Let us calculate the amount of air per Mm Btu fired for fuel oil. Let C=87.5,H=.125 and deg API=28,a typical # 2 fuel oil.
HHV is obtained from the formula: HHV=17887+57.5xdeg API-102.2S,where S=%sulfur.
Amount of theoretical dry air in lb/lb fuel from above is:
wa=11.53x0.875+34.34x0.125=14.38 lb/lb fuel.
1 MM Btu fuel fired requires (1x106/19497)=51.28 lb fuel
Hence air required for 1 MM Btu fuel=51.28x14.38=737 lb
Take the case of natural gas with a volumetric fuel analysis:CH4=83.4,C2H6=15.8,N2=0.8
Converting to weight basis:% CH4=83.4x16/(83.4x16+15.8x30+.8x28)=72.89
similarly,C2H6 =25.89 and N2=1.22.
Using the above formula,wa=17.265x0.7289+16.12x0.2589=16.75 lb/lb fuel
HHV =0.7289x23876+0.2589x22320=23,181 Btu/lb. Combustion constants 23,876 and 22,320 were taken from tables available in books.
The amount of fuel equivalent to 1 Mm Btu fired=1x106/23181=43.1 lb and air required for this amount=43.1x16.75=722 lb.
Take the case of 100% propane. 1 lb fuel requires 15.7 lb air from fundementals. 1 MM Btu fired has 1x106/21661=46.17 lb of propane. hence 1 MM Btu fired requires =46.17x15.7=725 lb air.
of combustion constants C
Blast furnace gas 575
CO gas 670
Refinery and oil gas 720
Natural gas 730
Furnace oil and lignite 745-750
Bituminous coals 760
C is air required in lb/MM Btu(HHV)
on Boilers,Steam Plant calculations