Experimental study on gas desorption characteristics for different coal particle sizes and adsorption pressures under the action of pressured water and superheated steam

Gas (i.e. methane and CO2) ad-/desorption characteristics are essential for unconventional gas production, and they are related to many factors such as coal particle size, adsorption pressure, external moisture and heat. In order to investigate the effect of these factors, as well as those arising from pressured water and superheated steam on gas desorption, a series of experiments were conducted. The experimental equipment designed by our research group could be used to supply pressured water and superheated steam during the gas ad-/desorption process. Our results were: 1) High-pressure water injection after adsorption resulted in a reduced gas desorption capacity. With an increase in the equilibrium adsorption pressure and water injection pressure, the desorption capacity of coal increased and decreased, respectively. 2) The desorption capacity of the residual adsorbed gas in coal increased with steam action, and it eliminated the influence of low gas adsorption pressure and high-pressure water injection on gas desorption. 3) The gas desorption velocity increased with steam action, which was reflected by a decrease in the critical value of time effect. The coal particle size had a certain influence on the desorption of the adsorbed gas. Finally, with an increase in the water injection pressure, the influence of coal particle size became larger. However, the desorption under steam was less affected by the coal particle size. These results may have significant implications for energy exploitation and utilization.