Arc Furnace Electrode Research Articles

Application of a protective coating based on magnesium hydroxide to reduce oxidation of the side surface of graphitized electrodes in electric arc furnaces

Application of a protective coating based on magnesium hydroxide to reduce oxidation of the side surface of graphitized electrodes in electric arc furnaces

Iron ore wires as consumable electrodes for the hydrogen plasma smelting reduction in future green steel production

In this work we investigate the feasibility and optimisation pathways for using oxide-filled consumable electrodes as both ore feeding system and reducing/melting arc carrier in the hydrogen plasma smelting reduction process. Similar in nature to Söderberg-type electrodes, but free of C-containing substances, this approach has the potential advantage of eliminating the carbon emissions stemming from conventional electric arc furnace electrodes while drastically simplifying the ore feeding into the process. Using a commercial welding setup with a 1.2 mm thick oxide-cored steel wire, area investigations indicate that approximately 50% of the introduced iron ore could be reduced to metallic iron at 100 A arc current under an Ar-10% H2 atmosphere independent from deposition time. The reduction efficiency was negatively affected by increasing arc current and it was increased by using the wire as the anode. Based on the performed variation of deposition parameters, microstructural characterisation results, high speed footage and first upscaling trials, the key scientific questions and engineering pathways for technological optmisiation towards future green steel production technology are outlined and discussed.

Electric Arc Furnace Electrode Movement Control System Based on a Fuzzy Arc Length Identifier

From the point of view of the synthesis of control influences, arc steelmaking furnaces are complex nonlinear objects with strongly expressed mutual influences. It has been demonstrated that at a given supply voltage, the distribution of the current values of the phase currents in the quasi-steady-state mode makes it possible to estimate the situation in the arc space of an arc steelmaking furnace and identify the value of arc lengths. This dependence is preserved in transient modes. In order to identify arc lengths from the phase currents, it is proposed to use an approach based on the theory of fuzzy sets. The construction of the fuzzy arc length identifier rule base was carried out in two stages: the first stage used data from quasi-steady-state modes and the Wang–Mendel algorithm; the second stage involved adding a new rule to the database if the activity level of the formed rules was lower than the established level α for the data obtained in the dynamic mode. Further optimization of the parameters of the fuzzy identifier for operation in dynamic modes was carried out using the “back-propagation” algorithm. Based on the identified values of arc lengths, a control system for the movement of electrodes in an arc steelmaking furnace was synthesised. The proposed control system makes it possible to eliminate unproductive electrode movements due to changes in the situation in other phases of the arc steelmaking furnace and simplifies the application of modern methods of synthesising a control system for such complex objects. The results obtained in the mathematical model have confirmed the effectiveness of the proposed control system for the movement of electrodes in an arc steelmaking furnace.

Investigation of a novel ceramic coating for graphite electrodes in electric ARC furnaces using numerical simulation, experimental method, and industrial testing

Electric ARC furnaces (EAF) are referred to as a set of furnaces in which the process of melting metal materials takes place using an electric ARC. The temperature of melting and discharging in these furnaces is different and can vary between 1600 and 3000 ℃. These furnaces can use lime, fluorine, iron, etc., and ferroalloys to produce metal products such as steel or cast iron. The production of EAF metal products depends on various factors, including graphite electrodes. Electric electrodes are one of the main components of EAF, which transfer the current by creating an electric ARC from the electrode arms to the furnace load. Nowadays, a growing need is felt for using graphite electrodes in electric ARC furnaces (EAF). The validity of SiO2/ TiO2 productive coating is evaluated to decrease the corrosion resistance of graphite electrodes through the experiments. The corrosion of the graphite samples was simulated using finite element (FE) simulation in ANSYS software. FE simulation was used to model the actual working condition of electrodes in the EAF. The validity of SiO2/TiO2 productive coating is evaluated to decrease the corrosion of electrodes by using numerical simulation, experimental methods, and industrial testing in the EAF. All the tests and experiments performed in this study were to obtain a more precise consideration of the corrosion of electrodes. Also, using the TGA (Thermo-gravimetric analysis), the results show that this ceramic coating has a prominent role in decreasing the corrosion of electrodes at high temperatures. Finally, it was realized that coating the surface of graphite electrode with two layers of SiO2/ TiO2 would effectively decrease the consumption of graphite electrodes.

