Electric Arc Furnace Steelmaking Research Articles

Present Situation and Prospect of EAF Gas Waste Heat Utilization Technology

AbstractWith the increase of hot metal ratio in electric arc furnace (EAF) steelmaking process, physical sensible heat and chemical latent heat of gas increased significantly. As EAF raw material condition is similar to basic oxygen furnace (BOF), and the condition of BOF gas waste heat utilization technology is mature, waste heat utilization technology in EAF steelmaking will be getting more and more attention. Scrap preheating and steam production as mature technology is the main way of EAF gas waste heat utilization. Power generation converted high temperature steam to electricity will further improve the EAF gas utilization value. The previous ways are to recycle physical sensible heat of EAF gas. To use chemical latent heat of gas, the secondary combustion technology is usually adopted to make CO fully burn into CO2. Coal gas production can fully recycle the chemical latent heat of gas theoretically, which is higher efficiency than other ways. Coal gas production needs a stable steelmaking process to stabilize high temperature gas. And the way need to develop EAF sealing technology, oxygen removal technology and gas purification technology, to make gas content meet the requirements of coal gas production in EAF steelmaking process.

Study on the Fluid Flow Characteristics of Coherent Jets with CO2 and O2 Mixed Injection in Electric Arc Furnace Steelmaking Processes

As an efficient oxygen supplying technology, coherent jets are widely applied in electric arc furnace (EAF) steelmaking processes to strengthen chemical energy input, speed up smelting rhythm, and promote the uniformity of molten bath temperature and compositions. Recently, the coherent jet with CO2 and O2 mixed injection (COMI) was proposed and demonstrated great application potentiality in reducing the dust production in EAF steelmaking. In the present study, based on the eddy dissipation concept model, a computational fluid dynamics model of coherent jets with COMI was built with the overall and detailed chemical kinetic mechanisms (GRI-Mech 3.0). Compared with one-step combustion reaction, GRI-Mech 3.0 consists of 325 elementary reactions with 53 components and can predict more accurate results. The numerical simulation results were validated by the combustion experiment data. The jet behavior and the fluid flow characteristics of coherent jets with COMI under 298 K and 1700 K (25 °C and 1427 °C) were studied and the results showed that for coherent jets with COMI, the chemical effect of CO2 significantly weakened the shrouding combustion reactions of CH4 and the relative importance of the chemical effect of CO2 increases with CO2 concentration increasing. The potential core length of coherent jet decreases with the volume fraction of CO2 increasing. Moreover, it also can be found that the potential core length of coherent jets was prolonged with higher ambient temperature.

Levels and sources of heavy metals in soil, sediment, and food crop in the vicinity of electric arc furnace (EAF) steelmaking plant: a case study from Taiwan

The distribution and characteristics of heavy metals around an electric arc furnace (EAF) plant in Taichung City, Taiwan, were investigated. The aim of this research was to predict the main steelmaking processes causing contamination of As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn in the environment. Food crop, surface water, sediments, and soils were collected from a total of 65 and 53 sampling sites during November 2011 and June 2012, thus establishing the basic environmental information. The heavy metals in samples were assessed by potential ecological risk indices. The correlation between the source and receptors of contamination was evaluated through the statistical significance of isotope approach and hierarchical cluster analysis. The heavy metal contamination was mainly from the storage facility of waste iron and the discharging device of fly ash in the EAF plant. Surface runoff and rainwash were the two potential routes distributing the metallurgical Cd and Pb to the surrounding environment. Based on the mathematical simulation of dispersion modeling, the impact of heavy metals through the two specific flue gases on the farmland was insignificant; the particulate matter (PM), SO2, and NOx were concentrated southward in the atmosphere, and they were 1.71 μg—PM/Nm3, 2.80 ppb—SO2, and 1.87 ppb—NOx, respectively. Because of topographical features, the contaminated sediment produced by steelmaking activities is washed into downstream via surface runoff, which is supposed to be the major source of long-term accumulation of heavy metals in the environments, although the contamination with heavy metals was graded as low.

