174 / 2022-02-14 13:20:49

Precise characterization of three-dimensional structure and permeability of coal-based porous media

porous media,3d reconstruction,finite element model,infiltration simulation

（9）能源资源清洁加工与转化 > 7. CO2转化与利用

The porous carbon was prepared by using coal char particles and coal pitch as raw materials, and the porous carbon sample was scanned and tested by using a three-dimensional(3d) X-ray microscopic imaging system to obtain a large number of high-precision two-dimensional (2d) images. The iterative method is used to segment the threshold and realize the 2d pore structure characterization of the porous medium and the 3d reconstruction of the porous medium based on the gray value. The finite element model of the coal-based porous carbon is obtained by repairing and meshing the 3d structure and simulations of water and carbon dioxide infiltration are performed. The results showed that the maximum, minimum and average area porosity of the 2d images of sample1#is 38.15%, 22.37%and 27.96%, respectively. The maximum, minimum and average area porosity of the 2d images of sample 2# is 29.25%, 21.36% and 23.31%, respectively. The volume porosity of sample 1# is 26.02% with 15030 pores, and the minimum, the maximum and the average value equivalent diameter are 9.82μm, 395.61μm and 25.1μm, respectively. Correspondingly, the volume porosity of sample 2# is 23.45% with 27280 pores, and the minimum, the maximum and the average value equivalent diameter are 12.19μm, 414.17μm and 24.44μm, respectively. Through 3D reconstruction from the CT images, the finite element model of sample 1# contains 1169601 tetrahedral meshes, 300263 inner surface triangular meshes, and that of sample 2# contains 2215418 tetrahedral meshes, 630173 inner surface triangles grid, respectively. Consequently, the finite element model which can be directly imported into CFD software and close to the pore structure of real porous carbon is obtained, which avoids the simplification and correction of the heterogeneous porous medium structure in CFD calculation, and helps to obtain more realistic simulation results. The percolation patterns of different media in coal-based porous carbon are generally similar, with local differences. Under the same conditions, the starting pressures of water and carbon dioxide are 3 MPa and 0.5 MPa; the stabilization pressures are 9 MPa and 6 MPa. Gases are more permeable than liquids, and the corresponding starting and stabilization pressures are lower.