A kinetic model for the vacuum refining of inductively stirred copper melts

An experimental investigation into the removal of impurities (bismuth, lead, arsenic, and antimony) from baths of molten copper (blister, anode and cathode type copper) under vacuum was carried out. A pilot scale vacuum induction melting facility was used for these tests. The effects of (1) vacuum levels of 8.0 to 40.0 Pascals, (2) melt temperatures of 1150 to 1350 °C, (3) melt surface area to volume ratios of 6 to 10 m⁻¹, (4) a water cooled condenser placed within a distance of two centimeters above the melt surface, and finally, (5) different levels of dissolved oxygen and/or sulfur contained in the melt, were studied. Kinetic data were obtained for evaluating the potential of a full scale vacuum melting facility. A mathematical model was also developed for the proper interpretation of the experimental results and for making projections for lower pressure and higher temperature levels. The rate of removal of bismuth and lead increased as the chamber pressure was lowered and the melt temperature increased, while removal of arsenic and antimony was negligible. Neither the melt surface area to volume ratio nor the distance of the condenser to melt surface had any significant effects on the rate constants governing the rate of removal of impurities. The rate of elimination of bismuth and lead over the range of 1150 to 1350 °C and 40.0 to 8.0 Pa followed first order kinetics. Removal rates were largely controlled by mass transport in the gas phase. Formerly Graduate Student at McGill University, Montreal, PQ, Canada     

Thermodynamics for arsenic and antimony in copper matte converting—computer simulation

Thermodynamic data for arsenic and antimony and their sulfide and oxide gases have been critically reviewed and compiled. The entropy values for AsS(g), SbS(g), and BiS(g) have been recalculated based on a statistical thermodynamic method. The standard heat of formation and entropy of As₂O₃(g) have been newly assessed to be △H₂₉₈⁰ = −81,500 cal/mole and S₂₉₈⁰ = 81.5 cal/deg/mole. Copper matte converting has been mathematically described using the stepwise equilibrium simulation technique together with quadratic approximations of oxygen and magnetite solubilities in molten mattes. A differential equation for the volatilization of arsenic and antimony has been derived and solved for successive reaction microsteps, whereby the volatilization, slagging, and alloying of the minor elements in copper matte converting have been examined as functions of reaction time and other process variables. Only the first (slag-making) stage of converting is responsible for the elimination of arsenic and antimony by volatilization. Arsenic volatilizes mainly as AsS(g) and AsO(g), with As₂(g) also contributing when initial mattes are unusually rich in arsenic (above 0.5 pct arsenic). Antimony volatilizes chiefly as SbS(g), and the contributions of other gases such as SbO(g) and Sb(g) always remain negligibly low. The results of the stepwise equilibrium simulation compare favorably with the industrial operating data. Formerly Assistant Professor, Department of Metallurgy and Metallurgical Engineering, University of Utah, Salt Lake City, Utah 84112     

铜精炼过程中砷、锑的脱除研究现状

由冰铜吹炼而成的粗铜中含有一定的杂质,这些杂质会对铜的工业性能产生不同程度的影响,因此需要对粗铜进行精炼处理.为了进一步提高阴极铜质量,生产满足市场需求的铜产品,在火法、电解精炼等方面对有害杂质进行有效处理成为了国内外专家学者研究的热点.其中火法精炼处理砷、锑的方法有:氧化挥发法、碱性造渣法、真空精炼法、FRHC技术等...     

