In this study, different existing methods to remove alloyed and coated copper from steel are summarized, compared, and discussed. None of these methods have been scaled up industrially so far. Characterization of industrial steel scrap will indicate in which forms and quantities copper is present. Based on environment, economics and process efficiency, the most promising techniques will be selected for further investigation. The study will then focus on ways to bring the process efficiency to the level required for industrial application, by better understanding of thermodynamic limits and the reaction kinetics. Possible removal of other undesired elements from the scrap will be taken into account as well.

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An evaluation of neodymium‑iron‑boron permanent magnets (NdFeB PMs) from different end-of-life products, as a secondary resource of rare-earth elements (REEs), is presented. De-coating of PM was investigate as pre-treatment to facilitate efficient direct magnet recycling. Thus, critical aspects from disassembling to the de-coating of the magnets were addressed. A challenge for the de-coating process is that the magnets have different sizes, weights, and their coating compositions are not known beforehand. It was shown that ammonia-based solutions was thermodynamically suitable to dissolve nickel and zinc coatings selectively, while keeping the bulk magnet stable. Nevertheless, the dissolution of Zn was much faster than the Ni one, and more efficient.

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In the pre-reduction cyclone of the HIsarna process, both thermal decomposition and gas reduction of the injected iron ores occur simultaneously at gas temperatures of 1723–1773 K. In this study, the kinetics of the thermal decomposition of three iron ores (namely OreA, OreB and OreC) for HIsarna ironmaking were analysed as an isolated process with a symmetrical thermogravimetric analyser (TGA) under an inert atmosphere. Using various methods, the chemical and mineralogical composition, particle size distribution, morphology and phase distribution of the ores were analysed. The ores differ in their mineralogy and morphology, where OreA only contains hematite as iron-bearing phase and OreB and OreC include goethite and hematite. To obtain the kinetic parameters in non-isothermal conditions, the Coats–Redfern Integral Method was applied for heating rates of 1, 2 and 5 K/min and a maximum temperature of 1773 K. The TGA results indicate that goethite and hematite decomposition occur as a two-stage process in an inert atmosphere of Ar. The proposed reaction mechanism for the first stage of goethite decomposition is chemical reaction with an activation energy ranging from 46.55 to 60.38 kJ/mol for OreB and from 69.90 to 134.47 kJ/mol for OreC. The proposed reaction mechanism for the second stage of goethite decomposition is diffusion, showing an activation energy ranging between 24.43 and 44.76 kJ/mol for OreB and between 3.32 and 23.29 kJ/mol for OreC. In terms of hematite decomposition, only the first stage was analysed. The proposed reaction mechanism is chemical reaction control. OreA shows an activation energy of 545.47 to 670.50 kJ/mol, OreB one of 587.68 to 831.54 kJ/mol and OreC one of 424.31 to 592.32 kJ/mol.@en

The demand for lithium-ion batteries (LiBs) is rising, resulting in a growing need to recycle the critical raw materials (CRMs) which they contain. Typically, all spent LiBs from consumer electronics end up in a single waste stream that is processed to produce black mass (BM) for further recovery. It is desired to design a recycling process that can deal with a mixture of LiBs. Hence, this study investigates the structure and composition of battery modules in common appliances such as laptops, power banks, smart watches, wireless earphones and mobile phones. The battery cells in the module were disassembled into cell casing, cathode, anode and separator. Then, the cathode active materials (CAMs) were characterized in detail with XRD-, SEM-, EDX- and ICP-OES-analysis. No direct link was found between the chemistry of the active materials (NMC, LCO, LMO, LFP etc.) and the application. Various BM samples were submitted to a leaching procedure (2 M H2SO4, 50 °C, 2 h, 60 g BM/L) with varying concentration (0–4 vol%) of H2O2 to study the influence of their chemical composition on the dissolution of Li, Ni, Mn and Co. Only a part of the BMs dissolved completely at 4 vol% H2O2, which was attributed to the oxidation state of the transition metals (TMs). Exact determination of H2O2 consumption by redox titration confirmed this hypothesis.@en

