Dry low NOx hydrocarbon combustion apparatus

Abstract

A fuel with or without fuel bound nitrogen (FBN) is burned in a high pressure machine (20 atm) comprising fuel and air compressors, combustor and turbine at an ER of about 2-3 and temperature below the threshold for creating thermal NO x . Prompt and FBN NO x are avoided due to the rich mixture, having a dearth of O and OH, producing CO and H 2 and little CH. The turbine cools the products to reduce their temperature. The cooled products are mixed with the remaining air and burned at a temperature below the thermal NO 2 threshold temperature at an ER of about 0.6. Commercial stand alone machines can be used for the rich and for the lean combustors wherein air and fuel are supplied to the rich combustor and only air and the cooled combustion products of the rich machine are supplied to the lean combustor.

What is claimed is: 
     
       1. Gas turbine apparatus for dry low NO x  combustion comprising: a first gas turbine set including a first compressor means for compressing incoming air to about 20 atmospheres, a first combustor having fuel injector means and being coupled to said first compressor means, said first combustor having an exit equivalence ratio of about 2.0 to 3.0 so as to produce hot combustion products comprising substantially CO and H 2  and negligible NO x , and first turbine means coupled to the output of said first combustor for cooling the hot combustion products below a temperature at which ignition and thermal NO x  occur; and   a second gas turbine set including a second compressor means for compressing incoming air to about 10 atmospheres, a mixer coupled to said second compressor means for receiving air from said second compressor means, said mixer also coupled to the output of said first turbine means, the output pressure of said first turbine means being about 5% higher than the output of said second compressor .Iadd.means.Iaddend., so that rapid and homogeneous mixing in the mixer is assured, a second combustor having fuel injector means coupled to the output of said mixer, said second combustor having an exit equivalence ratio of about 0.2 to 0.3, so that production of NO x  and CO is minimized, and second turbine means coupled to the output of said second combustor.   
     
     
       2. The gas turbine apparatus of claim 1, wherein the quantity of air supplied by said second compressor means is approximately ten times the quantity of air supplied by said first compressor means. 
     
     
       3. The gas turbine apparatus of claim 2 wherein the temperature of the output of said first compressor means is approximately 840° F. and the temperature of the output of said second compressor means is approximately 600° F. 
     
     
       4. The apparatus of claim 3 wherein the temperature of the combustion products at the exit of the first turbine means is approximately .[.1860.]. .Iadd.2136.Iaddend.° F. at a pressure of 10.5 atmospheres and the temperature of the combustion products at the exit of the second turbine means is approximately 1005° F. at a pressure of 1 atmosphere. 
     
     
       5. A gas turbine apparatus for dry low NO x  combustion comprising: a compressor for compressing incoming air;   a first combustor connected to said compressor for receiving a portion of the compressed air from the compressor and having fuel injection means for receiving fuel, said first combustor having an exit equivalence ratio of about 2.0 to 3.0 so as to produce hot combustion products comprising substantially CO and H 2  .Iadd.and .Iaddend.negligible NO x  ;   cooling means connected to said first combustor for cooling the hot combustion products below a temperature at which ignition and thermal NO x  occur;   a mixer having inlet means and outlet means, said inlet means being connected to said cooling means for receiving the cooled combustion products and to said compressor for receiving the remaining portion of the compressed air;   a second combustor connected to said outlet means of said mixer for receiving the output of said mixer, said second combustor having an exit equivalence ratio of about 0.2 to 0.3 so that production of NO x  and CO is minimized; and   turbine means connected to said second combustor for being driven by the output of said second combustor. .Iadd.   
     
     
       6.  A gas turbine apparatus for dry low NO x  combustion comprising: a compressor for producing first and second portions of combustion air;   a first combustor receiving said first portion of combustion air and a fuel and in which combustion products are produced;   cooling means connected to said first combustor for cooling said combustion products;   a second combustor receiving said cooled combustion products and said second portion of combustion air, said second combustor having an exit equivalence ratio sufficiently low so that very little NO x  is generated in a lean combustion process; and   a turbine driven by the products of combustion from said second combustor. .Iaddend. .Iadd.7. The gas turbine apparatus for dry low NO x  combustion of claim 6 wherein said second combustor includes a mixer in which said cooled combustion products and said second portion of combustion air are mixed. .Iaddend. .Iadd.8. A gas turbine apparatus for dry low NO x  combustion comprising:   a first compressor for producing a first portion of combustion air;   a second compressor for producing a second portion of combustion air;   a first combustor receiving said first portion of combustion air and a fuel and in which combustion products are produced;   cooling means connected to said first combustor for cooling said combustion products;   a second combustor receiving said cooled combustion products and said second portion of combustion air, said second combustor having an exit equivalence ratio sufficiently low so that very little NO x  is generated in a lean combustion process; and   a turbine driven by the products of combustion from said second combustor.   
     
     
        .Iaddend. .Iadd.9.  The gas turbine apparatus for dry low NO x  combustion of claim 8 wherein said second combustor includes a mixer in which said cooled combustion products and said second portion of combustion air are mixed. .Iaddend. .Iadd.10. A method of generating power comprising the steps of: burning a fuel with a first portion of combustion air in a first combustor to produce combustion products;   cooling said combustion products;   burning said cooled combustion products with a second portion of combustion air in a second combustor at an equivalence ratio sufficiently low so that very little NO x  is generated in a lean combustion process; and   driving a turbine with the products of combustion of said second combustor. .Iaddend.