Catalytic combustor and method for substantially eliminating nitrous oxide emissions

Abstract

A combustor for a gas powered turbine which employs a heat exchanger and a catalyst to combust a fuel without the emission of undesired chemical species. A gas powered turbine requires expanding gases to power the turbine blades. Fuel is combusted to produce the required gases. A catalyst is employed to lower the combustion temperature of the fuel. The catalyst is placed on a set of tubes in the heat exchanger such that a portion of the thermal energy may be transferred to the air before it engages the catalyst. After encountering the catalyst, the combusted fuel increases the temperature of the air to an auto-ignition temperature so that no other ignition source is needed to combust additional fuel.

What is claimed is:  
     
         1 . A combustion system for use in a turbine which combusts a fuel in the presence of air, which substantially eliminates nitrous oxide emissions, comprising: 
 a heat exchanger including: 
 a catalyst pathway extending along a first axis;  
 a cooling pathway extending along a second axis;  
 wherein said catalyst pathway is in thermal contact with said cooling pathway;  
 wherein the air is adapted to first flow through said cooling pathway and then through said catalyst pathway;  
   a catalyst, disposed within said catalyst pathway, adapted to combust the fuel with the air; and    wherein the air is adapted to first flow past said catalyst pathway and through said cooling pathway, thereby receiving thermal energy from said catalyst pathway.    
     
     
         2 . The combustion system of  claim 1 , 
 wherein said catalyst pathway comprises a plurality of catalyst members, which form a plurality of catalyst columns each spaced apart transversally to said first axis and which define a plurality of channels adapted for allowing the air to flow therethrough;    wherein said cooling pathway comprises a plurality of cooling tubes, which form a plurality of cooling tube columns each spaced apart transversally to said second axis; and    wherein said cooling tubes extend substantially adjacent said catalyst members along said second axis for at least a portion of the length of said catalyst members.    
     
     
         3 . The combustion system of  claim 2 , wherein said catalyst members, said cooling tubes, and said channels define a flow path for the air such that the air is able to receive thermal energy from the catalyst members by flowing through said channels and said cooling tubes.  
     
     
         4 . The combustion system of  claim 1 , wherein said thermal energy allows the fuel to be combusted with said catalyst.  
     
     
         5 . The combustion system of  claim 1 , wherein said catalyst comprises a material able to combust a fuel in the air below about 1500° C.  
     
     
         6 . The combustion system of  claim 1 , further comprising: 
 a heat exchange area;    a pre-mix area for mixing a first portion of the fuel with the air;    a main injector area comprising at least one injector for said catalyst members;    wherein a second portion of the fuel is mixed with the air with said main injector; and    wherein said main injector is adapted to mix the second portion of fuel with the air such that the temperature throughout the area of the injector is substantially equal.    
     
     
         7 . The combustion system of  claim 1 , further comprising fins adapted to direct the flow of air around said catalyst tube.  
     
     
         8 . The combustion system of  claim 1 , wherein said cooling pathway includes a cooling fin and said catalyst pathway includes a catalyst fin.  
     
     
         9 . The combustion system of  claim 1 , wherein said first axis and said second axis are parallel for at least a portion of said catalyst pathway and said cooling pathway.  
     
     
         10 . A turbine, comprising: 
 a compressor adapted to produce compressed atmospheric air;    a combustion system for mixing and combusting a fuel injected into the compressed atmospheric air to produce expanding gases;    a turbine which is powered by the expanding gases:    wherein said combustion system comprises: 
 a first fuel supply to supply fuel to the compressed atmospheric air;  
 a heat exchanger comprising a catalyst section including a catalyst disposed within said catalyst section, wherein the compressed air and the fuel flow through said catalyst section; and  
 a second fuel supply to supply fuel to the compressed atmospheric air after the compressed atmospheric air has passed through said catalyst section.  
   
     
     
         11 . The turbine of  claim 10 , 
 wherein said catalyst section comprises a plurality of said catalyst members each extending along a first axis;    wherein said heat exchanger further includes a plurality of cooling tubes each extending along a second axis generally parallel to said first axis for at least a selected length;    wherein said catalyst members are arranged to form a plurality of columns spaced transversally to said first axis and defining a plurality of channels; and    wherein said cooling tubes are arranged in a plurality of columns and extend a distance along said catalyst members and generally perpendicular to said channels.    
     