In this paper a CFD analysis of HIsarna off-gas system for post combustion of CO-H2-carbon particle mixture is presented to evaluate the effect of different sub-models and parameters on the accuracy of predictions and simulation time. The effects of different mesh type, mesh grid size, radiation models, turbulent models, kinetic mechanism, turbulence chemistry interaction models, including and excluding gas-solid reactions, number of reactive solid particles are investigated in detail. Based on the accuracy of the predictions and agreement with counterpart measured values, the best combination is selected and conclusions are derived. It was found that radiation and turbulence chemistry interaction model have a major effect on the temperature and composition profile prediction along the studied off-gas system, compared to the variations in other models. The effect of these two models becomes even more evident when the temperature and fuel content of the flue gas are high.@en

The HIsarna off-gas system wall is a cooling jacket made of cooling pipes arranged in the radial direction and in a circular pattern. Part of the off-gas system cooling pipes are isolated using a low-thermal-conductivity refractory material to protect the cooling pipe from melting and thermal stresses. During long runs and due to thermomechanical stresses, the refractory material is lost, and its thickness is reduced. It is possible to measure the thickness of the refractory layer only during shutdown, which is a disadvantage during long runs. The aim is to investigate the possibility of predicting the thickness of the refractory material by using other parameters that are possible to measure during the operation. A combination of FEM and CFD modeling is used to develop a methodology for detailed wall modeling and refractory material loss prediction. Finite element method (FEM) analysis is used to obtain the thermal properties of the wall using detailed geometries for variable refractory thickness. The obtained properties are then used to build CFD models to study the effect of refractory thickness on wall heat loss, temperature and composition profiles. The proposed procedure is validated against the plant measurement, and according to the findings, it is possible to relate the wall thickness to measured parameters such as heat loss through the walls, temperature and carbon conversion. @en

Cobalt is considered a key metal in the energy transition, and demand is expected to increase substantially by 2050. This demand is for an important part because of cobalt use in (electric vehicle) batteries. This study investigated the environmental impacts of the production of cobalt and how these could change in the future. We modeled possible future developments in the cobalt supply chain using four variables: (v1) ore grade, (v2) primary market shares, (v3) secondary market shares, and (v4) energy transition. These variables are driven by two metal-demand scenarios, which we derived from scenarios from the shared socioeconomic pathways, a “business as usual” (BAU) and a “sustainable development” (SD) scenario. We estimated future environmental impacts of cobalt supply by 2050 under these two scenarios using prospective life cycle assessment. We found that the environmental impacts of cobalt production could likely increase and are strongly dependent on the recycling market share and the overall energy transition. The results showed that under the BAU scenario, climate change impacts per unit of cobalt production could increase by 9% by 2050 compared to 2010, while they decreased by 28% under the SD scenario. This comes at a trade-off to other impacts like human toxicity, which could strongly increase in the SD scenario (112% increase) compared to the BAU scenario (71% increase). Furthermore, we found that the energy transition could offset most of the increase of climate change impacts induced by a near doubling in cobalt demand in 2050 between the two scenarios.

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HIsarna is a novel ironmaking process with great raw materials versatility that is attractive for various secondary resources. Among the materials that can be recycled, there is steel scrap which is fed to the furnace bath through an inclined chute. The velocity distribution of the scrap particles along the chute affects the particles’ distribution on the liquid slag and, thereupon, the efficient operation of the reactor. In this study, the flow of steel scrap particles along an inclined chute with the same dimensions as those of the actual chute of the HIsarna plant is investigated experimentally and numerically. The simulations are validated using chute tip velocity and mass fractions collected at the different compartments of a sampling device. Translational and angular velocity distributions along and across the chute are reported, and the effect of different parameters are investigated. The impact of the shape of the particles on the simulation process is found to be negligible. The angular velocity distribution in cross-sections of the chute exhibited a V-shaped orientation, whereas the translational velocity displayed similar values across the cross-sections. Moreover, translational velocity appeared to increase with increasing inclination angles, whereas angular velocity increased with decreasing batch size.

