Dehydration of mineral raw materials on a vibrating screen occurs as a result of the passage of liquid through the cells of the screening surface. With fine and ultrafine screening, this process is hindered by the surface tension of the liquid. None of the screening theories makes it possible to determine which vibration excitation modes ensure dehydration. With the help of numerical experiments on a mathematical model, the influence of vibration excitation modes on the intensity of the passage of liquid through the cells of various screening surfaces during dehydration on a vibrating screen was studied. In doing so, two tasks were solved: 1) determination of the amplitude and frequency of vibration excitation, when the required balance of water and the size of the cells of the screening surface are set; 2) determination of the remaining water on the screening surface depending on the cell size of the screening surface, the amplitude and frequency of vibration excitation. The developed mathematical model made it possible to solve both problems. On the basis of calculations and analysis, rational range of mode parameters of the vibrating screen for effective dehydration of various screening surfaces was established. The calculation algorithm is implemented on the basis of a mathematical model in the PC program «Sifting Surface» in C ++ with the connection of mathematical libraries and «Excel». The results of calculations, demonstration of the possibilities of various screening surfaces and modes are shown in the figures, which show the dependences of the residual water on the amplitude and frequency vibration excitation parameters. It is established that the vibro-impact effect, in comparison with the harmonic effect, provides better results in cleaning the cells from the liquid retained in them by surface tension forces, under less intensive modes. The results obtained will be used in the development of a mathematical model of dehydration and a method for calculating technological parameters that ensure effective removal of liquid during fine and ultrafine screening of mineral raw materials, as well as to determine the rational design and dynamic parameters of the screen.

A high degree of industrialization and urbanization characterizes the modern working environment. As a result, there is constant contact with various man-made factors (dust, smoke, fog or gas, steam), the concentration of which in the air is higher than the maximum permissible concentrations. The purpose of the paper is to develop a procedure for assessing risks when working with chemicals, which allows substantiating the selection of adequate means of respiratory protective equipment to protect workers when performing production tasks. Methods. To substantiate the selection of the type of respiratory protective equipment when working with chemical substances, a five-step approach to risk assessment is used. The approach is based on classification of chemical substances in terms of “R-phrase”. This means risk factors that arise while working with hazardous substances described in Annex III of the EEC Directive 67/548/EEC. Together with the recommendations of the Approval of the Minimum Requirements for Safety and Health Protection When Employees Use Personal Protective Equipment at the Workplace (NPAOP 0.00-7.17-18), it allows to assess the occupational risk of danger from chemical substances taking into account their toxicity and substantiate the type of respiratory protective equipment. Findings. An approach was developed to substantiate the selection of the type of respiratory protective equipment based on the hazard risk assessment. The correlation between the hazard group according to the “phrases” of a chemical substance and severity of the worker’s health loss was defined. An algorithm for selecting respiratory protective equipment while working with chemical substances was proposed. An example of assessing the impact of sulphur dioxide during the work of miners with a recommendation of the type of respiratory protective equipment was considered. Originality. A correlation between the protection class of the respiratory protective equipment and toxicity of the chemical substance according to the R-phrase was determined. Practical value. An algorithm for selecting respiratory protective equipment to protect workers from chemical substances was proposed. The algorithm is based on five steps making it possible to develop an appropriate form of substantiation for the appropriate type and class of respiratory protective equipment.

The Volmer diffusion coefficient of methane adsorbed in the micropores of coal in the elastic zone of the coal seam bearing pressure, which normally is under conditions of significant compressive stress, was calculated with taking into account the energy of the methane sorption connection with coal, the energy of Volmer diffusion activation in the porous space of coal, and the stressed state of the elastic zone with its influence on the change of Volmer porosity. During the calculations, such parameters as the diameter of Volmer micropores and the length of the descending branch of the bearing pressure diagram were varied. As a result of the approximation of these calculations, both pairwise dependences of the Volmer diffusion coefficient on the listed parameters and its multifactorial relationship with them were established. Therefore, it is concluded that the process of methane diffusion in the elastic zone of bearing pressure is not blocked by the rock pressure, as previously thought, but is actively developing. The diffusion of free methane will be determined by the established regularity of changes in the Volmer diffusion coefficient in the elastic zone of the coal seam bearing pressure. The calculations show that as the distance from the maximum of the bearing pressure increases, the Volmer diffusion coefficient of methane in the coal seam increases, which is due to a decrease in the pressure of rocks in the descending branch of the bearing pressure diagram. However, this growth is not great due to the weak compressibility of pores. Therefore, for pores of the same diameter, the Volmer diffusion coefficient in the elastic zone of the coal seam bearing pressure for the given mining geological conditions can be considered a constant. For depths of, for example, 1000 m and pore diameters of 10 Å, the value of the Volmer diffusion coefficient will be approximately 3.77·10-8 m2/s. This confirms that methane gas release is caused not only by filtration of free gas, but also by Volmer diffusion of adsorbed methane. In turn, the reserves of the latter are known to be the main reserves of methane in coal. Therefore, the established regularity makes it possible to more accurately calculate the volumes of methane, which will be released from the coal massif during mining operations, in order to assess safety of conditions for coal deposits mining and to develop technologies for coal mine methane production.

