Effect of water immersion pressure on oxidation characteristics and spontaneous combustion characteristics of long-flame coal

Coal seam water injection has an obvious effect on coal dust prevention. The high-pressure water environment of coal seam water injection changes the structure of coal which brings new effects on the characteristics of coal spontaneous combustion disaster. To reveal the effects of water immersion pressure on the oxidation characteristics of long-flame coal, coal samples immersed in water at 0.1 MPa, 2.5 MPa, 5.0 MPa, 7.5 MPa and 10.0 MPa were prepared. Four experiments were conducted to study the changes in oxidation characteristics and its main reasons. The results showed that elevated water immersion pressure promoted the spontaneous combustion tendency of coal, and the composite judgment index of coal decreased to 521.1. Coal immersed in pressurized water entered the stages of oxygen-absorbing oxidation and thermal decomposition earlier than coal immersed in atmospheric pressure water. The specific surface area and average pore diameter of coal immersed in high-pressure water increased, where the pore volume proportion of mesopores of the coal immersed in water at 10.0 MPa increased by 138.5 % compared with that of the coal immersed in atmospheric pressure water. The elevated water immersion pressure prompted coal to produce further aliphatic hydrocarbons and hydroxyl groups, which improved the low-temperature oxidation capacity.