Experimental investigation on the characteristics of long-term submerged coal spontaneous combustion under varying heating rates

The low-temperature oxidation experiments were conducted on lignite immersed in water with short (50 days) and long (200 days) at three different heating rates (0.25℃/min,0.5℃/min, and 1℃/min), providing a theoretical foundation for the assessment of spontaneous combustion risk in goaf coal. Research shows that the heating rate of 1℃/min significantly increases the risk of spontaneous combustion for coal submerged in water, when compared to the other two heating rates. After undergoing a short-time of immersion, the coal sample demonstrates pronounced characteristics of low-temperature oxidation, with both carbon-oxygen gas and heat release intensity showing an exponential relationship with temperature. Compared with short-term soaked coal, coal samples soaked for a long time have lower apparent activation energy and the highest risk of spontaneous combustion. The analysis of the limit parameters suggests that a longer immersion time elevates the susceptibility to spontaneous combustion.