煤中灰分和钠添加剂对煤燃烧中氮释放的影响

EFFECTS OF MINERALS AND SODIUM ADDITION ON NITROGEN RELEASE DURING COAL COMBUSTION

利用TG/EGA分析设备,实验研究了煤中灰分和钠添加剂对煤燃烧过程中氮排放特性的影响。研究结果表明,在程序升温燃烧过程中,燃料氮除了以NO释放外,还以HCN和NH3的形式释放。在燃烧过程中,部分燃料氮会在焦中富集,并在燃烧后期以NO的形式释放出来。脱灰后,煤燃烧的NO和NH3的排放量增加,HCN排放量减少。分析表明这主要是由于煤灰降低了煤的活性以及惰性组分对扩散阻力的影响所造成的。钠添加剂能够增加煤的活性,使燃烧提前,并且钠的存在也催化原位焦炭对NO的还原,从而显著降低煤燃烧NO和HCN排放量。该实验中NaCl对NO和HCN的催化减排效果比Na2CO3好。

Experiments have been carried out to investigate the effects of indigenous minerals and sodium additives on the releases of coal nitrogen during combustion on a TGA using Yibin coal of China. The experimental results show that much HCN and little NH3 can be evolved during temperature -programmed combustion, as well as NO. During the combustion process, part of coal nitrogen can be firstly retained in the char and then released as NO at the later stage of coal combustion. The fractions of nitrogen released as NO and NH3 are higher for parent coal than that for demineralized coal, but the fraction as HCN is lower. This is attributed to the low activity of parent coal and the diffusion resistance caused by the minerals in parent coal, which retards the HCN release and induces more NO and NH3 conversion. Sodium compounds remarkably reduce NO and HCN release during temperature -programmed combustion. The effect of sodium chloride on NO reduction is greater than that of sodium carbonate. The catalysis of sodium containing compounds on the reactions between HCN precursor and NO may lead to the drastic reduction of both species.