Coanda Gas Burner Apparatus and Methods

Abstract

A gas burner apparatus for discharging a mixture of fuel gas, air and flue gas into a furnace space of a furnace wherein the mixture is burned and flue gas having a low content of nitrous oxides and carbon monoxide is formed is provided. The burner tile includes at least one gas circulation port extending though the wall of the tile. The interior surface of the wall of the tile includes a Coanda surface. Fuel gas and/or flue gas conducted through the gas circulation port follows the path of the Coanda surface which allows more flue gas to be introduced into the stream. The exterior surface of the wall of the tile also includes a Coanda surface for facilitating the creation of a staged combustion zone. Also provided are improved burner tiles, improved gas tips and methods of burning a mixture of air, fuel gas and flue gas in a furnace space.

1 . A gas burner apparatus for discharging a mixture of fuel gas and air into a furnace wherein the mixture is burned in the presence of flue gas while producing a low content of nitrous oxides comprising:
 a housing for attachment to said furnace, said housing including:
 an upper end attached to said furnace, said upper end having an air outlet disposed therein; 
 a lower end opposing said upper end; and 
 a sidewall connecting said upper end and said lower end together, wherein at least one of said sidewall and said lower end has an air inlet disposed therein; 
   a burner tile having a central opening therein for receiving air from said combustion air outlet of said housing, said tile including:
 a bottom end attached to said upper end of said housing over said air outlet; 
 a top end opposing said bottom end, said top end including a discharge outlet; and 
 a wall connecting said bottom end to said top end and surrounding said central opening, said wall extending into said furnace and having an interior surface, an exterior surface and at least one gas circulation port extending though said wall, said interior surface of said wall including an internal Coanda surface which bulges into said central opening; 
   primary fuel gas injection means connected to a source of fuel gas and operably associated with said burner apparatus for injecting primary fuel gas into said central opening of said burner tile, said primary fuel gas injection means including a pre-mix unit comprising:
 a pre-mix membrane extending around the interior surface of said wall of said burner tile below said gas circulation port therein and having a plurality of pre-mix gas ports in the top thereof; and 
 a venturi mixer including an inner gas riser connected to said source of fuel gas and having an inner primary fuel gas discharge nozzle connected thereto, and a venturi housing operably associated with said inner gas riser and primary fuel gas discharge nozzle and connected to said pre-mix membrane for feeding a mixture of primary fuel gas and air into said pre-mix membrane; and 
   secondary fuel gas injection means connected to a source of fuel gas and operably associated with said burner apparatus for injecting secondary stage fuel gas from outside of said burner tile to a point adjacent to said discharge outlet of said burner tile.   
     
     
         2 . The gas burner apparatus of  claim 1  wherein said burner tile further includes circulation choke means positioned in said gas circulation port for inhibiting the flow of fluids from within said central opening of said tile through said gas circulation port. 
     
     
         3 . The gas burner apparatus of  claim 2  wherein said circulation choke means includes a shield attached to said wall of said burner tile and extending upwardly into said gas circulation port. 
     
     
         4 . A burner tile for use in association with a burner plenum to form a gas burner apparatus for discharging a mixture of fuel gas and air into a furnace wherein the mixture is burned in the presence of flue gas while producing a low content of nitrous oxides, wherein the burner plenum includes a housing for attachment to the furnace that includes an upper end having an air outlet disposed therein, said burner tile having a central opening therein for receiving air from the outlet of the plenum housing and comprising:
 a bottom end attachable to the upper end of the plenum housing over the air outlet disposed therein;   a top end opposing said bottom end, said top end including a discharge outlet; and   a wall connecting said bottom end to said top end and surrounding said central opening, said wall extendable into said furnace and having an interior surface, an exterior surface and at least one gas circulation port extending through said wall, said interior surface of said wall including an internal Coanda surface which bulges into said central opening.   
     
