Search Results (57)

The metallurgical industry is integral to industrial development. As technology advances and industrial demand grows, the annual output of metallurgical waste slag continues to rise. Combined with the substantial historical stockpile, this has made the utilization of metallurgical slag a new research focus. This study comprehensively sums up the composition and fundamental characteristics of metallurgical waste slag. It delves into the application potential of non-ferrous metal smelting waste slag, such as copper slag, nickel slag, and lead slag, in both sensible and latent heat storage. In sensible heat storage, copper slag, with its low cost and high thermal stability, is suitable as a storage material. After appropriate treatment, it can be combined with other materials to produce composite phase change energy storage materials, thus expanding its role into latent heat storage. Nickel slag, currently mainly used in infrastructure materials, still needs in-depth research to confirm its suitability for sensible heat storage. Nevertheless, in latent heat storage, it has been utilized in making the support framework of composite phase change materials. While there are no current examples of lead slag being used in sensible heat storage, the low leaching concentration of lead and zinc in lead slag concrete under alkaline conditions offers new utilization ideas. Given the strong nucleation effect of iron and impurities in lead slag, it is expected to be used in the skeleton preparation of composite phase change materials. Besides the aforementioned waste slags, other industrial waste slags also show potential as sensible heat storage materials. This paper aims to evaluate the feasibility of non-ferrous metal waste slag as energy storage materials. It analyses the pros and cons of their practical applications, elaborates on relevant research progress, technical hurdles, and future directions, all with the goal of enhancing their effective use in heat storage. Full article

As a legacy of historical metal mining and the processing and smelting of metalliferous ores, metal pollution is a serious environmental problem in many areas around the globe. This review summarizes the history, technical development and environmental hazards of historic metal mining and metallurgical activities in the Harz Region (Germany), one of the oldest and most productive mining landscapes in Central Europe. The release of large amounts of metal-containing waste into rivers during historic ore processing and the ongoing leaching of metals from slag heaps, tailings dumps and contaminated soils and sediments are the main sources of metal pollution in the Harz Mountains and its foreland. This pollution extends along river systems with tributaries from the Harz Mountains and can even be detected in mudflats of the North Sea. In addition to fluvial discharges, atmospheric pollution by smelter smoke has led to long-term damage to soils and vegetation in the Harz Region. Currently, the ecological hazards caused by the legacy pollution from historical metal mining and metallurgy in the Harz Region are only partially known, particularly regarding the effects of changes in river ecosystems as a consequence of climate change. This review discusses the complexity and dynamics of human–environment interactions in the Harz Mountains and its surroundings, with a focus on lead (Pb) pollution. The paper also identifies future research directions with respect to metal contamination. Full article

Heavy metals in lead refining waste slag pose persistent environmental risks, challenging conventional treatment methods that struggle to balance long-term stabilization with resource recovery potential. To address this issue, we developed a sustainable stabilization strategy. The simultaneous and long-lasting stabilization of Zn, Pb, and As heavy metals in lead refining waste slag was achieved by using an Fe-S(II) stabilizer, and the leaching toxicity of Zn, As and Pb was less than 1 mg/L, which is lower than the concentration limit of the Identification standards for hazardous wastes–Identification for extraction toxicity (GB5085.3-2007). The samples were analyzed by characterization before and after stabilization, and it was found that Fe-S(II) formed a protective layer of sulfide capsule on the surface of the samples. This stabilization mechanism, which has been termed the “nucleation-capture-sulfide encapsulation” process, involves after the oxidation of Fe⁰ to form a core–shell structure for trapping metal ions, where the external oxide layer undergoes mineralization via S(II) sulfide reduction. This microencapsulation-based passivation not only ensures long-term heavy metal immobilization but also preserves the slag’s potential for secondary resource recovery, aligning with circular economy principles. By minimizing environmental leakage risks while retaining metal reclamation feasibility, this approach offers a green and sustainable solution for heavy-metal-laden industrial waste management. Full article

