This paper is aimed at studying the main design solutions of the TGME-444 boiler, which ensure reliable operation of heating surfaces and high economic indicators when burning fuel oil. In the Russian context, such boilers relied on fuel oil from the period 1973-1993, whereas, from 1993 to the present time, the fuel was switched to natural gas. Extensive experience of boiler operation when burning natural gas shows that, according to the temperature regime reliability of the curtain convective superheater of the drop flue gas duct, the boilers cannot operate with the loads more than ~117 kg/s (420 t/h). The reasons for the increased injections when burning natural gas are due to the project decisions on the composition of boiler heating surfaces. The main engineering solutions for the boiler thermal circuit were optimised for fuel oil as the heaviest fuel. Thus, consideration was given to the several variants of thermal circuits formed with regard to their potential implementation within existing furnace and convective gas duct configurations taking the conversion to natural gas fuel into account. These are: replacement of steam superheating furnace curtains with steam generators and inclusion of the latter in the boiler circulation cycle; increase in heat absorption of water-containing heating surfaces (under reduced injection flow) by the introduction of recirculation gases withdrawn after the economiser into the furnace. Calculations were performed using TRAKT, Hydraulics, Boiler Designer programs for thermal and hydraulic calculation of steam boilers. The results of calculated variants informed changes in the design and heat absorption of boiler reheating surfaces that significantly reduced the cost of injections and thermal upset, whereas operational reliability was able to be increased while maintaining a high-level of economic indicators. The greatest effect of reducing injection costs is achieved in cases when reheating furnace curtains are replaced by steam generating curtains, with the latter included in a boiler circulation scheme. Thus, increasing the heat absorption of water-containing heating surfaces by converting superheating furnace curtains into steam-generating curtains decreases water overheating at the economiser outlet, improving operational stability.

The study is aimed at the provision of an underlying rationale for the use of active filters to reduce voltage non-sinusoidality in the power supply system of a coal mine in Vietnam. Power supply systems of coal mines and quarries are characterised by many voltage levels and various types of loads, with new electrical equipment working in parallel with outdated equipment. Coal mines and quarries are maintained under high power loads, with non-linear current-voltage characteristics introducing distortion into the electrical network. Therefore, power supply systems for industrial coal mining areas are determined by a quality of electric energy that is inconsistent with Vietnamese regulatory requirements. Additional economic damage is caused by low quality of electric energy. In order to improve the quality of electric energy, it is necessary to apply special technical means, such as active harmonic filters. The quality assessment of electric energy in the coal mine power supply system was carried out using the PQ-Box150 instrument for measuring electric energy quality indicators and mode parameters. An analysis of the measured quality indicators of electric energy is conducted, including the parameters of non-sinusoidal mode. For indicators characterising the distortion degree of the voltage curve shape, the results of the analysis indicate them to exceed the limit established in the regulatory documents of Vietnam. From the analysis of measured parameters in non-sinusoidal mode, the presence of a wide range of voltage and current interharmonics is also detected. According to the analysis of the reactive power mode at the fundamental frequency, the load power factor in one of the phases is established to be less than the minimum value given in the Vietnamese regulatory documents. In accordance with the measurement results of electric energy quality indicators and parameters of the non-sinusoidal mode of the load power factor and reactive power of the fundamental frequency, as well as characteristics of active harmonic filters, the application of an active harmonic filter was demonstrated to be appropriate for reducing voltage non-sinusoidality and increasing the load power factor in the power supply system of a coal mine.