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In order to take full advantage of the secondary resources, in this paper, we reported a template-free process to prepare porous Co microfibers from spent lithium-ion batteries (LIBs). First, the waste LiCoO₂ powders were leached by oxalic acid at a suitable temperature, and rod-like cobalt oxalate powders were obtained. Second, the porous Co microfibers were prepared by using the cobalt oxalate as precursors through a thermal decomposition at 420 °C under nitrogen atmosphere. The prepared Co microfibers possess diameters of 1–2 μm, and each microfiber consists of small particles with size of 100–200 nm. The Co microfibers (25 wt%)/paraffin composite exhibited excellent microwave absorption performance. When the sample thickness is 4.5 mm, the reflection losses reach − 36.14 and − 38.20 dB at 4.16 and 17.60 GHz, respectively, and the effective bandwidth reaches up to 5.52 GHz. This indicates that the Co microfibers can be used as a promising microwave absorber. Therefore, this paper demonstrates a novel process to make a high value-added product through recycling from the spent lithium-ion batteries. In addition, it is advantageous to eliminate the hazard of spent lithium-ion batteries and electromagnetic radiation to environment and human health. Graphical abstract: [Figure not available: see fulltext.].

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For all industrial applications, predicting system characteristics and behavior plays a vital role before constructing costly and complex multi-physic systems. Correct and reliable predictions become even more important once the aim is to go from small- to large-scale processes to establish an industrial demonstrations. In this study, a CFD-based scale-up of HIsarna off-gas system based on the Eulerian–Lagrangian approach is investigated and detailed step in scale-up procedure is discussed. A three-dimensional CFD model is developed and validated based on the available pilot scale data and used to design and scale up the post-combustion chamber (also known as reflux chamber). Detailed kinetics for volumetric and gas–solid reactions are incorporated in validated CFD model with a special attention to the wall boundary condition and modeling. The effect of reflux chamber geometry, oxygen injection ports, oxygen injection flowrate, isolation wall thickness, and inlet flue gas composition on different system characteristics such as heat loss through the wall, CO–H₂–carbon mixture conversion, flue gas, and wall temperature are investigated. The aim of the scaled up geometry, like pilot scale, is to achieve full combustion of unwanted species inside the reflux chamber to assure zero emissions from the off-gas system. Compared to the pilot scale, the scaled up reflux chamber is capable of handling and removing higher amount of unwanted species coming from the main reactor and therefore lower CO–H₂ and carbon particle emissions, mainly due to a larger size which provides larger volume and residence time for volumetric and gas–solid reaction to proceed.

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Galvanized steel scrap flow and injection into the HIsarna reactor are investigated using discrete element method (DEM). The scrap particle is fed into the reactor through an inclined chute and hits the slag surface where the zinc content is evaporated and solid particles melt. A DEM model is setup and validated using experimental data obtained from the exact plant-scale chute geometry and scrap particles. Using the DEM model, the effect of chute inclination, injection elevation, injection mode (batch and continuous), batch size, and flowrate on particle distribution and exerted pressure on the slag surface are investigated. It is found that continuous mode of injection is the most suitable method to increase the spread of particles and also to reduce the exerted pressure on the slag surface. Placing dent-like obstacles at the tip of the chute significantly increases the impact area, especially for batchwise injection, thus reducing force and pressure on the slag surface that minimizes the risk of liquid splash. Larger particle impact area is also beneficial to obtain higher zinc evaporation rate from particle surface and also to minimize the slag surface temperature disturbance.

