mass transfer

1. A packed column is to be designed to absorb benzene vapor from air by contacting it with a hydrocarbon oil at 25C and 760mmHg. The partial pressure of benzene will be reduced from 6mmHg to 0.5mmHg. The entering hydrocarbon oil is benzene-free. Calculate: a. The minimum value of L/G ratio, b. The number of the over-all gas transfer units needed, for an operating L/G ratio which is 1.25 times the minimum L/G ratio. Equilibrium relationship at 25C and 760mmHg is y=0.12x, where y and x are the mole fractions of benzene in gas and liquid respectively. 2. A packed absorption column is to be used to reduce solute A content of a gas mixture of A+B, from 1.7 mole percent to 0.2 mole percent by washing it with solvent S at 1 bar and 25C. The solvent is not pure and contains 0.1 mole percent solute A. a) Calculate the minimum molar ratio of liquid to gas (L/G)min. b) Write the operating line equations for an operating L/G ratio which is 1.6 times the minimum L/G ratio; and draw on the equilibrium diagram. Equilibrium data at the operating conditions are given below, where x and y are the mole fraction of solute A in liquid and gas