The study is aimed at determining criteria for a mathematical model of an asynchronous generator used to assess the state of an electrical power system. The relevance of the study is predicated on the current inadequacy of measuring instruments for electrical distribution networks, resulting in low measurement redundancy. Mathematical data processing methods, including tasks of measurement verification and state assessment, are developed to support technical measures for increasing the volume of information. The paper considers the problem of choosing a mathematical model for an asynchronous generator widely used in assessing the state of an electric power system at wind turbine power plants. In this paper, PQ and RX mathematical models of an asynchronous generator are used. Quality studies of the obtained active power of the asynchronous generator depending on the generator model are carried out and recommendations concerning the choice of model presented. The selected mathematical model should provide the opportunity to solve the problem of measurement verification, causing no loss in the node observability. The recommendations are based on an analysis of the Jacobi matrix, with the structure determined by the measurement elements. The calculations were performed on an IEEE 30-node test circuit using simulated load schedules and generation of wind farm data. Based on the research results, the following recommendations were developed. In the case of asynchronous generator measurement where the active power belongs to a group with low redundancy, the RX model is appropriate for authenticating measurements of the asynchronous generator active power and its flow in the line leaving this node. In the case of critical active power measurement, the PQ model should be used to ensure the observability of this node.

The aim of this study was to analyse the energy indices of pulse semiconductor converters, including efficiency as an important characteristic of their operation. This aim was achieved through the use of the simulation modelling methods in the MATLAB 7.5 Simulink environment. In particular, blocks from the SimPowerSystem library were used. The authors developed the models of semiconductor converters with pulse-width modulation having a single power switch on the IGBT type transistor, coupled with a semiconductor converter with pulse-frequency modulation having four power switches on the permanently-open SCR type thyristors. The operation accuracy of the models was confirmed in a series of experimental studies carried out on the laboratory mock-ups of pulse converters implemented in the power electronics laboratory of the Department of Electric Drive and Electrical Transport. This article presents the developed models of semiconductor converters with pulse-width and pulse-frequency modulation. The dynamic and static characteristics of pulse semiconductor converters are determined. An analysis of the obtained static characteristics of pulse converter diagrams showed that the stiffness of output characteristics of the converter with pulse-frequency modulation is higher than that of a converter with pulse-width modulation. The calculation results of the efficiency of pulse semiconductor converters conducted on the basis of the analysis of static output characteristics presume that the efficiency of the semiconductor converter with pulse-frequency modulation is more than one percent higher than the efficiency of a semiconductor converter with pulse-width modulation. The developed models of converters with pulse-width and pulse-frequency modulation can be used for studies of DC electric drive angular velocity controls.

The present study is aimed at determining criteria for selecting the optimal composition of fuel applied in gas turbine installations while avoiding major alterations of the fuel system. During operation and commissioning of gas turbine units, all fuel parameters must meet quality re-quirements. Although the primary fuel used in gas turbine units included in combined-cycle plants is natural gas, it is possible to apply a wide range of gaseous fuels. Due to the content of the main components and impurities, the thermodynamic properties of each fuel can vary significantly, af-fecting the composition of the combustion products, as well as the integral parameters of the gas turbine installation. In this connection, since the automatic control system must reliably perform its functions within a certain limit of this characteristic, the flow rate of the fuel gas comprises a critical parameter. The Wobbe index is applicable in technical approaches for approving the use of a particular fuel gas for a given gas turbine with a certain accuracy and without reconfiguring the automatic control system. In the present study, a GE PG111 6FA gas turbine unit was used. A mathematical model was created to study the effect of fuel variant on turbine performance. In order to eliminate damage of the combustion chamber and hot gas path, it is necessary to fulfil the requirements for condensation of moisture and hydrocarbons in the fuel gas. Therefore, conden-sation dependences for hydrocarbons and moisture in the fuel gas are also presented. In cases of acceptable application of fuel gases satisfying the Wobbe index, the effect of these values on the performance of gas turbine fuel systems is shown. Out of four types of gas fuels considered in the study, only the gas obtained from the Stepanovskoye field met the requirements of the Wobbe index, allowing its substitution for the originally-intended fuel without necessitating alterations to the fuel system.

