Page 166 - Materials Chemistry, Second Edition

Mass-Balance Concept and Reactor Design 149

C = 12.2 mg/kg
1

Reactor 2: C 1 = e − (0.1)(150) = e − 15
1,800

C = 0.00055 mg/kg
2
Use Equation (4.31) to find out the concentration of the com-
bined effluent

−
4
+
×
2(12.2)2(5.5 10 )
C f = = 6.1 mg/kg
22+
The combined final effluent is below the cleanup level.
(d) The residence time of the first reactor = 1 m /(0.01 m /min)
3
3
= 100 min
The residence time of the second reactor
= 1 m /(0.04 m /min) = 100 min
3
3
Q/4, C 0 Q/4, C 1
1 m 3
Q, C 0 Q, C f
3Q/4, C 0 3Q/4, C 2
3 m 3

Use Equation (4.24) to find the effluent concentration from each
reactor:

C out C out − (0.1)(100) − 10
= = e = e
C in 1,800
C = 0.082 mg/kg for both reactors (The combined final effluent
out
is below the cleanup level.)

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 the configurations are below
the cleanup level. The configurations (a), (b), and (d) have the
same effluent concentrations because the residence times of all
reactors are identical. The effluent concentration from configura-
tion (c) is the worst among the four.