Sustainability and Stability - Bioprocess Engineering: Kinetics, Biosystems, Sustainability and Reactor Design - page 805

I

H G or r (- H R )

H R
Slope = C HV

II

III

0

T H

0

T

FIGURE 16.10 Heat of generation and heat of removal in a nonisothermal CSTR.

and

UA H T c W s
V

T 0 D P N S

j¼1 C j0 C Pj þ

T H ¼ (16.24)

UA H

V þD P N S

j¼1 C j0 C Pj

Now that the similarity of Figs. 16.8 and 16.3 clearly indicates that the solution procedure
and qualitative behaviors of the steady solutions are similar. In this nonisothermal CSTR
case, we have more feed parameters: feed concentration, feed temperature, feed rate,
heat-exchange capacity (heat-exchange area and heat-exchange coefficient), heat-exchange
fluid temperature, and stirrer energy input. All these parameters can be lumped to three
parameters: D, C HV , and T H . The feed parameters change will alter one or more among
D, C HV , and T H differently. Furthermore, the dilution rate affects the heat of generation
(via r, see Table 16.1 ). If we leave the heat of generation curve alone (assuming constant),
then the feed parameters can be reduced to two lumped parameters: C HV and T H . Feed
concentrations, dilution rate, and heat-exchange capacity will have a dominant effect on
C HV , while feed temperature, heat-exchange fluid temperature, and stirrer energy input
have a dominant effect on T H .
Example 16-3 Thermal hysteresis: ignition/extinction curve.
The hydrogenation of aromatics (A) in an oil is to be carried out in a continuous well-
mixed tank reactor at a constant hydrogen pressure. The reactor contains 20 g of catalyst
and is operated adiabatically. The feed oil contains 30 wt% of A and the average molecular
mass is 210. The average heat capacity is 1.75 J/(g $ K) and the heat of reaction for hydroge-
nation of aromatics (A) is 2.0 10 5 J/mol. The rate function is

r 0 A ¼ 1:310 11 e 16300=T C A moles -A=ð h $ g - cat Þ