Environmental Engineering Reference
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1
y
0.9
Equilibrium line
0.8
1
y
=
x
line
2
x
D
0.7
3
4
Feed line
0.6
5
Top operating line
0.5
6
0.4
0.3
7
0.2
Bottom operating line
0.1
8
x
F
0
x
B
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
x
Liquid ethanol
Figure 4.8
Complete McCabe-Thiele analysis of a distillation process.
(a)
(b)
Feed line
Pinch
point
Pinch
Feed
line
y
x
B
x
F
x
D
x
B
x
F
x
D
x
x
Figure 4.9
Minimum reflux analysis for pinch points (a) at, and (b) above the
feed plate.
equilibrium lines. Since there is no gap between the lines, it is not possible to step off
stages beyond this point. This usually occurs at the intersection of the operating,
q
, and
equilibrium lines. Some systems, however, do not have pinch points at this intersection
due to the shape of the vapor-liquid equilibrium line.
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