Electric Arc Furnace Operation Research Articles

Comparison of the Operating Conditions of Electric Arc Furnaces with Short and Long Arc Discharges

A mathematical model is developed to describe the electromagnetic energy transfer between the phases of an electric arc furnace. This model is used to study the efficiency of operation of a DSP-100 electric arc furnace with the coplanar arrangement of a secondary current lead for short, medium, and long arc discharges. The energy processes in the furnace are found to be determined by both the potential gradients in arc discharges and the electromagnetic coupling of the phases, which causes redistribution of the total power released in arc discharges between the phases. Recommendations for the application of a phase-by-phase controlled reactor during long-arc operation are made.

Electric Arc Furnace (EAF) Modelling and Comparative Study of Flicker Mitigation Techniques

In the steel production, electrical arc furnace EAF is mainly used for melting the scrap iron. In steel production is increased by using EAF. The EAF is an extremely non-linear and massive power load, but due to EAF is stochastic functioning of an EAF, in the research of the power quality enhancement is motivated. The EAF operation power quality is introduced, the power quality negative consequences decides are characteristics and non-characteristics harmonics, voltage flicker effect, low power factor that arises in the electrical network in operation of the EAF. The quality disturbance are harmonics and current flicker. In the dynamic analysis of the power quality to voltage flicker is studied. The dynamic and static analysis of the EAF we taken examined to study the survival of the voltage flicker in the power system, The analysis of the harmonic is conveyed out to current harmonic is clarify under different types of EAF operation in the power system, so that controller, filter and PWM are used. The controller is hysteresis current and vector current are used to reduce the harmonic through the filter. The pulse width modulation generates the sinusoidal waveform. The EAF operation is beyond the permitted levels as per IEEE references, so as to mitigate the harmonic problems due to an EAF , a rapid dynamic reactive power compensation devices like series passive filter with vector current and hysteresis current controller is being proposed as a solution, The power system has been simulated using MATLAB and the results were tabulated.

Comprehensive Electric Arc Furnace Electric Energy Consumption Modeling: A Pilot Study

The electric arc furnace operation at the Štore Steel company, one of the largest flat spring steel producers in Europe, consists of charging, melting, refining the chemical composition, adjusting the temperature, and tapping. Knowledge of the consumed energy within the individual electric arc operation steps is essential. The electric energy consumption during melting and refining was analyzed including the maintenance and technological delays. In modeling the electric energy consumption, 25 parameters were considered during melting (e.g., coke, dolomite, quantity), refining and tapping (e.g., injected oxygen, carbon, and limestone quantity) that were selected from 3248 consecutively produced batches in 2018. Two approaches were employed for the data analysis: linear regression and genetic programming model. The linear regression model was used in the first randomly generated generations of each of the 100 independent developed civilizations. More accurate models were subsequently obtained during the simulated evolution. The average relative deviation of the linear regression and the genetic programming model predictions from the experimental data were 3.60% and 3.31%, respectively. Both models were subsequently validated by using data from 278 batches produced in 2019, where the maintenance and the technological delays were below 20 minutes per batch. It was possible, based on the linear regression and the genetically developed model, to calculate that the average electric energy consumption could be reduced by up to 1.04% and 1.16%, respectively, in the case of maintenance and other technological delays.

Assessment Parameters of Total Load Graphs with Disordered and Coordinated Operation of Electric Arc Furnaces

Assessment Parameters of Total Load Graphs with Disordered and Coordinated Operation of Electric Arc Furnaces

Demand Side Management Scheduling Formulation for a Steel Plant Considering Electrode Degradation

