Nitrogen oxide reduction by biomass reburning and its reaction characteristics of homogeneous reduction

The nitrogen oxide (NO) reduction efficiencies of three biomass samples (rice husk, sawdust and corncob) by reburning were investigated under different conditions (reburning temperature and O2 concentration) in a fixed-bed reactor. The variations of CO, H2, hydrocarbons (mainly CH4), HCN and NH3 in the outlet gas from reburning zone under different conditions were evaluated. The experimental results indicated that the biomass type significantly influenced the NO reduction efficiency. The maximum NO reduction efficiency of sawdust reburning was 57.0%±2.1%, which was higher than those of rice husk reburning (50.0%±1.5%) and corncob reburning (51.0%±1.1%). During the reburning process, pyrolysis gases from the biomass could strengthen the reducing atmosphere and thus enhance the NO reduction efficiency by reburning, and highly efficient NO reduction was obtained at oxygen concentrations in the flue gas of 0%-1%. At reducing atmosphere (800-1200 ), the difference in NO reduction of the three biomass samples could be ascribed to the difference in yield of pyrolysis products of biomasses through the homogeneous reactions. Hydrocarbons were the key species causing the reduction in emissions of NO, whereas CO and H2 slightly affected NO reduction. The total concentration, summed by HCN and NH3, was an index reflecting the tendency of conversion from major nitrogen-containing species to N2. Thus, understanding the effect of pyrolysis gas on NO reduction by reburning was beneficial to NO reduction. ©, 2015, Editorial department of Molecular Catalysis. All right reserved.