Question $2$:

To meet some environmental regulations, it is has been decided to design a packed column absorber to recover ammonia $(N{H}_3)$ from a mixture that contains $4$mol$\%N{H}_3$ in air by water. The absorber$,$ packed with $1-$inch metal Pall rings, must handle $289\mathrm{.}7$kmo$\frac{l}{h}$ of gas at $20C$ the liquid stream leaving the column is $329\mathrm{.}4$kmo$\frac{l}{h},$ What is the optimum column diameter? At the bottom conditions of the column, the liquid density and viscosity are $1000k\frac{g}{m^3}$ and $1$mPa.$s,$ respectively.