7 46 h 4dt 4405 162 ft exercise 746 subject sizing

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Unformatted text preview: s: Liquid rate leaving drum = (3 + 1)120 = 480 lbmol/h Assume properties of pure n-hexane. From Fig. 2.4, boiling point of nC6 at 1 atm = 150oF. From Fig. 2.3, L = 0.63 g/cm3 = 39 lb/ft3 Assume a liquid residence time in the reflux drum of 5 minutes (0.0833 h), half full. From Eq. (7-44), 2 LM L t 2(480)(86.2)(0.0833) VV = = = 177 ft3 L 39 From Eq. (7-46), V DT = V 1/ 3 177 = 3.14 1/ 3 = 3.83 ft From Eq. (7-46), H = 4DT = 4(3.83) = 15.3 ft Might use a drum of 4 ft diameter and 16 ft long. Exercise 7.47 Subject: Sizing of a sieve-tray distillation column separating methanol and water. Given: Column top and bottom conditions in Fig. 7.50. Assumptions: Column feed is a bubble-point liquid. Constant molar overflow. Find: (a) Column diameters at top and bottom. Should column be swaged? (b) Length and diameter of horizontal reflux drum. Analysis: First, compute the liquid and vapor flow rates at the top and bottom of the column. Molecular weight of distillate = 0.9905(32.04) + 0.0095(18.02) = 31.91 Distillate flow rate = D = 462,385/...
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