Organization of technological process and design of a furnace significantly affect the parameters of post-combustion, determining the need to develop a mathematical model of post-combustion zone. Modeling of gas dynamics, chemical reactions, convective diffusion and heat transfer in the gas phase above the melt was carried out in an experimental melter-gasifier furnace at three different values of mass flow rates and two positions of post-combustion tuyeres. Temperature distributions and off-gas components concentrations were obtained. It was found that at the lower position of the tuyere, post-combustion is carried out in the area of reflected jet, stagnant zones are formed around the tuyere and between the reflected jet and the melt surface, which decrease the post-combustion level. At the upper position of the tuyere, post-combustion occurs inside the primary jet, intensive mixing of all components of the furnace atmosphere occurs, post-combustion undergoes more completely, which leads to an increase in the off-gases temperature with an increase in uniformity of temperature fields and concentrations compared with the lower position of the tuyere. At the lower position of the tuyere, the flame zone turns out to be open, its shape significantly depends on the mass flow, and the flame zone volume increases with an increase in the mass flow. At the upper position of the tuyere, the flame zone is closed, with an increase in the mass flow, its shape does not change, but the flame zone volume decreases. For reduction processes in slag melt, the upper position of the tuyere is preferable, while for production of the producer gas at the furnace outlet, position of the tuyere closer to the melt surface is preferable.

The distribution of natural gas, supplied into the blast channel of an air tuyere equipped with a heat-insulating insert, plays a positive role. On the one hand, it improves the mixing of natural gas with blast air and its combustion, and on the other hand, it reduces thermal stresses in the insert. The Ansys platform was used to perform mathematical simulation of gas dynamics, heat transfer, and combustion processes related to natural gas being supplied into the blast channel of a blast furnace tuyere through a series of holes in the flange. It has been shown that by supplying natural gas into the blast channel through the flange holes, it becomes possible to improve its combustion efficiency in the tuyere, leading to an increase in temperature and wind rate compared to the traditional method of supplying natural gas into the blast channel through a single tube via an inner sleeve. By using a model of the flange, containing only a manifold with a tube for supplying natural gas and its discharge through the holes, it was established that in order to minimize the non-uniformity in the natural gas supply distribution between the holes, the gas supply tube should be installed symmetrically relative to the manifold plugs, which in reality are formed by the tuyere cooling water supply and discharge tubes. It has been found that supplying natural gas through the flange holes leads to a decrease in thermal stresses in the insert by about 2 times compared to the traditional natural gas supply, which helps increase the durability of the insert. In this case, the resulting non-uniformity of supplying natural gas through the flange holes into the blast channel does not lead to a significant change in insert stresses.

The paper presents the results of studies on the production of semi-coated glazes with antibacterial activity by introducing variable valence oxides CeO2, WO3, Bi2O3, Fe2O3, MnO2 and MoO3 into their composition. The raw polycomponent compositions were comprised of aluminosilicate multi-calcium glass frit, dolomite powder, feldspar, alumina, quartz sand, wet-enriched kaolin and refractory clay. The coatings were obtained by single firing on a ceramic-based porcelain stoneware at a temperature of 1 200 ± 5 °C in a high-speed mode for 60 ± 2 minutes. The study focused on the processes of glaze formation of coatings and the influence of the components of glaze charges on decorative and aesthetic characteristics of coatings (color, texture, gloss and whiteness). Parameters of physical and chemical properties were determined in accordance with the existing specification for the products, i. e. temperature coefficient of linear expansion, heat resistance, chemical resistance, microhardness, frost resistance, wear resistance, etc. Antibacterial activity of the coatings towards Escherichia coli ATCC 8739 and Staphylococcus aureus ATCC 6538 test strains was studied.

