单轴应力下烟煤氧化‒自燃灾变温度

Catastrophic temperature of oxidation-spontaneous-combustion for bituminous coal under uniaxial stress

为探究不同埋藏深度裂隙煤体氧化-自燃过程在单轴应力作用下的影响规律,本文通过荷载加压煤自燃特性实验平台,采用新疆硫磺沟矿区烟煤煤样,开展了施加单轴应力在0~8 MPa下的贫氧环境程序升温试验.根据加压试验中烟煤产生气体随温度的变化关系,计算了烟煤在单轴应力下升温过程表观活化能和耗氧速率.结合煤自燃氧化动力学和热解参数,阐述了单轴应力下煤体由缓慢氧化到快速氧化的非线性发展过程,并基于突变理论解算出试验条件下烟煤氧化-燃烧过程的突变温度和临界温度,确定出4个特征参数:突变温度T CO(CO表征)和THY(耗氧速率表征),临界温度T′CO(CO表征)和T′HY(耗氧速率表征),并分析了不同特征参数随单轴应力的变化规律.结果表明:热解气体浓度、表观活化能和耗氧速率随单轴应力增大呈先增大后减小再增大的三次函数规律(其中1.8和5.5 MPa时为临界轴压),1.8 MPa时表观活化能和各项特征参数数值最低,煤氧反应速率最快,耗氧速率最高;单轴应力为5.5 MPa时耗氧速率最大,煤体新生裂隙最多;单轴应力对TCO特征参数影响最大,煤自燃缓慢过渡到快速氧化的温度指标,由CO浓度表征的突变温度T CO表征最为准确.该研究结果对于矿井不同埋深煤自燃预警和防控具有重要理论指导意义.

To explore the influence of the oxidation and spontaneous combustion process of fractured coal at different burial depths under uniaxial stress,the spontaneous combustion characteristics of coal under loading was studied within the testing device of coal spontaneous combustion and loading.Bituminous coal from the Liuhuanggou mining area in Xinjiang was selected and oxidized in the oxygen-lean environment loaded at the range of 0–8 MPa.Based on the relationship between the gas generated in the experiment and the temperature,we calculated the apparent activation energy and oxygen consumption rate of coal samples under uniaxial stress.We combined the oxidation kinetics and pyrolysis parameters of spontaneous coal combustion to describe the nonlinear development of coal from slow to rapid oxidation under uniaxial stress.Based on catastrophe theory,the catastrophic temperature and critical temperature of bituminous coal oxidation-combustion process under test conditions were calculated,and four characteristic parameters were determined:TCOTHY T′COT′HY TCO TCO catastrophic temperature(characterization of CO)and(characterization of oxygen consumption rate),and critical temperature(characterization of CO)and(characterization of oxygen consumption rate),and analyzed the variation of different characteristic parameters with uniaxial stress.The analysis results show that the pyrolysis gas concentration,apparent activation energy,and oxygen consumption rate follow a cubic function law that first increases,then decreases,and then increases with increases in the uniaxial stress(the critical axial pressures at 1.8 and 5.5 MPa).At 1.8 MPa,the apparent activation energy and various parameter values are lowest,the oxygen reaction rate of coal is fastest,and the oxygen consumption rate is the highest.When the uniaxial stress is5.5 MPa,the oxygen consumption rate is the highest,the greatest number of new cracks is created,and the characteristic parameters have the greatest impact.The temperature index of spontaneous coal combustion slowly transitions to rapid oxidation,and the catastrophic temperature characterized by the CO concentration is the most accurate.The research results have important theoretical guiding significance for the early warning and prevention and control of spontaneous combustion of coal at different buried depths.