大同烟煤增压富氧燃烧过程中硫、氯和氟的析出特性

利用高压热重结合傅里叶红外研究了大同烟煤在增压富氧燃烧过程中硫、氯和氟的释放行为,主要考察压力对其析出特性的影响。实验结果表明,压力的改变对煤中硫、氯和氟的迁移转化均有显著影响。随着压力的升高,黄铁矿硫向COS等中间产物的转化率逐渐增加,导致SO2的收率逐步上升,但在3 MPa时,燃煤SO2收率却有所降低。此外,压力升高后反应气氛中CO分压的增加促进了COS的生成,导致其收率逐渐上升。因为煤中有机氯析出和转化与挥发分的释放密切相关,所以高压下挥发分释放量的增加使得煤中有更多的有机氯析出并转化为HCl,而且压力升高后,挥发分燃烧速率和温度的升高促进了无机氟化物分解,HF生成量相应增加。此外,高压下水解反应的强化也提高了HF的收率。

Investigation on sulfur,chlorine and fluorine releasing characteristics during pressurized oxy-fuel combustion of Datong bituminous coal

The release behavior of sulfur, chlorine and fluorine during pressurized oxy-fuel combustion was investigated by a pressurized thermogravimetric analyzer (PTGA) combined with Fourier transform infrared (FT-IR) spectroscopy, in which the influence of pressure on the release characteristics was mainly focused on. The results show that the changes in pressure have a remarkable effect on the migration and transformation of sulfur, chlorine and fluorine. The conversion of pyrite to COS increases with the rise in pressure, which leads to an increase in SO₂ yield, but at 3 MPa, the SO₂ yield drops somewhat. Besides, the increase of CO partial pressure at higher pressure promotes the COS generation, leading to an increase in COS yield. Because the release of chlorine is close related to the volatile yield, the increase of volatile yield at higher pressure makes more organic chlorine release and conversion to HCl. Moreover, the enhanced burning rate and combustion temperature by volatiles at higher pressure accelerate the mineral fluorine resolving, and more HF is formed. Also, the hydrolytic reactions are strengthened at higher pressure, which results in an increase of HF yield.