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Unformatted text preview: alcohol and a 97% recovery of alcohol. Vapor-liquid equilibrium data. Assumptions: Constant molar overflow. Find: (a) (b) (c) (d)
Molar concentrations in the bottoms product. Minimum values of L/V, L/D, and VB/B. Minimum number of equilibrium stages and actual plates for Eo = 0.55. Number of actual plates for L/V = 0.80. Analysis: From the vapor-liquid equilibrium data for 1 atm., it is seen that ethanol is more volatile than water for ethanol mole fractions in the liquid from 0 to 0.8943, which is the azeotrope concentration. The distillate composition is within this region. (a) Take a basis of F = 100 kmol/h. (1) Overall total material balance: F = 100 = D + B (2) Ethanol recovery: 0.97FxF = 0.97(100)(0.20) = 19.4 = DxD = 0.85D Solving Eq. (2), D = 22.82 kmol/h. From Eq. (1), B = 100 - 22.82 = 77.18 kmol/h Ethanol in bottoms = 20 - 19.4 = 0.6 kmol/h Therefore, ethanol mole fraction in bottoms = 0.6/77.18 = 0.00777 Water mole fraction in bottoms = 1.0 - 0.00777 = 0.99223 (b) In the McCabe-Thiele diagram on the n...
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