Electric Arc Furnace Steelmaking Research Articles

Fumes exhaust control at the electrical arc furnace of Industeel Le Creusot

Electric Arc Furnace (EAF) steelmaking generates fumes that must be captured for economic and environmental reasons. The fumes exhaust control at the EAF must be adapted to the process in order to fulfil the steel plant requirements and to meet the environmental regulations. It is in this context that Irsid has implemented, on 6 EAF (5 in France and 1 in Belgium), a strategy of advanced control associated to a representative instrumentation of the fumes emissions. An on-line defect detection algorithm is added to the pressure control in order to improve its reliability. Latest results obtained in Le Creusot have shown that the fumes exhaust control has a direct impact on the EAF ratios with a reduction of energy consumption, a reduction of electrode consumption and a reduction of the amount of dust recovered in the filters.

Concept of dynamic foaming index and its application to control of slag foaming in electric arc furnace steelmaking

To sustain a foam in steelmaking processes, two basic requirements should be fulfilled, i.e. appropriate physical properties of the slag such as high viscosity, low density, and low superficial tension, and the generation of sufficient reaction gas. To date, foaming indexes have been focused on the physical properties of refining slags. In the present paper a dynamic foaming index (DFI) that involves both above requirements is proposed, using a kinetic model of the electric arc furnace process to calculate the generation rate of reaction gas, mainly CO. When the arc distortion, as affected by electrode submergence in the foam, is compared with the DFI, calculated via the kinetic model, it is observed that both parameters follow very similar trends. This finding indicates the feasibility of knowing the foaming conditions of a heat in advance, or of using the kinetic model online to control the foaming phenomena. Furthermore, experimental results relating to dynamic behaviour of the slag chemistry are well simulated using the kinetic model. To take into account the effect of size distribution of carbon particles injected into the slag to reduce FeO, a Monte Carlo simulation has been integrated into the process simulator, allowing a more realistic prediction of the current steelmaking process.

Process dynamics of electric arc furnace during direct reduced iron melting

A phenomenological mathematical model to simulate steelmaking operations in an electric arc furnace (EAF) has been developed. This model has been validated with industrial data from a Mexican company that employs direct reduced iron (DRI) as the main iron unit. The slag and steel composition can be predicted in real time with the aid of several components integrated into the simulator. The model starts with the optimization of mass and energy balances that yields the requirement of materials to produce a given quality of steel with the minimum cost. The rate of reduction of iron oxide is computed based on two reactions occurring between the FeO and carbon dissolved in the metal and FeO with the carbon particles injected into the slag. A mechanism of consumption of carbon particles has been completed, which includes the effect of surfactant species in the slag and operational variables of the industrial practice of carbon injection. A new concept, called dynamic foaming index, (DFI) is proposed to quantify the actual foaming behavior of industrial slags throughout a commercial heat. The results prove the versatility and robustness of the present mathematical model and provide a knowledge base to assist in the design, operation, and optimization of metallurgical practices for EAF steelmaking.

A Mathematical Simulator for the EAF Steelmaking Process Using Direct Reduced Iron

A mathematical simulator for the melting operation of direct reduced iron in electric arc furnaces (EAF) has been developed. The simulator takes into account the changes of physical properties of slag with time as well as the operating aspects of the process by using different input types of the raw materials into the furnace. Control of the bath oxidation is performed through the injection of carbon fines in the slag. Cost-optimized mass and energy balances are employed as generators of initial and boundary conditions to start the solution of a set of ordinary differential equations whose solution allows to know the dynamic changes of temperature and metal and slag chemistry with time. Simulation results indicate that the final bath oxidation level is more dependent on the process routes than on the quality of the direct reduced iron (DRI) being melted. High carbon wettability by slags and basic slags are the most suitable conditions to promote iron oxide reduction in order to maintain a low bath oxidation. Process outputs influenced by complex EAF operations using different DRI metallizations, different sequences for feeding raw materials in the furnace, injection of carbon and oxygen and different types of inputs are well predicted by the present mathematical simulator.