This paper considers data retrieval issues associated with the training and testing neural network algorithms for electric load short-term forecasting based on the analysis of factors affecting the behaviour of the time series of the electric load of default provider consumers. The study uses mathematical-statistical, correlation and factor analysis methods. In the context of district central heating and water supply, the paper considers the influence of time factors, meteorological conditions, reliability of power grid equipment and the operation mode of large electric energy consumers on the electric load of default provider consumers. The main factors having a decisive effect on the time-series behaviour of electric energy consumption are identified. In order to reduce the dimension of the space factor, several factors are combined into one. Issues concerning the sampling of statistical data necessary for short-term forecasting of electric energy consumption using artificial intelligence and machine learning tools are considered. The sample is then used as a basis for the training and testing of predictive models. The behaviour of electric energy consumption time series is mainly determined by temporal and meteorological factors. The following factors are also determining for the electric load time series of the delivery point cluster default provider: blackouts of 6-220 kV electric grid equipment, operation mode of consumers of 670-10000 kW electric energy, availability of central heating and water supply in a certain town or settlement. However, these factors are considered insignificant for the electrical load of the energy system as a whole. Having considered the group of meteorological factors, we found that hourly volumes of power consumption are affected not only by the temperature of the outside air, but also by the variations in the temperature regime having occurred in the previous period.

The present study is aimed at investigating possibilities for increasing the reliability of power supply to remote consumers via electric networks having distributed power generation sources by means of automatic circuit reclosers (ACRs) and appropriate management systems. At the present time, the number of small electrical networks based on renewable energy generation sources in local areas is growing. Although consumers located in remote rural areas continue to suffer from low power supply reliability, in case of loss of the main source, all or part of the consumer base in such areas can be supplied with electricity from available small power generation sources. However, the assurance of reliable power supply to consumers in remote areas is hampered by a lack of appropriate technological solutions for managing such networks when the main power source fails. A decentralised method for controlling a network with autonomous power generation in case of loss of main power source supply, allowing the subsequent restoration of normal circuit and mode for a recloser electric network, is proposed and studied. Such networks acquire the properties of a Microgrid, capable of working both autonomously and in parallel with an external network. Division and restoration of integrity occurs at automatic sectioning points using reclosers, while the restoration of the integrity of the network with parallel operation of sources requires synchronisation of components at reclosers remote from sources. As a solution, the addition of a synchroniser at the recloser control cabinet is proposed.

This research aims to investigate resonant modes in electric power systems with a traction load, as well as to study the cross-effect of the traction network and the external power supply network. Powerful non-linear loads represent one of the major reasons for the deterioration of the quality of electricity in high voltage networks. Among these loads are traction power supply systems, which have a significant effect on power supply systems with low values of the short circuit power. In the present study, a Matlab simulation model of a power supply system with a traction load was developed in order to investigate the effect of various parameters of the power supply system, such as the line length and the short circuit power of the external power supply system, on the resonant modes. Additionally, the effect of the spectral composition of currents in electric vehicles on the degree of voltage distortion in the traction and external networks was considered. Analytical expressions were obtained for the resonance frequencies in the "external network - traction transformer - traction network" system. Using the developed simulation model, an analysis of the resonant modes in the power supply system comprising a traction AC network and an external network was carried out. It is shown that voltage distortions in power supply systems with a traction load result from non-sinusoidal currents and the resonant modes of the traction network emerging in the external power supply system. When studying resonant modes, the traction power supply system and the external network should be considered as a single system. The frequency response characteristics of this system have resonance maxima, the frequency and amplitude of which depend on the parameters of both the traction network and the external power supply system.

