The paper deals with the experimental studies of the quality of electrical energy in the stand alone system of power supply of one of the enterprises of the oil and gas industry on 0.4 kV buses of 6/0.4 kV substation as well as estimates the harmonic composition of current and voltage in various nodes of the electrical network. Numerical analysis of the distortion degree of the voltage and current waveform in the distribution network is performed using instrumental measurements by means of Resource-UF2M power quality analyzer and Hantek DSO 1102B digital oscilloscope. The analysis is given to process flow disruptions caused by the presence of harmonic distortions in the power supply system. Failure statistics for various kinds of electrical equipment exposed to higher harmonics has been collected on the base of the obtained operational data. Higher harmonics of current and voltage significantly worsen the operating conditions of the main elements of the energy system power equipment, have an adverse effect on relay protection, automation, telecontrol and communication devices, which according to the presented statistics of emergency events leads to serious technological failures and significant economic costs.

Today, the number of distributed generation facilities in the world is growing mainly due to renewable energy sources. However, the integration of a large volume of distributed generation (on the basis of wind power plants) into the existing electric power systems of power grids is associated with a number of significant problems. A comprehensive study and absolute solution of these problems require to conduct a detailed simulation of real electric power systems, which is impossible with the use of existing means. Therefore, for this purpose, the article proposes to use an alternative solution - an All-Mode real time modeling complex of power systems (AMRTMC PS). The conducted experimental studies involved the comparison of the modeling results of a small test circuit of electric power systems obtained by means of the AMRTMC PS and a widely used digital software and hardware complex RTDS. The article partially presents the results of complex comparison when reproducing similar models of electric power systems in both complexes, which confirm the adequacy of the information about the processes in equipment and electric power systems in general obtained by means of the real-time all-mode modeling complex of electric power systems. It is proved that the further application of the real-time all-mode modeling complex of electric power systems as a tool for detailed and adequate modeling of real electric power systems with distributed generation will provide complete and reliable information about normal and abnormal quasi-steady-state and transient processes in electric power systems with distributed generation, which is necessary for reliable and effective solution of design problems, research and subsequent operation of electric power systems with distributed generation.

Abstraсt: The article proposes methods predicting the distribution of harmonic components of voltages and currents in three-wire power transmission lines operating in the mode of electric energy transmission to consumers. It is shown that the transmission of electric energy to consumers is provided by three pairs of waves of an electromagnetic field, while this energy transmission rate is determined by the primary parameters of the corresponding power transmission line. The electrical energy transmission rate through linear wires of the power transmission line is determined by the propagation velocity of electromagnetic field waves in a material medium. It is shown that the wavelength of the electromagnetic field and its propagation velocity along the linear wires of the power transmission line are much less than the wavelength and the propagation velocity of this field in vacuum. An example of calculation and visual determination of the electromagnetic field wavelength in linear wires of a three-wire power transmission line is given. A propagation diagram of electromagnetic field wave amplitude values along a linear wire of a three-wire transmission line is presented. Electrical energy transmission through the three-wire power transmission line is a complex oscillation process. This is confirmed by a graphical interpretation of phase voltage distribution along the three-wire power transmission line. It is noted that electrical energy transmission through a linear wire of a homogeneous section of the three-wire power transmission line can be represented as a propagation of the resultant wave obtained due to the superposition of three incident and three reflected waves of the electromagnetic field. Illustrations of amplitude-frequency characteristics for voltage and current are presented.

Absract: The study is given to the normal vector of the power hypersurface of power system steady states. The interrelation of the components of the normal vector is determined through incremental transmission loss coefficients. The analysis of the normal vector components has revealed that in the marginal state of the power system the component of the normal vector of slack bus active power equals zero, and the incremental transmission loss coefficient of the slack bus active power is one. Therefore, any attempts of the slack bus to support the power system active power balance in the marginal state are fully compensated by the associated power losses. In real power systems, variation of slack bus location makes this steady state non-marginal. The only power system where the marginal state does not depend upon a slack bus location is a lossless one.