MFA-based analysis of CO2 emissions from typical industry in urban — As a case of steel industry

Industrial metabolism has closely impact on urban economic, resources and environment condition. As an intensively consuming-energy and heavily polluting industry, steel industry has emitted extremely large quantitate of CO2. Presently, there are two typical production processes in steel enterprises, which are the long process and the short process. However, to compensate the insufficient scrap resources, some steel enterprises have taken a great deal of hot iron in the electric arc furnace steelmaking, which only happens in China. This unique process called the “Chinese style” short process. Coupling material flow analysis and emission factor method, the CO2 emissions for these different three production processes are analysed and their different carbon flow networks diagram are built. The flow diagram could provide basements on emissions reduction located. Results show that the CO2 emissions of long process, “Chinese-style” short process and short process are 3.102t/t-s, 2.994t/t-s and 1.613t/t-s, respectively. The focus of CO2 emissions reduction are the blast furnace steelmaking in long process, electric arc furnace steelmaking in “Chinese-style” short process and short process, whose CO2 emissions are 2.079t/t-s, 2.748t/t-s and 1.367t/t-s, respectively. Specially, the reason why the CO2 emissions of “Chinese style” short process are too high is excessive hot iron utility. For lower CO2 emissions, it is suggested that scrap resources should be recycled as many as possible and the short process ought to rationally develop based on the existing environmental strategies.

Discussion of Carbon Emissions for Charging Hot Metal in EAF Steelmaking Process

AbstractAs the cost of hot metal is reduced for iron ore prices are falling in the international market, more and more electric arc furnace (EAF) steelmaking enterprises use partial hot metal instead of scrap as raw materials to reduce costs and the power consumption. In this paper, carbon emissions based on 1,000 kg molten steel by charging hot metal in EAF steelmaking is studied. Based on the analysis of material and energy balance calculation in EAF, the results show that 146.9, 142.2, 137.0, and 130.8 kg/t of carbon emissions are produced at a hot metal ratio of 0 %, 30 %, 50 %, and 70 %, while 143.4, 98.5, 65.81, and 31.5 kg/t of carbon emissions are produced at a hot metal ratio of 0 %, 30 %, 50 %, and 70 % by using gas waste heat utilization (coal gas production) for EAF steelmaking unit process. However, carbon emissions are increased by charging hot metal for the whole blast furnace–electric arc furnace (BF–EAF) steelmaking process. In the condition that the hot metal produced by BF is surplus, as carbon monoxide in gas increased by charging hot metal, the way of coal gas production can be used for waste heat utilization, which reduces carbon emissions in EAF steelmaking unit process.

Assessment of residual exposure to PCBs in metallurgy.

To evaluate the occupational exposure to polychlorinated biphenyls (PCBs) in 56 workers employed in 6 electric arc furnace steelmaking plants and 2 secondary aluminum smelting plants located in the highly industrialized area of Brescia, Northern Italy. Thirty-four PCB congeners were found in both environmental and biological samples from workers engaged in scrap yards, electric arc furnaces, casting and maintenance departments. The highest airborne PCB levels were found in the aluminum plant, even 100 times those detected in the steelwork plants. Dioxin-like PCB congeners (DL-PCBs) were poorly represented in all biological samples, whereas non Dioxin-Like PCB congeners (noDL-PCBs), in particular environmentally widespread congeners (PCB 153, 138, 180), could be detected in almost all samples. The mean total PCB serum level was 3.9 ng/ml, with a range of 1.3-10.3 ng/ml, while the geometric mean for airborne PCBs levels was 9305 pg/m3, with a range of 1138-217806 pg/m3. Despite the higher PCB values recorded in some metallurgical plant workplaces, we failed to find any significant difference between serum concentrations in workers from steel or aluminum production, even in consideration of different tasks or different job seniority, while positive association was found only according to the age of the workers. A possible explanation may be identified in the effectiveness of the individual and collective preventive measures adopted in the workplace. Assessment of the occupational exposure to such compounds, in consideration of the recent classifications as carcinogenic to humans, should be encouraged.

Achieving zero waste of municipal incinerator fly ash by melting in electric arc furnaces while steelmaking

The main objective of this work was to promote zero waste of municipal incinerator fly ash (MIFA) by full-scale melting in electric arc furnaces (EAFs) of steel mini mills around the world. MIFA, generally, is considered as a hazardous waste. Like in many countries, MIFA in Taiwan is first solidified/stabilized and then landfilled. Due to the scarcity of landfill space, the cost of landfilling increases markedly year by year in Taiwan. This paper presents satisfactory results of treating several hundred tons of MIFA in a full-scale steel mini mill using the approach of “melting MIFA while EAF steelmaking”, which is somewhat similar to “molten salt oxidation” process. It was found that this practice yielded many advantages such as (1) about 18wt% of quicklime requirement in EAF steelmaking can be substituted by the lime materials contained in MIFA; (2) MIFA would totally end up as a material in fractions of recyclable EAF dust, oxidized slag and reduced slag; (3) no waste is needed for landfilling; and (4) a capital cost saving through the employment of existing EAFs in steel mini mills instead of building new melting plants for the treatment of MIFA. Thus, it is technically feasible to achieve zero waste of MIFA by the practice of this innovative melting technology.

