Conversions of fuel-N, volatile-N, and char-N to NO and N_2O during combustion of a single coal particle in O_2/N_2 and O_2/H_2O at low temperature

Oxy-steam combustion is a promising next-generation combustion technology.Conversions of fuel-N,volatile-N,and char-N to NO and N2O during combustion of a single coal particle in O2/N2and O2/H2O were studied in a tube reactor at low temperature.In O2/N2,NO reaches the maximum value in the devolatilization stage and N2O reaches the maximum value in the char combustion stage.In O2/H2O,both NO and N2O reach the maximum values in the char combustion stage.The total conversion ratios of fuel-N to NO and N2O in O2/N2are obviously higher than those in O2/H2O,due to the reduction of H2O on NO and N2O.Temperature changes the trade-off between NO and N2O.In O2/N2and O2/H2O,the conversion ratios of fuel-N,volatile-N,and char-N to NO increase with increasing temperature,and those to N2O show the opposite trends.The conversion ratios of fuel-N,volatile-N,and char-N to NO reach the maximum values at 〈O2〉=30 vol%in O2/N2.In O2/H2O,the conversion ratios of fuel-N and char-N to NO reach the maximum values at 〈O2〉=30 vol%,and the conversion ratio of volatile-N to NO shows a slightly increasing trend with increasing oxygen concentration.The conversion ratios of fuel-N,volatile-N,and char-N to N2O decrease with increasing oxygen concentration in both atmospheres.A higher coal rank has higher conversion ratios of fuel-N to NO and N2O.Anthracite coal exhibits the highest conversion ratios of fuel-N,volatile-N,and char-N to NO and N2O in both atmospheres.This work is to develop efficient ways to understand and control NO and N2O emissions for a clean and sustainable atmosphere.