$(3)$ A fuel gas consists of butane $75\%(C_4{H}_{10}),$ Propane $10\%(C_3{H}_8)$ & butere $15\%(C_4{H}_8)$ by volume.

It is to be fed to the conbustion chamber in $10\%$ excess air at $25C,$ where it is completely buunt to carbon diovide & water. The flue gases produced are to be used to generate $5$ bar steam from water at $90C.$

with the aid of data provided, Steam tables $ enthalpy tuble:

$($A$)$ Write bulanced equations for the combustion of each component?

$($B$)$ Explain the need for excess air?

$($c$)$ Determine the fuel: air ratio

i$.$ By volume?

ii$.$ By mass. $?$

$(1)$ Calculate:

i$.$ The met calorific value $($cu$)$ per $m^3$ of the fuel $/$air mix at $25C.$

ii The net calorifio value $($ev$)$ fer kmol of the Wel lair mix at $25C.$

$($c$)$ Defermine the composition of the flue guses by volome $($assuming the air inlet is dry$)$

i$.$ on a wet basis?

ii on a dry Dasis?

$($f$)$ Determine the "furnace efficiency" if the flue gases leave the baler at $300C.$

$(6)$ Give two advantages of preneating the water in this way $$ one disadvantage?

$(11)$ Cive two reasons why the presence of any sulphor in the fuel mix would be undesirable?

DATA SUPPliEN:

Net calorific valve $(MJ{m}^{-3})$ at $25C$ of:

Butare $(($:$C_4{H}_{10}\}$

Butene $(C_4+18)$:$105\mathrm{.}2msi{n}^{-3}$

propare $(C_3{H}_8)=85\mathrm{.}8mJ{m}^{-3}$

Air is $21\%$ oxygen, $79\%$ nitrogen by volume & $233\%$ oxygen $ $76.$ E$7\%$ nitrogen by mass.

Atomic mass of $C=12,0=16,N=14,H=1.$