In this paper, an algorithm is presented for enabling software to predict the trajectory of machining allowance removal, which will provide the possibility to create various surfaces by the turning process. Economic realities in the manufacturing sector of the economy constantly push manufacturers to reduce production costs simultaneously increasing quality indicators. The analysis and application of an innovative processing method allows a fresh look at the application and modernisation of modern equipment available at a factory and expansion of its technological capabilities by reducing the number of operations performed by various types of metal-cutting equipment, as well as by automation of the process of obtaining the required surface configuration with the possibility of quick readjustment, which results in increased productivity and an expanded range of products. A pattern of surface obtaining under turning with a rotating tool is developed. The formulae for complex asymmetric product profile production are derived. The algorithm is compiled and the software code is developed in the Scilab environment for modelling in order to obtain the cutting tool movements along a complex path and its analysis. The tool movements per one revolution of the workpiece are calculated and a model of the tool trajectory is constructed. A table of profile modelling data obtained at various rotation speeds of the tool and workpiece has been compiled. The presented algorithm and algorithm-based software allow the trajectory of machining allowance removal to be predicted, which can facilitate the production of various surfaces by turning, e.g. ellipses, polyhedrons, cams in the form of flat spirals, etc.

The aim of the study is to develop an installation for increasing the hardness of the surface layer of cylindrical low-carbon steel components. An argon-arc welding apparatus was used as a plasma-arc source. The movements of the burner and the workpieces are provided by a numerical control to perform specific operations according to preprogramed commands, i.e. the unit operates during a work cycle according to a specially-designed program without operator intervention. Thus, the setup is designed for processing parts having complex geometric shapes to a given tolerance. For carburisation, a paste composed of graphite, sodium silicate (waterglass) and water was used. The waterglass is dissolved in water; then, after drying, a colloidal solution is formed with graphite powder. The layout of the installation was elaborated and the main components were selected. The installation comprises the following components: a personal computer for process control; a TIG 250P power source; a plasma arc source; guides fitted with mechanisms for ensuring the movement of tables and burners located on them; a table for affixing flat workpieces; a table equipped with a jaw chuck for securing and rotating cylindrical workpieces. The personal computer used to control the entire process of increasing hardness comprises a key element in the operation of the installation. The results of the study of workpiece samples following processing by means of the designed installation are presented. The installation provides a controlled process for heating the surface layer of a metal workpiece. A light-grey layer of increased hardness is observed on the surface of the hardened metal. The hardness of this layer achieves up to 50-55 HRC, while the roughness is in the range of 3-10 microns. Due to the high accuracy of the plasma carburisation process automated by means of the developed installation, it is possible to significantly reduce the carburisation time and ensure uniform quality properties of the carburised layers.

In order to obtain the desired shape of long size panels and skins for the aerospace industry, the technology of shot peen forming with subsequent grinding with a flap wheel is successfully applied. This includes sequentially-performed operations of shot peen forming, grinding and shot hardening. In the present study, a special UDF-4 (shot peen forming equipment of the 4th version of modernisation) installation, designed and manufactured for this purpose, is described. The latest version of this installation is equipped with a numerical program control system and a turret grinding head with 4 flap wheels for optimising grinding operations. Grinding of double curvature surfaces involves the use of both cylindrical and shaped wheels. The present paper considers the option of using cylindrical flap wheels. Depending on the curvature and width of the panel or skin under grinding, the possibility to select a wheel of desired width and shape has significantly expanded the technological capabilities of the installation. At the same time, there is a problem of selecting a specific flap wheel for the current processing conditions. The purpose of the work is to select the width of the cylindrical flap wheel for the turret head when grinding double curvature surfaces. The paper provides the research results of the influence of ground surface curvature for four values of the wheel width at the different values of hold-down (the amount of wheel deformation depending on its pressing to the machined surface). In order to evaluate the possibilities of efficient grinding of large size outer-forming parts, the analytical and graphic dependences between the values of hold-down deformation and panel curvature for specific values of the width of selected wheels are presented. According to the given data, a flap wheel of 100mm width can be used for processing panels with the curvature radius from 2.5 m or more at any value of flap hold-down (from 0.5 to 3.5 mm). A flap wheel with the width of 200 mm can be used for processing of panels having a curvature radius of more than 10 m in the considered range of flap deformation, while a flap wheel with a width of 300 mm can be used for processing panels with a curvature radius of more than 22.5.

