Page 433 - Elements of Chemical Reaction Engineering Ebook

404 Nonelementary Reaction Kinetics Chap. 7

2.5
2.0

rate 1.5
g/dm3-1.., 1.0

0.5

0.0
0 2 4 6 8 1012
t (W

"I
0.4

0.3

0.1

0.0
0 2 4 6 8 1012
t (hr)
Figure E7-9.1 Concentrations and rates as a function of time.

7.5.5 Chemostats

Chemostats are essentially CSTRs that contain microorganisms. A typi-
cal chemostat is shown in Figure 7-16, along with the associated monitoring
equipment and pH controller. One of the most important features of the
chemostat is that it allows the operator to conthl the cell growth rate. qis
control of the growth rate is achieved by adjusting the volumetric feed rate
(dilution rate).

7.5.6 Design Equations

In this section we return to mass equations on the cells [Equation
(7-1 17)] and substrate [Equation (7-1 18)] and consider the case where the vol-
CSTR umetric flow rates in and out are the same and that no live @e., viable) cells
enter the chemostat. We next define a parameter common to bioreactors called
the dilution rate, D. The dilution rate is