Vacuum refining copper melts to remove bismuth,arsenic, and antimony

Experiments were carried out on 35 kg melts of doped cathode copper and anode copper in a 3 m³, 150 kW vacuum induction furnace. Rates of removal of bismuth, arsenic, and antimony were measured over temperature and pressure ranges of 1450 to 1610 K and 3 to 30 pascals, respectively. Bismuth removal was found to be rapid: 1 to 18 x 10^-5 m/s. Arsenic and antimony removal were quite slow: 0.2 to 3 x 10^-5 and 0.1 x 10^-5 m/s, respectively, and evaporation controlled rates of refining. It is shown that, at typical concentrations of these elements in copper, monatomic evaporation is the predominant evaporation mechanism. An expression for the melt phase mass transport rate coefficient is developed from Machlin’s model. In this expression, melt diffusion is a function of melt temperature, and melt surface velocity is a function of the square root of melt surface area to volume ratio and the square of melt temperature, i.e.: it = 1.11 x 10^-7[(A/V)/]^1/4Tr^1/2 exp(-2515/T). This coefficient is used to examine rate control in previous small scale studies and in the present and previous pilot scale studies. The gas phase mass transport coefficient is found to be proportional to the overpressure ratio defined as: total initial melt vapor pressure/chamber pressure, and is also found to be dependent on the geometry of the gas space immediately above the melt.     

铜火法冶炼过程中新型脱杂剂的应用实践

通过对铜火法吹炼、精炼过程中铅、砷、锑、铋等主要杂质的分布状态、脱除机理和物相进行分析研究,开发出一种新型脱杂剂(主要成分为含钠钙的高活性碳酸盐),通过新型脱杂剂在铜火法吹炼、精炼段的生产应用,形成了铜火法吹炼、精炼联合除杂工艺,砷、锑、铋脱除率分别由42.19%、22.98%、74.02%提高至54.18%、36.35%、80.41%,确保了高杂原料条件下的阳极铜质量稳定,拓宽了公司原料适应范围。      

The activities of sulfide and oxide components and the solubility of oxygen in copper-iron-sulfur-oxygen mattes at 1300 °C

The activities of iron and copper and the solubilities of oxygen in copper-iron-sulfur-oxygen mattes have been determined by equilibrating mattes with CO−CO₂−SO₂ gas mixtures of fixed partial pressures of oxygen and sulfur and equilibrating a small mass of platinum with the melt. Iron and copper transferred from the matte to form a platinum-iron-copper alloy in which the activities of iron and copper are the same as in the matte. The activities of iron and copper in the matte were then determined from knowledge of the activities of iron and copper in the system platinum-iron-copper. Sulfides ofW _Fe=0.1, 0.3, and 0.5 were studied, whereW _Fe=wt pct Fe/(wt pct Fe+wt pct Cu), and sulfur pressures of 0.005, 0.0158, and 0.025 atm and oxygen pressures of 3.16×10⁻¹⁰, 7.94×10⁻¹⁰, 2.00×10⁻⁹, and 3.16×10⁻⁹ were used. The activity of copper, which varied in the range 0.06 to 0.165, decreases with increasingp _{O 2} at constantW _Fe andp _{S 2} and decreases with increasingp _{S 2} at constantW _Fe and constantp _{O 2}. The activity of iron, which varied in the range 0.002 to 0.06, increases with increasingp _{O 2} at constantW _Fe andp _{S 2} and decreases with increasingp _{S 2} at constantW _Fe andp _{O 2}. The activities of the components Cu₂S, FeS, Cu₂O, FeO, and Fe₃O₄ were calculated from the activities of iron and copper, the partial pressures of oxygen and sulfur, and the approapriate equilibrium constants. The variations of the activities of these components with matte grade, oxygen pressure, and sulfur pressure are presented and discussed. Within the range of experimental conditions studied, the solubility of oxygen in the melts is given by wt pct O=2.59pO₂/0.225pS₂/−0.18 (1+9.0W _Fe)^1.86     

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 .     

Thermodynamic behavior of bismuth in copper pyrometallurgy: Molten matte,white metal and blister copper phases

This study developed thermodynamic data relating to the behavior of bismuth in copper smelting, converting and refining processes. The activity of bismuth was set by establishing a known vapor pressure of bismuth over melts of various phases. The melts were equilibrated with the vapor, and the resulting bismuth content used to establish bismuth activity coefficients. Experiments were carried out, under controlled oxygen potentials, at 1200 and 1250 °C. Results show that bismuth deviates positively from Raoult's Law at both 1200 and 1250 °C in copper (γ_Bi = 2.17, 2.27), white metal (γ_Bi = 6.1, 6.1), Cu₂S with 2 wt pct FeS (γ_Bi = 8.0, 8.0), Cu₂S with 4 to 6 wt pct FeS (γ_Bii = 16.4, 16.4) and Cu2S with 8 to 70 wt pct FeS (γ_Bi = 13.6, 13.6), respectively. Sabri Arac formerly Research Assistant at University of Arizona Gordon H. Geiger formerly head of the Department of Metallurgical Engineering at the University of Arizona     

