Distribution behavior of cobalt, selenium, and tellurium between nickel-copper-iron matte and silica-saturated iron silicate slag

The distribution coefficients (D _X) of cobalt, selenium, and tellurium between nickel-copper-iron matte and silica-saturated iron silicate slag were determined as a function of matte and slag compositions, temperature, and the partial pressure of oxygen. The effect of slag additives, such as CaO, MgO, and Al₂O₃, on the distribution behavior of the minor elements was also investigated. Analysis of the data indicated that D _Co, D _Se, and D _Te were strongly dependent on the matte grade and slag additives. The effect of slag additives on the solubility of Co, Se, and Te in slag was discussed in terms of various experimental conditions. Cobalt distribution coefficients were found to decrease with increasing oxygen partial pressure, indicating the oxidic dissolution of cobalt in the slag. Based on the experimental results and available thermodynamic data, the activity coefficients of CoS in the nickel-copper-iron matte were estimated as a function of mole fraction of FeS in the matte at 1250 °C. Meanwhile, the distribution coefficients of both selenium and tellurium increased when raising the partial pressure of oxygen, implying that there was molecular dissolution of selenium and tellurium in the slag within the oxygen partial-pressure range investigated in this study.     

Development of Kinetic Model for Reactions Between Cu-Containing Multicomponent Slag and Liquid Sulfide Using Coupled Reaction Model

Copper smelting slag contains less than 2 mass pct of Cu oxide and 30–50 mass pct of Fe_xO. Each year, the grade of copper ore decreases, while the amount of slag generated in the copper smelting process increases. In this study, a coupled reaction model to simulate the reaction between multicomponent slag and FeS-based matte was developed using reported thermodynamic data and double-film theory for the recycling of copper smelting slag. The activity coefficients of oxides in the multicomponent slag were calculated using a regular solution. The activity coefficients of Cu₂O in the slag and those of FeS, Cu₂S, and CaS in the FeS-based matte used previously reported data. The behaviors of Cu in slag and matte were confirmed by comparing the simulated results and the reported solubility of Cu in the slag in the temperatures ranging from 1473 K to 1573 K. In addition, the effect of the input amount of FeS on the copper content of the slag was verified by comparing the results of reaction model to experimental results. Using the reaction model, the influences of the initial ratio of FeO/SiO₂ of the slag, temperature, and matte composition on the behaviors of Cu in the slag and matte were investigated.     

Precious Metal Distributions in Direct Nickel Matte Smelting with Low-Cu Mattes

Base metal (Cu, Fe, and Ni) and trace element (Ag, Au, Co, Pd, and Pt) distributions between low-iron nickel mattes with [Ni]:[Cu] = 4 (w/w) have been studied at 1623 K to 1723 K (1350 °C to 1450 °C). We equilibrated small slag–matte samples with CO–CO₂–SO₂–Ar atmospheres in pre-selected \( P_{{{\text{S}}_{2} }} \)–\( P_{{{\text{O}}_{2} }} \) points, maintaining silica saturation by fused silica crucibles. The slags studied contained about 0 to 8.5 wt pct MgO. The matte–slag distribution coefficients L ^m/s[Me] were obtained from assays by electron probe X-ray microanalysis for the matte and by laser ablation-ICP-mass spectrometry for the slag. The measured L ^m/s[Me] values were clearly dependent on iron concentration of the matte and on MgO concentration of the slag, with values on the order of 10⁴, 10⁵, and 10⁴ for gold, platinum, and palladium, respectively, in the 5 wt pct iron in matte experiments. The obtained data for silver were scattered, due to volatilization, resulting in depletion of most silver and its escape from matte to gas phase during the 3-hour equilibration period. The matte-to-slag distribution coefficient for silver was estimated to be L ^m/s[Ag] = 100 to 400. We also measured the distributions of the base metals Cu and Ni in the same conditions as the trace elements.     

Equilibrations of copper matte and fayalite slag under controlled partial pressures of SO2

Equilibrium distributions of Cu, S and O between silica saturated fayalite slags and copper mattes (25 to 79 pct Cu) have been examined experimentally under controlled partial pressures of SO₂. The temperature range of the experiments was 1423 to 1573 K and pSO₂ was varied between 0.1 and 1 atm. Concentrations of copper in the experimental slags were found to be low (<1 pct Cu) under these conditions, as long as the grade of the coexistent matte was below 60 pct copper. Copper in slag concentration rose dramatically, however, when matte grade was increased above this level. The work also showed that whereas FeS has a high solubility for oxygen and is itself soluble in slag under oxidizing conditions, Cu₂S and slag are almost completely immiscible. Cu-Fe-S mattes behave in an intermediate manner. Formerly graduate student with the Department of Mining and Metallurgical Engineering, McGill University.     

