Fine Characterization of Pore Structure of Acidified Anthracite Based on Liquid Intrusion Method and Micro-Ct

Abstract

To investigate the effect of acidification erosion on the pore structure characteristics of anthracite. In this paper, the low-temperature nitrogen adsorption method, mercury intrusion method, and Micro-CT scanning were used to analyze coal samples. The microscopic morphology and spatial structure of coal samples were characterized by fractal dimension calculation and three-dimensional(3D) reconstruction technology. The results show that HCl has the highest removal efficiency of minerals in the Yuwu coal sample. The demineralization and pore expansion is mainly concentrated in the macropore and mesopore sections, increasing the proportion of mesopore pore volume by 11.4%. However, HNO3 mainly acts as an oxidative etching effect on the micropores and pore surfaces, which increases the roughness of the coal pore surface and the volume of micropores by 4.93%. In the 3D reconstruction of coal pore structure and minerals, minerals content in coal decreased by 48.14% after HCl dissolution. The spatial distribution of minerals shows the characteristics of inhomogeneity. Minerals content of coal samples decreased significantly along the direction of strong flowability. The throat of pores increases by 56.72%, the peak frequency of pore coordination number increases by four units, and the pore connectivity increases, which significantly improves fluid transport capacity in the coal matrix.

Keywords: Acid treatment, Pore morphology, Pore size distribution, Fractal characteristic, Coordination number