Catalytic combustor 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 first axis and said second axis are substantially parallel;  
 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, placed within said catalyst pathway, and 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 tubes, which form a plurality of catalyst tube 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 tubes along said second axis for at least a portion of the length of said catalyst tubes.    
     
     
         3 . The combustion system of  claim 2 , wherein said catalyst tubes, 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 tubes 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 mixture of palladium and platinum.  
     
     
         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 tubes;    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 . 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 comprising a catalyst coated on the inside of 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.  
 
   
     
     
         10 . The turbine of  claim 9 , 
 wherein said catalyst section comprises a plurality of said catalyst tubes each extending along a first axis;    wherein said heat exchanger further includes a plurality of cooling tubes each extending along a second axis which is parallel to said first axis;    wherein said catalyst tubes 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 tubes and generally perpendicular to said channels.    
     
     
         11 . The turbine of  claim 10 , wherein said catalyst tubes, 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 tubes by flowing through said channels and said cooling tubes.  
     
     
         12 . The turbine of  claim 10 , 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 on said catalyst.  
     
     
         13 . The turbine of  claim 10 , 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.    
     
     
         14 . The combustion system of  claim 10 , further comprising fins adapted to direct the flow of the compressed atmospheric air around said catalyst tube.  
     
     
         15 . The combustion system of  claim 10 , wherein said catalyst comprises a mixture of palladium and platinum.  
     
     
         16 . The combustion system of  claim 9 , wherein said catalyst section comprises a catalyst fin.  
     
     
         17 . 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;    placing a catalyst on at least a portion of an interior of a number 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.    
     
     
         18 . The method of  claim 17 , 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.    
     
     
         19 . The method of  claim 18 , further comprising powering a turbine with said expanding gas.  
     
     
         20 . The method of  claim 17 , wherein said first fuel-air mixture has an equivalence ratio of between about 0.10 and about 0.30.  
     
     
         21 . The method of  claim 18 , wherein said second fuel-air mixture has an equivalence ratio of between about 0.40 and about 0.60.  
     
     
         22 . The method of  claim 17 , wherein said auto-ignition air stream has a temperature between about 1400° F. and 1600° F.  
     
     
         23 . The method of  claim 17 , 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.