     
         12 . The turbine of  claim 11 , wherein said catalyst members, said cooling tubes and said channels define a flow path for the compressed atmospheric air such that the compressed atmospheric air is adapted to receive thermal energy from said catalyst members by flowing through said channels and said cooling tubes.  
     
     
         13 . The turbine of  claim 11 , wherein thermal energy is transferred to the compressed atmospheric air as it flows through said heat exchanger such that the fuel from the first fuel supply is combusted via said catalyst.  
     
     
         14 . The turbine of  claim 11 , further comprising: 
 a heat exchange area;    a pre-mix area for mixing a first portion of the fuel with the air;    a main injector area comprising at least one injector for said catalyst tube;    wherein a second portion of the fuel is mixed with the compressed atmospheric air in said main injector; and    wherein said main injector is adapted to mix the second portion of fuel with the compressed atmospheric air such that the temperature throughout the area of the injector is substantially equal.    
     
     
         15 . The turbine of  claim 10 , wherein said catalyst section comprises a catalyst fin.  
     
     
         16 . For a turbine, a method of combusting a fuel in the presence of atmospheric air while substantially eliminating the emission of nitrous oxide compounds, the method comprising: 
 providing a heat exchanger comprising a plurality of pathways;    disposing a catalyst in at least a sub-plurality of said pathways;    forming a first fuel-air mixture by mixing a first portion of the fuel and the air;    producing a auto-ignition air stream by combusting the first fuel-air mixture by contacting the first fuel-air mixture with the catalyst; and    heating the air by transferring a portion of thermal energy from the pathways to the air.    
     
     
         17 . The method of  claim 16 , further comprising: 
 forming a second fuel-air mixture by adding a second portion of fuel to the auto-ignition air stream; and    producing an expanding gas by combusting said second fuel-air mixture, said expanding gas occurring when the fuel in the second fuel-air mixture reaches the temperature of the auto-ignition air stream.    
     
     
         18 . The method of  claim 17 , further comprising powering a turbine with said expanding gas.  
     
     
         19 . The method of  claim 16 , wherein said first fuel-air mixture has an equivalence ratio of between about 0.10 and about 0.30.  
     
     
         20 . The method of  claim 17 , wherein said second fuel-air mixture has an equivalence ratio of between about 0.40 and about 0.60.  
     
     
         21 . The method of  claim 16 , wherein said auto-ignition air stream has a temperature between about 760° C. (1400° F.) and 871° C. (1600° F.).  
     
     
         22 . The method of  claim 16 , wherein the step of heating the air comprises transferring a portion of the thermal energy produced in the pathways when the catalyst forms the auto-ignition air stream.  
     
     
         23 . A combustion system for use in a gas powered turbine which combusts a fuel in the presence of air while substantially eliminating nitrous oxide emissions, comprising: 
 a pre-heater to heat a volume of an oxidizer to form a volume of high energy oxidizer;    an injector member to inject a fuel, including a high temperature, into said volume of high energy oxidizer;    an injector port, defined by said injector member, to provide the fuel to said volume of high energy oxidizer before a substantial portion of the fuel combusts; and    wherein substantially all the fuel provided through said injector port reaches its said high temperature at substantially the same time.    
     
     
         24 . The combustion system of  claim 23 , wherein said pre-heater includes: 
 a catalyst pathway having a catalyst disposed therein;    a cooling pathway; and    wherein said catalyst pathway and said cooling pathway extend substantially parallel for a selected distance.    
     
     
         25 . The combustion system of  claim 24 , 
 wherein said catalyst pathway comprises a plurality of catalyst members, that form a plurality of catalyst columns each spaced apart transversally to said first axis and which define a plurality of channels adapted for allowing the oxidizer to flow therethrough;    wherein said cooling pathway comprises a plurality of cooling tubes that form a plurality of cooling columns each spaced apart transversally to said second axis; and    wherein said cooling columns extend substantially adjacent said catalyst columns along said second axis for at least a portion of the length of said catalyst columns.    
     