砷、锑、铋在铜冶炼过程中的分布及其 在冶炼副产物中的回收综述

以铜冶炼过程中杂质元素砷、锑、铋为对象,通过对比分析实际生产数据,初步理清了砷、锑、铋在铜冶炼过程中不同工艺及工序中的分布情况.结果表明,不同冶炼工艺中砷、锑、铋的分布情况有较大差异,赋存在铜精矿中的砷、锑、铋经过熔炼、吹练、电解精炼过程后,主要流向烟尘、炉渣、阳极泥及黑铜等副产品中.介绍了近年来从铜冶炼副产物中回收砷、锑、铋的主要方法、工艺流程、工艺参数以及取得的成果.      

Thermodynamic Modeling of Arsenic in Copper Smelting Processes

Published data on the activity coefficients of arsenic in liquid copper, matte and, slag have been reviewed, assessed, and used in the development of thermodynamic databases for solution models of melts. The databases were validated against the literature data on the equilibrium distribution of arsenic between the matte and the slag. The models and databases were used in investigating the effects of matte grade, slag chemistry, SO₂ partial pressure, arsenic loading, and temperature on the equilibrium distribution of arsenic between the melts and gas phase during copper smelting and converting. The results obtained show that the continuous smelting processes operates close to equilibrium between condensed phases with most arsenic reporting to the gas phase. A comparison of the batch and continuous converting processes showed a considerable difference with respect to the elimination of the arsenic from condensed phases. These results indicate batch processes to be more efficient in the removal of arsenic through the gas stream.     

Activities of As,Sb, Bi,and Pb in copper mattes—impurity elimination

The theoretical possibilities for the elimination of As, Sb, Bi, and Pb from copper matte were evaluated on the basis of the activity behavior of these impurity elements in the matte, considering removal by purge gas blowing, chlorination, vacuum evaporation, and slagging. The calculations were made assuming equilibrium conditions between the prevailing phases and using different combinations of sulfur, oxygen, and chlorine potentials. Present evaluations show that (1) As can be evaporated from the matte, using moderate amounts of purge gas at a high sulfur pressure of about 10⁻² atm (1013.3 Pa) and a temperature of 1200°C (1473. 15 K); (2) Sb, Bi, and Pb can also be eliminated under similar conditions using a chloridizing purge gas; (3) the purge gas, consumption can be decreased by lowering the total pressure of the system; (4) on a thermodynamic basis, the vacuum evaporation rates of these impurity elements should be much higher from the matte than from copper, the actual differences not, however, having been so apparent in previously published experimental studies, due possibly to kinetic reasons; and (5) the distribution coefficients of As and Sb between slag and matte increase along with the sulfur pressure, although not sufficiently to utilize this phenomenon on an industrial scale. A. ROINE, formerly with Institution of Process Metallurgy, Helsinki University of Technology, SF-02150, ESPOO, Finland     

