Low emission combustion process and apparatus

A combustion process for producing exhaust gases having a low content of carbon monoxide and nitrogen oxides, said process comprising:

• introducing a mixture of hydrocarbon fuel and air into a combustion zone having a volume which is sufficient to support stable combustion under the desired combustion conditions, with the mixture being premixed to a sufficient extent to provide a substantially uniform and homogeneous mixture within the combustion zone;
• igniting and burning the mixture within the combustion zone;
• maintaining the walls which define the combustion zone at temperatures which are sufficiently close to the combustion temperature to prevent quenching of the combustion reaction in the regions adjacent the walls to an extent which forms excessive quantities of carbon moxoxide and unburned hydrocarbons adjacent the burner walls;
• providing a dilution zone which is positioned downstream from the combustion zone and in flow communication with the combustion zone;
• splitting the incoming stream of air into a first stream which is introduced into the combustion zone and a second stream which is introduced into the dilution zone;
• controlling the flow split of the said first stream to provide a ratio of fuel to air within the combustion zone at lean fuel-to-air ratios of about 0.0035 to about 0.035 under stable combustion conditions which exceed lean blowout to a sufficient extent to reduce the carbon monoxide levels in the exhaust gases to about 12.0 grams or less per kilogram of consumed fuel while maintaining the combustion temperature at about 3,000.degree. F. or less to reduce the content of nitrogen oxides in the exhaust gases to a level of about 1.5 grams or less for each kilogram of consumed fuel, and
• maintaining the flow rate of the fuel-air mixture into the combustion zone at a level which exceeds the turbulent flame velocity within the combustion zone to prevent flashback to the point of introduction of the combustible mixture.

A process for operating a gas turbine to reduce the content of carbon monoxide and nitrogen oxides in the turbine exhaust gases, said process comprising:

• introducing a mixture of a hydrocarbon fuel and air into a combustion zone having a volume sufficient to support stable combustion under the desired combustion conditions and burning the mixture with the combustible mixture being well mixed to provide a substantially uniform and homogeneous mixture within the combustion zone;
• maintaining the combustion temperature within the combustion zone at a level of about 3,000.degree. F or less to reduce the nitrogen oxides content in the exhaust gases to a level of about 1.5 grams or less for each kilogram of consumed fuel;
• maintaining a lean fuel-to-air ratio in the combustion zone of about 0.0035 to about 0.035 under stable combustion conditions and at a sufficient level above lean blowout to reduce the carbon monoxide level in the exhaust gases to about 12.0 grams or less per kilogram of consumed fuel;
• maintaining the flow rate of the fuel-air mixture into the combustion zone at a level in excess of the turbulent flame velocity in the combustion zone to prevent flashback to the point of introduction of the combustible mixture, and
• conveying the exhaust gases from the combustion zone to a turbine rotor to drive the rotor in producing power.

A process for operating a gas turbine to reduce the content of carbon monoxide and nitrogen oxides in the turbine exhaust gases, said process comprising:

• introducing a mixture of a hydrocarbon fuel and air into a combustion zone having a volume sufficient to support stable combustion under the desired combustion conditions and burning the mixture with the combustible mixture being well mixed to provide a substantially uniform and homogeneous mixture within the combustion zone;
• providing a dilution zone which is positioned downstream of the combustion zone in flow communication with the combustion zone;
• splitting the incoming stream of air into a first stream which is introduced into the combustion zone and a second stream which is introduced into the dilution zone;
• controlling the flow split of the first stream to maintain the combustion temperature within the combustion zone at a level of about 3,000.degree. F. or less to reduce the nitrogen oxides content in the exhaust gases to a level of about 1.5 grams or less for each kilogram of consumed fuel while maintaining a lean fuel-to-air ratio in the combustion zone of about 0.0035 to about 0.035 under stable combustion conditions at a sufficient level above lean flowout to reduce the carbon monoxide level in the exhaust gases to about 12.0 grams or less per kilogram of consumed fuel;
• maintaining the flow rate of the fuel-air mixture into the combustion zone at a level in excess of the turbulent flame velocity in the combustion zone to prevent flashback to the point of introduction of the combustible mixture;
• and
• conveying the exhaust gases from the combustion zone to a turbine rotor to drive the rotor in producing power.