Experimental Study On Identifying Tendency Of Coal To Spontaneous Combustion Based On DSC

It is very important to scientifically identify the spontaneous combustion tendency of coal for the prevention and control of coal mine fire and safe mining,but due to the complexity of coal and its spontaneous combustion process,there is no a uniform identification method and index at home and abroad.In this paper,the main identification methods are analyzed,and the limitations and shortcomings of the methods are pointed out.The study on the mechanism of coal spontaneous combustion,the spontaneous combustion process and the performance characteristics shows that it is feasible to use the apparent activation energy of low temperature oxidation of coal as the identification index.In order to make the apparent activation energy of low temperature oxidation of coal can be effectively applied to the study of coal spontaneous combustion tendency,the coal spontaneous combustion tendency of different coal samples is studied by differential scanning calorimeter.The DSC curves of coal samples with different grain size show that with the decrease of the particle size of coal sample,the DSC curve moves to the low temperature,the heat release rate of coal sample is accelerated,and the ignition of coal sample is advanced.The apparent activation energy of low temperature oxidation of coal was calculated by the DSC kinetic method.The results show that the apparent activation energy decreases with the decrease of the particle size of coal sample,that is,the smaller the particle size is,the easier it is to ignite and the greater the spontaneous combustion tendency.In this paper,the low temperature oxidation activation energy of 3 coal samples with different grain size and the spontaneous combustion period are compared.And it is found that the correlation between activation energy and spontaneous combustion of coal samples is very good when the coal particle size is 100-150 mesh,which indicates that 100-150 mesh can be used as a suitable particle size for studying coal spontaneous combustion tendency.At the same time,it is found that the linear correlation is not high by testing the quantity of oxygen absorption of the same coal samples and comparing with the coal spontaneous combustion period.The results show that the apparent activation energy of low temperature oxidation of coal can reflect the degree of spontaneous combustion of coal,namely coal spontaneous combustion tendency.The DSC curves of coal samples with different heating rates show that the higher the heating rate,the greater the thermal effect in the unit time,the higher the peak and the higher the peak temperature,which leads to the decrease of resolution and the increase of the sensitivity.On the contrary,the smaller the heating rate,the lower the peak value,which leads to the increase of resolution and the decrease of the sensitivity.Therefore,the heating rate is one of the experimental conditions which have obvious influence on the DSC curves.In order to improve the accuracy of the calculation results of the activation energy of low temperature oxidation and make the identification results reasonable and effective,the appropriate heating rate should be used for the experimental study.