A study on the fractal and permeability characteristics of coal-based porous graphite for filtration and impregnation

In order to distinguish the differences in the heterogeneous fractal structure of porous graphite adopted in the filtration and impregnation, the fractal dimensions (FDs) were obtained by the mercury intrusion porosimetry (MIP) to calculate the volumetric FDs of ten graphite samples, following the fractal theory. The FD expression of the tortuosity along with all the parameters from the MIP test was optimized to simplify the calculation. In addition, the percolation evolution process of mercury in the porous media was analyzed based on the data collected in the experiment. According to the analysis conducted, the FDs in the backbone formation regions of samples varied from 2.695 to 2.984, with 2.923 to 2.991 in the percolation regions and 1.224 to 1.544 in the tortuosity. Based on the correlation coefficients ( R-2) ranging between 0.906 and 0.999, and the root mean square errors ranging between 0.0001 and 0.0065 mL g(-1), a high level of reliability was identified. According to the MIP test, the mercury distribution in porous graphite demonstrated a transitional process from the local aggregation, the gradual expansion, the infinite cluster connection to the global connection.