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

317 001765 using the shortcut fug model of chemcad the

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Unformatted text preview: very of nC4 to the distillate = 95%. Recovery of iC5 to the bottoms = 95%. Number of equilibrium stages = 2 times that of the minimum stages by the Fenske equation. SRK for K-values and enthalpies. Find: A suitable design. Assume this consists of products, profiles, and stage compositions. Analysis: The Shortcut model of Chemcad computes a minimum number of stages = 10.7 and a minimum reflux ratio of 3.36. Therefore, select 2(10.7) = 21.4 or 22 stages (including the partial reboiler). Estimate the reflux ratio at 1.3(3.36) = 4.4. For the rigorous TOWER model of chemcad, use the following specifications: Total condenser Top pressure = 125 psia No condenser or stage pressure drop. Therefore, bottom pressure also = 125 psia Number of stages = 23 (includes total condenser and partial reboiler) Feed stage = 12 from the top At the top, component recovery of n-butane (component 2) = 0.95 At the bottom, component recovery of isopentane (component 3) = 0.95 Estimated distillate rate = 50 lbmol/h (actual rate) Estimated reflux rate = 50(3.36) = 168 lbmol/h (actual rate) Estimated temperature of stage 1 = 120oF Estimated temperature of bottom stage = 250oF Estimated temperature of stage 2 = 140oF The feed is given as a bubble-point liquid at 125 psia. Using the SRK correlation, the temperature is computed to be 210oF. After 4 iterations, the calculations are converged, while increasing the reflux rate to 267.9 lbmol/h, and the distillate rate to 52.11 lbmol/h, at which the 95% recoveries of the two key components are achieved. The computed results are as follows on this page and the next pages. Condenser duty = 2,517,800 Btu/h Reboiler duty = 2,582,500 Btu/h Top temperature = 160.8oF compared to assumed value of 120oF Bottom temperature = 233.2oF compared to assumed value of 250oF Stage 2 temperature = 165.8oF compared to assumed value of 140oF Exercise 10.29 (continued) Analysis: (continued) Analysis: (continued) Exercise 10.29 (continued) Exercise 10.30 Subject: Design of a depropanizer distillation column. Given: Feed at column average pressure of 315 psia and 66 mol% vaporized. Composition of feed in lbmol/h is as follows: 26 C1, 9 C2, 25 C3, 17 nC4, 11 nC5, 12 nC6. Separation is between C3 (0.4 lbmol/h in bottoms) and nC4 (0.3 lbmol/h in distillate). Cooling water available at 65oF and steam available at 315 psia. Total column pressure drop = 2 psi. Assumptions: Partial reboiler. Grayson-Streed correlation for K-values and Redlich-Kwong equation for enthalpies. Find: (a) Type condenser. (b) Feed temperature. K-values and relative volatilities at feed temperature and pressure. (c) Reflux ratio for 1.3 times minimum reflux ratio. Number of equilibrium stages in rectifying and stripping sections. (d) Separation. Separation for reflux ratio = 1.5 times minimum, 15 theoretical stagess, feed stage at stage 9. (e) Temperature and compositions at each stage for Part (c). Effect on these results if reflux and stages of Part (d) are used. Analysis: Use the Flash, Shortcut, and TOWER models of Chemcad to make the...
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This document was uploaded on 02/24/2014 for the course CBE 2124 at NYU Poly.

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