HIGH PERFORMANCE LOW NOx BURNER AND SYSTEM AND METHOD OF OPERATION

Abstract

According to embodiments, burner systems include a first plurality of main fuel nozzles positioned in a flame tube or combustion chamber and configured to supply a flow of main fuel to a burner in the flame tube, and a second plurality of main fuel nozzles positioned outside the flame tube or combustion chamber and configured to introduce a flow of main fuel into a combustion air flow that is introduced to the burner.

What is claimed is: 
     
         1 . A horizontally-fired burner system, comprising:
 a flange configured to be mounted to an opening of a flame tube or combustion chamber and structured to support a burner within the flame tube or combustion chamber;   a burner mounted to the flange and configured to extend into the flame tube or combustion chamber, the burner including:
 a mixing tube extending transverse to the flange and having a proximal inlet and a distal outlet, and 
 a first plurality of main fuel nozzles positioned adjacent to the proximal inlet of the mixing tube and configured to introduce main fuel into the mixing tube via the proximal inlet; 
   a combustion air conduit coupled at a first end to an opening in the flange on a side of the flange opposite the burner and configured to supply combustion air through the flange to the proximal inlet of the mixing tube; and   a second plurality of main fuel nozzles positioned within the combustion air conduit and configured to introduce main fuel into a combustion air flow upstream of the first plurality of main fuel nozzles and the proximal inlet of the mixing tube.   
     
     
         2 . The horizontally-fired burner system of  claim 1 , comprising a pilot burner positioned adjacent to the distal outlet of the mixing tube and configured to ignite a mixture of combustion air and main fuel flowing from the distal outlet. 
     
     
         3 . The horizontally-fired burner system of  claim 1 , comprising a first main fuel source operatively coupled to and configured to supply main fuel to the first plurality of main fuel nozzles. 
     
     
         4 . The horizontally-fired burner system of  claim 3 , comprising a second main fuel source operatively coupled to and configured to supply main fuel to the second plurality of main fuel nozzles. 
     
     
         5 . The horizontally-fired burner system of  claim 1 , comprising an annular fuel gallery disposed around the combustion air conduit and configured to supply main fuel to the second plurality of main fuel nozzles. 
     
     
         6 . The horizontally-fired burner system of  claim 5 , comprising a plurality of tubes extending radially into the combustion air conduit and in fluid communication with the annular fuel gallery, each of the plurality of tubes having at least one nozzle aperture formed therein, the nozzle apertures of each of the plurality of tubes together constituting the second plurality of main fuel nozzles. 
     
     
         7 . The horizontally-fired burner system of  claim 6 , wherein each of the plurality of tubes includes a plurality of nozzle apertures. 
     
     
         8 . The horizontally-fired burner system of  claim 1 , wherein the proximal inlet of the mixing tube has a flared shape and the first plurality of main fuel nozzles is arranged in a radially symmetrical pattern concentric with the proximal inlet. 
     
     
         9 . The horizontally-fired burner system of  claim 1 , comprising a blower having an output coupled to a second end of the combustion air conduit and configured to blow combustion air through the combustion air conduit to the burner. 
     
     
         10 . The horizontally-fired burner system of  claim 1 , comprising a main fuel pipe coupled to the annular fuel gallery and configured to supply main fuel to the annular gallery and the second plurality of main fuel nozzles. 
     
     
         11 . The horizontally-fired burner system of  claim 1 , wherein the flange and burner are configured to be horizontally fired. 
     
     
         12 . A start-up method for a horizontally-fired burner system, comprising:
 introducing a flow of combustion air into a mixing tube of a horizontally-fired burner, positioned in a flame tube or combustion chamber, via a combustion air conduit and a proximal inlet of the mixing tube;   introducing a first flow of main fuel into the proximal inlet of the mixing tube via a first plurality of main fuel nozzles positioned adjacent to the proximal inlet;   igniting a combustion reaction near a distal outlet of the mixing tube, supported by a mixture of fuel and air; and   introducing a second flow of main fuel into the combustion air conduit via a second plurality of main fuel nozzles positioned upstream of the first plurality of main fuel nozzles and the proximal inlet.   
     
     
         13 . The method of  claim 12 , comprising, during or after introducing the second flow of main fuel, reducing a volume of the first flow of main fuel into the mixing tube. 
     
     
         14 . The method of  claim 12 , wherein the reducing the volume of the first flow of main fuel into the mixing tube includes completely stopping the first flow of main fuel into the mixing tube. 
     
     
         15 . The method of  claim 12 , wherein the reducing the volume of the first flow of main fuel into the mixing tube includes reducing the first flow of main fuel until a ratio of the volumes of the first flow relative to the second flow is approximately 40:60. 
     
     
         16 . The method of  claim 12 , wherein the reducing the volume of the first flow of main fuel into the mixing tube includes reducing the first flow of main fuel until a ratio of the volumes of the first flow relative to the second flow is approximately 50:50. 
     
     
         17 . The method of  claim 12 , comprising performing the introducing the second flow of main fuel and the reducing the volume of the first flow of main fuel substantially simultaneously. 
     
     
         18 . The method of  claim 17 , wherein the performing the introducing the second flow of main fuel and the reducing the volume of the first flow of main fuel substantially simultaneously includes holding a total volume of main fuel substantially constant while introducing the second flow of main fuel and reducing the volume of the first flow of main fuel. 
     
     
         19 . The method of  claim 13 , comprising performing the introducing the second flow of main fuel and the reducing the volume of the first flow of main fuel in alternating incremental steps. 
     
     
         20 . The method of  claim 12 , wherein the reducing the volume of the first flow of main fuel into the mixing tube includes reducing the first flow of main fuel until a ratio of the volumes of the first flow relative to the second flow is approximately 60:40. 
     
     
         21 . The method of  claim 12 , further comprising, prior to performing the introducing the first flow of main fuel:
 providing a pilot fuel supply to a pilot burner positioned adjacent to the distal outlet of the mixing tube; and   igniting the pilot fuel at the pilot burner.   
     
     
         22 . The method of  claim 21 , comprising, after performing the igniting the combustion reaction:
 reducing flow of the pilot fuel supply to the pilot burner.   
     
     
         23 . The method of  claim 21 , comprising, after performing the igniting the combustion reaction:
 stopping the pilot fuel supply to the pilot burner after the flame from the main fuel is stabilized.