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Electric Arc Furnaces (EAFs) are widely used in the steel manufacturing industry to melt scrap steel by employing a large number of electric arcs. EAFs play an important role in ensuring the efficient production of steel. However, their nonlinear and variable load characteristics have a significant impact on power quality. Because the active power of an electric arc depends on its length, a system for controlling the electrode positions is necessary. This paper presents a control system based on a fuzzy logic controller for the active power control of an electric arc furnace. Individual simulation scenarios were chosen with both reference values and the process taken into consideration. The reference, constant value, step variation, and the sequence of step variation were investigated, as well as step disturbances and the sequence of step disturbances from the viewpoint of the process. Furthermore, the procedure of changing the tap on a transformer was investigated. The proposed solution minimizes the time required for charge elaboration, but the main benefit is that there are no additional costs in the implementation process because the installation remains identical, with the only changes being improvements to soft control management.

Gas burners play a crucial role in various ironmaking and steelmaking processes, particularly for heating and cutting operations. In Electric Arc Furnaces (EAFs), high-speed gas burners are widely used to enhance thermal efficiency. While the majority of heat in EAF is generated by electric arcs, gas burners help distribute heat more uniformly, improving overall energy efficiency. Currently, most of these burners operate with natural gas (primarily methane (CH4)) as fuel and oxygen or air as oxidiser. The gases are supplied through separate ports, forming non-premixed flames. As these flames impinge on scrap metal inside the furnace, heat is transferred primarily through convection and radiation to the scrap metal. However, despite their efficiency, these flames contribute to carbon dioxide (CO2) emissions, increasing the furnace’s overall carbon footprint. With the steel industry striving to reduce carbon emissions, hydrogen is emerging as a promising alternative fuel-particularly green hydrogen, which is produced with zero carbon emissions. Due to challenges associated with hydrogen transportation and storage, blending hydrogen with natural gas is becoming an economical transition strategy in the early stages of decarbonisation. However, before implementing this approach, it is essential to understand the combustion and heat transfer characteristics of hydrogen-enriched non-premixed impinging flames. Despite its significance, research in this area remains limited. This study aims to investigate the combustion and heat transfer behaviour of non-premixed flames impinging on a steel plate. A numerical approach using computational fluid dynamics (CFD) modelling, coupled with a thermodynamic combustion mechanism, is employed to analyse the flow field, combustion zone, and heat transfer characteristics. Large Eddy Simulation (LES) with the GRIMech3.0 combustion mechanism is applied to study different cases with 10 pct, 25 pct, 50 pct, and 75 pct hydrogen blending with natural gas and hydrogen flames. In all cases, the burner geometry remained identical, with only flow variables altered. The findings indicate that, despite hydrogen-blended fuels being supplied at a higher velocity than that of methane to maintain equivalent heat release, it results in approximately the same wall jet region as methane-impinging flame. The results show that the temperature of the flame increases as the hydrogen content increases in the flame. Also, flames with 100 pct hydrogen fuel are predicted to heat the steel plate to 735K compared to 665K for methane flame.

In steel recycling, the optimization of Electric Arc Furnaces (EAFs) is of central importance in order to increase efficiency and reduce costs. This study focuses on the optimization of electric arcs, which make a significant contribution to the energy consumption of EAFs. A three-phase equivalent circuit integrated with the Cassie–Mayr arc model is used to capture the nonlinear and dynamic characteristics of arcs, including arc breakage and ignition process. A particle swarm optimization technique is applied to real EAF data containing current and voltage measurements to estimate the parameters of the Cassie–Mayr model. Based on the Cassie–Mayr arc parameters, a novel Arc Quality Index (AQI) is introduced in the study, which can be used to evaluate arc quality based on deviations from optimal conditions. The AQI provides a qualitative assessment of arc quality, analogous to indices such as arc coverage and arc stability. The study concludes that the AQI serves as an effective operational tool for EAF operators to optimize production and increase the efficiency and sustainability of steel production. The results underline the importance of understanding electric arc dynamics for the development of EAF technology.

China’s vast power grid, with its intricate line configuration, occasionally experiences unpredictable malfunctions. The neutral grounding method holds a pivotal role in addressing these failures and maintaining the distribution network’s operation. This article delves into an innovative low-current grounding system that incorporates arc suppression coils and parallel resistance grounding technology. This grounding technique not only mitigates arcs but also facilitates rapid line selection and tripping. Even in high-resistance conditions, it can precisely detect fault points in overhead distribution lines and promptly isolate the faulty segment. Its characteristics have been validated through simulation

Electro-arc machining (EAM) is a new electrical discharge machining method based on thermal energy. A large amount of thermal energy is released during arc formation to melt and vaporize the workpiece material. Many factors affect arc machining performance, such as electrical parameters (peak current, etc.), non-electrical parameters (flushing pressure, etc.), workpiece and electrode shape, and material parameters. The electrode shape influences the machining performance. Single-factor, single-pulse arc discharge experiments are carried out to evaluate the effect of the electrode’s shape. The polarity effect is verified, and the following results are obtained. For the same workpiece conditions, the arc pit diameter is larger for positive polarity than for negative polarity, suggesting that the arc machining performance is also better for positive polarity. The radius of curvature of the crater has a larger influence than the crater diameter. If a larger etching volume is required, the radius of curvature can be increased, but the etching depth is slightly reduced. The positive and negative polarity also affect the arc plasma characteristic. The compression-expansion effect of the plasma is more pronounced when the direct current is large and positive polarity is used. Waveform analysis shows that the processing stability is higher for positive polarity, whereas negative polarity is more likely to result in bridges and short circuits. As the radius of curvature increases, the processing time, processing instability, and the height of the crater wall increase. The height of the crater wall is higher for positive polarity than for negative polarity.

