深部开采高温热液侵蚀煤自燃特性

Spontaneous combustion characteristics of hydrothermal eroded coal in deep mining

深部开采过程中,矿井水温度显著高于浅部煤层,高温热液侵蚀作用影响着煤体物化特征,进而对其自然发火特性产生影响。为研究深部开采热液侵蚀作用下的煤自然发火特性及其影响机制,通过低场核磁共振、分子动力学模拟、力学测试及C600微量热实验,分析了热液侵蚀作用对煤体孔隙度、孔径分布、力学强度、氧化热特征参数的影响规律,并结合相关性分析,定量描述了各个参数间的相关度。研究结果表明:热液侵蚀煤体受热应力和溶胀作用的双重影响,内部孔隙结构发生显著变化,热液温度与煤体总孔隙度之间存在显著正相关关系,相关系数为0.97;随着热液温度的升高,煤体总孔隙度由0.24%增长至1.35%,微孔占比由69%以上降至60%以下,中孔、大孔占比增大;煤体孔隙大小显著影响着氧气的扩散系数,随着煤体孔隙宽度的线性增加,氧气扩散系数呈指数增加;受高温热液侵蚀作用影响,煤体孔隙发育以及部分有机质的溶解显著降低了煤体的力学强度,从原煤到80℃热液侵蚀煤体,其抗压强度均值由23 MPa降低至11.6 MPa,降低了50%;相较于原煤,热液侵蚀煤体的放热强度更高,放热量更大,TH40、TH50、TH60、TH70、TH80放热量分别增加了12.61%、16.63%、17.32%、19.36%和25.02%,热液温度与煤氧化放热量间相关系数为0.92。高温热液侵蚀作用显著影响着煤的孔隙度及氧化过程,随着热液温度升高,煤体孔隙度增大,力学强度减弱,氧化过程耗氧量及氧化速率加快,放热量增加。高温热液侵蚀煤具有更高的自燃危险性,且热液温度越高,风险越大。

In the process of deep mining,the temperature of mine water is significantly higher than that of shallow coal seams.The erosion of high-temperature hydrothermal fluids affects the physical and chemical characteristics of coal,which in turn affects its spontaneous combustion process.To study the spontaneous combustion characteristics and influ-encing mechanisms of coal under the influence of hydrothermal erosion in deep mining,through low-field nuclear magnet-ic resonance,molecular dynamics simulation,mechanical test and C600 trace heat experiment,the influence of hydro-thermal erosion on coal porosity,pore size distribution,mechanical strength and oxidation heat characteristic parameters was analyzed.Combined with correlation analysis,the correlation between various parameters was quantitatively de-scribed.The study results show that under the dual influence of thermal stress and swelling,the internal pore structure of hydrothermal eroded coal changes significantly.There is a significant positive correlation between hydrothermal temperat-ure and total porosity of coal,and the correlation coefficient is 0.97.With the increase of hydrothermal temperature,the total porosity of coal increases from 0.24%to 1.35%,the proportion of micropores decreases from more than 69%to less than 60%,and the proportion of mesopores and macropores increases.Coal body pore size significantly affects the oxy-gen diffusion coefficient,which increases exponentially with a linear increase in coal body pore size.Under the influence of hydrothermal erosion,the development of coal pores and the dissolution of some organic matter significantly reduce the mechanical strength of coal.From raw coal to 80℃hydrothermal eroded coal,the average compressive strength de-creases from 23 MPa to 11.6 MPa,which is reduced by 50%.Compared with raw coal,the heat release intensity of hydro-thermal erosion coal is higher and the heat release is greater.The heat release of TH40,TH50,TH60,TH70 and TH80 in-crease by 12.61%,16.63%,17.32%,19.36%and 25.02%,respectively.The correlation coefficient between hydrothermal temperature and coal oxidation heat release is 0.92.Hydrothermal erosion significantly affects the porosity and oxidation process of coal.As the hydrothermal temperature increases,the porosity of the coal body increases,the mechanical strength weakens,the oxygen consumption and oxidation rate of the oxidation process accelerate,and the heat release in-creases.Hydrothermal erosion coal has a higher risk of spontaneous combustion,and the higher the hydrothermal temper-ature is,the greater the risk is.