Experimental study on thermal characteristics of spontaneous combustion process of coal with different moisture

The occurrence and development of coal spontaneous combustion is a dynamic process of coal oxidation heat release and heat loss. When the heat release is greater than the heat loss,it will promote the acceleration of coal oxygen reaction until spontaneous combustion.The presence of moisture in the coal affects the thermal oxidation of coal and the thermal conductivity of the loose coal. TG-DSC combined experimentwere carried out on the coal sample of 42201-1 working face of ShendongBuertai coal. According to the characteristic temperature points during coal spontaneous combustion,the coal spontaneous combustion process was divided,and the influence of coal moisture content on the weightlessness and heat release characteristics of coal spontaneous combustion were analyzed. The laser flash method was used to test and analyze the variation law of thermal diffusion coefficient (a),specific heat capacity (C_p)and thermal conductivity (λ) during low temperature oxidation of coal with different moisture content. The sensitivity of temperature to thermal diffusion coefficient and specific heat capacity is characterized by the variation of thermal diffusion coefficient and specific heat capacity caused by increasing unit temperature. And the heat conduction characteristics of coal at low temperature oxidation process was analyzes. Findings that the increase in the moisture content of coal inhibited the coal spontaneous combustion process under the experimental moisture content. At the end of the experiment,the weight loss of coal spontaneous combustion decreased with the increase of moisture content. It shows that too much moisture content in the coal hindered the coal oxygen reaction. The heat release decreases with the increase of moisture content of the coal. At each moisture content of the coal sample,the thermal diffusion coefficient decreases first and then increases with increasing temperature,and the critical temperature at sensitivity 0 increases with increasing moisture content. The specific heat capacity decreases with increasing temperature,and at the same temperature,the sensitivity of the specific heat capacity increases with increasing moisture content. Under the same temperature conditions,the low-temperature oxidation thermal diffusion coefficient and thermal conductivity of coal decreases with increasing moisture content,while the specific heat capacity increase with increasing moisture content. It shows that the increase of moisture content makes the heat required for the temperature rise of the coal body increase,and the heat transfer rate between the coal bodies becomes slow,which weakens the thermal conduction characteristics of coal spontaneous combustion.