Electric Arc Research Articles

Dissolution Behaviors of Recycled Cement Paste and Lime in EAF Slag Under Static Conditions

AbstractRecycled cement paste (RCP) is a CaO-rich resource that is recycled from waste concrete and waste cement. For reducing environmental impact and promoting comprehensive resource utilization, RCP could partially replace lime as flux in electric arc furnace (EAF) steelmaking process. In this study, the dissolution behaviors of RCP and lime in EAF slag at 1400 °C and 1500 °C were investigated using static dissolution experiments. The measured dissolution rate constant of lime at 1400 °C and 1500 °C is 3.12×10−5 and 8.42×10−5 m/s, respectively, while that for RCP is 1.37×10−4 and 2.91×10−4 m/s, respectively. For the lime dissolution, a dense dicalcium silicate (C2S) product layer was generated at the dissolution interface, with the diffusion of Ca2+ in the C2S layer being the limiting step for the lime dissolution. However, for the RCP dissolution, no product layer was observed at the dissolution interface. Instead, a dissolution intermediate layer forms due to slag penetration. During the dissolution of RCP, Ca2+ and SiO44− diffuse from RCP layer to slag, while Fe2+ and AlO45− diffuse from slag to RCP layer accumulating in the dissolution intermediate layer. Furthermore, a dissolution model was developed based on current experimental results, which helps to predict dynamic dissolution process of lime and RCP in EAF slag. In general, the dissolution rate of RCP in EAF slag was much higher than that of lime, partially adding RCP as flux in EAF could accelerate the liquid slag formation in EAF steelmaking process.

Reverse water-gas shift in a novel spark-coupled dielectric barrier discharge plasma: Effects of electrode structure and gas parameters

The reverse water–gas shift (RWGS) reaction holds promise for producing raw materials used in the synthesis of high-value chemicals. However, the reaction is often hindered by low CO2 conversion rates at atmospheric pressure and low temperatures. To overcome this limitation, this study developed a novel reactor based on strengthened spark-coupled dielectric barrier discharge (SSCDBD) without a catalyst, leveraging local high temperatures to enhance performance. The effects of reactor structure and gas parameters on conversion rate and energy efficiency were systematically investigated. The results indicated that the SSCDBD device notably improved CO2 conversion compared to conventional plasma techniques, such as dielectric barrier discharge (DBD), spark discharge, and spark-coupled dielectric barrier discharge (SCDBD), with respective increases of 1000 %, 12.65 %, and 2.79 %. Notably, varying the length of the auxiliary electrode affects the capacitance of the equivalent capacitor and, consequently, the discharge intensity. Furthermore, Increasing the electrode length from 4 cm to 20 cm improved the CO2 conversion rate from 43.7 % to 59.8 %. Moreover, CO2 conversion was positively correlated with the discharge distance, which also affected the volume of the electric arc. However, distances exceeding 1.2 cm interfered with arc formation. At a CO2:H2 molar ratio of 1:1, with an auxiliary electrode length of 12 cm and a discharge distance of 0.8 cm, the maximum CO2 conversion rate of 66 % was achieved at a total feed flow rate of 100 mL min−1, while maintaining a CO selectivity higher than 99 %. Additionally, with a total feed flow rate of 400 mL min−1, CO2 conversion reached 29 % and energy efficiency peaked at 6.34 %.

All-fiber tunable mode converter for a mini-two-arm Mach-Zehnder interferometer.

In this Letter, an all-fiber tunable mode converter for a mini-two-arm Mach-Zehnder interferometer (MTA-MZI) is proposed and realized for the first time to our knowledge. Employing an electric arc discharge technology, we couple a multi-mode fiber (MMF) and a single-mode fiber (SMF), resulting in an MZI characterized by centimeter-scale arms. The varied sensitivity of fiber modes to curvature makes the high-order modes of the MMF more prone to leakage when subjected to bending, leading to alterations in the output interference fringe pattern of the MZI. Through continuous monitoring of the interference fringes of the MZI, we effectively detect the mode properties within the MZI in real time. In addition, a verification experiment is conducted by introducing a peanut structure to excite further higher-order modes of light to enter the MZI in advance. Upon modifying the curvature of the MZI, these excited higher-order modes leak, causing the interference fringe pattern to revert to its initial state without a peanut structure. This experimental validation highlights the potential employment of the MTA-MZI as an all-fiber mode converter and paves the way for optical field mode conversion within an all-fiber framework.

