基于低温氮吸附法的酸化煤样孔隙分形特征研究

Study on pore fractal characteristics of acidified coal samples based on low temperature nitrogen experiment

为研究并改善富含矿物质煤体孔隙结构特征,基于X射线衍射和低温氮吸附实验测试了贫瘦煤酸化前后碳酸盐矿物质含量及孔隙结构参数,并根据孔隙分形理论利用FHH模型求得了酸化前后不同孔段的分形维数。结果表明:酸化可以有效溶解煤体孔隙中的矿物质并溶蚀煤基质,减少煤体孔隙中微孔所占比例,增加中孔和大孔的比例,增强了孔隙结构之间的连通性,同时减少了煤的比表面积,有利于吸附态瓦斯向游离态进行转化;煤样低压段分形维数大于中高压段的分形维数,煤体孔隙中微孔结构较中孔大孔结构更加复杂,煤样经酸化后孔隙分形维数变小,煤样孔隙结构趋于简单化。

In order to study and improve the pore structure characteristics of mineral-rich coal, the content of carbonate minerals and pore structure parameters of lean coal before and after acidification were measured based on X-ray diffraction and low temperature nitrogen adsorption experiments, and the fractal dimensions of different pore sections before and after acidification were obtained by using FHH model according to pore fractal theory. The results show that: acidizing can effectively dissolve the minerals in the pores of coal and dissolve the coal matrix, reduce the proportion of micro-pores in the pores of coal, increase the proportion of meso-pores and macro-pores, enhance the connectivity between pore structures, reduce the specific surface area of coal, and facilitate the conversion of adsorbed gas to free gas. The fractal dimension of low pressure section of coal sample is larger than that of medium high pressure section. The micro-pore structure of coal pore is more complex than that of large pore structure. After acidification, the fractal dimension of coal pore becomes smaller and the pore structure of coal sample tends to be simplified.