Page 13 - The engineering of chemical reactions

Preface XIII
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important) in that task. Process design is basically reactor design, because the chemical
reactors control the sizes and functions of other units.
2. The most important reactor by far in twentieth century technology is the fluidized
catalytic cracker. It processes more chemicals than any other reactor (except the au-
tomotive catalytic converter), the products it creates are the raw materials for most of
chemical technology, and this reactor is undoubtedly the largest and most complex piece
of equipment in our business. Yet it is very possible that a student can receive a B.S.
degree in chemical engineering without ever hearing of it.
3. Most industrial processes use catalysts. Homogeneous single reaction systems are fairly
rare and unimportant. The most important homogeneous reaction systems in fact involve
free radical chains, which are very complex and highly nonlinear.
4. Energy management in chemical reactors is essential in reactor design.
5. Most industrial reactors involve multiple phases, and mass transfer steps between phases
are essential and usually control the overall rates of process.
6. Polymers and their monomers are the major commodity and fine chemicals we deal with;
yet they are considered mostly in elective polymer chemistry and polymer properties
courses for undergraduates.
7. Chemical engineering is rapidly changing such that petroleum processing and commod-
ity chemical industries are no longer the dominant employers of chemical engineers.
Polymers, bioprocesses, microelectronics, foods, films, and environmental concerns are
now the growth industries needing chemical engineers to handle essential chemical
processing steps.
8. The greatest safety hazard in chemical engineering operations is without question
caused by uncontrolled chemical reactions, either within the chemical reactor or when
flammable chemicals escape from storage vessels or pipes. Many undergraduate students
are never exposed to the extremely nonlinear and potentially hazardous characteristics
of exothermic free radical processes.

It is our belief that a course in chemical reaction engineering should introduce all
undergraduate students to all these topics. This is an ambitious task for a one-semester
course, and it is therefore essential to focus carefully on the essential aspects. Certainly,
each of these subjects needs a full course to lay out the fundamentals and to describe the
reaction systems peculiar to them. At the same time, we believe that a course that considers
chemical reactors in a unified fashion is essential to show the common features of the diverse
chemical reactors that our students will be called on to consider.
Perhaps the central idea to come from Minnesota is the notion of modeling in chemical
engineering. This is the belief that the way to understand a complex process is to construct
the simplest description that will allow one to solve the problem at hand. Sometimes a single
equation gives this insight in a back-of-the-envelope calculation, and sometimes a complete
simulation on a supercomputer is necessary. The chemical engineer must be prepared to
deal with problems at whatever level of sophistication is required. We want to show students
how to do simple calculations by capturing the essential principles without getting lost in
details. At the same time, it is necessary to understand the complex problem with sufficient
clarity that the further steps in sophistication can be undertaken with confidence. A modeling