In the present study, issues affecting the detection of internal defects, such as thin voids, adhesion failure and soldering / welding defects in multilayer construction materials, are considered. The approach involving thermal imaging control and data processing programs can be used to investigate materials including plastic and thin-film products, metallic multilayer products and carbon-fibre reinforced plastics. Results of applying the dynamic thermal tomography method to identify internal defects in both multilayer and homogeneous products are presented. The study assessed the use of the described method to detect thin internal defects in the form of voids and poor-quality gluing of layers in multilayer products. In the experiments, the FLIR E60 thermal imager and FLIR Tools software environment were used in conjunction with the ThermoFit Pro software program. Dynamic thermal tomography is acknowledged to provide for accurate evaluation of internal defect parameters. Maxigrams and timegrams used in thermal control applications are applicable in defectometry due to the dependence on the depth and thickness of the defects. In this case, a one-dimensional algorithm for determining defect parameters is used with the disregarded defect transverse dimensions. Thus, the algorithm is based on a combination of maxigrams and timegrams. During the study, the results of thermal imaging control are obtained in the form of an infrared image sequence. This sequence was processed in the ThermoFit Pro software for both timegram and maxigram construction. Based on the results obtained, the advantages and disadvantages of the studied method, as well as the software for thermal imaging control, were formulated. The method of dynamic thermal tomography is feasible for wide application in control of various material multilayer products of such sectors of industry as the aircraft engineering, as well as the manufacture and control of composite materials.

This simulation study was aimed at developing rational recommendations on the selection of tool coatings when turning 09H17N7YU corrosion-resistant specialised stainless steel. The performed simulation, carried out in the Deform software environment, comprises the parameters of temperature, stress and deformation. The simulation results were compared with the operational parameters, i.e. the extent of tool material wear. Simulation modelling is performed for 11 various types of coatings on a VK8 hard-alloy substrate. A hard-alloy tool of the VK8 brand is taken as a base tool material. The other tool materials differ only in terms of the architecture (design, composition, structure and coating method) of the coatings applied to the VK8 substrate. Tool materials are distributed according to their rational application for processing 09H17N7YU corrosion-resistant specialised stainless steel, which has no analogues in terms of its physical and mechanical characteristics and operational properties. The application range of this steel is constantly expanding. It was found that the most rational multi-layer tool coatings for longitudinal turning of 09H17N7YU steel are TiCN (5 µm) + (TiAl)N (3 µm) + Al₂O₃ (5 µm) + TiC (5 µm); Al₂O₃ (2 µm) + (Ti)CN (5 µm) + (TiAl)N (3 µm) + TiN (3 µm); (TiAl)N (3 µm) + Al₂O₃ (3 µm) + (TiAl)N (3 µm) + Al₂O₃ (3 µm). The results of simulation modelling were tested experimentally. A good match of results was achieved (the regression coefficient varies between 0.9806 and 1.0). By means of the computer simulation, the most rational tool coatings required for turning of 09H17N7U specialised stainless steel were identified and experimentally proved.

In this work, we aim to calculate gains in the economic efficiency of primary aluminium production (on the example of RUSAL Krasnoyarsk JSC) when increasing the use of alumina obtained from sintering nepheline raw materials at the Achinsk alumina plant. A series of experiments was conducted to determine the optimal conditions for cooling of nepheline cakes using a SNOL 6.7/1300 laboratory muffle furnace. An industrial sample of limestone-nepheline-soda mixture was used as a research object. In order to determine the phase composition of nepheline cakes, a DRON-6 diffractometer (Russia) was used. The sintering conditions of charges were as follows: the heating rate of the sample charge was 10.4ºC/min; exposure at the temperature of 1250 ºC was 15 minutes. It is determined that the effect of the cooling rate on the content of α'-modification in 2CaO.SiO2 cake is inverse. The analysis of phase data does not demonstrate any changes in the qualitative and quantitative composition of other phases (sodium aluminate, calcium ferrite, carnegieite) that make up the cake structure. This indicates that solid-phase 2CaO.SiO2 recrystallisation reactions develop exclusively under cooling. The obtained dependences of modification content variation upon cake cooling with different rates show that there is a characteristic change in the slope of the curve, which reflects the content of α'-, β-forms of 2CaO.SiO2 in cakes at the temperature of 1000ºС for all cooling rates. It was found that slow cooling (at the rate of no more than 15°C/min) of nepheline cake up to only 1000ºC is sufficient for the completion of 2CaO.SiO2 transition from α'- to β-modification. The results of the conducted technological leaching of the obtained cakes and the processing of experimental data of cake cooling (at 1250-1000 ºC) for the content of 2CaO.SiO2 α'-form in cakes demonstrate that a 1% decrease in this modification content provides a 0.2% increase in alumina extraction. The expected annual effect of reducing the production cost of 1 tonne of primary aluminium due to savings on purchase of imported alumina amounts to 55.83 million rubles.

