Page 159 - Distillation theory

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5.4 Evolution of Section Trajectory Bundles for Three-Component Mixture 133

all components along side 2-3 (Fig. 5.15a) and to define maximum value of x max
B3
with the help of Eq. (4.20) (Fig. 5.15b). In the example under consideration, x max =
B3
0.266. Reversible distillation trajectory tear-off point x t = A= 0.44 corresponds
rev
to this composition of the bottom product.
1
The existence of possible bottom segment Reg at side 2-3 means that sharp
B
2,3
split 1: 2,3 is feasible in two-section column at finite reflux, which is unfeasible
according to the rule of connectedness (see Chapter 3) in the mode of infinite
reflux. The feasibility of such separation was shown first by means of calculation
in the work (Kondrat’ev et al., 1977).
(2) max
For any point x B located at possible bottom segment Reg ≡ [0, x ], there
B B3
are two trajectories of reversible distillation (Fig. 5.16) – with the node N rev in

2
+
N
x B
1 t
a) α 23 x rev
2 t
x rev
α 13

1 α 23 13 3

2 Figure 5.16. The evolution of separatrix
trajectory bundle and separatrix sharp
L
V/
x D ( ) 1 1
x B
α split region S → N ≡ Reg sh,R of the
+
V/L
b) 23 ( ) 2 sep,s
2,3
x F N 1 + S1 stripping section for the acetone(1)-
+
N 2 S 2 benzene(2)-chloroform(3) mixture: (a)
x B
α 13 V/L < (V/L) t1 , (b) (V/L) t1 < V/L <
rev
rev
(V/L) t2 , (c) V/L > (V/L) t2 .(V/L) t1
rev
rev
rev
and (V/L) t2 , ratios of flow rates V and
rev
Lat first and second reversible trajectory
1 α 23 13 3 tear-off points for bottom point x B .
2
x B
c) α 23
+
N
α 13
1 α 23 13 3