Page 272 - Distillation theory

P1: JPJ/FFX P2: JMT/FFX QC: FCH/FFX T1: FCH
0521820928c07 CB644-Petlyuk-v1 June 11, 2004 20:18

246 Trajectories of the Finite Columns and Their Design Calculation

The distillation trajectory for the column under consideration may be presented
as follows:

x B → qS s → x f ⇐⇓ x f −1 → x e ⇐⇓ x e−1 → x D
Reg B Reg t s [x f ] ∈ Reg qsh,R [x f −1 ] ∈ Reg qsh,R Reg t e Reg att Reg D
sep,e
sep,s
We now examine the calculation of section trajectories by method “from tray
to tray” for various splits of multicomponent mixtures by extractive distillation.

7.4.2. The Multicomponent Mixtures: The Top Product and the Entrainer Are Pure
Components (m r = 1, m e = 2)
Section 6.5 shows that the joining of section trajectories in the feed cross-section
and in the cross-section of the entrainer input at such split is similar to direct
separation in two-section column (Fig. 7.13a). Because the bottom product of the

x D 1
2 S r 2 x
a) b) 1 − e
x E +
x ≡ N
S 2 e m
x F m S 2
x max s
−
f 1 1
S
x min s
x B − f 1
+ x min −
x f ≡ N s f N m
x F x F
− x
N F+ E
x − x m
e 1 F+ E
1 4 1 4
x ≡ N + x +
x D e m E N s S m x E
1
S
1
3 S m 2 3 s
c) S
m
1
S
s
+
N
s
x F N −
m
x F+
1 E 4
x x
D E
+
x ≡ N
x e 1 − e m
S 1 r 3
Figure 7.13. Section separatrix sharp split regions for extractive distillation of ideal four-
2,3
component mixtures (K 1 > K 2 > K 3 > K 4 ): (a) Reg R (component 1 is overhead product, com-
w,e
3 1,2 1,4
ponent 4 is entrainer), (b) Reg R and Reg R (mixture 1,2 is overhead product, component
w,e sep,s
2 1,2,4 3,4
4 is entrainer), (c) Reg R w,e (component 1 is overhead product, mixture 3,4 is entrainer). The
1,3,4
separatrix sharp split surfaces (Reg sh,R and Reg sh,R ) are shaded.
sep,e
sep,s