When supplying natural gas to a blast-furnace tuyere, it is necessary to strive to increase the efficiency of the combustion of natural gas in the blast channel of the tuyere on the one hand and to protect the inner shell of the tuyere against burnout on the other hand. One of the methods to achieve both of these contradictory goals is to install a heat-insulating ceramic insert in the blast channel. We consider the possibility of increasing the efficiency of the ceramic insert by making one or more annular grooves on its surface to improve the mixing between natural gas and blast air for more efficient combustion. Ansys 21.1 software is used to simulate the motion of fluids, heat transfer, and combustion of natural gas in the blast channel with a ceramic insert that has annular grooves of quadrangular cross-section. The influence of the depth and width of grooves and the distance between them on the processes in the tuyere is studied. It is shown that an annular groove in the insert increases the total heat from the combustion of natural gas, which is confirmed by an increase in the concentration of CO 2 and the temperature and rate of blast at the outlet of the tuyere. The maximum thermal stresses in the insert increase as well, exceeding the maximum stresses in the insert without grooves by no more than 30%.

The purpose of this work was to analyze the effect of a heat-insulating insert, as well as the flow rate and temperature of natural gas on the processes occurring in blast channel of an air tuyere. The paper analyzes the results of industrial and numerical experiments obtained by different researchers on the use of various methods for increasing the completeness of combustion reaction within the air tuyere of natural gas (NG) fed into it: increase of NG flow rate; increase of NG temperature; the use of heat-insulating inserts installed in the inner glass of the air tuyere. Using the Ansys Fluent software complex, the effect of a heat-insulating insert and increase in NG flow rate on the temperature and composition of gases leaving the tuyere of blast furnace no. 5 of PJSC Severstal was studied. It was found that with an increase in NG flow rate from 0.283 to 0.328 kg/s, the temperature of the gas medium at the tuyere outlet decreases by 6 °С for the variant without an insert and increases by 3 °С for the variant with it. When studying the effect of a heat-insulating insert and increase in NG temperature (in different combinations) on the processes occurring in a tuyere, it was found that temperature of the gaseous medium at the tuyere outlet in case of using a heat-insulating insert without NG heating is slightly higher than when NG is heated to 200 °С without inserts. However, the effect of NG heating in the presence of an insert is significantly higher than without it – there is mutual amplification of two factors influencing the completeness of NG combustion within the tuyere, accompanied by protection of the tuyere inner nozzle from burnout.

Приведены результаты исследований по синтезу молибденсодержащих глазурных покрытий, обладающих антибактериальными свойствами и применяемых в производстве керамических плиток. Исследована поликомпонентная сырьевая композиция, включающая стеклофритту системы Na2O – K2O – CaO – MgO – Al2O3 – B2O3 – SiO2, доломит и оксид молибдена при постоянном содержании полевого шпата, кварцевого песка, глины огнеупорной и каолина. Белые глушеные глазурные покрытия получены однократным обжигом при температуре (1180 ± 5)°С и продолжительности (55 ± 2) мин. Установлены зависимости свойств покрытий от технологических факторов (степень помола, температурно-временные режимы и др.). Изучены декоративные характеристики полученных покрытий, их физико-химические свойства во взаимосвязи со структурой и фазовым составом. Определена антибактериальная активность покрытий в отношении тест-штаммов Escherichia coli ATCC 8739 и Staphylococcus aureus ATCC 6538. Исследованы фазовые переходы в глазурных сырьевых смесях при их термообработке. Изучены особенности формирования структуры покрытий методом ИК-спектроскопии. Установлен фазовый состав и микроструктура глазурей. Определена возможность применения МоO3 для синтеза глушеных глазурных биоцидных покрытий для керамических плиток.

