Copper Converter Slag Research Articles

Regulating the pore structure of periclase refractories by adding Y2O3 to enhance corrosion resistance for copper slag

AbstractThe penetration of copper‐smelting slag into refractories is a major challenge to the research of chromium‐free refractories for copper‐smelting furnace. In this paper, Y2O3 was added to regulate the pore structure of periclase refractories, which enhanced their various properties, especially corrosion resistance to copper converter slag. The results showed that the periclase refractories doped with 1.0 wt.% Y2O3 (1Y sample) possessed the optimum properties. Compared to the sample without Y2O3, the apparent porosity of 1Y sample was decreased by 7.3%, and its average pore diameter was only 3.7 μm. The addition of Y2O3 filled the pores among MgO grains and promoted the expansion of high melting point silicates, thereby reducing the pore size and causing more complex pore structures. This was beneficial to improving the corrosion resistance of periclase to copper slag, especially to prevent the penetration of Cux+ and Na+. After static slag corrosion, the permeability index was significantly decreased by 41% compared to periclase refractories without Y2O3. Moreover, compared to industrial MgO–Cr2O3 refractories, the 1Y sample possessed better resistance to copper slag erosion based on rotating finger tests, and its permeability index and penetration depth decreased by almost 50%.

Investigation of Reusing Copper Converter Slag Residue with the Flash Sintering Method

Investigation of Reusing Copper Converter Slag Residue with the Flash Sintering Method

A novel slag cleaning method to recover copper from molten copper converter slag

To recover copper from copper slag, a novel slag cleaning method was proposed. The thermodynamics and binary phase diagram of FeO–SiO2 were calculated first. Then, the effects of experimental parameters on the reduction of Fe3O4, recovery of copper, and slag cleaning mechanism were investigated. The results showed that the addition of SiO2 significantly reduced the initial reduction temperature of magnetite and pyrite. The contents of Fe3O4 and copper decreased to 2.45 wt.% and 0.39 wt.%, respectively, with copper recovery of 92.52% under the optimum conditions. More than 94% silver and 99% gold subsided into the copper matte after slag cleaning. Approximately 72% of zinc and 75% of lead volatilized in the flue gas. The viscosity of the copper slag decreased from 0.68 to 0.12 Pa·s due to the reduction of magnetite. The sedimentation of copper matte droplets could be enhanced by mechanical stirring.

Corrosion mechanism of magnesia-chrome refractory bricks with FetO-SiO2-Cr2O3 copper converter slag

The paper investigates the effect of Cr2O3 on the resistance of magnesia-chrome refractory bricks to copper converter slag. The static crucible method was employed to carry out the slag resistance experiment. The corrosion of magnesia-chrome refractory bricks under the action of FetO-SiO2-xCr2O3 (x = 0–5 wt%) slag at 1300 °C was discussed. The microstructure of the corroded sample was analyzed by XRD and SEM-EDS to elucidate the corrosion mechanisms of magnesia-chrome refractory bricks with FetO-SiO2-Cr2O3 slag. The results indicated that the permeability index of the slag-resistant samples gradually decreased with increasing Cr2O3 content in the FetO-SiO2-Cr2O3 slag. Combined with SEM and XRD characterization, the MgO in the refractory reacted with FeO and SiO2 in the molten slag, leading to dissolution and reaction corrosion of the refractories. Meanwhile, forming a (Mg, Fe)O solid solution layer in corroded samples can prevent further chemical reactions and high-temperature dissolution between the FetO-SiO2-Cr2O3 slag and refractories. With the addition of Cr2O3 in the FetO-SiO2-Cr2O3 slag, the corrosion effect of slag on refractories was weakened, and the (Mg, Fe)O solid solution layer became thinner. The magnesia-chrome refractory bricks showed excellent slag resistance when the Cr2O3 content in the copper converter slag was 5 wt%.