ЭФФЕКТИВНОСТЬ ИСПОЛЬЗОВАНИЯ ИСПАРИТЕЛЬНОГО ОХЛАЖДЕНИЯ ДЛЯ СНИЖЕНИЯ РАСХОДА ГРАФИТИРОВАННЫХ ЭЛЕКТРОДОВ В ДУГОВЫХ ПЕЧАХ МАЛОЙ ЕМКОСТИ

Graphite electrodes used in arc furnaces are consumable material. In the cost of produced castings of finished products in the foundry production, the cost of graphite electrodes is a significant part of the costs, so the reduction in their specific consumption is an urgent task. An analysis of the reasons determining the specific consumption of graphite electrodes, and the existing methods of reducing the specific of graphite electrodes waste, among the considered methods it was established that the most promising direction is the use of water evaporative cooling. The aim of the work is a theoretical analysis of the effectiveness of evaporative cooling with water side surface of graphite electrodes in arc furnaces of low capacity. Computer simulation of the thermal state of a graphite electrode was carried out on the example of a three-phase alternating current arc furnace with a capacity of 6 tons. It has been established that the evaporative cooling of graphite electrodes can be recommended for operation on active and projected arc furnaces of small capacity. It is determined that the use of water evaporative cooling in arc furnace with a capacity of 6 tons reduces the temperature of the graphite electrode, primarily in its upper part. It has been established that there is an optimal consumption of water that corresponds to a minimum of graphite electrodes and additional electricity. The use of evaporative cooling on arc furnaces of low-capacity is economically more appropriate when using low-quality graphite with respect to its thermal resistance.

Soft-Sensing Model for Submerged Arc Furnace Electrode Current Based on Machine Learning

Soft-Sensing Model for Submerged Arc Furnace Electrode Current Based on Machine Learning

Investigation of the TiO2/SiC/SiO2 Coating Effect On the Wear Rate of Needle Graphite Electrode by using Electrical Discharge Machining

Needle graphite electrodes are one of the main parts used in electric arc furnaces. These electrodes have a significant impact on melt quality and product quality, and their consumption is one of the most important parameters of steel production cost in EAF furnaces. Therefore, reducing the consumption of needle graphite electrodes in these furnaces is very important. The main reasons for continuous use of needle graphite electrodes in arc furnaces are oxidation of the sidewalls and sublimation of their tips, and many solutions have been proposed to reduce them. In the present study, the effect of coating consisting of TiO2/SiC/SiO2 elements on the wear rate of the needle graphite electrode in the sublimation state is investigated using EDM (Electrical Discharge Machining- Spark device). For this purpose, the effect of voltage, current, pulse on time and pulse off time on the electrode wear rate are investigated and in this regard, Taguchi design method has been used to reduce the number of experiments. Based on the test results, TiO2/SiC/SiO2 coating reduces the wear rate of the needle graphite electrode due to sublimation.

Дослідження динамічних властивостей частотно-регульованого електропривода механізму пересування електродів дугової електропечі шляхом математичного моделювання

Considered literature devoted to the modernization of control systems, controllers and variable-frequency drive mechanism for movement of the electric arc furnace electrodes. The research of current and proposed drives through mathematical modeling. Models of the control system of the electrode mechanism for the basic and proposed variants with scalar and vector control are made in the MATLAB software. Survey on simulation models confirmed that the system provides vector control speed transient time 16% less than the DC system and a static error is 0% to 3%. The implementation of the electric drive of the mechanism of movement of electrodes based on the frequency converter with vector control and an induction motor is a promising direction of modernization.

Efficiency of Application of Evaporative Cooling of Graphite Electrodes to Reduce their Consumption in Arc Furnaces

A significant part of the cost of released products in the smelting of steel is the cost of graphite electrodes, so reducing their specific consumption is an urgent task. The aim of the work is to study on a computer model and analyze the efficiency of using evaporative cooling to reduce the consumption of graphite electrodes in electric arc furnaces of three-phase alternating and direct current of small capacity. A computer simulation of the thermal state and fame of graphite electrodes for arc furnaces of three-phase and direct current with the capacity of 12 tons was performed. The efficiency of using evaporative cooling of graphite electrodes was revealed. It is established that for arc furnaces operating on direct and three-phase alternating current, the use of electrodes water cooling allows to reduce the consumption of graphite by about one and a half times. It is established that the water supply to the evaporative cooling system is the most rational during 1–2 minutes after the current is turned on. The use of evaporative cooling of graphite electrodes in arc furnaces can be recommended to reduce their consumption on operating and designed small capacity alternating and direct current arc furnaces.