Abstract Stainless steel production consumes a large amount of electricity. Demand side management (DSM) has been identified as a key way to reduce costs in steel plant operations by responding to time-varying electricity prices. The electric arc furnace (EAF) is responsible for the majority of a steel plant’s electricity consumption and has been identified as having sufficient flexibility to participate in DSM schemes as it is run in batch mode with variable operating settings. Often neglected in steel plant scheduling is the degradation of the electrodes of the EAF units and the associated cost of replacing them. However, there exists a complex tradeoff between the intensity at which the EAF is operated, and the lifetime of the electrode. The intensity in this case also strongly affects both electricity consumption and the length of a batch. This work proposes a novel scheduling formulation that explicitly considers DSM and its relation to electrode degradation. Results show on the one hand, that the novel formulation is able to more realistically model the EAF operations by explicitly considering electrode consumption. On the other hand, the model is also able to effectively balance the trade-offs between DSM-related costs and electrode replacement costs by extending the lifetime of the electrodes while still having the flexibility to be able to participate in DSM schemes.

Real-Time Dynamic Optimization-Based Advisory System for Electric Arc Furnace Operation

Electric arc furnaces (EAFs) are widely applied in the steel industry for producing steel by melting scrap metal. This highly energy-intensive steelmaking process is subject to limited automation, with decisions related to input amounts and timings typically made by operators. This leads to suboptimal EAF batch operation due to complex behavior and relationships between variables that are inevitably overlooked in the decision making. In this work, we introduce an advisory system that employs a first-principles EAF model to support the operator decision making in real-time for economically optimal process operation. A dynamic optimization calculation can be triggered by the operator at any point in the batch, an action that can be repeated multiple times during the batch. The advisory system incorporates a multirate moving horizon estimator (MHE) that continually computes estimates of the process states utilizing current and past inputs and measurements. End-point constraints and potential extension of the batch duration are handled through a multitiered optimization algorithm. Case studies demonstrate a major economic improvement when the dynamic optimization-based advisory system is used. We show that the online computational load is under 5 s on average when a proposed multitiered initialization scheme is used for solving the large-scale optimal control problems.

Smelting of ferrosilicum from the position of energy and technology criteria of ferroalloys electric arc furnace operation

For estimation of ferroalloy-producing electric arc furnace operation efficiency an energy and technology criteria proposed. Its physical meaning is as follows: it determines a share of energy from the current source, in particular its useful part, spent by ore reduction carbon-thermal process of a ferroalloy production (ferrosilicum, ferrochrome, ferromanganeese), taking into account heat losses and degree of extraction of the leading element into the alloy.Results of an analysis of ferroalloys smelting parameters in electric arc furnaces via carbon-thermal process by example of smelting FeSi using energy and technology criteria of ferroalloys furnace operation presented. It was shown, that while increasing values of energy and technology criteria, the specific consumption of electric power per one basic tonne of the alloy is reducing. For mid power electric furnaces that melted 75% FeSi, the energy and technology criteria of ferroalloys furnace operation corresponds to a range from 0.300 to 0.314. At the same time, the specific electric power consumption is from 9.0 to 8.6 MW∙h/t of the alloy. A satisfactory, but less efficient version of the furnace operation is the range of energy and technology criteria from 0.272 to 0.293 and specific electricity consumption of electric power varies from 9.8 to 9.2 MW∙h/t of alloy. Such a complex value can be considered as the main element of the energy and technological audit of the ferroalloy furnace facility, as well as to identify effective operating modes, analysis of usage of various types of charge materials (ore raw materials, carbonaceous reductants) and the application of innovative melting technologies.

Programming of Operation in Electric Arc Furnaces

The objective of this paper is to analyze the decrease of the “tap to tap,” or operating time, of arc furnaces. A study that includes dynamic programming is carried out in the programming of operation of electric arc furnaces. Optimization of the operation is performed at a later phase of the research. Each step of the process is analyzed or put into operation following the direction of an expert. Following specific operating conditions, the behavior of the furnace is characterized and the relationship between voltage levels in the secondary arc is identified using a circular diagram in order to find the feasible region for the optimal solution. The search is carried out in the furnace feeder, and the furnace specific mechanisms are identified in order to decrease the “tap to tap.” This analysis allows the proposal of a new optimization model that considers dynamic.