Thermodynamics of the Fe-Ni-S system at 1250°C

The activity of sulfur in the Fe-S and Ni-S binary and the Fe-Ni-S ternary systems was investigated at 1250°C by equilibrating molten mattes with gaseous mixtures of H₂S and H₂. From the sulfur activity data the activities of iron and nickel in the Fe-S and Ni-S binary systems as well as the activities of FeS and Ni₃S₂ in the ternary system were calculated. Isoactivity diagrams are presented for S, FeS, and Ni₃S₂ in the Fe-Ni-S ternary system. Some comments are offered on the industrial problems of nickel slag loss and ferronickel separation.     

Thermodynamic prediction of melting of copper-electrolyte slime

Balance calculations of multicomponent equilibrium compositions in the gas–liquid–solid system under oxidizing smelting of the copper-free copper-electrolyte slime, during which sulfur, selenium, and tellurium dioxides transfer into the gas phase, while compounds of lead, copper, antimony, iron, and aluminum are concentrated in the composition of the silicate slag, are performed with the help of the Outotec’s Chemical Reaction and Equilibrium Software HSC Chemistry program. It is established that, under optimal conditions of oxidizing smelting of the charge (100 kg) of the electrolyte slime (O₂ ≈ 0.9 kg, SiO₂ ≥ 6%, CaO ~ 3%, t = 1200°C), lead, antimony, and arsenic almost completely transfer into the silicate slag, while copper and silver (above 91%) transfer into the matte. Selenium is distributed between the gas phase (49.8%), matte (24.1%), and metallic phase (26.1%), while tellurium is distributed between sublimates (14.4%), silicate slag (8.4%), and matte (77.2%).     

Electrocapillary motion of copper and nickel matte droplets on fayalite-based slag surfaces

The electrocapillary motion of Cu₂S and Ni₃S₂ droplets on the surface of fayalite-based slags under 50% Ar-CO atmosphere has been studied for the effects of droplet size, temperature, electric field strength. Cu content m Cu₂S-FeS droplets, Ni content in Ni₃S₂ FeS droplets and slag composition. The copper matte droplets migrate to the anode (positive electrode) while the nickel matte droplets migrate to the cathode (negative electrode). Typical speeds encountered are of the order of 0.05–0.80 cm/s (Cu) and 0.16–0.62 cm^−s (Ni) with droplet diameters between 0.10 and 0.28 cm, applied potentials between 0.17 and 2.0 V/cm (Cu) and 0.75 and 3.3 V cm (Ni) and for temperatures between 1473 and 1573 K. The migration rate appears to be independent of droplet size for droplet diameters between 0.10 and 0.28 cm, but it increases with applied potential field and temperature.The effects of matte and slag contents on the migratory behavior are complex. As the Cu content in the Cu₂S-FeS matte droplet increases above 40% Cu. the migration rates also increase. Below 40% Cu matte grade, the migration rates are not significantly different. As the Ni content in the Ni₃S₂-FeS matte droplet increases, the migration rates decrease. These migration rates are also affected by the slag composition. As the Cu and Ni matte droplets migrate in opposite directions under the influence of the electric field, electrocapillary phenomena may be used to enhance metal recovery in slag cleaning operations using electric furnaces.     

Kinetic study on the reaction of solid silica with molten matte

Quartz glass rods, 5.5 mm in diameter, were immersed in ternary Fe-S-O melts and quaternary Cu-Fe-S-O melts at 1493 K, and the decrease in rod diameter was measured. The rate of slag formation increased with the rotating speed of the rod and the FeO activity of the molten matte. A thin film of slag was formed on the rod surface when the FeO activity of the molten matte was higher than that of silica-saturated slag. The mass transfer coefficient of the FeO component in the boundary layer of the molten matte on the slag film was calculated on the assumption that the rate of slag formation was controlled by the mass transfer, and the results showed a dependency on the rotating speed of the rod close to the reported value. The rate of slag formation also increased with the Cu content of the molten matte, probably due to an accelerated upward movement of slag along the rod surface. At the time of lower FeO activity of the matte, the SiO₂ rod was thought to dissolve in the matte, and the rate of dissolution increased with the FeO activity and Cu content of the matte. Y. CHIBA, formerly Graduate Student.     

