Page 180 - Distillation theory

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

154 Distillation Trajectories and Conditions of Mixture Separability

2 2
R = R R > R
min min
a) b)
R < R x f-1 R = R
R < R min R = R min
x f-1
min min
x f ≡ N s
+
x f ≡ N s
1 3 1 3
x D x D
2
R = R min
c)

R < R
R < R min x f-1 min

+
x ≡ N
f s
1 3
x
D
Figure 5.31. The joining of section trajectories under minimum reflux for the direct
split of (a) the ideal mixture, (b) the nonideal mixture with the convex boundary of the
1
attraction region Reg , and (c) the nonideal mixture with the concave boundary of the
att
1
attraction region Reg .
att
of the method “product simplex” (see Chapter 3) taking into consideration all the
2(2)
stationary points. Then the working point S r identified.
5.6.4. Intermediate Splits

For the intermediate splits, it is possible to take into consideration in the best
way the regularities of location of section trajectory bundles, using two- or three-
stage algorithm of search for (L/V) min with gradual precise of the value of this
r
parameter.
At the first stage, the simplified model of feed tray (Fig. 5.29b) and assumption
about linearity of minimum reflux bundles are accepted. At this stage, the value
(L/V) min is determined taking into consideration the coordinates of stationary
r
points from the condition of intersection of linearized minimum reflux bundles
2
2
+
S − N and S − N (i.e., the smallest value of parameter [L/V] r is found at
+
r r s s
1
2
2
+
which there is intersection of linearized bundles S − N and S − S − N or
+
r r s s s
2
1
2
S − N and S − S − N ). The coordinates of intersection point should meet
+
+
s s r r r
the linear equation system, describing each of two intersecting bundles. Along
with that, if the bundles intersect each other, then the point of intersection should
be located inside corresponding linear manifolds, but not at their continuation.
This criterion is checked at each trial value of (L/V) r , gradually increasing this