Reuse and Recycling of By-Products in the Steel Sector: Recent Achievements Paving the Way to Circular Economy and Industrial Symbiosis in Europe

Sustainable approaches in concrete production: An in-depth review of waste foundry sand utilization and environmental considerations

This review critically evaluates the potential of Waste Foundry Sand (WFS) as a substitute for fine aggregate in concrete, conducting a comparative analysis of its physical and chemical properties against those of natural sand. The study synthesizes findings from various research experiments to determine concrete's most effective WFS replacement percentage. It compiles and analyzes data on how different WFS ratios affect concrete's mechanical properties, including modulus of elasticity and compressive strength. The review also consolidates research on the impact of WFS on concrete's workability, density, and flowability. A key finding is that WFS, categorized as a non-hazardous waste, possesses a diverse particle size distribution, rendering it suitable for recycling in various industrial applications.The study identifies that a 20%-30% replacement of WFS in concrete significantly improves properties such as voids, specific gravity, and density. However, it is essential to note that exceeding a 30% WFS replacement can result in increased carbonation depth and decreased resistance, primarily due to sulfur trioxide (SO3). Further observations indicate that incorporating higher levels of WFS in self-compacting concrete reduces its flowability and increases water permeability. Moreover, the review highlights the regulatory and classification challenges associated with using WFS, particularly its classification as waste, which hampers its widespread adoption in construction. In conclusion, the study recommends implementing End-of-Waste (EoW) regulations to facilitate sustainable recycling and environmental protection. Additionally, it includes a bibliometric analysis of foundry sand research spanning from 1971 to 2020, providing a comprehensive summary of the field's historical and recent developments.

Investigating technology development in the energy sector and its implications for Indonesia

Innovations for a low-carbon economy and carbon neutrality are the focal points of technology development in the energy sector. This paper aims to investigate the progress of technology and advancements in the energy sector and the implications for Indonesia via two routes, viz., renewable energy and energy efficiency. The methodology employed in this research is divided into two parts. Firstly, an extensive literature review was conducted to identify prevalent research trends within the energy sector. Second, a case study method was performed to gain a comprehensive understanding of energy transformation within the electricity and steel sectors. The study presents two key findings. First, the energy sector has experienced significant technological disruption, providing the opportunity for Indonesia to transition towards a low-carbon development. This includes smart grids, energy-intensive industries, electric vehicles, and storage (pumped storage and battery). Second, lessons from the steel industry show that the technology selection is sensitive to parent company, and this is not easily captured in literature studies. Indonesian has gained many benefits from the global technological disruption, but this is not sufficient without developing changes in support system and consumer behavior.

Unveiling the spatial differentiation drivers of major soil element behavior along traffic network accessibility

Advancements in transportation networks have induced a spatial-temporal convergence effect, accelerating socio-economic elements flow and dismantling the conventional "core-periphery" urbanization gradient. Accessibility of transportation networks emerges as a reliable indicator of urbanization. There has been a growing global and Chinese focus on the various forms of metal pollution in urban soil. This study aims to investigate the driving forces and effects of urbanization factors (Gross Domestic Product (GDP), value added of secondary industries (VA), night light (NL), population density (PD), and road density (Distance)), soil property factors (pH, electrical conductivity (EC), and total organic carbon (TOC)), and topographic factors (elevation (DEM), aspect, and slope) on toxic heavy metal elements (Cd, As, and Hg) and trace elements (Mn, Ti, V) in surface soil (0-20 cm) across varying accessibility levels in the Beijing-Tianjin-Hebei urban agglomeration. Results reveal significant influence of accessibility on Cd and Hg levels (p < 0.05), with higher accessibility areas displaying elevated element concentrations. According to the evaluation results of the single-factor pollution index, Cd and V have the highest pollution exceedance rates (93.18% and 75.76%, respectively). Moran's Index results highlight typical spatial clustering of elements, with hotspots in areas of high accessibility. Urbanization has led to distinct spatial agglomeration patterns in element concentrations and environmental factors. Geographic detector analysis reveal that in low accessibility areas, metal element pollution and distribution are influenced by a combination of complex factors, including soil properties (pH), terrain conditions (DEM), and the urbanization process (VA). In high accessibility areas, toxic heavy metal elements are primarily driven by urbanization factors, largely influenced by transportation activities, industrial development, and population density, while elements Mn, Ti, and V are still influenced by both natural processes and urbanization activities. These findings suggest that urbanization intensifies the impact on potential toxic elements in soil, and that trace elements are increasingly affected by urbanization, warranting further attention.

Synergistic effect from combined use of scrap-recycling slag and hydrated lime to stabilize Pb and Zn in highly contaminated soil

For the soil in an area which has been repeatedly chosen as one of the 10 most polluted places in the world, stabilization of Pb and Zn was assessed in batch, incubation, and column experiments. Single and combined amendment of scrap-recycling slag (Slag-R), charcoal, coal ash, hydrated lime, and basic oxygen furnace (BOF) slag were applied for the stabilization. Notably, the combined amendment of Slag-R and hydrated lime exhibited superior stabilization efficiencies than the individual use of all stabilizing agents and combined use of charcoal and hydrated lime. The combined amendment of Slag-R and hydrated lime decreased Pb levels by 92-99% and Zn levels by 63-88% in the incubation experiments and by 75% and 89-93%, respectively, in the column experiments. In particular, the combined amendment showed a synergistic effect for Pb stabilization because a higher pH enhanced sorption onto the slag and because sorption onto Fe (hydr)oxides of the sorbent possibly helped to remove Pb. Zinc had a relatively lower sorption tendency, so it was mainly controlled by the pH increase from hydrated lime. Although the addition of hydrated lime was very effective in stabilizing high concentrations of Pb and Zn, the dosage should be controlled carefully because excessively high pH redissolves Pb and Zn as anions.

3-Methyl-1-phenyl-4-thioacetylpyrazol-5-one

The novel compound 3-methyl-1-phenyl-4-thioacetylpyrazol-5-one is obtained in excellent yield via a thionation of the corresponding oxygen analogue. The product is isolated in pure form using column chromatography and is characterised using 1D and 2D NMR experiments, ATR IR and HRMS spectra, and single-crystal XRD.