Apparent Viscosity Evolution of Copper Converter Slag During a Reduction Process

Apparent Viscosity Evolution of Copper Converter Slag During a Reduction Process

Reactions between magnesia-chrome refractories and copper converter slags: Corrosion behavior and prevention by Fe-rich layer formation

Magnesia-chrome refractories act as a lining for electric furnaces when valuable metals are recovered from copper converter slags. However, the lifetime of refractories does not exceed six months. To address the leakage problem, the corrosion behavior of a magnesia-chrome refractory immersed in a copper converter slag at different temperatures was investigated by adopting static corrosion test. The thermodynamic simulations of solubility and reactions of the slag with the refractory were first conducted. The laboratory corroded samples showed that Fe and Si penetrated the refractory material, resulting in material dissolution and reactive corrosions. Meanwhile, an Fe-rich layer formed at the slag-refractory interface which could prevent further corrosion. Given the Fe3O4 content, 1300 °C was concluded as the optimal temperature to facilitate the formation of the protective layer. The laboratory findings were in agreement with the simulation well. On the basis of the corrosion behavior, this study proposed a novel approach that prolongs the lifetime of furnaces.

Effects of Cr2O3 content on viscosity and microstructure of copper converter slag

The influences of Cr2O3 on the viscosity of copper converter slag were investigated employing the rotating method in air atmosphere. The free running temperature was determined according to the viscosity-temperature curve and the activation energy was calculated based on Arrhenius-type relationship. The molten slag microstructure evolution was researched by Raman spectroscopy and Fourier Transform Infrared spectroscopy (FTIR). The results showed that the viscosity, free running temperature as well as activation energy increased significantly after the addition of Cr2O3. The viscosity of the original slag was 0.464 Pa·s at 1573K, exceeded 8.000 Pa·s after 5 wt% Cr2O3 being incorporated. Meanwhile, the Raman spectrums demonstrated that silicate network structure components of the molten slag samples converted from Q0 ([SiO4]4−, monomer) / Q1 ([Si2O7]6−, dimer) to Q2 ([SiO3]4−, chains) / Q3 ([Si2O5]2−, sheets), which indicated the formation of more complex structures and finally contributed to the increase of the viscosity. The influence mechanism of Cr2O3 on the copper converter slag viscosity and microstructures were uncovered to give reference for understanding the excellent slag resistance property of Cr2O3 containing refractories used in copper smelting furnaces.

Treatment of copper converter slag with deep eutectic solvent as green chemical.

Industrial copper slag is among the most important wastes to be evaluated in terms of containing valuable metals and the amount of waste approaching 30 million tons per year. Therefore, in this study, it was aimed to propose a feasible route for copper and zinc recovery from copper converter slag (CCS) by using choline chloride (ChCl) based deep eutectic solvent which is applied on this type of slag for the first time. During the leaching experiments with the pure ChCl-2urea mixture, temperature (25-95°C), leaching duration (2-72h), and pulp density (1/10-1/40g/mL) were selected as the parameters to be investigated for Cu and Zn extraction. After the experimental results, the optimized conditions for the ChCl-2urea leaching process, which gave 89.9% Cu and 65.3% Zn extraction was found at 48h, 95°C, 1/20g/mL pulp density with 600rpm stirring speed. It is noted that the iron dissolution ratio is very low (max. 4.7%) under the selected conditions. At the end of the iron cementation stage, the total recovery efficiency as a pure metallic copper was 63%. The calculated activation energy for the dissolution of the copper and zinc from CCS is 8.86kJmol-1 and 14.48kJmol-1, respectively.

Study on the role of copper converter slag in simultaneously removing SO2 and NOx using KMnO4/copper converter slag slurry

To achieve “waste controlled by waste”, a novel wet process using KMnO4/copper converter slag slurry for simultaneously removing SO2 and NOx from acid-making tail gas was proposed. Through the solid-liquid separation for copper slag slurry, the liquid-phase part has a critical influence on removing NOx and SO2. Also, the leached metal ions played a crucial role in the absorption of SO2 and NOx. Subsequently, the effects of single/multi-metal ions on NOx removal was investigated. The results showed that the leached metal from copper converter slag (Al3+, Cu2+, and Mg2+) and KMnO4 had a synergistic effect on NOx removal, thereby improving the NOx removal efficiency. Whereas Fe2+ had an inhibitory effect on the NOx removal owing to the reaction between Fe2+ and KMnO4, thereby consuming the KMnO4. Besides, SO2 was converted to SO42− completely partly due to the liquid catalytic oxidation by metal ions. The XRD and XPS results indicated that the Fe (II) species (Fe2SiO4, Fe3O4) in copper slag can react with H+ ions with the generation of Fe2+, and further consumed the KMnO4, thereby resulting in a decrease in the NOx removal. The characterization of the slags and solutions before and after reaction led us to propose the possible mechanisms. The role of copper slag is as follows: (1) the alkaline substances in copper slag can absorb SO2 and NO2 by KMnO4 oxidation. (2) copper slag may function as a catalyst to accelerate SO2 conversion and improve NOx removal by synergistic effect between leached metal ions and KMnO4.