A New Electrode Regulator System Identification of Arc Furnace Based on Time-Variant Nonlinear-Linear-Nonlinear Model

<p>In this paper, we express arc furnace electrode regulator system as a time-variant nonlinear-linear-nonlinear model. On this basis, we propose an online identification method based on nonlinear-linear-nonlinear model system. This new scheme solves the problem of model variation and prediction precision decline causing by time-varying of arc characteristic. In order to dispose the difficulty of parameters separation in the online identification process, this new method adopts the mind of update the parameters of linear parts and nonlinear parts respectively. It realizes the parameters separation of system effectively. Simulation results show that this method can track the changes of arc characteristics effectively. That it achieves the aim of real-time monitoring and controlling system parameters.</p>

Research and Development of Automatic Control System for Electric Arc Furnace Electrode Positioning

The article is concerned with the advanced automatic control system of electrode positioning at electric arc steel making furnaces and ladle furnaces. Analysis of structure of modern electrode positioning control systems’ nonlinear controllers for electric arc furnaces and ladle furnaces is considered. Disadvantages of these systems were analyzed. A control system with a conventional structure from well-established foreign suppliers was compared with the advanced automatic control system of electrode positioning.

An online outlier detection method based on wavelet technique and robust RBF network

We focus on the issue of outlier detection for time-series data in a process control system (PCS), since outlier detection is a critical step before performing data-based system analysis. Several published articles have proved that a wavelet transform (WT) technique can be used to detect outliers in time-series data, but the standard WT detection method, as well as any other univariate outlier detection technique, does not distinguish between the sudden change caused by the changes of inputs and the fluctuations caused by outliers in PCS. In order to improve this shortcoming of the conventional WT method for the data in a PCS, a new algorithm combining the wavelet technique with a robust radial basis function (RBF) network is proposed here. In this method, a robust RBF network (RBFN) training algorithm is proposed, which can train the RBFN online using the original data as a training set without the need of clean data and thus fits the application of online detection. Furthermore, a hidden Markov model is adopted as an analysis tool to accomplish online automatic detection without pre-selecting the threshold. We compare the performance of our proposed method with the conventional wavelet method and the AR model method to demonstrate its validity through simulation and experimental applications to the data pretreatment process in an electric arc furnace electrode regulator system.

Application of Disturbance Rejecting Fuzzy Controller in Electric Arc Furnace

In this paper, the design of a disturbance rejecting fuzzy controller (DRFC) is applied to the electric arc furnace electrode regulation system. In order to improve traditional PID which is slow response and vulnerable to disturbance, we introduce two model reference fuzzy adaptive control mechanism, one of which is designed to improve response speed and reduce the sine disturbance of the length of arc, and the other of which is designed to reduce the current coupling random disturbance. Simulation results showed that by using a DRFC can acquire better dynamic characteristics in the electric arc furnace electrode regulation system, and has stronger suppression capacity.

Research on Intelligence Control of Electric Arc Furnace Electrode Regulator System

Research on Intelligence Control of Electric Arc Furnace Electrode Regulator System

An Artificial Intelligence Approach to Develop a Time-Series Prediction Model of the Arc Furnace Resistance

The control scheme of an arc furnace electrode positioning system aims to deliver an optimum stable reaction zone below the electrodes by maintaining a fixpoint resistance. However, because of random movement of melted materials during melting period, the resistance of the arc furnace changes randomly. As a result, the electrodes have to move accordingly to obtain a fix-point resistance. Moreover, it is often found that the arc furnace resistance changes very fast and it is impossible for the electrode to track the random change of resistance. Consequently, the furnace becomes unstable and it is often impossible to achieve required production per unit power. Hence, the control system often relies on prediction tools. However, it is difficult to predict the arc furnace resistance using conventional mathematical models. As a result, in this paper, Adaptive Neuro-Fuzzy Inference System (ANFIS) is used to capture the random and time-varying nature of arc furnace resistance. The performance of the proposed model is evaluated by presenting a case study where the outputs of the proposed model are compared with the data recorded from an actual metallurgical plant.

