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By Francis Vanbellen

Umicore Precious Metals Refining operates an integrated precious metals smelting and refining plant in Hoboken, Belgium. Once a smelter and refiner of complex concentrates, the plant today?s feed consists exclusively of industrial and consumer recycled products, making it the world?s largest recycling facility for precious metals. Unlike the fairy tale of the Frog Prince, it took much more than a princess? kiss to successfully realize this makeover. A completely renewed plant has been built over the past decade.

Jan 1, 2006

By John Nauman

Liquid ferrous silicates that are related to cop- per slags have been studied as media for the transfer of heat in pyrometallurgical processes. The effective thermal diffusivities have been measured from 1025Oto 1400°C, and values in the range of 0.004 to 0.007 cm2/ sec have been obtained. The heat-transfer characteristics of these slags have been determined by measuring the rise of temperature of a cold nickel sphere immersed in the liquid slag. The sphere is spun about its vertical axis to obtain a well characterized flow of liquid about the sphere. The principal barrier to the transfer of heat from the bulk slag to the metal sphere is a solid shell of slag that forms around the sphere and subsequently melts. It appears that the detailed nature of this shell is important to theheat- transfer process. A mathematical model is used to predict the rate of heating of the sphere, and to evaluate various aspects of the system that can influence the transfer of heat.

Jan 1, 1976

By Nils Eivind Kamfjord, Mari K. Næss, Gabriella M. Tranell

"In oxidative ladle refining (OLR) of silicon, the metal surface is oxidized resulting in the formation of a condensed silica fume (SiO2). In the current work, industrial measurement campaigns were performed aiming to measure the fume generation during OLR. A thorough discussion of the possible mechanisms has been included in order to improve our understanding of the Si(1)-O2(g) system.The measurement campaigns were performed at the Elkem Salten plant in Norway. In addition to fume generation from OLR, the metal temperatures and ladle purge gas amount were recorded. The results of this work suggest that fume generation during OLR results from splashing of the metal and/or oxidation of the metal surface, with oxygen transport to the metal surface being the limiting factor. Other mechanisms of SiO2 formation were investigated, however insignificant.IntroductionOne of the main environmental and economical challenges facing the metallurgical industry is fugitive emissions of both materials and energy. In the production of metallurgical grade silicon (MG-Si), refining of the silicon generally takes place through an oxidative ladle treatment (purging with an air-O2 mixture). In the refining process, exposure of silicon to air results in the formation of condensed silica fumes (SiO2) – one of the main sources of fugitive emissions in silicon production plants. The oxidation of liquid silicon, as opposed to solid silicon, has not been widely studied and described in the literature [1], thus a thorough investigation of the oxidation mechanisms, and factors affecting the oxidation reaction rate are essential in order to deal with the problem. In the current work, the rate of liquid silicon oxidation has been studied through industrial measurements of fume generation from refining adles, where the purge gas rate and composition have been varied. The results from these measurements were discussed in light of existing models describing the liquid silicon oxidation kinetics."

Jan 1, 2011

By J. P. R. deVilliers

A procedure is described whereby gold-containing calcined concentrates and leach residues from refractory gold ores are smelted with carbon to form a small amount of metal. The gold is liberated upon smelting, and is collected in the molten metallic phase, which is easily separable from the slag. The metallic phase consists of approximately 1 to 15 per cent (by mass) of the material after smelting, and the gold content is generally upgraded by a factor of greater than 6 compared with that of the original roasted material. Recoveries better than 95% have routinely been achieved. The quenched metal contains predominant Fe-Ni alloy, as well as minor Fe sulphides and Cu-Fe sulphides. Trace amounts of Fe-Ni arsenide and Au-Cu alloy are also present. The gold content of the metallic phase can be increased further by oxidation of the hot metal in the presence of silica or slag. This will reduce the amount of metal, and will concentrate the gold in a smaller volume. The metallic phase can then be treated hydrometallurgically to recover the nickel and the gold.

Jan 1, 1989

By Y. C. Avniel, T. E. Warner

"It is important to be able to measure sulphur and nitrogen in molten iron and steel on-line. Unfortunately, there are no solid electrolytes which are stable under oxidising conditions and in which the ions of these species are mobile. In this paper, novel applications of beta alumina electrolytes are described and the results compared with data in the literature. Excellent agreement was obtained confirming this approach as a viable method of detecting elements whose ions are not mobile in solid electrolytes.IntroductionIn the past two decades, the rate of many processes in steelmaking have increased substantially. The sophistication of chemical analysis has also increased but analytical equipment is frequently positioned a significant distance from the operating plant which dictates that time is spent taking a sample, sending it to the analytical facility, preparation of the analytical sample prior to insertion into the equipment. In many cases, the time taken for analysis can exceed the time taken for the actual process and is now the rate defining step. Furthermore, most analytical methods are unable to distinguish between the amount of element which is dissolved in the steel and that contained in precipitates. Even if the analytical equipment could separate these two, the distribution would have changed between the molten steel and the cast sample. It would be an advantage to analyse on-line for impurities in molten metals."

