Matte Smelting Research Articles

Significant improvement of oxidation resistance and slag penetration resistance of MgO-SiC-C refractories with Si3N4-Fe addition

MgO-SiC-C refractories demonstrate distinguished thermal shock resistance and slag resistance, making them a promising alternative to magnesia-chrome refractories in matte smelting furnaces. Herein, we propose a novel approach to enhance both oxidation resistance and slag penetration resistance of such refractories by incorporating Si3N4-Fe powder. The results demonstrated that adding Si3N4-Fe powder effectively enhanced their overall performance. The oxidation resistance of the specimen with 6 wt% Si3N4-Fe was greatly improved because Si3N4 in Si3N4-Fe could promote in-situ reactions to form more forsterite, and the FeO formed by iron oxidation could react with SiC to form Fe-Si alloys; the formed forsterite and Fe-Si alloys worked together to prevent oxygen intrusion. Meanwhile, Si3N4 in Si3N4-Fe promoted the formation of forsterite layer in the corrosion area of refractories, and the reaction of Si3N4 and Fe in Si3N4-Fe formed Fe-Si alloys to prevent slag penetration, which greatly improved the resistance to matte slag penetration of the refractories.

Industrial Deportment of Minor and Trace Elements in Direct Nickel Matte Smelting

A sampling campaign was carried out at an industrial nickel flash smelter with the aim of evaluating the trace element distributions along the smelting line from raw materials to high-grade nickel matte and discard slag. The industrial technology was direct-to-nickel matte smelting without conventional Peirce–Smith converters, thus having two different nickel mattes as smelting products and feeds in the refinery: the sulfidic low-iron nickel matte from smelting furnace and the low-sulfur electric furnace matte from slag cleaning. Major and trace element concentrations were obtained from the solidified samples by electron probe microanalysis and laser ablation–inductively coupled plasma–mass spectrometry. Due to the industrial sampling environment, i.e., the slow cooling rate of the samples, not all the trace element concentrations were able to be measured at the lowest detection limits of the techniques used in some of the phases formed after cooling. However, the obtained results and element distribution coefficients were in good agreement with equilibrium values published in the literature.

The enrichment of low-grade antimony concentrate by matte smelting and the metallurgy of antimony matte

ABSTRACT This study employed the B2O3-Al2O3-CaO-SiO2 slag system, characterised by a low melting point, to conduct matte smelting for concentrating antimony in low-grade antimony concentrate. The process effectively eliminated major impurities, particularly quartz. An investigation delved into the reaction mechanism between the additive and the concentrate. A single-factor experiment was conducted to investigate the impact of temperature, SiO2 mass ratio, and basicity on the direct recovery rate of Sb. Optimal conditions were achieved at a temperature of 1050°C, a WSiO2/Wslag ratio of 40:100, and a basicity of 0.5. Under these conditions, the direct retrieval rate of antimony reached 91.16%, with the concentration of antimony in the slag measured at 2.34%. The acquired matte contained 53.27% antimony, further utilised in the mainstream process of antimony metallurgy. This study aimed to address the issue of exorbitant smelting expenses associated with low-grade antimony concentrate.

Improved oxidation resistance while maintaining slag corrosion resistance of MgO–SiC–C refractories with moderate amounts of liquid phase

AbstractMgO–SiC–C refractories with superior hot strength, oxidation resistance and slag resistance have potential to become substitute refractories for matte smelting furnace. In the present work, the influence of glass powder addition on phase compositions, hot strength, oxidation resistance, and slag resistance of MgO–SiC–C refractories was investigated. The liquid phase introduced by glass powder filled the pores, blocking the channel for the ingress of the oxygen and thus improving the oxidation resistance. Although the oxidation resistance of such refractories was improved with 1–3 wt% glass powder addition, their hot strength and slag corrosion resistance decreased when the glass powder content was 2–3 wt%. To balance the mechanical properties, oxidation resistance and slag resistance, low amount glass powder addition (1 wt%) was considered better choice.