Processing of Waste Copper Converter Slag Using Organic Acids for Extraction of Copper, Nickel, and Cobalt

An innovative, economical, and environmentally sound hydrometallurgical process has been proposed for recovering Cu, Ni, and Co from copper-rich converter slag by organic acids. In the leaching experiments, the effects of organic acid concentrations, pulp density, temperature, and time were investigated. Optimum recovery of 99.1% Cu, 89.2% Ni, 94% Co, and 99.2% Fe was achieved in 9–10 h at 308 K (35 °C) temperature and 15% pulp density with 2 N citric acid using <45 µm particles. Pourbaix diagrams of metal-water-citrate systems were supplemented to examine solubility of ligands at the desired conditions. Furthermore, the leaching mechanism was based on the SEM-EDS (energy-dispersive X-ray spectroscopy) and XRD characterization as well as the leaching results obtained.

Evaluation of performance of copper converter slag as oxygen carrier in chemical-looping combustion (CLC)

In this study, copper converter slag sample was utilized as oxygen carrier (OC) for Chemical Looping Combustion (CLC) of synthetic syngas. The CLC cycles were substantiated in a bench-scale fluidized bed reactor by altering the inlet atmosphere between fuel and air consecutively. The tests were conducted at 4 times the minimum fluidization velocity, and 1123 K (850 °C) reduction half-cycle temperature (TRHC) for 50 cycles. The mean fuel gas conversion values obtained during 30 s of RHC time (tRHC) were as; 78% for 1:1 CO in nitrogen, 84–89% for syngas, and 97% for 1:1 H2 in nitrogen. Copper converter slag sample was stable and sufficiently reactive throughout the tests, moreover, the reactivity increased substantially by the consecutive CLC cycles. The increase of the porosity and the formation of the copper ferrite during the CLC cycles were found to be the main contributors to the activation of the copper converter slag. It is concluded that the evaluation of copper converter slag in the CLC process is both an economical option for OC supply (especially in coal-fueled CLC processes where some OC loss is inevitable), and an environmentally favorable alternative for recycling copper converter slag unless wasting the precious metals in it.

Magnetite reduction in copper converter slag using biodiesel produced from waste cooking oil

ABSTRACTIn copper smelting process, oxygen-enriched smelting leads to the enrichment of magnetite and increase of slag viscosity, which is not conducive to the sedimentation and separation of copper. Therefore, it is necessary to reduce magnetite in order to improve the recovery rate of copper. In this work, biodiesel produced from waste cooking oil was used to replace carbon and diesel, which should be more economical and environment-friendly. Effects of temperature and reaction time on biodiesel pyrolysis, magnetite reduction and slag viscosity were studied. It was found that the main products of biodiesel pyrolysis were carbon monoxide, hydrogen, methane, and carbon. Because methane will decompose to carbon and hydrogen at 823 K, the main reducing agents during magnetite reduction were hydrogen and carbon. With increasing reduction time and temperature, the magnetite phase in the copper slag gradually decreased, while the fayalite phase gradually increased. After injecting biodiesel into molten copper slag at 1523 K for 4 minutes, magnetite was reduced from 31.6% to less than 0.6% and the viscosity decreased from 1.43 poise to 0.68 poise. This low viscosity is beneficial for separation and recovery of copper from the molten slag.

Calculation of Distribution Coefficients of Cobalt and Copper in Matte and Slag Phases in Reduction–Vulcanization Process of Copper Converter Slag

Copper and cobalt are two of the most valuable metals that can be recovered from copper converter slag. In the reduction–vulcanization process, copper is reduced before cobalt, while FeS vulcanizes Cu2O into Cu2S and forms the matte phase. The matte phase can dissolve the reduced metals as solvent. In this study, the distribution coefficient of cobalt between metallic cobalt in matte and CoO in slag, namely L Co, was calculated to be 5000–8500 at the reaction temperature of 1600–1700 K, while the distribution coefficient between CoS and CoO, namely $$L_{\text{Co}}^{{^{\prime } }}$$ , was calculated to be between 6 and 8. The distribution coefficient of copper between metallic copper in matte and Cu2O in slag, namely L Cu, was calculated to be in the range of 7500–8500, while the coefficient between Cu2S and Cu2O, namely $$L_{\text{Cu}}^{{^{\prime } }}$$ , was calculated to be in the range of 60,000–75,000.

