Method for determining the ultimate sorption capacity of coal matter by EPR-spectroscopy

Abstract

Purpose. Improving the method for determining the ultimate sorption capacity of coal matter using EPR-spectroscopy (electron paramagnetic resonance) by adjusting the proportionality coefficient between the ultimate sorption capacity of coal and the concentration of paramagnetic centers and the conjugation coefficient in accordance with the degree of coalification. Methodology. The ultimate sorption capacity of the matter was estimated by EPR-spectroscopy, based on the content of paramagnetic centers (PMC) in coal, which are able to come into physical (sorption) interaction with molecules of paramagnetic gas (O2) when the pressure increases. Processing of the research results was carried out by methods of mathematical statistics. Findings. Analysis of long-term results for determining the ultimate sorption capacity of coal matter by EPR-spectroscopy was carried out. The analysis testified about the need to adjust the proportionality coefficient  between the ultimate sorption capacity of coal and the concentration of paramagnetic centers Na and the conjugation coefficient Ksc, depending on the coal rank metamorphism. The values of the proportionality coefficient  by hard coal ranks for the yield of volatile components Vdaf and the reflectivity of vitrinite R° were calculated. Appropriate changes were made to the express-method for estimating the ultimate sorption capacity of coal by the EPR method. Originality. It is proved that the proportionality coefficient β between the ultimate sorption capacity of coal and the concentration of paramagnetic centers Na and the conjugation coefficient Ksc is not a constant value, but changes (decreases) with the degree of metamorphism. It is established that this relationship is satisfactorily characterized by the sigmoid model, whose inflection (on the graph) is confined to the gas and fat ranks of coals (volatile-matter yield is 29 %) and is caused by the second main jump of coalification during a cardinal change in the molecular structure of coal, associated with the completion of the intensive decomposition of the polymer-lipoidin component in the coal matter. Practical values. The express-method was improved for estimating the ultimate sorption capacity of coal by the EPR-method, which differs by specified proportionality coefficients according to ranks in the series of coalification.