Pore Structure and Methane Adsorption Characteristics of Primary Structural and Tectonic Coals

In this paper, the pore structure and methane adsorption properties of the primary structural and tectonic coals of the Handan Jiulong Mine were analyzed using low-temperature nitrogen adsorption experiments and isothermal adsorption tests. The relationship between pore structure and adsorption properties was discussed. The study results show that the total pore volume and specific surface area of the tectonic coal in the Jiulong Mine are larger than those of the primary structural coal. Small pores comprise most of the pore volume in the primary structural coal, followed by micropores and medium pores. The pore volume of the tectonic coal primarily consists of small pores, followed by micropores and medium pores. Micropores and medium pores consist of approximately the same volume. The specific surface area of both the tectonic coal and the primary structural coal is primarily micropores, followed by small, and medium pores. The microporous and small pore structures of the tectonic coal have open pore morphology. The pore shapes are primarily in the shape of ink bottles. The coal sample of primary structural coal contains both open pore morphology and numerous closed pore morphology. The pore shape is mainly columnar. The pressure-boosting adsorption process of coal samples conforms to the Langmuir isothermal adsorption equation. The maximum adsorption capacity of tectonic coals is greater than that of primary structural coals. The adsorption capacity and Langmuir volume (VL) of coal samples decrease with increasing temperature, while the Langmuir pressure (PL) increases with temperature. The larger the pore volume of coal samples, especially the micropore volume, the greater the adsorption capacity, and the richer the specific surface area of micro-pores, creating a more substantial adsorption capacity.