Exam 1 Fall 2017 Solutions.pdf

# Exam 1 Fall 2017 Solutions.pdf - 1[15 pt Use the x‐y and...

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1) [15 pt] Use the x‐y and T‐x‐y diagrams below for isopropanol/water mixtures at a pressure of 101.3 kPa to answer the following based on a feed of 130 kmol/h of a mixture of 20% isopropanol and 80% water . You can draw on the charts to indicate your procedure, or describe it. (a) If the mixture is flashed so that the vapor contains 30 mol% isopropanol, what temperature is required and what flowrate of vapor is generated? [6 pt] From the Txy diagram, T = 90 °C. z = 0.2, y = 0.3 and x = 0.04. Therefore, V/F = (z-x)/(y-x) = (0.2-0.04)/(0.3-0.04) = 0.615. Therefore, V = 130*0.615 = 80 kmol/h. (b) If the feed (containing 20% isopropanol) is flashed so that 80% of the product is liquid, what would be the mole fraction of isopropanol in the vapor and liquid produced? [6 pt] q = L/F = 0.8. Therefore the slope of the feed line is q/(q-1) = 0.8/(0.8-1) = -4. From the q-line intersection with the equilibrium x-y data, x = 0.13 and y = 0.48. (c) If any number of flash units were used in any configuration, what is the highest mole fraction of isopropanol that could be generated in any vapor product at this pressure? [3 pt] This maximum mole fraction is defined by the azeotrope, which occurs at x = y = 0.68. y=0.3 x=0.04

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2) [25 pt] A feed is available at 30 °C as a mixture of 50 mol% n‐pentane (C5) and 50 mol% n‐hexane (C6) with F=100 kmol/h. The mixture is ideal, so the K values can be found using Raoult’s law with the Antoine equation for vapor
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