Study On Oxy-fuel Combustion Characteristic And Pollutant Emission Of Coal Blent With Biomass

The development of society needs the support of energy. But the unreasonable use of fossil energy brings increasingly serious energy crisis and environmental pollution.Based on this background, oxy-fuel combustion, as a new clean-burning technology, not only can achieve CO2 capture easily, but also reduce emissions of NOx and SO2. And co-combustion of coal and biomass technology has important significance in energy structure reformation and pollutant emissions reduction. The combination of these two technologies will have broad prospects in application.Combustion characteristics and thermal dynamic characteristics of blends of bituminous coal and biomass under an O2/CO2 atmosphere were investigated using thermogravimetric analysis. Influences of oxygen concentration, blend ratio and alkali metal of biomass on combustion characteristics were considered. And the fixed bed combustion system was used to research the pollutant emission characteristics of blend of bituminous coal and biomass in an O2/CO2 atmosphere. Influences of biomass ratio,oxygen concentration and combustion temperature on emissions of NOx and SO2 were considered.Main contents and results of the combustion experiment include as follows:(1)In an O2/CO2 atmosphere, with oxygen concentration increasing, both TG curves and DTG curves moved to lower temperature zone, the burning rate became faster, the burnout temperature decreased significantly, and the combustion characteristic index increased.(2)Combustion characteristics of blend of bituminous coal and biomass improved apparently. With the blending ratio increased, the DTGmax of volatile increased but the DTGmax of fixed carbon decreased, while the ignition performance and the burnout performance were improved.(3)The Coats-Redfern integral method was used to calculate the combustion kinetics parameters of blends of coal and biomass. The result showed apparent activation energy of fixed carbon combustion segment increased as the oxygen concentration increasing, and decreased as the biomass ratio increasing.The results of pollutant emissions in fixed bed combustion experiment showed that:(1) NO emission reduced under an oxygen-enriched atmosphere. When oxygen concentration rised, the NO release rate became faster, and the concentration of NO increased, but the NO conversion ratio decreased. Blend of coal and biomass led to reduction of NO concentration and NO conversion ratio. NO conversion rate fell inhigher temperature.(2)Compared with conventional combustion, SO2 emission was lower in an O2/CO2 atmosphere. But SO2 concentration and conversion ratio increased as oxygen concentration or combustion temperature increasing. SO2 emission and conversion ratio significantly reduced under blend of coal and biomass.