The study is aimed at the urgent problem for disposal of accumulated copper-containing enrichment by-products. The equilibrium distribution of Pb, Zn and S was determined in the "Cu-Zn intermediate product - CaCO₃ - C - sulphide-metal product - gas phase (Pb, Zn sublimates)" system corresponding to the calcination conditions of the copper-zinc sulphide intermediate product. In order to solve this problem, the thermodynamic modelling method was applied using the HSC Chemistry 6 software application package (Finland). A copper-zinc sulphide intermediate product with the following composition (wt%) was taken as the initial reagents: Cu - 10.14, Zn - 22.70, Pb - 0.49, Fe - 21.00, S - 36.29, CaO - 0.51, SiO₂ - 2.49, Al₂O₃ - 5.47, having 80.0 wt% C coke and 94.91 wt% CaCO₃ limestone. Additionally, the component equilibrium distribution in the copper-zinc intermediate product between the initial reagents and the products of calcination was simulated, depending on the temperature characteristic of solid-phase reactions. A thermodynamic modelling of the component solid-phase equilibrium distribution in the mixture under study at a temperature of 1150 ºС was carried out. The possibility of 90% zinc extraction into the gas phase, metallisation of iron and the formation of CaS was demonstrated. Following dezincification, the solid residue was established to contain CaS, Fe_met and C in amount of 48.7, 15.0 and 3.4 wt%, respectively, with the possibility of application for autogenous smelting slag depletion in the Pobeda smelting unit. The performed thermodynamic modelling of metallurgical systems - in particular, the calcination of copper-zinc materials mixed with limestone and coke - demonstrated the possibility of solving optimisation problems using information technologies. The technological efficiency of a sulphide-metal product application is evidenced by the example of an electric furnace used to reduce the converter slag composed by Cu, Zn, Fe and SiO₂ in amounts of 3.75, 6.64, 43.79 and 21.88 wt%, respectively. The matte (> 20% Cu) with a copper recovery of 96% and dump slag (0.3% Cu) was obtained. The consumption of sulphide-metal product in this case comprised 15% of the slag weight.

This study seeks to obtain new information on the behaviour of oxidised and sulphide ores in the Ozernoye deposit during their thermal decomposition. Lead and zinc are produced from complex polymetallic lead-zinc ores containing other valuable components, such as copper and silver. The market demand for zinc and lead remains high both in Russia and globally. In this regard, the development of the Ozernoye polymetallic deposit (Republic of Buryatia, Russia) is of particular importance, since its resources can cover the domestic deficit in zinc and other non-ferrous metals. However, in terms of mineral and phase composition, the ores in this deposit are heterogeneous and complex, containing an increased fraction of refractory ores with finely disseminated sulphide minerals and a high content of oxidised forms. The required efficiency of processing finely disseminated sulphide and oxidised lead-zinc ores can be achieved by a new method on the basis of steam-gas technologies allowing the selective decomposing and activation of complex mineral assemblages in a single technological step. A differential thermal analysis was performed using a Netzsch STA 449 F1 Jupiter instrument. Thermogramms were recorded in a platinum crucible under argon atmosphere and linear heating to 850оС. The conducted thermal analysis of technological ore samples from the Ozernoye deposit showed that, in terms of weight loss, the thermal decomposition of oxidised ores consists of two stages - goethite dehydration at 246-318оС and carbonate and plumbojarosite decomposition at 360оС and higher. However, the decomposition of sulphide ores undergoes three stages, i.e. a sequential decomposition of various carbonates and thermal dissociation of pyrite followed by the formation of magnetite and the reduction of sulphur. The thermal effects of the reactions and the temperature decomposition ranges of the main compounds in the studied samples were determined.

