$H_{2}O$ is used to scrub HCHO $($formaldehyde$)$ from a waste gas stream in an absorption column. The waste gas contains $500kg{h}^{-1}$HCHO and $1900kg{h}^{-1}{N}_2$ and is at $60C.$ The ratio of water to waste gas flow rates is $4$:$1.$

The waste gas is fed into the bottom of the absorption column and meets a counter current stream of $H_{2}O$ entering the top of the column at $20C.$ The scrubbed $N_2$ leaves the top of the column at $20C.$

$($i$)$ What is the flow rate of the $H_{2}O-$HCHO solution leaving the base of the column? Assume that all the HCHO is scrubbed from the waste gas and dissolves in the water.

$($ii$)$ What is the temperature of the $H_{2}O-$HCHO solution which leaves the base of the column?

Hints: $(1)$ Assume datum$/$reference temperature $(T_D)$ as $0C,$

$(2)$ Energy in $=$ Energy out $+$ Accumulation,

$(3)$ Energy $=$ Stream flow rate $x$ Specific heat $x$ Change in temperature $(T-T_D)$

Where accumulation could be a heat of reaction or heat of solution

Data

Specific heat of $N_2($gas$)$

Specific heat of HCHO $($gas$)$

$=,1\mathrm{.}04kJk{g}^{-1}{K}^{-1}$

Specific heat of $H_{2}O($liquid$)$

$=,1\mathrm{.}18kJk{g}^{-1}{K}^{-1}$

Specific heat of $H_{2}O-$HCHO solution

$=,4\mathrm{.}187kJk{g}^{-1}{K}^{-1}$

$=,4\mathrm{.}187kJk{g}^{-1}{K}^{-1}$

Heat of solution of formaldehyde in water $,=,-87\mathrm{.}9kJmo{l}^{-1}$

Atomic weights:

$H=1$;$C=12$;$O=16$;$N=14$