Based on the chosen path, reaction kinetics, and required production rate of the process, a reactor system was then designed. Next, the process was designed to deliver the reactants to the reactor at the proper operating conditions, and the separations, purification, and waste management steps were designed. Cost estimates were made using costing software and hand calculations. Finally, the process was iterated and optimized to reduce costs.

==Background==
===General information===
BDO is an organic chemical with the molecular formula <math>C_4H_{10}O_2</math>. It is also a diol with its two hydroxyl groups located at the terminal carbons. BDO has a boiling point of 235 degrees C and is therefore a colorless liquid at standard temperatures and pressures [3].

There are many precursors that petrochemical synthesis of BDO uses. The commonality between all of the precursor acids is that they are hydrogenatable. In replacement of one of these petrochemical precursors, our team has been tasked with the challenge of deriving BDO from the bio-based precursor succinic acid. This catalyzed reaction will take place in the presence of hydrogen as the hydrogenating component shown below:

<math>C_4H_6O_4 + 4H_2 = C_4H_{10}O_2 + 2H_2O</math>

As described in the above reaction, there will need to be at least 4:1 stoichiometric ratio of hydrogen gas to succinic acid. Two moles of water will also be produced along with each mole of BDO. This reaction is exothermic, which requires the reactor to be continuously cooled to maintain our reactor temperature. There are also side products that are produced which include tetrahydrofuran (THF) and γ-butyrolactone (GBL); however, thanks to catalyst selectivity these byproducts are produced in small quantities.

===Market analysis===
Butanediol has a quickly expanding market due to new technological evolutions and its growing use as a chemical intermediary in advanced materials. With biological routes being optimized, the potential of biomass-derived chemicals is tremendous. The global demand of BDO was estimated at 1.5 million metric tons in 2011 and is projected to grow at an annual rate of 4.5% for the next several years [1]. Unlike other chemical products, BDO’s profitability and attractiveness to producers lies in its downstream potential. Figure 1 below demonstrates several potential downstream products that can be directly or indirectly synthesized from BDO. The largest of these contributors include THF and GBL.

[[File:BioButanediol_Downstream.JPG|center|frame|Figure 1. BDO downstream potential flow chart]]

The current market demand of BDO is being supplemented by several global chemical companies. These companies include BASF, BioAmber, Purac, Myriant, DSM, Mitsubishi Chemical, Roquette, and OPXBIO. The market shares of these companies were not available for this product; however, with the consistent growth of the BDO market our team feels that the market is not saturated or impenetrable. The current market price of BDO fluctuates between $3.06 and $3.31 per kg for US-made products [4]. These prices correlate to a nearly 7 billion dollar industry.

===Process alternatives===
1,4-butanediol is traditionally made from petroleum-derived feedstocks in a variety of processes [5]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Several companies are currently implementing bio-routes of producing butanediol. Genomatica is using a bioengineered microorganism to convert sugar feedstocks directly to BDO via fermentation [6], but most companies are instead using microorganisms to convert sugar to succinic acid. The bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, which is the path that most are choosing, although research is being conducted on alternative pathways [7].

==Process overview==
The newly proposed plant can be divided into four stages: pre-reactor, reactor, post-reactor and distillation. Each section is an integral part to the overall process and demands close attention. See the complete process flow diagram in Figure 2.

[[File:PFD.JPG|center|frame|Figure 2. Process flow diagram]]

===Pre-reactor===
This chemical process begins with two feedstocks: hydrogen gas and bio-succinic acid. The hydrogen gas will be obtained from a pipeline at 150 atm and will be used in molar excess inside the reactor. The bio-succinic acid will be purchased by Myriant Corporation which is located near the planned plant site. The pricing for this feedstock is approximately $2.12 per kg. The plant will require 63,000 metric tonnes of bio-succinic acid per year to meet the proposed plant capacity. First the bio-succinic acid feed is pumped up to 150 atm to match the hydrogen gas feed, and then it is mixed with the hydrogen gas prior to being sent into heat exchanger E-101 for heating. The heat exchanger brings the two feeds up to 110oC and sends them to the jacketed packed bed reactor.

===Reactor===
The hydrogenation reaction occurs inside of the reactor thanks to the packed catalyst bed. The catalyst used is 0.4% Fe, 1.9% Na, 2.66% Ag, 2.66% Pd, 10.0% Re on 1.5mm carbon support. With this catalyst, BDO is produced with over 90% selectivity and minimal side reactions of THF and GBL [8]. The reaction has an operating pressure of 2000-4000 psi and internal reactor temperature of 165°C. This temperature allows for about 99.7% conversion of succinic acid [8]. Due to the exothermic nature of the reaction, a cooling jacket is required which utilizes downstream cold streams to cool the internal bed to maintain the desired reaction temperature.

===Post-reactor===
The effluent of the reactor is sent back to E-101 as the hot stream. After exiting E-101, the reactor product stream is sent to a secondary exchanger, E-102, where utility cooling water is used to reduce the temperature to an acceptable temperature prior to sending it to a pressure let-down valve. At this point the pressure of the stream is taken from 150 atm to 1 atm. This large pressure drop allows for the stream to split into its vapor and liquid portions in a gas-liquid separator. The vapor stream of the gas liquid separator is primarily hydrogen gas and sent to a flare for disposal. The liquid effluent is at approximately 45oC leaving the separator and is therefore pumped to the reactor jacket for the reaction cooling mentioned previously. After running through the reactor jacket, the stream enters the separation processes.

===Distillation===
The first distillation column, T-101, is a 10 stage column whose primary purpose is separating the THF from the product feed. Due to THF’s lower boiling point, the byproduct comes off of the top of the column with mostly water. This distillate is sent to the plant's THF waste storage tank that has the capacity of two weeks. The bottoms of the column is sent to the subsequent distillation column that separates the BDO from the GBL and water. The relatively close boiling points of BDO and GBL, 235oC and 204oC, respectively, create a difficult separation that requires a 15 stage column. The distillate of the column is approximately 23% GBL with balance water. This stream is sent to a storage tank with similar sizing parameters as the THF storage tank. The bottom stream is the final 99.5wt% BDO product. This stream is sent to the final product tank, S-104. Depending on our customer demands and the plant location we have the ability to barge, rail or pipe our product to its final destination. Due to low purity of the byproducts, future iterations are needed to optimize either purifying byproducts or selling impure byproducts. There is definitely an available market for these byproducts that should be researched more extensively to increase profit. A detailed description of the equipment from the PFD can be found in Appendix C, in addition to sizing specifications and purpose of equipment.

===Mass and energy balances===
Using an Aspen HYSYS simulation we were able to record the material and energy streams going in and out of the process system. Mass and energy balances are provided Appendix D where each inlet and outlet stream is described and quantified. As expected, the material and energy totals for the inlet and outlet streams add together to equal 0. This proves that our system is mathematically prudent and thermodynamically feasible. The total mass flow of the system is 15,639 kg/h and the total energy in and out of the system is 1.41e8 kJ/h.

===HYSYS simulation===
The HYSYS simulation was performed using the NRTL ideal fluid package. After using AspenPlus to verify that the HYSYS package had the appropriate vapor-liquid equilibrium information between THF and water, and between GBL and water, we concluded it was feasible to proceed with that fluid package. The simulation consists of a reactor, a gas-liquid separator, 2 pumps, 3 heaters, a valve, and 2 distillation columns (see Figure 2). The simulation successfully converted the succinic acid feed into the desired products. Also, the combination of the two distillation columns was able to effectively separate the BDO to obtain a 99.5% pure product with 99.5% recovery. In addition, a set was made between the energy required to heat stream 12 and the energy required to cool the reactor so that these values were made equal. Lastly, the condenser and reboiler duties were used in four heat exchangers in order to determine the appropriate size of this equipment as well as the necessary utility flow rates.

==Health and safety==
===Chemical properties===
Inherent to this process are a number of toxic chemicals. Table 1 summarizes the important safety data including hazard type, odor, color, and exposure limits.

As shown in the above table, the chemicals that this facility will be dealing with will be relatively mild and non-life threatening. Regardless of their perceived threat, chemicals should always be handled with care especially when they are at high temperatures and pressures.

===Safety procedures===

'''Fire'''. There are many flammable materials that will be included in this process; therefore, fire safety is imperative for all employees. There are countless possible causes of ignition and care should be taken while handling any flammable material whether in the lab or in the field.

In case a fire is present on, the following protocol should be implemented:

* Small fire: Use DRY chemical powder.
* Large fire: Use alcohol foam, water spray, or fog.
* Call for backup if unable to control.
* Immediately contact supervisor and emergency personnel on site.
* Evacuate to safe distance in case of fires around any hazardous materials or pressure vessels.

'''Spills'''. Process chemical spills will eventually occur in a plant of this scale. Small spills are likely to occur in a laboratory setting. Large spills could be a result of loss of containment in the system. We must ensure that all personnel are aware of proper spill mitigation protocol.

* Small spill: Dilute with water and mop or absorb with inert dry material. Dispose of in proper receptacle.
* Large spill: Keep away from sources of ignition and heat. Prevent rundown to any drains or sewers. Call for assistance on disposal. Absorb material with DRY earth or other non-combustible materials.
* If spill is due to a loss of containment in the system, quickly consult the PLC and shut any valves to prevent further loss.

'''Exposure'''. We must ensure that our employees are aware of the possible toxicity levels of each substance and how to handle exposure. The chemicals that are being used in this process are known chemical irritants to the eyes, skin, and throat. Safety measures must be in place to acknowledge this hazard. Due to the possibility of high pressure releases, we will have 2-minute emergency oxygen masks placed strategically throughout the plant to ensure the safety of any operator in the presence of a large release.

If exposed to the process chemicals, find nearest eye wash station or safety shower immediately and flush exposed skin for at least 15 minutes. Remove any contaminated clothing. Seek medical attention immediately.

'''Storage'''. Store chemicals in segregated and approved areas. Any closed containers for laboratory purposes should be placed in cool, well-ventilated areas.

==Economics==
===Equipment costing===
The calculated capital costs from Aspen Economic Analyzer are reported in Table 2 for all process equipment. The size of the reactor was calculated from the liquid hourly space velocity given in the 2011 ISP patent [8] and a void fraction estimate of 0.4. Storage tanks were sized to contain up to two continuous weeks of material. The number of distillation trays in each tower and the flow rates through pumps, vessels, and the flare were calculated in HYSYS. Heat exchange areas were given in Aspen Energy Analyzer or from HYSYS.

In addition to the above equipment, our plant will require an ion exchanger to produce deionized process water from the municipal water. This is estimated to cost $42,000 in capital cost.

===Cash flow analysis===
Summarizing the important takeaways from the economic analysis, this process will return a revenue of 144 MM$ annually. Offset by production costs, the yearly cash flow is approximately 2.7 MM$, except for in the years in which the catalyst must be reinstalled (approximately every 5 years). At a cost of 2.5 MM$, the cash flows in those years decrease to approximately 0.2 MM$. This analysis assumes the plant will take 2 years to construct, and will operate at 50% in its first year. Furthermore, an interest rate of 10% was assumed with a tax rate of 38% (the maximum for corporate gains taxes). Using the 7-year MACRS depreciation method, the 20 year NPV for the project is 4.3 MM$. With an IRR of 15.1%, which is greater than the assumed interest rate, this project looks to be profitable. Further optimization techniques should be used in future iterations to further increase profitability. See Tables 3 and 4 for key economic information.

===Sensitivity analysis===
As seen in Figure 3, the economic evaluation of this process is influenced the most by changes in the sales price and feed cost. A 20% increase in sales price will result in an approximate 120 MM$ increase in NPV whereas a decrease of the same percentage will result in over a 120 MM$ decrease in NPV. Inversely, a 20% increase in feed cost will result in a 115 MM$ decrease in NPV and a 20% decrease in feed cost will result in a 60 MM$ increase in NPV.

To alleviate the risk associated with feed price, the team researched the price forecasting of bio-succinic acid. Figure 4 provides the bio-succinic acid price over the six years between 2006 and 2012. The price of bio-succinic, shown by the blue line, has remained relatively stable over this time period. This price history can be compared to adipic acid, the green line, which is a common petrochemical precursor for BDO production. Adipic acid as shown has had large fluctuations in price that result in unstable cash flows and uncertainty from shareholders. Thankfully, the stability of bio-succinic acid is a good sign that this process has a huge potential to be profitable especially if the demand for BDO continues to rise as projected.

==Discussion==
As described previously, the Davy process was selected as the most promising process of BDO production. The modified Davy process involves the hydrogenation of bio-succinicic acid with a Pa,Ag,Re catalyst and hydrogen gas. This process has many advantages, one being that it has mature technology that has been improved over the last 20 years. Additionally, the conversion to of succinic acid is virtually complete. Finally, overall plant yields can reach as high as 94 mol%.
As shown in Appendix B, streams ahead of the pressure valve (PRV-101) are at approximately 1.51e4 kPa, and streams after the pressure valve are between 100 and 450 kPa. Furthermore, operating temperatures do not exceed 200°C, including safety factors. These operating conditions contribute to the feasibility of the process, as all the components can be designed with reasonable dimensions (wall thickness, cap type, etc.).

Of particular interest are the large costs of the reactor and pump P-101. The reactor costs nearly 2 MM$ because it has a moderate size with a liquid volume of 16.7 m3, and it operates at 150 atm, which requires a strong stainless steel shell for safety purposes. Pump P-101 has such a large capital cost because it is a centrifugal multistage pump that also needs to be made of stainless steel to withstand pressuring the succinic acid feed to 150 atm.

Financial indicators for the proposed plant suggest that it will be moderately profitable, and additional optimization should be performed before making the capital investment. There is a fair amount of risk associated with the implementation of this production facility, and the return at this juncture may not justify the risk.

The process design and simulation in HYSYS has relied on several key assumptions, which are cause for certain limitations to the results. First, the conversions and selectivity of the catalyst, while taken from literature sources, are assumed to be true. Furthermore, the assumption of negligible side reactions and products was made. It is possible that small waste products in the form of succinates also form in the reactor. Therefore, the main limitation of this model is generally due to reaction specifications.

There are certain safety concerns that go along with the proposed process. First, there are many pipes and vessels that will be at a pressure of approximately 150 atm. Extra insulation and protection must be applied to the piping that contains highly pressurized fluids, to prevent operator injury. Furthermore, the PFR is at a slight risk for runaway reactions due to the exothermic nature of the reaction. The temperature of the reactor must always be monitored by an operator, and the jacket cooling system requires a backup system as well. A benefit of this process is that there are no toxic or severely hazardous components in the process. Additionally, there are no instances of temperature greater than 200°C.

The process design will be fitted with instrumentation and controls to ensure stable operation. These controls, including sensors and valves, minimize potential damage to components due to variation in plant conditions, as well as optimizing the overall performance. For example, the piping entering the tower will be fitted with a control loop. In the direction of flow, a sensing instrument first detects the pressure of the fluid, and then sends a signal to the controller. If the pressure is not within the operating limits, the actuator is signaled to close or open a control valve which is located farther down the stream.

==Conclusion==
The Evanston Chemical Engineering Division suggests a process that produces 45,000 tonnes/year of 99.5 wt% 1,4-butandeiol to enter the market with an appropriate market share. The feasibility of producing BDO as a significant process was investigated. A wide range of BDO production processes were researched, with a modified Davy process being identified as having the most potential. Using a Pa,Ag,Re catalyst on carbon support, this process converts bio-succinic acid to BDO with approximately 94% conversion. This process was designed in Aspen HYSYS, and economic analysis was conducted in Aspen Economic Analyzer. Total capital costs of the project are 12.2 MM$, with a simple payback period of 5.2 years. Total operational costs annually are 139.7 MM$. The process design was successful, with the capability of producing the desired production of BDO.

==Recommendations==
Given the moderate profitability of this process design, it is recommended that Evanston Chemicals explores further optimization techniques to increase the profitability of this process. This includes investigating sales of the γ-butyrolactone byproduct, recycling process water, and further optimizing utility streams for the distillation tower.

Second, we would like to investigate recycling the 2300 kg/h of water produced in the reaction. Our succinic acid enters the reactor as a 50 wt% solution in water, so we should look into replacing some of this with the product water. Not only will this decrease our water bill, but it will also lower the cost of ion exchange.

==References==
# Nexant.''Is Bio-Butanediol Here to Stay?'' White Plains, NY: ChemSystems Products; 2012.
# De Guzman D. Chemical industry awaits for bio-succinic acid potential. ICIS. Available at: http://www.icis.com/resources/news/2012/01/30/9527521/chemical-industry-awaits-for-bio-succinic-acid-potential/. Accessed January 24, 2014.
# Australian Government: Department of Health. 1,4-butanediol factsheet. National Industrial Chemicals Notification and Assessment Scheme. Available at: http://www.nicnas.gov.au/communications/publications/information-sheets/existing-chemical-info-sheets/other-information-sheets. Accessed January 24, 2014.
# TecnonOrbiChem. Chem-net facts: 1,4-butanediol. TecnonOrbiChem. Available at: http://www.orbichem.com/userfiles/CNF%20Samples/bdo_13_11.pdf. Accessed January 23, 2014.
# Nexant. 1,4-butanediol/tetrahydrofuran (BDO/THF). ChemSystems. Available at: http://www.chemsystems.com/about/cs/news/items/ PERP2012_3_BDO_THF.cfm. Accessed February 6, 2014.
# Burk MJ, Van Dien SJ, Burgard AP, inventors; Genomatica, Inc., assignee. Compositions and methods for the biosynthesis of 1,4-butanediol and its precursors. US patent 8,067,214. Nov. 29, 2011.
# Chung S-H, Kim M-S, Eom H-H, Lee K-Y. Catalytic hydrogenation of bio-based succinic acid for the production of 1,4-butanediol through the indirect pathway. AIChE. Available at: https://aiche.confex.com/aiche/2013/webprogram/Paper327470.html. Accessed January 23, 2014.
# Bhattacharyya A, Manila MD, inventors; ISP Investments Inc., assignee. Catalysts for maleic acid hydrogenation to 1,4-Butanediol. US patent 7,935,834 B2. May 3, 2011.

File:S2 HYSYS Simulation.JPG

2014-03-15T05:16:19Z

Karetstik:

Design S2

2014-03-15T05:14:29Z

Karetstik: /* Process overview */

Title: Production of 1,4-butanediol

Authors: Nick Pinkerton, Karen Schmidt, and James Xamplas

Date Presented: March 14, 2014

==Introduction==
1,4-butanediol (BDO) is traditionally made from petroleum-derived feedstocks in a variety of processes such as the Reppe (acetylene-based), Mitsubishi (butadiene-based), and Davy (maleic acid-based) processes [1]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, BDO [1]. It is this process that Team S2Kool4Skool has chosen to develop for a new bio-butanediol plant, because the Davy method is mature and requires no new innovations, and because an appropriate feedstock of bio-succinic acid is now available. The plant will be located in East Carroll Parish, Louisiana. This county is also home to Myriant; located in Lake Providence, they are the largest domestic provider of bio-succinic acid [2]. Furthermore, Lake Providence is conveniently located on the Mississippi River, which will allow for affordable transportation of our bio-based butanediol product. The intent of this project is to produce 45,000 metric tonnes of 99.5 wt% 1,4-butanediol per year in a new plant in Lake Providence, LA. The plant will run 24 hours per day for 350 days out of the year, allowing approximately two weeks for a maintenance shutdown.

As there are several techniques for producing 1,4 butanediol in industry, the first step was to determine a synthesis path. Based on the chosen path, reaction kinetics, and required production rate of the process, a reactor system was then designed. Next, the process was designed to deliver the reactants to the reactor at the proper operating conditions, and the separations, purification, and waste management steps were designed. Cost estimates were made using costing software and hand calculations. Finally, the process was iterated and optimized to reduce costs.

==Background==
===General information===
BDO is an organic chemical with the molecular formula <math>C_4H_{10}O_2</math>. It is also a diol with its two hydroxyl groups located at the terminal carbons. BDO has a boiling point of 235 degrees C and is therefore a colorless liquid at standard temperatures and pressures [3].

There are many precursors that petrochemical synthesis of BDO uses. The commonality between all of the precursor acids is that they are hydrogenatable. In replacement of one of these petrochemical precursors, our team has been tasked with the challenge of deriving BDO from the bio-based precursor succinic acid. This catalyzed reaction will take place in the presence of hydrogen as the hydrogenating component shown below:

<math>C_4H_6O_4 + 4H_2 = C_4H_{10}O_2 + 2H_2O</math>

As described in the above reaction, there will need to be at least 4:1 stoichiometric ratio of hydrogen gas to succinic acid. Two moles of water will also be produced along with each mole of BDO. This reaction is exothermic, which requires the reactor to be continuously cooled to maintain our reactor temperature. There are also side products that are produced which include tetrahydrofuran (THF) and γ-butyrolactone (GBL); however, thanks to catalyst selectivity these byproducts are produced in small quantities.

===Market analysis===
Butanediol has a quickly expanding market due to new technological evolutions and its growing use as a chemical intermediary in advanced materials. With biological routes being optimized, the potential of biomass-derived chemicals is tremendous. The global demand of BDO was estimated at 1.5 million metric tons in 2011 and is projected to grow at an annual rate of 4.5% for the next several years [1]. Unlike other chemical products, BDO’s profitability and attractiveness to producers lies in its downstream potential. Figure 1 below demonstrates several potential downstream products that can be directly or indirectly synthesized from BDO. The largest of these contributors include THF and GBL.

[[File:BioButanediol_Downstream.JPG|center|frame|Figure 1. BDO downstream potential flow chart]]

The current market demand of BDO is being supplemented by several global chemical companies. These companies include BASF, BioAmber, Purac, Myriant, DSM, Mitsubishi Chemical, Roquette, and OPXBIO. The market shares of these companies were not available for this product; however, with the consistent growth of the BDO market our team feels that the market is not saturated or impenetrable. The current market price of BDO fluctuates between $3.06 and $3.31 per kg for US-made products [4]. These prices correlate to a nearly 7 billion dollar industry.

===Process alternatives===
1,4-butanediol is traditionally made from petroleum-derived feedstocks in a variety of processes [5]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Several companies are currently implementing bio-routes of producing butanediol. Genomatica is using a bioengineered microorganism to convert sugar feedstocks directly to BDO via fermentation [6], but most companies are instead using microorganisms to convert sugar to succinic acid. The bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, which is the path that most are choosing, although research is being conducted on alternative pathways [7].

==Process overview==
The newly proposed plant can be divided into four stages: pre-reactor, reactor, post-reactor and distillation. Each section is an integral part to the overall process and demands close attention. See the complete process flow diagram in Figure 2.

[[File:PFD.JPG|center|frame|Figure 2. Process flow diagram]]

===Pre-reactor===
This chemical process begins with two feedstocks: hydrogen gas and bio-succinic acid. The hydrogen gas will be obtained from a pipeline at 150 atm and will be used in molar excess inside the reactor. The bio-succinic acid will be purchased by Myriant Corporation which is located near the planned plant site. The pricing for this feedstock is approximately $2.12 per kg. The plant will require 63,000 metric tonnes of bio-succinic acid per year to meet the proposed plant capacity. First the bio-succinic acid feed is pumped up to 150 atm to match the hydrogen gas feed, and then it is mixed with the hydrogen gas prior to being sent into heat exchanger E-101 for heating. The heat exchanger brings the two feeds up to 110oC and sends them to the jacketed packed bed reactor.

===Reactor===
The hydrogenation reaction occurs inside of the reactor thanks to the packed catalyst bed. The catalyst used is 0.4% Fe, 1.9% Na, 2.66% Ag, 2.66% Pd, 10.0% Re on 1.5mm carbon support. With this catalyst, BDO is produced with over 90% selectivity and minimal side reactions of THF and GBL [8]. The reaction has an operating pressure of 2000-4000 psi and internal reactor temperature of 165°C. This temperature allows for about 99.7% conversion of succinic acid [8]. Due to the exothermic nature of the reaction, a cooling jacket is required which utilizes downstream cold streams to cool the internal bed to maintain the desired reaction temperature.

===Post-reactor===
The effluent of the reactor is sent back to E-101 as the hot stream. After exiting E-101, the reactor product stream is sent to a secondary exchanger, E-102, where utility cooling water is used to reduce the temperature to an acceptable temperature prior to sending it to a pressure let-down valve. At this point the pressure of the stream is taken from 150 atm to 1 atm. This large pressure drop allows for the stream to split into its vapor and liquid portions in a gas-liquid separator. The vapor stream of the gas liquid separator is primarily hydrogen gas and sent to a flare for disposal. The liquid effluent is at approximately 45oC leaving the separator and is therefore pumped to the reactor jacket for the reaction cooling mentioned previously. After running through the reactor jacket, the stream enters the separation processes.

===Distillation===
The first distillation column, T-101, is a 10 stage column whose primary purpose is separating the THF from the product feed. Due to THF’s lower boiling point, the byproduct comes off of the top of the column with mostly water. This distillate is sent to the plant's THF waste storage tank that has the capacity of two weeks. The bottoms of the column is sent to the subsequent distillation column that separates the BDO from the GBL and water. The relatively close boiling points of BDO and GBL, 235oC and 204oC, respectively, create a difficult separation that requires a 15 stage column. The distillate of the column is approximately 23% GBL with balance water. This stream is sent to a storage tank with similar sizing parameters as the THF storage tank. The bottom stream is the final 99.5wt% BDO product. This stream is sent to the final product tank, S-104. Depending on our customer demands and the plant location we have the ability to barge, rail or pipe our product to its final destination. Due to low purity of the byproducts, future iterations are needed to optimize either purifying byproducts or selling impure byproducts. There is definitely an available market for these byproducts that should be researched more extensively to increase profit. A detailed description of the equipment from the PFD can be found in Appendix C, in addition to sizing specifications and purpose of equipment.

===Mass and energy balances===
Using an Aspen HYSYS simulation we were able to record the material and energy streams going in and out of the process system. Mass and energy balances are provided Appendix D where each inlet and outlet stream is described and quantified. As expected, the material and energy totals for the inlet and outlet streams add together to equal 0. This proves that our system is mathematically prudent and thermodynamically feasible. The total mass flow of the system is 15,639 kg/h and the total energy in and out of the system is 1.41e8 kJ/h.

===HYSYS simulation===
The HYSYS simulation was performed using the NRTL ideal fluid package. After using AspenPlus to verify that the HYSYS package had the appropriate vapor-liquid equilibrium information between THF and water, and between GBL and water, we concluded it was feasible to proceed with that fluid package. The simulation consists of a reactor, a gas-liquid separator, 2 pumps, 3 heaters, a valve, and 2 distillation columns (see Figure 2). The simulation successfully converted the succinic acid feed into the desired products. Also, the combination of the two distillation columns was able to effectively separate the BDO to obtain a 99.5% pure product with 99.5% recovery. In addition, a set was made between the energy required to heat stream 12 and the energy required to cool the reactor so that these values were made equal. Lastly, the condenser and reboiler duties were used in four heat exchangers in order to determine the appropriate size of this equipment as well as the necessary utility flow rates.

==Health and safety==
===Chemical properties===
Inherent to this process are a number of toxic chemicals. Table 1 summarizes the important safety data including hazard type, odor, color, and exposure limits.

As shown in the above table, the chemicals that this facility will be dealing with will be relatively mild and non-life threatening. Regardless of their perceived threat, chemicals should always be handled with care especially when they are at high temperatures and pressures.

===Safety procedures===

'''Fire'''. There are many flammable materials that will be included in this process; therefore, fire safety is imperative for all employees. There are countless possible causes of ignition and care should be taken while handling any flammable material whether in the lab or in the field.

In case a fire is present on, the following protocol should be implemented:

* Small fire: Use DRY chemical powder.
* Large fire: Use alcohol foam, water spray, or fog.
* Call for backup if unable to control.
* Immediately contact supervisor and emergency personnel on site.
* Evacuate to safe distance in case of fires around any hazardous materials or pressure vessels.

'''Spills'''. Process chemical spills will eventually occur in a plant of this scale. Small spills are likely to occur in a laboratory setting. Large spills could be a result of loss of containment in the system. We must ensure that all personnel are aware of proper spill mitigation protocol.

* Small spill: Dilute with water and mop or absorb with inert dry material. Dispose of in proper receptacle.
* Large spill: Keep away from sources of ignition and heat. Prevent rundown to any drains or sewers. Call for assistance on disposal. Absorb material with DRY earth or other non-combustible materials.
* If spill is due to a loss of containment in the system, quickly consult the PLC and shut any valves to prevent further loss.

'''Exposure'''. We must ensure that our employees are aware of the possible toxicity levels of each substance and how to handle exposure. The chemicals that are being used in this process are known chemical irritants to the eyes, skin, and throat. Safety measures must be in place to acknowledge this hazard. Due to the possibility of high pressure releases, we will have 2-minute emergency oxygen masks placed strategically throughout the plant to ensure the safety of any operator in the presence of a large release.

If exposed to the process chemicals, find nearest eye wash station or safety shower immediately and flush exposed skin for at least 15 minutes. Remove any contaminated clothing. Seek medical attention immediately.

'''Storage'''. Store chemicals in segregated and approved areas. Any closed containers for laboratory purposes should be placed in cool, well-ventilated areas.

==Economics==
===Equipment costing===
The calculated capital costs from Aspen Economic Analyzer are reported in Table 2 for all process equipment. The size of the reactor was calculated from the liquid hourly space velocity given in the 2011 ISP patent [8] and a void fraction estimate of 0.4. Storage tanks were sized to contain up to two continuous weeks of material. The number of distillation trays in each tower and the flow rates through pumps, vessels, and the flare were calculated in HYSYS. Heat exchange areas were given in Aspen Energy Analyzer or from HYSYS.

In addition to the above equipment, our plant will require an ion exchanger to produce deionized process water from the municipal water. This is estimated to cost $42,000 in capital cost.

===Cash flow analysis===
Summarizing the important takeaways from the economic analysis, this process will return a revenue of 144 MM$ annually. Offset by production costs, the yearly cash flow is approximately 2.7 MM$, except for in the years in which the catalyst must be reinstalled (approximately every 5 years). At a cost of 2.5 MM$, the cash flows in those years decrease to approximately 0.2 MM$. This analysis assumes the plant will take 2 years to construct, and will operate at 50% in its first year. Furthermore, an interest rate of 10% was assumed with a tax rate of 38% (the maximum for corporate gains taxes). Using the 7-year MACRS depreciation method, the 20 year NPV for the project is 4.3 MM$. With an IRR of 15.1%, which is greater than the assumed interest rate, this project looks to be profitable. Further optimization techniques should be used in future iterations to further increase profitability. See Tables 3 and 4 for key economic information.

===Sensitivity analysis===
As seen in Figure 3, the economic evaluation of this process is influenced the most by changes in the sales price and feed cost. A 20% increase in sales price will result in an approximate 120 MM$ increase in NPV whereas a decrease of the same percentage will result in over a 120 MM$ decrease in NPV. Inversely, a 20% increase in feed cost will result in a 115 MM$ decrease in NPV and a 20% decrease in feed cost will result in a 60 MM$ increase in NPV.

To alleviate the risk associated with feed price, the team researched the price forecasting of bio-succinic acid. Figure 4 provides the bio-succinic acid price over the six years between 2006 and 2012. The price of bio-succinic, shown by the blue line, has remained relatively stable over this time period. This price history can be compared to adipic acid, the green line, which is a common petrochemical precursor for BDO production. Adipic acid as shown has had large fluctuations in price that result in unstable cash flows and uncertainty from shareholders. Thankfully, the stability of bio-succinic acid is a good sign that this process has a huge potential to be profitable especially if the demand for BDO continues to rise as projected.

==Discussion==
As described previously, the Davy process was selected as the most promising process of BDO production. The modified Davy process involves the hydrogenation of bio-succinicic acid with a Pa,Ag,Re catalyst and hydrogen gas. This process has many advantages, one being that it has mature technology that has been improved over the last 20 years. Additionally, the conversion to of succinic acid is virtually complete. Finally, overall plant yields can reach as high as 94 mol%.
As shown in Appendix B, streams ahead of the pressure valve (PRV-101) are at approximately 1.51e4 kPa, and streams after the pressure valve are between 100 and 450 kPa. Furthermore, operating temperatures do not exceed 200°C, including safety factors. These operating conditions contribute to the feasibility of the process, as all the components can be designed with reasonable dimensions (wall thickness, cap type, etc.).

Of particular interest are the large costs of the reactor and pump P-101. The reactor costs nearly 2 MM$ because it has a moderate size with a liquid volume of 16.7 m3, and it operates at 150 atm, which requires a strong stainless steel shell for safety purposes. Pump P-101 has such a large capital cost because it is a centrifugal multistage pump that also needs to be made of stainless steel to withstand pressuring the succinic acid feed to 150 atm.

Financial indicators for the proposed plant suggest that it will be moderately profitable, and additional optimization should be performed before making the capital investment. There is a fair amount of risk associated with the implementation of this production facility, and the return at this juncture may not justify the risk.

The process design and simulation in HYSYS has relied on several key assumptions, which are cause for certain limitations to the results. First, the conversions and selectivity of the catalyst, while taken from literature sources, are assumed to be true. Furthermore, the assumption of negligible side reactions and products was made. It is possible that small waste products in the form of succinates also form in the reactor. Therefore, the main limitation of this model is generally due to reaction specifications.

There are certain safety concerns that go along with the proposed process. First, there are many pipes and vessels that will be at a pressure of approximately 150 atm. Extra insulation and protection must be applied to the piping that contains highly pressurized fluids, to prevent operator injury. Furthermore, the PFR is at a slight risk for runaway reactions due to the exothermic nature of the reaction. The temperature of the reactor must always be monitored by an operator, and the jacket cooling system requires a backup system as well. A benefit of this process is that there are no toxic or severely hazardous components in the process. Additionally, there are no instances of temperature greater than 200°C.

The process design will be fitted with instrumentation and controls to ensure stable operation. These controls, including sensors and valves, minimize potential damage to components due to variation in plant conditions, as well as optimizing the overall performance. For example, the piping entering the tower will be fitted with a control loop. In the direction of flow, a sensing instrument first detects the pressure of the fluid, and then sends a signal to the controller. If the pressure is not within the operating limits, the actuator is signaled to close or open a control valve which is located farther down the stream.

==Conclusion==
The Evanston Chemical Engineering Division suggests a process that produces 45,000 tonnes/year of 99.5 wt% 1,4-butandeiol to enter the market with an appropriate market share. The feasibility of producing BDO as a significant process was investigated. A wide range of BDO production processes were researched, with a modified Davy process being identified as having the most potential. Using a Pa,Ag,Re catalyst on carbon support, this process converts bio-succinic acid to BDO with approximately 94% conversion. This process was designed in Aspen HYSYS, and economic analysis was conducted in Aspen Economic Analyzer. Total capital costs of the project are 12.2 MM$, with a simple payback period of 5.2 years. Total operational costs annually are 139.7 MM$. The process design was successful, with the capability of producing the desired production of BDO.

==Recommendations==
Given the moderate profitability of this process design, it is recommended that Evanston Chemicals explores further optimization techniques to increase the profitability of this process. This includes investigating sales of the γ-butyrolactone byproduct, recycling process water, and further optimizing utility streams for the distillation tower.

Second, we would like to investigate recycling the 2300 kg/h of water produced in the reaction. Our succinic acid enters the reactor as a 50 wt% solution in water, so we should look into replacing some of this with the product water. Not only will this decrease our water bill, but it will also lower the cost of ion exchange.

==References==
# Nexant.''Is Bio-Butanediol Here to Stay?'' White Plains, NY: ChemSystems Products; 2012.
# De Guzman D. Chemical industry awaits for bio-succinic acid potential. ICIS. Available at: http://www.icis.com/resources/news/2012/01/30/9527521/chemical-industry-awaits-for-bio-succinic-acid-potential/. Accessed January 24, 2014.
# Australian Government: Department of Health. 1,4-butanediol factsheet. National Industrial Chemicals Notification and Assessment Scheme. Available at: http://www.nicnas.gov.au/communications/publications/information-sheets/existing-chemical-info-sheets/other-information-sheets. Accessed January 24, 2014.
# TecnonOrbiChem. Chem-net facts: 1,4-butanediol. TecnonOrbiChem. Available at: http://www.orbichem.com/userfiles/CNF%20Samples/bdo_13_11.pdf. Accessed January 23, 2014.
# Nexant. 1,4-butanediol/tetrahydrofuran (BDO/THF). ChemSystems. Available at: http://www.chemsystems.com/about/cs/news/items/ PERP2012_3_BDO_THF.cfm. Accessed February 6, 2014.
# Burk MJ, Van Dien SJ, Burgard AP, inventors; Genomatica, Inc., assignee. Compositions and methods for the biosynthesis of 1,4-butanediol and its precursors. US patent 8,067,214. Nov. 29, 2011.
# Chung S-H, Kim M-S, Eom H-H, Lee K-Y. Catalytic hydrogenation of bio-based succinic acid for the production of 1,4-butanediol through the indirect pathway. AIChE. Available at: https://aiche.confex.com/aiche/2013/webprogram/Paper327470.html. Accessed January 23, 2014.
# Bhattacharyya A, Manila MD, inventors; ISP Investments Inc., assignee. Catalysts for maleic acid hydrogenation to 1,4-Butanediol. US patent 7,935,834 B2. May 3, 2011.

Design S2

2014-03-15T05:12:56Z

Karetstik: /* Process overview */

Title: Production of 1,4-butanediol

Authors: Nick Pinkerton, Karen Schmidt, and James Xamplas

Date Presented: March 14, 2014

==Introduction==
1,4-butanediol (BDO) is traditionally made from petroleum-derived feedstocks in a variety of processes such as the Reppe (acetylene-based), Mitsubishi (butadiene-based), and Davy (maleic acid-based) processes [1]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, BDO [1]. It is this process that Team S2Kool4Skool has chosen to develop for a new bio-butanediol plant, because the Davy method is mature and requires no new innovations, and because an appropriate feedstock of bio-succinic acid is now available. The plant will be located in East Carroll Parish, Louisiana. This county is also home to Myriant; located in Lake Providence, they are the largest domestic provider of bio-succinic acid [2]. Furthermore, Lake Providence is conveniently located on the Mississippi River, which will allow for affordable transportation of our bio-based butanediol product. The intent of this project is to produce 45,000 metric tonnes of 99.5 wt% 1,4-butanediol per year in a new plant in Lake Providence, LA. The plant will run 24 hours per day for 350 days out of the year, allowing approximately two weeks for a maintenance shutdown.

As there are several techniques for producing 1,4 butanediol in industry, the first step was to determine a synthesis path. Based on the chosen path, reaction kinetics, and required production rate of the process, a reactor system was then designed. Next, the process was designed to deliver the reactants to the reactor at the proper operating conditions, and the separations, purification, and waste management steps were designed. Cost estimates were made using costing software and hand calculations. Finally, the process was iterated and optimized to reduce costs.

==Background==
===General information===
BDO is an organic chemical with the molecular formula <math>C_4H_{10}O_2</math>. It is also a diol with its two hydroxyl groups located at the terminal carbons. BDO has a boiling point of 235 degrees C and is therefore a colorless liquid at standard temperatures and pressures [3].

There are many precursors that petrochemical synthesis of BDO uses. The commonality between all of the precursor acids is that they are hydrogenatable. In replacement of one of these petrochemical precursors, our team has been tasked with the challenge of deriving BDO from the bio-based precursor succinic acid. This catalyzed reaction will take place in the presence of hydrogen as the hydrogenating component shown below:

<math>C_4H_6O_4 + 4H_2 = C_4H_{10}O_2 + 2H_2O</math>

As described in the above reaction, there will need to be at least 4:1 stoichiometric ratio of hydrogen gas to succinic acid. Two moles of water will also be produced along with each mole of BDO. This reaction is exothermic, which requires the reactor to be continuously cooled to maintain our reactor temperature. There are also side products that are produced which include tetrahydrofuran (THF) and γ-butyrolactone (GBL); however, thanks to catalyst selectivity these byproducts are produced in small quantities.

===Market analysis===
Butanediol has a quickly expanding market due to new technological evolutions and its growing use as a chemical intermediary in advanced materials. With biological routes being optimized, the potential of biomass-derived chemicals is tremendous. The global demand of BDO was estimated at 1.5 million metric tons in 2011 and is projected to grow at an annual rate of 4.5% for the next several years [1]. Unlike other chemical products, BDO’s profitability and attractiveness to producers lies in its downstream potential. Figure 1 below demonstrates several potential downstream products that can be directly or indirectly synthesized from BDO. The largest of these contributors include THF and GBL.

[[File:BioButanediol_Downstream.JPG|center|frame|Figure 1. BDO downstream potential flow chart]]

The current market demand of BDO is being supplemented by several global chemical companies. These companies include BASF, BioAmber, Purac, Myriant, DSM, Mitsubishi Chemical, Roquette, and OPXBIO. The market shares of these companies were not available for this product; however, with the consistent growth of the BDO market our team feels that the market is not saturated or impenetrable. The current market price of BDO fluctuates between $3.06 and $3.31 per kg for US-made products [4]. These prices correlate to a nearly 7 billion dollar industry.

===Process alternatives===
1,4-butanediol is traditionally made from petroleum-derived feedstocks in a variety of processes [5]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Several companies are currently implementing bio-routes of producing butanediol. Genomatica is using a bioengineered microorganism to convert sugar feedstocks directly to BDO via fermentation [6], but most companies are instead using microorganisms to convert sugar to succinic acid. The bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, which is the path that most are choosing, although research is being conducted on alternative pathways [7].

==Process overview==
The newly proposed plant can be divided into four stages: pre-reactor, reactor, post-reactor and distillation. Each section is an integral part to the overall process and demands close attention. The process flow diagram (Figure 2) and stream table (Appendix B) provide more detailed information.

[[File:PFD.JPG|center|frame|Figure 2. Process flow diagram]]

===Pre-reactor===
This chemical process begins with two feedstocks: hydrogen gas and bio-succinic acid. The hydrogen gas will be obtained from a pipeline at 150 atm and will be used in molar excess inside the reactor. The bio-succinic acid will be purchased by Myriant Corporation which is located near the planned plant site. The pricing for this feedstock is approximately $2.12 per kg. The plant will require 63,000 metric tonnes of bio-succinic acid per year to meet the proposed plant capacity. First the bio-succinic acid feed is pumped up to 150 atm to match the hydrogen gas feed, and then it is mixed with the hydrogen gas prior to being sent into heat exchanger E-101 for heating. The heat exchanger brings the two feeds up to 110oC and sends them to the jacketed packed bed reactor.

===Reactor===
The hydrogenation reaction occurs inside of the reactor thanks to the packed catalyst bed. The catalyst used is 0.4% Fe, 1.9% Na, 2.66% Ag, 2.66% Pd, 10.0% Re on 1.5mm carbon support. With this catalyst, BDO is produced with over 90% selectivity and minimal side reactions of THF and GBL [8]. The reaction has an operating pressure of 2000-4000 psi and internal reactor temperature of 165°C. This temperature allows for about 99.7% conversion of succinic acid [8]. Due to the exothermic nature of the reaction, a cooling jacket is required which utilizes downstream cold streams to cool the internal bed to maintain the desired reaction temperature.

===Post-reactor===
The effluent of the reactor is sent back to E-101 as the hot stream. After exiting E-101, the reactor product stream is sent to a secondary exchanger, E-102, where utility cooling water is used to reduce the temperature to an acceptable temperature prior to sending it to a pressure let-down valve. At this point the pressure of the stream is taken from 150 atm to 1 atm. This large pressure drop allows for the stream to split into its vapor and liquid portions in a gas-liquid separator. The vapor stream of the gas liquid separator is primarily hydrogen gas and sent to a flare for disposal. The liquid effluent is at approximately 45oC leaving the separator and is therefore pumped to the reactor jacket for the reaction cooling mentioned previously. After running through the reactor jacket, the stream enters the separation processes.

===Distillation===
The first distillation column, T-101, is a 10 stage column whose primary purpose is separating the THF from the product feed. Due to THF’s lower boiling point, the byproduct comes off of the top of the column with mostly water. This distillate is sent to the plant's THF waste storage tank that has the capacity of two weeks. The bottoms of the column is sent to the subsequent distillation column that separates the BDO from the GBL and water. The relatively close boiling points of BDO and GBL, 235oC and 204oC, respectively, create a difficult separation that requires a 15 stage column. The distillate of the column is approximately 23% GBL with balance water. This stream is sent to a storage tank with similar sizing parameters as the THF storage tank. The bottom stream is the final 99.5wt% BDO product. This stream is sent to the final product tank, S-104. Depending on our customer demands and the plant location we have the ability to barge, rail or pipe our product to its final destination. Due to low purity of the byproducts, future iterations are needed to optimize either purifying byproducts or selling impure byproducts. There is definitely an available market for these byproducts that should be researched more extensively to increase profit. A detailed description of the equipment from the PFD can be found in Appendix C, in addition to sizing specifications and purpose of equipment.

===Mass and energy balances===
Using an Aspen HYSYS simulation we were able to record the material and energy streams going in and out of the process system. Mass and energy balances are provided Appendix D where each inlet and outlet stream is described and quantified. As expected, the material and energy totals for the inlet and outlet streams add together to equal 0. This proves that our system is mathematically prudent and thermodynamically feasible. The total mass flow of the system is 15,639 kg/h and the total energy in and out of the system is 1.41e8 kJ/h.

===HYSYS simulation===
The HYSYS simulation was performed using the NRTL ideal fluid package. After using AspenPlus to verify that the HYSYS package had the appropriate vapor-liquid equilibrium information between THF and water, and between GBL and water, we concluded it was feasible to proceed with that fluid package. The simulation consists of a reactor, a gas-liquid separator, 2 pumps, 3 heaters, a valve, and 2 distillation columns (see Figure 2). The simulation successfully converted the succinic acid feed into the desired products. Also, the combination of the two distillation columns was able to effectively separate the BDO to obtain a 99.5% pure product with 99.5% recovery. In addition, a set was made between the energy required to heat stream 12 and the energy required to cool the reactor so that these values were made equal. Lastly, the condenser and reboiler duties were used in four heat exchangers in order to determine the appropriate size of this equipment as well as the necessary utility flow rates.

==Health and safety==
===Chemical properties===
Inherent to this process are a number of toxic chemicals. Table 1 summarizes the important safety data including hazard type, odor, color, and exposure limits.

As shown in the above table, the chemicals that this facility will be dealing with will be relatively mild and non-life threatening. Regardless of their perceived threat, chemicals should always be handled with care especially when they are at high temperatures and pressures.

===Safety procedures===

'''Fire'''. There are many flammable materials that will be included in this process; therefore, fire safety is imperative for all employees. There are countless possible causes of ignition and care should be taken while handling any flammable material whether in the lab or in the field.

In case a fire is present on, the following protocol should be implemented:

* Small fire: Use DRY chemical powder.
* Large fire: Use alcohol foam, water spray, or fog.
* Call for backup if unable to control.
* Immediately contact supervisor and emergency personnel on site.
* Evacuate to safe distance in case of fires around any hazardous materials or pressure vessels.

'''Spills'''. Process chemical spills will eventually occur in a plant of this scale. Small spills are likely to occur in a laboratory setting. Large spills could be a result of loss of containment in the system. We must ensure that all personnel are aware of proper spill mitigation protocol.

* Small spill: Dilute with water and mop or absorb with inert dry material. Dispose of in proper receptacle.
* Large spill: Keep away from sources of ignition and heat. Prevent rundown to any drains or sewers. Call for assistance on disposal. Absorb material with DRY earth or other non-combustible materials.
* If spill is due to a loss of containment in the system, quickly consult the PLC and shut any valves to prevent further loss.

'''Exposure'''. We must ensure that our employees are aware of the possible toxicity levels of each substance and how to handle exposure. The chemicals that are being used in this process are known chemical irritants to the eyes, skin, and throat. Safety measures must be in place to acknowledge this hazard. Due to the possibility of high pressure releases, we will have 2-minute emergency oxygen masks placed strategically throughout the plant to ensure the safety of any operator in the presence of a large release.

If exposed to the process chemicals, find nearest eye wash station or safety shower immediately and flush exposed skin for at least 15 minutes. Remove any contaminated clothing. Seek medical attention immediately.

'''Storage'''. Store chemicals in segregated and approved areas. Any closed containers for laboratory purposes should be placed in cool, well-ventilated areas.

==Economics==
===Equipment costing===
The calculated capital costs from Aspen Economic Analyzer are reported in Table 2 for all process equipment. The size of the reactor was calculated from the liquid hourly space velocity given in the 2011 ISP patent [8] and a void fraction estimate of 0.4. Storage tanks were sized to contain up to two continuous weeks of material. The number of distillation trays in each tower and the flow rates through pumps, vessels, and the flare were calculated in HYSYS. Heat exchange areas were given in Aspen Energy Analyzer or from HYSYS.

In addition to the above equipment, our plant will require an ion exchanger to produce deionized process water from the municipal water. This is estimated to cost $42,000 in capital cost.

===Cash flow analysis===
Summarizing the important takeaways from the economic analysis, this process will return a revenue of 144 MM$ annually. Offset by production costs, the yearly cash flow is approximately 2.7 MM$, except for in the years in which the catalyst must be reinstalled (approximately every 5 years). At a cost of 2.5 MM$, the cash flows in those years decrease to approximately 0.2 MM$. This analysis assumes the plant will take 2 years to construct, and will operate at 50% in its first year. Furthermore, an interest rate of 10% was assumed with a tax rate of 38% (the maximum for corporate gains taxes). Using the 7-year MACRS depreciation method, the 20 year NPV for the project is 4.3 MM$. With an IRR of 15.1%, which is greater than the assumed interest rate, this project looks to be profitable. Further optimization techniques should be used in future iterations to further increase profitability. See Tables 3 and 4 for key economic information.

===Sensitivity analysis===
As seen in Figure 3, the economic evaluation of this process is influenced the most by changes in the sales price and feed cost. A 20% increase in sales price will result in an approximate 120 MM$ increase in NPV whereas a decrease of the same percentage will result in over a 120 MM$ decrease in NPV. Inversely, a 20% increase in feed cost will result in a 115 MM$ decrease in NPV and a 20% decrease in feed cost will result in a 60 MM$ increase in NPV.

To alleviate the risk associated with feed price, the team researched the price forecasting of bio-succinic acid. Figure 4 provides the bio-succinic acid price over the six years between 2006 and 2012. The price of bio-succinic, shown by the blue line, has remained relatively stable over this time period. This price history can be compared to adipic acid, the green line, which is a common petrochemical precursor for BDO production. Adipic acid as shown has had large fluctuations in price that result in unstable cash flows and uncertainty from shareholders. Thankfully, the stability of bio-succinic acid is a good sign that this process has a huge potential to be profitable especially if the demand for BDO continues to rise as projected.

==Discussion==
As described previously, the Davy process was selected as the most promising process of BDO production. The modified Davy process involves the hydrogenation of bio-succinicic acid with a Pa,Ag,Re catalyst and hydrogen gas. This process has many advantages, one being that it has mature technology that has been improved over the last 20 years. Additionally, the conversion to of succinic acid is virtually complete. Finally, overall plant yields can reach as high as 94 mol%.
As shown in Appendix B, streams ahead of the pressure valve (PRV-101) are at approximately 1.51e4 kPa, and streams after the pressure valve are between 100 and 450 kPa. Furthermore, operating temperatures do not exceed 200°C, including safety factors. These operating conditions contribute to the feasibility of the process, as all the components can be designed with reasonable dimensions (wall thickness, cap type, etc.).

Of particular interest are the large costs of the reactor and pump P-101. The reactor costs nearly 2 MM$ because it has a moderate size with a liquid volume of 16.7 m3, and it operates at 150 atm, which requires a strong stainless steel shell for safety purposes. Pump P-101 has such a large capital cost because it is a centrifugal multistage pump that also needs to be made of stainless steel to withstand pressuring the succinic acid feed to 150 atm.

Financial indicators for the proposed plant suggest that it will be moderately profitable, and additional optimization should be performed before making the capital investment. There is a fair amount of risk associated with the implementation of this production facility, and the return at this juncture may not justify the risk.

The process design and simulation in HYSYS has relied on several key assumptions, which are cause for certain limitations to the results. First, the conversions and selectivity of the catalyst, while taken from literature sources, are assumed to be true. Furthermore, the assumption of negligible side reactions and products was made. It is possible that small waste products in the form of succinates also form in the reactor. Therefore, the main limitation of this model is generally due to reaction specifications.

There are certain safety concerns that go along with the proposed process. First, there are many pipes and vessels that will be at a pressure of approximately 150 atm. Extra insulation and protection must be applied to the piping that contains highly pressurized fluids, to prevent operator injury. Furthermore, the PFR is at a slight risk for runaway reactions due to the exothermic nature of the reaction. The temperature of the reactor must always be monitored by an operator, and the jacket cooling system requires a backup system as well. A benefit of this process is that there are no toxic or severely hazardous components in the process. Additionally, there are no instances of temperature greater than 200°C.

The process design will be fitted with instrumentation and controls to ensure stable operation. These controls, including sensors and valves, minimize potential damage to components due to variation in plant conditions, as well as optimizing the overall performance. For example, the piping entering the tower will be fitted with a control loop. In the direction of flow, a sensing instrument first detects the pressure of the fluid, and then sends a signal to the controller. If the pressure is not within the operating limits, the actuator is signaled to close or open a control valve which is located farther down the stream.

==Conclusion==
The Evanston Chemical Engineering Division suggests a process that produces 45,000 tonnes/year of 99.5 wt% 1,4-butandeiol to enter the market with an appropriate market share. The feasibility of producing BDO as a significant process was investigated. A wide range of BDO production processes were researched, with a modified Davy process being identified as having the most potential. Using a Pa,Ag,Re catalyst on carbon support, this process converts bio-succinic acid to BDO with approximately 94% conversion. This process was designed in Aspen HYSYS, and economic analysis was conducted in Aspen Economic Analyzer. Total capital costs of the project are 12.2 MM$, with a simple payback period of 5.2 years. Total operational costs annually are 139.7 MM$. The process design was successful, with the capability of producing the desired production of BDO.

==Recommendations==
Given the moderate profitability of this process design, it is recommended that Evanston Chemicals explores further optimization techniques to increase the profitability of this process. This includes investigating sales of the γ-butyrolactone byproduct, recycling process water, and further optimizing utility streams for the distillation tower.

Second, we would like to investigate recycling the 2300 kg/h of water produced in the reaction. Our succinic acid enters the reactor as a 50 wt% solution in water, so we should look into replacing some of this with the product water. Not only will this decrease our water bill, but it will also lower the cost of ion exchange.

==References==
# Nexant.''Is Bio-Butanediol Here to Stay?'' White Plains, NY: ChemSystems Products; 2012.
# De Guzman D. Chemical industry awaits for bio-succinic acid potential. ICIS. Available at: http://www.icis.com/resources/news/2012/01/30/9527521/chemical-industry-awaits-for-bio-succinic-acid-potential/. Accessed January 24, 2014.
# Australian Government: Department of Health. 1,4-butanediol factsheet. National Industrial Chemicals Notification and Assessment Scheme. Available at: http://www.nicnas.gov.au/communications/publications/information-sheets/existing-chemical-info-sheets/other-information-sheets. Accessed January 24, 2014.
# TecnonOrbiChem. Chem-net facts: 1,4-butanediol. TecnonOrbiChem. Available at: http://www.orbichem.com/userfiles/CNF%20Samples/bdo_13_11.pdf. Accessed January 23, 2014.
# Nexant. 1,4-butanediol/tetrahydrofuran (BDO/THF). ChemSystems. Available at: http://www.chemsystems.com/about/cs/news/items/ PERP2012_3_BDO_THF.cfm. Accessed February 6, 2014.
# Burk MJ, Van Dien SJ, Burgard AP, inventors; Genomatica, Inc., assignee. Compositions and methods for the biosynthesis of 1,4-butanediol and its precursors. US patent 8,067,214. Nov. 29, 2011.
# Chung S-H, Kim M-S, Eom H-H, Lee K-Y. Catalytic hydrogenation of bio-based succinic acid for the production of 1,4-butanediol through the indirect pathway. AIChE. Available at: https://aiche.confex.com/aiche/2013/webprogram/Paper327470.html. Accessed January 23, 2014.
# Bhattacharyya A, Manila MD, inventors; ISP Investments Inc., assignee. Catalysts for maleic acid hydrogenation to 1,4-Butanediol. US patent 7,935,834 B2. May 3, 2011.

File:PFD.JPG

2014-03-15T05:11:27Z

Karetstik:

Design S2

2014-03-15T05:08:02Z

Karetstik: /* Market analysis */

Title: Production of 1,4-butanediol

Authors: Nick Pinkerton, Karen Schmidt, and James Xamplas

Date Presented: March 14, 2014

==Introduction==
1,4-butanediol (BDO) is traditionally made from petroleum-derived feedstocks in a variety of processes such as the Reppe (acetylene-based), Mitsubishi (butadiene-based), and Davy (maleic acid-based) processes [1]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, BDO [1]. It is this process that Team S2Kool4Skool has chosen to develop for a new bio-butanediol plant, because the Davy method is mature and requires no new innovations, and because an appropriate feedstock of bio-succinic acid is now available. The plant will be located in East Carroll Parish, Louisiana. This county is also home to Myriant; located in Lake Providence, they are the largest domestic provider of bio-succinic acid [2]. Furthermore, Lake Providence is conveniently located on the Mississippi River, which will allow for affordable transportation of our bio-based butanediol product. The intent of this project is to produce 45,000 metric tonnes of 99.5 wt% 1,4-butanediol per year in a new plant in Lake Providence, LA. The plant will run 24 hours per day for 350 days out of the year, allowing approximately two weeks for a maintenance shutdown.

As there are several techniques for producing 1,4 butanediol in industry, the first step was to determine a synthesis path. Based on the chosen path, reaction kinetics, and required production rate of the process, a reactor system was then designed. Next, the process was designed to deliver the reactants to the reactor at the proper operating conditions, and the separations, purification, and waste management steps were designed. Cost estimates were made using costing software and hand calculations. Finally, the process was iterated and optimized to reduce costs.

==Background==
===General information===
BDO is an organic chemical with the molecular formula <math>C_4H_{10}O_2</math>. It is also a diol with its two hydroxyl groups located at the terminal carbons. BDO has a boiling point of 235 degrees C and is therefore a colorless liquid at standard temperatures and pressures [3].

There are many precursors that petrochemical synthesis of BDO uses. The commonality between all of the precursor acids is that they are hydrogenatable. In replacement of one of these petrochemical precursors, our team has been tasked with the challenge of deriving BDO from the bio-based precursor succinic acid. This catalyzed reaction will take place in the presence of hydrogen as the hydrogenating component shown below:

<math>C_4H_6O_4 + 4H_2 = C_4H_{10}O_2 + 2H_2O</math>

As described in the above reaction, there will need to be at least 4:1 stoichiometric ratio of hydrogen gas to succinic acid. Two moles of water will also be produced along with each mole of BDO. This reaction is exothermic, which requires the reactor to be continuously cooled to maintain our reactor temperature. There are also side products that are produced which include tetrahydrofuran (THF) and γ-butyrolactone (GBL); however, thanks to catalyst selectivity these byproducts are produced in small quantities.

===Market analysis===
Butanediol has a quickly expanding market due to new technological evolutions and its growing use as a chemical intermediary in advanced materials. With biological routes being optimized, the potential of biomass-derived chemicals is tremendous. The global demand of BDO was estimated at 1.5 million metric tons in 2011 and is projected to grow at an annual rate of 4.5% for the next several years [1]. Unlike other chemical products, BDO’s profitability and attractiveness to producers lies in its downstream potential. Figure 1 below demonstrates several potential downstream products that can be directly or indirectly synthesized from BDO. The largest of these contributors include THF and GBL.

[[File:BioButanediol_Downstream.JPG|center|frame|Figure 1. BDO downstream potential flow chart]]

The current market demand of BDO is being supplemented by several global chemical companies. These companies include BASF, BioAmber, Purac, Myriant, DSM, Mitsubishi Chemical, Roquette, and OPXBIO. The market shares of these companies were not available for this product; however, with the consistent growth of the BDO market our team feels that the market is not saturated or impenetrable. The current market price of BDO fluctuates between $3.06 and $3.31 per kg for US-made products [4]. These prices correlate to a nearly 7 billion dollar industry.

===Process alternatives===
1,4-butanediol is traditionally made from petroleum-derived feedstocks in a variety of processes [5]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Several companies are currently implementing bio-routes of producing butanediol. Genomatica is using a bioengineered microorganism to convert sugar feedstocks directly to BDO via fermentation [6], but most companies are instead using microorganisms to convert sugar to succinic acid. The bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, which is the path that most are choosing, although research is being conducted on alternative pathways [7].

==Process overview==
The newly proposed plant can be divided into four stages: pre-reactor, reactor, post-reactor and distillation. Each section is an integral part to the overall process and demands close attention. The process flow diagram (see Appendix A) and stream table (Appendix B) provide more detailed information.

===Pre-reactor===
This chemical process begins with two feedstocks: hydrogen gas and bio-succinic acid. The hydrogen gas will be obtained from a pipeline at 150 atm and will be used in molar excess inside the reactor. The bio-succinic acid will be purchased by Myriant Corporation which is located near the planned plant site. The pricing for this feedstock is approximately $2.12 per kg. The plant will require 63,000 metric tonnes of bio-succinic acid per year to meet the proposed plant capacity. First the bio-succinic acid feed is pumped up to 150 atm to match the hydrogen gas feed, and then it is mixed with the hydrogen gas prior to being sent into heat exchanger E-101 for heating. The heat exchanger brings the two feeds up to 110oC and sends them to the jacketed packed bed reactor.

===Reactor===
The hydrogenation reaction occurs inside of the reactor thanks to the packed catalyst bed. The catalyst used is 0.4% Fe, 1.9% Na, 2.66% Ag, 2.66% Pd, 10.0% Re on 1.5mm carbon support. With this catalyst, BDO is produced with over 90% selectivity and minimal side reactions of THF and GBL [8]. The reaction has an operating pressure of 2000-4000 psi and internal reactor temperature of 165°C. This temperature allows for about 99.7% conversion of succinic acid [8]. Due to the exothermic nature of the reaction, a cooling jacket is required which utilizes downstream cold streams to cool the internal bed to maintain the desired reaction temperature.

===Post-reactor===
The effluent of the reactor is sent back to E-101 as the hot stream. After exiting E-101, the reactor product stream is sent to a secondary exchanger, E-102, where utility cooling water is used to reduce the temperature to an acceptable temperature prior to sending it to a pressure let-down valve. At this point the pressure of the stream is taken from 150 atm to 1 atm. This large pressure drop allows for the stream to split into its vapor and liquid portions in a gas-liquid separator. The vapor stream of the gas liquid separator is primarily hydrogen gas and sent to a flare for disposal. The liquid effluent is at approximately 45oC leaving the separator and is therefore pumped to the reactor jacket for the reaction cooling mentioned previously. After running through the reactor jacket, the stream enters the separation processes.

===Distillation===
The first distillation column, T-101, is a 10 stage column whose primary purpose is separating the THF from the product feed. Due to THF’s lower boiling point, the byproduct comes off of the top of the column with mostly water. This distillate is sent to the plant's THF waste storage tank that has the capacity of two weeks. The bottoms of the column is sent to the subsequent distillation column that separates the BDO from the GBL and water. The relatively close boiling points of BDO and GBL, 235oC and 204oC, respectively, create a difficult separation that requires a 15 stage column. The distillate of the column is approximately 23% GBL with balance water. This stream is sent to a storage tank with similar sizing parameters as the THF storage tank. The bottom stream is the final 99.5wt% BDO product. This stream is sent to the final product tank, S-104. Depending on our customer demands and the plant location we have the ability to barge, rail or pipe our product to its final destination. Due to low purity of the byproducts, future iterations are needed to optimize either purifying byproducts or selling impure byproducts. There is definitely an available market for these byproducts that should be researched more extensively to increase profit. A detailed description of the equipment from the PFD can be found in Appendix C, in addition to sizing specifications and purpose of equipment.

===Mass and energy balances===
Using an Aspen HYSYS simulation we were able to record the material and energy streams going in and out of the process system. Mass and energy balances are provided Appendix D where each inlet and outlet stream is described and quantified. As expected, the material and energy totals for the inlet and outlet streams add together to equal 0. This proves that our system is mathematically prudent and thermodynamically feasible. The total mass flow of the system is 15,639 kg/h and the total energy in and out of the system is 1.41e8 kJ/h.

===HYSYS simulation===
The HYSYS simulation was performed using the NRTL ideal fluid package. After using AspenPlus to verify that the HYSYS package had the appropriate vapor-liquid equilibrium information between THF and water, and between GBL and water, we concluded it was feasible to proceed with that fluid package. The simulation consists of a reactor, a gas-liquid separator, 2 pumps, 3 heaters, a valve, and 2 distillation columns (see Figure 2). The simulation successfully converted the succinic acid feed into the desired products. Also, the combination of the two distillation columns was able to effectively separate the BDO to obtain a 99.5% pure product with 99.5% recovery. In addition, a set was made between the energy required to heat stream 12 and the energy required to cool the reactor so that these values were made equal. Lastly, the condenser and reboiler duties were used in four heat exchangers in order to determine the appropriate size of this equipment as well as the necessary utility flow rates.

