Separation Process Principles- 2n - Seader & Henley - Solutions Manual

5 67 nd nv ne 3c 10 2c 6 c 4 total condenser have

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Unformatted text preview: 55 kmol/h (reflux ratio = 155/45), gives: kmol/h: Component Feed Distillate Bottoms C3 5 4.996 0.004 iC 4 15 14.987 0.013 nC 4 25 24.587 0.413 iC 5 20 0.354 19.646 nC 5 35 0.077 34.923 Total 100 45.001 54.999 Exercise 5.25 Subject: Degrees of freedom analyses for a partial reboiler and a total condenser. Given: A partial reboiler with exiting vapor and liquid in equilibrium. A total condenser. Find: Number of variables, number of independent equations, and degrees of freedom. Analysis: Partial reboiler: Have 3 streams with C + 3 variables each, plus the heat transfer rate. Therefore, NV = 3(C + 3) + 1 = 3C + 10 The independent relationships are: C Component material balances 1 Enthalpy balance 1 Equality of temperatures of exiting vapor and liquid 1 Equality of pressures of exiting vapor and liquid C Component phase equilibrium between exiting vapor and liquid 3 Mole fraction summations for 3 streams Therefore, NE = 2C + 6 From Eq. (5-67), ND = NV - NE = (3C + 10) - (2C + 6) = C + 4 Total condenser: Have 2 streams with C + 3 variables each, plus the heat transfer rate. Therefore, NV = 2(C + 3) + 1 = 2C + 7 The independent relationships are: C Component material balances 1 Enthalpy balance 2 Mole fraction summations for 2 streams Therefore, NE = C + 3 From Eq. (5-67), ND = NV - NE = (2C + 7) - (C + 3) = C + 4 Exercise 5.26 Subject: Given: Degrees of freedom analyses for a stream mixer and a stream divider. A steam mixer and a stream divider, each with heat transfer. Find: Number of variables, number of independent equations, and degrees of freedom. Analysis: Stream mixer with two inlet streams: Have 3 streams with C + 3 variables each, plus the heat transfer rate. Therefore, NV = 3(C + 3) + 1 = 3C + 10 The independent relationships are: C Component material balances 1 Enthalpy balance 3 Mole fraction summations for 3 streams Therefore, NE =C + 4 From Eq. (5-67), ND = NV - NE = (3C + 10) - (C + 4) = 2C + 6 Stream divider with two exiting streams: Have 3 streams with C + 3 variables each, plus the heat transfer rate. Therefore, NV = 3(C + 3) + 1 = 3C + 10 The independent relationships are: 1 Total material balance Component mole fraction equalities for exiting streams relative to the feed 2(C - 1) 1 Enthalpy balance 1 Equality of temperatures of exiting streams 1 Equality of pressures of exiting streams 3 Mole fraction summations for 3 streams Therefore, NE = 2C + 5 From Eq. (5-67), ND = NV - NE = (3C + 10) - (2C + 5) = C + 5 Exercise 5.27 Subject: Degrees of freedom analysis for the specifications of a distillation column. Given: Feed of 10 mol% benzoic acid and 90 mol% maleic anhydride. Column has a total condenser and a partial reboiler. Operation is at 100 torr with a reflux ratio of 1.2 times minimum. Desired products are a distillate of 99.5 mol% maleic anhydride and a bottoms of 0.5 mol% anhydride. Find: Whether problem is completely specified. Analysis: From operation (b) in Table 5.4, N D = 2N + C + 9 = 2N + 11 The given specifications are equivalent to: Pressure at each stage, including partial reboil...
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