Define product and feed

Authors: Michael Gleeson, Sean Kelton, Thomas Considine

Introduction

A key step in the initial phases of chemical process design is the project definition. Along with the customer definition and location of the facility, the definition of the key feeds and products is important (Towler, 17). Both feed and product specifications are found in the Design Basis, a non-exhaustive document containing key information and details of the plant and process.

Primary Raw Materials

The definition of raw materials on the Design Basis is located in Section 5 (see image). There are 6 main categories: Feedstock name and grade, MSDS form number, Feedstock availability, Feedstock price, Known feedstock impurities, and Additional specifications. It is of vital importance to recognize that when deciding upon feed specifications, not only stoichiometric chemistry should be considered, but also safety, yield, and environmental hazards (Biegler, 14).

Each component of the feed, once decided upon, must be entered in the Design Basis section:

Feedstock name and grade

In this section, the the name of each component of the feed is entered. Along with the generic name of the compound, its formal chemical name, as well as grade should be included. Again, no feedstock available in industry will have 100% purity. The most common grade will be "technical" or "industrial". However, "laboratory" or "reagent" grade (higher purity) is less common.

MSDS form number

The MSDS (material safety data sheet) is an important part of dealing with any compound, with regards to operational hazards. In this section, the specific MSDS number of each component must be listed so as to be readily available in case more information is requested. MSDSs contain key physical data, such as flash point, melting point, etc.; as well as information on storage and disposal. Sources such as Perry's Chemical Engineers' Handbook also contains sources of flammability hazards of many chemicals (Seider 37).

Feedstock availability

The availability of each feedstock must also be recorded. Whether on a per year or per day basis depends primarily on the frequency of use of each specific material. This information is dependent on the overall production rate of the facility.

Feedstock price

The price of each material is listed in this sub-section. This information is highly relevant when completing the economic analysis. Note that feedstock price is highly dependent on quantity purchased. Often, the quotes of bulk chemical prices must be obtained directly from suppliers.

Known feedstock impurities

Along with the general feedstock grade (recorded in the Feedstock name and grade sub-section), the specific known impurities are recorded in this section. The name of each compound (commonly water, minerals, etc.) is recorded along with their concentrations in ppmw. The impurities are listed with the sale of the feedstock product.

Additional specifications

Any additional pertinent information about the feedstock is listed in this section. Examples include potential alternatives sources or uses.