The Effect of CaO on Gas/Slag/Matte/Tridymite Equilibria in Fayalite-Based Copper Smelting Slags at 1473 K (1200 °C) and <Emphasis Type="Italic">P</Emphasis>(SO<Subscript>2</Subscript>) = 0.25 Atm

Fundamental experimental studies have been undertaken to determine the effect of CaO on the equilibria between the gas phase (CO/CO₂/SO₂/Ar) and slag/matte/tridymite phases in the Cu-Fe-O-S-Si-Ca system at 1473 K (1200 °C) and P(SO₂) = 0.25 atm. The experimental methodology developed in the Pyrometallurgy Innovation Centre was used. New experimental data have been obtained for the four-phase equilibria system for fixed concentrations of CaO (up to 4 wt pct) in the slag phase as a function of copper concentration in matte, including the concentrations of dissolved sulfur and copper in slag, and Fe/SiO₂ ratios in slag at tridymite saturation. The new data provided in the present study are of direct relevance to the pyrometallurgical processing of copper and will be used as an input to optimize the thermodynamic database for the copper-containing multi-component multi-phase system.     

还原气氛下渣-锍两相平衡反应

通过考察还原气氛下熔渣与锍相之间的平衡情况,研究了渣-锍两相反应的影响因素及机理,探讨了还原产物的分配规律。结果表明,熔渣碱度提高有利于锍相还原反应的进行,添加CaS抑制锍相的还原。由于锍相成分及密度不同出现分层现象,造成锍相在熔渣中的夹杂损失。CaS与金属铁具有互斥性,当熔渣中CaS质量分数超过0.9%之后,渣相中几乎没有金属铁的存在;在选取的实验条件下,CaS在渣、锍两相的平衡分配比维持在0.5左右。     

Distribution equilibria and slag chemistry of DON smelting

Equilibrium fluxing chemistry and metal value distributions of nickel matte smelting in the one-step direct nickel matte technology have been determined experimentally at 1350–1450°C in MgO-bearing iron silicate slags at silica saturation. The aim was to approach the detailed smelting chemistry at typical concentrations 2.5–10?wt-% iron in MgO-bearing iron silicate slags at silica saturation by quenching and X-ray microanalysis. The results obtained under controlled P(O₂) and P(S₂) as well as constant P(SO₂)?=?0.1?atm show that copper and nickel solubilities in the slag as well as matte-to-slag distributions favour matte when the slag is modified by magnesia. At the same time, along with increasing magnesia content of the slag, its iron activity is affected by the dissolution of MgO in the slag, and iron concentration of the formed nickel matte is lowered considerably, and its sulphur concentration increased at constant oxygen and sulphur pressures of the gas phase.     

Kinetic Analysis of Alumina Change in Mold Slag for High Aluminum Steel during Continuous Casting

A kinetic calculation model considering both a molten slag reaction with molten steel and an Al₂O₃ inclusion absorption in molten slag was developed to estimate the change in Al₂O₃ in molten slag during the continuous casting of high aluminum steel. Practical casting experiments of high aluminum steel were conducted to investigate the change in composition in the molten slag and to validate the proposed model. The calculated results show that the Al₂O₃ concentration in the molten slag increases quickly during the initial stage and gradually approaches a steady-state value after 900 seconds of casting, which agrees well with the experiment outcome. The change in Al₂O₃ in molten slag is mainly affected by the initial Al₂O₃ concentration w ⁰ of the mold powder, reaction equilibrium concentration of Al₂O₃ w* at the slag-steel interface, mass transfer coefficient \textk_{\textF,\textAl2 \textO3} {\text{k}}_{{{\text{F}},{\text{Al}}_{2} {\text{O}}_{3} }} in molten slag, Al₂O₃ inclusion concentration w _M , and absorption coefficient β in molten steel during continuous casting of high aluminum steel. The experiment result shows that the concentration of Al₂O₃ in molten slag increases significantly and that SiO₂ decreases strongly, while the other components in the molten slag can be negligible comparatively. Mold slag properties at 0, 5, and 45 minutes change greatly, which can deteriorate the performance of the mold slag.     