The rate of constrained fall of mineral particles in suspensions of different densities is necessary for calculating the design and operating modes of gravity concentrating equipment. During hydraulic classification and separation, a mixed, laminar-turbulent, flow regime is observed in real pulps. There are no theoretical velocity formulas for such a regime, and most of the known semi-experimental and experimental formulas have limited application. This article proposes a new method for comparing different formulas with each other in a wide range of suspension densities. The method uses an analytical calculation of the hydraulic characteristics of the medium - porosity, concentration and viscosity. What is new is that all these characteristics depend on only one indicator - the density of the suspension, which is easily determined in practice by weighing a pulp sample. In these calculations, the weighted average density of heterogeneous particles in suspension is used. A feature of the method is the approximation of the analyzed calculation formulas to the conditions of free fall in order to obtain only one control point and compare it with known experimental data. This method allows to set the limits of the application of formulas depending on the density of the suspension. The choice of a more precise formula is necessary for the design hydraulic devices for the classification and separation of mineral suspensions and finely ground composite raw materials. The application of this method for the most common formulas of Ergan and Todes-Rosenbaum is shown. It was found that the latter formula іs actually not suitable for dilute suspensions with a density below 1.65 g/cm3. A new linear equation for calculating the rate of constrained particles deposition is proposed, which provides high accuracy in a wide range of suspension densities. The resulting equation has a simple form and, together with an analytical calculation of the characteristics of the medium, forms a system of linear equations for calculating the rate of constrained particles deposition of any size and density in mineral pulps of different densities. The calculation of the velocity of constrained settling and the ascent of particles is the basis for the design of hydraulic classifiers and separators for mineral dressing. Such calculations are necessary for determining of hydraulic devices optimal modes and monitoring indicators during their operation.

Today, hydrogen is recognized as a promising fuel, which is characterized by high heat generation and combustion temperature. It is also characterized by environmental safety due to the fact that no greenhouse gases are formed during the combustion of hydrogen. There are various methods of hydrogen production: traditional methods, which include electrolysis of water and conversion of hydrocarbons, and thermochemical ones. A cheap method of hydrogen obtaining from natural gas and coke is accompanied by the carbon oxides formationю Thermochemical methods are require high temperatures (up to 1000°C). The method for hydrogen production by electrolysis of aqueous solutions of alkali metal hydroxides is the most energy-intensive. However, it is considered one of the most promising in the European Union. To reduce energy consumption for hydrogen production, the authors suggest replacingthe positive electrode, which normally produces oxygen, with a dissolving anode with an equilibrium potential lower than that of oxygen, such as an iron electrode. In this case, with such a combined electrochemical method, the decomposition voltage in the system will be 0.44 V against 1.23 V with traditional water electrolysis. The overvoltage of iron dissolution in a chloride medium is several tens of millivolts. However, the potential difference between the anode and cathode ΔU becomes smaller than the equilibrium potential difference ΔE0 = 0.44 V. This research aims to substantiate the choice of the composition and concentration of electrolytes: catholyte –to ensure conditions for reducing energy consumption for hydrogen release; anolyte – to prevent passivation of the iron anode, which can lead to the oxygen release. This work results in research of the cathodic process of hydrogen release in the following solutions: 1 M (= mol/L) NaCl with the addition of 1 M hydrochloric acid in the amount of 5, 10, 15, 20 mL. Platinum is used as a cathode for the electrolysis process. The anode material is an iron, St3 grade. It has been found that in the range of changes in the composition of the electrolyte from neutral (1 M NaCl) to acidic (1 M HCl), a change in the mechanism of water discharge is observed. In a neutral medium, the discharging occurs according to the Heyrovsky mechanism, and in an acidic medium - according to the Volmer mechanism. The choice of the anolyte composition and concentration is complicated by the need to provide an acidic medium containing chlorine ions to prevent passivation of the anode. The acidity of the solution must be at least 3 for the successful extraction of dissolution products of the iron anode.

