What is a chemical engineer?

So the first post of the summer blog series on chemical engineering is appropriately about what a chemical engineer is. Crazy, I know.

It seems that there is a lot of confusion about what a chemical engineer actually does, judging by the questions that I am asked about what I study and what I could do with my degree. I can't say I'm surprised, since I didn't even know what chemical engineering was before I decided to be one! This may stem from the fact that chemical engineers are significantly different than the traditional types of engineers that long ago made bridges, fortresses, cannons, steam engines, and radios. These engineers have gone on to make skyscrapers, airplanes, car engines, and computers. Chemical engineers might be able to work on any of these applications, though we may not be the best at designing or maintaining any of them. We are most appropriately suited for work in the chemical industry, making products as diverse as shampoo, explosives, pharmaceuticals, and fuels.

Chemical engineers design the chemical plants that produce many of the compounds that are used today. There are many, many steps of heating, mixing, fermenting, pressurizing, filtering, and distilling that are required to make even the most basic products, and I hope to describe many of them in the coming weeks. Chemical engineers have knowledge of the physical, chemical, and thermal properties of a wide range of substances, and we use those properties to manipulate and create a desired product. To get the discussion started, I have made a list of characteristics of chemical engineers.

1. We don't actually use that much chemistry.

This comes as a shock to most people. "But you are a chemical engineer, aren't you?" Well, yes, but that probably doesn't mean the same thing to you that it means to me or to the chemical industry. Chemistry and chemicals generally conjure images of color-changing reactions in a beaker, seen through the foggy goggles provided by the school. The key difference between myself and a chemist is that, I don't make new chemicals. Chemists and pharmacists are responsible for making things like new plastics and cures for diseases, but chemical engineers are responsible for figuring out how to make lots of a new chemical. Almost always there are steps that are performed on a lab bench that could never be used on a large scale, and there are additional complications that arise when trying to mass produce a chemical. When I say that we have to figure out how to make lots of a chemical, I mean that we have to figure out how to make the chemical cheaply and without too much waste, all while using the resources that are available at the location of the plant. Often these goals are at odds with one another, in that doing better at one will cause problems with another. In my opinion, the core of any discipline of engineering is finding the solution that best satisfies conflicting goals.

We also don't do that much chemistry because for every reaction that occurs in a chemical plant, there are inevitably a dozen other large pieces of equipment used to make that reaction happen. Reactions almost always need to be heated or cooled, and often pressure has to drop or increase to achieve the proper reaction conditions. Reactions also always produce a mixture of products, and the desired products must be separated before they can be sold and used. In reality, all of these things occurred on your lab bench in general chemistry lab, but the auxiliary processes of heating, cooling, and separation were probably very expensive compared to the product you made; it just didn't matter at all, since you weren't trying to sell what you made. These concerns of cost, waste, and resources become central to the industrial chemical engineer.

2. Chemical engineers are very good at thermodynamics, heat transfer, fluids, and mass transfer.

I mentioned that I'm not very good at chemistry. This is true in that my skill in chemistry pales in comparison to a real chemist, though I am probably a lot better at chemistry than most people. I am really good at this strange science called thermodynamics, which describes how materials react to heating, cooling, and pressure and volume changes. It is very helpful in the chemical plant, where one must know, for example, how much heat it takes to make your chemical react or separate itself from the mixture it is in. Heat transfer, mass transfer, and fluids are three other areas of study that are fairly similar and help determine things like how long it will take for the heating to occur, or how much energy pump must use be to actually accomplish the
desired change in pressure.

3. We only know one equation.

In-Out+Generation=Accumulation

I'm beginning to realize that almost every chemical engineering equation I know is a special case of this equation. It says that if you put stuff into something, there will be more there, and if you take stuff out, there will be less stuff in there. Also, if somehow more stuff appears in your something, then there will be more stuff in there. I know I'm not explaining it very well, but I could write at least one note about this equation, and I probably will this summer. I'm also making the equation sound easier to use than it actually is: the terms "In" and "Out" often account for several different factors, and they are also often represented with complex mathematical expressions. "Generation" is even more tricky, as it is the term we use for chemical reactions and other confusing phenomena like nuclear reactions. "Accumulation" just makes your life a mess when it has to be included, as it is almost always represented as a differential in time that requires integration.

4. We're marginally good at biology.

In recent decades, there has been much interest within the scientific community in engineering using biological materials. The potential uses are diverse: using microbes and algae to produce fuel, the engineering of better synthetic joints, and the treatment of diseases using modified viruses. Chemical engineers have participated in many of these efforts because of the chemical basis of life. At the fundamental level of almost every biological phenomenon, there is a chemical reaction taking place. Chemical engineering departments (including the dept. at CSM) are beginning to integrate more biology in their curricula, and the chemical and biological engineering departments are combined at many schools (including the dept. at UW Madison). Again, my knowledge of biology is marginal compared to a real biologist or biochemist, but I know enough to apply the principles of biology to mass production of biochemicals. My senior design project was the design of a biofuel plant, for example.

Four is an awkward number, but I'm going to stop there because I've covered everything I wanted to. Next week, tune in for a description of how Worcestershire sauce is made!