Page 19 - The engineering of chemical reactions

Chapter 1

INTRODUCTION
-

CHEMICAL REACTORS

he chemical reactor is the heart of any chemical process. Chemical processes turn
inexpensive chemicals into valuable ones, and chemical engineers are the only
T people technically trained to understand and handle them. While separation units
are usually the largest components of a chemical process, their purpose is to purify raw
materials before they enter the chemical reactor and to purify products after they leave
the reactor.
Here is a very generic flow diagram of a chemical process.

Raw materials from another chemical process or purchased externally must usually be
purified to a suitable composition for the reactor to handle. After leaving the reactor, the
unconverted reactants, any solvents, and all byproducts must be separated from the desired
product before it is sold or used as a reactant in another chemical process.
The key component in any process is the chemical reactor; if it can handle impure raw
materials or not produce impurities in the product, the savings in a process can be far greater
than if we simply build better separation units. In typical chemical processes the capital
and operating costs of the reactor may be only 10 to 25% of the total, with separation
units dominating the size and cost of the process. Yet the performance of the chemical
reactor totally controls the costs and modes of operation of these expensive separation
units, and thus the chemical reactor largely controls the overall economics of most processes.
Improvements in the reactor usually have enormous impact on upstream and downstream
separation processes.
Design of chemical reactors is also at the forefront of new chemical technologies.
The major challenges in chemical engineering involve
3