==Health and safety==
===Chemical properties===
Inherent to this process are a number of toxic chemicals. Table 1 summarizes the important safety data including hazard type, odor, color, and exposure limits.

As shown in the above table, the chemicals that this facility will be dealing with will be relatively mild and non-life threatening. Regardless of their perceived threat, chemicals should always be handled with care especially when they are at high temperatures and pressures.

===Safety procedures===

'''Fire'''. There are many flammable materials that will be included in this process; therefore, fire safety is imperative for all employees. There are countless possible causes of ignition and care should be taken while handling any flammable material whether in the lab or in the field.

In case a fire is present on, the following protocol should be implemented:

* Small fire: Use DRY chemical powder.
* Large fire: Use alcohol foam, water spray, or fog.
* Call for backup if unable to control.
* Immediately contact supervisor and emergency personnel on site.
* Evacuate to safe distance in case of fires around any hazardous materials or pressure vessels.

'''Spills'''. Process chemical spills will eventually occur in a plant of this scale. Small spills are likely to occur in a laboratory setting. Large spills could be a result of loss of containment in the system. We must ensure that all personnel are aware of proper spill mitigation protocol.

* Small spill: Dilute with water and mop or absorb with inert dry material. Dispose of in proper receptacle.
* Large spill: Keep away from sources of ignition and heat. Prevent rundown to any drains or sewers. Call for assistance on disposal. Absorb material with DRY earth or other non-combustible materials.
* If spill is due to a loss of containment in the system, quickly consult the PLC and shut any valves to prevent further loss.

'''Exposure'''. We must ensure that our employees are aware of the possible toxicity levels of each substance and how to handle exposure. The chemicals that are being used in this process are known chemical irritants to the eyes, skin, and throat. Safety measures must be in place to acknowledge this hazard. Due to the possibility of high pressure releases, we will have 2-minute emergency oxygen masks placed strategically throughout the plant to ensure the safety of any operator in the presence of a large release.

If exposed to the process chemicals, find nearest eye wash station or safety shower immediately and flush exposed skin for at least 15 minutes. Remove any contaminated clothing. Seek medical attention immediately.

'''Storage'''. Store chemicals in segregated and approved areas. Any closed containers for laboratory purposes should be placed in cool, well-ventilated areas.

==Economics==
===Equipment costing===
The calculated capital costs from Aspen Economic Analyzer are reported in Table 2 for all process equipment. The size of the reactor was calculated from the liquid hourly space velocity given in the 2011 ISP patent [8] and a void fraction estimate of 0.4. Storage tanks were sized to contain up to two continuous weeks of material. The number of distillation trays in each tower and the flow rates through pumps, vessels, and the flare were calculated in HYSYS. Heat exchange areas were given in Aspen Energy Analyzer or from HYSYS.

In addition to the above equipment, our plant will require an ion exchanger to produce deionized process water from the municipal water. This is estimated to cost $42,000 in capital cost.

===Cash flow analysis===
Summarizing the important takeaways from the economic analysis, this process will return a revenue of 144 MM$ annually. Offset by production costs, the yearly cash flow is approximately 2.7 MM$, except for in the years in which the catalyst must be reinstalled (approximately every 5 years). At a cost of 2.5 MM$, the cash flows in those years decrease to approximately 0.2 MM$. This analysis assumes the plant will take 2 years to construct, and will operate at 50% in its first year. Furthermore, an interest rate of 10% was assumed with a tax rate of 38% (the maximum for corporate gains taxes). Using the 7-year MACRS depreciation method, the 20 year NPV for the project is 4.3 MM$. With an IRR of 15.1%, which is greater than the assumed interest rate, this project looks to be profitable. Further optimization techniques should be used in future iterations to further increase profitability. See Tables 3 and 4 for key economic information.

===Sensitivity analysis===
As seen in Figure 3, the economic evaluation of this process is influenced the most by changes in the sales price and feed cost. A 20% increase in sales price will result in an approximate 120 MM$ increase in NPV whereas a decrease of the same percentage will result in over a 120 MM$ decrease in NPV. Inversely, a 20% increase in feed cost will result in a 115 MM$ decrease in NPV and a 20% decrease in feed cost will result in a 60 MM$ increase in NPV.

To alleviate the risk associated with feed price, the team researched the price forecasting of bio-succinic acid. Figure 4 provides the bio-succinic acid price over the six years between 2006 and 2012. The price of bio-succinic, shown by the blue line, has remained relatively stable over this time period. This price history can be compared to adipic acid, the green line, which is a common petrochemical precursor for BDO production. Adipic acid as shown has had large fluctuations in price that result in unstable cash flows and uncertainty from shareholders. Thankfully, the stability of bio-succinic acid is a good sign that this process has a huge potential to be profitable especially if the demand for BDO continues to rise as projected.

==Discussion==
As described previously, the Davy process was selected as the most promising process of BDO production. The modified Davy process involves the hydrogenation of bio-succinicic acid with a Pa,Ag,Re catalyst and hydrogen gas. This process has many advantages, one being that it has mature technology that has been improved over the last 20 years. Additionally, the conversion to of succinic acid is virtually complete. Finally, overall plant yields can reach as high as 94 mol%.
As shown in Appendix B, streams ahead of the pressure valve (PRV-101) are at approximately 1.51e4 kPa, and streams after the pressure valve are between 100 and 450 kPa. Furthermore, operating temperatures do not exceed 200°C, including safety factors. These operating conditions contribute to the feasibility of the process, as all the components can be designed with reasonable dimensions (wall thickness, cap type, etc.).

Of particular interest are the large costs of the reactor and pump P-101. The reactor costs nearly 2 MM$ because it has a moderate size with a liquid volume of 16.7 m3, and it operates at 150 atm, which requires a strong stainless steel shell for safety purposes. Pump P-101 has such a large capital cost because it is a centrifugal multistage pump that also needs to be made of stainless steel to withstand pressuring the succinic acid feed to 150 atm.

Financial indicators for the proposed plant suggest that it will be moderately profitable, and additional optimization should be performed before making the capital investment. There is a fair amount of risk associated with the implementation of this production facility, and the return at this juncture may not justify the risk.

The process design and simulation in HYSYS has relied on several key assumptions, which are cause for certain limitations to the results. First, the conversions and selectivity of the catalyst, while taken from literature sources, are assumed to be true. Furthermore, the assumption of negligible side reactions and products was made. It is possible that small waste products in the form of succinates also form in the reactor. Therefore, the main limitation of this model is generally due to reaction specifications.

There are certain safety concerns that go along with the proposed process. First, there are many pipes and vessels that will be at a pressure of approximately 150 atm. Extra insulation and protection must be applied to the piping that contains highly pressurized fluids, to prevent operator injury. Furthermore, the PFR is at a slight risk for runaway reactions due to the exothermic nature of the reaction. The temperature of the reactor must always be monitored by an operator, and the jacket cooling system requires a backup system as well. A benefit of this process is that there are no toxic or severely hazardous components in the process. Additionally, there are no instances of temperature greater than 200°C.

The process design will be fitted with instrumentation and controls to ensure stable operation. These controls, including sensors and valves, minimize potential damage to components due to variation in plant conditions, as well as optimizing the overall performance. For example, the piping entering the tower will be fitted with a control loop. In the direction of flow, a sensing instrument first detects the pressure of the fluid, and then sends a signal to the controller. If the pressure is not within the operating limits, the actuator is signaled to close or open a control valve which is located farther down the stream.

==Conclusion==
The Evanston Chemical Engineering Division suggests a process that produces 45,000 tonnes/year of 99.5 wt% 1,4-butandeiol to enter the market with an appropriate market share. The feasibility of producing BDO as a significant process was investigated. A wide range of BDO production processes were researched, with a modified Davy process being identified as having the most potential. Using a Pa,Ag,Re catalyst on carbon support, this process converts bio-succinic acid to BDO with approximately 94% conversion. This process was designed in Aspen HYSYS, and economic analysis was conducted in Aspen Economic Analyzer. Total capital costs of the project are 12.2 MM$, with a simple payback period of 5.2 years. Total operational costs annually are 139.7 MM$. The process design was successful, with the capability of producing the desired production of BDO.

==Recommendations==
Given the moderate profitability of this process design, it is recommended that Evanston Chemicals explores further optimization techniques to increase the profitability of this process. This includes investigating sales of the γ-butyrolactone byproduct, recycling process water, and further optimizing utility streams for the distillation tower.

Second, we would like to investigate recycling the 2300 kg/h of water produced in the reaction. Our succinic acid enters the reactor as a 50 wt% solution in water, so we should look into replacing some of this with the product water. Not only will this decrease our water bill, but it will also lower the cost of ion exchange.

==References==
# Nexant.''Is Bio-Butanediol Here to Stay?'' White Plains, NY: ChemSystems Products; 2012.
# De Guzman D. Chemical industry awaits for bio-succinic acid potential. ICIS. Available at: http://www.icis.com/resources/news/2012/01/30/9527521/chemical-industry-awaits-for-bio-succinic-acid-potential/. Accessed January 24, 2014.
# Australian Government: Department of Health. 1,4-butanediol factsheet. National Industrial Chemicals Notification and Assessment Scheme. Available at: http://www.nicnas.gov.au/communications/publications/information-sheets/existing-chemical-info-sheets/other-information-sheets. Accessed January 24, 2014.
# TecnonOrbiChem. Chem-net facts: 1,4-butanediol. TecnonOrbiChem. Available at: http://www.orbichem.com/userfiles/CNF%20Samples/bdo_13_11.pdf. Accessed January 23, 2014.
# Nexant. 1,4-butanediol/tetrahydrofuran (BDO/THF). ChemSystems. Available at: http://www.chemsystems.com/about/cs/news/items/ PERP2012_3_BDO_THF.cfm. Accessed February 6, 2014.
# Burk MJ, Van Dien SJ, Burgard AP, inventors; Genomatica, Inc., assignee. Compositions and methods for the biosynthesis of 1,4-butanediol and its precursors. US patent 8,067,214. Nov. 29, 2011.
# Chung S-H, Kim M-S, Eom H-H, Lee K-Y. Catalytic hydrogenation of bio-based succinic acid for the production of 1,4-butanediol through the indirect pathway. AIChE. Available at: https://aiche.confex.com/aiche/2013/webprogram/Paper327470.html. Accessed January 23, 2014.
# Bhattacharyya A, Manila MD, inventors; ISP Investments Inc., assignee. Catalysts for maleic acid hydrogenation to 1,4-Butanediol. US patent 7,935,834 B2. May 3, 2011.

Design S2

2014-03-15T05:05:35Z

Karetstik: /* Market analysis */

Title: Production of 1,4-butanediol

Authors: Nick Pinkerton, Karen Schmidt, and James Xamplas

Date Presented: March 14, 2014

==Introduction==
1,4-butanediol (BDO) is traditionally made from petroleum-derived feedstocks in a variety of processes such as the Reppe (acetylene-based), Mitsubishi (butadiene-based), and Davy (maleic acid-based) processes [1]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, BDO [1]. It is this process that Team S2Kool4Skool has chosen to develop for a new bio-butanediol plant, because the Davy method is mature and requires no new innovations, and because an appropriate feedstock of bio-succinic acid is now available. The plant will be located in East Carroll Parish, Louisiana. This county is also home to Myriant; located in Lake Providence, they are the largest domestic provider of bio-succinic acid [2]. Furthermore, Lake Providence is conveniently located on the Mississippi River, which will allow for affordable transportation of our bio-based butanediol product. The intent of this project is to produce 45,000 metric tonnes of 99.5 wt% 1,4-butanediol per year in a new plant in Lake Providence, LA. The plant will run 24 hours per day for 350 days out of the year, allowing approximately two weeks for a maintenance shutdown.

As there are several techniques for producing 1,4 butanediol in industry, the first step was to determine a synthesis path. Based on the chosen path, reaction kinetics, and required production rate of the process, a reactor system was then designed. Next, the process was designed to deliver the reactants to the reactor at the proper operating conditions, and the separations, purification, and waste management steps were designed. Cost estimates were made using costing software and hand calculations. Finally, the process was iterated and optimized to reduce costs.

==Background==
===General information===
BDO is an organic chemical with the molecular formula <math>C_4H_{10}O_2</math>. It is also a diol with its two hydroxyl groups located at the terminal carbons. BDO has a boiling point of 235 degrees C and is therefore a colorless liquid at standard temperatures and pressures [3].

There are many precursors that petrochemical synthesis of BDO uses. The commonality between all of the precursor acids is that they are hydrogenatable. In replacement of one of these petrochemical precursors, our team has been tasked with the challenge of deriving BDO from the bio-based precursor succinic acid. This catalyzed reaction will take place in the presence of hydrogen as the hydrogenating component shown below:

<math>C_4H_6O_4 + 4H_2 = C_4H_{10}O_2 + 2H_2O</math>

As described in the above reaction, there will need to be at least 4:1 stoichiometric ratio of hydrogen gas to succinic acid. Two moles of water will also be produced along with each mole of BDO. This reaction is exothermic, which requires the reactor to be continuously cooled to maintain our reactor temperature. There are also side products that are produced which include tetrahydrofuran (THF) and γ-butyrolactone (GBL); however, thanks to catalyst selectivity these byproducts are produced in small quantities.

===Market analysis===
Butanediol has a quickly expanding market due to new technological evolutions and its growing use as a chemical intermediary in advanced materials. With biological routes being optimized, the potential of biomass-derived chemicals is tremendous. The global demand of BDO was estimated at 1.5 million metric tons in 2011 and is projected to grow at an annual rate of 4.5% for the next several years [1]. Unlike other chemical products, BDO’s profitability and attractiveness to producers lies in its downstream potential. Figure 1 below demonstrates several potential downstream products that can be directly or indirectly synthesized from BDO. The largest of these contributors include THF and GBL.

[[File:BioButanediol_Downstream.jpg|center|frame|Figure 1. BDO downstream potential flow chart]]

The current market demand of BDO is being supplemented by several global chemical companies. These companies include BASF, BioAmber, Purac, Myriant, DSM, Mitsubishi Chemical, Roquette, and OPXBIO. The market shares of these companies were not available for this product; however, with the consistent growth of the BDO market our team feels that the market is not saturated or impenetrable. The current market price of BDO fluctuates between $3.06 and $3.31 per kg for US-made products [4]. These prices correlate to a nearly 7 billion dollar industry.

===Process alternatives===
1,4-butanediol is traditionally made from petroleum-derived feedstocks in a variety of processes [5]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Several companies are currently implementing bio-routes of producing butanediol. Genomatica is using a bioengineered microorganism to convert sugar feedstocks directly to BDO via fermentation [6], but most companies are instead using microorganisms to convert sugar to succinic acid. The bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, which is the path that most are choosing, although research is being conducted on alternative pathways [7].

==Process overview==
The newly proposed plant can be divided into four stages: pre-reactor, reactor, post-reactor and distillation. Each section is an integral part to the overall process and demands close attention. The process flow diagram (see Appendix A) and stream table (Appendix B) provide more detailed information.

===Pre-reactor===
This chemical process begins with two feedstocks: hydrogen gas and bio-succinic acid. The hydrogen gas will be obtained from a pipeline at 150 atm and will be used in molar excess inside the reactor. The bio-succinic acid will be purchased by Myriant Corporation which is located near the planned plant site. The pricing for this feedstock is approximately $2.12 per kg. The plant will require 63,000 metric tonnes of bio-succinic acid per year to meet the proposed plant capacity. First the bio-succinic acid feed is pumped up to 150 atm to match the hydrogen gas feed, and then it is mixed with the hydrogen gas prior to being sent into heat exchanger E-101 for heating. The heat exchanger brings the two feeds up to 110oC and sends them to the jacketed packed bed reactor.

===Reactor===
The hydrogenation reaction occurs inside of the reactor thanks to the packed catalyst bed. The catalyst used is 0.4% Fe, 1.9% Na, 2.66% Ag, 2.66% Pd, 10.0% Re on 1.5mm carbon support. With this catalyst, BDO is produced with over 90% selectivity and minimal side reactions of THF and GBL [8]. The reaction has an operating pressure of 2000-4000 psi and internal reactor temperature of 165°C. This temperature allows for about 99.7% conversion of succinic acid [8]. Due to the exothermic nature of the reaction, a cooling jacket is required which utilizes downstream cold streams to cool the internal bed to maintain the desired reaction temperature.

===Post-reactor===
The effluent of the reactor is sent back to E-101 as the hot stream. After exiting E-101, the reactor product stream is sent to a secondary exchanger, E-102, where utility cooling water is used to reduce the temperature to an acceptable temperature prior to sending it to a pressure let-down valve. At this point the pressure of the stream is taken from 150 atm to 1 atm. This large pressure drop allows for the stream to split into its vapor and liquid portions in a gas-liquid separator. The vapor stream of the gas liquid separator is primarily hydrogen gas and sent to a flare for disposal. The liquid effluent is at approximately 45oC leaving the separator and is therefore pumped to the reactor jacket for the reaction cooling mentioned previously. After running through the reactor jacket, the stream enters the separation processes.

===Distillation===
The first distillation column, T-101, is a 10 stage column whose primary purpose is separating the THF from the product feed. Due to THF’s lower boiling point, the byproduct comes off of the top of the column with mostly water. This distillate is sent to the plant's THF waste storage tank that has the capacity of two weeks. The bottoms of the column is sent to the subsequent distillation column that separates the BDO from the GBL and water. The relatively close boiling points of BDO and GBL, 235oC and 204oC, respectively, create a difficult separation that requires a 15 stage column. The distillate of the column is approximately 23% GBL with balance water. This stream is sent to a storage tank with similar sizing parameters as the THF storage tank. The bottom stream is the final 99.5wt% BDO product. This stream is sent to the final product tank, S-104. Depending on our customer demands and the plant location we have the ability to barge, rail or pipe our product to its final destination. Due to low purity of the byproducts, future iterations are needed to optimize either purifying byproducts or selling impure byproducts. There is definitely an available market for these byproducts that should be researched more extensively to increase profit. A detailed description of the equipment from the PFD can be found in Appendix C, in addition to sizing specifications and purpose of equipment.

===Mass and energy balances===
Using an Aspen HYSYS simulation we were able to record the material and energy streams going in and out of the process system. Mass and energy balances are provided Appendix D where each inlet and outlet stream is described and quantified. As expected, the material and energy totals for the inlet and outlet streams add together to equal 0. This proves that our system is mathematically prudent and thermodynamically feasible. The total mass flow of the system is 15,639 kg/h and the total energy in and out of the system is 1.41e8 kJ/h.

===HYSYS simulation===
The HYSYS simulation was performed using the NRTL ideal fluid package. After using AspenPlus to verify that the HYSYS package had the appropriate vapor-liquid equilibrium information between THF and water, and between GBL and water, we concluded it was feasible to proceed with that fluid package. The simulation consists of a reactor, a gas-liquid separator, 2 pumps, 3 heaters, a valve, and 2 distillation columns (see Figure 2). The simulation successfully converted the succinic acid feed into the desired products. Also, the combination of the two distillation columns was able to effectively separate the BDO to obtain a 99.5% pure product with 99.5% recovery. In addition, a set was made between the energy required to heat stream 12 and the energy required to cool the reactor so that these values were made equal. Lastly, the condenser and reboiler duties were used in four heat exchangers in order to determine the appropriate size of this equipment as well as the necessary utility flow rates.

==Health and safety==
===Chemical properties===
Inherent to this process are a number of toxic chemicals. Table 1 summarizes the important safety data including hazard type, odor, color, and exposure limits.

As shown in the above table, the chemicals that this facility will be dealing with will be relatively mild and non-life threatening. Regardless of their perceived threat, chemicals should always be handled with care especially when they are at high temperatures and pressures.

===Safety procedures===

'''Fire'''. There are many flammable materials that will be included in this process; therefore, fire safety is imperative for all employees. There are countless possible causes of ignition and care should be taken while handling any flammable material whether in the lab or in the field.

In case a fire is present on, the following protocol should be implemented:

* Small fire: Use DRY chemical powder.
* Large fire: Use alcohol foam, water spray, or fog.
* Call for backup if unable to control.
* Immediately contact supervisor and emergency personnel on site.
* Evacuate to safe distance in case of fires around any hazardous materials or pressure vessels.

'''Spills'''. Process chemical spills will eventually occur in a plant of this scale. Small spills are likely to occur in a laboratory setting. Large spills could be a result of loss of containment in the system. We must ensure that all personnel are aware of proper spill mitigation protocol.

* Small spill: Dilute with water and mop or absorb with inert dry material. Dispose of in proper receptacle.
* Large spill: Keep away from sources of ignition and heat. Prevent rundown to any drains or sewers. Call for assistance on disposal. Absorb material with DRY earth or other non-combustible materials.
* If spill is due to a loss of containment in the system, quickly consult the PLC and shut any valves to prevent further loss.

'''Exposure'''. We must ensure that our employees are aware of the possible toxicity levels of each substance and how to handle exposure. The chemicals that are being used in this process are known chemical irritants to the eyes, skin, and throat. Safety measures must be in place to acknowledge this hazard. Due to the possibility of high pressure releases, we will have 2-minute emergency oxygen masks placed strategically throughout the plant to ensure the safety of any operator in the presence of a large release.

If exposed to the process chemicals, find nearest eye wash station or safety shower immediately and flush exposed skin for at least 15 minutes. Remove any contaminated clothing. Seek medical attention immediately.

'''Storage'''. Store chemicals in segregated and approved areas. Any closed containers for laboratory purposes should be placed in cool, well-ventilated areas.

==Economics==
===Equipment costing===
The calculated capital costs from Aspen Economic Analyzer are reported in Table 2 for all process equipment. The size of the reactor was calculated from the liquid hourly space velocity given in the 2011 ISP patent [8] and a void fraction estimate of 0.4. Storage tanks were sized to contain up to two continuous weeks of material. The number of distillation trays in each tower and the flow rates through pumps, vessels, and the flare were calculated in HYSYS. Heat exchange areas were given in Aspen Energy Analyzer or from HYSYS.

In addition to the above equipment, our plant will require an ion exchanger to produce deionized process water from the municipal water. This is estimated to cost $42,000 in capital cost.

===Cash flow analysis===
Summarizing the important takeaways from the economic analysis, this process will return a revenue of 144 MM$ annually. Offset by production costs, the yearly cash flow is approximately 2.7 MM$, except for in the years in which the catalyst must be reinstalled (approximately every 5 years). At a cost of 2.5 MM$, the cash flows in those years decrease to approximately 0.2 MM$. This analysis assumes the plant will take 2 years to construct, and will operate at 50% in its first year. Furthermore, an interest rate of 10% was assumed with a tax rate of 38% (the maximum for corporate gains taxes). Using the 7-year MACRS depreciation method, the 20 year NPV for the project is 4.3 MM$. With an IRR of 15.1%, which is greater than the assumed interest rate, this project looks to be profitable. Further optimization techniques should be used in future iterations to further increase profitability. See Tables 3 and 4 for key economic information.

===Sensitivity analysis===
As seen in Figure 3, the economic evaluation of this process is influenced the most by changes in the sales price and feed cost. A 20% increase in sales price will result in an approximate 120 MM$ increase in NPV whereas a decrease of the same percentage will result in over a 120 MM$ decrease in NPV. Inversely, a 20% increase in feed cost will result in a 115 MM$ decrease in NPV and a 20% decrease in feed cost will result in a 60 MM$ increase in NPV.

To alleviate the risk associated with feed price, the team researched the price forecasting of bio-succinic acid. Figure 4 provides the bio-succinic acid price over the six years between 2006 and 2012. The price of bio-succinic, shown by the blue line, has remained relatively stable over this time period. This price history can be compared to adipic acid, the green line, which is a common petrochemical precursor for BDO production. Adipic acid as shown has had large fluctuations in price that result in unstable cash flows and uncertainty from shareholders. Thankfully, the stability of bio-succinic acid is a good sign that this process has a huge potential to be profitable especially if the demand for BDO continues to rise as projected.

==Discussion==
As described previously, the Davy process was selected as the most promising process of BDO production. The modified Davy process involves the hydrogenation of bio-succinicic acid with a Pa,Ag,Re catalyst and hydrogen gas. This process has many advantages, one being that it has mature technology that has been improved over the last 20 years. Additionally, the conversion to of succinic acid is virtually complete. Finally, overall plant yields can reach as high as 94 mol%.
As shown in Appendix B, streams ahead of the pressure valve (PRV-101) are at approximately 1.51e4 kPa, and streams after the pressure valve are between 100 and 450 kPa. Furthermore, operating temperatures do not exceed 200°C, including safety factors. These operating conditions contribute to the feasibility of the process, as all the components can be designed with reasonable dimensions (wall thickness, cap type, etc.).

Of particular interest are the large costs of the reactor and pump P-101. The reactor costs nearly 2 MM$ because it has a moderate size with a liquid volume of 16.7 m3, and it operates at 150 atm, which requires a strong stainless steel shell for safety purposes. Pump P-101 has such a large capital cost because it is a centrifugal multistage pump that also needs to be made of stainless steel to withstand pressuring the succinic acid feed to 150 atm.

Financial indicators for the proposed plant suggest that it will be moderately profitable, and additional optimization should be performed before making the capital investment. There is a fair amount of risk associated with the implementation of this production facility, and the return at this juncture may not justify the risk.

The process design and simulation in HYSYS has relied on several key assumptions, which are cause for certain limitations to the results. First, the conversions and selectivity of the catalyst, while taken from literature sources, are assumed to be true. Furthermore, the assumption of negligible side reactions and products was made. It is possible that small waste products in the form of succinates also form in the reactor. Therefore, the main limitation of this model is generally due to reaction specifications.

There are certain safety concerns that go along with the proposed process. First, there are many pipes and vessels that will be at a pressure of approximately 150 atm. Extra insulation and protection must be applied to the piping that contains highly pressurized fluids, to prevent operator injury. Furthermore, the PFR is at a slight risk for runaway reactions due to the exothermic nature of the reaction. The temperature of the reactor must always be monitored by an operator, and the jacket cooling system requires a backup system as well. A benefit of this process is that there are no toxic or severely hazardous components in the process. Additionally, there are no instances of temperature greater than 200°C.

The process design will be fitted with instrumentation and controls to ensure stable operation. These controls, including sensors and valves, minimize potential damage to components due to variation in plant conditions, as well as optimizing the overall performance. For example, the piping entering the tower will be fitted with a control loop. In the direction of flow, a sensing instrument first detects the pressure of the fluid, and then sends a signal to the controller. If the pressure is not within the operating limits, the actuator is signaled to close or open a control valve which is located farther down the stream.

==Conclusion==
The Evanston Chemical Engineering Division suggests a process that produces 45,000 tonnes/year of 99.5 wt% 1,4-butandeiol to enter the market with an appropriate market share. The feasibility of producing BDO as a significant process was investigated. A wide range of BDO production processes were researched, with a modified Davy process being identified as having the most potential. Using a Pa,Ag,Re catalyst on carbon support, this process converts bio-succinic acid to BDO with approximately 94% conversion. This process was designed in Aspen HYSYS, and economic analysis was conducted in Aspen Economic Analyzer. Total capital costs of the project are 12.2 MM$, with a simple payback period of 5.2 years. Total operational costs annually are 139.7 MM$. The process design was successful, with the capability of producing the desired production of BDO.

==Recommendations==
Given the moderate profitability of this process design, it is recommended that Evanston Chemicals explores further optimization techniques to increase the profitability of this process. This includes investigating sales of the γ-butyrolactone byproduct, recycling process water, and further optimizing utility streams for the distillation tower.

Second, we would like to investigate recycling the 2300 kg/h of water produced in the reaction. Our succinic acid enters the reactor as a 50 wt% solution in water, so we should look into replacing some of this with the product water. Not only will this decrease our water bill, but it will also lower the cost of ion exchange.

==References==
# Nexant.''Is Bio-Butanediol Here to Stay?'' White Plains, NY: ChemSystems Products; 2012.
# De Guzman D. Chemical industry awaits for bio-succinic acid potential. ICIS. Available at: http://www.icis.com/resources/news/2012/01/30/9527521/chemical-industry-awaits-for-bio-succinic-acid-potential/. Accessed January 24, 2014.
# Australian Government: Department of Health. 1,4-butanediol factsheet. National Industrial Chemicals Notification and Assessment Scheme. Available at: http://www.nicnas.gov.au/communications/publications/information-sheets/existing-chemical-info-sheets/other-information-sheets. Accessed January 24, 2014.
# TecnonOrbiChem. Chem-net facts: 1,4-butanediol. TecnonOrbiChem. Available at: http://www.orbichem.com/userfiles/CNF%20Samples/bdo_13_11.pdf. Accessed January 23, 2014.
# Nexant. 1,4-butanediol/tetrahydrofuran (BDO/THF). ChemSystems. Available at: http://www.chemsystems.com/about/cs/news/items/ PERP2012_3_BDO_THF.cfm. Accessed February 6, 2014.
# Burk MJ, Van Dien SJ, Burgard AP, inventors; Genomatica, Inc., assignee. Compositions and methods for the biosynthesis of 1,4-butanediol and its precursors. US patent 8,067,214. Nov. 29, 2011.
# Chung S-H, Kim M-S, Eom H-H, Lee K-Y. Catalytic hydrogenation of bio-based succinic acid for the production of 1,4-butanediol through the indirect pathway. AIChE. Available at: https://aiche.confex.com/aiche/2013/webprogram/Paper327470.html. Accessed January 23, 2014.
# Bhattacharyya A, Manila MD, inventors; ISP Investments Inc., assignee. Catalysts for maleic acid hydrogenation to 1,4-Butanediol. US patent 7,935,834 B2. May 3, 2011.

File:BioButanediol Downstream.JPG

2014-03-15T05:02:56Z

Karetstik: From: Nexant.Is Bio-Butanediol Here to Stay? White Plains, NY: ChemSystems Products; 2012.

From:
Nexant.Is Bio-Butanediol Here to Stay? White Plains, NY: ChemSystems Products; 2012.

Design S2

2014-03-15T04:57:38Z

Karetstik: /* Reactor */

Title: Production of 1,4-butanediol

Authors: Nick Pinkerton, Karen Schmidt, and James Xamplas

Date Presented: March 14, 2014

==Introduction==
1,4-butanediol (BDO) is traditionally made from petroleum-derived feedstocks in a variety of processes such as the Reppe (acetylene-based), Mitsubishi (butadiene-based), and Davy (maleic acid-based) processes [1]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, BDO [1]. It is this process that Team S2Kool4Skool has chosen to develop for a new bio-butanediol plant, because the Davy method is mature and requires no new innovations, and because an appropriate feedstock of bio-succinic acid is now available. The plant will be located in East Carroll Parish, Louisiana. This county is also home to Myriant; located in Lake Providence, they are the largest domestic provider of bio-succinic acid [2]. Furthermore, Lake Providence is conveniently located on the Mississippi River, which will allow for affordable transportation of our bio-based butanediol product. The intent of this project is to produce 45,000 metric tonnes of 99.5 wt% 1,4-butanediol per year in a new plant in Lake Providence, LA. The plant will run 24 hours per day for 350 days out of the year, allowing approximately two weeks for a maintenance shutdown.

As there are several techniques for producing 1,4 butanediol in industry, the first step was to determine a synthesis path. Based on the chosen path, reaction kinetics, and required production rate of the process, a reactor system was then designed. Next, the process was designed to deliver the reactants to the reactor at the proper operating conditions, and the separations, purification, and waste management steps were designed. Cost estimates were made using costing software and hand calculations. Finally, the process was iterated and optimized to reduce costs.

==Background==
===General information===
BDO is an organic chemical with the molecular formula <math>C_4H_{10}O_2</math>. It is also a diol with its two hydroxyl groups located at the terminal carbons. BDO has a boiling point of 235 degrees C and is therefore a colorless liquid at standard temperatures and pressures [3].

There are many precursors that petrochemical synthesis of BDO uses. The commonality between all of the precursor acids is that they are hydrogenatable. In replacement of one of these petrochemical precursors, our team has been tasked with the challenge of deriving BDO from the bio-based precursor succinic acid. This catalyzed reaction will take place in the presence of hydrogen as the hydrogenating component shown below:

<math>C_4H_6O_4 + 4H_2 = C_4H_{10}O_2 + 2H_2O</math>

As described in the above reaction, there will need to be at least 4:1 stoichiometric ratio of hydrogen gas to succinic acid. Two moles of water will also be produced along with each mole of BDO. This reaction is exothermic, which requires the reactor to be continuously cooled to maintain our reactor temperature. There are also side products that are produced which include tetrahydrofuran (THF) and γ-butyrolactone (GBL); however, thanks to catalyst selectivity these byproducts are produced in small quantities.

===Market analysis===
Butanediol has a quickly expanding market due to new technological evolutions and its growing use as a chemical intermediary in advanced materials. With biological routes being optimized, the potential of biomass-derived chemicals is tremendous. The global demand of BDO was estimated at 1.5 million metric tons in 2011 and is projected to grow at an annual rate of 4.5% for the next several years [1]. Unlike other chemical products, BDO’s profitability and attractiveness to producers lies in its downstream potential. Figure 1 below demonstrates several potential downstream products that can be directly or indirectly synthesized from BDO. The largest of these contributors include THF and GBL.

The current market demand of BDO is being supplemented by several global chemical companies. These companies include BASF, BioAmber, Purac, Myriant, DSM, Mitsubishi Chemical, Roquette, and OPXBIO. The market shares of these companies were not available for this product; however, with the consistent growth of the BDO market our team feels that the market is not saturated or impenetrable. The current market price of BDO fluctuates between $3.06 and $3.31 per kg for US-made products [4]. These prices correlate to a nearly 7 billion dollar industry.

===Process alternatives===
1,4-butanediol is traditionally made from petroleum-derived feedstocks in a variety of processes [5]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Several companies are currently implementing bio-routes of producing butanediol. Genomatica is using a bioengineered microorganism to convert sugar feedstocks directly to BDO via fermentation [6], but most companies are instead using microorganisms to convert sugar to succinic acid. The bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, which is the path that most are choosing, although research is being conducted on alternative pathways [7].

==Process overview==
The newly proposed plant can be divided into four stages: pre-reactor, reactor, post-reactor and distillation. Each section is an integral part to the overall process and demands close attention. The process flow diagram (see Appendix A) and stream table (Appendix B) provide more detailed information.

===Pre-reactor===
This chemical process begins with two feedstocks: hydrogen gas and bio-succinic acid. The hydrogen gas will be obtained from a pipeline at 150 atm and will be used in molar excess inside the reactor. The bio-succinic acid will be purchased by Myriant Corporation which is located near the planned plant site. The pricing for this feedstock is approximately $2.12 per kg. The plant will require 63,000 metric tonnes of bio-succinic acid per year to meet the proposed plant capacity. First the bio-succinic acid feed is pumped up to 150 atm to match the hydrogen gas feed, and then it is mixed with the hydrogen gas prior to being sent into heat exchanger E-101 for heating. The heat exchanger brings the two feeds up to 110oC and sends them to the jacketed packed bed reactor.

===Reactor===
The hydrogenation reaction occurs inside of the reactor thanks to the packed catalyst bed. The catalyst used is 0.4% Fe, 1.9% Na, 2.66% Ag, 2.66% Pd, 10.0% Re on 1.5mm carbon support. With this catalyst, BDO is produced with over 90% selectivity and minimal side reactions of THF and GBL [8]. The reaction has an operating pressure of 2000-4000 psi and internal reactor temperature of 165°C. This temperature allows for about 99.7% conversion of succinic acid [8]. Due to the exothermic nature of the reaction, a cooling jacket is required which utilizes downstream cold streams to cool the internal bed to maintain the desired reaction temperature.

===Post-reactor===
The effluent of the reactor is sent back to E-101 as the hot stream. After exiting E-101, the reactor product stream is sent to a secondary exchanger, E-102, where utility cooling water is used to reduce the temperature to an acceptable temperature prior to sending it to a pressure let-down valve. At this point the pressure of the stream is taken from 150 atm to 1 atm. This large pressure drop allows for the stream to split into its vapor and liquid portions in a gas-liquid separator. The vapor stream of the gas liquid separator is primarily hydrogen gas and sent to a flare for disposal. The liquid effluent is at approximately 45oC leaving the separator and is therefore pumped to the reactor jacket for the reaction cooling mentioned previously. After running through the reactor jacket, the stream enters the separation processes.

===Distillation===
The first distillation column, T-101, is a 10 stage column whose primary purpose is separating the THF from the product feed. Due to THF’s lower boiling point, the byproduct comes off of the top of the column with mostly water. This distillate is sent to the plant's THF waste storage tank that has the capacity of two weeks. The bottoms of the column is sent to the subsequent distillation column that separates the BDO from the GBL and water. The relatively close boiling points of BDO and GBL, 235oC and 204oC, respectively, create a difficult separation that requires a 15 stage column. The distillate of the column is approximately 23% GBL with balance water. This stream is sent to a storage tank with similar sizing parameters as the THF storage tank. The bottom stream is the final 99.5wt% BDO product. This stream is sent to the final product tank, S-104. Depending on our customer demands and the plant location we have the ability to barge, rail or pipe our product to its final destination. Due to low purity of the byproducts, future iterations are needed to optimize either purifying byproducts or selling impure byproducts. There is definitely an available market for these byproducts that should be researched more extensively to increase profit. A detailed description of the equipment from the PFD can be found in Appendix C, in addition to sizing specifications and purpose of equipment.

===Mass and energy balances===
Using an Aspen HYSYS simulation we were able to record the material and energy streams going in and out of the process system. Mass and energy balances are provided Appendix D where each inlet and outlet stream is described and quantified. As expected, the material and energy totals for the inlet and outlet streams add together to equal 0. This proves that our system is mathematically prudent and thermodynamically feasible. The total mass flow of the system is 15,639 kg/h and the total energy in and out of the system is 1.41e8 kJ/h.

===HYSYS simulation===
The HYSYS simulation was performed using the NRTL ideal fluid package. After using AspenPlus to verify that the HYSYS package had the appropriate vapor-liquid equilibrium information between THF and water, and between GBL and water, we concluded it was feasible to proceed with that fluid package. The simulation consists of a reactor, a gas-liquid separator, 2 pumps, 3 heaters, a valve, and 2 distillation columns (see Figure 2). The simulation successfully converted the succinic acid feed into the desired products. Also, the combination of the two distillation columns was able to effectively separate the BDO to obtain a 99.5% pure product with 99.5% recovery. In addition, a set was made between the energy required to heat stream 12 and the energy required to cool the reactor so that these values were made equal. Lastly, the condenser and reboiler duties were used in four heat exchangers in order to determine the appropriate size of this equipment as well as the necessary utility flow rates.

==Health and safety==
===Chemical properties===
Inherent to this process are a number of toxic chemicals. Table 1 summarizes the important safety data including hazard type, odor, color, and exposure limits.

As shown in the above table, the chemicals that this facility will be dealing with will be relatively mild and non-life threatening. Regardless of their perceived threat, chemicals should always be handled with care especially when they are at high temperatures and pressures.

===Safety procedures===

'''Fire'''. There are many flammable materials that will be included in this process; therefore, fire safety is imperative for all employees. There are countless possible causes of ignition and care should be taken while handling any flammable material whether in the lab or in the field.

In case a fire is present on, the following protocol should be implemented:

* Small fire: Use DRY chemical powder.
* Large fire: Use alcohol foam, water spray, or fog.
* Call for backup if unable to control.
* Immediately contact supervisor and emergency personnel on site.
* Evacuate to safe distance in case of fires around any hazardous materials or pressure vessels.

'''Spills'''. Process chemical spills will eventually occur in a plant of this scale. Small spills are likely to occur in a laboratory setting. Large spills could be a result of loss of containment in the system. We must ensure that all personnel are aware of proper spill mitigation protocol.

* Small spill: Dilute with water and mop or absorb with inert dry material. Dispose of in proper receptacle.
* Large spill: Keep away from sources of ignition and heat. Prevent rundown to any drains or sewers. Call for assistance on disposal. Absorb material with DRY earth or other non-combustible materials.
* If spill is due to a loss of containment in the system, quickly consult the PLC and shut any valves to prevent further loss.

'''Exposure'''. We must ensure that our employees are aware of the possible toxicity levels of each substance and how to handle exposure. The chemicals that are being used in this process are known chemical irritants to the eyes, skin, and throat. Safety measures must be in place to acknowledge this hazard. Due to the possibility of high pressure releases, we will have 2-minute emergency oxygen masks placed strategically throughout the plant to ensure the safety of any operator in the presence of a large release.

If exposed to the process chemicals, find nearest eye wash station or safety shower immediately and flush exposed skin for at least 15 minutes. Remove any contaminated clothing. Seek medical attention immediately.

'''Storage'''. Store chemicals in segregated and approved areas. Any closed containers for laboratory purposes should be placed in cool, well-ventilated areas.

==Economics==
===Equipment costing===
The calculated capital costs from Aspen Economic Analyzer are reported in Table 2 for all process equipment. The size of the reactor was calculated from the liquid hourly space velocity given in the 2011 ISP patent [8] and a void fraction estimate of 0.4. Storage tanks were sized to contain up to two continuous weeks of material. The number of distillation trays in each tower and the flow rates through pumps, vessels, and the flare were calculated in HYSYS. Heat exchange areas were given in Aspen Energy Analyzer or from HYSYS.

In addition to the above equipment, our plant will require an ion exchanger to produce deionized process water from the municipal water. This is estimated to cost $42,000 in capital cost.

===Cash flow analysis===
Summarizing the important takeaways from the economic analysis, this process will return a revenue of 144 MM$ annually. Offset by production costs, the yearly cash flow is approximately 2.7 MM$, except for in the years in which the catalyst must be reinstalled (approximately every 5 years). At a cost of 2.5 MM$, the cash flows in those years decrease to approximately 0.2 MM$. This analysis assumes the plant will take 2 years to construct, and will operate at 50% in its first year. Furthermore, an interest rate of 10% was assumed with a tax rate of 38% (the maximum for corporate gains taxes). Using the 7-year MACRS depreciation method, the 20 year NPV for the project is 4.3 MM$. With an IRR of 15.1%, which is greater than the assumed interest rate, this project looks to be profitable. Further optimization techniques should be used in future iterations to further increase profitability. See Tables 3 and 4 for key economic information.

===Sensitivity analysis===
As seen in Figure 3, the economic evaluation of this process is influenced the most by changes in the sales price and feed cost. A 20% increase in sales price will result in an approximate 120 MM$ increase in NPV whereas a decrease of the same percentage will result in over a 120 MM$ decrease in NPV. Inversely, a 20% increase in feed cost will result in a 115 MM$ decrease in NPV and a 20% decrease in feed cost will result in a 60 MM$ increase in NPV.

To alleviate the risk associated with feed price, the team researched the price forecasting of bio-succinic acid. Figure 4 provides the bio-succinic acid price over the six years between 2006 and 2012. The price of bio-succinic, shown by the blue line, has remained relatively stable over this time period. This price history can be compared to adipic acid, the green line, which is a common petrochemical precursor for BDO production. Adipic acid as shown has had large fluctuations in price that result in unstable cash flows and uncertainty from shareholders. Thankfully, the stability of bio-succinic acid is a good sign that this process has a huge potential to be profitable especially if the demand for BDO continues to rise as projected.

==Discussion==
As described previously, the Davy process was selected as the most promising process of BDO production. The modified Davy process involves the hydrogenation of bio-succinicic acid with a Pa,Ag,Re catalyst and hydrogen gas. This process has many advantages, one being that it has mature technology that has been improved over the last 20 years. Additionally, the conversion to of succinic acid is virtually complete. Finally, overall plant yields can reach as high as 94 mol%.
As shown in Appendix B, streams ahead of the pressure valve (PRV-101) are at approximately 1.51e4 kPa, and streams after the pressure valve are between 100 and 450 kPa. Furthermore, operating temperatures do not exceed 200°C, including safety factors. These operating conditions contribute to the feasibility of the process, as all the components can be designed with reasonable dimensions (wall thickness, cap type, etc.).

Of particular interest are the large costs of the reactor and pump P-101. The reactor costs nearly 2 MM$ because it has a moderate size with a liquid volume of 16.7 m3, and it operates at 150 atm, which requires a strong stainless steel shell for safety purposes. Pump P-101 has such a large capital cost because it is a centrifugal multistage pump that also needs to be made of stainless steel to withstand pressuring the succinic acid feed to 150 atm.

Financial indicators for the proposed plant suggest that it will be moderately profitable, and additional optimization should be performed before making the capital investment. There is a fair amount of risk associated with the implementation of this production facility, and the return at this juncture may not justify the risk.

The process design and simulation in HYSYS has relied on several key assumptions, which are cause for certain limitations to the results. First, the conversions and selectivity of the catalyst, while taken from literature sources, are assumed to be true. Furthermore, the assumption of negligible side reactions and products was made. It is possible that small waste products in the form of succinates also form in the reactor. Therefore, the main limitation of this model is generally due to reaction specifications.

There are certain safety concerns that go along with the proposed process. First, there are many pipes and vessels that will be at a pressure of approximately 150 atm. Extra insulation and protection must be applied to the piping that contains highly pressurized fluids, to prevent operator injury. Furthermore, the PFR is at a slight risk for runaway reactions due to the exothermic nature of the reaction. The temperature of the reactor must always be monitored by an operator, and the jacket cooling system requires a backup system as well. A benefit of this process is that there are no toxic or severely hazardous components in the process. Additionally, there are no instances of temperature greater than 200°C.

The process design will be fitted with instrumentation and controls to ensure stable operation. These controls, including sensors and valves, minimize potential damage to components due to variation in plant conditions, as well as optimizing the overall performance. For example, the piping entering the tower will be fitted with a control loop. In the direction of flow, a sensing instrument first detects the pressure of the fluid, and then sends a signal to the controller. If the pressure is not within the operating limits, the actuator is signaled to close or open a control valve which is located farther down the stream.

==Conclusion==
The Evanston Chemical Engineering Division suggests a process that produces 45,000 tonnes/year of 99.5 wt% 1,4-butandeiol to enter the market with an appropriate market share. The feasibility of producing BDO as a significant process was investigated. A wide range of BDO production processes were researched, with a modified Davy process being identified as having the most potential. Using a Pa,Ag,Re catalyst on carbon support, this process converts bio-succinic acid to BDO with approximately 94% conversion. This process was designed in Aspen HYSYS, and economic analysis was conducted in Aspen Economic Analyzer. Total capital costs of the project are 12.2 MM$, with a simple payback period of 5.2 years. Total operational costs annually are 139.7 MM$. The process design was successful, with the capability of producing the desired production of BDO.

==Recommendations==
Given the moderate profitability of this process design, it is recommended that Evanston Chemicals explores further optimization techniques to increase the profitability of this process. This includes investigating sales of the γ-butyrolactone byproduct, recycling process water, and further optimizing utility streams for the distillation tower.

Second, we would like to investigate recycling the 2300 kg/h of water produced in the reaction. Our succinic acid enters the reactor as a 50 wt% solution in water, so we should look into replacing some of this with the product water. Not only will this decrease our water bill, but it will also lower the cost of ion exchange.

==References==
# Nexant.''Is Bio-Butanediol Here to Stay?'' White Plains, NY: ChemSystems Products; 2012.
# De Guzman D. Chemical industry awaits for bio-succinic acid potential. ICIS. Available at: http://www.icis.com/resources/news/2012/01/30/9527521/chemical-industry-awaits-for-bio-succinic-acid-potential/. Accessed January 24, 2014.
# Australian Government: Department of Health. 1,4-butanediol factsheet. National Industrial Chemicals Notification and Assessment Scheme. Available at: http://www.nicnas.gov.au/communications/publications/information-sheets/existing-chemical-info-sheets/other-information-sheets. Accessed January 24, 2014.
# TecnonOrbiChem. Chem-net facts: 1,4-butanediol. TecnonOrbiChem. Available at: http://www.orbichem.com/userfiles/CNF%20Samples/bdo_13_11.pdf. Accessed January 23, 2014.
# Nexant. 1,4-butanediol/tetrahydrofuran (BDO/THF). ChemSystems. Available at: http://www.chemsystems.com/about/cs/news/items/ PERP2012_3_BDO_THF.cfm. Accessed February 6, 2014.
# Burk MJ, Van Dien SJ, Burgard AP, inventors; Genomatica, Inc., assignee. Compositions and methods for the biosynthesis of 1,4-butanediol and its precursors. US patent 8,067,214. Nov. 29, 2011.
# Chung S-H, Kim M-S, Eom H-H, Lee K-Y. Catalytic hydrogenation of bio-based succinic acid for the production of 1,4-butanediol through the indirect pathway. AIChE. Available at: https://aiche.confex.com/aiche/2013/webprogram/Paper327470.html. Accessed January 23, 2014.
# Bhattacharyya A, Manila MD, inventors; ISP Investments Inc., assignee. Catalysts for maleic acid hydrogenation to 1,4-Butanediol. US patent 7,935,834 B2. May 3, 2011.

Design S2

2014-03-15T04:56:57Z

Karetstik: /* Cash flow analysis */

Title: Production of 1,4-butanediol

Authors: Nick Pinkerton, Karen Schmidt, and James Xamplas

Date Presented: March 14, 2014

==Introduction==
1,4-butanediol (BDO) is traditionally made from petroleum-derived feedstocks in a variety of processes such as the Reppe (acetylene-based), Mitsubishi (butadiene-based), and Davy (maleic acid-based) processes [1]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, BDO [1]. It is this process that Team S2Kool4Skool has chosen to develop for a new bio-butanediol plant, because the Davy method is mature and requires no new innovations, and because an appropriate feedstock of bio-succinic acid is now available. The plant will be located in East Carroll Parish, Louisiana. This county is also home to Myriant; located in Lake Providence, they are the largest domestic provider of bio-succinic acid [2]. Furthermore, Lake Providence is conveniently located on the Mississippi River, which will allow for affordable transportation of our bio-based butanediol product. The intent of this project is to produce 45,000 metric tonnes of 99.5 wt% 1,4-butanediol per year in a new plant in Lake Providence, LA. The plant will run 24 hours per day for 350 days out of the year, allowing approximately two weeks for a maintenance shutdown.

As there are several techniques for producing 1,4 butanediol in industry, the first step was to determine a synthesis path. Based on the chosen path, reaction kinetics, and required production rate of the process, a reactor system was then designed. Next, the process was designed to deliver the reactants to the reactor at the proper operating conditions, and the separations, purification, and waste management steps were designed. Cost estimates were made using costing software and hand calculations. Finally, the process was iterated and optimized to reduce costs.

==Background==
===General information===
BDO is an organic chemical with the molecular formula <math>C_4H_{10}O_2</math>. It is also a diol with its two hydroxyl groups located at the terminal carbons. BDO has a boiling point of 235 degrees C and is therefore a colorless liquid at standard temperatures and pressures [3].

There are many precursors that petrochemical synthesis of BDO uses. The commonality between all of the precursor acids is that they are hydrogenatable. In replacement of one of these petrochemical precursors, our team has been tasked with the challenge of deriving BDO from the bio-based precursor succinic acid. This catalyzed reaction will take place in the presence of hydrogen as the hydrogenating component shown below:

<math>C_4H_6O_4 + 4H_2 = C_4H_{10}O_2 + 2H_2O</math>

As described in the above reaction, there will need to be at least 4:1 stoichiometric ratio of hydrogen gas to succinic acid. Two moles of water will also be produced along with each mole of BDO. This reaction is exothermic, which requires the reactor to be continuously cooled to maintain our reactor temperature. There are also side products that are produced which include tetrahydrofuran (THF) and γ-butyrolactone (GBL); however, thanks to catalyst selectivity these byproducts are produced in small quantities.

===Market analysis===
Butanediol has a quickly expanding market due to new technological evolutions and its growing use as a chemical intermediary in advanced materials. With biological routes being optimized, the potential of biomass-derived chemicals is tremendous. The global demand of BDO was estimated at 1.5 million metric tons in 2011 and is projected to grow at an annual rate of 4.5% for the next several years [1]. Unlike other chemical products, BDO’s profitability and attractiveness to producers lies in its downstream potential. Figure 1 below demonstrates several potential downstream products that can be directly or indirectly synthesized from BDO. The largest of these contributors include THF and GBL.

The current market demand of BDO is being supplemented by several global chemical companies. These companies include BASF, BioAmber, Purac, Myriant, DSM, Mitsubishi Chemical, Roquette, and OPXBIO. The market shares of these companies were not available for this product; however, with the consistent growth of the BDO market our team feels that the market is not saturated or impenetrable. The current market price of BDO fluctuates between $3.06 and $3.31 per kg for US-made products [4]. These prices correlate to a nearly 7 billion dollar industry.

===Process alternatives===
1,4-butanediol is traditionally made from petroleum-derived feedstocks in a variety of processes [5]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Several companies are currently implementing bio-routes of producing butanediol. Genomatica is using a bioengineered microorganism to convert sugar feedstocks directly to BDO via fermentation [6], but most companies are instead using microorganisms to convert sugar to succinic acid. The bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, which is the path that most are choosing, although research is being conducted on alternative pathways [7].

==Process overview==
The newly proposed plant can be divided into four stages: pre-reactor, reactor, post-reactor and distillation. Each section is an integral part to the overall process and demands close attention. The process flow diagram (see Appendix A) and stream table (Appendix B) provide more detailed information.

===Pre-reactor===
This chemical process begins with two feedstocks: hydrogen gas and bio-succinic acid. The hydrogen gas will be obtained from a pipeline at 150 atm and will be used in molar excess inside the reactor. The bio-succinic acid will be purchased by Myriant Corporation which is located near the planned plant site. The pricing for this feedstock is approximately $2.12 per kg. The plant will require 63,000 metric tonnes of bio-succinic acid per year to meet the proposed plant capacity. First the bio-succinic acid feed is pumped up to 150 atm to match the hydrogen gas feed, and then it is mixed with the hydrogen gas prior to being sent into heat exchanger E-101 for heating. The heat exchanger brings the two feeds up to 110oC and sends them to the jacketed packed bed reactor.

===Reactor===
The hydrogenation reaction occurs inside of the reactor thanks to the packed catalyst bed. The catalyst used is 0.4% Fe, 1.9% Na, 2.66% Ag, 2.66% Pd, 10.0% Re on 1.5mm carbon support. With this catalyst, BDO is produced with over 90% selectivity and minimal side reactions of THF and GBL.8 The reaction has an operating pressure of 2000-4000 psi and internal reactor temperature of 165°C. This temperature allows for about 99.7% conversion of succinic acid.8 Due to the exothermic nature of the reaction, a cooling jacket is required which utilizes downstream cold streams to cool the internal bed to maintain the desired reaction temperature.

===Post-reactor===
The effluent of the reactor is sent back to E-101 as the hot stream. After exiting E-101, the reactor product stream is sent to a secondary exchanger, E-102, where utility cooling water is used to reduce the temperature to an acceptable temperature prior to sending it to a pressure let-down valve. At this point the pressure of the stream is taken from 150 atm to 1 atm. This large pressure drop allows for the stream to split into its vapor and liquid portions in a gas-liquid separator. The vapor stream of the gas liquid separator is primarily hydrogen gas and sent to a flare for disposal. The liquid effluent is at approximately 45oC leaving the separator and is therefore pumped to the reactor jacket for the reaction cooling mentioned previously. After running through the reactor jacket, the stream enters the separation processes.

===Distillation===
The first distillation column, T-101, is a 10 stage column whose primary purpose is separating the THF from the product feed. Due to THF’s lower boiling point, the byproduct comes off of the top of the column with mostly water. This distillate is sent to the plant's THF waste storage tank that has the capacity of two weeks. The bottoms of the column is sent to the subsequent distillation column that separates the BDO from the GBL and water. The relatively close boiling points of BDO and GBL, 235oC and 204oC, respectively, create a difficult separation that requires a 15 stage column. The distillate of the column is approximately 23% GBL with balance water. This stream is sent to a storage tank with similar sizing parameters as the THF storage tank. The bottom stream is the final 99.5wt% BDO product. This stream is sent to the final product tank, S-104. Depending on our customer demands and the plant location we have the ability to barge, rail or pipe our product to its final destination. Due to low purity of the byproducts, future iterations are needed to optimize either purifying byproducts or selling impure byproducts. There is definitely an available market for these byproducts that should be researched more extensively to increase profit. A detailed description of the equipment from the PFD can be found in Appendix C, in addition to sizing specifications and purpose of equipment.

===Mass and energy balances===
Using an Aspen HYSYS simulation we were able to record the material and energy streams going in and out of the process system. Mass and energy balances are provided Appendix D where each inlet and outlet stream is described and quantified. As expected, the material and energy totals for the inlet and outlet streams add together to equal 0. This proves that our system is mathematically prudent and thermodynamically feasible. The total mass flow of the system is 15,639 kg/h and the total energy in and out of the system is 1.41e8 kJ/h.

===HYSYS simulation===
The HYSYS simulation was performed using the NRTL ideal fluid package. After using AspenPlus to verify that the HYSYS package had the appropriate vapor-liquid equilibrium information between THF and water, and between GBL and water, we concluded it was feasible to proceed with that fluid package. The simulation consists of a reactor, a gas-liquid separator, 2 pumps, 3 heaters, a valve, and 2 distillation columns (see Figure 2). The simulation successfully converted the succinic acid feed into the desired products. Also, the combination of the two distillation columns was able to effectively separate the BDO to obtain a 99.5% pure product with 99.5% recovery. In addition, a set was made between the energy required to heat stream 12 and the energy required to cool the reactor so that these values were made equal. Lastly, the condenser and reboiler duties were used in four heat exchangers in order to determine the appropriate size of this equipment as well as the necessary utility flow rates.

==Health and safety==
===Chemical properties===
Inherent to this process are a number of toxic chemicals. Table 1 summarizes the important safety data including hazard type, odor, color, and exposure limits.

As shown in the above table, the chemicals that this facility will be dealing with will be relatively mild and non-life threatening. Regardless of their perceived threat, chemicals should always be handled with care especially when they are at high temperatures and pressures.

===Safety procedures===

'''Fire'''. There are many flammable materials that will be included in this process; therefore, fire safety is imperative for all employees. There are countless possible causes of ignition and care should be taken while handling any flammable material whether in the lab or in the field.

In case a fire is present on, the following protocol should be implemented:

* Small fire: Use DRY chemical powder.
* Large fire: Use alcohol foam, water spray, or fog.
* Call for backup if unable to control.
* Immediately contact supervisor and emergency personnel on site.
* Evacuate to safe distance in case of fires around any hazardous materials or pressure vessels.

'''Spills'''. Process chemical spills will eventually occur in a plant of this scale. Small spills are likely to occur in a laboratory setting. Large spills could be a result of loss of containment in the system. We must ensure that all personnel are aware of proper spill mitigation protocol.

* Small spill: Dilute with water and mop or absorb with inert dry material. Dispose of in proper receptacle.
* Large spill: Keep away from sources of ignition and heat. Prevent rundown to any drains or sewers. Call for assistance on disposal. Absorb material with DRY earth or other non-combustible materials.
* If spill is due to a loss of containment in the system, quickly consult the PLC and shut any valves to prevent further loss.

'''Exposure'''. We must ensure that our employees are aware of the possible toxicity levels of each substance and how to handle exposure. The chemicals that are being used in this process are known chemical irritants to the eyes, skin, and throat. Safety measures must be in place to acknowledge this hazard. Due to the possibility of high pressure releases, we will have 2-minute emergency oxygen masks placed strategically throughout the plant to ensure the safety of any operator in the presence of a large release.

If exposed to the process chemicals, find nearest eye wash station or safety shower immediately and flush exposed skin for at least 15 minutes. Remove any contaminated clothing. Seek medical attention immediately.

'''Storage'''. Store chemicals in segregated and approved areas. Any closed containers for laboratory purposes should be placed in cool, well-ventilated areas.

==Economics==
===Equipment costing===
The calculated capital costs from Aspen Economic Analyzer are reported in Table 2 for all process equipment. The size of the reactor was calculated from the liquid hourly space velocity given in the 2011 ISP patent [8] and a void fraction estimate of 0.4. Storage tanks were sized to contain up to two continuous weeks of material. The number of distillation trays in each tower and the flow rates through pumps, vessels, and the flare were calculated in HYSYS. Heat exchange areas were given in Aspen Energy Analyzer or from HYSYS.

In addition to the above equipment, our plant will require an ion exchanger to produce deionized process water from the municipal water. This is estimated to cost $42,000 in capital cost.

===Cash flow analysis===
Summarizing the important takeaways from the economic analysis, this process will return a revenue of 144 MM$ annually. Offset by production costs, the yearly cash flow is approximately 2.7 MM$, except for in the years in which the catalyst must be reinstalled (approximately every 5 years). At a cost of 2.5 MM$, the cash flows in those years decrease to approximately 0.2 MM$. This analysis assumes the plant will take 2 years to construct, and will operate at 50% in its first year. Furthermore, an interest rate of 10% was assumed with a tax rate of 38% (the maximum for corporate gains taxes). Using the 7-year MACRS depreciation method, the 20 year NPV for the project is 4.3 MM$. With an IRR of 15.1%, which is greater than the assumed interest rate, this project looks to be profitable. Further optimization techniques should be used in future iterations to further increase profitability. See Tables 3 and 4 for key economic information.

===Sensitivity analysis===
As seen in Figure 3, the economic evaluation of this process is influenced the most by changes in the sales price and feed cost. A 20% increase in sales price will result in an approximate 120 MM$ increase in NPV whereas a decrease of the same percentage will result in over a 120 MM$ decrease in NPV. Inversely, a 20% increase in feed cost will result in a 115 MM$ decrease in NPV and a 20% decrease in feed cost will result in a 60 MM$ increase in NPV.

To alleviate the risk associated with feed price, the team researched the price forecasting of bio-succinic acid. Figure 4 provides the bio-succinic acid price over the six years between 2006 and 2012. The price of bio-succinic, shown by the blue line, has remained relatively stable over this time period. This price history can be compared to adipic acid, the green line, which is a common petrochemical precursor for BDO production. Adipic acid as shown has had large fluctuations in price that result in unstable cash flows and uncertainty from shareholders. Thankfully, the stability of bio-succinic acid is a good sign that this process has a huge potential to be profitable especially if the demand for BDO continues to rise as projected.

==Discussion==
As described previously, the Davy process was selected as the most promising process of BDO production. The modified Davy process involves the hydrogenation of bio-succinicic acid with a Pa,Ag,Re catalyst and hydrogen gas. This process has many advantages, one being that it has mature technology that has been improved over the last 20 years. Additionally, the conversion to of succinic acid is virtually complete. Finally, overall plant yields can reach as high as 94 mol%.
As shown in Appendix B, streams ahead of the pressure valve (PRV-101) are at approximately 1.51e4 kPa, and streams after the pressure valve are between 100 and 450 kPa. Furthermore, operating temperatures do not exceed 200°C, including safety factors. These operating conditions contribute to the feasibility of the process, as all the components can be designed with reasonable dimensions (wall thickness, cap type, etc.).

Of particular interest are the large costs of the reactor and pump P-101. The reactor costs nearly 2 MM$ because it has a moderate size with a liquid volume of 16.7 m3, and it operates at 150 atm, which requires a strong stainless steel shell for safety purposes. Pump P-101 has such a large capital cost because it is a centrifugal multistage pump that also needs to be made of stainless steel to withstand pressuring the succinic acid feed to 150 atm.

Financial indicators for the proposed plant suggest that it will be moderately profitable, and additional optimization should be performed before making the capital investment. There is a fair amount of risk associated with the implementation of this production facility, and the return at this juncture may not justify the risk.

The process design and simulation in HYSYS has relied on several key assumptions, which are cause for certain limitations to the results. First, the conversions and selectivity of the catalyst, while taken from literature sources, are assumed to be true. Furthermore, the assumption of negligible side reactions and products was made. It is possible that small waste products in the form of succinates also form in the reactor. Therefore, the main limitation of this model is generally due to reaction specifications.

There are certain safety concerns that go along with the proposed process. First, there are many pipes and vessels that will be at a pressure of approximately 150 atm. Extra insulation and protection must be applied to the piping that contains highly pressurized fluids, to prevent operator injury. Furthermore, the PFR is at a slight risk for runaway reactions due to the exothermic nature of the reaction. The temperature of the reactor must always be monitored by an operator, and the jacket cooling system requires a backup system as well. A benefit of this process is that there are no toxic or severely hazardous components in the process. Additionally, there are no instances of temperature greater than 200°C.

The process design will be fitted with instrumentation and controls to ensure stable operation. These controls, including sensors and valves, minimize potential damage to components due to variation in plant conditions, as well as optimizing the overall performance. For example, the piping entering the tower will be fitted with a control loop. In the direction of flow, a sensing instrument first detects the pressure of the fluid, and then sends a signal to the controller. If the pressure is not within the operating limits, the actuator is signaled to close or open a control valve which is located farther down the stream.

==Conclusion==
The Evanston Chemical Engineering Division suggests a process that produces 45,000 tonnes/year of 99.5 wt% 1,4-butandeiol to enter the market with an appropriate market share. The feasibility of producing BDO as a significant process was investigated. A wide range of BDO production processes were researched, with a modified Davy process being identified as having the most potential. Using a Pa,Ag,Re catalyst on carbon support, this process converts bio-succinic acid to BDO with approximately 94% conversion. This process was designed in Aspen HYSYS, and economic analysis was conducted in Aspen Economic Analyzer. Total capital costs of the project are 12.2 MM$, with a simple payback period of 5.2 years. Total operational costs annually are 139.7 MM$. The process design was successful, with the capability of producing the desired production of BDO.

