Patent ID: 7491055

Claim:
A method of reducing NO x emission consisting of the steps of: creating a first combustion zone by combusting a first fuel with a first air stream, wherein the first combustion zone is provided with an excess of the first air stream to produce a fuel-lean combustion environment, producing a plurality of NO x species in the first combustion zone, creating a reburn zone downstream of the first combustion zone by combusting a second fuel with a oxygen stream, wherein the reburn zone is provided with an excess of the second fuel to produce a fuel-rich combustion environment having a stoichiometric ratio between about 0.6 and about 0.70, increasing the local flame temperature and producing a plurality of NO x reducing precursors in the reburn zone during combustion, and reacting the plurality of NO x reducing precursors with NO x produced in first combustion zone, wherein a substantial portion of the NO x is converted to molecular nitrogen.