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Truth and Empiricism in Chemical Engineering

By: , Posted on: May 21, 2015


I have written An Applied Guide to Process and Plant Design in order to address the shortcomings of Chemical Engineering Education. These shortcomings have become so entrenched that academics now think that their mistaken approaches are superior to those of real engineers. To quote from chapter 5 of the book:

“Some areas of physics have, to outsiders, clearly lost themselves in abstraction. Seduced by the beauty of higher mathematics, they pursue things which seem to look right, even though they are piling unsupported speculation on top of itself many times over to get there.

The theorists responsible are now crying to be freed from the requirement to prove any part of their theories empirically. They think that they should instead be allowed to pursue mathematics and philosophy where they think they lead.

“The partial differential equation entered theoretical physics as a handmaid, but has gradually become mistress.”


The problem is that mathematics and philosophy deal what is plausible within their conventions, rather than the truth. Without a grounding in empiricism, physics of this type is pure self-indulgence, which is why the product of this lost school of physics is sometimes called “physics porn”.

The philosophical tool which protects us against losing ourselves in abstraction in this way is the beefed up version of Occam’s Razor known colorfully as “Newton’s Flaming Laser Sword”: “what cannot be settled by experiment is not worth debating”.

We seem to have developed a similar problem in process plant design. In a computer model’s mathematical space, many things seem plausible, but we only find out what is possible when we build the plant. Some are even generating things they call rules of thumb for design by repeated simulation, as if we had proven that such models are reliable analogues of the real world.

This approach is similar enough to physics porn in its lack of empirical support that we might call it “process porn”. In the resultant academic discourse on process design, it seems now to be considered axiomatic that the approach followed by all professional engineers is hopelessly obsolete.

An approach based on higher mathematics, theoretical sciences, modeling and simulation programs, and network analysis techniques is now thought in academia to be the future of process design. This may have something to do with the fact that these disciplines and tools are those which academics know and, further, that the vast majority of chemical engineering lecturers worldwide have never designed a real process plant.

The idea that engineering is just applied mathematics and science is commonplace in these circles, but this is an idea held only by those who have never practiced, or have never reflected upon their practice.

All practitioners know that much of what they were taught in university is worthless in practice, and much that would have been of value was not taught (the supposed exception to this rule are French engineers, who according to the old engineering joke ask “So eet works in practice, but does eet work in theory?”).

Universities feel that they have to staff their departments with scientific researchers, and few engineers want to do research – we want to be engineers, not scientists. Scientists are also a lot cheaper than chemical engineers. All of this was fine as long as staff knew that they were stand-ins for the engineers who were not available or affordable, but they have started making a virtue of their deficiencies.

I hear that many research-led universities teach the process plant design methodology:

  • Look for bench scale experiments which give possible process chemistry
  • Use these unproven techniques as the basis of a costing exercise which goes only as far as comparing feedstock and product prices.
  • If product sells for more than feedstock, assume process is economic
  • Use the unproven technique as the basis of a hysys model
  • “Optimize” the hysys model (which means only getting recycles to converge)
  • Grind through pinch analysis by explicitly defined rote methodology
  • Produce short word document which describes how they navigated the decision tree provided by the lecturer

At the end of this time-consuming exercise, all we have a worthless hysys model based on bench scale experiments without any scale-up consideration, limited in scope to a reactor and an associated separation process.

We have given no thought to whether the standard hysys data and assumptions are valid in our case (they will probably not be), and we apparently think that getting recycles to converge in a computer model can be called optimization.

We have not required students to give any thought to cost, safety, or robustness, or produce any engineering deliverables. They have at no point been required to exercise the slightest judgment, imagination, or intelligence.”

applied guide to process and plant designAn Applied Guide to Process and Plant Design is available for pre-order on the Elsevier Store.

Use discount code “STC215” at checkout and save up to 30% on your very own copy!

About the Author

sean moranProfessor Moran is a Chartered Chemical Engineer with over twenty years’ experience in process design, commissioning and troubleshooting. He started his career with international process engineering contractors and worked worldwide on water treatment projects before setting up his own consultancy in 1996, specializing in process and hydraulic design, commissioning and troubleshooting of industrial effluent and water treatment plants.

In his role as Associate Professor at the University of Nottingham, he co-ordinates the design teaching program for chemical engineering students. Professor Moran’s university work focuses on increasing industrial relevance in teaching, with a particular emphasis on process design, safety and employability.

Connect with Sean on LinkedIn here, check out his Facebook page here and stay up-to-date on his thoughts, research and practice at his personal blog here.

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