Page 167 - Distillation theory

P1: JPJ/FFX P2: FCH/FFX QC: FCH/FFX T1: FCH
0521820928c05 CB644-Petlyuk-v1 June 11, 2004 20:15

5.5 Trajectory Bundles for Four- and Multicomponent Mixtures 141

three-component mixture, if it is unstable (x D ≡ N ) or stable node (x B ≡ N )
+
−
of concentration space. Such splits are correspondingly direct or indirect splits as
at the product – pure component. These splits can be used, for example, in the
units, where entrainer, forming azeotrope with one of the components of the ini-
tial mixture, is used for separation of binary azeotropic mixture (see Chapter 8).

5.5. Structure and Evolution of Section Trajectory Bundles for
Four- and Multicomponent Mixtures

5.5.1. Four-Component Mixture

General regularities of the evolutions of sections trajectory bundles, discussed
in the previous section for three-component mixtures, are valid also for the
mixtures with bugger number of components. Figure 5.23 shows evolution of
top section trajectory bundle at separation of four-component ideal mixture,
when the product is pure component (i.e., at direct split) (K 1 > K 2 > K 3 >

2 2
a) b)

+ +
N N
S
1 4 1 4
x D x D

3 3

2 2
D
c) d)
F

B S 2
− +
S 1 N + N N
1 4 1 4
x D
x D
S 2 3
S
3 3
Figure 5.23. The evolution of trajectory region of the rectifying section for
anidealmixturewith K 1 > K 2 > K 3 > K 4 (component1istheproduct):(a)
1
1
1
1
1
1
L/V < K , (b) K < L/V < K , (c) K < L/V < K , (d) L/V > K (the
4 4 3 3 2 2
2,3,4
1
1
1
attraction region Reg R ≡ Reg 1 att shaded). K , K , and K , phase equilib-
w,r
4
2
3
1
rium coefficients of components 2, 3, and 4, respectively, in vertex 1.