# Sidestream is 15 kmolh of 20 mol methanol reflux

This preview shows page 1. Sign up to view the full content.

This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: tions: Constant molar overflow. Raoult's law K-values. Find: Number of theoretical stages and optimal locations of feed and sidestream. Analysis: First compute the material balance. Overall total material balance: F = 100 = D + B + S = D + B + 15 (1) (2) Overall methanol material balance: 75 = 0.96D + 0.05B + 0.20(15) Solving Eqs. (1) and (2), D = 74.45 kmol/h and B = 10.55 kmol/h Now determine the equilibrium curve. At 1 atm (14.696 psia), methanol boils at 64.7oC and ethanol boils at 78.4oC. From Fig. 2.4, the vapor pressure of ethanol at 64.7oC = 8.2 psia. The vapor pressure of methanol at 78.4oC = 25 psia. For the Raoult's law K-value, Eq. (2-44) applies. Combining this equation with the definition of the relative volatility of Eq. (2-21), gives, for methanol with respect to the less volatile ethanol, , = (Ps)M/ (Ps)E . At 64.7oC, , = 14.696/8.2 = 1.79. At 78.4oC, , = 25/14.696 = 1.70. Since these values are close (within about 5%), use an equilibrium curve based on a constant = (1.70 + 1.79)/2 = 1.745. From Eq. (7-3), the curve is computed from, y = x/[1 + x(-1)] = 1.74...
View Full Document

## 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 .

Ask a homework question - tutors are online