Abstract
Accurately characterizing the pore structure of tectonically deformed coal (TDC) is an essential prerequisite for investigating the porosity change rules of coal during coal deformation. This paper aims to discuss the possibility of conducting gas adsorption on original coal chunks of TDCs instead of ground coal particles and to investigate the influence of mechanical grinding during coal preparation on pore structure characterization. First, we conducted N2 and CO2 adsorption tests on coal chunks and crushed coal (60 mesh particles) of primary structure coal and ductile TDCs (Ro, max = 0.93%~1.15%). Then, the influences of grinding coal into 60 mesh particles on the micro-mesopore structure of coal were investigated by contrastive analysis. N2 adsorption tests showed that the pore volume of the > 10 mesopores (especially the > 40 nm mesopores) significantly increased in crushed coal from that of coal chunks, and the observed increases in pore volume decreased progressively with the enhancement of ductile deformation. The difference in pore volume (by N2 adsorption), pore surface area, and surface fractal dimension (DFHH) of < 10 nm pores was insignificant, indicating that mechanical grinding hardly affected < 10 nm pores. During CO2 adsorption, incomplete equilibrium was observed in partial coal chunks of primary structure coal and weakly crumpled coal. After coal being ground into 60 mesh particles, incomplete equilibrium was effectively eliminated as grinding significantly shortened the distance between adsorbate molecules and micropores. Apart from that, there were no noticeable influences on the total pore surface area and micropore size distribution (by CO2 adsorption). Thus, during characterizing the pore structure of different types of TDCs (a micro- and mesoporous material), it is recommended to conduct N2 adsorption on the original state and conduct CO2 adsorption on 60 mesh particles if possible.
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This research was sponsored by the National Natural Science Foundation of China (Grand No: 41430317, 41402136) and the National Major Science and Technology Project of China (2016ZX05044).
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Cheng, G., Jiang, B., Li, F. et al. Influence of mechanical grinding on characterization of nanopores of tectonically deformed coal: a comparative study between coal chunks and crushed coal. Arab J Geosci 14, 805 (2021). https://doi.org/10.1007/s12517-021-07121-3
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DOI: https://doi.org/10.1007/s12517-021-07121-3