Slab heating before hot rolling is necessary for obtaining required metal ductility. The most effective for this purpose are furnaces with walking beams that provide heat supply to all sides of the slab. However, the areas of slabs lower surfaces, contacting with water-cooled beams, are shielded from the radiation of the furnace lower heating zones and take the heat from the beams.To study the inhomogeneity of the slab temperature field and its dependence on the peculiarities of their transport system design, a mathematical model of slab heating in a furnace with walking beams was developed and programmatically implemented, based on numerical solution of a three-dimensional heat conduction problem with piecewise defined boundary conditions on the lower surface. For the open areas of the slab bottom surface, the same boundary conditions were set as on the top surface; and for the areas of contact with the beams, modified boundary conditions were set, taking into account the duration of this contact. For the numerical solution of the system of difference equations, the line-by-line method was applied, which allows us to obtain a system with a three-diagonal matrix of coefficients. The calculations carried out in the approximation of adiabaticity of the contact areas of the slab with the beams during the contact period allowed us to obtain temperature fields for different slab sections. As a result, a significant irregularity of temperature field of the slab lower surface was revealed, affecting the irregularity of temperature field of the entire slab. The developed program for calculating and visualizing the results can be used to study the temperature field of the slab under various heating modes if there is experimental information that allows one to clarify the tuning parameters of the model.

The work makes it possible to simplify development of pulsed metal heating technology. A software product was created to select the optimal values of operating parameters of pulsed heating on a mathematical model, which significantly reduces the setup time of a thermal unit using this technology. Test calculations showed adequacy of the results obtained to the operating parameters of functioning through-pass heating furnaces equipped with high-speed jet burners. The problems of controlling metal heating became particularly relevant due to the proliferation of high-performance rolling mills and increasing requirements for the quality of metal heating. In this regard, full implementation of the research program will make it possible to develop specific recommendations for increasing the productivity of heating furnaces and improving their energy efficiency.

One of the main disadvantages when supplying natural gas to the air tuyere of a blast furnace is low intensity of its combustion inside the tuyere blast channel. Ring groove on the surface of blast channel improves the mixing of natural gas with blast and increases completeness of gas combustion in it, but reduces the tuyere durability. One of the ways to simultaneously solve these problems is to install a heat-insulating ceramic insert in the tuyere blast channel. The insert significantly reduces heat losses through the tuyere surface, improves natural gas combustion in the blast channel due to its contact with hot walls of the insert instead of cold copper walls in its absence. This increases the temperature of the hot blast at the tuyere outlet. In addition, the insert affects the tuyere durability by reducing the heat flow acting on the tuyere. In this work, we studied influence of the ring groove and its parts in the insert on efficiency of its work. In the Ansys 21.1 software, the processes occurring in the blast channel of a blast furnace tuyere with a ceramic insert installed in it, having a groove of a quadrangular section in the form of a ring or its part in the circumferential direction, were simulated. It was established that improvement of natural gas combustion in the tuyere blast channel is achieved using a ring groove or part of it from the side of gas supply.

The authors investigated the intensity of heating of a moving strip of thermally thin metal on a finite length section by a system of attacking neutral gas jets. The article is devoted to solving the problem of creating a system for heating a strip of moving metal by attacking jets of neutral gas by estimating the intensity of heating a metal strip using mathematical modeling methods. The main options for heat treatment of sheet metal are named. The article describes the differential heat conduction problem and its subsequent simplification, considering the assumptions made to obtain an effective calculation algorithm; the empirical relations selected for calculating local and average values of heat transfer coefficients; and the basic parameters for variant calculations. For comparative modeling, a 20m-long section was considered, where a strip entering with a temperature of 500 °С is heated by neutral gas with temperature of 800 °С. The results of calculating the dependence of average cross-sectional temperature of the strip on its movement speed (in the range from 0.1 m/s to 2 m/s) at two values of the gas flow velocity (20 m/s and 40 m/s) are presented, on the basis of which the authors concluded that acceptable heating intensity is achieved only at low speeds of the strip, and the gas flow rate (in the considered range) is not a reserve for a significant increase in this intensity.

The results of studying the crystallization ability and the thermal linear expansion coefficient of glasses of the BaO–La2O3-B2O3–ZrO2–TiO2–SiO2–Nb2O5 system, intended for the production of a light-guiding core of a rigid optical fiber, are presented. Transmission electron microscopy has established the nature of silencing of the studied glasses during production. With the help of X-ray phase analysis, the main crystalline phases that precipitate during heat treatment of glass samples were established. The compositions of glasses characterized by a minimum tendency to crystallization are determined. The effect of the chemical composition of glasses on their structure was established by infrared spectroscopy.

