Research and evaluation on the inhibition of coal spontaneous combustion characteristics by different concentrations of chloride salts

Coal spontaneous combustion disaster seriously threatens mine safety production. Spraying inhibitor technology plays an important role in mine fire control. Chlorine salt is a commonly used inhibitor in mine coal spontaneous combustion prevention and control. In order to study the inhibition characteristics of different concentrations of halogen salt and sodium chloride on coal spontaneous combustion, and to evaluate and optimize the inhibitor according to the inhibition performance index. The temperature programmed-gas chromatography and synchronous thermal analysis experiments were used to analyze the variation of parameters such as prediction index, characteristic temperature and apparent activation energy of different temperature stages in the process of coal spontaneous combustion under the action of different concentrations of halogen salt and sodium chloride. Combined with the thermodynamic characteristics of oxidation reaction, the inhibition mechanism of chloride inhibitor was discussed. The entropy weight method was used to evaluate and optimize the inhibitor. The results show that the prediction index V (O₂) ∶ V (CO + CO₂) of 30% halogen salt or 20% sodium chloride in the 30−80 ℃ stage of coal spontaneous combustion oxidation is the highest. In the stage of 80−200 ℃, the temperature point of the first CH₄ gas index produced by each coal sample is delayed, and the amount of CH₄ gas produced is less than that of raw coal. Only the prediction index V (CO₂) ∶ V (CO) of 40% halogen salt in 200−240 ℃ stage is lower than that of raw coal; the ignition temperature of coal samples with halogen salt and sodium chloride is 23−31 ℃ and 7−15 ℃ higher than that of raw coal, respectively. Moreover, it effectively improves the apparent activation energy of coal and reduces the tendency of coal spontaneous combustion. Halogen salt or sodium chloride absorbs water in the air on the surface of coal to form a liquid film with the function of isolating oxygen and endothermic cooling, and reacts with coal molecules to delay the process of coal-oxygen composite reaction.The comprehensive evaluation value of 30% halogen salt or 20% sodium chloride is higher than that of other concentrations of similar inhibitors. The comprehensive inhibition performance of 30% halogen salt or 20% sodium chloride in the same type of inhibitor is the best.