Steel-melting Furnaces Research Articles

Composite (cored) graphitized electrodes for industrial DC and AC steel-melting furnaces

Composite (cored) graphitized electrodes for industrial DC and AC steel-melting furnaces

Композитні (гнотові) графітовані електроди для промислових дугових сталеплавильних печей постійного та змінного струму

Композитні (гнотові) графітовані електроди для промислових дугових сталеплавильних печей постійного та змінного струму

Complex heat transfer in a bath under arcs of high-power arc steel-melting furnaces. Part II. Conversion of radiant arc flows into convection and heat conduction flows in the bath

Complex heat transfer in a bath under arcs of high-power arc steel-melting furnaces. Part II. Conversion of radiant arc flows into convection and heat conduction flows in the bath

Complex heat transfer in a bath under arcs of high-power arc steel-melting furnaces.

Complex heat transfer in a bath under arcs of high-power arc steel-melting furnaces.

Double-Circuit Adaptive System of Fuzzy Phase-Autonomous and Energy-Efficient Control of Arc Furnace Electric Modes

The article provides an overview of the existing structures of fuzzy model systems for arc length control and optimal control of arc steel-melting furnaces (ASFs) electrical mode. The analysis of known adaptive optimal control strategies of alternating current steel-melting arc furnaces modes according to complex criteria of energy efficiency, energy saving and reliability was performed. Expedient system engineering solutions are proposed for the comprehensive improvement of energy efficiency and electromagnetic compatibility of arc furnaces and the power grid, which are implemented by improving automatic power and arc length control systems. Control principles, indicators of arc length control dynamics, energy efficiency and electromagnetic compatibility of various systems are analyzed. The expediency of using fuzzy control models for comprehensive improvement of dynamics, energy efficiency and electromagnetic compatibility indicators is substantiated. The expediency of implementing simultaneous phase-independent control of arc lengths and fast-acting arc currents control is substantiated. A variant of the double-circuit structure of fuzzy arc lengths control system and implementation of the multi-criteria optimal control strategy of electrical modes (EM) is proposed. The design of fuzzy inference systems for the synthesis of the electrode movement control signal was carried out in order to improve the dynamic accuracy of the ASF electrical mode coordinates stabilization. A computer Simulink model of the developed double-circuit system was created, and studies of the dynamics and energy efficiency indicators when handling deterministic and random perturbations were performed. The obtained results of model studies showed an improvement of the control dynamics quality indicators under the influence of deterministic and random perturbations and an increase in the energy efficiency of ASF EM at various technological stages of melting. The expediency of the practical use of the proposed solutions for operating arc furnaces is substantiated.

Effect of Steel Slag and Manufactured Sand as Fine Aggregate on the Strength, Durability and Structural Properties of Self-Compacting Concrete

Abstract: The growing demand for building materials in the modern era contributes to excessive sand quarrying from river beds, depleting sand supplies and contributing to global warming. Thermal power plant fly ash, quarry Fines produced by crushing rocks into aggregates, as well as steel slag from steel melting furnaces, regularly cause significant environmental and disposal issues, Experimentally defined aggregate in SCC grades M40. steel slag as fine aggregate in M40 grades of SCC was developed and compared to those of traditional SCC specimens, with better performance

Дослідження ефективності схеми керування напругою конденсатора уніфікованого регулятора якості електроенергії для зменшення коливань напруги

This article investigated the effectiveness of using a unified power quality regulator (UPQR) to reduce voltage fluctuations in electrical networks with a rapidly changing nonlinear load. It is proposed to use a voltage control scheme on the URYAE storage capacitor based on an FIR filter in order to minimize rapid voltage changes and the flicker indicator, as well as the total coefficient of harmonic distortions in the distribution system. The final simulation of the study is carried out using MATLAB/Simulink. To demonstrate the effectiveness of the proposed control scheme, a comparison of simulation results with a PI controller is made from the point of view of improving the specified power quality indicators. The initial data for performing calculations of voltage fluctuations are information on the parameters of the electrical network and the graph of a random, rapidly changing electrical load. Rapidly changing loads cause rapid changes in the network voltage, the amplitudes of which can reach unacceptable values, for example, in the case of frequent start-ups of an asynchronous motor with a large starting current. Voltage fluctuations can also be caused by technological installations, the operation of which is accompanied by active and reactive power surges , such as the drive of reversible rolling mills, arc steel melting furnaces, contact electric welding installations, etc. The main task of the research is to improve the quality of electricity, and, as a result, to increase the service life of electrical equipment and to ensure the conditions for the normal technological process of electricity consumers. Indicators characterizing voltage fluctuations were quantified: voltage change range (δUt) and flicker indicator (Pt). The effectiveness of the new capacitor voltage control scheme for reducing higher current harmonics compared to the classical one based on the PI-regulator is verified.