It is known that the maximum heat loss in the air-cooled tuyere of a blast furnace occur in the blowing channel. An effective way to reduce them is to install a heat-insulating ceramic insert. The heat-insulating inserts installed in the inner shell of air tuyeres for blast furnace no. 5 of PAO Severstal reduce the heat loss through a tuyere by 30%, and the inserts that insulate most of the inner surface of the head end additionally reduce the heat loss through a tuyere by 26.2%. The effect of design parameters on the thermal processes in the air tuyere of a blast furnace with a heat-insulating insert has been studied using the ANSYS software. In this work, to make the simulations more accurate, the whole air tuyere including a water-cooling circuit has been as a simulation area. The protrusion of the insert into the blowing channel by 2 mm improves the mixing of natural gas and blast, contributes to the gas combustion in the blowing channel, which leads to an increase in the heat loss through a blowing channel and a decrease in the durability of the insert. To increase the resistance of the insert and reduce the heat loss through a blowing channel, it is justified to use an elongated insert with variable thickness, which ranges from 13 to 8 mm in the blast direction, does not protrude into the blowing channel and has an angle between the normal to a wall of the inner nozzle and the axis of a hole for natural gas supply of about 30°. It is shown that to obtain the maximum heat content of the blast, which is affected by the combustion of natural gas and heat loss with cooling water in the blowing channel, the preferred option is one with an elongated insert with variable thickness, which changes from 10 to 8 mm in the blast direction, and with the axis of a hole for supplying natural gas perpendicular to a wall of the inner cup.

The work analyzes the results of industrial and numerical experiments obtained by various researchers on the application of various methods for ensuring the ignition and subsequent tuyere combustion of a fed natural gas: oxygen-enriched hot blast; gas-oxygen mixture; thermal-insulating inserts installed into the tuyere inner cup. The effect of a thermal-insulating insert and a gas-oxygen mixture (GOM) in various combinations on the ignition and the subsequent combustion of natural gas in a tuyere was studied using Ansys Fluent software. Simulation results show that the quantitative effect of applying a thermal-insulating insert without a gas-oxygen mixture is expressed more strongly than that of applying a gas-oxygen mixture with 5% O2 without an insert. However, the effect of this gas-oxygen mixture in the presence of an insert is substantially higher than without it. The mutual strengthening of two factors acting on the completeness of natural gas combustion in the tuyere is accompanied by burnout protection provided by an inner tuyere cup.

The tuyere designs that meet the conditions of PAO NLMK are simulated in the Ansys Fluent 18.2 environment. A hot blast supply angle of 5° and the inner diameter of the natural gas pipe of 22 mm are found to be rational. For more effective combustion of pulverized coal fuel and natural gas in the blast duct and the tuyere zone of the furnace, the angle of supply of pulverized coal fuel should be increased to 20.0° and the distance between the natural gas nozzle and the flange should be decreased to 30 mm.

Приведен обзорный материал в области разработки составов и технологии получения радиопрозрачных стекол и ситаллов. Отражены вопросы взаимодействия силикатных материалов с электромагнитным излучением сверхвысокочастотного диапазона и причины его ослабления. Представлены основные подходы на предприятиях и в научных институтах к разработке силикатных материалов радиопрозрачного назначения, а также основные характеристики стекол и ситаллов, имеющих практическое значение. В статье приведены основные требования к радиопрозрачным стеклам и ситаллам, рассмотрены вопросы, касающиеся природы проявления поляризации в неорганических материалах.

Clinker brick was obtained on the basis of polymineral raw materials, including low-melting and refractory clays, loams, and granitoid screenings in the plastic method of manufacturing. The interrelation of the physical and chemical properties of products was determined as a function of the mass content of the components and the oxide composition of the charge, and the optimal temperature_time regimes of firing were determined — 1150 ± 5°C with exposure of 4 h at an optimal temperature. The data obtained on the oxide and mineral composition make it possible to predict the composition of the charge for producing clinker brick, the heat-treatment regimes, and the properties of the products.

