Recycling of electric arc furnace slag from hydrogen-based iron production in cementitious binders

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Desphosphorization in ironmaking and oxygen steelmaking

Steelmaking is an extensive industry based on modifying the physical properties of iron to fit a wide range of applications by either adding alloying elements or removal of impurities. Thus, the effects of various elemental components on final steel properties are at the heart of the steelmaking process whether in small concentrations coming from the raw materials or being in larger concentrations as alloying elements. Owing to increased demand of iron ore raw materials, the access to high-quality ores has been under stress and thus, increased usage of low-quality ores, which contains high concentrations of impurities such as phosphorus and sulphur has become more economical. Such impurities have been known to have adverse impacts on the final steel properties and need special management in conventional steel making operation. This report primarily focuses on the management strategies of phosphorus in steelmaking including the behavior of phosphorus and its removal strategies in several core components of the process: blast furnace (BF), basic oxygen furnace (BOF), electric arc furnace (EAF) and argon oxygen decarburization (AOD). The objective of the report is to review underlying research in the area giving a reference to the available literature and support propagation of future research projects addressing various aspects of dephosphorization in steelmaking

Uncovering temperature-tempted coordination of inclusions within ultra-high-strength-steel via in-situ spectro-microscopy

Funding Information: Authors acknowledge Academy of Finland grant #311934 and Kvantum Institute, University of Oulu (Project CLEAN2STEEL) for the financial support. We also thank the crew of the MAX IV laboratory for their support during the beamtime operation. Authors would like to thank Mr. Tun Nyo for the assistance in sample preparation for SEM and X-PEEM, Mr. Jaakko Hannula for insightful discussions, and the Centre for Material Analysis, University of Oulu is also acknowledged for in-house characterizations. Publisher Copyright: © 2022 The Author(s)Despite the common challenge of investigating non-metallic inclusions within ultra-high-strength-steel (UHSS) at sub-micrometer scale via conventional methods, probing nitride inclusions at elevated temperatures is vital for guiding steel’ performance. Herein, an in-situ spectro-microscopic determination using advanced Synchrotron X-ray absorption spectroscopy (XAS) coupled with photoelectron emission microscopy (PEEM) is employed to explore the local structure and electronic properties of selective h-boron nitride (h-BN) containing inclusions (A1 and A2) embedded within steel matrix. While the variation in the relative intensity of π∗/σ∗ excitonic peaks at spatially different locations refers to the polarization and or thickness effects. Several minute features observed in the 192–195 eV energy range show oxygen (O) substituted nitrogen (N) defects (ON,2N,3N), which are more dominant in A2 inclusion. The observed dominance further explains the relatively high intense π∗ peak in A2 due to increased localization. Weak shoulder on the left side of π∗ peak in both room and high-temperature XAS spectra is ascribed to the interaction between h-BN and the local environment, such as Ca-based inclusion or steel matrix. Defects are commonly found in h-BN, and precise identification of the same is vital as they affect the overall physical, chemical, and mechanical properties. Moreover, significant changes in high-temperature B K-edge XAS spectra, such as relative intensity of π∗/σ∗ excitonic peaks at the same location and reduced intensity of defects, suggest the adjusting nature of BN inclusion, complicating their precise prediction and control towards clean steel production.Peer reviewe

Towards More Sustainable Ironmaking—An Analysis of Energy Wood Availability in Finland and the Economics of Charcoal Production

Replacement of fossil carbon by renewable biomass-based carbon is an effective measure to mitigate CO2 emission intensity in the blast furnace ironmaking process. Depending on the substitution rate of fossil fuels, the required amount of biomass can be substantial. This raises questions about the availability of biomass for multiple uses. At the same time, the economic competitiveness of biomass-based fuels in ironmaking applications should also be a key consideration. In this assessment, availability of energy wood, i.e., logging residues, small-diameter wood and stumps, in Finland is discussed. Since biomass must be submitted to a thermochemical process before use in a blast furnace, the paper describes the production chain, from biomass to charcoal, and economics related to each processing step. The economics of biomass-based reducing agents is compared to fossil-based ones by taking into account the effect of European Union Emissions Trading System (EU ETS). The assessment reveals that there would be sufficient amounts of energy wood available for current users as well as for ironmaking. At present, the economics of biomass-based reducing agents in ironmaking applications is unfavorable. High CO2 emission allowance prices would be required to make such a scheme competitive against fossil-based reducing agents at current fuel prices

Towards More Sustainable Ironmaking—An Analysis of Energy Wood Availability in Finland and the Economics of Charcoal Production

Replacement of fossil carbon by renewable biomass-based carbon is an effective measure to mitigate CO2 emission intensity in the blast furnace ironmaking process. Depending on the substitution rate of fossil fuels, the required amount of biomass can be substantial. This raises questions about the availability of biomass for multiple uses. At the same time, the economic competitiveness of biomass-based fuels in ironmaking applications should also be a key consideration. In this assessment, availability of energy wood, i.e., logging residues, small-diameter wood and stumps, in Finland is discussed. Since biomass must be submitted to a thermochemical process before use in a blast furnace, the paper describes the production chain, from biomass to charcoal, and economics related to each processing step. The economics of biomass-based reducing agents is compared to fossil-based ones by taking into account the effect of European Union Emissions Trading System (EU ETS). The assessment reveals that there would be sufficient amounts of energy wood available for current users as well as for ironmaking. At present, the economics of biomass-based reducing agents in ironmaking applications is unfavorable. High CO2 emission allowance prices would be required to make such a scheme competitive against fossil-based reducing agents at current fuel prices