Metallurgical resource recovery from waste steelmaking slag from electric arc furnace

Steel slag from an electric arc furnace (EAF) may contain significant amounts of oxides of valuable metals. The recovery of iron and other metals from the EAF slag using smelt-reduction process was studied with coal as the reductant. A pig iron phase with high carbon and a final slag depleted of the valuable metals were generated. SEM-EDS and ICP analysis indicated that valuable metals could be successfully recovered in the pig iron. Nearly 84% recovery of Fe was observed with about 85%, 95% and 84% recovery of Mo, Ni and Co, respectively. In addition, 48% Cr, 30% V and 7% Mn were also recovered with a total metal yield of about 20%. An experimental design was developed using the three most important process variables, dwell time, reaction temperature and basicity, with a view to optimize the process and identify the most favourable process conditions. A total of 15 experiments were carried out per the Box-Behnken design using Response Surface Methodology. The response variables included metal yield, total yield, slag yield, Fe recovery, Cr recovery, Mo recovery as well as C and S content of the metal. Statistically significant empirical models for the response variables were developed and the process was optimized. The optimum was obtained at a dwell time of 20 min, reaction temperature of 1681 K and basicity of 1.025. The recovered pig iron with 3.32% C and 0.1% S is suitable for use in steelmaking as hot metal. The final slag may be used in construction applications.

Ferrous Industrial Wastes-Valuable Resources for Water and Wastewater Decontamination

Ferrous waste by-products from the metallurgical industry have a high potential for valorization in the context of the circular economy, and can be converted to value-added products used in environmental remediation. This research reviews the latest data available in the literature with a focus on: (i) sources from which these types of iron-based wastes originate; (ii) the types of ferrous compounds that result from different industries; (iii) the different methods (with respect to the circular economy) used to convert them into products applied in water and wastewater decontamination; (iv) the harmful effects ferrous wastes can have on the environment and human health; and (v) the future perspectives for these types of waste.

Microbial diversity and geochemistry of groundwater impacted by steel slag leachates

To understand long-term impacts of steel slag material on aquifer geochemistry and microbial communities, we conducted four sampling campaigns in the Gier alluvial groundwater (Loire, France). In its northern part, the aquifer flows under a 200,000 m³ steel slag exhibiting high levels of chromium and molybdenum. Geochemical analyses of the water table revealed the existence of water masses with different chemical signatures. They allowed us to identify an area particularly contaminated by leachates from the slag heap, whatever the sampling period. Water samples from this area were compared to non-contaminated samples, with geochemical characteristics similar to the river samples. To follow changes in microbial communities, the V3-V4 region of 16 s rRNA gene was sequenced. Overall, we observed lower diversity indices in contaminated areas, with higher relative abundances of Verrucomicrobiota and Myxococcota phyla, while several Proteobacteria orders exhibited lower relative abundances. In particular, one single genus among the Verrucomicrobiota, Candidatus Omnitrophus, represented up to 36 % of total taxon abundance in areas affected by steel slag leachates. A large proportion of taxa identified in groundwater were also detected in the upstream river, indicating strong river-groundwater interactions. Our findings pave the way for future research work on C. Omnitrophus remediation capacities.

Recovery of Waste with a High Iron Content in the Context of the Circular Economy

In order to apply the concepts that allow the transition from a linear to a circular economy, waste generators and/or processors must identify those variants that generate products that can be used as secondary raw materials, thus also respecting the actions governing sustainable development. This paper presents such a variant, the briquetting of waste with high iron content, waste generated on current flows in steel enterprises or deposited in industrial sites. The obtained briquettes are analyzed for chemical and mechanical characteristics so that can be used as secondary materials in the steel production. An optimization of the chemical composition using generic algorithms is also proposed in order to obtain the mechanical characteristics necessary for the proper handling of these products.

Comparative Study on the Isothermal Reduction Kinetics of Iron Oxide Pellet Fines with Carbon-Bearing Materials

The isothermal reduction of iron oxide pellet fines–carbon composites was investigated at temperatures of 900–1100 °C. The reduction reactions were monitored using the thermogravimetric (TG) technique. Alternatively, a Quadruple Mass Spectrometer (QMS) analyzed the CO and CO2 gases evolved from the reduction reactions. The effect of temperature, carbon source, and reaction time on the rate of reduction was extensively studied. The phase composition and the morphological structure of the reduced composites were identified by X-ray diffraction (XRD) and a scanning electron microscope (SEM). The results showed that the reduction rate was affected by the temperature and source of carbon. For all composite compacts, the reduction rate, as well as the conversion degree (α) increased with increasing temperature. Under the same temperature, the conversion degree and the reduction rate of composites were greater according to using the following carbon sources order: Activated charcoal > charcoal > coal. The reduction of the different composites was shown to occur stepwise from hematite to metallic iron. The reduction, either by activated charcoal or charcoal, is characterized by two behaviors. During the initial stage, the chemical reaction model (1 − α)−2 controls the reduction process whereas the final stage is controlled by gas diffusion [1 − (1 − α)1/2]2. In the case of reduction with coal, the reduction mechanism is regulated by the Avrami–Erofeev model [−ln (1−α)2] at the initial stage. The rate-controlling mechanism is the 3-D diffusion model (Z-L-T), namely [(1−α)−1/3−1]2 at the latter stage. The results indicated that using biomass carbon sources is favorable to replace fossil-origin carbon-bearing materials for the reduction of iron oxide pellet fines.

