When $1000mo\frac{l}{h}$ of gas containing $87$mol$\%C{H}_4,5mo{l}_2{C}_2{H}_6,5mol{C}_3{H}_8$ and $3$mol$\%n{C}_4{H}_{10}$ is scrubbed with $2500mo\frac{l}{h}$ of a hydrocarbon oil containing $0\mathrm{.}25mo{l}_{N}n{C}_4{H}_{10}$ in a packed tower operating at $500$kPa and $40C,90\%$ of the $C_3{H}_8$ is removed from the gas. For process considerations the gas flow rate is to be increased to $1200mo\frac{l}{h}$ whilst remaining at the same composition.

a$)$ Calculate the outlet gas composition at the increased gas flow rate.

$22$

b$)$ If the absorption of $C_3{H}_8$ is to be brought back to $90\%,$ what value should the flow rate of the hydrocarbon be increased to$?$

A nomograph of distribution coefficients is provided as Figure $3$ and the graphical relationship between Nog, absorption factor $(A)$ and fractional absorption is provided as Figure $4.$