Vol 52, No 6 (2018)

The solid-phase reaction of sodium percarbonate with brown coal was investigated. The results of determining the effect of a peroxide component of sodium percarbonate on an increase in the yield of humic acids as a result of the reaction are presented. It was found that the mechanism of radical oxidation makes a significant contribution to the course of the reaction. Changes in the structure of humic acids because of oxidation in the mechanochemical reaction of brown coal with sodium percarbonate were studied by IR spectroscopy and elemental analysis. An increase in the concentration of phenolic and carboxyl groups in the structure of humic acids from brown coal after the reaction was caused by the appearance of new groups as a result of oxidation and their release due to the destruction of stable complexes with metals.

The effect of the temperature of hydrothermal carbonization of peat on the yield and composition of the resulting biocoal was studied. It was found that an increase in the temperature from 160 to 230°C leads to a significant decrease in the moisture and ash contents of biocoal, but it significantly increased (from 52 to 68%) the fraction of carbon and the net and gross calorific values (from 20.2 to 26.77 and from 21.5 to 28.03 MJ/kg, respectively).

The results of the calculation of the reactivity descriptors of structurally different polyaromatic hydrocarbons (PAHs), which act as starting compounds in condensation and polymerization reactions and the subsequent formation of coke occurring on the heating of hydrocarbon raw materials in the course of visbreaking in tube furnaces are presented. The activation energies and preexponential factors of chemical reactions of hydrogen atom removal from PAH molecules, which simulate the local environment of a coke layer, as a result of their interaction with the radical ^⋅CH₃ were calculated using quantum chemical methods.

The results of studies of the extraction of Mo, V, and Ni compounds contained in the semicoking product of tar hydroconversion residue by an acid leaching method are presented. The aqueous solutions of HNO₃, H₂SO₄, and H₂O₂ were used as reagents for the leaching. Conditions for the extraction of 80–90% metals from the semicoke were determined. The possibility of decreasing the sulfur content of the semicoke by a factor of more than 2 was demonstrated. According to the calculated kinetic characteristics, the reaction of molybdenum leaching by the test reagents corresponds to a higher degree to a first-order kinetic equation (R² > 98%).

Coal flotation wastes from of OOO MMK–UGOL’ were studied using a semiquantitative method; air and fire shrinkage, sintering, refractoriness, and tensile strength were determined. It has been proposed to use the wastes in an amount of 10–30% as an inert and combustible additive to clay mixtures for ceramic brick production by a semidry method in order to produce bricks of M100, M75, and M50 grades. The addition of wastes increased the porosity of finished products, improved their heat-insulating properties, and decreased shrinkage.