Comparative Study of Steel Mill Dust Leaching with Phosphoric Acid and Sodium Hydroxide

Steel mill dust (SMD), produced by electric arc furnaces, is a highly polluting industrial waste due to its high content of metals (Zn, Fe, and Pb) and fine particle size (ca. 5.4 µm). This residue can be valorized to recover Zn using pyro and hydrometallurgical methods, with hydrometallurgy offering greater selectivity and lower energy costs. However, composition of SMD presents a challenge in identifying an optimal leaching agent. This study investigates the preferential extraction of Zn using two leaching agents, namely 150 g L−1 (1.5 M) phosphoric acid (H3PO4) and 240 g L−1 (6 M) sodium hydroxide (NaOH), in a two-stage leaching process (80 °C). Metallic Zn from the alkaline pregnant solution was recovered by electrodeposition (750 A/m2, graphite anode, stainless-steel cathode) and smelting (450 °C). The samples of SMD contained 26.3% Zn, 20.1% Fe, and 0.9% Pb, in compounds such as magnetite (Fe3O4), zincite (ZnO), and franklinite (ZnFe2O4). Each leaching agent successfully attained a 99% Zn recovery, demonstrating the proposed procedure’s high efficacy. However, H3PO4 leached also Fe and corroded the cathode during electrodeposition, thereby restricting the final recovery of metallic Zn. NaOH demonstrated greater selectivity for Zn over Fe and Pb, producing high-purity Zn deposits on the cathode by electrodeposition and 99% metallic zinc by smelting.

Experiments and Theory on Droplet Ignition with Spark Discharges

ABSTRACT Ignition experiments were performed with individual n-decane droplets, initially, about 1 mm in diameter, which were suspended in quartz fibers and subjected to electrical discharges (sparks) of controlled power and duration. Experiments were performed with glow and arc discharges in air at 1 atm and approximately 300 K . Theory is developed to predict the probability of ignition of a fuel droplet as a function of time when it is exposed to an ignition spark. The theory considers the effect of random spark-to-spark fluctuations in the heat flux into the liquid on the time for the droplet surface temperature to be high enough to enable ignition. A Bayesian analysis is also performed to evaluate confidence intervals for parameters related to droplet ignition. Reasonable agreement between theory and experiment is demonstrated, suggesting that spark-to-spark fluctuations of the heat flux into a droplet may lead to a sigmoidal variation of the probability of ignition with respect to time.

Synthesis of titanium diboride by electric arc plasma in air

The paper reports data that demonstrate the feasibility of vacuum-free electric arc synthesis of titanium diboride. An optimal energy mode was found to synthesize submicron titanium diboride powder with the hexagonal lattice parameters a = 3.03 ± 0.04 Å, c = 3.23 ± 0.04 Å with no impurity crystal phases in its composition. A bulk ceramic sample with relative density of 99.1 % and hardness of 18 GPa was consolidated from the synthesized powder. The powder and bulk ceramic samples were analyzed by scanning electron microscopy and transmission electron microscopy. Structure of the synthesized material has a positive effect on the densification of the material. The sintered grains already formed in the process of synthesis under the influence of external pressure and heating from the current flow sinter each other, forming a single target structure with a minimum number of pores, of oxide impurities. Raman spectroscopy was employed to analyze the homogenized precursor mixture, synthesized powder, and TiB2-based bulk ceramic sample. The obtained Raman spectrum of sintering powder is characteristic of TiB2-based materials with a low concentration.

Research on Process Characteristics and Properties in Deep-Penetration Variable-Polarity Tungsten Inert Gas Welding of AA7075 Aluminum Alloy

In this study, a new deep-penetration variable-polarity tungsten inert gas (DP-VPTIG) welding process, which is performed by a triple-frequency-modulated pulse, was employed in the welding fabrication of 8 mm AA7075 aluminum plates. The electric signal, arc shape, and weld pool morphology of the welding process were obtained by means of high-speed photography and an electric signal acquisition system under varying parameters of the intermediate frequency (IF) pulse current. The principle of the arc characteristics and the dynamic mechanism of the weld melting during the process are explained. In addition, the macroforming, microstructure, and microhardness of the welded joints were investigated. The results indicate that, with an intermediate frequency pulse of 750 Hz, the arc displayed a higher energy density and a more effective arc contraction, which improved weld appearance and penetration. Moreover, the impact and stirring action of the arc refined the microstructure grains of the weld center. Therefore, this new welding method is feasible for welding medium-thickness aluminum alloy plates without a groove.

