# 7 17 r ld lvmin1 lvmin 03771 0377

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Unformatted text preview: iddle section to see if the operating line there is below the equilibrium curve. The liquid rate in the middle section = L' = L + F2 = 60.5 + 83.3 = 143.8 kmol/h. The vapor rate in the middle section = V' = V = L + D = 60.5 + 100 = 160.5 kmol/h. Therefore the slope of the operating line in the middle section = L'/V' = 143.8/160.5 = 0.896. As seen in the McCabe-Thiele diagram on the next page, this operating line does not cross over the equilibrium curve. Therefore, the pinch does occur at Feed 2 (the upper feed). For an operating reflux ratio of 1.33 times minimum, L = 1.33(60.5) = 80.5 kmol/h. The vapor rate in the upper section = L + D = 80.5 + 100 = 180.5 kmol/h. Analysis: (continued) Exercise 7.30 (continued) Therefore the upper section operating line has a slope, L/V = 80.5/180.5 = 0.446 and passes through the point y = x = 0.95. It intersects the vertical q-line at x = 0.6 and for the slope of 0.446 = (0.95 - y)/(0.95 - 0.6), y = 0.794. For the middle section, L' = L + F2 = 80.5 + 83.3 = 163.8 k...
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