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

Analysis reference 55 in chap 2 presents ll

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Unformatted text preview: al reboiler. Absorbent oil enters stage 1 (top stage). Feed enters stage 9. Interreboiler with a heat duty of 1.0 MMBtu/h at stage13. Column operates at 230 psia. Overhead flow rate = 103 lbmol/h. Assumptions: SRK for K-values and enthalpies. Find: Product rates and compositions, stage temperatures, and interstage vapor and liquid flow rates and compositions. Reboiler duty with and without the interreboiler. Whether an interreboiler is worthwhile and if an intercooler should be considered. Analysis: The calculations were made with the Tower model (Inside-out method) of Chemcad, with the following specifications: No condenser Top pressure = 230 psia Column pressure drop = 0 psi. Number of stages = 15 plus a partial reboiler Absorbent oil (1st feed) to stage 1 Feed (2nd feed) to stage 9 Interreboiler (3rd feed) to stage 13 At the top, no condenser At the bottom, bottoms flow rate = 459 - 103 = 356 lbmol/h Estimated distillate rate = 103 lbmol/h (specified rate) Estimated reflux rate = 40 lbmol/h Estimated temperature of stage 1 = 80oF Estimated temperature of bottom stage = 300oF Estimated temperature of stage 2 = 90oF Note that the interreboiler is treated as the 3rd feed with a specification as a stream of 1.00 MMBtu/h. Convergence was achieved in 7 iterations. The results are shown on the following two pages. The column feed is 14.2% vaporized. The distillate rate is set to send the methane and ethane overhead, while a portion of the propane and all heavier components to the bottoms. The temperature of the interreboiler stage is 202.6oF compared to a bottoms temperature of 302.4oF. The heat duty of the reboiler is 3.164 MMBtu/h. Thus, almost 25% of the total required heat duty can be supplied by waste heat.. Results without the interreboiler, on a subsequent page, show only a small effect on the separation, with the major effect being 17% more ethane leaving in the overhead vapor and a reboiler duty of 4.177 MMBtu/h. If an intercooler of a heat duty of 100,000 MMBtu/h is added at stage 4, along with the interreboiler at stage 13, as shown below, less ethane leaves in the overhead vapor. Thus, the use of an intercooler is not desirable. Exercise 10.40 (continued) Analysis: (continued) With interreboiler Exercise 10.40 (continued) Analysis: (continued) With interreboiler Exercise 10.40 (continued) Analysis: (continued) Without interreboiler Exercise 10.40 (continued) Analysis: (continued) With interreboiler and intercooler Exercise 10.41 Subject: Design of a reboiled stripper. Given: Feed of composition below at 39.2oF and 150 psia. Column with 7 equilibrium stages plus a partial reboiler, operating at 150 psia. Bottoms flow rate of 99.33 lbmol/h. Assumptions: SRK for K-values and enthalpies. Find: Product compositions, stage temperatures, interstage flow rates and compositions, and reboiler duty. Analysis: : The calculations were made with the Tower model (Inside-out method) of Chemcad, with the following specifications: No condenser Top pressure = 230 psia Column pressure drop =...
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