Volume 27, Nº 4 (2023)

A research study into using vibration technologies for the transport of granular working medium was carried out. A vibration testing machine, whose calculation model includes a mechanical vibration system having two degrees of freedom with a rigid body on elastic supports, was selected as an object of research. The study involved analysing the variation in the system vibrations by using the structural theory for vibration isolation systems, where a dynamic equivalent represented by a structural diagram of an automatic control system is compared to the initial calculation model. The structural diagram of the system is based on the motion equations in operator form obtained using Lagrange differential equations of the second kind. The Laplace transform was used to transform the initial data for the system of differential motion equations. The paper addresses the characteristics of a new structural and technical solution in the field of vibratory displacement of a granular working medium using the working body of a vibration technological machine, which involves introducing a number of additional weights, levers, springs, and hinges. Here, springs comprise generalised structures containing both elastic elements and vibration dampers. To connect the coordinates of the endpoints in the working body of the vibration technological machine, analytical relations were obtained. It was established that varying the parameters of the elements within the elastic-lever blocks allows the dynamic state of the vibration technological machine to be controlled. In addition, it was shown that the obtained structural diagram helps to derive mathematical expressions for transfer functions, comprising the ratio between the motion coordinates of a technical object and an external force disturbance. On the basis of these expressions, the transfer function for the ratio of the motion coordinates of the vibration technological machine was formulated. A mathematical model of a vibration technological machine was obtained in the form of a transfer function, including a large number of additional elastic and massinertial elements, where the parameters of vibration displacement can be adjusted automatically. The research results will allow the existing technical solutions in the field of technological engineering to be modernised.

The aim is to develop a method for ensuring the stability and efficiency of the braking process by differentiating the friction linings of brake pads of pad-type disc braking mechanisms. The research applied differentiation of the interaction time of friction pairs and their area, which provides the highest stability indicators of braking mechanisms. The non-standardized bench equipment developed by the author, as well as segmental braking mechanisms providing differentiation of friction pairs by area were used in the study. A method of designing the resultant braking torque was developed using the relationship between the transverse movement of the pads and the developed braking torque of the friction unit. As a result of bench tests, the stability and fluctuation coefficients of the braking torque of the developed pad-type disc brake mechanisms with six pressing elements increased by 12.2 and 34.9%. These values were obtained as compared to serial brake mechanisms equipped with a monopressing mechanism with a single brake pad. The discrepancies between the simulated and obtained data during the bench test on the stability criteria averaged 5.1 and 6.7% for the stability coefficients and braking torque fluctuations for the three brake mechanism variants under consideration, respectively. Differentiation of pressing elements and segmentation of brake pads has the effect of increasing the stability criteria and braking efficiency for pad-type disc brakes. With the analysis of the dependence of the transverse displacement and the developed braking torque, a guaranteed result on the stability criterion and braking torque fluctuations of pad-type disc brakes was modeled. Based on the conducted bench tests, the model developed for obtaining the resultant braking torque for the braking mechanism with segmental pads can be used for designing friction pairs with the set parameters.

This work presents a literature review devoted to increasing the efficiency and quality of managing wind power plants. The analysis focuses on mitigating the adverse effects of wind turbines on the power system and providing system services, such as primary frequency regulation. Nearly 150 scientific publications and reviews, selected from various scientific sources (such as IEEE, Web of Science and Scopus) by the keywords, including “wind power station”, “wind turbine”, “multi-agent control”, “virtual inertia”, “microgrid”, “virtual power plant”, and “frequency control”, were evaluated.A systematic review methodology of specialised sources was applied, which offers a defined structure for this field of research by categorising articles. The study emphasises the urgency of developing technologies to increase the regulation capacity of a wind power plant, since the low inertia of renewable energy sources leads to a decrease in the stability of power systems, a significant proportion of which accounts for wind power plants. It follows from the literature review that one of the means to increase the stability of such power systems is the creation of virtual inertia for wind power plants. However, due to the limited capacity and control capabilities of each individual wind turbine, the efficiency of introduced virtual inertia may be insufficient, when implemented for individual units. Moreover, it is shown that uncoordinated control can affect the stability of the system. In this review, the specific sources considering coordinated multi-agent control of the virtual inertia for several wind turbines (wind power plants) were analysed. The review concludes that the proposed approach is currently understudied, while the outlined theses can be confirmed by developing the necessary algorithms and analysing the results.