Investigation of Power Quality Disturbances in an Electric Arc Furnace

Stochastic performance of an electric arc furnace (EAF) has drawn researcher’s attention due to power quality problems introduced by EAF operation. In this paper, Electric arc furnace is modeled to investigate power quality problems. Voltage flicker, harmonics and inter-harmonics are the main power quality disturbances that arise in the electrical network as a result of arc furnace operation due to the non-linear nature of EAF. A time domain model is derived to study the behavior in various operating conditions (melting and refining). The characteristic modeling of an EAF is carried out in MATLAB (Simulink).

Real-time energy management for electric arc furnace operation

Electric arc furnaces are used extensively in the steel industry for steel production. Development of energy savings strategies for the highly energy-intensive batch process is extremely challenging due to the complexity of the process and lack of measurements due to the harsh operating conditions. Here we introduce a new energy management approach that effectively curtails the energy cost in real-time through the implementation of economically optimal operating decisions. An economics- oriented shrinking horizon nonlinear model predictive control (NMPC) algorithm that exploits time-varying electricity prices is coupled with a multi-rate moving horizon estimator (MHE) to form an integrated decision- making framework. With a detailed first-principles dynamic model functioning at the core, the multi-variable interactions and plant variations are successfully incorporated into the control strategy to achieve reliable performance. We also present a novel initialization scheme for obtaining fast on-line solutions of the economic NMPC and multi-rate MHE dynamic optimization problems. Using this initialization algorithm, we show that the optimal input decisions are obtained with sufficient computational speed for real-time implementation. The energy usage optimization results indicate a significant reduction in the operating cost and peak electricity demand compared to the case where the electricity price profile is not updated.

Installation, Startup, and Performance of a Static VAR Compensator for an Electric Arc Furnace Upgrade

This steel maker upgraded the electric arc furnace (EAF) melt shop to increase production and improve the metallurgical quality of their product. The increased electrical load and harmonic generation for the new 50 MVA furnace operation necessitated the installation of an 80 MVAR static VAR compensator (SVC) to meet utility interconnect requirements. This paper is a follow-up and companion to the author's previous paper that documented comprehensive analysis to specify the SVC. This paper describes the sequence of events during the installation, commissioning, and operation of the SVC. It will assess the performance of the SVC compared with the electrical requirements of the utility for voltage regulation, flicker, harmonics, and power factor. Power quality measurements during EAF operation without the SVC established a baseline to compare improvements provided by the SVC as well as compliance with the utility limits. Additionally, events encountered during the commissioning are shared as lessons learned.

Способы улучшения эффективности работы сверхмощной дуговой печи за счет электрооборудования

In this article, the specifics of the operation of ultra-high electric arc furnaces on the example of EAF-180 PJSC Magnitogorsk Iron and Steel Works are considered, the main methods for regulating the secondary voltage of the furnace transformer are given. Based on the analysis carried out by the authors, an improved power scheme for the thyristor contactless control of the secondary voltage of the furnace transformer is proposed, which ensures an increase in the stability of the electric regime of the furnace. The questions of the choice of the power of the elements of a static var compensator are noted.

Optimization-based Online Decision Support Tool for Electric Arc Furnace Operation

Electric arc furnaces (EAFs) are broadly used in the steel industry for producing different grades of steel by melting steel scrap and modifying its chemistry The EAF process is highly energy intensive and involves a low level of automation. The decisions associated with the amount and timing of injected inputs depend heavily on the EAF operators. Although the operators’ practical experience is crucial in running the EAF, important multivariable interactions and subtle relationships may not be apparent. In this work, a multi-rate moving horizon estimator (MHE) is coupled with an economics-based dynamic optimizer to form an online decision support tool (DST). The tool is able to reconstruct the states and provide optimal decisions to operators in less than 18 CPU seconds on average despite the use of a highly nonlinear large-scale EAF model. This framework is developed using entirely open source tools to have a high appeal to industrial practitioners. A case study is presented which demonstrates the increase in profit through the use of the DST.