Effect of blast furnace sludge (BFS) characteristics on suitable recycling process determining

Abstract The present study aims to give a detailed characterization of blast furnace sludge (BFS) by using different techniques, in order to determine the most effective recycling method to recover valuable metals from this waste. BFS is composed mainly of hematite, as its iron-bearing phase, and carbon, in addition to fractions of silicate and carbonate materials. The studied BFS shows relatively high contents of iron (Fe) (390 g.kg-1), and carbon (C) (290 g.kg-1), due to abundance of hematite and coke, while the concentration of zinc (Zn) (2.5 g.kg-1) is low. The XRD analyses indicated that, hematite is more concentrated in the fine fraction (<20 μm), while the coarser fraction (90 - 250 μm) is dominated by calcite, quartz and X-ray amorphous coke. SEM-EDX analyses confirmed that particles rich in iron and zinc were detected in the fine fraction (<20 μm) of the sludge. Due to high Fe and C content in BFS, it can be utilized as self-reducing material and briquetting represent a potential method for recycling of blast furnace sludge

Effects of MoO₃ + C on Crystallization and Radiative Heat Transfer of CaO–SiO₂–B₂O₃-Based Glassy Fluoride-Free Mold Fluxes

The fluorine in traditional mold fluxes could be harmful in steel-plant environments. Accordingly, fluoride-free mold fluxes have received great attention in recent years. In this work, a method to adjust the crystallization and radiative heat transfer of fluoride-free mold fluxes is proposed. MoO3 and C mixtures (mass ratio: 4:1) were added into CaO−SiO2−B2O3-based mold fluxes and produced MoB, Mo2CB and Mo2C foreign particles. The influences of foreign particles on the radiation of glassy CaO−SiO2−B2O3-based mold fluxes were investigated by measuring the transmissivity of a glassy disk for light in the wavenumber range of 300 to 2500 nm. It was found that transmissivity in all wavenumber ranges were reduced and extinction coefficients were enhanced by the scattering of foreign particles. The effect of foreign particles on crystallization (devitrification) of bulk glassy CaO−SiO2−B2O3-based mold fluxes was also investigated. The crystallization mechanism of glassy mold fluxes disks is mainly surface crystallization. The introduction of foreign particles induced heterogeneous nucleation and the crystallization mechanism of the bulk sample with MoO3% = 2% changed into bulk crystallization

Effect of steelmaking dust characteristics on suitable recycling process determining:ferrochrome converter (CRC) and electric arc furnace (EAF) dusts

Abstract Utilization of dusts generated from steelmaking industries will avoid disposal of wastes, enhance the use of secondary raw material fines and save costs. Understanding the properties of dust is necessary before determining the suitable recycling method. The present paper describes the chemical, morphological and mineralogical characterization of steelmaking dusts produced in steel plants in Finland. In this paper three different steelmaking dusts: ferrochrome converter (CRC) and electric arc furnace stainless steel (EAFSS) dusts from Outokumpu (Tornio, Finland), and electric arc furnace carbon steel (EAFCS) dust from Ovako (Imatra, Finland) were characterized. The characterization study showed that, the dusts from carbon steelmaking (EAFCS) are rich in zinc, while the dusts from stainless steelmaking (CRC) and (EAFSS) are relatively low in zinc, but richer in chromium. The zinc contents in CRC, EAFSS and EAFCS dusts are 10.83, 19.84 and 35.76 wt%, respectively, while the chromium contents are 20.88, 3.19 and 0.47 wt%, respectively. In the dust from CRC, zinc is found as zinc oxide (zincite, ZnO), while in the dusts from EAFSS & EAFCS zinc is found mostly as zinc ferrite (franklinite, ZnFe₂O₄). Scanning electron microscopy (SEM) investigations indicated that CRC dust is dominated by non-spherical form and composed mainly of aggregates of irregular particles of chromite, in addition to zincite sphere. EAFSS dust particles are characterized by encapsulation phenomenon, franklinite particles enclosed inside calcium-iron-silicate glass sphere. Manganese (Mn) concentrations show positive correlation with Zn, which suggests the occurrence of Mn mainly with franklinite phase. EAFCS dust is dominated by spherical form, and zinc found as franklinite and zincite. In the large particles > 3 μm of EAFCS dust, franklinite enclosed inside glass sphere, while in finer particles < 1 μm, both zincite and franklinite existed as spheres. The investigations indicate that steelmaking dusts from CRC, EAFSS, and EAFCS show significant difference in concentration and mode of occurrence of zinc in the dusts, which will influence the determination of suitable processing methods