==Recommendations==
Given the moderate profitability of this process design, it is recommended that Evanston Chemicals explores further optimization techniques to increase the profitability of this process. This includes investigating sales of the γ-butyrolactone byproduct, recycling process water, and further optimizing utility streams for the distillation tower.

Second, we would like to investigate recycling the 2300 kg/h of water produced in the reaction. Our succinic acid enters the reactor as a 50 wt% solution in water, so we should look into replacing some of this with the product water. Not only will this decrease our water bill, but it will also lower the cost of ion exchange.

==References==
# Nexant.''Is Bio-Butanediol Here to Stay?'' White Plains, NY: ChemSystems Products; 2012.
# De Guzman D. Chemical industry awaits for bio-succinic acid potential. ICIS. Available at: http://www.icis.com/resources/news/2012/01/30/9527521/chemical-industry-awaits-for-bio-succinic-acid-potential/. Accessed January 24, 2014.
# Australian Government: Department of Health. 1,4-butanediol factsheet. National Industrial Chemicals Notification and Assessment Scheme. Available at: http://www.nicnas.gov.au/communications/publications/information-sheets/existing-chemical-info-sheets/other-information-sheets. Accessed January 24, 2014.
# TecnonOrbiChem. Chem-net facts: 1,4-butanediol. TecnonOrbiChem. Available at: http://www.orbichem.com/userfiles/CNF%20Samples/bdo_13_11.pdf. Accessed January 23, 2014.
# Nexant. 1,4-butanediol/tetrahydrofuran (BDO/THF). ChemSystems. Available at: http://www.chemsystems.com/about/cs/news/items/ PERP2012_3_BDO_THF.cfm. Accessed February 6, 2014.
# Burk MJ, Van Dien SJ, Burgard AP, inventors; Genomatica, Inc., assignee. Compositions and methods for the biosynthesis of 1,4-butanediol and its precursors. US patent 8,067,214. Nov. 29, 2011.
# Chung S-H, Kim M-S, Eom H-H, Lee K-Y. Catalytic hydrogenation of bio-based succinic acid for the production of 1,4-butanediol through the indirect pathway. AIChE. Available at: https://aiche.confex.com/aiche/2013/webprogram/Paper327470.html. Accessed January 23, 2014.
# Bhattacharyya A, Manila MD, inventors; ISP Investments Inc., assignee. Catalysts for maleic acid hydrogenation to 1,4-Butanediol. US patent 7,935,834 B2. May 3, 2011.

Design S2

2014-03-15T04:56:24Z

Karetstik: /* References */

Title: Production of 1,4-butanediol

Authors: Nick Pinkerton, Karen Schmidt, and James Xamplas

Date Presented: March 14, 2014

==Introduction==
1,4-butanediol (BDO) is traditionally made from petroleum-derived feedstocks in a variety of processes such as the Reppe (acetylene-based), Mitsubishi (butadiene-based), and Davy (maleic acid-based) processes [1]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, BDO [1]. It is this process that Team S2Kool4Skool has chosen to develop for a new bio-butanediol plant, because the Davy method is mature and requires no new innovations, and because an appropriate feedstock of bio-succinic acid is now available. The plant will be located in East Carroll Parish, Louisiana. This county is also home to Myriant; located in Lake Providence, they are the largest domestic provider of bio-succinic acid [2]. Furthermore, Lake Providence is conveniently located on the Mississippi River, which will allow for affordable transportation of our bio-based butanediol product. The intent of this project is to produce 45,000 metric tonnes of 99.5 wt% 1,4-butanediol per year in a new plant in Lake Providence, LA. The plant will run 24 hours per day for 350 days out of the year, allowing approximately two weeks for a maintenance shutdown.

As there are several techniques for producing 1,4 butanediol in industry, the first step was to determine a synthesis path. Based on the chosen path, reaction kinetics, and required production rate of the process, a reactor system was then designed. Next, the process was designed to deliver the reactants to the reactor at the proper operating conditions, and the separations, purification, and waste management steps were designed. Cost estimates were made using costing software and hand calculations. Finally, the process was iterated and optimized to reduce costs.

==Background==
===General information===
BDO is an organic chemical with the molecular formula <math>C_4H_{10}O_2</math>. It is also a diol with its two hydroxyl groups located at the terminal carbons. BDO has a boiling point of 235 degrees C and is therefore a colorless liquid at standard temperatures and pressures [3].

There are many precursors that petrochemical synthesis of BDO uses. The commonality between all of the precursor acids is that they are hydrogenatable. In replacement of one of these petrochemical precursors, our team has been tasked with the challenge of deriving BDO from the bio-based precursor succinic acid. This catalyzed reaction will take place in the presence of hydrogen as the hydrogenating component shown below:

<math>C_4H_6O_4 + 4H_2 = C_4H_{10}O_2 + 2H_2O</math>

As described in the above reaction, there will need to be at least 4:1 stoichiometric ratio of hydrogen gas to succinic acid. Two moles of water will also be produced along with each mole of BDO. This reaction is exothermic, which requires the reactor to be continuously cooled to maintain our reactor temperature. There are also side products that are produced which include tetrahydrofuran (THF) and γ-butyrolactone (GBL); however, thanks to catalyst selectivity these byproducts are produced in small quantities.

===Market analysis===
Butanediol has a quickly expanding market due to new technological evolutions and its growing use as a chemical intermediary in advanced materials. With biological routes being optimized, the potential of biomass-derived chemicals is tremendous. The global demand of BDO was estimated at 1.5 million metric tons in 2011 and is projected to grow at an annual rate of 4.5% for the next several years [1]. Unlike other chemical products, BDO’s profitability and attractiveness to producers lies in its downstream potential. Figure 1 below demonstrates several potential downstream products that can be directly or indirectly synthesized from BDO. The largest of these contributors include THF and GBL.

The current market demand of BDO is being supplemented by several global chemical companies. These companies include BASF, BioAmber, Purac, Myriant, DSM, Mitsubishi Chemical, Roquette, and OPXBIO. The market shares of these companies were not available for this product; however, with the consistent growth of the BDO market our team feels that the market is not saturated or impenetrable. The current market price of BDO fluctuates between $3.06 and $3.31 per kg for US-made products [4]. These prices correlate to a nearly 7 billion dollar industry.

===Process alternatives===
1,4-butanediol is traditionally made from petroleum-derived feedstocks in a variety of processes [5]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Several companies are currently implementing bio-routes of producing butanediol. Genomatica is using a bioengineered microorganism to convert sugar feedstocks directly to BDO via fermentation [6], but most companies are instead using microorganisms to convert sugar to succinic acid. The bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, which is the path that most are choosing, although research is being conducted on alternative pathways [7].

==Process overview==
The newly proposed plant can be divided into four stages: pre-reactor, reactor, post-reactor and distillation. Each section is an integral part to the overall process and demands close attention. The process flow diagram (see Appendix A) and stream table (Appendix B) provide more detailed information.

===Pre-reactor===
This chemical process begins with two feedstocks: hydrogen gas and bio-succinic acid. The hydrogen gas will be obtained from a pipeline at 150 atm and will be used in molar excess inside the reactor. The bio-succinic acid will be purchased by Myriant Corporation which is located near the planned plant site. The pricing for this feedstock is approximately $2.12 per kg. The plant will require 63,000 metric tonnes of bio-succinic acid per year to meet the proposed plant capacity. First the bio-succinic acid feed is pumped up to 150 atm to match the hydrogen gas feed, and then it is mixed with the hydrogen gas prior to being sent into heat exchanger E-101 for heating. The heat exchanger brings the two feeds up to 110oC and sends them to the jacketed packed bed reactor.

===Reactor===
The hydrogenation reaction occurs inside of the reactor thanks to the packed catalyst bed. The catalyst used is 0.4% Fe, 1.9% Na, 2.66% Ag, 2.66% Pd, 10.0% Re on 1.5mm carbon support. With this catalyst, BDO is produced with over 90% selectivity and minimal side reactions of THF and GBL.8 The reaction has an operating pressure of 2000-4000 psi and internal reactor temperature of 165°C. This temperature allows for about 99.7% conversion of succinic acid.8 Due to the exothermic nature of the reaction, a cooling jacket is required which utilizes downstream cold streams to cool the internal bed to maintain the desired reaction temperature.

===Post-reactor===
The effluent of the reactor is sent back to E-101 as the hot stream. After exiting E-101, the reactor product stream is sent to a secondary exchanger, E-102, where utility cooling water is used to reduce the temperature to an acceptable temperature prior to sending it to a pressure let-down valve. At this point the pressure of the stream is taken from 150 atm to 1 atm. This large pressure drop allows for the stream to split into its vapor and liquid portions in a gas-liquid separator. The vapor stream of the gas liquid separator is primarily hydrogen gas and sent to a flare for disposal. The liquid effluent is at approximately 45oC leaving the separator and is therefore pumped to the reactor jacket for the reaction cooling mentioned previously. After running through the reactor jacket, the stream enters the separation processes.

===Distillation===
The first distillation column, T-101, is a 10 stage column whose primary purpose is separating the THF from the product feed. Due to THF’s lower boiling point, the byproduct comes off of the top of the column with mostly water. This distillate is sent to the plant's THF waste storage tank that has the capacity of two weeks. The bottoms of the column is sent to the subsequent distillation column that separates the BDO from the GBL and water. The relatively close boiling points of BDO and GBL, 235oC and 204oC, respectively, create a difficult separation that requires a 15 stage column. The distillate of the column is approximately 23% GBL with balance water. This stream is sent to a storage tank with similar sizing parameters as the THF storage tank. The bottom stream is the final 99.5wt% BDO product. This stream is sent to the final product tank, S-104. Depending on our customer demands and the plant location we have the ability to barge, rail or pipe our product to its final destination. Due to low purity of the byproducts, future iterations are needed to optimize either purifying byproducts or selling impure byproducts. There is definitely an available market for these byproducts that should be researched more extensively to increase profit. A detailed description of the equipment from the PFD can be found in Appendix C, in addition to sizing specifications and purpose of equipment.

===Mass and energy balances===
Using an Aspen HYSYS simulation we were able to record the material and energy streams going in and out of the process system. Mass and energy balances are provided Appendix D where each inlet and outlet stream is described and quantified. As expected, the material and energy totals for the inlet and outlet streams add together to equal 0. This proves that our system is mathematically prudent and thermodynamically feasible. The total mass flow of the system is 15,639 kg/h and the total energy in and out of the system is 1.41e8 kJ/h.

===HYSYS simulation===
The HYSYS simulation was performed using the NRTL ideal fluid package. After using AspenPlus to verify that the HYSYS package had the appropriate vapor-liquid equilibrium information between THF and water, and between GBL and water, we concluded it was feasible to proceed with that fluid package. The simulation consists of a reactor, a gas-liquid separator, 2 pumps, 3 heaters, a valve, and 2 distillation columns (see Figure 2). The simulation successfully converted the succinic acid feed into the desired products. Also, the combination of the two distillation columns was able to effectively separate the BDO to obtain a 99.5% pure product with 99.5% recovery. In addition, a set was made between the energy required to heat stream 12 and the energy required to cool the reactor so that these values were made equal. Lastly, the condenser and reboiler duties were used in four heat exchangers in order to determine the appropriate size of this equipment as well as the necessary utility flow rates.

==Health and safety==
===Chemical properties===
Inherent to this process are a number of toxic chemicals. Table 1 summarizes the important safety data including hazard type, odor, color, and exposure limits.

As shown in the above table, the chemicals that this facility will be dealing with will be relatively mild and non-life threatening. Regardless of their perceived threat, chemicals should always be handled with care especially when they are at high temperatures and pressures.

===Safety procedures===

'''Fire'''. There are many flammable materials that will be included in this process; therefore, fire safety is imperative for all employees. There are countless possible causes of ignition and care should be taken while handling any flammable material whether in the lab or in the field.

In case a fire is present on, the following protocol should be implemented:

* Small fire: Use DRY chemical powder.
* Large fire: Use alcohol foam, water spray, or fog.
* Call for backup if unable to control.
* Immediately contact supervisor and emergency personnel on site.
* Evacuate to safe distance in case of fires around any hazardous materials or pressure vessels.

'''Spills'''. Process chemical spills will eventually occur in a plant of this scale. Small spills are likely to occur in a laboratory setting. Large spills could be a result of loss of containment in the system. We must ensure that all personnel are aware of proper spill mitigation protocol.

* Small spill: Dilute with water and mop or absorb with inert dry material. Dispose of in proper receptacle.
* Large spill: Keep away from sources of ignition and heat. Prevent rundown to any drains or sewers. Call for assistance on disposal. Absorb material with DRY earth or other non-combustible materials.
* If spill is due to a loss of containment in the system, quickly consult the PLC and shut any valves to prevent further loss.

'''Exposure'''. We must ensure that our employees are aware of the possible toxicity levels of each substance and how to handle exposure. The chemicals that are being used in this process are known chemical irritants to the eyes, skin, and throat. Safety measures must be in place to acknowledge this hazard. Due to the possibility of high pressure releases, we will have 2-minute emergency oxygen masks placed strategically throughout the plant to ensure the safety of any operator in the presence of a large release.

If exposed to the process chemicals, find nearest eye wash station or safety shower immediately and flush exposed skin for at least 15 minutes. Remove any contaminated clothing. Seek medical attention immediately.

'''Storage'''. Store chemicals in segregated and approved areas. Any closed containers for laboratory purposes should be placed in cool, well-ventilated areas.

==Economics==
===Equipment costing===
The calculated capital costs from Aspen Economic Analyzer are reported in Table 2 for all process equipment. The size of the reactor was calculated from the liquid hourly space velocity given in the 2011 ISP patent [8] and a void fraction estimate of 0.4. Storage tanks were sized to contain up to two continuous weeks of material. The number of distillation trays in each tower and the flow rates through pumps, vessels, and the flare were calculated in HYSYS. Heat exchange areas were given in Aspen Energy Analyzer or from HYSYS.

In addition to the above equipment, our plant will require an ion exchanger to produce deionized process water from the municipal water. This is estimated to cost $42,000 in capital cost.

===Cash flow analysis===
Summarizing the important takeaways from the economic analysis (see Appendix G), this process will return a revenue of 144 MM$ annually. Offset by production costs, the yearly cash flow is approximately 2.7 MM$, except for in the years in which the catalyst must be reinstalled (approximately every 5 years). At a cost of 2.5 MM$, the cash flows in those years decrease to approximately 0.2 MM$. This analysis assumes the plant will take 2 years to construct, and will operate at 50% in its first year. Furthermore, an interest rate of 10% was assumed with a tax rate of 38% (the maximum for corporate gains taxes). Using the 7-year MACRS depreciation method, the 20 year NPV for the project is 4.3 MM$. With an IRR of 15.1%, which is greater than the assumed interest rate, this project looks to be profitable. Further optimization techniques should be used in future iterations to further increase profitability. See Tables 3 and 4 for key economic information.

===Sensitivity analysis===
As seen in Figure 3, the economic evaluation of this process is influenced the most by changes in the sales price and feed cost. A 20% increase in sales price will result in an approximate 120 MM$ increase in NPV whereas a decrease of the same percentage will result in over a 120 MM$ decrease in NPV. Inversely, a 20% increase in feed cost will result in a 115 MM$ decrease in NPV and a 20% decrease in feed cost will result in a 60 MM$ increase in NPV.

To alleviate the risk associated with feed price, the team researched the price forecasting of bio-succinic acid. Figure 4 provides the bio-succinic acid price over the six years between 2006 and 2012. The price of bio-succinic, shown by the blue line, has remained relatively stable over this time period. This price history can be compared to adipic acid, the green line, which is a common petrochemical precursor for BDO production. Adipic acid as shown has had large fluctuations in price that result in unstable cash flows and uncertainty from shareholders. Thankfully, the stability of bio-succinic acid is a good sign that this process has a huge potential to be profitable especially if the demand for BDO continues to rise as projected.

==Discussion==
As described previously, the Davy process was selected as the most promising process of BDO production. The modified Davy process involves the hydrogenation of bio-succinicic acid with a Pa,Ag,Re catalyst and hydrogen gas. This process has many advantages, one being that it has mature technology that has been improved over the last 20 years. Additionally, the conversion to of succinic acid is virtually complete. Finally, overall plant yields can reach as high as 94 mol%.
As shown in Appendix B, streams ahead of the pressure valve (PRV-101) are at approximately 1.51e4 kPa, and streams after the pressure valve are between 100 and 450 kPa. Furthermore, operating temperatures do not exceed 200°C, including safety factors. These operating conditions contribute to the feasibility of the process, as all the components can be designed with reasonable dimensions (wall thickness, cap type, etc.).

Of particular interest are the large costs of the reactor and pump P-101. The reactor costs nearly 2 MM$ because it has a moderate size with a liquid volume of 16.7 m3, and it operates at 150 atm, which requires a strong stainless steel shell for safety purposes. Pump P-101 has such a large capital cost because it is a centrifugal multistage pump that also needs to be made of stainless steel to withstand pressuring the succinic acid feed to 150 atm.

Financial indicators for the proposed plant suggest that it will be moderately profitable, and additional optimization should be performed before making the capital investment. There is a fair amount of risk associated with the implementation of this production facility, and the return at this juncture may not justify the risk.

The process design and simulation in HYSYS has relied on several key assumptions, which are cause for certain limitations to the results. First, the conversions and selectivity of the catalyst, while taken from literature sources, are assumed to be true. Furthermore, the assumption of negligible side reactions and products was made. It is possible that small waste products in the form of succinates also form in the reactor. Therefore, the main limitation of this model is generally due to reaction specifications.

There are certain safety concerns that go along with the proposed process. First, there are many pipes and vessels that will be at a pressure of approximately 150 atm. Extra insulation and protection must be applied to the piping that contains highly pressurized fluids, to prevent operator injury. Furthermore, the PFR is at a slight risk for runaway reactions due to the exothermic nature of the reaction. The temperature of the reactor must always be monitored by an operator, and the jacket cooling system requires a backup system as well. A benefit of this process is that there are no toxic or severely hazardous components in the process. Additionally, there are no instances of temperature greater than 200°C.

The process design will be fitted with instrumentation and controls to ensure stable operation. These controls, including sensors and valves, minimize potential damage to components due to variation in plant conditions, as well as optimizing the overall performance. For example, the piping entering the tower will be fitted with a control loop. In the direction of flow, a sensing instrument first detects the pressure of the fluid, and then sends a signal to the controller. If the pressure is not within the operating limits, the actuator is signaled to close or open a control valve which is located farther down the stream.

==Conclusion==
The Evanston Chemical Engineering Division suggests a process that produces 45,000 tonnes/year of 99.5 wt% 1,4-butandeiol to enter the market with an appropriate market share. The feasibility of producing BDO as a significant process was investigated. A wide range of BDO production processes were researched, with a modified Davy process being identified as having the most potential. Using a Pa,Ag,Re catalyst on carbon support, this process converts bio-succinic acid to BDO with approximately 94% conversion. This process was designed in Aspen HYSYS, and economic analysis was conducted in Aspen Economic Analyzer. Total capital costs of the project are 12.2 MM$, with a simple payback period of 5.2 years. Total operational costs annually are 139.7 MM$. The process design was successful, with the capability of producing the desired production of BDO.

==Recommendations==
Given the moderate profitability of this process design, it is recommended that Evanston Chemicals explores further optimization techniques to increase the profitability of this process. This includes investigating sales of the γ-butyrolactone byproduct, recycling process water, and further optimizing utility streams for the distillation tower.

Second, we would like to investigate recycling the 2300 kg/h of water produced in the reaction. Our succinic acid enters the reactor as a 50 wt% solution in water, so we should look into replacing some of this with the product water. Not only will this decrease our water bill, but it will also lower the cost of ion exchange.

==References==
# Nexant.''Is Bio-Butanediol Here to Stay?'' White Plains, NY: ChemSystems Products; 2012.
# De Guzman D. Chemical industry awaits for bio-succinic acid potential. ICIS. Available at: http://www.icis.com/resources/news/2012/01/30/9527521/chemical-industry-awaits-for-bio-succinic-acid-potential/. Accessed January 24, 2014.
# Australian Government: Department of Health. 1,4-butanediol factsheet. National Industrial Chemicals Notification and Assessment Scheme. Available at: http://www.nicnas.gov.au/communications/publications/information-sheets/existing-chemical-info-sheets/other-information-sheets. Accessed January 24, 2014.
# TecnonOrbiChem. Chem-net facts: 1,4-butanediol. TecnonOrbiChem. Available at: http://www.orbichem.com/userfiles/CNF%20Samples/bdo_13_11.pdf. Accessed January 23, 2014.
# Nexant. 1,4-butanediol/tetrahydrofuran (BDO/THF). ChemSystems. Available at: http://www.chemsystems.com/about/cs/news/items/ PERP2012_3_BDO_THF.cfm. Accessed February 6, 2014.
# Burk MJ, Van Dien SJ, Burgard AP, inventors; Genomatica, Inc., assignee. Compositions and methods for the biosynthesis of 1,4-butanediol and its precursors. US patent 8,067,214. Nov. 29, 2011.
# Chung S-H, Kim M-S, Eom H-H, Lee K-Y. Catalytic hydrogenation of bio-based succinic acid for the production of 1,4-butanediol through the indirect pathway. AIChE. Available at: https://aiche.confex.com/aiche/2013/webprogram/Paper327470.html. Accessed January 23, 2014.
# Bhattacharyya A, Manila MD, inventors; ISP Investments Inc., assignee. Catalysts for maleic acid hydrogenation to 1,4-Butanediol. US patent 7,935,834 B2. May 3, 2011.

Design S2

2014-03-15T04:55:58Z

Karetstik: /* Recommendations */

Title: Production of 1,4-butanediol

Authors: Nick Pinkerton, Karen Schmidt, and James Xamplas

Date Presented: March 14, 2014

==Introduction==
1,4-butanediol (BDO) is traditionally made from petroleum-derived feedstocks in a variety of processes such as the Reppe (acetylene-based), Mitsubishi (butadiene-based), and Davy (maleic acid-based) processes [1]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, BDO [1]. It is this process that Team S2Kool4Skool has chosen to develop for a new bio-butanediol plant, because the Davy method is mature and requires no new innovations, and because an appropriate feedstock of bio-succinic acid is now available. The plant will be located in East Carroll Parish, Louisiana. This county is also home to Myriant; located in Lake Providence, they are the largest domestic provider of bio-succinic acid [2]. Furthermore, Lake Providence is conveniently located on the Mississippi River, which will allow for affordable transportation of our bio-based butanediol product. The intent of this project is to produce 45,000 metric tonnes of 99.5 wt% 1,4-butanediol per year in a new plant in Lake Providence, LA. The plant will run 24 hours per day for 350 days out of the year, allowing approximately two weeks for a maintenance shutdown.

As there are several techniques for producing 1,4 butanediol in industry, the first step was to determine a synthesis path. Based on the chosen path, reaction kinetics, and required production rate of the process, a reactor system was then designed. Next, the process was designed to deliver the reactants to the reactor at the proper operating conditions, and the separations, purification, and waste management steps were designed. Cost estimates were made using costing software and hand calculations. Finally, the process was iterated and optimized to reduce costs.

==Background==
===General information===
BDO is an organic chemical with the molecular formula <math>C_4H_{10}O_2</math>. It is also a diol with its two hydroxyl groups located at the terminal carbons. BDO has a boiling point of 235 degrees C and is therefore a colorless liquid at standard temperatures and pressures [3].

There are many precursors that petrochemical synthesis of BDO uses. The commonality between all of the precursor acids is that they are hydrogenatable. In replacement of one of these petrochemical precursors, our team has been tasked with the challenge of deriving BDO from the bio-based precursor succinic acid. This catalyzed reaction will take place in the presence of hydrogen as the hydrogenating component shown below:

<math>C_4H_6O_4 + 4H_2 = C_4H_{10}O_2 + 2H_2O</math>

As described in the above reaction, there will need to be at least 4:1 stoichiometric ratio of hydrogen gas to succinic acid. Two moles of water will also be produced along with each mole of BDO. This reaction is exothermic, which requires the reactor to be continuously cooled to maintain our reactor temperature. There are also side products that are produced which include tetrahydrofuran (THF) and γ-butyrolactone (GBL); however, thanks to catalyst selectivity these byproducts are produced in small quantities.

===Market analysis===
Butanediol has a quickly expanding market due to new technological evolutions and its growing use as a chemical intermediary in advanced materials. With biological routes being optimized, the potential of biomass-derived chemicals is tremendous. The global demand of BDO was estimated at 1.5 million metric tons in 2011 and is projected to grow at an annual rate of 4.5% for the next several years [1]. Unlike other chemical products, BDO’s profitability and attractiveness to producers lies in its downstream potential. Figure 1 below demonstrates several potential downstream products that can be directly or indirectly synthesized from BDO. The largest of these contributors include THF and GBL.

The current market demand of BDO is being supplemented by several global chemical companies. These companies include BASF, BioAmber, Purac, Myriant, DSM, Mitsubishi Chemical, Roquette, and OPXBIO. The market shares of these companies were not available for this product; however, with the consistent growth of the BDO market our team feels that the market is not saturated or impenetrable. The current market price of BDO fluctuates between $3.06 and $3.31 per kg for US-made products [4]. These prices correlate to a nearly 7 billion dollar industry.

===Process alternatives===
1,4-butanediol is traditionally made from petroleum-derived feedstocks in a variety of processes [5]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Several companies are currently implementing bio-routes of producing butanediol. Genomatica is using a bioengineered microorganism to convert sugar feedstocks directly to BDO via fermentation [6], but most companies are instead using microorganisms to convert sugar to succinic acid. The bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, which is the path that most are choosing, although research is being conducted on alternative pathways [7].

==Process overview==
The newly proposed plant can be divided into four stages: pre-reactor, reactor, post-reactor and distillation. Each section is an integral part to the overall process and demands close attention. The process flow diagram (see Appendix A) and stream table (Appendix B) provide more detailed information.

===Pre-reactor===
This chemical process begins with two feedstocks: hydrogen gas and bio-succinic acid. The hydrogen gas will be obtained from a pipeline at 150 atm and will be used in molar excess inside the reactor. The bio-succinic acid will be purchased by Myriant Corporation which is located near the planned plant site. The pricing for this feedstock is approximately $2.12 per kg. The plant will require 63,000 metric tonnes of bio-succinic acid per year to meet the proposed plant capacity. First the bio-succinic acid feed is pumped up to 150 atm to match the hydrogen gas feed, and then it is mixed with the hydrogen gas prior to being sent into heat exchanger E-101 for heating. The heat exchanger brings the two feeds up to 110oC and sends them to the jacketed packed bed reactor.

===Reactor===
The hydrogenation reaction occurs inside of the reactor thanks to the packed catalyst bed. The catalyst used is 0.4% Fe, 1.9% Na, 2.66% Ag, 2.66% Pd, 10.0% Re on 1.5mm carbon support. With this catalyst, BDO is produced with over 90% selectivity and minimal side reactions of THF and GBL.8 The reaction has an operating pressure of 2000-4000 psi and internal reactor temperature of 165°C. This temperature allows for about 99.7% conversion of succinic acid.8 Due to the exothermic nature of the reaction, a cooling jacket is required which utilizes downstream cold streams to cool the internal bed to maintain the desired reaction temperature.

===Post-reactor===
The effluent of the reactor is sent back to E-101 as the hot stream. After exiting E-101, the reactor product stream is sent to a secondary exchanger, E-102, where utility cooling water is used to reduce the temperature to an acceptable temperature prior to sending it to a pressure let-down valve. At this point the pressure of the stream is taken from 150 atm to 1 atm. This large pressure drop allows for the stream to split into its vapor and liquid portions in a gas-liquid separator. The vapor stream of the gas liquid separator is primarily hydrogen gas and sent to a flare for disposal. The liquid effluent is at approximately 45oC leaving the separator and is therefore pumped to the reactor jacket for the reaction cooling mentioned previously. After running through the reactor jacket, the stream enters the separation processes.

===Distillation===
The first distillation column, T-101, is a 10 stage column whose primary purpose is separating the THF from the product feed. Due to THF’s lower boiling point, the byproduct comes off of the top of the column with mostly water. This distillate is sent to the plant's THF waste storage tank that has the capacity of two weeks. The bottoms of the column is sent to the subsequent distillation column that separates the BDO from the GBL and water. The relatively close boiling points of BDO and GBL, 235oC and 204oC, respectively, create a difficult separation that requires a 15 stage column. The distillate of the column is approximately 23% GBL with balance water. This stream is sent to a storage tank with similar sizing parameters as the THF storage tank. The bottom stream is the final 99.5wt% BDO product. This stream is sent to the final product tank, S-104. Depending on our customer demands and the plant location we have the ability to barge, rail or pipe our product to its final destination. Due to low purity of the byproducts, future iterations are needed to optimize either purifying byproducts or selling impure byproducts. There is definitely an available market for these byproducts that should be researched more extensively to increase profit. A detailed description of the equipment from the PFD can be found in Appendix C, in addition to sizing specifications and purpose of equipment.

===Mass and energy balances===
Using an Aspen HYSYS simulation we were able to record the material and energy streams going in and out of the process system. Mass and energy balances are provided Appendix D where each inlet and outlet stream is described and quantified. As expected, the material and energy totals for the inlet and outlet streams add together to equal 0. This proves that our system is mathematically prudent and thermodynamically feasible. The total mass flow of the system is 15,639 kg/h and the total energy in and out of the system is 1.41e8 kJ/h.

===HYSYS simulation===
The HYSYS simulation was performed using the NRTL ideal fluid package. After using AspenPlus to verify that the HYSYS package had the appropriate vapor-liquid equilibrium information between THF and water, and between GBL and water, we concluded it was feasible to proceed with that fluid package. The simulation consists of a reactor, a gas-liquid separator, 2 pumps, 3 heaters, a valve, and 2 distillation columns (see Figure 2). The simulation successfully converted the succinic acid feed into the desired products. Also, the combination of the two distillation columns was able to effectively separate the BDO to obtain a 99.5% pure product with 99.5% recovery. In addition, a set was made between the energy required to heat stream 12 and the energy required to cool the reactor so that these values were made equal. Lastly, the condenser and reboiler duties were used in four heat exchangers in order to determine the appropriate size of this equipment as well as the necessary utility flow rates.

==Health and safety==
===Chemical properties===
Inherent to this process are a number of toxic chemicals. Table 1 summarizes the important safety data including hazard type, odor, color, and exposure limits.

As shown in the above table, the chemicals that this facility will be dealing with will be relatively mild and non-life threatening. Regardless of their perceived threat, chemicals should always be handled with care especially when they are at high temperatures and pressures.

===Safety procedures===

'''Fire'''. There are many flammable materials that will be included in this process; therefore, fire safety is imperative for all employees. There are countless possible causes of ignition and care should be taken while handling any flammable material whether in the lab or in the field.

In case a fire is present on, the following protocol should be implemented:

* Small fire: Use DRY chemical powder.
* Large fire: Use alcohol foam, water spray, or fog.
* Call for backup if unable to control.
* Immediately contact supervisor and emergency personnel on site.
* Evacuate to safe distance in case of fires around any hazardous materials or pressure vessels.

'''Spills'''. Process chemical spills will eventually occur in a plant of this scale. Small spills are likely to occur in a laboratory setting. Large spills could be a result of loss of containment in the system. We must ensure that all personnel are aware of proper spill mitigation protocol.

* Small spill: Dilute with water and mop or absorb with inert dry material. Dispose of in proper receptacle.
* Large spill: Keep away from sources of ignition and heat. Prevent rundown to any drains or sewers. Call for assistance on disposal. Absorb material with DRY earth or other non-combustible materials.
* If spill is due to a loss of containment in the system, quickly consult the PLC and shut any valves to prevent further loss.

'''Exposure'''. We must ensure that our employees are aware of the possible toxicity levels of each substance and how to handle exposure. The chemicals that are being used in this process are known chemical irritants to the eyes, skin, and throat. Safety measures must be in place to acknowledge this hazard. Due to the possibility of high pressure releases, we will have 2-minute emergency oxygen masks placed strategically throughout the plant to ensure the safety of any operator in the presence of a large release.

If exposed to the process chemicals, find nearest eye wash station or safety shower immediately and flush exposed skin for at least 15 minutes. Remove any contaminated clothing. Seek medical attention immediately.

'''Storage'''. Store chemicals in segregated and approved areas. Any closed containers for laboratory purposes should be placed in cool, well-ventilated areas.

==Economics==
===Equipment costing===
The calculated capital costs from Aspen Economic Analyzer are reported in Table 2 for all process equipment. The size of the reactor was calculated from the liquid hourly space velocity given in the 2011 ISP patent [8] and a void fraction estimate of 0.4. Storage tanks were sized to contain up to two continuous weeks of material. The number of distillation trays in each tower and the flow rates through pumps, vessels, and the flare were calculated in HYSYS. Heat exchange areas were given in Aspen Energy Analyzer or from HYSYS.

In addition to the above equipment, our plant will require an ion exchanger to produce deionized process water from the municipal water. This is estimated to cost $42,000 in capital cost.

===Cash flow analysis===
Summarizing the important takeaways from the economic analysis (see Appendix G), this process will return a revenue of 144 MM$ annually. Offset by production costs, the yearly cash flow is approximately 2.7 MM$, except for in the years in which the catalyst must be reinstalled (approximately every 5 years). At a cost of 2.5 MM$, the cash flows in those years decrease to approximately 0.2 MM$. This analysis assumes the plant will take 2 years to construct, and will operate at 50% in its first year. Furthermore, an interest rate of 10% was assumed with a tax rate of 38% (the maximum for corporate gains taxes). Using the 7-year MACRS depreciation method, the 20 year NPV for the project is 4.3 MM$. With an IRR of 15.1%, which is greater than the assumed interest rate, this project looks to be profitable. Further optimization techniques should be used in future iterations to further increase profitability. See Tables 3 and 4 for key economic information.

===Sensitivity analysis===
As seen in Figure 3, the economic evaluation of this process is influenced the most by changes in the sales price and feed cost. A 20% increase in sales price will result in an approximate 120 MM$ increase in NPV whereas a decrease of the same percentage will result in over a 120 MM$ decrease in NPV. Inversely, a 20% increase in feed cost will result in a 115 MM$ decrease in NPV and a 20% decrease in feed cost will result in a 60 MM$ increase in NPV.

To alleviate the risk associated with feed price, the team researched the price forecasting of bio-succinic acid. Figure 4 provides the bio-succinic acid price over the six years between 2006 and 2012. The price of bio-succinic, shown by the blue line, has remained relatively stable over this time period. This price history can be compared to adipic acid, the green line, which is a common petrochemical precursor for BDO production. Adipic acid as shown has had large fluctuations in price that result in unstable cash flows and uncertainty from shareholders. Thankfully, the stability of bio-succinic acid is a good sign that this process has a huge potential to be profitable especially if the demand for BDO continues to rise as projected.

==Discussion==
As described previously, the Davy process was selected as the most promising process of BDO production. The modified Davy process involves the hydrogenation of bio-succinicic acid with a Pa,Ag,Re catalyst and hydrogen gas. This process has many advantages, one being that it has mature technology that has been improved over the last 20 years. Additionally, the conversion to of succinic acid is virtually complete. Finally, overall plant yields can reach as high as 94 mol%.
As shown in Appendix B, streams ahead of the pressure valve (PRV-101) are at approximately 1.51e4 kPa, and streams after the pressure valve are between 100 and 450 kPa. Furthermore, operating temperatures do not exceed 200°C, including safety factors. These operating conditions contribute to the feasibility of the process, as all the components can be designed with reasonable dimensions (wall thickness, cap type, etc.).

Of particular interest are the large costs of the reactor and pump P-101. The reactor costs nearly 2 MM$ because it has a moderate size with a liquid volume of 16.7 m3, and it operates at 150 atm, which requires a strong stainless steel shell for safety purposes. Pump P-101 has such a large capital cost because it is a centrifugal multistage pump that also needs to be made of stainless steel to withstand pressuring the succinic acid feed to 150 atm.

Financial indicators for the proposed plant suggest that it will be moderately profitable, and additional optimization should be performed before making the capital investment. There is a fair amount of risk associated with the implementation of this production facility, and the return at this juncture may not justify the risk.

The process design and simulation in HYSYS has relied on several key assumptions, which are cause for certain limitations to the results. First, the conversions and selectivity of the catalyst, while taken from literature sources, are assumed to be true. Furthermore, the assumption of negligible side reactions and products was made. It is possible that small waste products in the form of succinates also form in the reactor. Therefore, the main limitation of this model is generally due to reaction specifications.

There are certain safety concerns that go along with the proposed process. First, there are many pipes and vessels that will be at a pressure of approximately 150 atm. Extra insulation and protection must be applied to the piping that contains highly pressurized fluids, to prevent operator injury. Furthermore, the PFR is at a slight risk for runaway reactions due to the exothermic nature of the reaction. The temperature of the reactor must always be monitored by an operator, and the jacket cooling system requires a backup system as well. A benefit of this process is that there are no toxic or severely hazardous components in the process. Additionally, there are no instances of temperature greater than 200°C.

The process design will be fitted with instrumentation and controls to ensure stable operation. These controls, including sensors and valves, minimize potential damage to components due to variation in plant conditions, as well as optimizing the overall performance. For example, the piping entering the tower will be fitted with a control loop. In the direction of flow, a sensing instrument first detects the pressure of the fluid, and then sends a signal to the controller. If the pressure is not within the operating limits, the actuator is signaled to close or open a control valve which is located farther down the stream.

==Conclusion==
The Evanston Chemical Engineering Division suggests a process that produces 45,000 tonnes/year of 99.5 wt% 1,4-butandeiol to enter the market with an appropriate market share. The feasibility of producing BDO as a significant process was investigated. A wide range of BDO production processes were researched, with a modified Davy process being identified as having the most potential. Using a Pa,Ag,Re catalyst on carbon support, this process converts bio-succinic acid to BDO with approximately 94% conversion. This process was designed in Aspen HYSYS, and economic analysis was conducted in Aspen Economic Analyzer. Total capital costs of the project are 12.2 MM$, with a simple payback period of 5.2 years. Total operational costs annually are 139.7 MM$. The process design was successful, with the capability of producing the desired production of BDO.

==Recommendations==
Given the moderate profitability of this process design, it is recommended that Evanston Chemicals explores further optimization techniques to increase the profitability of this process. This includes investigating sales of the γ-butyrolactone byproduct, recycling process water, and further optimizing utility streams for the distillation tower.

Second, we would like to investigate recycling the 2300 kg/h of water produced in the reaction. Our succinic acid enters the reactor as a 50 wt% solution in water, so we should look into replacing some of this with the product water. Not only will this decrease our water bill, but it will also lower the cost of ion exchange.

==References==
# Nexant.Is Bio-Butanediol Here to Stay? White Plains, NY: ChemSystems Products; 2012.
# De Guzman D. Chemical industry awaits for bio-succinic acid potential. ICIS. Available at: http://www.icis.com/resources/news/2012/01/30/9527521/chemical-industry-awaits-for-bio-succinic-acid-potential/. Accessed January 24, 2014.
# Australian Government: Department of Health. 1,4-butanediol factsheet. National Industrial Chemicals Notification and Assessment Scheme. Available at: http://www.nicnas.gov.au/communications/publications/information-sheets/existing-chemical-info-sheets/other-information-sheets. Accessed January 24, 2014.
# TecnonOrbiChem. Chem-net facts: 1,4-butanediol. TecnonOrbiChem. Available at: http://www.orbichem.com/userfiles/CNF%20Samples/bdo_13_11.pdf. Accessed January 23, 2014.
# Nexant. 1,4-butanediol/tetrahydrofuran (BDO/THF). ChemSystems. Available at: http://www.chemsystems.com/about/cs/news/items/ PERP2012_3_BDO_THF.cfm. Accessed February 6, 2014.
# Burk MJ, Van Dien SJ, Burgard AP, inventors; Genomatica, Inc., assignee. Compositions and methods for the biosynthesis of 1,4-butanediol and its precursors. US patent 8,067,214. Nov. 29, 2011.
# Chung S-H, Kim M-S, Eom H-H, Lee K-Y. Catalytic hydrogenation of bio-based succinic acid for the production of 1,4-butanediol through the indirect pathway. AIChE. Available at: https://aiche.confex.com/aiche/2013/webprogram/Paper327470.html. Accessed January 23, 2014.
# Bhattacharyya A, Manila MD, inventors; ISP Investments Inc., assignee. Catalysts for maleic acid hydrogenation to 1,4-Butanediol. US patent 7,935,834 B2. May 3, 2011.

Design S2

2014-03-15T04:55:39Z

Karetstik: /* Discussion */

Title: Production of 1,4-butanediol

Authors: Nick Pinkerton, Karen Schmidt, and James Xamplas

Date Presented: March 14, 2014

==Introduction==
1,4-butanediol (BDO) is traditionally made from petroleum-derived feedstocks in a variety of processes such as the Reppe (acetylene-based), Mitsubishi (butadiene-based), and Davy (maleic acid-based) processes [1]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, BDO [1]. It is this process that Team S2Kool4Skool has chosen to develop for a new bio-butanediol plant, because the Davy method is mature and requires no new innovations, and because an appropriate feedstock of bio-succinic acid is now available. The plant will be located in East Carroll Parish, Louisiana. This county is also home to Myriant; located in Lake Providence, they are the largest domestic provider of bio-succinic acid [2]. Furthermore, Lake Providence is conveniently located on the Mississippi River, which will allow for affordable transportation of our bio-based butanediol product. The intent of this project is to produce 45,000 metric tonnes of 99.5 wt% 1,4-butanediol per year in a new plant in Lake Providence, LA. The plant will run 24 hours per day for 350 days out of the year, allowing approximately two weeks for a maintenance shutdown.

As there are several techniques for producing 1,4 butanediol in industry, the first step was to determine a synthesis path. Based on the chosen path, reaction kinetics, and required production rate of the process, a reactor system was then designed. Next, the process was designed to deliver the reactants to the reactor at the proper operating conditions, and the separations, purification, and waste management steps were designed. Cost estimates were made using costing software and hand calculations. Finally, the process was iterated and optimized to reduce costs.

==Background==
===General information===
BDO is an organic chemical with the molecular formula <math>C_4H_{10}O_2</math>. It is also a diol with its two hydroxyl groups located at the terminal carbons. BDO has a boiling point of 235 degrees C and is therefore a colorless liquid at standard temperatures and pressures [3].

There are many precursors that petrochemical synthesis of BDO uses. The commonality between all of the precursor acids is that they are hydrogenatable. In replacement of one of these petrochemical precursors, our team has been tasked with the challenge of deriving BDO from the bio-based precursor succinic acid. This catalyzed reaction will take place in the presence of hydrogen as the hydrogenating component shown below:

<math>C_4H_6O_4 + 4H_2 = C_4H_{10}O_2 + 2H_2O</math>

As described in the above reaction, there will need to be at least 4:1 stoichiometric ratio of hydrogen gas to succinic acid. Two moles of water will also be produced along with each mole of BDO. This reaction is exothermic, which requires the reactor to be continuously cooled to maintain our reactor temperature. There are also side products that are produced which include tetrahydrofuran (THF) and γ-butyrolactone (GBL); however, thanks to catalyst selectivity these byproducts are produced in small quantities.

===Market analysis===
Butanediol has a quickly expanding market due to new technological evolutions and its growing use as a chemical intermediary in advanced materials. With biological routes being optimized, the potential of biomass-derived chemicals is tremendous. The global demand of BDO was estimated at 1.5 million metric tons in 2011 and is projected to grow at an annual rate of 4.5% for the next several years [1]. Unlike other chemical products, BDO’s profitability and attractiveness to producers lies in its downstream potential. Figure 1 below demonstrates several potential downstream products that can be directly or indirectly synthesized from BDO. The largest of these contributors include THF and GBL.

The current market demand of BDO is being supplemented by several global chemical companies. These companies include BASF, BioAmber, Purac, Myriant, DSM, Mitsubishi Chemical, Roquette, and OPXBIO. The market shares of these companies were not available for this product; however, with the consistent growth of the BDO market our team feels that the market is not saturated or impenetrable. The current market price of BDO fluctuates between $3.06 and $3.31 per kg for US-made products [4]. These prices correlate to a nearly 7 billion dollar industry.

===Process alternatives===
1,4-butanediol is traditionally made from petroleum-derived feedstocks in a variety of processes [5]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Several companies are currently implementing bio-routes of producing butanediol. Genomatica is using a bioengineered microorganism to convert sugar feedstocks directly to BDO via fermentation [6], but most companies are instead using microorganisms to convert sugar to succinic acid. The bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, which is the path that most are choosing, although research is being conducted on alternative pathways [7].

==Process overview==
The newly proposed plant can be divided into four stages: pre-reactor, reactor, post-reactor and distillation. Each section is an integral part to the overall process and demands close attention. The process flow diagram (see Appendix A) and stream table (Appendix B) provide more detailed information.

===Pre-reactor===
This chemical process begins with two feedstocks: hydrogen gas and bio-succinic acid. The hydrogen gas will be obtained from a pipeline at 150 atm and will be used in molar excess inside the reactor. The bio-succinic acid will be purchased by Myriant Corporation which is located near the planned plant site. The pricing for this feedstock is approximately $2.12 per kg. The plant will require 63,000 metric tonnes of bio-succinic acid per year to meet the proposed plant capacity. First the bio-succinic acid feed is pumped up to 150 atm to match the hydrogen gas feed, and then it is mixed with the hydrogen gas prior to being sent into heat exchanger E-101 for heating. The heat exchanger brings the two feeds up to 110oC and sends them to the jacketed packed bed reactor.

===Reactor===
The hydrogenation reaction occurs inside of the reactor thanks to the packed catalyst bed. The catalyst used is 0.4% Fe, 1.9% Na, 2.66% Ag, 2.66% Pd, 10.0% Re on 1.5mm carbon support. With this catalyst, BDO is produced with over 90% selectivity and minimal side reactions of THF and GBL.8 The reaction has an operating pressure of 2000-4000 psi and internal reactor temperature of 165°C. This temperature allows for about 99.7% conversion of succinic acid.8 Due to the exothermic nature of the reaction, a cooling jacket is required which utilizes downstream cold streams to cool the internal bed to maintain the desired reaction temperature.

===Post-reactor===
The effluent of the reactor is sent back to E-101 as the hot stream. After exiting E-101, the reactor product stream is sent to a secondary exchanger, E-102, where utility cooling water is used to reduce the temperature to an acceptable temperature prior to sending it to a pressure let-down valve. At this point the pressure of the stream is taken from 150 atm to 1 atm. This large pressure drop allows for the stream to split into its vapor and liquid portions in a gas-liquid separator. The vapor stream of the gas liquid separator is primarily hydrogen gas and sent to a flare for disposal. The liquid effluent is at approximately 45oC leaving the separator and is therefore pumped to the reactor jacket for the reaction cooling mentioned previously. After running through the reactor jacket, the stream enters the separation processes.

===Distillation===
The first distillation column, T-101, is a 10 stage column whose primary purpose is separating the THF from the product feed. Due to THF’s lower boiling point, the byproduct comes off of the top of the column with mostly water. This distillate is sent to the plant's THF waste storage tank that has the capacity of two weeks. The bottoms of the column is sent to the subsequent distillation column that separates the BDO from the GBL and water. The relatively close boiling points of BDO and GBL, 235oC and 204oC, respectively, create a difficult separation that requires a 15 stage column. The distillate of the column is approximately 23% GBL with balance water. This stream is sent to a storage tank with similar sizing parameters as the THF storage tank. The bottom stream is the final 99.5wt% BDO product. This stream is sent to the final product tank, S-104. Depending on our customer demands and the plant location we have the ability to barge, rail or pipe our product to its final destination. Due to low purity of the byproducts, future iterations are needed to optimize either purifying byproducts or selling impure byproducts. There is definitely an available market for these byproducts that should be researched more extensively to increase profit. A detailed description of the equipment from the PFD can be found in Appendix C, in addition to sizing specifications and purpose of equipment.

===Mass and energy balances===
Using an Aspen HYSYS simulation we were able to record the material and energy streams going in and out of the process system. Mass and energy balances are provided Appendix D where each inlet and outlet stream is described and quantified. As expected, the material and energy totals for the inlet and outlet streams add together to equal 0. This proves that our system is mathematically prudent and thermodynamically feasible. The total mass flow of the system is 15,639 kg/h and the total energy in and out of the system is 1.41e8 kJ/h.

===HYSYS simulation===
The HYSYS simulation was performed using the NRTL ideal fluid package. After using AspenPlus to verify that the HYSYS package had the appropriate vapor-liquid equilibrium information between THF and water, and between GBL and water, we concluded it was feasible to proceed with that fluid package. The simulation consists of a reactor, a gas-liquid separator, 2 pumps, 3 heaters, a valve, and 2 distillation columns (see Figure 2). The simulation successfully converted the succinic acid feed into the desired products. Also, the combination of the two distillation columns was able to effectively separate the BDO to obtain a 99.5% pure product with 99.5% recovery. In addition, a set was made between the energy required to heat stream 12 and the energy required to cool the reactor so that these values were made equal. Lastly, the condenser and reboiler duties were used in four heat exchangers in order to determine the appropriate size of this equipment as well as the necessary utility flow rates.

==Health and safety==
===Chemical properties===
Inherent to this process are a number of toxic chemicals. Table 1 summarizes the important safety data including hazard type, odor, color, and exposure limits.

As shown in the above table, the chemicals that this facility will be dealing with will be relatively mild and non-life threatening. Regardless of their perceived threat, chemicals should always be handled with care especially when they are at high temperatures and pressures.

===Safety procedures===

'''Fire'''. There are many flammable materials that will be included in this process; therefore, fire safety is imperative for all employees. There are countless possible causes of ignition and care should be taken while handling any flammable material whether in the lab or in the field.

In case a fire is present on, the following protocol should be implemented:

* Small fire: Use DRY chemical powder.
* Large fire: Use alcohol foam, water spray, or fog.
* Call for backup if unable to control.
* Immediately contact supervisor and emergency personnel on site.
* Evacuate to safe distance in case of fires around any hazardous materials or pressure vessels.

'''Spills'''. Process chemical spills will eventually occur in a plant of this scale. Small spills are likely to occur in a laboratory setting. Large spills could be a result of loss of containment in the system. We must ensure that all personnel are aware of proper spill mitigation protocol.

* Small spill: Dilute with water and mop or absorb with inert dry material. Dispose of in proper receptacle.
* Large spill: Keep away from sources of ignition and heat. Prevent rundown to any drains or sewers. Call for assistance on disposal. Absorb material with DRY earth or other non-combustible materials.
* If spill is due to a loss of containment in the system, quickly consult the PLC and shut any valves to prevent further loss.

'''Exposure'''. We must ensure that our employees are aware of the possible toxicity levels of each substance and how to handle exposure. The chemicals that are being used in this process are known chemical irritants to the eyes, skin, and throat. Safety measures must be in place to acknowledge this hazard. Due to the possibility of high pressure releases, we will have 2-minute emergency oxygen masks placed strategically throughout the plant to ensure the safety of any operator in the presence of a large release.

If exposed to the process chemicals, find nearest eye wash station or safety shower immediately and flush exposed skin for at least 15 minutes. Remove any contaminated clothing. Seek medical attention immediately.

'''Storage'''. Store chemicals in segregated and approved areas. Any closed containers for laboratory purposes should be placed in cool, well-ventilated areas.

==Economics==
===Equipment costing===
The calculated capital costs from Aspen Economic Analyzer are reported in Table 2 for all process equipment. The size of the reactor was calculated from the liquid hourly space velocity given in the 2011 ISP patent [8] and a void fraction estimate of 0.4. Storage tanks were sized to contain up to two continuous weeks of material. The number of distillation trays in each tower and the flow rates through pumps, vessels, and the flare were calculated in HYSYS. Heat exchange areas were given in Aspen Energy Analyzer or from HYSYS.

In addition to the above equipment, our plant will require an ion exchanger to produce deionized process water from the municipal water. This is estimated to cost $42,000 in capital cost.

===Cash flow analysis===
Summarizing the important takeaways from the economic analysis (see Appendix G), this process will return a revenue of 144 MM$ annually. Offset by production costs, the yearly cash flow is approximately 2.7 MM$, except for in the years in which the catalyst must be reinstalled (approximately every 5 years). At a cost of 2.5 MM$, the cash flows in those years decrease to approximately 0.2 MM$. This analysis assumes the plant will take 2 years to construct, and will operate at 50% in its first year. Furthermore, an interest rate of 10% was assumed with a tax rate of 38% (the maximum for corporate gains taxes). Using the 7-year MACRS depreciation method, the 20 year NPV for the project is 4.3 MM$. With an IRR of 15.1%, which is greater than the assumed interest rate, this project looks to be profitable. Further optimization techniques should be used in future iterations to further increase profitability. See Tables 3 and 4 for key economic information.

===Sensitivity analysis===
As seen in Figure 3, the economic evaluation of this process is influenced the most by changes in the sales price and feed cost. A 20% increase in sales price will result in an approximate 120 MM$ increase in NPV whereas a decrease of the same percentage will result in over a 120 MM$ decrease in NPV. Inversely, a 20% increase in feed cost will result in a 115 MM$ decrease in NPV and a 20% decrease in feed cost will result in a 60 MM$ increase in NPV.

To alleviate the risk associated with feed price, the team researched the price forecasting of bio-succinic acid. Figure 4 provides the bio-succinic acid price over the six years between 2006 and 2012. The price of bio-succinic, shown by the blue line, has remained relatively stable over this time period. This price history can be compared to adipic acid, the green line, which is a common petrochemical precursor for BDO production. Adipic acid as shown has had large fluctuations in price that result in unstable cash flows and uncertainty from shareholders. Thankfully, the stability of bio-succinic acid is a good sign that this process has a huge potential to be profitable especially if the demand for BDO continues to rise as projected.

==Discussion==
As described previously, the Davy process was selected as the most promising process of BDO production. The modified Davy process involves the hydrogenation of bio-succinicic acid with a Pa,Ag,Re catalyst and hydrogen gas. This process has many advantages, one being that it has mature technology that has been improved over the last 20 years. Additionally, the conversion to of succinic acid is virtually complete. Finally, overall plant yields can reach as high as 94 mol%.
As shown in Appendix B, streams ahead of the pressure valve (PRV-101) are at approximately 1.51e4 kPa, and streams after the pressure valve are between 100 and 450 kPa. Furthermore, operating temperatures do not exceed 200°C, including safety factors. These operating conditions contribute to the feasibility of the process, as all the components can be designed with reasonable dimensions (wall thickness, cap type, etc.).

Of particular interest are the large costs of the reactor and pump P-101. The reactor costs nearly 2 MM$ because it has a moderate size with a liquid volume of 16.7 m3, and it operates at 150 atm, which requires a strong stainless steel shell for safety purposes. Pump P-101 has such a large capital cost because it is a centrifugal multistage pump that also needs to be made of stainless steel to withstand pressuring the succinic acid feed to 150 atm.

Financial indicators for the proposed plant suggest that it will be moderately profitable, and additional optimization should be performed before making the capital investment. There is a fair amount of risk associated with the implementation of this production facility, and the return at this juncture may not justify the risk.

The process design and simulation in HYSYS has relied on several key assumptions, which are cause for certain limitations to the results. First, the conversions and selectivity of the catalyst, while taken from literature sources, are assumed to be true. Furthermore, the assumption of negligible side reactions and products was made. It is possible that small waste products in the form of succinates also form in the reactor. Therefore, the main limitation of this model is generally due to reaction specifications.

There are certain safety concerns that go along with the proposed process. First, there are many pipes and vessels that will be at a pressure of approximately 150 atm. Extra insulation and protection must be applied to the piping that contains highly pressurized fluids, to prevent operator injury. Furthermore, the PFR is at a slight risk for runaway reactions due to the exothermic nature of the reaction. The temperature of the reactor must always be monitored by an operator, and the jacket cooling system requires a backup system as well. A benefit of this process is that there are no toxic or severely hazardous components in the process. Additionally, there are no instances of temperature greater than 200°C.

The process design will be fitted with instrumentation and controls to ensure stable operation. These controls, including sensors and valves, minimize potential damage to components due to variation in plant conditions, as well as optimizing the overall performance. For example, the piping entering the tower will be fitted with a control loop. In the direction of flow, a sensing instrument first detects the pressure of the fluid, and then sends a signal to the controller. If the pressure is not within the operating limits, the actuator is signaled to close or open a control valve which is located farther down the stream.

==Conclusion==
The Evanston Chemical Engineering Division suggests a process that produces 45,000 tonnes/year of 99.5 wt% 1,4-butandeiol to enter the market with an appropriate market share. The feasibility of producing BDO as a significant process was investigated. A wide range of BDO production processes were researched, with a modified Davy process being identified as having the most potential. Using a Pa,Ag,Re catalyst on carbon support, this process converts bio-succinic acid to BDO with approximately 94% conversion. This process was designed in Aspen HYSYS, and economic analysis was conducted in Aspen Economic Analyzer. Total capital costs of the project are 12.2 MM$, with a simple payback period of 5.2 years. Total operational costs annually are 139.7 MM$. The process design was successful, with the capability of producing the desired production of BDO.

==Recommendations==
Given the moderate profitability of this process design, it is recommended that Evanston Chemicals explores further optimization techniques to increase the profitability of this process. This includes investigating sales of the γ-butyrolactone byproduct, recycling process water, and further optimizing utility streams for the distillation tower.
Second, we would like to investigate recycling the 2300 kg/h of water produced in the reaction. Our succinic acid enters the reactor as a 50 wt% solution in water, so we should look into replacing some of this with the product water. Not only will this decrease our water bill, but it will also lower the cost of ion exchange.

==References==
# Nexant.Is Bio-Butanediol Here to Stay? White Plains, NY: ChemSystems Products; 2012.
# De Guzman D. Chemical industry awaits for bio-succinic acid potential. ICIS. Available at: http://www.icis.com/resources/news/2012/01/30/9527521/chemical-industry-awaits-for-bio-succinic-acid-potential/. Accessed January 24, 2014.
# Australian Government: Department of Health. 1,4-butanediol factsheet. National Industrial Chemicals Notification and Assessment Scheme. Available at: http://www.nicnas.gov.au/communications/publications/information-sheets/existing-chemical-info-sheets/other-information-sheets. Accessed January 24, 2014.
# TecnonOrbiChem. Chem-net facts: 1,4-butanediol. TecnonOrbiChem. Available at: http://www.orbichem.com/userfiles/CNF%20Samples/bdo_13_11.pdf. Accessed January 23, 2014.
# Nexant. 1,4-butanediol/tetrahydrofuran (BDO/THF). ChemSystems. Available at: http://www.chemsystems.com/about/cs/news/items/ PERP2012_3_BDO_THF.cfm. Accessed February 6, 2014.
# Burk MJ, Van Dien SJ, Burgard AP, inventors; Genomatica, Inc., assignee. Compositions and methods for the biosynthesis of 1,4-butanediol and its precursors. US patent 8,067,214. Nov. 29, 2011.
# Chung S-H, Kim M-S, Eom H-H, Lee K-Y. Catalytic hydrogenation of bio-based succinic acid for the production of 1,4-butanediol through the indirect pathway. AIChE. Available at: https://aiche.confex.com/aiche/2013/webprogram/Paper327470.html. Accessed January 23, 2014.
# Bhattacharyya A, Manila MD, inventors; ISP Investments Inc., assignee. Catalysts for maleic acid hydrogenation to 1,4-Butanediol. US patent 7,935,834 B2. May 3, 2011.

Design S2

2014-03-15T04:55:18Z

Karetstik: /* Equipment costing */

Title: Production of 1,4-butanediol

Authors: Nick Pinkerton, Karen Schmidt, and James Xamplas

Date Presented: March 14, 2014

==Introduction==
1,4-butanediol (BDO) is traditionally made from petroleum-derived feedstocks in a variety of processes such as the Reppe (acetylene-based), Mitsubishi (butadiene-based), and Davy (maleic acid-based) processes [1]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, BDO [1]. It is this process that Team S2Kool4Skool has chosen to develop for a new bio-butanediol plant, because the Davy method is mature and requires no new innovations, and because an appropriate feedstock of bio-succinic acid is now available. The plant will be located in East Carroll Parish, Louisiana. This county is also home to Myriant; located in Lake Providence, they are the largest domestic provider of bio-succinic acid [2]. Furthermore, Lake Providence is conveniently located on the Mississippi River, which will allow for affordable transportation of our bio-based butanediol product. The intent of this project is to produce 45,000 metric tonnes of 99.5 wt% 1,4-butanediol per year in a new plant in Lake Providence, LA. The plant will run 24 hours per day for 350 days out of the year, allowing approximately two weeks for a maintenance shutdown.

As there are several techniques for producing 1,4 butanediol in industry, the first step was to determine a synthesis path. Based on the chosen path, reaction kinetics, and required production rate of the process, a reactor system was then designed. Next, the process was designed to deliver the reactants to the reactor at the proper operating conditions, and the separations, purification, and waste management steps were designed. Cost estimates were made using costing software and hand calculations. Finally, the process was iterated and optimized to reduce costs.

==Background==
===General information===
BDO is an organic chemical with the molecular formula <math>C_4H_{10}O_2</math>. It is also a diol with its two hydroxyl groups located at the terminal carbons. BDO has a boiling point of 235 degrees C and is therefore a colorless liquid at standard temperatures and pressures [3].

There are many precursors that petrochemical synthesis of BDO uses. The commonality between all of the precursor acids is that they are hydrogenatable. In replacement of one of these petrochemical precursors, our team has been tasked with the challenge of deriving BDO from the bio-based precursor succinic acid. This catalyzed reaction will take place in the presence of hydrogen as the hydrogenating component shown below:

<math>C_4H_6O_4 + 4H_2 = C_4H_{10}O_2 + 2H_2O</math>

As described in the above reaction, there will need to be at least 4:1 stoichiometric ratio of hydrogen gas to succinic acid. Two moles of water will also be produced along with each mole of BDO. This reaction is exothermic, which requires the reactor to be continuously cooled to maintain our reactor temperature. There are also side products that are produced which include tetrahydrofuran (THF) and γ-butyrolactone (GBL); however, thanks to catalyst selectivity these byproducts are produced in small quantities.

===Market analysis===
Butanediol has a quickly expanding market due to new technological evolutions and its growing use as a chemical intermediary in advanced materials. With biological routes being optimized, the potential of biomass-derived chemicals is tremendous. The global demand of BDO was estimated at 1.5 million metric tons in 2011 and is projected to grow at an annual rate of 4.5% for the next several years [1]. Unlike other chemical products, BDO’s profitability and attractiveness to producers lies in its downstream potential. Figure 1 below demonstrates several potential downstream products that can be directly or indirectly synthesized from BDO. The largest of these contributors include THF and GBL.

The current market demand of BDO is being supplemented by several global chemical companies. These companies include BASF, BioAmber, Purac, Myriant, DSM, Mitsubishi Chemical, Roquette, and OPXBIO. The market shares of these companies were not available for this product; however, with the consistent growth of the BDO market our team feels that the market is not saturated or impenetrable. The current market price of BDO fluctuates between $3.06 and $3.31 per kg for US-made products [4]. These prices correlate to a nearly 7 billion dollar industry.

===Process alternatives===
1,4-butanediol is traditionally made from petroleum-derived feedstocks in a variety of processes [5]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Several companies are currently implementing bio-routes of producing butanediol. Genomatica is using a bioengineered microorganism to convert sugar feedstocks directly to BDO via fermentation [6], but most companies are instead using microorganisms to convert sugar to succinic acid. The bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, which is the path that most are choosing, although research is being conducted on alternative pathways [7].

==Process overview==
The newly proposed plant can be divided into four stages: pre-reactor, reactor, post-reactor and distillation. Each section is an integral part to the overall process and demands close attention. The process flow diagram (see Appendix A) and stream table (Appendix B) provide more detailed information.

===Pre-reactor===
This chemical process begins with two feedstocks: hydrogen gas and bio-succinic acid. The hydrogen gas will be obtained from a pipeline at 150 atm and will be used in molar excess inside the reactor. The bio-succinic acid will be purchased by Myriant Corporation which is located near the planned plant site. The pricing for this feedstock is approximately $2.12 per kg. The plant will require 63,000 metric tonnes of bio-succinic acid per year to meet the proposed plant capacity. First the bio-succinic acid feed is pumped up to 150 atm to match the hydrogen gas feed, and then it is mixed with the hydrogen gas prior to being sent into heat exchanger E-101 for heating. The heat exchanger brings the two feeds up to 110oC and sends them to the jacketed packed bed reactor.

===Reactor===
The hydrogenation reaction occurs inside of the reactor thanks to the packed catalyst bed. The catalyst used is 0.4% Fe, 1.9% Na, 2.66% Ag, 2.66% Pd, 10.0% Re on 1.5mm carbon support. With this catalyst, BDO is produced with over 90% selectivity and minimal side reactions of THF and GBL.8 The reaction has an operating pressure of 2000-4000 psi and internal reactor temperature of 165°C. This temperature allows for about 99.7% conversion of succinic acid.8 Due to the exothermic nature of the reaction, a cooling jacket is required which utilizes downstream cold streams to cool the internal bed to maintain the desired reaction temperature.

