Vol 53, No 5 (2019)

The effect of alkaline extraction parameters on the yield, biological activity, and functional group composition of the humic acids (HAs) of brown coals was investigated. It was found that the functional group composition of the HAs can be intentionally affected by varying alkaline extraction parameters (the amount of an alkali and the duration and temperature of the process). The biological activity of humic preparations in the form of sodium humates as functions of the following structural group parameters was determined: the degree of aromaticity (  f_a) and a parameter reflecting the ratio between aromatic and aliphatic fragments in the organic matter of humic acids (  f_a/al). It was established that the milder the conditions of alkaline extraction, the lower the yield of HAs, but the higher their degree of aromaticity (  f_a) and biological activity.

Molecular simulations of CH₄/CO₂ competitive adsorption in moisture coals are carried out. The synergistic effect of micropore walls has a significant impact on the spatial distribution of adsorbates. Water molecules in micropores can prevent CO₂ and CH₄ from smoothly diffusing and adsorbing in the pore. The micropore is more favorable to the advantage of CO₂ in the competitive adsorption. The variation of excess adsorption capacity is related to the density difference between adsorbed phase and free phase. Relative to CH₄ density, CO₂ density is easier to affect the variation trend of adsorption capacity in the competitive adsorption.

The thermal decomposition of peat in a drop tube furnace was studied under conditions typical of the low-temperature combustion chambers of industrial heat-generating plants, and the combustion of peat charcoal was examined on a thermogravimetric analyzer with dynamic heating. It was established that the thermal properties of peat are well combined with the properties of woody biomass, primarily, with coniferous wood (spruce and pine). The main differences are that the process of peat pyrolysis occurred in a wider temperature range and two extremum points at temperatures of 277 and 320°C were observed in this case.

The necessary conditions and integral characteristics of the ignition and subsequent combustion of mixed fuels prepared on the basis of peat, crude oil, and water were studied. Fuel mixtures were burned in the form of a layer (a weighed sample), slurry droplets, or pellets in a model combustion chamber at a temperature of 300–900°C. The results were compared with data obtained upon the combustion of lean coal under analogous conditions. The experimental results illustrate the energy and environmental feasibility of the combined burning of peat and oil-containing components in a fuel and energy cycle. As found experimentally, the composite fuels have a sufficiently high energy and environmental potential, and they can be used as a primary or secondary energy source.

It was established that a shift of equilibrium in the graphite–calcium oxide system toward the formation of calcium carbide can be observed at a temperature of 900°C due to the formation of a volatile substance—carbon monoxide. Upon the addition of anthracite, a maximum of calcium carbonate decomposition decreased from 813 to 780°C, and the endothermic effect of the formation of calcium carbide manifested itself at 1350°C. In a mixture of calcium chloride with anthracite or graphite in stoichiometric amounts, the formation of calcium carbide and carbon tetrachloride was observed at 1100°C. The formation of calcium carbide was confirmed by chemical reactions of pyrolysis products with water (the release of acetylene) and by calculations of weight losses from thermogravimetric curves.

Experimental results on the kinetics of hydrogenation of a wide fraction of coal tar (bp 230–300°C) in the presence of a Fe₃O₄ nanocatalyst are presented. The rate constants, overall rate constants, and activation energies were calculated. It was established that the conversion of preasphaltenes into asphaltenes is the rate-limiting stage of the conversion of a wide fraction (230–300°C) of coal tar into reaction products. The process of converting the wide fraction (230–300°C) into products takes place in the kinetic region of a heterogeneous process.