Gas diffusion-sorption is a critical step in coalbed methane (CBM) exploitation and carbon dioxide sequestration. Because of the particularity of gas physical properties, it is difficult to visualize the gas diffusion-sorption process in coal by experimental methods. Due to the limitation of experimental approaches to image the three-dimensional coal pore structure, it is impossible to obtain the three-dimensional pore structure images of coal. As a result, the visualization of gas diffusion-sorption in coal pore structure by numerical ways is impossible. In this study, gas diffusion coefficients were firstly estimated by experiments. Then, a gas diffusion-sorption coupled model was developed which can be applied to the nanoscale geometry imaged by synchrotron radiation nano-CT. The dynamic process of gas diffusion and ad-/desorption in the nanoscale microstructure of coal was visualized by the developed gas diffusion-adsorption coupled model and the numerical simulation based on MATLAB. The simulation results show a good agreement with the experimental results. The gas diffusion-sorption coupled model and numerical method can help to investigate the effect of microstructure on gas diffusion and ad-/desorption and provides a possibility to investigate the multiscale gas transportation and adsorption in coal pore-fracture system.

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煤中气体扩散吸附的可视化：基于同步辐射纳米 CT 的研究

气体扩散吸附是煤层气（CBM）开采和二氧化碳封存的关键步骤。由于气体物理性质的特殊性，很难通过实验方法对煤中的气体扩散吸附过程进行可视化。由于煤三维孔隙结构成像实验方法的局限性，无法获得煤三维孔隙结构图像。因此，不可能通过数值方法对煤孔隙结构中的气体扩散吸附进行可视化。本研究首先通过实验估算了气体扩散系数。然后，开发了一种气体扩散-吸附耦合模型，该模型可应用于同步辐射纳米 CT 成像的纳米级几何结构。通过开发的气体扩散-吸附耦合模型和基于MATLAB的数值模拟，对煤纳米级微观结构中气体扩散和吸附/解吸的动态过程进行了可视化。仿真结果与实验结果吻合良好。气体扩散-吸附耦合模型和数值方法有助于研究微观结构对气体扩散和吸附/解吸的影响，为研究煤孔隙-裂缝系统中的多尺度气体输运和吸附提供了可能。