===Post-reactor===
The effluent of the reactor is sent back to E-101 as the hot stream. After exiting E-101, the reactor product stream is sent to a secondary exchanger, E-102, where utility cooling water is used to reduce the temperature to an acceptable temperature prior to sending it to a pressure let-down valve. At this point the pressure of the stream is taken from 150 atm to 1 atm. This large pressure drop allows for the stream to split into its vapor and liquid portions in a gas-liquid separator. The vapor stream of the gas liquid separator is primarily hydrogen gas and sent to a flare for disposal. The liquid effluent is at approximately 45oC leaving the separator and is therefore pumped to the reactor jacket for the reaction cooling mentioned previously. After running through the reactor jacket, the stream enters the separation processes.

===Distillation===
The first distillation column, T-101, is a 10 stage column whose primary purpose is separating the THF from the product feed. Due to THF’s lower boiling point, the byproduct comes off of the top of the column with mostly water. This distillate is sent to the plant's THF waste storage tank that has the capacity of two weeks. The bottoms of the column is sent to the subsequent distillation column that separates the BDO from the GBL and water. The relatively close boiling points of BDO and GBL, 235oC and 204oC, respectively, create a difficult separation that requires a 15 stage column. The distillate of the column is approximately 23% GBL with balance water. This stream is sent to a storage tank with similar sizing parameters as the THF storage tank. The bottom stream is the final 99.5wt% BDO product. This stream is sent to the final product tank, S-104. Depending on our customer demands and the plant location we have the ability to barge, rail or pipe our product to its final destination. Due to low purity of the byproducts, future iterations are needed to optimize either purifying byproducts or selling impure byproducts. There is definitely an available market for these byproducts that should be researched more extensively to increase profit. A detailed description of the equipment from the PFD can be found in Appendix C, in addition to sizing specifications and purpose of equipment.

===Mass and energy balances===
Using an Aspen HYSYS simulation we were able to record the material and energy streams going in and out of the process system. Mass and energy balances are provided Appendix D where each inlet and outlet stream is described and quantified. As expected, the material and energy totals for the inlet and outlet streams add together to equal 0. This proves that our system is mathematically prudent and thermodynamically feasible. The total mass flow of the system is 15,639 kg/h and the total energy in and out of the system is 1.41e8 kJ/h.

===HYSYS simulation===
The HYSYS simulation was performed using the NRTL ideal fluid package. After using AspenPlus to verify that the HYSYS package had the appropriate vapor-liquid equilibrium information between THF and water, and between GBL and water, we concluded it was feasible to proceed with that fluid package. The simulation consists of a reactor, a gas-liquid separator, 2 pumps, 3 heaters, a valve, and 2 distillation columns (see Figure 2). The simulation successfully converted the succinic acid feed into the desired products. Also, the combination of the two distillation columns was able to effectively separate the BDO to obtain a 99.5% pure product with 99.5% recovery. In addition, a set was made between the energy required to heat stream 12 and the energy required to cool the reactor so that these values were made equal. Lastly, the condenser and reboiler duties were used in four heat exchangers in order to determine the appropriate size of this equipment as well as the necessary utility flow rates.

==Health and safety==
===Chemical properties===
Inherent to this process are a number of toxic chemicals. Table 1 summarizes the important safety data including hazard type, odor, color, and exposure limits.

As shown in the above table, the chemicals that this facility will be dealing with will be relatively mild and non-life threatening. Regardless of their perceived threat, chemicals should always be handled with care especially when they are at high temperatures and pressures.

===Safety procedures===

'''Fire'''. There are many flammable materials that will be included in this process; therefore, fire safety is imperative for all employees. There are countless possible causes of ignition and care should be taken while handling any flammable material whether in the lab or in the field.

In case a fire is present on, the following protocol should be implemented:

* Small fire: Use DRY chemical powder.
* Large fire: Use alcohol foam, water spray, or fog.
* Call for backup if unable to control.
* Immediately contact supervisor and emergency personnel on site.
* Evacuate to safe distance in case of fires around any hazardous materials or pressure vessels.

'''Spills'''. Process chemical spills will eventually occur in a plant of this scale. Small spills are likely to occur in a laboratory setting. Large spills could be a result of loss of containment in the system. We must ensure that all personnel are aware of proper spill mitigation protocol.

* Small spill: Dilute with water and mop or absorb with inert dry material. Dispose of in proper receptacle.
* Large spill: Keep away from sources of ignition and heat. Prevent rundown to any drains or sewers. Call for assistance on disposal. Absorb material with DRY earth or other non-combustible materials.
* If spill is due to a loss of containment in the system, quickly consult the PLC and shut any valves to prevent further loss.

'''Exposure'''. We must ensure that our employees are aware of the possible toxicity levels of each substance and how to handle exposure. The chemicals that are being used in this process are known chemical irritants to the eyes, skin, and throat. Safety measures must be in place to acknowledge this hazard. Due to the possibility of high pressure releases, we will have 2-minute emergency oxygen masks placed strategically throughout the plant to ensure the safety of any operator in the presence of a large release.

If exposed to the process chemicals, find nearest eye wash station or safety shower immediately and flush exposed skin for at least 15 minutes. Remove any contaminated clothing. Seek medical attention immediately.

'''Storage'''. Store chemicals in segregated and approved areas. Any closed containers for laboratory purposes should be placed in cool, well-ventilated areas.

==Economics==
===Equipment costing===
The calculated capital costs from Aspen Economic Analyzer are reported in Table 2 for all process equipment. The size of the reactor was calculated from the liquid hourly space velocity given in the 2011 ISP patent [8] and a void fraction estimate of 0.4. Storage tanks were sized to contain up to two continuous weeks of material. The number of distillation trays in each tower and the flow rates through pumps, vessels, and the flare were calculated in HYSYS. Heat exchange areas were given in Aspen Energy Analyzer or from HYSYS.

In addition to the above equipment, our plant will require an ion exchanger to produce deionized process water from the municipal water. This is estimated to cost $42,000 in capital cost.

===Cash flow analysis===
Summarizing the important takeaways from the economic analysis (see Appendix G), this process will return a revenue of 144 MM$ annually. Offset by production costs, the yearly cash flow is approximately 2.7 MM$, except for in the years in which the catalyst must be reinstalled (approximately every 5 years). At a cost of 2.5 MM$, the cash flows in those years decrease to approximately 0.2 MM$. This analysis assumes the plant will take 2 years to construct, and will operate at 50% in its first year. Furthermore, an interest rate of 10% was assumed with a tax rate of 38% (the maximum for corporate gains taxes). Using the 7-year MACRS depreciation method, the 20 year NPV for the project is 4.3 MM$. With an IRR of 15.1%, which is greater than the assumed interest rate, this project looks to be profitable. Further optimization techniques should be used in future iterations to further increase profitability. See Tables 3 and 4 for key economic information.

===Sensitivity analysis===
As seen in Figure 3, the economic evaluation of this process is influenced the most by changes in the sales price and feed cost. A 20% increase in sales price will result in an approximate 120 MM$ increase in NPV whereas a decrease of the same percentage will result in over a 120 MM$ decrease in NPV. Inversely, a 20% increase in feed cost will result in a 115 MM$ decrease in NPV and a 20% decrease in feed cost will result in a 60 MM$ increase in NPV.

To alleviate the risk associated with feed price, the team researched the price forecasting of bio-succinic acid. Figure 4 provides the bio-succinic acid price over the six years between 2006 and 2012. The price of bio-succinic, shown by the blue line, has remained relatively stable over this time period. This price history can be compared to adipic acid, the green line, which is a common petrochemical precursor for BDO production. Adipic acid as shown has had large fluctuations in price that result in unstable cash flows and uncertainty from shareholders. Thankfully, the stability of bio-succinic acid is a good sign that this process has a huge potential to be profitable especially if the demand for BDO continues to rise as projected.

==Discussion==
As described previously, the Davy process was selected as the most promising process of BDO production. The modified Davy process involves the hydrogenation of bio-succinicic acid with a Pa,Ag,Re catalyst and hydrogen gas. This process has many advantages, one being that it has mature technology that has been improved over the last 20 years. Additionally, the conversion to of succinic acid is virtually complete. Finally, overall plant yields can reach as high as 94 mol%.
As shown in Appendix B, streams ahead of the pressure valve (PRV-101) are at approximately 1.51e4 kPa, and streams after the pressure valve are between 100 and 450 kPa. Furthermore, operating temperatures do not exceed 200°C, including safety factors. These operating conditions contribute to the feasibility of the process, as all the components can be designed with reasonable dimensions (wall thickness, cap type, etc.).

Of particular interest are the large costs of the reactor and pump P-101. The reactor costs nearly 2 MM$ because it has a moderate size with a liquid volume of 16.7 m3, and it operates at 150 atm, which requires a strong stainless steel shell for safety purposes. Pump P-101 has such a large capital cost because it is a centrifugal multistage pump that also needs to be made of stainless steel to withstand pressuring the succinic acid feed to 150 atm.

Financial indicators for the proposed plant suggest that it will be moderately profitable, and additional optimization should be performed before making the capital investment. There is a fair amount of risk associated with the implementation of this production facility, and the return at this juncture may not justify the risk.

The process design and simulation in HYSYS has relied on several key assumptions, which are cause for certain limitations to the results. First, the conversions and selectivity of the catalyst, while taken from literature sources, are assumed to be true. Furthermore, the assumption of negligible side reactions and products was made. It is possible that small waste products in the form of succinates also form in the reactor. Therefore, the main limitation of this model is generally due to reaction specifications.

There are certain safety concerns that go along with the proposed process. First, there are many pipes and vessels that will be at a pressure of approximately 150 atm. Extra insulation and protection must be applied to the piping that contains highly pressurized fluids, to prevent operator injury. Furthermore, the PFR is at a slight risk for runaway reactions due to the exothermic nature of the reaction. The temperature of the reactor must always be monitored by an operator, and the jacket cooling system requires a backup system as well. A benefit of this process is that there are no toxic or severely hazardous components in the process. Additionally, there are no instances of temperature greater than 200°C.

The process design will be fitted with instrumentation and controls to ensure stable operation. These controls, including sensors and valves, minimize potential damage to components due to variation in plant conditions, as well as optimizing the overall performance. For example, the piping entering the tower will be fitted with a control loop. In the direction of flow, a sensing instrument first detects the pressure of the fluid, and then sends a signal to the controller. If the pressure is not within the operating limits, the actuator is signaled to close or open a control valve which is located farther down the stream.

==Conclusion==
The Evanston Chemical Engineering Division suggests a process that produces 45,000 tonnes/year of 99.5 wt% 1,4-butandeiol to enter the market with an appropriate market share. The feasibility of producing BDO as a significant process was investigated. A wide range of BDO production processes were researched, with a modified Davy process being identified as having the most potential. Using a Pa,Ag,Re catalyst on carbon support, this process converts bio-succinic acid to BDO with approximately 94% conversion. This process was designed in Aspen HYSYS, and economic analysis was conducted in Aspen Economic Analyzer. Total capital costs of the project are 12.2 MM$, with a simple payback period of 5.2 years. Total operational costs annually are 139.7 MM$. The process design was successful, with the capability of producing the desired production of BDO.

==Recommendations==
Given the moderate profitability of this process design, it is recommended that Evanston Chemicals explores further optimization techniques to increase the profitability of this process. This includes investigating sales of the γ-butyrolactone byproduct, recycling process water, and further optimizing utility streams for the distillation tower.
Second, we would like to investigate recycling the 2300 kg/h of water produced in the reaction. Our succinic acid enters the reactor as a 50 wt% solution in water, so we should look into replacing some of this with the product water. Not only will this decrease our water bill, but it will also lower the cost of ion exchange.

==References==
# Nexant.Is Bio-Butanediol Here to Stay? White Plains, NY: ChemSystems Products; 2012.
# De Guzman D. Chemical industry awaits for bio-succinic acid potential. ICIS. Available at: http://www.icis.com/resources/news/2012/01/30/9527521/chemical-industry-awaits-for-bio-succinic-acid-potential/. Accessed January 24, 2014.
# Australian Government: Department of Health. 1,4-butanediol factsheet. National Industrial Chemicals Notification and Assessment Scheme. Available at: http://www.nicnas.gov.au/communications/publications/information-sheets/existing-chemical-info-sheets/other-information-sheets. Accessed January 24, 2014.
# TecnonOrbiChem. Chem-net facts: 1,4-butanediol. TecnonOrbiChem. Available at: http://www.orbichem.com/userfiles/CNF%20Samples/bdo_13_11.pdf. Accessed January 23, 2014.
# Nexant. 1,4-butanediol/tetrahydrofuran (BDO/THF). ChemSystems. Available at: http://www.chemsystems.com/about/cs/news/items/ PERP2012_3_BDO_THF.cfm. Accessed February 6, 2014.
# Burk MJ, Van Dien SJ, Burgard AP, inventors; Genomatica, Inc., assignee. Compositions and methods for the biosynthesis of 1,4-butanediol and its precursors. US patent 8,067,214. Nov. 29, 2011.
# Chung S-H, Kim M-S, Eom H-H, Lee K-Y. Catalytic hydrogenation of bio-based succinic acid for the production of 1,4-butanediol through the indirect pathway. AIChE. Available at: https://aiche.confex.com/aiche/2013/webprogram/Paper327470.html. Accessed January 23, 2014.
# Bhattacharyya A, Manila MD, inventors; ISP Investments Inc., assignee. Catalysts for maleic acid hydrogenation to 1,4-Butanediol. US patent 7,935,834 B2. May 3, 2011.

Design S2

2014-03-15T04:54:58Z

Karetstik: /* Safety procedures */

Title: Production of 1,4-butanediol

Authors: Nick Pinkerton, Karen Schmidt, and James Xamplas

Date Presented: March 14, 2014

==Introduction==
1,4-butanediol (BDO) is traditionally made from petroleum-derived feedstocks in a variety of processes such as the Reppe (acetylene-based), Mitsubishi (butadiene-based), and Davy (maleic acid-based) processes [1]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, BDO [1]. It is this process that Team S2Kool4Skool has chosen to develop for a new bio-butanediol plant, because the Davy method is mature and requires no new innovations, and because an appropriate feedstock of bio-succinic acid is now available. The plant will be located in East Carroll Parish, Louisiana. This county is also home to Myriant; located in Lake Providence, they are the largest domestic provider of bio-succinic acid [2]. Furthermore, Lake Providence is conveniently located on the Mississippi River, which will allow for affordable transportation of our bio-based butanediol product. The intent of this project is to produce 45,000 metric tonnes of 99.5 wt% 1,4-butanediol per year in a new plant in Lake Providence, LA. The plant will run 24 hours per day for 350 days out of the year, allowing approximately two weeks for a maintenance shutdown.

As there are several techniques for producing 1,4 butanediol in industry, the first step was to determine a synthesis path. Based on the chosen path, reaction kinetics, and required production rate of the process, a reactor system was then designed. Next, the process was designed to deliver the reactants to the reactor at the proper operating conditions, and the separations, purification, and waste management steps were designed. Cost estimates were made using costing software and hand calculations. Finally, the process was iterated and optimized to reduce costs.

==Background==
===General information===
BDO is an organic chemical with the molecular formula <math>C_4H_{10}O_2</math>. It is also a diol with its two hydroxyl groups located at the terminal carbons. BDO has a boiling point of 235 degrees C and is therefore a colorless liquid at standard temperatures and pressures [3].

There are many precursors that petrochemical synthesis of BDO uses. The commonality between all of the precursor acids is that they are hydrogenatable. In replacement of one of these petrochemical precursors, our team has been tasked with the challenge of deriving BDO from the bio-based precursor succinic acid. This catalyzed reaction will take place in the presence of hydrogen as the hydrogenating component shown below:

<math>C_4H_6O_4 + 4H_2 = C_4H_{10}O_2 + 2H_2O</math>

As described in the above reaction, there will need to be at least 4:1 stoichiometric ratio of hydrogen gas to succinic acid. Two moles of water will also be produced along with each mole of BDO. This reaction is exothermic, which requires the reactor to be continuously cooled to maintain our reactor temperature. There are also side products that are produced which include tetrahydrofuran (THF) and γ-butyrolactone (GBL); however, thanks to catalyst selectivity these byproducts are produced in small quantities.

===Market analysis===
Butanediol has a quickly expanding market due to new technological evolutions and its growing use as a chemical intermediary in advanced materials. With biological routes being optimized, the potential of biomass-derived chemicals is tremendous. The global demand of BDO was estimated at 1.5 million metric tons in 2011 and is projected to grow at an annual rate of 4.5% for the next several years [1]. Unlike other chemical products, BDO’s profitability and attractiveness to producers lies in its downstream potential. Figure 1 below demonstrates several potential downstream products that can be directly or indirectly synthesized from BDO. The largest of these contributors include THF and GBL.

The current market demand of BDO is being supplemented by several global chemical companies. These companies include BASF, BioAmber, Purac, Myriant, DSM, Mitsubishi Chemical, Roquette, and OPXBIO. The market shares of these companies were not available for this product; however, with the consistent growth of the BDO market our team feels that the market is not saturated or impenetrable. The current market price of BDO fluctuates between $3.06 and $3.31 per kg for US-made products [4]. These prices correlate to a nearly 7 billion dollar industry.

===Process alternatives===
1,4-butanediol is traditionally made from petroleum-derived feedstocks in a variety of processes [5]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Several companies are currently implementing bio-routes of producing butanediol. Genomatica is using a bioengineered microorganism to convert sugar feedstocks directly to BDO via fermentation [6], but most companies are instead using microorganisms to convert sugar to succinic acid. The bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, which is the path that most are choosing, although research is being conducted on alternative pathways [7].

==Process overview==
The newly proposed plant can be divided into four stages: pre-reactor, reactor, post-reactor and distillation. Each section is an integral part to the overall process and demands close attention. The process flow diagram (see Appendix A) and stream table (Appendix B) provide more detailed information.

===Pre-reactor===
This chemical process begins with two feedstocks: hydrogen gas and bio-succinic acid. The hydrogen gas will be obtained from a pipeline at 150 atm and will be used in molar excess inside the reactor. The bio-succinic acid will be purchased by Myriant Corporation which is located near the planned plant site. The pricing for this feedstock is approximately $2.12 per kg. The plant will require 63,000 metric tonnes of bio-succinic acid per year to meet the proposed plant capacity. First the bio-succinic acid feed is pumped up to 150 atm to match the hydrogen gas feed, and then it is mixed with the hydrogen gas prior to being sent into heat exchanger E-101 for heating. The heat exchanger brings the two feeds up to 110oC and sends them to the jacketed packed bed reactor.

===Reactor===
The hydrogenation reaction occurs inside of the reactor thanks to the packed catalyst bed. The catalyst used is 0.4% Fe, 1.9% Na, 2.66% Ag, 2.66% Pd, 10.0% Re on 1.5mm carbon support. With this catalyst, BDO is produced with over 90% selectivity and minimal side reactions of THF and GBL.8 The reaction has an operating pressure of 2000-4000 psi and internal reactor temperature of 165°C. This temperature allows for about 99.7% conversion of succinic acid.8 Due to the exothermic nature of the reaction, a cooling jacket is required which utilizes downstream cold streams to cool the internal bed to maintain the desired reaction temperature.

===Post-reactor===
The effluent of the reactor is sent back to E-101 as the hot stream. After exiting E-101, the reactor product stream is sent to a secondary exchanger, E-102, where utility cooling water is used to reduce the temperature to an acceptable temperature prior to sending it to a pressure let-down valve. At this point the pressure of the stream is taken from 150 atm to 1 atm. This large pressure drop allows for the stream to split into its vapor and liquid portions in a gas-liquid separator. The vapor stream of the gas liquid separator is primarily hydrogen gas and sent to a flare for disposal. The liquid effluent is at approximately 45oC leaving the separator and is therefore pumped to the reactor jacket for the reaction cooling mentioned previously. After running through the reactor jacket, the stream enters the separation processes.

===Distillation===
The first distillation column, T-101, is a 10 stage column whose primary purpose is separating the THF from the product feed. Due to THF’s lower boiling point, the byproduct comes off of the top of the column with mostly water. This distillate is sent to the plant's THF waste storage tank that has the capacity of two weeks. The bottoms of the column is sent to the subsequent distillation column that separates the BDO from the GBL and water. The relatively close boiling points of BDO and GBL, 235oC and 204oC, respectively, create a difficult separation that requires a 15 stage column. The distillate of the column is approximately 23% GBL with balance water. This stream is sent to a storage tank with similar sizing parameters as the THF storage tank. The bottom stream is the final 99.5wt% BDO product. This stream is sent to the final product tank, S-104. Depending on our customer demands and the plant location we have the ability to barge, rail or pipe our product to its final destination. Due to low purity of the byproducts, future iterations are needed to optimize either purifying byproducts or selling impure byproducts. There is definitely an available market for these byproducts that should be researched more extensively to increase profit. A detailed description of the equipment from the PFD can be found in Appendix C, in addition to sizing specifications and purpose of equipment.

===Mass and energy balances===
Using an Aspen HYSYS simulation we were able to record the material and energy streams going in and out of the process system. Mass and energy balances are provided Appendix D where each inlet and outlet stream is described and quantified. As expected, the material and energy totals for the inlet and outlet streams add together to equal 0. This proves that our system is mathematically prudent and thermodynamically feasible. The total mass flow of the system is 15,639 kg/h and the total energy in and out of the system is 1.41e8 kJ/h.

===HYSYS simulation===
The HYSYS simulation was performed using the NRTL ideal fluid package. After using AspenPlus to verify that the HYSYS package had the appropriate vapor-liquid equilibrium information between THF and water, and between GBL and water, we concluded it was feasible to proceed with that fluid package. The simulation consists of a reactor, a gas-liquid separator, 2 pumps, 3 heaters, a valve, and 2 distillation columns (see Figure 2). The simulation successfully converted the succinic acid feed into the desired products. Also, the combination of the two distillation columns was able to effectively separate the BDO to obtain a 99.5% pure product with 99.5% recovery. In addition, a set was made between the energy required to heat stream 12 and the energy required to cool the reactor so that these values were made equal. Lastly, the condenser and reboiler duties were used in four heat exchangers in order to determine the appropriate size of this equipment as well as the necessary utility flow rates.

==Health and safety==
===Chemical properties===
Inherent to this process are a number of toxic chemicals. Table 1 summarizes the important safety data including hazard type, odor, color, and exposure limits.

As shown in the above table, the chemicals that this facility will be dealing with will be relatively mild and non-life threatening. Regardless of their perceived threat, chemicals should always be handled with care especially when they are at high temperatures and pressures.

===Safety procedures===

'''Fire'''. There are many flammable materials that will be included in this process; therefore, fire safety is imperative for all employees. There are countless possible causes of ignition and care should be taken while handling any flammable material whether in the lab or in the field.

In case a fire is present on, the following protocol should be implemented:

* Small fire: Use DRY chemical powder.
* Large fire: Use alcohol foam, water spray, or fog.
* Call for backup if unable to control.
* Immediately contact supervisor and emergency personnel on site.
* Evacuate to safe distance in case of fires around any hazardous materials or pressure vessels.

'''Spills'''. Process chemical spills will eventually occur in a plant of this scale. Small spills are likely to occur in a laboratory setting. Large spills could be a result of loss of containment in the system. We must ensure that all personnel are aware of proper spill mitigation protocol.

* Small spill: Dilute with water and mop or absorb with inert dry material. Dispose of in proper receptacle.
* Large spill: Keep away from sources of ignition and heat. Prevent rundown to any drains or sewers. Call for assistance on disposal. Absorb material with DRY earth or other non-combustible materials.
* If spill is due to a loss of containment in the system, quickly consult the PLC and shut any valves to prevent further loss.

'''Exposure'''. We must ensure that our employees are aware of the possible toxicity levels of each substance and how to handle exposure. The chemicals that are being used in this process are known chemical irritants to the eyes, skin, and throat. Safety measures must be in place to acknowledge this hazard. Due to the possibility of high pressure releases, we will have 2-minute emergency oxygen masks placed strategically throughout the plant to ensure the safety of any operator in the presence of a large release.

If exposed to the process chemicals, find nearest eye wash station or safety shower immediately and flush exposed skin for at least 15 minutes. Remove any contaminated clothing. Seek medical attention immediately.

'''Storage'''. Store chemicals in segregated and approved areas. Any closed containers for laboratory purposes should be placed in cool, well-ventilated areas.

==Economics==
===Equipment costing===
The calculated capital costs from Aspen Economic Analyzer are reported in Table 2 for all process equipment. The size of the reactor was calculated from the liquid hourly space velocity given in the 2011 ISP patent8 and a void fraction estimate of 0.4. Storage tanks were sized to contain up to two continuous weeks of material. The number of distillation trays in each tower and the flow rates through pumps, vessels, and the flare were calculated in HYSYS. Heat exchange areas were given in Aspen Energy Analyzer or from HYSYS.

In addition to the above equipment, our plant will require an ion exchanger to produce deionized process water from the municipal water. This is estimated to cost $42,000 in capital cost.

===Cash flow analysis===
Summarizing the important takeaways from the economic analysis (see Appendix G), this process will return a revenue of 144 MM$ annually. Offset by production costs, the yearly cash flow is approximately 2.7 MM$, except for in the years in which the catalyst must be reinstalled (approximately every 5 years). At a cost of 2.5 MM$, the cash flows in those years decrease to approximately 0.2 MM$. This analysis assumes the plant will take 2 years to construct, and will operate at 50% in its first year. Furthermore, an interest rate of 10% was assumed with a tax rate of 38% (the maximum for corporate gains taxes). Using the 7-year MACRS depreciation method, the 20 year NPV for the project is 4.3 MM$. With an IRR of 15.1%, which is greater than the assumed interest rate, this project looks to be profitable. Further optimization techniques should be used in future iterations to further increase profitability. See Tables 3 and 4 for key economic information.

===Sensitivity analysis===
As seen in Figure 3, the economic evaluation of this process is influenced the most by changes in the sales price and feed cost. A 20% increase in sales price will result in an approximate 120 MM$ increase in NPV whereas a decrease of the same percentage will result in over a 120 MM$ decrease in NPV. Inversely, a 20% increase in feed cost will result in a 115 MM$ decrease in NPV and a 20% decrease in feed cost will result in a 60 MM$ increase in NPV.

To alleviate the risk associated with feed price, the team researched the price forecasting of bio-succinic acid. Figure 4 provides the bio-succinic acid price over the six years between 2006 and 2012. The price of bio-succinic, shown by the blue line, has remained relatively stable over this time period. This price history can be compared to adipic acid, the green line, which is a common petrochemical precursor for BDO production. Adipic acid as shown has had large fluctuations in price that result in unstable cash flows and uncertainty from shareholders. Thankfully, the stability of bio-succinic acid is a good sign that this process has a huge potential to be profitable especially if the demand for BDO continues to rise as projected.

==Discussion==
As described previously, the Davy process was selected as the most promising process of BDO production. The modified Davy process involves the hydrogenation of bio-succinicic acid with a Pa,Ag,Re catalyst and hydrogen gas. This process has many advantages, one being that it has mature technology that has been improved over the last 20 years. Additionally, the conversion to of succinic acid is virtually complete. Finally, overall plant yields can reach as high as 94 mol%.
As shown in Appendix B, streams ahead of the pressure valve (PRV-101) are at approximately 1.51e4 kPa, and streams after the pressure valve are between 100 and 450 kPa. Furthermore, operating temperatures do not exceed 200°C, including safety factors. These operating conditions contribute to the feasibility of the process, as all the components can be designed with reasonable dimensions (wall thickness, cap type, etc.).

Of particular interest are the large costs of the reactor and pump P-101. The reactor costs nearly 2 MM$ because it has a moderate size with a liquid volume of 16.7 m3, and it operates at 150 atm, which requires a strong stainless steel shell for safety purposes. Pump P-101 has such a large capital cost because it is a centrifugal multistage pump that also needs to be made of stainless steel to withstand pressuring the succinic acid feed to 150 atm.

Financial indicators for the proposed plant suggest that it will be moderately profitable, and additional optimization should be performed before making the capital investment. There is a fair amount of risk associated with the implementation of this production facility, and the return at this juncture may not justify the risk.

The process design and simulation in HYSYS has relied on several key assumptions, which are cause for certain limitations to the results. First, the conversions and selectivity of the catalyst, while taken from literature sources, are assumed to be true. Furthermore, the assumption of negligible side reactions and products was made. It is possible that small waste products in the form of succinates also form in the reactor. Therefore, the main limitation of this model is generally due to reaction specifications.

There are certain safety concerns that go along with the proposed process. First, there are many pipes and vessels that will be at a pressure of approximately 150 atm. Extra insulation and protection must be applied to the piping that contains highly pressurized fluids, to prevent operator injury. Furthermore, the PFR is at a slight risk for runaway reactions due to the exothermic nature of the reaction. The temperature of the reactor must always be monitored by an operator, and the jacket cooling system requires a backup system as well. A benefit of this process is that there are no toxic or severely hazardous components in the process. Additionally, there are no instances of temperature greater than 200°C.

The process design will be fitted with instrumentation and controls to ensure stable operation. These controls, including sensors and valves, minimize potential damage to components due to variation in plant conditions, as well as optimizing the overall performance. For example, the piping entering the tower will be fitted with a control loop. In the direction of flow, a sensing instrument first detects the pressure of the fluid, and then sends a signal to the controller. If the pressure is not within the operating limits, the actuator is signaled to close or open a control valve which is located farther down the stream.

==Conclusion==
The Evanston Chemical Engineering Division suggests a process that produces 45,000 tonnes/year of 99.5 wt% 1,4-butandeiol to enter the market with an appropriate market share. The feasibility of producing BDO as a significant process was investigated. A wide range of BDO production processes were researched, with a modified Davy process being identified as having the most potential. Using a Pa,Ag,Re catalyst on carbon support, this process converts bio-succinic acid to BDO with approximately 94% conversion. This process was designed in Aspen HYSYS, and economic analysis was conducted in Aspen Economic Analyzer. Total capital costs of the project are 12.2 MM$, with a simple payback period of 5.2 years. Total operational costs annually are 139.7 MM$. The process design was successful, with the capability of producing the desired production of BDO.

==Recommendations==
Given the moderate profitability of this process design, it is recommended that Evanston Chemicals explores further optimization techniques to increase the profitability of this process. This includes investigating sales of the γ-butyrolactone byproduct, recycling process water, and further optimizing utility streams for the distillation tower.
Second, we would like to investigate recycling the 2300 kg/h of water produced in the reaction. Our succinic acid enters the reactor as a 50 wt% solution in water, so we should look into replacing some of this with the product water. Not only will this decrease our water bill, but it will also lower the cost of ion exchange.

==References==
# Nexant.Is Bio-Butanediol Here to Stay? White Plains, NY: ChemSystems Products; 2012.
# De Guzman D. Chemical industry awaits for bio-succinic acid potential. ICIS. Available at: http://www.icis.com/resources/news/2012/01/30/9527521/chemical-industry-awaits-for-bio-succinic-acid-potential/. Accessed January 24, 2014.
# Australian Government: Department of Health. 1,4-butanediol factsheet. National Industrial Chemicals Notification and Assessment Scheme. Available at: http://www.nicnas.gov.au/communications/publications/information-sheets/existing-chemical-info-sheets/other-information-sheets. Accessed January 24, 2014.
# TecnonOrbiChem. Chem-net facts: 1,4-butanediol. TecnonOrbiChem. Available at: http://www.orbichem.com/userfiles/CNF%20Samples/bdo_13_11.pdf. Accessed January 23, 2014.
# Nexant. 1,4-butanediol/tetrahydrofuran (BDO/THF). ChemSystems. Available at: http://www.chemsystems.com/about/cs/news/items/ PERP2012_3_BDO_THF.cfm. Accessed February 6, 2014.
# Burk MJ, Van Dien SJ, Burgard AP, inventors; Genomatica, Inc., assignee. Compositions and methods for the biosynthesis of 1,4-butanediol and its precursors. US patent 8,067,214. Nov. 29, 2011.
# Chung S-H, Kim M-S, Eom H-H, Lee K-Y. Catalytic hydrogenation of bio-based succinic acid for the production of 1,4-butanediol through the indirect pathway. AIChE. Available at: https://aiche.confex.com/aiche/2013/webprogram/Paper327470.html. Accessed January 23, 2014.
# Bhattacharyya A, Manila MD, inventors; ISP Investments Inc., assignee. Catalysts for maleic acid hydrogenation to 1,4-Butanediol. US patent 7,935,834 B2. May 3, 2011.

Design S2

2014-03-15T04:54:20Z

Karetstik: /* HYSYS simulation */

Title: Production of 1,4-butanediol

Authors: Nick Pinkerton, Karen Schmidt, and James Xamplas

Date Presented: March 14, 2014

==Introduction==
1,4-butanediol (BDO) is traditionally made from petroleum-derived feedstocks in a variety of processes such as the Reppe (acetylene-based), Mitsubishi (butadiene-based), and Davy (maleic acid-based) processes [1]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, BDO [1]. It is this process that Team S2Kool4Skool has chosen to develop for a new bio-butanediol plant, because the Davy method is mature and requires no new innovations, and because an appropriate feedstock of bio-succinic acid is now available. The plant will be located in East Carroll Parish, Louisiana. This county is also home to Myriant; located in Lake Providence, they are the largest domestic provider of bio-succinic acid [2]. Furthermore, Lake Providence is conveniently located on the Mississippi River, which will allow for affordable transportation of our bio-based butanediol product. The intent of this project is to produce 45,000 metric tonnes of 99.5 wt% 1,4-butanediol per year in a new plant in Lake Providence, LA. The plant will run 24 hours per day for 350 days out of the year, allowing approximately two weeks for a maintenance shutdown.

As there are several techniques for producing 1,4 butanediol in industry, the first step was to determine a synthesis path. Based on the chosen path, reaction kinetics, and required production rate of the process, a reactor system was then designed. Next, the process was designed to deliver the reactants to the reactor at the proper operating conditions, and the separations, purification, and waste management steps were designed. Cost estimates were made using costing software and hand calculations. Finally, the process was iterated and optimized to reduce costs.

==Background==
===General information===
BDO is an organic chemical with the molecular formula <math>C_4H_{10}O_2</math>. It is also a diol with its two hydroxyl groups located at the terminal carbons. BDO has a boiling point of 235 degrees C and is therefore a colorless liquid at standard temperatures and pressures [3].

There are many precursors that petrochemical synthesis of BDO uses. The commonality between all of the precursor acids is that they are hydrogenatable. In replacement of one of these petrochemical precursors, our team has been tasked with the challenge of deriving BDO from the bio-based precursor succinic acid. This catalyzed reaction will take place in the presence of hydrogen as the hydrogenating component shown below:

<math>C_4H_6O_4 + 4H_2 = C_4H_{10}O_2 + 2H_2O</math>

As described in the above reaction, there will need to be at least 4:1 stoichiometric ratio of hydrogen gas to succinic acid. Two moles of water will also be produced along with each mole of BDO. This reaction is exothermic, which requires the reactor to be continuously cooled to maintain our reactor temperature. There are also side products that are produced which include tetrahydrofuran (THF) and γ-butyrolactone (GBL); however, thanks to catalyst selectivity these byproducts are produced in small quantities.

===Market analysis===
Butanediol has a quickly expanding market due to new technological evolutions and its growing use as a chemical intermediary in advanced materials. With biological routes being optimized, the potential of biomass-derived chemicals is tremendous. The global demand of BDO was estimated at 1.5 million metric tons in 2011 and is projected to grow at an annual rate of 4.5% for the next several years [1]. Unlike other chemical products, BDO’s profitability and attractiveness to producers lies in its downstream potential. Figure 1 below demonstrates several potential downstream products that can be directly or indirectly synthesized from BDO. The largest of these contributors include THF and GBL.

The current market demand of BDO is being supplemented by several global chemical companies. These companies include BASF, BioAmber, Purac, Myriant, DSM, Mitsubishi Chemical, Roquette, and OPXBIO. The market shares of these companies were not available for this product; however, with the consistent growth of the BDO market our team feels that the market is not saturated or impenetrable. The current market price of BDO fluctuates between $3.06 and $3.31 per kg for US-made products [4]. These prices correlate to a nearly 7 billion dollar industry.

===Process alternatives===
1,4-butanediol is traditionally made from petroleum-derived feedstocks in a variety of processes [5]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Several companies are currently implementing bio-routes of producing butanediol. Genomatica is using a bioengineered microorganism to convert sugar feedstocks directly to BDO via fermentation [6], but most companies are instead using microorganisms to convert sugar to succinic acid. The bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, which is the path that most are choosing, although research is being conducted on alternative pathways [7].

==Process overview==
The newly proposed plant can be divided into four stages: pre-reactor, reactor, post-reactor and distillation. Each section is an integral part to the overall process and demands close attention. The process flow diagram (see Appendix A) and stream table (Appendix B) provide more detailed information.

===Pre-reactor===
This chemical process begins with two feedstocks: hydrogen gas and bio-succinic acid. The hydrogen gas will be obtained from a pipeline at 150 atm and will be used in molar excess inside the reactor. The bio-succinic acid will be purchased by Myriant Corporation which is located near the planned plant site. The pricing for this feedstock is approximately $2.12 per kg. The plant will require 63,000 metric tonnes of bio-succinic acid per year to meet the proposed plant capacity. First the bio-succinic acid feed is pumped up to 150 atm to match the hydrogen gas feed, and then it is mixed with the hydrogen gas prior to being sent into heat exchanger E-101 for heating. The heat exchanger brings the two feeds up to 110oC and sends them to the jacketed packed bed reactor.

===Reactor===
The hydrogenation reaction occurs inside of the reactor thanks to the packed catalyst bed. The catalyst used is 0.4% Fe, 1.9% Na, 2.66% Ag, 2.66% Pd, 10.0% Re on 1.5mm carbon support. With this catalyst, BDO is produced with over 90% selectivity and minimal side reactions of THF and GBL.8 The reaction has an operating pressure of 2000-4000 psi and internal reactor temperature of 165°C. This temperature allows for about 99.7% conversion of succinic acid.8 Due to the exothermic nature of the reaction, a cooling jacket is required which utilizes downstream cold streams to cool the internal bed to maintain the desired reaction temperature.

===Post-reactor===
The effluent of the reactor is sent back to E-101 as the hot stream. After exiting E-101, the reactor product stream is sent to a secondary exchanger, E-102, where utility cooling water is used to reduce the temperature to an acceptable temperature prior to sending it to a pressure let-down valve. At this point the pressure of the stream is taken from 150 atm to 1 atm. This large pressure drop allows for the stream to split into its vapor and liquid portions in a gas-liquid separator. The vapor stream of the gas liquid separator is primarily hydrogen gas and sent to a flare for disposal. The liquid effluent is at approximately 45oC leaving the separator and is therefore pumped to the reactor jacket for the reaction cooling mentioned previously. After running through the reactor jacket, the stream enters the separation processes.

===Distillation===
The first distillation column, T-101, is a 10 stage column whose primary purpose is separating the THF from the product feed. Due to THF’s lower boiling point, the byproduct comes off of the top of the column with mostly water. This distillate is sent to the plant's THF waste storage tank that has the capacity of two weeks. The bottoms of the column is sent to the subsequent distillation column that separates the BDO from the GBL and water. The relatively close boiling points of BDO and GBL, 235oC and 204oC, respectively, create a difficult separation that requires a 15 stage column. The distillate of the column is approximately 23% GBL with balance water. This stream is sent to a storage tank with similar sizing parameters as the THF storage tank. The bottom stream is the final 99.5wt% BDO product. This stream is sent to the final product tank, S-104. Depending on our customer demands and the plant location we have the ability to barge, rail or pipe our product to its final destination. Due to low purity of the byproducts, future iterations are needed to optimize either purifying byproducts or selling impure byproducts. There is definitely an available market for these byproducts that should be researched more extensively to increase profit. A detailed description of the equipment from the PFD can be found in Appendix C, in addition to sizing specifications and purpose of equipment.

===Mass and energy balances===
Using an Aspen HYSYS simulation we were able to record the material and energy streams going in and out of the process system. Mass and energy balances are provided Appendix D where each inlet and outlet stream is described and quantified. As expected, the material and energy totals for the inlet and outlet streams add together to equal 0. This proves that our system is mathematically prudent and thermodynamically feasible. The total mass flow of the system is 15,639 kg/h and the total energy in and out of the system is 1.41e8 kJ/h.

===HYSYS simulation===
The HYSYS simulation was performed using the NRTL ideal fluid package. After using AspenPlus to verify that the HYSYS package had the appropriate vapor-liquid equilibrium information between THF and water, and between GBL and water, we concluded it was feasible to proceed with that fluid package. The simulation consists of a reactor, a gas-liquid separator, 2 pumps, 3 heaters, a valve, and 2 distillation columns (see Figure 2). The simulation successfully converted the succinic acid feed into the desired products. Also, the combination of the two distillation columns was able to effectively separate the BDO to obtain a 99.5% pure product with 99.5% recovery. In addition, a set was made between the energy required to heat stream 12 and the energy required to cool the reactor so that these values were made equal. Lastly, the condenser and reboiler duties were used in four heat exchangers in order to determine the appropriate size of this equipment as well as the necessary utility flow rates.

==Health and safety==
===Chemical properties===
Inherent to this process are a number of toxic chemicals. Table 1 summarizes the important safety data including hazard type, odor, color, and exposure limits.

As shown in the above table, the chemicals that this facility will be dealing with will be relatively mild and non-life threatening. Regardless of their perceived threat, chemicals should always be handled with care especially when they are at high temperatures and pressures.

===Safety procedures===

Fire. There are many flammable materials that will be included in this process; therefore, fire safety is imperative for all employees. There are countless possible causes of ignition and care should be taken while handling any flammable material whether in the lab or in the field.

In case a fire is present on, the following protocol should be implemented:

* Small fire: Use DRY chemical powder.
* Large fire: Use alcohol foam, water spray, or fog.
* Call for backup if unable to control.
* Immediately contact supervisor and emergency personnel on site.
* Evacuate to safe distance in case of fires around any hazardous materials or pressure vessels.

Spills. Process chemical spills will eventually occur in a plant of this scale. Small spills are likely to occur in a laboratory setting. Large spills could be a result of loss of containment in the system. We must ensure that all personnel are aware of proper spill mitigation protocol.

* Small spill: Dilute with water and mop or absorb with inert dry material. Dispose of in proper receptacle.
* Large spill: Keep away from sources of ignition and heat. Prevent rundown to any drains or sewers. Call for assistance on disposal. Absorb material with DRY earth or other non-combustible materials.
* If spill is due to a loss of containment in the system, quickly consult the PLC and shut any valves to prevent further loss.

Exposure. We must ensure that our employees are aware of the possible toxicity levels of each substance and how to handle exposure. The chemicals that are being used in this process are known chemical irritants to the eyes, skin, and throat. Safety measures must be in place to acknowledge this hazard. Due to the possibility of high pressure releases, we will have 2-minute emergency oxygen masks placed strategically throughout the plant to ensure the safety of any operator in the presence of a large release.

If exposed to the process chemicals, find nearest eye wash station or safety shower immediately and flush exposed skin for at least 15 minutes. Remove any contaminated clothing. Seek medical attention immediately.

Storage. Store chemicals in segregated and approved areas. Any closed containers for laboratory purposes should be placed in cool, well-ventilated areas.

==Economics==
===Equipment costing===
The calculated capital costs from Aspen Economic Analyzer are reported in Table 2 for all process equipment. The size of the reactor was calculated from the liquid hourly space velocity given in the 2011 ISP patent8 and a void fraction estimate of 0.4. Storage tanks were sized to contain up to two continuous weeks of material. The number of distillation trays in each tower and the flow rates through pumps, vessels, and the flare were calculated in HYSYS. Heat exchange areas were given in Aspen Energy Analyzer or from HYSYS.

In addition to the above equipment, our plant will require an ion exchanger to produce deionized process water from the municipal water. This is estimated to cost $42,000 in capital cost.

===Cash flow analysis===
Summarizing the important takeaways from the economic analysis (see Appendix G), this process will return a revenue of 144 MM$ annually. Offset by production costs, the yearly cash flow is approximately 2.7 MM$, except for in the years in which the catalyst must be reinstalled (approximately every 5 years). At a cost of 2.5 MM$, the cash flows in those years decrease to approximately 0.2 MM$. This analysis assumes the plant will take 2 years to construct, and will operate at 50% in its first year. Furthermore, an interest rate of 10% was assumed with a tax rate of 38% (the maximum for corporate gains taxes). Using the 7-year MACRS depreciation method, the 20 year NPV for the project is 4.3 MM$. With an IRR of 15.1%, which is greater than the assumed interest rate, this project looks to be profitable. Further optimization techniques should be used in future iterations to further increase profitability. See Tables 3 and 4 for key economic information.

===Sensitivity analysis===
As seen in Figure 3, the economic evaluation of this process is influenced the most by changes in the sales price and feed cost. A 20% increase in sales price will result in an approximate 120 MM$ increase in NPV whereas a decrease of the same percentage will result in over a 120 MM$ decrease in NPV. Inversely, a 20% increase in feed cost will result in a 115 MM$ decrease in NPV and a 20% decrease in feed cost will result in a 60 MM$ increase in NPV.

To alleviate the risk associated with feed price, the team researched the price forecasting of bio-succinic acid. Figure 4 provides the bio-succinic acid price over the six years between 2006 and 2012. The price of bio-succinic, shown by the blue line, has remained relatively stable over this time period. This price history can be compared to adipic acid, the green line, which is a common petrochemical precursor for BDO production. Adipic acid as shown has had large fluctuations in price that result in unstable cash flows and uncertainty from shareholders. Thankfully, the stability of bio-succinic acid is a good sign that this process has a huge potential to be profitable especially if the demand for BDO continues to rise as projected.

==Discussion==
As described previously, the Davy process was selected as the most promising process of BDO production. The modified Davy process involves the hydrogenation of bio-succinicic acid with a Pa,Ag,Re catalyst and hydrogen gas. This process has many advantages, one being that it has mature technology that has been improved over the last 20 years. Additionally, the conversion to of succinic acid is virtually complete. Finally, overall plant yields can reach as high as 94 mol%.
As shown in Appendix B, streams ahead of the pressure valve (PRV-101) are at approximately 1.51e4 kPa, and streams after the pressure valve are between 100 and 450 kPa. Furthermore, operating temperatures do not exceed 200°C, including safety factors. These operating conditions contribute to the feasibility of the process, as all the components can be designed with reasonable dimensions (wall thickness, cap type, etc.).

Of particular interest are the large costs of the reactor and pump P-101. The reactor costs nearly 2 MM$ because it has a moderate size with a liquid volume of 16.7 m3, and it operates at 150 atm, which requires a strong stainless steel shell for safety purposes. Pump P-101 has such a large capital cost because it is a centrifugal multistage pump that also needs to be made of stainless steel to withstand pressuring the succinic acid feed to 150 atm.

Financial indicators for the proposed plant suggest that it will be moderately profitable, and additional optimization should be performed before making the capital investment. There is a fair amount of risk associated with the implementation of this production facility, and the return at this juncture may not justify the risk.

The process design and simulation in HYSYS has relied on several key assumptions, which are cause for certain limitations to the results. First, the conversions and selectivity of the catalyst, while taken from literature sources, are assumed to be true. Furthermore, the assumption of negligible side reactions and products was made. It is possible that small waste products in the form of succinates also form in the reactor. Therefore, the main limitation of this model is generally due to reaction specifications.

There are certain safety concerns that go along with the proposed process. First, there are many pipes and vessels that will be at a pressure of approximately 150 atm. Extra insulation and protection must be applied to the piping that contains highly pressurized fluids, to prevent operator injury. Furthermore, the PFR is at a slight risk for runaway reactions due to the exothermic nature of the reaction. The temperature of the reactor must always be monitored by an operator, and the jacket cooling system requires a backup system as well. A benefit of this process is that there are no toxic or severely hazardous components in the process. Additionally, there are no instances of temperature greater than 200°C.

The process design will be fitted with instrumentation and controls to ensure stable operation. These controls, including sensors and valves, minimize potential damage to components due to variation in plant conditions, as well as optimizing the overall performance. For example, the piping entering the tower will be fitted with a control loop. In the direction of flow, a sensing instrument first detects the pressure of the fluid, and then sends a signal to the controller. If the pressure is not within the operating limits, the actuator is signaled to close or open a control valve which is located farther down the stream.

==Conclusion==
The Evanston Chemical Engineering Division suggests a process that produces 45,000 tonnes/year of 99.5 wt% 1,4-butandeiol to enter the market with an appropriate market share. The feasibility of producing BDO as a significant process was investigated. A wide range of BDO production processes were researched, with a modified Davy process being identified as having the most potential. Using a Pa,Ag,Re catalyst on carbon support, this process converts bio-succinic acid to BDO with approximately 94% conversion. This process was designed in Aspen HYSYS, and economic analysis was conducted in Aspen Economic Analyzer. Total capital costs of the project are 12.2 MM$, with a simple payback period of 5.2 years. Total operational costs annually are 139.7 MM$. The process design was successful, with the capability of producing the desired production of BDO.

==Recommendations==
Given the moderate profitability of this process design, it is recommended that Evanston Chemicals explores further optimization techniques to increase the profitability of this process. This includes investigating sales of the γ-butyrolactone byproduct, recycling process water, and further optimizing utility streams for the distillation tower.
Second, we would like to investigate recycling the 2300 kg/h of water produced in the reaction. Our succinic acid enters the reactor as a 50 wt% solution in water, so we should look into replacing some of this with the product water. Not only will this decrease our water bill, but it will also lower the cost of ion exchange.

==References==
# Nexant.Is Bio-Butanediol Here to Stay? White Plains, NY: ChemSystems Products; 2012.
# De Guzman D. Chemical industry awaits for bio-succinic acid potential. ICIS. Available at: http://www.icis.com/resources/news/2012/01/30/9527521/chemical-industry-awaits-for-bio-succinic-acid-potential/. Accessed January 24, 2014.
# Australian Government: Department of Health. 1,4-butanediol factsheet. National Industrial Chemicals Notification and Assessment Scheme. Available at: http://www.nicnas.gov.au/communications/publications/information-sheets/existing-chemical-info-sheets/other-information-sheets. Accessed January 24, 2014.
# TecnonOrbiChem. Chem-net facts: 1,4-butanediol. TecnonOrbiChem. Available at: http://www.orbichem.com/userfiles/CNF%20Samples/bdo_13_11.pdf. Accessed January 23, 2014.
# Nexant. 1,4-butanediol/tetrahydrofuran (BDO/THF). ChemSystems. Available at: http://www.chemsystems.com/about/cs/news/items/ PERP2012_3_BDO_THF.cfm. Accessed February 6, 2014.
# Burk MJ, Van Dien SJ, Burgard AP, inventors; Genomatica, Inc., assignee. Compositions and methods for the biosynthesis of 1,4-butanediol and its precursors. US patent 8,067,214. Nov. 29, 2011.
# Chung S-H, Kim M-S, Eom H-H, Lee K-Y. Catalytic hydrogenation of bio-based succinic acid for the production of 1,4-butanediol through the indirect pathway. AIChE. Available at: https://aiche.confex.com/aiche/2013/webprogram/Paper327470.html. Accessed January 23, 2014.
# Bhattacharyya A, Manila MD, inventors; ISP Investments Inc., assignee. Catalysts for maleic acid hydrogenation to 1,4-Butanediol. US patent 7,935,834 B2. May 3, 2011.

Design S2

2014-03-15T04:53:59Z

Karetstik: /* Process overview */

Title: Production of 1,4-butanediol

Authors: Nick Pinkerton, Karen Schmidt, and James Xamplas

Date Presented: March 14, 2014

==Introduction==
1,4-butanediol (BDO) is traditionally made from petroleum-derived feedstocks in a variety of processes such as the Reppe (acetylene-based), Mitsubishi (butadiene-based), and Davy (maleic acid-based) processes [1]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, BDO [1]. It is this process that Team S2Kool4Skool has chosen to develop for a new bio-butanediol plant, because the Davy method is mature and requires no new innovations, and because an appropriate feedstock of bio-succinic acid is now available. The plant will be located in East Carroll Parish, Louisiana. This county is also home to Myriant; located in Lake Providence, they are the largest domestic provider of bio-succinic acid [2]. Furthermore, Lake Providence is conveniently located on the Mississippi River, which will allow for affordable transportation of our bio-based butanediol product. The intent of this project is to produce 45,000 metric tonnes of 99.5 wt% 1,4-butanediol per year in a new plant in Lake Providence, LA. The plant will run 24 hours per day for 350 days out of the year, allowing approximately two weeks for a maintenance shutdown.

As there are several techniques for producing 1,4 butanediol in industry, the first step was to determine a synthesis path. Based on the chosen path, reaction kinetics, and required production rate of the process, a reactor system was then designed. Next, the process was designed to deliver the reactants to the reactor at the proper operating conditions, and the separations, purification, and waste management steps were designed. Cost estimates were made using costing software and hand calculations. Finally, the process was iterated and optimized to reduce costs.

==Background==
===General information===
BDO is an organic chemical with the molecular formula <math>C_4H_{10}O_2</math>. It is also a diol with its two hydroxyl groups located at the terminal carbons. BDO has a boiling point of 235 degrees C and is therefore a colorless liquid at standard temperatures and pressures [3].

There are many precursors that petrochemical synthesis of BDO uses. The commonality between all of the precursor acids is that they are hydrogenatable. In replacement of one of these petrochemical precursors, our team has been tasked with the challenge of deriving BDO from the bio-based precursor succinic acid. This catalyzed reaction will take place in the presence of hydrogen as the hydrogenating component shown below:

<math>C_4H_6O_4 + 4H_2 = C_4H_{10}O_2 + 2H_2O</math>

As described in the above reaction, there will need to be at least 4:1 stoichiometric ratio of hydrogen gas to succinic acid. Two moles of water will also be produced along with each mole of BDO. This reaction is exothermic, which requires the reactor to be continuously cooled to maintain our reactor temperature. There are also side products that are produced which include tetrahydrofuran (THF) and γ-butyrolactone (GBL); however, thanks to catalyst selectivity these byproducts are produced in small quantities.

===Market analysis===
Butanediol has a quickly expanding market due to new technological evolutions and its growing use as a chemical intermediary in advanced materials. With biological routes being optimized, the potential of biomass-derived chemicals is tremendous. The global demand of BDO was estimated at 1.5 million metric tons in 2011 and is projected to grow at an annual rate of 4.5% for the next several years [1]. Unlike other chemical products, BDO’s profitability and attractiveness to producers lies in its downstream potential. Figure 1 below demonstrates several potential downstream products that can be directly or indirectly synthesized from BDO. The largest of these contributors include THF and GBL.

The current market demand of BDO is being supplemented by several global chemical companies. These companies include BASF, BioAmber, Purac, Myriant, DSM, Mitsubishi Chemical, Roquette, and OPXBIO. The market shares of these companies were not available for this product; however, with the consistent growth of the BDO market our team feels that the market is not saturated or impenetrable. The current market price of BDO fluctuates between $3.06 and $3.31 per kg for US-made products [4]. These prices correlate to a nearly 7 billion dollar industry.

===Process alternatives===
1,4-butanediol is traditionally made from petroleum-derived feedstocks in a variety of processes [5]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Several companies are currently implementing bio-routes of producing butanediol. Genomatica is using a bioengineered microorganism to convert sugar feedstocks directly to BDO via fermentation [6], but most companies are instead using microorganisms to convert sugar to succinic acid. The bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, which is the path that most are choosing, although research is being conducted on alternative pathways [7].

==Process overview==
The newly proposed plant can be divided into four stages: pre-reactor, reactor, post-reactor and distillation. Each section is an integral part to the overall process and demands close attention. The process flow diagram (see Appendix A) and stream table (Appendix B) provide more detailed information.

===Pre-reactor===
This chemical process begins with two feedstocks: hydrogen gas and bio-succinic acid. The hydrogen gas will be obtained from a pipeline at 150 atm and will be used in molar excess inside the reactor. The bio-succinic acid will be purchased by Myriant Corporation which is located near the planned plant site. The pricing for this feedstock is approximately $2.12 per kg. The plant will require 63,000 metric tonnes of bio-succinic acid per year to meet the proposed plant capacity. First the bio-succinic acid feed is pumped up to 150 atm to match the hydrogen gas feed, and then it is mixed with the hydrogen gas prior to being sent into heat exchanger E-101 for heating. The heat exchanger brings the two feeds up to 110oC and sends them to the jacketed packed bed reactor.

===Reactor===
The hydrogenation reaction occurs inside of the reactor thanks to the packed catalyst bed. The catalyst used is 0.4% Fe, 1.9% Na, 2.66% Ag, 2.66% Pd, 10.0% Re on 1.5mm carbon support. With this catalyst, BDO is produced with over 90% selectivity and minimal side reactions of THF and GBL.8 The reaction has an operating pressure of 2000-4000 psi and internal reactor temperature of 165°C. This temperature allows for about 99.7% conversion of succinic acid.8 Due to the exothermic nature of the reaction, a cooling jacket is required which utilizes downstream cold streams to cool the internal bed to maintain the desired reaction temperature.

===Post-reactor===
The effluent of the reactor is sent back to E-101 as the hot stream. After exiting E-101, the reactor product stream is sent to a secondary exchanger, E-102, where utility cooling water is used to reduce the temperature to an acceptable temperature prior to sending it to a pressure let-down valve. At this point the pressure of the stream is taken from 150 atm to 1 atm. This large pressure drop allows for the stream to split into its vapor and liquid portions in a gas-liquid separator. The vapor stream of the gas liquid separator is primarily hydrogen gas and sent to a flare for disposal. The liquid effluent is at approximately 45oC leaving the separator and is therefore pumped to the reactor jacket for the reaction cooling mentioned previously. After running through the reactor jacket, the stream enters the separation processes.

===Distillation===
The first distillation column, T-101, is a 10 stage column whose primary purpose is separating the THF from the product feed. Due to THF’s lower boiling point, the byproduct comes off of the top of the column with mostly water. This distillate is sent to the plant's THF waste storage tank that has the capacity of two weeks. The bottoms of the column is sent to the subsequent distillation column that separates the BDO from the GBL and water. The relatively close boiling points of BDO and GBL, 235oC and 204oC, respectively, create a difficult separation that requires a 15 stage column. The distillate of the column is approximately 23% GBL with balance water. This stream is sent to a storage tank with similar sizing parameters as the THF storage tank. The bottom stream is the final 99.5wt% BDO product. This stream is sent to the final product tank, S-104. Depending on our customer demands and the plant location we have the ability to barge, rail or pipe our product to its final destination. Due to low purity of the byproducts, future iterations are needed to optimize either purifying byproducts or selling impure byproducts. There is definitely an available market for these byproducts that should be researched more extensively to increase profit. A detailed description of the equipment from the PFD can be found in Appendix C, in addition to sizing specifications and purpose of equipment.

===Mass and energy balances===
Using an Aspen HYSYS simulation we were able to record the material and energy streams going in and out of the process system. Mass and energy balances are provided Appendix D where each inlet and outlet stream is described and quantified. As expected, the material and energy totals for the inlet and outlet streams add together to equal 0. This proves that our system is mathematically prudent and thermodynamically feasible. The total mass flow of the system is 15,639 kg/h and the total energy in and out of the system is 1.41e8 kJ/h.

===HYSYS simulation===
The HYSYS simulation was performed using the NRTL ideal fluid package. After using AspenPlus to verify that the HYSYS package had the appropriate vapor-liquid equilibrium information between THF and water, and between GBL and water (see Appendix E), we concluded it was feasible to proceed with that fluid package. The simulation consists of a reactor, a gas-liquid separator, 2 pumps, 3 heaters, a valve, and 2 distillation columns (see Figure 2). The simulation successfully converted the succinic acid feed into the desired products. Also, the combination of the two distillation columns was able to effectively separate the BDO to obtain a 99.5% pure product with 99.5% recovery. In addition, a set was made between the energy required to heat stream 12 and the energy required to cool the reactor so that these values were made equal. Lastly, the condenser and reboiler duties were used in four heat exchangers in order to determine the appropriate size of this equipment as well as the necessary utility flow rates.

==Health and safety==
===Chemical properties===
Inherent to this process are a number of toxic chemicals. Table 1 summarizes the important safety data including hazard type, odor, color, and exposure limits.

As shown in the above table, the chemicals that this facility will be dealing with will be relatively mild and non-life threatening. Regardless of their perceived threat, chemicals should always be handled with care especially when they are at high temperatures and pressures.

===Safety procedures===

Fire. There are many flammable materials that will be included in this process; therefore, fire safety is imperative for all employees. There are countless possible causes of ignition and care should be taken while handling any flammable material whether in the lab or in the field.

In case a fire is present on, the following protocol should be implemented:

* Small fire: Use DRY chemical powder.
* Large fire: Use alcohol foam, water spray, or fog.
* Call for backup if unable to control.
* Immediately contact supervisor and emergency personnel on site.
* Evacuate to safe distance in case of fires around any hazardous materials or pressure vessels.

Spills. Process chemical spills will eventually occur in a plant of this scale. Small spills are likely to occur in a laboratory setting. Large spills could be a result of loss of containment in the system. We must ensure that all personnel are aware of proper spill mitigation protocol.

* Small spill: Dilute with water and mop or absorb with inert dry material. Dispose of in proper receptacle.
* Large spill: Keep away from sources of ignition and heat. Prevent rundown to any drains or sewers. Call for assistance on disposal. Absorb material with DRY earth or other non-combustible materials.
* If spill is due to a loss of containment in the system, quickly consult the PLC and shut any valves to prevent further loss.

Exposure. We must ensure that our employees are aware of the possible toxicity levels of each substance and how to handle exposure. The chemicals that are being used in this process are known chemical irritants to the eyes, skin, and throat. Safety measures must be in place to acknowledge this hazard. Due to the possibility of high pressure releases, we will have 2-minute emergency oxygen masks placed strategically throughout the plant to ensure the safety of any operator in the presence of a large release.

If exposed to the process chemicals, find nearest eye wash station or safety shower immediately and flush exposed skin for at least 15 minutes. Remove any contaminated clothing. Seek medical attention immediately.

Storage. Store chemicals in segregated and approved areas. Any closed containers for laboratory purposes should be placed in cool, well-ventilated areas.

==Economics==
===Equipment costing===
The calculated capital costs from Aspen Economic Analyzer are reported in Table 2 for all process equipment. The size of the reactor was calculated from the liquid hourly space velocity given in the 2011 ISP patent8 and a void fraction estimate of 0.4. Storage tanks were sized to contain up to two continuous weeks of material. The number of distillation trays in each tower and the flow rates through pumps, vessels, and the flare were calculated in HYSYS. Heat exchange areas were given in Aspen Energy Analyzer or from HYSYS.

In addition to the above equipment, our plant will require an ion exchanger to produce deionized process water from the municipal water. This is estimated to cost $42,000 in capital cost.

===Cash flow analysis===
Summarizing the important takeaways from the economic analysis (see Appendix G), this process will return a revenue of 144 MM$ annually. Offset by production costs, the yearly cash flow is approximately 2.7 MM$, except for in the years in which the catalyst must be reinstalled (approximately every 5 years). At a cost of 2.5 MM$, the cash flows in those years decrease to approximately 0.2 MM$. This analysis assumes the plant will take 2 years to construct, and will operate at 50% in its first year. Furthermore, an interest rate of 10% was assumed with a tax rate of 38% (the maximum for corporate gains taxes). Using the 7-year MACRS depreciation method, the 20 year NPV for the project is 4.3 MM$. With an IRR of 15.1%, which is greater than the assumed interest rate, this project looks to be profitable. Further optimization techniques should be used in future iterations to further increase profitability. See Tables 3 and 4 for key economic information.

===Sensitivity analysis===
As seen in Figure 3, the economic evaluation of this process is influenced the most by changes in the sales price and feed cost. A 20% increase in sales price will result in an approximate 120 MM$ increase in NPV whereas a decrease of the same percentage will result in over a 120 MM$ decrease in NPV. Inversely, a 20% increase in feed cost will result in a 115 MM$ decrease in NPV and a 20% decrease in feed cost will result in a 60 MM$ increase in NPV.

To alleviate the risk associated with feed price, the team researched the price forecasting of bio-succinic acid. Figure 4 provides the bio-succinic acid price over the six years between 2006 and 2012. The price of bio-succinic, shown by the blue line, has remained relatively stable over this time period. This price history can be compared to adipic acid, the green line, which is a common petrochemical precursor for BDO production. Adipic acid as shown has had large fluctuations in price that result in unstable cash flows and uncertainty from shareholders. Thankfully, the stability of bio-succinic acid is a good sign that this process has a huge potential to be profitable especially if the demand for BDO continues to rise as projected.