Modelling of three-phase electric arc furnace for estimation of voltage flicker in power transmission network

This paper presents a dynamic model of an electric arc furnace (EAF) developed in Matlab/Simulink environment. Model is based on simulating varying resistance of the electric arc in time-domain while taking into account its stochastic behaviour. The model was applied for estimation of voltage flicker in power transmission network at the point of common coupling caused by operation of EAF. Modelling and simulation of an International Eletrotechnical Commission (IEC) flickermeter were also performed in order to calculate voltage flicker from the simulated EAF voltage. In order to verify the developed EAF model, calculations of voltage flicker were compared to measurements obtained from various operating conditions of the EAF such as boring, melting and refining. Influence of short circuit power and switching operating condition of the transmission network on flicker levels at point of common coupling was investigated.

Electric arc modeling of the EAF using differential evolution algorithm

ABSTRACTŠtore Steel Ltd. makes more than 1400 steel grades. The highest costs in steel production from scrap stems from the electric arc furnace electric energy consumption. Electrical energy is used to produce heat energy generated by the burning arc between the graphite electrodes and steel scrap. In general, the balanced heat input of all electrodes is essential. Based on the input of thermal energy from all electrodes, also the possibility of occurrence of hot and cold spots in the electric arc furnace can be determined. Perception of and the elimination of the unequal heat load of electrodes have a major impact on reducing operating costs and increasing the efficiency of the electric arc furnace production. Most authors have modeled the arc furnace as an electrical equivalent circuit, where the electric arc is modeled using the macroscopic approach. In this paper, the microscopic approach to the electric arc model is described, where a set of equations (electrical neutrality, Dalton law, Saha–Eggert) was solved using differential evolution algorithm. The results of modeling were practically confirmed by measuring electric parameters (voltage, current, active power) during the electric arc furnace operation. In November 2016, the investment in a new electrode controller using implemented logic will be carried out.

EAF optimal managing elements

Electric Arc Furnaces (EAF) is an important and complex aggregate. We present elements of EAF operating efficiency. The reliability of the EAF is mainly determined by electric circuit reliability and especially of the transformator of the furnace. This due to the fact that, in an electric steel plant, the objective „24 tapping/day” involves. Due to the complexity of the process, the EAF operation needs a computer usage and, in his componence, it must have two independent calculation units (UC1) and (UC2). Based on these two input sets (Σi1) and ((Σi2), the calculation unit (UC1) builds the general operation procedure based on mathematical methods. For that purpose, there are used the results of the 5 mathematical methods: the mathematical model to write-off the function objective (M.F.O.); the mathematical model of calculating the charge (M.C.C.); the mathematical model of conducting the effective melt (M.C.M.); the mathematical model of reheating the charge (M.R.C.); the mathematical model of blasting the reactive dusts (M.B.R.D.).

Parameters estimation of electric arc furnace based on an analytical solution of power balance equation

Summary A closed-form solution for power balance equation of electric arc furnace (EAF) is proposed in this paper based on field measurements of the instantaneous furnace voltage and current. The method is developed based on an analytical solution of power balance equation in general case. The closed-form solution is dependent on the EAF parameters, which should be found by parameter identification procedure carrying out by minimization of an appropriate objective function. The minimization is performed by means of a calculus-based optimization method, namely, interior-point method. The validity of the proposed method is verified by comparing its results with those of the field measurements. The results show quite satisfactory correlation between the proposed method and the actual EAF operation.