Reconditioning by Welding of Prosthesis Obtained through Additive Manufacturing

Biocompatible titanium alloys are increasingly being used to make custom medical implants using additive manufacturing processes. This paper considered the welding reconditioning of a titanium-alloy customized additive manufactured hip implant with several manufacturing defects. The personalized implants are made starting from a Computer-Aided Design (CAD) model as a direct result from the medical imaging investigations of the areas of interest. Then the customized implant is fabricated using an additive manufacturing process (in this case Powder Bed Fusion—Direct Metal Laser Sintering—DMLS). The analysis of the chemical composition values as well as the values of the mechanical properties of the samples obtained via DMLS additive manufacturing process, revealed that such a manufacturing process can be successfully used to make customized surgical implants. The mechanical properties values of the DMLS samples are approximately equal to those specified by the manufacturer of the titanium powder used for sintering. On average, the tensile strength was found to be 24.75% higher, while yield strength 22.7% higher than the values provided in the standard for surgical implants applications. In case the additive manufacturing process produces products with defects one might want to try and recover the implant due to costs and time constraints. The Tungsten Inert Gas (TIG) welding reconditioning process with ERTi-5 Ti64 rod for welding titanium alloys with a content of 6% aluminum and 4% vanadium filler material was used to restore the geometric characteristics as well as the functional properties of a custom hip medical prosthesis. After welding depositing successive layers of materials, the surfaces of the prosthesis were machined to restore the functional properties according to the characteristics of the original 3D model. A 3D scan was used to compare the geometrical characteristics between the original part and reconditioned one. Deviations were less than 1 mm and were acceptable from the medical point of view.

70 Years of LD-Steelmaking—Quo Vadis?

Basic Oxygen Furnace (BOF) steelmaking is, worldwide, the most frequently applied process. According to the world steel organization statistical report, 2021, it saw a total production share of 73.2%, or 1371.2 million tons per year of the world steel production in 2020. The rest is produced in Electric Arc Furnace (EAF)-based steel mills (26.3%), and only a very few open-hearth and induction furnace-based steel mills. The BOF technology remains the leading technology applied based on its undoubted advantages in productivity and liquid steel composition control. The BOF technology started as the LD process 70 years ago, with the first heat applied in November 1952 in a steel mill in Linz, Austria. The name LD was formed from the first letters of the two sites with the first industrial scale plants, Linz and Donawitz, both in Austria. The history and development of the process have been honored in multiple anniversary publications over the last few decades. Nevertheless, the focus of the steel industry worldwide is significantly changing following a social and political trend and the requirement for fossil-free energy generation and industrial production to be in accordance with the world climate targets committed to in relation to the decades leading up to 2050. Iron and steel production is one of the major polluters of climate changing greenhouse gases; it must change to renewable primary energy sources and the use of climate-neutral reduction agents. Because it is very obvious that carbon, as the main component for steel strength properties, cannot be eliminated totally from the steel production process, the question arises of where a “zero carbon” approach can lead? This paper will review the ongoing success story of the LD-process, discuss the recent technology advancements, and give an outlook on the future role of the process in the steel industry.

Metallurgical Wastes as Resources for Sustainability of the Steel Industry

The industrial pollution caused by metallurgical waste accumulation has a negative impact on the three environmental factors: soil, air and water. Therefore, the correct management of these wastes would lead to: protection of the environmental factors, the saving of natural resources and sustainability of the steel industry. The purpose of this paper is to assess the chemical and mineralogical compositions of metallurgical wastes landfilled in the Păgida slag dump (Alba County, Romania), for sustainability of the steel industry and metal conservation. The chemical compositions of the two waste samples were analyzed by the XRF (X-ray fluorescence) technique. According to the chemical characterization, magnesium oxide (MgO) has potential to be used as an additional and raw material in the cement industry. The presence of oxides such as CaO, SiO2 FeO and Al2O3 in the compositions of the metallurgical waste samples indicate that they have the potential for use as clinker materials in cement production. The iron and manganese contents from metallurgical wastes can be reused in the iron and steel industry. The presence of V2O5 and TiO2 is connected with the making of stainless steel, and for this reason they have the potential to be reused in the stainless steel industry. The predominant chemical compounds are SiO2, Fetotal, Cao and MgO. The mineralogical compositions were analyzed by the XRD (X-ray diffraction) technique. The mineralogical compounds presenting reuse potential in different domains are Fayalite, Magnetite, Magnesioferrite and Periclase. The mineralogical compounds from metallurgical wastes can be reused as: raw and/or additional materials in the process from which they originate (steelmaking); raw and/or additional materials in road construction and concrete production; pigments in paints; micronutrients in fertilizers; ore of iron, etc. Then, the theoretical assessments of the recovery potentials of the metals were estimated for slag dumps. Copper (Cu), vanadium (V), molybdenum (Mo) and nickel (Ni) have high recovery potential. The total economic value of the recovery potential of metals from slag dumps was assessed to be USD 1175.7440 million.

The Importance of Individual Actor Characteristics and Contextual Aspects for Promoting Industrial Symbiosis Networks

Factors that affect and influence industrial symbiosis (IS) collaborations have been researched extensively in the literature, where they are mostly reported at a network level or for IS in general, and lack the individual actor’s perspective. This review article contributes to and expands knowledge of influencing factors and their effect on the individual actor. In a systematic review, guided by the PRISMA 2020 guidelines, this study reviews 53 scientific papers examining planned or existing IS networks. It examines literature from 1 January 2000 to 28 March 2022, and it identifies drivers, barriers, and enablers influencing actors to participate in IS. It explores whether and how the perception and impact of these factors differs depending on the characteristics of individual actors and their specific context. The main findings of this study reveal that an actor’s specific characteristics and the network’s context have a significant impact on decision making and how actors both perceive and are affected by factors influencing collaboration. Furthermore, an additional novel contribution to this field of research is that the study identifies three underlying and recurring considerations that actors appear to find critical, namely, perceived business opportunities/risks, regulatory and political setting, and potential inequalities in the network. The results show that an actor’s take on these critical considerations determines whether the actor is willing to engage in IS.

Review on Zigzag Air Classifier

The zigzag (ZZ) classifier is a sorting and classification device with a wide range of applications (e.g., recycling, food industry). Due to the possible variation of geometry and process settings, the apparatus is used for various windows of operation due to the specifications of the separation (e.g., cut sizes from 100 µm to several decimetres, compact and fluffy materials as well as foils). Since the ZZ classifier gains more and more interest in recycling applications, it is discussed in this paper, with regards to its design, mode of operation, influencing parameters and the research to date. Research on the ZZ-classifier has been ongoing on for more than 50 years and can be divided into mainly experimental studies and modelling approaches.

