Underground coal mining in the Bulli Seam of Sydney Basin, Australia encounters the problems of coal and gas outburst as the coal contains high concentration of CO
, where certain parts of the seam have been found to be especially hard-to-drain. In order to better understand these problems, the influence of temperature and moisture on sorption capacity of bituminous coal was investigated at 35°C, 45°C and 55°C and at pressure up to 4 MPa. Based on the principle of surface chemistry, the reduced value of surface tension (RVST) was calculated and analysed. The theory of coal surface free energy was found to be capable of explaining coal sorption characteristics. These findings provide the basic knowledge for a better understanding of coal sorption characteristics associated with coal seam gas drainage, which will benefit ventilation and degasification design and hence help to prevent coal mine operations from gas outburst disaster.
Keywords: coal sorption, coal surface tension, isotherm, surface free energy