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

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.