Activities of As,Sb, Bi,and Pb in copper mattes— Effect of O,Ni, and Co

The effects of oxygen, nickel, and cobalt on the activity coefficients of As, Sb, Bi, and Pb in copper mattes were measured at 1200 °C (1473.15 K) using the transportation method. The transportation experiments concerning the effect of oxygen were carried out as a function of the SO₂ content (1 to 100 vol pct) in the carrier gas and using high- and low-grade matte samples, ≈80 and ≈40 wt pct Cu, respectively. The prevailing sulfur and oxygen partial pressures were evaluated on the basis of matte and carrier gas compositions. The effect of the SO₂ pressure on the activity coefficients was found to be very small compared with the effect of the sulfur pressure, whereas the effect of the SO₂ partial pressure on the vaporization behavior, especially of As, was very significant, due to the additional vaporization of As as AsO gas molecules, which caused an increase in the As removal rate. At a higher oxygen partial pressure than 10^−8.5 atm (3.2·10⁻⁴ Pa) a noticeable decrease in the Sb activity coefficients was observed due to the oxidation. This did not, however, decrease the Sb removal rate, since the relative proportion of the oxide gas molecules in the gas phase increased simultaneously. The interactions between dissolved Ni or Co and the impurity elements were investigated by doping (1 wt pct) the high grade (Cu ≈75 wt pct) matte samples with Ni or Co. At stoichiometric and sulfur-deficient matte compositions, Ni and especially Co decreased the activity coefficients of As and Sb, but did not have any effect on the activity coefficients of Bi and Pb, compared with the corresponding sulfur content in the Ni- and Co-free mattes. For mattes of higher sulfur content Ni and Co did not show any marked effect on the activity coefficients of As, Sb, Bi, and Pb. A. ROINE, formerly with Institution of Process Metallurgy, Helsinki University of Technology, SF-02150, ESPOO, Finland     

Antimony activities in copper mattes

A mass spectrometric technique combined with a double Knudsen cell was used to determine the antimony and copper activities in the Cu-Sb binary system at 1373 K and in the two-melt composition range of the Cu−S−Sb ternary system at 1423 K. The antimony and copper activities were calculated based on the intensity ration of the gaseous Sb and Cu species, over the unknown and known activity samples, respectively. γ _Sb ^o were found to be 1.1×10⁻² in molten copper at 1373 K, and 1.8×10⁻² and 0.44 in a copper-rich phase and in a matter phase, of the Cu−S−Sb ternary system at 1423 K, respectively. These values indicate, that antimony can be removed during the matte smelting and slagging stage of the copper smelting process. Interaction parameters of antimony in molten copper slagging stage of the copper smelting process. Interaction parameters of antimony in molten copper at 1423 K were calculated and found to be 10.7, −5.4, and 6.3 for ε _Sb ^Sb · ρ_Sb ^Sb, and ε _Sb ^S , respectively. M. HINO, formerly Visiting Scientist at the University of Toronto     

Phase equilibrium and minor-element distribution between Ni3S2-FeS matte and calcium ferrite slag under high partial pressures of SO2

Calcium ferrite slag has been successfully used in the copper smelting process, but no attempt has been made to use it in the nickel smelting process. The phase equilibrium and the distribution of minor elements between the Ni₃S₂-FeS matte and the CaO-FeO_x-based slag (containing about 2 wt pct MgO) in a magnesia crucible were investigated at 1523 K under controlled partial pressures of S₂, O₂, and SO₂ of 10.1, 50.7, and 101.3 kPa, respectively. The results were compared with those for the iron-silicate-based slag, and the following conclusions were obtained: (1) there is no significant difference in the solubility of nickel between both slags in the high-matte-grade range, (2) the dissolution of cobalt in the calcium ferrite slag is clearly smaller than that in the iron silicate slag, (3) detrimental arsenic, antimony, and bismuth are preferentially collected and fixed in the calcium ferrite slag rather than in the iron silicate slag, and (4) it is considered, with regard to technical feasibility, that the use of the calcium ferrite slag in a converting process of the Bessemer matte will have a prominent future for the nickel converting stage.     

Entrainment behavior of copper and copper matte in copper smelting operations

In copper smelting, the loss of copper to the slag due to entrainment is largely influenced by the flotation of copper metal and/or matte in the slag phase. To evaluate this behavior, the surface tension of copper as a function of temperature and oxygen pressure and the interfacial tension of the copper-iron matte-slag system as a function of matte grade were measured. From the surface and interfacial tension values, the spreading and flotation coefficients of the copper, matte, and slag system were calculated. Ternary interfacial energy diagrams were also con-structed using these data. It is shown that matte droplets containing higher than 32 mass pct Cu will not form a film on rising gas bubbles when they collide in the slag phase. However, matte droplets will attach to gas bubbles upon collision and thus can be floated over the entire range of matte composition. Spreading of copper on bubbles is not possible at oxygen pressures between 10⁻¹² and 10⁻⁸ atm. Flotation of copper by gas bubble in slag is possible at oxygen pressure higher than 10⁻⁹ atm. However, it is feasible for rising matte droplets (attached to rising bubble) to trap and float copper irrespective of the matte grade.     

