A kinetic model for the oxidation of selenium and tellurium in an industrial kaldo furnace

A kinetic model for the oxidation of selenium and tellurium in the molten bath of an industrial Kaldo furnace during the refining step is presented in this article. During plant experiments, samples of the molten metal were collected hourly and chemically analyzed for selenium, tellurium, and silver. Selenium oxidized from the beginning of the refining step, whereas oxidation of tellurium only occurred until the Se/Te mass ratio decreased to a value of 0.55. Good agreement between the model predictions and the experimental data was obtained. For more information, contact Manuel Perez-Tello, Universidad de Sonora, Departamento de Ingeniería Química y Metalurgia, Hermosillo, Sonora, Mexico 83000; +52-662-259-2107; fax +52-662-259-2107; e-mail mperezt@iq.uson.mx.     

Minimization of Copper Losses in Copper Smelting Slag During Electric Furnace Treatment

In the quest to achieve the highest metal recovery during the smelting of copper concentrates, this study has evaluated the minimum level of soluble copper in iron-silicate slags. The experimental work was performed under slag-cleaning conditions for different levels of Fe in the matte and for a range of Fe/SiO₂ ratios in the slag. All experiments were carried out under conditions where three phases were present (copper?Cmatte?Cslag), which is the condition typically prevailing in many slag-cleaning electric furnaces. The %Fe in the electric furnace matte was varied between 0.5?wt.% and 11?wt.%, and two different Fe/SiO₂ ratios in the slag were used (targeted values were 1.4 and 1.6). All experiments were performed at 1200°C. From thermodynamic considerations, from industrial experience, and from the results obtained in this study, the minimum soluble copper content in the electric furnace slag is expected to be near 0.55?wt.% Cu. This level does not account for a portion of the copper present as mechanically entrained matte/metal droplets. Taking this into account, the current authors believe an overall copper level in discard slag between 0.7?wt.% and 0.8?wt.% can be obtained with optimal operating conditions. For these conditions, the copper losses in the slag are roughly 75% as dissolved copper and 25% as entrained matte and copper. Such conditions include operating the electric furnace at metallic copper saturation, maintaining the %Fe in the electric furnace matte between 6?wt.% and 9?wt.%, not exceeding a slag temperature of 1250°C, and controlling the Fe/SiO₂ ratio in the smelting furnace slag at ??1.5. In addition, magnetite reduction needs to be performed efficiently during the slag-cleaning cycle so as to maintain a total magnetite content of ??7?wt.% in the discard slag. The authors further consider that under exceptionally well-controlled conditions, a copper content in electric furnace discard slag between 0.55?wt.% and 0.7?wt.% can be obtained, by minimizing entrained matte and copper solubility in the discard slag.     

氧气底吹铜熔池熔炼过程的机理及产物的微观分析

对氧气底吹熔炼过程气体喷吹行为、造锍熔炼化学反应机理及熔炼炉内热工作状态进行理论分析及水模型实验和取样分析验证。结果表明,氧气底吹气流能使熔体形成均匀的扩散区,实现熔体的搅拌,在气体连续相区和液体连续相区,气液、液液之间的相互作用强烈,为炉内化学反应及传热传质提供了良好的动力学条件;氧气底吹熔炼过程在零配煤的情况下能达到自热熔炼,在节能减排方面,该工艺具有很强的优势;获得了铜渣、冰铜和蘑菇头中各组分的形貌,确定了铜渣、冰铜和蘑菇头的物相组成,渣样主要由冰铜相、磁铁矿相、铁橄榄石相和玻璃体相组成,熔炼内的氧势和硫势分布有利于反应的进行,能有效抑制Fe3O4的形成以及降低渣含铜。     

含钴铜转炉渣的工艺矿物学

研究了铜转炉渣的化学与矿物学特征,用光学显微镜查明了炉渣各主要渣相为铁橄榄石,磁铁矿和无定形玻璃体,铜主要以冰铜相裹夹于渣相中,铜滴的尺度与渣的冷却历史有关。用X射线衍射谱,扫描电子显微镜,X射线能谱和X射线波谱及化学物相分析,对铜和钴的赋存状态及在各相中的分布进行了表征和量化。结果表明,钴主要以类质同象形式取代铁橄榄石和磁铁矿晶格中部分Fe^2 ,作为氧化物富集其中,二者约占钴总量的95％,渣中钴的提取需要以铁橄榄石和磁铁矿的分解为前提,使钴的氧化的游离出来而酸溶。     

