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By Oleg I. Platonov

Method of high-temperature reduction of oxygen-bearing sulfurous gas has been developed at Copper Plant (CP) of MMC ?Norilsk Nickel? Trans-Polar Division (PD) with the aim of producing elemental sulfur from Vanyukov furnace? off-gas. Non-explosive reduction technology of oxygen-bearing sulfurous gas by methane utilized at Copper Plant has been designed to separate the processes of gas heating and sulfur dioxide reduction based on different kinetic of the reactions oxygen fixing and SO2 reduction. First, natural gas promptly reacts with oxygen contained in the process gas to heat a gas mixture up to the temperature of sulfur dioxide reduction (1200C). Then isothermal reduction takes place within 1 sec. Combustion chamber (pre-chamber) design developed based on the above principles is presented. Practical experience of the two reduction reactors operation at CP since 1996 proves high efficiency of the developed reduction process. The volume efficiency rises dramatically thanks to the fact that both fuel and reducing agent are fed into the reactor volume in the form of high-speed turbulent jets providing an intensive mixing of the reacting gases. On condition of equal internal volume of the reactors, the developed process offers higher efficiency of reagent interaction resulting in sulfur conversion exceeding 90%, as compared to the equilibrium one.

Jan 1, 2006

By Ramiro Escudero

Michoacan?s beach sands with interesting concentrations of ilmenite were studied to produce titanium by hydrometallurgical techniques. Nevertheless, among titanium species, there are different additional components of Michoacan?s beach sands which could be of interesting applications. Some of them are likely to be applied for the manufacture of nanocrystalline ceramics. Although, the most applied mineral dressing to treat these kind of sands, that contain magnetic species (i.e., ilmenite, magnetite), is a combination of gravity separation and magnetic separation, it could be of a great deal of benefit to apply the information regarding the surface characteristics of the sands? components, in order to study the application of flotation technologies to separate selectively those species with commercial value.

Jan 1, 2006

By Sylvie C. Bouffard

The need for a better understanding of the heap biooxidation pretreatment of pyritic refractory gold ores has prompted us to develop a rigorous mathematical model of the process. The hydrological structure of the model takes the form of lateral stagnant pores in contact with a uniformly distributed gas stream and connected to vertical plug flow channels, as suggested by the results of an independent study of column hydrology. A model of pyrite oxidation kinetics was derived based on electrochemical leaching theory and the results of potentiostatic stirred tank and column tests. The growth rates of attached and planktonic iron- and sulfur-oxidizing cells are modeled with separate Monod expressions over three separate temperature ranges corresponding to mesophiles, moderate thermophiles, and extreme thermophiles. Isothermal column tests validate the model simulations. Excellent fits of several leaching indicators (potential, extent of sulfide oxidation, iron concentration, cell numbers) reveal the rate-limiting step to shift from particle kinetics to oxygen gas/liquid mass transfer with increasing temperatures and pyrite head grades. Competition for oxygen between sulfur- and iron-oxidizing microorganisms lowers potentials and slows down pyrite oxidation. This modeling tool may assist engineers in the design and operation of heaps to give more complete gold liberation in a shorter time.

Jan 1, 2003

By Roberto Parra

The wear and corrosion phenomena in the furnace lining of the ferrous and non ferrous pyrometallurgical processes are complex problems where chemical, interfacial and mechanical phenomena are presents. The characteristics of the processes determine the conditions to which these materials are submitted, where the thermal conditions reached during the operation is one of the most important parameter. Assuming that all the degradation phenomena are thermal activated, the rate of the different steps of the wear mechanism will depend on the thermal field in the lining. In view to apply the independent physicochemical knowledge of degradation mechanisms to the analysis and design of furnace lining the methodology of the Nodal Wear Model (NWM) was done. It combines the mathematical modelling of the heat transfer in the lining with the physicochemical control equation for the wear-corrosion phenomena. The NWM has been applied to different examples: theoretical analysis, laboratory scale test and industrial applications. We present in this paper the theoretical background of the model and two examples of applications: the sole of an electric furnace and the earth of a blast furnace.

