Abstract
Selection of the optimal properties of coal as a natural sorbent, both as a sample collected from a seam or of the coal seam itself, requires various parameters to be determined and may not be based on the knowledge of metamorphism degree only. In order to improve the predictions of sorption capacity and the kinetics, analyses of correlation and multiple regression based on the results of laboratory studies were performed for 15 coal samples with various coal rank. The maximum vitrinite reflectance (R0) for low-rank coals was 0.78%–0.85%, and 0.98%–1.15% and 1.85%–2.03% for medium- and high-rank coals, respectively. Coal samples were subjected to technical and petrographic analysis. The gravimetric method was used to perform sorption tests using methane, in order to determine the sorption capacity and the effective diffusion coefficient for each of the coals. Pycnometric methods were used to determine the textural parameters of coals, such as the percentage porosity and specific pore volume. The studies were further supplemented with an evaluation of the mechanical properties of the coals, Vickers micro-hardness, and elastic modulus. This work shows that the statistical multiple regression method enables a computational model including the selected petrophysical parameters displaying synergy with the specific sorption property—capacity or kinetics—to be created. The results showed the usefulness of this analysis in providing improved predictions of the optimal sorption properties of coal as a natural sorbent.
Highlights
Coal is a natural, microporous material with an extended pore structure, surrounded by cracks and splitting planes
Measured reflectance encompassed the characteristic values of medium-rank hard coal—types A, B, and C according the UN-ECE classification [51]
Regardless of the metamorphism degree, almost all of the analysed coal samples showed vitrinite as the dominant maceral; only the 227/22 sample showed the domination of inertinite group macerals (53.28 %) over vitrinite (43.39%) (Table 1, Figure2020, 3). 13, Liptinite group macerals are the most abundant in low-rank coals
Summary
Microporous material with an extended pore structure, surrounded by cracks and splitting planes. This material shows high sorption affinity to gases genetically related to coal deposits: carbon dioxide and methane [1]. Even though CO2 is naturally present in nature, its excessive emission into the environment as a result of anthropogenic activity places it among gases with the strongest influence on climate warming. Processes included in carbon capture and storage (CCS) are still considered in the case of yet unused coal deposits [3]. Coal has recently been considered as a low-cost sorbent, selective towards CO2 , especially at low pressures [4], and still, all topics related to this fossil fuel are extremely desirable from the practical point of view in this context [5,6,7]
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