Comprehensive Fractal Model and Pore Structural Features of Medium- and Low-Rank Coal from the Zhunnan Coalfield of Xinjiang, China

Abstract

Medium and low-rank coal from the Zhunnan coalfield of Xinjiang in China was investigated for quantitatively characterizing its range of aperture structure. The pore parameters were determined by nitrogen adsorption at low temperature and mercury injection at high pressure, and the full aperture was determined. The FHH model, Menger model, Sierpinski model, and a thermodynamic model were used to calculate the comprehensive fractal dimension of the coal samples over the full range of aperture. The fractal characteristics of the pores of medium- and low-rank coal were quantitatively analyzed, which provided a reference for the overall characterization of pore structure heterogeneity in this coalfield. The results show that the FHH model and thermodynamic model more accurately calculate the fractal dimensions of less and greater than the joint pore position, respectively. The comprehensive fractal dimension of the low-rank coal pore is 2.8005–2.8811 and that of medium rank coal is 2.5710–2.6147. When compared with the medium-rank coal, pores of the low-rank coal are more developed and they exhibit a more complex structure with stronger heterogeneity. The comprehensive fractal dimension of the pores is a negative correlation with average pore size, vitrinite content, and maximum vitrinite reflectance, and positive correlation with pore volume, pore specific surface area, inertinite content, and exinite content.

Recent Trends and Challenges in Lead-Free Perovskite Solar Cells: A Critical Review

“…Sn can also satisfy both the requirements of coordination and charge balance. 61,62 In the general formula of ABX 3 , A is generally methylammonium (MA), cesium (Cs), and formamidinium (FA), and X is generally chlorine (Cl), bromine (Br), and iodine(I). However, the B position is occupied by Pb, and it can be therefore replaced by Sn.…”

“…Sn 2+ and Pb 2+ have alike electronic configurations, crystal structures, and ionic radii (Sn, 1.35 Å; Pb, 1.19 Å), and thus, Sn is seen as an alternative to Pb (Figure ). Sn can also satisfy both the requirements of coordination and charge balance. , In the general formula of ABX 3 , A is generally methylammonium (MA), cesium (Cs), and formamidinium (FA), and X is generally chlorine (Cl), bromine (Br), and iodine­(I). However, the B position is occupied by Pb, and it can be therefore replaced by Sn.…”

Effect of disturbed coal pore structure on gas adsorption characteristics: mercury intrusion porosimetry

“…Agbabiaka et al (2013) studied the fractal features of spherical pores using scanning electron microscopy and a small-angle X-ray scattering method. Jia et al (2022) and Lin et al (2020) explored the porosity and pore size of coal at different metamorphic grades by conducting mercury injection and low-temperature liquid nitrogen adsorption experiments. By using scanning electron microscopy and low-pressure N 2 /CO 2 adsorption, Mangi et al (2020) systematically evaluated influences of pore size distribution and fractal dimension on gas adsorption and desorption quantities.…”

Joint Characterization and Fractal Laws of Pore Structure in Low-Rank Coal

“…Due to the limitations of the type of pore structure testing method, different experiments could only characterize the pore distribution at a certain scale but cannot fully reflect the pore structure characteristics. In recent years, scholars have successively attempted to combine multiple testing methods to jointly characterize the pore structure features and pore distribution of coal [35][36][37][38]. However, some scholars have only tested mesopores and macropores [39], while others have not quantified the complexity of the pore structure [40,41].…”