Experimental study on thermal characteristics of spontaneous combustion process of coal with different moisture
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摘要: 煤自燃的发生发展是煤氧化放热与热量散失的动态过程，当放热量大于散失的热量，便促进煤氧反应加速，直至自燃。煤中水分的存在影响着煤氧化产热与松散煤体的热传导能力，因此，以神东布尔台42201-1工作面煤样为实验对象，开展了热重(Thermogravimetric，TG)和差示扫描量热法(Differential Scanning Calorimetry，DSC)联用实验，根据煤自燃过程中特征温度点划分出煤自燃进程，并分析煤中水分含量对煤自燃过程失重特性与放热特性的影响。采用激光闪射法测试分析了不同水分含量煤低温氧化过程中热扩散系数a、比热容Cp与导热系数λ的变化规律，以升高单位温度引起的热扩散系数变化量与比热容变化量表征温度对热扩散系数与比热容的敏感度，并分析煤低温氧化过程热传导特性。结果表明:在实验的水分含量下，煤中水分含量的增加抑制了煤自燃过程，实验终止时煤自燃失重量随着水分含量的增大而减小，煤中过多水分含量阻碍了煤氧反应进行，放热量随煤中水分含量的增加而降低。在煤样各水分含量下，热扩散系数随温度的升高呈先减后增趋势，敏感度为0时的临界温度随水分含量的增加而增加。比热容随温度的升高呈减小趋势，且同等温度下，比热容的敏感度随水分含量的增大而增大。在同等温度条件下，煤低温氧化热扩散系数与导热系数随着煤中水分含量的增大呈减小趋势，而比热容随煤中水分含量的增大呈增大趋势，说明煤中水分的增加使得煤体温度上升所需热量增高，煤体间的热量传递速率变慢，削弱了煤自燃热传导特性。Abstract: 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 (Cp)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.
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