It is proposed that oxygen be separated from nitrogen by absorbing and desorbing air in water. Pressures from 101.3 to 10,130 kPa and temperatures between 0 and 100^οC are to be used. 

(a) Devise a scheme for the separation if the air is 79 mol% N₂ and 21 mol% O₂.
(b) Henry’s law constants for O₂ and N₂ are given in Figure 4.26. How many batch absorption steps would be necessary to make 90 mol% oxygen? What yield of oxygen (based on the oxygen feed) would be obtained?

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4 Values of mole fraction per atmosphere 2 10-1 -00 to 8 6 4 2 y 00 co -10-2 st N m00 CD 10 -18 6 st 2 104 8 6 4 IL 10-5 I 2 CO Cl₂ 0 CHA NH₂ C₂H 0,₂ I I 10 20 30 H₂ 50₂ H₂S •C₂H₂ CO₂ Brz H₂S IN₂ 1 40 50 60 70 80 Temperature, °C 11 L 90 100 Figure 4.26 Henry's law constant for solubility of gases in water. [Adapted from O.A. Hougen, K.M. Watson, and R.A. Ragatz, Chemical Pro- cess Principles. Part I, 2nd ed., John Wiley & Sons, New York (1954).]