Evolution of Furnaces

Abstract: A new generation of industrial melting furnaces has been developed during the last 25 years. Present practices followed in Furnaces are discussed in this paper. Through a literature review account of various practices presently being followed in industries using Furnaces has been carried out with a view to gather principal of working. Apart from this a pilot study has also been carried out in few industries in India. We provide some recommendations for the productivity improvement. Due to lack of proper instruments the effect of the ill practices cannot be precisely judged. If this is properly measured, the percentage of productivity improvement in steel melting Furnace can be calculated. The review is carried out from the literature in the various journals and manuals. The first controlled use of fire in metallurgy dates from the eighth millennium ВС, when native copper was deliberately heated to form artifacts. Problems how to distinguish between native copper and smelted copper are addressed, especially what concerns the role of iron in copper. kilns. Metallurgy is an independent development. The decisive factor was the introduction of charcoal that was important to produce reducing conditions during firing. The earliest stages in metallurgy are represented by a non-slagging process. Reduction of ores was carried out in crucibles as exemplified by finds from Anatolia, Iran, Jordan, and the Iberian Peninsula. Special attention is paid to the putative early stages of metallurgy claimed to exist at that age. The is called Neolithic and Chalcolithic copper smelting there is critically prooved in the light of radio carbon data. Wind-powered furnaces played a major role in Early Bronze Age copper metallurgy, as exemplified by sites in the Feinan-area, in Wadi Dara, Egypt, and at numerous sites in the Aegean. Later, artificial air supply by bellows and tuyeres was introduced.

Calculation and analysis of the arcs efficiency of small and large capacity arc steel-melting furnaces

In the course of the research, the calculation and performed analysis of the arc efficiency of furnaces ASF-5 and ASF-100 power furnaces were performed and the average arc efficiency for melting was determined. The reasons of the increased specific consumption of electric power on charge melting by arc steel-melting furnaces of small capacity in comparison with heavy-load furnaces are revealed. Efficiency of arcs of low-tonnage furnaces is much less than the same indicator of modern heavy-duty arc steel-melting furnaces (ASF). Low efficiency of arcs of light-duty furnaces leads to a significant specific power consumption for smelting, comprising 700-750 kWh/t, that is 1.9-2 times higher than the specific energy consumption in modern furnaces ASF-120, amounting to 375 kWh/t. With the use of devices for foaming slag in furnaces ASF-5 the average melting efficiency of furnaces can be increased, and the specific electricity consumption for melting will be reduced to 440-480 kWh/t.

Stating Diagnosis of Current State of Electric Furnace Transformer on the Basis of Analysis of Partial Discharges

The article is dedicated to research of the technical state of a furnace transformer. The study was conducted on the basis of statistical processing of continuously measured parameters of partial discharges (PD). The authors characterize the causes of PD occurrence and their impact on the insulation condition. The article provides information on the on-line monitoring system applied at high-voltage transformers of superpowered arc steel-melting furnaces and ladle furnaces at metallurgical plants. The system implements (among other methods) the method of diagnosing the insulation state by means of mathematical processing of PD parameters. Continuously measured values are apparent charge and the parameter called partial discharge intensity (PDI) characterizing the power and intensity of PD. The authors studied the parameter trends and conducted the statistical processing of the measurements results. In addition, the authors give the rationale for the application of the parameter “reciprocal stochastic connection force” between the PD amplitude and PDI as a generalized criterion of the insulation state and failure localization. The article compares trends of power and PD amplitude at various transformer technical states (before and after unscheduled repair). The authors confirm the possibility to diagnose emerging defects by comparing the correlation factors of these dependences. An example of defect occurrence and its location is provided. As a result, the authors manage to prove the efficiency of the proposed method of analysis of the high-voltage transformer state. This research has produced an integrated approach that enables on-the-go technical diagnosis, fault localization, and accident prevention. The key product of this research is a transformer diagnosis method based on processing the data of online PD monitoring. To that end, the proposed method uses statistical toolkits available for a PC. The areas for further prospective research are outlined. The authors also give recommendations on a more extensive application of the developed method.

Automatic control system development and implementation for melting in electric arc furnaces

Automated control systems for arc steel-melting furnaces feature a number of disadvantages and limitations with respect to complete control of technological process. The issues of automation of state-of-the-art metallurgical plants are considered. The main directions of studies of arc furnaces thermal state are detected. Studies of factor changes in the main technological parameters of ASMF-90 are carried out. The necessity of introducing the automated control over arc steel-melting furnaces melting process is substantiated. On the base of the process study, a method for arc steel-melting furnaces thermal state monitoring is proposed. A project is proposed for a modernized automatic control system for an arc steel-melting furnace operated at the modern Russian enterprise under consideration.

