Vol 335, No 7 (2024)

Relevance. An analysis of the current state of the global energy agenda shows that the problem of anthropogenic impact on the planet’s atmosphere by thermal energy facilities is one of the most important for humanity. At the same time, the growth in electricity consumption stimulates the introduction of ever new power generating capacities. For a long time, it was believed that the solution to this problem was the large-scale introduction of non-traditional renewable energy sources (wind generators and solar panels) into the overall balance of electricity generation. However, it is now becoming obvious that renewable energy sources cannot fully cover all electricity needs. The latter creates incentives for the commissioning of new thermal power plants, usually operating on coal fuel. But the main problem of coal energy – its anthropogenic impact – still remains unresolved. This situation creates the prerequisites for the development of new “clean” coal technologies with a full cycle of sequestration of combustion products. One of the most promising technologies for burning coal with low emissions is coal combustion in the composition of coal-water fuel. However, coal-water fuel technology has a number of disadvantages. One of the most significant is the high ignition delays of typical (with a characteristic size of 3–5 mm) droplets of coal-water fuel. One of the most promising methods for solving this problem is spraying coal-water fuel in an ultra-fine state (with a characteristic droplet size of 0.1–1 mm). Aim. Experimental study of the conditions and characteristics of crushing droplets of coal-water fuel in a high-speed air flow. Object. Coal-water fuel prepared on the basis of lean coal. Method. Special experimental stand to establish the main characteristics and conditions of dispersion of coal-water fuel droplets. Results. The results of experimental studies show that for stable fragmentation of typical droplets of coal-water fuel, the speed of the latter (during the spraying process) must be at least 40 m/s. 

Relevance. The search for suitable materials for creating a new generation of anodes in lithium-ion batteries that have not only high capacity, but also high electrical conductivity. For this purpose, the attempts have been made to use silicon Si, which has a high specific capacitance, instead of graphite C, but this material does not have high electrical conductivity. Copper silicides, in addition to high specific capacity, have high electrical conductivity values, since they do not react with lithium during operation, and therefore can be used to solve problems in the development of the above-mentioned lithium-ion anodes. Aim. To obtain dispersed materials in a high-speed jet of electric discharge plasma in the Cu-Si-C system. Objects. Dispersed materials obtained in the Cu-Si-C system. Methods. Plasma dynamic synthesis, X-ray diffractometry (X-ray phase analysis), scanning electron microscopy, transmission electron microscopy. Results. The authors have carried out the experimental studies to obtain dispersed materials of the Cu-Si-C system in a high-speed electric-discharge plasma jet and studied the microstructure and composition of the synthesized materials. It was revealed that the product consists of nanodispersed particles, which is confirmed by the results of scanning and electron microscopy. According to the results of X-ray diffractometry, crystalline phases of copper of the cubic system and copper silicides Cu₃Si and Cu₇Si of the hexagonal system are identified in the composition of the synthesized material.

Relevance. Understanding the mechanisms of liquid droplets interaction with each other is important for many industrial and technical applications related to solving a range of problems like slag removal in a high-temperature environment, obtaining components of the desired fraction in the food industry, etc. Aim. Establishment of the main patterns of suspension droplets interaction in a gas-air environment with temperature variation. Methods. Using shadow high-speed video recording, the main patterns of the binary collision of suspensions droplets were determined. The paper introduces the results of experimental studies of the coal-water suspensions droplets collisions characteristics in a gas-air environment with a temperature of 90–120°C. Parameters of the generated droplets: radius 1.0–2.2 mm, velocity 0.5–2.0 m/s. Results and conclusions. The authors have determined the modes of suspensions droplets collision (coagulation and separation) and the main characteristics of secondary fragments and constructed the maps of the modes of suspensions droplets interaction with each other when varying the concentration of solid particles in the suspension, the temperature of the gas-air environment and the time the target drop spent in a gas-air environment with an elevated temperature. The conditions were established for the coagulation of droplets, as well as their intensive secondary grinding to intensify their drying, ignition and combustion in boiler furnaces. It was established that an increase in the temperature of the gas-air environment leads to a significant change in the size and properties of droplets, as well as to the occurrence of oscillatory phenomena in the system. It is substantiated that collision of droplets of suspensions in a gas-air environment with elevated temperature is complex and multi-parametric. Its characteristics depend on a combination of factors (surface tension and liquid viscosity, size and shape of droplets, speed of their movement, density and viscosity of gas-air environment). The authors obtained mathematical expressions to describe the boundaries of the modes of the studied processes and schemes for using the results obtained in order to increase the efficiency of the corresponding technological processes.