This paper carries out optimization studies of the 660 MW coal-fired power unit for elevated steam parameters by the criterion of maximum net efficiency and minimum specific investment. The dependence between the power unit efficiency and the lowest specific investment is built. Taking into account the need for accounting a large number of coal-fired power unit parameters the optimization studies were carried out using gradient methods of nonlinear mathematical programming. Due to the large number of calculations the computerized programming system (CPS) computational environment is used. The maximum efficiency obtained as a result of optimization calculation is 47.74%. The corresponding specific investment equals 3545.7 $/kW and the initial steam parameters are 35.4 MPa, 657/613^оС. The minimum specific investment is 1884.6 $/kW. The corresponding efficiency equals 42.08%. The initial steam parameters are 15.5 MPa, 613/540^оС. The 660 MW coal-fired power unit was optimized for elevated steam parameters by the criterion of maximum net efficiency and minimum specific investment. The dependence of the minimum specific investment on power unit net efficiency was obtained. It is shown that the minimum specific investment was obtained at low pressure and relatively high temperature of the main steam.

Use of coal as a main fuel at thermal power plants (TPP) and significant wear of TPP boiler equipment cause the relevance of environmental aspect consideration when organizing rational energy supply to consumers. Hence, the purpose of this study is to propose a methodical approach for planning the development of regional thermal power plants in terms of environmentally friendly energy supply. The proposed approach is oriented at using the best available technologies, based on expert appraisals and estimation methods of investment project efficiency. The object of research is described. A multistage algorithm of regional TPP development planning is presented in terms of environmentally friendly long-term energy supply. This algorithm is designed to be built in the system of economic and mathematical models for predicting the development of the fuel and energy complex. A methodical approach ensuring environmentally friendly long-term energy supply has been proposed for planning the development of regional thermal power plants.

The article considers the possibility of using thermodynamic indicators of ideal (similar to the Carno heat machine) and idealized analogs to study real processes in various sectors of economy. These indicators include ideal and idealized efficiency coefficients, theoretical and minimum required energy/exergy costs of process implementation. The methods of their determination are presented and it is shown how these indicators can be used to estimate the thermodynamic efficiency of the process, theoretical potential and resources of energy saving when improving it and making long-term predictions (more than 20 years) of energy costs. The developed methods are illustrated by the examples of researches of metals and some inorganic and organic substances production. The analysis is given to the tendencies in the change of specific energy consumption for aluminium production by the Hall-Heroult method during the whole period of its use. The given graphs prove that process current energy costs are asymptotically close to the costs of its ideal analog (real efficiency is close to the efficiency of the ideal process). This means that the process should be replaced, i.e. it is necessary to switch to a new aluminum production technology. The calculation procedure of the minimum required and maximum (maximum degree of process idealization) energy (exergy) costs per product is shown by the example of metal and chemicals production by different technologies. The subsequent extrapolation of the efficiency of these processes allows to make a long-term prediction of the volume and structure of their energy consumption in the absence of reliable statistics. Such forecasts provide quite accurate results, since they are based on the fundamental laws of thermodynamics. The involvement of the second principle of thermodynamics using the concept of "exergy" in these studies further increases the level of reliability and significance of the results obtained.

Significant resources of high-quality coal in Mongolia provide the conditions for the development of coal production for domestic consumption by the energy sector as well as for the export of coal and electric power. High availability of coal reserves allows to consider coal as a reliable long term source of fuel. Among the sources of energy coal is the most important fuel in Mongolia. Retrospectively its percentage in primary energy resources consumption was from 60 to 80%. The main consumers of coal are power engineering facilities. The study uses the official statistics and the documents of official Mongolian and international bodies. The study has been conducted using system analysis methods. The article overviews the state of the Mongolian energy sector. The leading role of coal in provision power plants with fuel is shown. The coal reserves suitable for the use at Mongolian power plants are estimated. The main qualitative characteristics of coal deposits are given including calorific value, content of ash, sulfur and moisture. The construction projects of coal-fired power plants are presented. In the future, coal will continue to be one of the main fuel and energy resources in the fuel and energy balance of Mongolia. Further development of the Mongolian coal-fired power industry depends on the possibilities of increasing the volumes of geological exploration, development of transport and production infrastructures, growth of the internal and domestic markets of electrical power and mineral resources. The spatial location of Mongolia, availability of significant coal resources necessary for the development of the energy sector, the relevance and interest in increasing the domestic consumption of energy creates favorable conditions for Mongolia’s participation in the Asian Super Grid - Interstate energy associations in Northeast Asia. International companies are involved in the development and implementation of various projects related to coal, which significantly increases the opportunities for the development of coal-fired power industry in Mongolia.

