采空区复合灾害环境下含瓦斯煤自燃特征研究进展

Research progress of spontaneous combustion of coal containing gas under the compound disaster environment in the goaf

采空区瓦斯与煤自燃复合灾害日趋成为制约矿井安全生产的主要灾害模式,煤自燃作为瓦斯燃烧、爆炸等灾害事故的“点火源”,无疑是防范煤矿采空区复合灾害的关键。目前关于采空区遗煤残余瓦斯(吸附态为主)与风流瓦斯(游离态)对煤自燃影响机理的认识还不够深入,为此探究了含瓦斯条件下煤自燃相关研究的最新进展。现阶段针对含瓦斯风流/气氛下煤自燃特性的研究内容较为丰富,但吸附态瓦斯影响条件下的煤自燃特性实验平台及相关研究成果较匮乏。研究表明,游离瓦斯易引起煤低温氧化气体产物出现明显的“滞后效应”,同时煤体放热强度减弱、活化能整体增大,这反映出氧化气氛中的瓦斯对煤自燃具有抑制作用;相应地,煤自燃过程中的官能团、自由基及煤微晶结构等微观特征参数均会随瓦斯体积分数呈现规律性演变。进一步,考虑到遗煤内部残余瓦斯与风流瓦斯的赋存状态差异,探究了瓦斯对煤自燃过程的影响机理,包括CH4对O_(2)的驱替稀释作用、CH_(4)与O_(2)的竞争吸附解吸引起的置换效应,以及高温环境下的O_(2)分子化学吸附和煤氧复合效应作用。基于此,提出了采空区遗煤在吸附态瓦斯影响下的自燃过程特性、含瓦斯煤自燃流–固–热–化多场耦合特征、含瓦斯煤自燃监测预警理论应用等亟待突破的瓶颈问题。

The compound disasters of gas and coal spontaneous combustion have become the main disaster mode that restricts safe mine production.As the“ignition source”of gas combustion and gas explosion accidents in goaf,coal spontaneous combustion is undoubtedly the key influence factor for preventing compound disasters.At present,there is still insufficient understanding on the influence characteristics and mechanism of both the methane gas(free state)of the airflow filed and the residual methane gas(mainly adsorbed state)of the fractured coals on the coal spontaneous combustion.Therefore,the latest research progress in the field of the spontaneous combustion under gas-containing conditions was explored.It was found that the rich research results have been obtained on the characteristics of coal spontaneous combustion under the gas-containing airflow/environment.However,there is a lack of experimental platforms and the research results for simulating the impacts of the adsorbed gas on the coal spontaneous combustion.It is pointed out that the free gas can leads to a significant“hysteresis effect”in the generation on the oxidation gas products of coal,the weakening of the heat release intensity of coal oxidation and the overall increase in the activation energy,all of which reflect the inhibitory effect of the methane in the free state on coal spontaneous combustion.Correspondingly,the microscopic characteristic parameters of functional groups,free radicals,and coal microcrystalline structure exhibit the regular change with methane concentration during coal spontaneous combustion process.Furthermore,considering the difference in the occurrence state of the residual methane inside the fractured coal and the free methane in the goaf environment,the influence mechanisms of methane on the coal spontaneous combustion are investigated including the displacement and dilution effects of methane,the effect of competition adsorption/desorption between methane and oxygen,as well as the chemical adsorption of oxygen molecules and the coal-oxygen reaction effects under the high temperature environment.At last,it is proposed that the research urgently needs to breakthrough the bottleneck issues of the evolution characteristics of coal spontaneous combustion under the impact of adsorbed gas,the multi-filed characteristics of gas-containing coal spontaneous combustion,and the monitoring and warning of gas-containing coal spontaneous combustion.