Ideal Flow Reactors - Bioprocess Engineering: Kinetics, Biosystems, Sustainability and Reactor Design - page 230

at its minimal while the product concentration is at its maximal. This situation is not ideal if the
product is an intermediate product as the product concentration is high in the reactor and conse-
quently its further reaction to decomposition products is enhanced. On the other hand, in a PFR,
the reactant concentration is at its highest and the products are at their lowest in the reactor. This
situation favors the product that is the immediate from the reactants. At intermediate contact
times, the productivity of the intermediate products reaches maximum.

5. 9. STEADY NONISOTHERMAL FLOW REACTO RS

We have been focused on the ideal flow reactors so far without considering the change of
temperatures. If temperature is not constant, the rate of reaction will not be constant and in
turn it will affect the reactor performance. For steady nonisothermal flow reactors, the
temperature change in the reactor is governed by the energy balance equation:

F j0 H j H j0

X

N S

þ V X

N R

X

N S

d T
d t

d ðpVÞ

d t ¼ Q W s

r i DH R i þ C Pj n j (3.134)

j¼1 i¼1 j¼1

by setting d

d t ¼

0 . Thus, for a steady nonisothermal CSTR as shown in Fig. 5.19 , Eqn (3.134) is

reduced to

F j0 H j H j0

X

N S

þ V X

N R

r i DH R i ¼ Q W s (5.95)

j¼1 i¼1

Q 0 ,C j0 , T

0

Reactor feed

Heat transfer area is the surface area
between the jacket and reactor

Heat exchanging jacket

Reactor volume

Heat exchanging f luid in

T c

T

Heat exchanging fluid out

Reactor output

Q, C j , T

FIGURE 5.19 A schematic of a nonisothermal CSTR with a heat-transfer jacket.