Design 1

Team BAT Final Report

Authors: Anne Disabato, Tim Hanrahan, Brian Merkle

Instructors: Fengqi You, David Wegerer, David Chen

Date Presented: March 14, 2014

Executive Summary

In an effort to build a new bio-product facility for Evanston Chemical, Team BAT is considering producing 99.7% propylene glycol solution. Team BAT designed a small-scale process to use the crude glycerin waste from an up-steam biodiesel facility. It was assumed that capital is available at 12%.

Research on an industrially available propylene glycol manufacturing process, patented by GTC Technology, and a universal process for purifying crude glycerin were used guided the final design [1], [2]. The facility is divided into two sub-processes: pre-treatment of crude glycerin and continuous hydrogenolysis of glycerin to propylene glycol. Microsoft Visio and Aspen HYSYS were used to design the process flow diagram and simulate the production. All other calculations were performed in Microsoft Excel. The plant was designed to operate safely, and have minimal environmental impact.

Team BAT’s plant produces 18.6 tonnes per year of 99.7% propylene glycol. Economic analysis predicts a net present value of - $4.2 million on a twenty-year basis. Based on this analysis, the proposed propylene glycol production facility would be not be economically viable without considerable scale-up and optimization.

Introduction

Propylene glycol, C3H8O2, is a non-corrosive, non-toxic, low volatility liquid, used as chemical feedstock for the production of unsaturated polyester resins, and in the food, beverage, cosmetic, and pharmaceutical industry [3]. The freezing point of water is lowered when mixed with propylene glycol, and the latter is therefore used as an anti-freeze and de-icing fluid. Propylene glycol also lowers vapor pressure, making it an ideal burst protection fluid in pipes and vessels. As a cleaning product additive, propylene glycol acts as a stabilizer for the dirt-removing ingredients and helps retain their function at low temperatures.

In food and beverage products, propylene glycol is mainly used as a solvent and carrier of flavor and color, or as a thickener, clarifier, and stabilizer in items such as beer, salad dressing, and baking mixtures. It provides lipstick with its consistent texture, preserves the homogenous consistency of body lotions containing both oil and water, and ensures that shampoos foam nicely. In the pharmaceuticals industry, propylene glycol is used to solubilize and provide equal distribution of the active ingredient in the formulation.

The market for propylene glycol is currently dominated by Dow Chemical and BASF, with 1.8 million tonnes produced globally in 2011 [4]. Assuming a price of $1.16 per lb, the current market value is $3.97 billion per year [3]. Evanston Chemical Technology Division challenged their employees to design a bioproducts facility in Blue Island, IL capable of taking advantage of a small fraction of this market.

The goal of this report is to evaluate Team BAT’s design of a propylene glycol plant, to determine if Evanston Chemical should invest in independent production. The design of our plant was driven by current manufacturing processes found in literature. The design is split into two sections for simplicity: batch purification of crude glycerin and continuous hydrogenolysis of glycerin to propylene glycol. The facility, project economics, and process flow diagram were modeled on Aspen, Aspen Process Economic Analyzer, and Microsoft Visio, respectively.

Design Basis

As a part of Evanston Chemicals, Team BAT studied an industrial method of producing propylene glycol through continuous hydrogenolysis as described in the GTC Technology 2013 patent. Evanston Chemicals corresponding biodiesel facility produces 4,700 lbs / week crude glycerin as a byproduct. With crude glycerin being a commodity in excess, the option of selling crude glycerin will be ignored and the available 4,700 lbs / week will be considered free. Our process was designed to increase biodiesel facility profits by taking advantage of the unwanted crude glycerin byproduct.

Team BAT also considered the Davy Process Technology Limited patent, which uses minimal hydrogen and carried out the reaction in multiple stages [5]. After careful process and market considerations, the GTC process was chosen based on low capital-costs, possible reduced operating costs due to multiple energy integration options, high selectivity in a one-step reaction, and relatively low temperatures.

If the GTC style facility produces the maximum possible 18.6 tonnes per year of propylene glycol, Evanston Chemical will account for less than 0.01% of the market. Team BAT decided not to produce and market additional propylene glycol because it is not the primary objective of the larger biodiesel facility.

Project Economics

The total fixed capital cost of the current design is $1.3 MM. The ISBL is $800K, and the OSBL is $300K, with an engineering and contingency cost of $200K. This cost, and all other price data, were adjusted for US Midwest and 2014 dollars. The propylene glycol product revenue is a net of $73K. The cost of raw material is $109K, assuming crude glycerol is free, and the annual cost of hydrogen, 37 wt% HCl and NaOH pellets is $60 K, $1K, and $42K, respectively. Other variable capital costs include $5K in continuous process utilities, $500K in salaries and overhead, and $10K in maintenance. The catalyst costs approximately $1,170 per year, and would need to be changed during the annual scheduled downtime.

Using a 10 year MACRS depreciation method, a tax rate of 28% and capital available at 12%, the project is not economically feasible, with the 10 and 20 year NPV coming in at -$3.2 MM and -$4.2 MM, respectively.

See Appendix I and II for the equipment costs and full economic analysis, respectively. The majority of equipment costing was done on ASPEN Economic Evaluation, with some smaller equipment costs found on Northern Tool & Equipment, Global Industrial, and PKG Equipment [6], [7], [8]. Utility costs for water and steam were estimated from the City of Chicago website and DailyFinance.com, respectively, [9], [10].

Plant Location

The propylene glycol plant will be located at 13636 Western Ave, Blue Island, Illinois 60406. The 10,000 square foot site includes: a truck loading dock, potential rail access, and connections to electric, water, and natural gas. The lease cost is $1,400 per month. Due to other operations at the site, including the biodiesel process, only 2,000 square feet will be allocated to the PG process. The effective lease cost will be spatially prorated for the PG process at $280/month.

Process Overview

In order to obtain purified glycerin, crude glycerin from the upstream biodiesel is batch purified in a network of vessels. After initial micro-filtration, the glycerin is sent to a vessel that undergoes five stages (A-E) of purification. In Stage A, it is sent to a vacuum evaporation unit, where methanol and water are removed. In Stage B, impurities are converted to more easily separated substances via saponification. After cooling, Stage C consists of acidification to further convert impurities. In stage D, the batch is neutralized. In stage E, the batch undergoes vacuum evaporation for a second time to remove water. Subsequent stages include a settling tank to separate liquid phases and extraction via petroleum ether and denatured ethanol.

In the GTC Technology process, a feed mixture comprising of purified glycerin, hydrogen, and methanol is preheated in a heat exchanger, and fed to a fixed-bed reactor. The reactor effluent is sent to a heat exchanger, where the stream is cooled. It is then separated into a vapor phase stream and a liquid phase stream. The vapor phase stream is released into the atmosphere. The liquid-phase stream is distilled in three distillation columns to obtain purified propylene glycol.

The following sections explain the above process in detail, outlining the results from HYSYS simulations and the rationale for design choices. See Appendix III for Process Flow Diagram of both the batch purification and continuous process.

Production Schedule

Calculations assume 8,424 hr/yr operation, implying approximately 351 days of continuous operation, leaving adequate time for maintenance. The primary maintenance consideration remains the catalyst regeneration, which must occur every year. This involves emptying the reactor tubes and refilling with new catalyst. A second maintenance consideration is cleaning the batch equipment. This issue is not pressing as the batch sub process is not run at full capacity. The shutdown, cleanup, and refilling should not require more than a week, ensuring compliance with the production schedule.