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

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.