Self-compacting concrete incorporating electric arc-furnace steelmaking slag as aggregate

Electric arc-furnace slag (EAFS) is an industrial by-product that can be employed in hydraulic mixes used in the field of construction and civil engineering. The design and preparation of self-compacting mixes with this aggregate is a challenge, due to the loss of workability that always accompanies its use in concrete. Only through careful design of the characteristics and proportions of the components in each mixture will an acceptable workability be achieved. Thus, criteria and methods are proposed in this paper for successful preparation of these types of mixtures. Several concrete mixes are manufactured to obtain self-compaction characteristics and their main properties are analyzed with regard to their use as structural concrete. Electron microscopy observations and dispersive energy analysis are used to study the microstructural features of these mixes. Finally, a numerical simulation is proposed as a useful method that estimates the viscous properties of the mixes and their workability, based on the dosage and the characteristics of their components.

Environmental impacts and benefits of organic Rankine cycle power generation technology and wood pellet fuel exemplified by electric arc furnace steel industry

Iron- and steel-mill manufacturing are the material- and energy-intensive industries in the world, accounting for 22% of total industrial energy use in 2011; thereby leading to significant carbon dioxide (CO2) emissions. In this study, the environmental impacts and benefits for the applications of organic Rankine cycle (ORC) power generation and wood pellet fuel in the electric arc furnace (EAF) steel industry were evaluated using a cradle-to-gate life-cycle approach. The business-as-usual scenario of the EAF manufacturing was first established, and then compared with the scenarios of ORC facility and wood pellet fuel. The system boundary of heavy fuel oil production includes resource extraction, refining and processing, and transportation. The inventory data used in life cycle assessment were gathered from the information of real plant operation. The results indicated that both the ORC facility and replacement of heavy fuel oil by wood pellet fuel can mitigate the environmental impacts on ecosystems, human health and resource depletion. The environmental benefits of integrating the ORC power generation in an EAF steelmaking plant were less than those of applying wood pellet fuel for reheating furnace. However, the benefit-cost ratio of ORC process was greater than that of wood pellet fuel because the capital, and operation and maintenance costs of ORC process were lower than that of wood pellet fuel process.

Research and Analysis on the Physical and Chemical Properties of Molten Bath with Bottom-Blowing in EAF Steelmaking Process

Bottom-blowing technology is widely adopted in electric arc furnace (EAF) steelmaking to promote the molten bath fluid flow, accelerate the metallurgical reaction, and improve the quality of molten steel. In this study, a water model experiment and a computational fluid dynamics model were established to investigate the effects of bottom-blowing gas flow rate on the fluid flow characteristics in the EAF molten bath. The results show that the interaction among the bottom-blowing gas streams influences the molten bath flow field, and increasing the bottom-blowing gas flow rate can accelerate the fluid flow and decrease the volume of the dead zone. Based on industrial application research, the physical and chemical properties of the molten bath with bottom-blowing were analyzed. Compared with traditional melting conditions without bottom-blowing, bottom-blowing technology demonstrates obvious advantages in promoting the heat transfer and metallurgical reactions in the molten bath. With the bottom-blowing arrangement, the dephosphorization and decarburization rates are accelerated, the contents of FeO and T. Fe in endpoint slag are decreased, and the endpoint carbon-oxygen equilibrium of molten steel is improved.

Process modelling and simulation of electric arc furnace steelmaking to allow prognostic evaluations of process environmental and energy impacts

Several studies have been carried out in order to evaluate optimal process management practices and to assess specific aspects related to the environmental impacts (e.g. CO2 emission) of steelmaking facilities. On the other hand, limited efforts have been spent so far to jointly evaluate the enhancement of process performances, resource management and the overall environmental and energy impact. This paper describes a simulation tool, which is a part of the integrated framework that is under development within the research project entitled “EIRES – Environmental Impact Evaluation and Effective Management of Resources in the EAF Steelmaking”. The modelling approach and validation for one steel grade is described to represent the electric steelmaking route through Aspen Plus® . Results show a global error on energy consumption of about 0.4%, negligible differences in steel composition and temperature. The model application for the evaluation of environmental impact of the process is depicted. The model computes energy consumptions and emissions that can be used to evaluate KPIs to allow evaluation of plant environmental impact during scenario analyses. Thus it can be a powerful instrument for plant manager in feasibility studies in order to enhance process sustainability.

