Insight on coal molecular⁃scale pore reconstruction of Tunliu mine and its characterization and analysis

To study the molecular⁃scale pore structure of coal，the coal sample in the Tunliu mine was taken as the re⁃ search object. The chemical structure of the coal sample from Tunliu mine was tested and analyzed by ultimate analy⁃ sis，solid 13 C NMR and X⁃ray photoelectron spectroscopy，and a molecular model of coal was constructed. Then the mo⁃ lecular pores of the coal sample were reconstructed using molecular simulation techniques. The maximal ball method was used for the pore identification of molecular pore model，and the simplified calculation of pore structure parameters based on the extracted pore network model，which realized the three⁃dimensional visual characterization and quantita⁃ tive analysis of coal molecular pore structure. The pore structure parameters such as the pore size distribution，specific surface area and pore volume of the coal sample were tested by the CO2 adsorption method and compared with the pore distribution characteristics corresponding to the model. The results are as follows:the pore size distribution curve of molecular pores with pore size less than 1 nm in the Tunliu coal sample shows a bimodal feature. The pore size of pores in the first peak range is less than 0.7 nm，which belongs to narrow micropore，and the pore size of pores in the second peak range is greater than 0.7 nm，which belongs to ultra⁃micropore. The number of pores with pore sizes in the range of 0.40-0.65 nm and 0.70-0.89 nm is higher，and they have larger specific surface area and pore volume. The average coordination number of pores is 2.32，and most of the pores are connected by two or more throats，indicating a good pore connectivity. The pore⁃throat radius ratios are mainly in the range of 1.00-2.00 and rarely in the range of 4.50-7.50，indicating that the molecular⁃scale pore space of the coal sample is uniformly developed，but large size var⁃ iations existed in local areas of the pore space. Compared with the results measured by the CO2 adsorption method，the pore size distribution curve trend and numerical value of the model are similar，which indicates that it is feasible to re⁃ construct the molecular⁃scale pore structure of coal，characterize and analyze the pore structure by using coal molecules.