铜闪速炉沉淀池渣中锍液滴沉降机理及其影响因素

通过分析沉淀池内锍液滴的沉降机理,导出了渣中最大锍液滴直径的计算公式。根据闪速炉的实际生产条件,计算出渣中最大锍液滴直径的理论值为0.063 mm,并用矿相显微镜对沉淀池出口处的渣样进行了观察,渣中最大锍颗粒粒径为0.06 mm,两者结果一致。由此证明了沉降机理分析的正确性。在此基础上,进一步分析渣中锍夹带损失影响因素。结果表明:增大熔体中离散态分布的锍液滴直径是降低渣中铜夹带损失的重要措施;其次是升高渣温度有助于渣中锍的沉降;减小渣层厚度等措施对降低渣中铜夹带损失作用不大。     

Thermodynamic Consideration for Oxygen Pressure in a Copper Flash Smelting Furnace at Toyo Smelter

JOM - Based on the emf measurements of the galvanic cell (Fe, MgO/O in slag or matte) and the equilibrium calculations, the oxygen pressure in a copper flash smelting furnace at Toyo smelter is...     

Numerical analysis on fluid flow and heat transfer in the smelting furnace of mitsubishi process for Cu refining

To understand complex behavior in the smelting furnace of Mitsubishi continuous process for copper refining, comprehensive 3-D numerical simulation and field experiment were performed. The numerical simulation results showed that strong and complex velocity fields of gas, matte and slag were generated in the furnace and large amounts of matte and slag were splashed into the gas area. Temperature measurements at the lance during field operation revealed that wide range of temperature variation appeared depending on the injection condition of concentrates. Numerical simulation results provided good agreements with experiments results and showed that the chemical reaction induces temperature increase during gas injection period. On the other hand, lance temperature is decreasing because of cold concentrates during gas and particles injection period. From the FFT analysis results, the fluctuations of matte and slag volume fraction near the lance induce temperature fluctuations of the lance. Through these experimental and simulation results, it was revealed that the lances in the smelting furnace were exposed to severe conditions such as high temperature, repeated large temperature change and cyclic change of large temperature gradient across the thickness.     

基于数值模拟的闪速连续炼铜炉型结构研究

分析4种闪速连续炼铜炉型的本质特性,提出将闪速连续炼铜过程视为由相对独立的闪速造锍熔炼过程和连续吹炼造铜过程构成,分别建立闪速造锍熔炼多相平衡数学模型和连续吹炼造铜局域平衡数学模型,并通过中间物料的传递将两模型有机结合,从而构建完整的闪速连续炼铜过程热力学模型。运用此模型,考察炉型结构对闪速连续炼铜过程的粗铜生成条件、Fe3O4行为、铜在渣中损失以及铜直收率等因素的影响。结果表明：相对于其他3种炉型,甩渣吹炼双烟道D型炉是比较理想的连续炼铜炉体;对于闪速连续炼铜,造锍熔炼段和铜锍吹炼段宜在相对独立的分区进行,各自炉渣和烟气也应分开排出炉体。     

Thermodynamic Assessment of Slag–Matte–Metal Equilibria in the Cu-Fe-O-S-Si System

Equilibria among the slag, matte and metal phases in the Cu-Fe-O-S-Si system are critically assessed using thermodynamic modeling. The relationships among matte grade, temperature, partial pressure of SO₂, Fe/SiO₂ in the slag, and the copper concentration in the slag are described by the model, as well as the concentrations of other elements in all phases. A thermodynamic database is created, which can be used for understanding and improving the pyrometallurgical production of copper. An extensive experimental dataset includes the most recent results obtained by the equilibration/quenching/EPMA analysis technique. These data allow to distinguish the physical entrainment of the matte and solid phases in the slag from chemical solubility. As a result, it is possible to describe the copper solubility in the slag with high accuracy and establish the relationship between copper and sulfur in the slag. The thermodynamic database of the present study is consistent with previously reported thermodynamic evaluations of binary, ternary and quaternary subsystems. The slag phase is modeled using the two-sublattice modified quasichemical model in the quadruplet approximation. The matte and metal liquid phases are modeled as one solution using the single-sublattice modified quasichemical model in the pair approximation.     