     
         5 . The burner tile of  claim 4  wherein said internal Coanda surface is positioned on said interior surface of said wall adjacent to said gas circulation port. 
     
     
         6 . The burner tile of  claim 5  wherein said interior surface of said wall of said tile includes a recessed section, and said gas circulation port and said internal Coanda surface are positioned in said recessed section. 
     
     
         7 . The burner tile of  claim 6  wherein said recessed section includes opposing sidewalls extending outwardly from said interior surface into said central opening of said tile, said opposing sidewalls extending further into said central opening than said internal Coanda surface extends into said central opening. 
     
     
         8 . A burner tile for use in association with a burner plenum to form a gas burner apparatus for discharging a mixture of fuel gas and air into a furnace wherein the mixture is burned in the presence of flue gas while producing a low content of nitrous oxides, wherein the burner plenum includes a housing for attachment to the furnace that includes an upper end having an air outlet disposed therein, said burner tile having a central opening therein for receiving air from the air outlet of the plenum housing and comprising:
 a bottom end attachable to the upper end of the plenum housing over the air outlet disposed therein;   a top end opposing said bottom end, said top end including a discharge outlet; and   a wall connecting said bottom end to said top end and surrounding said central opening, said wall extendable into said furnace and having an interior surface and an exterior surface, said exterior surface of said wall including an external Coanda surface which bulges outwardly from said exterior surface.   
     
     
         9 . The burner tile of  claim 8  wherein said exterior surface of said wall of said burner tile includes a plurality of external Coanda surfaces, each of said external Coanda surfaces bulging outwardly from said exterior surface. 
     
     
         10 . The burner tile of  claim 9  wherein said external Coanda surface extends completely around said exterior surface of said wall of said burner tile. 
     
     
         11 . A burner tile for use in association with a burner plenum to form a gas burner apparatus for discharging a mixture of fuel gas and air into a furnace wherein the mixture is burned in the presence of flue gas while producing a low content of nitrous oxides, wherein the burner plenum includes a housing for attachment to the furnace that includes an upper end having an air outlet disposed therein, said burner tile having a central opening therein for receiving air from the air outlet of the plenum housing and comprising:
 a bottom end attachable to the upper end of the plenum housing over the air outlet disposed therein;   a top end opposing said bottom end, said top end including a discharge outlet; and   a wall connecting said bottom end to said top end and surrounding said central opening, said wall extendable into said furnace and having an interior surface, an exterior surface and at least one gas circulation port extending through said wall, said interior surface of said wall including an internal Coanda surface which bulges into said central opening, said exterior surface of said wall including an external Coanda surface which bulges outwardly from said exterior surface.   
     
     
         12 . The burner tile of  claim 11  wherein said wall of said burner tile includes a plurality of gas circulation ports extending through said wall. 
     
     
         13 . The burner tile of  claim 12  wherein said interior surface of said wall includes a plurality of internal Coanda surfaces, each of said internal Coanda surfaces bulging into said central opening of said burner tile. 
     
     
         14 . The burner tile of  claim 13  wherein said exterior surface of said wall of said burner tile includes a plurality of external Coanda surfaces, each of said external Coanda surfaces bulging outwardly from said exterior surface. 
     
     
         15 . The burner tile of  claim 13  wherein said external Coanda surface extends completely around said exterior surface of said wall of said burner tile. 
     
     
         16 . The burner tile of  claim 15  wherein said tile has a substantially circular cross-sectional shape. 
     
     
         17 . A gas tip for use in association with a gas burner apparatus, comprising:
 a gas barrel for connection to a source of fuel gas;   a gas deflector attached to said gas barrel; and   a fuel gas outlet disposed between said gas barrel and said gas deflector, said gas deflector having an exterior surface that includes a Coanda surface positioned with respect to said fuel gas outlet such that fuel gas discharged from said fuel gas outlet follows the path of said Coanda surface.   
     
