Calculation of the diffusion coefficient of gas diffusion in coal: The comparison of numerical model and traditional analytical model

Abstract

The prediction and calculation of the gas diffusion coefficient in a coal matrix is a key scientific issue in the study of gas diffusion behavior in coal. Due to its inherent shortcomings, the diffusion coefficient obtained from analytical models and widely used in academia does not fully reflect the gas diffusion law in actual coal seams. Therefore, numerical models have received increasing attention because they consider the actual conditions of gas diffusion in coal. In this work, four coal types were selected for adsorption/desorption kinetics experiments. The diffusion coefficients calculated by the analytical model and numerical model were compared. The results indicate that the diffusion coefficient obtained from the numerical model is much larger than that from the analytical model. The bidisperse numerical model is more accurate than the bidisperse analytical model. The evolution of the diffusion coefficient with the gas pressure differs for the adsorption and desorption stage.