Ignition and combustion of synthetic nickel mattes in simulated flash smelting conditions

The ignition and oxidation behavior of synthesized sulfur-lean nickel mattes was investigated using a laminar flow furnace simulating the conditions in the flash smelting reaction shaft to explore the ignition and oxidation processes of sulfur-lean electric furnace mattes obtained from slag cleaning. The experiments were conducted at 800–1100 °C with 40–85 vol% O2 in the reaction gas. Scanning electron microscopy equipped with energy-dispersive X-ray spectrometry was used to analyze the surface morphology and mineralogical compositions of the samples. Chemical analysis was employed to determine the sulfur remaining in the samples. The ignition temperature of the sulfur-lean nickel mattes was found to be below 800 °C. The highest sulfur removal from mattes was achieved under the most oxidizing conditions. The oxidation of the metallized nickel mattes started with preferential oxidation of iron and sulfur, forming sulfur dioxide and a porous iron oxide-rich rim. Particles were observed to melt completely and even to fragment due to fast combustion reactions and the formation of sulfur dioxide inside. The present results provide valuable insights into the mechanism of sulfur-lean nickel matte smelting in flash smelting furnaces.

A Crucial Step Toward Carbon Neutrality in Pyrometallurgical Reduction of Nickel Slag

This study aims at recovering valuable metals from nickel slag by employing pyrometallurgical techniques. A large amount of slag is generated during the nickel matte smelting. Nickel slag contains valuable elements such as copper, nickel, and cobalt, which can be recovered. Disposal of this slag results in loss of resources and may cause pollution of the environment. It is important to retrieve these metals for environmental and economic reasons. In this study, the slag was reacted with non-fossil reducing agents (biochar) which were produced from hydrolysis lignin and black pellet biomass by pyrolysis at 600 and 1200 °C, and with metallurgical coke for comparison. The reduction experiments were done at 1400 °C for 15, 30, and 60 min under inert gas atmosphere. The samples were quickly quenched and analyzed with Electron Probe X-ray Microanalysis. The results showed that the use of biochar resulted in faster reaction kinetics in the reduction process compared to coke. Moreover, thermodynamic modeling was also performed using Factsage to simulate equilibria with different amounts of biochar. The metal-to-slag distribution coefficient calculated from the results of thermodynamic modeling was consistent with experimental results.Graphical

Selective alkaline leaching of antimony from Low-grade refractory gold ores and process optimization

To eliminate the adverse effect of antimony on extracting of gold in matte smelting process from Sb-bearing refractory gold ores, the sodium sulfide leaching method was proposed to selectively remove antimony in advance. On the basis of the analysis and characterization of raw materials (XRD, SEM-EDS, mineralogical phase analysis, etc.), it can be detected that the antimony in refractory gold ores is mainly in form of stibnite with small quantities of oxides, and the gold is mainly wrapped up in sulfides and silicates. The effects of sodium sulfide and sodium hydroxide concentration, temperature, leaching time and liquid–solid ratio on the extraction rate of antimony and gold were discussed. Furthermore, the response surface method was applied to distinguish the interaction influence of process parameters on the antimony and gold extraction rate. It is detected that the polysulfides and thiosulfates are the main cause of associated leaching of gold. Furthermore, the regression equation model is established adopting the antimony extraction rate as response value, and it can be deduced that the relevance degree is Na2S concentration > temperature > NaOH concentration. Accordingly, the optimized process results are determined as follows: the extraction rates of antimony and gold reach 94.15% and 3.37%, respectively, under Na2S concentration of 85.66 g/L, NaOH concentration of 45.5 g/L, liquid–solid ratio of 1.5, leaching at 90 °C for 5 min, which are very consistent with the predicted values of the regression equation, proving the feasibility of the proposed optimization model.

Novel fluxing strategy of copper matte smelting and trace metals in E-Waste recycling

The distribution behavior of trace metals between copper matte and spinel-saturated iron silicate slags was investigated at 1250 °C and pSO2 of 0.25 atm at low silica concentrations. The experiments were conducted in magnetite (Fe3O4) spinel crucibles in controlled CO-CO2-SO2-Ar gas mixtures using a high-temperature equilibration-quenching technique. The concentrations of trace elements in matte, spinel, and slag were quantified by electron probe X-ray microanalysis and laser ablation-inductively coupled plasma-mass spectrometry. The trace metals (Ag, Ni, Co, and Sn) in all phases and their distribution coefficients were calculated as a function of matte grade. Results show that silver and nickel can be effectively recovered into matte, whereas cobalt and tin are predominantly deported into slag and gas phases, respectively. These results augment the fundamental thermodynamic data of trace metal distributions in copper smelting processes at low-silica fluxing practices.