Control of greenhouse gas emissions from electric arc furnace steelmaking: evaluation methodology with case studies

The energy intensive nature of electric arc furnace (EAF) steelmaking necessitates that efforts to reduce greenhouse gas (GHG) emissions will affect steelmakers directly and/or through electric power producers. A model of GHG emissions from an EAF meltshop has been developed using the life cycle assessment approach. Direct and indirect sources of GHG gas emissions are estimated and ranked. Furnace combustion optimisation was evaluated in case studies conducted on a Canadian conventional EAF and a British scrap preheating `shaft' furnace. The analysis assumed 32 and 68% fossil fuel electricity generation, respectively. These case studies show that indirect GHG emission sources, in particular electricity generation, are more significant than direct emissions from the EAF. For the conventional EAF, offgas analysis and improved combustion control reduced electricity consumption by 40 kWh t-1, costs by US$1·05/t, and GHG emissions by 20 kg CO2-eq./t. For the shaft EAF, real time offgas monitoring and closed loop burner control reduced electricity consumption by 25 kWh t-1, costs by US$3·6/t, and GHG emissions by 15 kg CO2-eq./t. The case studies show that combustion optimisation using an EAF offgas analysis and combustion control system provides greater electricity, cost, and GHG reductions than previously reported in the literature.

Automation of the power regime in a modern electric-arc steelmaking furnace

Automation of the power regime in a modern electric-arc steelmaking furnace

Recent advances in near-net shape flat steel manufacturing

Near-Net Shape Casting (NNSC) has been one of the major paradigms of process development in the steel industry in the last ten years. It has also made possible the development of flat product mini-mills, in conjunction with electric arc furnace steelmaking and in-line rolling on compact hot-strip mills. More development is still to come, with the adoption of NNSC casting in integrated mills and the emergence of strip casting.

A quarter century of steel cord manufacture. State of the art technology and critical topics for the future

By the early 1970’s, ingot casting was predominant for critical applications. In the 1980’s continuous casting of large blooms became the metallurgical standard in a production route blast furnace / basic oxygen furnace / ladle metallurgy. By the early 1990’s, the steel industry began to consider a new compact, cost effective production route comprising electric arc furnace steelmaking in line with direct billet casting. Concurrently, new developments, as higher strength grades, put a more stringent demand on wire rod quality. This paper reviews the changing situation, and highlights critical topics towards horizon 2000.

Influence of tramp elements in the production of high quality steels using the scrap/electric arc furnace route

Driving forces for increasing the share of electric arc furnace steelmaking are strong : availability of scrap, pressure to recycle materials, economic benefits. This trend leads to an increase in the level of tramp elements in the steel products. The purpose of this work is to investigate quantitatively the potential problems related to increased levels in tramp elements. Our objectives are to discuss, on a case by case basis, the currently existing practical limits and to devise countermeasures to further extend these limits.

The Slag Foaming Practice in EAF and Its Influence on the Steelmaking Shop Productivity.

IMEXSA steel has a four electric arc furnaces (EAF) steelmaking shop which was originally designed to melt a DRI/scrap ratio of 80/20 for producing steel slab, but logistical and economical circumstances led to a change in this ratio to 98.2/1.8. This decision brought about increases on specific consumptions of energy, electrodes, refractories and a loss of metallic yield among other items. In order to improve melting performance a study involving industrial measurements and thermodynamic-kinetic aspects of slag foaming was carried out. Implementation of a slag foaming practice gave very encouraging results in the main process variables; energy consumption decreased from 730 to 640 kWh/t of steel while electrode consumption decreased from 2.25 kg/t of steel to 1.81 kg/t of steel. With regard to iron oxidation, iron oxide contents in slag decreased from previous 36-40 wt% values to 23-25 wt% increasing substantially metallic yield. Overall process performance was improved and consequences of this program can be directly seen during seconday refining process of steel in LF.

Factors influencing the diffusion of electric arc furnace steelmaking technology

In this paper, the adoption of electric arc furnace steelmaking technology is examined within a growth model of technological diffusion. The results indicate that the trend rate of adoption of electric are furnace technology is well represented by the S-shaped growth curve. Further results indicate that the trend rate of adoption is, for the most part, stable with respect to locally changing factors to production, such as input prices and activity levels. It appears that inertial aspects have an overwhelming influence on the diffusion process.

Mechanism of Spinel Ferrite Dust Formation in Electric Arc Furnace Steelmaking.

By investigating the behavior of spinel ferrite particles in EAF dust, an insight into the mechanism of spinel ferrite dust generation was examined. The results are summarized as follows: (1) the chemical formula of spinel ferrite particles in EAF dust is (MnxZnyFe1-x-y)Fe2O4; (2) when oxygen is transferred at the slag-metal interface, a series of oxide layers form on the molten steel (going from the surface to the interior of the liquid, one progresses through (Mn, Zn)Fe2O4, (Mn, Zn)Fe2O4-Fe3O4, Fe3O4-(Mn, Fe)O and (Mn, Fe)O, respectively); (3) some of the coarse spinel ferrite powders are often hollow contain surface blowholes suggesting that CO gas atomizes liquid iron oxides; and (4) CO gas evolution atomizes various liquid oxides. These droplets may oxidize to varying degrees as they solidify and cool producing various compositions of (Mn, Zn)Fe2O4 and/or (Mn, Zn)Fe2O4-Fe3O4 powders.