Flash smelting copper concentrates

Flash smelting is a comparatively new method of smelting copper and nickel sulfide concentrates. It takes place when the concentrate, with or without additional fuel, is suspended in gases containing oxygen whereby the heat of oxidation reactions bring the suspended particles to a smelting temperature. From the suspended state the hot particles are separated and molten slag and matte are deposited on the furnace hearth.     

Chemical Degradation Mechanisms of Magnesia–Chromite Refractories in the Copper Smelting Furnace

Magnesia–chromite refractory has been extensively used in the copper-making industry. It is necessary to understand the degradation mechanisms of the current refractory to develop new refractories. In the present study, post mortem refractories from a smelting furnace were analyzed and compared with the results of static corrosion tests on magnesia–chromite refractories in the laboratory at high temperatures. The microstructure and phase composition were carefully investigated by electron probe x-ray microanalysis to understand the degradation mechanisms of the magnesia–chromite refractory in copper smelting conditions. The degradation mechanisms between the magnesia–chromite refractory and the copper smelting slag and CuO transformed from matte are discussed based on the analysis of the post mortem refractory samples and laboratory tests. These results will enable optimization of the industrial process and development of new refractories for copper smelting furnaces.     

Slag Characterization: A Necessary Tool for Modeling and Simulating Refractory Corrosion on a Pilot Scale

The slag in pyrometallurgical operations plays a major role affecting the life of furnace refractory. As such, comprehensive mineralogical and chemical slag examination, physical property determination including the slag melting point or liquidus, and viscosity are necessary for precise understanding of a slag. At the RHI Technology Center Leoben, Austria, the main objective of slag characterization work is to reach a better understanding of refractory corrosion. This corrosion testwork is performed at the laboratory and pilot scale. Typically, corrosion tests are performed in an induction furnace or rotary kiln, with the main purpose being the improved selection of the most suitable refractory products to improve refractory performance in operating metallurgical furnaces. This article focuses on characterization of samples of six non-ferrous, customer-provided slags. This includes slag from a copper Peirce-Smith converter, a short rotary furnace for lead smelting, a titania-processing furnace, and a Ni-Cu top blowing rotary converter (TBRC) plant.     

Direct Production of Copper

The use of commercially pure oxygen in flash smelting a typical chalcopyrite concentrate or a low grade comminuted matte directly to copper produces a large excess of heat. The heat balance is controlled by adjusting the calorific value of the solid feed. A portion of the sulfide material is roasted to produce a calcine which is blended with unroasted material, and the blend is then autogeneously smelted with oxygen and flux directly to copper. Either iron silicate or iron calcareous slags are produced, both being subject to a slag cleaning treatment. Practically all of the sulfur is contained in a continuous stream of SO₂ gas, most of which is strong enough for liquefaction. A particularly attractive feature of these technologies is that no radically new metallurgical equipment needs to be developed. The oxygen smelting can be carried out not only in the Inco type flash furnace but in other suitable smelters such as cyclone furnaces. Another major advantage stems from abolishion of the ever-troublesome converter aisle, which is replaced with continuous roasting of a fraction of the copper sulfide feed.     

Copper Anode Furnace: Chemical,Mineralogical and Thermo-Chemical Considerations of Refractory Wear Mechanisms

In copper anode furnaces, the installed refractory lining is exposed to chemical attack caused by slag and copper oxide. This results in infiltration of the brick microstructure and corrosion of the bricks’ inherent components. Increased temperature level changes the temperature and partial pressure during the furnace operation, as well as the copper infiltration into the brick microstructure, leading to further degeneration of the microstructure and decreased lining life. The mechanical load includes the erosion caused by primary movement of the metal bath, slag and charging material, as well as stresses in the brickwork due to improper lining procedures. Thus, chemical and mineralogical investigation carried out on “post-mortem samples”, together with thermochemical calculations by FactSage? software, enables better understanding of refractory wear in the copper anode furnace.     

