Steel-smelting Furnaces Research Articles

MAGNETIC-CONTROLLED SORBENT FOR WATER SURFACE CLEANING FROM OIL POLLUTION

The modern structure of industry, outdated technologies form a wide range of environmental problems and sharply worsen the ecological situation. Various methods are used to clean water sources from oil spills: mechanical, thermal, physicochemical, biological. Among the available alternatives, oil sorbents are considered as one the most economical, efficient and environmentally friendly materials because oils can be properly absorbed by oil sorbents without causing secondary water pollution.
 The purpose of the research is to study the possibility of obtaining an effective magnetically controlled sorption material for cleaning the water surface from oil spills.
 Research objectives are to analyze the composition of electric arc steel-smelting furnaces (EASSF) dust; conduct research on the hydrophobization EASSF dust with paraffin; determine the optimal proportions of dust and hydrophobizator, which allow the material to maintain buoyancy and magnetic susceptibility; evaluate the interaction of the obtained material with an oil spills on water surface.
 The dust sample elemental composition was obtained using the ARL9900 Intellipower Workstation.
 The sorption material was prepared as follows: the EASSF dust was mixed with a sample of paraffin, then it was heated to 105 °C in an oven, mixed, and cooled to a temperature of 20 °C.
 The true density was determined by the pycnometric method. The method ASTM D2854-70 «Standard Test Method for Apparent Density of Activated Carbons» was used to determine the bulk density.
 Electric steelmaking waste was used as a magnetically susceptible component. Studies have been carried out on its hydrophobization with paraffin for possible use in water treatment. With the waste : paraffin ratio of 1 : 0.07, a material with high hydrophobicity and buoyancy was obtained. Tests for thickening and extracting a crude oil spill from water surface proved the promise of using the obtained material for cleaning water from oil pollution.

СРАВНИТЕЛЬНЫЙ АНАЛИЗ ЭФФЕКТИВНОСТИ РАЗЛИЧНЫХ МОДЕЛЕЙ ЭЛЕКТРИЧЕСКОГО КОНТУРА ЭЛЕКТРОДУГОВОЙ ПЕЧИ ДЛЯ ИСПОЛЬЗОВАНИЯ В ЦИФРОВОМ ДВОЙНИКЕ

usRelevance Nowadays the metallurgical industry is rapidly developing, which requires a continuous search for innovative solutions aimed at providing consumers with high-quality metal products in the required volumes. To achieve this goal, modern enterprises are faced with a number of scientific and technical tasks, which include increasing the energy efficiency of production. An innovative tool in this case is the development of methods for the digitalization of production, including implementation of digital twins for the control of complicated technological systems. The most energy-intensive equipment at metallurgical enterprises is electric arc furnace (EAF). As operating experience shows, control systems for electrical modes of such units do not always allow EAFs to operate with optimal time, energy and technological parameters, which in turn leads to increased operating costs, such as increased specific energy consumption, consumption of electrodes, etc. As a solution to this problem, a number of scientific studies propose the use of a digital twin for dynamic adaptation of the parameters of the EAF electrical mode control system, capable of calculating the settings of control algorithms during the melting process in such a way as to obtain optimal electrical and technological modes at different stages, as well as optimal dynamic performance quality of impedance regulation on the secondary side of the furnace transformer. One of the important stages in this case is the form of representation of the electrical circuit inside of the digital twin, since the adequacy of the output parameters and the accuracy of the operation of the entire control system will depend on this. Based on the above, an urgent task is to develop an effective method for modeling the electrical circuit of the electric arc furnace for application in a digital twin. Aim of research The paper is devoted to the results of research aimed at the use of various mathematical models of the electrical circuit for application in electric arc furnace’s digital twin. Research methods To process the experimental data, mathematical modeling methods were used in the Matlab environment with the Simulink application. All studies were carried out on the basis of experimental data obtained at operating equipment at domestic and foreign metallurgical plants. Results The significance of the research results lies in increasing the energy efficiency of arc steel-smelting furnaces through the use of a digital twin. This solution will allow to provide the optimal selection of transformer tap reactor tap and operating curve number for each stage of melting, as well as analyze the position of operating points on the electrical characteristics and generate additional control signals for dynamic correction of the lengths of electric arcs. The methods of electric circuit modeling in digital twins presented in the work allow to configure the melting program and optimize the parameters of nonlinear impedance or conductivity controllers of the secondary side of the EAF’s transformer. In addition, it makes possible the analyze and adaptation of the auxiliary blocks in control system — arc ignition, current control and correction of regulator setting signals as a function of the voltage deviation on the primary side of the furnace transformer (relatively to the rated value). Problems associated with calculating matrices of settings for impedances and conductances of the secondary circuit of an EAF for all combinations of transformer taps, reactor taps and all values of operating curves can also be solved. Mathematical models are implemented in the Matlab software environment with the Simulink application.

