Low NOx and low CO burner and method for operating same

Abstract

A round burner capable of being operated with reduced CO and NO x emissions includes a venturi tube positioned to direct a flow of air through the burner and into a combustion zone in a combustion chamber through an entrance in a wall of the combustion chamber. The venturi tube has inlet and outlet ends and a throat. The outlet end of the venturi tube has a larger internal diameter than either the inlet end or the throat and the same is positioned adjacent the entrance to the combustion chamber. The inlet end of the venturi tube is also positioned further from the entrance than the outlet end of the venturi tube. The burner may include a duct system that includes an inlet disposed in fluid communication with the combustion zone and an outlet disposed in fluid communication with the venturi tube adjacent the throat thereof. The system is arranged and adapted to recirculate a stream of flue gas from a location within said combustion chamber adjacent the combustion zone by induction into the venturi tube at a low pressure location adjacent the throat of the venturi tube so that the recirculated stream of internal flue gas is inducted into and intermixed with the flow of air at the throat of the venturi tube. Alternatively or cumulatively, the burner may include a fuel gas injector arrangement having an injector nozzle extending through the wall at a location adjacent the combustion zone. The injector nozzle is in fluid communication with the combustion chamber and is positioned to direct a flow of fuel gas into the combustion chamber at a location in the wall radially beyond the inner edge of the entrance. Also disclosed is a method for operating the burner to reduce CO and NO x emissions.

We claim:  
     
         1 . A round burner capable of reduced CO and NO x  emissions comprising: 
 a venturi tube positioned to direct a flow of air through the burner and into a combustion zone in a combustion chamber through an entrance in a wall of the combustion chamber, said venturi tube having an outer periphery and inlet and outlet ends, said outlet end of the venturi tube having a larger internal diameter than said inlet end, said outlet end of the venturi tube being positioned adjacent said entrance to the combustion chamber, said inlet end of the venturi tube being positioned further from said entrance than said outlet end of the venturi tube, said entrance having an inner edge; and    a fuel gas injector arrangement including at least one injector nozzle extending through said wall at a location adjacent said combustion zone, said nozzle being in fluid communication with said combustion chamber and positioned to direct a flow of fuel gas into said combustion chamber at a location in the wall beyond said inner edge of the entrance.    
     
     
         2 . A round burner as set forth in    claim 1   , wherein said burner includes at least one first fuel gas nozzle located in said venturi and positioned to introduce a supply of fuel gas into said flow of air.  
     
     
         3 . A round burner as set forth in    claim 1   , wherein said burner includes a swirler positioned so that at least a primary portion of said flow of air passes therethrough.  
     
     
         4 . A round burner as set forth in    claim 2   , wherein said burner includes a swirler positioned so that at least a primary portion of said flow of air passes therethrough.  
     
     
         5 . A round burner as set forth in    claim 1   , wherein said burner is adapted for burning fuel oil introduced into said flow of air.  
     
     
         6 . A round burner capable of reduced CO and NO x  emissions comprising: 
 a venturi tube for directing a flow of air through the burner and into a combustion zone in a combustion chamber through an entrance in a wall of the combustion chamber, said venturi tube having an inlet end, an outlet end and a throat having a lesser internal diameter than either of said ends located between said ends, said throat being operable when said flow of air passes through the venturi tube to create a low pressure zone therein, said venturi tube being positioned with its outlet end located adjacent said entrance to the combustion chamber, said venturi tube including a flue gas inlet connection located adjacent said throat for introducing recirculated flue gas directly into said low pressure zone, said tube further having an outer periphery and said entrance having an inner edge;    a fuel gas injector arrangement including an injector nozzle extending through said wall at a location adjacent said combustion zone, said nozzle being in fluid communication with said combustion chamber and positioned to direct a flow of fuel gas into said combustion chamber at a location in the wall beyond said inner edge of the entrance; and    a duct system including at least one inlet disposed in fluid communication with the combustion zone and at least one outlet connected to the flue gas inlet connection of the venturi tube, said system being arranged and adapted to recirculate a stream of flue gas from a location in said combustion chamber adjacent said combustion zone and into said flue gas inlet connection, whereby said stream of flue gas is inducted into said low pressure zone through said flue gas inlet connection and intermixed in the low pressure zone with said flow of air.    
     