Magnetic separation-sulphuric acid leaching of Cu–Co–Fe matte obtained from copper converter slag for recovering Cu and Co

Cu–Co–Fe matte obtained from copper converter slag by reductive-sulfidizing smelting was treated by magnetic separation-sulphuric acid leaching (MS-SAL) process to recover the metal values, copper and cobalt. The MS-SAL process was proposed on the basis of mineralogical analysis of matte, which showed that the main copper-bearing phases were bornite and chalcocite (non-magnetic substances), and the main cobalt-bearing phase was cobalt–iron alloy (magnetic substances). The matte sample was crushed, wet ground and then magnetic separated to produce magnetically susceptible concentrate (mainly Co–Fe alloy). 95.75% of cobalt was recovered by magnetic separation and 87.8% of copper and 44.39% of iron remained in the tailings. The concentrate was leached further by sulphuric acid. Under the optimum conditions of 1.15 times the stoichiometric amount of sulphuric acid, 1h of leaching time and temperature 80°C, 99.81% of cobalt in concentrate was selectively leached into the solution while the 99.86% of copper remained in residue. The tailings containing mainly bornite and chalcocite and the leaching residue containing mainly metal copper were treated by ore proportioning with copper concentrate and fed to the copper smelting furnace. In this process, cobalt in matte was selectively extracted and the copper was almost entirely recovered for copper smelting rather than extracted from leaching liquor as in existing copper matte leaching technologies. Recovery yields of cobalt and copper by MS-SAL were 95.57% and 99.98%, respectively.

Complex treatment of mining and metallurgical wastes for recovery of base metals

A complex process for the recovery of copper and zinc from mining and metallurgical wastes has been investigated and proposed. It includes sulfuric acid leaching of old pyrite flotation tailings to produce ferric containing leach solution; followed by ferric leaching of copper converter slag flotation tailings with the leach solution. A sample of old pyrite flotation tailings from the concentrator containing 0.36% of copper and 0.23% of zinc was leached with 10% sulfuric acid in the column. Recovery of copper and zinc reached 47.1% and 47.2%, respectively. The pregnant leach solutions contained 15.9g/L of ferric iron. The subsequent ferric leaching of copper converter slag flotation tailings containing 0.53% copper and 2.77% zinc with the pregnant leach solution was conducted. The effects of various process parameters on the leaching dynamics of metals under batch conditions were investigated. Under the best conditions (temperature 70°C, pulp density 30%, ferric iron concentration 15.9g/L, initial pH of the pulp 0) the recovery of copper and zinc reached 79.6% and 43.7%, respectively. It was concluded that acid leaching of base metals from old pyrite flotation tailings with pregnant leach solution for the ferric leaching of copper converter slag flotation tailings is a prospective and promising technique for the complex treatment of mining and metallurgical wastes.

Bioregeneration of the pregnant leach solutions obtained during the leaching of nonferrous metals from slag waste by acidophilic microorganisms

The bioregeneration of the solutions obtained after the leaching of copper and zinc from slag waste by sulfuric acid solutions containing ferric iron was examined. For bioregeneration, associations of mesophilic and moderately thermqophilic acidophilic chemolithotrophic microorganisms were made. It has been shown that the complete oxidation of iron ions in solutions is possible at a dilution of the pregnant leach solution with a nutrient medium. It has been found that the maximal rate of oxidation of iron ions is observed at the use of a mesophilic association of microorganisms at a threefold dilution of the pregnant leach solution with a nutrient medium. The application of bioregeneration during the production of nonferrous metals from both copper converter slag and its waste would make it possible to approach the technology of their processing using the closed cycle of workflows.

