Experimental Study On Spontaneous Combustion Characteristics Of Coal At Different Initial Temperatures

Last several years,due to the reduction of shallow coal resources and the improvement of mining technology,the depth of coal mining gradually increased,accidents caused by self-heating of coal are increasing gradually,so the high temperature on the influence of coal spontaneous combustion process is particularly important.This paper simulates high temperature environment to conduct experimental research on the coal sample.Compared the difference between the coal sample treated by high temperature and the raw coal in micro and macro,the influence of high ground temperature on spontaneous combustion characteristics of coal is obtained.Through the specific surface area experiment,it can be discovered that the proportion of micropores in coal samples treated by high temperature is higher than that of raw coal.The proportion of medium pores decreases,and the proportion of large pores is almost unchanged.High temperature causes new micro-pores in coal samples and increases the specific surface area of coal.It is beneficial for oxygen to contact with active sites on coal samples,and increase the strength of coal-oxygen composite reaction Through the infrared spectrum experiment,the infrared spectrum curves of four groups of coal samples are obtained.It is found that after high temperature treatment,the hydroxyl content of coal samples increases,the fatty hydrocarbon content decreases,the oxygen-containing functional group content first decreases and then increases.The aromatic hydrocarbon content basically remains unchanged,among them,the content of aromatic ether continues to increase,and the content of substituted aromatic hydrocarbons basically does not change.Temperature programmed experiments were carried out on coal samples at different initial temperatures,and the variation laws of coal spontaneous combustion limit parameters,intersection temperature and activation energy with the initial reaction temperature were obtained.It was found that with the increase of initial temperature,the lower limit coal thickness of coal samples decreased,the lower limit oxygen concentration decreased,the upper limit air leakage intensity increased,the intersection temperature decreased and the activation energy decreased.The above indicators show that high temperature enhances the possibility of coal spontaneous combustion accidents.The law of gas generation in the process of programmed temperature rise is analyzed,it is found that CO is suitable to be used as the main index gas for the prediction of coal spontaneous combustion.When CO is used as the index gas of high-temperature mine,the critical value should be appropriately increased.The values of C₂H₄,C₃H₈,C₃H₈/C₂H₆ and C₃H₈/CH₄ can be used as the index gas auxiliary prediction of high-temperature points.When they are used as the prediction index of high-temperature mines,their gas indication threshold should be appropriately reduced.