Structure and adaptability of FexO-SiO2-MgO-15 wt% CaO-0.026 wt% NiO slag with the Fe/SiO2 mass ratio of 1.2 in flash matte smelting

The high-magnesium gangue severely affects the melting performance and fluidity of slag in nickel matte smelting. To detect the adaptability when the CaO-modified slag for treating high-magnesia nickel sulfide concentrate in flash smelting, the synergistic effect of MgO and other oxides on the microstructure and physicochemical properties of slag were analyzed through molecular dynamics simulation associated with the experimental analysis. The results indicate that the MgO content increases from 5 wt% to 11 wt%, part of the Fe2+ ions in silicate are gradually replaced by Mg2+, and some of them are transformed into Fe3+ in the external atmosphere. Accordingly, the generated Fe3+ may destroy the bridge oxygen between Si4+-O2--Si4+ and more complex silicate ions will be dissociated into SiO44+. As a consequence, the Q0 proportion in the modified high-magnesia smelting slag improved from 24.33% to 29.69%, and the n(BO/T) decreased from 1.45 to 1.29. However, when MgO content is high enough, SiO44+ tetrahedron ions may attract Fe2+ and Mg2+ to form (Fe, Mg)2SiO4 with a more robust interaction network structure, resulting in an adverse effect on melting temperature and ions diffusion coefficient. The modified nickel slags with 5–11 wt% MgO represent hospitable melting temperature less than 1320 °C, viscosity lower than 0.091 Pa s, and surface tension between 0.4811 N/m to 0.4838 N/m. In brief, the CaO-modified slag turned out to be conducive for treating high-magnesium nickel sulfide concentrates in flash matte smelting, especially for those containing MgO less than 7 wt%.

Recovery and Enrichment of Platinum from Spent Al2O3 Carrier Catalysts by Matte Smelting-Acid Leaching Process

Recovery of platinum from spent catalysts can meet the comprehensive recycling of secondary resources. Recovery and enrichment of platinum from the spent Al2O3 carrier catalyst using matte smelting for the pyrite-acid leaching process were studied. In melting process, the effects of pyrite, CaO, quartz sand, and Na2B4O7 dosage on the recovery rate of Pt were investigated. In leaching process, the effect of H2SO4 concentration, temperature, time, and liquid/solid (L/S) ratio on Pt enriching efficiency was also investigated. The slag, iron matte, and leaching residue were analyzed using XRD. The molten platinum content in the slag was measured using an atomic absorption spectrometer. The experimental results showed that 98% recovery of platinum was obtained under the following optimum conditions: 1400°C temperature, 50 min smelting time, 1 : 2 mass ratio of pyrite to spent catalysts, 0.5 : 1 ratio of CaO to spent catalysts, and 2 : 1 ratio of quartz sand to the raw material with optimum conditions, which include 15% dosage of Na2B4O7. Moreover, the acid leaching was more efficient under the following optimum conditions: H2SO4 concentration of 1.8 mol/L, time of 70 min, temperature of 60°C, and L/S ratio of 10 : 1. The enrichment and recovery of Pt were achieved at the disappearance of FeS during the acid-leaching process.

A new method for continuous recovery of fine copper droplets from copper matte smelting slag via super-gravity

Copper matte smelting slag inevitably entrains amounts of copper droplets, which brings about a high loss of copper in copper slag. In this study, a new method was proposed to continuously recover copper droplets from copper matte smelting slag via super-gravity. Motion behavior of copper droplets indicated that a long time of 60–120 min was needed for settling of copper droplets in copper matte smelting slag at 1573–1673 K under gravity. In contrast, copper droplets were directionally separated from copper matte smelting slag within 3–5 min at 1523–1573 K via super-gravity with a high Cu recovery ratio of 97.98%. Moreover, the application experiment of continuous recovery of copper droplets from copper matte smelting slag was carried out in a laboratory-scale apparatus. On this basis, this study provides a cleaner approach to efficiently recover copper resources in copper matte smelting slag with no additives and no additional heat.