     
         18 . A method of burning a mixture of air, fuel gas and flue gas in a furnace space of a furnace to generate heat in the furnace space wherein a gas burner apparatus having a mixing zone for mixing the air, fuel gas and flue gas prior to combustion thereof is utilized, comprising:
 providing a Coanda surface in said mixing zone;   injecting fuel gas on or adjacent to said Coanda surface in a manner that entrains flue gas from outside said mixing zone into said mixing zone and causes said flue gas to mix with said air and fuel gas in said mixing zone;   discharging said mixture of air, fuel gas and flue gas from said mixing zone into said furnace space; and   burning said mixture of combustion air, fuel gas and flue gas discharged from said mixing zone in said furnace space.   
     
     
         19 . The method of  claim 18  wherein said mixing zone is surrounded by a wall and said mixture of air, fuel gas and flue gas is discharged from said mixing zone into a primary reaction zone in said furnace space, and wherein said method further comprises the steps of:
 providing an external Coanda surface on the exterior surface of said wall; 
 injecting a stream of secondary stage fuel gas on or adjacent to said external Coanda surface in a manner that entrains flue gas into the stream to create a secondary fuel gas/flue gas mixture and causes said secondary fuel gas/flue gas mixture to burn in a secondary reaction zone in said furnace space. 
 
     
     
         20 . A method of burning a mixture of air, fuel gas and flue gas in a furnace space of a furnace to generate heat in the furnace space wherein a gas burner apparatus including a wall surrounding a mixing zone for mixing the air, fuel gas and flue gas prior to combustion thereof is utilized, comprising:
 providing a Coanda surface on the exterior surface of the wall of the burner apparatus;   injecting primary fuel gas into the mixing zone in a manner that causes the fuel gas to mix with air in the mixing zone;   discharging the mixture of air and fuel gas from the mixing zone;   burning the mixture of air and fuel gas discharged from the mixing zone in a primary reaction zone in the furnace space;   injecting a stream of secondary stage fuel gas on or adjacent to the external Coanda surface in a manner that entrains flue gas into the stream to create a secondary fuel gas/flue gas mixture and causes such secondary fuel gas/flue gas mixture to burn in a secondary reaction zone in the furnace space.   
     
     
         21 . The method of  claim 20  wherein the interior surface of the wall of the burner apparatus includes an internal Coanda surface, and the fuel gas injected into the mixing zone is injected on or adjacent to the internal Coanda surface in a manner that entrains flue gas from outside the mixing zone into the mixing zone and causes the flue gas to mix with the air and fuel gas in the mixing zone. 
     
     
         22 . A gas burner apparatus for discharging a mixture of fuel gas and air into a furnace wherein the mixture is burned in the presence of flue gas while producing a low content of nitrous oxides, comprising:
 a plenum including a housing for attachment to said furnace, said housing including:
 an upper end attached to said furnace, said upper end having an air outlet disposed therein; 
 a lower end opposing said upper end; and 
 a sidewall connecting said upper end and said lower end together, wherein at least one of said sidewall and said lower end has an air inlet disposed therein; 
   a burner tile having a central opening therein for receiving air from said air outlet of said housing, said tile including:
 a bottom end attached to said upper end of said housing over said air outlet; 
 a top end opposing said bottom end, said top end including a discharge outlet; and 
 a wall connecting said bottom end to said top end and surrounding said central opening, said wall extending into said furnace and having an interior surface and an exterior surface; and 
 primary fuel gas injection means connected to a source of fuel gas and operably associated with said burner apparatus for injecting primary fuel gas into said central opening of said burner tile, said primary fuel gas injection means including a pre-mix unit, said pre-mix unit including:
 a pre-mix membrane extending around the interior surface of said wall of said burner tile for injecting a pre-mixed stream of primary fuel gas and air around the interior surface of said wall and around said central opening of said burner tile, said pre-mix membrane including at least one inlet and at least one outlet therein; and 
 a venturi mixer including an inner gas riser connected to a source of fuel gas and having an inner primary fuel gas discharge nozzle connected thereto, and a venturi housing operably associated with said inner gas riser and primary fuel gas discharge nozzle and connected to said inlet of said pre-mix membrane for feeding a mixture of primary fuel gas and air into said pre-mix membrane. 
 
