Smelting Slag Research Articles

Model development and probabilistic risks of cadmium transport in slag-soil-groundwater systems with heterogeneous conditions

Prediction of the long-term risk of trace metals leaching from soils at smelting sites is essential for groundwater protection. Herein, a mass balance-based stochastic model was developed to simulate the transport and probabilistic risks of trace metals in heterogeneous slag-soil-groundwater systems. The model was applied to a smelting slag yard with three stacking scenarios, including (A) fixed stacking amount, (B) stacking amount increasing yearly, and (C) slag removal after 20 years. The simulations suggested that the leaching flux and net accumulation of Cd in soils of the slag yard and abandoned farmland were greatest for scenario (B), which was followed by scenarios (A) and (C). In the slag yard, a plateau occurred in the Cd leaching flux curves, followed by a sharp increase. After 100 years of leaching, only scenario (B) had a high probabilistic risk (>99.9 %) of threatening groundwater safety under heterogeneous conditions. <11.1 % of the exogenous Cd may leach into groundwater under the worst scenario. The key parameters affecting Cd leaching risk include runoff interception rate (IRCR), input flux from slag release (I), and stacking time (ST). The simulation results were consistent with the values measured in a field investigation and laboratory leaching experiments. The results should help guide remediation objectives and measures to minimize the leaching risk at smelting sites.

Material composition and microstructure of ceramic glass й hearth of blast furnace No. 6 of JSC EVRAZ NTMK after service. Refractory microstructure after service

The results of a comprehensive study of the material microstructure of refractory samples after service in the furnace of a blast furnace with a useful volume of 2200 m3 for 14 years are presented. Structural and genetic analysis established a characteristic sequence of processes of degeneration and wear of the ceramic furnace stack, including 6 stages: the formation of micro-and macro-cracks; condensation of vaporous zinc; zinc oxidation with the formation of fire-resistant ZnO zincite and the deposition of carbon black by the; chemical interaction of zinkite with mullite and corundum to form ZnAl2O4 ganite and 2ZnO·SiO2 willemite; partial oxidation of silicon carbide with the release of silica glass SiO2, eutectic melt of complex composition, and wellimite. Due to intensive accumulation of capillary pores, infiltration of the slag melt in the volume of refractories does not occur. Wear of refractories in the furnace has a complex, mainly thermochemical mechanism and a low speed due to the formation of a garnish containing refractory compounds. Ill. 5. Ref. 14.

Novel metallic Fe recovery from copper smelting slag by the deep reduction method with renewable biochar reducing agent: Phase transformation process and Fe particle growth optimization

The land stockpiling of copper smelting slag causes serious environmental pollution and resource waste. It contains a large amount of Fe, which is difficult to recover by traditional methods. In this paper, a novel metallic Fe recovery method was presented by deep reduction with renewable biochar as a reducing agent. It not only recovers metallic Fe but also relieves the pressure of iron ore with a sustainable and eco-friendly method. It was found that the metallization ratio variation trend was explored by the temperature, time, CaO content and C/O molar ratio increasing. When biochar was used as a reducing agent, the metallization ratios of Fe under different reduction conditions were better than the traditional reducing agent coal, which indicated that biochar could replace coal as a reducing agent. The phase transition and microstructure change during the deep reduction process were analyzed by XRD, XPS and SEM-EDS. The metallic Fe particles were formed from the copper smelting slag particle outside and spread to the inside gradually, distinguishing the slag phase and metal phase eventually. The growth kinetic equations of the two stages were obtained after calculation and simulation. There's a certain amount of truth to the predicted value because R2 is 0.9745 with experimental measurements. This study demonstrates that the deep reduction is a green and effective technology for copper smelting slag utilization.

Immobilization of chromium ore processing residue by alkali-activated composite binders and leaching characteristics.