Waste Foundry Sand in Concrete Production Instead of Natural River Sand: A Review

The by-product of the foundry industry is waste foundry sand (WFS). The use of WFS in building materials will safeguard the ecosystem and environmental assets while also durable construction. The use of industrial waste in concrete offsets a shortage of environmental sources, solves the waste dumping trouble and provides another method of protecting the environment. Several researchers have investigated the suitability of WFS in concrete production instead of natural river sand in the last few decades to discover a way out of the trouble of WFS in the foundry region and accomplish its recycling in concrete production. However, a lack of knowledge about the progress of WFS in concrete production is observed and compressive review is required. The current paper examines several properties, such as the physical and chemical composition of WFS, fresh properties, mechanical and durability performance of concrete with partially substituting WFS. The findings from various studies show that replacing WFS up to 30% enhanced the durability and mechanical strength of concrete to some extent, but at the same time reduced the workability of fresh concrete as the replacement level of WFS increased. In addition, this review recommended pozzolanic material or fibre reinforcement in combination with WFS for future research.

A comprehensive review on comparison among effluent treatment methods and modern methods of treatment of industrial wastewater effluent from different sources

In recent years, rapid development in the industrial sector has offered console to the people but at the same time, generates numerous amounts of effluent composed of toxic elements like nitrogen, phosphorus, hydrocarbons, and heavy metals that influences the environment and mankind hazardously. While the technological advancements are made in industrial effluent treatment, there arising stretch in the techniques directing on hybrid system that are effective in resource recovery from effluent in an economical, less time consuming and viable manner. The key objective of this article is to study, propose and deliberate the process and products obtained from different industries and the quantity of effluents produced, and the most advanced and ultra-modern theoretical and scientific improvements in treatment methods to remove those dissolved matter and toxic substances and also the challenges and perspectives in these developments. The findings of this review appraise new eco-friendly technologies, provide intuition into the efficiency in contaminants removal and aids in interpreting degradation mechanism of toxic elements by various treatment assemblages.

Explorative Multiple-Case Research on the Scrap-Based Steel Slag Value Chain: Opportunities for Circular Economy

This paper analyses the scrap-based steel slag from the electric arc furnace and secondary metallurgy and proposes a framework for valorising its value chain. Toward this aim, the role of slag features, technological advancements for the treatment of slag, applications, legislation, and their value chain in the circular economy and industrial symbiosis opportunities are discussed within the proposed framework. By interviewing a group of Italian steelmakers, accounting for around 30% of Italian scrap-based steel volume, we analyse various value chain key factors, namely, technology, legislation, production volume, and economic aspects. Consequently, we assess the as-is situation of the sector and elaborate on the challenges and expectations for the future in terms of collaboration frameworks. The results show how vertical (by internal treatment) and horizontal integrations (by collaborating with other potential industries) support decisions on material flow and facilitate circularity in sharing this kind of material. The most influential enabler in a vertical integration is the economic aspect, while in the horizontal integration the enablers are the market and technology. We also address the importance of raw-material self-sufficiency through analysing closed-loop supply chains and collaborative supply-chain networks.

Effect of Grinding Media Size on Ferronickel Slag Ball Milling Efficiency and Energy Requirements Using Kinetics and Attainable Region Approaches

The aim of this study is to evaluate the effect that the size of grinding media exerts on ferronickel slag milling efficiency and energy savings. A series of tests were performed in a laboratory ball mill using (i) three loads of single size media, i.e., 40, 25.4, and 12.7 mm and (ii) a mixed load of balls with varying sizes. In order to simulate the industrial ball milling operation, the feed to the mill consisted of slag with natural size distribution less than 850 μm. Grinding kinetic modeling and the attainable region (AR) approach were used as tools to evaluate the data obtained during the ball milling of slag. Particular importance was given to the determination of the specific surface area of the grinding products, the identification of the grinding limit, and the maximum specific surface area which could be achieved when different grinding media sizes were used. The results showed that, in general, the breakage rates of particles obey non-first-order kinetics and coarse particles are ground more efficiently than fines. The AR approach proved that there is an optimal grinding time (or specific energy input) dependent on the ball size used for which the volume fraction of the desired size class is maximized. The use of either 25.4 mm balls or a mixed load of balls with varying sizes results in 31 and 24% decrease in energy requirements, compared to the use of balls with small size (12.7 mm).

Sustainable biodiesel generation through catalytic transesterification of waste sources: a literature review and bibliometric survey

Sustainable renewable energy production is being intensely disputed worldwide because fossil fuel resources are declining gradually. One solution is biodiesel production via the transesterification process, which is environmentally feasible due to its low-emission diesel substitute. Significant issues arising with biodiesel production are the cost of the processes, which has stuck its sustainability and the applicability of different resources. In this article, the common biodiesel feedstock such as edible and non-edible vegetable oils, waste oil and animal fats and their advantages and disadvantages were reviewed according to the Web of Science (WOS) database over the timeframe of 1970–2020. The biodiesel feedstock has water or free fatty acid, but it will produce soap by reacting free fatty acids with an alkali catalyst when they present in high portion. This reaction is unfavourable and decreases the biodiesel product yield. This issue can be solved by designing multiple transesterification stages or by employing acidic catalysts to prevent saponification. The second solution is cheaper than the first one and even more applicable because of the abundant source of catalytic materials from a waste product such as rice husk ash, chicken eggshells, fly ash, red mud, steel slag, and coconut shell and lime mud. The overview of the advantages and disadvantages of different homogeneous and heterogeneous catalysts is summarized, and the catalyst promoters and prospects of biodiesel production are also suggested. This research provides beneficial ideas for catalyst synthesis from waste for the transesterification process economically, environmentally and industrially.

Sustainable renewable energy production is being intensely disputed worldwide because fossil fuel resources are declining gradually.

