1.Huadian Coal Industry Group Co.,Ltd.,Beijing ,China; 2.China National Coal Group Corp.,Beijing ,China;3.CCTEG Shenyang Research Institute,Shenyang ,China

In order to investigate the fractal characteristic of coal pore and its impact on methane adsorption property,low temperature liquid nitrogen gas adsorption experiments were conducted on eight coal samples collected from Qinshui Basin.FHH fractal theory was adopted to explore the pore fractal features of coal surface.The adsorption constants a and b were measured for each coal sample,and the effect of coal pore fractal dimension on methane adsorption was also analyzed.The research results show that different fractal features of coal surface pore were observed at different relative pressure stages.D1and D2 represent the fractal features of micropore,mesopore and macropore,respectively.As coalification increases,D1 presents a good positively linear relationship with R0,but a parabolic correlation was found between D1 and R0.Methane adsorption is closely related to the pore fractal features of coal surface.The larger values of the fractal dimension D1and D2,the greater the adsorption constant a,indicating the methane adsorption capacity is stronger.However,the adsorption constant b is less affected by the fractal features.