Application of New Generation Electromagnetic Stirring in Electric Arc Furnace

Today's electric arc furnace (EAF) normally operates with high power input and short tap-to-tap time and has high demands on the bath mixing capacity to improve the heat and mass transfer. A new generation of electromagnetic stirrer (ArcSave) for EAF operation has been developed by ABB Metallurgy and applied in the industrial furnaces. The stirrer installed underneath the furnace bottom creates a whole bath mixing effect thus accelerates the homogenization of the temperature and chemical composition of the steel. Two ArcSave systems have been installed in 2014. One has been installed on a 90 ton Eccentric Bottom Tapping (EBT) furnace for carbon steel production in the United States and the other installed on a 90 ton spout tapping furnace for stainless steel production in Sweden. The effect of ArcSave on the EAF process has been studied during the hot test period and the resulting performance has been compared based on 6-month-data without stirring and 6-month-data with ArcSave. This paper will present the detailed information of the investigation results obtained from these two installations. ArcSave speeds up the scrap and FeCr melt-down, reduces the scrap cave-ins, homogenizes the temperature and chemical composition of the steel bath, forces the metal/slag reactions closer to equilibrium state, increases the decarburization rate. ArcSave reduces the consumption of electric energy and increase the scrap yield which makes the electric arc furnace more cost effectiveness. ArcSave is a potential and reliable solution to improve the operation safety, increase the productivity, and reduce the cost.

Correlation Between Multiple Electric Arc Furnace Operations and Unscheduled Power Flows in the Interconnection Lines at the Eastern Cross Border of ENTSO-E

In this paper, the correlation between unscheduled power flows in the interconnection lines at the eastern cross border of the European Network of Transmission System Operators for Electricity (ENTSO-E) and multiple electric arc furnace (EAF) operations in Turkey has been assessed. Turkey is interconnected to ENTSO-E at the eastern cross border via Greece and Bulgaria, with a 400-MW export and a 550-MW import agreement. In order to determine the degree of the relationship between the unscheduled power exchange between Turkey and Europe, and the multiple high-power EAF operations, Pearson correlation method has been employed. For this purpose, time-synchronized data of active power consumption have been collected from 17 major EAF plants during 1 week with a time resolution of 3 s, by using custom-design, synchronized power-quality (PQ) analyzers. A total peak-power consumption of nearly 1.5 GW of multiple EAF loads has been recorded. The results obtained have been evaluated by the use of the National Power Quality Monitoring System of Turkey, which continuously monitors the power flows in the interconnection lines of the ENTSO-E by PQ analyzers. The rate of change in total EAF power consumptions higher than 200 MW in less than 15 s against the rate of change in area control error (ACE) index is found to be closely correlated to each other, with a Pearson correlation coefficient (CC) of 0.8. Since the response of the frequency restoration reserve of power plants is much slower, such rapid fluctuations in the power consumption of multiple EAFs collectively result in uncontrollable power flows in the interconnection lines at the eastern cross border of ENTSO-E.

Fast and Robust Predictive Current Controller for Flicker Reduction in DC Arc Furnaces

A fast and robust predictive current controller for reduction of flicker caused by dc electric arc furnaces (EAFs) supplied by thyristor converters is presented in this paper. During normal EAF operation, large active- and reactive-power variations can occur at the point of furnace connection, causing unwanted variations of network voltage and correspondingly a flicker phenomenon. The main cause of this phenomenon are electrode short-circuits with large current swings, which occur during the so-called bore-in period of the furnace cycle. The proposed controller reduces the flicker caused mainly by reactive-power variations during the electrode short-circuits by providing fast and robust predictive control of the arc current without relying on the accurate arc model. The obtained simulation and experimental results demonstrate the ability of the presented current controller to effectively compensate for the electrode short-circuits, thereby enabling a reduction of the unwanted fluctuations of the reactive power, which are the main cause of the induced flicker. The simulation results show that the proposed controller can reduce the induced flicker by up to 50%, compared to the traditionally used system with PI current controller. Also, the controller is robust to the asymmetries and the abrupt changes of the network voltage.