Experimental analysis of the effect of temperature on coal pore structure transformation

Coal has a complex pore network, which affects the reserves and production capacity of coalbed methane. To analyze the feasibility of coal seam heat injection mining and improve the theory of the influence of temperature on coal adsorption and desorption characteristics, scanning electron microscopy, mercury intrusion, and low-temperature liquid-nitrogen adsorption were used to evaluate the pore structure of coal at different temperatures. With the increase in temperature, the volume of macropores increased from 0.0249 to 0.0454 mL/g, and the specific surface area of micropores decreased from 2.6836 to 0.7250 m2/g. In addition, the pore fractal dimension of the large pore section, D1, increased gradually, while the pore fractal dimension of small pore section, D3, decreases with the increase in temperature. A higher temperature led to a larger pore fractal dimension of the large pores in coal and more developed pores, which is conducive to the migration of gas in the coal seam. The pore fractal dimension of the small pores decreased with the increase in temperature. The structure of the micropores became increasingly regular. The temperature has an obvious transformation effect on the structure of coal pores, especially on macropores and micropores.