The paper studies the mathematical model of the half-wavelength transmission line with intermediate power take-off. The methods of direct calculation of parameters of an equivalent circuit and a four-terminal network are used for the development of the mathematical model of the half-wavelength transmission line with intermediate power takeoff. The calculations are carried out using MathCAD. The presented results demonstrate the features of accounting the individual elements of the mathematical model of the half-wavelength transmission line, which are included in the appropriate power transmission nodes, and their effect on regime parameter calculation. It is shown that the wave character of line parameters variations should be taken into account for the complete and reliable calculation of the regime parameters in any point of the half-wavelength transmission line. Otherwise, the calculation results are contradictory. At the same time, the calculation of regime parameters in the intermediate points should consider that the parameters of long distance transmission lines have a distributed character while the nature of the included element parameters is concentrated.

The purpose of the paper is the experimental comparison of the application efficiency of multi-disk grinding heads forming and restoring the sealing surfaces of pipeline valves on example of the part simulating the “saddle” of DN 65 low pressure valve. Experiments on contact surface sealing in the gate valve are conducted with the use of grinding heads with three and five working disks. Increase in the number of working disks in multi-disk grinding heads from three to five has improved the quality of the processed surface by reducing the deviation from the plane for EFCO abrasive tool from 6.57 to 5.14 μm; for L251SM40 grinding cloth - from 8.14 to 7.14 μm, as well has decreased the average value of the roughness parameter Ra from (0.226 - 0.277 μm) to (0.087 - 0.148 μm) depending on the type of the abrasive cloth. An increase in the gradient of the friction coefficient at multidisc treatment improves the processing quality of sealing surfaces. Since the deviation from the nominal plane is decisive after processing, grinding of sealing surfaces is recommended to perform with the use of a 5-disk grinding head with EFCO abrasive cloth. This is confirmed by the formation of a closed zone of contact spots on the sealing surfaces of witness parts providing the tightness of the gate valve assembly of pipeline fittings. For sealing surface lapping, it is recommended to use a 5-disc grinding head with the use of EFCO abrasive cloth, which ensures the tightness of the gate valve assembly of the pipeline fittings.

The paper deals with the methodological foundation for the processes of estimation, adjustment, monitoring and changing of the dynamic states of mechanical oscillatory systems. The purpose of the proposed studies is to develop a method for estimation and variation of the dynamic properties of technical objects on the basis of additional ties introduction into basic mechanical vibrational structures. It is shown that such ties can be implemented by lever mechanisms introduced into the original structure. The methods of structural mathematical modeling are used, within which a mechanical oscillatory system is treated as a dynamically equivalent automatic control system. A method of mathematical modeling has been developed and technologies for constructing the transfer functions of the system have been proposed. The concept of inter-partial tie transfer functions is introduced on the basis of which a technology for determining analytical relationships defining the possibilities of obtaining vibration fields with specified properties is developed. The choices for vibration field adjusting parameters are offered. The features of dynamic properties and new dynamic effects reflecting the specificity of dynamic interactions of system elements are studied. The results of numerical experiments are provided.

