Page 162 - Materials Chemistry, Second Edition

Mass-Balance Concept and Reactor Design 145

Solution:
(a) For the 4-m reactor,
3
the residence time = V/Q = 4 m /(0.04 m /min) = 100 min
3
3
Q, C in Q, C out
4 m 3

Use Equation (4.20) to find the final effluent concentration:

C out C out 1
= =
+
C in 1,800 1(0.1)(100)
C = 164 mg/kg (It exceeds the cleanup level.)
out
3
(b) For the two 2-m reactors,
the residence time = V/Q = 2 m /(0.02 m /min) = 100 min each
3
3
Q/2, C 0 Q/2, C 1
2 m 3
Q, C 0 Q, C f
Q/2, C 0 Q/2, C 2
2 m 3

Use Equation (4.20) to find the effluent concentration from each
reactor:

1
C out C out
= =
+
C in 1,800 1(0.1)(100)
C = 164 mg/kg for both reactors (The combined final effluent
out
exceeds the cleanup level.)
(c) The residence time of the first reactor = 1 m /(0.02 m /min)
3
3
= 50 min
The residence time of the second reactor
= 3 m /(0.02 m /min) = 150 min
3
3
Q/2, C 0 Q/2, C 1
1 m 3
Q, C 0 Q, C f
Q/2, C 0 Q/2, C 2
3 m 3