Jan 1, 1997

By Ma Ying

The continuous directional solidification technique of five kinds of special ZA alloys with eutectic, peritectic and eutectoid transformation under the condition of continuous casting by heated mold was studied. The mechanism of surface defects appearing in ZA alloy line was discussed and the structure of some defects were analyzed by SEM. The results show that only when the fitting of various technique factors, pressure head, outlet temperature, pulling speed and cooling condition are reasonable under a certain range, can the ZA alloy smooth line be continuously pulled out. Unreasonable techniques will result in hot tear, rough surface, mush outlet, leaking and other defects. The shape and location of solid-liquid zone have an important influence on the formation of the above defects. When the solid-liquid zone is located in the mould outlet or inner mould, the surface of solidification will protrude into the inner mould. If the remaining liquid cannot counteract the solidification contraction, a rough surface will appear. If the solidification surface further into the mould, the ingot in the mould will have a great friction force when pulling and will form a hot tear. When the solid-liquid zone is moved out of mould, the solidification surface will turn into a plane, which easily results in leaking. A vibration or unstable operation will cause an ingot winding during pulling

Jan 1, 2003

By Kazuya Kitatani, Gen Sasaki, Naoto Ohta, Hideharu Fukunaga, Makoto Yoshida, Jin Pan, Kenya Nagahisa, Toshihiro Ishikawa

"A sintered SiC (Tyranno-SA) fiber-reinforced MAS glass matrix composite was fabricated by using a slurry infiltration method and hot-pressing. The microstructure and mechanical properties were investigated: To prepare the preform, the MAS glass slurry including a dispersing agent was infiltrated into a bundle of the fibers. The preform was then hot-pressed under the conditions of 1473 K, 30 MPa, 3.6 ksec. A unidirectionally-reinforced oxide matrix composite with 50% Vf. of the fiber and a density of 2.84 g/cm3 was obtained. As the mechanical properties at room temperature, the three-point flexural strength- and quasi-static adsorbed energy were 500 MPa arid 6,000 J/m2, respectively. Without graphite or an h-BN pre-coating on the surface of the fiber, pull-out and bridging of the fibers from the matrix was found, and this leads to a high value of the adsorbed energy. By TEM observation, nano-scale crystalline products were found between the fibers and the glass matrix. The push-out test reveals that this layer causes the appropriate debonding of the interface during the fracture process of the composite.Introduction It is known that the CFCCs (continuous-fiber-reinforced ceramic matrix composites) are characterized by their non-linear fracture behavior, which is' hardly found in monolithic ceramic materials. It is inevitable for the CFCCs to exhibit a large fracture toughness so 'that debonding of the fiber/matrix interface; pull-out and bridging of the fibers then' occurs during the fracture process. This series of fracture behavior is known as the so-called ""the mechanism of toughening of the CFCCs"". Thus, different from the MMCs in which strong interfacial bonding is necessary, the interfacial strength of the CFCCs has to be controlled. As techniques for controlling the interfacial strength, it is also known that both a CVD-graphite coating and an h-BN coating are effective to induce the mechanism of toughening[1,2]. In the case, of the Si-C-O or Si-Ti-C-O fibers/glass or crystalline oxide matrix composites, it is reported that the formation of the in-situ graphite layer, which is also effective to increase the fracture toughness of the CFCCs, is often found during the fabrication process such as hot-pressing. The lower the crystallinity of the Si-C-O fibers, the higher is the tendency to form the in-situ graphite layer as found by the chemical reaction between the fibers and the glass matrices[3-12]. On the-other hand crystallized stoichiometric 'SiC fibers are attractive for high temperature service because of the higher phase stability compared to the Si¬C-O or Si-Ti-C-O fibers. However, in the previous, studies, the mechanical properties and the interfacial chemical reaction of the crystallized SiC fibers / glass matrix Composites have still been unknown. In this study, a polycrystalline 'sintered SiC fiber-reinforced MAS glass composite was fabricated. The mechanical properties and microstructure were then investigated. The slurry infiltration technique followed by hot-pressing was used to prepare the composites. The formation of the in-situ graphite layer and the relationship between microstructure and mechanical properties at room temperature were examined by the TEM observation of the fiber/matrix interface."