Chromium ore processing residue (COPR) is classified as hazardous solid waste because of the leachable Cr(VI). Cementitious materials are often used to solidify and stabilize heavy metals. However, most of them focus on the leaching concentration of particles after solidification and stabilization and lack research on leaching characteristics. This study investigated the leaching characteristics of heavy metals in three simulated environments (HJ557-2010, HJ/T299-2007, TCLP) after immobilizing COPR with composite binders. Industrial solid waste coal fly ash and lead-zinc smelting slag are used to prepare composite binders through alkali activation technology. Compressive strength, particle leaching toxicity, acid neutralization capability, and semi-dynamic leaching test are used to evaluate the performance of the solidified body. The solidified body can be applied to building materials or treated as general industrial waste. Heavy metals are mainly released from the matrix by surface washing at a low rate. The analysis results, including XRD, FTIR, and SEM-EDS, show that chemical binding and physical encapsulation are the main immobilizing mechanisms to realize the coordinated disposal of Zn and Cr(VI).

Drying shrinkage of waste-based concrete reinforced with pristine graphene (PRG) nanomaterial

Drying shrinkage because of moisture loss is one of the main concerns in construction, as it can result in the creation of early cracking in concrete. This study presents the results of an experimental study on the use of pristine graphene (PRG) nanomaterial to improve drying shrinkage properties of waste-based concrete. In this study, the conventional materials of concrete are completely replaced with waste-based materials and industrial by-products including: 20 % fly ash and 80 % ground granulated blast furnace slag as binder, 100% recycled concrete aggregate as coarse aggregate, and 100% lead smelter slag as fine aggregate. Four different mixes were prepared with PRG contents of 0% (control mix), 0.05%. 0.1%, and 0.3% by the weight of binders. Drying shrinkage test (up to 28 days of curing) and scanning electron micrography (SEM) were carried out on the concrete specimens to examine the influence of the PRG concentration on the drying shrinkage properties of the concretes. The results show that increasing the PRG dosage decreases the drying shrinkage of the concrete to a minimum value which is achieved by 0.1% PRG dosage. However, it is found that beyond the 0.1% dosage the drying shrinkage increases. According to SEM analysis, this increased shrinkage is because of the agglomeration of the PRG nanomaterials at higher concentrations.

Valorization of the Zellidja Lead Smelter Slag (Eastern Morocco) in Road Building

Valorization of the Zellidja Lead Smelter Slag (Eastern Morocco) in Road Building

Performance calculation of slag from vanadium titano-magnetite by full oxygen bath smelting process

Vanadium titano-magnetite is an important iron ore resource containing iron, vanadium and titanium. Although iron and vanadium can be recovered by the traditional blast furnace process, titanium can only be stored in the form of TiO2 bearing slag, which resulting in a great waste of titanium resources. In the full oxygen bath smelting process, thanks to high oxygen potential, low nitrogen content and no coke bed in the furnace, the reduction of TiO2 in the slag. This may lead to slag viscosity, inhibit the smelting of vanado-titano-magnetite, and obtain a slag with high TiO2 content. Based on slag coexistence theory, a multi system coexistence theoretical model of vanadium titano-magnetite smelting slag is established, and the influence of slag basicity on the concentration of slag components and the ratio of sulfur between slag and iron is calculated. The results show that with the increase of slag basicity, the interaction concentration of TiO2 in slag decreases gradually, which makes the reduction of TiO2 more difficult and is conducive to the smelting of vanadium–titanomagnetite. Under the optimum alkalinity and reduction temperature (R=1.1, melting temperature is 1500 °C), the distribution ratio of S element between slag and iron is 6.57, and the theoretical S concentration in molten iron is 0.073%. The molten iron can meet the steel-making requirements after pretreatment and desulfurization.