==Discussion==
As described previously, the Davy process was selected as the most promising process of BDO production. The modified Davy process involves the hydrogenation of bio-succinicic acid with a Pa,Ag,Re catalyst and hydrogen gas. This process has many advantages, one being that it has mature technology that has been improved over the last 20 years. Additionally, the conversion to of succinic acid is virtually complete. Finally, overall plant yields can reach as high as 94 mol%.
As shown in Appendix B, streams ahead of the pressure valve (PRV-101) are at approximately 1.51e4 kPa, and streams after the pressure valve are between 100 and 450 kPa. Furthermore, operating temperatures do not exceed 200°C, including safety factors. These operating conditions contribute to the feasibility of the process, as all the components can be designed with reasonable dimensions (wall thickness, cap type, etc.).

Of particular interest are the large costs of the reactor and pump P-101. The reactor costs nearly 2 MM$ because it has a moderate size with a liquid volume of 16.7 m3, and it operates at 150 atm, which requires a strong stainless steel shell for safety purposes. Pump P-101 has such a large capital cost because it is a centrifugal multistage pump that also needs to be made of stainless steel to withstand pressuring the succinic acid feed to 150 atm.

Financial indicators for the proposed plant suggest that it will be moderately profitable, and additional optimization should be performed before making the capital investment. There is a fair amount of risk associated with the implementation of this production facility, and the return at this juncture may not justify the risk.

The process design and simulation in HYSYS has relied on several key assumptions, which are cause for certain limitations to the results. First, the conversions and selectivity of the catalyst, while taken from literature sources, are assumed to be true. Furthermore, the assumption of negligible side reactions and products was made. It is possible that small waste products in the form of succinates also form in the reactor. Therefore, the main limitation of this model is generally due to reaction specifications.

There are certain safety concerns that go along with the proposed process. First, there are many pipes and vessels that will be at a pressure of approximately 150 atm. Extra insulation and protection must be applied to the piping that contains highly pressurized fluids, to prevent operator injury. Furthermore, the PFR is at a slight risk for runaway reactions due to the exothermic nature of the reaction. The temperature of the reactor must always be monitored by an operator, and the jacket cooling system requires a backup system as well. A benefit of this process is that there are no toxic or severely hazardous components in the process. Additionally, there are no instances of temperature greater than 200°C.

The process design will be fitted with instrumentation and controls to ensure stable operation. These controls, including sensors and valves, minimize potential damage to components due to variation in plant conditions, as well as optimizing the overall performance. For example, the piping entering the tower will be fitted with a control loop. In the direction of flow, a sensing instrument first detects the pressure of the fluid, and then sends a signal to the controller. If the pressure is not within the operating limits, the actuator is signaled to close or open a control valve which is located farther down the stream.

==Conclusion==
The Evanston Chemical Engineering Division suggests a process that produces 45,000 tonnes/year of 99.5 wt% 1,4-butandeiol to enter the market with an appropriate market share. The feasibility of producing BDO as a significant process was investigated. A wide range of BDO production processes were researched, with a modified Davy process being identified as having the most potential. Using a Pa,Ag,Re catalyst on carbon support, this process converts bio-succinic acid to BDO with approximately 94% conversion. This process was designed in Aspen HYSYS, and economic analysis was conducted in Aspen Economic Analyzer. Total capital costs of the project are 12.2 MM$, with a simple payback period of 5.2 years. Total operational costs annually are 139.7 MM$. The process design was successful, with the capability of producing the desired production of BDO.

==Recommendations==
Given the moderate profitability of this process design, it is recommended that Evanston Chemicals explores further optimization techniques to increase the profitability of this process. This includes investigating sales of the γ-butyrolactone byproduct, recycling process water, and further optimizing utility streams for the distillation tower.
Second, we would like to investigate recycling the 2300 kg/h of water produced in the reaction. Our succinic acid enters the reactor as a 50 wt% solution in water, so we should look into replacing some of this with the product water. Not only will this decrease our water bill, but it will also lower the cost of ion exchange.

==References==
# Nexant.Is Bio-Butanediol Here to Stay? White Plains, NY: ChemSystems Products; 2012.
# De Guzman D. Chemical industry awaits for bio-succinic acid potential. ICIS. Available at: http://www.icis.com/resources/news/2012/01/30/9527521/chemical-industry-awaits-for-bio-succinic-acid-potential/. Accessed January 24, 2014.
# Australian Government: Department of Health. 1,4-butanediol factsheet. National Industrial Chemicals Notification and Assessment Scheme. Available at: http://www.nicnas.gov.au/communications/publications/information-sheets/existing-chemical-info-sheets/other-information-sheets. Accessed January 24, 2014.
# TecnonOrbiChem. Chem-net facts: 1,4-butanediol. TecnonOrbiChem. Available at: http://www.orbichem.com/userfiles/CNF%20Samples/bdo_13_11.pdf. Accessed January 23, 2014.
# Nexant. 1,4-butanediol/tetrahydrofuran (BDO/THF). ChemSystems. Available at: http://www.chemsystems.com/about/cs/news/items/ PERP2012_3_BDO_THF.cfm. Accessed February 6, 2014.
# Burk MJ, Van Dien SJ, Burgard AP, inventors; Genomatica, Inc., assignee. Compositions and methods for the biosynthesis of 1,4-butanediol and its precursors. US patent 8,067,214. Nov. 29, 2011.
# Chung S-H, Kim M-S, Eom H-H, Lee K-Y. Catalytic hydrogenation of bio-based succinic acid for the production of 1,4-butanediol through the indirect pathway. AIChE. Available at: https://aiche.confex.com/aiche/2013/webprogram/Paper327470.html. Accessed January 23, 2014.
# Bhattacharyya A, Manila MD, inventors; ISP Investments Inc., assignee. Catalysts for maleic acid hydrogenation to 1,4-Butanediol. US patent 7,935,834 B2. May 3, 2011.

Design S2

2014-03-15T04:53:48Z

Karetstik: /* Pre-reactor */

Title: Production of 1,4-butanediol

Authors: Nick Pinkerton, Karen Schmidt, and James Xamplas

Date Presented: March 14, 2014

==Introduction==
1,4-butanediol (BDO) is traditionally made from petroleum-derived feedstocks in a variety of processes such as the Reppe (acetylene-based), Mitsubishi (butadiene-based), and Davy (maleic acid-based) processes [1]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, BDO [1]. It is this process that Team S2Kool4Skool has chosen to develop for a new bio-butanediol plant, because the Davy method is mature and requires no new innovations, and because an appropriate feedstock of bio-succinic acid is now available. The plant will be located in East Carroll Parish, Louisiana. This county is also home to Myriant; located in Lake Providence, they are the largest domestic provider of bio-succinic acid [2]. Furthermore, Lake Providence is conveniently located on the Mississippi River, which will allow for affordable transportation of our bio-based butanediol product. The intent of this project is to produce 45,000 metric tonnes of 99.5 wt% 1,4-butanediol per year in a new plant in Lake Providence, LA. The plant will run 24 hours per day for 350 days out of the year, allowing approximately two weeks for a maintenance shutdown.

As there are several techniques for producing 1,4 butanediol in industry, the first step was to determine a synthesis path. Based on the chosen path, reaction kinetics, and required production rate of the process, a reactor system was then designed. Next, the process was designed to deliver the reactants to the reactor at the proper operating conditions, and the separations, purification, and waste management steps were designed. Cost estimates were made using costing software and hand calculations. Finally, the process was iterated and optimized to reduce costs.

==Background==
===General information===
BDO is an organic chemical with the molecular formula <math>C_4H_{10}O_2</math>. It is also a diol with its two hydroxyl groups located at the terminal carbons. BDO has a boiling point of 235 degrees C and is therefore a colorless liquid at standard temperatures and pressures [3].

There are many precursors that petrochemical synthesis of BDO uses. The commonality between all of the precursor acids is that they are hydrogenatable. In replacement of one of these petrochemical precursors, our team has been tasked with the challenge of deriving BDO from the bio-based precursor succinic acid. This catalyzed reaction will take place in the presence of hydrogen as the hydrogenating component shown below:

<math>C_4H_6O_4 + 4H_2 = C_4H_{10}O_2 + 2H_2O</math>

As described in the above reaction, there will need to be at least 4:1 stoichiometric ratio of hydrogen gas to succinic acid. Two moles of water will also be produced along with each mole of BDO. This reaction is exothermic, which requires the reactor to be continuously cooled to maintain our reactor temperature. There are also side products that are produced which include tetrahydrofuran (THF) and γ-butyrolactone (GBL); however, thanks to catalyst selectivity these byproducts are produced in small quantities.

===Market analysis===
Butanediol has a quickly expanding market due to new technological evolutions and its growing use as a chemical intermediary in advanced materials. With biological routes being optimized, the potential of biomass-derived chemicals is tremendous. The global demand of BDO was estimated at 1.5 million metric tons in 2011 and is projected to grow at an annual rate of 4.5% for the next several years [1]. Unlike other chemical products, BDO’s profitability and attractiveness to producers lies in its downstream potential. Figure 1 below demonstrates several potential downstream products that can be directly or indirectly synthesized from BDO. The largest of these contributors include THF and GBL.

The current market demand of BDO is being supplemented by several global chemical companies. These companies include BASF, BioAmber, Purac, Myriant, DSM, Mitsubishi Chemical, Roquette, and OPXBIO. The market shares of these companies were not available for this product; however, with the consistent growth of the BDO market our team feels that the market is not saturated or impenetrable. The current market price of BDO fluctuates between $3.06 and $3.31 per kg for US-made products [4]. These prices correlate to a nearly 7 billion dollar industry.

===Process alternatives===
1,4-butanediol is traditionally made from petroleum-derived feedstocks in a variety of processes [5]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Several companies are currently implementing bio-routes of producing butanediol. Genomatica is using a bioengineered microorganism to convert sugar feedstocks directly to BDO via fermentation [6], but most companies are instead using microorganisms to convert sugar to succinic acid. The bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, which is the path that most are choosing, although research is being conducted on alternative pathways [7].

==Process overview==
The newly proposed plant can be divided into four stages: pre-reactor, reactor, post-reactor and distillation. Each section is an integral part to the overall process and demands close attention. The process flow diagram (see Appendix A) and stream table (Appendix B) provide more detailed information.

===Pre-reactor===
This chemical process begins with two feedstocks: hydrogen gas and bio-succinic acid. The hydrogen gas will be obtained from a pipeline at 150 atm and will be used in molar excess inside the reactor. The bio-succinic acid will be purchased by Myriant Corporation which is located near the planned plant site. The pricing for this feedstock is approximately $2.12 per kg. The plant will require 63,000 metric tonnes of bio-succinic acid per year to meet the proposed plant capacity. First the bio-succinic acid feed is pumped up to 150 atm to match the hydrogen gas feed, and then it is mixed with the hydrogen gas prior to being sent into heat exchanger E-101 for heating. The heat exchanger brings the two feeds up to 110oC and sends them to the jacketed packed bed reactor.

===Reactor===
The hydrogenation reaction occurs inside of the reactor thanks to the packed catalyst bed. The catalyst used is 0.4% Fe, 1.9% Na, 2.66% Ag, 2.66% Pd, 10.0% Re on 1.5mm carbon support. With this catalyst, BDO is produced with over 90% selectivity and minimal side reactions of THF and GBL.8 The reaction has an operating pressure of 2000-4000 psi and internal reactor temperature of 165°C. This temperature allows for about 99.7% conversion of succinic acid.8 Due to the exothermic nature of the reaction, a cooling jacket is required which utilizes downstream cold streams to cool the internal bed to maintain the desired reaction temperature.

===Post-reactor===
The effluent of the reactor is sent back to E-101 as the hot stream. After exiting E-101, the reactor product stream is sent to a secondary exchanger, E-102, where utility cooling water is used to reduce the temperature to an acceptable temperature prior to sending it to a pressure let-down valve. At this point the pressure of the stream is taken from 150 atm to 1 atm. This large pressure drop allows for the stream to split into its vapor and liquid portions in a gas-liquid separator. The vapor stream of the gas liquid separator is primarily hydrogen gas and sent to a flare for disposal. The liquid effluent is at approximately 45oC leaving the separator and is therefore pumped to the reactor jacket for the reaction cooling mentioned previously. After running through the reactor jacket, the stream enters the separation processes.

===Distillation===
The first distillation column, T-101, is a 10 stage column whose primary purpose is separating the THF from the product feed. Due to THF’s lower boiling point, the byproduct comes off of the top of the column with mostly water. This distillate is sent to the plant's THF waste storage tank that has the capacity of two weeks. The bottoms of the column is sent to the subsequent distillation column that separates the BDO from the GBL and water. The relatively close boiling points of BDO and GBL, 235oC and 204oC, respectively, create a difficult separation that requires a 15 stage column. The distillate of the column is approximately 23% GBL with balance water. This stream is sent to a storage tank with similar sizing parameters as the THF storage tank. The bottom stream is the final 99.5wt% BDO product. This stream is sent to the final product tank, S-104. Depending on our customer demands and the plant location we have the ability to barge, rail or pipe our product to its final destination. Due to low purity of the byproducts, future iterations are needed to optimize either purifying byproducts or selling impure byproducts. There is definitely an available market for these byproducts that should be researched more extensively to increase profit. A detailed description of the equipment from the PFD can be found in Appendix C, in addition to sizing specifications and purpose of equipment.

===Mass and energy balances===
Using an Aspen HYSYS simulation we were able to record the material and energy streams going in and out of the process system. Mass and energy balances are provided Appendix D where each inlet and outlet stream is described and quantified. As expected, the material and energy totals for the inlet and outlet streams add together to equal 0. This proves that our system is mathematically prudent and thermodynamically feasible. The total mass flow of the system is 15,639 kg/h and the total energy in and out of the system is 1.41e8 kJ/h.

===HYSYS simulation===
The HYSYS simulation was performed using the NRTL ideal fluid package. After using AspenPlus to verify that the HYSYS package had the appropriate vapor-liquid equilibrium information between THF and water, and between GBL and water (see Appendix E), we concluded it was feasible to proceed with that fluid package. The simulation consists of a reactor, a gas-liquid separator, 2 pumps, 3 heaters, a valve, and 2 distillation columns (see Figure 2). The simulation successfully converted the succinic acid feed into the desired products. Also, the combination of the two distillation columns was able to effectively separate the BDO to obtain a 99.5% pure product with 99.5% recovery. In addition, a set was made between the energy required to heat stream 12 and the energy required to cool the reactor so that these values were made equal. Lastly, the condenser and reboiler duties were used in four heat exchangers in order to determine the appropriate size of this equipment as well as the necessary utility flow rates.

==Health and safety==
===Chemical properties===
Inherent to this process are a number of toxic chemicals. Table 1 summarizes the important safety data including hazard type, odor, color, and exposure limits.

As shown in the above table, the chemicals that this facility will be dealing with will be relatively mild and non-life threatening. Regardless of their perceived threat, chemicals should always be handled with care especially when they are at high temperatures and pressures.

===Safety procedures===

Fire. There are many flammable materials that will be included in this process; therefore, fire safety is imperative for all employees. There are countless possible causes of ignition and care should be taken while handling any flammable material whether in the lab or in the field.

In case a fire is present on, the following protocol should be implemented:

* Small fire: Use DRY chemical powder.
* Large fire: Use alcohol foam, water spray, or fog.
* Call for backup if unable to control.
* Immediately contact supervisor and emergency personnel on site.
* Evacuate to safe distance in case of fires around any hazardous materials or pressure vessels.

Spills. Process chemical spills will eventually occur in a plant of this scale. Small spills are likely to occur in a laboratory setting. Large spills could be a result of loss of containment in the system. We must ensure that all personnel are aware of proper spill mitigation protocol.

* Small spill: Dilute with water and mop or absorb with inert dry material. Dispose of in proper receptacle.
* Large spill: Keep away from sources of ignition and heat. Prevent rundown to any drains or sewers. Call for assistance on disposal. Absorb material with DRY earth or other non-combustible materials.
* If spill is due to a loss of containment in the system, quickly consult the PLC and shut any valves to prevent further loss.

Exposure. We must ensure that our employees are aware of the possible toxicity levels of each substance and how to handle exposure. The chemicals that are being used in this process are known chemical irritants to the eyes, skin, and throat. Safety measures must be in place to acknowledge this hazard. Due to the possibility of high pressure releases, we will have 2-minute emergency oxygen masks placed strategically throughout the plant to ensure the safety of any operator in the presence of a large release.

If exposed to the process chemicals, find nearest eye wash station or safety shower immediately and flush exposed skin for at least 15 minutes. Remove any contaminated clothing. Seek medical attention immediately.

Storage. Store chemicals in segregated and approved areas. Any closed containers for laboratory purposes should be placed in cool, well-ventilated areas.

==Economics==
===Equipment costing===
The calculated capital costs from Aspen Economic Analyzer are reported in Table 2 for all process equipment. The size of the reactor was calculated from the liquid hourly space velocity given in the 2011 ISP patent8 and a void fraction estimate of 0.4. Storage tanks were sized to contain up to two continuous weeks of material. The number of distillation trays in each tower and the flow rates through pumps, vessels, and the flare were calculated in HYSYS. Heat exchange areas were given in Aspen Energy Analyzer or from HYSYS.

In addition to the above equipment, our plant will require an ion exchanger to produce deionized process water from the municipal water. This is estimated to cost $42,000 in capital cost.

===Cash flow analysis===
Summarizing the important takeaways from the economic analysis (see Appendix G), this process will return a revenue of 144 MM$ annually. Offset by production costs, the yearly cash flow is approximately 2.7 MM$, except for in the years in which the catalyst must be reinstalled (approximately every 5 years). At a cost of 2.5 MM$, the cash flows in those years decrease to approximately 0.2 MM$. This analysis assumes the plant will take 2 years to construct, and will operate at 50% in its first year. Furthermore, an interest rate of 10% was assumed with a tax rate of 38% (the maximum for corporate gains taxes). Using the 7-year MACRS depreciation method, the 20 year NPV for the project is 4.3 MM$. With an IRR of 15.1%, which is greater than the assumed interest rate, this project looks to be profitable. Further optimization techniques should be used in future iterations to further increase profitability. See Tables 3 and 4 for key economic information.

===Sensitivity analysis===
As seen in Figure 3, the economic evaluation of this process is influenced the most by changes in the sales price and feed cost. A 20% increase in sales price will result in an approximate 120 MM$ increase in NPV whereas a decrease of the same percentage will result in over a 120 MM$ decrease in NPV. Inversely, a 20% increase in feed cost will result in a 115 MM$ decrease in NPV and a 20% decrease in feed cost will result in a 60 MM$ increase in NPV.

To alleviate the risk associated with feed price, the team researched the price forecasting of bio-succinic acid. Figure 4 provides the bio-succinic acid price over the six years between 2006 and 2012. The price of bio-succinic, shown by the blue line, has remained relatively stable over this time period. This price history can be compared to adipic acid, the green line, which is a common petrochemical precursor for BDO production. Adipic acid as shown has had large fluctuations in price that result in unstable cash flows and uncertainty from shareholders. Thankfully, the stability of bio-succinic acid is a good sign that this process has a huge potential to be profitable especially if the demand for BDO continues to rise as projected.

==Discussion==
As described previously, the Davy process was selected as the most promising process of BDO production. The modified Davy process involves the hydrogenation of bio-succinicic acid with a Pa,Ag,Re catalyst and hydrogen gas. This process has many advantages, one being that it has mature technology that has been improved over the last 20 years. Additionally, the conversion to of succinic acid is virtually complete. Finally, overall plant yields can reach as high as 94 mol%.
As shown in Appendix B, streams ahead of the pressure valve (PRV-101) are at approximately 1.51e4 kPa, and streams after the pressure valve are between 100 and 450 kPa. Furthermore, operating temperatures do not exceed 200°C, including safety factors. These operating conditions contribute to the feasibility of the process, as all the components can be designed with reasonable dimensions (wall thickness, cap type, etc.).

Of particular interest are the large costs of the reactor and pump P-101. The reactor costs nearly 2 MM$ because it has a moderate size with a liquid volume of 16.7 m3, and it operates at 150 atm, which requires a strong stainless steel shell for safety purposes. Pump P-101 has such a large capital cost because it is a centrifugal multistage pump that also needs to be made of stainless steel to withstand pressuring the succinic acid feed to 150 atm.

Financial indicators for the proposed plant suggest that it will be moderately profitable, and additional optimization should be performed before making the capital investment. There is a fair amount of risk associated with the implementation of this production facility, and the return at this juncture may not justify the risk.

The process design and simulation in HYSYS has relied on several key assumptions, which are cause for certain limitations to the results. First, the conversions and selectivity of the catalyst, while taken from literature sources, are assumed to be true. Furthermore, the assumption of negligible side reactions and products was made. It is possible that small waste products in the form of succinates also form in the reactor. Therefore, the main limitation of this model is generally due to reaction specifications.

There are certain safety concerns that go along with the proposed process. First, there are many pipes and vessels that will be at a pressure of approximately 150 atm. Extra insulation and protection must be applied to the piping that contains highly pressurized fluids, to prevent operator injury. Furthermore, the PFR is at a slight risk for runaway reactions due to the exothermic nature of the reaction. The temperature of the reactor must always be monitored by an operator, and the jacket cooling system requires a backup system as well. A benefit of this process is that there are no toxic or severely hazardous components in the process. Additionally, there are no instances of temperature greater than 200°C.

The process design will be fitted with instrumentation and controls to ensure stable operation. These controls, including sensors and valves, minimize potential damage to components due to variation in plant conditions, as well as optimizing the overall performance. For example, the piping entering the tower will be fitted with a control loop. In the direction of flow, a sensing instrument first detects the pressure of the fluid, and then sends a signal to the controller. If the pressure is not within the operating limits, the actuator is signaled to close or open a control valve which is located farther down the stream.

==Conclusion==
The Evanston Chemical Engineering Division suggests a process that produces 45,000 tonnes/year of 99.5 wt% 1,4-butandeiol to enter the market with an appropriate market share. The feasibility of producing BDO as a significant process was investigated. A wide range of BDO production processes were researched, with a modified Davy process being identified as having the most potential. Using a Pa,Ag,Re catalyst on carbon support, this process converts bio-succinic acid to BDO with approximately 94% conversion. This process was designed in Aspen HYSYS, and economic analysis was conducted in Aspen Economic Analyzer. Total capital costs of the project are 12.2 MM$, with a simple payback period of 5.2 years. Total operational costs annually are 139.7 MM$. The process design was successful, with the capability of producing the desired production of BDO.

==Recommendations==
Given the moderate profitability of this process design, it is recommended that Evanston Chemicals explores further optimization techniques to increase the profitability of this process. This includes investigating sales of the γ-butyrolactone byproduct, recycling process water, and further optimizing utility streams for the distillation tower.
Second, we would like to investigate recycling the 2300 kg/h of water produced in the reaction. Our succinic acid enters the reactor as a 50 wt% solution in water, so we should look into replacing some of this with the product water. Not only will this decrease our water bill, but it will also lower the cost of ion exchange.

==References==
# Nexant.Is Bio-Butanediol Here to Stay? White Plains, NY: ChemSystems Products; 2012.
# De Guzman D. Chemical industry awaits for bio-succinic acid potential. ICIS. Available at: http://www.icis.com/resources/news/2012/01/30/9527521/chemical-industry-awaits-for-bio-succinic-acid-potential/. Accessed January 24, 2014.
# Australian Government: Department of Health. 1,4-butanediol factsheet. National Industrial Chemicals Notification and Assessment Scheme. Available at: http://www.nicnas.gov.au/communications/publications/information-sheets/existing-chemical-info-sheets/other-information-sheets. Accessed January 24, 2014.
# TecnonOrbiChem. Chem-net facts: 1,4-butanediol. TecnonOrbiChem. Available at: http://www.orbichem.com/userfiles/CNF%20Samples/bdo_13_11.pdf. Accessed January 23, 2014.
# Nexant. 1,4-butanediol/tetrahydrofuran (BDO/THF). ChemSystems. Available at: http://www.chemsystems.com/about/cs/news/items/ PERP2012_3_BDO_THF.cfm. Accessed February 6, 2014.
# Burk MJ, Van Dien SJ, Burgard AP, inventors; Genomatica, Inc., assignee. Compositions and methods for the biosynthesis of 1,4-butanediol and its precursors. US patent 8,067,214. Nov. 29, 2011.
# Chung S-H, Kim M-S, Eom H-H, Lee K-Y. Catalytic hydrogenation of bio-based succinic acid for the production of 1,4-butanediol through the indirect pathway. AIChE. Available at: https://aiche.confex.com/aiche/2013/webprogram/Paper327470.html. Accessed January 23, 2014.
# Bhattacharyya A, Manila MD, inventors; ISP Investments Inc., assignee. Catalysts for maleic acid hydrogenation to 1,4-Butanediol. US patent 7,935,834 B2. May 3, 2011.

Design S2

2014-03-15T04:53:28Z

Karetstik: /* Process alternatives */

Title: Production of 1,4-butanediol

Authors: Nick Pinkerton, Karen Schmidt, and James Xamplas

Date Presented: March 14, 2014

==Introduction==
1,4-butanediol (BDO) is traditionally made from petroleum-derived feedstocks in a variety of processes such as the Reppe (acetylene-based), Mitsubishi (butadiene-based), and Davy (maleic acid-based) processes [1]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, BDO [1]. It is this process that Team S2Kool4Skool has chosen to develop for a new bio-butanediol plant, because the Davy method is mature and requires no new innovations, and because an appropriate feedstock of bio-succinic acid is now available. The plant will be located in East Carroll Parish, Louisiana. This county is also home to Myriant; located in Lake Providence, they are the largest domestic provider of bio-succinic acid [2]. Furthermore, Lake Providence is conveniently located on the Mississippi River, which will allow for affordable transportation of our bio-based butanediol product. The intent of this project is to produce 45,000 metric tonnes of 99.5 wt% 1,4-butanediol per year in a new plant in Lake Providence, LA. The plant will run 24 hours per day for 350 days out of the year, allowing approximately two weeks for a maintenance shutdown.

As there are several techniques for producing 1,4 butanediol in industry, the first step was to determine a synthesis path. Based on the chosen path, reaction kinetics, and required production rate of the process, a reactor system was then designed. Next, the process was designed to deliver the reactants to the reactor at the proper operating conditions, and the separations, purification, and waste management steps were designed. Cost estimates were made using costing software and hand calculations. Finally, the process was iterated and optimized to reduce costs.

==Background==
===General information===
BDO is an organic chemical with the molecular formula <math>C_4H_{10}O_2</math>. It is also a diol with its two hydroxyl groups located at the terminal carbons. BDO has a boiling point of 235 degrees C and is therefore a colorless liquid at standard temperatures and pressures [3].

There are many precursors that petrochemical synthesis of BDO uses. The commonality between all of the precursor acids is that they are hydrogenatable. In replacement of one of these petrochemical precursors, our team has been tasked with the challenge of deriving BDO from the bio-based precursor succinic acid. This catalyzed reaction will take place in the presence of hydrogen as the hydrogenating component shown below:

<math>C_4H_6O_4 + 4H_2 = C_4H_{10}O_2 + 2H_2O</math>

As described in the above reaction, there will need to be at least 4:1 stoichiometric ratio of hydrogen gas to succinic acid. Two moles of water will also be produced along with each mole of BDO. This reaction is exothermic, which requires the reactor to be continuously cooled to maintain our reactor temperature. There are also side products that are produced which include tetrahydrofuran (THF) and γ-butyrolactone (GBL); however, thanks to catalyst selectivity these byproducts are produced in small quantities.

===Market analysis===
Butanediol has a quickly expanding market due to new technological evolutions and its growing use as a chemical intermediary in advanced materials. With biological routes being optimized, the potential of biomass-derived chemicals is tremendous. The global demand of BDO was estimated at 1.5 million metric tons in 2011 and is projected to grow at an annual rate of 4.5% for the next several years [1]. Unlike other chemical products, BDO’s profitability and attractiveness to producers lies in its downstream potential. Figure 1 below demonstrates several potential downstream products that can be directly or indirectly synthesized from BDO. The largest of these contributors include THF and GBL.

The current market demand of BDO is being supplemented by several global chemical companies. These companies include BASF, BioAmber, Purac, Myriant, DSM, Mitsubishi Chemical, Roquette, and OPXBIO. The market shares of these companies were not available for this product; however, with the consistent growth of the BDO market our team feels that the market is not saturated or impenetrable. The current market price of BDO fluctuates between $3.06 and $3.31 per kg for US-made products [4]. These prices correlate to a nearly 7 billion dollar industry.

===Process alternatives===
1,4-butanediol is traditionally made from petroleum-derived feedstocks in a variety of processes [5]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Several companies are currently implementing bio-routes of producing butanediol. Genomatica is using a bioengineered microorganism to convert sugar feedstocks directly to BDO via fermentation [6], but most companies are instead using microorganisms to convert sugar to succinic acid. The bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, which is the path that most are choosing, although research is being conducted on alternative pathways [7].

==Process overview==
The newly proposed plant can be divided into four stages: pre-reactor, reactor, post-reactor and distillation. Each section is an integral part to the overall process and demands close attention. The process flow diagram (see Appendix A) and stream table (Appendix B) provide more detailed information.

===Pre-reactor===
This chemical process begins with two feedstocks: hydrogen gas and bio-succinic acid. The hydrogen gas will be obtained from a pipeline at 150 atm and will be used in molar excess inside the reactor. The bio-succinic acid will be purchased by Myriant Corporation which is located near the planned plant site. The pricing for this feedstock is approximately $2.12 per kg. The plant will require 63,000 metric tonnes of bio-succinic acid per year to meet the proposed plant capacity. First the bio-succinic acid feed is pumped up to 150 atm to match the hydrogen gas feed, and then it is mixed with the hydrogen gas prior to being sent into heat exchanger E-101 for heating. The heat exchanger brings the two feeds up to 110oC and sends them to the jacketed packed bed reactor.

===Reactor===
The hydrogenation reaction occurs inside of the reactor thanks to the packed catalyst bed. The catalyst used is 0.4% Fe, 1.9% Na, 2.66% Ag, 2.66% Pd, 10.0% Re on 1.5mm carbon support. With this catalyst, BDO is produced with over 90% selectivity and minimal side reactions of THF and GBL.8 The reaction has an operating pressure of 2000-4000 psi and internal reactor temperature of 165°C. This temperature allows for about 99.7% conversion of succinic acid.8 Due to the exothermic nature of the reaction, a cooling jacket is required which utilizes downstream cold streams to cool the internal bed to maintain the desired reaction temperature.

===Post-reactor===
The effluent of the reactor is sent back to E-101 as the hot stream. After exiting E-101, the reactor product stream is sent to a secondary exchanger, E-102, where utility cooling water is used to reduce the temperature to an acceptable temperature prior to sending it to a pressure let-down valve. At this point the pressure of the stream is taken from 150 atm to 1 atm. This large pressure drop allows for the stream to split into its vapor and liquid portions in a gas-liquid separator. The vapor stream of the gas liquid separator is primarily hydrogen gas and sent to a flare for disposal. The liquid effluent is at approximately 45oC leaving the separator and is therefore pumped to the reactor jacket for the reaction cooling mentioned previously. After running through the reactor jacket, the stream enters the separation processes.

===Distillation===
The first distillation column, T-101, is a 10 stage column whose primary purpose is separating the THF from the product feed. Due to THF’s lower boiling point, the byproduct comes off of the top of the column with mostly water. This distillate is sent to the plant's THF waste storage tank that has the capacity of two weeks. The bottoms of the column is sent to the subsequent distillation column that separates the BDO from the GBL and water. The relatively close boiling points of BDO and GBL, 235oC and 204oC, respectively, create a difficult separation that requires a 15 stage column. The distillate of the column is approximately 23% GBL with balance water. This stream is sent to a storage tank with similar sizing parameters as the THF storage tank. The bottom stream is the final 99.5wt% BDO product. This stream is sent to the final product tank, S-104. Depending on our customer demands and the plant location we have the ability to barge, rail or pipe our product to its final destination. Due to low purity of the byproducts, future iterations are needed to optimize either purifying byproducts or selling impure byproducts. There is definitely an available market for these byproducts that should be researched more extensively to increase profit. A detailed description of the equipment from the PFD can be found in Appendix C, in addition to sizing specifications and purpose of equipment.

===Mass and energy balances===
Using an Aspen HYSYS simulation we were able to record the material and energy streams going in and out of the process system. Mass and energy balances are provided Appendix D where each inlet and outlet stream is described and quantified. As expected, the material and energy totals for the inlet and outlet streams add together to equal 0. This proves that our system is mathematically prudent and thermodynamically feasible. The total mass flow of the system is 15,639 kg/h and the total energy in and out of the system is 1.41e8 kJ/h.

===HYSYS simulation===
The HYSYS simulation was performed using the NRTL ideal fluid package. After using AspenPlus to verify that the HYSYS package had the appropriate vapor-liquid equilibrium information between THF and water, and between GBL and water (see Appendix E), we concluded it was feasible to proceed with that fluid package. The simulation consists of a reactor, a gas-liquid separator, 2 pumps, 3 heaters, a valve, and 2 distillation columns (see Figure 2). The simulation successfully converted the succinic acid feed into the desired products. Also, the combination of the two distillation columns was able to effectively separate the BDO to obtain a 99.5% pure product with 99.5% recovery. In addition, a set was made between the energy required to heat stream 12 and the energy required to cool the reactor so that these values were made equal. Lastly, the condenser and reboiler duties were used in four heat exchangers in order to determine the appropriate size of this equipment as well as the necessary utility flow rates.

==Health and safety==
===Chemical properties===
Inherent to this process are a number of toxic chemicals. Table 1 summarizes the important safety data including hazard type, odor, color, and exposure limits.

As shown in the above table, the chemicals that this facility will be dealing with will be relatively mild and non-life threatening. Regardless of their perceived threat, chemicals should always be handled with care especially when they are at high temperatures and pressures.

===Safety procedures===

Fire. There are many flammable materials that will be included in this process; therefore, fire safety is imperative for all employees. There are countless possible causes of ignition and care should be taken while handling any flammable material whether in the lab or in the field.

In case a fire is present on, the following protocol should be implemented:

* Small fire: Use DRY chemical powder.
* Large fire: Use alcohol foam, water spray, or fog.
* Call for backup if unable to control.
* Immediately contact supervisor and emergency personnel on site.
* Evacuate to safe distance in case of fires around any hazardous materials or pressure vessels.

Spills. Process chemical spills will eventually occur in a plant of this scale. Small spills are likely to occur in a laboratory setting. Large spills could be a result of loss of containment in the system. We must ensure that all personnel are aware of proper spill mitigation protocol.

* Small spill: Dilute with water and mop or absorb with inert dry material. Dispose of in proper receptacle.
* Large spill: Keep away from sources of ignition and heat. Prevent rundown to any drains or sewers. Call for assistance on disposal. Absorb material with DRY earth or other non-combustible materials.
* If spill is due to a loss of containment in the system, quickly consult the PLC and shut any valves to prevent further loss.

Exposure. We must ensure that our employees are aware of the possible toxicity levels of each substance and how to handle exposure. The chemicals that are being used in this process are known chemical irritants to the eyes, skin, and throat. Safety measures must be in place to acknowledge this hazard. Due to the possibility of high pressure releases, we will have 2-minute emergency oxygen masks placed strategically throughout the plant to ensure the safety of any operator in the presence of a large release.

If exposed to the process chemicals, find nearest eye wash station or safety shower immediately and flush exposed skin for at least 15 minutes. Remove any contaminated clothing. Seek medical attention immediately.

Storage. Store chemicals in segregated and approved areas. Any closed containers for laboratory purposes should be placed in cool, well-ventilated areas.

==Economics==
===Equipment costing===
The calculated capital costs from Aspen Economic Analyzer are reported in Table 2 for all process equipment. The size of the reactor was calculated from the liquid hourly space velocity given in the 2011 ISP patent8 and a void fraction estimate of 0.4. Storage tanks were sized to contain up to two continuous weeks of material. The number of distillation trays in each tower and the flow rates through pumps, vessels, and the flare were calculated in HYSYS. Heat exchange areas were given in Aspen Energy Analyzer or from HYSYS.

In addition to the above equipment, our plant will require an ion exchanger to produce deionized process water from the municipal water. This is estimated to cost $42,000 in capital cost.

===Cash flow analysis===
Summarizing the important takeaways from the economic analysis (see Appendix G), this process will return a revenue of 144 MM$ annually. Offset by production costs, the yearly cash flow is approximately 2.7 MM$, except for in the years in which the catalyst must be reinstalled (approximately every 5 years). At a cost of 2.5 MM$, the cash flows in those years decrease to approximately 0.2 MM$. This analysis assumes the plant will take 2 years to construct, and will operate at 50% in its first year. Furthermore, an interest rate of 10% was assumed with a tax rate of 38% (the maximum for corporate gains taxes). Using the 7-year MACRS depreciation method, the 20 year NPV for the project is 4.3 MM$. With an IRR of 15.1%, which is greater than the assumed interest rate, this project looks to be profitable. Further optimization techniques should be used in future iterations to further increase profitability. See Tables 3 and 4 for key economic information.

===Sensitivity analysis===
As seen in Figure 3, the economic evaluation of this process is influenced the most by changes in the sales price and feed cost. A 20% increase in sales price will result in an approximate 120 MM$ increase in NPV whereas a decrease of the same percentage will result in over a 120 MM$ decrease in NPV. Inversely, a 20% increase in feed cost will result in a 115 MM$ decrease in NPV and a 20% decrease in feed cost will result in a 60 MM$ increase in NPV.

To alleviate the risk associated with feed price, the team researched the price forecasting of bio-succinic acid. Figure 4 provides the bio-succinic acid price over the six years between 2006 and 2012. The price of bio-succinic, shown by the blue line, has remained relatively stable over this time period. This price history can be compared to adipic acid, the green line, which is a common petrochemical precursor for BDO production. Adipic acid as shown has had large fluctuations in price that result in unstable cash flows and uncertainty from shareholders. Thankfully, the stability of bio-succinic acid is a good sign that this process has a huge potential to be profitable especially if the demand for BDO continues to rise as projected.

==Discussion==
As described previously, the Davy process was selected as the most promising process of BDO production. The modified Davy process involves the hydrogenation of bio-succinicic acid with a Pa,Ag,Re catalyst and hydrogen gas. This process has many advantages, one being that it has mature technology that has been improved over the last 20 years. Additionally, the conversion to of succinic acid is virtually complete. Finally, overall plant yields can reach as high as 94 mol%.
As shown in Appendix B, streams ahead of the pressure valve (PRV-101) are at approximately 1.51e4 kPa, and streams after the pressure valve are between 100 and 450 kPa. Furthermore, operating temperatures do not exceed 200°C, including safety factors. These operating conditions contribute to the feasibility of the process, as all the components can be designed with reasonable dimensions (wall thickness, cap type, etc.).

Of particular interest are the large costs of the reactor and pump P-101. The reactor costs nearly 2 MM$ because it has a moderate size with a liquid volume of 16.7 m3, and it operates at 150 atm, which requires a strong stainless steel shell for safety purposes. Pump P-101 has such a large capital cost because it is a centrifugal multistage pump that also needs to be made of stainless steel to withstand pressuring the succinic acid feed to 150 atm.

Financial indicators for the proposed plant suggest that it will be moderately profitable, and additional optimization should be performed before making the capital investment. There is a fair amount of risk associated with the implementation of this production facility, and the return at this juncture may not justify the risk.

The process design and simulation in HYSYS has relied on several key assumptions, which are cause for certain limitations to the results. First, the conversions and selectivity of the catalyst, while taken from literature sources, are assumed to be true. Furthermore, the assumption of negligible side reactions and products was made. It is possible that small waste products in the form of succinates also form in the reactor. Therefore, the main limitation of this model is generally due to reaction specifications.

There are certain safety concerns that go along with the proposed process. First, there are many pipes and vessels that will be at a pressure of approximately 150 atm. Extra insulation and protection must be applied to the piping that contains highly pressurized fluids, to prevent operator injury. Furthermore, the PFR is at a slight risk for runaway reactions due to the exothermic nature of the reaction. The temperature of the reactor must always be monitored by an operator, and the jacket cooling system requires a backup system as well. A benefit of this process is that there are no toxic or severely hazardous components in the process. Additionally, there are no instances of temperature greater than 200°C.

The process design will be fitted with instrumentation and controls to ensure stable operation. These controls, including sensors and valves, minimize potential damage to components due to variation in plant conditions, as well as optimizing the overall performance. For example, the piping entering the tower will be fitted with a control loop. In the direction of flow, a sensing instrument first detects the pressure of the fluid, and then sends a signal to the controller. If the pressure is not within the operating limits, the actuator is signaled to close or open a control valve which is located farther down the stream.

==Conclusion==
The Evanston Chemical Engineering Division suggests a process that produces 45,000 tonnes/year of 99.5 wt% 1,4-butandeiol to enter the market with an appropriate market share. The feasibility of producing BDO as a significant process was investigated. A wide range of BDO production processes were researched, with a modified Davy process being identified as having the most potential. Using a Pa,Ag,Re catalyst on carbon support, this process converts bio-succinic acid to BDO with approximately 94% conversion. This process was designed in Aspen HYSYS, and economic analysis was conducted in Aspen Economic Analyzer. Total capital costs of the project are 12.2 MM$, with a simple payback period of 5.2 years. Total operational costs annually are 139.7 MM$. The process design was successful, with the capability of producing the desired production of BDO.

==Recommendations==
Given the moderate profitability of this process design, it is recommended that Evanston Chemicals explores further optimization techniques to increase the profitability of this process. This includes investigating sales of the γ-butyrolactone byproduct, recycling process water, and further optimizing utility streams for the distillation tower.
Second, we would like to investigate recycling the 2300 kg/h of water produced in the reaction. Our succinic acid enters the reactor as a 50 wt% solution in water, so we should look into replacing some of this with the product water. Not only will this decrease our water bill, but it will also lower the cost of ion exchange.

==References==
# Nexant.Is Bio-Butanediol Here to Stay? White Plains, NY: ChemSystems Products; 2012.
# De Guzman D. Chemical industry awaits for bio-succinic acid potential. ICIS. Available at: http://www.icis.com/resources/news/2012/01/30/9527521/chemical-industry-awaits-for-bio-succinic-acid-potential/. Accessed January 24, 2014.
# Australian Government: Department of Health. 1,4-butanediol factsheet. National Industrial Chemicals Notification and Assessment Scheme. Available at: http://www.nicnas.gov.au/communications/publications/information-sheets/existing-chemical-info-sheets/other-information-sheets. Accessed January 24, 2014.
# TecnonOrbiChem. Chem-net facts: 1,4-butanediol. TecnonOrbiChem. Available at: http://www.orbichem.com/userfiles/CNF%20Samples/bdo_13_11.pdf. Accessed January 23, 2014.
# Nexant. 1,4-butanediol/tetrahydrofuran (BDO/THF). ChemSystems. Available at: http://www.chemsystems.com/about/cs/news/items/ PERP2012_3_BDO_THF.cfm. Accessed February 6, 2014.
# Burk MJ, Van Dien SJ, Burgard AP, inventors; Genomatica, Inc., assignee. Compositions and methods for the biosynthesis of 1,4-butanediol and its precursors. US patent 8,067,214. Nov. 29, 2011.
# Chung S-H, Kim M-S, Eom H-H, Lee K-Y. Catalytic hydrogenation of bio-based succinic acid for the production of 1,4-butanediol through the indirect pathway. AIChE. Available at: https://aiche.confex.com/aiche/2013/webprogram/Paper327470.html. Accessed January 23, 2014.
# Bhattacharyya A, Manila MD, inventors; ISP Investments Inc., assignee. Catalysts for maleic acid hydrogenation to 1,4-Butanediol. US patent 7,935,834 B2. May 3, 2011.

Design S2

2014-03-15T04:52:51Z

Karetstik: /* Market analysis */

Title: Production of 1,4-butanediol

Authors: Nick Pinkerton, Karen Schmidt, and James Xamplas

Date Presented: March 14, 2014

==Introduction==
1,4-butanediol (BDO) is traditionally made from petroleum-derived feedstocks in a variety of processes such as the Reppe (acetylene-based), Mitsubishi (butadiene-based), and Davy (maleic acid-based) processes [1]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, BDO [1]. It is this process that Team S2Kool4Skool has chosen to develop for a new bio-butanediol plant, because the Davy method is mature and requires no new innovations, and because an appropriate feedstock of bio-succinic acid is now available. The plant will be located in East Carroll Parish, Louisiana. This county is also home to Myriant; located in Lake Providence, they are the largest domestic provider of bio-succinic acid [2]. Furthermore, Lake Providence is conveniently located on the Mississippi River, which will allow for affordable transportation of our bio-based butanediol product. The intent of this project is to produce 45,000 metric tonnes of 99.5 wt% 1,4-butanediol per year in a new plant in Lake Providence, LA. The plant will run 24 hours per day for 350 days out of the year, allowing approximately two weeks for a maintenance shutdown.

As there are several techniques for producing 1,4 butanediol in industry, the first step was to determine a synthesis path. Based on the chosen path, reaction kinetics, and required production rate of the process, a reactor system was then designed. Next, the process was designed to deliver the reactants to the reactor at the proper operating conditions, and the separations, purification, and waste management steps were designed. Cost estimates were made using costing software and hand calculations. Finally, the process was iterated and optimized to reduce costs.

==Background==
===General information===
BDO is an organic chemical with the molecular formula <math>C_4H_{10}O_2</math>. It is also a diol with its two hydroxyl groups located at the terminal carbons. BDO has a boiling point of 235 degrees C and is therefore a colorless liquid at standard temperatures and pressures [3].

There are many precursors that petrochemical synthesis of BDO uses. The commonality between all of the precursor acids is that they are hydrogenatable. In replacement of one of these petrochemical precursors, our team has been tasked with the challenge of deriving BDO from the bio-based precursor succinic acid. This catalyzed reaction will take place in the presence of hydrogen as the hydrogenating component shown below:

<math>C_4H_6O_4 + 4H_2 = C_4H_{10}O_2 + 2H_2O</math>

As described in the above reaction, there will need to be at least 4:1 stoichiometric ratio of hydrogen gas to succinic acid. Two moles of water will also be produced along with each mole of BDO. This reaction is exothermic, which requires the reactor to be continuously cooled to maintain our reactor temperature. There are also side products that are produced which include tetrahydrofuran (THF) and γ-butyrolactone (GBL); however, thanks to catalyst selectivity these byproducts are produced in small quantities.

===Market analysis===
Butanediol has a quickly expanding market due to new technological evolutions and its growing use as a chemical intermediary in advanced materials. With biological routes being optimized, the potential of biomass-derived chemicals is tremendous. The global demand of BDO was estimated at 1.5 million metric tons in 2011 and is projected to grow at an annual rate of 4.5% for the next several years [1]. Unlike other chemical products, BDO’s profitability and attractiveness to producers lies in its downstream potential. Figure 1 below demonstrates several potential downstream products that can be directly or indirectly synthesized from BDO. The largest of these contributors include THF and GBL.

The current market demand of BDO is being supplemented by several global chemical companies. These companies include BASF, BioAmber, Purac, Myriant, DSM, Mitsubishi Chemical, Roquette, and OPXBIO. The market shares of these companies were not available for this product; however, with the consistent growth of the BDO market our team feels that the market is not saturated or impenetrable. The current market price of BDO fluctuates between $3.06 and $3.31 per kg for US-made products [4]. These prices correlate to a nearly 7 billion dollar industry.

===Process alternatives===
1,4-butanediol is traditionally made from petroleum-derived feedstocks in a variety of processes.5 Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Several companies are currently implementing bio-routes of producing butanediol. Genomatica is using a bioengineered microorganism to convert sugar feedstocks directly to BDO via fermentation,6 but most companies are instead using microorganisms to convert sugar to succinic acid. The bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, which is the path that most are choosing, although research is being conducted on alternative pathways.7

==Process overview==
The newly proposed plant can be divided into four stages: pre-reactor, reactor, post-reactor and distillation. Each section is an integral part to the overall process and demands close attention. The process flow diagram (see Appendix A) and stream table (Appendix B) provide more detailed information.

===Pre-reactor===
This chemical process begins with two feedstocks: hydrogen gas and bio-succinic acid. The hydrogen gas will be obtained from a pipeline at 150 atm and will be used in molar excess inside the reactor. The bio-succinic acid will be purchased by Myriant Corporation which is located near the planned plant site. The pricing for this feedstock is approximately $2.12 per kg. The plant will require 63,000 metric tonnes of bio-succinic acid per year to meet the proposed plant capacity. First the bio-succinic acid feed is pumped up to 150 atm to match the hydrogen gas feed, and then it is mixed with the hydrogen gas prior to being sent into heat exchanger E-101 for heating. The heat exchanger brings the two feeds up to 110oC and sends them to the jacketed packed bed reactor.

===Reactor===
The hydrogenation reaction occurs inside of the reactor thanks to the packed catalyst bed. The catalyst used is 0.4% Fe, 1.9% Na, 2.66% Ag, 2.66% Pd, 10.0% Re on 1.5mm carbon support. With this catalyst, BDO is produced with over 90% selectivity and minimal side reactions of THF and GBL.8 The reaction has an operating pressure of 2000-4000 psi and internal reactor temperature of 165°C. This temperature allows for about 99.7% conversion of succinic acid.8 Due to the exothermic nature of the reaction, a cooling jacket is required which utilizes downstream cold streams to cool the internal bed to maintain the desired reaction temperature.

===Post-reactor===
The effluent of the reactor is sent back to E-101 as the hot stream. After exiting E-101, the reactor product stream is sent to a secondary exchanger, E-102, where utility cooling water is used to reduce the temperature to an acceptable temperature prior to sending it to a pressure let-down valve. At this point the pressure of the stream is taken from 150 atm to 1 atm. This large pressure drop allows for the stream to split into its vapor and liquid portions in a gas-liquid separator. The vapor stream of the gas liquid separator is primarily hydrogen gas and sent to a flare for disposal. The liquid effluent is at approximately 45oC leaving the separator and is therefore pumped to the reactor jacket for the reaction cooling mentioned previously. After running through the reactor jacket, the stream enters the separation processes.

===Distillation===
The first distillation column, T-101, is a 10 stage column whose primary purpose is separating the THF from the product feed. Due to THF’s lower boiling point, the byproduct comes off of the top of the column with mostly water. This distillate is sent to the plant's THF waste storage tank that has the capacity of two weeks. The bottoms of the column is sent to the subsequent distillation column that separates the BDO from the GBL and water. The relatively close boiling points of BDO and GBL, 235oC and 204oC, respectively, create a difficult separation that requires a 15 stage column. The distillate of the column is approximately 23% GBL with balance water. This stream is sent to a storage tank with similar sizing parameters as the THF storage tank. The bottom stream is the final 99.5wt% BDO product. This stream is sent to the final product tank, S-104. Depending on our customer demands and the plant location we have the ability to barge, rail or pipe our product to its final destination. Due to low purity of the byproducts, future iterations are needed to optimize either purifying byproducts or selling impure byproducts. There is definitely an available market for these byproducts that should be researched more extensively to increase profit. A detailed description of the equipment from the PFD can be found in Appendix C, in addition to sizing specifications and purpose of equipment.

===Mass and energy balances===
Using an Aspen HYSYS simulation we were able to record the material and energy streams going in and out of the process system. Mass and energy balances are provided Appendix D where each inlet and outlet stream is described and quantified. As expected, the material and energy totals for the inlet and outlet streams add together to equal 0. This proves that our system is mathematically prudent and thermodynamically feasible. The total mass flow of the system is 15,639 kg/h and the total energy in and out of the system is 1.41e8 kJ/h.

===HYSYS simulation===
The HYSYS simulation was performed using the NRTL ideal fluid package. After using AspenPlus to verify that the HYSYS package had the appropriate vapor-liquid equilibrium information between THF and water, and between GBL and water (see Appendix E), we concluded it was feasible to proceed with that fluid package. The simulation consists of a reactor, a gas-liquid separator, 2 pumps, 3 heaters, a valve, and 2 distillation columns (see Figure 2). The simulation successfully converted the succinic acid feed into the desired products. Also, the combination of the two distillation columns was able to effectively separate the BDO to obtain a 99.5% pure product with 99.5% recovery. In addition, a set was made between the energy required to heat stream 12 and the energy required to cool the reactor so that these values were made equal. Lastly, the condenser and reboiler duties were used in four heat exchangers in order to determine the appropriate size of this equipment as well as the necessary utility flow rates.

==Health and safety==
===Chemical properties===
Inherent to this process are a number of toxic chemicals. Table 1 summarizes the important safety data including hazard type, odor, color, and exposure limits.

As shown in the above table, the chemicals that this facility will be dealing with will be relatively mild and non-life threatening. Regardless of their perceived threat, chemicals should always be handled with care especially when they are at high temperatures and pressures.

===Safety procedures===

Fire. There are many flammable materials that will be included in this process; therefore, fire safety is imperative for all employees. There are countless possible causes of ignition and care should be taken while handling any flammable material whether in the lab or in the field.

In case a fire is present on, the following protocol should be implemented:

* Small fire: Use DRY chemical powder.
* Large fire: Use alcohol foam, water spray, or fog.
* Call for backup if unable to control.
* Immediately contact supervisor and emergency personnel on site.
* Evacuate to safe distance in case of fires around any hazardous materials or pressure vessels.

Spills. Process chemical spills will eventually occur in a plant of this scale. Small spills are likely to occur in a laboratory setting. Large spills could be a result of loss of containment in the system. We must ensure that all personnel are aware of proper spill mitigation protocol.

* Small spill: Dilute with water and mop or absorb with inert dry material. Dispose of in proper receptacle.
* Large spill: Keep away from sources of ignition and heat. Prevent rundown to any drains or sewers. Call for assistance on disposal. Absorb material with DRY earth or other non-combustible materials.
* If spill is due to a loss of containment in the system, quickly consult the PLC and shut any valves to prevent further loss.

Exposure. We must ensure that our employees are aware of the possible toxicity levels of each substance and how to handle exposure. The chemicals that are being used in this process are known chemical irritants to the eyes, skin, and throat. Safety measures must be in place to acknowledge this hazard. Due to the possibility of high pressure releases, we will have 2-minute emergency oxygen masks placed strategically throughout the plant to ensure the safety of any operator in the presence of a large release.

If exposed to the process chemicals, find nearest eye wash station or safety shower immediately and flush exposed skin for at least 15 minutes. Remove any contaminated clothing. Seek medical attention immediately.

Storage. Store chemicals in segregated and approved areas. Any closed containers for laboratory purposes should be placed in cool, well-ventilated areas.

==Economics==
===Equipment costing===
The calculated capital costs from Aspen Economic Analyzer are reported in Table 2 for all process equipment. The size of the reactor was calculated from the liquid hourly space velocity given in the 2011 ISP patent8 and a void fraction estimate of 0.4. Storage tanks were sized to contain up to two continuous weeks of material. The number of distillation trays in each tower and the flow rates through pumps, vessels, and the flare were calculated in HYSYS. Heat exchange areas were given in Aspen Energy Analyzer or from HYSYS.

In addition to the above equipment, our plant will require an ion exchanger to produce deionized process water from the municipal water. This is estimated to cost $42,000 in capital cost.

===Cash flow analysis===
Summarizing the important takeaways from the economic analysis (see Appendix G), this process will return a revenue of 144 MM$ annually. Offset by production costs, the yearly cash flow is approximately 2.7 MM$, except for in the years in which the catalyst must be reinstalled (approximately every 5 years). At a cost of 2.5 MM$, the cash flows in those years decrease to approximately 0.2 MM$. This analysis assumes the plant will take 2 years to construct, and will operate at 50% in its first year. Furthermore, an interest rate of 10% was assumed with a tax rate of 38% (the maximum for corporate gains taxes). Using the 7-year MACRS depreciation method, the 20 year NPV for the project is 4.3 MM$. With an IRR of 15.1%, which is greater than the assumed interest rate, this project looks to be profitable. Further optimization techniques should be used in future iterations to further increase profitability. See Tables 3 and 4 for key economic information.

===Sensitivity analysis===
As seen in Figure 3, the economic evaluation of this process is influenced the most by changes in the sales price and feed cost. A 20% increase in sales price will result in an approximate 120 MM$ increase in NPV whereas a decrease of the same percentage will result in over a 120 MM$ decrease in NPV. Inversely, a 20% increase in feed cost will result in a 115 MM$ decrease in NPV and a 20% decrease in feed cost will result in a 60 MM$ increase in NPV.

To alleviate the risk associated with feed price, the team researched the price forecasting of bio-succinic acid. Figure 4 provides the bio-succinic acid price over the six years between 2006 and 2012. The price of bio-succinic, shown by the blue line, has remained relatively stable over this time period. This price history can be compared to adipic acid, the green line, which is a common petrochemical precursor for BDO production. Adipic acid as shown has had large fluctuations in price that result in unstable cash flows and uncertainty from shareholders. Thankfully, the stability of bio-succinic acid is a good sign that this process has a huge potential to be profitable especially if the demand for BDO continues to rise as projected.

==Discussion==
As described previously, the Davy process was selected as the most promising process of BDO production. The modified Davy process involves the hydrogenation of bio-succinicic acid with a Pa,Ag,Re catalyst and hydrogen gas. This process has many advantages, one being that it has mature technology that has been improved over the last 20 years. Additionally, the conversion to of succinic acid is virtually complete. Finally, overall plant yields can reach as high as 94 mol%.
As shown in Appendix B, streams ahead of the pressure valve (PRV-101) are at approximately 1.51e4 kPa, and streams after the pressure valve are between 100 and 450 kPa. Furthermore, operating temperatures do not exceed 200°C, including safety factors. These operating conditions contribute to the feasibility of the process, as all the components can be designed with reasonable dimensions (wall thickness, cap type, etc.).

Of particular interest are the large costs of the reactor and pump P-101. The reactor costs nearly 2 MM$ because it has a moderate size with a liquid volume of 16.7 m3, and it operates at 150 atm, which requires a strong stainless steel shell for safety purposes. Pump P-101 has such a large capital cost because it is a centrifugal multistage pump that also needs to be made of stainless steel to withstand pressuring the succinic acid feed to 150 atm.

Financial indicators for the proposed plant suggest that it will be moderately profitable, and additional optimization should be performed before making the capital investment. There is a fair amount of risk associated with the implementation of this production facility, and the return at this juncture may not justify the risk.

The process design and simulation in HYSYS has relied on several key assumptions, which are cause for certain limitations to the results. First, the conversions and selectivity of the catalyst, while taken from literature sources, are assumed to be true. Furthermore, the assumption of negligible side reactions and products was made. It is possible that small waste products in the form of succinates also form in the reactor. Therefore, the main limitation of this model is generally due to reaction specifications.

There are certain safety concerns that go along with the proposed process. First, there are many pipes and vessels that will be at a pressure of approximately 150 atm. Extra insulation and protection must be applied to the piping that contains highly pressurized fluids, to prevent operator injury. Furthermore, the PFR is at a slight risk for runaway reactions due to the exothermic nature of the reaction. The temperature of the reactor must always be monitored by an operator, and the jacket cooling system requires a backup system as well. A benefit of this process is that there are no toxic or severely hazardous components in the process. Additionally, there are no instances of temperature greater than 200°C.

The process design will be fitted with instrumentation and controls to ensure stable operation. These controls, including sensors and valves, minimize potential damage to components due to variation in plant conditions, as well as optimizing the overall performance. For example, the piping entering the tower will be fitted with a control loop. In the direction of flow, a sensing instrument first detects the pressure of the fluid, and then sends a signal to the controller. If the pressure is not within the operating limits, the actuator is signaled to close or open a control valve which is located farther down the stream.

==Conclusion==
The Evanston Chemical Engineering Division suggests a process that produces 45,000 tonnes/year of 99.5 wt% 1,4-butandeiol to enter the market with an appropriate market share. The feasibility of producing BDO as a significant process was investigated. A wide range of BDO production processes were researched, with a modified Davy process being identified as having the most potential. Using a Pa,Ag,Re catalyst on carbon support, this process converts bio-succinic acid to BDO with approximately 94% conversion. This process was designed in Aspen HYSYS, and economic analysis was conducted in Aspen Economic Analyzer. Total capital costs of the project are 12.2 MM$, with a simple payback period of 5.2 years. Total operational costs annually are 139.7 MM$. The process design was successful, with the capability of producing the desired production of BDO.

==Recommendations==
Given the moderate profitability of this process design, it is recommended that Evanston Chemicals explores further optimization techniques to increase the profitability of this process. This includes investigating sales of the γ-butyrolactone byproduct, recycling process water, and further optimizing utility streams for the distillation tower.
Second, we would like to investigate recycling the 2300 kg/h of water produced in the reaction. Our succinic acid enters the reactor as a 50 wt% solution in water, so we should look into replacing some of this with the product water. Not only will this decrease our water bill, but it will also lower the cost of ion exchange.

==References==
# Nexant.Is Bio-Butanediol Here to Stay? White Plains, NY: ChemSystems Products; 2012.
# De Guzman D. Chemical industry awaits for bio-succinic acid potential. ICIS. Available at: http://www.icis.com/resources/news/2012/01/30/9527521/chemical-industry-awaits-for-bio-succinic-acid-potential/. Accessed January 24, 2014.
# Australian Government: Department of Health. 1,4-butanediol factsheet. National Industrial Chemicals Notification and Assessment Scheme. Available at: http://www.nicnas.gov.au/communications/publications/information-sheets/existing-chemical-info-sheets/other-information-sheets. Accessed January 24, 2014.
# TecnonOrbiChem. Chem-net facts: 1,4-butanediol. TecnonOrbiChem. Available at: http://www.orbichem.com/userfiles/CNF%20Samples/bdo_13_11.pdf. Accessed January 23, 2014.
# Nexant. 1,4-butanediol/tetrahydrofuran (BDO/THF). ChemSystems. Available at: http://www.chemsystems.com/about/cs/news/items/ PERP2012_3_BDO_THF.cfm. Accessed February 6, 2014.
# Burk MJ, Van Dien SJ, Burgard AP, inventors; Genomatica, Inc., assignee. Compositions and methods for the biosynthesis of 1,4-butanediol and its precursors. US patent 8,067,214. Nov. 29, 2011.
# Chung S-H, Kim M-S, Eom H-H, Lee K-Y. Catalytic hydrogenation of bio-based succinic acid for the production of 1,4-butanediol through the indirect pathway. AIChE. Available at: https://aiche.confex.com/aiche/2013/webprogram/Paper327470.html. Accessed January 23, 2014.
# Bhattacharyya A, Manila MD, inventors; ISP Investments Inc., assignee. Catalysts for maleic acid hydrogenation to 1,4-Butanediol. US patent 7,935,834 B2. May 3, 2011.

Design S2

2014-03-15T04:52:22Z

Karetstik: /* General information */

Title: Production of 1,4-butanediol

Authors: Nick Pinkerton, Karen Schmidt, and James Xamplas

Date Presented: March 14, 2014

==Introduction==
1,4-butanediol (BDO) is traditionally made from petroleum-derived feedstocks in a variety of processes such as the Reppe (acetylene-based), Mitsubishi (butadiene-based), and Davy (maleic acid-based) processes [1]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, BDO [1]. It is this process that Team S2Kool4Skool has chosen to develop for a new bio-butanediol plant, because the Davy method is mature and requires no new innovations, and because an appropriate feedstock of bio-succinic acid is now available. The plant will be located in East Carroll Parish, Louisiana. This county is also home to Myriant; located in Lake Providence, they are the largest domestic provider of bio-succinic acid [2]. Furthermore, Lake Providence is conveniently located on the Mississippi River, which will allow for affordable transportation of our bio-based butanediol product. The intent of this project is to produce 45,000 metric tonnes of 99.5 wt% 1,4-butanediol per year in a new plant in Lake Providence, LA. The plant will run 24 hours per day for 350 days out of the year, allowing approximately two weeks for a maintenance shutdown.

As there are several techniques for producing 1,4 butanediol in industry, the first step was to determine a synthesis path. Based on the chosen path, reaction kinetics, and required production rate of the process, a reactor system was then designed. Next, the process was designed to deliver the reactants to the reactor at the proper operating conditions, and the separations, purification, and waste management steps were designed. Cost estimates were made using costing software and hand calculations. Finally, the process was iterated and optimized to reduce costs.

==Background==
===General information===
BDO is an organic chemical with the molecular formula <math>C_4H_{10}O_2</math>. It is also a diol with its two hydroxyl groups located at the terminal carbons. BDO has a boiling point of 235 degrees C and is therefore a colorless liquid at standard temperatures and pressures [3].

There are many precursors that petrochemical synthesis of BDO uses. The commonality between all of the precursor acids is that they are hydrogenatable. In replacement of one of these petrochemical precursors, our team has been tasked with the challenge of deriving BDO from the bio-based precursor succinic acid. This catalyzed reaction will take place in the presence of hydrogen as the hydrogenating component shown below:

<math>C_4H_6O_4 + 4H_2 = C_4H_{10}O_2 + 2H_2O</math>

As described in the above reaction, there will need to be at least 4:1 stoichiometric ratio of hydrogen gas to succinic acid. Two moles of water will also be produced along with each mole of BDO. This reaction is exothermic, which requires the reactor to be continuously cooled to maintain our reactor temperature. There are also side products that are produced which include tetrahydrofuran (THF) and γ-butyrolactone (GBL); however, thanks to catalyst selectivity these byproducts are produced in small quantities.

