Method of regulating the amount of underfire air for combustion of wood fuels in spreader-stroke boilers

Claim 1

A method for reducing particulate emissions from wood residue fuel combustion on a pinhole grate in a spreader-stoker furnace comprising: evenly distributing wood residue fuel feed over a fuel bed on said grate, distributing an underfire portion of the combustion air equal to about one pound of air per pound of dry fuel to said fuel through said pinhole grate sufficient to convert the solid carbon in said fuel to carbon monoxide gas, distributing an overfire remainder of the combustion air equal to from about 51/2 to 12 pounds of air per pound of air per pound of dry fuel above said fuel bed to complete combustion of said carbon monoxide gas and combustible volatile matter, and maintaining said fuel bed at a depth equal to from about 3 to 8 inches sufficient to convert said carbon to carbon monoxide and to entrap char particles inside said fuel bed by providing a continuous layer of fresh fuel over the surface of said fuel bed with the depth of the fuel bed indicating that the correct amount of air is being supplied underfire to minimize emissions and maximize efficiency.

Claim 2

A method for reducing particulate emissions from wood residue fuel combustion on a pinhole grate in a spreader-stoker furnace comprising: evenly distributing wood residue fuel feed over a fuel bed on said grate, distributing an underfire portion of the combustion air equal to about one pound of air per pound of dry fuel to said fuel through said pinhole grate sufficient to convert the solid carbon in said fuel to carbon monoxide gas, distributing an overfire remainder of the combustion air equal to from about 51/2 to 12 pounds of air per pound of air per pound of dry fuel above said fuel bed to complete combustion of said carbon monoxide gas and combustible volatile matter, and maintaining said fuel bed at a depth equal to from about 3 to 8 inches sufficient to convert said carbon to carbon monoxide and to entrap char particles inside said fuel bed by providing a continuous layer of fresh fuel over the surface of said fuel bed with the depth of the fuel bed indicating that the correct amount of air is being supplied underfire to minimize emissions and maximize efficiency.