Pore pressure changes accompanying exchange sorption of CO2/CH4 in a coal briquette

The paper presents the study of CO2/CH4 exchange sorption in a coal briquette. The briquette was formed inside a heavy-walled steel pipe that served the purpose of a measuring chamber. The briquette with a porosity of 8.3%, a diameter of 0.096 m and a length of 0.280 m was used. Three laboratory experiments were conducted. The experiments consisted in CO2 injecting onto the input of the briquette previously saturated with CH4. In each experiment, during the exchange sorption process, the input CO2 pressure and output gas mixture pressure were stabilized at the level of 11, 12 and 13 bar at the input and 10 bar at the output of the briquette. Pressure changes along the briquette and concentration of the gas mixture flowing out of the briquette were analyzed. It was observed that a pore pressure depression moving along the briquette accompanies the exchange sorption. The presence of the pore pressure depression indicated existence of a separated zone where exchange sorption takes place. It was also observed that from the moment that CO2 appeared at the output of the briquette, sudden changes of its concentration were recorded. This phenomenon confirms the thesis of the exchange zone occurrence accompanying the CO2/CH4 exchange sorption in the briquette. A description method of the observed phenomenon was proposed.