Relation between Viscosity and Conductivity of CaO-MgO-FeO-Al2O3-SiO2 System for Copper Smelting Slags

The viscosity and conductivity of the smelting slag of copper oxide concentrate are important for reducing the operating temperature. In this study, seven slag samples were prepared by the reductive smelting of copper oxide concentrate with different ferrous oxide contents. The viscosity and conductivity data of these CaO-MgO-FeO-Al2O3-SiO2 samples were measured in the temperature range of 1290~1410 °C. Based on the structural features of aluminosilicate melts, the change and dependency relationships of their viscosity and conductivity were analyzed. The results show that there is a strong tendency to form orthosilicate even when the slag composition is acidic. The formation of fayalite would allow more Al3+ to form pyroxene with the six-coordinated structure. As a result, the polymerization degree and viscosity of the melt will be reduced. The [AlO]45− as a network former will reduce the bonding strength of the structural units, thus reducing the slag viscosity at high temperature. In the experimental range, the logarithm of viscosity of each slag sample has a good linear relationship with its logarithm of conductivity. However, there is no uniform linear equation for these complex slags with wide composition variations. These results have potential guiding significance for the copper smelting process.

Computational Modelling on Gasification Processes of Municipal Solid Wastes Including Molten Slag

The formulation of the CFD-DEM model, CD-MELT, is established in this study to include three-phase non-isothermal processes with simultaneous combustion and melting for gasification simulations. To demonstrate the model capability, CD-MELT is used to assess the need for slag recycling for the non-isothermal melting of municipal solid wastes (MSW) in a prototype waste-to-energy research facility. The simulation encompasses the full fixed-bed slagging gasification process, including chemical reactions and melting of MSW and slag. In order to assess the need for slag recycling, comparisons are made for the two cases of with and without, in terms of the slag mass, liquid slag volume fraction, exit gas composition, and temperature distribution in the gasifier. The prediction results enable the tracking of liquid molten slag as it permeates through the solids-packed bed for the first time in the literature as far as we are aware, which is crucial to address design considerations such as distribution of bed temperature and optimal location for slag-tap holes at the bottom, as well as potential slag clogging within the porous media. The model also predicts an uneven and intermittent slag permeation through the packed bed without the recycling, and provides a plausible explanation for the operators’ experience of why slag recycling is important for process stability. Finally, the predicted slag outlet temperature using the proposed CFD approach also agrees well with the measurement data published in an earlier case study for the same facility.

Effective recovery of rare earth and fluorine from REF3 smelting slag by a mechanochemical process

The rare earth fluoride (REF3) solid wastes (such as REF3 smelting slag, rare earth molten salt electrolytic slag, and cerium fluorocarbon tailings, etc.) are widely sourced and have high recycling value. Traditional technology for the recovering of rare earths from REF3 solid wastes mainly includes the method of concentrated sulfuric acid roasting, high-temperature concentrated alkali boiling, and alkali roasting, but sulfuric acid roasting will produce harmful gases containing fluorine and sulfur, which seriously pollute the environment; high temperature concentrated alkali boiling and alkali roasting method also has the disadvantages of large consumption of chemicals and heavy burden of wastewater treatment. In this work, a mechanochemical process was introduced to treat the REF3 smelting slag (RSS) produced by calcium-thermal reduction of REF3, and then the product was leached directly by dilute acid. The results showed that REF3 can be completely converted to rare earth hydrate (RE(OH)3) by the mechanochemical process, and the REEs in the product can be leached efficiently by HCl at room temperature. In particular, the properties of the mechanochemical process and the acid-leaching process were studied. Under the optimal operation conditions (sodium hydroxide/RSS mass ratio was 0.4:1, milling speed was 400 rpm, milling time was 40 min), the transformation rate of REF3 was above 96%. The residue consisted of RE(OH)3 and CaF2 were obtained by leaching the product with water. The NaF crystal by-product was obtained by evaporation crystallization of filtrate. The REEs leaching rate was above 96% by acid-leaching the residue under the optimal acid-leaching process (2 mol/L hydrochloric acid, liquid–solid ratio was 5:1, acid-leaching time was 20 min, stirring speed was 600 rpm), and the by-product of CaF2 was obtained after filtration. The whole process was carried out at room temperature, in a short time, with zero-emission, and recyclable water, which is in line with the concept of green, clean, and environment-friendly, and is expected to be a new technology with good prospects for industrial application.

