Experimental study on spontaneous combustion prediction index gas of water immersed long flame coal

Prediction of spontaneous combustion of long-term water immersed coal is still a problem for coal mines, the research on which is limited. This paper presents an experimental study on predicting the spontaneous combustion of long-term water immersed coal in 22 gob of Bulianta Mine.A temperature programmed experiment on long flame coal with five different water cuts was conducted to analyze the changes of auto thermal oxidation gas products and their concentrations in the process of temperature increase. Then the index gas for coal spontaneous combustion prediction was optimized. The results show that the low-temperature oxidation of the water immersed coal has phased characteristics.It is proposed that φ (CO)/φ (CO2),φ (O2)/Δφ (CO2-CO),φ (C2H4)/φ(C2H6), and C2H6,C2H4 and C3H8 are used as prediction indexes for coal spontaneous combustion. When φ(CO)/φ(CO2)≤0.1 or φ(O2)/Δφ(CO2-CO)≥0.02, the coal is in the oxygen absorption and heat storage stage(30～100 ℃),when 0.8≤φ(C2H4)/φ(C2H6) ≤1.10, the coal is in the auto thermal oxidation stage(100～140 ℃), and when φ(CO)/φ(CO2)≥0.5 or φ(O2)/Δφ(CO2-CO)≤0.005, the coal is in the accelerated oxidation stage(140～230 ℃). The experimental results have the guiding role for the prevention and control of spontaneous combustion of coal in gob.In combination with the actual situation on the site, the parameter indicators should be corrected in time to improve the coal spontaneous combustion prediction index, which can effectively prevent coal spontaneous combustion disasters.