Reduction of nitrogen oxides by biomass reburning
Date
1999
Authors
Sweterlitsch, Jeffrey James
Major Professor
Advisor
Brown, Robert C.
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Abstract
The goal of this research is to demonstrate that biomass reburning is an effective means to reduce nitrogen oxides emitted from a coal-fired utility boiler. Nitrogen oxides are formed during the combustion of coal and contribute to the formation of smog and acid rain. The 1990 Clean Air Act Amendments set emission limits of several sources of nitrogen oxides, including coal-fired utilities, and encouraged the development of new technologies in order to reduce the emission of nitrogen oxides. One method to reduce the emission of nitrogen oxides is to employ reburning technology. Reburning technology involves staging fuel within a boiler to create a regime where nitrogen oxides are reduced to molecular nitrogen. There are three stages of reburning, the primary zone, the reburning zone, and the burnout zone.
In the primary zone coal is combusted, producing nitrogen oxides. In the secondary zone, more fuel is added, creating a fuel-rich regime, and producing free radicals that are necessary for the conversion from nitrogen oxides to molecular nitrogen. Additional air is added in the burnout zone to complete the combustion process. This research focuses on the reburning zone. A bench-scale, down-flow combustor was constructed to simulate a coal-fired utility boiler. The primary fuel was natural gas, and the reburning fuel was biomass, specifically switchgrass. Spatially resolved measurements of temperature and nitrogen oxides concentrations were made to determine switchgrass' efficiency as a reburning fuel.
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thesis