Experimental study of pore structure and fractal characteristics of pulverized intact coal and tectonic coal by low temperature nitrogen adsorption

To study the pore structure and fractal characteristics of pulverized intact coal and tectonic coal, proximate analysis, gas adsorption/desorption, and N-2 (77K) adsorption experiments were performed. The results show that micropore, minipore and mesopore volumes, as well as specific surface areas (SSAs), are dependent on the particle size and that they all exhibit a positive correlation with decreasing particle size, a correlation which also promotes gas adsorption. Many complex pores became simpler with the destruction of coal, and some long pores were also converted into short pores; that is, the pore structures of coals (referring to changes in pore shapes and lengths) may become increasingly simple. The mineral matter of samples increases with decreasing particle size and contributes more to the mesopore volume and SSA than to the micropore and minipore volumes. The increased D-1 and reduced D-2 of samples with decreasing particle sizes indicate a greater pore surface roughness and a smaller pore structure anisotropy. Compared with pulverized intact coal, the mineral matter, pore structure and gas adsorption capacity of tectonic coal have significantly increased or decreased. Although they are in the same coal seam, they are no longer the same type. This study of pulverized coal, especially tectonic coal, is of great significance for the further understanding of gas outbursts. (C) 2019 Elsevier B.V. All rights reserved.