Evolution features of coal matrix porosity with the variation in temperature and stress

Abstract

To clarify the differentiated effect of temperature and stress on coal matrix pores, the coals from No. 8 coal bed in Taoyuan coal mine of Huaibei Coalfield, Anhui Province, were chosen as experimental samples. Cryogenic nitrogen adsorption methods were used in laboratories to test the matrix pore parameters of the dried coal samples treated under the temperature of 60°C, 70°C, 80°C, 90°C and 100°C. Also efforts were made to test the parameters of matrix pore structure of dried coals after being treated under the stress of 10 MPa, 15 MPa, 20 MPa and 25 MPa respectively. The results show that: the specific surface area of coal matrix pore decreases, the average pore diameter and median pore diameter increases with the increase of temperature. As the stress goes up, the coal matrix pore first experiences increase in specific surface area, average pore diameter and median pore diameter, followed by a slight decrease after rising to a certain point. Therefore, the change in specific surface area of coal from the same coal bed can, to some extent, reflect the variation in temperature and ground stress.