Monitoring the environmental and energy impacts of electric arc furnace steelmaking

The problem of rating the environmental impact of industrial plants has been widely studied in recent years with a specific focus on CO2 emission and energy consumption. On the contrary, only limited attention has been paid to the evaluation of the resource efficiency and overall environmental impact of industrial plants. This paper presents the first results of the research project entitled “Environmental Impact Evaluation and Effective Management of Resources in the EAF Steelmaking” (EIRES), which aims at a plant-oriented approach with an internal reporting of environmental and energy issues. For this purpose, several Key Performance Indicators (KPIs) have been selected both from literature and operational practices, which can be easily interpreted by plant operators and managers. Furthermore a software tool has been implemented which allows to follow the evolution of these KPIs over time. The tool is not intended to compare the environmental performance of different companies, but to provide a practical support to the personnel of each single steelwork, in order to have an updated overview on the way the processes in the plant are operated from an environmental perspective and in order to identify measures and modifications of operational practices allowing to lower the environmental footprint of the production cycle.

Effect of Ambient and Oxygen Temperature on Flow Field Characteristics of Coherent Jet

The coherent jets are now used widely in electric arc furnace steelmaking process to increase the stirring ability, reaction rates, and energy efficiency. However, there has been limited research on the basic physics of the coherent jets. In the present study, the characteristics of flow field of supersonic coherent jet in hot and cold condition were studied. The total temperature and axial velocity were measured by combustion experiment. Flow field characteristics of supersonic coherent jet were simulated by Fluent software. The detailed chemical kinetic mechanism is presently used for the modeling of reactions. It consists of 53 species, plus Ar and N2, for a total of 325 reversible reactions. The present study showed that the shrouding flame decreases the entrainment of the ambient gas to the central supersonic jet, which results in a low expansion rate for the coherent supersonic jet. The higher ambient temperature can prolong the potential core of coherent jet and conventional jet. However, the potential core of coherent jet reduces with oxygen temperature increasing, which is opposite to conventional jet.

Development of an Innovative Technology for Making Steel

An innovative technology that includes the production, deoxidation, and refining of steel in a single piece of equipment instead of two expensive units – an ultrahigh-power electric-arc steelmaking furnace and a secondary steel-treatment unit – has been invented. The technology was developed based on results from studies of carbonization and decarbonization in a steelmaking (open-hearth) bath and experience in the ladle treatment of steel with nitrogen and slag-forming reagents injected through the discharge opening of the slide gate. The bath carbonization and decarbonization took place while natural gas and compressed air were injected deep into the metal through the furnace’s tap hole.

Temperature Conditions in the Working Space of a Modern Electric-Arc Steelmaking Furnace

The temperature distribution in the working space of an electric-arc steelmaking furnace built by the company “Danieli” and equipped with radially positioned fuel-burning devices is analyzed. It is concluded that the temperature field is quite nonuniform, and the suggestion is made to reposition the gas-oxygen burners into a tangential configuration. Computer modeling is used to determine the temperature distribution in the furnace’s working space for radially and tangentially arranged burners.

Analysis of Energy Content and CO2 Emissions in Different Combinations of Coke-Using and Coke-Less Processes for Steel Production

Comparative estimates are made of energy content and emissions of carbon dioxide – a greenhouse gas – for different combinations of coke-using processes (blast-furnace – BOF, blast-furnace – electric-arc-furnace (EAF)) and coke-less processes (HyL-3 – EAF, MIDREX – EAF; ROMELT – EAF, COREX – EAF, direct alloying with vanadium (DAV), EAF operation on scrap) that are performed in the course of producing steel. These processes were compared as part of an energy-environmental analysis by examining both energy content and a parameter that characterizes the emission of the greenhouse gas CO2 – the technological greenhouse number (TGN). It was determined that the advantages in terms of energy content and CO2 emissions belong to EAF steelmaking with the use of scrap, the DAV process, the HyL-3 – EAF process, and the Midrex – EAF process. It should be noted that the steel obtained in the DAV process is alloyed with vanadium. In each case, the processes that do not involve the use of molten pig iron in steel production should be given the highest priority based on their ratings for energy content and greenhouse-gas emissions.