Amid escalating global climate crises and the urgent imperative to meet the Paris Agreement’s carbon neutrality targets, the steel industry—a leading contributor to global greenhouse gas emissions—confronts unprecedented challenges in driving sustainable industrial transformation through innovative low-carbon steelmaking technologies. This paper examines decarbonization technologies across three stages (source, process, and end-of-pipe) for two dominant steel production routes: the long process (BF-BOF) and the short process (EAF). For the BF-BOF route, carbon reduction at the source stage is achieved through high-proportion pellet charging in the blast furnace and high scrap ratio utilization; at the process stage, carbon control is optimized via bottom-blowing O₂-CO₂-CaO composite injection in the converter; and at the end-of-pipe stage, CO₂ recycling and carbon capture are employed to achieve deep decarbonization. In contrast, the EAF route establishes a low-carbon production system by relying on green and efficient electric arc furnaces and hydrogen-based shaft furnaces. At the source stage, energy consumption is reduced through the use of green electricity and advanced equipment; during the process stage, precision smelting is realized through intelligent control systems; and at the end-of-pipe stage, a closed-loop is achieved by combining cascade waste heat recovery and steel slag resource utilization. Across both process routes, hydrogen-based direct reduction and green power-driven EAF technology demonstrate significant emission reduction potential, providing key technical support for the low-carbon transformation of the steel industry. Comparative analysis of industrial applications reveals varying emission reduction efficiencies, economic viability, and implementation challenges across different technical pathways. The study concludes that deep decarbonization of the steel industry requires coordinated policy incentives, technological innovation, and industrial chain collaboration. Accelerating large-scale adoption of low-carbon metallurgical technologies through these synergistic efforts will drive the global steel sector toward sustainable development goals. This study provides a systematic evaluation of current low-carbon steelmaking technologies and outlines practical implementation strategies, contributing to the industry’s decarbonization efforts. Full article

Variations in slag properties critically influence smelting operations and product quality. The effects of K₂O on the CaO-SiO₂-MgO-Al₂O₃-K₂O slag system at 1823 K were systematically analyzed through an integrated approach combining viscosity measurements, FTIR spectroscopy, and molecular dynamics simulations. The results revealed a rapid 52% decrease in slag viscosity and an 18.32 kJ/mol reduction in activation energy as K₂O content increased from 0% to 3%. K₂O releases O²⁻ ions that depolymerize Si-O network structures. Within the 3% to 5% range, structural network formation is promoted by the K₂O-SiO₂ reaction, resulting in increased slag viscosity and elevated activation energy. Molecular dynamics simulations elucidate the depolymerization of complex Si-O networks, accompanied by a proliferation of smaller [AlO₄] tetrahedral fragments. The diminished Si-O-Si bridging oxygen (BO) bonds contrast with the enhanced increase in Si-O-K non-bridging oxygen (NBO) linkages. When K₂O exceeds 3%, the diffusion capacity of K atoms becomes constrained as K₂O participates in structural network assembly, a phenomenon validated by FTIR spectroscopic analysis. Elevated K₂O concentrations enhance slag network polymerization, leading to increased viscosity. Therefore, the precise control of K₂O content is critical during smelting operations and by-product manufacturing (e.g., glass or mineral wool) to optimize material performance. These findings provide theoretical support for controlling the alkali metal content during the actual metallurgical process and thus further optimizing blast furnace operation. Full article