Jan 1, 2000

By A. V. Tarasov, V. M. Paretsky

"Based on theoretical and experimental studies into the specific features of the mechanism, kinetics, aerodynamics and heat transfer parameters of the flame-type oxidation of metal sulfides in a stream of technical-grade oxygen, a three-dimensional deterministic mathematical model of an oxygen-flame smelting furnace has been developed on the basis of the zonal method for computation of heat exchange. The model is presented in the form of equations taking into consideration the radiation component of the selective radiation, the convection component of mass transfer between the space and surface zones, heating of charge particles due to heat conductivity, accretions formation on a multi-layer refractory lining with inserted cooling elements. The adaptation of the model for a full-scale furnace has demonstrated the possibility for its use for computation of main smelting process parameters. Multifactor model investigations were conducted and the results obtained were applied using statistical methods for development of a simplified computational regression model describing the interrelation of the main output parameters: temperatures of flame, lining, slag and off-gas; heat fluxes to the lining; thickness of accretions; heat removed by cooling elements; copper content of matte. On the basis of this model, a block diagram of the algorithm was developed for control of the thermal conditions of the furnace, as well as the control algorithm itself.IntroductionThis paper presents the results of an integrated modeling and development of principles for control of copper smelting process using as an example the oxygen-flame smelting process (KFP) for treatment of sulfide concentrates at the Kovoguty Krompahy copper smelter (Slovakia) with a capacity of 20,000 tpy of copper."

Jan 1, 2001

By A. Lackner

Using the CFD software package FIRE, the smelting process inside a cyclone reactor is modelled. The fluid flow is calculated 3 dim., using different turbulence models. The effects of design parameters (length and diameter of the cyclone, concentrate feeding tangentially or from the top,..) and operating conditions are investigated. Single particle traces illustrate how to increase particle retention time before the particles reach the liquid film flowing down the cyclone wall. Moreover a two phase flow approach is developed, based on the "Discrete Droplet Model". The position, velocity, diameter and temperature of each reacting particle is described. The results show the advantages of top concentrate feeding, large height/width ratio of the tuyeres and increasing number of tangentially gas inlets.

Jan 1, 1995

By Laihua Wang, Peter Hayes, Hae-Geon Lee

"This paper introduces a new process for the efficient removal of dissolved gases and inclusions from liquid metals. This process involves the creation and dispersion of fine bubbles in molten metals by introducing inert or reactive gas into a region of turbulent flow. The highly turbulent metal flow splits the gas into fine bubbles and results in good mixing between the gas and molten metal phases. These conditions are ideal for contacting inclusions in the metal with the bubbles and subsequent flotation of the inclusions to the metal-slag interface where the inclusions are then absorbed by the covering slag layer. Dissolved gases, such as [H], [0], [N] in the metals are also transferred to the gas bubbles and removed from solution.The process concept has been previously demonstrated using a full-scale air/water model to simulate the ladle-to-tundish system of continuous casting of steel. The present cold modelling work has further demonstrated the ability of the process to remove gas solutes. The results indicate that the efficiency of new process is several hundred times greater than that of conventional high speed rotating injectors which are currently applied in the treatment of liquid light metals.IntroductionDuring metal smelting, refining and alloying processes, unwanted gas and second phase liquid or solid impurities are incorporated into liquid metals. In the case of steelmaking, the gas-forming impurities include [0], [H] and [N], and the solid impurities as a result of deoxidation include Ah03, Si02 inclusions. Common impurities in liquid aluminium are dissolved hydrogen and solid Ah03. To avoid subsequent problems during processing and to improve the physical properties of the metal products it is necessary to significantly reduce the level of impurities."

