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In-Depth Information
L
/
V
of 0.8 is derived from the external reflux ratio specification, which is also shown
and corresponds to an operating external reflux ratio of 4.
An overall material balance yields the following results:
Distillate, D
=
24
.
8 lbmol/hr,
x
D
=
0
.
8
Sidestream, S
=
10 lbmol/hr,
x
S
=
0
.
4
Bottoms, B
=
65
.
2 lbmol/hr,
x
B
=
0
.
25
The various liquid and vapor flow rates throughout the column, based on equal molar
overflow, are given in Figure 11.8, from which the operating line slopes are derived:
Enriching section:
L/V
=
99
.
2
/
124
=
0
.
8
Sidestream section:
L
/V
=
89
.
2
/
124
=
0
.
72
Stripping section:
L
/V
=
189
.
2
/
124
=
1
.
53
The preliminary design is given in Figure 11.9. There are a total of eight theoretical
equilibrium contacts, one of which is the reboiler, as well as a total condenser. The
feed is on stage 7 and the sidestream is on stage 6, counting from the top down. This
v = 124
L = 99.2
D = 24.8
v = 124
S = 10
L
′
= 89.2
v = 124
F = 100
L
″
= 189.2
v = 124
Figure 11.8
Three-product distillation example with equal molal overflow.
