Just what is a Chemical Engineering Degree?

Well, it has chemistry in it, but it is not a chemistry degree. Like all engineering it is about design, but in our case the design of complex industrial processes that make the stuff that make the world. 

Like all engineers we must do calculations, and it is important that we get them right. 

The focus of IChemE accredited degrees is the design project. In the third or fourth year a group of students design an industrial process to produce some substance. The product could be an industrial chemical, a plastic, a pharmaceutical, an enzyme or many other things. 

To see what is needed, take a simple chemical reaction where A and B react to make a product P and waste W. (And don’t forget the heat of reaction ΔH!) 

A + B = P + W + ΔH 

The chemical engineer will of course design the reactor but consider the rest of the process. 

A and B need to be stored. Each might be a liquid in a tank, a solid in a silo or a gas in a pressurized vessel. Some mechanical engineering is needed to design these and other equipment. They need to be transported to the reactor, by pumping a liquid, blowing, or conveying a powder through a pipe, or from the pressure of a gas. The chemical engineer needs to know about all these technologies, but also the underlying science of fluid mechanics to be able to size the storage vessels, pipes, pumps, or compressors. It is the chemical engineer’s chemical and mechanical knowledge which enables the material of construction to be chosen. 

There might be other things needed in the reactor, e.g., a catalyst C and solvent S, which also need to be stored and transported. 

The materials and/or the reactor may need to be heated or cooled, so graduates become expert in the physics of heat. 

To mix materials requires a quite different and complex part of fluid mechanics, and the equipment and power requirements must be specified. Chemical engineers must have a good understanding of energy science as well as its practical applications. 

Chemical kinetics and thermodynamics are calculated for multiple reactions in changing concentrations, so conditions can be optimised for yield and selectivity. 

Once the reaction is finished the product P must be separated from the waste W. Any unreacted A and B, catalyst C and solvent S are also separated to be recycled. The separation processes can include many such as crystallization, distillation, filtration, liquid-liquid extraction, membranes, and chemical reactions e.g., precipitation. A lot of the plant, like a lot of the degree is taken up by these processes. 

One of the major successes of chemical engineering has been to convert the chemist’s reaction or distillation in a flask over a certain time into a continuous one. Materials go in and come out continuously. Suppose this is a continuous process. 

The product, the separation and recycle streams will need their own storage, piping and transport, making a complicated arrangement shown on a flow diagram. Communication with diagrams is an essential skill.

An example flow diagram for the production of Ammonia (Source: Wikipedia commons, attributed to Francis E Williams)

The flow rates, pressures and temperatures will be monitored by instruments and continuously adjusted by a control system, an essential part of the chemical engineering design, and a highly mathematical one. 

The disposal of waste is a major consideration from the outset, whether this is a solid, gas or liquid. Where it cannot be used it must be made safe for environmental protection. This along with human safety are absolute requirements of the student design project and the working chemical engineer. 

The degree will also consider biological processes and cover the costing, economic appraisal and management skills expected of a graduate chemical engineer. 

It is a challenging course, giving a versatile designer of many industrial processes.