Development and research of a water cooling automated control system for thyristor compensation facility of the reactive power for arc steel-smelting furnaces

An automated control system retrofit method for water cooling of a thyristor reactive power compensation facility for arc steel-smelting furnaces is considered. Keywords thyristor reactive power compensation facility, thyristor water cooling system

Development of an improved automatic control algorithm for combined RCB burners and carbonaceous material injectors of a flexible modular furnace

The control algorithm for combined ceramic regenerative burners (Regenerative Ceramic Burner, RCB) and carbon-containing material injectors of a flexible modular arc steel-smelting furnace DSP-1 operating at one of the domestic metallurgical enterprises is considered. It was revealed that in the concept adopted in production, the decision to switch the RCB burner from the burner mode to the oxygen lance mode, as well as to turn on the carbon-containing material injectors, is made directly by the operator of the furnace plant based on a set of empirical features characteristic of one or another technological stage of melting. In this regard, an improved control algorithm for RCB burners and carbon-containing material injectors has been developed and proposed for implementation, which will ensure the adoption of the above-mentioned decisions in automatic mode. This algorithm is based on the analysis of the slag coefficient, the value of which directly depends on the level of higher harmonics in the spectrum of electric arc current signals, as well as physical processes occurring inside the furnace bath. The implementation of the proposed algorithm enables to achieve the most timely adaptation of operating modes of combined burners and carbon-containing material injectors, which in turn will increase the overall energy efficiency of the steelmaking complex as a result of an increase in the total thermal efficiency of electric arcs and the optimal operating mode of the burners.This work was supported financially by the Ministry of Science and Higher Education of the Russian Federation (Project No. FZRU-2020-0011).

Investigation of Alumina-Based Ceramic Production from Aluminum Black Dross

High-energy consumption in primary aluminum production (from bauxite ores) makes secondary aluminum production (from metallic raw materials such as scrap and dross) very critical. Aluminum dross, as a waste, arises in pyrometallurgical processes, and it is the mixture of metallic Al, Al2O3, other metal oxides, metal halides, and some other compounds like AlN. Aluminum dross has two subgroups (white and black) with respect to its metallic aluminum content. White dross is a secondary aluminum resource because of its high metallic aluminum content, whereas black dross, having low metallic aluminum content, is generally disposed in dumping areas. In the present study, it was aimed to develop a simple technique to valorize aluminum black dross in the form of alumina-based ceramic materials through pyrometallurgical (calcination) and hydrometallurgical (leaching) operations. Moreover, thermochemical simulations were conducted by using HSC Chemistry 6.12 software to simulate calcination conditions. After leaching experiments, an alumina-based ceramic containing approximately 36.8% Al2O3, 61.4% MgAl2O4 with 1.8% Na2FeO4, which might be available to use as a spinel refractory in steel smelting furnaces, was obtained in the experiment carried out in a solution containing 10 mL H2SO4 and 40 mL distilled water (3.5 M). Moreover, the sinterability of the alumina-based ceramic was investigated at the temperatures from 1350 to 1550 °C. In the sample which was sintered at 1550 °C, a density value of 3.15 g cm−3 and a hardness value of 69.58 HV were measured.

Theory and Practice of Heat Transfer in Electric Arc Steelmaking and Flare Metallurgical Furnaces and Power Plants

The author describes the fundamental laws of physics, the laws of thermal radiation of ionized and non-ionized gas volumes. Based on open laws, a modern theory of heat transfer and methods for calculating heat transfer in electric arc and flare metallurgical furnaces, furnaces of steam boilers, and combustion chambers of gas turbine plants of power plants have been developed. The use of scientific discovery makes it possible to create innovative electric arc steel-smelting furnaces, flare heating furnaces, and combustion chambers in which the consumption of electricity and fuel is reduced, productivity and service life are increased, and the amount of harmful emissions into the environment is reduced.

