The role of alkali metal in N_2O and NO emission during high-sodium Zhundong coals oxy-fuel circulating fluidized bed combustion

摘要

To explain the role of alkali metal in N2O and NO emission during Zhundong coals oxy-fuel circulating fluidized bed combustion, the influences of alkali metals on the fuel-N and recycled-N were investigated in the present work. Results were obtained based on the experiments performed on a 50 kW oxy-fuel circulating fluidized bed combustor system. First, the N2O and NO emission characteristics during high-sodium Zhundong coals oxy-fuel combustion were obtained. Though the emission characteristics varied with coal types due to the different coal properties, it can be concluded that high-sodium coal can achieve low N2O concentration. High inlet oxygen concentration was conducive to the decrease of N2O and NO concentrations. The simulated recycled SO2 can enhance the reduction of NO. Then, the influences of alkali metals on the fuel-N and recycled-N were identified via injecting NaCl/Na2SO4 during low-sodium coal combustion. Both NaCl and Na2SO4 can decrease CO and N2O concentrations but increase NO concentration. While there hardly exist any interactions between NaCl/Na2SO4 and simulated recycled NO.