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

 

 

TABLE 12-3. Absorption of ammonia in water Weight NH, per 100 weight Partial pressure of NH, mm Hg 30C 40C 50C 20C 60C H,0 0C 10C 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