A thermodynamic database for copper smelting and converting

The thermodynamic properties of the slag, matte, and liquid copper phases in the Cu-Ca-Fe-Si-O-S system have been critically assessed and optimized over the ranges of compositions of importance to copper smelting/converting based on thermodynamic and phase equilibria information available in the literature and using the modified quasichemical model. A thermodynamic database has been developed, which can be used for the calculation of matte-slag-copper-gas phase equilibria of interest for the production of copper. The model reproduces within experimental error limits all available experimental data on phase diagrams, matte-alloy miscibility gap and tie-lines, enthalpies of mixing, and activities of Cu and S in the matte and liquid alloy. The calculated solubilities of Cu in both S-free slag and slag equilibrated with matte are also in good agreement with experiment under all studied conditions, such as at SiO₂ saturation, in equilibrium with Fe, Cu, or Cu-Au alloys, at fixed oxygen or SO₂ partial pressures and at different contents of CaO in the slag. Sulfide contents (sulfide capacities) of the slags are predicted within experimental error limits from the modified Reddy-Blander model, with no adjustable parameters. As an example of the application of the database, the stability field of matte/slag equilibrium is calculated, and the matte and slag compositions are plotted vs iron to silica ratio in the slag at various SO₂ pressures over this field. The matte-slag two-phase field is limited by the calculated lines corresponding to precipitation of copper, silica, and magnetite.     

A New Technology for Copper Slag Reduction to Get Molten Iron and Copper Matte

The change of iron composition as well as the removal of copper from iron was investigated in the reduction process,and a new way to deal with copper slag was proposed.The iron in copper slag exists mainly in the form of fayalite,and the copper sulfide content accounts for just about 50%.Therefore,the magnetic separation as well as grinding floatation method is not suitable,and a pyrogenic treatment on copper slag is necessary.The carburization and desulfurization process is restricted to a degree within the carbon composite pellets,and copper matte phase precipitates from copper slag in the reduction process,which is immiscible with molten iron and slag.The copper content decreases to 0.4% as the carbon content in molten iron reaches 3.84%,and the removal ratio of copper from molten iron approaches to 80%.The reduction and sulfurization process can be completed in one step,and the copper is separated from iron based on the ternary system of iron-matte-slag.     

铜闪速熔炼过程中渣-冰铜-气三相平衡研究

在铜闪速熔炼中,高富氧强化熔炼可提高单炉处理能力及烟气中SO2浓度,但也增加了控制冰铜品位及渣含铜的难度。熔体温度需高于熔体的液相温度方可保证熔体的流动性,使熔体在沉淀池中顺利分层及排放。但过高的温度会增大耐火材料侵蚀,缩短炉子寿命。为确定优化的生产条件,通过冷淬、EPMA分析技术测定了铜闪速熔炼过程中熔炼渣、冰铜的显微结构及成分,并通过FactSage 8.1热力学分析软件研究了冰铜品位、硫分压及氧分压之间的关系,以及熔炼渣成分（Fe/SiO2、Al2O3、CaO、MgO、ZnO含量）和硫分压对熔炼渣液相温度的影响。     

Kinetics of As,Sb, Bi and Pb volatilization from industrial copper matte during Ar+O<Subscript>2</Subscript> bubbling

A kinetic study on minor elements removal during copper matte oxidation was designed under the presumptions of low FeO activity and of no fayalite slag formation. Copper matte with a mass fraction of Cu of 59 pct was mixed by Ar gas blowing during preheating. The matte was oxidized at 1523 and 1673 K by bubbling Ar+O₂ gas through a submerged nozzle. The effects of melt temperature and input oxygen content on the oxidation rate of matte and the volatilization rate of minor elements in copper matte are discussed. The competition reaction composed of the oxygen dissolution into matte and SO₂ gas evolution rate results in the preferential oxidation of FeS in copper matte. The desulfurization rate of matte and the volatilization of minor elements in copper matte were primarily controlled by the mass-transfer rate through the gas film boundary layer around rising gas bubbles. The As, Pb, and Bi were significantly removed during Ar gas blowing with the volatilization rates of Bi and Pb markedly increasing with the melt temperature. However, the dependences of the volatilization rates on the input oxygen partial pressure were affected in a complicated way by the effects of the melt temperature and the reduced amount of exhaust gas.     