Theoretical basis of energy efficiency criterion-based optimal control of arc steel-melting furnace modes taking into account 3-dimensional phase current distribution

The purpose of the article is to develop a method for synthesis of the operative adaptive optimal control of the electric mode (EM) of an arc steel-melting furnace (ASF) by energy efficiency criteria based on three-dimensional (3-D) distribution of arc currents. The basis of the created method is the use of operative information on the parameters of 3-D distribution of arc currents and the search for the appropriate optimal control – set points for arc currents of a double-loop system of controlling the electric mode of an arc steel-melting furnace. There have been obtained partial optimality criteria to minimize the specific energy consumption, the steel price per ton, and to maximize the hourly productivity of an arc furnace, as well as an algorithm for operational synthesis and implementation of the optimal control vector according to the chosen criterion, taking into account the model of 3-D current distribution. For the first time, based on the operative on-line control of 3-D arc currents distribution, partial criteria have been obtained for the synthesis of adaptive optimal control of the electric mode of an arc furnace, which makes it possible to comprehensively improve the energy efficiency and electromagnetic compatibility of the arc furnace modes and the electric supply network. The implementation of the created method of adaptive optimal control and the algorithm for its implementation in the structure of a double-loop control system of electric melting mode will allow us, in comparison with the known single-loop control structures, to improve the indices of electrotechnological efficiency and electromagnetic compatibility, and to obtain higher dynamic accuracy of stabilization the electric mode coordinates at the level of the operatively synthesized optimal arc current set points.

Analytical study of heat exchange and efficiency of arc in arc steel-melting furnaces of small and large capacity

An analytical study of heat transfer and efficiency of arcs in arc steel furnaces of small and large capacity, 1.5-20 tons and 100-120 tons, respectively. We found out that the reason for the increased specific consumption of electricity for melting the batch in small capacity furnaces is the low efficiency of arcs equal to 0.55-0.57 and the corresponding specific energy consumption for melting 475-500 kWh/t. In furnaces of large capacity the efficiency of arcs is 0.78-0.8 and specific energy consumption is 360-375 kWh/t.

SYNTHESIS AND ANALYSIS OF ARC FURNACE ELECTRICAL MODE CONTROL SYSTEM ON THE BASIS OF THREE-DIMENSIONAL PHASE CURRENTS VECTOR DISTRIBUTION

Goal. The purpose of the article is to create the method for the operative synthesis of an arc steel-melting furnace (ASF) electric mode (EM) control signal on the basis of a three-dimensional arc currents vector, which takes into account the stochastic nature of the processes in the melting space and power circuit and has low sensitivity to the control object parameters changes, as well as development of the control system structure for its implementation. Method. The basis of the created control method is formed on the statistical theory of dynamical systems, as well as the provisions of the statistical theory of optimal control based on the Fokker-Planck-Kolmogorov equation, which enables to synthesize operational control by the criterion of approaching the regulated coordinate distribution density to the d-function, that is to minimize the dispersion of the three-dimensional furnace phases arc currents vector. Results. The system of equations for operational real-time calculation of control influences of the thyristor switch of phase inductors, included in the power supply circuits of three-phase arcs, and the structural scheme of the adaptive contour for the formation of three-dimensional phase currents vector dispersion for the implementation of adaptive optimal control were obtained. Scientific novelty. For the first time, based on the Fokker-Planck-Kolmogorov equation, we obtain a system of equations representing a mathematical model of a stochastic adaptive optimal control of the arc furnace electric mode by the criterion of a minimum dispersion of three-dimensional phase (arcs) currents vector, which enables, in comparison with known methods, to increase dynamic precision of the arc currents stabilization at the level set by the criteria of energy efficiency and electromagnetic compatibility values. Practical value. The use of the proposed adaptive optimal control model and structural system scheme for its implementation allows, in comparison with the serial arc power regulators, to improve the dynamic accuracy of the arc current currents stabilization at the level of given optimal settings and, based on this, to improve the energy efficiency and electromagnetic compatibility indices of the arc furnace and power supply network.

