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

# The wt compositions of these points are read from the

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Unformatted text preview: ction of methylcyclohexane (MCH) from n-heptane (C) with aniline (S) at 25oC in a countercurrent-stage extractor. Given: Feed of 50 wt% MCH in C. On a solvent-free basis, extract contains 95 wt% MCH and raffinate contains 5 wt% MCH. Reflux at both ends as in Fig. 8.26a. Minimum extract reflux ratio = 3.49. Equilibrium data in Exercise 8.22. Find: With a right-triangle diagram: (a) Raffinate reflux ratio. (b) Amount of aniline that must be removed by solvent removal at the top of the extractor, as shown in Fig. 8.26a. (c) Amount of solvent that must be added to the mixer at the bottom of the extractor, as shown in Fig. 8.26a. Analysis: The liquid-liquid phase equilibrium data are given, for each phase, as mass % MCH on an aniline-free basis, and mass of aniline per mass of aniline-free mixture. To plot the data on a triangular diagram, it is necessary to convert the equilibrium data to mass % for each of the three components. For example, when the HC-rich layer contains 9.9 wt% MCH on an anilinefree basis and 0.0836 lb aniline per lb aniline-free mixture, we have for 1 lb of aniline-free mixture: 0.099 lb MCH, 0.901 lb n-heptane, and 0.0836 lb aniline, for a total of 1.0836 lb. The corresponding mass % values are: MCH 9.14 wt%, n-heptane 83.15 wt%, and aniline 7.71 wt%. Calculations for the other equilibrium compositions given in the table accompanying Exercise 8.22 are summarized in the following table: Hydrocarbon-rich layer: Wt% Wt% MCH nC7 0.00 92.60 9.14 83.15 18.58 73.41 21.94 69.85 33.73 57.68 40.63 50.68 45.96 45.05 59.66 30.74 67.14 22.86 71.58 18.23 73.57 16.04 83.30 5.41 88.11 0.00 Aniline-rich layer: Wt% Wt% Aniline MCH 7.40 0.00 7.71 0.80 8.01 2.70 8.21 3.00 8.59 4.61 8.69 6.00 8.99 7.40 9.60 9.80 10.00 11.32 10.19 12.69 10.39 13.10 11.29 15.59 11.89 16.89 Wt% nC7 6.20 5.99 5.30 5.11 4.50 4.00 3.60 2.98 2.11 1.60 1.39 0.62 0.00 Wt% Aniline 93.80 93.21 92.00 91.89 90.89 90.00 89.00 87.22 86.57 85.71 85.51 83.79 83.11 The triangular liquid-liquid equilibrium diagram is given on the next page. Referring to Fig. 8.26a, compositions of feed, F, solvent-free extract, D, and solvent-free raffinate, B, are plotted. Exercise 8.20 (continued) Analysis: (continued) Analysis: (continued) Exercise 8.20 (continued) By construction on the triangular diagram on the previous page, the compositions of the solvent-containing extract, VN , and the solvent-containing raffinate, L1 , are determined as intersections of straight lines (drawn from the solvent-free points toward the 100% solvent point, SB ) with the equilibrium curve. The wt% compositions of these points are read from the diagram to be: Wt%: Component Extract, VN Raffinate, L1 Aniline, S 84.0 7.5 n-Heptane, C 1.0 88.0 Methylcyclohexane, MCH 15.0 4.5 Total: 100.0 100.0 Take a basis of 1,000 kg/h of feed and make material balances for the minimum extract reflux condition. Because the feed is 50 wt% MCH and 50 wt% C, and the two solvent-free product compositions are symmetrical with respect to MCH and C, the solvent-free material balance is quickly determ...
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