Radiant wall burner including perforated flame holders

Abstract

A cracking furnace includes a combustion volume defined in part by a burner wall having a refractory lining. A plurality of perforated flame holders is arranged in an array that is spaced away from the wall, with fuel input faces facing the wall. Each of a plurality of fuel nozzles is positioned and configured to emit a fuel stream toward the input face of a respective one of the plurality of perforated flame holders. Combustion reactions, supported by the fuel streams emitted by the fuel nozzles, and held by the flame holders, release heat, which is emitted by the flame holders as thermal (blackbody) radiation, a portion of which impinges upon, and heats the inner face of the refractory lining. Thermal radiation from the flame holders and the wall impinges upon a load positioned in the approximate center of the combustion volume, between burner walls.

What is claimed is: 
     
         1 . A combustion system, comprising:
 a combustion volume defined in part by a wall having an inner face of refractory material;   a plurality of perforated flame holders, each having a first face and a second face, the plurality of perforated flame holders being arranged in an array and spaced away from the wall with the first faces of the plurality of perforated flame holders facing the inner face of the wall; and   a plurality of fuel nozzles, each positioned and configured to emit a fuel stream toward the first face of a respective one of the plurality of perforated flame holders.   
     
     
         2 . The system of  claim 1 , wherein each of the plurality of perforated flame holders includes a plurality of apertures extending between the first and second faces of the respective one of the plurality of perforated flame holders, and is configured to hold a majority of a combustion reaction supported by the respective one of the plurality of fuel nozzles. 
     
     
         3 . The system of  claim 1 , wherein the wall includes a plurality of nozzle apertures, and wherein each of the plurality of fuel nozzles is positioned in a respective one of the plurality of nozzle apertures. 
     
     
         4 . The system of  claim 1 , wherein the inner face of the wall includes a plurality of refractory panels, each lying at an angle relative to a wall plane defined by the plurality of wall panels in aggregate. 
     
     
         5 . The system of  claim 4 , wherein each of the plurality of refractory panels is lying at a common angle, relative to the wall plane. 
     
     
         6 . The system of  claim 1 , wherein the first faces of the plurality of perforated flame holders lie in a common plane. 
     
     
         7 . The system of  claim 1 , comprising a plurality of flame holder support structures, and wherein each of the plurality of perforated flame holders is coupled to the wall by a respective one of the plurality of flame holder support structures. 
     
     
         8 . The system of  claim 1 , wherein each of the plurality of perforated flame holders is coupled to others of the plurality of perforated flame holders in a substantially planar array, suspended to hang in a flame holder plane that lies substantially parallel to a wall plane defined by the wall. 
     
     
         9 . The system of  claim 1 , wherein the wall is a first wall, the combustion volume being further defined by a second wall having an inner face of refractory material, the second wall lying substantially parallel to the first wall with the inner face of the second wall facing the inner face of the first wall. 
     
     
         10 . The system of  claim 9 , comprising:
 a second plurality of perforated flame holders, each having a first face and a second face, the second plurality of perforated flame holders being arranged in an array and spaced away from the second wall with the first faces of the plurality of perforated flame holders facing the inner face of the second wall; and   a thermal load positioned between and substantially equidistant from the first and second walls.   
     
     
         11 . The combustion system of  claim 1 , wherein:
 a distance between the first face of each of the plurality of perforated flame holders and the inner face of the wall is such that, during normal operation of the combustion system, an average strength, per unit of surface area, of thermal radiation emitted by the first face and impinging on the inner face of the wall in a first region, directly opposite the first face, is substantially less than an average strength of thermal radiation emitted by the first face and impinging on the inner face of the wall in a second region contiguous to and surrounding the first region and extending outward from the first region a distance approximately equal to a width of the perforated flame holder.   
     
     
         12 . The combustion system of  claim 11 , wherein the first face of each of the plurality of perforated flame holders is spaced away from the inner face of the wall a distance such that, during normal operation, the average strength, per unit of surface area, of thermal radiation emitted by the first face and impinging on the inner face of the wall in the first region is less than half the average strength of thermal radiation emitted by the first face and impinging on the inner face of the wall in the second region. 
     
     
         13 . The combustion system of  claim 11 , wherein the first face of each of the plurality of perforated flame holders is spaced away from the inner face of the wall a distance by such that, during normal operation, the average strength, per unit of surface area, of thermal radiation emitted by the first face and impinging on the inner face of the wall in the first region is less than one third the average strength of thermal radiation emitted by the first face and impinging on the inner face of the wall in the second region. 
     
     
         14 . The combustion system of  claim 11 , wherein the first face of each of the plurality of perforated flame holders is spaced away from the inner face of the wall a distance such that, during normal operation, the average strength, per unit of surface area, of thermal radiation emitted by the first face and impinging on the inner face of the wall in the second region is at least one order of magnitude greater than the average strength of thermal radiation emitted by the first face and impinging on the inner face of the wall in the first region. 
     
     
         15 . The combustion system of  claim 11 , comprising a thermal load positioned within the combustion volume and configured to receive thermal energy produced by the combustion reactions, distances between the thermal load and the second faces of the plurality of perforated flame holders being such that thermal radiation impinges with a substantially even strength along a length of the thermal load. 
     
     
         16 . The combustion system of  claim 11 , wherein, during normal operation of the combustion system, no appreciable thermal radiation is emitted by the first and second faces of each of the plurality of perforated flame holders at angles of greater than about sixty degrees nor less than about ten degrees, relative to a vector normal to the respective face. 
     
     
         17 . The combustion system of  claim 16 , wherein, during normal operation of the combustion system, a maximum value of thermal radiation is emitted by the first and second faces of each of the plurality of perforated flame holders at angles of less than about forty-five degrees and greater than about twenty degrees, relative to a vector normal to the respective face. 
     
     
         18 . A combustion system, comprising:
 a combustion volume defined in part by a wall having an inner face of refractory material;   a plurality of perforated flame holders, each configured to hold a combustion reaction substantially between respective first and second faces, the plurality of perforated flame holders being arranged in an array and spaced away from the wall with the first face of each of the plurality of perforated flame holders facing the inner face of the wall; and   a thermal load positioned within the combustion volume and configured to receive thermal energy produced by the combustion reactions, the plurality of perforated flame holders being positioned and distributed within the combustion volume such that thermal radiation emitted by the second faces of the plurality of perforated flame holders and by the inner face of the wall impinges with a substantially even strength along a length of the thermal load.   
     
     
         19 . The combustion system of  claim 18 , wherein distances between adjacent pairs of the plurality of perforated flame holders are such that no appreciable thermal radiation emitted by a first one of each adjacent pair of the plurality of perforated flame holders impinges on the inner face of the wall in a region that is directly opposite the first face of the second one of each adjacent pair.