Process Technology: An Introduction - Haan A.B. 2015

3 Principles of chemical reaction engineering
3.1 Introduction

Design of a chemical reactor is no routine matter, and many alternatives can be proposed for a process. In searching for the optimum it is not just the cost of the reactor that must be minimized. One design may have low reactor cost, but the materials leaving the unit may be such that their treatment requires much higher cost than alternative design. Hence, the economics of the over-all process must be considered. Reactor design uses information, knowledge and experience from a variety of areas:

· — thermodynamics;

· — chemical kinetics;

· — fluid mechanics;

· — heat transfer;

· — mass transfer;

· — mechanical engineering;

· — economics.

Chemical reaction engineering is the synthesis of all these factors with the aim of properly designing a chemical reactor. The design of chemical reactors is probably the one activity which is unique to chemical engineering, and it is probably this function more than anything else which justifies the existence of chemical engineering as a distinct branch of engineering.

In reactor design we want to know what size and type of reactor and method of operation are best for a given job. To establish the actual behavior of a reactor for a certain application two major basic questions have to be answered:

· — What changes can we expect to occur?

· — How fast will these changes take place?

The first question concerns the thermodynamics, the second the various rate processes (chemical kinetics, heat transfer etc.). Tying these all together and trying to determine how these processes are interrelated can be an extremely difficult problem. Since this is far beyond the scope of this course, the content of this chapter is limited to the most essential basics and some simple situations that provide a basis to discuss and appreciate the work of chemical reaction engineers.