     
         26 . The combustion system of  claim 23 , further comprising: 
 at least a first and a second of said injector ports;    a first fuel stream produced by said first injector port; and    a second fuel stream produced by said second injector port;    wherein said first fuel stream and said second fuel stream impinge into one another to form a fuel plume prior to intersect the high energy air.    
     
     
         27 . The combustion system of  claim 26 , wherein said first fuel stream and said second fuel stream intersect at an angle between about 20° and about 150°.  
     
     
         28 . The combustion system of  claim 26 , further comprising: 
 a fuel path formed in said injector member such that the first fuel stream and the second fuel stream provided by said first and second injector ports intersect to produce said fuel plume.    
     
     
         29 . The combustion system of  claim 23 , wherein said injector port is substantially rectangular in shape such that a fuel stream is flattened as said fuel stream exits said injector port.  
     
     
         30 . A gas powered turbine, comprising: 
 a compressor to produce compressed atmospheric air to provide an oxidizer for the gas powered turbine;    a combustion system for mixing and combusting a fuel injected into the compressed atmospheric air to produce an expanding gas;    a turbine fan which is powered by the expanding gases:    wherein said combustion system comprises: 
 a pre-heat area;  
 a first fuel line to supply a first portion of fuel to the compressed atmospheric air which is combusted in the pre-heat area to heat the compressed atmospheric air to a hypergolic temperature so as to produce hypergolic air;  
 a second fuel line to supply a second portion of fuel to the hypergolic air;  
 an injector system to provide said second portion of fuel to said hypergolic air before any substantial portion of said second portion of fuel combusts; and  
   wherein substantially all of said second portion of fuel combusts at substantially the same time such that the gas powered turbine emits substantially no nitrous oxide compounds.    
     
     
         31 . The turbine of  claim 30 , further comprising: the air before the air enters the pre-heat area; 
 a main injector plate comprising at least a first and a second of said injectors; and    a combustion area wherein said second supply of fuel is combusted.    
     
     
         32 . The turbine of  claim 31 , further comprising: 
 a first fuel stream produced by said first injector port; and    a second fuel stream produced by said second injector port;    wherein said first fuel stream and said second fuel stream impinge into one another forming a fuel plume prior to intersecting the hypergolic air.    
     
     
         33 . A method of combusting a fuel for a gas powered turbine in the presence of atmospheric air while substantially eliminating the emission of nitrous oxide compounds, the method comprising: 
 producing an auto-ignition air stream wherein a fuel homogeneously combusts spontaneously upon reaching the temperature of said auto-ignition air stream;    providing a first portion of the fuel to said auto-ignition air stream; and    mixing said first portion of fuel with said auto-ignition air stream before substantially any of said first portion of fuel combusts to substantially eliminate emission of nitrous oxide compounds.    
     
     
         34 . The method of  claim 33 , further comprising: 
 producing an expanding gas by combusting said first portion of fuel in said auto-ignition air-stream, said expanding gas occurring when said portion of fuel in said auto-ignition air-stream combusts upon reaching the temperature of the auto-ignition air stream.    
     
     
         35 . The method of  claim 34 , further comprising powering a turbine with said expanding gas.  
     
     
         36 . The method of  claim 33 , wherein said auto-ignition air stream has a temperature between about 760° C. (1400° F.) and 871° C. (1600° F.).  
     
     
         37 . The method of  claim 33 , wherein mixing said first portion of fuel further comprises: 
 impinging a first fuel stream upon a second fuel stream to form a fuel plume.    
     
     
         38 . The method of  claim 37 , wherein impinging said first fuel stream upon said second fuel stream occurs at an angle between about 20° and about 150°.  
     
     
         39 . The method of  claim 38 , further comprising: 
 forming said first fuel stream and said second fuel stream as substantially flat streams before allowing said streams to impinge one another.    
     
     
         40 . The method of  claim 33 , wherein mixing said first portion of fuel further comprises providing a substantially flat fuel stream to said auto-ignition air stream.  
     
     
         41 . The method of  claim 33 , wherein producing an auto-ignition air-stream further comprises: 
 forming a fuel-air mixture by mixing a second portion of fuel with a volume of air; and    combusting said second portion of fuel in said volume of air, wherein combusting said second portion of fuel increases the temperature of said volume of air to an auto-ignition temperature.