A packed tower is to be designed for the countercurrent contact of a benzenenitrogen gas mixture with kerosene to wash out the benzene from the gas. The gas enters the tower at the rate of $1.5 \mathrm{~m}^{3} / \mathrm{s}$, measured at $110 \mathrm{kPa}$ and $298 \mathrm{~K}$, containing $5 \mathrm{~mol} \%$ benzene. Essentially, all the benzene is absorbed by the kerosene. The liquid enters the tower at the rate of $4.0 \mathrm{~kg} / \mathrm{s}$; the liquid density is $800 \mathrm{~kg} / \mathrm{m}^{3}$ and the viscosity is $2.3 \mathrm{cP}$. The packing will be metal Raschig Super-Rings No. 2, and the tower diameter will be chosen to produce a gas-pressure drop of $275 \mathrm{~Pa} / \mathrm{m}$ of irrigated packing. The gas viscosity, from Lucas method, is $1.66 \times 10^{-5} \mathrm{~kg} / \mathrm{m}-\mathrm{s}$.

(a) Calculate the tower diameter to be used, and the resulting fractional approach to flooding.

(b) Estimate the volumetric mass-transfer coefficients for the gas and liquid phases. Assume that $\mathrm{D}_{L}=5.0 \times 10^{-10} \mathrm{~m}^{2} / \mathrm{s}, \mathrm{D}_{G}=8.85 \times 10^{-6} \mathrm{~m}^{2} / \mathrm{s}$.

(c) Assume that for the diameter chosen, the irrigated packed height will be $5 \mathrm{~m}$ and that $1 \mathrm{~m}$ of unirrigated packing will be placed over the liquid inlet to act as entrainment separator. The blower-motor combination to be used at the gas inlet will have an overall mechanical efficiency of $60 \%$. Calculate the power required to blow the gas through the packing.