Page 326 - Distillation theory

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300 Synthesis of Separation Flowsheets

E+D+j
E D
42513
1 2 1-2-5
E 45213 42513 D
1 4 1-2-4; 1-5-4; 1-2-4-5
D 42153 E
1 3 1-3-5
D E
24135
2 3 1-2-3; 2-3-4; 1-2-3-4
D E
42135 42153
2 5 1-2-5; 2-3-5; 1-2-3-5
E 24135 24153 D
3 4 1-3-4; 3-4-5; 1-3-4-5
D 24153 42153 E
4 5 1-4-5; 2-4-5; 1-2-4-5
j(1) j(2)
t(2) t(2)
Figure 8.20. Tear-off segments Reg e and Reg e (shaded) for extrac-
i i
tive section on edges of the concentration pentahedron for the distillation
of three- and four-component constituents of the water(1)-methanol(2)-
acetic acid(3)-acetone(4)-pyridine(5) mixture for different entrainer (E)
and overhead product (D). To the left, present components i; to the right,
all components i + j.

t(3)
Reg e of intermediate sections in two-dimensional faces of the concentration
pentahedron. The analysis of possibility of separation for three sections proves
that there are several efficient splits meeting the three necessary conditions of
sharp separation: (1) 4 : 1,2,3,5 (entrainer 1,3), trajectory tear-off regions of inter-
2,5 4,5,2,1,3 4,2,5,1,3
t
mediate section Reg = Reg ord + Reg ord (Fig. 8.21a); (2) 2 : 1,3,4,5 (entrainer 3,5),
e
1,3,4 1,4 2,4,1,3,5 2,4,1,5,3
t
trajectory tear-off regions of intermediate section Reg = Reg ord + Reg ord (Fig.
e
2,3,5
8.21c); and (3) 4 : 1,2,3,5 (entrainer 3,5), trajectory tear-off region of intermediate
1,2 4,2,1,5,3
t
section Reg ≡ Reg ord (Fig. 8.21e).
e
3,4,5
8.5. Multicomponent Azeotropic Mixtures: Automatic Sequencing
and Selection
Automatic sequencing is carried out, beginning with the first column and examin-
ing it all possible splits. For each possible split in the first column, one obtains
composition of two products that for further separation go to the following
columns. All possible splits are also examined for each of following columns.
The tree of alternative sequences is obtained as a result. The products of each
sequence are the set target components or groups of components and, probably,
also azeotropes that cannot be separated into target components or groups of