We wish to absorb ammonia from an air stream using water at 0°C and a total pressure of 1.30 atm. The entering water stream is pure water. The entering vapor is 17.2 wt % ammonia. We desire to recover 98% of the ammonia in the water outlet stream. The total gas flow rate is 1050 kg/h. We want to use a solvent rate that is 1.5 times the minimum solvent rate. Assume that temperature is constant at 0°C, water is nonvolatile, and air does not dissolve in water. Equilibrium data are available in Table 12-3. Find L_min , L, and N.

Table 12-3. Absorption of ammonia in water

 

 

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TABLE 12-3. Absorption of ammonia in water Weight NH, per 100 weight Partial pressure of NH, mm Hg 30°C 40°C 50°C 20°C 60°C H,0 0°C 10°C 100.0 947.0 90.0 785.0 3300.0 987.0 1450.0 80.0 636.0 2760.0 780.0 1170.0 70.0 500.0 2130.0 60.0 380.0 600.0 945.0 1520.0 50.0 275.0 439.0 686.0 719.0 1065.0 40.0 190.0 301.0 470.0 454.0 692.0 30.0 119.0 190.0 298.0 144.0 227.0 352.0 534.0 825.0 25.0 89.5 103.5 166.0 260.0 395.0 596.0 20.0 64.0 70.1 114.0 179.0 273.0 405.0 15.0 42.7 25.1 41.8 69.6 110.0 167.0 247.0 10.0 7.5 17.7 29.9 50.0 79.7 120.0 179.0 5.0 11.2 19.1 31.7 51.0 76.5 115.0 4.0 16.1 24.9 40.1 60.8 91.1 3.0 11.3 18.2 23.5 29.6 45.0 67.1 2.5 15.0 19.4 24.4 (37.6) (55.7) 2.0 12.0 15.3 19.3 (30.0) (44.5) (24.1) (18.3) 1.6 12.0 15.3 (35.5) (26.7) (22.2) 1.2 9.1 11.5 1.0 7.4 (15.4) 0.5 3.4 "Extrapolated values. Source: Perry et al. (1963). Copyright 1963. Reprinted with permission of McGraw-Hill TABLE 12-3. Absorption of ammonia in water Weight NH, per 100 weight Partial pressure of NH, mm Hg 30°C 40°C 50°C 20°C 60°C H,0 0°C 10°C 100.0 947.0 90.0 785.0 3300.0 987.0 1450.0 80.0 636.0 2760.0 780.0 1170.0 70.0 500.0 2130.0 60.0 380.0 600.0 945.0 1520.0 50.0 275.0 439.0 686.0 719.0 1065.0 40.0 190.0 301.0 470.0 454.0 692.0 30.0 119.0 190.0 298.0 144.0 227.0 352.0 534.0 825.0 25.0 89.5 103.5 166.0 260.0 395.0 596.0 20.0 64.0 70.1 114.0 179.0 273.0 405.0 15.0 42.7 25.1 41.8 69.6 110.0 167.0 247.0 10.0 7.5 17.7 29.9 50.0 79.7 120.0 179.0 5.0 11.2 19.1 31.7 51.0 76.5 115.0 4.0 16.1 24.9 40.1 60.8 91.1 3.0 11.3 18.2 23.5 29.6 45.0 67.1 2.5 15.0 19.4 24.4 (37.6) (55.7) 2.0 12.0 15.3 19.3 (30.0) (44.5) (24.1) (18.3) 1.6 12.0 15.3 (35.5) (26.7) (22.2) 1.2 9.1 11.5 1.0 7.4 (15.4) 0.5 3.4 "Extrapolated values. Source: Perry et al. (1963). Copyright 1963. Reprinted with permission of McGraw-Hill