Experimental Study on the NO and N2O Formation Characteristics during Biomass Combustion
2013
Bai, Jisong | Yu, Chunjiang | Li, Lianming | Wu, Peng | Luo, Zhongyang | Ni, Mingjiang
In the present study, the NO and N₂O formation characteristics during combustion of five biomass fuels (rice straw, wheat straw, corn stalk, sugarcane leaf, and eucalyptus bark) and one bituminous coal, as a comparison, were investigated in a horizontal fixed-bed reactor. It showed that there was still a considerable degree of N₂O conversion for biomass fuels, although NO was formed in a much larger amount. Most of NO and N₂O were formed during the devolatilization stage for biomass fuels; therefore, optimizing the supply of air and fuel during biomass combustion in actual boilers can be expected to achieve ultralow emissions of nitrogen oxides. There was no clear correlation between the NO and N₂O yields and fuel N content, which indicated that the nitrogen functionality and other components, such as inherent mineral matter, present in biomass must have great influence on the nitrogen transformation during thermal processing. When rice straw was co-fired with eucalyptus bark, nonlinear behavior could be seen and the fuel N conversion to NO was largely enhanced. In the temperature range of 700–900 °C, the fuel N conversion to NO first increased and then decreased slightly, while the conversion to N₂O showed a continuous decreasing trend. The fuel N conversion to NO and N₂O showed a general increasing trend with the increase of the inlet oxygen concentration, and this phenomenon was more obvious at higher temperatures. The results presented in this study will help to gain some insight onto the fundamental mechanism of fuel N conversion during biomass combustion.
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