Relevance. Groundwater is the main source of industrial and technical water supply for mining facilities. The geological structure of the studied areas can be complicated by various factors that make it difficult to search for and localize groundwater. In this regard, electrical geophysical prospecting methods are often included in the complex of prospecting and exploration works, before which it is necessary to justify the application of the chosen method for solving the problems by performing numerical modelling. Aim. To substantiate the use of electrical resistivity tomography for the search for groundwater, taking into account complicating factors, including perennially frozen rocks, taliks, and fault zone, by numerical modelling. Objects. Geological environment represented by Quaternary system rocks and permafrost rocks of Cretaceous sediments of the Zazinskaya intermontane area, fault zone, talik zones. Methods. Solution of the direct problem, solution of the inverse problem, ground geophysical surveys using electrical resistivity tomography. Results. Based on the performed numerical modelling, it is shown that the use of electrical resistivity tomography is expedient when searching for groundwater in the area characterized by various factors: permafrost, talik, and a fault zone. Based on the results of solving direct and inverse problems of electrical survey, using field works performed in 2020 in the Eravninsky district of the Republic of Buryatia as an example, it is shown that pole-dipole arrays in electric resistivity survey with electrode distance of 5 m, successfully confirmed by drilling operations, allow us to reliably delineate the potential zones of water inflow. These zones, characterized by low values of electrical resistivity, in this area, are related to talik zones, which are powered by heat flow from the bowels of the earth.

Relevance. The need to expand the mineral resource base of the Trans-Baikal Territory. Aim. To study the geochemical composition of technozems of tailings dumps of gold deposits of the Trans-Baikal Territory, their correspondence, in terms of gold content, to technogenic deposits, to calculate the exceeding the maximum permissible concentrations of toxic elements in technozems of tailings dumps. Objects. Technozems of tailings dumps of gold deposits of the Trans-Baikal Territory. Methods. Silicate, X-ray fluorescence ISP-AES methods in analytical laboratories of the Geological Institute of the SB RAS (Ulan-Ude) and JSC "SGS Vostok Limited" (Chita). Results. It was found that in terms of gold content (Au>0.4 g/t), the technozems of the tailings of the gold deposits of the Trans-Baikal Territory, in general, correspond to technogenic gold deposits. Technozems of the Baleysky tailings dam deposits with insignificant gold contents: technozems of Darasunsky (0.36 g/t) and Kariysky (0.35 g/t) deposits, are characterized by the largest volumes and contents of gold (1.2 g/t). It is determined that the chemical composition of the technozems of the tailings depends on the composition of the host rocks developed in the areas of deposits. They correspond to the rocks of both basic and medium compositions. The distinctive features of the content of impurity elements in the technozems of tailings are due to the different compositions of the initial ores of gold deposits. These differences are reflected in the values of exceeding the maximum permissible concentrations relative to soils. Among the toxic elements, arsenic is characterized by maximum exceedances of the maximum permissible concentrations. In the technozems of the Lyubavinsky deposit, the excess of the maximum permissible concentrations of arsenic relative to the soil is 933 times, and the Baley deposit is 397 times.