Optimization of selective leaching of Zn from electric arc furnace steelmaking dust using response surface methodology

The aim of this work is to investigate and optimize the effects of the leaching parameters on the selective leaching of zinc from electric arc furnace steelmaking dust (EAFD). The response surface method was applied on the basis of a three-level Box–Behnken experimental design method for optimization of selective leaching parameters of zinc from EAFD. The leaching recoveries of zinc (YZn) and iron (YFe) were taken as the response variables, where the concentration of sulphuric acid (X1, mol/L), leaching temperature (X2, °C), leaching time (X3, min), and liquid/solid ratio (X4, mL/g) were considered as the independent variables (factors). The mathematical model was proposed. Statistical ANOVA analysis and confirmation tests were applied. A maximum of 79.09% of zinc was recovered while the minimum iron recovery was 4.08% under the optimum conditions of leaching time 56.42 min, H2SO4 concentration 2.35 mol/L, leaching temperature 25 °C and liquid/solid ratios. By using ANOVA, the most influential factors on leaching of zinc and iron were determined as H2SO4 concentration and leaching temperature, respectively. The proposed model equations using response surface methodology show good agreement with the experimental data, with correlation coefficients (R2) of 0.98 for zinc recovery and 0.97 for iron recovery.

Thermophysical characterization of a by-product from the steel industry to be used as a sustainable and low-cost thermal energy storage material

In the metallurgical industry, large amounts of waste called slag are accumulated besides the production of iron and steel. One part, considered as by-product, is recycled but the other part, considered as waste, is still landfilled with potential bad consequences for environment. In this paper, two electric arc furnace slag samples (most common steel production technology in Europe), have been considered and characterized to be used in medium and high temperature thermal energy storage systems. These slags have demonstrated relevant properties to store thermal energy by sensible heat from ambient temperature up to 1000 °C, and their representativeness of the worldwide produced slag in a wide EAF (electric arc furnace) steelmaking process range. The objective is to develop sustainable and low-cost thermal energy storage systems for industry waste heat recovery and in renewable energy applications. At the same time, this new valuable market for slag in the energy field could solve a big part of the waste management problem in the iron and steel sector.

Multi-objective particle swarm optimization with preference information and its application in electric arc furnace steelmaking process

In this paper, multi-objective particle swarm optimization with preference information (MOPSO-PI) has been proposed. In the proposed algorithm, the information entropy is employed for measuring the probability distribution of particles; the user's preference information is represented as the ranking of each particle through the possible matrix. The optimal procedure is guided by the preference information since the global best performance of particle is randomly chosen among non-dominated solutions with higher ranking value in each iteration. Finally, the MOPSO-PI is applied to optimize the steelmaking process; the power supply curve obtained reduces the electric energy consumption, shortens the smelting time and prolongs the lifespan of the furnace lining. The application results show the effectiveness of the proposed algorithm.

Toward the efficient recycling of alloying elements from end of life vehicle steel scrap

There has been a sharp increase in the production of automobiles over the past decade. In 2010, one billion automobiles were in circulation worldwide. The automobile industry is one of the largest metals consumers and plays an important role in their sustainable use. Steel materials, including alloy steels that contain alloying elements (AEs) such as manganese, chromium, nickel, and molybdenum, are the main component of automobiles. The recycling of end-of-life vehicles (ELVs) significantly affects the cycling of iron, steel, and AEs. Currently, ELV recycling is performed using the electric arc furnace (EAF). In this method, losses of AEs are likely to occur because their presence is rarely considered. This study evaluated the environmental and economic benefits of alternative ELV recycling schemes, which allow more efficient utilization of AEs found in ELV-derived steel scrap (ELV-dSS). The AE contents in ELV-dSS (as car-parts) were estimated by means of a waste input–output material flow analysis (WIO-MFA) model extended for the detailed analysis of automobile composition. Using Japanese data, it was found that sorting ELV-dSS by parts can result in a significant recovery of AEs; more specifically, a 10-fold saving in AEs was achieved by sorting exhaust parts. The recoverable mass of AEs from sorted ELV-dSS was found to correspond to 8.2% of the annual consumption of AEs in Japan, as virgin resources in EAF steelmaking. ELV-dSS sorting was found to be significantly effective in the conservation of AE resources.