Patent ID: 7776279

Claim:
A combustion apparatus for combusting comprising: a boiler defining an enclosed flue gas path having a combustion zone and a burnout zone, wherein flue gas is formed in the combustion zone and the combustion flue gas comprising nitrogen oxides; a fuel injector aligned with and introducing fuel into the combustion zone and a combustion air injector aligned with and introducing air into the combustion zone; an overfire air system adjacent the burnout zone comprising an overfire air port adjacent the burnout zone and through which overfire air flows into the burnout zone, and a nitrogen reagent injector having an outlet aligned with the overfire air system and injecting nitrogen reagent gas or small droplets into said overfire air, wherein said small droplets or nitrogen reagent particles in the gas have an average diameter of no greater than 50 microns and the small droplets or particles are introduced at a location of the burnout zone having a flue gas temperature above an optimal temperature range for reduction of the nitrogen reagent and wherein the optimal temperature range is above 1600° F.