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.