The historical industrial waste deposit Gater was used to dispose of different metallurgy wastes from lead and zinc production. The metallurgical waste deposit was situated in the open space, between the tailing waste deposit Žitkovac and river Ibar flow. Large amounts of lead-containing wastes are produced in the non-ferrous metallurgical industry, such as lead ash and lead slag generated in Pb smelting, lead anode slime, and lead sludge produced in the raw lead refining process. In addition to the lead concentration, numerous valuable components are found in the lead refinery waste from the group of Critical Raw Materials, such as antimony, arsenic, bismuth, copper, nickel, magnesium, scandium, as well as Rare-Earth Elements. Samples with eight characteristic points were taken to obtain relevant data indicating a possible recycling method. The chemical composition analysis was conducted using ICP; the scanning was completed using SEM-EDS. The mineralogical composition was determined by using XRD. The chemical analysis showed a wide range of valuable metal concentrations, from Ag (in the range from 14.2 to 214.6, with an average 86.25 mg/kg) to heavy metals such as Cu (in the range from 282.7 to 28,298, with an average 10,683.7 mg/kg or 1.0683% that corresponds to some active mines), Ni and Zn (in the range from 1.259 to 69,853.4, with an average 14,304.81 mg/kg), Sc (in the range from 2.4 to 75.3, with an average 33.61 mg/kg), Pb (in the range from 862.6 to 154,027.5, with an average 45,046 mg/kg), Sb (in the range from 51.7 to 18,514.7, with an average 2267.8 mg/kg), Ca (in the range from 167.5 to 63,963, with an average 19,880 mg/kg), Mg (in the range from 668.3 to 76,824.5, with an average 31,670 mg/kg), and As (in the range from 62.9 to 24,328.1, with an average 5829.53 mg/kg). The mineralogy analysis shows that all metals are in the form of oxides, but in the case of As and Fe, SEM-EDS shows some portion of elemental lead, pyrite, and silica-magnesium-calcium oxides as slag and tailing waste residues. The proposed recovery process should start with leaching, and further investigation should decide on the type of leaching procedure and agents, considering the waste’s heterogeneous nature and acidity and toxicity. Full article

On the basis of the theory of polyphase equilibrium and the utilization of the MetCal software platform (MetCal v7.81), we adopted the chemical equilibrium constant method and successfully constructed a multiphase equilibrium model and simulation system for the antimony–lead synergistic side-blown oxidation smelting process. In typical production conditions, which encompass factors such as the composition of raw material, the ratio of oxygen to material, and oxygen-enriched concentration, the equilibrium product composition and pivotal technical indices are modeled and computed. Calculation results indicated that, other than the trace elements in the smelting slag, the relative errors of the calculated values for the content of major elements in the antimony-rich crude lead and smelting slag were less than 10% of the measured value after average treatment in production. Therefore, our results showed that the developed model and system preferably embodied the practical production condition of the antimony–lead synergistic side-blown oxidation smelting process, which is capable of precisely forecasting the smelting outcomes and optimizing the process parameters, thereby offering effective guidance for the practical execution of the antimony–lead synergistic side-blown oxidation smelting process. Full article

This study explored the behavior of lead, copper, and iron during the leaching process of flash smelting slag from direct-to-blister copper flash smelting using l-ascorbic acid solutions. Flash smelting slag is generated in considerable quantities by various copper smelters worldwide. One drawback of the single-stage flash smelting technology for copper concentrates is the production of large quantities of metal-rich by-products. However, through appropriate management of postprocess waste, valuable components such as copper or lead can be recovered. In practice, the slag is typically subjected to decoppering processes involving electric and converter furnaces. The hydrometallurgical process proposed in this study is aimed at replacing high-temperature recovery methods. The primary objective of the experiments was to investigate the effects of variations in specific leaching parameters and the addition of auxiliary substances on the leaching efficiency of lead, copper, and iron. Four parameters were adjusted during the tests: concentration of l-ascorbic acid, liquid-to-solid phase ratio, temperature, and time. An oxidizing agent in the form of perhydrol and citric acid with an oxidant were used as additives. Optimal process conditions were determined to achieve maximum lead leaching efficiency while maintaining relatively low leaching of copper and iron. The experiments indicated that leaching in ascorbic acid solutions resulted in lead extraction efficiencies ranging from approximately 68% to more than 88%, depending on the conditions. Conversely, relatively low leaching efficiencies of iron (4–12%) and copper (0–29%) were observed. Full article

