Separation Process Principles- 2n - Seader & Henley - Solutions Manual

Find feasible product composition regions for a feed

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Unformatted text preview: a portion of a distillation curve for the system acetone - benzene n-heptane. Given:. Ternary system acetone - benzene - n-heptane at 1 atm. Assumptions: UNIFAC method for computing K-values. Find: Portion of a distillation curve starting from a bubble-point liquid of 20 mol% Acetone (1), 60 mol% Benzene (2), and 20 mol% n-Heptane (3), at 1 atm, using a simulation program. Analysis: The distillation curve is computed stagewise using the FLASH model in Chemcad, in the same manner as in Example 11.2, except that here the calculation is made in both directions. To begin, a bubble point is run with Chemcad on the above initial liquid composition, xi(1), at 1 atm. The computed vapor composition, yi(1), is set equal to xi(2), according to Eq. (11-14) so that the compositions of passing vapor and liquid streams are made equal, and the bubble-point calculation is repeated. In this manner, we step in the first direction. The sequence is repeated, starting again from xi(1), but this time running a sequence of dew points to step in the opposite direction. The results are as follows, with a plot on the following page. x (1) 0.0000 0.0000 0.0003 0.0024 0.0146 0.0633 0.2000 0.4384 0.6643 0.7996 0.8702 0.9076 x (2) 0.0445 0.0967 0.1953 0.3464 0.5125 0.6196 0.6000 0.4447 0.2695 0.1510 0.0879 0.0526 x (3) 0.9555 0.9033 0.8044 0.6512 0.4729 0.3171 0.2000 0.1169 0.0698 0.0494 0.0419 0.0397 y (1) 0.0000 0.0003 0.0024 0.0146 0.0633 0.2000 0.4384 0.6643 0.7996 0.8702 0.9076 0.0000 y (2) 0.0967 0.1953 0.3464 0.5125 0.6196 0.6000 0.4447 0.2695 0.1510 0.0879 0.0526 0.9996 y (3) 0.9033 0.8044 0.6512 0.4729 0.3171 0.2000 0.1169 0.0698 0.0494 0.0419 0.0397 0.0004 T, o C 96.65 94.59 91.23 86.98 82.59 77.39 70.19 70.20 63.31 59.44 57.73 56.94 Analysis: (continued) Exercise 11.6 (continued) Exercise 11.7 Subject: Regions of feasible product composition on a ternary diagram Given: Residue curve map of Fig. 11.13, which shows a highly curved distillation boundary Find: Feasible product composition regions for Feed F1. Analysis: The solution to this exercise is given in detail by Widagdo and Seider in Ref. 19 of Chapter 11. Their figure 20, shown below, shows the bow-tie regions. Because the distillation boundary is highly curved, as discussed in Section 11.1, feasible product compositions lie on both sides of the distillation boundary when the feed is at F1. The two dark-shaded feasible regions are on the feed side of the distillation boundary, while the two lightly shaded regions are on the other side of the distillation boundary. As stated by Widagdo and Seider, "The region of feasible compositions on the feed side is bounded by the distillation line p that passes through the feed, the distillation boundary (curve q), and the two overall mass-balance lines through pure species H and L. The bottoms products lie in the shaded portion of the F1RKHF1 region, and the distillates lie in the shaded portion of the F1PLF1 region. On the other side of the distillation boundary, the region of feasible bottoms-product compositions is bounded...
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This document was uploaded on 02/24/2014 for the course CBE 2124 at NYU Poly.

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