Deoxidation of steel with calcium carbide. Influence of calcium carbide addition on steel contamination by non‑metallic inclusions

One of the main factors determining the final properties of metal products is the quantity, morphology and distribution of non‑metallic inclusions in steel. The article deals with the issues related to the use of calcium carbide in steelmaking production, instead of secondary aluminum and other deoxidizing materials, in order to improve the quality of the products. During the experimental work on the use of calcium carbide in steelmaking production, instead of secondary aluminum and other deoxidizing materials, second grade calcium carbide according to GOST 1460–81 was used. To determine the contamination of steel with non‑metallic inclusions, sampling was carried out from hot‑rolled products obtained from continuously cast billets. According to the results, it was found that the improvement of melt deoxidation in melts using calcium carbide can be achieved by increasing its consumption. In turn, the use of calcium carbide for deoxidation of the melt upon its release from the electric arc furnace into the ladle, instead of secondary aluminum ingots of grade AB87 according to GOST 295–98, helps to reduce the contamination of steel with non‑metallic inclusions.

Production and characterization of geopolymers containing electric arc furnace dust (EAFD) for hazardous metals sequestration

The present research deals with the production and characterization of geopolymers prepared by mixing metakaolin with sodium silicate, sodium hydroxide solution and different amounts of electric arc furnace dust derived from the production of carbon steel, to be used by the construction industry. Specimens with compositions containing 90, 80, 70, 60 and 50 g of metakaolin and respectively 10, 20, 30, 40 and 50g of electric arc furnace dust powder were prepared. A blank composition containing metakaolin, sodium silicate, sodium hydroxide solution and free from electric arc furnace dust were also prepared for comparison. After production and hardening, all samples were characterized regarding compressive strength and water absorption. Hardened samples with compositions containing 10 and 30g of electric arc furnace dust were then submitted to a release test in order to evaluate the heavy metals elution. It has been observed that the addition of electric arc furnace dust worsens the pastes workability during their production in this way limiting the amount of electric arc furnace dust which may be added to the geopolymeric matrix. However, samples containing 90 g of metakaolin and 10 g of electric arc furnace dust still maintain fair compressive strength (about 27 MPa), low water absorption (about 28 %) and display limited elution of heavy metals. An additional thermal treatment of 1h at 700 °C, performed to induce sintering of the geopolymeric composites and therefore to reduce their porosity, did not lead to materials with improved performances.

MITIGATION OF POWER QUALITY PROBLEMS IN STEEL PLANTS USING STATIC SYNCHRONOUS COMPENSATOR

This paper focuses on mitigating various power quality issues from electric arc furnaces (EAF) in steel plants, including voltage flicker, sag, swell, and harmonics. Arc furnaces are recognized as one of the industry's most nonlinear electrically polluting loads. The proposed solution in this article to address all power quality issues caused by EAF is implementing a flexible power supply strategy known as a static synchronous compensator (STATCOM) for injecting reactive energy into the electrical grid. In this study, an experimental model of EAF is utilized based on real measurements of the variation of arc resistance and arc reactance during the melting phase. The pulse width modulation (PWM) technique is employed for current tracking feedback control to generate the required reactive current. A fuzzy logic controller (FLC) is employed for the DC bus.

Enhancing Efficiency in Electric Arc Furnace Steelmaking: A Multi‐Objective Optimization Approach Using the Non‐Dominated Sorting Genetic Algorithm II

To realize the overall optimization of electric arc furnace (EAF) steelmaking system, a multi‐objective optimization model including smelting cost, energy consumption per ton of steel, and carbon emission per ton of steel is established. The model is optimized by multi‐objective genetic algorithm to improve the charging structure. At the same time, the data in the optimal solution set are used to analyze the influence of the change of scrap ratio on smelting cost, carbon emission per ton of steel, and smelting cycle. According to the actual working conditions and the demand of steel plant, the optimized results are selected. Compared with the actual production data, the proportion of scrap steel increases to 50.9%, the ratio of molten iron decreases to 38.8%, the smelting cost per ton of steel decreases by 12 Yuan, the energy consumption per ton of steel decreases by 4%, the carbon emission per ton of steel significantly decreases by 13%, and the smelting cycle is shortened by 2 min, but at the cost of increasing the power consumption per ton of steel. The optimized results and the analysis of the change of scrap ratio provide reference for the optimization of EAF steelmaking system.