Preparation of new copper smelting slag-based mine backfill material and investigation of its mechanical properties

The stockpiling of copper smelting slag (CSS) has broken the ecological environment of the mining area, and the resource utilization of CSS is an urgent requirement to promote ecological sustainable development. The optimal cementitious material ratio determines as 69:15:6:2:8 for CSS: cement clinker (CC): gypsum powder (GP):NaOH: slaked lime (SL) by analyzing the physical and chemical properties of CSS and the uniaxial compressive strengths (UCS) at 3d, 7d and 28d curing ages investigate. The uniaxial compressive strengths reached 3.55 MPa, 9.48 MPa, and 32.43 MPa. In the meantime, XRF, XRD, EDS, and SEM microscopic analysis of the prepared gelling material specimens explored the hydration products and microstructural changes of the backfill gelling system and revealed the hydration mechanism of the gelling system and the strength formation mechanism of the specimens. The results of the experimental study showed that the strength of the specimens at different maintenance ages was subject to different significance arrangements of the factors. Based on the optimized ratio of composite cementitious materials, the 28d UCS of the filler prepared by synergistic tailing sand reaches 3.88 MPa, which can meet the jksg of partial mine filler mining. Applying copper smelting slag-based gelling backfill materials (CSSM) at mine sites reduces backfill costs while effectively reducing solid waste emissions, thereby protecting the environment and promoting the realization of waste-free mines and green mining.

Thermodynamic Calculations of Direct Reduction Smelting Technology of Copper Oxide Ores Based on Smelting Slag from the Yubeidi Site, Yunnan Province

The current research on metallurgical remains from scientific excavations in northeast Yunnan from the Bronze Age period is insufficient. In order to study the smelting technology of the Bronze Age in north-eastern Yunnan, samples of slag and mineral excavated from the Yubei Di site in Dongchuan were examined. Based on the outcome of the characterization analysis, a simulation was executed utilizing the software Factsage 7.1 in order to generate a phase diagram that accurately portrays the melting procedure. This simulation aimed to produce the most credible representation of the phase transition by employing computational methods. Characterisation methods included Metallographic Microscopy, Scanning Electron Microscopy Energy Dispersive Spectromicropy (SEM-EDS), X-ray diffraction (XRD), and Radiocarbon Date (14C dating). The results showed that there was much copper ore left in the slag of the site. Most of these copper ores were in the form of copper ferrite or cuprous oxide. The copper ore was copper oxide ore, and metal copper particles appeared in a small amount of the slag. Most of the slags unearthed from the site of the Yubeidi site were products of sulfur-containing oxide reduction and smelting into copper. Based on the outcomes of the simulations, it was established that the slag excavated from the Yubeidi site was mainly from the reduction and smelting process of sulphur-containing copper oxide minerals into copper, without consciously adding fluxes, not having mastered the slag-making techniques for different types of copper ores, and with primitive techniques. The carbon 14 dating results show that the age of the slag was during the Spring and Autumn Period and the Warring States Period.

Effect of injection of different gases on removal of arsenic in form of dust from molten copper smelting slag prior to recovery process

In order to reduce the environmental risks caused by arsenic in copper smelting slag, a method of dearsenisation from molten slag based on gas injection was proposed. It was expected to enrich arsenic in the form of dust prior to copper recovery process. The effects of inert, oxidising, and reducing gas on the removal of arsenic from molten slag were compared. When CO2 was injected, the removal of arsenic was mainly attributed to the oxidation of Cu—As inclusions and arsenic sulphide in the slag. Based on the injection of CO, the removal rate of arsenic reached more than 60%. Based on the injection of reducing gas, arsenic oxide in the FeOx—SiO2 slag was reduced and volatilised into the gas phase, resulting in the removal of arsenic. This study provides a reference with respect to the establishment of strategies for the mitigation of arsenic pollution caused by smelting slag.

