Page 158 - Materials Chemistry, Second Edition

Mass-Balance Concept and Reactor Design 141

The residence time of the second reactor
= 3 m /(0.04 m /min) = 75 min
3
3
Q, C 0 Q, C 1 Q, C 2
1 m 3 3 m 3

Use Equation (4.29) to find the final effluent concentration:

 C 2   C 2   C 1 
=   =     = e [ ]× e [ ]
C 2 − (0.1)(25) − (0.1)(75)
C 0  1,800  C 1   C 0 
+
= e − (0.1)(25 75) = e − 10

C = 0.082 mg/kg (It is below the cleanup level.)
out
3
3
(d) The residence time of the first reactor = 3 m /(0.04 m /min)
= 75 min
The residence time of the second reactor
3
= 1 m /(0.04 m /min) = 25 min
3
Q, C 0 Q, C 1 Q, C 2
3 m 3 1 m 3

Use Equation (4.29) to find the final effluent concentration:

 C 2   C 2   C 1 
C 2 − (0.1)(75) − (0.1)(25)
=   =     = e [ ]× e [ ]
C 0  1,800  C 1   C 0 
+
= e − (0.1)(75 25) = e − 10

C = 0.082 mg/kg (It is below the cleanup level.)
out

Discussion:
1. The total volume of the reactor(s) for each of the four configura-
tions is 4 m .
3
2. The effluent concentrations from all four different configurations
are the same.
3. The effluent concentration of PFRs is much lower than those of
CFSTRs in Example 4.18.