Relevance. The necessity to know the conditions and forms of W concentration in coals for solving a number of scientific and engineering problems at complex development of coal deposits. Aim. Complex estimation of W modes of occurrence in coal for development of measures for rational ecologically safe use of coal. Methods. Correlation analysis, scanning electron microscopy, infrared spectroscopy, coal group analysis, inductively coupled plasma mass spectrometry, instrumental neutron activation analysis. Results and conclusions. The modes of occurrence of W in coal were studied by a complex of methods. In the majority of W-enriched coal deposits, a negative significant correlation of its content in coal and coal ash with ash yield was found, indicating its association with organic matter. Using the method of coal group composition analysis, it was found that the main carrier and concentrator of W in the studied lignite deposits is organic matter. The contribution of the mineral phase in general in W-rich coals and in coals with its normal content does not exceed 20%, usually less than 5%. These conclusions are also confirmed by infrared spectroscopy data, according to which no more than 15% of the metal in the samples studied is associated with mineral phases. The association of W with high molecular humic acids predominates. In anomalously W-enriched lignites, the humic acid phase represents 76 to 88% of the gross metal content. The role of bitumen and low-molecular-weight humic acids in the balance of W is marginal at their different levels in the coals. Mineral phases of W are not characteristic of coal. Nano-microinclusions of scheelite, wolframite, hubnerite and ferberite were recorded as isolated occurrences. The main mineral phases are associated with Fe and Mn hydroxides, in which W is presented as a trace element in the amount of 1–5% together with other elements (Ge, As, etc.). In more metamorphosed bituminous and anthracite coals, authigenic mineral formations were found, represented by tungstite, phyllotungstite, native W and complex Fe-Mn-Ca-W-O mineral phases.

The practical importance of the tasks of utility networks design, namely, the problems of optimizing the structure of the main pipeline according to given criteria, such as efficiency, reliability etc., under conditions of limitations, for example, the compatibility of various types of utilities. Since the main pipeline is laid on the ground with various physical and geological factors, natural and situational conditions, it is advisable to take the reliability of its operation as a global criterion. The task of network optimization is proposed in the form of displaying the main pipeline along the selected routes in three-dimensional space, which considers various existing communications and objects, as well as elevation marks of the area. The paper presents the problems of optimizing networks, both in the continuous case and in the discrete case, and also studies various indicators of the reliability of the operation of the main pipeline. Aim. To develop a model for laying the main pipeline in three-dimensional space, considering the reliability of the pipeline transport; to conduct a comparative analysis for various reliability indicators and topologies of the main pipeline. Objects. Utility communications and networks laid in three-dimensional space. Methods. Calculus of variations, discrete optimization methods, graph theory and hypernet theory methods, network reliability analysis methods. Results. The task of optimizing the main pipeline transport is given taking into account its nesting along the route in three-dimensional space with the choice of an optimization criterion (economic efficiency, reliability, etc.). The problem is presented in the form of continuous and discrete formulations, which is important for its development both within the theory of the calculus of variations and discrete optimization. In this work, the problem was studied within the framework of the theory of graphs and hypernets, which allow, firstly, taking into account the nesting of one structure (main pipeline) into another (a discrete analogue of three-dimensional space) and, secondly, clearly illustrating the results of numerical experiments. It is shown that under the conditions of a given variants for laying a secondary network along the primary channels, various optimal structures are obtained when considering various reliability indicators as a criterion, which can be used to implement a design solution for the construction and operation of pipeline transport for various purposes.