Comprehensive use of raw materials through optimization of the concentration and metallurgical complex of Norilsk division

Using a concentration process introduced in 2016, Talnakh Concentrator produces copper and nickel-pyrrhotite concentrates by processing high-grade and cupriferous ores. Dump tailings comprise rock tailings separated at the early process stage and low-nickel pyrrhotite product obtained at the final concentration stage. The predominant mineral found in the ores processed by Talnakh Concentrator includes pyrrhotite, which in most cases contains nickel. Low-nickel pyrrhotite product contains pyrrhotite that bears maximum Ni 0.4% in the form of impurity. Another feature characterizing the pyrrhotites found in Norilsk is the presence of isomorphic inclusions of platinum group metals. Aimed at a more comprehensive use of raw materials, in 2018 Talnakh Concentrator introduced a process for repreparation of low-nickel pyrrhotite concentrate. A low-grade flotation concentrate is obtained with Ni 0.8÷1.2%, which is then sent to the hydrometallurgical circuit of Nadezhda Metallurgical Plant named after B.I. Kolesnikov (NMP). Being a sulphide, pyrrhotite enhances the autogenic performance of matte smelting process. The nickel concentrate produced by Norilsk Concentrator from disseminated and cupriferous ores is a low-energy material containing 15–17% of sulphur. So the heat generated during its oxidation flash smelting is insufficient to maintain the heat balance of the furnace. The nickel concentrate produced by Norilsk Concentrator is processed mixed with Ni-containing burden, which lowers the total heat balance of the flash smelting furnaces at NMP. In 2021, a process was introduced when a part of the tailings from the low-nickel pyrrhotite concentrate line of Talnakh Concentrator is used to recover high-pyrrhotite concentrate to be added to the nickel concentrate produced by Norilsk Concentrator in order to improve th e latter’s energy performance.

A review on the influence of copper slag as a natural fine aggregate replacement on the mechanical properties of concrete

Over the years, the construction industry is highly dependent on concrete for meeting the global demand of building new infrastructure. Various advancements in normal concrete have been made to make the concrete industry more efficient and developed. High strength concrete (HSC), and self-compacting concrete (SCC) are two revolutionary developments in the concrete industry that have increased the dependency of the world on concrete due to their enhanced mechanical and durability properties. However, CO2 emissions associated with cement and concrete manufacturing have created an alarming situation, and as the world is looking for sustainability and cleaner production, the pressure on the concrete industry to minimize the use of natural aggregates and cement is also increasing. Geopolymer concrete (GPC) is a type of concrete that uses various industrial wastes as a binder instead of cement and these by-products are activated by alkali. GPC is still under research and yet to be developed as a reliable product, however, the available research validates the lesser environmental impacts in GPC as compared to cement-based concrete. Other efforts have also been made to reduce the environmental impacts in concrete and substitution of natural fine aggregate (NFA) with industrial by-products is one such step that not only provides an efficient method of waste disposal but also reduces the dependency of concrete on natural resources. Copper slag (CS) is a type of nontoxic industrial waste that is obtained during matte smelting and refining of copper. CS resembles the size of NFA and can be used as partial or full replacement of NFA in various types of concrete. Various researchers have investigated the potential use of CS as NFA replacement in conventional concrete, HSC, SCC, and GPC. The current study summarizes the up-to-date trends as reported in available literature wherein CS has been used as fine aggregate in conventional concrete, HSC, SCC, and GPC. Present investigations support the use of CS as a fine aggregate in concrete. Apart from the key findings, various identified gaps, challenges, and future scope challenges have also been discussed to develop CS as a sustainable material in the construction industry.