Jan 1, 2006

The increasing need for robust pyrometallurgical furnace construction is driven by two trends in the copper and other base metals smelting industry: ? the desire for increased production within a single furnace line by greatly increasing smelting intensities, which generates high heat fluxes to the crucible. walls, and ? the operational and economic imperatives of maintaining high percentage on- line times and long campaign lives between rebuilds. A key feature of furnaces capable of producing at high rates, while containing intense processes, is a strong, thermally robust wall cooling system. Equally important design aspects include the furnace steel structure, refractories, a cooling water supply and piping arrangment for safety from leaks and disruptions, and instrumentation/controls for monitoring and rapid mitigation of process excursions. Integration of the cooling elements into these furnace systems is essential for optimum performance of the cooling elements, and indeed the entire furnace. This paper discusses the development of a composite copper / refractory water- cooled design, which has been successfully implemented on several copper smelting and converting furnaces, including Kennecott's flash converting furnace, INCO's MK reactor, and Kidd Creek's converting furnace.

Jan 1, 1999

By Andreas Nolte

In 1999 HÜTTENWERKE KAYSER AG (HK) in Germany will produce more than 180,000 t/y of electrolytic refined copper. To achieve this production from materials with copper grades from two to seventy percent and diverse copper alloys, HK operates three blast furnaces, one holding furnace two Peirce Smith converters and two anode furnaces. Technical, metallurgical and economic factors for the ongoing process optimization are outlined. The fluctuating quality and quantity of raw materials renders complex this optimization. The principal variables are the quality and quantity of process consumables: coke, copper-iron, limestone, oxygen, as well as the blending of feedstock and a new organization of the operating crews. The search for new metallurgical process parameters is ongoing. HK started with an intensive research programm in November 1997. As a result it will be possible to cut processing costs by about ten per cent, to increase the blast furnace capacity by ten per cent and to lower the metallurgical losses of copper and tin in the slag by more than ten percent. The presentation concludes with information on future steps to continue the optimization process.

Jan 1, 1999

By Howard K. Worner

Several features of smelting and refining operations make them appropriate technology to adapt to the processing of "wastes" not only from the minerals Industry itself, but for wastes in general. These features include significantly higher temperatures than are achieved in conventional Incinerators and also good thermal stability derived from the mass of molten metal and slag in the furnace. This paper expands on Information contributed to the Mervyn Willis Symposium in July 1992 and includes knowledge generated in the last two years of waste processing R&D in a sealed 100kg capacity DC arc furnace specially constructed for the "Environment" process being developed in Wollongong. As one product of-the process is a foundry-type iron, the feed always contained ferruginous dusts or heavily contaminated scrap. For the dusts, sewage sludge has been used as a binder and also as a proportion of the fuel-reductant. To achieve the necessary bath carburisation, It is beneficial to add other lower reactivity carbons such as "kish' graphite, carbon from electrode butts, dusts from coke ovens, carbon from aluminium pot line residues, dry cell batteries etc. Metallurgical factors involved In process control, Including metal and slag, compositions, are discussed.

Jan 1, 1994

By Sesha S. Srinivasan

Mechanochemical synthesis has been employed to prepare new light weight complex borohydrides, Zn(BH4)2. The thermal calorimetric and gravimetric analysis of these complex borohydrides shows the hydrogen decomposition temperature (Tdec) of about 100° C with theoretical capacity of ~8.0 wt%. This advanced materials based technology is considered to be suitable for attaining the US-DOE grand challenge technical targets. The powder x-ray diffraction analysis of the mechanically milled Zn(BH4)2 exhibits the presence of zinc borate and NaCl phase. The FTIR spectra of BH4-ion in NaBH4 has a characteristic band at 2290 cm-1,whereas in Zn(BH4)2, it occurs at ~2061 cm-1 (bridging B-H bonds) and ~2451 cm-1 (terminal B-H bonds) as well. The reversibility of hydrogen decomposition and recombination process is carried out by PCT measurements with multi-cycling procedure.