===Market analysis===
Butanediol has a quickly expanding market due to new technological evolutions and its growing use as a chemical intermediary in advanced materials. With biological routes being optimized, the potential of biomass-derived chemicals is tremendous. The global demand of BDO was estimated at 1.5 million metric tons in 2011 and is projected to grow at an annual rate of 4.5% for the next several years.1 Unlike other chemical products, BDO’s profitability and attractiveness to producers lies in its downstream potential. Figure 1 below demonstrates several potential downstream products that can be directly or indirectly synthesized from BDO. The largest of these contributors include THF and GBL.

The current market demand of BDO is being supplemented by several global chemical companies. These companies include BASF, BioAmber, Purac, Myriant, DSM, Mitsubishi Chemical, Roquette, and OPXBIO. The market shares of these companies were not available for this product; however, with the consistent growth of the BDO market our team feels that the market is not saturated or impenetrable. The current market price of BDO fluctuates between $3.06 and $3.31 per kg for US-made products.4 These prices correlate to a nearly 7 billion dollar industry.

===Process alternatives===
1,4-butanediol is traditionally made from petroleum-derived feedstocks in a variety of processes.5 Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Several companies are currently implementing bio-routes of producing butanediol. Genomatica is using a bioengineered microorganism to convert sugar feedstocks directly to BDO via fermentation,6 but most companies are instead using microorganisms to convert sugar to succinic acid. The bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, which is the path that most are choosing, although research is being conducted on alternative pathways.7

==Process overview==
The newly proposed plant can be divided into four stages: pre-reactor, reactor, post-reactor and distillation. Each section is an integral part to the overall process and demands close attention. The process flow diagram (see Appendix A) and stream table (Appendix B) provide more detailed information.

===Pre-reactor===
This chemical process begins with two feedstocks: hydrogen gas and bio-succinic acid. The hydrogen gas will be obtained from a pipeline at 150 atm and will be used in molar excess inside the reactor. The bio-succinic acid will be purchased by Myriant Corporation which is located near the planned plant site. The pricing for this feedstock is approximately $2.12 per kg. The plant will require 63,000 metric tonnes of bio-succinic acid per year to meet the proposed plant capacity. First the bio-succinic acid feed is pumped up to 150 atm to match the hydrogen gas feed, and then it is mixed with the hydrogen gas prior to being sent into heat exchanger E-101 for heating. The heat exchanger brings the two feeds up to 110oC and sends them to the jacketed packed bed reactor.

===Reactor===
The hydrogenation reaction occurs inside of the reactor thanks to the packed catalyst bed. The catalyst used is 0.4% Fe, 1.9% Na, 2.66% Ag, 2.66% Pd, 10.0% Re on 1.5mm carbon support. With this catalyst, BDO is produced with over 90% selectivity and minimal side reactions of THF and GBL.8 The reaction has an operating pressure of 2000-4000 psi and internal reactor temperature of 165°C. This temperature allows for about 99.7% conversion of succinic acid.8 Due to the exothermic nature of the reaction, a cooling jacket is required which utilizes downstream cold streams to cool the internal bed to maintain the desired reaction temperature.

===Post-reactor===
The effluent of the reactor is sent back to E-101 as the hot stream. After exiting E-101, the reactor product stream is sent to a secondary exchanger, E-102, where utility cooling water is used to reduce the temperature to an acceptable temperature prior to sending it to a pressure let-down valve. At this point the pressure of the stream is taken from 150 atm to 1 atm. This large pressure drop allows for the stream to split into its vapor and liquid portions in a gas-liquid separator. The vapor stream of the gas liquid separator is primarily hydrogen gas and sent to a flare for disposal. The liquid effluent is at approximately 45oC leaving the separator and is therefore pumped to the reactor jacket for the reaction cooling mentioned previously. After running through the reactor jacket, the stream enters the separation processes.

===Distillation===
The first distillation column, T-101, is a 10 stage column whose primary purpose is separating the THF from the product feed. Due to THF’s lower boiling point, the byproduct comes off of the top of the column with mostly water. This distillate is sent to the plant's THF waste storage tank that has the capacity of two weeks. The bottoms of the column is sent to the subsequent distillation column that separates the BDO from the GBL and water. The relatively close boiling points of BDO and GBL, 235oC and 204oC, respectively, create a difficult separation that requires a 15 stage column. The distillate of the column is approximately 23% GBL with balance water. This stream is sent to a storage tank with similar sizing parameters as the THF storage tank. The bottom stream is the final 99.5wt% BDO product. This stream is sent to the final product tank, S-104. Depending on our customer demands and the plant location we have the ability to barge, rail or pipe our product to its final destination. Due to low purity of the byproducts, future iterations are needed to optimize either purifying byproducts or selling impure byproducts. There is definitely an available market for these byproducts that should be researched more extensively to increase profit. A detailed description of the equipment from the PFD can be found in Appendix C, in addition to sizing specifications and purpose of equipment.

===Mass and energy balances===
Using an Aspen HYSYS simulation we were able to record the material and energy streams going in and out of the process system. Mass and energy balances are provided Appendix D where each inlet and outlet stream is described and quantified. As expected, the material and energy totals for the inlet and outlet streams add together to equal 0. This proves that our system is mathematically prudent and thermodynamically feasible. The total mass flow of the system is 15,639 kg/h and the total energy in and out of the system is 1.41e8 kJ/h.

===HYSYS simulation===
The HYSYS simulation was performed using the NRTL ideal fluid package. After using AspenPlus to verify that the HYSYS package had the appropriate vapor-liquid equilibrium information between THF and water, and between GBL and water (see Appendix E), we concluded it was feasible to proceed with that fluid package. The simulation consists of a reactor, a gas-liquid separator, 2 pumps, 3 heaters, a valve, and 2 distillation columns (see Figure 2). The simulation successfully converted the succinic acid feed into the desired products. Also, the combination of the two distillation columns was able to effectively separate the BDO to obtain a 99.5% pure product with 99.5% recovery. In addition, a set was made between the energy required to heat stream 12 and the energy required to cool the reactor so that these values were made equal. Lastly, the condenser and reboiler duties were used in four heat exchangers in order to determine the appropriate size of this equipment as well as the necessary utility flow rates.

==Health and safety==
===Chemical properties===
Inherent to this process are a number of toxic chemicals. Table 1 summarizes the important safety data including hazard type, odor, color, and exposure limits.

As shown in the above table, the chemicals that this facility will be dealing with will be relatively mild and non-life threatening. Regardless of their perceived threat, chemicals should always be handled with care especially when they are at high temperatures and pressures.

===Safety procedures===

Fire. There are many flammable materials that will be included in this process; therefore, fire safety is imperative for all employees. There are countless possible causes of ignition and care should be taken while handling any flammable material whether in the lab or in the field.

In case a fire is present on, the following protocol should be implemented:

* Small fire: Use DRY chemical powder.
* Large fire: Use alcohol foam, water spray, or fog.
* Call for backup if unable to control.
* Immediately contact supervisor and emergency personnel on site.
* Evacuate to safe distance in case of fires around any hazardous materials or pressure vessels.

Spills. Process chemical spills will eventually occur in a plant of this scale. Small spills are likely to occur in a laboratory setting. Large spills could be a result of loss of containment in the system. We must ensure that all personnel are aware of proper spill mitigation protocol.

* Small spill: Dilute with water and mop or absorb with inert dry material. Dispose of in proper receptacle.
* Large spill: Keep away from sources of ignition and heat. Prevent rundown to any drains or sewers. Call for assistance on disposal. Absorb material with DRY earth or other non-combustible materials.
* If spill is due to a loss of containment in the system, quickly consult the PLC and shut any valves to prevent further loss.

Exposure. We must ensure that our employees are aware of the possible toxicity levels of each substance and how to handle exposure. The chemicals that are being used in this process are known chemical irritants to the eyes, skin, and throat. Safety measures must be in place to acknowledge this hazard. Due to the possibility of high pressure releases, we will have 2-minute emergency oxygen masks placed strategically throughout the plant to ensure the safety of any operator in the presence of a large release.

If exposed to the process chemicals, find nearest eye wash station or safety shower immediately and flush exposed skin for at least 15 minutes. Remove any contaminated clothing. Seek medical attention immediately.

Storage. Store chemicals in segregated and approved areas. Any closed containers for laboratory purposes should be placed in cool, well-ventilated areas.

==Economics==
===Equipment costing===
The calculated capital costs from Aspen Economic Analyzer are reported in Table 2 for all process equipment. The size of the reactor was calculated from the liquid hourly space velocity given in the 2011 ISP patent8 and a void fraction estimate of 0.4. Storage tanks were sized to contain up to two continuous weeks of material. The number of distillation trays in each tower and the flow rates through pumps, vessels, and the flare were calculated in HYSYS. Heat exchange areas were given in Aspen Energy Analyzer or from HYSYS.

In addition to the above equipment, our plant will require an ion exchanger to produce deionized process water from the municipal water. This is estimated to cost $42,000 in capital cost.

===Cash flow analysis===
Summarizing the important takeaways from the economic analysis (see Appendix G), this process will return a revenue of 144 MM$ annually. Offset by production costs, the yearly cash flow is approximately 2.7 MM$, except for in the years in which the catalyst must be reinstalled (approximately every 5 years). At a cost of 2.5 MM$, the cash flows in those years decrease to approximately 0.2 MM$. This analysis assumes the plant will take 2 years to construct, and will operate at 50% in its first year. Furthermore, an interest rate of 10% was assumed with a tax rate of 38% (the maximum for corporate gains taxes). Using the 7-year MACRS depreciation method, the 20 year NPV for the project is 4.3 MM$. With an IRR of 15.1%, which is greater than the assumed interest rate, this project looks to be profitable. Further optimization techniques should be used in future iterations to further increase profitability. See Tables 3 and 4 for key economic information.

===Sensitivity analysis===
As seen in Figure 3, the economic evaluation of this process is influenced the most by changes in the sales price and feed cost. A 20% increase in sales price will result in an approximate 120 MM$ increase in NPV whereas a decrease of the same percentage will result in over a 120 MM$ decrease in NPV. Inversely, a 20% increase in feed cost will result in a 115 MM$ decrease in NPV and a 20% decrease in feed cost will result in a 60 MM$ increase in NPV.

To alleviate the risk associated with feed price, the team researched the price forecasting of bio-succinic acid. Figure 4 provides the bio-succinic acid price over the six years between 2006 and 2012. The price of bio-succinic, shown by the blue line, has remained relatively stable over this time period. This price history can be compared to adipic acid, the green line, which is a common petrochemical precursor for BDO production. Adipic acid as shown has had large fluctuations in price that result in unstable cash flows and uncertainty from shareholders. Thankfully, the stability of bio-succinic acid is a good sign that this process has a huge potential to be profitable especially if the demand for BDO continues to rise as projected.

==Discussion==
As described previously, the Davy process was selected as the most promising process of BDO production. The modified Davy process involves the hydrogenation of bio-succinicic acid with a Pa,Ag,Re catalyst and hydrogen gas. This process has many advantages, one being that it has mature technology that has been improved over the last 20 years. Additionally, the conversion to of succinic acid is virtually complete. Finally, overall plant yields can reach as high as 94 mol%.
As shown in Appendix B, streams ahead of the pressure valve (PRV-101) are at approximately 1.51e4 kPa, and streams after the pressure valve are between 100 and 450 kPa. Furthermore, operating temperatures do not exceed 200°C, including safety factors. These operating conditions contribute to the feasibility of the process, as all the components can be designed with reasonable dimensions (wall thickness, cap type, etc.).

Of particular interest are the large costs of the reactor and pump P-101. The reactor costs nearly 2 MM$ because it has a moderate size with a liquid volume of 16.7 m3, and it operates at 150 atm, which requires a strong stainless steel shell for safety purposes. Pump P-101 has such a large capital cost because it is a centrifugal multistage pump that also needs to be made of stainless steel to withstand pressuring the succinic acid feed to 150 atm.

Financial indicators for the proposed plant suggest that it will be moderately profitable, and additional optimization should be performed before making the capital investment. There is a fair amount of risk associated with the implementation of this production facility, and the return at this juncture may not justify the risk.

The process design and simulation in HYSYS has relied on several key assumptions, which are cause for certain limitations to the results. First, the conversions and selectivity of the catalyst, while taken from literature sources, are assumed to be true. Furthermore, the assumption of negligible side reactions and products was made. It is possible that small waste products in the form of succinates also form in the reactor. Therefore, the main limitation of this model is generally due to reaction specifications.

There are certain safety concerns that go along with the proposed process. First, there are many pipes and vessels that will be at a pressure of approximately 150 atm. Extra insulation and protection must be applied to the piping that contains highly pressurized fluids, to prevent operator injury. Furthermore, the PFR is at a slight risk for runaway reactions due to the exothermic nature of the reaction. The temperature of the reactor must always be monitored by an operator, and the jacket cooling system requires a backup system as well. A benefit of this process is that there are no toxic or severely hazardous components in the process. Additionally, there are no instances of temperature greater than 200°C.

The process design will be fitted with instrumentation and controls to ensure stable operation. These controls, including sensors and valves, minimize potential damage to components due to variation in plant conditions, as well as optimizing the overall performance. For example, the piping entering the tower will be fitted with a control loop. In the direction of flow, a sensing instrument first detects the pressure of the fluid, and then sends a signal to the controller. If the pressure is not within the operating limits, the actuator is signaled to close or open a control valve which is located farther down the stream.

==Conclusion==
The Evanston Chemical Engineering Division suggests a process that produces 45,000 tonnes/year of 99.5 wt% 1,4-butandeiol to enter the market with an appropriate market share. The feasibility of producing BDO as a significant process was investigated. A wide range of BDO production processes were researched, with a modified Davy process being identified as having the most potential. Using a Pa,Ag,Re catalyst on carbon support, this process converts bio-succinic acid to BDO with approximately 94% conversion. This process was designed in Aspen HYSYS, and economic analysis was conducted in Aspen Economic Analyzer. Total capital costs of the project are 12.2 MM$, with a simple payback period of 5.2 years. Total operational costs annually are 139.7 MM$. The process design was successful, with the capability of producing the desired production of BDO.

==Recommendations==
Given the moderate profitability of this process design, it is recommended that Evanston Chemicals explores further optimization techniques to increase the profitability of this process. This includes investigating sales of the γ-butyrolactone byproduct, recycling process water, and further optimizing utility streams for the distillation tower.
Second, we would like to investigate recycling the 2300 kg/h of water produced in the reaction. Our succinic acid enters the reactor as a 50 wt% solution in water, so we should look into replacing some of this with the product water. Not only will this decrease our water bill, but it will also lower the cost of ion exchange.

==References==
# Nexant.Is Bio-Butanediol Here to Stay? White Plains, NY: ChemSystems Products; 2012.
# De Guzman D. Chemical industry awaits for bio-succinic acid potential. ICIS. Available at: http://www.icis.com/resources/news/2012/01/30/9527521/chemical-industry-awaits-for-bio-succinic-acid-potential/. Accessed January 24, 2014.
# Australian Government: Department of Health. 1,4-butanediol factsheet. National Industrial Chemicals Notification and Assessment Scheme. Available at: http://www.nicnas.gov.au/communications/publications/information-sheets/existing-chemical-info-sheets/other-information-sheets. Accessed January 24, 2014.
# TecnonOrbiChem. Chem-net facts: 1,4-butanediol. TecnonOrbiChem. Available at: http://www.orbichem.com/userfiles/CNF%20Samples/bdo_13_11.pdf. Accessed January 23, 2014.
# Nexant. 1,4-butanediol/tetrahydrofuran (BDO/THF). ChemSystems. Available at: http://www.chemsystems.com/about/cs/news/items/ PERP2012_3_BDO_THF.cfm. Accessed February 6, 2014.
# Burk MJ, Van Dien SJ, Burgard AP, inventors; Genomatica, Inc., assignee. Compositions and methods for the biosynthesis of 1,4-butanediol and its precursors. US patent 8,067,214. Nov. 29, 2011.
# Chung S-H, Kim M-S, Eom H-H, Lee K-Y. Catalytic hydrogenation of bio-based succinic acid for the production of 1,4-butanediol through the indirect pathway. AIChE. Available at: https://aiche.confex.com/aiche/2013/webprogram/Paper327470.html. Accessed January 23, 2014.
# Bhattacharyya A, Manila MD, inventors; ISP Investments Inc., assignee. Catalysts for maleic acid hydrogenation to 1,4-Butanediol. US patent 7,935,834 B2. May 3, 2011.

Design S2

2014-03-15T04:49:32Z

Karetstik: /* Introduction */

Title: Production of 1,4-butanediol

Authors: Nick Pinkerton, Karen Schmidt, and James Xamplas

Date Presented: March 14, 2014

==Introduction==
1,4-butanediol (BDO) is traditionally made from petroleum-derived feedstocks in a variety of processes such as the Reppe (acetylene-based), Mitsubishi (butadiene-based), and Davy (maleic acid-based) processes [1]. Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, BDO [1]. It is this process that Team S2Kool4Skool has chosen to develop for a new bio-butanediol plant, because the Davy method is mature and requires no new innovations, and because an appropriate feedstock of bio-succinic acid is now available. The plant will be located in East Carroll Parish, Louisiana. This county is also home to Myriant; located in Lake Providence, they are the largest domestic provider of bio-succinic acid [2]. Furthermore, Lake Providence is conveniently located on the Mississippi River, which will allow for affordable transportation of our bio-based butanediol product. The intent of this project is to produce 45,000 metric tonnes of 99.5 wt% 1,4-butanediol per year in a new plant in Lake Providence, LA. The plant will run 24 hours per day for 350 days out of the year, allowing approximately two weeks for a maintenance shutdown.

As there are several techniques for producing 1,4 butanediol in industry, the first step was to determine a synthesis path. Based on the chosen path, reaction kinetics, and required production rate of the process, a reactor system was then designed. Next, the process was designed to deliver the reactants to the reactor at the proper operating conditions, and the separations, purification, and waste management steps were designed. Cost estimates were made using costing software and hand calculations. Finally, the process was iterated and optimized to reduce costs.

==Background==
===General information===
BDO is an organic chemical with the molecular formula C4H10O2. It is also a diol with its two hydroxyl groups located at the terminal carbons. BDO has a boiling point of 235oC and is therefore a colorless liquid at standard temperatures and pressures.3
There are many precursors that petrochemical synthesis of BDO uses. The commonality between all of the precursor acids is that they are hydrogenatable. In replacement of one of these petrochemical precursors, our team has been tasked with the challenge of deriving BDO from the bio-based precursor succinic acid. This catalyzed reaction will take place in the presence of hydrogen as the hydrogenating component shown below:

C4H6O4 + 4H2 --> C4H10O2 +2H2O

As described in the above reaction, there will need to be at least 4:1 stoichiometric ratio of hydrogen gas to succinic acid. Two moles of water will also be produced along with each mole of BDO. This reaction is exothermic, which requires the reactor to be continuously cooled to maintain our reactor temperature. There are also side products that are produced which include tetrahydrofuran (THF) and γ-butyrolactone (GBL); however, thanks to catalyst selectivity these byproducts are produced in small quantities.

===Market analysis===
Butanediol has a quickly expanding market due to new technological evolutions and its growing use as a chemical intermediary in advanced materials. With biological routes being optimized, the potential of biomass-derived chemicals is tremendous. The global demand of BDO was estimated at 1.5 million metric tons in 2011 and is projected to grow at an annual rate of 4.5% for the next several years.1 Unlike other chemical products, BDO’s profitability and attractiveness to producers lies in its downstream potential. Figure 1 below demonstrates several potential downstream products that can be directly or indirectly synthesized from BDO. The largest of these contributors include THF and GBL.

The current market demand of BDO is being supplemented by several global chemical companies. These companies include BASF, BioAmber, Purac, Myriant, DSM, Mitsubishi Chemical, Roquette, and OPXBIO. The market shares of these companies were not available for this product; however, with the consistent growth of the BDO market our team feels that the market is not saturated or impenetrable. The current market price of BDO fluctuates between $3.06 and $3.31 per kg for US-made products.4 These prices correlate to a nearly 7 billion dollar industry.

===Process alternatives===
1,4-butanediol is traditionally made from petroleum-derived feedstocks in a variety of processes.5 Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Several companies are currently implementing bio-routes of producing butanediol. Genomatica is using a bioengineered microorganism to convert sugar feedstocks directly to BDO via fermentation,6 but most companies are instead using microorganisms to convert sugar to succinic acid. The bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, which is the path that most are choosing, although research is being conducted on alternative pathways.7

==Process overview==
The newly proposed plant can be divided into four stages: pre-reactor, reactor, post-reactor and distillation. Each section is an integral part to the overall process and demands close attention. The process flow diagram (see Appendix A) and stream table (Appendix B) provide more detailed information.

===Pre-reactor===
This chemical process begins with two feedstocks: hydrogen gas and bio-succinic acid. The hydrogen gas will be obtained from a pipeline at 150 atm and will be used in molar excess inside the reactor. The bio-succinic acid will be purchased by Myriant Corporation which is located near the planned plant site. The pricing for this feedstock is approximately $2.12 per kg. The plant will require 63,000 metric tonnes of bio-succinic acid per year to meet the proposed plant capacity. First the bio-succinic acid feed is pumped up to 150 atm to match the hydrogen gas feed, and then it is mixed with the hydrogen gas prior to being sent into heat exchanger E-101 for heating. The heat exchanger brings the two feeds up to 110oC and sends them to the jacketed packed bed reactor.

===Reactor===
The hydrogenation reaction occurs inside of the reactor thanks to the packed catalyst bed. The catalyst used is 0.4% Fe, 1.9% Na, 2.66% Ag, 2.66% Pd, 10.0% Re on 1.5mm carbon support. With this catalyst, BDO is produced with over 90% selectivity and minimal side reactions of THF and GBL.8 The reaction has an operating pressure of 2000-4000 psi and internal reactor temperature of 165°C. This temperature allows for about 99.7% conversion of succinic acid.8 Due to the exothermic nature of the reaction, a cooling jacket is required which utilizes downstream cold streams to cool the internal bed to maintain the desired reaction temperature.

===Post-reactor===
The effluent of the reactor is sent back to E-101 as the hot stream. After exiting E-101, the reactor product stream is sent to a secondary exchanger, E-102, where utility cooling water is used to reduce the temperature to an acceptable temperature prior to sending it to a pressure let-down valve. At this point the pressure of the stream is taken from 150 atm to 1 atm. This large pressure drop allows for the stream to split into its vapor and liquid portions in a gas-liquid separator. The vapor stream of the gas liquid separator is primarily hydrogen gas and sent to a flare for disposal. The liquid effluent is at approximately 45oC leaving the separator and is therefore pumped to the reactor jacket for the reaction cooling mentioned previously. After running through the reactor jacket, the stream enters the separation processes.

===Distillation===
The first distillation column, T-101, is a 10 stage column whose primary purpose is separating the THF from the product feed. Due to THF’s lower boiling point, the byproduct comes off of the top of the column with mostly water. This distillate is sent to the plant's THF waste storage tank that has the capacity of two weeks. The bottoms of the column is sent to the subsequent distillation column that separates the BDO from the GBL and water. The relatively close boiling points of BDO and GBL, 235oC and 204oC, respectively, create a difficult separation that requires a 15 stage column. The distillate of the column is approximately 23% GBL with balance water. This stream is sent to a storage tank with similar sizing parameters as the THF storage tank. The bottom stream is the final 99.5wt% BDO product. This stream is sent to the final product tank, S-104. Depending on our customer demands and the plant location we have the ability to barge, rail or pipe our product to its final destination. Due to low purity of the byproducts, future iterations are needed to optimize either purifying byproducts or selling impure byproducts. There is definitely an available market for these byproducts that should be researched more extensively to increase profit. A detailed description of the equipment from the PFD can be found in Appendix C, in addition to sizing specifications and purpose of equipment.

===Mass and energy balances===
Using an Aspen HYSYS simulation we were able to record the material and energy streams going in and out of the process system. Mass and energy balances are provided Appendix D where each inlet and outlet stream is described and quantified. As expected, the material and energy totals for the inlet and outlet streams add together to equal 0. This proves that our system is mathematically prudent and thermodynamically feasible. The total mass flow of the system is 15,639 kg/h and the total energy in and out of the system is 1.41e8 kJ/h.

===HYSYS simulation===
The HYSYS simulation was performed using the NRTL ideal fluid package. After using AspenPlus to verify that the HYSYS package had the appropriate vapor-liquid equilibrium information between THF and water, and between GBL and water (see Appendix E), we concluded it was feasible to proceed with that fluid package. The simulation consists of a reactor, a gas-liquid separator, 2 pumps, 3 heaters, a valve, and 2 distillation columns (see Figure 2). The simulation successfully converted the succinic acid feed into the desired products. Also, the combination of the two distillation columns was able to effectively separate the BDO to obtain a 99.5% pure product with 99.5% recovery. In addition, a set was made between the energy required to heat stream 12 and the energy required to cool the reactor so that these values were made equal. Lastly, the condenser and reboiler duties were used in four heat exchangers in order to determine the appropriate size of this equipment as well as the necessary utility flow rates.

==Health and safety==
===Chemical properties===
Inherent to this process are a number of toxic chemicals. Table 1 summarizes the important safety data including hazard type, odor, color, and exposure limits.

As shown in the above table, the chemicals that this facility will be dealing with will be relatively mild and non-life threatening. Regardless of their perceived threat, chemicals should always be handled with care especially when they are at high temperatures and pressures.

===Safety procedures===

Fire. There are many flammable materials that will be included in this process; therefore, fire safety is imperative for all employees. There are countless possible causes of ignition and care should be taken while handling any flammable material whether in the lab or in the field.

In case a fire is present on, the following protocol should be implemented:

* Small fire: Use DRY chemical powder.
* Large fire: Use alcohol foam, water spray, or fog.
* Call for backup if unable to control.
* Immediately contact supervisor and emergency personnel on site.
* Evacuate to safe distance in case of fires around any hazardous materials or pressure vessels.

Spills. Process chemical spills will eventually occur in a plant of this scale. Small spills are likely to occur in a laboratory setting. Large spills could be a result of loss of containment in the system. We must ensure that all personnel are aware of proper spill mitigation protocol.

* Small spill: Dilute with water and mop or absorb with inert dry material. Dispose of in proper receptacle.
* Large spill: Keep away from sources of ignition and heat. Prevent rundown to any drains or sewers. Call for assistance on disposal. Absorb material with DRY earth or other non-combustible materials.
* If spill is due to a loss of containment in the system, quickly consult the PLC and shut any valves to prevent further loss.

Exposure. We must ensure that our employees are aware of the possible toxicity levels of each substance and how to handle exposure. The chemicals that are being used in this process are known chemical irritants to the eyes, skin, and throat. Safety measures must be in place to acknowledge this hazard. Due to the possibility of high pressure releases, we will have 2-minute emergency oxygen masks placed strategically throughout the plant to ensure the safety of any operator in the presence of a large release.

If exposed to the process chemicals, find nearest eye wash station or safety shower immediately and flush exposed skin for at least 15 minutes. Remove any contaminated clothing. Seek medical attention immediately.

Storage. Store chemicals in segregated and approved areas. Any closed containers for laboratory purposes should be placed in cool, well-ventilated areas.

==Economics==
===Equipment costing===
The calculated capital costs from Aspen Economic Analyzer are reported in Table 2 for all process equipment. The size of the reactor was calculated from the liquid hourly space velocity given in the 2011 ISP patent8 and a void fraction estimate of 0.4. Storage tanks were sized to contain up to two continuous weeks of material. The number of distillation trays in each tower and the flow rates through pumps, vessels, and the flare were calculated in HYSYS. Heat exchange areas were given in Aspen Energy Analyzer or from HYSYS.

In addition to the above equipment, our plant will require an ion exchanger to produce deionized process water from the municipal water. This is estimated to cost $42,000 in capital cost.

===Cash flow analysis===
Summarizing the important takeaways from the economic analysis (see Appendix G), this process will return a revenue of 144 MM$ annually. Offset by production costs, the yearly cash flow is approximately 2.7 MM$, except for in the years in which the catalyst must be reinstalled (approximately every 5 years). At a cost of 2.5 MM$, the cash flows in those years decrease to approximately 0.2 MM$. This analysis assumes the plant will take 2 years to construct, and will operate at 50% in its first year. Furthermore, an interest rate of 10% was assumed with a tax rate of 38% (the maximum for corporate gains taxes). Using the 7-year MACRS depreciation method, the 20 year NPV for the project is 4.3 MM$. With an IRR of 15.1%, which is greater than the assumed interest rate, this project looks to be profitable. Further optimization techniques should be used in future iterations to further increase profitability. See Tables 3 and 4 for key economic information.

===Sensitivity analysis===
As seen in Figure 3, the economic evaluation of this process is influenced the most by changes in the sales price and feed cost. A 20% increase in sales price will result in an approximate 120 MM$ increase in NPV whereas a decrease of the same percentage will result in over a 120 MM$ decrease in NPV. Inversely, a 20% increase in feed cost will result in a 115 MM$ decrease in NPV and a 20% decrease in feed cost will result in a 60 MM$ increase in NPV.

To alleviate the risk associated with feed price, the team researched the price forecasting of bio-succinic acid. Figure 4 provides the bio-succinic acid price over the six years between 2006 and 2012. The price of bio-succinic, shown by the blue line, has remained relatively stable over this time period. This price history can be compared to adipic acid, the green line, which is a common petrochemical precursor for BDO production. Adipic acid as shown has had large fluctuations in price that result in unstable cash flows and uncertainty from shareholders. Thankfully, the stability of bio-succinic acid is a good sign that this process has a huge potential to be profitable especially if the demand for BDO continues to rise as projected.

==Discussion==
As described previously, the Davy process was selected as the most promising process of BDO production. The modified Davy process involves the hydrogenation of bio-succinicic acid with a Pa,Ag,Re catalyst and hydrogen gas. This process has many advantages, one being that it has mature technology that has been improved over the last 20 years. Additionally, the conversion to of succinic acid is virtually complete. Finally, overall plant yields can reach as high as 94 mol%.
As shown in Appendix B, streams ahead of the pressure valve (PRV-101) are at approximately 1.51e4 kPa, and streams after the pressure valve are between 100 and 450 kPa. Furthermore, operating temperatures do not exceed 200°C, including safety factors. These operating conditions contribute to the feasibility of the process, as all the components can be designed with reasonable dimensions (wall thickness, cap type, etc.).

Of particular interest are the large costs of the reactor and pump P-101. The reactor costs nearly 2 MM$ because it has a moderate size with a liquid volume of 16.7 m3, and it operates at 150 atm, which requires a strong stainless steel shell for safety purposes. Pump P-101 has such a large capital cost because it is a centrifugal multistage pump that also needs to be made of stainless steel to withstand pressuring the succinic acid feed to 150 atm.

Financial indicators for the proposed plant suggest that it will be moderately profitable, and additional optimization should be performed before making the capital investment. There is a fair amount of risk associated with the implementation of this production facility, and the return at this juncture may not justify the risk.

The process design and simulation in HYSYS has relied on several key assumptions, which are cause for certain limitations to the results. First, the conversions and selectivity of the catalyst, while taken from literature sources, are assumed to be true. Furthermore, the assumption of negligible side reactions and products was made. It is possible that small waste products in the form of succinates also form in the reactor. Therefore, the main limitation of this model is generally due to reaction specifications.

There are certain safety concerns that go along with the proposed process. First, there are many pipes and vessels that will be at a pressure of approximately 150 atm. Extra insulation and protection must be applied to the piping that contains highly pressurized fluids, to prevent operator injury. Furthermore, the PFR is at a slight risk for runaway reactions due to the exothermic nature of the reaction. The temperature of the reactor must always be monitored by an operator, and the jacket cooling system requires a backup system as well. A benefit of this process is that there are no toxic or severely hazardous components in the process. Additionally, there are no instances of temperature greater than 200°C.

The process design will be fitted with instrumentation and controls to ensure stable operation. These controls, including sensors and valves, minimize potential damage to components due to variation in plant conditions, as well as optimizing the overall performance. For example, the piping entering the tower will be fitted with a control loop. In the direction of flow, a sensing instrument first detects the pressure of the fluid, and then sends a signal to the controller. If the pressure is not within the operating limits, the actuator is signaled to close or open a control valve which is located farther down the stream.

==Conclusion==
The Evanston Chemical Engineering Division suggests a process that produces 45,000 tonnes/year of 99.5 wt% 1,4-butandeiol to enter the market with an appropriate market share. The feasibility of producing BDO as a significant process was investigated. A wide range of BDO production processes were researched, with a modified Davy process being identified as having the most potential. Using a Pa,Ag,Re catalyst on carbon support, this process converts bio-succinic acid to BDO with approximately 94% conversion. This process was designed in Aspen HYSYS, and economic analysis was conducted in Aspen Economic Analyzer. Total capital costs of the project are 12.2 MM$, with a simple payback period of 5.2 years. Total operational costs annually are 139.7 MM$. The process design was successful, with the capability of producing the desired production of BDO.

==Recommendations==
Given the moderate profitability of this process design, it is recommended that Evanston Chemicals explores further optimization techniques to increase the profitability of this process. This includes investigating sales of the γ-butyrolactone byproduct, recycling process water, and further optimizing utility streams for the distillation tower.
Second, we would like to investigate recycling the 2300 kg/h of water produced in the reaction. Our succinic acid enters the reactor as a 50 wt% solution in water, so we should look into replacing some of this with the product water. Not only will this decrease our water bill, but it will also lower the cost of ion exchange.

==References==
# Nexant.Is Bio-Butanediol Here to Stay? White Plains, NY: ChemSystems Products; 2012.
# De Guzman D. Chemical industry awaits for bio-succinic acid potential. ICIS. Available at: http://www.icis.com/resources/news/2012/01/30/9527521/chemical-industry-awaits-for-bio-succinic-acid-potential/. Accessed January 24, 2014.
# Australian Government: Department of Health. 1,4-butanediol factsheet. National Industrial Chemicals Notification and Assessment Scheme. Available at: http://www.nicnas.gov.au/communications/publications/information-sheets/existing-chemical-info-sheets/other-information-sheets. Accessed January 24, 2014.
# TecnonOrbiChem. Chem-net facts: 1,4-butanediol. TecnonOrbiChem. Available at: http://www.orbichem.com/userfiles/CNF%20Samples/bdo_13_11.pdf. Accessed January 23, 2014.
# Nexant. 1,4-butanediol/tetrahydrofuran (BDO/THF). ChemSystems. Available at: http://www.chemsystems.com/about/cs/news/items/ PERP2012_3_BDO_THF.cfm. Accessed February 6, 2014.
# Burk MJ, Van Dien SJ, Burgard AP, inventors; Genomatica, Inc., assignee. Compositions and methods for the biosynthesis of 1,4-butanediol and its precursors. US patent 8,067,214. Nov. 29, 2011.
# Chung S-H, Kim M-S, Eom H-H, Lee K-Y. Catalytic hydrogenation of bio-based succinic acid for the production of 1,4-butanediol through the indirect pathway. AIChE. Available at: https://aiche.confex.com/aiche/2013/webprogram/Paper327470.html. Accessed January 23, 2014.
# Bhattacharyya A, Manila MD, inventors; ISP Investments Inc., assignee. Catalysts for maleic acid hydrogenation to 1,4-Butanediol. US patent 7,935,834 B2. May 3, 2011.

Design S2

2014-03-15T04:48:26Z

Karetstik: /* Safety procedures */

Title: Production of 1,4-butanediol

Authors: Nick Pinkerton, Karen Schmidt, and James Xamplas

Date Presented: March 14, 2014

==Introduction==
1,4-butanediol (BDO) is traditionally made from petroleum-derived feedstocks in a variety of processes such as the Reppe (acetylene-based), Mitsubishi (butadiene-based), and Davy (maleic acid-based) processes.1 Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, BDO.1 It is this process that Team S2Kool4Skool has chosen to develop for a new bio-butanediol plant, because the Davy method is mature and requires no new innovations, and because an appropriate feedstock of bio-succinic acid is now available. The plant will be located in East Carroll Parish, Louisiana. This county is also home to Myriant; located in Lake Providence, they are the largest domestic provider of bio-succinic acid.2 Furthermore, Lake Providence is conveniently located on the Mississippi River, which will allow for affordable transportation of our bio-based butanediol product. The intent of this project is to produce 45,000 metric tonnes of 99.5 wt% 1,4-butanediol per year in a new plant in Lake Providence, LA. The plant will run 24 hours per day for 350 days out of the year, allowing approximately two weeks for a maintenance shutdown.

As there are several techniques for producing 1,4 butanediol in industry, the first step was to determine a synthesis path. Based on the chosen path, reaction kinetics, and required production rate of the process, a reactor system was then designed. Next, the process was designed to deliver the reactants to the reactor at the proper operating conditions, and the separations, purification, and waste management steps were designed. Cost estimates were made using costing software and hand calculations. Finally, the process was iterated and optimized to reduce costs.

==Background==
===General information===
BDO is an organic chemical with the molecular formula C4H10O2. It is also a diol with its two hydroxyl groups located at the terminal carbons. BDO has a boiling point of 235oC and is therefore a colorless liquid at standard temperatures and pressures.3
There are many precursors that petrochemical synthesis of BDO uses. The commonality between all of the precursor acids is that they are hydrogenatable. In replacement of one of these petrochemical precursors, our team has been tasked with the challenge of deriving BDO from the bio-based precursor succinic acid. This catalyzed reaction will take place in the presence of hydrogen as the hydrogenating component shown below:

C4H6O4 + 4H2 --> C4H10O2 +2H2O

As described in the above reaction, there will need to be at least 4:1 stoichiometric ratio of hydrogen gas to succinic acid. Two moles of water will also be produced along with each mole of BDO. This reaction is exothermic, which requires the reactor to be continuously cooled to maintain our reactor temperature. There are also side products that are produced which include tetrahydrofuran (THF) and γ-butyrolactone (GBL); however, thanks to catalyst selectivity these byproducts are produced in small quantities.

===Market analysis===
Butanediol has a quickly expanding market due to new technological evolutions and its growing use as a chemical intermediary in advanced materials. With biological routes being optimized, the potential of biomass-derived chemicals is tremendous. The global demand of BDO was estimated at 1.5 million metric tons in 2011 and is projected to grow at an annual rate of 4.5% for the next several years.1 Unlike other chemical products, BDO’s profitability and attractiveness to producers lies in its downstream potential. Figure 1 below demonstrates several potential downstream products that can be directly or indirectly synthesized from BDO. The largest of these contributors include THF and GBL.

The current market demand of BDO is being supplemented by several global chemical companies. These companies include BASF, BioAmber, Purac, Myriant, DSM, Mitsubishi Chemical, Roquette, and OPXBIO. The market shares of these companies were not available for this product; however, with the consistent growth of the BDO market our team feels that the market is not saturated or impenetrable. The current market price of BDO fluctuates between $3.06 and $3.31 per kg for US-made products.4 These prices correlate to a nearly 7 billion dollar industry.

===Process alternatives===
1,4-butanediol is traditionally made from petroleum-derived feedstocks in a variety of processes.5 Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Several companies are currently implementing bio-routes of producing butanediol. Genomatica is using a bioengineered microorganism to convert sugar feedstocks directly to BDO via fermentation,6 but most companies are instead using microorganisms to convert sugar to succinic acid. The bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, which is the path that most are choosing, although research is being conducted on alternative pathways.7

==Process overview==
The newly proposed plant can be divided into four stages: pre-reactor, reactor, post-reactor and distillation. Each section is an integral part to the overall process and demands close attention. The process flow diagram (see Appendix A) and stream table (Appendix B) provide more detailed information.

===Pre-reactor===
This chemical process begins with two feedstocks: hydrogen gas and bio-succinic acid. The hydrogen gas will be obtained from a pipeline at 150 atm and will be used in molar excess inside the reactor. The bio-succinic acid will be purchased by Myriant Corporation which is located near the planned plant site. The pricing for this feedstock is approximately $2.12 per kg. The plant will require 63,000 metric tonnes of bio-succinic acid per year to meet the proposed plant capacity. First the bio-succinic acid feed is pumped up to 150 atm to match the hydrogen gas feed, and then it is mixed with the hydrogen gas prior to being sent into heat exchanger E-101 for heating. The heat exchanger brings the two feeds up to 110oC and sends them to the jacketed packed bed reactor.

===Reactor===
The hydrogenation reaction occurs inside of the reactor thanks to the packed catalyst bed. The catalyst used is 0.4% Fe, 1.9% Na, 2.66% Ag, 2.66% Pd, 10.0% Re on 1.5mm carbon support. With this catalyst, BDO is produced with over 90% selectivity and minimal side reactions of THF and GBL.8 The reaction has an operating pressure of 2000-4000 psi and internal reactor temperature of 165°C. This temperature allows for about 99.7% conversion of succinic acid.8 Due to the exothermic nature of the reaction, a cooling jacket is required which utilizes downstream cold streams to cool the internal bed to maintain the desired reaction temperature.

===Post-reactor===
The effluent of the reactor is sent back to E-101 as the hot stream. After exiting E-101, the reactor product stream is sent to a secondary exchanger, E-102, where utility cooling water is used to reduce the temperature to an acceptable temperature prior to sending it to a pressure let-down valve. At this point the pressure of the stream is taken from 150 atm to 1 atm. This large pressure drop allows for the stream to split into its vapor and liquid portions in a gas-liquid separator. The vapor stream of the gas liquid separator is primarily hydrogen gas and sent to a flare for disposal. The liquid effluent is at approximately 45oC leaving the separator and is therefore pumped to the reactor jacket for the reaction cooling mentioned previously. After running through the reactor jacket, the stream enters the separation processes.

===Distillation===
The first distillation column, T-101, is a 10 stage column whose primary purpose is separating the THF from the product feed. Due to THF’s lower boiling point, the byproduct comes off of the top of the column with mostly water. This distillate is sent to the plant's THF waste storage tank that has the capacity of two weeks. The bottoms of the column is sent to the subsequent distillation column that separates the BDO from the GBL and water. The relatively close boiling points of BDO and GBL, 235oC and 204oC, respectively, create a difficult separation that requires a 15 stage column. The distillate of the column is approximately 23% GBL with balance water. This stream is sent to a storage tank with similar sizing parameters as the THF storage tank. The bottom stream is the final 99.5wt% BDO product. This stream is sent to the final product tank, S-104. Depending on our customer demands and the plant location we have the ability to barge, rail or pipe our product to its final destination. Due to low purity of the byproducts, future iterations are needed to optimize either purifying byproducts or selling impure byproducts. There is definitely an available market for these byproducts that should be researched more extensively to increase profit. A detailed description of the equipment from the PFD can be found in Appendix C, in addition to sizing specifications and purpose of equipment.

===Mass and energy balances===
Using an Aspen HYSYS simulation we were able to record the material and energy streams going in and out of the process system. Mass and energy balances are provided Appendix D where each inlet and outlet stream is described and quantified. As expected, the material and energy totals for the inlet and outlet streams add together to equal 0. This proves that our system is mathematically prudent and thermodynamically feasible. The total mass flow of the system is 15,639 kg/h and the total energy in and out of the system is 1.41e8 kJ/h.

===HYSYS simulation===
The HYSYS simulation was performed using the NRTL ideal fluid package. After using AspenPlus to verify that the HYSYS package had the appropriate vapor-liquid equilibrium information between THF and water, and between GBL and water (see Appendix E), we concluded it was feasible to proceed with that fluid package. The simulation consists of a reactor, a gas-liquid separator, 2 pumps, 3 heaters, a valve, and 2 distillation columns (see Figure 2). The simulation successfully converted the succinic acid feed into the desired products. Also, the combination of the two distillation columns was able to effectively separate the BDO to obtain a 99.5% pure product with 99.5% recovery. In addition, a set was made between the energy required to heat stream 12 and the energy required to cool the reactor so that these values were made equal. Lastly, the condenser and reboiler duties were used in four heat exchangers in order to determine the appropriate size of this equipment as well as the necessary utility flow rates.

==Health and safety==
===Chemical properties===
Inherent to this process are a number of toxic chemicals. Table 1 summarizes the important safety data including hazard type, odor, color, and exposure limits.

As shown in the above table, the chemicals that this facility will be dealing with will be relatively mild and non-life threatening. Regardless of their perceived threat, chemicals should always be handled with care especially when they are at high temperatures and pressures.

===Safety procedures===

Fire. There are many flammable materials that will be included in this process; therefore, fire safety is imperative for all employees. There are countless possible causes of ignition and care should be taken while handling any flammable material whether in the lab or in the field.

In case a fire is present on, the following protocol should be implemented:

* Small fire: Use DRY chemical powder.
* Large fire: Use alcohol foam, water spray, or fog.
* Call for backup if unable to control.
* Immediately contact supervisor and emergency personnel on site.
* Evacuate to safe distance in case of fires around any hazardous materials or pressure vessels.

Spills. Process chemical spills will eventually occur in a plant of this scale. Small spills are likely to occur in a laboratory setting. Large spills could be a result of loss of containment in the system. We must ensure that all personnel are aware of proper spill mitigation protocol.

* Small spill: Dilute with water and mop or absorb with inert dry material. Dispose of in proper receptacle.
* Large spill: Keep away from sources of ignition and heat. Prevent rundown to any drains or sewers. Call for assistance on disposal. Absorb material with DRY earth or other non-combustible materials.
* If spill is due to a loss of containment in the system, quickly consult the PLC and shut any valves to prevent further loss.

Exposure. We must ensure that our employees are aware of the possible toxicity levels of each substance and how to handle exposure. The chemicals that are being used in this process are known chemical irritants to the eyes, skin, and throat. Safety measures must be in place to acknowledge this hazard. Due to the possibility of high pressure releases, we will have 2-minute emergency oxygen masks placed strategically throughout the plant to ensure the safety of any operator in the presence of a large release.

If exposed to the process chemicals, find nearest eye wash station or safety shower immediately and flush exposed skin for at least 15 minutes. Remove any contaminated clothing. Seek medical attention immediately.

Storage. Store chemicals in segregated and approved areas. Any closed containers for laboratory purposes should be placed in cool, well-ventilated areas.

==Economics==
===Equipment costing===
The calculated capital costs from Aspen Economic Analyzer are reported in Table 2 for all process equipment. The size of the reactor was calculated from the liquid hourly space velocity given in the 2011 ISP patent8 and a void fraction estimate of 0.4. Storage tanks were sized to contain up to two continuous weeks of material. The number of distillation trays in each tower and the flow rates through pumps, vessels, and the flare were calculated in HYSYS. Heat exchange areas were given in Aspen Energy Analyzer or from HYSYS.

In addition to the above equipment, our plant will require an ion exchanger to produce deionized process water from the municipal water. This is estimated to cost $42,000 in capital cost.

===Cash flow analysis===
Summarizing the important takeaways from the economic analysis (see Appendix G), this process will return a revenue of 144 MM$ annually. Offset by production costs, the yearly cash flow is approximately 2.7 MM$, except for in the years in which the catalyst must be reinstalled (approximately every 5 years). At a cost of 2.5 MM$, the cash flows in those years decrease to approximately 0.2 MM$. This analysis assumes the plant will take 2 years to construct, and will operate at 50% in its first year. Furthermore, an interest rate of 10% was assumed with a tax rate of 38% (the maximum for corporate gains taxes). Using the 7-year MACRS depreciation method, the 20 year NPV for the project is 4.3 MM$. With an IRR of 15.1%, which is greater than the assumed interest rate, this project looks to be profitable. Further optimization techniques should be used in future iterations to further increase profitability. See Tables 3 and 4 for key economic information.

===Sensitivity analysis===
As seen in Figure 3, the economic evaluation of this process is influenced the most by changes in the sales price and feed cost. A 20% increase in sales price will result in an approximate 120 MM$ increase in NPV whereas a decrease of the same percentage will result in over a 120 MM$ decrease in NPV. Inversely, a 20% increase in feed cost will result in a 115 MM$ decrease in NPV and a 20% decrease in feed cost will result in a 60 MM$ increase in NPV.

To alleviate the risk associated with feed price, the team researched the price forecasting of bio-succinic acid. Figure 4 provides the bio-succinic acid price over the six years between 2006 and 2012. The price of bio-succinic, shown by the blue line, has remained relatively stable over this time period. This price history can be compared to adipic acid, the green line, which is a common petrochemical precursor for BDO production. Adipic acid as shown has had large fluctuations in price that result in unstable cash flows and uncertainty from shareholders. Thankfully, the stability of bio-succinic acid is a good sign that this process has a huge potential to be profitable especially if the demand for BDO continues to rise as projected.

==Discussion==
As described previously, the Davy process was selected as the most promising process of BDO production. The modified Davy process involves the hydrogenation of bio-succinicic acid with a Pa,Ag,Re catalyst and hydrogen gas. This process has many advantages, one being that it has mature technology that has been improved over the last 20 years. Additionally, the conversion to of succinic acid is virtually complete. Finally, overall plant yields can reach as high as 94 mol%.
As shown in Appendix B, streams ahead of the pressure valve (PRV-101) are at approximately 1.51e4 kPa, and streams after the pressure valve are between 100 and 450 kPa. Furthermore, operating temperatures do not exceed 200°C, including safety factors. These operating conditions contribute to the feasibility of the process, as all the components can be designed with reasonable dimensions (wall thickness, cap type, etc.).

Of particular interest are the large costs of the reactor and pump P-101. The reactor costs nearly 2 MM$ because it has a moderate size with a liquid volume of 16.7 m3, and it operates at 150 atm, which requires a strong stainless steel shell for safety purposes. Pump P-101 has such a large capital cost because it is a centrifugal multistage pump that also needs to be made of stainless steel to withstand pressuring the succinic acid feed to 150 atm.

Financial indicators for the proposed plant suggest that it will be moderately profitable, and additional optimization should be performed before making the capital investment. There is a fair amount of risk associated with the implementation of this production facility, and the return at this juncture may not justify the risk.

The process design and simulation in HYSYS has relied on several key assumptions, which are cause for certain limitations to the results. First, the conversions and selectivity of the catalyst, while taken from literature sources, are assumed to be true. Furthermore, the assumption of negligible side reactions and products was made. It is possible that small waste products in the form of succinates also form in the reactor. Therefore, the main limitation of this model is generally due to reaction specifications.

There are certain safety concerns that go along with the proposed process. First, there are many pipes and vessels that will be at a pressure of approximately 150 atm. Extra insulation and protection must be applied to the piping that contains highly pressurized fluids, to prevent operator injury. Furthermore, the PFR is at a slight risk for runaway reactions due to the exothermic nature of the reaction. The temperature of the reactor must always be monitored by an operator, and the jacket cooling system requires a backup system as well. A benefit of this process is that there are no toxic or severely hazardous components in the process. Additionally, there are no instances of temperature greater than 200°C.

The process design will be fitted with instrumentation and controls to ensure stable operation. These controls, including sensors and valves, minimize potential damage to components due to variation in plant conditions, as well as optimizing the overall performance. For example, the piping entering the tower will be fitted with a control loop. In the direction of flow, a sensing instrument first detects the pressure of the fluid, and then sends a signal to the controller. If the pressure is not within the operating limits, the actuator is signaled to close or open a control valve which is located farther down the stream.

==Conclusion==
The Evanston Chemical Engineering Division suggests a process that produces 45,000 tonnes/year of 99.5 wt% 1,4-butandeiol to enter the market with an appropriate market share. The feasibility of producing BDO as a significant process was investigated. A wide range of BDO production processes were researched, with a modified Davy process being identified as having the most potential. Using a Pa,Ag,Re catalyst on carbon support, this process converts bio-succinic acid to BDO with approximately 94% conversion. This process was designed in Aspen HYSYS, and economic analysis was conducted in Aspen Economic Analyzer. Total capital costs of the project are 12.2 MM$, with a simple payback period of 5.2 years. Total operational costs annually are 139.7 MM$. The process design was successful, with the capability of producing the desired production of BDO.

==Recommendations==
Given the moderate profitability of this process design, it is recommended that Evanston Chemicals explores further optimization techniques to increase the profitability of this process. This includes investigating sales of the γ-butyrolactone byproduct, recycling process water, and further optimizing utility streams for the distillation tower.
Second, we would like to investigate recycling the 2300 kg/h of water produced in the reaction. Our succinic acid enters the reactor as a 50 wt% solution in water, so we should look into replacing some of this with the product water. Not only will this decrease our water bill, but it will also lower the cost of ion exchange.

==References==
# Nexant.Is Bio-Butanediol Here to Stay? White Plains, NY: ChemSystems Products; 2012.
# De Guzman D. Chemical industry awaits for bio-succinic acid potential. ICIS. Available at: http://www.icis.com/resources/news/2012/01/30/9527521/chemical-industry-awaits-for-bio-succinic-acid-potential/. Accessed January 24, 2014.
# Australian Government: Department of Health. 1,4-butanediol factsheet. National Industrial Chemicals Notification and Assessment Scheme. Available at: http://www.nicnas.gov.au/communications/publications/information-sheets/existing-chemical-info-sheets/other-information-sheets. Accessed January 24, 2014.
# TecnonOrbiChem. Chem-net facts: 1,4-butanediol. TecnonOrbiChem. Available at: http://www.orbichem.com/userfiles/CNF%20Samples/bdo_13_11.pdf. Accessed January 23, 2014.
# Nexant. 1,4-butanediol/tetrahydrofuran (BDO/THF). ChemSystems. Available at: http://www.chemsystems.com/about/cs/news/items/ PERP2012_3_BDO_THF.cfm. Accessed February 6, 2014.
# Burk MJ, Van Dien SJ, Burgard AP, inventors; Genomatica, Inc., assignee. Compositions and methods for the biosynthesis of 1,4-butanediol and its precursors. US patent 8,067,214. Nov. 29, 2011.
# Chung S-H, Kim M-S, Eom H-H, Lee K-Y. Catalytic hydrogenation of bio-based succinic acid for the production of 1,4-butanediol through the indirect pathway. AIChE. Available at: https://aiche.confex.com/aiche/2013/webprogram/Paper327470.html. Accessed January 23, 2014.
# Bhattacharyya A, Manila MD, inventors; ISP Investments Inc., assignee. Catalysts for maleic acid hydrogenation to 1,4-Butanediol. US patent 7,935,834 B2. May 3, 2011.

Design S2

2014-03-15T04:47:07Z

Karetstik: Created page with "Title: Production of 1,4-butanediol Authors: Nick Pinkerton, Karen Schmidt, and James Xamplas Date Presented: March 14, 2014 ==Introduction== 1,4-butanediol (BDO) is tradi..."

Title: Production of 1,4-butanediol

Authors: Nick Pinkerton, Karen Schmidt, and James Xamplas

Date Presented: March 14, 2014

==Introduction==
1,4-butanediol (BDO) is traditionally made from petroleum-derived feedstocks in a variety of processes such as the Reppe (acetylene-based), Mitsubishi (butadiene-based), and Davy (maleic acid-based) processes.1 Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, BDO.1 It is this process that Team S2Kool4Skool has chosen to develop for a new bio-butanediol plant, because the Davy method is mature and requires no new innovations, and because an appropriate feedstock of bio-succinic acid is now available. The plant will be located in East Carroll Parish, Louisiana. This county is also home to Myriant; located in Lake Providence, they are the largest domestic provider of bio-succinic acid.2 Furthermore, Lake Providence is conveniently located on the Mississippi River, which will allow for affordable transportation of our bio-based butanediol product. The intent of this project is to produce 45,000 metric tonnes of 99.5 wt% 1,4-butanediol per year in a new plant in Lake Providence, LA. The plant will run 24 hours per day for 350 days out of the year, allowing approximately two weeks for a maintenance shutdown.

As there are several techniques for producing 1,4 butanediol in industry, the first step was to determine a synthesis path. Based on the chosen path, reaction kinetics, and required production rate of the process, a reactor system was then designed. Next, the process was designed to deliver the reactants to the reactor at the proper operating conditions, and the separations, purification, and waste management steps were designed. Cost estimates were made using costing software and hand calculations. Finally, the process was iterated and optimized to reduce costs.

==Background==
===General information===
BDO is an organic chemical with the molecular formula C4H10O2. It is also a diol with its two hydroxyl groups located at the terminal carbons. BDO has a boiling point of 235oC and is therefore a colorless liquid at standard temperatures and pressures.3
There are many precursors that petrochemical synthesis of BDO uses. The commonality between all of the precursor acids is that they are hydrogenatable. In replacement of one of these petrochemical precursors, our team has been tasked with the challenge of deriving BDO from the bio-based precursor succinic acid. This catalyzed reaction will take place in the presence of hydrogen as the hydrogenating component shown below:

C4H6O4 + 4H2 --> C4H10O2 +2H2O

As described in the above reaction, there will need to be at least 4:1 stoichiometric ratio of hydrogen gas to succinic acid. Two moles of water will also be produced along with each mole of BDO. This reaction is exothermic, which requires the reactor to be continuously cooled to maintain our reactor temperature. There are also side products that are produced which include tetrahydrofuran (THF) and γ-butyrolactone (GBL); however, thanks to catalyst selectivity these byproducts are produced in small quantities.

===Market analysis===
Butanediol has a quickly expanding market due to new technological evolutions and its growing use as a chemical intermediary in advanced materials. With biological routes being optimized, the potential of biomass-derived chemicals is tremendous. The global demand of BDO was estimated at 1.5 million metric tons in 2011 and is projected to grow at an annual rate of 4.5% for the next several years.1 Unlike other chemical products, BDO’s profitability and attractiveness to producers lies in its downstream potential. Figure 1 below demonstrates several potential downstream products that can be directly or indirectly synthesized from BDO. The largest of these contributors include THF and GBL.

The current market demand of BDO is being supplemented by several global chemical companies. These companies include BASF, BioAmber, Purac, Myriant, DSM, Mitsubishi Chemical, Roquette, and OPXBIO. The market shares of these companies were not available for this product; however, with the consistent growth of the BDO market our team feels that the market is not saturated or impenetrable. The current market price of BDO fluctuates between $3.06 and $3.31 per kg for US-made products.4 These prices correlate to a nearly 7 billion dollar industry.

===Process alternatives===
1,4-butanediol is traditionally made from petroleum-derived feedstocks in a variety of processes.5 Recently, because of the continually high price of crude oil and the desire to be environmentally-conscious, there has been a push toward the use of feedstocks derived from biomass. Several companies are currently implementing bio-routes of producing butanediol. Genomatica is using a bioengineered microorganism to convert sugar feedstocks directly to BDO via fermentation,6 but most companies are instead using microorganisms to convert sugar to succinic acid. The bio-succinic acid can be easily used in the Davy process as a substitute for maleic acid to form the end product, which is the path that most are choosing, although research is being conducted on alternative pathways.7

==Process overview==
The newly proposed plant can be divided into four stages: pre-reactor, reactor, post-reactor and distillation. Each section is an integral part to the overall process and demands close attention. The process flow diagram (see Appendix A) and stream table (Appendix B) provide more detailed information.

===Pre-reactor===
This chemical process begins with two feedstocks: hydrogen gas and bio-succinic acid. The hydrogen gas will be obtained from a pipeline at 150 atm and will be used in molar excess inside the reactor. The bio-succinic acid will be purchased by Myriant Corporation which is located near the planned plant site. The pricing for this feedstock is approximately $2.12 per kg. The plant will require 63,000 metric tonnes of bio-succinic acid per year to meet the proposed plant capacity. First the bio-succinic acid feed is pumped up to 150 atm to match the hydrogen gas feed, and then it is mixed with the hydrogen gas prior to being sent into heat exchanger E-101 for heating. The heat exchanger brings the two feeds up to 110oC and sends them to the jacketed packed bed reactor.

===Reactor===
The hydrogenation reaction occurs inside of the reactor thanks to the packed catalyst bed. The catalyst used is 0.4% Fe, 1.9% Na, 2.66% Ag, 2.66% Pd, 10.0% Re on 1.5mm carbon support. With this catalyst, BDO is produced with over 90% selectivity and minimal side reactions of THF and GBL.8 The reaction has an operating pressure of 2000-4000 psi and internal reactor temperature of 165°C. This temperature allows for about 99.7% conversion of succinic acid.8 Due to the exothermic nature of the reaction, a cooling jacket is required which utilizes downstream cold streams to cool the internal bed to maintain the desired reaction temperature.

===Post-reactor===
The effluent of the reactor is sent back to E-101 as the hot stream. After exiting E-101, the reactor product stream is sent to a secondary exchanger, E-102, where utility cooling water is used to reduce the temperature to an acceptable temperature prior to sending it to a pressure let-down valve. At this point the pressure of the stream is taken from 150 atm to 1 atm. This large pressure drop allows for the stream to split into its vapor and liquid portions in a gas-liquid separator. The vapor stream of the gas liquid separator is primarily hydrogen gas and sent to a flare for disposal. The liquid effluent is at approximately 45oC leaving the separator and is therefore pumped to the reactor jacket for the reaction cooling mentioned previously. After running through the reactor jacket, the stream enters the separation processes.

===Distillation===
The first distillation column, T-101, is a 10 stage column whose primary purpose is separating the THF from the product feed. Due to THF’s lower boiling point, the byproduct comes off of the top of the column with mostly water. This distillate is sent to the plant's THF waste storage tank that has the capacity of two weeks. The bottoms of the column is sent to the subsequent distillation column that separates the BDO from the GBL and water. The relatively close boiling points of BDO and GBL, 235oC and 204oC, respectively, create a difficult separation that requires a 15 stage column. The distillate of the column is approximately 23% GBL with balance water. This stream is sent to a storage tank with similar sizing parameters as the THF storage tank. The bottom stream is the final 99.5wt% BDO product. This stream is sent to the final product tank, S-104. Depending on our customer demands and the plant location we have the ability to barge, rail or pipe our product to its final destination. Due to low purity of the byproducts, future iterations are needed to optimize either purifying byproducts or selling impure byproducts. There is definitely an available market for these byproducts that should be researched more extensively to increase profit. A detailed description of the equipment from the PFD can be found in Appendix C, in addition to sizing specifications and purpose of equipment.

===Mass and energy balances===
Using an Aspen HYSYS simulation we were able to record the material and energy streams going in and out of the process system. Mass and energy balances are provided Appendix D where each inlet and outlet stream is described and quantified. As expected, the material and energy totals for the inlet and outlet streams add together to equal 0. This proves that our system is mathematically prudent and thermodynamically feasible. The total mass flow of the system is 15,639 kg/h and the total energy in and out of the system is 1.41e8 kJ/h.

===HYSYS simulation===
The HYSYS simulation was performed using the NRTL ideal fluid package. After using AspenPlus to verify that the HYSYS package had the appropriate vapor-liquid equilibrium information between THF and water, and between GBL and water (see Appendix E), we concluded it was feasible to proceed with that fluid package. The simulation consists of a reactor, a gas-liquid separator, 2 pumps, 3 heaters, a valve, and 2 distillation columns (see Figure 2). The simulation successfully converted the succinic acid feed into the desired products. Also, the combination of the two distillation columns was able to effectively separate the BDO to obtain a 99.5% pure product with 99.5% recovery. In addition, a set was made between the energy required to heat stream 12 and the energy required to cool the reactor so that these values were made equal. Lastly, the condenser and reboiler duties were used in four heat exchangers in order to determine the appropriate size of this equipment as well as the necessary utility flow rates.

==Health and safety==
===Chemical properties===
Inherent to this process are a number of toxic chemicals. Table 1 summarizes the important safety data including hazard type, odor, color, and exposure limits.

As shown in the above table, the chemicals that this facility will be dealing with will be relatively mild and non-life threatening. Regardless of their perceived threat, chemicals should always be handled with care especially when they are at high temperatures and pressures.

===Safety procedures===

Fire. There are many flammable materials that will be included in this process; therefore, fire safety is imperative for all employees. There are countless possible causes of ignition and care should be taken while handling any flammable material whether in the lab or in the field.

In case a fire is present on, the following protocol should be implemented:

& Small fire: Use DRY chemical powder.
• Large fire: Use alcohol foam, water spray, or fog.
• Call for backup if unable to control.
• Immediately contact supervisor and emergency personnel on site.
• Evacuate to safe distance in case of fires around any hazardous materials or pressure vessels.

Spills. Process chemical spills will eventually occur in a plant of this scale. Small spills are likely to occur in a laboratory setting. Large spills could be a result of loss of containment in the system. We must ensure that all personnel are aware of proper spill mitigation protocol.

• Small spill: Dilute with water and mop or absorb with inert dry material. Dispose of in proper receptacle.
• Large spill: Keep away from sources of ignition and heat. Prevent rundown to any drains or sewers. Call for assistance on disposal. Absorb material with DRY earth or other non-combustible materials.
• If spill is due to a loss of containment in the system, quickly consult the PLC and shut any valves to prevent further loss.

Exposure. We must ensure that our employees are aware of the possible toxicity levels of each substance and how to handle exposure. The chemicals that are being used in this process are known chemical irritants to the eyes, skin, and throat. Safety measures must be in place to acknowledge this hazard. Due to the possibility of high pressure releases, we will have 2-minute emergency oxygen masks placed strategically throughout the plant to ensure the safety of any operator in the presence of a large release.

If exposed to the process chemicals, find nearest eye wash station or safety shower immediately and flush exposed skin for at least 15 minutes. Remove any contaminated clothing. Seek medical attention immediately.

Storage. Store chemicals in segregated and approved areas. Any closed containers for laboratory purposes should be placed in cool, well-ventilated areas.