Leaching and Geochemical Modelling of an Electric Arc Furnace (EAF) and Ladle Slag Heap

Old metallurgical dumps across Europe represent a loss of valuable land and a potential threat to the environment, especially to groundwater (GW). The Javornik electric arc furnace (EAF) and ladle slag heap, situated in Slovenia, was investigated in this study. The environmental impact of the slag heap was evaluated by combining leaching characterization tests of landfill samples and geochemical modelling. It was shown that throughout the landfill the same minerals and sorptive phases control the leaching of elements of potential concern, despite variations in chemical composition. Although carbonation of the disposed steel slags occurred (molar ratio CO₃/(Ca+Mg) = 0.53) relative to fresh slag, it had a limited effect on the leaching behaviour of elements of potential concern. The leaching from the slag heaps had also a limited effect on the quality of the GW. A site-specific case, however, was that leachates from the slag heap were strongly diluted, since a rapid flow of GW fed from the nearby Sava River was observed in the landfill area. The sampling and testing approach applied provides a basis for assessing the long-term impact of release and is a good starting point for evaluating future management options, including beneficial uses for this type of slag.

Automatic steel grades design for Jominy profile achievement through neural networks and genetic algorithms

The paper proposes an approach to the design of the chemical composition of steel, which is based on neural networks and genetic algorithms and aims at achieving a desired hardenability behavior possibly matching other constraints related to the steel production. Hardenability is a mechanical feature of steel, which is extremely relevant for a wide range of steel applications and refers to the steel capability to improve its hardness following a heat treatment. In the proposed approach, a neural-network-based predictor of the so-called Jominy hardenability profile is exploited, and an optimization problem is formulated, where the optimization function allows taking into account both the desired accuracy in meeting the target Jominy profile and other constraint. The optimization is performed through genetic algorithms. Numerical results are presented and discussed, showing the efficiency of the proposed approach together with its flexibility and easy customization with respect to the user demands and production objectives.

High-Performance Method of Recovery of Metals from EAF Dust-Processing without Solid Waste

A highly effective method of the processing of steelmaking dust in an arc-resistant furnace has been presented. The aim of the research was to investigate the possibility of processing steelmaking dust in terms of waste minimization and selective recovery of valuable components. For this purpose, an electric arc resistance furnace was used. Granulated steelmaking dust with reducer (coal dust) was the input material. The products of the process are zinc oxide, iron alloy and slag, with properties meeting high ecological requirements. The technology does not generate solid waste. Zinc recovery is over 99% and iron recovery over 98%. The content of heavy metals (Zn + Pb + Cu) in glassy slag is below 0.2%, which ensures very low leachability.

Eco-Innovation Diversity in a Circular Economy: Towards Circular Innovation Studies

Transition to a Circular Economy (CE) is about structural change and is predicated on the introduction of transformative eco-innovation (EI). Research on the CE–EI nexus has recently attracted attention both from an analytical and regulatory perspective. However, in-depth research exploring EI dynamics within the CE is still marginal, especially concerning the trends and dynamics of the pro-CE innovation policy and strategy. This paper addresses this gap by taking advantage of the burgeoning research on CE of the last 20 years and offers a new working synthesis. By implementing a “(systematic) review of (systematic) reviews”, this paper provides a new comprehensive framework for understanding pro-circular innovation strategies and, as a complement, argues the need to advance “circular innovation studies” as an agenda in its own right. Innovations related to recycling and recovery CE strategies along with business-model innovations and systemic/transformative innovations are found to be a major current trend in the research, connecting supply and demand side innovations and also driving other forms of innovation linked to design, product manufacturing, logistics and reverse logistics and end-of-life management and recovery. Additionally, of note is that the conceptual understanding of EI dynamics within a CE is still mainly implicit (rather than explicitly discussed) limiting the possibilities to advance knowledge in the area of innovation for CE: this is why we propose a “circular innovation studies” agenda.

Industrial Symbiosis and Energy Efficiency in European Process Industries: A Review

Over the last few decades, process industries have invested increasing efforts in developing technical and operating solutions related to industrial symbiosis and energy efficiency in both production processes and auxiliary services. In particular, new technologies that enable industrial symbiosis, such as novel treatment processes for byproduct extraction and valorization, water purification, and energy transformation, were implemented in different sectors. This work analyses recent relevant results in the implementation of industrial symbiosis and energy efficiency solutions within process industries across Europe, based on the transactions of energy and material flows. Current developments, based on the circular economy’s transformation levers and related achieved results, were taken into account by considering the achieved results coming from the literature, EU-funded projects, programmes, and initiatives on the implementation of technical solutions and practices related to industrial symbiosis and energy efficiency. In addition, the most relevant challenges deriving from the implementations of industrial symbiosis and energy efficiency were analysed. A comprehensive picture of the sectors involved in achieving more proactive cross-sectorial cooperation and integration was provided, as well as an analysis of the main drivers and barriers for IS and EE implementation in future scenarios for European process industries.

Residue Valorization in the Iron and Steel Industries: Sustainable Solutions for a Cleaner and More Competitive Future Europe

The steel industry is an important engine for sustainable growth, added value, and high-quality employment within the European Union. It is committed to reducing its CO2 emissions due to production by up to 50% by 2030 compared to 1990′s level by developing and upscaling the technologies required to contribute to European initiatives, such as the Circular Economy Action Plan (CEAP) and the European Green Deal (EGD). The Clean Steel Partnership (CSP, a public–private partnership), which is led by the European Steel Association (EUROFER) and the European Steel Technology Platform (ESTEP), defined technological CO2 mitigation pathways comprising carbon direct avoidance (CDA), smart carbon usage SCU), and a circular economy (CE). CE approaches ensure competitiveness through increased resource efficiency and sustainability and consist of different issues, such as the valorization of steelmaking residues (dusts, slags, sludge) for internal recycling in the steelmaking process, enhanced steel recycling (scrap use), the use of secondary carbon carriers from non-steel sectors as a reducing agent and energy source in the steelmaking process chain, and CE business models (supply chain analyses). The current paper gives an overview of different technological CE approaches as obtained in a dedicated workshop called “Resi4Future—Residue valorization in iron and steel industry: sustainable solutions for a cleaner and more competitive future Europe” that was organized by ESTEP to focus on future challenges toward the final goal of industrial deployment.

