44 assumptions constant molar overflow total

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Unformatted text preview: Find: (a) Equations to locate operating lines. (b) Number of equilibrium stages if optimal feed stage location is used. Analysis: First compute overall material balance. Take a basis of F = 100 kmol/h. Overall total mole balance: F = 100 = D + B (1) Overall hexane mole balance: FxF = 40 = DxD + BxB = 0.95D + 0.05B (2) Solving Eqs. (1) and (2), D = 38.9 kmol/h and B = 61.1 kmol/h (a) For a reflux ratio of 0.5, in the section above the intercooler, L = 0.5D = 19.45 kmol/h. The overhead vapor rate is V = L + D = 19.45 + 38.9 = 58.35 kmol/h. The slope of the operating line = L/V = 19.45/58.35 = 0.333. Using Eq. (7-6), the equation for the operating line y = 0.333x + DxD/V = 0.333x + (38.9)(0.95)/(58.35) = 0.333x + 0.633 (3) is, Now consider the section of stages between the intercooler at stage 2 from the top and the feed stage. Because 50 mol% of the vapor from this section is condensed at stage 2 by the intercooler, the vapor rate in this section = V' = 2V = 2(58.35) = 116.7 kmol/h. The liquid rate in this section is L' = V' - D = 116.7 - 38.9 = 77.8 kmol/h. The slope of...
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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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