Method and apparatus for reducing NO.sub.x emissions in a gas burner

A low NO.sub.x gaseous fuel burner for use in a furnace comprising:

• a fuel gas inlet for supplying fuel gas to said furnace,
• a primary air supply connected to said furnace for supplying primary air to said furnace,
• a secondary air supply connected to said furnace for supplying secondary air to said furnace,
• a conduit connected to said fuel gas inlet for transporting said fuel gas to said furnace,
• an injector connected to said conduit and extending into said furnace, said injector having primary and secondary jets,
• wherein said primary jets are capable of projecting a majority of said fuel gas from said injector radially into said furnace to be combusted with said primary air, and said secondary jets are capable of projecting a minority of said fuel gas axially into said furnace to be combusted with said secondary air inside said furnace to produce diluted air, said diluted air being recirculated and combusted with said majority of fuel gas and said primary air.

A low NO.sub.x gaseous fuel burner for use in a furnace comprising:

• a premix intake having a primary fuel inlet and a primary air supply,
• a conduit connected to said premix intake, said conduit having a combustion end located within said furnace, said combustion end having a plurality of premix jet tubes for projecting said premix into said furnace for combustion, said combustion producing spent gases,
• a secondary fuel supply located within said conduit and having a combustion end located within said furnace, said combustion end having at least one secondary jet,
• a secondary air supply connected to said furnace for supplying secondary air to said furnace,
• wherein said secondary jet is positioned relative to said plurality of premix jet tubes to supply secondary fuel to effect mixing of said secondary air with said spent gases inside said furnace to produce diluted air and to recirculate and combust said diluted air with said premix to reduce NO.sub.x emissions.

A low NO.sub.x gaseous fuel burner for use in a vertical furnace comprising:

• a primary fuel gas and primary air inlet,
• a burner array located in a wall of said vertical furnace and connected to said primary air and fuel gas inlet for projecting said primary air and fuel outwardly into said furnace, said primary air and fuel being combusted and producing spent gases,
• a plurality of secondary air vents defined in a wall of said furnace for supplying secondary air to said furnace,
• wherein said secondary air vents are positioned relative to said burner array to effect mixing of said secondary air with said spent gases inside said furnace to produce diluted air, and to recirculate said diluted air for combustion with said primary air and fuel to reduce NO.sub.x emissions.

A method for reducing NO.sub.x emissions in a gaseous fuel burner used in a furnace containing spent gases, comprising the steps of:

• supplying primary fuel gas and primary air to said furnace,
• projecting said primary fuel gas in a substantially radial direction into said furnace,
• combusting said fuel gas and primary air to produce spent gases,
• supplying secondary fuel gas and secondary air in a substantially axial direction and projecting it into said furnace,
• mixing said secondary air by combustion of secondary fuel gas in said furnace with said spent gases inside said furnace to produce diluted air, and
• recirculating and combusting said diluted air inside said furnace to reduce NO.sub.x emissions in the resulting combustion gases.

A low NO.sub.x gaseous fuel burner to be used in a furnace comprising:

• (a) a burner supply means for supplying fuel gas and primary air to said furnace for combustion to produce spent gases, said burner supply means comprising:
• a premix intake, said premix intake having an air supply means for supplying air to said fuel gas to form a premix of said fuel gas and said primary air for projection into said furnace, and
• a conduit means, connected to said premix intake for transporting said premix to said furnace, said conduit means extending into said furnace and having a plurality of jet tubes defined therein capable of projecting said premix radially into said furnace;
• (b) a secondary air supply means for supplying secondary air to said furnace;
• and
• (c) a recirculating means to effect mixing of said secondary air with said spent gases inside said furnace to produce diluted air, said diluted air being recirculated and combusted with said primary air and fuel gas to reduce NO.sub.x gases, said recirculating means comprising a secondary fuel inlet for supplying secondary fuel to said furnace, said secondary fuel inlet extending into said furnace and having at least one secondary jet capable of projecting said secondary fuel axially into said furnace, said secondary jet being capable of combusting said secondary fuel with said secondary air to mix said secondary air with said spent gases inside said furnace to produce said diluted air.