Page 98 - Distillation theory

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72 Trajectories of Distillation in Infinite Columns Under Infinite Reflux

2 x D(2)
a)

x F(1)+Az+2
D1
x=x F() 2
x F ) 1 ( = x F ) 1 ( + Az+ 2+ 1

x B(1) x B(3)
1 x F(1)+Az 13 x B(2) 3
x D(3)

x D(1)
b) 2 13

x F(2) x F()3
x F(1)

1 x B(2) 3

Figure 3.22. (a) A concentration triangle of three-
component azeotropic mixture with one binary
azeotrope and curvilinear separatrix, and (b) a column
sequence with recycles. (1), (2), (3), columns; x F(1) , ini-
tial feed; x F(1)+Az , initial feed and recycle of column (3)
overhead product; x F(1)+Az+2 , initial feed and recycles
of columns (3) and (2) overhead products; x F(1)+Az+2+1 ,
initial feed and recycles of columns (3) and (2) over-
head products and recycle of column (1) bottom
product.

a number of binary azeotropic mixtures using various entrainers (butanol-water
with methanol; methanol-methylacetate with hexane) is examined in the work
(Laroche et al., 1992). In spite of the fact that in the last example ternary mixture
with three binary and one ternary azeotropes appears, it can be separated into
two columns with recycle of ternary azeotrope.

3.7. Nonsingularity of Separation Products Compositions
at R =∞ and N =∞
For ideal mixtures at R =∞ and N =∞ and at fixed feed composition, unique
products compositions (point x D and x B at Figs. 3.3 and 3.4) correspond to each
value of parameter D/F at the interval [0,1]. That is, monotonous increase of
parameter D/F at the interval [0,1] corresponds to movement of point x D at the
segments 1 and 3 at Fig. 3.3 and at the segments 1, 2 and 3 at Fig. 3.4 and to