ANSWER TO QUESTIONS=Q3: b) xw=0.24, D=23.1 kmol; c) xw=0.12 D=37.5 kmol; d) Heat input = 5830 MJ (your answers will be a bit different depending on your reading of the graph)

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3) A binary mixture of ethanol and water is to be distilled in a batch column with 4 plates at a pressure of roughly 1 atmosphere. The initial liquid charge contains 36 kmol of ethanol and has ethanol mole-fraction 0.36 . The top-product concentration is fixed at 0.76 . a) Show that the initial reflux ratio is approximately R=2.0. b) Estimate the molar amount of distillate obtained part-way through the process, when R=3.0. c) The process is stopped when the reflux ratio has reached R=4.0. Calculate the mole-fraction of ethanol in the liquid remaining in the still (Xw), and the total amount of distillate produced (D). d) Hence find the total heat energy required to perform the separation if the average molar heat of vaporisation of the liquid is 40kJ/mol