STUDY OF CHANGES IN THE COMPOSITION OF OXIDE NON-METALLIC INCLUSIONS AT THE STAGES OF THE METALLURGICAL PROCESS

Using optical and electron microscopy methods, a study was made of the contamination of C45E carbon steel with non-metallic inclusions in samples taken at all stages of the metallurgical process, and the chemical compositions of non-metallic inclusions were determined. Smelting was carried out according to the following technology: production of an intermediate in an arc steel-smelting furnace → melt processing at out-of-furnace processing →vacuum treatment of steel → continuous casting. Using the methods of recalculation of the EDS-spectrum data, using the Thermocalc software, the phase compositions of non-metallic inclusions of metal samples determined at each stage of the metallurgical process are determined. It was found that complex oxide inclusions with a slag composition are increase in size with each subsequent step and are completely removed from the metal by the final stages of the treatment. At the same time, inclusions of calcium aluminates, on the contrary, decrease in size and, with inclusions of corundum, which remain almost unchanged throughout the treatment, are the main type of oxide that enters the finished metal.

Theory and Practice of Heat Transfer in Electric Arc and Flare Furnaces and Power Plants

The author describes the fundamental laws of physics, the laws of thermal radiation of ionized and non-ionized gas volumes. Based on open laws, a modern theory of heat transfer and methods for calculating heat transfer in electric arc and flare metallurgical furnaces, furnaces of steam boilers, and combustion chambers of gas turbine plants of power plants have been developed. The use of scientific discovery makes it possible to create innovative electric arc steel-smelting furnaces, flare heating furnaces, and combustion chambers in which the consumption of electricity and fuel is reduced, productivity and service life are increased, and the amount of harmful emissions into the environment is reduced.

The influence of technological parameters of smelting on the durability of the lining of an arc steel-smelting furnace under the conditions of Ural Steel JSC

The results of the study of the influence of the main technological parameters of steel smelting (composition of charge materials, duration of smelting and furnace downtime, oxidation refining intensity and metal temperature at the outlet) on the lining resistance of a small arch of a steel-smelting arc furnace in the Ural Steel JSC are presented. Recommendations have been developed for optimizing the technological and energetic regimes of steel smelting, which make it possible to prolong the service life of the lining of a small vault and reduce the cost of steel production. Ill. 5. Ref. 20. Tab. 1.

Increasing the level of control and management of arc steel-smelting furnaces

The urgent problems of modern steel-making devices are considered on the example of ASSF-90 arc steel-smelting furnace. The analysis of modern methods for controlling the parameters of arc steel-smelting furnaces is performed, the main shortcomings of the methods used are diagnosed. Laboratory studies of the parameters of arc steel-smelting furnaces were carried out, as a result of which the dependences of the temperature parameters of the furnace during different periods of melting were revealed. Based on the data obtained, an algorithm for controlling an electric steel-arc furnace has been developed and a computer program has been written. A project has been proposed for introducing the program into an existing SCADA system at one of the modern Russian electrometallurgical facilities.

Features of the Decomposition of Graphitization Furnace Electric Circuit in Modeling AC Electromagnetic Fields

The existing methods for the calculation of electromagnetic processes in the system of current feeders in a graphitization furnace and of busbar packages in a furnace loop require making substantial assumptions, which significantly distort the real picture and do not meet modern accuracy requirements. The use of three-dimensional field modeling is restricted by the stability of computational processes, as well as by a significant expenditure of computational resources and time. In this paper, a numerical simulation of the conjugate spatial electric and magnetic fields in the area of furnace loop busbar packages, current feeders and the core of ac graphitization furnaces using a finite element method. A novel method has been developed for decomposition and dynamic synthesis of parameters according to the criterion for minimizing the current error to the calculate the electrical circuits of power supply systems for electric resistance furnaces with direct heating. The method provides a high accuracy in the calculation of active and inductive resistance and a decrease in active power and magnetic field energy according to the data of three-dimensional numerical-field simulation of complex systems for the furnace-loop busbar packages, current feeders, and core of a graphitization furnace. Criteria are determined for the decomposition of three-dimensional domains of ac conductor systems having a complicated spatial-and-geometric configuration in the subdomain. The application of the finite element method and the decomposition of the 3D domain of the furnace loop for a low-power ac graphitization furnace has provided a high accuracy and computational efficiency of the numerical implementation of three-dimensional electromagnetic field modeling. The relative errors of the method do not exceed 0.35% for the magnetic field energy, 1.45% for the electrical loss, 1.48% for the voltage drop modulus, and 0.67% for the voltage drop phases compared with the numerical values from field simulation of the furnace loop electric circuit. The proposed method can be used to calculate the parameters of electrical machines and short electrical grids characteristic of arc steel-smelting furnaces.

