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

Bottoms conditions present no problems column 2 of

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Unformatted text preview: ches. From Exercise 8.34, for the conditions of Exercise 8.30, DT = 3.9 ft or 46.8 inches. Therefore, HETS = 4(46.8)1/3 = 14.4 inches. Exercise 8.37 Subject: HETS of a Karr column for extraction of benzoic acid (A) from water (C) by toluene (S). Given: Conditions in Exercises 8.32 and 8.35. Find: HETS. Analysis: From Fig. 8.40, for an interfacial tension of 22 dyne/c from Exercise 8.33, HETS = 5 with HETS and DT in inches. 1 DT/ 3 From Exercise 8.35, DT = 4.9 ft or 58.8 inches. Therefore, HETS = 5(58.8)1/3 = 19.4 inches. Exercise 9.1 Subject: Selection of type condenser and operating pressure for distillation of propionic and n-butyric acids. Given: Distillate of 95 mol% propionic acid. Bottoms of 98 mol% n-butyric acid. Assumptions: Ideal solutions so that Raoult's K-values apply. Find: type condenser and operating pressure Analysis: From Perry's Handbook or other source, the normal boiling points are: Propionic acid n-Butyric acid 141.1oC 163.5oC Using Fig. 7.16, an operating pressure of 30 psia or less, with a total condenser, might be used. Could also consider using subcooled reflux with a top pressure of just above atmospheric pressure. Exercise 9.2 Subject: Selection of type condenser and operating pressure for distillation of a mixture of light paraffin hydrocarbons in two columns Given: Feed and product compositions as follows: kmol/h: Component Feed Product 1 C1 160 160 C2 370 365 C3 240 5 nC 4 25 0 nC 5 5 0 Total: 800 530 Product 2 0 5 230 1 0 236 Product 3 0 0 5 24 5 34 Find: Type condensers and operating pressures for: (a) Direct sequence. (b) Indirect sequence. Analysis: Use Chemcad or other simulator to make the bubble-point and dew-point calculations, using the SRK equation of state. The results should be close to hand calculations using K-values from Figs. 2.8 and 2.9. Use Fig. 7.16 to determine pressure and type condenser. Column 1 of direct sequence: Distillate is Product 1. Can not condense at 120oF because this temperature is above the critical temperatures of methane and ethane. At 415 psia, the dew point temperature is 16oF. Therefore, use a partial condenser with a refrigerant boiling at a temperature of about 6oF. One choice of refrigerant is propane. Bottoms temperature would not be in the decomposition range. Column 2 of direct sequence: Distillate is Product 2, which is mainly propane. Bubble-point pressure at 120oF is 256 psia, which is greater than 215 psia. Dew-point pressure at 120oF is 248 psia. Use partial condenser with about 250 psia pressure at the top. Use cooling water in the condenser. Bottoms conditions present no problems. Column 1 of indirect sequence: Distillate is a mixture of Products 1 and 2. At 120oF, pressure is very high, even for a partial condenser. Dew-point temperature at 415 psia is 83oF. Raise pressure a little and use cooling water in the condenser. Bottoms conditions present no problems. Column 2 of indirect sequence: Conditions at the top are the same as Column 1 of the direct sequence. Therefore, use a partial con...
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