Abstract: Various methods for decreasing the amount of nitrogen oxides released to the atmosphere as a component of combustion gas mixtures are provided. The methods specifically provide for the removal of nitric oxide and nitrogen dioxide (NOx) from gas mixtures emitted from stationary combustion systems. In particular, methods for improving efficiency of nitrogen oxide reduction from combustion systems include injecting metal-containing compounds into the main combustion zone and/or the reburning zone of a combustion system. The metal containing compounds react with active combustion species, and these reactions change radical concentrations and significantly improve NOx conversion to molecular nitrogen. The metal-containing additives can be injected with the main fuel, in the main combustion zone, with secondary or reburning fuel addition, or at several locations in the main combustion zone and reburning zone.

Abstract: Methods are provided for decreasing the amount of nitrogen oxides released to the atmosphere as a component of combustion emissions. The methods are carried out by forming a combustion flue gas in a combustion zone, the combustion flue gas including nitrogen oxides, injecting overfire air and droplets of a solution or a powder of a selective reducing agent into a burnout zone, and contacting the combustion flue gas with the overfire air and the selective reducing agent in the burnout zone to thereby decrease the concentration of nitrogen oxides therein. The selective reducing agent is provided in an aqueous solution or powder which is injected into the overfire air in optimized droplet or particle form prior to or concurrently with injection of the overfire air into the burnout zone.

Abstract: A method and system for the use of waste coal fines to reduce nitrogen oxides emissions from a coal-fired cyclone boiler. A coal water slurry including waste coal fines is injected as a co-firing fuel into a cyclone barrel of the cyclone boiler to partially oxidize the coal water slurry in a central portion of the cyclone barrel where injected. This produces a reducing zone having reducing gas species that convert nitrogen oxides to diatomic nitrogen. The coal water slurry can alternatively be injected into the cyclone barrel from a secondary combustion air conduit. The evaporation of the water from the coal water slurry reduces the overall combustion temperature in the cyclone barrel, further reducing the production of nitrogen oxides.