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

The column feed is 142 vaporized the distillate rate

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Unformatted text preview: intercooler stage 5 Liquid out, lbmol/h 452.04 498.69 500.53 500.74 500.74 Temp., gas out, oF 144.9 133.8 137.3 138.6 138.6 Because the temperature was still significantly higher than the lower limit of 100oF, a higher intercooler heat duty of -2,000,000 Btu/h was tried at stage 5. However, the temperature of that stage dropped to 84oF. For a duty of -1,500,000 Btu/h, the temperature of stage 5 was an acceptable value of 102oF. The liquid out increased to 599.68 lbmol/h and the temperature of the gas out decreased to 127.5oF. The corresponding component absorption rates compared to those of the base case (no intercooler) were as follows: lbmol/h: Component No intercooler -1,500,000 Btu/h, stage 5 C1 13.75 21.09 C2 101.17 171.52 C3 143.59 212.32 nC 4 23.94 24.98 nC 5 5.57 5.66 Total: 288.02 435.57 Thus, the effect of the intercooler is very significant. The corresponding stage temperatures compared to those of the base case are also of interest: o Stage No intercooler -1,500,000 Btu/h - stage 5 F: 1 144.9 127.5 2 153.1 134.1 3 156.1 135.1 4 157.3 128.5 5 154.6 102.1 6 144.3 114.9 Exercise 10.39 Subject: Design of a an absorber with two absorbent oil feeds. Given: Feed gas at 90oF and 400 psia with the composition given below. Column has 8 equilibrium stages. Lean oil, assumed to be nC12, at 80oF and 400 psia at 250 lbmol/h enters the top stage. Secondary oil at 80oF and 400 psia, of the composition given below, enters stage 7 from the top. 150,000 Btu/h (-0.15 MMBtu/h) is removed by intercooling from stage 7. The feed gas enters stage 8. Assumptions: SRK for K-values and enthalpies. Find: Product rates and compositions, stage temperatures, and interstage vapor and liquid flow rates and compositions. Analysis: The calculations were made with the Tower model (Inside-out method) of Chemcad, with the following specifications: No condenser Top pressure = 400 psia Column pressure drop = 0 psi. Number of stages = 8 Lean oil (1st feed) to stage 1 Secondary oil (2nd feed) to stage 4 Intercooler (3rd feed) at stage 7 Feed gas (4th feed) to stage 8 At the top, no condenser At the bottom, no reboiler Estimated distillate rate = 450 lbmol/h Estimated reflux rate = 350 lbmol/h Estimated temperature of stage 1 = 110oF Estimated temperature of bottom stage = 100oF Estimated temperature of stage 2 = 100oF Note that the intercooler is treated as the 3rd feed with a specification as a stream of -0.15 MM Btu/h. Convergence was achieved in 4 iterations. The results are shown on the following two pages. Note that the degree of absorption was good with following results: Component C1 C2 C3 nC 4 nC 5 % in Feed gas absorbed 15.2 73.4 99.2 99.98 100.00 Exercise 10.39 (continued) Analysis: (continued) Exercise 10.39 (continued) Analysis: (continued) Exercise 10.40 Subject: Reboiled absorber for the separation of a hydrocarbon mixture. Given: Absorbent oil of nC9 at 60oF and 230 psia and 40 lbmol/h. Feed at 120oF and 230 psia with the composition given below. Column has 15 equilibrium stages plus a parti...
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