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Unformatted text preview: ges at 80% tray efficiency, need 15.8/0.8 = 19.8 or 20 trays. If they are on 18-inch spacing, column height = 19(1.5) + 4 + 10 = 42.5 ft. (d) For HOG = 1.2 ft, packed height = 1.2(2.4 + 12.4) = 18 ft. Add 14 ft for disengagement at the top and sump at the bottom. Need 18 + 14 = 32 ft column. (e) We would need data on individual values of HL and HG. From Eq. (6-132), 1 H L is proportional to DL 1/ 2 . Therefore, can ratio with the liquid diffusivities. V V -3/ 4 From Eq. (6-133), H G is proportional to V V DV -1/ 3 . Therefore, we can ratio off these properties. Then from Eq. (7.52), HOG = HG + mH L , where m = dy / dx , which varies over the equilibrium curve. Exercise 7.52 Subject: Doubling plant capacity for distillation of methanol-water by adding a packed column. Given: Conditions to duplicate those of Exercise 7.41. Design for 70% of flooding. Two packings to be considered: 1. 50-mm plastic NOR PAC rings and 2. Montz metal B1-300. Assumptions: Constant molar overflow. Partial reboiler is an equilibrium stage. Find: (a) Liquid holdup. (b) Column diameter. (c) HOG. (d) Packed...
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