Experimental Study on Spontaneous Combustion of Low Rank Coal Containing High Sulfur in Goaf Atmosphere

To study the effect of pyrite on coal spontaneous combustion characteristics in low-rank coal under an oxygen atmosphere in goaf, this paper selected PZ brown coal impregnated with pyrite and its reaction products and monitored the changes in the generation of characteristic gases CO and CO₂ during the programmed heating process of coal samples. The experiment found that oxygen concentration has the greatest impact on the spontaneous combustion characteristics of coal with added Fe³⁺. When the oxygen concentration in goaf coal increases to 9%, the promotion rate of high sulfur coal spontaneous combustion is the highest, which easily increases the range of goaf spontaneous combustion risk areas. When the temperature rises to 60°C, the catalytic effect of pyrite reaction products on coal spontaneous combustion is greatly enhanced. Through FTIR testing, it was found that Fe³⁺ ions, as strong oxidative free radicals, promote the reaction of –CH₂–, –COOH, and –OH in coal at low oxygen concentrations, leading to a further increase in the tendency of coal to self ignite at low oxygen concentrations.