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Unformatted text preview: by the distillation
boundary (curve q) and the overall mass-balance line that passes through pure species L (line
LF1M); that is, the lightly shaded region RMKR. The region of distillate compositions is also
bounded by the distillation boundary (curve q). In addition, it is bounded by the end points of the
chords (BiDi) that are tangent to the distillation lines at the tangent points (K, B1,…, B4 ,..., I)
forming the dashed curve in the figure below. Because the distillate and bottoms-product
compositions must lie on the same distillation line, for the feed composition at F1, the distillate
compositions must lie to the left of the overall mass-balance lines through the tangent points at
Bi (Di F1 Bi).
It follows that, for the feed at F1, the regions of feasible distillate and bottoms-product
compositions, are the shaded portions of the union of F1PLF1 and LD0 ... D3L regions, and the
F1MHF1 regions, respectively." Analysis: (continued) Exercise 11.7 (continued) Exercise 11.8
Subject: Regions of feasible product composition on a ternary diagram
Given: Residue curve map and distillation curve map of Fig. 11.10 for the ternary system,
acetone, methanol, and chloroform, which has one maximum-boiling binary azeotrope, two
minimum-boiling azeotropes and one ternary azeotrope, all homogeneous.
Find: Feasible product composition regions for a feed of 50 mol% chloroform, 25 mol%
acetone, and 25 mol% methanol.
In the right-triangle diagram on the next page, the feed composition is shown at F. Thus,
the feed is in Region 1, which is bounded by distillation boundaries A and B, the binary mixture
of chloroform and acetone from pure methanol to the azeotrope, and the binary mixture of
chloroform and methanol from pure chloroform to the binary azeotrope. For Region 1, the
minimum boiling product is AZ1, the azeotrope of chloroform and methanol, boiling at 53.9oC,
while the maximum boiling product is AZ2, the azeotrope of chloroform and acetone, boiling at
65.5oC. To determine the feasible product compositions, one straight line is drawn from AZ1 to
its intersection with distillation boundary B. Another straight line is drawn from AZ2 to its
intersection with distillation boundary A. These two lines define an approximate bow-tie region
through which a line from the feed point F to either pure chloroform and the ternary azeotrope
(both infeasible products) does not pass. This approximate bow tie region is refined by adding a
residue curve (or distillation curve) that passes through the feed point F. The final feasible
product composition region is confined to the convex side of this added residue curve, as shown
by the shaded bow-tie region. Typical bow-tie regions are shown for this system in the
equilateral triangle diagram of Figure 11.12b. For the feed of this exercise, the feasible product
composition regions are shown on an equilateral triangle residue curve map diagram, drawn by
Aspen Plus, on the last page of this exercise. Analysis: (continued) E...
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This document was uploaded on 02/24/2014 for the course CBE 2124 at NYU Poly.
- Spring '11
- The Land