Non-Isothermal Reduction Kinetics of Iron Ore Fines with Carbon-Bearing Materials

This study investigates the non-isothermal reduction of iron ore fines with two different carbon-bearing materials using the thermogravimetric technique. The iron ore fines/carbon composites were heated from room temperature up to 1100 °C with different heating rates (5, 10, 15, and 20 °C/min) under an argon atmosphere. The effect of heating rates and carbon sources on the reduction rate was intensively investigated. Reflected light and scanning electron microscopes were used to examine the morphological structure of the reduced composite. The results showed that the heating rates affected the reduction extent and the reduction rate. Under the same heating rate, the rates of reduction were relatively higher by using charcoal than coal. The reduction behavior of iron ore-coal was proceeded step wisely as follows: Fe2O3 → Fe3O4 → FeO → Fe. The reduction of iron ore/charcoal was proceeded from Fe2O3 to FeO and finally from FeO to metallic iron. The reduction kinetics was deduced by applying two different methods (model-free and model-fitting). The calculated activation energies of Fe2O3/charcoal and of Fe2O3/coal are 40.50–190.12 kJ/mol and 55.02–220.12 kJ/mol, respectively. These indicated that the reduction is controlled by gas diffusion at the initial stages and by nucleation reaction at the final stages.

Comprehensive Analysis of Steel Slag as Aggregate for Road Construction: Experimental Testing and Environmental Impact Assessment

Blast Oxygen Furnace (BOF) slag represents one of the largest waste fractions from steelmaking. Therefore, slag valorisation technologies are of high importance regarding the use of slag as a secondary resource, both in the steel sector and in other sectors, such as the construction or cement industries. The main issue regarding the use of BOF slag is its volumetric instability in the presence of water; this hampers its use in sectors and requires a stabilisation pre-treatment. These treatments are also cost-inefficient and cause other environmental issues. This paper analyses the use of untreated BOF slag from a technical and environmental point of view, suggesting it as an alternative to natural aggregates in road surface layers and asphalt pavements. A comprehensive analysis of the requirements to be met by raw materials used in asphalt mixes was performed, and a pilot test was carried out with two different mixtures: one mix with limestone as coarse aggregate and another with 15% BOF slag. Furthermore, the global warming impacts derived from each mix with different aggregates were measured by Life Cycle Analysis (LCA), and a transport sensitivity analysis was also performed. The results show how the utilization of BOF slag as coarse aggregate in road construction improves the technical performance of asphalt mixtures (Marshall Quotient 4.9 vs. 6.6). Moreover, the introduction of BOF slag into the asphalt mix as a coarse aggregate, instead of limestone, causes a carbon emissions reduction rate of more than 14%.

Acoustic Characterization of Some Steel Industry Waste Materials

From a circular economy perspective, the acoustic characterization of steelwork by-products is a topic worth investigating, especially because little or no literature can be found on this subject. The possibility to reuse and add value to a large amount of this kind of waste material can lead to significant economic and environmental benefits. Once properly analyzed and optimized, these by-products can become a valuable alternative to conventional materials for noise control applications. The main acoustic properties of these materials can be investigated by means of a four-microphone impedance tube. Through an inverse technique, it is then possible to derive some non-acoustic properties of interest, useful to physically characterize the structure of the materials. The inverse method adopted in this paper is founded on the Johnson–Champoux–Allard model and uses a standard minimization procedure based on the difference between the sound absorption coefficients obtained experimentally and predicted by the Johnson–Champoux–Allard model. The results obtained are consistent with other literature data for similar materials. The knowledge of the physical parameters retrieved applying this technique (porosity, airflow resistivity, tortuosity, viscous and thermal characteristic length) is fundamental for the acoustic optimization of the porous materials in the case of future applications.

Social, Economic, and Institutional Configurations of the Industrial Symbiosis Process: A Comparative Analysis of the Literature and a Proposed Theoretical and Analytical Framework

This paper aims at comparatively analyzing the IS process in three remarkable empirical cases. Ostrom’s Institutional Analysis and Development framework and its categories for analysis are used to understand each process. A theoretical and analytical framework is proposed based on a survey of contextual elements that shaped the behavior of organizations towards Industrial Symbiosis practices. The results show that although there was no clear, linear order in which the actors developed symbiotic relationships, the decisions related to Industrial Symbiosis are shaped by a similar set of variables. These variables range from technical and economic aspects, such as the diversity of industries and the viability of exchanges, to social and institutional aspects, encompassing critical environmental issues; bilateral agreements; collective engagement; trust to build cooperative relationships; communication and information sharing strategies; integrated regulatory framework at three levels; congruence between government and company actions to create a cooperative environment; and governance structures involving local government, companies, research and development institutions, and a coordinating entity or the champion. This framework may serve as a reference for diagnostic analyses assessing aspects that can be improved wherein Industrial Symbiosis is already underway. It may also be useful in prescriptive analyses assessing the potential for implementing IS.

Synergistic utilization of diverse industrial wastes for reutilization in steel production and their geopolymerization potential

Recycling wastes back into a manufacturing process, or into a separate product, is an important challenge. The primary aim of this work was to combine wastes from the steel industry, the galvanizing industry and the pulp and paper industry to form two new useful products. The steel industry generates the wastes red dust, mill scale, blast oxygen furnace slag and iron ore fines. Galvanizing industrial facilities dispose of sulfuric acid contaminated with iron. The pulp and paper industry produces the byproduct black liquor, which is high in lignin. Inserting these wastes as resources into the steel industry, or as stand-alone products, could reduce the need for virgin materials. The main methodology of the work was three-fold. First, spent sulfuric acid was used to precipitate the lignin from black liquor. Second, this lignin was combined with steel industry wastes and geopolymeric materials to make briquettes, a sustainable reducing material for steelmaking furnaces. Briquettes contained red dust, mill scale, blast oxygen furnace slag, iron ore fines and lignin precipitated from black liquor with spent sulfuric acid. Key research findings of compressive strength and weight loss testing showed the briquettes to be feasible for steel-making furnace use. Third, these steel industry wastes were investigated as a partial fly ash replacement in geopolymers. Main research findings were that compared to the control geopolymer, these geopolymer samples improved compressive strength and gave similar workability. Thus, the investigated wastes have the potential to both increase recycling in the steel industry and to improve geopolymeric products.