   
     
     
         23 . The gas burner apparatus of  claim 22  wherein said pre-mix membrane extends around the interior surface of said wall of said burner tile in a manner that allows it to symmetrically inject a pre-mixed stream of primary fuel gas and air around the interior surface of said wall and around said central opening of said burner tile. 
     
     
         24 . The gas burner apparatus of  claim 22  wherein said pre-mix membrane extends continuously around the interior surface of said wall of said burner tile. 
     
     
         25 . The gas burner apparatus of  claim 22  wherein said pre-mix membrane is inset somewhat in the interior surface of said wall of said burner tile. 
     
     
         26 . The gas burner apparatus of  claim 22  wherein said pre-mix membrane includes a plurality of pre-mix gas ports in the top thereof. 
     
     
         27 . The gas burner apparatus of  claim 22  wherein said pre-mix membrane includes two inlets and said pre-mix unit includes two venturi mixers, each venturi mixer including an inner gas riser connected to said source of fuel gas and having an inner primary fuel gas discharge nozzle connected thereto, and a venturi housing operably associated with said inner gas riser and primary fuel gas discharge nozzle and connected to one of said inlets of said pre-mix membrane for feeding a mixture of primary fuel gas and air into said pre-mix membrane. 
     
     
         28 . The gas burner apparatus of  claim 22 , wherein said primary fuel gas injection means further includes a primary fuel gas injection assembly separate from said pre-mix unit for injecting primary fuel gas into said central opening of said burner tile. 
     
     
         29 . The gas burner apparatus of  claim 28  wherein said primary fuel gas injection assembly includes an inner gas riser connected to a source of fuel gas and positioned inside of said housing, said inner gas riser having an inner primary fuel gas discharge nozzle connected thereto for injecting primary fuel gas into said central opening of said burner tile. 
     
     
         30 . The gas burner apparatus of  claim 28  wherein said primary fuel gas injection assembly includes an inner gas riser connected to a source of fuel gas and positioned inside of said housing, said inner gas riser having an inner primary fuel gas discharge nozzle connected thereto and a venturi housing operably associated therewith for injecting a mixture of primary fuel gas and air into said central opening of said burner tile. 
     
     
         31 . The gas burner apparatus of  claim 28  wherein said pre-mix unit and said primary fuel gas injection assembly are connected to separate sources of fuel gas. 
     
     
         32 . The gas burner apparatus of  claim 22 , further comprising secondary fuel gas injection means connected to a source of fuel gas and operably associated with said burner apparatus for injecting secondary stage fuel gas from outside of said burner tile to a point adjacent to said discharge outlet of said burner tile. 
     
     
         33 . The gas burner apparatus of  claim 32  wherein said secondary fuel gas injection means includes an outer gas riser connected to said source of fuel gas and having a secondary fuel gas discharge nozzle connected thereto for injecting secondary stage fuel gas on or adjacent to said exterior surface of said wall of said burner tile. 
     
     
         34 . The gas burner apparatus of  claim 22  wherein said burner tile and said pre-mix membrane of said pre-mix unit have substantially round cross-sectional shapes. 
     
     
         35 . The gas burner apparatus of  claim 22  wherein said burner tile further comprises a lip transversely extending from said interior surface of said wall into said central opening, said lip being attached to said wall adjacent to said top end of said burner tile and extending around said interior surface of said wall of said burner tile. 
     
     
         36 . The gas burner apparatus of  claim 35  wherein said lip includes a lower end, a top end and a body connecting said lower end and said top end together, said body including a plurality of protrusions extending into said central opening. 
     
