6 moles e at minimum reflux with the feed sent to the

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Unformatted text preview: (e) At minimum reflux, with the feed sent to the still pot (partial reboiler), an infinite number of theoretical plates is needed between the condenser and reboiler. This part is not completely specified. In order to compute the distillate, we must assume a bottoms benzene mole fraction less than that in the feed. Suppose we choose that mole fraction to be 0.45. Then the operating line will intersect the equilibrium line at x = 0.45, creating the pinch zone of infinite stages. The value of y at the intersection is given by Eq. (1): 2.5(0.45) = 0.672 1 + 15(0.45) . Therefore the operating line passes through the two points, as {y, x}, of {0.75, 0.75} and {0.672, 0.450}. Therefore, the slope = L/V = (0.75 - 0.672)/(0.75 - 0.45) = 0.260. Now compute the overall material balances: Overall total material balance, F = 100 = D + B (18) Overall benzene material balance, xFF = yDD + xBB or 50 = 0.75D + 0.45B (19) Solving Eqs. (18) and (19), D = 16.67 moles or 16.67 mol/100 mol feed, and B = 83.33 moles...
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This note was uploaded on 09/08/2008 for the course CHE 244 taught by Professor Selebi during the Spring '06 term at Lehigh University .

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