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Unformatted text preview: ges plus a partial reboiler. Analysis: (continued) Exercise 7.31 (continued) Exercise 7.32
Subject: Distillation of a mixture of ethyl alcohol and water at 1 atm using open steam instead of a reboiler. Given: 100 kmol/h of a saturated liquid feed containing 12 mol% ethyl alcohol in water. Distillate to contain 85 mol% alcohol with a recovery of 90%. Reflux ratio, L/D = 3 with saturated liquid reflux. Feed stage located optimally. Vapor-liquid equilibrium data in Exercise 7.29. Assumptions: Constant molar overflow. Total condenser. Find: (a) (b) (c) (d)
Open steam requirement, kmol/h Number of equilibrium stages Optimal feed stage location. Minimum reflux ratio. Analysis: First compute material balance. Because the ethanol mole fraction in the distillate is less than that of the azeotrope (89.43 mol% in Exercise 7.29), the ethanol is always the more volatile component. The feed contains 12 kmol/h of ethanol and 88 kmol/h of water. For a 90% recovery, the distillate contains 0.9(12) = 10.8 kmol/h of ethanol....
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