Decrease in the consumption of graphitized electrodes in arc furnaces during their forced cooling

The cost of electrodes during steelmaking is a substantial (up to 12.5%) expenditure part of the end product and is sometimes higher than the cost of the consumed electric power. Therefore, it is necessary to perform a set of measures aimed at decreasing the exploitation consumption of graphitized electrodes. In order to enhance the competitive ability of electric steel products, it is necessary to increase the strength and exploitation reliability of graphitized electrodes, which is controlled, to a great extent, by their technical characteristics. Russian industry produces (TU 48-12-52‐93) electrodes with a diameter from 75 to 555 mm operating at a current density from 10 to 25 A/cm 2 . The technical characteristics of electrodes for both ac and dc furnaces depend on the graphite density ( γ = 1.6‐2.2 g/cm 3 ) and porosity ( σ = 1.4‐2) × 10 5 ( Ω m) ‐1 ). The material density exerts a greater effect on the thermal stability of the electrode, and the porosity mostly affects its oxidation. In addition, the density and electrical conductivity of electrodes affect their electrical resistance and, hence, the electric losses during electric-power transmission. Under the formed economical conditions, the quality of graphitized electrodes is a determining factor; therefore, imported rather than Russian electrodes are most frequently used for the exploitation of furnaces, especially high-power furnaces. Although the imported electrodes are more expensive (by a factor of 1.5‐2.0) but have higher technical characteristics.

Compact Modelling of Electric Arc Furnace Electrodes for Vibration Analysis, Detection and Suppression

Compact Modelling of Electric Arc Furnace Electrodes for Vibration Analysis, Detection and Suppression

Numerical thermal simulation of graphite electrode in EAF during normal operation

Working temperature has a crucial effect on the consumption of graphite electrodes in electric arc furnaces (EAFs). In this work, temperature distribution within the EAF electrodes during normal operation was simulated using the finite element method in both 2D and 3D scales. The contributions of electrical current passing the electrode, thermal effects of the furnace sidewall refractory, slag layer, a titanium based coating as a protective layer, and the process parameters such as water spraying at the end of the electrodes were investigated. The proximity effect of the graphite electrodes in EAF was analysed using a 3D thermal model. The numerical model was validated against experimental measurements of temperature distribution over the electrode surface as well as the published results in literature. The results showed a relatively deep temperature gradient at the electrode tip. Among the environmental and processing parameters affecting the temperature distribution of the electrode, the heat transfer coefficient in the water cooling zone was found to be more important for predicting the accurate thermal field of the electrode. The value 8500 W m−2 K−1 was proposed for the investigated electrode based on the validated 3D numerical results. The results also indicated the importance of the proximity effect on temperature distribution not being ignored.

Investigations concerning the work function of doped graphite

In order to reduce the burning off of electrodes in electric arc furnaces, it is necesary to decrease the specific thermal load at the tip in the arc attachment area. This can be achieved by minimizing the work function of the electrode materials, whereby the peak temperature is reduced. The work function of doped graphite electrodes was investigated under conditions prevailing during standard industrial practice in order to achieve transferrable results. The measurement equipment developed to meet this requirement is based on a design first proposed by Bade and Yos. By measuring the peak temperature of the electrode and its current density, the value of the work function of the material was calculated with a modified Richardson equation. Starting from materials with well-known values of the work function, to verify, the accuracy of the experimental method and the mathematical model, those of pure and dopedgraphites were determined. The additives, oxides as a rule, result in a significant reduction in electron work function in the case of magnesium, calcium and cerium oxides.

Experimental investigations on the consumption of graphite electrodes doped with various oxides

In order to reduce the burning off of electrodes in electric arc furnaces it is necessary to decrease the specific thermal load at the tip in the arc attachment area. This can be achieved by minimizing the work function of the electrode materials, whereby the peak temperature is reduced. The work function of doped graphite electrodes was investigated under conditions prevailing during standard industrial practice in order to achieve transferable results. The measurement equipment developed to meet this requirement bases on a design, which first was put forward by Bade & Yos. By measuring the peak temperature of the electrode and its current density the value of the work function of the material was calculated with a modified Richardson equation. Starting from materials with well‐known values of the work function, to verify the accuracy of the experimental method and the mathematical model, those of pure and doped graphites were determined. The additives, oxides as a rule, result in a significant reduction in electron work function in the case of magnesium, calcium and cerium oxides.