Investigation on Fuel-N Transformation Properties of Coal/Biomass Heating Process in CO_(2)Atmosphere

To understand the effect of a CO_(2)atmosphere on the properties of the transformation from fuel-N to NO_(x)precursors(mainly NH_(3)and HCN),pyrolysis experiment on Pingliang coal(PL coal),wheat straw and their corresponding blends was carried out in a fluidized bed reactor within a temperature range of 750℃to 850℃.The results indicated that the PL coal and wheat straw show different NO_(x)precursor formation properties owing to the discrepancy between the N-containing structures in the raw materials.Compared with an argon atmosphere,CO_(2)can effectively suppress the formation of NH_(3).For HCN,the HCN yield of PL coal is suppressed and the HCN yield of wheat straw is promoted.Furthermore,CO_(2)can suppress the overall nitrogen conversion rate of NH_(3)^(+)HCN for both coal and biomass,which causes more fuel-N to convert into tar-N and N_(2)-N.For the blends of PL coal and wheat straw,the copyrolysis synergistic effect of coal/biomass influences the selectivity of HCN and NH_(3).The copyrolysis synergistic effect favors the formation of copyrolyzed HCN but has an opposite impact on the transformation from fuel-N to NH_(3).The synergistic effect of coal/biomass promotes the overall nitrogen conversion rate of NH_(3)^(+)HCN under a CO_(2)atmosphere,and the overall nitrogen conversion rate of NH_(3)+HCN is suppressed under an argon atmosphere,conversely.In addition,the synergistic effect of coal/biomass suppresses the yield of environmentally harmless N_2,and more fuel-N was retained in the char.