Jan 1, 1996

By B. Q. Li, S. P. Song

"This paper describes an on-going research on developing coupled boundary element and finite element algorithms for the solution of thermal and electrodynamic problems relating to materials processing. The coupled methods are uniquely suitable for field problems involving composite regions, in which detailed information on field distributions within one particular region is of more interest and yet the solution can be obtained only if the effects of other regions are all considered. Problems of this type include heat transfer in multiple regions and also magnetic induction involving an infinite boundary. The hybrid boundary and finite element formulation, algorithm development and the applications are discussed. Two examples are given to demonstrate the capability and accuracy of the coupled algorithm for heat transfer problems. Various treatments of corner discontinuity are discussed. It is found that the double flux treatment is an ideal choice amongst those tested as it is easy to implement and also gives the most accurate solution. 1. INTRODUCTIONElectrodynamic and transport problems occur frequently in materials processing systems. Accurate solution of these problems is of great importance not only for our fundamental understanding of physical principles governing these phenomena in the processing systems but also for optimization of the existing processes as well as development of new processes. For this purpose, many numerical algorithms have been developed. These computational schemes in general can be classified into three categories, that is, the finite element and finite difference schemes and the boundary element scheme. The former two are domain based numerical algorithms while the latter the boundary-based algorithm.The finite element method, which is based on the variational calculus, is a very useful and yet popular engineering numerical method for boundary value problems defined over irregular boundaries. The use of the method requires the discretization of the entire domain. It can be applied to solve both linear and nonlinear problems, but is particularly powerful for nonlinear problems that involve the field variables defined within the computational domain. On the other hand, the boundary element method, with its root in the Green's function method, is very efficient for linear boundary value problems or nonlinear problems that involve field variables only along the boundaries. The primary advantage of the boundary element method lies in the fact that only the boundaries of the computational domain need to be discretized, and hence the dimension of the problem is reduced by one, compared with the finite element method."

Jan 1, 1994

By V. M. Sokolov, Jr. DuPlessis

The technology for recycling fine wastes, grinding sludges or swarf, and solids such as slag that contain a high content of metallic material needed improving. The objective was to produce a master alloy that met the tight requirements of the Western manufacturers and achieve improved yields of the valuable elements, nickel and cobalt, to over 90%. The alloys from the production of Alnico. magnets were chosen for this work. A process is proposed .that is able to recycle all kinds of Alnico wastes. This process is able to reduce all detrimental elements, which are contained in the wastes, to within acceptable levels. Molybdenum, if present, is an exception. Depending on the levels of contamination of undesirable elements different recycling strategies are proposed. The majority of the wastes can be recycled by melting and refining with a liquid slag layer using unique melting furnaces that are relatively unknown in Western nations. The proposed technologies allow the reelamation of over 95% of the cobalt and nickel from any kind of Alnico waste, and there are no limitations on the proportion of different kinds of wastes in the charge. The proposed processes and technologies could also be applied to the recycling of grindings, turnin

Jan 1, 2000

By Guo Xueyi

The electrochemical couple behavior of manganese dioxide with ferrous/ferric ions in acidic chloride medium was investigated, It was proven that the dissolution of Mn01 is due to the electrochemical couple reaction between MnO2/Mn2+ and Fe2+/lFe3+ in the solution, The driving force for the process originates from the rest potential difference of the two couples. The reduction of Mn02 is controlled by clectrochemical kinetics, whereas the conversion of F e2+ to Fe3+ is limited by diffusion, The factors such as the Mn2+, Fe2+, Fe3+, Cl concentration, pH of the solution and the temperature, have much influence on the kinetics of the couple process, This study will be useful to elucidate the mechanism for the leaching of manganese nodule from the deep ocean as well as manganese dioxide ores in land,

Jan 1, 2003

By Oszkar Bíró, Peter Mittag, Bernhard Aigner, Stefan Pirkeri, Philipp Glttleri

"This paper considers CFD modeling of processing and melting of small metallic particles by means of electrical heating. The particles fall continuously onto a liquid metal bath which is heated by an electric arc. After melting of the particles liquid metal is tapped.The charging behavior of the particles in the supply unit as well as in the reactor freeboard is studied by means of Euler-Euler granular simulations. The flow situation in the metal bath due to gas injection and magnetic fields is calculated by combining Navier-Stokes and Maxwell solvers. The macroscopic melting process occurring during the continuous charging of the particles is studied by kinetic laws for melting reactions. The temperature field is evaluated by balancing heat sources due to Joule's heating and heat losses due to latent heat of melting as well as convection and radiation.As a result of these simulations the fully three-dimensional flow fields of particles and gas in the atmosphere is obtained. Furthermore the flow field as well as the magnetic field in the metal bath can be studied. As a main result the three-dimensional concentration field of the still unsolved particles in the liquid metal can be evaluated.IntroductionIn this paper a metallurgical process for melting small iron particles is investigated by means of CFD-simulations. In a first process step the preheated and already mostly reduced iron particles fall continuously into the reactor through a vertical tube mounted at the lid of the furnace. In a second step the particles are melted in the liquid metal bath. Meanwhile the melt is heated by electric arcs to provide the heat needed for melting the incoming particles.In Figure I a sketch of the geometry setup considered in this paper is provided. The particles fall from a height of approximately 12 meters onto the bath surface in the center of the furnace. The melt is heated by electric arcs that are placed symmetrically around the center axis."