Preliminary Validation of Steel Slag-Aggregate Concrete for Rigid Pavements: A Full-Scale Study

The high wear resistance and toughness of electric arc furnace slag (EAFS) means that this industrial by-product can successfully replace natural aggregate in hydraulic or bituminous concretes that withstand vehicle traffic. This article validates the use of concrete made with large amounts of EAFS for rigid pavements. Accordingly, three EAFS–concrete mixes made with metallic or synthetic fibers were designed. Their performance was studied through laboratory tests (compressive strength, modulus of elasticity, splitting tensile strength, and abrasion resistance) and field observations on full-scale slabs made with each of the studied mixes. All mechanical properties yielded adequate results for concrete for rigid pavements. The metallic fibers increased the strength and elastic stiffness by 7–10%, while the addition of synthetic fibers slowed the development of these properties over time. On the other hand, all the mixes allowed for a successful implementation of full-scale slabs, with none of them showing excessive deterioration after five years of exposure to the outdoor environment. Only minor cracking and some chips in the surface-treatment layer were detected. The strength development of the slabs and their slipperiness were adequate for use in high-speed pavements. The overall analysis of the results shows that concrete made with EAFS can be used in real rigid pavements.

A circular economic approach to the phytoextraction of Zn from basic oxygen steelmaking filtercake using Lemna minor and CO2

Two billion tonnes of alkaline metallurgical waste is generated per year as a product of industry, mining, and metal processing. Filtercake is one such residue formed as a bi-product of steelmaking. Metal rich bi-products can be both an environmental concern and potential resource. High concentrations of heavy metals, if accessed, could be utilised and reprocessed reducing both pollution and the demand for raw metal ores. Phytoextraction is one such method of recovering metals from contaminated mediums. Research interest in Lemna sp. has grown due to their phytoremediation potential. Facilitated by rapid growth and accumulation of nutrients and metals, Lemna minor has been described as one of the most effective macrophytes for remediating contaminated water. The present study outlines a system using L. minor to extract Zn from filtercake when submerged in static water. To facilitate phytoremediation, CO₂ carbonation can be employed to solubilise elements and utilise this greenhouse gas, another a bi-product of steel industry. The addition of CO₂ to vessels of water containing filtercake lowered the pH from as high as 8.8 to 5.6 and significantly increased Zn in solution compared to vessels receiving no CO₂. Results suggest the potential of L. minor to accumulating 68.7 kg Zn per year from 20.5 Mt. filtercake ha^-1. This system facilitates a circular economy with re-use of multiple existing bi-products. In addition, the potential employment of biomass in biofuel production and use of remediated filtercake in carbon sequestration adds further environmental and socio-economic impact. The extent to which the approach was consistent with circular economy was discussed and its wider integration considered.

Research on Reduction of Selected Iron-Bearing Waste Materials

During the steel production process, nearly twice as many input materials are used as compared to finished products. This creates a large amount of post-production waste, including slag, dust, and sludge. New iron production technologies enable the reuse and recycling of metallurgical waste. This paper presents an investigation on the reduction of selected iron-bearing waste materials in a laboratory rotary furnace. Iron-bearing waste materials in the form of dust, scale, and sludge were obtained from several Polish metallurgical plants as research material. A chemical analysis made it possible to select samples with sufficiently high iron content for testing. The assumed iron content limit in waste materials was 40 wt.% Fe. A sieve analysis of the samples used in the subsequent stages of the research was also performed. The tests carried out with the use of a CO as a reducer, at a temperature of 1000 °C, allowed to obtain high levels of metallization of the samples for scale 91.6%, dust 66.9%, and sludge 97.3%. These results indicate that in the case of sludge and scale, the degree of metallization meets the requirements for charge materials used in both blast furnace (BF) and electric arc furnace (EAF) steelmaking processes, while in the case of reduced dust, this material can be used as enriched charge in the blast furnace process. Reduction studies were also carried out using a gas mixture of CO and H₂ (50 vol.% CO + 50 vol.% H₂). The introduction of hydrogen as a reducing agent in reduction processes meets the urgent need of reducing CO₂ emissions. The obtained results confirm the great importance and influence of the selection of the right amount of reducer on the achievement of a high degree of metallization and that these materials can be a valuable source of metallic charge for blast furnace and steelmaking processes. At an earlier stage of the established research program, experiments of the iron oxides reduction from iron-bearing waste materials in a stationary layer in a Tammann furnace were also conducted.

New EAF Slag Characterization Methodology for Strategic Metal Recovery

The grown demand of current and future development of new technologies for high added value and strategic metals, such as molybdenum, vanadium, and chromium, and facing to the depletion of basic primary resources of these metals, the metal extraction and recovery from industrial by-products and wastes is a promising choice. Slag from the steelmaking sector contains a significant amount of metals; therefore, it must be considered to be an abundant secondary resource for several strategic materials, especially chromium. In this work, the generated slag from electric arc furnace (EAF) provided by the French steel industry was characterized by using multitude analytical techniques in order to determine the physico-chemical characteristics of the targeted slag. The revealed main crystallized phases are larnite (Ca₂SiO₄), magnetite (Fe₃O₄), srebrodolskite (Ca₂Fe₂O₅), wüstite (FeO), maghemite (Fe_2.6O₃), hematite (Fe₂O₃), chromite [(Fe,Mg)Cr₂O₄], and quartz (SiO₂). The collected slag sample contains about 34.1% iron (48.5% Fe₂O₃) and 3.5% chromium, whilst the vanadium contents is around 1500 ppm. The Mössbauer spectroscopy suggested that the non-magnetic fraction represents 42 wt% of the slag, while the remainder (58 wt%) is composed of magnetic components. The thermal treatment of steel slag up to 900 °C indicated that this solid is almost stable and few contained phases change their structures.

