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Unformatted text preview: te to contain 99.5 mol% anhydride and bottoms to contain 0.5 mol% acid. Vapor pressure data. Assumptions: Raoult's law to compute K-values from vapor pressure data. Constant molar overflow. Find: Number of theoretical plates needed if a reflux ratio, L/D = 1.6 times minimum. Analysis: First compute an equilibrium y, x curve using Raoult's law with the vapor pressure data. Eq. (2-44 ) applies, as well as the sum of the mole fractions in the phases in equilibrium. Thus, Ps T Ps T y y KA = A = A , KB = B = B (1, 2) xA P xB P yA + y B = 1 , xA + x B = 1 (3, 4)
Equations (1) to (4) can be reduced to the following equations for the mole fractions of maleic anhydride (A) in terms of the K-values: 1 - KB (5, 6) , y A = KA x A KA - KB If the given vapor pressure data are fitted to Antoine equations, we obtain: xA = PAs = exp 16.6541 - PBs = exp 23.0155 - 4088.12 T + 203.924 9336.97 T + 321434 . (7) (8) Where vapor pressure is in torr and temperature is in oC. Solving, Eqs. (1) to (8), In solving the equations, P = 13.3...
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