Low NOx burner having split air flow

Abstract

A refractory block for a burner comprises a collection chamber that receives the nozzle of a burner. A primary combustion passage extends horizontally from the collection chamber. Also, two secondary air passages extend from the collection chamber and diverge outwardly and upwardly to provide for secondary air outlets vertically above and on either side of the main combustion outlet. By delaying complete combustion, NOx emissions are reduced.

1 . A refractory block for a burner, comprising: 
 a body formed at least in part from aggregated granular material, the body having an inlet side and an outlet side;    a recess in the inlet side forming a collection chamber;    a combustion passage extending from the collection chamber through the body to the outlet side to provide a combustion outlet; and    first and second oxidant passages extending from the collection chamber to the outlet side to provide at least first and second secondary oxidant outlets, the first and second oxidant outlets being disposed vertically above the combustion outlet, the first and second oxidant outlets being on opposed sides of the combustion outlet.    
   
   
       2 . The refractory block of  claim 1 , wherein the combustion passage extends along a combustion passage axis, and wherein the first and second oxidant passages diverge outwardly and vertically upward relative to the combustion passage axis along first and second secondary axes, respectively.  
   
   
       3 . The refractory block of  claim 2 , wherein the axes of the oxidant passages form an angle A when projected on a horizontal plane of between about 22 and about 28 degrees.  
   
   
       4 . The refractory block of  claim 2 , wherein either of the axes of the oxidant passages form an angle B with the combustion axis when projected on a vertical plane that is generally parallel to the combustion passage axis of between about 10 and about 15 degrees.  
   
   
       5 . The refractory block of  claim 2 , wherein the axes of the oxidant passages form an angle C when projected on a vertical plane that is generally perpendicular to the combustion passage axis of between about 85 and about 95 degrees.  
   
   
       6 . The refractory block of  claim 2 , wherein an angle E between each of the oxidant passages and a horizontal plane through the combustion passage is between about 16 and about 20 degrees.  
   
   
       7 . The refractory block of  claim 2 , wherein the axes of the oxidant passages form an angle A when projected on a horizontal plane through the combustion passage of between about 22 and about 28 degrees, wherein either of the axes of the oxidant passages form an angle B with the combustor axis when projected on a vertical plane that is generally parallel to the combustion passage axis of between about 10 and about 15 degrees, wherein the axes of the oxidant passages form an angle C when projected on a vertical plane that is generally perpendicular to the combustion passage axis of between about 85 and about 95 degrees, wherein an angle E between each of the oxidant passages and the horizontal plane through the combustion passage is between about 16 and about 20 degrees.  
   
   
       8 . The refractory block of  claim 1 , wherein only two oxidant passages are provided including only the first and second oxidant passages.  
   
   
       9 . The refractory block of  claim 8 , wherein the combustion passage is generally cylindrical about a combustion axis, the combustion passage including a necked down section between a combustion passage entrance at the combustion chamber and the combustion outlet, such that the combustion outlet is of a substantially smaller diameter than the combustion passage entrance.  
   
   
       10 . The refractory block of  claim 9 , wherein the collection chamber is symmetrical about a center point that is offset vertically above the combustion axis.  
   
   
       11 . A refractory block and burner apparatus for mounting to a furnace for burning a fuel with an oxidant, comprising: 
 a burner including a burner housing, a gas inlet for receipt of fuel, an oxidant inlet for receipt of combustion oxidant, a nozzle for mixing of the oxidant and the fuel, a oxidant flow passage between the oxidant inlet and the nozzle, a fuel passage between the fuel inlet and the nozzle, and an igniter arranged proximate to the nozzle adapted to ignite the oxidant and the fuel;    a refractory block positioned over the nozzle, the refractory block including:    (i) a body formed at least in part from aggregated granular material, the body having an inlet side and an outlet side;    (ii) a recess in the inlet side forming a collection chamber, the nozzle of the burner being received into the recess;    (iii) a combustion passage extending from the collection chamber through the body to the outlet side to provide a combustion outlet; and    (iv) first and second oxidant passages extending from the collection chamber to the outlet side to provide at least first and second secondary oxidant outlets, the first and second oxidant outlets being disposed vertically above the combustion outlet, the first and second oxidant outlets being on opposed sides of the combustion outlet.    
   