Converting practices at the stillwater precious metals smelter

At the Stillwater Mining Company’s precious metals smelter in Columbus, Montana, flotation concentrates containing copper, nickel, and platinum-group metals are smelted in a submerged-arc electric furnace. The matte, containing 30% copper plus nickel, is granulated, dried, remelted in a top-blown rotary converter, and blown with oxygen to ”white metal” containing approximately 75% copper plus nickel and 2.5% precious metals. For the first month of converter operation (July 1990), conventional fluxing with quartz was practiced. An excessive number of slag foams and heavy accretion formation at the mouth of the converter led to a switch to lime fluxing as a replacement for silica. This resulted in eliminating slag foams and decreasing accretion build-up. It is believed that the Stillwater works is the only commercial smelter in the world following this practice.     

Kinetics of the reactions in the smelting furnace of the Mitsubishi process

In this paper, the authors present the results of theoretical calculations on the rates at which copper concentrate particles and silica particles dissolve in the matte in the smelting furnace of Mitsubishiprocess. Those calculations indicate that the concentrate particles dissolve rapidly in matte, in less than 1 ms, whereas silica particles dissolve at a much slower rate, and they dissolve mainly in the bulk matte in the smelting furnace. Some advantages of bath smelting over flash smelting are given. For more information, contact Zenjiro Asaki, Mitsubishi Materials Corporation, Central Research Institute, 1-297 Kitabukuro-cho, Omiya, Saimtama, 330-8508, Japan.     

闪速炉沉淀池中熔体流动特性的数值模拟(英文)

采用CFX4.3对闪速炉沉淀池中的熔体流动和温度分布进行数值模拟研究。针对1个出渣口对应1个冰铜出口(1-to-1)与1个出渣口对应2个冰铜出口(1-to-2)这两种操作方案共设立16种计算工况。模拟结果表明,两种方案下熔体流动相似,但采用1-to-2操作方案时,熔池中可见明显的回流。仿真中还发现,渣口与冰铜出口的不同组合方式对沉淀池中熔体温度分布的影响显著,其中在1-to-2操作方案下,沉淀池中的熔体温度更均匀。在实际生产中,当采用远离沉淀池入口的放铜口进行操作时将更有利于实现沉淀池内熔体温度的均匀分布。     

Extending the life of water-cooled copper cooling fingers for furnace refractories

To extend the service life of refractory linings in high-temperature furnaces, it is becoming common to embed copper cooling devices in the lining. These devices extract enough heat from the hearth of the furnace to freeze a protective thin layer of slag onto the surface of the lining. However, the cooling devices may lose their efficiency over time. It is believed that high-temperature oxidation of copper is responsible for the loss in heat-extraction capacity. To test coolers under severe conditions, immersion tests were carried out in molten matte and slag of laboratory-scale cooling elements protected by various means. A composite cooler was developed that consists of a copper core shielded by a Cu-4 wt.% Al alloy sheet. Although the rate of heat extraction is not as high as that of the un-alloyed copper, this cooler still extracts heat at a very high rate. For more information, contact Gabriel Plascencia, CIITEC-IPN, Cerrada Cecati s/n, C.P. 02250, Mexico, D.F.; e-mail g.plascencia@utoronto.ca.     

铅鼓风炉中铜、硫、砷和锑对银分布的影响(英文)

研究铅鼓风炉中杂质对银分布的影响。将含有不同Cu、S、As和Sb含量的铅烧结块在管式炉中于1573K下进行烧结,然后随炉冷却。烧结气氛为还原性的CO+CO2气体(p(CO)/p(CO2)=2.45)。采用SEM-EDS对所得样品进行表征。结果表明:烧结样品中含有5种不互溶的相,即炉渣(CaO,FeO,SiO2)、冰铜(S,Cu,Fe)、硬渣(As,Fe,Cu)、Cu-Sb相和铅块。银在Cu与Sb形成的熔体中的溶解度比在液态铅中的高。S与Cu形成冰铜,As与Cu形成硬渣。S和As能减少Cu-Sb合金的生成量,从而降低铅块中银的损失。     

EFFECTS OF TEMPERATURE ON DISTRIBUTION BEHAVIORS OF MINOR ELEMENTS IN COPPER FLASH SMELTING──COMPUTER SIMULATION

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