Integration of direct combustion with gasification for reduction of NOx Emissions

The methods and systems of the present invention reduce NOx emissions in combustion systems, e.g., power plants, boilers, furnaces, incinerators, engines, and any combinations thereof. The inventive process decreases NOx emissions from stationary combustion sources and provides improved utilization of low-grade biomass and other waste fuels without slagging and fouling problems. The invention reduces NOx emissions while utilizing gasified fuels, including biomass and low-grade waste fuels, by gasifying solid fuels and injecting produced gas into a reburning zone of, for example, a boiler at relatively low temperatures and in relatively small amounts. By feeding the gas directly into a reburning zone, the need for gas cleaning is eliminated or substantially reduced as tars are burned in the flame and alkali species may be present at much lower levels than is the case with direct combustion applications.