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The consequences on the Italian steel sector following the conversion of the sole integrated steel plant and the establishment of a direct reduction/electric arc furnace (DR/EAF) grid in the period 2022–2050 were analyzed. Imported natural gas (pathway 0), green hydrogen (pathway 1) and biomethane (pathway 2) were studied as possible reducing gases to be exploited in the DR plant and to be introduced as a methane substitute in EAFs. The results showed that the environmental targets for the sustainable development scenario could be achieved in both 2030 and 2050. In particular, the main reduction would occur by 2030 as a result of the cease of the integrated plant itself, allowing for an overall reduction of 71% of the CO2 emitted in 2022. On the other hand, reaching the maximum production capacity of the DR plants by 2050 (6 Mton) would result in final emission reductions of 25%, 80% and 35% for pathways 0, 1 and 2, respectively. Finally, the creation of a DR/EAF grid would increase the energy demand burden, especially for pathway 1, which would require three times as much green energy as pathway 0 and/or 2 (36 TWh/y vs. ca. 12 TWh/y). [ABSTRACT FROM AUTHOR]

The in‐plant recycling routes of side streams produced in electric arc furnace (EAF) steelmaking remain underexplored. Briquetting is an attractive technique to enable their recycle. Briquettes introduced into EAF must possess certain mechanical and chemical properties. However, no standard is available to determine the suitability of briquettes used in the EAF process. Herein, eight side streams are characterized, and used to produce seven different briquettes to be used in EAF. Briquettes tested consist of four self‐reducing briquettes and three slag‐forming briquettes produced using different recipes. The briquettes are subjected to several mechanical and thermal tests which reflect their intended use in EAF. The mechanical tests include compression and drop tests, and the thermal tests include optical dilatometry, thermogravimetric analysis (TGA)–derivative thermogravimetry (DTG)–mass spectrometry (MS), and full‐scale briquette reduction tests. Moreover, melting trials are performed to assess the melting behavior of selected briquettes and their interaction with slag. Suitability of briquettes characteristics is assessed based on values from the literature and against reference ferroalloys and lime stones used in one of the steel plants. Two briquettes are deemed suitable for EAF use, while three briquettes are deemed unsuitable, and two briquettes are considered of limited use. [ABSTRACT FROM AUTHOR]

The pneumatic lime injection during the electric arc furnace (EAF) process by insufflation lances mounted on the furnace walls has gained much interest in the latest years. The main advantages, in comparison to the traditional procedure of lime lumps addition within the scrap bucket, can be summarized in raw materials consumption reduction, foaming benefits, operational cost benefits, and improvement in environmental aspects. In the proposed work, the advantages of a new lime injection system developed by Unicalce S.p.A. and installed on a 90 t EAF of Acciaierie di Calvisano are analyzed. Data from more than 1200 heats are acquired and compared with the traditional practice from an energetically and emissions point of view. To evaluate the benefits on the slag foamability, several slag samples, taken at the beginning and at the end of refining stage, are analyzed through isothermal solubility diagrams (ISDs). The ISD analysis results are then compared and validated with the total harmonic distortion (THD) of the arc in the corresponding heat. The upgrade to lime injection drives to considerable savings in electrical consumptions, oxygen, methane, and lime, with an overall save of more than 4,000 t year−1 of equivalent CO2. [ABSTRACT FROM AUTHOR]

In the recent years, a revolution of the worldwide development policies has taken place, mainly driven by the idea of achieving the sustainable development scenario (SDS). The electric steelmaking route mainly based on the scrap recycling can be already considered as a successful example of circular economy: the possibility of recycling metallic scraps a theoretically infinite number of times allowed the increase of crude steel production by electric arc furnace (EAF) especially in the Eastern and developing countries. Therefore, the optimization of the charge mix, by empirical mathematical models, has become a fundamental practice aimed at decreasing the metallic loss, increasing the furnace performance and obtaining a proper melt chemistry. Herein, regression modeling is used to investigate the relationship between the metallic loss and the charging material. For the calibration and validation of the model, the data regarding 56 experimental heats, performed by a continuous charging EAF, are used. In particular, the model developed to foresee the metallic loss starting from a given charge mix, highlighting, furthermore, the interactions among the several charging materials. [ABSTRACT FROM AUTHOR]

