Page 157 - Distillation theory

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5.4 Evolution of Section Trajectory Bundles for Three-Component Mixture 131

2
a)
x t
rev
+
N
x
D

1 3

S 3 2
x D S 2
b) (L V)
S 1 1
t
x rev (L V)
x F 2
(L V) = 1
3
x B
x D
+
N
1
+
N 2
1 + 3
N
3
Figure 5.14. The evolution of separatrix trajectory bun-
3
dle and separatrix sharp split region S → N ≡ Reg sh,R
+
sep,r
1,2
of the rectifying section for an ideal mixture with K 1 >
K 2 > K 3 (mixture 1, 2 is the product): (a) (L/V) <
(L/V) t rev , (b) (L/V) > (L/V) t rev , (L/V) 3 = 1, (L/V) 3 >
(L/V) 2 > (L/V) 1 .

L/V > (L/V) t rev for top product point under consideration there is one distillation
trajectory).
Deviations from the above evolution of distillation trajectory found at separa-
tion of nonideal zeotropic and, especially, of azeotropic mixtures are connected
with the peculiarities of location of reversible distillation trajectories and with
nonmonotony of change of the parameter L/V along these trajectories (see Chap-
ter 4).
The most important peculiarities of location of reversible distillation trajecto-
ries of azeotropic mixtures, influencing the evolution of distillation trajectories at
the change of the parameter L/V, are limitedness of trajectory tear-off segment
j j j j
Reg t(k) or Reg t(k) and of possible product composition segment Reg (k) or Reg (k)
r s D B
i i i i
at the side of concentration triangle, availability of two node points or absence of
node points of reversible distillation trajectories.