Metal loss to slag: Part II. oxidic dissolution of nickel in fayalite slag and thermodynamics of continuous converting of nickel-copper matte

FeO-Fe₂O₃-SiO₂ slags were equilibrated in pure nickel crucibles under a CO-CO₂ atmosphere. The Fe/SiO₂ ratios in the slag were fixed at 1.51 and 1.97 at temperatures of 1200 and 1300°C. The CO₂/CO ratios were varied up to values corresponding to magnetite saturation. On the basis of solubility data obtained, a computer model was developed to predict the solubilities of nickel and copper in slag during the continuous converting of nickel-copper matte. These are given as a function of five parameters: temperature, iron content and Cu/Ni ratio in the matte, partial pressure of SO₂ in the gas phase, and magnetite activity in the slag. The model is helpful in comprehending converting reactions and of practical applicability in optimizing the conventional as well as continuous converting processes. Noranda Research Centre, Pointe Claire, Quebec.     

Phase equilibrium and minor element distribution between FeO x -SiO2-MgO-based slag and Cu2S-FeS matte at 1573 K under high partial pressures of SO2

As part of a fundamental study of copper smelting processes using oxygen or oxygen-enriched air as a blowing gas, phase equilibrium and distribution of minor elements between copper matte and SiO₂-saturated FeO _x -SiO₂-MgO-based slag containing 5 to 10 wt pct MgO have been investigated at 1573 K under the SO₂ partial pressures of 10.1, 50.7, and 101.3 kPa. The copper and sulfur solubilities in the slag were found to be independent of when the matte grade was specified, and this behavior was ascribed to the constancy of against at a given matte grade. When the distribution ratio of a minor element (X) between the slag and matte phases was defined as L _x ^s/m =(wt pct X in slag)/{wt pct X in matter}, L _x ^s/m for arsenic, antimony, and bismuth at a given matte grade increased with increasing . On the other hand, the distribution ratio of silver at a given matte grade was almost constant against .     

Effects of oxygen atmosphere,FeOx and basicity on mineralogical phases of CaO–SiO2–MgO–Al2O3–FetO–P2O5 steelmaking slag

ABSTRACT

The mineralogical phase of slag after crystallisation is essential to utilisation of steelmaking slag. The mineralogical phases of cooled multicomponent CaO–SiO₂–MgO–Al₂O₃–Fe_tO–P₂O₅ slag with different iron oxide contents and basicities (defined as the ratio of mass percentage of CaO to mass percentage of SiO₂ (w(CaO)/w(SiO₂))) in different atmospheres were investigated in the present work by scanning electronic microscopy and energy dispersed spectroscopy analysis and X-ray diffraction. The mineralogical phases in steelmaking slag cooled in argon are mainly nCa₂SiO₄-Ca₃(PO₄)₂ (thereafter nC₂S-C₃P) solid solution, (Fe, Mn, Mg)O (RO) phase. Some CaMgSiO₄ phases could be found in slag with lower basicity. The mineralogical phases in steelmaking slag cooled in air are mainly nC₂S-C₃P solid solution, spinel phase. The overall crystallisation of slag cooled in both argon and air was enhanced with increasing basicity. However, the crystal sizes become smaller in sample with high basicity. The Fe-enriched phases were transformed from non-faceted RO phase in sample cooled in argon to faceted spinel phases in sample cooled in air. The crystallisation of slag cooled in both argon and air was promoted with increasing FeO_x content. The phosphorus content in solid solution was elevated with decreasing basicity and increasing FeO_x content. It was implied by the present work that appropriate basicity and air oxidation would be beneficial to magnetic separation and phosphorus utilisation.     

Evaluation of Sulfur Addition to the High Basicity Slag on the Sulfur,Aluminum, and Cleanliness of High Sulfur Al‐Killed Molten Steel

In the present work, the influence of sulfur addition to the high basicity slag on the Al‐killed molten steel with high sulfur content was investigated by using a vacuum induction furnace at 1873 K in MgO crucibles. CaO–SiO₂–Al₂O₃–MgO–CaS slags were used to study the effect of high basicity slags with different CaS contents on sulfur loss, aluminum loss, and total oxygen content in the molten steel. It is shown that the sulfur content in the molten steel decreased with the time, and the addition of CaS into the slag can reduce the sulfur loss in the molten steel. Moreover, there was a decreasing tendency of the aluminum content in the molten steel with the time, and the addition of CaS into the slag can reduce the aluminum loss in the molten steel. Total oxygen content in the molten steel first increased and then decreased with the time when no CaS was added into the slag. However, it decreased monotonically with the time when the addition of CaS was made into the slag.