Electric arcs are a necessary heat source in many industrial processes that take place in Submerged Arc Furnaces (SAFs). Arcs exhibit non-linear electrical characteristics and behave in a complex manner. Therefore, an improved understanding of their behavior enables better control of furnace operation. Modeling of industrial arcs is a multiphysics process that involves simultaneously solving several coupled physical phenomena, such as electromagnetics, fluid dynamics, and heat transfer, including a radiative heat transfer from the plasma arc. Coupling fluid dynamics and electromagnetics is known as Magnetohydrodynamics (MHD). For practical applications, however, there are also simpler approaches to arc modeling, either based on simplified physical principles or empirical behavior. In this paper, a combined Cassie–Mayr model (CMM) and a channel arc model (CAM) are implemented and coupled with a submerged arc furnace electrical circuit model. The complete circuit model parameters such as resistances and inductances are estimated using modeling of a full size furnace, and then, actual measurements from a SAF are used to validate the models by comparing current and voltage waveform. Both models are then used to estimate harmonic distortion in a SAF for different arc current ratios, which should help operators to estimate the arc current in real time thus be able to lower and raise the electrode to keep operating conditions constant.

Since the European Union defined ambitious CO2 emission targets, low-carbon-emission alternatives to the widespread integrated blast furnace (BF)—basic oxygen furnace (BOF) steelmaking strategy—are demanded. Direct reduction (DR) with natural gas as the reducing agent, already an industrially applied technology, is such an alternative. Consequently, the melting behavior of its intermediate product, i.e., direct reduced iron (DRI), in either an electric arc furnace (EAF) or a submerged arc furnace (SAF), is of great interest. Based on the conditions in these aggregates, a test series to experimentally simulate the first few seconds after charging DRI was defined. DRI samples with different carbon contents and hot briquetted iron (HBI) were immersed in high- and low-carbon melts as well as high- and low-iron oxide slags. The reacted samples were quenched in liquid nitrogen. The specimens were qualitatively evaluated by investigating their surfaces and cross sections. The dissolution of carbon-free DRI progressed relatively slowly and was driven by heat transfer. However, carbon, present either in the DRI sample or in the melt, not only accelerated the dissolution process, but also reacted with residual iron oxide in the pellet or the slag.

—The electrical and technological operating conditions of a DSP-120 modular electric arc furnace are analyzed. The problems associated with suboptimal furnace operation at a low power factor, lack of automation in gas-oxygen equipment, and the absence of an informative parameter characterizing the efficiency of shielding arcs by a foamed slag have been described. As a solution to these problems, we propose an improved technique for setting the electrotechnological conditions of the modular electric arc furnace, which is used to develop new optimized heat profiles. Recommendations for optimizing the injection of a carbon-containing material into the furnace using a slag coefficient calculated using the harmonic composition of the arc currents are developed. The implementation of these measures in the operating production is found to cause a technical effect in the form of reduced specific energy consumption, which is crucial for a modular electric arc furnace as an energy-intensive technological unit.

The effect of CaO fluxing on slag morphology was investigated during the reduction of FeO in electric arc furnace slag by aluminum black dross (ABD). Macro- and microscopic observations, by evaluating entrapped gas bubbles and reduced iron droplets related to gas evolution, apparent slag morphologies, and vertical section of slag at different initial CaO contents and reaction times, confirmed that both aluminothermic (dominant reaction) and carbothermic (minor) reduction occurred. Thus, the production of CO(+CO2) gas caused swelling-shrinking phenomena with repeated expansion and collapse of the slag pellet. In addition, macroscopic observation of slag morphologies as a function of the initial CaO content is well associated with quantitative consideration of the apparent viscosity as well as spinel ([Mg,Fe]Al2O4) activity. Consequently, appropriate CaO fluxing is necessary to control the composition of highly fluid slag by changing the slag from a high-alumina system to calcium–aluminosilicate melts when utilizing ABD as a reducing agent.

The Swedish and Finnish steel industry has a world-leading position in terms of efficient blast furnace operations with low CO2 emissions. This is a result of a successful development work carried out in the 1980s at LKAB (Luossavaara-Kiirunavaara Aktiebolag, mining company) and SSAB (steel company) followed by the closing of sinter plants and transition to 100% pellet operation at all of SSAB’s five blast furnaces. However, to further reduce CO2 emission in iron production, a new breakthrough technology is necessary. In 2016, SSAB teamed up with LKAB and Vattenfall AB (energy company) and launched a project aimed at investigating the feasibility of a hydrogen-based sponge iron production process with fossil-free electricity as the primary energy source: HYBRIT (Hydrogen Breakthrough Ironmaking Technology). A prefeasibility study was carried out in 2017, which concluded that the proposed process route is technically feasible and economically attractive for conditions in northern Sweden/Finland. A decision was made in February 2018 to build a pilot plant, and construction started in June 2018, with completion of the plant planned in summer 2020 followed by experimental campaigns the following years. Parallel with the pilot plant activities, a four-year research program was launched from the autumn of 2016 involving several research institutes and universities in Sweden to build knowledge and competence in several subject areas.