The purpose of this work is comparison of the surface layer quality of samples treated by new hardening methods and by traditional rolling with a roller. The obtained results of the work are based on experimental studies where it was found out that the quality of the surface layer obtained by oscillating burnishing is higher than the one obtained by rolling but lower than the one obtained by transverse rolling with flat plates. Grain sizes change only in the surface layer, the central region practically is not subjected to plastic deformations and the grains do not change their sizes. The area of significant grain distortion extends to the depth of 0.1-0.2 mm with transverse rolling with flat plates and oscillating burnishing and to 0.1 mm under rolling with a roller. The microhardness and hardness obtained under oscillating burnishing is more than under rolling with a roller, but less than under transverse rolling with flat plates. The smallest deviation from roundness of cylindrical parts was obtained under transverse rolling with flat plates (2.9 times), and under rolling with a roller it is 2.1 times. The maximum axial residual stress is obtained under oscillating burnishing, then under rolling with a roller and transverse rolling with flat plates (1.8 times). However, the greatest tangential stress is formed under transverse rolling with flat plates, and the minimum stress under oscillating burnishing (1.3 times). Wear resistance of hardened samples is several times higher than the wear resistance of samples without hardening. The maximum wear resistance is characteristic of the parts reinforced by transverse rolling with flat plates, and the minimum wear resistance - of parts reinforced by rolling with a roller.

Abstraсt: The article studies heat transfer processes in the working space of the electric furnace firing modules in order to identify additional opportunities to reduce the energy intensity of bulk material firing when using a new heating system. The study includes the modeling of radiant energy transfer from heating elements to the heat-treated medium using a balance-flow method. In addition, a comparative analysis is given to new data and the data obtained earlier on previous modifications of heating systems of similar furnaces when burning vermiculite. The design of a new suspended heating system of firing modules of electric modular trigger furnaces providing high-quality swelling of vermiculite under the reduced by 22.1% specific energy has been developed. The surface temperature of the intumescent vermiculite granules has been calculated. The equation of heater and grain surface temperature relationship has been obtained at a steady temperature. The conducted researches have proved the efficiency of the new design of the suspended heating system of electric modular trigger furnace firing modules. The calculations showed that under otherwise equal conditions the application of the suspended heating system in the furnace modules provides a complete calcination of the vermiculite under reduced to 79.3 kW consumption of electric power.

Abstraсt: Machining operations are unavoidably accompanied with oscillations, which, in case of their coincidence with the natural oscillations of one of the elements of the system, can cause a resonance. The latter results in the premature failure of expensive equipment, tools and tool attachment, reduces the quality characteristics of the finished product as well as leads to rejects. Therefore, the question is raised on controlling the natural oscillation frequencies of the elements of the machine-tool system, a tool and a workpiece. Based on the finite element model of the machine-tool-device-tool-workpiece system oscillations the recommendations for choosing non-resonant rotational speeds of the milling machine spindle have been developed. The studies employed experimental, analytical, and finite element modeling methods with the use of Femap automated engineering calculation system. The experiments were carried out using Polytec measuring equipment, National Instruments LabVIEW software package, Sound and Vibration module. We have obtained the finite-element models of the device-tool-workpiece system oscillations, on the basis of which recommendations are given on setting the permissible spindle rotational speeds. The approach can find application in adjusting cutting modes when milling box-type workpieces or panel-type parts, whose workpiece geometric shape and weight differ significantly from the finished part ones.

The article studies the sorption properties of red mud, which is the waste of alumina production. Processing of slag is accompanied with the increased release of hydrogen sulfide into the atmosphere in the areas of near furnace slag granulation. This has an adverse effect on human health. The use of red mud as an absorber of toxic sulfur compounds contained in industrial gases can be an alternative to expensive lime and limestone. A laboratory installation of the granulation basin was assembled to study red mud sorption properties. Red mud pulp was used as a coolant with the ratio of S:L = 1:5. A high-temperature open-bottom furnace was used to melt blast furnace slag. Having reached the critical temperature, the molten material got into water and granulated. A portable device PGA-200 was used to determine the content of harmful compounds in the atmosphere of the installation space. The optimum ratio of the components of the red mud composition was determined for the maximum trapping degree of sulfur compounds, which was confirmed by its absorption activity. The sorption properties of the material were studied. It was found out that its high absorption capacity was determined by the proportion of calcium, magnesium and aluminum oxides to silicon oxide. It was determined that the modified granulated slag had improved technical properties including drying speed and granulation energy costs as compared to conventional granulated slag. Conducted laboratory studies allowed to conclude that red mud could be used as a new sorbent both for air purification systems and directly at the work site. The use of red mud as a slag granulation modifier has a great advantage over other granulation methods using calcium oxide and calcium hydroxide. The additive is not only a desulfurizing agent, but also serves as a valuable component for slag processing with its further application in construction industry, e.g. in the production of cement, expanded clay, etc., which improves product technical characteristics.

