Combustion Calculations Using the Million BTU ( MJ) Method Savings Produced by Preheating Combustion Air Combustion of Coal Fuel in a Furnace Percent Excess Air While Burning Coke Combustion of Fuel Oil in a Furnace Combustion of Natural Gas in a Furnace Combustion of Wood Fuel in a Furnace Molal Method of Combustion Analysis Final Combustion Products Temperature Estimate | Source HANDBOOK OF MECHANICAL ENGINEERING CALCULATIONS SECTION 3 COMBUSTION Combustion Calculations Using the Million BTU MJ Method Savings Produced by Preheating Combustion Air Combustion of Coal Fuel in a Furnace Percent Excess Air While Burning Coke Combustion of Fuel Oil in a Furnace Combustion of Natural Gas in a Furnace Combustion of Wood Fuel in a Furnace Molal Method of Combustion Analysis Final Combustion Products Temperature Estimate COMBUSTION CALCULATIONS USING THE MILLION BTU METHOD The energy absorbed by a steam boiler fired by natural gas is 100-million Btu hr MW . Boiler efficiency on a higher heating value HHV basis is 83 percent. If 15 percent excess air is used determine the total air and flue-gas quantities produced. The approximate HHV of the natural gas is 23 000 Btu lb 53 590 kJ kg . Ambient air temperature is 80 F C and relative humidity is 65 percent. How can quick estimates be made of air and flue-gas quantities in boiler operations when the fuel analysis is not known Calculation Procedure 1. Determine the energy input to the boiler The million Btu method combustion calculations is a quick way of estimating air and flue-gas quantities generated in boiler and heater operations when the ultimate fuel analysis is not available and all the engineer is interested in is good estimates. Air and flue-gas quantities determined may be used to calculate the size of fans ducts stacks etc. It can be shown through comprehensive calculations that each fuel such as coal oil natural gas bagasse blast-furnace gas etc. requires a certain amount of dry stochiometric air per million Btu fired on an HHV basis and that this quantity does not vary much with the fuel analysis. The listing below gives the dry air required per million Btu of fuel fired on an HHV basis for various fuels. Downloaded from Digital Engineering Library @ McGraw-Hill .