Vertical distribution of nutrients, enzyme activities, microbial properties, and heavy metals in zinc smelting slag site revegetated with two herb species: Implications for direct revegetation

Direct revegetation is an important measure to immobilize heavy metals and improve the microecological properties of metal smelting slag sites. However, the vertical distribution of nutrients, microecological properties, and heavy metals at a directly revegetated metal smelting slag site remains unclear. Here, the distribution characteristics of nutrients, enzyme activities, microbial properties, and heavy metals in the vertical profile at a zinc smelting slag site directly revegetated with two herb species (Lolium perenne and Trifolium repens) for 5 years were investigated. The results showed that the nutrient contents, enzyme activities, and microbial properties decreased with increasing slag depth after revegetation with the two herb species. The nutrient contents, enzyme activities, and microbial properties of the surface slag revegetated with Trifolium repens were better than those in the surface slag revegetated with Lolium perenne. The higher root activity in the surface slag (0–30 cm) resulted in relatively higher contents of pseudo-total and available heavy metals in the surface slag. Moreover, the contents of pseudo-total heavy metals (except for Zn) and available heavy metals in the slag revegetated with Trifolium repens were lower than those in the slag revegetated with Lolium perenne at most slag depths. Overall, the greater phytoremediation efficiency of the two herb species occurred mainly in the surface slag (0–30 cm), and the phytoremediation efficiency of Trifolium repens was higher than that of Lolium perenne. The findings are beneficial for understanding the phytoremediation efficiency of direct revegetation strategies for metal smelting slag sites.

Adsorption of Volatile Organic Compounds via Cellular Material Produced from Aluminum Dross

In this study, the aluminum dross collected in the production process of the aluminum smelting industry was used as the raw material for mixing with an alkaline solution to make aluminum hydroxide where aluminum was extracted by a titration procedure. When the pH value of the solution is 10~13, the crystal forms of the precipitation products are monoclinic and hexagonal, and the particle size is about 0.25~4 μm. To develop and establish a circular economy in the aluminum industry for aluminum smelting slag where aluminum hydroxide and alumina are environmentally friendly adsorption materials can help to solve environmental problems caused by waste, increase the life cycle of resources. Cellular material produced from aluminum dross are used to carry out the adsorption characteristics test of volatile organic compounds, and the average adsorption amounts for acetone and toluene were 1.20 and 1.87 μg/g, respectively. This cornerstone results had demonstrated the design and development of the expansion of resource-based adsorption materials can meet the needs of various industries.

In-Situ Observation of Steel/Slag/Inclusion Interaction by Means of High-Temperature Confocal Scanning Laser Microscopy

Non-metallic inclusions (NMIs) in steels have been the focus of various experimental studies due to their detrimental character. While isolated processes, such as agglomeration or dissolution, have been well investigated, holistic in-situ views with high-temperature confocal scanning laser microscopy (HT-CSLM) have been rare. In this work a novel and suitable method is presented to simultaneously observe agglomeration, movement, detachment, and dissolution of non-metallic inclusions by combined the melting of steel and slag with a dual-crucible approach. Therefore, different steel/slag combinations were tested. It is shown that, with transparent that does not become tarnished by the ions stemming from the steel, the steel’s surface and non-metallic inclusions are observable. Furthermore, technological limitations are discussed, including restrictions regarding the melting point of steels and certain steel/slag combinations.

Material Recycling for Manufacturing Aggregates Using Melting Slag of Automobile Shredder Residues