Physicochemical Properties of Air-Quenched Electric Arc Furnace Slag as Free-State Sandblasting Abrasives and Application Potential Analysis

Physicochemical Properties of Air-Quenched Electric Arc Furnace Slag as Free-State Sandblasting Abrasives and Application Potential Analysis

Application of Surge Arrester in Limiting Voltage Stress at Direct Current Breaker

Hybrid DC circuit breakers combine mechanical switches with a redirecting current path, typically controlled by power electronic devices, to prevent arcing during switch contact separation. The authors’ past work includes a bipolar hybrid DC circuit breaker that effectively redirects the fault current and returns it to the source. This reduces arcing between the mechanical breaker’s contacts and prevents large voltage overshoots across them. However, the breaker’s performance declines as the upstream line inductance increases, causing overvoltage. This work introduces a modification to the originally proposed hybrid DC breaker to make it suitable to use anywhere along DC grid lines. By using a switch-controlled surge arrester in parallel with the DC breaker, part of the arc energy is dissipated in the surge arrester, preventing an overvoltage across the mechanical switches. Based on the experimental results, the proposed method can effectively interrupt the fault current with minimal arcing and reduce the voltage stress across the mechanical switches. To address practical fault currents, tests at high fault currents (900 A) and voltage levels (500 V) are conducted and compared with simulation models and analytical studies. Furthermore, the application of the breaker for the protection of DC distribution grids is illustrated through simulations, and the procedure for designing the breaker components is explained.

Experimental recurrence of an unreported fire risk of power cable: Discharge of bracket cable metallic grounding under coupled vibration conditions

In environments like bridges and tunnels, power cables are laid on metal brackets (hereinafter referred to as bracket cables). If the aluminum sheath and metal bracket form a metallic grounding fault, the air gap near the contact point may bear an intermittent discharge under the cable vibration, which is a potential source of cable fires. However, current research on cable grounding systems does not focus on analyzing the physical metallic grounding process. Discharge from coupled vibrations has been overlooked. This study accomplished the experimental recurrence of discharge at the metallic grounding point of cables under coupled vibration. According to the experimental observations, intermittent electric sparks and AC arc occur with the contact and separation of the aluminum sheath and the metal bracket due to vibrations. Under coupled vibration conditions, metallic grounding faults in cables pose a risk of causing cable fires.

Magnetic field assisted blasting erosion arc machining (M-BEAM): A novel efficient and quality improved machining method for Inconel 718

Electrical Arc Machining (EAM) presents an efficient technique for processing difficult-to-cut materials such as Inconel 718. However, despite its extremely high machining efficiency, the high energy density in machining makes it difficult to achieve a desirable surface quality that can be compatible with the subsequent cutting process. To solve this issue, this study explores the application of a magnetic field to enhance the performance of Blasting Erosion Arc Machining (BEAM), namely Magnetic Field assisted BEAM (M-BEAM). It leads to an increased Material Removal Rate (MRR) and reductions in both the Tool Wear Ratio (TWR) and the Surface Roughness (represented by Sa) with the increasing magnetic field strength, attributed to the improvements of the arc deflection and molten metal expelling. Moreover, the electromagnetic force is positively correlated with the discharge energy, which can further improve the machining performance of BEAM, especially when the hydrodynamic force is hard to act at large discharge energy. The MRR and Sa are enhanced and reduced by 14.52 % and 41.86 % respectively due to the stronger control effect at large energy. After multi-objective optimization, the optimized MRR in M-BEAM achieves a 9.22 % enhancement and Sa also decreases by 25.96 % and 60.61 % in the roughing and finishing process. This advancement also elevates machining precision as well as mitigates defects such as debris adhesion, overburning, and cracks. Moreover, the recast layer is significantly reduced by 88.59 % and 89.96 %. Consequently, M-BEAM promises extensive applications in aerospace industries for machining Inconel 718 and even for other difficult-to-cut materials with high efficiency and quality.

Evaluation of Biochar and Coke Blends for Slag Foaming Applications in Electric Arc Furnace Steelmaking

Evaluation of Biochar and Coke Blends for Slag Foaming Applications in Electric Arc Furnace Steelmaking

Закономерности износа плазмотронов при плазменной резке толстолистового проката на токе обратной полярности

The introduction describes the features of the process of plasma cutting of various metals and alloys using reverse-polarity plasma torches with and the features of cutting thick sheets. The purpose of the work is to study the wear process of plasma torches operating on reverse polarity current when cutting thick rolled sheets of aluminum and titanium alloys. Research methods include optical and scanning electron microscopy, filming of the cutting process and visual inspection of plasma torch elements after receiving specimens. Results and discussion. The section shows the appearance of the main working elements of the plasma torch after cutting in various modes, which led to both stable and gradual wear and to catastrophic failure of the plasma torch. The results of structural studies of the main characteristic zones of nozzles and electrodes after cutting are presented. The studies carried out made it possible to establish the main reasons for the failure of the working elements reverse-polarity plasma torches. The causes of catastrophic failure of plasma torches include failure to maintain the gap between the nozzle and the electrode and melting of the channel of gas supply into the discharge chamber. The wear of nozzles and electrodes in a stable mode can be intensified due to abnormal operation of the starting arc, the presence of manufacturing inaccuracies and excess gas pressure. In conclusion, the main conclusions based on the results of the research are formulated. The process of wear of electrodes, nozzles and body elements of plasma torches during operation at high electric arc power values is described.

