Burner assembly and method for reducing nox emissions

Abstract

A burner assembly for combusting fuel in a combustion zone to reduce NOx emissions includes a water spray subassembly including a water outlet configured to direct water at an angle with respect to an axis of the burner assembly, the water outlet further configured to direct the water in a direction for mixing with the air upstream of the combustion zone. A method is also provided for combusting fuel in a combustion zone to reduce NO x emissions.

1 . A burner assembly for combusting fuel in a combustion zone to reduce NOx emissions, comprising:
 an air nozzle subassembly including an air nozzle conduit extending along an axis toward a distal end portion of the burner assembly, the air nozzle conduit having an interior region to accommodate air flow;   a gas nozzle subassembly including a fuel gas conduit positioned at least partially within the interior region of the air nozzle conduit, the fuel gas conduit configured to direct fuel in a direction generally along the axis for delivery to the combustion zone;   a passage arranged between the air nozzle conduit and the fuel gas conduit, the passage configured to direct air in a direction generally along the axis for delivery to the combustion zone; and   a water spray subassembly including a water outlet configured to direct water at an angle with respect to the axis, the water outlet further configured to direct the water in a direction toward the passage for mixing with the air upstream of the combustion zone.   
     
     
         2 . The burner assembly of  claim 1 , wherein the water outlet comprises a spray nozzle. 
     
     
         3 . The burner assembly of  claim 2 , wherein the spray nozzle is configured to direct the water in a direction radially outward with respect to the axis. 
     
     
         4 . The burner assembly of  claim 3 , wherein the spray nozzle is configured to direct the water radially outward at a spray angle greater than 180 degrees such that an angle between the axis and a spray direction of the water is less than 90 degrees. 
     
     
         5 . The burner assembly of  claim 4 , wherein the spray nozzle is configured to direct the water radially outward at a spray angle from 190 to 230 degrees such that an angle between the axis and a spray direction of the water is less than 85 degrees. 
     
     
         6 . The burner assembly of  claim 5 , wherein the spray nozzle is configured to direct the water radially outward at a spray angle of about 210 degrees such that an angle between the axis and a spray direction of the water is about 75 degrees. 
     
     
         7 . The burner assembly of  claim 3 , wherein the spray nozzle is configured to direct water radially outward in a hollow cone such that the water is not directed outward from the spray nozzle along the axis. 
     
     
         8 . The burner assembly of  claim 3 , wherein the water spray subassembly further comprises a water conduit extending within the fuel gas conduit, and the spray nozzle is connected to a distal end of the water conduit. 
     
     
         9 . The burner assembly of  claim 8 , further comprising an inner annular passage disposed between the water conduit and the fuel gas conduit, the inner annular passage configured to direct the fuel in a direction generally along the axis for delivery to the combustion zone. 
     
     
         10 . The burner assembly of  claim 1 , wherein the air nozzle conduit comprises cooling coils through which the water can be circulated. 
     
     
         11 . A method for combusting fuel in a combustion zone to reduce NOx emissions, comprising:
 providing fuel through a fuel gas conduit in a direction generally along an axis for delivery to the combustion zone;   providing air toward the combustion zone in a direction generally along the axis through an annular passage disposed between an air nozzle conduit and the fuel gas conduit; and   providing water at an angle with respect to the axis and in a direction toward the annular passage for mixing with air upstream of the combustion zone.   
     
     
         12 . The method of  claim 11 , wherein the providing water comprises directing the water in a direction radially outward with respect to the axis. 
     
     
         13 . The method of  claim 12 , wherein the providing water comprises directing the water radially outward at a spray angle greater than 180 degrees such that an angle between the axis and a spray direction of the water is less than 90 degrees. 
     
     
         14 . The method of  claim 13 , wherein the providing water comprises directing the water radially outward at a spray angle from 190 to 230 degrees such that an angle between the axis and a spray direction of the water is less than 85 degrees. 
     
     
         15 . The method of  claim 14 , wherein the providing water comprises directing the water radially outward at a spray angle of about 210 degrees such that an angle between the axis and a spray direction of the water is about 75 degrees. 
     
     
         16 . The method of  claim 11 , wherein the providing water comprises directing water radially outward in a hollow cone from a water spray nozzle such that the water is not directed outward from the water spray nozzle along the axis.