Page 212 - Distillation theory

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186 Distillation Trajectories in Infinite Complex Columns and Complexes

6.4.2. Sharp Extractive Distillation of Four- and Multicomponent Mixtures

We now examine the structure of intermediate section trajectory bundle for four-
component mixtures at the example of ideal mixture (K 1 > K 2 > K 3 > K 4 ).
In accordance with the structural conditions of trajectory tear-off, three fol-
lowing variants of extractive distillation are feasible for such a mixture: (1) the
top product is component 1, the entrainer is component 4, and the pseudoproduct

point x lies in the continuation of edge 1-4 (Fig. 6.9a); (2) the top product is
D

mixture 1,2, the entrainer is component 4, and the pseudoproduct point x lies in
D
continuation of face 1-2-4 (Fig. 6.9b); and (3) the top product is component 1, the
entrainer is mixture 3,4, and the pseudoproduct point x lies in the continuation

D
of face 1-3-4 (Fig. 6.9c). 2,3
The working trajectory region Reg R at Fig. 6.9a is three dimensional. It is
w,e
1,4
1
2
limited by the saddle points S and S at reversible distillation trajectories in
m
m
faces 1-3-4 and 1-2-4 and by node points N and N at edge 1-4.
−
+
m m

R
Figure 6.9. Regions extractive section Reg w,e (shaded) for the extractive distillation of an ideal
2,3
R
four-component mixtures (K 1 > K 2 > K 3 > K 4 ): (a) Reg w,e (component 1, top product; com-
3 1,4 2
ponent 4, entrainer); (b) Reg R (mixture 1,2, top product; component 4, entrainer); (c) Reg R
w,e w,e
1,2,4 1,3,4
(component 1, top product; mixture 3,4, entrainer).