Leaching of nonferrous metals from copper converter slag with application of acidophilic microorganisms

The leaching process of copper and zinc from copper converter slag with ferric iron in sulfuric acid solutions obtained using the association of acidophilic chemolithotrophic microorganisms was investigated. The best parameters of chemical leaching (temperature 70°C, an initial concentration of ferric iron in the leaching solution of 10.1 g/L, and a solid phase content in the pulp of 10%) were selected. Carrying out the process under these parameters resulted in the recovery of 89.4% of copper and 39.3% of zinc into the solution. The possibility of the bioregeneration of ferric iron in the solution obtained after the chemical leaching of slag by iron-oxidizing acidophilic chemolithotrophic microorganisms without inhibiting their activity was demonstrated.

Bioprocessing of Mining and Metallurgical Wastes Containing Non-Ferrous and Precious Metals

Mining and metallurgical treatments of sulphide ores are characterised by present significant losses of non-ferrous and precious metals as different types of waste. These elements are accumulated in heaps due to the lack of efficient technology for the recovery of the metals from metallurgical waste. The treatment of two types of industrial metallurgical waste (copper converter slag and old flotation pyrite tailings) containing non-ferrous and precious metals were examined in the laboratory. Leaching of the slag containing 2.74% Cu (as digenite, bornite, and free metal) and 2.49% Zn (as a ferrite ZnFe2O4 and silicate) by an Fe3+-containing solution was studied. The effect of various experimental parameters on the leaching dynamics of copper, zinc, and iron under batch conditions was investigated. The following experimental parameters were recommended: a pH of 1.5, a pulp density of 10% (w/v), a temperature of 70 °C, and an initial Fe3+ concentration of 15 g/L. Leaching under these conditions resulted in the solubilisation of 89.4% copper and 35.3% zinc within 2.5 hours. Percolation leaching of the pyrite tailings containing 0.29% Cu (as chalcopyrite), 0.26% Zn (as sphalerite), 0.00007% gold, and 0.00108% silver was also studied. Acidic percolation leaching and the resulting biooxidation lasting 134 days resulted in the solubilisation of 73.4% zinc and 50.8% copper. The recovery rates of gold and silver from the bioleaching residues by cyanidation were 57.2% and 50.7%, respectively. The data obtained in the present work may be used to estimate the operating parameters for the industrial-scale processing of non-ferrous and precious metals from mining and metallurgical waste.

Recovery of Cobalt from Copper Converter Slag by a Selective Reduction-Roasting Process

An industrial converter slag was treated by a selective reduction-roasting process to recovery cobalt and copper in this study. To maximizing the recovery of cobalt and copper, the major process parameters such as reducing agent, curing agent and roasting temperature were investigated. Under the determined conditions, 95% cobalt and 96% copper can be recovered. According to the mineralogical analysis, it is found that cobalt in the converter slag mainly distributes in the iron-bearing minerals, which migrates with iron during the reduction-roasting process. After the reduction-roasting, most cobalt distributes in the metallic iron in the form of Co-Fe alloy.

Leaching of copper and zinc from copper converter slag flotation tailings using H2SO4 and biologically generated Fe2(SO4)3

Leaching of converter slag flotation tailings from the Svyatogor copper smeltery (Sverdlovsk region, Russia) by sulfuric acid solutions containing ferric ions was investigated. The solutions were obtained using oxidation of ferrous sulfate by a consortium of moderately thermophilic acidophilic chemolithotrophic microorganisms, including Sulfobacillus species. Flotation tailings contained 0.56% Cu and 4.74% Zn. Copper was present mostly as digenite, bornite, and free metal. Zinc was present as a ferrite (franklinite) ZnFe2O4 and, to a lesser degree, as silicate. The effects of pH, pulp density, temperature, initial Fe3+ concentration, and the presence of oxygen in the leaching solution on the leaching dynamics of copper, zinc, and iron were investigated. Increasing Fe3+ concentrations was found to have an inhibitory effect on zinc and iron leaching, but not on copper leaching. Temperature had the most pronounced effect on the kinetics of copper and zinc leaching. Kinetic analysis was carried out, and the calculated activation energies for copper and zinc leaching were 51.3 and 53.8kJ/mol, indicating control of this process by a chemical reaction on the particle surface. The recommended technological parameters for leaching of copper (the most important component) from converter slag flotation tailings are: pulp density of 30% (w/v), pH 1.5, temperature of 70°C, initial Fe3+ concentration of 15.7g/L, no aeration, leaching for 1.5h. This process resulted in solubilization of 81.6% copper and 37.7% zinc with the relatively low iron recovery of 26.2%. Metal content in the leach residue was 0.13% Cu and 3.69% Zn.