Hydrogen sulphide has to be removed from a light refinery hydrocarbon stream before the gas is subjected to further processing. The feed gas contains 0.035 mole fraction of H 2S, 99% of which has to be removed by scrubbing with an aqueous weakly basic solution. The 1.5 m diameter absorption column operates at 25°C and 101.3 kPa total pressure. The feed gas rate is 45 kmol/h?m2 and the concentration of the solute(H2S) in the absorbent solution leaving the tower is 0.015 mole H2S per mole of the H2S-free liquid. The equilibrium relation is linear and is given by y= 1.95xand the overall gas-phase film coefficient is Kya= 130 kmol/ (m3)(h)(Dy).
Calculate (a) the rate of solvent flow, (b) the slope of the operating line in small concentration range if mole fraction units are used in the calculations, (c) the overall driving forces at the top and at the bottom of the tower on (i) gas phase basis and (ii) liquid phase basis, (d) the number of transfer units, and (e) the packed height