Relevance. The need to evaporate large quantities of brines at potash industry enterprises. Evaporation of brines in surface evaporators is difficult due to the encrustation of heat exchange surfaces by salt deposits. Therefore, such evaporation is most expedient to be carried out in submerged combustion apparatuses, since they do not contain heat-transmitting surfaces. However, in this type of apparatus, malfunctions may occur due to uncontrolled solid phase deposition. At the moment, the dynamics of the solid phase in submerged combustion devices is poorly studied. This study is part of a scientific program aimed at a comprehensive review of the laws of motion of solid particles in submerged combustion apparatuses. Aim. To study the hydrodynamic processes in the submerged combustion setup in the time interval corresponding to the beginning of its operation; describe the patterns of solid phase motion as a function of time. Object. Laboratory setup of submerged combustion. A simplified model of the thermal mode of operation without the subsequent transition of the liquid phase to steam is analyzed.
Methods. The study was conducted by numerical experiment. The hybrid finite volume method was used in simulation in combination with the technology of the finite element method. The multiphase system was considered as two coexisting subsystems: gas–liquid and liquid–solid. Results. The paper considers the final time interval of the setup operation. It is found that during the time under consideration, a stationary mode of solid particle deposition is achieved. The authors have detected liquid flow velo-city oscillations, leading to fluctuations in the mass flow rate of solid particles at the bottom of the setup. It was found that the velocity at the tip of the flue gas jet escaping from the burner nozzle, as well as the pressure at the nozzle section, have a similar form of oscillation. The authors substantiated the hypothesis about the determining influence of the instability of the jet movement of flue gases on the oscillatory behavior of the entire hydrodynamic system.

Relevance. The need to increase the use of renewable energy sources in the economy to reduce the harmful effects on the environment. Aim. To assess the possibility of obtaining by the thermochemical method high-quality carbon adsorbents from a granular mixture of various wastes of plant origin. Objects. Samples of illiquid lumpy birch wood, walnut shells, sunflower seed husk, flax fires, anthracite coal. Methods. Physical experiments: conductive pyrolysis, water-steam activation and differential thermal analysis. The ash content and moisture content of the samples were determined according to SS R 56881-2016 and SS 33503-2015. Nitrogen adsorption isotherms were measured using a NOVA-1200e analyzer. The equilibrium activity for toluene was determined according to SS 8703-74, the adsorption activity for iodine was determined according to SS 6217-74. The determination of the density of the granules was carried out according to SS 15139-69. Results. The authors have established rational parameters for obtaining carbon adsorbents from granules of vegetable raw materials. The specific yield of pyrolysis products of a mixture of vegetable raw materials with pyrolysis resin was determined. The specific yield of carbonization products of the granular compacted mass showed an increase of 25% in comparison with the non-compacted mixture of vegetable raw materials. Rational parameters for obtaining activated carbon with the highest adsorption capacity are granules with a density of 1200 kg/m³ with a degree of burnout of the carbonization product of 70%. It was established that the obtained samples of adsorbents from granules of plant raw materials have high adsorption characteristics comparable to activated carbons obtained from fossil raw materials.

Relevance. The use of anti-turbulent additives for transporting hydrocarbon liquids through main pipelines allows reducing significantly the energy consumption of pumping power stations. Aim. Comparative analysis of the anti-turbulent efficiency of high-molecular polymers and compositions of surfactants. Methods. Laboratory-scale experimentation aimed to study the flow of dilute polymer solutions and dispersed surfactant systems through a cylindrical channel of a turbulent rheometer. Results. The author has carried out the comparative experimental studies of the anti-turbulent efficiency of extremely dilute solutions of polymers and colloidal systems. The results were obtained that suggest a higher anti-turbulent efficiency of high-molecular-weight polymers compared to micellar surfactant systems. Solutions of high molecular weight polybutadiene and aluminum polyhydroxydicarboxylates in gasoline were used as samples for the experimental comparison of hydrodynamic efficiency. The paper describes the laboratory setup, on which the studies were carried out, and introduces the formulas used for quantitative calculations. The structure of polymer solutions and colloidal systems is considered and a theoretical explanation is given for the preferential use in industrial practice of high-molecular polymers in extremely low concentrations in real pipelines. It was found out that the mechanisms of degradation of anti-turbulent properties of polymer solutions and dispersed surfactant systems are different. This is due to the difference in the structure of macromolar coils of polymer with an immobilized solvent and that of micelles from low molecular amphiphilic compounds. The paper introduces the arguments that explain the degradation of the anti-turbulent properties of polymers not by the destruction of carbon-chain macromolecules, but by decomposition in a turbulent flow of the original large associates, consisting of a large number of chains, into individual and smaller macromolecular coils with an immobilized solvent.