Jan 1, 2006

By Kwan Soo Han

A thermodynamic model for predicting the distribution coefficients has been developed by taking into account the extraction mech-.ism and the chloride complexation when Sm, Eu, Gd, Tb, Dy and Ho for single component systems are extracted from acidic chloride solutions by di-2-ethylhexyl phosphoric acid and 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester in kerosene, respectively. The model equation includes two constants, of which one corresponds to the apparent extraction equilibrium constant and the other is due to the variation of the activity coefficients of organic species. These values are determined from a few experimental data by the curve fitting method Then, the distribution coefficients under untried conditions have been predicted from only the initial data by iterative calculations. Bromley's formulation is used to estimate the activity coefficients of aqueous species and the interaction parameters for some rare earth chlorides are reported in terms of molality and molarity using data from Spedding et al. The validity of this method has been confirmed by excellent agreement between the experimental and the predicted distribution coefficients.

Jan 1, 1989

By Guozhu Ye, Eric’ Burstrom

"Despite of numerous solutions for recovery of zinc from EAF dust have been suggested and tested in laboratory scale over the last three decades, Waelz kiln process is still the most dominating process for treatment of EAF dust. Few of the proposed alternative methods have gone beyond the laboratory tests. This paper will give you insights to some of the concepts that have been pilot tested at MEFOS. The innovative aspects of these concepts will be shown and the major results will be highlighted. These include the following concepts: - Production of a crude zinc oxide product with low halide content for zinc electrowinning using a DC furnace with hollow electrode- Production of a bypass filter dust containing more than 50%ZnO by injection of EAF dust to the electric arc furnace during refining combined with a bypass filter system- Elimination of zinc ferrite by CaO treatment for electrowinning with EZINEX process - Selective reduction of iron oxide in zinc ferrite for simultaneous recovery of ZnO andmetallic ironIntroductionRecovery of zinc from EAF dust is dominated by the Waelz process since EAF dust has been classified as hazardous waste by EPA in the early 1980´s. A large number of alternative processes have been suggested and tested without commercial success due to two major reasons [1]:- High content of chlorine and fluorine for the pyrometallurgical alternatives- High content of ZnOFe2O3 for the hydrometallurgical processesMany innovative concepts for treatment of EAF dust for zinc recovery have been pilot tested at MEFOS in the past 20 years. This paper will review some of the concepts focusing on the two problems mentioned above."

Jan 1, 2008

By Anita E. Lam

The thiosulfate leaching of gold generally requires the presence of a catalyst such as cupric tetraammine, Cu(NH3)42+, to obtain reasonable leaching rates and gold extractions. Unfortunately, this same catalyst that accelerates gold leaching also tends to accelerate thiosulfate oxidation to tetrathionate and other species. It is therefore imperative that a detailed understanding of the role of this catalyst and the factors affecting it is obtained. It is equally important for plant application that a method of assessing the catalyst be developed. In this work the role of the cupric tetraammine catalyst was studied using geochemical modeling for speciation prediction, thiosulfate leaching of gold ores, and chemical analyses of resulting leach solutions. It was found that the variables of pH, temperature, and the concentrations of ammonia, thiosulfate, and total copper all work in concert to affect the concentration of the cupric tetraammine species. It was also found that the presence of sufficient thiosulfate and cupric tetraammine was critical to the success of the leach.

Jan 1, 2003

By Steven E. Follin

In-situ leaching is commonly used to recover uranium from low-grade deposits in sandstone formations. Acceptable recovery rates can only be obtained if the formation retains its permeability during leaching. Field experiences indicate that microbial growth, stimulated by the leaching pro- cess, can cause plugging problems. To investigate this hypothesis, leach solution and solid samples from well casings and submersible pumps were obtained from four in-situ mining sites. Chemical and microbiological analyses were performed. Bacillus species, Micrococcus species, pseudomonads, and xanthomonads were isolated from these samples. A mixed culture of these organisms was inoculated into a uranium core that was being leached in the laboratory. The permeability of this ore sample decreased to one-third its original value after 16 days. The addition of hydrogen peroxide (0.2 g L-1) to the leach solution killed the microbes and restored the permeability to its original value. This suggests that periodic injection of hydrogen peroxide into production wells may reduce microbial plugging in these wells and the immediate surrounding formation.