     
         37 . A burner tile for use in association with a burner plenum to form a gas burner apparatus for discharging a mixture of fuel gas and air into a furnace wherein the mixture is burned in the presence of flue gas while producing a low content of nitrous oxides, wherein the burner plenum includes a housing for attachment to the furnace that includes an upper end having an air outlet disposed therein, said burner tile having a central opening therein for receiving air from the outlet of the plenum housing and comprising:
 a bottom end attachable to the upper end of said plenum housing over the air outlet disposed therein;   a top end opposing said bottom end, said top end including a discharge outlet; and   a wall connecting said bottom end to said top end and surrounding said central opening, said wall extendable into said furnace and having an interior surface and an exterior surface; and   a pre-mix membrane extending around the interior surface of said wall for injecting a pre-mixed stream of primary fuel gas and air around the interior surface of said wall and around said central opening, said pre-mix membrane including at least one inlet for connection to a source of fuel gas and air and at least one outlet therein,   
     
     
         38 . The burner tile of  claim 37  wherein said pre-mix membrane extends around the interior surface of said wall in a manner that allows it to symmetrically inject a pre-mixed stream of primary fuel gas and air around the interior surface of said wall and around said central opening. 
     
     
         39 . The burner tile of  claim 37  wherein said pre-mix membrane extends continuously around the interior surface of said wall. 
     
     
         40 . The burner tile of  claim 37  wherein said pre-mix membrane is inset somewhat in the interior surface of said wall of said burner tile. 
     
     
         41 . The burner tile of  claim 37  wherein said pre-mix membrane includes a plurality of pre-mix gas ports in the top thereof. 
     
     
         42 . The burner tile of  claim 37  wherein said burner tile and said pre-mix membrane have substantially round cross-sectional shapes. 
     
     
         43 . The burner tile of  claim 37  wherein said burner tile further comprises a lip transversely extending from said interior surface of said wall into said central opening, said lip being attached to said wall adjacent to said top end of said burner tile and extending around said interior surface of said wall of said burner tile. 
     
     
         44 . The burner tile of  claim 43  wherein said lip includes a lower end, a top end and a body connecting said lower end and said top end together, said body including a plurality of protrusions extending into said central opening. 
     
     
         45 . A method of burning a mixture of air, fuel gas and flue gas in a furnace space of a furnace to generate heat in the furnace space wherein a gas burner apparatus including a wall surrounding a mixing zone for mixing the air, fuel gas and flue gas prior to combustion thereof is utilized, comprising:
 providing a pre-mix membrane in said mixing zone, said pre-mix membrane extending around the interior surface of said wall and the perimeter of said mixing zone;   discharging a mixture of fuel gas and air from said pre-mix membrane around the perimeter of said mixing zone;   igniting said mixture of fuel gas and air discharged from said pre-mix membrane around the perimeter of said mixing zone;   injecting primary fuel gas into said mixing zone from a primary fuel gas injection assembly separate from said pre-mix unit in a manner that entrains flue gas from outside said mixing zone into said mixing zone and causes said flue gas to mix with air and fuel gas in said mixing zone;   using said ignited mixture of fuel gas and air discharged from said pre-mix membrane around the perimeter of said mixing zone to ignite the mixture of primary fuel gas, flue gas and air formed by injecting primary fuel gas into said mixing zone from said primary fuel gas injection assembly;   discharging said mixture of air, fuel gas and flue gas from said mixing zone into said furnace space; and   burning said mixture of combustion air, fuel gas and flue gas discharged from said mixing zone in said furnace space.   
     
     
         46 . The method of  claim 45  wherein said mixture of air, fuel gas and flue gas is discharged from said mixing zone into a primary reaction zone in said furnace space, and wherein said method further comprises the steps of:
 injecting a stream of secondary stage fuel gas on or adjacent to the exterior surface of said wall in a manner that entrains flue gas into the stream to create a secondary fuel gas/flue gas mixture and causes said secondary fuel gas/flue gas mixture to burn in a secondary reaction zone in said furnace space.