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Unformatted text preview: with Eqs. (2-21) and (2-44), the relative volatility of butane with respect to pentane is = 1.1/0.38 = 2.9. Assuming a 5 psi pressure drop, gives a bottoms pressure of 75 psia and a corresponding temperature of 200oF. Using Fig. 2.8 with Eqs. (2-21) and (2-44), = 2.1/0.9 = 2.3. Take the average relative volatility as 2.6 and draw a y-x equilibrium curve using Eq. (7-3), y= 2.6 x x = 1 + x ( - 1) 1 + 16 x . (1) The equilibrium curve, based on Eq. (1) is shown below in a McCabe-Thiele diagram. Included on the diagram are arbitrary operating lines and a q-line for an equimolar feed that is 50 mol% vaporized. Using these lines, 15 equilibrium stages are stepped off between the compositions of the actual operation, xD = 1 - 0.1349 = 0.8651 and xB = 0.0428. The slope, L/V, of the rectifying section operating line is 0.52. Analysis: Actual operation before addition (continued) Exercise 7.38 (continued) Exercise 7.38 (continued)
Analysis: Addition (continued)
When an interreboiler is added bet...
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