The quantity of waste from end-of-life vehicles is increasing with an increase in the number of scrapped internal combustion engine vehicles owing to international trends such as carbon neutrality and particulate matter reduction. The recycling rate must be ≥95%; however, the average recycling rate remains at approximately 89%. Therefore, the improvement of the recycling of automobile shredder residues (ASR) is gaining attention. In this study, four types of products (interlocking, clay, and lightweight swelled ceramic (LSC) bricks, and asphalt paving aggregate (APA)) were manufactured using ASR melting slag (ASRMS). Environmental performance, quality standards, and technology were evaluated to assess the recyclability of the manufactured bricks. The interlocking brick substituted melting slag for sand and stone powder as an aggregate. As melting slag content increased, absorption decreased and bending strength increased. Clay brick was manufactured by replacing kaolin and feldspar with melting slag that substituted for 20%. The quality of clay bricks mixed with over 15% melting slag was not better than standard. Asphalt paving aggregate was used to investigate the optimum condition of slag content in mixed asphalt; the mixture ratio showed that 61% broken stone of 13 mm, 6% screenings, 10% melting slag, 15% sand and 8% filler was most effective. A lightweight swelled ceramic brick was manufactured by using melting slag, front glass, and so on. Specific gravity and compressive strength ranged from 0.38 to 0.51 and from 339.7 to 373.6 N/cm2. ASRMS exhibited an environmental performance suitable for recycling and the manufactured bricks satisfied the quality standards. The recyclability of ASR was also assessed in terms of waste usage, conformance to quality standards, market size, and demand prediction. APA showed the best results followed by interlocking, clay, and LSC bricks.

The release analysis of As and Cr metals in lead-zinc smelting slag: Mineralogical analysis, bioavailability and leachability analysis

Mining and smelting are the main sources of soil heavy metal pollution. Leaching and release of heavy metals in soils has been extensively studied. However, there are few researches on the release behavior of heavy metals from the Angle of mineralogy of smelting slag. This study focuses on the pollution of arsenic and chromium by traditional pyrometallurgical lead-zinc smelting slag in southwest China. Based on the mineralogy of smelting slag, the release behavior of heavy metals in smelting slag was studied. As and Cr deposit minerals were identified by MLA analysis, and the weathering degree and bioavailability of As and Cr deposit minerals were analyzed. The results showed that the weathering degree of slag was positively correlated with the bioavailability of heavy metals. The leaching experiment results showed that the higher pH was beneficial to the release of As and Cr. It was found that the chemical forms of As and Cr changed from relatively stable forms to easily released forms (As5+ to As3+ and Cr3+ to Cr6+) by characterizing the metallurgical slag during leaching. In the transformation process, the S in the pyrite as the enclosing layer is eventually oxidized to SO42-, which will accelerate the dissolution of the enclosing mineral. SO42- will occupy the adsorption site of As on the mineral surface, thus reducing the adsorption amount of As on the mineral surface. Fe is finally oxidized to Fe2O3, and the increase of Fe2O3 content in the waste residue will produce strong adsorption effect on Cr6+ and slow down the release of Cr6+. The results show that the release of As and Cr is controlled by the pyrite coating.

Recycled Smelter Slags for In Situ and Ex Situ Water and Wastewater Treatment—Current Knowledge and Opportunities

Slags from the ferrous and nonferrous metallurgical industries have been used to treat toxic contaminants in water and wastewater. Using slag as a recycling or renewable resource rather than a waste product has environmental and economic benefits. Recycled smelter slags can be used in both in situ and ex situ treatment. However, their application has some limitations. One of the challenges is how to handle spent slag adsorbents, as they contain the accumulation of solid waste loaded with high concentrations of toxic contaminants. These challenges can be overcome by regeneration, recycling, reuse, and immobilization treatment of spent slag adsorbents. The present paper explored the scientific and technical information about the composition, reaction mechanisms, adsorption capacity, and opportunities of recycled slags while adsorbing toxic compounds from contaminated water. It comprehensively reviewed the current state of the art for using smelting slags as sustainable adsorbents for water and wastewater. The study revealed that ferrous slags are more effective in removing a wide range of toxic chemicals than nonferrous smelter slags. It investigated the necessary improved approach through the 5Rs (i.e., reduce, reuse, recycle, remove, and recover) using smelter slags as reactive materials in ex situ and in situ treatment.

Element migration from the copper smelting slag recycling waste to the soil–plant system (Middle Urals, Russia)

Element migration from the copper smelting slag recycling waste to the soil–plant system (Middle Urals, Russia)