==Economics==
===Equipment costing===
The calculated capital costs from Aspen Economic Analyzer are reported in Table 2 for all process equipment. The size of the reactor was calculated from the liquid hourly space velocity given in the 2011 ISP patent8 and a void fraction estimate of 0.4. Storage tanks were sized to contain up to two continuous weeks of material. The number of distillation trays in each tower and the flow rates through pumps, vessels, and the flare were calculated in HYSYS. Heat exchange areas were given in Aspen Energy Analyzer or from HYSYS.

In addition to the above equipment, our plant will require an ion exchanger to produce deionized process water from the municipal water. This is estimated to cost $42,000 in capital cost.

===Cash flow analysis===
Summarizing the important takeaways from the economic analysis (see Appendix G), this process will return a revenue of 144 MM$ annually. Offset by production costs, the yearly cash flow is approximately 2.7 MM$, except for in the years in which the catalyst must be reinstalled (approximately every 5 years). At a cost of 2.5 MM$, the cash flows in those years decrease to approximately 0.2 MM$. This analysis assumes the plant will take 2 years to construct, and will operate at 50% in its first year. Furthermore, an interest rate of 10% was assumed with a tax rate of 38% (the maximum for corporate gains taxes). Using the 7-year MACRS depreciation method, the 20 year NPV for the project is 4.3 MM$. With an IRR of 15.1%, which is greater than the assumed interest rate, this project looks to be profitable. Further optimization techniques should be used in future iterations to further increase profitability. See Tables 3 and 4 for key economic information.

===Sensitivity analysis===
As seen in Figure 3, the economic evaluation of this process is influenced the most by changes in the sales price and feed cost. A 20% increase in sales price will result in an approximate 120 MM$ increase in NPV whereas a decrease of the same percentage will result in over a 120 MM$ decrease in NPV. Inversely, a 20% increase in feed cost will result in a 115 MM$ decrease in NPV and a 20% decrease in feed cost will result in a 60 MM$ increase in NPV.

To alleviate the risk associated with feed price, the team researched the price forecasting of bio-succinic acid. Figure 4 provides the bio-succinic acid price over the six years between 2006 and 2012. The price of bio-succinic, shown by the blue line, has remained relatively stable over this time period. This price history can be compared to adipic acid, the green line, which is a common petrochemical precursor for BDO production. Adipic acid as shown has had large fluctuations in price that result in unstable cash flows and uncertainty from shareholders. Thankfully, the stability of bio-succinic acid is a good sign that this process has a huge potential to be profitable especially if the demand for BDO continues to rise as projected.

==Discussion==
As described previously, the Davy process was selected as the most promising process of BDO production. The modified Davy process involves the hydrogenation of bio-succinicic acid with a Pa,Ag,Re catalyst and hydrogen gas. This process has many advantages, one being that it has mature technology that has been improved over the last 20 years. Additionally, the conversion to of succinic acid is virtually complete. Finally, overall plant yields can reach as high as 94 mol%.
As shown in Appendix B, streams ahead of the pressure valve (PRV-101) are at approximately 1.51e4 kPa, and streams after the pressure valve are between 100 and 450 kPa. Furthermore, operating temperatures do not exceed 200°C, including safety factors. These operating conditions contribute to the feasibility of the process, as all the components can be designed with reasonable dimensions (wall thickness, cap type, etc.).

Of particular interest are the large costs of the reactor and pump P-101. The reactor costs nearly 2 MM$ because it has a moderate size with a liquid volume of 16.7 m3, and it operates at 150 atm, which requires a strong stainless steel shell for safety purposes. Pump P-101 has such a large capital cost because it is a centrifugal multistage pump that also needs to be made of stainless steel to withstand pressuring the succinic acid feed to 150 atm.

Financial indicators for the proposed plant suggest that it will be moderately profitable, and additional optimization should be performed before making the capital investment. There is a fair amount of risk associated with the implementation of this production facility, and the return at this juncture may not justify the risk.

The process design and simulation in HYSYS has relied on several key assumptions, which are cause for certain limitations to the results. First, the conversions and selectivity of the catalyst, while taken from literature sources, are assumed to be true. Furthermore, the assumption of negligible side reactions and products was made. It is possible that small waste products in the form of succinates also form in the reactor. Therefore, the main limitation of this model is generally due to reaction specifications.

There are certain safety concerns that go along with the proposed process. First, there are many pipes and vessels that will be at a pressure of approximately 150 atm. Extra insulation and protection must be applied to the piping that contains highly pressurized fluids, to prevent operator injury. Furthermore, the PFR is at a slight risk for runaway reactions due to the exothermic nature of the reaction. The temperature of the reactor must always be monitored by an operator, and the jacket cooling system requires a backup system as well. A benefit of this process is that there are no toxic or severely hazardous components in the process. Additionally, there are no instances of temperature greater than 200°C.

The process design will be fitted with instrumentation and controls to ensure stable operation. These controls, including sensors and valves, minimize potential damage to components due to variation in plant conditions, as well as optimizing the overall performance. For example, the piping entering the tower will be fitted with a control loop. In the direction of flow, a sensing instrument first detects the pressure of the fluid, and then sends a signal to the controller. If the pressure is not within the operating limits, the actuator is signaled to close or open a control valve which is located farther down the stream.

==Conclusion==
The Evanston Chemical Engineering Division suggests a process that produces 45,000 tonnes/year of 99.5 wt% 1,4-butandeiol to enter the market with an appropriate market share. The feasibility of producing BDO as a significant process was investigated. A wide range of BDO production processes were researched, with a modified Davy process being identified as having the most potential. Using a Pa,Ag,Re catalyst on carbon support, this process converts bio-succinic acid to BDO with approximately 94% conversion. This process was designed in Aspen HYSYS, and economic analysis was conducted in Aspen Economic Analyzer. Total capital costs of the project are 12.2 MM$, with a simple payback period of 5.2 years. Total operational costs annually are 139.7 MM$. The process design was successful, with the capability of producing the desired production of BDO.

==Recommendations==
Given the moderate profitability of this process design, it is recommended that Evanston Chemicals explores further optimization techniques to increase the profitability of this process. This includes investigating sales of the γ-butyrolactone byproduct, recycling process water, and further optimizing utility streams for the distillation tower.
Second, we would like to investigate recycling the 2300 kg/h of water produced in the reaction. Our succinic acid enters the reactor as a 50 wt% solution in water, so we should look into replacing some of this with the product water. Not only will this decrease our water bill, but it will also lower the cost of ion exchange.

==References==
# Nexant.Is Bio-Butanediol Here to Stay? White Plains, NY: ChemSystems Products; 2012.
# De Guzman D. Chemical industry awaits for bio-succinic acid potential. ICIS. Available at: http://www.icis.com/resources/news/2012/01/30/9527521/chemical-industry-awaits-for-bio-succinic-acid-potential/. Accessed January 24, 2014.
# Australian Government: Department of Health. 1,4-butanediol factsheet. National Industrial Chemicals Notification and Assessment Scheme. Available at: http://www.nicnas.gov.au/communications/publications/information-sheets/existing-chemical-info-sheets/other-information-sheets. Accessed January 24, 2014.
# TecnonOrbiChem. Chem-net facts: 1,4-butanediol. TecnonOrbiChem. Available at: http://www.orbichem.com/userfiles/CNF%20Samples/bdo_13_11.pdf. Accessed January 23, 2014.
# Nexant. 1,4-butanediol/tetrahydrofuran (BDO/THF). ChemSystems. Available at: http://www.chemsystems.com/about/cs/news/items/ PERP2012_3_BDO_THF.cfm. Accessed February 6, 2014.
# Burk MJ, Van Dien SJ, Burgard AP, inventors; Genomatica, Inc., assignee. Compositions and methods for the biosynthesis of 1,4-butanediol and its precursors. US patent 8,067,214. Nov. 29, 2011.
# Chung S-H, Kim M-S, Eom H-H, Lee K-Y. Catalytic hydrogenation of bio-based succinic acid for the production of 1,4-butanediol through the indirect pathway. AIChE. Available at: https://aiche.confex.com/aiche/2013/webprogram/Paper327470.html. Accessed January 23, 2014.
# Bhattacharyya A, Manila MD, inventors; ISP Investments Inc., assignee. Catalysts for maleic acid hydrogenation to 1,4-Butanediol. US patent 7,935,834 B2. May 3, 2011.

Estimation of production cost and revenue

2014-02-24T05:58:01Z

Karetstik: /* Taxes and Insurance */

==Variable Cost of Production==
Variable costs of production are dependent primarily on plant output and rate of production. There are many variables to consider when costing a plant.
# Raw materials consumed
# Utilities-steam, electricity, cooling water, fuel, etc.
# Consumables - acids, bases, solvents, catalysts, etc.
# Disposal
# Shipping
The majority of the variable costs for a production plant are the raw materials and utilities costs. Variable costs can be greatly cut through optimization techniques and intelligent plant design [1].
===Raw Materials Cost===
Calculating the annual cost of a raw material is calculated by simply multiplying the feed rate of the process by the appropriate price per volume or mass. These are the costs of chemical feed stocks required by the process. Feed stocks flow rates are obtained from PFD [5].There are several ways to optimize this cost to ensure that a process is not costing more than it should. First one should assess the actual consumption of a plant to see if it is significantly different from what should be expected based on process stoichiometry and selectivities [1]. Finding may prove that a process is less efficient than it originally claimed.
It is smart to benchmark a new plant design against an existing plant or pilot plant. Raw materials are typically the largest contributor to overall variable costs. For bulk chemicals and petrochemicals, raw materials represent 80-90% of the total cash cost of production (CCOP).
===Utilities Cost===
These are the costs of the various utilities streams required by the process. The flowrates for the utilities streams are located on the PFD [5]. This includes:
*Fuel gas, oil, or coal
*Electric power
*Steam
*Cooling water
*Process water
*Boiler feed water
*Air
*Inert gas
*Refrigeration

Utility streams are excellent ways to streamline a process and are often indicative of how efficient of a process the project is. Process methods such as steam generation and pinch analysis can be used to greatly reduce utility costs across a plant. Further analysis of pinch analysis techniques and optimizing heat exchanger networks can be found in plant design texts such as first reference from Gavin Towler. The determination of process utility costs is often more difficult than the determination of raw material costs; however, the utilities are typically between 5-10% of CCOP [1]. The cost of heating a process can be reduced by using process waste streams as fuel which consequently also reduces the need for waste disposal.

===Waste Disposal Costs===
These are defined as the cost of waste treatment to protect the environment [5]. These are materials that cannot be recycled or sold off as by-products. Often times these streams require additives or additional treatment to meet governmental regulations.
Hydrocarbon waste can often be incinerated directly to the atmosphere or used as process fuel to heat other streams in the system. Using the stream as process fuel allows the fuel value of the stream to be recovered into the system. The substituted value can be calculated by multiplying the conventional fuel price by the heat of combustion of the waste stream.

<math>P_{WFV} = P_F * \Delta H_C^o</math>

where
<math>P_{WFV}</math> = waste value of fuel ($/lb or $/kg)

<math>P_F</math> = price of fuel ($/MMBtu or $/GJ)

<math>\Delta H_C^o</math> = heat of combustion (MMBtu/lb or GJ/kg)

Dilute aqueous streams must be sent to wastewater treatment typically prior to purging from the plant. Acidic or basic wastes are neutralized prior to treatment by salting out the acid or base. The cost of wastewater treatment is typically about $6 per 1000 gal but this is only an estimate that doesn't account for regional charges [1].

Solid waste treatment can typically be sent to a landfill at a cost of approximately $50/ton [1].

Hazardous wastes arise from the production of concentrated liquid streams that cannot be incinerated. Hazardous wastes should be avoided if possible, but that is not always feasible for some processes. The cost of hazardous waste disposal is strongly dependent on the location of the plant, the plants proximity to waste disposal plants and the degree of hazard of the waste.

==Fixed Cost of Production==
Fixed costs are those whose amounts are independent of production rates. Much of these costs are personnel salaries, taxes, insurance, and legal payments.
===Labor Costs===
These are the costs attributed to the personnel required to operate the process plant [5].

The number of operators required per shift, <math>N_{OL}</math> can be estimated by

<math>N_{OL}=(6.29+31.7P^2+0.23N_{np})^{0.5}</math>

where <math>P</math> is the number of processing steps involving particulate solids and <math>N_{np}</math> is the number of other processing steps [5]. For each of the <math>N_{OL}</math> operators per 8-hour shift, approximately 4.5 operators must be hired for a plant that runs 24 hours per day, to account for the 3 shifts per day and the 3 weeks of leave typically taken by each operator per year [5]. The salary for a chemical plant operator varies by location, and the estimator should look up the average value for the area.

===Maintenance Costs===
These are the costs associated with labor and materials necessary to maintain plant production. An estimate of these are 6% of the fixed capital investment [5].

===Research and Development===
These are the costs of research done in developing the process and/or products. This includes salaries for researchers as well as funds for research related equipment and supplies. An estimate of these costs are 5% of the total manufacturing cost [5].

===Taxes and Insurance===
Taxes vary by location, but a first estimate of property taxes and liability insurance is 3% of the fixed capital investment [5].

===Plant Overhead===
Overhead costs are the miscellaneous but necessary costs of running a business, including payroll, employee benefits, and janitorial services. This may be estimated as 70% of the operating labor costs, added to 4% of the fixed capital costs [5].

===Licensing and Royalties===
The costs of paying for the use of intellectual property clearly varies, but an estimate that may be used is 3% of the total manufacturing cost [5].

==Revenues==
The revenues of a process are the income earned form sales of the main products and the by-products. Revenue can be impacted by market fluctuations and production rates.
===By-Product Revenues===
Besides selling the main product from a process, by-products from separations and reactions can also be valuable in the market. Often it is more difficult to decide which by-products to recover and purify than it is to make decisions on the main product.

By-products made in stoichiometric ratios from reactions must be either sold off or managed through waste disposal. Other by-products are sometimes produced through feed impurities or by nonselective reactions. There are several potential valuable by-products from a process:
# Materials produced in stoichiometric quantities by the reactions that create the main product. If they are not recovered then the waste disposal expenses will be large.
# Components that are produced in high yield by side reactions.
# Components formed in high yield from feed impurities. Many sulfurs are produced as a by-product of fuels manufacture.
# Components that are produced in low yield but have high value. An example includes acetophenone which is recovered as a by-product of phenol manufacture.
# Degraded consumables (e.g. solvents, etc.) that have reuse value.

A rule of thumb that can be used for preliminary screening of by-products for large plants is that for by-product recovery to be economically feasible the net benefit must be greater than $200,000 a year. A net benefit can be calculated by adding the possible resale value of the by-product and the avoided waste disposal cost [1].

===Margin===
The gross margin of a process is defined as the sum of product and by-product revenues minus the raw material cost.

Gross margin = Revenues - Raw materials costs

Because raw materials are most often the most expensive variable cost of a process, the gross margin is a good gauge as to what the total profitability of a process will be. Raw materials and product pricing are often subject to high degrees of variability which can be difficult to forecast. The size of margins are highly versatile depending on the
industry. For many petrochemical industries the margin may be only 10%; however, for industries such as food additives and pharmaceuticals the margins are generally much higher [1].

===Profits===
There are several standards for calculating company profits. The cash cost of production (CCOP) is the sum of the fixed and variable production costs.

''CCOP = VCOP + FCOP''

where VCOP is the variable cost of production and FCOP is the fixed cost of production.

Gross profit, which should not be confused with gross margin, is then calculated by the following equation,

''Gross profit = Main product revenues - CCOP''

Finally profit can be calculated by subtracting the income taxes that the plant would be subject to depending on the tax code of the county the plant is located in.

''Net profit = gross profit - taxes''

==Pricing Products and Raw Materials==
The revenues and costs of a project are vital to determining its economic feasibility. To calculate these values one needs to multiply the respective product and feed streams by their respective prices. The major difficulty of this process is determining the prices that should be used in this formula. When analyzing a plant, not only do the current prices need to be acknowledged but also the stability of the market to forecast future fluctuations and deviations.
===Pricing Fundamentals===
The pricing of a substance is determined by the fundamental economic principles of supply and demand. A supply curve and demand curve can be graphed and added to determine the market equilibrium price and projected market size. There are many ways a company can combat if the market equilibrium pricing is not suitable for a process. One of these ways is changing the market that the company is selling to. Instead of selling industrial grade product there may be markets for pharmaceutical grade or food grade that would allow for a company to sell their product at higher margins. Another avenue to look into is changing the geographic market being sold to. Rarely is there a global synchronous market, but rather a variation depending on where in the world the product is being sold. It is possible that a company could make more money by dedicating their sales to the Asian market as opposed to the US or vise versa.
===Price Data Sources===
There are many resources when trying to determine the price of a chemical or utility. This are important for looking at current pricing information as well as historical data that can be used for forecasting purposes.
====Internal Company Forecasts====
Large companies will often have the marketing or development departments develop a forecasting database that can be used internally in the company. Forecasts of this magnitude will often have multiple scenarios and projects that are evaluated under the given parameters. Companies may even license these forecasts to other companies for high fees if they desire.

[[File:Capture.JPG]]

Table 1 provides common industry acronyms that are used to indicate certain key words when determining pricing information.

====Trade Journals====
There are also many publications that report pricing data weekly. ''ICIS Chemical Business Americas'' used to publish the prices for hundreds of chemicals but have more recently changed their data to an online database that requires a subscription. This service is very expensive, but necessary for many companies. ''Oil and Gas Journal'' publishes the market prices of many crude oils and other petrochemicals using data from several continents. This journal also provides margin data for many refineries and plants on a monthly basis. ''Chemical Week'' provides the spot and contract prices for 22 chemicals in the US and European markets.

====Consultants====
If trade journals are not adequate for the information needed, some companies will contract consultants to do deep research into the subject. Consultants are excellent resources for providing economic and marketing information but come at a large price. There are several companies that provide this type of service but some of the larger firms include: ''Purvin and Gertz'', ''Cambidge Energy Research Associates'', ''Chemical Markets Associates Inc.'', and ''SRI: The Chemical Economics Handbook''

====Online Brokers and Suppliers====
Often time price data can be supplied by the supplier themselves and using online directories. Restraint should be used when quoting these prices however because they are often spot prices that are much higher than what would be expected from bulk contract supplying.

==Example Case: Estimating Cost of Production==

Use the following information to estimate the manufacturing cost of a nitric acid plant producing 92,000 tonnes/year.

:Fixed Capital Investment: $11,000,000
:Raw Material Cost: $7,950,000/yr
:Waste Treatment Cost: $1,000,000/yr
:Utilities: $356,000/year
:Direct Labor Cost: $300,000/yr
:Fixed Costs: $1,500,000/yr

To find the manufacturing cost, multiply the value of the variable cost by the appropriate cost factor. In this case, we get,

<math>COM_d = (0.180)($11,000,000) + (2.73)($300,000) + (1.23($356,000 + $1,000,000 + $7,950,000) = $14,245,000/yr</math>

<math>($14,245,000/yr)/(92,000\ tonne/yr) = $155/tonne</math>

==References==
# Towler, G.P. and Sinnot, R. (2012). ''Chemical Engineering Design: Principles, Practice and Economics of Plant and Process Design.''Elsevier.
# Biegler, L.T., Grossmann, L.E., and Westerberg, A.W. (1997). ''Systematic Methods of Chemical Process Design.'' Upper Saddle River: Prentice-Hall.
# Peters, M.S. and Timmerhaus, K.D. (2003). ''Plant Design and Economics for Chemical Engineers, 5th Edition.'' New York: McGraw-Hill.
# Seider, W.D., Seader, J.D., and Lewin, D.R. (2004). ''Process Design Principles: Synthesis, Analysis, and Evaluation.'' New York: Wiley.
# Turton, R.T., Bailie, R.C., Whiting, W.B., and Shaewitz, J.A. (2003). ''Analysis, Synthesis, and Design of Chemical Processes'' Upper Saddle River: Prentice-Hall.

Estimation of production cost and revenue

2014-02-24T05:57:20Z

Karetstik: /* Fixed Cost of Production */

==Variable Cost of Production==
Variable costs of production are dependent primarily on plant output and rate of production. There are many variables to consider when costing a plant.
# Raw materials consumed
# Utilities-steam, electricity, cooling water, fuel, etc.
# Consumables - acids, bases, solvents, catalysts, etc.
# Disposal
# Shipping
The majority of the variable costs for a production plant are the raw materials and utilities costs. Variable costs can be greatly cut through optimization techniques and intelligent plant design [1].
===Raw Materials Cost===
Calculating the annual cost of a raw material is calculated by simply multiplying the feed rate of the process by the appropriate price per volume or mass. These are the costs of chemical feed stocks required by the process. Feed stocks flow rates are obtained from PFD [5].There are several ways to optimize this cost to ensure that a process is not costing more than it should. First one should assess the actual consumption of a plant to see if it is significantly different from what should be expected based on process stoichiometry and selectivities [1]. Finding may prove that a process is less efficient than it originally claimed.
It is smart to benchmark a new plant design against an existing plant or pilot plant. Raw materials are typically the largest contributor to overall variable costs. For bulk chemicals and petrochemicals, raw materials represent 80-90% of the total cash cost of production (CCOP).
===Utilities Cost===
These are the costs of the various utilities streams required by the process. The flowrates for the utilities streams are located on the PFD [5]. This includes:
*Fuel gas, oil, or coal
*Electric power
*Steam
*Cooling water
*Process water
*Boiler feed water
*Air
*Inert gas
*Refrigeration

Utility streams are excellent ways to streamline a process and are often indicative of how efficient of a process the project is. Process methods such as steam generation and pinch analysis can be used to greatly reduce utility costs across a plant. Further analysis of pinch analysis techniques and optimizing heat exchanger networks can be found in plant design texts such as first reference from Gavin Towler. The determination of process utility costs is often more difficult than the determination of raw material costs; however, the utilities are typically between 5-10% of CCOP [1]. The cost of heating a process can be reduced by using process waste streams as fuel which consequently also reduces the need for waste disposal.

===Waste Disposal Costs===
These are defined as the cost of waste treatment to protect the environment [5]. These are materials that cannot be recycled or sold off as by-products. Often times these streams require additives or additional treatment to meet governmental regulations.
Hydrocarbon waste can often be incinerated directly to the atmosphere or used as process fuel to heat other streams in the system. Using the stream as process fuel allows the fuel value of the stream to be recovered into the system. The substituted value can be calculated by multiplying the conventional fuel price by the heat of combustion of the waste stream.

<math>P_{WFV} = P_F * \Delta H_C^o</math>

where
<math>P_{WFV}</math> = waste value of fuel ($/lb or $/kg)

<math>P_F</math> = price of fuel ($/MMBtu or $/GJ)

<math>\Delta H_C^o</math> = heat of combustion (MMBtu/lb or GJ/kg)

Dilute aqueous streams must be sent to wastewater treatment typically prior to purging from the plant. Acidic or basic wastes are neutralized prior to treatment by salting out the acid or base. The cost of wastewater treatment is typically about $6 per 1000 gal but this is only an estimate that doesn't account for regional charges [1].

Solid waste treatment can typically be sent to a landfill at a cost of approximately $50/ton [1].

Hazardous wastes arise from the production of concentrated liquid streams that cannot be incinerated. Hazardous wastes should be avoided if possible, but that is not always feasible for some processes. The cost of hazardous waste disposal is strongly dependent on the location of the plant, the plants proximity to waste disposal plants and the degree of hazard of the waste.

==Fixed Cost of Production==
Fixed costs are those whose amounts are independent of production rates. Much of these costs are personnel salaries, taxes, insurance, and legal payments.
===Labor Costs===
These are the costs attributed to the personnel required to operate the process plant [5].

The number of operators required per shift, <math>N_{OL}</math> can be estimated by

<math>N_{OL}=(6.29+31.7P^2+0.23N_{np})^{0.5}</math>

where <math>P</math> is the number of processing steps involving particulate solids and <math>N_{np}</math> is the number of other processing steps [5]. For each of the <math>N_{OL}</math> operators per 8-hour shift, approximately 4.5 operators must be hired for a plant that runs 24 hours per day, to account for the 3 shifts per day and the 3 weeks of leave typically taken by each operator per year [5]. The salary for a chemical plant operator varies by location, and the estimator should look up the average value for the area.

===Maintenance Costs===
These are the costs associated with labor and materials necessary to maintain plant production. An estimate of these are 6% of the fixed capital investment [5].

===Research and Development===
These are the costs of research done in developing the process and/or products. This includes salaries for researchers as well as funds for research related equipment and supplies. An estimate of these costs are 5% of the total manufacturing cost [5].

===Taxes and Insurance===
Taxes vary by location, but a first estimate of taxes and insurance is 3% of the fixed capital investment [5].

===Plant Overhead===
Overhead costs are the miscellaneous but necessary costs of running a business, including payroll, employee benefits, and janitorial services. This may be estimated as 70% of the operating labor costs, added to 4% of the fixed capital costs [5].

===Licensing and Royalties===
The costs of paying for the use of intellectual property clearly varies, but an estimate that may be used is 3% of the total manufacturing cost [5].

==Revenues==
The revenues of a process are the income earned form sales of the main products and the by-products. Revenue can be impacted by market fluctuations and production rates.
===By-Product Revenues===
Besides selling the main product from a process, by-products from separations and reactions can also be valuable in the market. Often it is more difficult to decide which by-products to recover and purify than it is to make decisions on the main product.

By-products made in stoichiometric ratios from reactions must be either sold off or managed through waste disposal. Other by-products are sometimes produced through feed impurities or by nonselective reactions. There are several potential valuable by-products from a process:
# Materials produced in stoichiometric quantities by the reactions that create the main product. If they are not recovered then the waste disposal expenses will be large.
# Components that are produced in high yield by side reactions.
# Components formed in high yield from feed impurities. Many sulfurs are produced as a by-product of fuels manufacture.
# Components that are produced in low yield but have high value. An example includes acetophenone which is recovered as a by-product of phenol manufacture.
# Degraded consumables (e.g. solvents, etc.) that have reuse value.

A rule of thumb that can be used for preliminary screening of by-products for large plants is that for by-product recovery to be economically feasible the net benefit must be greater than $200,000 a year. A net benefit can be calculated by adding the possible resale value of the by-product and the avoided waste disposal cost [1].

===Margin===
The gross margin of a process is defined as the sum of product and by-product revenues minus the raw material cost.

Gross margin = Revenues - Raw materials costs

Because raw materials are most often the most expensive variable cost of a process, the gross margin is a good gauge as to what the total profitability of a process will be. Raw materials and product pricing are often subject to high degrees of variability which can be difficult to forecast. The size of margins are highly versatile depending on the
industry. For many petrochemical industries the margin may be only 10%; however, for industries such as food additives and pharmaceuticals the margins are generally much higher [1].

===Profits===
There are several standards for calculating company profits. The cash cost of production (CCOP) is the sum of the fixed and variable production costs.

''CCOP = VCOP + FCOP''

where VCOP is the variable cost of production and FCOP is the fixed cost of production.

Gross profit, which should not be confused with gross margin, is then calculated by the following equation,

''Gross profit = Main product revenues - CCOP''

Finally profit can be calculated by subtracting the income taxes that the plant would be subject to depending on the tax code of the county the plant is located in.

''Net profit = gross profit - taxes''

==Pricing Products and Raw Materials==
The revenues and costs of a project are vital to determining its economic feasibility. To calculate these values one needs to multiply the respective product and feed streams by their respective prices. The major difficulty of this process is determining the prices that should be used in this formula. When analyzing a plant, not only do the current prices need to be acknowledged but also the stability of the market to forecast future fluctuations and deviations.
===Pricing Fundamentals===
The pricing of a substance is determined by the fundamental economic principles of supply and demand. A supply curve and demand curve can be graphed and added to determine the market equilibrium price and projected market size. There are many ways a company can combat if the market equilibrium pricing is not suitable for a process. One of these ways is changing the market that the company is selling to. Instead of selling industrial grade product there may be markets for pharmaceutical grade or food grade that would allow for a company to sell their product at higher margins. Another avenue to look into is changing the geographic market being sold to. Rarely is there a global synchronous market, but rather a variation depending on where in the world the product is being sold. It is possible that a company could make more money by dedicating their sales to the Asian market as opposed to the US or vise versa.
===Price Data Sources===
There are many resources when trying to determine the price of a chemical or utility. This are important for looking at current pricing information as well as historical data that can be used for forecasting purposes.
====Internal Company Forecasts====
Large companies will often have the marketing or development departments develop a forecasting database that can be used internally in the company. Forecasts of this magnitude will often have multiple scenarios and projects that are evaluated under the given parameters. Companies may even license these forecasts to other companies for high fees if they desire.

[[File:Capture.JPG]]

Table 1 provides common industry acronyms that are used to indicate certain key words when determining pricing information.

====Trade Journals====
There are also many publications that report pricing data weekly. ''ICIS Chemical Business Americas'' used to publish the prices for hundreds of chemicals but have more recently changed their data to an online database that requires a subscription. This service is very expensive, but necessary for many companies. ''Oil and Gas Journal'' publishes the market prices of many crude oils and other petrochemicals using data from several continents. This journal also provides margin data for many refineries and plants on a monthly basis. ''Chemical Week'' provides the spot and contract prices for 22 chemicals in the US and European markets.

====Consultants====
If trade journals are not adequate for the information needed, some companies will contract consultants to do deep research into the subject. Consultants are excellent resources for providing economic and marketing information but come at a large price. There are several companies that provide this type of service but some of the larger firms include: ''Purvin and Gertz'', ''Cambidge Energy Research Associates'', ''Chemical Markets Associates Inc.'', and ''SRI: The Chemical Economics Handbook''

====Online Brokers and Suppliers====
Often time price data can be supplied by the supplier themselves and using online directories. Restraint should be used when quoting these prices however because they are often spot prices that are much higher than what would be expected from bulk contract supplying.

==Example Case: Estimating Cost of Production==

Use the following information to estimate the manufacturing cost of a nitric acid plant producing 92,000 tonnes/year.

:Fixed Capital Investment: $11,000,000
:Raw Material Cost: $7,950,000/yr
:Waste Treatment Cost: $1,000,000/yr
:Utilities: $356,000/year
:Direct Labor Cost: $300,000/yr
:Fixed Costs: $1,500,000/yr

To find the manufacturing cost, multiply the value of the variable cost by the appropriate cost factor. In this case, we get,

<math>COM_d = (0.180)($11,000,000) + (2.73)($300,000) + (1.23($356,000 + $1,000,000 + $7,950,000) = $14,245,000/yr</math>

<math>($14,245,000/yr)/(92,000\ tonne/yr) = $155/tonne</math>

==References==
# Towler, G.P. and Sinnot, R. (2012). ''Chemical Engineering Design: Principles, Practice and Economics of Plant and Process Design.''Elsevier.
# Biegler, L.T., Grossmann, L.E., and Westerberg, A.W. (1997). ''Systematic Methods of Chemical Process Design.'' Upper Saddle River: Prentice-Hall.
# Peters, M.S. and Timmerhaus, K.D. (2003). ''Plant Design and Economics for Chemical Engineers, 5th Edition.'' New York: McGraw-Hill.
# Seider, W.D., Seader, J.D., and Lewin, D.R. (2004). ''Process Design Principles: Synthesis, Analysis, and Evaluation.'' New York: Wiley.
# Turton, R.T., Bailie, R.C., Whiting, W.B., and Shaewitz, J.A. (2003). ''Analysis, Synthesis, and Design of Chemical Processes'' Upper Saddle River: Prentice-Hall.

Estimation of production cost and revenue

2014-02-24T05:56:53Z

Karetstik: /* Fixed Cost of Production */

==Variable Cost of Production==
Variable costs of production are dependent primarily on plant output and rate of production. There are many variables to consider when costing a plant.
# Raw materials consumed
# Utilities-steam, electricity, cooling water, fuel, etc.
# Consumables - acids, bases, solvents, catalysts, etc.
# Disposal
# Shipping
The majority of the variable costs for a production plant are the raw materials and utilities costs. Variable costs can be greatly cut through optimization techniques and intelligent plant design [1].
===Raw Materials Cost===
Calculating the annual cost of a raw material is calculated by simply multiplying the feed rate of the process by the appropriate price per volume or mass. These are the costs of chemical feed stocks required by the process. Feed stocks flow rates are obtained from PFD [5].There are several ways to optimize this cost to ensure that a process is not costing more than it should. First one should assess the actual consumption of a plant to see if it is significantly different from what should be expected based on process stoichiometry and selectivities [1]. Finding may prove that a process is less efficient than it originally claimed.
It is smart to benchmark a new plant design against an existing plant or pilot plant. Raw materials are typically the largest contributor to overall variable costs. For bulk chemicals and petrochemicals, raw materials represent 80-90% of the total cash cost of production (CCOP).
===Utilities Cost===
These are the costs of the various utilities streams required by the process. The flowrates for the utilities streams are located on the PFD [5]. This includes:
*Fuel gas, oil, or coal
*Electric power
*Steam
*Cooling water
*Process water
*Boiler feed water
*Air
*Inert gas
*Refrigeration

Utility streams are excellent ways to streamline a process and are often indicative of how efficient of a process the project is. Process methods such as steam generation and pinch analysis can be used to greatly reduce utility costs across a plant. Further analysis of pinch analysis techniques and optimizing heat exchanger networks can be found in plant design texts such as first reference from Gavin Towler. The determination of process utility costs is often more difficult than the determination of raw material costs; however, the utilities are typically between 5-10% of CCOP [1]. The cost of heating a process can be reduced by using process waste streams as fuel which consequently also reduces the need for waste disposal.

===Waste Disposal Costs===
These are defined as the cost of waste treatment to protect the environment [5]. These are materials that cannot be recycled or sold off as by-products. Often times these streams require additives or additional treatment to meet governmental regulations.
Hydrocarbon waste can often be incinerated directly to the atmosphere or used as process fuel to heat other streams in the system. Using the stream as process fuel allows the fuel value of the stream to be recovered into the system. The substituted value can be calculated by multiplying the conventional fuel price by the heat of combustion of the waste stream.

<math>P_{WFV} = P_F * \Delta H_C^o</math>

where
<math>P_{WFV}</math> = waste value of fuel ($/lb or $/kg)

<math>P_F</math> = price of fuel ($/MMBtu or $/GJ)

<math>\Delta H_C^o</math> = heat of combustion (MMBtu/lb or GJ/kg)

Dilute aqueous streams must be sent to wastewater treatment typically prior to purging from the plant. Acidic or basic wastes are neutralized prior to treatment by salting out the acid or base. The cost of wastewater treatment is typically about $6 per 1000 gal but this is only an estimate that doesn't account for regional charges [1].

Solid waste treatment can typically be sent to a landfill at a cost of approximately $50/ton [1].

Hazardous wastes arise from the production of concentrated liquid streams that cannot be incinerated. Hazardous wastes should be avoided if possible, but that is not always feasible for some processes. The cost of hazardous waste disposal is strongly dependent on the location of the plant, the plants proximity to waste disposal plants and the degree of hazard of the waste.

==Fixed Cost of Production==
Fixed costs are those whose amounts are independent of production rates. Much of these costs are personnel salaries, taxes, insurance, and legal payments.
===Labor Costs===
These are the costs attributed to the personnel required to operate the process plant [5].

The number of operators required per shift, <math>N_{OL}</math> can be estimated by

<math>N_{OL}=(6.29+31.7P^2+0.23N_{np})^{0.5}</math>

where <math>P</math> is the number of processing steps involving particulate solids and <math>N_{np}</math> is the number of other processing steps[5]. For each of the <math>N_{OL}</math> operators per 8-hour shift, approximately 4.5 operators must be hired for a plant that runs 24 hours per day, to account for the 3 shifts per day and the 3 weeks of leave typically taken by each operator per year[5]. The salary for a chemical plant operator varies by location, and the estimator should look up the average value for the area.

===Maintenance Costs===
These are the costs associated with labor and materials necessary to maintain plant production. An estimate of these are 6% of the fixed capital investment[5].

===Research and Development===
These are the costs of research done in developing the process and/or products. This includes salaries for researchers as well as funds for research related equipment and supplies. An estimate of these costs are 5% of the total manufacturing cost[5].

===Taxes and Insurance===
Taxes vary by location, but a first estimate of taxes and insurance is 3% of the fixed capital investment[5].

===Plant Overhead===
Overhead costs are the miscellaneous but necessary costs of running a business, including payroll, employee benefits, and janitorial services. This may be estimated as 70% of the operating labor costs, added to 4% of the fixed capital costs[5].

===Licensing and Royalties===
The costs of paying for the use of intellectual property clearly varies, but an estimate that may be used is 3% of the total manufacturing cost[5].

==Revenues==
The revenues of a process are the income earned form sales of the main products and the by-products. Revenue can be impacted by market fluctuations and production rates.
===By-Product Revenues===
Besides selling the main product from a process, by-products from separations and reactions can also be valuable in the market. Often it is more difficult to decide which by-products to recover and purify than it is to make decisions on the main product.

By-products made in stoichiometric ratios from reactions must be either sold off or managed through waste disposal. Other by-products are sometimes produced through feed impurities or by nonselective reactions. There are several potential valuable by-products from a process:
# Materials produced in stoichiometric quantities by the reactions that create the main product. If they are not recovered then the waste disposal expenses will be large.
# Components that are produced in high yield by side reactions.
# Components formed in high yield from feed impurities. Many sulfurs are produced as a by-product of fuels manufacture.
# Components that are produced in low yield but have high value. An example includes acetophenone which is recovered as a by-product of phenol manufacture.
# Degraded consumables (e.g. solvents, etc.) that have reuse value.

A rule of thumb that can be used for preliminary screening of by-products for large plants is that for by-product recovery to be economically feasible the net benefit must be greater than $200,000 a year. A net benefit can be calculated by adding the possible resale value of the by-product and the avoided waste disposal cost [1].

===Margin===
The gross margin of a process is defined as the sum of product and by-product revenues minus the raw material cost.

Gross margin = Revenues - Raw materials costs

Because raw materials are most often the most expensive variable cost of a process, the gross margin is a good gauge as to what the total profitability of a process will be. Raw materials and product pricing are often subject to high degrees of variability which can be difficult to forecast. The size of margins are highly versatile depending on the
industry. For many petrochemical industries the margin may be only 10%; however, for industries such as food additives and pharmaceuticals the margins are generally much higher [1].

===Profits===
There are several standards for calculating company profits. The cash cost of production (CCOP) is the sum of the fixed and variable production costs.

''CCOP = VCOP + FCOP''

where VCOP is the variable cost of production and FCOP is the fixed cost of production.

Gross profit, which should not be confused with gross margin, is then calculated by the following equation,

''Gross profit = Main product revenues - CCOP''

Finally profit can be calculated by subtracting the income taxes that the plant would be subject to depending on the tax code of the county the plant is located in.

''Net profit = gross profit - taxes''

==Pricing Products and Raw Materials==
The revenues and costs of a project are vital to determining its economic feasibility. To calculate these values one needs to multiply the respective product and feed streams by their respective prices. The major difficulty of this process is determining the prices that should be used in this formula. When analyzing a plant, not only do the current prices need to be acknowledged but also the stability of the market to forecast future fluctuations and deviations.
===Pricing Fundamentals===
The pricing of a substance is determined by the fundamental economic principles of supply and demand. A supply curve and demand curve can be graphed and added to determine the market equilibrium price and projected market size. There are many ways a company can combat if the market equilibrium pricing is not suitable for a process. One of these ways is changing the market that the company is selling to. Instead of selling industrial grade product there may be markets for pharmaceutical grade or food grade that would allow for a company to sell their product at higher margins. Another avenue to look into is changing the geographic market being sold to. Rarely is there a global synchronous market, but rather a variation depending on where in the world the product is being sold. It is possible that a company could make more money by dedicating their sales to the Asian market as opposed to the US or vise versa.
===Price Data Sources===
There are many resources when trying to determine the price of a chemical or utility. This are important for looking at current pricing information as well as historical data that can be used for forecasting purposes.
====Internal Company Forecasts====
Large companies will often have the marketing or development departments develop a forecasting database that can be used internally in the company. Forecasts of this magnitude will often have multiple scenarios and projects that are evaluated under the given parameters. Companies may even license these forecasts to other companies for high fees if they desire.

[[File:Capture.JPG]]

Table 1 provides common industry acronyms that are used to indicate certain key words when determining pricing information.

====Trade Journals====
There are also many publications that report pricing data weekly. ''ICIS Chemical Business Americas'' used to publish the prices for hundreds of chemicals but have more recently changed their data to an online database that requires a subscription. This service is very expensive, but necessary for many companies. ''Oil and Gas Journal'' publishes the market prices of many crude oils and other petrochemicals using data from several continents. This journal also provides margin data for many refineries and plants on a monthly basis. ''Chemical Week'' provides the spot and contract prices for 22 chemicals in the US and European markets.

====Consultants====
If trade journals are not adequate for the information needed, some companies will contract consultants to do deep research into the subject. Consultants are excellent resources for providing economic and marketing information but come at a large price. There are several companies that provide this type of service but some of the larger firms include: ''Purvin and Gertz'', ''Cambidge Energy Research Associates'', ''Chemical Markets Associates Inc.'', and ''SRI: The Chemical Economics Handbook''

====Online Brokers and Suppliers====
Often time price data can be supplied by the supplier themselves and using online directories. Restraint should be used when quoting these prices however because they are often spot prices that are much higher than what would be expected from bulk contract supplying.

==Example Case: Estimating Cost of Production==

Use the following information to estimate the manufacturing cost of a nitric acid plant producing 92,000 tonnes/year.

:Fixed Capital Investment: $11,000,000
:Raw Material Cost: $7,950,000/yr
:Waste Treatment Cost: $1,000,000/yr
:Utilities: $356,000/year
:Direct Labor Cost: $300,000/yr
:Fixed Costs: $1,500,000/yr

To find the manufacturing cost, multiply the value of the variable cost by the appropriate cost factor. In this case, we get,

<math>COM_d = (0.180)($11,000,000) + (2.73)($300,000) + (1.23($356,000 + $1,000,000 + $7,950,000) = $14,245,000/yr</math>

<math>($14,245,000/yr)/(92,000\ tonne/yr) = $155/tonne</math>

==References==
# Towler, G.P. and Sinnot, R. (2012). ''Chemical Engineering Design: Principles, Practice and Economics of Plant and Process Design.''Elsevier.
# Biegler, L.T., Grossmann, L.E., and Westerberg, A.W. (1997). ''Systematic Methods of Chemical Process Design.'' Upper Saddle River: Prentice-Hall.
# Peters, M.S. and Timmerhaus, K.D. (2003). ''Plant Design and Economics for Chemical Engineers, 5th Edition.'' New York: McGraw-Hill.
# Seider, W.D., Seader, J.D., and Lewin, D.R. (2004). ''Process Design Principles: Synthesis, Analysis, and Evaluation.'' New York: Wiley.
# Turton, R.T., Bailie, R.C., Whiting, W.B., and Shaewitz, J.A. (2003). ''Analysis, Synthesis, and Design of Chemical Processes'' Upper Saddle River: Prentice-Hall.

Estimation of production cost and revenue

2014-02-24T05:56:14Z

Karetstik: /* Fixed Cost of Production */

==Variable Cost of Production==
Variable costs of production are dependent primarily on plant output and rate of production. There are many variables to consider when costing a plant.
# Raw materials consumed
# Utilities-steam, electricity, cooling water, fuel, etc.
# Consumables - acids, bases, solvents, catalysts, etc.
# Disposal
# Shipping
The majority of the variable costs for a production plant are the raw materials and utilities costs. Variable costs can be greatly cut through optimization techniques and intelligent plant design [1].
===Raw Materials Cost===
Calculating the annual cost of a raw material is calculated by simply multiplying the feed rate of the process by the appropriate price per volume or mass. These are the costs of chemical feed stocks required by the process. Feed stocks flow rates are obtained from PFD [5].There are several ways to optimize this cost to ensure that a process is not costing more than it should. First one should assess the actual consumption of a plant to see if it is significantly different from what should be expected based on process stoichiometry and selectivities [1]. Finding may prove that a process is less efficient than it originally claimed.
It is smart to benchmark a new plant design against an existing plant or pilot plant. Raw materials are typically the largest contributor to overall variable costs. For bulk chemicals and petrochemicals, raw materials represent 80-90% of the total cash cost of production (CCOP).
===Utilities Cost===
These are the costs of the various utilities streams required by the process. The flowrates for the utilities streams are located on the PFD [5]. This includes:
*Fuel gas, oil, or coal
*Electric power
*Steam
*Cooling water
*Process water
*Boiler feed water
*Air
*Inert gas
*Refrigeration

Utility streams are excellent ways to streamline a process and are often indicative of how efficient of a process the project is. Process methods such as steam generation and pinch analysis can be used to greatly reduce utility costs across a plant. Further analysis of pinch analysis techniques and optimizing heat exchanger networks can be found in plant design texts such as first reference from Gavin Towler. The determination of process utility costs is often more difficult than the determination of raw material costs; however, the utilities are typically between 5-10% of CCOP [1]. The cost of heating a process can be reduced by using process waste streams as fuel which consequently also reduces the need for waste disposal.

===Waste Disposal Costs===
These are defined as the cost of waste treatment to protect the environment [5]. These are materials that cannot be recycled or sold off as by-products. Often times these streams require additives or additional treatment to meet governmental regulations.
Hydrocarbon waste can often be incinerated directly to the atmosphere or used as process fuel to heat other streams in the system. Using the stream as process fuel allows the fuel value of the stream to be recovered into the system. The substituted value can be calculated by multiplying the conventional fuel price by the heat of combustion of the waste stream.

<math>P_{WFV} = P_F * \Delta H_C^o</math>

where
<math>P_{WFV}</math> = waste value of fuel ($/lb or $/kg)

<math>P_F</math> = price of fuel ($/MMBtu or $/GJ)

<math>\Delta H_C^o</math> = heat of combustion (MMBtu/lb or GJ/kg)

Dilute aqueous streams must be sent to wastewater treatment typically prior to purging from the plant. Acidic or basic wastes are neutralized prior to treatment by salting out the acid or base. The cost of wastewater treatment is typically about $6 per 1000 gal but this is only an estimate that doesn't account for regional charges [1].

Solid waste treatment can typically be sent to a landfill at a cost of approximately $50/ton [1].

Hazardous wastes arise from the production of concentrated liquid streams that cannot be incinerated. Hazardous wastes should be avoided if possible, but that is not always feasible for some processes. The cost of hazardous waste disposal is strongly dependent on the location of the plant, the plants proximity to waste disposal plants and the degree of hazard of the waste.

==Fixed Cost of Production==
Fixed costs are those whose amounts are independent of production rates. Much of these costs are personnel salaries, taxes, insurance, and legal payments.
===Labor Costs===
These are the costs attributed to the personnel required to operate the process plant [5].

The number of operators required per shift, <math>N_{OL}</math> can be estimated by

<math>N_{OL}=(6.29+31.7P^2+0.23N_{np})^{0.5}</math>

where <math>P</math> is the number of processing steps involving particulate solids and <math>N_{np}</math> is the number of other processing steps.[5] For each of the <math>N_{OL}</math> operators per 8-hour shift, approximately 4.5 operators must be hired for a plant that runs 24 hours per day, to account for the 3 shifts per day and the 3 weeks of leave typically taken by each operator per year.[5] The salary for a chemical plant operator varies by location, and the estimator should look up the average value for the area.

===Maintenance Costs===
These are the costs associated with labor and materials necessary to maintain plant production. An estimate of these are 6% of the fixed capital investment.[5]

===Research and Development===
These are the costs of research done in developing the process and/or products. This includes salaries for researchers as well as funds for research related equipment and supplies. An estimate of these costs are 5% of the total manufacturing cost.[5]

===Taxes and Insurance===
Taxes vary by location, but a first estimate of taxes and insurance is 3% of the fixed capital investment.[5]

===Plant Overhead===
Overhead costs are the miscellaneous but necessary costs of running a business, including payroll, employee benefits, and janitorial services. This may be estimated as 70% of the operating labor costs, added to 4% of the fixed capital costs.[5]

===Licensing and Royalties===
The costs of paying for the use of intellectual property clearly varies, but an estimate that may be used is 3% of the total manufacturing cost.[5]

==Revenues==
The revenues of a process are the income earned form sales of the main products and the by-products. Revenue can be impacted by market fluctuations and production rates.
===By-Product Revenues===
Besides selling the main product from a process, by-products from separations and reactions can also be valuable in the market. Often it is more difficult to decide which by-products to recover and purify than it is to make decisions on the main product.

By-products made in stoichiometric ratios from reactions must be either sold off or managed through waste disposal. Other by-products are sometimes produced through feed impurities or by nonselective reactions. There are several potential valuable by-products from a process:
# Materials produced in stoichiometric quantities by the reactions that create the main product. If they are not recovered then the waste disposal expenses will be large.
# Components that are produced in high yield by side reactions.
# Components formed in high yield from feed impurities. Many sulfurs are produced as a by-product of fuels manufacture.
# Components that are produced in low yield but have high value. An example includes acetophenone which is recovered as a by-product of phenol manufacture.
# Degraded consumables (e.g. solvents, etc.) that have reuse value.

A rule of thumb that can be used for preliminary screening of by-products for large plants is that for by-product recovery to be economically feasible the net benefit must be greater than $200,000 a year. A net benefit can be calculated by adding the possible resale value of the by-product and the avoided waste disposal cost [1].

===Margin===
The gross margin of a process is defined as the sum of product and by-product revenues minus the raw material cost.

Gross margin = Revenues - Raw materials costs

Because raw materials are most often the most expensive variable cost of a process, the gross margin is a good gauge as to what the total profitability of a process will be. Raw materials and product pricing are often subject to high degrees of variability which can be difficult to forecast. The size of margins are highly versatile depending on the
industry. For many petrochemical industries the margin may be only 10%; however, for industries such as food additives and pharmaceuticals the margins are generally much higher [1].

===Profits===
There are several standards for calculating company profits. The cash cost of production (CCOP) is the sum of the fixed and variable production costs.

''CCOP = VCOP + FCOP''

where VCOP is the variable cost of production and FCOP is the fixed cost of production.

Gross profit, which should not be confused with gross margin, is then calculated by the following equation,

''Gross profit = Main product revenues - CCOP''

Finally profit can be calculated by subtracting the income taxes that the plant would be subject to depending on the tax code of the county the plant is located in.

''Net profit = gross profit - taxes''

==Pricing Products and Raw Materials==
The revenues and costs of a project are vital to determining its economic feasibility. To calculate these values one needs to multiply the respective product and feed streams by their respective prices. The major difficulty of this process is determining the prices that should be used in this formula. When analyzing a plant, not only do the current prices need to be acknowledged but also the stability of the market to forecast future fluctuations and deviations.
===Pricing Fundamentals===
The pricing of a substance is determined by the fundamental economic principles of supply and demand. A supply curve and demand curve can be graphed and added to determine the market equilibrium price and projected market size. There are many ways a company can combat if the market equilibrium pricing is not suitable for a process. One of these ways is changing the market that the company is selling to. Instead of selling industrial grade product there may be markets for pharmaceutical grade or food grade that would allow for a company to sell their product at higher margins. Another avenue to look into is changing the geographic market being sold to. Rarely is there a global synchronous market, but rather a variation depending on where in the world the product is being sold. It is possible that a company could make more money by dedicating their sales to the Asian market as opposed to the US or vise versa.
===Price Data Sources===
There are many resources when trying to determine the price of a chemical or utility. This are important for looking at current pricing information as well as historical data that can be used for forecasting purposes.
====Internal Company Forecasts====
Large companies will often have the marketing or development departments develop a forecasting database that can be used internally in the company. Forecasts of this magnitude will often have multiple scenarios and projects that are evaluated under the given parameters. Companies may even license these forecasts to other companies for high fees if they desire.

[[File:Capture.JPG]]

Table 1 provides common industry acronyms that are used to indicate certain key words when determining pricing information.

====Trade Journals====
There are also many publications that report pricing data weekly. ''ICIS Chemical Business Americas'' used to publish the prices for hundreds of chemicals but have more recently changed their data to an online database that requires a subscription. This service is very expensive, but necessary for many companies. ''Oil and Gas Journal'' publishes the market prices of many crude oils and other petrochemicals using data from several continents. This journal also provides margin data for many refineries and plants on a monthly basis. ''Chemical Week'' provides the spot and contract prices for 22 chemicals in the US and European markets.

====Consultants====
If trade journals are not adequate for the information needed, some companies will contract consultants to do deep research into the subject. Consultants are excellent resources for providing economic and marketing information but come at a large price. There are several companies that provide this type of service but some of the larger firms include: ''Purvin and Gertz'', ''Cambidge Energy Research Associates'', ''Chemical Markets Associates Inc.'', and ''SRI: The Chemical Economics Handbook''

====Online Brokers and Suppliers====
Often time price data can be supplied by the supplier themselves and using online directories. Restraint should be used when quoting these prices however because they are often spot prices that are much higher than what would be expected from bulk contract supplying.

==Example Case: Estimating Cost of Production==

Use the following information to estimate the manufacturing cost of a nitric acid plant producing 92,000 tonnes/year.

:Fixed Capital Investment: $11,000,000
:Raw Material Cost: $7,950,000/yr
:Waste Treatment Cost: $1,000,000/yr
:Utilities: $356,000/year
:Direct Labor Cost: $300,000/yr
:Fixed Costs: $1,500,000/yr

To find the manufacturing cost, multiply the value of the variable cost by the appropriate cost factor. In this case, we get,

<math>COM_d = (0.180)($11,000,000) + (2.73)($300,000) + (1.23($356,000 + $1,000,000 + $7,950,000) = $14,245,000/yr</math>

<math>($14,245,000/yr)/(92,000\ tonne/yr) = $155/tonne</math>

==References==
# Towler, G.P. and Sinnot, R. (2012). ''Chemical Engineering Design: Principles, Practice and Economics of Plant and Process Design.''Elsevier.
# Biegler, L.T., Grossmann, L.E., and Westerberg, A.W. (1997). ''Systematic Methods of Chemical Process Design.'' Upper Saddle River: Prentice-Hall.
# Peters, M.S. and Timmerhaus, K.D. (2003). ''Plant Design and Economics for Chemical Engineers, 5th Edition.'' New York: McGraw-Hill.
# Seider, W.D., Seader, J.D., and Lewin, D.R. (2004). ''Process Design Principles: Synthesis, Analysis, and Evaluation.'' New York: Wiley.
# Turton, R.T., Bailie, R.C., Whiting, W.B., and Shaewitz, J.A. (2003). ''Analysis, Synthesis, and Design of Chemical Processes'' Upper Saddle River: Prentice-Hall.

Estimation of production cost and revenue

2014-02-24T05:35:20Z

Karetstik: /* Labor Costs */

==Variable Cost of Production==
Variable costs of production are dependent primarily on plant output and rate of production. There are many variables to consider when costing a plant.
# Raw materials consumed
# Utilities-steam, electricity, cooling water, fuel, etc.
# Consumables - acids, bases, solvents, catalysts, etc.
# Disposal
# Shipping
The majority of the variable costs for a production plant are the raw materials and utilities costs. Variable costs can be greatly cut through optimization techniques and intelligent plant design [1].
===Raw Materials Cost===
Calculating the annual cost of a raw material is calculated by simply multiplying the feed rate of the process by the appropriate price per volume or mass. These are the costs of chemical feed stocks required by the process. Feed stocks flow rates are obtained from PFD [5].There are several ways to optimize this cost to ensure that a process is not costing more than it should. First one should assess the actual consumption of a plant to see if it is significantly different from what should be expected based on process stoichiometry and selectivities [1]. Finding may prove that a process is less efficient than it originally claimed.
It is smart to benchmark a new plant design against an existing plant or pilot plant. Raw materials are typically the largest contributor to overall variable costs. For bulk chemicals and petrochemicals, raw materials represent 80-90% of the total cash cost of production (CCOP).
===Utilities Cost===
These are the costs of the various utilities streams required by the process. The flowrates for the utilities streams are located on the PFD [5]. This includes:
*Fuel gas, oil, or coal
*Electric power
*Steam
*Cooling water
*Process water
*Boiler feed water
*Air
*Inert gas
*Refrigeration

Utility streams are excellent ways to streamline a process and are often indicative of how efficient of a process the project is. Process methods such as steam generation and pinch analysis can be used to greatly reduce utility costs across a plant. Further analysis of pinch analysis techniques and optimizing heat exchanger networks can be found in plant design texts such as first reference from Gavin Towler. The determination of process utility costs is often more difficult than the determination of raw material costs; however, the utilities are typically between 5-10% of CCOP [1]. The cost of heating a process can be reduced by using process waste streams as fuel which consequently also reduces the need for waste disposal.

===Waste Disposal Costs===
These are defined as the cost of waste treatment to protect the environment [5]. These are materials that cannot be recycled or sold off as by-products. Often times these streams require additives or additional treatment to meet governmental regulations.
Hydrocarbon waste can often be incinerated directly to the atmosphere or used as process fuel to heat other streams in the system. Using the stream as process fuel allows the fuel value of the stream to be recovered into the system. The substituted value can be calculated by multiplying the conventional fuel price by the heat of combustion of the waste stream.

<math>P_{WFV} = P_F * \Delta H_C^o</math>

where
<math>P_{WFV}</math> = waste value of fuel ($/lb or $/kg)

<math>P_F</math> = price of fuel ($/MMBtu or $/GJ)

<math>\Delta H_C^o</math> = heat of combustion (MMBtu/lb or GJ/kg)

Dilute aqueous streams must be sent to wastewater treatment typically prior to purging from the plant. Acidic or basic wastes are neutralized prior to treatment by salting out the acid or base. The cost of wastewater treatment is typically about $6 per 1000 gal but this is only an estimate that doesn't account for regional charges [1].

Solid waste treatment can typically be sent to a landfill at a cost of approximately $50/ton [1].

Hazardous wastes arise from the production of concentrated liquid streams that cannot be incinerated. Hazardous wastes should be avoided if possible, but that is not always feasible for some processes. The cost of hazardous waste disposal is strongly dependent on the location of the plant, the plants proximity to waste disposal plants and the degree of hazard of the waste.

==Fixed Cost of Production==
Fixed costs are those whose amounts are independent of production rates. Much of these costs are personnel salaries, rent, taxes, insurance, and legal payments.
===Labor Costs===
These are the costs attributed to the personnel required to operate the process plant [5].

The number of operators required per shift, <math>N_{OL}</math> can be calculated by

<math>N_{OL}=(6.29+31.7P^2+0.23N_{np})^{0.5}</math>

where <math>P</math> is the number of processing steps involving particulate solids and <math>N_{np}</math> is the number of other processing steps.[5] For each of the <math>N_{OL}</math> operators per 8-hour shift, approximately 4.5 operators must be hired for a plant that runs 24 hours per day, to account for the 3 shifts per day and the 3 weeks of leave typically taken by each operator per year.[5] The salary for a chemical plant operator varies by location, and the estimator should look up the average value for the area.

===Maintenance Costs===
Part of these costs are associated with labor and materials necessary to maintain plant production [5].

===Research and Development===
These are the costs of research done in developing the process and/or products. This includes salaries for researchers as well as funds for research related equipment and supplies [5].

===Land, Rent, Taxes===
===Insurance===
===Interest Payments===
===Corporate Overhead===
===Licensing and Royalties===

==Revenues==
The revenues of a process are the income earned form sales of the main products and the by-products. Revenue can be impacted by market fluctuations and production rates.
===By-Product Revenues===
Besides selling the main product from a process, by-products from separations and reactions can also be valuable in the market. Often it is more difficult to decide which by-products to recover and purify than it is to make decisions on the main product.

By-products made in stoichiometric ratios from reactions must be either sold off or managed through waste disposal. Other by-products are sometimes produced through feed impurities or by nonselective reactions. There are several potential valuable by-products from a process:
# Materials produced in stoichiometric quantities by the reactions that create the main product. If they are not recovered then the waste disposal expenses will be large.
# Components that are produced in high yield by side reactions.
# Components formed in high yield from feed impurities. Many sulfurs are produced as a by-product of fuels manufacture.
# Components that are produced in low yield but have high value. An example includes acetophenone which is recovered as a by-product of phenol manufacture.
# Degraded consumables (e.g. solvents, etc.) that have reuse value.

A rule of thumb that can be used for preliminary screening of by-products for large plants is that for by-product recovery to be economically feasible the net benefit must be greater than $200,000 a year. A net benefit can be calculated by adding the possible resale value of the by-product and the avoided waste disposal cost [1].

===Margin===
The gross margin of a process is defined as the sum of product and by-product revenues minus the raw material cost.

Gross margin = Revenues - Raw materials costs

Because raw materials are most often the most expensive variable cost of a process, the gross margin is a good gauge as to what the total profitability of a process will be. Raw materials and product pricing are often subject to high degrees of variability which can be difficult to forecast. The size of margins are highly versatile depending on the
industry. For many petrochemical industries the margin may be only 10%; however, for industries such as food additives and pharmaceuticals the margins are generally much higher [1].

===Profits===
There are several standards for calculating company profits. The cash cost of production (CCOP) is the sum of the fixed and variable production costs.

''CCOP = VCOP + FCOP''

where VCOP is the variable cost of production and FCOP is the fixed cost of production.

Gross profit, which should not be confused with gross margin, is then calculated by the following equation,

''Gross profit = Main product revenues - CCOP''

Finally profit can be calculated by subtracting the income taxes that the plant would be subject to depending on the tax code of the county the plant is located in.

''Net profit = gross profit - taxes''

==Pricing Products and Raw Materials==
The revenues and costs of a project are vital to determining its economic feasibility. To calculate these values one needs to multiply the respective product and feed streams by their respective prices. The major difficulty of this process is determining the prices that should be used in this formula. When analyzing a plant, not only do the current prices need to be acknowledged but also the stability of the market to forecast future fluctuations and deviations.
===Pricing Fundamentals===
The pricing of a substance is determined by the fundamental economic principles of supply and demand. A supply curve and demand curve can be graphed and added to determine the market equilibrium price and projected market size. There are many ways a company can combat if the market equilibrium pricing is not suitable for a process. One of these ways is changing the market that the company is selling to. Instead of selling industrial grade product there may be markets for pharmaceutical grade or food grade that would allow for a company to sell their product at higher margins. Another avenue to look into is changing the geographic market being sold to. Rarely is there a global synchronous market, but rather a variation depending on where in the world the product is being sold. It is possible that a company could make more money by dedicating their sales to the Asian market as opposed to the US or vise versa.
===Price Data Sources===
There are many resources when trying to determine the price of a chemical or utility. This are important for looking at current pricing information as well as historical data that can be used for forecasting purposes.
====Internal Company Forecasts====
Large companies will often have the marketing or development departments develop a forecasting database that can be used internally in the company. Forecasts of this magnitude will often have multiple scenarios and projects that are evaluated under the given parameters. Companies may even license these forecasts to other companies for high fees if they desire.

[[File:Capture.JPG]]

Table 1 provides common industry acronyms that are used to indicate certain key words when determining pricing information.

====Trade Journals====
There are also many publications that report pricing data weekly. ''ICIS Chemical Business Americas'' used to publish the prices for hundreds of chemicals but have more recently changed their data to an online database that requires a subscription. This service is very expensive, but necessary for many companies. ''Oil and Gas Journal'' publishes the market prices of many crude oils and other petrochemicals using data from several continents. This journal also provides margin data for many refineries and plants on a monthly basis. ''Chemical Week'' provides the spot and contract prices for 22 chemicals in the US and European markets.

====Consultants====
If trade journals are not adequate for the information needed, some companies will contract consultants to do deep research into the subject. Consultants are excellent resources for providing economic and marketing information but come at a large price. There are several companies that provide this type of service but some of the larger firms include: ''Purvin and Gertz'', ''Cambidge Energy Research Associates'', ''Chemical Markets Associates Inc.'', and ''SRI: The Chemical Economics Handbook''

====Online Brokers and Suppliers====
Often time price data can be supplied by the supplier themselves and using online directories. Restraint should be used when quoting these prices however because they are often spot prices that are much higher than what would be expected from bulk contract supplying.

==References==
# Towler, G.P. and Sinnot, R. (2012). ''Chemical Engineering Design: Principles, Practice and Economics of Plant and Process Design.''Elsevier.
# Biegler, L.T., Grossmann, L.E., and Westerberg, A.W. (1997). ''Systematic Methods of Chemical Process Design.'' Upper Saddle River: Prentice-Hall.
# Peters, M.S. and Timmerhaus, K.D. (2003). ''Plant Design and Economics for Chemical Engineers, 5th Edition.'' New York: McGraw-Hill.
# Seider, W.D., Seader, J.D., and Lewin, D.R. (2004). ''Process Design Principles: Synthesis, Analysis, and Evaluation.'' New York: Wiley.
# Turton, R.T., Bailie, R.C., Whiting, W.B., and Shaewitz, J.A. (2003). ''Analysis, Synthesis, and Design of Chemical Processes'' Upper Saddle River: Prentice-Hall.