A Review of the Influence of Steel Furnace Slag Type on the Properties of Cementitious Composites

The type of steel furnace slag (SFS), including electric arc furnace (EAF) slag, basic oxygen furnace (BOF) slag, ladle metallurgy furnace (LMF) slag, and argon oxygen decarburization (AOD) slag, can significantly affect the composite properties when used as an aggregate or as a supplementary cementitious material in bound applications, such as concretes, mortars, alkali-activated materials, and stabilized soils. This review seeks to collate the findings from the literature to express the variability in material properties and to attempt to explain the source(s) of the variability. It was found that SFS composition and properties can be highly variable, including different compositions on the exterior and interior of a given SFS particle, which can affect bonding conditions and be one source of variability on composite properties. A suite of tests is proposed to better assess a given SFS stock for potential use in bound applications; at a minimum, the SFS should be evaluated for free CaO content, expansion potential, mineralogical composition, cementitious composite mechanical properties, and chemical composition with secondary tests, including cementitious composite durability properties, microstructural characterization, and free MgO content.

Renewable Hydrogen Production Processes for the Off-Gas Valorization in Integrated Steelworks through Hydrogen Intensified Methane and Methanol Syntheses

Within integrated steelmaking industries significant research efforts are devoted to the efficient use of resources and the reduction of CO2 emissions. Integrated steelworks consume a considerable quantity of raw materials and produce a high amount of by-products, such as off-gases, currently used for the internal production of heat, steam or electricity. These off-gases can be further valorized as feedstock for methane and methanol syntheses, but their hydrogen content is often inadequate to reach high conversions in synthesis processes. The addition of hydrogen is fundamental and a suitable hydrogen production process must be selected to obtain advantages in process economy and sustainability. This paper presents a comparative analysis of different hydrogen production processes from renewable energy, namely polymer electrolyte membrane electrolysis, solid oxide electrolyze cell electrolysis, and biomass gasification. Aspen Plus® V11-based models were developed, and simulations were conducted for sensitivity analyses to acquire useful information related to the process behavior. Advantages and disadvantages for each considered process were highlighted. In addition, the integration of the analyzed hydrogen production methods with methane and methanol syntheses is analyzed through further Aspen Plus®-based simulations. The pros and cons of the different hydrogen production options coupled with methane and methanol syntheses included in steelmaking industries are analyzed.

OXYFINES Technique for Upgrading Zinc Containing Blast Furnace Sludge—Part 1: Pilot Trials

In the Swedish steel industry, much work is put on further increasing the recycling and use of residual materials. However, blast furnace sludge is one residual which currently, despite its valuable contents of iron and carbon, is put on landfill or long-term storage due to its zinc content. Linde has developed the OXYFINES technique which is suitable for upgrading of fine particulate and zinc containing materials. The material is fed to the OXYFINES burner whereby its zinc content is vaporised to a generated dust phase whereas other non-gasifiable contents, such as iron, forms an oxidic sinter phase in the bottom of the reactor. The technique has proven a high degree of zinc separation, is relatively flexible and straightforward, and does not require sludge pre-treatment such as drying. Pilot set-up and trials, using the OXYFINES technique, were performed at Swerim’s research facility. In the trials, the effects from altering different process parameters were tested aiming to develop an optimal concept for upgrading the blast furnace sludge. The pilot trials’ results showed the required process settings to attain a high degree of zinc separation from the sludge, and to generate an iron oxide product, suitable for straightforward charging to the steelmaking process.

OXYFINES Technique for Upgrading Zinc Containing Blast Furnace Sludge—Part 2: System Analysis

Integrating novel technology in production systems for the upgrading and further use of residual materials is a potential way of improving the resource efficiency. Assessing technology integration prospects, by performing system analysis, assists in the forecasting of effects and opportunities for different concepts. Based on pilot trials results, using Linde’s OXYFINES technique for upgrading zinc containing blast furnace sludge, a system analysis was performed on the prospects of integrating an OXYFINES concept in an iron and steel production route. The calculations were made based on one option for a full-scale OXYFINES concept for indicating the effects on the blast furnace zinc load, raw material consumption, energy use and carbon dioxide emissions from using the OXYFINES sinter product as a raw material in blast furnace ironmaking or in the basic oxygen furnace steelmaking. The summarised system analysis results showed that the most advantageous metallurgical, environmental, and economic potential was realised in the calculations of using the sinter in the basic oxygen furnace. However, the sinter was found as well suitable for use in the blast furnace when considering mainly the metallurgical and the economic effects.

Valorization of Slags Produced by Smelting of Metallurgical Dusts and Lateritic Ore Fines in Manufacturing of Slag Cements

A pyrometallurgical process was developed for the recycling of Ni bearing dusts and laterite ore fines by direct reduction smelting in DC (direct current) arc furnace. In the course of the performed industrial trials, besides the Ni-recovery in the liquid bath, slag composition was deliberately adjusted in order to produce a series of metallurgical slags with different chemical and mineralogical composition. The aim of this study was to investigate their suitability as clinker substitute in cement manufacturing. Examined parameters were slag FeOx content, basicity and applied cooling media (air, water cooling). A series of composite Portland and slag cements were manufactured in laboratory scale incorporating 20% and 40% of each slag, respectively; the rest being clinker of OPC (ordinary Portland cement) and 5% gypsum. The extended mineralogical analysis and microstructural properties of the produced slags were examined and correlated with the properties of the produced cements. The physical and mechanical characteristics of all examined cement products were found to meet the requirements of the regulation set for cements. The present research revealed that the most critical parameter in the compressive strength development of the slag cements is the mineralogical composition of the slag. Even in cases where rapid cooling to obtain glassy matrix is not feasible, adjustment of slag analysis to obtain mineralogical phases similar to those met in clinker of OPC, even at higher FeO contents (up to ~21wt.%), can result in production of slag with considerable latent hydraulic properties. These results indicate that there is potentially space for adjustments in conventional EAF (electric arc furnace) steel slags composition to allow for their wider use in cement manufacturing with significant environmental and economic benefits resulting from the reduction of energy requirements, CO2 emissions and natural raw materials consumption.