The effect of microstructure on the leaching behaviour of electric arc furnace (EAF) carbon steel slag

Mombelli, Davide; Mapelli, Carlo; Barella, Silvia; Cecca, Cosmo Di; Saoût, Gwenn Le; Garcia-Diaz, E.

doi:10.1016/j.psep.2016.05.027

Cited by 34 publications

(32 citation statements)

References 44 publications

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“…Being the slag mainly composed of gehlenite and having a composition favourable to vitrify is a great advantage, since gehlenite matrix compounds have been shown a poor reactivity in water and a strong hindering behaviour against metals leaching [73,74].…”

Section: Cast Iron and Slag Characterizationmentioning

confidence: 99%

Iron Recovery from Bauxite Tailings Red Mud by Thermal Reduction with Blast Furnace Sludge

et al. 2019

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More than 100 million tons of red mud were produced annually in the world over the short time range from 2011 to 2018. Red mud represents one of the metallurgical by-products more difficult to dispose of due to the high alkalinity (pH 10–13) and storage techniques issues. Up to now, economically viable commercial processes for the recovery and the reuse of these waste were not available. Due to the high content of iron oxide (30–60% wt.) red mud ranks as a potential raw material for the production of iron through a direct route. In this work, a novel process at the laboratory scale to produce iron sponge (≤ 1300 °C) or cast iron (> 1300 °C) using blast furnace sludge as a reducing agent is presented. Red mud-reducing agent mixes were reduced in a muffle furnace at 1200, 1300, and 1500 °C for 15 min. Pure graphite and blast furnace sludges were used as reducing agents with different equivalent carbon concentrations. The results confirmed the blast furnace sludge as a suitable reducing agent to recover the iron fraction contained in the red mud. For all the conditions tested, the metallization degree was higher than 70%, and the best condition to reduce red mud through blast furnace sludge was identified at 1:1 red mud/blast furnace (B.F.) sludges equal to 0.85 C/Fe2O3.

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Section: Cast Iron and Slag Characterizationmentioning

confidence: 99%

Iron Recovery from Bauxite Tailings Red Mud by Thermal Reduction with Blast Furnace Sludge

et al. 2019

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“…Thanks to the comparison among different steel slags, the role of mayenite in Ba leaching is clarified (in [17,31] mayenite was only suspected to leach Ba). Mayenite, along with Ca 2 SiO 4 , not only was responsible for Ba leaching, but also could be used as a marker of mixing efficiency between slag and stabilizer.…”

Section: Discussionmentioning

confidence: 99%

The Influence of Slag Tapping Method on the Efficiency of Stabilization Treatment of Electric Arc Furnace Carbon Steel Slag (EAF-C)

et al. 2019

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Studies conducted over the past 10 years have demonstrated the technical suitability of the electric arc furnace slag as an alternative to natural stone in several applications. Steel slag can be profitably used as a road surface layer, for foundations and embankments, or for concrete aggregates. However, a strong limitation to their use is due to the presence of toxic metals (Ba, Cr, V, Mo, etc.) that can be released into the environment in particular conditions, especially for unbound products in which the slag can come into contact with water. Recent studies have investigated the role of chemical composition and microstructure of slag on toxic metal leaching, allowing for the design of suitable stabilization treatments for hindering such leaching. In this work, four batches of electric arc furnace carbon steel slag underwent a stabilization treatment and the obtained results were compared. In two batches, the stabilizer was added directly in the slag pot and the slag was cooled down in the same pot. The other two batches were stabilized during the downfall from slag door to slag pit. Several slag samples were collected before and after the stabilization treatment and were characterized by means of ED-XRF, XRD, and SEM analysis. Leaching tests were carried out in agreement with EN 12457-2 standard on 4 mm granulated slag, and the leachate concentration was compared with the current Italian limits listed in D.M. 3 August 2005 N. 201 and D.M. 5 April 2006 N. 186. The results clearly indicated that the cooling in the slag pot improved the efficiency of the stabilization treatment, leading to a complete transformation of the microstructure by a full development of homogeneous gehlenite matrix and a coarsening of Cr-spinels, assuring better toxic metal retention behavior. On the contrary, stabilization in the slag-pit was rapid and reduced the interaction between slag and stabilizer, leading only to partial transformation of larnite into gehlenite, and also reducing the coarsening of Cr-spinel. In addition, a layering effect was observed, resulting in an inhomogeneous product from top to bottom in terms of chemical composition, microstructure, and leaching behavior.

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“…However, the composition of EAF slags can be subjected to substantial variations since it depends on the chemistry of the steel scraps that are fed into the electrical-arc furnace. Mineralogical characterization of various EAF slags shows that, as in BOF slags, iron is both divalent and trivalent and hosted in spinel-structure phases (including magnetite), Mg-bearing wüstite, and substituted brownmillerite (Mombelli et al, 2016 and references therein).…”

Section: Hydrogen and Magnetite Production From Hydrothermally Procesmentioning

confidence: 99%

Hydrothermal Production of H2 and Magnetite From Steel Slags: A Geo-Inspired Approach Based on Olivine Serpentinization

Brunet

2019

Front. Earth Sci.

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The interaction between ultramafic rocks and hot seawater at slow-spreading mid-oceanic ridges triggers hydrothermal redox reactions which are known to produce magnetite and H 2 under appropriate pressure and temperature conditions. Steel slags share some common properties with ultramafic rocks. They are composed of anhydrous and refractory minerals formed at temperatures exceeding 1,200 • C and they contain ferrous iron in comparable amounts. Consequently, when submitted to hydrothermal conditions both types of materials, natural and anthropogenic, are prone to form magnetite and H 2 according to the simplified redox reaction:is the ferrous iron component of the corresponding material that can be present under different mineralogical forms. Since H 2 and magnetite are two valuable products for applications in new technologies, the hydrothermal treatment of steel slags can be seen as a way to valorize a byproduct of the steel industry, a few tenths of a billion tons of which are produced yearly. The hydrothermal behavior of steel slags which arise from basic oxygen furnace (BOF) operations and that of olivine (Mg,Fe) 2 SiO 4 , the main mineral constituent of abyssal peridotites, are described here based on data from the literature. The thermochemical characteristics of Reaction 1 are reviewed for both types of materials in the perspective of optimizing a process that would valorize BOF steel slags for the production of nanomagnetite (and high-purity H 2 ). In particular, the kinetics effect of temperature, pH and solution-to-solid mass ratio on the hydrothermal oxidation of wüstite (FeO), considered here as an analog of the ferrous-iron component of steel slags, are modeled. The possible role of additives (impurity) on the hydrothermal oxidation of wüstite through the catalysis of the water-splitting reaction is discussed. Finally, the lack of kinetics constraints on nanomagnetite growth under hydrothermal conditions in a wide range of pH is identified as a major gap in the understanding of two important issues: (1) the catalysis of abiotic molecules in the course of serpentinization reactions, and (2) the tailoring of the size of the magnetite produced by hydrothermal treatment of BOF steel slags.

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The effect of microstructure on the leaching behaviour of electric arc furnace (EAF) carbon steel slag

Cited by 34 publications

References 44 publications

Iron Recovery from Bauxite Tailings Red Mud by Thermal Reduction with Blast Furnace Sludge

Iron Recovery from Bauxite Tailings Red Mud by Thermal Reduction with Blast Furnace Sludge

The Influence of Slag Tapping Method on the Efficiency of Stabilization Treatment of Electric Arc Furnace Carbon Steel Slag (EAF-C)

Hydrothermal Production of H2 and Magnetite From Steel Slags: A Geo-Inspired Approach Based on Olivine Serpentinization

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