Estimation of production cost and revenue

2014-02-24T05:34:53Z

Karetstik: /* Fixed Cost of Production */

==Variable Cost of Production==
Variable costs of production are dependent primarily on plant output and rate of production. There are many variables to consider when costing a plant.
# Raw materials consumed
# Utilities-steam, electricity, cooling water, fuel, etc.
# Consumables - acids, bases, solvents, catalysts, etc.
# Disposal
# Shipping
The majority of the variable costs for a production plant are the raw materials and utilities costs. Variable costs can be greatly cut through optimization techniques and intelligent plant design [1].
===Raw Materials Cost===
Calculating the annual cost of a raw material is calculated by simply multiplying the feed rate of the process by the appropriate price per volume or mass. These are the costs of chemical feed stocks required by the process. Feed stocks flow rates are obtained from PFD [5].There are several ways to optimize this cost to ensure that a process is not costing more than it should. First one should assess the actual consumption of a plant to see if it is significantly different from what should be expected based on process stoichiometry and selectivities [1]. Finding may prove that a process is less efficient than it originally claimed.
It is smart to benchmark a new plant design against an existing plant or pilot plant. Raw materials are typically the largest contributor to overall variable costs. For bulk chemicals and petrochemicals, raw materials represent 80-90% of the total cash cost of production (CCOP).
===Utilities Cost===
These are the costs of the various utilities streams required by the process. The flowrates for the utilities streams are located on the PFD [5]. This includes:
*Fuel gas, oil, or coal
*Electric power
*Steam
*Cooling water
*Process water
*Boiler feed water
*Air
*Inert gas
*Refrigeration

Utility streams are excellent ways to streamline a process and are often indicative of how efficient of a process the project is. Process methods such as steam generation and pinch analysis can be used to greatly reduce utility costs across a plant. Further analysis of pinch analysis techniques and optimizing heat exchanger networks can be found in plant design texts such as first reference from Gavin Towler. The determination of process utility costs is often more difficult than the determination of raw material costs; however, the utilities are typically between 5-10% of CCOP [1]. The cost of heating a process can be reduced by using process waste streams as fuel which consequently also reduces the need for waste disposal.

===Waste Disposal Costs===
These are defined as the cost of waste treatment to protect the environment [5]. These are materials that cannot be recycled or sold off as by-products. Often times these streams require additives or additional treatment to meet governmental regulations.
Hydrocarbon waste can often be incinerated directly to the atmosphere or used as process fuel to heat other streams in the system. Using the stream as process fuel allows the fuel value of the stream to be recovered into the system. The substituted value can be calculated by multiplying the conventional fuel price by the heat of combustion of the waste stream.

<math>P_{WFV} = P_F * \Delta H_C^o</math>

where
<math>P_{WFV}</math> = waste value of fuel ($/lb or $/kg)

<math>P_F</math> = price of fuel ($/MMBtu or $/GJ)

<math>\Delta H_C^o</math> = heat of combustion (MMBtu/lb or GJ/kg)

Dilute aqueous streams must be sent to wastewater treatment typically prior to purging from the plant. Acidic or basic wastes are neutralized prior to treatment by salting out the acid or base. The cost of wastewater treatment is typically about $6 per 1000 gal but this is only an estimate that doesn't account for regional charges [1].

Solid waste treatment can typically be sent to a landfill at a cost of approximately $50/ton [1].

Hazardous wastes arise from the production of concentrated liquid streams that cannot be incinerated. Hazardous wastes should be avoided if possible, but that is not always feasible for some processes. The cost of hazardous waste disposal is strongly dependent on the location of the plant, the plants proximity to waste disposal plants and the degree of hazard of the waste.

==Fixed Cost of Production==
Fixed costs are those whose amounts are independent of production rates. Much of these costs are personnel salaries, rent, taxes, insurance, and legal payments.
===Labor Costs===
These are the costs attributed to the personnel required to operate the process plant [5].

The number of operators required per shift, <math>N_{OL}</math> can be calculated by

<math>N_{OL}=(6.29+31.7*P^2+0.23*N_{np})^0.5</math>

where <math>P</math> is the number of processing steps involving particulate solids and <math>N_{np}</math> is the number of other processing steps.[5] For each of the <math>N_{OL}</math> operators per 8-hour shift, approximately 4.5 operators must be hired for a plant that runs 24 hours per day, to account for the 3 shifts per day and the 3 weeks of leave typically taken by each operator per year.[5] The salary for a chemical plant operator varies by location, and the estimator should look up the average value for the area.

===Maintenance Costs===
Part of these costs are associated with labor and materials necessary to maintain plant production [5].

===Research and Development===
These are the costs of research done in developing the process and/or products. This includes salaries for researchers as well as funds for research related equipment and supplies [5].

===Land, Rent, Taxes===
===Insurance===
===Interest Payments===
===Corporate Overhead===
===Licensing and Royalties===

==Revenues==
The revenues of a process are the income earned form sales of the main products and the by-products. Revenue can be impacted by market fluctuations and production rates.
===By-Product Revenues===
Besides selling the main product from a process, by-products from separations and reactions can also be valuable in the market. Often it is more difficult to decide which by-products to recover and purify than it is to make decisions on the main product.

By-products made in stoichiometric ratios from reactions must be either sold off or managed through waste disposal. Other by-products are sometimes produced through feed impurities or by nonselective reactions. There are several potential valuable by-products from a process:
# Materials produced in stoichiometric quantities by the reactions that create the main product. If they are not recovered then the waste disposal expenses will be large.
# Components that are produced in high yield by side reactions.
# Components formed in high yield from feed impurities. Many sulfurs are produced as a by-product of fuels manufacture.
# Components that are produced in low yield but have high value. An example includes acetophenone which is recovered as a by-product of phenol manufacture.
# Degraded consumables (e.g. solvents, etc.) that have reuse value.

A rule of thumb that can be used for preliminary screening of by-products for large plants is that for by-product recovery to be economically feasible the net benefit must be greater than $200,000 a year. A net benefit can be calculated by adding the possible resale value of the by-product and the avoided waste disposal cost [1].

===Margin===
The gross margin of a process is defined as the sum of product and by-product revenues minus the raw material cost.

Gross margin = Revenues - Raw materials costs

Because raw materials are most often the most expensive variable cost of a process, the gross margin is a good gauge as to what the total profitability of a process will be. Raw materials and product pricing are often subject to high degrees of variability which can be difficult to forecast. The size of margins are highly versatile depending on the
industry. For many petrochemical industries the margin may be only 10%; however, for industries such as food additives and pharmaceuticals the margins are generally much higher [1].

===Profits===
There are several standards for calculating company profits. The cash cost of production (CCOP) is the sum of the fixed and variable production costs.

''CCOP = VCOP + FCOP''

where VCOP is the variable cost of production and FCOP is the fixed cost of production.

Gross profit, which should not be confused with gross margin, is then calculated by the following equation,

''Gross profit = Main product revenues - CCOP''

Finally profit can be calculated by subtracting the income taxes that the plant would be subject to depending on the tax code of the county the plant is located in.

''Net profit = gross profit - taxes''

==Pricing Products and Raw Materials==
The revenues and costs of a project are vital to determining its economic feasibility. To calculate these values one needs to multiply the respective product and feed streams by their respective prices. The major difficulty of this process is determining the prices that should be used in this formula. When analyzing a plant, not only do the current prices need to be acknowledged but also the stability of the market to forecast future fluctuations and deviations.
===Pricing Fundamentals===
The pricing of a substance is determined by the fundamental economic principles of supply and demand. A supply curve and demand curve can be graphed and added to determine the market equilibrium price and projected market size. There are many ways a company can combat if the market equilibrium pricing is not suitable for a process. One of these ways is changing the market that the company is selling to. Instead of selling industrial grade product there may be markets for pharmaceutical grade or food grade that would allow for a company to sell their product at higher margins. Another avenue to look into is changing the geographic market being sold to. Rarely is there a global synchronous market, but rather a variation depending on where in the world the product is being sold. It is possible that a company could make more money by dedicating their sales to the Asian market as opposed to the US or vise versa.
===Price Data Sources===
There are many resources when trying to determine the price of a chemical or utility. This are important for looking at current pricing information as well as historical data that can be used for forecasting purposes.
====Internal Company Forecasts====
Large companies will often have the marketing or development departments develop a forecasting database that can be used internally in the company. Forecasts of this magnitude will often have multiple scenarios and projects that are evaluated under the given parameters. Companies may even license these forecasts to other companies for high fees if they desire.

[[File:Capture.JPG]]

Table 1 provides common industry acronyms that are used to indicate certain key words when determining pricing information.

====Trade Journals====
There are also many publications that report pricing data weekly. ''ICIS Chemical Business Americas'' used to publish the prices for hundreds of chemicals but have more recently changed their data to an online database that requires a subscription. This service is very expensive, but necessary for many companies. ''Oil and Gas Journal'' publishes the market prices of many crude oils and other petrochemicals using data from several continents. This journal also provides margin data for many refineries and plants on a monthly basis. ''Chemical Week'' provides the spot and contract prices for 22 chemicals in the US and European markets.

====Consultants====
If trade journals are not adequate for the information needed, some companies will contract consultants to do deep research into the subject. Consultants are excellent resources for providing economic and marketing information but come at a large price. There are several companies that provide this type of service but some of the larger firms include: ''Purvin and Gertz'', ''Cambidge Energy Research Associates'', ''Chemical Markets Associates Inc.'', and ''SRI: The Chemical Economics Handbook''

====Online Brokers and Suppliers====
Often time price data can be supplied by the supplier themselves and using online directories. Restraint should be used when quoting these prices however because they are often spot prices that are much higher than what would be expected from bulk contract supplying.

==References==
# Towler, G.P. and Sinnot, R. (2012). ''Chemical Engineering Design: Principles, Practice and Economics of Plant and Process Design.''Elsevier.
# Biegler, L.T., Grossmann, L.E., and Westerberg, A.W. (1997). ''Systematic Methods of Chemical Process Design.'' Upper Saddle River: Prentice-Hall.
# Peters, M.S. and Timmerhaus, K.D. (2003). ''Plant Design and Economics for Chemical Engineers, 5th Edition.'' New York: McGraw-Hill.
# Seider, W.D., Seader, J.D., and Lewin, D.R. (2004). ''Process Design Principles: Synthesis, Analysis, and Evaluation.'' New York: Wiley.
# Turton, R.T., Bailie, R.C., Whiting, W.B., and Shaewitz, J.A. (2003). ''Analysis, Synthesis, and Design of Chemical Processes'' Upper Saddle River: Prentice-Hall.

Estimation of production cost and revenue

2014-02-24T05:05:23Z

Karetstik: /* Price data Sources */

==Variable Cost of Production==
Variable costs of production are dependent primarily on plant output and rate of production. There are many variables to consider when costing a plant.
# Raw materials consumed
# Utilities-steam, electricity, cooling water, fuel, etc.
# Consumables - acids, bases, solvents, catalysts, etc.
# Disposal
# Shipping
The majority of the variable costs for a production plant are the raw materials and utilities costs. Variable costs can be greatly cut through optimization techniques and intelligent plant design [1].
===Raw Materials Cost===
Calculating the annual cost of a raw material is calculated by simply multiplying the feed rate of the process by the appropriate price per volume or mass. These are the costs of chemical feed stocks required by the process. Feed stocks flow rates are obtained from PFD [5].There are several ways to optimize this cost to ensure that a process is not costing more than it should. First one should assess the actual consumption of a plant to see if it is significantly different from what should be expected based on process stoichiometry and selectivities [1]. Finding may prove that a process is less efficient than it originally claimed.
It is smart to benchmark a new plant design against an existing plant or pilot plant. Raw materials are typically the largest contributor to overall variable costs. For bulk chemicals and petrochemicals, raw materials represent 80-90% of the total cash cost of production (CCOP).
===Utilities Cost===
These are the costs of the various utilities streams required by the process. The flowrates for the utilities streams are located on the PFD [5]. This includes:
*Fuel gas, oil, or coal
*Electric power
*Steam
*Cooling water
*Process water
*Boiler feed water
*Air
*Inert gas
*Refrigeration

Utility streams are excellent ways to streamline a process and are often indicative of how efficient of a process the project is. Process methods such as steam generation and pinch analysis can be used to greatly reduce utility costs across a plant. Further analysis of pinch analysis techniques and optimizing heat exchanger networks can be found in plant design texts such as first reference from Gavin Towler. The determination of process utility costs is often more difficult than the determination of raw material costs; however, the utilities are typically between 5-10% of CCOP [1]. The cost of heating a process can be reduced by using process waste streams as fuel which consequently also reduces the need for waste disposal.

===Waste Disposal Costs===
These are defined as the cost of waste treatment to protect the environment [5]. These are materials that cannot be recycled or sold off as by-products. Often times these streams require additives or additional treatment to meet governmental regulations.
Hydrocarbon waste can often be incinerated directly to the atmosphere or used as process fuel to heat other streams in the system. Using the stream as process fuel allows the fuel value of the stream to be recovered into the system. The substituted value can be calculated by multiplying the conventional fuel price by the heat of combustion of the waste stream.

<math>P_{WFV} = P_F * \Delta H_C^o</math>

where
<math>P_{WFV}</math> = waste value of fuel ($/lb or $/kg)

<math>P_F</math> = price of fuel ($/MMBtu or $/GJ)

<math>\Delta H_C^o</math> = heat of combustion (MMBtu/lb or GJ/kg)

Dilute aqueous streams must be sent to wastewater treatment typically prior to purging from the plant. Acidic or basic wastes are neutralized prior to treatment by salting out the acid or base. The cost of wastewater treatment is typically about $6 per 1000 gal but this is only an estimate that doesn't account for regional charges [1].

Solid waste treatment can typically be sent to a landfill at a cost of approximately $50/ton [1].

Hazardous wastes arise from the production of concentrated liquid streams that cannot be incinerated. Hazardous wastes should be avoided if possible, but that is not always feasible for some processes. The cost of hazardous waste disposal is strongly dependent on the location of the plant, the plants proximity to waste disposal plants and the degree of hazard of the waste.

==Fixed Cost of Production==
===Labor Costs===
These are the costs attributed to the personnel required to operate the process plant [5].

===Maintenance Costs===
Part of these costs are associated with labor and materials necessary to maintain plant production [5].

===Research and Development===
These are the costs of research done in developing the process and/or products. This includes salaries for researchers as well as funds for research related equipment and supplies [5].

===Land, Rent, Taxes===
===Insurance===
===Interest Payments===
===Corporate Overhead===
===Licensing and Royalties===

==Revenues==
The revenues of a process are the income earned form sales of the main products and the by-products. Revenue can be impacted by market fluctuations and production rates.
===By-Product Revenues===
Besides selling the main product from a process, by-products from separations and reactions can also be valuable in the market. Often it is more difficult to decide which by-products to recover and purify than it is to make decisions on the main product.

By-products made in stoichiometric ratios from reactions must be either sold off or managed through waste disposal. Other by-products are sometimes produced through feed impurities or by nonselective reactions. There are several potential valuable by-products from a process:
# Materials produced in stoichiometric quantities by the reactions that create the main product. If they are not recovered then the waste disposal expenses will be large.
# Components that are produced in high yield by side reactions.
# Components formed in high yield from feed impurities. Many sulfurs are produced as a by-product of fuels manufacture.
# Components that are produced in low yield but have high value. An example includes acetophenone which is recovered as a by-product of phenol manufacture.
# Degraded consumables (e.g. solvents, etc.) that have reuse value.

A rule of thumb that can be used for preliminary screening of by-products for large plants is that for by-product recovery to be economically feasible the net benefit must be greater than $200,000 a year. A net benefit can be calculated by adding the possible resale value of the by-product and the avoided waste disposal cost [1].

===Margin===
The gross margin of a process is defined as the sum of product and by-product revenues minus the raw material cost.

Gross margin = Revenues - Raw materials costs

Because raw materials are most often the most expensive variable cost of a process, the gross margin is a good gauge as to what the total profitability of a process will be. Raw materials and product pricing are often subject to high degrees of variability which can be difficult to forecast. The size of margins are highly versatile depending on the
industry. For many petrochemical industries the margin may be only 10%; however, for industries such as food additives and pharmaceuticals the margins are generally much higher [1].

===Profits===
There are several standards for calculating company profits. The cash cost of production (CCOP) is the sum of the fixed and variable production costs.

''CCOP = VCOP + FCOP''

where VCOP is the variable cost of production and FCOP is the fixed cost of production.

Gross profit, which should not be confused with gross margin, is then calculated by the following equation,

''Gross profit = Main product revenues - CCOP''

Finally profit can be calculated by subtracting the income taxes that the plant would be subject to depending on the tax code of the county the plant is located in.

''Net profit = gross profit - taxes''

==Pricing Products and Raw Materials==
The revenues and costs of a project are vital to determining its economic feasibility. To calculate these values one needs to multiply the respective product and feed streams by their respective prices. The major difficulty of this process is determining the prices that should be used in this formula. When analyzing a plant, not only do the current prices need to be acknowledged but also the stability of the market to forecast future fluctuations and deviations.
===Pricing Fundamentals===
The pricing of a substance is determined by the fundamental economic principles of supply and demand. A supply curve and demand curve can be graphed and added to determine the market equilibrium price and projected market size. There are many ways a company can combat if the market equilibrium pricing is not suitable for a process. One of these ways is changing the market that the company is selling to. Instead of selling industrial grade product there may be markets for pharmaceutical grade or food grade that would allow for a company to sell their product at higher margins. Another avenue to look into is changing the geographic market being sold to. Rarely is there a global synchronous market, but rather a variation depending on where in the world the product is being sold. It is possible that a company could make more money by dedicating their sales to the Asian market as opposed to the US or vise versa.
===Price Data Sources===
There are many resources when trying to determine the price of a chemical or utility. This are important for looking at current pricing information as well as historical data that can be used for forecasting purposes.
====Internal Company Forecasts====
Large companies will often have the marketing or development departments develop a forecasting database that can be used internally in the company. Forecasts of this magnitude will often have multiple scenarios and projects that are evaluated under the given parameters. Companies may even license these forecasts to other companies for high fees if they desire.

[[File:Capture.JPG]]

Table 1 provides common industry acronyms that are used to indicate certain key words when determining pricing information.

====Trade Journals====
There are also many publications that report pricing data weekly. ''ICIS Chemical Business Americas'' used to publish the prices for hundreds of chemicals but have more recently changed their data to an online database that requires a subscription. This service is very expensive, but necessary for many companies. ''Oil and Gas Journal'' publishes the market prices of many crude oils and other petrochemicals using data from several continents. This journal also provides margin data for many refineries and plants on a monthly basis. ''Chemical Week'' provides the spot and contract prices for 22 chemicals in the US and European markets.

====Consultants====
If trade journals are not adequate for the information needed, some companies will contract consultants to do deep research into the subject. Consultants are excellent resources for providing economic and marketing information but come at a large price. There are several companies that provide this type of service but some of the larger firms include: ''Purvin and Gertz'', ''Cambidge Energy Research Associates'', ''Chemical Markets Associates Inc.'', and ''SRI: The Chemical Economics Handbook''

====Online Brokers and Suppliers====
Often time price data can be supplied by the supplier themselves and using online directories. Restraint should be used when quoting these prices however because they are often spot prices that are much higher than what would be expected from bulk contract supplying.

==References==
# Towler, G.P. and Sinnot, R. (2012). ''Chemical Engineering Design: Principles, Practice and Economics of Plant and Process Design.''Elsevier.
# Biegler, L.T., Grossmann, L.E., and Westerberg, A.W. (1997). ''Systematic Methods of Chemical Process Design.'' Upper Saddle River: Prentice-Hall.
# Peters, M.S. and Timmerhaus, K.D. (2003). ''Plant Design and Economics for Chemical Engineers, 5th Edition.'' New York: McGraw-Hill.
# Seider, W.D., Seader, J.D., and Lewin, D.R. (2004). ''Process Design Principles: Synthesis, Analysis, and Evaluation.'' New York: Wiley.
# Turton, R.T., Bailie, R.C., Whiting, W.B., and Shaewitz, J.A. (2003). ''Analysis, Synthesis, and Design of Chemical Processes'' Upper Saddle River: Prentice-Hall.

Estimation of production cost and revenue

2014-02-24T05:05:06Z

Karetstik:

==Variable Cost of Production==
Variable costs of production are dependent primarily on plant output and rate of production. There are many variables to consider when costing a plant.
# Raw materials consumed
# Utilities-steam, electricity, cooling water, fuel, etc.
# Consumables - acids, bases, solvents, catalysts, etc.
# Disposal
# Shipping
The majority of the variable costs for a production plant are the raw materials and utilities costs. Variable costs can be greatly cut through optimization techniques and intelligent plant design [1].
===Raw Materials Cost===
Calculating the annual cost of a raw material is calculated by simply multiplying the feed rate of the process by the appropriate price per volume or mass. These are the costs of chemical feed stocks required by the process. Feed stocks flow rates are obtained from PFD [5].There are several ways to optimize this cost to ensure that a process is not costing more than it should. First one should assess the actual consumption of a plant to see if it is significantly different from what should be expected based on process stoichiometry and selectivities [1]. Finding may prove that a process is less efficient than it originally claimed.
It is smart to benchmark a new plant design against an existing plant or pilot plant. Raw materials are typically the largest contributor to overall variable costs. For bulk chemicals and petrochemicals, raw materials represent 80-90% of the total cash cost of production (CCOP).
===Utilities Cost===
These are the costs of the various utilities streams required by the process. The flowrates for the utilities streams are located on the PFD [5]. This includes:
*Fuel gas, oil, or coal
*Electric power
*Steam
*Cooling water
*Process water
*Boiler feed water
*Air
*Inert gas
*Refrigeration

Utility streams are excellent ways to streamline a process and are often indicative of how efficient of a process the project is. Process methods such as steam generation and pinch analysis can be used to greatly reduce utility costs across a plant. Further analysis of pinch analysis techniques and optimizing heat exchanger networks can be found in plant design texts such as first reference from Gavin Towler. The determination of process utility costs is often more difficult than the determination of raw material costs; however, the utilities are typically between 5-10% of CCOP [1]. The cost of heating a process can be reduced by using process waste streams as fuel which consequently also reduces the need for waste disposal.

===Waste Disposal Costs===
These are defined as the cost of waste treatment to protect the environment [5]. These are materials that cannot be recycled or sold off as by-products. Often times these streams require additives or additional treatment to meet governmental regulations.
Hydrocarbon waste can often be incinerated directly to the atmosphere or used as process fuel to heat other streams in the system. Using the stream as process fuel allows the fuel value of the stream to be recovered into the system. The substituted value can be calculated by multiplying the conventional fuel price by the heat of combustion of the waste stream.

<math>P_{WFV} = P_F * \Delta H_C^o</math>

where
<math>P_{WFV}</math> = waste value of fuel ($/lb or $/kg)

<math>P_F</math> = price of fuel ($/MMBtu or $/GJ)

<math>\Delta H_C^o</math> = heat of combustion (MMBtu/lb or GJ/kg)

Dilute aqueous streams must be sent to wastewater treatment typically prior to purging from the plant. Acidic or basic wastes are neutralized prior to treatment by salting out the acid or base. The cost of wastewater treatment is typically about $6 per 1000 gal but this is only an estimate that doesn't account for regional charges [1].

Solid waste treatment can typically be sent to a landfill at a cost of approximately $50/ton [1].

Hazardous wastes arise from the production of concentrated liquid streams that cannot be incinerated. Hazardous wastes should be avoided if possible, but that is not always feasible for some processes. The cost of hazardous waste disposal is strongly dependent on the location of the plant, the plants proximity to waste disposal plants and the degree of hazard of the waste.

==Fixed Cost of Production==
===Labor Costs===
These are the costs attributed to the personnel required to operate the process plant [5].

===Maintenance Costs===
Part of these costs are associated with labor and materials necessary to maintain plant production [5].

===Research and Development===
These are the costs of research done in developing the process and/or products. This includes salaries for researchers as well as funds for research related equipment and supplies [5].

===Land, Rent, Taxes===
===Insurance===
===Interest Payments===
===Corporate Overhead===
===Licensing and Royalties===

==Revenues==
The revenues of a process are the income earned form sales of the main products and the by-products. Revenue can be impacted by market fluctuations and production rates.
===By-Product Revenues===
Besides selling the main product from a process, by-products from separations and reactions can also be valuable in the market. Often it is more difficult to decide which by-products to recover and purify than it is to make decisions on the main product.

By-products made in stoichiometric ratios from reactions must be either sold off or managed through waste disposal. Other by-products are sometimes produced through feed impurities or by nonselective reactions. There are several potential valuable by-products from a process:
# Materials produced in stoichiometric quantities by the reactions that create the main product. If they are not recovered then the waste disposal expenses will be large.
# Components that are produced in high yield by side reactions.
# Components formed in high yield from feed impurities. Many sulfurs are produced as a by-product of fuels manufacture.
# Components that are produced in low yield but have high value. An example includes acetophenone which is recovered as a by-product of phenol manufacture.
# Degraded consumables (e.g. solvents, etc.) that have reuse value.

A rule of thumb that can be used for preliminary screening of by-products for large plants is that for by-product recovery to be economically feasible the net benefit must be greater than $200,000 a year. A net benefit can be calculated by adding the possible resale value of the by-product and the avoided waste disposal cost [1].

===Margin===
The gross margin of a process is defined as the sum of product and by-product revenues minus the raw material cost.

Gross margin = Revenues - Raw materials costs

Because raw materials are most often the most expensive variable cost of a process, the gross margin is a good gauge as to what the total profitability of a process will be. Raw materials and product pricing are often subject to high degrees of variability which can be difficult to forecast. The size of margins are highly versatile depending on the
industry. For many petrochemical industries the margin may be only 10%; however, for industries such as food additives and pharmaceuticals the margins are generally much higher [1].

===Profits===
There are several standards for calculating company profits. The cash cost of production (CCOP) is the sum of the fixed and variable production costs.

''CCOP = VCOP + FCOP''

where VCOP is the variable cost of production and FCOP is the fixed cost of production.

Gross profit, which should not be confused with gross margin, is then calculated by the following equation,

''Gross profit = Main product revenues - CCOP''

Finally profit can be calculated by subtracting the income taxes that the plant would be subject to depending on the tax code of the county the plant is located in.

''Net profit = gross profit - taxes''

==Pricing Products and Raw Materials==
The revenues and costs of a project are vital to determining its economic feasibility. To calculate these values one needs to multiply the respective product and feed streams by their respective prices. The major difficulty of this process is determining the prices that should be used in this formula. When analyzing a plant, not only do the current prices need to be acknowledged but also the stability of the market to forecast future fluctuations and deviations.
===Pricing Fundamentals===
The pricing of a substance is determined by the fundamental economic principles of supply and demand. A supply curve and demand curve can be graphed and added to determine the market equilibrium price and projected market size. There are many ways a company can combat if the market equilibrium pricing is not suitable for a process. One of these ways is changing the market that the company is selling to. Instead of selling industrial grade product there may be markets for pharmaceutical grade or food grade that would allow for a company to sell their product at higher margins. Another avenue to look into is changing the geographic market being sold to. Rarely is there a global synchronous market, but rather a variation depending on where in the world the product is being sold. It is possible that a company could make more money by dedicating their sales to the Asian market as opposed to the US or vise versa.
===Price data Sources===
There are many resources when trying to determine the price of a chemical or utility. This are important for looking at current pricing information as well as historical data that can be used for forecasting purposes.
====Internal Company Forecasts====
Large companies will often have the marketing or development departments develop a forecasting database that can be used internally in the company. Forecasts of this magnitude will often have multiple scenarios and projects that are evaluated under the given parameters. Companies may even license these forecasts to other companies for high fees if they desire.

[[File:Capture.JPG]]

Table 1 provides common industry acronyms that are used to indicate certain key words when determining pricing information.

====Trade Journals====
There are also many publications that report pricing data weekly. ''ICIS Chemical Business Americas'' used to publish the prices for hundreds of chemicals but have more recently changed their data to an online database that requires a subscription. This service is very expensive, but necessary for many companies. ''Oil and Gas Journal'' publishes the market prices of many crude oils and other petrochemicals using data from several continents. This journal also provides margin data for many refineries and plants on a monthly basis. ''Chemical Week'' provides the spot and contract prices for 22 chemicals in the US and European markets.

====Consultants====
If trade journals are not adequate for the information needed, some companies will contract consultants to do deep research into the subject. Consultants are excellent resources for providing economic and marketing information but come at a large price. There are several companies that provide this type of service but some of the larger firms include: ''Purvin and Gertz'', ''Cambidge Energy Research Associates'', ''Chemical Markets Associates Inc.'', and ''SRI: The Chemical Economics Handbook''

====Online Brokers and Suppliers====
Often time price data can be supplied by the supplier themselves and using online directories. Restraint should be used when quoting these prices however because they are often spot prices that are much higher than what would be expected from bulk contract supplying.

==References==
# Towler, G.P. and Sinnot, R. (2012). ''Chemical Engineering Design: Principles, Practice and Economics of Plant and Process Design.''Elsevier.
# Biegler, L.T., Grossmann, L.E., and Westerberg, A.W. (1997). ''Systematic Methods of Chemical Process Design.'' Upper Saddle River: Prentice-Hall.
# Peters, M.S. and Timmerhaus, K.D. (2003). ''Plant Design and Economics for Chemical Engineers, 5th Edition.'' New York: McGraw-Hill.
# Seider, W.D., Seader, J.D., and Lewin, D.R. (2004). ''Process Design Principles: Synthesis, Analysis, and Evaluation.'' New York: Wiley.
# Turton, R.T., Bailie, R.C., Whiting, W.B., and Shaewitz, J.A. (2003). ''Analysis, Synthesis, and Design of Chemical Processes'' Upper Saddle River: Prentice-Hall.

Separation processes

2014-02-24T05:02:01Z

Karetstik: /* Conclusion */

Title: Separation Processes

Authors: Nick Pinkerton, Karen Schmidt, and James Xamplas

Date Presented: February 9, 2014 /Date Revised: February 1, 2014

==Introduction==
Essentially all chemical processes require the presence of a separation stage. Most chemical plants comprise of a reactor surrounded by many separators. Separators have a countless number of jobs inside of a chemical plant. A separator can process raw materials prior to the reaction, remove incondensable gases, remove undesired side products, purify a product stream, recycle materials back into the process, and many other jobs that are essential to the process.

Chemical engineers must understand the science of separation and the variety of ways that separation can take place. There are many ways to perform a separation some of these including: distillation, absorption, stripping, and extraction. The science of separation revolves around the presence of two phases that are in contact and equilibrium [1].

[[File:Sepmeth.JPG|frame|Figure 1. Separation methods by property]]

==Theory==
===Vapor-Liquid Equilibrium===
Separation processes are based on the theory of vapor-liquid equilibrium. This theory states that streams leaving a stage in a separation process are in equilibrium with one another. The idea of equilibrium revolves around the idea that when there is vapor and liquid in contact with one another they are in constantly vaporizing and condensing. Different components in the mixture will condense and vaporize at different rates. There are three types of equilibrium conditions that can be subdivided into thermal, mechanical and chemical potential categories. These separate equilibrium states are given as:

<math>T_{liquid} = T_{vapor}</math>

<math>p_{liquid} = p_{vapor}</math>

<math>chemical potential_{liquid} = chemical potential_{vapor}</math>

==Distillation==
===Flash Distillation===
Flash Distillation is one of the simpler separation processes to be employed in a chemical plant. The main premise of flash distillation is that a portion of a liquid feed stream vaporizes in a flash chamber or a vapor feed condenses. Vapor-liquid equilibrium will cause the vapor phase and the liquid phase to have different compositions. The more volatile component of the mixture will compose of a larger portion of the vapor. This simple separation is easy to manufacture but does not result in large degrees of separation.

Flash distillation requires a feed stream that is pressurized and heated and then passed through a valve into a flash drum. The large pressure drop across the valve will result in a partial vaporization of the fluid. Vapor will be removed overhead from the flash drum while the remaining liquid will collect at the bottom of the drum and be removed. Most flash drums will contain an entrainment eliminator which is a screen that prevents liquid from being carried into the vapor effluent. Figure 2 shows a simple overview of the flash distillation process. As shown, there is a heater that flows into a let-down valve where the two-phase flow begins. Variables y and x are the mole fractions of the more volatile component in the vapor and liquid effluents, respectively.

[[File:Flash.gif|center|frame|Figure 2. Flash Distillation Flow Diagram]]

===Column Distillation===
Distillation columns are the most widely used separation technique used in the chemical industry, accounting for approximately 90% of all separations [1]. Distillations in columns consist of multiple trays that each act at their own equilibrium conditions. Large columns are able to perform complete separations of binary mixtures as well as more complex multi-component mixtures.

[[File:column.jpg|250px|center|]]
===Stages===
Columns are separated into stages by the presence of trays. These trays allow for vapor-liquid contact and equilibrium to occur. Typically, the more stages in a column, the larger separation that can be achieved. There are many different types of trays that can be used in a column.
====Sieve Trays====
The simplest and least expensive tray type is the sieve tray which is a sheet of metal with holes punched into it to allow vapor flow. Sieve trays can have different hole patterns and sizes that will affect the tray efficiency and flow rates.

[[File:sieve.jpg|200px|center|]]

====Bubble-Cap Trays====
Bubble-cap trays consist of a weir around each hole in the tray which is covered with a cap that has holes or slots to allow vapor passage. Entrainment is about three times larger than a sieve tray. Bubble-cap trays require larger tray spacing than sieve tray design. Bubble-cap trays have been known to have problems with coking, polymer formation, or high fouling mixtures. Recently, very few new bubble-cap columns are being built due to the expense and marginal benefits. However, engineers will likely encounter bubble-cap columns still currently in operation.

====Flow Patterns====
Cross flow columns are the most common pattern for distillation columns. For liquid flows between 50 and 500 Gal/min, a cross flow column is appropriate. When liquid flow is increased above 500 Gal/min, an engineer should consider designing a double pass or multi-pass column. This will reduce the liquid gradient on the tray and reduce the downcomer loading [1].

===Column Sizing===
Column height will be dependent on the amount of trays required and the spacing between the trays. Normally, tray spacing of 0.15 m to 1 m is used. For columns, above 1 meter in diameter, 0.5 m can be used as an initial estimate.

Column diameter is influenced by the vapor flow rate in the column. The trays can not have excess liquid entrainment or high pressure drops; therefore, vapor velocity in the column must be maintained at a reasonable level.

An equation based on the Souders and Brown equation can be used as an estimate for the max allowable superficial vapor velocity,

<math>\hat u_v = (-0.171l_t^2 + 0.27l_t - 0.047){\frac{\rho_L - \rho_v}{\rho_v}}^{1/2}</math>

where <math>l_t</math> is the plate spacing in meters, <math>\rho_L</math> is the density of the liquid stream, and <math>\rho_V</math> is the density of the vapor stream.

Column diameter, <math>D_c</math>, can then be estimated using the relation,

<math>D_c = \sqrt{\frac{4\hat{V_w}}{\pi\rho_v\hat{u_v}}}</math>

where <math>\hat{V_w}</math> is the maximum vapor rate in kg/s [2].

===Distillation Applications===

Distillation is a process that can be implemented in various scales. There is both laboratory scaled distillation as well as very large industrial distillation. Other applications for distillation include food/alcohol processing and herb distillation for the perfume and medical industries. Typically laboratory scaled distillation occurs in batches whereas industrial distillation (e.g. fractional distillation of crude oil) occurs continuous with a constant distillate and bottom effluent streams.

Some applications of distillation are concerned the top stream only, some the bottom stream only and others both streams can be used for future products. In alcohol distillation for example, the water that is separated from the ethanol/water binary solution is discarded as waste water. In fractional distillation of crude oils, the heavy hydrocarbons at the bottom of the column are collected and sold along with the light hydrocarbons that appear in higher side draws [1].

===Example Case: Ideal Distillation===

Assume an equimolar mixture flowing at 10 mol/s of 20 mol% n-pentane, 30 mol% n-hexane, and 50 mol% n-heptane. Separate the mixture into 3 products: 99% pure n-pentane, 99% pure n-hexane, 99% n-heptane. Assume the feed and products are all liquids at the bubble points. There are two process alternatives to consider in this example. The direct sequence removes the most volatile species, pentane, in the first column, and then separates hexane and heptane in the second column. The indirect sequence separates the heaviest product, heptane, and then separates pentane from hexane in the second column. This example will consider the direct sequence. Next, we must decide if these species exhibit fairly ideal behavior during distillation. Since the n-alkanes have very similar properties, it is safe to assume they will display close to ideal behavior. The next step is to look up the boiling points of the 3 species. In this case, the normal boiling points of pentane, hexane, and heptane are 309 K, 342 K, and 372 K, respectively. Also, it is a good idea to look up relative volatilites, to further verify near-ideality of the mixture, but also to obtain the information necessary for the Underwood method, which we will employ to obtain a solution. The next step is to write out material balances based on molar flows and the design specifications. They go as follows:

<math>\mu_I(nC5) + \mu_{II}(nC5) = 2 mol/s</math>

<math>\mu_I(nC6) + \mu_{II}(nC6) + \mu_{III}(nC6) = 3 mol/s</math>

<math>\mu_{II}(nC7) + \mu_{III}(nC7) = 5 mol/s</math>

<math>\mu_I(nC5) = 99\mu_I(nC6)</math>

<math>\mu_{II}(nC5) = (5/990)\mu_{II}(nC6)</math>

<math>\mu_{II}(nC7) = (5/990)\mu_{II}(nC6)</math>

<math>\mu_{III}(nC7) = 99\mu_{III}(nC7)</math>

where <math>\mu</math> represents the molar flow, and the subscript represents the product stream.

Solving this system of equations:

<math>\mu_I(nC5) = 1.985\ mol/s</math>

<math>\mu_{II}(nC5) = 0.015\ mol/s</math>

<math>\mu_I(nC6) = 0.020\ mol/s</math>

<math>\mu_{II}(nC6) = 2.930\ mol/s</math>

<math>\mu_{III}(nC6) = 0.050\ mol/s</math>

<math>\mu_{II}(nC7) = 0.015\ mol/s</math>

<math>\mu_{III}(nC7) = 4.985\ mol/s</math>

At this point we have enough information to use Underwood's method to estimate the minimum vapor flows in the column. The following three equations are used in Underwood's method:

<math>\sum_i \frac{\alpha_{ik}}{\alpha_{ik}-\phi}f_i = (1-q)F</math>

<math>(R_{min}+1)D = \sum_i \frac{\alpha_{ik}}{\alpha_{ik}-\phi}d_i = V_{min}</math>

<math>\bar R_{min}B = -\sum_i \frac{\alpha_{ik}}{\alpha_{ik}-\phi}b_i = \bar V_{min}</math>

where <math>\alpha_{ik}</math> is the relative volatility of species <math>i</math> to species <math>k</math>, <math>f_i</math> the molar flow of species <math>i</math> in the feed, <math>q</math> the fraction of the feed that joins the liquid stream at the feed tray, <math>F</math> the total molar flow of the feed, <math>D</math> the molar flow of the distillate, <math>R_{min}</math> the minimum reflux ratio <math>(=L_{min}/D)</math>, <math>d_i</math> the molar flow of species <math>i</math> in the distillate, <math>V_{min}</math> the minimum vapor flow possible in the top section of the column to accomplish the desired separation, <math>\bar R_{min}</math> the minimum reboil ratio <math>(=\bar V_{min}/B)</math>, <math>b_i</math> the molar flow of species <math>i</math> in the bottoms product, and <math>\bar V_{min}</math> the minimum vapor flow in the bottom section of the column. The final variable, <math>\phi</math>, will be solved for using the first Underwood equation, and it's value will be decided based on the relative volatilities of the key components in the column.

So, after solving the first Underwood equation, we get two values for <math>\phi</math>, 3.806 and 1.462. Because 3.806 is between the relative volatilities of the key components, we will substitute that value for <math>\phi</math> into the second Underwood equation. Doing so for both columns gives <math>V_{min} = 6.4\ mol/s</math> for the first column and <math>V_{min} = 8.9\ mol/s</math> for the second column, for a total minimum vapor flow of 15.3 mol/s. The process would then be repeated for the indirect sequence, and the decision for which process to use would be justified by the process with the overall minimum vapor flow [3].

==Absorption==
An alternative to distillation for separating solutes from gas streams is absorption. The gas mixture comes into contact with a liquid solvent that readily absorbs the undesirable components from the gas stream, purifying the gas stream. This separation process is determined by the inputs of the liquid flow rate, temperature, and pressure.

The absorption factor, which can be determined mathematically, determines how readily a component will absorb in the liquid phase. The absorption factor of component i is

<math>A_i=L/K_iV</math>

where <math>L</math> is the liquid flow rate entering the column, <math>V</math> is the vapor flow rate entering the column, and <math>K_i</math> is the vapor/liquid equilibrium ratio for component i [4]. Higher absorption factors result in higher absorptivity into the liquid and a decrease in the number of trays required for separation, however a diminishing return occurs after the absorption factor is greater than 2.0. An absorption factor of 1.4 is most commonly used.

An industrial example is lean oil absorption, which is used to separate nitrogen and other impurities from natural gas. A lean oil is contacted with low quality natural gas, and the methane is selectively absorbed by the lean oil, leaving the impurities behind. The methane is subsequently regenerated from the rich oil as high quality natural gas [7].

==Stripping==
This process separates solutes from solvents (often after absorption, to purify the solvent so that it can be recycled to an absorber). Stripping will depend on the vapor and liquid flow rates, as well as the temperature and pressure of the column. There is a temperature drop down the column, so columns generally have either an increased operating temperature or decreased operating pressure.

The stripping factor of component i is

<math>S_i=K_iV/L</math>

where <math>K_i</math> is the vapor/liquid equilibrium ratio, <math>V</math> is the vapor flow rate entering the column, and <math>L</math> is the liquid flow rate entering the column, will determine how much of solute i will be stripped from the liquid into the vapor phase [4]. The usual range for the stripping factor is between 1.2 and 2.0, with a stripping factor of 1.4 being most economic.

An example of stripping in industry is the deodorization of food items such as oils. The oil is heated and allowed to trickle down the column while steam flows up from the bottom of the column. At the vapor-liquid interface, volatile components of the oil transfer to the steam and are carried off the top of the column, leaving a purified oil product [8].

==Other Separation Processes==
===Extraction===
Liquid-liquid extraction is a process for components with overlapping boiling points and azeotropes. The process requires a solvent such that some of the components of the mixture are soluble, and then the components will be separated based on this solubility in the liquid. This process can operate at moderate temperatures and pressures, so is not very energy intensive. However, a distillation column is required to extract the solvent for recycle. More recently, supercritical fluids have replaced liquid solvents in some processes for L/L extraction, due to the solute’s ability to more rapidly diffuse through them. The issue with these fluids, however, is that they must be operated at extremely high pressures and temperatures, increasing both capital and operating expenses of the process [4].

===Crystallization===
This process recovers solutes that have been dissolved in solution. The resulting product is in the solid phase. Depending on the material properties of the solute and solvent, the solute is recovered by precipitation after cooling, removal of solvent, or adding precipitating agents. Crystallizers are designed based on phase equilibria, solubilities, rates and amounts of nuclei generated, and rates of crystal growth. Every crystallization process is a unique system, so plant evaluation is usually required before complete implementation. Crystallization can be performed in both batch and continuous processes, and design features can control crystal size to an extent [4].

===Membrane Separation===
This separations process uses selectively permeable membranes to separate components in a mixture. Typically, one of the components will freely pass through the barrier while the other components will not. The stream that passes through the membrane is the permeate and the stream that does not pass is the retentate. The driving force behind this separation is a pressure gradient. Membrane separation is beneficial because it can separate mixtures at the molecular and small particle level. Furthermore, there is no phase change required so the energy input is low. Limitations of this process include achieving high product purity, incompatibility with certain stream components, low operating temperature, and low flow rates. Although membrane separation is generally not scaled up, examples of scaled-up membrane separation include seawater desalination and hydrogen recovery [4].

===Adsorption===
Adsorption involves an adsorbent and adsorbate. The adsorbent is typically a solid, and will typically separate the adsorbate from the stream. This process usually includes a desorption step that regenerates the adsorbent for further use. Raising the temperature or increasing the concentration of the adsorbate can reverse the adsorption process. Although the recycle of the adsorbent is a very economic design feature, the downside of this step is that it results in a cyclic process, which introduces complexity to the overall process. Industrial applications of this process are for bulk separations and gas purification. The adsorption/desorption process in these situations involves a large amount of heat transfer, which design engineers must take into account when sizing and selecting equipment material [4].

===External Field/Gradient Separation===
These separations use external force fields or temperature gradients to separate responsive molecules or ions. The use of these processes is fairly limited to a few specialized industrial applications [4].

===Settling and Sedimentation===
In settling processes, solid particles or liquid drops are separated from a stream by gravity. The stream can be in either the liquid or gas phase. For vapor-liquid mixtures, flash drums are generally used to separate the mixture. The velocity of the vapor must be less than the settling velocity of the liquid drops for this separation to occur. For liquid-liquid separation, the horizontal velocity of the fluid must be low enough to allow the low-density droplets to rise to the interface and the high-density droplets to move away from the interface and coalesce. In sedimentation, the result of the process is a more concentrated slurry. Typically a flocculating agent is used to aid in the settling process. One way to perform this separation is to use a cone-shaped tank with a slowly revolving rake that scrapes and moves the thickened slurry to the center of the cone for removal [4].

===Flotation===
Flotation is a process designed for specific solid-solid mixtures. It works by generating gas bubbles in a liquid that attach to selected solid particle. Afterwards, the particles rise to the liquid surface where they are removed by an overflow weir or mechanical scraper. The separation depends on the surface properties of the particles and its preference to attach to the gas bubbles. To meet the necessary requirements of the flotation process, a number of additives can be used to control things like the pH of the liquid-solid mixture, the activity of the solid surface, and the froth that can assist in separation. The bubbles can be produced by gaseous dispersion, dissolution, or electrolysis of the liquid [4].

===Centrifugation===
This process is similar to external field separation in that an external force field is applied to separate a mixture. When gravity separation is too slow due to particle densities, particle size, settling velocity, or the formation of an emulsion, centrifugation is commonly used. Centrifugal force increases the total force acting on the particle and results in faster separation times. This process is generally used to separate solids from liquids, however it can also be used to separate two liquids with very different densities [4].

===Drying===
Drying is performed to remove liquid from a liquid-solid mixture and produce a dry solid. Water is most often the liquid removed, but organic liquids are removed from solids on occasion as well. The heat required to vaporize the liquid is usually obtained by a series of gas-solid contacting devices. Feed condition and temperature sensitivity of the solid dictate the type of contacting device that is used. There are two groups of dryers that differ by the dependence of either mechanical means or fluid motion for gas solid contact. Another feature of dryers is to use either direct (hot gas) or indirect (conductive surface) heating [4].

===Evaporation===
Evaporators separate solvents from a solution by evaporation. The difference between evaporation and distillation is that evaporation requires the solute be nonvolatile. Because of this, a high separation can be achieved with one stage. Evaporators are essentially reboilers, so evaporation is a very energy-intensive process with a high thermal economy [4].

===Filtration===
Filtration is a process that separates a mixture of solid in a liquid or gas by passing the mixture through a porous medium in which the particles do not pass. Filtration is done by either cake filtration (particles found on the surface of the filter) or depth filtration (particles found within the filter). Cake filtration is generally performed with a cloth as the filtration medium [4].

==Conclusion==
Separation is a key part of most chemical processes, and there is a great variety of techniques to perform separation of compounds based on size, volatility, charge, and many other features. A common technique with which the process engineer should be familiar is distillation, but he or she should also be aware of the other available options. Some techniques may be less expensive, less energy-intensive, or more effective than distillation, depending on the specific separation problem. Therefore, the separation strategy should be carefully considered.

==References==
# Wankat, P.C. (2012). ''Separation Process Engineering.'' Upper Saddle River: Prentice-Hall.
# Towler, G.P. and Sinnot, R. (2012). ''Chemical Engineering Design: Principles, Practice and Economics of Plant and Process Design.''Elsevier.
# Biegler, L.T., Grossmann, L.E., and Westerberg, A.W. (1997). ''Systematic Methods of Chemical Process Design.'' Upper Saddle River: Prentice-Hall.
# Peters, M.S. and Timmerhaus, K.D. (2003). ''Plant Design and Economics for Chemical Engineers, 5th Edition.'' New York: McGraw-Hill.
# Seider, W.D., Seader, J.D., and Lewin, D.R. (2004). ''Process Design Principles: Synthesis, Analysis, and Evaluation.'' New York: Wiley.
# Turton, R.T., Bailie, R.C., Whiting, W.B., and Shaewitz, J.A. (2003). ''Analysis, Synthesis, and Design of Chemical Processes'' Upper Saddle River: Prentice-Hall.
# Stripping Column. Alfa Laval Web site. Available at: http://www.alfalaval.com/solution-finder/products/soft-column/Documents/Stripping%20Column.pdf. Accessed February 19, 2014.
# Lean Oil Absorption. PetroGas Systems Web site. Available at: http://petrogassystems.com/technology/natural-gas-processing-and-dew-point-control/lean-oil-absorption. Accessed February 19, 2014.

Separation processes

2014-02-20T05:02:24Z

Karetstik:

Title: Separation Processes

Authors: Nick Pinkerton, Karen Schmidt, and James Xamplas

Date Presented: February 9, 2014 /Date Revised: February 1, 2014

==Introduction==
Essentially all chemical processes require the presence of a separation stage. Most chemical plants comprise of a reactor surrounded by many separators. Separators have a countless number of jobs inside of a chemical plant. A separator can process raw materials prior to the reaction, remove incondensable gases, remove undesired side products, purify a product stream, recycle materials back into the process, and many other jobs that are essential to the process.

Chemical engineers must understand the science of separation and the variety of ways that separation can take place. There are many ways to perform a separation some of these including: distillation, absorption, stripping, and extraction. The science of separation revolves around the presence of two phases that are in contact and equilibrium [1].

[[File:Sepmeth.JPG|frame|Figure 1. Separation methods by property]]

==Theory==
===Vapor-Liquid Equilibrium===
Separation processes are based on the theory of vapor-liquid equilibrium. This theory states that streams leaving a stage in a separation process are in equilibrium with one another. The idea of equilibrium revolves around the idea that when there is vapor and liquid in contact with one another they are in constantly vaporizing and condensing. Different components in the mixture will condense and vaporize at different rates. There are three types of equilibrium conditions that can be subdivided into thermal, mechanical and chemical potential categories. These separate equilibrium states are given as:

<math>T_{liquid} = T_{vapor}</math>

<math>p_{liquid} = p_{vapor}</math>

<math>chemical potential_{liquid} = chemical potential_{vapor}</math>

==Distillation==
===Flash Distillation===
Flash Distillation is one of the simpler separation processes to be employed in a chemical plant. The main premise of flash distillation is that a portion of a liquid feed stream vaporizes in a flash chamber or a vapor feed condenses. Vapor-liquid equilibrium will cause the vapor phase and the liquid phase to have different compositions. The more volatile component of the mixture will compose of a larger portion of the vapor. This simple separation is easy to manufacture but does not result in large degrees of separation.

Flash distillation requires a feed stream that is pressurized and heated and then passed through a valve into a flash drum. The large pressure drop across the valve will result in a partial vaporization of the fluid. Vapor will be removed overhead from the flash drum while the remaining liquid will collect at the bottom of the drum and be removed. Most flash drums will contain an entrainment eliminator which is a screen that prevents liquid from being carried into the vapor effluent. Figure 2 shows a simple overview of the flash distillation process. As shown, there is a heater that flows into a let-down valve where the two-phase flow begins. Variables y and x are the mole fractions of the more volatile component in the vapor and liquid effluents, respectively.

[[File:Flash.gif|center|frame|Figure 2. Flash Distillation Flow Diagram]]

===Column Distillation===
Distillation columns are the most widely used separation technique used in the chemical industry, accounting for approximately 90% of all separations [1]. Distillations in columns consist of multiple trays that each act at their own equilibrium conditions. Large columns are able to perform complete separations of binary mixtures as well as more complex multi-component mixtures.

[[File:column.jpg|250px|center|]]
===Stages===
Columns are separated into stages by the presence of trays. These trays allow for vapor-liquid contact and equilibrium to occur. Typically, the more stages in a column, the larger separation that can be achieved. There are many different types of trays that can be used in a column.
====Sieve Trays====
The simplest and least expensive tray type is the sieve tray which is a sheet of metal with holes punched into it to allow vapor flow. Sieve trays can have different hole patterns and sizes that will affect the tray efficiency and flow rates.

[[File:sieve.jpg|200px|center|]]

====Bubble-Cap Trays====
Bubble-cap trays consist of a weir around each hole in the tray which is covered with a cap that has holes or slots to allow vapor passage. Entrainment is about three times larger than a sieve tray. Bubble-cap trays require larger tray spacing than sieve tray design. Bubble-cap trays have been known to have problems with coking, polymer formation, or high fouling mixtures. Recently, very few new bubble-cap columns are being built due to the expense and marginal benefits. However, engineers will likely encounter bubble-cap columns still currently in operation.

====Flow Patterns====
Cross flow columns are the most common pattern for distillation columns. For liquid flows between 50 and 500 Gal/min, a cross flow column is appropriate. When liquid flow is increased above 500 Gal/min, an engineer should consider designing a double pass or multi-pass column. This will reduce the liquid gradient on the tray and reduce the downcomer loading [1].

===Column Sizing===
Column height will be dependent on the amount of trays required and the spacing between the trays. Normally, tray spacing of 0.15 m to 1 m is used. For columns, above 1 meter in diameter, 0.5 m can be used as an initial estimate.

Column diameter is influenced by the vapor flow rate in the column. The trays can not have excess liquid entrainment or high pressure drops; therefore, vapor velocity in the column must be maintained at a reasonable level.

An equation based on the Souders and Brown equation can be used as an estimate for the max allowable superficial vapor velocity,

<math>\hat u_v = (-0.171l_t^2 + 0.27l_t - 0.047){\frac{\rho_L - \rho_v}{\rho_v}}^{1/2}</math>

where <math>l_t</math> is the plate spacing in meters, <math>\rho_L</math> is the density of the liquid stream, and <math>\rho_V</math> is the density of the vapor stream.

Column diameter, <math>D_c</math>, can then be estimated using the relation,

<math>D_c = \sqrt{\frac{4\hat{V_w}}{\pi\rho_v\hat{u_v}}}</math>

where <math>\hat{V_w}</math> is the maximum vapor rate in kg/s [2].

===Example Case: Ideal Distillation===

Assume an equimolar mixture flowing at 10 mol/s of 20 mol% n-pentane, 30 mol% n-hexane, and 50 mol% n-heptane. Separate the mixture into 3 products: 99% pure n-pentane, 99% pure n-hexane, 99% n-heptane. Assume the feed and products are all liquids at the bubble points. There are two process alternatives to consider in this example. The direct sequence removes the most volatile species, pentane, in the first column, and then separates hexane and heptane in the second column. The indirect sequence separates the haeviest product, heptane, and then separates pentane from hexane in the second column. Next, we must decide if these species exhibit fairly ideal behavior during distillation. Since the n-alkanes have very similar properties, it is safe to assume they will display close to ideal behavior. The next step is to look up the boiling points of the 3 species. In this case, the normal boiling points of pentane, hexane, and heptane are 309 K, 342 K, and 372 K, respectively. Also, it is a good idea to look up relative volatilites, to further verify near-ideality of the mixture, but also to obtain the information necessary for the Underwood method, which we will employ to obtain a solution. The next step is to write out material balances based on molar flows and the design specifications. They go as follows:

<math>\mu_I(nC5) + \mu_{II}(nC5) = 2 mol/s</math>

<math>\mu_I(nC6) + \mu_{II}(nC6) + \mu_{III}(nC6) = 3 mol/s</math>

<math>\mu_{II}(nC7) + \mu_{III}(nC7) = 5 mol/s</math>

<math>\mu_I(nC5) = 99\mu_I(nC6)</math>

<math>\mu_{II}(nC5) = (5/990)\mu_{II}(nC6)</math>

<math>\mu_{II}(nC7) = (5/990)\mu_{II}(nC6)</math>

<math>\mu_{III}(nC7) = 99\mu_{III}(nC7)</math>

where <math>\mu</math> represents the molar flow, and the subscript represents the product stream.

Solving this system of equations

At this point we have enough information to use Underwood's method to estimate the minimum vapor flows in the column. The following three equations are used in Underwood's method:

<math>\sum_i \frac{\alpha_{ik}}{\alpha_{ik}-\phi}f_i = (1-q)F</math>

<math>(R_{min}+1)D = \sum_i \frac{\alpha_{ik}}{\alpha_{ik}-\phi}d_i = V_{min}</math>

<math>\bar R_{min}B = -\sum_i \frac{\alpha_{ik}}{\alpha_{ik}-\phi}b_i = \bar V_{min}</math>

==Absorption==
An alternative to distillation for separating solutes from gas streams is absorption. The gas mixture comes into contact with a liquid solvent that readily absorbs the undesirable components from the gas stream, purifying the gas stream. This separation process is determined by the inputs of the liquid flow rate, temperature, and pressure.

The absorption factor, which can be determined mathematically, determines how readily a component will absorb in the liquid phase. The absorption factor of component i is

<math>A_i=L/K_iV</math>

where <math>L</math> is the liquid flow rate entering the column, <math>V</math> is the vapor flow rate entering the column, and <math>K_i</math> is the vapor/liquid equilibrium ratio for component i [4]. Higher absorption factors result in higher absorptivity into the liquid and a decrease in the number of trays required for separation, however a diminishing return occurs after the absorption factor is greater than 2.0. An absorption factor of 1.4 is most commonly used.

An industrial example is lean oil absorption, which is used to separate nitrogen and other impurities from natural gas. A lean oil is contacted with low quality natural gas, and the methane is selectively absorbed by the lean oil, leaving the impurities behind. The methane is subsequently regenerated from the rich oil as high quality natural gas [7].

==Stripping==
This process separates solutes from solvents (often after absorption, to purify the solvent so that it can be recycled to an absorber). Stripping will depend on the vapor and liquid flow rates, as well as the temperature and pressure of the column. There is a temperature drop down the column, so columns generally have either an increased operating temperature or decreased operating pressure.

The stripping factor of component i is

<math>S_i=K_iV/L</math>

where <math>K_i</math> is the vapor/liquid equilibrium ratio, <math>V</math> is the vapor flow rate entering the column, and <math>L</math> is the liquid flow rate entering the column, will determine how much of solute i will be stripped from the liquid into the vapor phase [4]. The usual range for the stripping factor is between 1.2 and 2.0, with a stripping factor of 1.4 being most economic.

An example of stripping in industry is the deodorization of food items such as oils. The oil is heated and allowed to trickle down the column while steam flows up from the bottom of the column. At the vapor-liquid interface, volatile components of the oil transfer to the steam and are carried off the top of the column, leaving a purified oil product [8].

==Other Separation Processes==
===Extraction===
Liquid-liquid extraction is a process for components with overlapping boiling points and azeotropes. The process requires a solvent such that some of the components of the mixture are soluble, and then the components will be separated based on this solubility in the liquid. This process can operate at moderate temperatures and pressures, so is not very energy intensive. However, a distillation column is required to extract the solvent for recycle. More recently, supercritical fluids have replaced liquid solvents in some processes for L/L extraction, due to the solute’s ability to more rapidly diffuse through them. The issue with these fluids, however, is that they must be operated at extremely high pressures and temperatures, increasing both capital and operating expenses of the process [4].

===Crystallization===
This process recovers solutes that have been dissolved in solution. The resulting product is in the solid phase. Depending on the material properties of the solute and solvent, the solute is recovered by precipitation after cooling, removal of solvent, or adding precipitating agents. Crystallizers are designed based on phase equilibria, solubilities, rates and amounts of nuclei generated, and rates of crystal growth. Every crystallization process is a unique system, so plant evaluation is usually required before complete implementation. Crystallization can be performed in both batch and continuous processes, and design features can control crystal size to an extent [4].

===Membrane Separation===
This separations process uses selectively permeable membranes to separate components in a mixture. Typically, one of the components will freely pass through the barrier while the other components will not. The stream that passes through the membrane is the permeate and the stream that does not pass is the retentate. The driving force behind this separation is a pressure gradient. Membrane separation is beneficial because it can separate mixtures at the molecular and small particle level. Furthermore, there is no phase change required so the energy input is low. Limitations of this process include achieving high product purity, incompatibility with certain stream components, low operating temperature, and low flow rates. Although membrane separation is generally not scaled up, examples of scaled-up membrane separation include seawater desalination and hydrogen recovery [4].

===Adsorption===
Adsorption involves an adsorbent and adsorbate. The adsorbent is typically a solid, and will typically separate the adsorbate from the stream. This process usually includes a desorption step that regenerates the adsorbent for further use. Raising the temperature or increasing the concentration of the adsorbate can reverse the adsorption process. Although the recycle of the adsorbent is a very economic design feature, the downside of this step is that it results in a cyclic process, which introduces complexity to the overall process. Industrial applications of this process are for bulk separations and gas purification. The adsorption/desorption process in these situations involves a large amount of heat transfer, which design engineers must take into account when sizing and selecting equipment material [4].

===External Field/Gradient Separation===
These separations use external force fields or temperature gradients to separate responsive molecules or ions. The use of these processes is fairly limited to a few specialized industrial applications [4].

===Settling and Sedimentation===
In settling processes, solid particles or liquid drops are separated from a stream by gravity. The stream can be in either the liquid or gas phase. For vapor-liquid mixtures, flash drums are generally used to separate the mixture. The velocity of the vapor must be less than the settling velocity of the liquid drops for this separation to occur. For liquid-liquid separation, the horizontal velocity of the fluid must be low enough to allow the low-density droplets to rise to the interface and the high-density droplets to move away from the interface and coalesce. In sedimentation, the result of the process is a more concentrated slurry. Typically a flocculating agent is used to aid in the settling process. One way to perform this separation is to use a cone-shaped tank with a slowly revolving rake that scrapes and moves the thickened slurry to the center of the cone for removal [4].

===Flotation===
Flotation is a process designed for specific solid-solid mixtures. It works by generating gas bubbles in a liquid that attach to selected solid particle. Afterwards, the particles rise to the liquid surface where they are removed by an overflow weir or mechanical scraper. The separation depends on the surface properties of the particles and its preference to attach to the gas bubbles. To meet the necessary requirements of the flotation process, a number of additives can be used to control things like the pH of the liquid-solid mixture, the activity of the solid surface, and the froth that can assist in separation. The bubbles can be produced by gaseous dispersion, dissolution, or electrolysis of the liquid [4].

===Centrifugation===
This process is similar to external field separation in that an external force field is applied to separate a mixture. When gravity separation is too slow due to particle densities, particle size, settling velocity, or the formation of an emulsion, centrifugation is commonly used. Centrifugal force increases the total force acting on the particle and results in faster separation times. This process is generally used to separate solids from liquids, however it can also be used to separate two liquids with very different densities [4].

===Drying===
Drying is performed to remove liquid from a liquid-solid mixture and produce a dry solid. Water is most often the liquid removed, but organic liquids are removed from solids on occasion as well. The heat required to vaporize the liquid is usually obtained by a series of gas-solid contacting devices. Feed condition and temperature sensitivity of the solid dictate the type of contacting device that is used. There are two groups of dryers that differ by the dependence of either mechanical means or fluid motion for gas solid contact. Another feature of dryers is to use either direct (hot gas) or indirect (conductive surface) heating [4].

===Evaporation===
Evaporators separate solvents from a solution by evaporation. The difference between evaporation and distillation is that evaporation requires the solute be nonvolatile. Because of this, a high separation can be achieved with one stage. Evaporators are essentially reboilers, so evaporation is a very energy-intensive process with a high thermal economy [4].

===Filtration===
Filtration is a process that separates a mixture of solid in a liquid or gas by passing the mixture through a porous medium in which the particles do not pass. Filtration is done by either cake filtration (particles found on the surface of the filter) or depth filtration (particles found within the filter). Cake filtration is generally performed with a cloth as the filtration medium [4].

==Conclusion==

==References==
# Wankat, P.C. (2012). ''Separation Process Engineering.'' Upper Saddle River: Prentice-Hall.
# Towler, G.P. and Sinnot, R. (2012). ''Chemical Engineering Design: Principles, Practice and Economics of Plant and Process Design.''Elsevier.
# Biegler, L.T., Grossmann, L.E., and Westerberg, A.W. (1997). ''Systematic Methods of Chemical Process Design.'' Upper Saddle River: Prentice-Hall.
# Peters, M.S. and Timmerhaus, K.D. (2003). ''Plant Design and Economics for Chemical Engineers, 5th Edition.'' New York: McGraw-Hill.
# Seider, W.D., Seader, J.D., and Lewin, D.R. (2004). ''Process Design Principles: Synthesis, Analysis, and Evaluation.'' New York: Wiley.
# Turton, R.T., Bailie, R.C., Whiting, W.B., and Shaewitz, J.A. (2003). ''Analysis, Synthesis, and Design of Chemical Processes'' Upper Saddle River: Prentice-Hall.
# Stripping Column. Alfa Laval Web site. Available at: http://www.alfalaval.com/solution-finder/products/soft-column/Documents/Stripping%20Column.pdf. Accessed February 19, 2014.
# Lean Oil Absorption. PetroGas Systems Web site. Available at: http://petrogassystems.com/technology/natural-gas-processing-and-dew-point-control/lean-oil-absorption. Accessed February 19, 2014.