Low nox burner

Claim 1

A fluid fuel burner designed to produce minimum quantities of NOx, comprising: a. a nozzle for injection of fuel into a first combustion zone surrounded by a first ceramic tile, and means to supply said fuel under pressure to said nozzle; b. means adjacent said nozzle to supply a limited volume of primary air in the region of said nozzle, the volume being insufficient for complete combustion of said fuel; c. an enclosure means surrounding and spaced from said first ceramic tile to define a first annular space communicating the outlet of said first combustion zone with the region of said nozzle; d. means to recirculate a portion of the products of combustion from said first combustion zone around the outside of said first tile through said annular space to the vicinity of said nozzle; e. a cylindrical wall annularly spaced from and surrounding said enclosure, said wall having openings therein to supply therethrough air, a portion of which becomes said volume of primary air, a remaining and larger portion being secondary air; f. means to supply said secondary air in heat exchange relation with the outside of said enclosure means to cool said recirculated products thence to a second combustion zone downstream from said first combustion zone, the quantity of secondary air being sufficient to theoretically completely combust said fuel, said second zone surrounded by second ceramic tile; g. a second annular space surrounding said second tile in communication with the outlet of said second combustion zone; and h. means to supply tertiary air to said outlet of said second combustion zone via said second annular space.

Claim 6

A method of burning fuels so as to produce minimum quantities of NOx, comprising the steps of: injecting said fuel under pressure through a nozzle to a first combustion zone surrounded by a first refractory, supplying, to the region of said nozzle, a volume of primary air in an amount insufficient to complete the combustion of said fuel, recirculating a confined portion of the products of combustion from the outlet of said first zone to the vicinity of said fuel injection, supplying air to a space surrounding said first combustion zone, and dividing said air such that a portion becomes said volume of primary air, while a remaining and larger portion becomes secondary air, supplying said secondary air in heat exchange relation with said recirculating products to a second combustion zone axially downstream from said first zone, said second zone surrounded by a second refractory, the quantity of said secondary air being sufficient to completely combust said fuel, and supplying a separate confined volume of tertiary air around and on heat exchange relation with said second refractory to the outlet of said second combustion zone.

Claim 7

A method of burning fuels so as to produce minimum quantities of NOx, comprising the steps of: injecting said fuel under pressure through a nozzle to a first combustion zone surrounded by a first refractory, supplying, to the region of said nozzle, a volume of primary air in an amount insufficient to complete the combustion of said fuel, recirculating a confined portion of the products of combustion from the outlet of said first zone to the vicinity of said fuel injection, supplying air to a space surrounding said first combustion zone, and dividing said air such that a portion becomes said volume of primary air, while a remaining and larger portion becomes secondary air, supplying said secondary air in heat exchange relation with said recirculating products to a second combustion zone axially downstream from said first zone, said second zone surrounded by a second refractory, the quantity of said secondary air being sufficient to completely combust said fuel, and supplying a separate confined volume of tertiary air around and on heat exchange relation with said second refractory to the outlet of said second combustion zone.