单轴应力–温度作用下煤中吸附瓦斯解吸特征

DESORPTION CHARACTERISTICS OF ADSORBED GAS IN COAL SAMPLES UNDER COUPLING TEMPERATURE AND UNIAXIAL COMPRESSION

利用自主研发的深部煤岩温度–压力耦合瓦斯解吸试验系统,对鹤岗南山矿煤样进行单轴应力–温度作用下吸附瓦斯运移过程。该试验系统通过对煤样施加不同应力和温度,促使煤中原生吸附瓦斯解吸,模拟煤体变形中吸附瓦斯解吸–释放过程。试验中分别在恒温和升温条件下对煤样依次进行单轴破坏和施加围压,实时监测逸出气体压力、流量,抽样检测气体成分和浓度。研究结果表明煤体在单轴压缩破坏过程中出现气体逸出压力降低导致气体回流现象;对破裂煤样施加围压后短时间内排出大量高浓度气体。试验结果证实温度升高是诱发煤样中吸附瓦斯大量解吸因素之一,而煤体内是否存在大量贯通裂隙是影响瓦斯运移的重要因素。

The desorption process of adsorbed gas in coal from Nanshan coal mine is studied using an experimental system with temperature-pressure coupling in particular to treat the multiphysical effect on deep coal sample. This experimental system has been designed to apply triaxial pressure and temperature to coal sample,and reproduce the desorption-releasing process of absorbed gas as a result of combination of pressure and temperature. Uniaxial compression tests are carried out on coal samples under constant temperature and increasing temperature,respectively. After failure,the deformed samples were subjected to confining pressures. In test,the releasing gas pressure and flow are real-time monitored. The mixed gases is sampled and detected by using a gas chromatography. The results show that a spontaneous negative value observed in gas pressure is consistent with the refluence of gas determined from the volumetric dilatancy development. A large amount of gas is expelled during the closure of fracture due to the present of the confining pressure. Correspondingly,the concentrations ofmethane,carbon dioxide and ethane are increased sharply. Temperature change is one of desorption-induced factors for adsorbed gas. The existence of a large number of connected cracks in coal matrix may play an important role in gas transport. The mechanism of gas emission is also preliminarily discussed.