Slags from the Silesia–Cracow Upland (Poland), including ten historical slags (deposited in waste dumps) and four contemporary slags (from current production), were examined to compare their chemical and mineralogical properties as well as to assess their potential for the recovery of selected metals and critical raw materials. The historical slags associated with the smelting of polymetallic ores originating from Mississippi Valley-type (MVT) deposits consisted primarily of gypsum. The contemporary slags, obtained from industrial waste rich in zinc and lead, were predominantly spinels (magnesium-aluminate and ferric) that exhibited higher iron content (up to 46.6 wt% of Fe₂O₃) compared to the historical slags (up to 26.1 wt% of Fe₂O₃). The zinc content was similar for both the slag types (3.5 wt% Zn). The average titanium and arsenic contents in the old and contemporary slags were at the same level as well, with 0.21 wt% (Ti) and 0.13 wt% (As), respectively. The contemporary slags contained higher levels of critical raw materials, such as cobalt, nickel, copper, and manganese, compared to the historical slags. Rare earth elements (REEs) were also more abundant in the contemporary slags, with an average content of 212 ppm, while the historical slags averaged 124 ppm. These findings underscore the potential for recovering valuable metals and critical raw materials from such slags, presenting opportunities for resource optimisation and environmental management. Full article

Computational fluid dynamics (CFD) software was used to simulate the feeding behavior in a bottom-blown lead-smelting furnace. The results show that when the particle size is less than 30 μm, 20% of the particles are suspended in the gas phase and do not enter the melt pool for smelting, thus resulting in material loss. When the particle size exceeds 75 μm, the particles settle in the metal layer. When the particle size is 40–60 μm, the particles are distributed in the slag and metal phases, and the material is uniformly distributed in the molten pool; additionally, the average velocity of the particles exceeds 1.4 m/s, the average temperature exceeds 960 K, and the particles exhibit better behavior within this range, thus rendering it the optimal range of particle sizes for feeding. Full article

The study object was slag from the Balkhash copper smelter, obtained by re-melting anode mud containing nonferrous metals. The process flow for processing these slags includes sintering with Na₂SO₄, Na₂CO₃, and coal, followed by soda-alkaline leaching of the sinter and extraction of metals from the solution into marketable products. Since sintering is the main operation providing high selectivity, the composition of the products of this process was studied. The main transformations during sintering were determined, and the optimal parameters were identified. The structures of slags and sintered materials obtained during the experiments were studied by electron-probe microanalysis. Sintering was performed at 600–800 °C. The best results for sulphidization of slag components were obtained at 800 °C; a further increase in temperature leads to the smelting of sinter particles and slows down sulphidization. The optimal quantities of additives, based on the weight of the slag, are Na₂SO₄—45%, Na₂CO₃—15%, and reducing agent—41%, with a sintering time of 2 h. These conditions enable the sulphidization of non-ferrous metals in the slag to the entire depth of the polymetallic globules. The distinct concentration of harmful impurities (Ni, As, and Sb) was observed in the fine structure of the polymetallic globules. Full article

The purpose of this work is to obtain the optimum conditions for leaching the zinc contained in an industrial lead smelting slag. In this type of slag, zinc oxide, sulfide, and ferrite are contained. Zinc extraction from these compounds consists of using a single aqueous medium, where oxidant alkaline leaching with NaOH and NaClO was used. The parameters evaluated during the experiment were as follows: percentage of solids, NaOH/NaClO ratio, and temperature. The maximum amount of recovered Zn obtained during the leaching was 58%. This percentage was achieved by using the following optimal conditions: temperature of 60 °C, 0.22 of NaOH/NaClO ratio, 10% of solids, and a reaction time of 40 min. The calculated values of activation energy confirmed that the rate-limiting step of the reaction using the decreasing particle model is diffusion. The maximum percentage of zinc obtained could only have been achieved if the zinc oxide and part of the zinc sulfide (both present in almost equal proportions in the sample) were leached into the alkaline aqueous medium in the presence of NaClO. Full article