     
         7 . A round burner as set forth in    claim 6   , wherein said burner includes at least one first fuel gas nozzle located in said venturi tube and positioned to introduce a supply of fuel gas into said flow of air.  
     
     
         8 . A round burner as set forth in    claim 6   , wherein said burner includes a swirler positioned so that at least a primary portion of said flow of air passes therethrough.  
     
     
         9 . A round burner as set forth in    claim 7   , wherein said burner includes a swirler positioned so that at least a primary portion of said flow of air passes therethrough.  
     
     
         10 . A round burner as set forth in    claim 6   , wherein said burner is adapted for burning fuel oil introduced into said flow of air.  
     
     
         11 . A round burner as set forth in    claim 7   , wherein said burner is adapted for burning fuel oil introduced into said flow of air.  
     
     
         12 . A method for operating a venturi tube equipped round burner with reduced CO and NO x  emissions, said method comprising: 
 directing a flow of air through the venturi tube and into a combustion zone in a combustion chamber through an entrance in a wall of the combustion chamber, said entrance having an inner edge; and    injecting a flow of fuel gas into said combustion chamber at a location radially beyond said inner edge of the entrance and adjacent said combustion zone.    
     
     
         13 . A method for operating a venturi tube equipped round burner as set forth in    claim 12   , wherein is included a step of introducing a first supply of fuel gas into said flow of air.  
     
     
         14 . A method for operating a venturi tube equipped round burner as set forth in    claim 12   , wherein is included a step of passing at least a primary portion of said flow of air through a swirler.  
     
     
         15 . A method for operating a venturi tube equipped round burner as set forth in    claim 13   , wherein is included a step of passing at least a primary portion of said flow of air through a swirler.  
     
     
         16 . A method for operating a venturi tube equipped round burner as set forth in    claim 12   , wherein a supply of fuel oil is introduced into said flow of air.  
     
     
         17 . A method for operating a venturi tube equipped round burner so as to achieve reduced CO and NO x  emissions, said venturi tube having an inlet end, an outlet end and a throat disposed between said ends, said throat having a lesser internal diameter than either of said ends and being operable when a flow of fluid passes through the venturi tube to create a low pressure zone therein, said venturi tube including a flue gas inlet connection located adjacent said throat to permit induction of recirculated flue gas directly into said low pressure zone, said venturi tube being positioned with its outlet end located adjacent an entrance to a combustion chamber, said entrance having an inner edge, said method comprising: 
 directing a flow of air through said venturi tube and into a combustion zone in said combustion chamber through said entrance to thereby create a low pressure zone in said venturi tube adjacent said flue gas inlet connection;    injecting a flow of fuel gas into said combustion chamber at a location radially beyond said inner edge of the entrance and adjacent said combustion zone; and    using the low pressure in said low pressure zone to induce a recirculation of flue gas from a location in said combustion chamber adjacent said combustion zone, through the flue gas inlet connection and directly into said low pressure zone, whereby recirculated flue gas is intermixed with said flow of air in said low pressure zone.    
     
     
         18 . A method for operating a venturi tube equipped round burner as set forth in    claim 17   , wherein is included a step of introducing a first supply of fuel gas into said flow of air.  
     
     
         19 . A method for operating a venturi tube equipped round burner as set forth in    claim 17   , wherein is included a step of passing at least a primary portion of said flow of air through a swirler.  
     
     
         20 . A method for operating a venturi tube equipped round burner as set forth in    claim 18   , wherein is included a step of passing at least a primary portion of said flow of air through a swirler.  
     
     
         21 . A method for operating a venturi tube equipped round burner as set forth in    claim 17   , wherein a supply of fuel oil is introduced into said flow of air.