Equilibria between silica-saturated iron silicate slags and molten Cu-As,Cu-Sb,and Cu-Bi Alloys

The solubilities of copper, arsenic, antimony, and bismuth in silica-saturated iron silicate slag, equilibrated with molten copper which included the corresponding element, were measured at temperatures 1473 and 1523 K under oxygen pressures ranging from 10⁻¹ to 10⁻⁷ atm. The results confirm that copper is dissolved as CuO^0.5 in silica-saturated fayalite slag. Dissolution of As, Sb, and Bi was found to be dependent upon the oxygen potential, suggesting oxidic rather than atomic dissolution. The data obtained also support models in which these elements exist in the slag mainly as two different types of oxides, but occasionally these oxides coexist with neutral atoms. Based on these models, equations were obtained that related the solubilities of these elements in the slags to the oxygen potential in them. The knowledge obtained in this investigation will be helpful in eliminating deleterious minor elements in copper smelting.     

Measurement of pH in the vicinity of a cathode during the chloride electrowinning of nickel

An antimony microelectrode was prepared by quenching a molten Sb-Sb₂O₃ mixture (2 pct Sb₂O₃). The local pH in the vicinity of a nickel-plated copper cathode was directly measured using the microelectrode during the chloride electrowinning of nickel for a MCLE (matte chlorine leach electrowinning) process, where nickel metal is electrodeposited with a high current efficiency, 94 to 97 pct, from low-pH baths. The local pH at 328 K was increased by proton consumption during the electrolysis of aqueous electrolytes containing NiCl₂ (1.20 mol dm⁻³) and NaCl (0.43 mol dm⁻³) with the same concentrations as employed for the MCLE process. The difference in pH between the cathode surface and bulk solution increased with increasing cathodic current density. Nickel deposits with a metallic luster were obtained when the difference was not more than 1.2 pH units. The current efficiency was a maximum for electrolysis with a current density of 265 A m⁻² and bulk pH of 1.0 to 1.5; these optimal conditions coincided with those reported for the MCLE process: temperature 328 to 333 K, bulk pH 1.1 to 1.5, and current density 230 to 260 A m⁻². Electrolytes with lower NiCl₂ and NaCl concentrations resulted in a drop in current efficiency.     

Arsenic activities in molten copper and copper sulfide melts

In recent years, the concentration of the group Va elements such as arsenic, antimony, and bismuth has been increasing in copper concentrates. The elimination and recovery of these elements during the copper smelting process have presented serious problems. While the distribution of minor elements has been studied extensively, very little knowledge exists on the activities of these minor elements in copper mattes. Consequently, in this study the activities of arsenic were measured to determine activity coefficients of arsenic in the dilute solution region of molten copper, in Cu₂S saturated copper, and in copper mattes equilibrated with copper at 1423 K by a mass spectrometric Knudsen effusion technique. Formerly with the Department of Metallurgy and Materials Science, University of Toronto, Toronto, ON, Canada     

Pressure leaching of copper arsenic-containing mattes with copper sulfate solutions

The topicality is shown to improve the processing technology of complex polymetallic raw material containing a considerable amount of toxic impurities of arsenic and lead. Results on pressure leaching the mattes formed after reduction smelting the dusts of OAO Sredneural’skii Copper Smeltery (SUMZ) by solutions of copper sulfate are discussed. These mattes contain a considerable amount of lead and arsenic. According to the data of X-ray phase analysis of matte samples, phases of sulfides (PbS, PbS ? As₂S₃, Cu₂S, FeS, and (Zn,Fe)S) and arsenides (FeAs₂, Cu₃As, FeAs, and Cu_0.85As_0.15), as well as inclusions of metallic copper, are revealed in them. Optimal parameters of matte leaching by copper sulfate solutions are the temperature of 150–180°C, acidity from 5 to 30 g/dm³, and copper concentration of 14–32 g/dm³. This process made it possible to extract 85% As into the solution, while copper and lead remained in the cake in this case.