Abstract: This invention discloses the synergistic integration of solid fuel combustion, low NOx control technologies (such as Low NOx Burners, reburning and Advanced Reburning) with partial in-duct gasification of coal or other solid fuels. For partial gasification, the solid fuel can be transported and injected by recycled flue gas stream at 600-800° F. in the reburning zone or in the upper section of the main combustion zone of a boiler. This allows the fuel to be preheated and partially pyrolyzed and gasified in the duct and then injected into the boiler as a mixture of coal, gaseous products, and char. Gasification increases coal reactivity and results in lower carbon-in-ash levels. As an option, the gaseous and solid products can be split using a cyclone separator. Splitting the gasified fuel stream will allow the volatile matter to be used for reburning and the fixed carbon to be injected into the high-temperature main combustion zone.

Abstract: 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.

Abstract: This invention discloses the synergistic integration of solid fuel combustion, low NOx control technologies (such as Low NOx Burners, reburning and Advanced Reburning) with partial in-duct gasification of coal or other solid fuels. For partial gasification, the solid fuel can be transported and injected by recycled flue gas stream at 600-800° F. in the reburning zone or in the upper section of the main combustion zone of a boiler. This allows the fuel to be preheated and partially pyrolyzed and gasified in the duct and then injected into the boiler as a mixture of coal, gaseous products, and char. Gasification increases coal reactivity and results in lower carbon-in-ash levels. As an option, the gaseous and solid products can be split using a cyclone separator. Splitting the gasified fuel stream will allow the volatile matter to be used for reburning and the fixed carbon to be injected into the high-temperature main combustion zone.