

Example
1
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 API102.2S,where S=%sulfur. HHV=17887+57.5x28102.2x0=19497 Btu/lb 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 (1x10^{6}/19497)=51.28 lb fuel Hence air required for 1 MM Btu fuel=51.28x14.38=737 lb Example 2 Take the case of natural gas with a volumetric fuel analysis:CH_{4}=83.4,C_{2}H_{6}=15.8,N_{2}=0.8 Converting to weight basis:% CH_{4}=83.4x16/(83.4x16+15.8x30+.8x28)=72.89 similarly,C_{2}H_{6 }=25.89 and N_{2}=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. Example 3 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. 
Table
of combustion constants C
Blast furnace gas 575 Bagasse 650 CO gas 670 Refinery and oil gas 720 Natural gas 730 Furnace oil and lignite 745750 Bituminous coals 760 Anthracite 780 Coke 800 C is air required in lb/MM Btu(HHV) 
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