Приведены результаты разработки составов ангобов для покрытия тыльной стороны керамических плиток. Установлена зависимость физико-химических свойств ангобов от массового содержания компонентов при исследованных режимах обжига. Область оптимальных составов характеризуется следующими показателями: ТКЛР в интервале температур 20–300°С составляет 5,7–6,1 · 10{–7} К{–1}, кажущаяся плотность 2340–2470 кг/м{3}; открытая пористость – 11,2–12,7%, огнеупорность – более 1350°С, водопоглощение – 5,1–6,5%, общая усадка 9,2–11,7%. Дифференциально-сканирующей калориметрией определены основные термические эффекты, наблюдаемые в ангобных составах при нагревании. Методом РФА установлено наличие следующих кристаллических фаз: α-ангидрит, α-корунд, анортит, алит, ранкинит. Структура ангобов сформирована преимущественно кристаллическими образованиями, отвечающими по габитусу ангидриту.

To reach optimal indices of blast furnace smelting when injecting pulverized coal (PCI), it is necessary to rationalize the modes of its supply and create conditions for the process of powdered coal particles burning, which ensure the maximum degree of its combustion in the tuyere zone. With this purpose, the study of influence of temperature, coal particles sizes and angle of PCI supply on the thermal balance in the blast channel was accomplished without changing conditions of hot blast supply. Simulation of heat exchange processes and possible natural gas and PCI burning in the blast channel of blast furnace air tuyeres was accomplished based on program package Ansys Fluent 18.2 application. The simulation accomplished for the type of tuyeres, used by PJSC NLMK showed, that substitution of a part of natural gas by the PCI results in temperature increase of gas medium at the exit of the tuyere because of smaller volume of natural gas not entering into reaction of burning. It was determined, that during natural gas supply in the blast flow, the process of mixing of gaseous mediums takes place inside the air tuyere and the process of natural gas combustion takes place in the narrow area near the wall not far from the tuyere exit section. When a part of natural gas is substituted by PCI, the processes of PCI heating have time to take place inside the tuyere, resulting in emission and possibly partly combustion of volatiles, as well as heating of the coke residual (without its burning). The substitution of a part of natural gas by PCI results in heat increase, emitted inside the tuyere because of less volume of natural gas not entering into burning reaction and in gas medium temperature increase at the tuyere exit. Increasing of temperature and angle of coal particles supply, decreasing of their sizes results in an increase of volatiles yield in the blast channel, which creates conditions for more effective combustion of coke residual in the furnace tuyere zone.

The use of natural gas can reduce the amount of coke needed to produce cast iron. In a common tuyere natural gas is pressed against the surface of the air passage by a stream of hot blow and mixes poorly with it. It leads to incomplete burning of natural gas and its pyrolysis. One way to improve the mixing of natural gas and hot blow is to install the swirler in the air passage. In this case, however, intensification of natural gas burning inside the tuyere can lead to a burnout of the inner cylinder. In Ansys Fluent 18.2, using insulation insert with a swirler made in the form of a collar step at different places along the length of the insert, simulation of gas dynamics and its thermal state is carried out to solve the problem of mixing natural gas and hot blow in the air passage of tuyere. Simpler assumptions were adopted. Among which the simulation area included not only the fluid medium inside the air passage, but also the insulation insert, i.e. the associated problem of heat exchange was solved, and the processes of transfer of heat to water of the cooling system are taken into account in extended boundary conditions. The simplified calculation area scheme was created in the DesignModeler application, and the calculated grid was created in the AnsysMeshing application. The boundary conditions were set for blow (natural gas), as well as for the border of the insert with an air gap separating it from the internal cylinder and the fluid with the tuyere nose. Taking into account the symmetry of the computation region, the calculations were made for the half of tuyere. It has been found that mixing of natural gas and hot blow improves as the swirler moves along the length of the insert to the exit from the air passage. At the same time, in the swirler place the diameter of air passage is not less than downstream of the tuyere. The swirler`s shift toward the exit from air passage reduces the thermal load on the insert, thereby increasing its service life.