Abstract
In order to investigate the difference of pore structure characteristics between mudstone and coal under different particle size conditions, samples acquired from Henan province were smashed and screened into three different particle sizes (20–40, 80–100, and >200 mesh) to conduct the experiments, using the high-pressure mercury intrusion porosimetry (MIP) and low-temperature N2 adsorption (LT-N2A) techniques. The results demonstrated that the proportion of open pores or semi-enclosed pores increased, and the pores became preferable contacted each other for both mudstone and coal during the crushing process. These variations of pore structure characteristics in the coal were beneficial to methane storage and migration. The total specific surface areas and pore volumes all showed a tendency of increasing continually for both mudstone and coal, as the particle sizes decreased from the LT-N2A test. The mudstone and coal were non-rigid aggregates with micropores, plate-shaped pores, and slit-shaped pores developed inside. The effect of the crushing process on the pore shape for the mudstone and coal was inappreciable. Moreover, the influence of the particle sizes on the mesopore was the most significant, followed by the macropore; and on the micropore, the influence was negligible for both mudstone and coal. The crushing process only had a significant impact on the pore structure of mudstone with a particle size of less than 100 mesh, while it could still alter the pore structure of coal with a particle size of larger than 100 mesh. It is believed that this work has a significant meaning to explore the diffusion and migration rules of coal-bed methane in coal.
Highlights
Coal is a structurally and chemically heterogeneous organic rock with a complicated dual-porosity structure [1,2]
Cheng et al demonstrated that the pore volume and specific surface area of coal were negatively correlated with the reducing particle size, using the LT-N2 A method, which might ascribe to that the crushing process opened inaccessible and closed pores
The mudstone and coal samples collected from the Pingdingshan coal mine were smashed and sieved into three distinct granule diameters
Summary
Coal is a structurally and chemically heterogeneous organic rock with a complicated dual-porosity structure [1,2]. Various analysis technologies have been applied for characterizing the pore and fissure structure of coal, mainly including (1) the fluid penetration and gas adsorption method, such as high-pressure mercury intrusion porosimetry (MIP) [7], low-temperature. Cheng et al demonstrated that the pore volume and specific surface area of coal were negatively correlated with the reducing particle size, using the LT-N2 A method, which might ascribe to that the crushing process opened inaccessible and closed pores. They found that the optimal adsorption equilibrium time for the LT-N2 A test was 8 min [26]. Chen’s group verified that decreasing the particle size of coal leads to a consecutive increase in mesopore- and macropore-specific surface areas and volumes for the pulverized anthracite subsamples, and the closed pores’
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