煤粉浓度对HCN与NH3析出特性的影响

为探索煤粉浓度对含氮化合物生成与转化过程的影响机理，以连续给粉的一维沉降炉试验台为依托，在不同煤种、粒径和炉温下，对不同煤粉浓度下HCN与NH3的析出浓度进行了测试，并对HCN与NH3析出量与NOx转化率及燃尽率之间的关系进行了分析。试验结果表明：挥发分越高，煤粉粒径越小，HCN、NH3析出浓度越大。细颗粒煤粉更容易在高浓度下析出NH3，在低浓度下析出HCN，而粗颗粒煤粉情况正好相反。炉温越高，HCN析出量越低，NH3析出量越高，炉温700℃是HCN与NH3析出浓度发生显著变化的转折温度。在煤粉燃烧过程中，含氮化合物主要以HCN的形式析出。NOx转化率主要取决于NH3/HCN析出浓度比，煤粉的燃尽程度主要与HCN的析出特性有关。高浓度煤粉燃烧非常有利于抑制含氮化合物向NOx的转化。

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. 700℃ 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.