CONFIDENTIAL 377 (b) An air-ammonia mixture containing 5% ammonia by volume is absorbed in water in a packed column operated at 20C and 1 atm so as to recover 98% of ammonia. If the inert gas flow rate in the column is 1200 kg/(hr.m), determine the following: 0 The minimum mass velocity of water for this column. . (5 marks) ) (i) The number of transfer unit in the column taking the operating liquid rate to be 1.25 times the minimum (6 marks) ( (1) The height of the packed tower taking the overall transfer coefficient Kca to be 128 kgmol hr m'atm. The relationship for equilibrium in the column is y 1.154 where y and x are in mole fraction units (2 marks)