Question

Chemical Engineering Question

A hydrocarbon gas is burned in a combustion furnace. the composition of the stack gases exiting the firebox is 1.6 mol% CO, 9.6 mol% CO2, 4.9 mol% O2, and 83.9 mol% N2 on a dry basis. a) determine what is the fuel entering the combustion reactor? What is the amount of the fuel input?

Answer 1

assume a basis of 100 mol going out

1.6 CO

9.6 CO2

4.9 O2

83.9 N2

x mol of H2O

then...

balance of nitrogen

in = out (no reaction)

83.9 mol of N2...

therefore... the reatio of air:

0.21 mol of O2 : 0.79 mol of MN2

83.9*0.21/0.79 = 22.30 mol of O2 were fed

then..

atomic balance of Carbon:

mol of C = 1.6 + 9.6 = 11.2 mol of C

Oxygen balance:

inlet - reaction = outlet

22.30 - reaction = 4.9

reacted O2 = 22.3-4.9 = 17.4 mol

ratio of C:O2

11.2:17.4

--> 1.55 = 3/2

this is most likely methane:

CH4 + 3/2 O2 -->CO2 + H2O

fuel input --> for 22.30 mol of O2 claculated...

then

2/3*22.30 =14.8666 mol of methane were fed