| This thesis presents a systematic approach of conducting gas addesorption tests ofparticles coal to solve the large deviation problem in measuring coal seam gas contentby underground direct method. The reasons were taken into consideration in thesetests. The test results show that the gas desorption content measurement approach onthe basis of the constant diffusion coefficient of coal usually results in low gas contentmeasurement of coal seam. The time-related of the gas adsorption-diffusion propertyof particles coal was studied by the adsorption-diffusion tests subjected to differentconditions using invariant diffusion coefficient method. Based on the results, theauthor considers that the time-related of gas diffusion of coal underlies the causeresulting from the variation of gas concentration in the inner surface of coal and thechange of gas concentration gradient during the gas diffusion process. The externalfactors of the time-related are the equilibrium pressure, temperature and so on.Based on the Fick’s law, the time-related of gas diffusion of particles coal wasmodeled and the diffusion coefficient was obtained by solving the mathematic model.Comparing model results and laboratory results, it was found that the new model wasmore accurate than the old. The gas diffusion model embedded with time-relatedenhanced the approach of coal seam gas measurements, which offered a solidfoundation for the gas content accurate measurement in both theoretical level andfield application. |
