Study of methane gas migration in coal by sorption tests

The research reported in this thesis is concerned with a study of the mechanism of methane gas flow in coal. An indirect method of adsorption-desorption tests was conducted on cylindrical coal samples to simulate coal seam gas migration. The gas content of the cores was determined and physical and parametric characteristics of isotherms were investigated using the Langmuir equation as the representation of an ideal single molecular layer system. An attempt to investigate a potential outburst condition was carried out by pressurising a coal cylinder trepanned normal to the bedding plane provided with a central hole which was filled with coal fines. The innovative computer-based method developed for direct data collection of gas desorption employs gravimetric methods with progressive desorbed gas escape (in contrast to the method of collecting desorbed gas for progressive volume measurement). Nguyen's theoretical treatment of the problem using both diffusive and laminar flow and interchange between adsorbed and free gas phases is explained and demonstrated in some detail. This unified theory is most appropriate for solution using the numerical model involving flow only for gas and moisture and couple codes for gas and stress-deformation problem. Finally, detailed recommendations are proposed to the existing adsorptiondesorption tests for any follow-up work.