The paper evaluates the generation of electrical energy by a solar power plant equipped with a solar tracking system using the ASHRAE clear-sky method for calculating solar insolation. The mathematical algorithm uses the MathCad system with data export and analysis in Microsoft Excel. Collected over a month and the operation period in 2022–2023, data on electricity generation by solar stations characterised by an optimal constant angle of inclination of the solar panel and equipped with a solar tracking system were used. By taking into account the varying ambient temperature, dust content, and solar transmission by the solar panel coating, the given algorithm allowed electricity generation by a solar panel to be forecasted with an average absolute error ranging from 0.22 to 9.8. To determine solar insolation for a specific day and the geographical coordinates of the intended construction site of a solar power plant, a mathematical model was developed using MathCad software. The experimental and computational studies carried out on selected clear days, accounting for varying weather conditions, demonstrated the adequacy of this method and its applicability for forecasting electricity generation with different inclination angles of a solar panel. It was established that a solar power plant with a solar tracking system generated 37% more electricity per year than that with fixed solar panels. The ASHRAE Clear-Sky method for calculating solar insolation allows the amount of electricity generated for a specific region to be estimated with minimal input data. Further research will focus on defining and improving methods for forecasting electricity generation by a solar power plant on overcast days.

This article is aimed at developing an algorithm for optimizing the operation modes of the electric power system of Mongolia, particularly the central power system that include not only conventional thermal power plants, but also renewable sources (wind and solar power plants). This power system accounts for a large share of electricity consumption and generation in Mongolia. The method of linear programming was chosen to minimize financial costs and active power losses during power generation at thermal power plants, while Newton’s method was used to minimize power losses. In addition, the article uses load schedules of each node of the studied power system for its modeling based on the ranking model. Load graphs are predicted using ensemble machine learning algorithms. After the optimization by the criterion of power loss minimization in the grid, power losses were found to be 3.05% of the total power consumption (with power losses in the basic variant of 3.12% and the average selling price of thermal power plants of 0.51 units). Thus, the reduction in losses amounted to 0.07 percentage points, or 2.24%. In terms of the cost minimization criterion, the average selling price of electricity was 0.49 units, i.e., decreased by 3.92%. Average losses of electric power in the grid decreased by 0.6%. According to empirical data, the suggested algorithms can be applied to the optimization of power distribution between thermal power plants by given criteria. The suggested algorithms are implemented using pandapower, a Python-based tool for power system analysis, thus creating a unified system of predictive analytics of power system operation modes

The aim is to develop an alternative technology of bauxite raw material processing based on low-temperature sintering of bauxite with caustic alkali, as well as to solve the issue of carbon footprint control at alumina refineries in the Urals. Laboratory tests were carried out by sintering artificial bemite and hematite with chemically pure caustic alkali at temperatures of 300, 500 and 700°C and their further leaching in weakly alkaline solutions. To study the phase, chemical, and particle size distribution of red muds after leaching, various physical and chemical methods of analysis were used, such as X-ray fluorescence, titration method, X-ray phase analysis, scanning electron microscopy, magnetometry with a vibrating sample. The Brunauer – Emmett – Teller method was used to determine the specific surface area and porosity. The study of the kinetics of the solid-phase reaction of the bemite interaction with caustic alkali has shown the kinetic interaction in the temperature range under study. Moreover, sintering of hematite at temperatures of 300 and 500°C and further leaching of the sinter with water resulted in mineralogical changes in the sludge with the production of a new mineral, maghemite, which possesses magnetic properties. When studying the magnetic properties of red mud of lowtemperature sintering of bauxite, we determined that the magnetization was as high as 19–20 electromagnetic units per g (at a sample density of 2.38 g/cm3) at a magnetic field of 10 kE. The specific surface area of these samples was 54.97 and 51.77 m2/g. The performed studies confirm that the proposed technology can be adapted for bauxite to produce highiron red slimes, thus contributing to the integrated processing of bauxite raw materials. In addition, ways to reduce carbon emissions at alumina refineries by eliminating the sintering operation with soda and limestone, which is accompanied by CO2 emission during decomposition of these compounds, can be studied.

The study aims to investigate the most efficient method for significant minimization of the impact of organic carbon on gold recovery from double refractory raw materials. We tested three double refractory gold-sulfide concentrates from different deposits with the content of gold from 23.5 to 40.9 g/t and total carbon from 1.2 to 9.5 wt %. Thermal treatment was carried out in a tubular rotary furnace that provided permanent temperature setting and rotation speed in the reactor. The initial concentrate was grinded as pulp in a Fritsch planetary mono mill Pulverisette 6. Autoclave oxidation was performed in Premex and Büchi titanium autoclaves. The technology of autoclave oxidation with the addition of a secondary oxidizer was found to be the most efficient, since it can increase gold recovery up to 97%. Another technology – hightemperature autoclave oxidation – also proved high performance; however, a significant increase in the residence time of the material in the autoclave (up to 120 min) at elevated temperatures is required to achieve this performance. According to the results, thermal treatment in general can provide a small increase in gold recovery (up to 4%). Due to this, it can be used as an additional processing with other methods analyzed in this article rather than as a self-sufficient technological solution. The studies revealed that the preliminary thermal treatment of concentrates entering autoclave oxidation shows a positive effect; high-temperature autoclave oxidation of concentrates with different carbon content provides high gold recovery for high-carbon concentrates; the use of a secondary oxidizer (in the form of nitric acid) also benefits the gold recovery. The high efficiency of the technology for concentrates with different carbon content allows us to recommend it for further research.