Jan 1, 1985

By Sheng-hai Yang

The electrochemical synthesis was conducted in anhydrous ethanol solvent mixed with conductive reagent when tantalum plate was used as anode and stainless steel plate as cathode. The effects of different conductive reagents (such as NH4Br, (CH3)4NCl, (C4H9)4NCl), conductive reagent concentration and the space on the cell voltage and the current density were investigated. The current efficiency of electrosynthesis was more than 95%. The electrolyte, a mixed solution was then undergone air distillation and vacuum distillation to get the final product which was characterized by Fourier Transform Infrared(FTIR) spectroscopy, Raman spectra, 1H-Neclear Magnetic Resonance(1H-NMR) spectroscopy. Carbon and hydrogen contents in the product were determined by elemental analysis instrument. Results consistently show that the product was tantalum penta-ethoxide.

Jan 1, 2006

By D. C. Cupertino

Oxime based solvent extraction provides the user with a selective concentration process for copper prior to electrowinning. The selectivity required is largely for copper(II) over iron(III) and this is achieved by the preferential formation of the square planar copper-oxime complex in the organic phase. The copper/iron selectivity of oximes can however, be altered by modifiers or other types of oximes and may be enhanced in the presence of certain esters. Whilst the oxime based SX processes is important for operations leaching copper from laterite ores, the high selectivity will also be significant in processing streams arising from other leaching regimes which are currently under development, for example leaching of sulfide mineral ores. This paper presents some initial results using Molecular Modelling techniques to further our understanding of the nature of the copper/iron-oxime complexation processes together with some plant studies undertaken at a number of different mine sites investigating selectivity, and other properties, for some modified reagents. Some studies of the interfacial properties of the these systems are reported to explain in part the practical observations.

Jan 1, 1999

Environmental and public concerns and the banned use of cyanide for the recovery of gold in some parts of the world have heightened the search for an alternative lixiviant to cyanide. Thiosulfate appears to be the most promising alternative to cyanide due to thiosulfate being non-toxic, relatively cheap compared to cyanide and generally gold recoveries are similar to those of cyanide. The most widely researched thiosulfate process is one where copper ions and ammonia are added to the solution. This paper reviews the leaching of gold in thiosulfate solutions and the contributions of the research at Monash University to the understanding of the gold oxidation reaction in thiosulfate solutions, the solution chemistry when copper ions, ammonia and oxygen are present, the influence of the changing solution chemistry on the gold leach kinetics, and the application of thiosulfate in the leaching of gold from ores. It is clearly shown that the gold oxidation rate is hindered in thiosulfate solutions. In the presence of copper ions the gold oxidation rate though is significantly enhanced and thus is why copper(II) is more effective than other oxidants in the thiosulfate leach system. The copper-ammonia-thiosulfate leach solution chemistry is shown to be very complex, especially in the presence of oxygen as the rate of thiosulfate oxidation increases and the majority of the copper ions are not maintained in the copper(II) oxidation state. The thiosulfate oxidation rate must also be maintained low as an intermediate thiosulfate oxidation product hinders gold leaching. In optimising the recovery of gold from ores with copper-ammonia-thiosulfate leach solutions it is important to evaluate and minimise any negative effect an ore may have on the leach solution chemistry and hence gold leaching.

Jan 1, 2003

By C. K. Gupta

Electrometallurgical processes have a definite place in the extraction technology of rare earth metals and alloys. Some of the advantages of the molten-salt electrometallurgical processes include fast electrode reaction, providing accurately controlled large amount of energy to a relatively small reactor volume, negligible over voltage, simplicity of operation, and possibility of accomplishing continuous or semicontinuoue operations. This paper provides a vivid account of the theoretical and practical aspects of electrometallurgical processes for the production and processing of some of the rare earth metals and alloys. Reference has been drawn to the work reported on electrometallurgical processes as applied to the preparation of lanthanum, cerium and misch metal from author's laboratory.

