Page 318 - Distillation theory

P1: JPJ/FFX P2: FCH/FFX QC: FCH/FFX T1: FCH
0521820928c08 CB644-Petlyuk-v1 June 11, 2004 20:20

292 Synthesis of Separation Flowsheets

45213 42513 42153 42135 42135 42153 24153
1 2 2 4
24
45213 42513 42153 42135 24135 42135 42153
1 3 2 5
45213 42513 42153 24153 24135 24153
1 4 3 4
45213 42513 42153 24135 24153 42153
1 5 3 5
15 35
42135 24135 24153 42153
2 3 4 5
i, j,k
(2)
Figure 8.12. Component-order Reg ord and tear-off (double line for the overhead product
j j
t(2) t(2)
Reg r and thick line for the bottom product Reg s ) segments on edges of the water(1)-
i i
methanol(2)-acetic acid(3)-acetone(4)-pyridine(5) concentration pentahedron.
2,3
t
The following splits are feasible: (1) 1 : 2,3,4 (entrainer 4, Reg − tear-off edge
e
4 1,4
1-4) because component 1 is possible top product Reg D at separation of mixture
1 1
1,4 and in face 2-3-4 there is possible bottom product region Reg B ; (2) 1 : 2,3,4
3 1,3,2,4 2,3,4
t
(entrainer 2,4, Reg − tear-off region Reg ord in face 1-2-4) because component 1
e
1,2,4 2,4
is possible top product Reg D at separation of mixture 1,2,4 and in face 2-3-4 there
1 1 2
t
is possible bottom product region Reg B ; and (3) 1,3 : 2,4 (entrainer 4, Reg −
e
2,3,4 1,3,4
3,1,2,4 1,3,2,4
tear-off regions Reg ord and Reg ord in face 1-3-4) because mixture 1,3 is possible
4
top product Reg D at separation of mixture 1,3,4 and mixture 2,4 is possible bottom
1,3 1,3
product Reg B at separation of the initial mixture.
2,4 2,3
t
We note that split 3 : 1,2,4 (entrainer 4, Reg − tear-off segment [3, α 13 ] in edge
e
3,4
3-4) is not feasible in spite of the fact that, as was shown, trajectory tear-off from
edge 3-4 is possible in the intermediate section and component 3 can be the top
product of separation of mixture 3,4. In this case, the third necessary condition –
possible bottom product composition region is absent in face 1-2-4 – is not valid.
3 1,2,3,4
t
Splits 1,2 : 3,4 (entrainer 4, Reg − tear-off region Reg ord in face 1-2-4) and 3 :
e
1 1,2,4 3,1,2,4
t
1,2,4 (entrainer 2,4, Reg − tear-off region Reg ord in face 2-3-4) are not valid for
e
2,3,4
the reasons given above.
8.4.6.3. Example 2: Simple Columns
We now discuss a more complicated task: separation of five-component mix-
ture water(1)-methanol(2)-acetic acid(3)-acetone(4)-pyridin(5) with three bi-
nary azeotropes 15, 24, 35 (Petlyuk et al., 1985). Figure 8.12 shows seg-
ijk
ments Reg ord of identical order of components; Figs. 8.13 and 8.14 show