Dendric Fractal Characteristics of Pores in Anthracite and Their Influences on Gas Adsorption Characteristics

Abstract

The characteristics of pores in anthracite from Guhanshan Coal Mine in the Jiaozuo mining area were tested by the mercury injection method. According to the pore size, pores in the coal sample were classified into gas seepage pores and gas adsorption pores which were in line with the stochastic fractal model and the dendric fractal model, respectively. Besides, the fractal characteristics of adsorption pores were analyzed by using a dendric fractal model, and the influence law of the tortuosity fractal dimension D t on the gas adsorption capacity was obtained. The research results show that the amount of mercury injected into each experimental coal sample is directly proportional to its porosity, but has no obvious correlation with specific surface area. Seepage pores with sizes over 65 nm fit the stochastic fractal model, and their fractal dimension D increases with the increase of specific surface area. Adsorption pores with sizes of below 65 nm fit the dendric fractal model, and their tortuosity fractal dimension D t is positively correlated with the specific surface area. Through the gas adsorption experiment on coal samples, it is found that a larger D t corresponds to a stronger gas adsorption capacity. The research results can provide a theoretical basis for elucidating the gas adsorption characteristics of anthracite from a microscopic point of view.

Fractal Analysis of Coal Pore Structure Based on Computed Tomography and Fluid Intrusions

“…Ni et al [30], based on low temperature N 2 adsorption, SEM, and fractal theory, concluded that D 1 of acidified coal samples is positively correlated with their specific surface area and total pore volume, and D 2 is inversely proportional to them. Wen et al [31] analyzed the fractal characteristics of adsorption pores using a dendritic fractal model and obtained the law of the effect of bending fractal dimension on gas adsorption capacity. Percolation pores of >65 nm in each experimental coal sample conformed to the random fractal model, and their fractal dimension was positively correlated with their specific surface area.…”