Research of heat exchange and efficiency of the arcs in the arc steel-melting furnaces with usual conveyor and loaded

The analysis of heat exchange and the efficiency of the arcs in the arc steel-melting furnaces with usual conveyor and loaded. For comparison, accepted arc furnace close in power and performance. The analysis revealed that the average efficiency of arcs furnace Consteel ASF-120co 8-9% less than particle ASF-120us. Analysis of the efficiency of the arcs of electric arc furnaces allowed to explain more 8-9% lower specific energy consumption in the furnace ASF-120co compared to the same period in the furnace ASF-120us. Calculation and the analysis of efficiency of various ways of input of heat in a bathtub of metal of ASF-120co and ASF-120us furnaces is performed. The most effective way is introduction of heat by means of electric arches which efficiency is 0,69-0,78. Heating of the metal charge by means of torches of gas-oxygen torches, efficiency of the method 0,45-0,55 is less effectively carried out. Heating of a metal bath by means of oxidation of coke which is continuously entered into slag for foaming of the last is carried out with the efficiency of a way of the method 0,28-0,36.

Practical application of mathematical models of electro-thermo-mechanical processes in industrial induction furnaces with the aim of increasing their energy efficiency

The object of research is an industrial induction steel-melting furnace. One of the most problematic places in induction steel-melting furnaces is low energy efficiency due to their constructive imperfections and the existing technological process of thermal work, which leads to excessive energy consumption. In the course of the study, mathematical modeling of the influence of the electromagnetic field on the elements of an induction furnace was used. Experiments were also carried out to verify the action of the electromagnetic field on the trajectory and speed of movement of the molten metal both in laboratory conditions and in an induction furnace. To study the movement of the molten metal, a special thermal float was manufactured. The float consists of a ceramic heat-resistant sleeve, into which a tungsten rod is inserted. For greater accuracy of the experiment, the float weight is equal to the weight of the melt of the same volume. Thanks to the experiments conducted in the laboratory and on the furnace, an algorithm was developed for the operating modes of the electric inductor. The analysis of the inductor operation modes at different frequencies is carried out. The influence of the frequency of the current supplying the inductor to the penetration depth of the electromagnetic field is revealed. With decreasing current frequency (f 50 Hz) it decreases. It is also confirmed that the maximum effect of the electromagnetic field on the melt is concentrated inside (along the height) of the melt. The main issues of practical application of the mathematical model of electro-thermo-mechanical processes arising in industrial induction furnaces during heating and melting of various metals and their alloys, which are widely used in mechanical engineering, are considered. The system of equations in the form of boundary-value problems of electrodynamics for a quasi-stationary magnetic field, non-stationary heat conduction and non-isothermal thermoplasticity is used. The practical application of the proposed methods of using the capabilities of mathematical modeling of electrometallurgical processes is the basis for the creation of modern computer programs with the aim of improving energy efficiency by significantly reducing unnecessary, unreasonable energy losses.

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.

EFFECTIVENESS OF STATIC THYRISTOR COMPENSATORS SYSTEMS ON THE EXAMPLE OF OJSC «BSW»

The issues of technical and cost efficiency of system of statistical thyristor compensators on the example of the Belarusian steel works are considered. Information on researches of system of power supply of arc-furnace melting shops is provided. The data of the highest harmonicas of the arc steel-melting furnace and ladle furnace are specified. The diagrams of current, voltage, capacities during the operation of the arc steel-melting furnace both with system of thyristor compensators, and without it are provided.

Changing the Arc Efficiency during Melting of a Charge in Arc Steel Melting Furnaces

The article presents the results stemming from the calculation of the arc efficiency of arc steel melting furnaces during melting of scrap and metallized pellets. Furnaces that use metallized pellets are characterized by less arc efficiency and a higher electric energy consumption than similar pellet furnaces. The calculation results are confirmed by experimental investigations of energy balances of arc steel melting furnaces during melting of scrap and metallized pellets.

Design and Implementation of a Hybrid System for the Mitigation of PQ Problems of Medium-Frequency Induction Steel-Melting Furnaces

This paper describes a hybrid system for the mitigation of power quality (PQ) problems of medium-frequency coreless induction steel-melting furnaces. The hybrid system is composed of passive shunt-detuned filters and a hybrid active power filter (HAPF). Since the single-phase load-resonant thyristor inverter of the work coil operates at variable frequency and supplied from a multipulse thyristor rectifier, interharmonic current components, due to cross-modulation phenomenon across ac–dc–ac link, appear in supply lines. The frequencies of these interharmonics are migrating in time over a wide range, and they interact with passive shunt LC filters and other power-system components resulting in harmful effects on the overall system. Reactive power compensation of medium-frequency coreless induction steel-melting furnace is achieved by passive shunt-detuned filter banks, thus avoiding the amplification risk of interharmonic current components. Interharmonics are satisfactorily suppressed by a HAPF with K control strategy. The performance of controller is improved by modifying the conventional K control strategy and adding feedforward control loops for dominant characteristic harmonics. The resulting hybrid system is operating in a steel-melt shop successfully since March 2013.