5.4 The equilibrium adsorption of benzene vapor on a certain activated charcoal at 33.3C is reported as follows: Benzene vapor adsorbed, cm' (STP)/8 charcoal 15 25 40 50 65 80 90 100 Partial pressure benzene, mmHg 0.0010 0.0045 0.0251 0.115 0.251 1.00 2.81 | 7.82 (a) A nitrogen-benzene vapor mixture containing 1.0% benzene by volume is to be passed countercurrently at the rate 100 ft/min (4.72 x 10-2 m3/s) to a moving stream of the activated charcoal so as to remove 95% of the benzene from the gas in a continuous process. The entering charcoal contains 15 cm benzene vapor (at STP) adsorbed per gram charcoal. The temperature and total pressure are to be maintained at 33.3C and 1 std atm, respectively, throughout. Nitrogen is not adsorbed. What is the least amount of charcoal which can be used per unit time? If twice as much is used, what will be the concentration of benzene adsorbed upon the charcoal leaving? (b) Repeat part (a) for a cocurrent flow of gas and charcoal. (c) Charcoal which has adsorbed upon it 100 cin' (at STP) benzene vapor per gram is to be stripped at the rate 100 16/h (45.4 kg/h) of its benzene content to a concentration of 55 cm adsorbed benzene per gram charcoal by continuous countercurrent contact with a stream of pure nitrogen gas at 1 std atm. The temperature will be maintained at 33.3C. What is the minimum rate of nitrogen flow? What will be the benzene content of the exit gas if twice as much nitrogen is fed? What will be the number of stages? Ans.: 3 theoretical stages