In the article, the authors establish and analyze the relationship between the contents of germanium, toxic elements and the total sulfur content of the coal seam of the Dniprovska Mine field. In the process of the research, in order to achieve the purpose set in the work, correlation and regression analysis was carried out using methods that are implemented in one of the most popular professional mining and geological information systems for 3D modeling of deposits, statistical processing of mining and geological data and construction of actual mine workings and planning of mining operations – Micromine, and their analysis in geological concepts was performed. It is proved that the distribution of germanium, toxic elements and total sulfur content in the coal seam с8н of the Dniprovska Mine field differ from the Gauss-Laplace and lognormal distributions. It is established that analyzes of graphs of polynomial pair regression models of the relationship between the normalized concentrations of germanium and the contents of toxic elements make it possible to identify different areas of their concentrations, which differ significantly in their nature. It is substantiated that the minimum contents of arsenic, germanium and total sulfur in the coal seam с8н of the Dniprovska Mine were jointly accumulated at the syngenetic stage of its formation. A decrease in the concentrations of germanium with an increase in the content of fluorine, mercury, arsenic, and total sulfur is associated with epigenetic processes, which in this particular case lead to the outcrop of germanium. The synchronous increase in the contents of germanium and beryllium in the area of their low and abnormally low concentrations is due to the compatible accumulation of these elements at the syngenetic stage of formation of the coal seam, and their increase in the area of maximum contents is caused by the manifestation of the empirical regularity of the “Zilbermints law”. It was established that there is a very low correlation between the concentrations of germanium and toxic elements and total sulfur, therefore, the extraction of germanium from the coal seam will not be accompanied by their significant accumulation during technological processes. It is proven that for a more realistic assessment of the central tendency of the content of germanium, toxic elements and total sulfur, it is necessary to use the median values instead of the median values. The influence of syngenetic and epigenetic processes on the nature of the relationship between germanium concentrations, toxic elements and total sulfur content in the coal seam с8н of the Dniprovska Mine was revealed.

The development of efficient and environmentally friendly technological processes for processing zircon concentrate is an urgent problem in the technology of producing reactor-pure zirconium and hafnium used in nuclear power. The review presents the environmental, technical and economic characteristics of zircon decomposition processes using existing industrial technologies and provides data on the environmental safety of each technology. It is shown that current industrial technologies do not meet the criteria of sustainable development and allow emissions of toxic reagents into the environment. New applications of particularly pure zirconium and hafnium compounds which have emerged in recent decades, with impurity content of 10-3–10-5%, require less corrosive reagents than chlorine and fluorine, new resource-saving processes and equipment. Today, technical zirconium oxide with a purity of 98% is the main industrial product of zircon processing, but it allows for losses of hafnium, scandium and silicon. This is equivalent to financial losses of over USD 150 million per year. Based on the analysis of promising halogen-free technologies, a new integrated zircon processing technology is proposed which allows producing scarce hafnium, scandium and silicon compounds along with reactor-pure zirconium and its high-purity chemical compounds. The chemicals consumed in the zircon processing process are utilized in the production of mineral fertilizers, eliminating environmental pollution. The use of the highly efficient refining extraction process in a nitric acid environment using centrifugal extractors with an available tributilphosphate extractant allows us to obtain reactor metals with a purity of 99.95%. The production of high-purity zirconium, hafnium, scandium and silicon oxides meets the demand for non-nuclear products, which expands the volume of integrated zircon processing and meets the growing market demand for new functional materials. The integrated approach to zircon processing can reduce the cost of zircon by producing by-products, recycling consumed reagents and eliminating non-recyclable solid and liquid waste. This will ensure environmental protection even with relatively small volumes of reactor-pure metal production.

Currently, vibrating jaw crushers show a fairly high efficiency of the technological process. An extensive amount of research carried out at the Dnipro University of Technology made it possible for the first time to substantiate the possibility of using a vibratory jaw crusher with a vertically located chamber and a pendulum suspension of the jaws as an independent grinding unit for the production of powder materials. The high-frequency impact nature of the load on the material implemented in vibrating jaw crushers made it possible to reduce the energy consumption and metal consumption of the plant, to increase the degree of crushing, which can reach the value i > 100. However, the specifics of the process of interaction of the material with the surface of the jaws in the vertical working chamber and the features of its unloading remain unknown. The refinement of this process was carried out by an experimental method on a laboratory sample of a vibratory jaw crusher ВЩД-130 using high-speed photography. The crusher includes the main elements: a body mounted on elastic elements, crushing jaws, articulated with the body by means of axes. The side surfaces of the crushing chamber are limited by transparent glass walls rigidly connected to the crusher body. The vertical movement of the jaws was determined by the readings of the vernier. The starting material was pieces larger than 40 mm and large bulk material with a grain size of 10…15 mm. An analysis of the nature of the movement of material throughout the crushing chamber showed the need to consider the chamber of a vibratory jaw crusher as two interconnected zones: crushing and grinding. Further studies were carried out for each zone.The productivity of the crushing zone is determined by a known method. It is necessary to create a rational profile of the working surface of the jaws on the basis of additional studies. Studies of the grinding zone made it possible to obtain a physical picture of the interaction of the material with the jaws over the period. In the lowest position, at the initial moment of unloading, the speed of the finished product is practically zero. When determining the productivity of the grinding zone, it is advisable not to take into account the unloading of the material at the initial speed.