Ferronickel slag is the solid waste slag produced by smelting nickel–iron alloy. After grinding ferronickel slag into powder, it has potential chemical activity. It can partially replace cement and reduce the amount of cement, and is conducive to environmental protection. The mechanical properties of soil cement were investigated through the compressive strength test and inter-split tensile test of ferronickel slag powder soil cement with different dosages. To further study the mechanism of ferronickel slag powder’s action on soil cement microscopically, the microstructure of soil cement was analyzed by using a scanning electron microscope and nuclear magnetic resonance equipment. The results of the study show that the incorporation of ferronickel slag powder can enhance the compressive and tensile strength of soil cement. The best performance enhancement of ferronickel slag powder was achieved when it was doped with 45% of its mass. The hydration products of soil cement increased with the increase in the doping amount, but the excessive doping of ferronickel slag powder would lead to a weakening of the hydration reaction and a decrease in the strength of the soil cement. At the same time, ferronickel slag powder plays the role of filling the void of soil cement. With the increase in ferronickel slag powder, the large pores inside the soil cement are reduced and the structure is denser. Full article

According to physical property tests of lead-containing slag, the volatilisation behaviour of lead slag will have adverse impacts on test accuracy and further affect the control of chemical reactions, solidification and removal of inclusions during smelting. To analyse the volatilisation characteristics of lead slag, in this paper, four kinds of lead slags from lead direct reduction smelting with different PbO and ZnO content are taken. thermogravimetry, ISP-TOF were used. Additionally, the changes in volatiles and slag composition and phases were analysed with XRD and ICPS, and the volatilisation reaction mechanism was discussed. The results indicated that the volatilisation of lead slag can lead to a big weight loss of about to the slag with higher PbO content. The weight loss increases with the PbO content in slag increases. The volatile corresponding to the weight loss above 900 °C is mainly PbO and less ZnO. The higher the temperature is, the stronger the volatilisation is. With the increase in temperature and keeping time, most of the PbO can be evaporated and leaves little PbO in the residual slag. This will has great effect to physico-chemical property measurement of the slag with higher PbO content, especially to the property measurement that be kept at high temperature for a long time. Because the volatiles is trend to condense with the temperature decrease, mass spectrometer is limited by the condensation of volatiles, i.e., PbO, ZnO and so on, in the connection pipeline. The device should be modified for this use. Full article

In response to the development of low-carbon smelting technology, reducing the use of fluor-containing materials in desulfurizers is an important research topic. The development of new-generation KR (Kambara Reactor) desulfurizers is shifting towards a higher Al₂O₃ content rather than CaF₂, yet there is currently an absence of thorough and comprehensive mechanisms for desulfurization. Consequently, this research provides an extensive comparison using a specially constructed small-scale KR desulfurization hot model test, alongside FactSage simulation and SEM analysis (of desulfurization process). The findings indicate that at 1400 °C, for the desulfurization of molten iron, the capacity for desulfurization initially increases and then diminishes as the Al₂O₃ content in the KR desulfurizer rises. With Al₂O₃ content in the desulfurizer below 22 wt.%, the phase composition predominantly consists of C₃A, employing a solid_(slag)–liquid_(metal) diffusion method for desulfurization. The optimal desulfurization capacity (Ls: 64.1) is observed when the Al₂O₃ content is 15 wt.%, attributed to the simultaneous presence of CaO particle precipitation and C₃A. However, as the Al₂O₃ content reaches 20 wt.%, all the oversaturated CaO integrates into C₃A, leading to a reduction in Ls from 64.1 to 10.7, thereby diminishing the desulfurization capacity by approximately sixfold. When Al₂O₃ exceeds 22 wt.%, the phase composition transitions from the C₃A to C₁₂A₇ phase, and the desulfurization approach shifts from solid_(slag)–liquid_(metal) to liquid_(slag)–liquid_(metal) diffusion, with Ls decreasing to 23.4. This reduction is due to C₁₂A₇’s lower sulfur capacity compared to C₃A and the absence of saturated CaO particle precipitation. Therefore, for Al₂O₃ to effectively replace fluorite in KR desulfurizers, a higher presence of C₃A phases and CaO particle precipitation are essential. The desulfurizer must contain over 65 wt.% CaO and maintain A_l2O₃ levels at 10~16.2 wt.%. Full article