Metal Evaporation in the Area of an Anode Spot in Plasma and Direct Current Arc Steel Smelting Furnaces

Results are given for laboratory research making it possible to describe identical processes in industrial direct current arc furnaces. On the basis of studying the dependence of iron specific evaporation rate in the anode spot zone on current density and time, an expression is obtained making it possible to evaluate the evaporation rate in the anode spot zone in these furnaces of any capacity. It is based on an analytical relationship of permissible current density on electrode diameter over a broad range of change.

Change in Arc Efficiency During Melting in Steel-Melting Arc Furnaces

Results are provided for calculating arc efficiency of steel-smelting arc furnaces in various stages of charge melting with a change in slag layer thickness. Arc efficiency is at a maximum after cutting a well in a charge. Charge thickness decreases during melting and arc efficiency is reduced. An increase in slag layer thickness in the opening period leads to an increase in arc efficiency. Calculated data are confirmed by experimental studies in steel melting arc furnaces.

Математическая модель кинетики движения переходной зоны при нагреве цилиндрического тела из трехкомпонентного сплава

If due to heating or cooling of an object, a phase transition occurs, the propagation of heat significantly changes. Behavior of the enthalpy, heat capacity, density, coefficient of the heat-conductivity as a function of temperature, changes in a complicated manner. For example, when a ternary eutectic alloy is cooling, one solid phase is formed first, then the second, and finally the entire alloy crystallizes. By heating the surface of the solid metal cylindrical object with three-component composition above the liquidus temperature, the two- or three-phase zone occurs at the surface, and moves to the cylinder axis. We propose a method of introducing “effective” specific heat that allows calculating the speed of this zone movement, as well as the temperature of the object at any point and at any time. The ordinary equation of heat conductivity with variable coefficients was used. For each point of a sample for each corresponding temperature, the fractions of liquid and all solid phases were calculated. Specific volume, thermal conductivity and specific enthalpy were calculated as the weighted average of the corresponding values for the liquid and solid states. The specific heat was calculated as the derivative of the enthalpy with respect to temperature. The resulting system of differential equations is reduced to finite-difference equations. A compu­ter program was developed to solve the resulting system of difference equations. Results of one of such calculations are given in the article. The developed method allows to calculate the velocity of the phase boundary, as well as the object temperature at any point and at any time. The presented method may be useful for metallurgists (calculation of heating of parts in heat treatment, calculation of heating of pieces of charge in the steel smelting furnace), for metrologists (self-testing temperature sensors) and others.

Simulation of electromagnetic processes in three-phase electric arc furnaces

A formulation is presented of physical and mathematical parts of models of electromagnetic processes in electric arc steel-smelting furnaces. The model makes it possible to take into account energy release due to current flowing in the furnace workspace, including conduction currents and induced currents in the charge from interaction of electromagnetic fields in a three-phase system with the charge and melt. As a result of defining the problem of electromagnetic field parameters, the maximum field intensity located inside an area that is limited by the pitch circle diameter is found. It can also be roughly proposed that the magnetic field strength decreases inversely to squared radios. The magnetic field strength decreases by more than 20 times on the surface of water-cooled wall panels, and, consequently, the electromagnetic losses in these panels appear negligibly small for the furnace system under consideration. Solution of the electromagnetic problem of examination conduction currents flows gives a vector distribution of current density in electrodes and charge for different periods of melting—the period of initial trunk melting, the period of trunk formation before trunk decay, and the period of burning of arc discharges on melt of slag and metal. Simulation results allow the causes to be fund of unstable burning of arc discharges during initial melting periods, as well as the variations of sound furnace characteristics and the apparent changes of potential gradients in the arcs during trunk melting in the charge.

MODERN ARC FURNACES WORK ENERGY REGIMES AT DIFFERENT TYPE ELECTRODES USE STUDY

The article discusses the increase in efficiency of the modern EAF working on technology to non-continuous load metallized pellets. The method of calculation of rational energy regimes of modern EAF working on energy-technology with continuous loading of pellets using different electrode- tion design. The algorithm for calculating and created computer program that calculates the rational mode of arc steel-smelting furnace, as well as rational download speed metallized pellets in the bath furnace. On the basis of calculations that the use of hollow (tubular) electrodes can reduce the total melting time of 5.9 min in comparison with the standard (solid) electrodes. In this case, the average download speed of metallizovannyh pellet stoves can be increased to 183 kg/min, which in turn will reduce the specific energy consumption of 63 kW·h/t. The results of computer simulations are in qualitative agreement with the data on physical models, thus promising applications of hollow (tubular) electrodes in a production environ- ment.