An Experimental Analysis on Behaviour of Concrete with Copper Slag and Dolomite

It is believed that concrete is the extensively used material next to water because of its versatility and it also leaves a carbon footprint on the environment during the manufacturing of cement, which is one of its main constituents. In the present scenario, sustainability is regarded as the need of the hour. In search of development of eco-friendly concrete, the acceptance of industrial by products in the modern concrete has gained the momentum. The study focusses on utilization of compatible materials with OPC concrete like copper slag and dolomite powder as a fractional substitute to the cement and fine aggregate accordingly in concrete. Copper slag is the derivative of matte smelting and refining of copper pyrites in the furnace. Dolomite powder was acquired from the mineral dolostone. The experimental research is made by in lieu of a 40% of fine aggregate (FA) with copper slag and cement is replaced with varying percentages of dolomite powder in 0%, 5%, 10% and 15%. The experimental investigations depicted that selected mineral admixtures enhances the strength and density of material, by lessening the pores count from durability test results. This study also helps to conclude that there are a few connected capillary pores in the cast specimens.

The smelting of copper in the third millennium cal BC Trentino, north-eastern Italy

This paper presents observations and analyses on seven slag pieces from two third-millennium cal BC (Late Copper Age/Early Bronze Age) rock shelters in the Trentino, north-eastern Italy: La Vela di Valbusa and the Riparo di Monte Terlago. We review previous work on contemporary slags from the region and show that the smelting did not follow the well-known ‘Timna’, ‘Eibner’ or so-called ‘Chalcolithic’ copper smelting processes. We show that ethnographic accounts of copper smelting in the Himalayas (Sikkim and Nepal) illuminate the smelting process, in particular the lack of preliminary roasting or ore beneficiation by washing, the use of slags as fluxes for the first smelt (matte smelting) and the use of wooden (?) implements to lift the hot slags from the furnace during the smelt. The rock inclusions in the slag are consistent with an ore origin from mines at Calceranica or Vetriolo, as previously reported in the literature.

Smelting Experiments with Chalcopyrite Ore based on Evidence from the Eastern Alps

In order to assess the fractionation of copper isotopes during smelting under reconstructed conditions, smelting experiments with chalcopyrite ore were conducted in built furnaces based on archaeometallurgical evidence from the Bronze Age Eastern Alps and ethnographic examples from Nepal. Two experimental series, S2 and S4 were chosen for analysis. Each series consisted of a number of roasting and smelting experiments with different experimental parameters, and both series yielded metallic copper. Each type of experiment, their outcomes, and observations made during them are described in detail to facilitate future experimental work. Both series differ significantly in their outcome. XRD analyses and chemical analyses were carried out to reveal the reasons for the observed differences. The chemistry of the obtained matte shows that roasting is pivotal for a successful smelting process and that two cycles of matte roasting and subsequent smelting can be sufficient to remove most of the sulphur and iron from the matte. Furthermore, different conditions in the shaft furnaces resulted in a more efficient oxidation of iron in series S4. During the subsequent smelting of the matte in the pit furnace, it was possible to extract larger amounts of metallic copper and sponge copper, as well as to produce a thin well-melted plate-like slag. The pit furnace did not always show clear traces of metallurgical activity and thus might not be identifiable in the archaeological records without chemical analysis of the pit lining and surrounding soil. Although more trials are needed to replicate the process, these experiments give a strong hint towards the reconstruction of the matte smelting process in the Bronze Age alpine area.

Copper production and supra-regional exchange networks – Cu-matte smelting in the Balkans between 2000 and 1500 BC

The Balkan Peninsula played a crucial role for the introduction of metallurgy during the Copper Age and numerous archaeometallurgical examinations have delivered highly interesting insights on this topic. However, there is a lack of systematic analytical research on copper ore smelting and metal exchange for the later Bronze Age. In this paper we focus on the first archaeometallurgical results of slags from the sites Ružana, Trnjane and Čoka Njica, Eastern Serbia, complimented by the discussion of XRF and lead isotope analyses carried out on 28 copper-based artefacts. Importantly, radiocarbon dating from these sites points to copper production already being undertaken at the end of the Early Bronze Age (19th–18th centuries BC), more than 500 years earlier than previously assumed. This enables us to investigate the flow of metal during the 1st half of the 2nd millennium BC. The analyses of the metallurgical slags indicate a copper matte smelting process in small open pit furnaces and the use of local sulfidic copper ore sources. The fact that these intensive smelting activities in Eastern Serbia can be paralleled with the early production hotspots in central Europe e.g. on the Hochkönig (Mitterberg mining areas) sheds new light on the development of copper based metallurgy in Europe. At the same time, the evidence from Eastern Serbia shows that this area was a source of raw material for copper and bronze alloys providing a regional and supra-regional perspective. Furthermore, our analyses revealed the remarkable result, that by the start of the Middle Bronze Age (ca. 1700 BC) copper from the Northern Italian mining areas in the Trentino region also reached the western and central Balkans.

