Page 96 - Distillation theory

P1: JPJ/FFX P2: FCH/FFX QC: VINOD/IYP T1: FCH
0521820928c03 CB644-Petlyuk-v1 June 11, 2004 20:12

70 Trajectories of Distillation in Infinite Columns Under Infinite Reflux

2

x
D(1) x
B(2)
Figure 3.21. Some possible splits
12
23 (x D(1) : x B(1) , x D(2) : x B(2) , x D(3) : x B(3) ,
x D(4) : x B(4) ) of ternary azeotropic
x
D(4) x B(3) mixture at m > n. Product simplexes
Reg simp are shaded.
x F

1 3
x x
D(2) B(1)
x D(3) x B(4)

The rule of product simplex gives us the instrument that allows not only to
determine feasible splits in the first column, but also gives an opportunity to
determine at once the compositions of the products in the sequence of (n − 1)
columns. Compositions corresponding to the vertexes of the product simplex the
feed point belongs to can be obtained as columns’ system products.
If m > n, then feed point belongs to several product simplex. Therefore, several
sets of products, corresponding to vertexes of each product simplex, can be got
from such feeding. Let’s examine a few examples.
For the product simplex Reg simp ≡ 2 → 13 → 1(2 ⇒ 1), the set of products in
the system of two columns is 2; 13; 1 (Fig. 3.6). For the product simplex Reg simp ≡
12 → 1 → 3 (12 ⇒ 3), the set of products is 12; 1; 3 (Fig. 3.10a). For the product
simplex Reg simp ≡ 1 → 13 → 2 → 4(1 ⇒ 4), the set of products is 1; 13; 2; 4 (Fig.
3.18a).
Therefore,themixtureacetone(1)-benzene(2)-chloroform(3)-toluene(4)ofthe
composition (0.25; 0.30; 0.20; 0.25) can be separated into three columns without
recycles into acetone, benzene, toluene, and the azeotrope of acetone and chloro-
form.
Feeding x F at Fig. 3.21 (12 ⇒ 23) gets into two product simplexes Reg simp ≡
12 → 1 → 3 and Reg simp ≡ 1 → 3 → 23. Therefore, this mixture can be separated
into two columns and into products 12; 1 and 3 or products 1; 3 and 23.
Feeding at Fig. 3.15 (12 ⇒ 24) can get into several product simplex, for example,
into simplexes Reg simp ≡ 1 → 3 → 23 → 24 and Reg simp ≡ 12 → 3 → 23 → 24
(bonds chain 12 → 1 → 3 → 23 → 24). In this case, sets of products 1; 3; 23 and
24 or 12; 3; 23 and 24 are feasible (simplex Reg simp ≡ 12 → 3 → 23 → 24 shown
at Fig. 3.15). At the other composition, feeding can get into simplexes Reg simp ≡
12 → 1 → 3 → 4; Reg simp ≡ 12 → 3 → 4 → 24; and Reg simp ≡ 1 → 3 → 4 → 24