Featured Application: The aim of this investigation is a simple and easily adaptable agglomeration process for the different quantities and qualities of EAF by-products. The costs and need of disposal for these by-products will be omitted if internal, on-site recycling is possible. In addition to the blast furnace converter route, electric steel production in the electric arc furnace (EAF) is one of the two main production routes for crude steel. In 2019, the global share of crude steel produced via the electric steel route was 28%, which in numbers is 517 million metric tons of crude steel. The production and processing of steel leads to the output of a variety of by-products, such as dusts, fines, sludges and scales. At the moment, 10–67% of these by-products are landfilled and not recycled. These by-products contain metal oxides and minerals including iron oxide, zinc oxide, magnesia or alumina. Apart from the wasted valuable materials, the restriction of landfill space and stricter environmental laws are additional motivations to avoid landfill. The aim of the Fines2EAF project, funded by the European Research Fund for Coal and Steel, is to develop a low-cost and flexible solution for the recycling of fines, dusts, slags and scales from electric steel production. During this project, an easy, on-site solution for the agglomeration of fine by-products from steel production has to be developed from lab scale to pilot production for industrial tests in steel plants. The solution is based on the stamp press as the central element of the agglomeration process. The stamp press provides the benefit of being easily adapted to different raw materials and different pressing parameters, such as pressing-force and -speed, or mold geometry. Further benefits are that the stamp press process requires less binding material than the pelletizing process, and that no drying process is required as is the case with the pelletizing process. Before advancing the agglomeration of by-products via stamp press to an industrial scale, different material recipes are produced in lab-scale experiments and the finished agglomerates are tested for their use as secondary raw materials in the EAF. Therefore, the tests focus on the chemical and thermal behavior of the agglomerates. Chemical behavior, volatilization and reduction behavior of the agglomerates were investigated by differential thermogravimetric analysis combined with mass spectroscopy (TGA-MS). In addition, two melts with different agglomerates are carried out in a technical-scale electric arc furnace to increase the sample size. [ABSTRACT FROM AUTHOR]

The slag's chromium leaching is one of the most pressing concerns in Electric Arc Furnace (EAF) carbon and stainless steels production. In recent years, many studies have aimed at understanding which properties (basicity, cooling speed) and phases (spinels, wustite, silicates) determine the Cr leaching, defining different indices (sp-factor, cs-factor) in order to forecast the slag's behavior compared to the leaching of this toxic metal. The literature suggests that spinel formation is usually a good way to fix Cr and prevent its leaching. However, in some conditions (high basicity, low amount of spinel-forming species) soluble Cr-bearing phases can be formed, i.e., Ca-chromite or unstable spinel. In these conditions, Cr can be leached easily, even if it is bound in a spinel structure. In this paper, the effects of basicity and impurities (Ca, Si) on the instability of Cr-spinel was investigated, with respect to slag mesh. The influence of basicity was also studied on Mg-wustite stability, which might contribute to the leaching of Cr. Different samples of carbon steel slag, suspected of forming unstable spinels, belonging to different steel grade production, were also investigated. Both granulated (4 mm) and milled (<100 μm) slag were analyzed. Scanning Electron Microscopy coupled with Energy Dispersive Spectroscopy (SEM-EDS) analyses were carried out to measure the local chemical composition of Cr-bearing phases. This data was correlated with slag basicity (by X-Ray Fluorescence: XRF), spinel fraction (by X-Ray Diffraction: XRD), and Cr leaching (by Inductively Coupled Plasma Mass Spectrometry: ICP-MS). The main results indicate that the increase of the slag basicity implies an increase of the impurity content (Ca, Si) in the spinel, also over-saturated by Cr. This aspect, coupled with spinel geometrical features, seems to justify the unexpected Cr leaching of some slag samples. Basicity does not influence the chemistry of wustite, thus excluding it as an additional Cr leaching source. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]