17 continued b 1 for a saturated vapor feed minimum

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Unformatted text preview: or a saturated vapor feed, minimum reflux corresponds to a pinch point located at the intersection of a horizontal q-line passing through xF = y = 0.5 and the equilibrium curve. From the equilibrium data, this intersection is at y = 0.50 and x = 0.293. Then, the slope of the rectifying section operating line, (L/V)min is (0.96 - 0.50)/(0.96 - 0.293) = 0.690. From a rearrangement of Eq. (7-7), Rmin = (L/V)min /[1 - (L/V)min ] = 0.69/(1 - 0.69) = 2.23. (2) Reflux ratio = 2(2.23) = 4.46. From Eq. (7-7), the slope of the rectifying section operating line = L/V = R/(1 + R) = 4.46/5.46 = 0.817. To determine the bottoms composition, use a McCabe-Thiele diagram in terms of benzene, the more volatile component. The q-line and the rectifying section operating line are fixed and 4 trays are stepped off from the top, starting at the distillate mole fraction for benzene, xD , of 0.96. Then, the stripping section operating line is positioned by trial and error so that 3 more stages plus the reboiler stage are stepped off to arrive at the point where the assumed location of the stripping section operating line intersects the 45o line. The result is shown below,...
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