A Co-firing technology with coal:biomass blends is expected to reduce land application requirements for manure based biomass wastes, and provide a renewable, low cost, and zero net fossil based CO2 fuel. The choice of low BTU biomass fuels may include conventional agricultural or unconventional animal based biomass fuels depending upon local availability and transportation costs. For power plants located near feedlots where cattle are fattened for slaughter, the best choice of renewable biomass fuel is feedlot manure, properly referred to as feedlot biomass (FB). Coal can be mixed with FB in a 90:10 (coal:FB) ratio by mass and fired in existing boiler burners. A 30 KW (100,000 BTU/hr) boiler burner facility was built and tested for firing coal or coal-FB blends at Texas A&M University. FB has a moisture content ranging from 20% to 40% moisture, but most of the previous data have been generated using low moisture FB (<10% moisture) due to problems processing moist manure. The current work will investigate the effect of different moisture levels using external water injection. The boiler burner was modified with an air atomizing water injector. At a fixed equivalence ratio and swirl number for the secondary inlet air stream, the effect of different moisture levels and different biomass particles on boiler performance was investigated. NOx, O2, and CO profiles along the axis of the furnace were obtained. The effect of atomizing air on the co-firing performance was also investigated. The results are summarized as follows: just with atomizing air is the wter injector, the NOx concentrations increased from 350 ppm to 650 ppm while CO decreased from 46,000 ppm to 18,000 ppm. External water injection decreased the NOx pollutant emissions from 570 ppm (zero external water) to 300 ppm (40% water in FB), but increased CO emissions from 2,500 ppm (zero external water) to 10,500 ppm (40% water in FB) due to incomplete combustion. Smaller sized particles of FB in the blended fuel produced less NOx but more CO.

Volume Subject Area:
Combustion and Alternative Energy
Topics:
Boilers, Underground injection, Biomass, Coal, Fuels, Water, Nitrogen oxides, Co-firing, Ejectors, Emissions, Particulate matter, Carbon dioxide, Combustion, Firing, Furnaces, Pollution, Power stations, Transportation systems
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Copyright © 2002
 by ASME
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