屯留矿煤分子孔隙重构及其表征与分析
Insight on coal molecular⁃scale pore reconstruction of Tunliu mine and its characterization and analysis
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摘要: 为定性和定量研究煤的分子孔隙分布情况,选取屯留矿区煤样为研究对象,通过元素分析、 固体13 C 核磁共振和 X 射线光电子能谱等实验测试并分析了屯留矿煤样的化学结构,构建了煤分 子模型。 利用分子模拟技术,重构了煤样的分子孔隙。 采用最大球算法原理,对分子孔隙模型进行 孔隙识别,基于提取的孔隙网络模型对孔隙结构参数进行简化计算,实现了对煤分子孔隙结构的三 维可视化表征和定量分析。 利用CO2吸附法测试了煤样的孔径分布、比表面积和孔容等孔隙结构 参数,与模型对应的孔隙分布特征进行了对比。 结果表明,屯留煤样孔径小于 1 nm 的分子孔隙孔 径分布曲线呈现双峰特征,第 1 峰范围内孔隙的孔径小于 0.7 nm,属于极微孔,第 2 峰范围内孔隙 的孔径大于 0.7 nm,属于超微孔;孔径在 0.40 ~ 0.65 和 0.70 ~ 0.89 nm 的孔隙数量较多,比表面积和 孔容较大;孔隙平均配位数为 2.32,大多数孔隙由 2 个及以上的喉道连通,说明孔隙连通性较好;孔 喉半径比主要在 1.00 ~ 2.00,极少在 4.50 ~ 7.50,说明煤样孔径小于 1 nm 的分子孔隙空间发育比较 均匀,但在孔隙空间的局部区域存在较大尺寸变化;模型的孔隙分布特征与 CO2 吸附法测试结果相 比,孔径分布曲线趋势相似,数值相近,说明利用煤分子重构煤的分子孔隙并进行孔隙结构的表征 与分析是可行的。Abstract: 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.