Patent ID: 6957955

Claim:
A method for combusting hydrocarbon fuel, comprising: feeding into the fuel rich region of a single combustion stage or the fuel rich region of the first combustion stage of first and second combustion stages fuel containing one or more nitrogenous hydrocarbon compound and gaseous oxidant having an average oxygen concentration of more than 21 vol. % oxygen, at a stoichiometric ratio below that at which, if the stage were operated with air as the only oxidant, the same amount of NOx would be produced, and combusting said fuel with said gaseous oxidant in said single or first combustion stage to produce combustion products and unburned fuel, further comprising combusting said unburned fuel in a second combustion stage with additional gaseous oxidant comprised such that the average oxygen content of the oxidant fed to said first and second stages is in the range of 20.9-27.4 vol. % oxygen while removing sufficient heat from the combustion products and unburned fuel produced in said single or first stage to reach a temperature low enough to minimize additional formation of NOx in said combustion in said second stage.