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

of lbmolh feed gas 16000 37000 24000 2500 500 000

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Unformatted text preview: number of stages, absorbent flow rate, and absorbent temperature on the absorption of a paraffin hydrocarbon gas. Given: 2,000 lbmol/h of a gas mixture containing in mole fractions, 0.830 C1, 0.084 C2, 0.048 C3, 0.026 nC4, and 0.012 nC5, at 75 psia and 60oF. Absorbent oil of MW = 161. Assumptions: SRK for K-values and enthalpies. Find: For the following four cases, compute product flow rates and compositions, and interstage vapor and liquid flowrates and compositions: Case No. of Stages (a) (b) (c) (d) 6 12 6 6 Absorbent rate, lbmol/h 500 500 1,000 500 Absorbent temperature, oF 90 90 90 60 Analysis: Chose nC11 , MW = 156, for the absorbent oil The calculations were made with the Tower model (Inside-out method) of Chemcad. For Case (a), the specs are: No condenser with top pressure = 75 psia Column pressure drop = 0 psi. Number of stages = 6 Feed gas to stage 6 Absorbent to stage 1 At the top, no condenser At the bottom, no reboiler Estimated distillate rate = 2,000 lbmol/h Estimated reflux rate = 500 lbmol/h Estimated temperature of stage 1 = 100oF Estimated temperature of bottom stage = 100oF Estimated temperature of stage 2 = 100oF Specifications for the other 3 cases differed only in the number of equilibrium stages and the flow and temperature of the absorbent oil, plus changes in the estimates. Convergence of each case was achieved in 3 or 4 iterations. The results for each case are given on the following s, where it is observed that 1. Doubling the number of stages, only increases the absorption of nC5. It is the only feed gas component with an absorption factor, A = L/KV, > 1. 2. Doubling the absorbent rate almost doubles the amount absorbed of each feed gas component. 3. Lowering the absorbent temperature increases somewhat the absorption of lighter components Analysis: (a) (continued) Exercise 10.36 (continued) Exercise 10.36 (continued) Analysis: (a) (continued) Exercise 10.36 (continued) Analysis: (b) (continued) Exercise 10.36 (continued) Analysis: (b) (continued) Exercise 10.36 (continued) Analysis: (c) (continued) Exercise 10.36 (continued) Analysis: (c) (continued) Exercise 10.36 (continued) Analysis: (d) (continued) Exercise 10.37 Subject: Absorption of a hydrocarbon gas with n-decane. Given: 1000 lbmol/h of a paraffin hydrocarbon gas, of composition below, at 90oF and 75 psia. 1000 lbmol/h of nC10 absorbent at the same temperature and pressure. Absorber has 4 equilibrium stages and operates at 75 psia. Assumptions: SRK for K-values and enthalpies. Find: Product rates and compositions, stage temperatures, and interstage vapor and liquid flow rates and compositions. Analysis: As shown below, when the gas feed was flashed, it was found to contain 7.2 mol% liquid. The calculations were made with the Tower model (Inside-out method) of Chemcad, with the following specifications: No condenser Column pressure drop = 0 psi. Number of stages = 4 Feed gas to stage 4 Absorbent to stage 1 At the top, no condenser At the bottom, no reboiler Estimated distillate rate...
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This document was uploaded on 02/24/2014 for the course CBE 2124 at NYU Poly.

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