Patent ID: 7363867

Claim:
A method of minimizing discharge of nitrogen oxides from a combustion boiler, the method comprising the steps of: supplying an overfire air stream to a combustion chamber of the combustion boiler; spraying mist of droplets of a reducing agent directly into the overfire air stream with the sprayed droplets of the reducing agent having a particle size of between 1 micron and 40 microns; allowing the overfire air stream to mix with the sprayed droplets of the reducing agent, prior to the mixture of the overfire air stream and the sprayed reducing agent entering into the combustion boiler, so as to commence conversion of the sprayed droplets of the reducing agent into a vapor as the sprayed reducing agent mixes with the overfire air stream; completely vaporizing the sprayed reducing agent at least within 0.1 seconds of the sprayed reducing agent entering the combustion boiler; and reacting the vaporized reducing agent with the nitrogen oxides within the combustion chamber to reduce the nitrogen oxides and minimize discharge of nitrogen oxides from the combustion boiler dividing at least one initial overfire air duct, for supplying an initial overfire air stream to the combustion boiler and facilitating substantially complete combustion of fuel supplied to the combustion boiler, into an initial primary overfire air stream and an initial secondary overfire air stream, and adding the reducing agent only to the initial secondary overfire air stream, but not the initial primary overfire air stream, prior to the initial secondary overfire air stream discharging into the combustion chamber; and heating the initial overfire air stream to a temperature of between 300 and 800 degrees F. prior to the initial overfire air stream being divided into the initial primary and the initial secondary overfire air streams.