Precious Metal Distributions Between Copper Matte and Slag at High P_{{{text{SO}}_{ 2} }} in WEEE Reprocessing

The distributions of precious metals (gold, silver, platinum, and palladium) between copper matte and silica-saturated FeOx-SiO2/FeOx-SiO2-Al2O3/FeOx-SiO2-Al2O3-CaO slags were investigated at 1300 °C and P_{{{text{SO}}_{ 2} }} = 0.5 atm. The experiments were carried out in silica crucibles under flowing CO-CO2-SO2-Ar gas atmosphere. The concentrations of precious metals in matte and slag were analyzed by Electron Probe X-ray Microanalysis and Laser Ablation-High-Resolution Inductively Coupled Plasma-Mass Spectrometry, respectively. The precious metal concentrations in matte and slag, as well as the distribution coefficients of precious metals between matte and slag, were displayed as a function of matte grade. The present results obtained at P_{{{text{SO}}_{ 2} }} of 0.5 atm were compared with previous results at P_{{{text{SO}}_{ 2} }} of 0.1 atm for revealing the effects of P_{{{text{SO}}_{ 2} }} and selected slag modifiers (CaO and Al2O3) on precious metal distributions at copper matte smelting conditions. The present results also contribute experimental thermodynamic data of precious metal distributions in pyrometallurgical reprocessing of electronic waste via copper smelting processes.

Utilization of waste coal flotation concentrate for copper matte smelting

In this work, the process of copper matte smelting with the utilization of a fine-grained coal-bearing material (the so-called coal flotation concentrate) as fuel is presented. This material is obtained by the process of coal sludge utilization, and, currently, it constitutes an undeveloped waste due to environmental restrictions. There have been postulated methods for using this fuel in technological processes. The addition of this material to the copper concentrate briquettes was acknowledged as the best solution. Those briquettes were tested taken into account the practical strength requirements, and they were re-molten to obtain copper matte. The introduction of the floto-concentrate in the mixture to the briquetting process in quantities of up to 10% by mass allows obtaining of the briquettes with the technologically required discharge strength and compressive strength. The Cu content in the copper matte, obtained in the process of smelting briquettes containing Cu concentrate and coal flotation concentrate, is within the range of values obtained under industrial conditions.

Solubility of Chromium in DON Smelting

ABSTRACT Chromia-bearing raw materials in nickel and copper matte smelting are difficult to process due to their tendency of forming solid chromite spinel precipitates, leading to formation of mushy slag and buildups in the smelting vessel. The solubility of chromia in smelting slags, and especially in mattes, are not known accurately and new data for iron-silicate slags in equilibrium with low-iron nickel mattes have been measured at 1350–1450°C. Typical copper-bearing nickel mattes with Ni:Cu≈2 (w/w) in the DON (Direct Outotec Nickel) process with 2 to 10 wt% [Fe]matte have been equilibrated in carefully controlled S2-O2-SO2-Ar gas atmosphere experiments with the corresponding silica saturated iron-silicate slags. The phase assays post quenching were measured by electron probe X-ray microanalysis, including the molten slag and matte as well as the solid phase of chromite spinel. Laser ablation ICP mass spectrometry was used to measure the trace elements in the matte. An additional variable in the slag composition was magnesia concentration, varying from zero to 10 wt% (MgO)slag. The solubility of chromium in the slag at 1400°C was ≈0.7 wt% (Cr) and in the nickel matte 30–100 ppm [Cr], depending on the iron concentration of the sulfide matte. The impact of MgO on the chromium concentration in slag was small and within the experimental error of the measurements.