Page 298 - Introduction to chemical reaction engineering and kinetics

Chapter 11

Preliminary Considerations

in Chemical Reaction

Engineering

In this chapter, we return to the main theme of this book, chemical reaction engineering
(CRE). We amplify some of the general considerations introduced in Chapter 1, before
the detailed consideration of quantitative design methods in Chapter 12 and subsequent
chapters.
We begin by considering general aspects of reactor selection, performance, and de-
sign, primarily from the point of view of process design, but with passing reference to
mechanical design. We then present a number of equipment/flow diagrams, some gener-
ically schematic and some relating to specific industrial processes, to illustrate many of
these aspects (see also Figure 1.4). In this way, we attempt to develop a general ap-
preciation for reactors and CRE before the detailed consideration of their design and
performance.

11.1 PROCESS DESIGN AND MECHANICAL DESIGN
Process design has to do with specifying matters relating to the process itself, such as
operating conditions, and size, configuration, and mode of operation of the reactor.
Mechanical design has to do with specifying matters relating to the equipment itself
in the sense of structural and mixing requirements, among others. Both are necessary
for complete design, but our scope in this book is confined to process design, which is
primarily the domain of the chemical engineer.

11.1.1 Process Design
11.1.1.1 Nature of Process Design in CRE
The problem of process design in CRE typically stems from the requirement to pro-
duce a specified product at a particular rate (e.g., 1000 tonnes day -I of NH,). The sub-
stance(s) from which the product is made may be specified or may have to be chosen
from more than one option. Process design then involves making decisions, as quan-
titatively as possible, about the type of reactor and its mode of operation (e.g., batch
or continuous), its size (e.g., volume or amount of catalyst), and processing conditions
(e.g., T, P, product distribution, if relevant). The criteria constraining these decisions

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