A study was carried out into the effect of the loading method and surface distribution of charges at the furnace top on the parameters of carbon reduction of silica in submerged arc furnaces. In the study, the direct physical modelling method was applied. The experiments were carried out under large-scale laboratory conditions using a 200 kVA single-electrode furnace of the Zh. Abishev Chemical and Metallurgical Institute (Kazakhstan). An additional dynamic industrial experiment was conducted in the 30 MVA furnace of Tau-Ken Temir LLP. In a large laboratory furnace, two smelting campaigns were performed, each using different approaches to the treatment of the furnace top. In the first campaign, no balancing in the energy and material flows of the system took place, resulting in forced slipping and an uncontrolled feed rate of the charge. The second campaign, conversely, included the specified balancing measures. A similar study took place over 3 days under industrial conditions. The following technological parameters were empirically determined: specific electricity consumption, furnace average active power and performance, as well as power per unit area of the furnace hearth. The Fe, Al, Ca, Si material balance of the smelting was compiled. In order to assess the load balance, the concept of charge excess in relation to charge demand at the current furnace power was used for the first time. This concept value was determined as the ratio of number of batches actually loaded relative to the theoretically-calculated number ensuring the harmonisation of material and energy flows in the furnace. As a result of the research, an increase in the interval between the furnace top treatments up to 30 min and maintenance of harmonisation between material and thermal flows in the ore smelting furnace was established for increasing silicon extraction efficiency by 10-15%. In addition, oscillations in the phase current were stabilised. The proposed balancing concept was established to support the rapid elimination of crisis conditions in an industrial furnace.

The paper represents the results of studying certain physicochemical patterns occurring during hydrochemical oxidation of non-ferrous metal sulphide minerals in nitric acid media. The study was aimed at establishing the thermodynamic probability of the occurrence of particular interactions and determining the most favourable conditions for effecting processes in given modes. Changes in the Gibbs energy and the logarithm of the reaction equilibrium constants at various process temperatures are calculated to assess the possibility of various reactions between nitric acid and the main minerals present in sulphide raw materials of non-ferrous metals. For the purpose of visualising thermodynamically stable compounds when changing the oxidising conditions of the studied heterogeneous systems, Purbe Eh-pH diagrams were constructed. In order to obtain most accurate prediction of obtaining the necessary interaction products of nitric acid and the studied sulphide minerals, the equilibrium component distribution was calculated for liquid and solid phases of the studied systems. All thermodynamic calculations were performed using the HSC Chemistry software (Finland). As a result of calculations for the Gibbs energy change and the logarithms of the interaction equilibrium constants of sulphide minerals with nitric acid, the significant thermodynamic probability of the reaction occurrence with the formation of the desired compounds is established. By constructing the Purbe diagrams, the necessary conditions for the occurrence of certain interactions and stable state of the detected products across a wide range of potentials and pH values of the heterogeneous systems under consideration are established. The calculations of the component equilibrium distribution in the studied systems confirmed the results of the thermodynamic calculations, relating them to the real hydrochemical conditions of nitric acid leaching in terms of acid consumption for obtain the desired products. The performed study allows an assessment of the reaction progress and the formation of certain products during the interaction of the raw material main components with nitric acid carried out from the perspective of thermodynamic patterns.