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Within the steelmaking industry, a large amount of zinc-bearing waste is produced which cannot be effectively treated through integrated steel mills. Concurrently, zinc smelters generate waste residues containing significant amounts of iron and zinc which are stored or landfilled. The zinc concentration of iron and steelmaking residues inhibits its recycling to the blast furnace but is insufficient to be sent directly to the zinc producers. Consequently, a means of up-concentration is required. The pilot HIsarna ironmaking furnace has shown potential for processing secondary iron-bearing resources. Furthermore, zinc can be concentrated in the off-gas flue dust, providing an enriched input for zinc smelters. The potential recyclability of blast furnace (BF) and basic oxygen furnace (BOF) dust and ‘goethite’ residue from the zinc industry has been studied. The input materials have been comprehensively characterized and their reduction–vaporization behavior, has been investigated. Individual samples were tested at temperatures of up to 1300 °C. Here, it was shown that minimal reduction of iron and volatilization of zinc occurred in the goethite and BOF samples. Conversely, even at 1000 °C, the BF dust showed complete reduction of iron and removal of zinc within 30 min. This was due to its high carbon content (40 wt%) which can act as a reductant. Consequently, mixtures of BOF dust and goethite with BF dust were studied. It has been shown that mixtures of 30:70 BF dust to goethite and 20:80 BF dust to BOF dust are suitable for recovering zinc to the gas phase and fully reducing the contained iron. Graphical Abstract: [Figure not available: see fulltext.]

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Exploring more efficient and low-cost electrocatalysts to replace platinum (Pt) is highly desired to promote the practical hydrogen production through water splitting. Herein, a facile and effective strategy is proposed to fabricate self-standing Al₃Ni₂/Ni electrode with controlled phase composition and surface morphology, which is obtained by one-step electrochemical reduction of Al³⁺ on commercially available nickel in eutectic NaCl-KCl melt. Different from previously reported approaches, uniform Al₃Ni₂ monolith catalyst can directly grow onto Ni substrate. The deposit possesses unique three-dimensional (3D) cauliflower-like morphology comprising of nano- and microparticles due to the rapid nucleation rate during molten salt electrolysis. The as-fabricated Al₃Ni₂/Ni electrode can be directly used as the cathode to catalyze Hydrogen evolution reaction (HER). Impressively, it exhibits remarkable HER activity comparable to commercial Pt, including a low overpotential of 83.4 mV for a current density of 10 mA cm⁻², a small Tafel slope of 40.7 mV dec^-1, and excellent long-term stability over 36 h of continuous HER operation in 0.5 M H₂SO₄ solution. The intrinsic catalytic ability of Al₃Ni₂ with the unique hierarchical structure of nano/microsized grains can offer multiple effects, including massive exposed active sites, enhanced charge transfer and mass transport, and fast gas releasing that synergistically contribute to improving the electrocatalytic performance of HER. This work represents a highly promising approach to the design and one-step controllable fabrication of efficient and self-standing base metal electrode for electrocatalytic hydrogen production.

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The HIsarna process is a new and breakthrough smelting reduction process for hot metal (liquid iron) production from iron ores and coal directly fed into the reactor. The flue gas from the main reactor enters the off-gas system containing small amounts of H₂, CO and carbon particles which need to be removed before further treatment by post combustion oxygen injection. A three-dimensional Computational Fluid Dynamics (CFD) simulation of the HIsarna off-gas system is performed and validated using a detailed reaction mechanism and kinetic data for post-combustion of a CO–H₂ mixture and carbon particles. Using the validated model, a series of simulations were performed to investigate the effect of water quenching and post combustion oxygen injection. It was found that water quenching can significantly reduce the off-gas temperature. It is also possible to reduce oxygen injection during operations where inlet CO content of the off-gas system is low.

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HIsarna reactor is characterized by a high raw materials versatility and is therefore attractive for processing secondary iron sources. Among the materials that can be recycled through HIsarna, zinc-bearing material has drawn a special attention. Based on the plant data, once dust-containing Zinc was injected into the main reactor, a final collected dust with a zinc content of 16% was achieved which opened up possibilities of higher enrichment for direct reuse in Zn smelting as a secondary source and an alternative for Zn ore (the primary source). However Zn vapor can react with iron oxide to form zinc ferrite (ZnFe₂O₄), which is an undesired product. Hence, the main focus of this study is to minimize the formation of ZnFe₂O using thermodynamic (FactSage) and computational fluid dynamic tools. After detecting regions with high potential of ZnFe₂O₄ formation, proper geometrical and operational modifications of the off-gas system is proposed to minimize the formation of zinc ferrite.

