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Unformatted text preview: ext page, the given equilibrium data are plotted. For a bubble-point liquid feed, the q-line is vertical at xF = 0.2. The minimum reflux in terms of L/V is obtained from the slope of the rectifying section operating line, which passes through the point, y = xD = 0.85 and is tangent to the equilibrium curve, rather than being drawn through the intersection of the q-line and the equilibrium curve because that would cause the operating line to mistakenly cross over the equilibrium curve. The slope of the operating line = (L/V)min = 0.65. From Eq. (7-27), Rmin = (L/D)min = 0.65/(1-0.65) = 1.86. The liquid rate in the rectifying section = L = 1.86D = 1.86(22.82) = 42.44 kmol/h. Below the feed plate, L = L + F = 42.44 + 100 = 142.44 kmol/h. Vapor rate from the reboiler = VB = L - B = 142.44 - 77.18 = 65.26 kmol/h. Therefore, boilup ratio = VB/B = 65.26/77.18 = 0.846.
(c) In the second McCabe-Thiele diagram on the next page, the minimum number of stages is determined by stepping off stages between the equilibrium curve and the 45o line (total reflux) from the points 0.85 and 0.00777 on the 45o line. The result is approximately 10 minimum equilibrium stages. For a stage efficiency of...
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