Jan 1, 1992

By Katsunori Okaya, Gjergj Dodbiba, Hiroyuki Ono, Toyohisa Fujita, Seiji Matsuo

"In an attempt to raise the copper grade of Printed Circuit board (PCB) by removing other components, carbonization treatment was investigated. The crushed PCB without surface-mounted parts was carbonized under nitrogen atmosphere. After screening, the char was classified by size into oversized pieces, undersized pieces and powder. The copper foil and glass fiber pieces were liberated and collected in undersized fraction. The liberation of copper foil from the oversized pieces was also investigated. The copper foil was liberated easily from glass fiber by stamping treatment. Liberation rate of copper foil was high at high carbonized temperature. The experimental results indicated that 90% of oversized char was liberated and the copper foil recovery from PCB carbonized at 1073K was 110kg/t. The copper recovery from char powder by flotation was also investigated. 15% of the copper grade and 80 % of the copper recovery were obtained, whereas the removal rate of silicon was 55%.IntroductionWaste Electrical and Electronic Equipments (WEEEs) should be recycled because they have many kinds of valuable materials and most WEEEs include Printed Circuit Boards (PCBs). In Japan, about 30 km2 per year of Printed Circuit board (PCB) has been produced [1], PCBs are normally separated from WEEEs and picked up by hand and sold to non-ferrous metal market because PCBs include high grade of copper and other precious metal such as gold, silver and palladium [2]. However, PCB also has impurities such as silicon, aluminum and calcium which are slag materials in non-ferrous smelting process, and other harmful elements such as lead, bromine and antimony. Low grade PCBs are sold after removal of invaluable parts or sometimes land filled without any treatment"

Jan 1, 2011

By Yong Hack Lee

Electric Arc Furnace (EAF) dust is generated when scraps are treated in the electric arc furnace and usually classified as hazardous industrial waste in most countries. EAF dust usually contains 15 to 25% of zinc and 3% of lead. It is usually treated in rotary kiln (Waelz process) or landfilled after a solidification and stabilization treatment. Numerous methods have been proposed as the EAF dust treatment technology, but few of them are in operation as a commercial scale except the Waelz process. Korea Zinc performed a plant test in which 600 tons of EAF dust was treated using TSL (Top Submerged Lance) technology. The TSL technology is a low cost, proven technology for processing zinc-bearing residues. The EAF dust was first de-chlorinated and fed to the TSL furnace. Finally, clean slag satisfying toxicity criteria was generated and valuable metals such as zinc and lead were recovered as fume oxide. The fume oxide was de-halogenated by sodium carbonate and sent to zinc refinery to recover zinc and lead. The recovery of zinc and lead was 90% and 93%, respectively. Most of the dioxin in the EAF dust was discomposed so dioxin less than the Korean regulation limit was detected in the offgas, which proves that the TSL technology is the best solution to treat EAF dust.

Jan 1, 2006

By W. Gong

Their outstanding thermal stability and high energy product make Sm(Co,Fe,Cu,Zr),-type alloys attractive for advanced applications. The near net-shape production of Sm(Co,Fe,Cu,Zr), bonded magnets make them potentially superior to any magnets made by sintering. Although pioneering work done by Shimoda et al. and other investigators provide insights on the proper compositions and process control of this alloy system, additional work is still necessary to improve our understanding of alloy behavior at various processing stages and to increase the production yield during powder processing. In this paper we report on the development of anisotropic Sm(Co,Fe,Cu,Zr), alloy powders for the bonded magnet application. Our focus is on the development of a moderate coercivity powder requiring a relatively low magnetizing field to charge the magnets to their optimum Br, Hci and BHmax. The magnetic properties are related to the evolution of the microstructure at various processing stages and the average particle size and size distribution of powders.

Jan 1, 1997

By Varadajan Seshadri

Torpedo cars have been extensively used for pig iron desulfurization although its geometry is not considered to be ideal as far as mixing and mass transfer are concerned. Complications arise from scaffolds formed through aggregation of flux, slag and pig iron during operation. Following industry demand a 1:6 torpedo car physical model was operated to assess the optimum refining conditions for pig iron desulfurization. Similarity between the model and prototype were established through Froude and turbulent Reynolds criteria. Mixing times were evaluated by pulse tracer addition and the kinetics of metal/slag interactions were assessed from experiments investigating iodine transfer from kerosene to water. The influence of parameters such as level of metal, gas flow rate, lance penetration, lance orientation, presence of scaffold were evaluated. Mixing times were found to be shorter than regular desulfurization time and also not very sensitive to scaffold presence. Scaffold contributes to the reduction of the useful volume only. Mass transfer at the permanent reactor is more effective when the torpedo is operated at its full capacity. The experiments also highlight the dominance of the transitory reactor as compared with the permanent reactor.

Jan 1, 2006