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Silicon [Si] in hot metal is an impurity acting in the steel shop as an energy source that is released by oxidation during oxygen blowing in the converter. Preferred silicon concentration in hot steel is typically 0.4 wt-% (± 0.1 wt-%), helping predictable and low-cost processing. In practice, the Si concentration is difficult to control and may occasionally reach levels higher than 1 wt-%. The authors studied data from observations, samples and autopsies of a chilled blast furnace, a core drill and a furnace in operation. In addition, production data from a melting reduction pilot plant (HIsarna) and FactSage® calculations were used. The amount of FeO in the raceway, the area in which hot gas and powdered coal (PCI) are introduced in the blast furnace, in relation to [Si] in hot metal, is observed. The goal of this paper is to contribute to a better understanding about the mechanism of the dissolution of silicon in hot metal.

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A three-dimensional computational fluid dynamics (CFD) model for the HIsarna off-gas system is set up and validated by real plant data. In the model detailed reaction mechanism and kinetic data for post-combustion of CO-H2 mixture and carbon particles are incorporated. The results are presented and discussed in another study (Part 1) by the same authors. In the present paper, the focus will be on geometry modification of the off-gas system and the effects on the operating parameters. The effect of this modification on heat loss, temperature profile, carbon conversion and gaseous phase composition across the off-gas system is investigated. It is shown that the modified geometry leads to a higher heat loss through the reflux chamber walls which can change the temperature profile and consequently species composition. The modified geometry also offers possibility of higher CO-H2 mixture and carbon particles conversion rate and reduce unwanted emission from the reflux chamber.

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In order to understand the pre-reduction behaviour of fine hematite particles in the HIsarna process, change of morphology, phase and crystallography during the reduction were investigated in the high temperature drop tube furnace. Polycrystalline magnetite shell formed within 200 ms during the reduction. The grain size of the magnetite is in the order of magnitude of 10 µm. Lath magnetite was observed in the partly reduced samples. The grain boundary of magnetite was reduced to molten FeO firstly, and then the particle turned to be a droplet. The Johnson-Mehl-Avrami-Kolmogorov model is proposed to describe the kinetics of the reduction process. Both bulk and surface nucleation occurred during the reduction, which leads to the effect of size on the reduction rate in the nucleation and growth process. As a result, the reduction rate constant of hematite particles increases with the increasing particle size until 85 µm. It then decreases with a reciprocal relationship of the particle size above 85 µm.

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The HIsarna process is one of the emerging low-CO₂ ironmaking processes that could help the steel industry in achieving their carbon footprint goals. HIsarna hot metal contains 3–4 times more sulfur than hot metal from blast furnaces (BFs). Therefore, a literature study, a thermodynamic analysis, and plant data analysis from Tata Steel, IJmuiden, are used herein to investigate the consequences of HIsarna hot metal for the current hot metal desulfurization process. Although the high sulfur concentration and low temperature of HIsarna hot metal lead to a higher total reagent consumption, compared with desulfurization of BF hot metal, the specific magnesium consumption decreases. The higher oxygen concentration in HIsarna hot metal only leads to a small increase in reagent consumption.

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Suspension reduction kinetics of hematite ore particles at 1710 K to 1785 K was described by the Johnson-Mehl-Avrami-Kolmogorov model with Avrami exponent of 1.405. The apparent activation energy is 105.5 kJ mol⁻¹ with the rate determining step of nucleation and growth. The reduction degree of the hematite at the endpoint is a linear function of temperature and the logarithmic oxygen potential of the reacting gas. A peak function of reaction rate constant with particle size has been verified in this work, and the maximum value of the reaction rate is located at around 85 µm particle size. The influence of heat transfer on the reaction process has been evaluated. The results suggest that the heating-up process for large particles, 244 µm particles, for instance, cannot be ignored. It can retard the reaction rate compared to small particles. Normally, the reaction rate constant decreases linearly with the increase of ln[p(O₂)] of the reacting gas mixture. However, 95 vol pct CO₂ in the reacting gas can accelerate the reaction rate of thermal decomposition of hematite due to the emissivity of CO₂ gas. It results in a higher reaction rate of 110 µm particles in 95 vol pct CO₂-containing gas than that in other less CO₂-containing gases.

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