Prediction interval soft sensor for dissolved oxygen content estimation in an electric arc furnace

In this study, a novel soft sensor modeling approach using Takagi–Sugeno (TS) fuzzy models and Prediction Intervals (PIs) is presented to quantify uncertainties in Electric Arc Furnace (EAF) steel production processes, namely to estimate the dissolved oxygen content in the steel bath. In real EAF operation, dissolved oxygen content is measured only a few times in the refining stage; therefore, the approach addresses the challenge of predicting unobserved output under conditions of irregular and scarce output measurements, using two distinct methods: Instant TS (I-TS) and Input Integration TS (II-TS). In the I-TS method, the model is computed for each individual indirect measurement, while the II-TS approach integrates these indirect measurements. The inclusion of PIs in TS models allows the derivation of the narrowest band containing a prescribed percentage of data, despite the presence of heteroscedastic noise. These PIs provide valuable insight into potential variability and allow decision-makers to evaluate worst-case scenarios. When evaluated against real EAF data, these methods were shown to effectively overcome the obstacles posed by scarce output measurements. Despite its simplicity, the I-TS model performed better in terms of interpretability and robustness to the operational reality of the EAF process. The II-TS model, on the other hand, showed excellent performance on all metrics but exhibited theoretical inconsistencies when deviating from typical operations. In addition, the proposed method successfully estimates carbon content in the steel bath using the established dissolved oxygen/carbon equilibrium, eliminating the need for direct carbon measurements. This shows the potential of the proposed methods to increase productivity and efficiency in the EAF steel industry.

A CuO/MoO3-based SO2 gas sensor with moisture resistance and ultra-fast response at 90°C

Sulfur dioxide (SO2) is a toxic and harmful decomposition product generated during arc discharge or partial discharge in sulfur hexafluoride (SF6) electrical equipment, which can corrode internal pipelines. Detecting SO2 is crucial for assessing the insulation condition of equipment and preventing faults. To overcome the challenges faced by traditional SO2 gas sensors, including high operating temperatures, slow response times, and poor moisture resistance, this paper proposes a novel SO2 gas sensor based on CuO/MoO3. The morphology, composition, and chemical states of the materials were analyzed using different characterization techniques. At 90°C, the S2 sensor (CuO: MoO3=1: 1) exhibited a fast response time (10 s) to 10 ppm SO2 and demonstrated good moisture resistance (a 1 % change in relative humidity (RH) has the same effect on the sensor as 25.9 ppb SO2). The response of the S2 sensor to 100 ppm SO2 was 26.5. Additionally, the voltage sensitivity of the S2 sensor at low (1–10 ppm) and high (10–100 ppm) concentrations are 658.74 mV/ppm and 33.43 mV/ppm, respectively. Therefore, the S2 sensor is more suitable for low concentration conditions. These good sensing characteristics of the S2 sensor are owing to the high content of oxygen vacancies (39.2 %) and the heterojunction effect in the composite material. Additionally, this sensor exhibits excellent anti-interference capabilities, including moisture resistance and high selectivity. Therefore, the CuO/MoO3-based SO2 gas sensor can be effectively applied to detect the decomposition of SF6.

Failure mechanism and thermal runaway behavior of lithium-ion battery induced by arc faults

As the widespread of lithium-ion battery systems such as electric vehicles and energy storage systems, the number of safety incidents due to electrical faults are increasing. Many accident reports have demonstrated that arc faults have become one of the main triggers of LIB system accidents, however, the related studies are inadequate. In this study, an arc imitation system is employed to investigate the influence of different arc energies on battery safety valve, as well as the electrochemical characteristics of faulty batteries. The results show that the minimum arc power to breach the safety valve ranges from 110 to 441 W. The maximum temperature rise rate on the battery surface can exceed 15 °C/s with arc power of around 1000 W. Further, the testing of in-situ and ex-situ indicate the faulty batteries undergo degradation and failure due to that moisture in the air enters the battery interior, resulting in increased internal resistance, loss of active materials and cyclable lithium. Finally, the faulty battery has no valve opening during thermal runaway, and the ignition time is four hundred seconds earlier than that of the normal battery, indicating more severe fire dangers. The results are valuable for safety design of battery systems in relation to arc faults, as well as the characteristic for fault detection and early warning.