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No 4 (2023)
Articles
Памяти Ивана Ивановича Лиштвана
3-4
Supramolecular Structure of Coals of the Metamorphism Series
Abstract
The molecular structure characteristics of brown and hard coals of the metamorphism series were determined using IR spectroscopy. Based on the data of X-ray diffraction analysis and the kinetics of swelling in solvents, their supramolecular structure and the mechanism of molecular diffusion in the organic mass of coals were studied. Relationships between the supramolecular structure and molecular composition indices were established, and the structure evolution in the series of coal metamorphism was considered. It was found that tetrahydrofuran and quinoline molecules penetrated into the bulk of the organic mass of most coals by molecular Fickian diffusion complicated by steric hindrances of the microporous structure.
5-15
Effect of the Chemical Composition of Coals on Surface Wettability and Filtration Properties
Abstract
The method of liquid filtration through a layer of coal powder was used for a comprehensive characterization of surface wettability in conjunction with the determination of the contact angle. The effect of the degree of chemical maturity (metamorphism) of coal on the filtration characteristics of a layer with fractured porous properties was evaluated. Different activity of coal surfaces to water wettability upon a change from the native state to the surface-oxidized one was established. It was shown that the wetting and filtration properties of the coal surfaces increased from native to surface-oxidized coals and decreased as the degree of metamorphism increased from low to medium metamorphosed coals.
16-22
Thermodynamic Characteristics of the Reactions of Formation of Iron and Magnesium Humates in Aqueous Solution
Abstract
The thermodynamic stability of iron and magnesium ions at different acidity of an aqueous medium was determined using chemical thermodynamics methods and Pourbaix diagrams. The temperature dependence of the thermodynamic functions of corresponding reactions was calculated. The thermodynamic feasibility of the reactions of replacing potassium and sodium ions in aqueous solutions of humic acid salts containing carboxyl and hydroxyl functional groups with iron and magnesium ions was established. The resulting water-soluble iron and magnesium humates can have a high potential for practical use.
23-30
Ignition of Coals with Continuous-Wave Lasers at Wavelengths of 450 and 808 nm
Abstract
The kinetic and energy characteristics of the ignition of microparticle powders of coals of G (gas), Zh (fat), and K (coking) grades with a bulk density of 0.4 g/cm3 under the action of continuous-wave laser radiation at wavelengths λ = 450 and 808 nm with an exposure time of 1 s were measured. Coals were ignited only under irradiation, and the effect of flame propagation was absent. Ignition delay times were measured as a function of the radiation power density, and the critical values of the coal ignition energy density were determined. Energy consumption for the ignition of coals with radiation at λ = 808 nm was greater than that at λ = 450 nm for all grades of coals. It was established that the absorption of laser radiation by coal samples had a quantum character.
31-38
Modification of Zinc–copper Catalysts for the Process Production of Methanol From Synthesis Gas
Abstract
Variants of modification of a zinc–copper catalyst for the synthesis of methanol are considered. The main physicochemical characteristics of the modified catalysts have been studied. The effect of modification on catalyst operation in the process of methanol production from synthesis gas with the ratio H2 : CO = 2.1 was demonstrated.
39-45
Influence of Interstructural Bonds in Biomass on the Thermophysical Characteristics of Biochar Produced by Hydrothermal Carbonization and Torrefaction
Abstract
The influence of the temperature of hydrothermal carbonization and torrefaction on the properties of biochar obtained from biomasses (peat and sawdust) and model mixtures of structural components (cellulose, hemicellulose, and lignin) prepared in percentage ratios corresponding to their amounts in real biomass was studied. It was found that the yield of biochar decreased with temperature in both of the processes, whereas the degree of deoxygenation, the amount of carbon in the biochar, and its calorific value increased. A comparison of biochars from biomass and model mixtures was carried out. An assumption on the screening effect of lignin in heat treatment, which reduced the degree of degradation of the structural components of biomasses, was made.
46-54
Use of Natural Flake Graphite in the Calibration of Instrumental Research Methods
Abstract
The size of mosaic blocks along the graphite layers (that is, the average diameter of crystallites in the basal plane) was determined by two methods for specially made model materials based on narrow fractions of flake graphite powders and milled pyrographite with lamellar particles. The first method consisted in the calculation of mosaic block sizes from a minimum of the temperature dependence of electrical conductivity using an empirical law according to Mason; the second method based on mathematical modeling used the values of the magnetoresistance of carbon materials at temperatures of 80 and 300 K. The correspondence between the sizes of mosaic blocks calculated by these methods along the graphite layers in the considered materials was shown. A correction for the lamellar shape of graphite crystallites was determined to calculate the sizes of mosaic blocks in the direction perpendicular to the graphite layers from the 002 peak broadening in the diffraction pattern.
55-63
Mobility of the Major and Trace Elements in the Coal Mining Wastes
Abstract
Domestic and foreign static tests are considered to assess the impact of mineral waste from coal mining and processing on water objects when waste is placed in dumps or used for reclamation purposes. The results of static tests according to GOST R 58914–2020 for three samples of mineral waste taken from hard and brown coal deposits are presented. The wastes differ significantly in mineral and chemical composition, including sulfur content. It is shown that the high content of sulfur in the waste, including it in a water-soluble form, determines the low pH value of the aqueous extract. This, in turn, leads to an increase in the yield of water-soluble substances and to an increase in the mobility of major and trace elements.
64-72