Page 62 - Elements of Chemical Reaction Engineering Ebook

Conversion 2

and Reactor Sizing

Be more concerned with your character than with your
reputation, because character is what you really are
while reputation is merely what others think you are.
John Wooden, coach, UCLA Bruins

The first chapter Focused on the general mole balance equation; the balance
was applied to the four most common types of indushial reactors, and a design
equation was developed for each reactor type. In Chapter 2 we first define con-
version and then rewrite the design equations in terms of conversion. After car-
rying out this operation, we show how one may size a reactor (i.e., determine
the reactor volumt: necessary to achieve a specified conversion) once the rella-
tionship between reaction rate, rA, and conversion is known.

2.1 Definition of Conversion

In defining conversion, we choose one of the reactants as the basis of calculla-
tion and then relate the other species involved in the reaction to this basis. In
most instances it is best to choose the limiting reactant as the basis of calculla-
tion. We develop the stoichiometric relationships and design equations by con-
sidering the general reaction

aA+bB cC+dD (2-1)

The uppercase letters represent chemical species and the lowercase letters rep-
resent stoichiometric coefficients. Taking species A as our basis of calculation,
we divide the reaction expression through by the stoichiometric coefficient of
species A, in order to arrange the reaction expression in the form

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