Multicriterial optimization of the batch composition for steel-smelting arc furnaces

A strategy for optimization of the batch composition in steel-smelting arc furnaces is considered. In this approach, the optimization problem is divided into two parts: the first step is to optimize the ratio of metal scrap and hot metal; the second is to optimize the chemical composition of the scrap in terms of the chromium, nickel, and copper content. As an example, this approach is applied to OAO Magnitogorskii Metallurgicheskii Kombinat (MMK), in terms of the requirements for each grade of steel. A generalized protocol for application of the optimization strategy is presented.

ДОСЛіДЖЕННЯ ВПЛИВУ ЕЛЕКТРОМАГНіТНОГО ПОЛЯ іНДУКТОРА НА ЕЛЕКТРОДУГОВИЙ ПРОЦЕС

Проведено дослідження взаємодії електромагнітного поля, створеного індуктором, та електродугового процесу перетворення електричної енергії в теплову в індукційно-дугових сталеплавильних комплексах, виявлені позитивні фактори, які впливають на покращення техніко-економічних показників роботи електросталеплавильних печей.

Air pollution by large steel-smelting arc furnaces

Air pollution by large steel-smelting arc furnaces

Thermal-destruction products of coal in the blast-furnace gas-purification system

Given the shortage and high price of coking coal, efforts are underway to reduce their consumption in their primary uses, including blast-furnace production and the smelting of copper and nickel ore in shaft furnaces. A promising approach is the replacement of some or all of the coke by less expensive coal [1] or by dust‐coal mixture injected in the blast furnace [2]. The lean, poorly clinkering coal and anthracite used to replace coke in blast furnaces has a considerable content of volatile components (low-molecular thermaldestruction products), which enter the water and sludge of the blast-furnace gas-purification system as petroleum products. Therefore, it is important to study the influence of coal on the petroleum-product content in the water and sludge within this system. The liberation of primary thermal-destruction products is investigated for anthracite with around 4 wt % volatiles, using a STA 449C Jupiter thermoanalyzer equipped with a QMC 230 mass spectrometer. The thermoanalyzer determines small changes in mass and thermal effects with high accuracy (weighing accuracy 10 ‐8 g; error in measuring thermal effects 1 mV). This permits experiments with single layers of coal particles, eliminating secondary reactions of its thermal-destruction products. Samples are prepared from natural anthracite in powder form. Particles of size class 0.5‐2 mm (first series of experiments) or <0.5 mm (second series) form a single layer; in the third series, (0.5‐2)-mm particles form several layers. The experiments are conducted in a current of argon. The results are shown in Figs. 1 and 2 in the form of curves of the mass (TG) and the rate of mass change (DTG) and differential scanning-calorimetry (DSC) plots with standard leucosapphire samples, along with mass-spectrometric data. According to experimental data, the evaporation of free water ends at 200‐220 ° C, and the formation of low-molecular thermal-destruction products of coal begins at 250 ° C. The liberation rate of volatiles from a single layer of (0.5‐2)-mm particles, like the evaporation rate of water (Fig. 1), is considerably higher than for the other series of experiments. In the particle layer, more favorable conditions for the reaction of intermediate products released from a single particle with other particles or thermal-destruction products are created. When the coal is ground to powder, the structure of the macromolecules is destroyed, and the resulting fragments of different molecular mass and chemical activity react at once with each other and with the partially disintegrated coal grain. This necessarily affects the decomposition rate. These aspects of the thermal destruction of anthracite particles must be taken into account in selecting the fraction of coal-dust fuel for injection in steel-smelting furnaces. According to mass-spectrometric data (Fig. 2), the basic components of the gas phase in the thermal destruction of anthracite are CH 4 , CO 2 , H 2 , and H 2 O. No carbon monoxide is observed, in contrast to [3]. The content of C n H m and N 2 is no more than 1 vol %, according to [3]; this is probably why it is not detected mass-spectrometrically. The composition of the gas phases varies considerably as a function of the temperature. Intense methane liberation occurs in the range 440‐500 ° C, while the CO 2 content gradually declines. At 580 ° C, hydrogen begins to predominate in the gas. Above 580 ° C, the hydrogen content increases, and the methane content declines; this is associated with displacement of the equilibrium in the reaction CH 4 = C + 2H 2 toward the products.