Effect of pulverized coal concentration on emission characteristics of HCN and NH3

Experiments were carried out in the one-dimensional drop-tube furnace to discover the mechanism in influencing of pulverized coal concentration on formation and conversion of nitrogen compounds. Concentration of HCN and NH3 were measured under the different coal species and particle size as well as furnace temperature, and relations of among NH3/HCN and NOx conversion ratio as well as burnout rate of pulverized coal were analyzed under the different pulverized coal concentration. Results show that both concentration of HCN and NH3 are high under high volatile and fine pulverized coal particles. For the fine pulverize coal particles, NH3 is easier to release under the high pulverized coal concentration, and HCN is easier to release under the low pulverized coal concentration. But for the coarse pulverize coal particles, there are the opposite results. The higher the furnace temperature is, the lower the concentration of HCN is, and the higher the concentration of NH3 is. 700C is the turning temperature for the significant changes in the concentration of HCN and NH3. Nitrogen compounds are released mainly by HCN during the pulverized coal combustion. Conversion ratio of NOx mainly depends on the concentration ratio of NH3 to HCN. The burnout rate of pulverized coal is correlated with the releasing characteristics of HCN. The combustion of high concentration pulverized coal is in favor of restraining the conversion of nitrogen compounds to NOx.