Zinc Recovery via the Flame Reactor Process

A major objective of the zinc industry for the 1990s will be to maintain high zinc recovery while eliminating the disposal of copious quantities of hazardous iron residues. The flame reactor process has demonstrated the potential of meeting this objective by either treating the residues or smelting zinc directly. The process has been proven commercially viable for treating flue dusts generated during electric arc furnace steelmaking. Zinc, lead and cadmium are recovered from the dust as a crude oxide for recycle while a nonhazardous slag is produced for sale. Similar products are efficiently produced from electrolytic zinc plant neutral leach and iron precipitation residues. In addition, the reactor shows promise of fulfilling its original objective of being a low-energy primary zinc smelter by fuming and condensing zinc from roasted concentrates.

数式モデルによる電気炉製鋼の計算機制御

数式モデルによる電気炉製鋼の計算機制御

電気炉製鋼法の変遷

電気炉製鋼法の変遷

The plasmadust process for recovery of metals from waste oxides

Considerable quantities of waste oxides are generated in the iron and steel industry. Present methods are not well suited for recycling these, and there are increasing environmental problems associated with their dumping or stockpiling. With the PLASMADUST process, many of these wastes can be treated economically to produce a liquid iron as well as metallic zinc and lead. Without previous sintering the fine material is pneumatically injected with coal powder into the lower part of a coke filled shaft furnace provided with plasma arc heaters where the material is injected. The oxides are instantaneously reduced, and liquid and gaseous metals are formed. The latter are extracted in a normal condenser. As the heat losses are small, the utilization of electrical energy is efficient, and the operating costs are well competitive with conventional methods. Because of the simple equipment required, the specific investment is low. Successful tests have been carried out in a small plant with a plasma arc heater of maximum 1.5 MW electric power and a feed rate of waste oxides of about 300 kg/h. Tests with normal baghouse dust from electric arc furnace steelmaking resulted in metal yields of more than 97 % for both iron, zinc and lead. Similar tests with dust from stainless steel-making resulted in a liquid iron alloyed with chromium, nickel and molybdenum, again with high metal yields. A central PLASMADUST plant in each steelmaking area could recycle most of the waste oxides from that area, thus solving an environmental problem and at the same time recovering valuable metals from waste material.

Analytical Electron Microscopy Characterization of Electric Arc Furnace Dust

Alloy scrap metal is increasingly being used in electric arc furnace (EAF) steelmaking and the alloying elements are also found in the resulting dust. A comprehensive characterization program of EAF dust has been undertaken in collaboration with the steel industry and AISI. Samples have been collected from the furnaces of 28 steel companies representing the broad spectrum of industry practice. The program aims to develop an understanding of the mechanisms of formation so that procedures to recover residual elements or recycle the dust can be established. The multi-phase, multi-component dust particles are amenable to individual particle analysis using modern analytical electron microscopy (AEM) methods.Particles are ultrasonically dispersed and subsequently supported on carbon coated formvar films on berylium grids for microscopy. The specimens require careful treatment to prevent agglomeration during preparation which occurs as a result of the combined effects of the fine particle size and particle magnetism. A number of approaches to inhibit agglomeration are currently being evaluated including dispersal in easily sublimable organic solids and size fractioning by centrifugation.

Improved output governors for electric-arc steelmaking furnaces

Improved output governors for electric-arc steelmaking furnaces

Electric Arc Furnace Steelmaking with Sponge Iron

Electric Arc Furnace Steelmaking with Sponge Iron

Electric Arc Furnace Steelmaking with Sponge Iron

Abstract The technology of melting sponge iron is presently in an evolutionary state as steelmakers learn how to take best advantage of sponge iron's unique physical and chemical characteristics. Several of sponge iron's effects on electric arc furnace operation are discussed and it is concluded that best use of sponge iron generally results from continuous charging. The chemistry of sponge iron is shown to affect favorably both steel quality and the fabricability of the resultant steels. Resume La technologie de la fusion d'eponge de fer est actuellement dans une peri ode d'evolution car les acieristes ont appris comment tirer profit des caracteristiques physiques et chimiques particulieres a l'eponge de fer. Plusieurs effets de l'eponge de fer sur la conduite d'un four a arc sont discutes et la conclusion est que le meilleur emploi de l'eponge de fer consiste en un chargement en continu du four. Il est montre que la chimie de l'eponge de fer est un facteur favorable tant en ce qui concerne la qualite de...