The article deals with the study of the influence of the electrolysis cell working space form (in particular, the hearth accretion buildup length) on the bath magnetohydrodynamic parameters under aluminum production by the electrolysis of cryolite-alumina melts. The methods of mathematical modeling with the use of Blums v5.07 and MHD-Valdis programs were applied to analyze the effect of the accretion buildup length on the electrolysis bath magnetohydrodynamic (MHD) stability resource and the maximum density of the horizontal currents arising in the metal melt. The models of the S-8BM electrolyzer were built in the program Blums v5.07 for different hearth accretion lengths (depending on the service life of the electrolysis cell). 13 variants of horizontal current distribution were calculated for the baths with accretion buildup length from 30 cm to 150 cm with a 10 cm pitch. The obtained results are presented in the form of dependences of the MHD stability resource and maximum density of horizontal currents on the accretion buildup length formed in the electrolysis cell during operation. The results of calculated variants of horizontal currents distribution have showed that high horizontal currents can be formed both in the case of accretion buildup spreading under the anode and in the case of a small just originating accretion buildup. Dependences of the MHD stability resource and maximum current density in the metal melt on the accretion buildup length were obtained. It has been determined that the probability of MHD instability occurrence in S-8BM electrolysis cells during the accretion buildup originating is much lower (the difference in the values of MHD stability resource is 500 mV) than in the period when the electrolyzer has long spreading beyond the anode projection accretion buildups.

The paper studies the possibility of processing refractory gold-arsenic flotation concentrate from Ikkijelon deposit (Republic of Tajikistan) by arsenatizing roasting. The chemical composition of initial samples and derivative products are studied using the methods of optical emission, atomic absorption, IR-spectroscopy, X-ray phase, gravimetric, titrimetric and photometric analysis methods. The content of gold and silver were determined by a fire assay atomic absorption analysis. Precious metals were extracted from the flotation concentrate and the resulting calcine by sorption cyanidation in an agitation mode. The obtained cyanidation results have showed that the initial flotation concentrate is resistant to cyanidation: only 55.1% of gold and 75.8% of silver are extracted by sorption cyanidation. Under calcine cyanidation the content of extracted gold and silver by the method of oxidation arsenatizing roasting reaches 68.3% and 49.1% respectively in optimal conditions. The studies have shown that gold recovery after the processing of gold-arsenic flotation concentrates by the technology of “arsenatizing roasting - cyanidation” has increased by 13.2% compared to the cyanidation of the initial flotation concentrate. The directions of further technological studies aimed at searching for rational methods for processing of refractory gold-arsenic flotation concentrate from Ikkijelon deposit are proposed.

Abstraсt: The paper deals with the process of obtaining Mg-Zn-REM (rare earth metal) master alloys and determination of the list of factors of the magnesium thermal process in order to identify optimal technological regimes. The study uses modern analysis methods. X-ray fluorescence analysis is carried out using the XRF-1800 sequential X-ray fluorescence spectrometer (Shimadzu). Phase identification is performed with the use of X-ray powder diffractometer XRD-6000 (Shimadzu). A complex thermal analysis is carried out on the STA 429 CD (NETZSCH) installation in alundum crucibles with lids in the argon stream using a crucible holder of the Tg+DTA type. As a result of the metallothermic reduction of neodymium, gadolinium and yttrium from fluoride-chloride melts by magnesium in the presence of zinc the master alloys Mg-Zn-REM have been obtained with different percentages of alloying elements. The proposed method of REM recovery from fluoride-chloride melts allows to extract neodymium, gadolinium and yttrium in the percentage ratio up to 99.6%. The obtained master alloys are homogeneous and fluid, able to be evenly poured into molds.