   
       12 . The refractory block of  claim 1   1 , wherein the combustion passage extends along a combustion passage axis, and wherein the first and second oxidant passages diverge outwardly and vertically upward relative to the combustion passage axis along first and second secondary axes, respectively.  
   
   
       13 . The refractory block of  claim 12 , wherein the axes of the oxidant passages form an angle A when projected on a horizontal plane of between about 22 and about 28 degrees.  
   
   
       14 . The refractory block of  claim 12 , wherein either of the axes of the oxidant passages form an angle B with the combustor axis when projected on a vertical plane that is generally parallel to the combustion passage axis of between about 10 and about 15 degrees.  
   
   
       15 . The refractory block of  claim 12 , wherein the axes of the oxidant passages form an angle C when projected on a vertical plane that is generally perpendicular to the combustion passage axis of between about 85 and about 95 degrees.  
   
   
       16 . The refractory block of  claim 12 , wherein an angle E between each of the oxidant passages and a horizontal plane through the combustion passage is between about 16 and about 20 degrees.  
   
   
       17 . The refractory block of  claim 12 , wherein the axes of the oxidant passages form an angle A when projected on a horizontal plane through the combustion passage of between about 22 and about 28 degrees, wherein either of the axes of the oxidant passages form an angle B with the combustor axis when projected on a vertical plane that is generally parallel to the combustion passage axis of between about 10 and about 15 degrees, wherein the axes of the oxidant passages form an angle C when projected on a vertical plane that is generally perpendicular to the combustion passage axis of between about 85 and about 95 degrees, wherein an angle E between each of the oxidant passages and the horizontal plane through the combustion passage is between about 16 and about 20 degrees.  
   
   
       18 . The refractory block of  claim 11 , wherein only two oxidant passages are provided including only the first and second oxidant passages.  
   
   
       19 . The refractory block of  claim 18 , wherein the combustion passage is generally cylindrical about a combustion axis, the combustion passage including a necked down section between a combustion passage entrance at the combustion chamber and the combustion outlet, such that the combustion outlet is of a substantially smaller diameter than the combustion passage entrance.  
   
   
       20 . The refractory block of  claim 19 , wherein the collection chamber is symmetrical about a center point that is offset vertically above the combustion axis.  
   
   
       21 . An apparatus for mounting to a furnace adapted for burning an oxidant and a fuel, comprising: 
 a burner including a burner housing, a gas inlet for receipt of fuel, an oxidant inlet for receipt of combustion oxidant, a nozzle for mixing of the oxidant and the fuel, a oxidant flow passage between the oxidant inlet and the nozzle, a fuel passage between the fuel inlet and the nozzle, and an igniter arranged proximate to the nozzle adapted to ignite the oxidant and the fuel;    a flow divider having an inlet side and an outlet side, the flow divider including a collection chamber in communication with the nozzle, the flow divider further including:    (i) a main combustion passage generally aligned with the nozzle projecting from the collection chamber to a combustion outlet;    (ii) at least first and second secondary oxidant passages connected to the collection chamber and having secondary oxidant passage outlets disposed vertically above and horizontally spaced on opposed sides of the combustion outlet.    
   
   
       22 . The apparatus of  claim 21 , wherein each secondary air passage generally diverges vertically upward and outwardly relative to the combustion passage to form secondary air passage outlets.  
   
   
       23 . The apparatus of  claim 21 , wherein the combustion passage intersects the collection chamber at a combustion passage entrance, wherein the combustion passage is generally cylindrical about a combustion axis, the combustion passage including a necked down section between a combustion passage entrance at the combustion chamber and the combustion outlet, such that the combustion outlet is of a substantially smaller diameter than the combustion passage entrance.  
   
   
       24 . The apparatus of  claim 23 , wherein the collection chamber is symmetrical about a center point that is offset vertically above the combustion axis.  
   
   
       25 . The apparatus of  claim 21 , wherein only two oxidant passages are provided including only the first and second oxidant passages.  
   
   
       26 . The apparatus of  claim 21 , wherein the flow divider comprises a refractory block formed from aggregated granular material.