Jan 1, 2001

By James P. Bennett

The successful reuse/recycling of refractory materials after removal from industrial service is limited because of contamination, the low value of spent materials, the low cost of virgin raw materials, the lack of driving forces such as regulations or taxes, and low disposal costs. Most spent refractory is disposed in landfills. Concerns over future liability for waste materials, corporate images, and IS0 14000 have helped to encourage recycling at some companies. The recycling practices and application for spent refractory materials at facilities successfully recycling used refractory materials will be discussed, with emphasis on similarities.

Jan 1, 2002

By Mark Jolly

"Over the last ten years or so many man hours have been dedicated to developing methods for simulating shape casting processes. The majority of the methods developed have been devised by a combination of computer, mathematics and materials specialists often with limited knowledge of foundries and foundrymen. As a result of this it would appear that although there are many software packages for the foundryman to use there still exist fundamental misunderstandings as to their usefulness and suitability within the foundry.The paper aims to identify how well current software packages perform. The relationships between physical phenomena, practical defects and software capabilities are presented. Some discussion of the use of criteria functions is also presented. Finally issues arising from the postprocessing of results are discussed as the presentation of the results to the lay-person in simulation techniques is possibly one of the most important aspects in influencing the adoption of this type of software in the foundry community."

Jan 1, 1999

By Gerardo Muñoz

All along this century CODELCO's smelters have been operating on conventional technology, which Codelco has streamlined by using oxygen, developing oxy-fuel burners for reverberatory furnaces and introducing oxygen smelting of concentrates in converters (Teniente Converters). Chuquicamata began capturing sulfur from its first Teniente Converter in 1985. Since then, it has implemented a program allowing to gradually increase such capture. In 1994 a Frame Law on the Environment was enacted in Chile. By virtue thereof and of CODELCO's corporate environmental policy, an investment program aimed at capturing more than 95% of gaseous pollutants in all its smelters in a term not exceeding twelve years was established. The above entails a substantial improvement of the operational management as regards fugitive gases capture and treatment. This paper describes the way CODELCO is to deal with this challenge with a view to fully complying with environmental regulations and obtaining the required environmental certifications of its operations.

Jan 1, 1996

By M. J. Adam

As part of its research programs, the Bureau of Mines is investigating the partitioning of complex sulfide minerals to simpler sulfide phases by sulfidation reactions. Partitioning in this manner can afford opportunity to improve selective extraction of mineral constituents of value. This report describes research involving the sulfidation partitioning of the mineral pentlandite, which is an important source of Ni in primary production. For the laboratory studies, the pentlandite was synthesized in nominally equiatomic proportions of Ni and Fe. Elemental Ni, Fe, and S powders were blended, compacted, and sealed under reduced He pressure in vitreous silica tubes. The tubes were heated under controlled conditions at SOD? C for 24 h. The product was verified by X-ray diffraction and chemical analysis to consist essentially of (Ni,Fe)9S8. Small samples of the (Ni,Fe) S were encapsulated with sulfur in silica tubes at reduced He pressures and heated for 1 to 24 h at specific temperatures between 400? and 600? C, both below and above the boiling point of sulfur (_445° Cl. Reaction rate increased with temperature. Within this temperature range, partitioning to individual Ni and Fe disu1fides proceeded to essential completion according to the reaction

Jan 1, 1988

By João M. S. Rodrigues

The use of sandblasting as a treatment method for conditioning anodes for zinc electro-winning was investigated and compared with conventional fluoride preconditioning. The anodes were made from two different lead-based alloys (Pb-Ag-Ca and Pb-Ag). Laboratory results showed that sandblasting and preconditioning both minimize lead contamination in the zinc and sludge generation. Sandblasting was found to have no aggravating effect on the anode corrosion. The sandblasting treatment was tested on Pb- Ag-Ca anodes on an industrial scale in the celJhouse of a local zinc producer. An unexpected finding of the large-scale tests was that the sandblasting appeared to strengthen the anodes, resulting in reduced warping during handling and operation.

Jan 1, 1996

By D. Tahija

The Getchell Mine produces gold from a geologically complex ore bearing high concentrations of arsenic and carbonate minerals. The mill treats the ore using high temperature aqueous oxidation in autoclaves, followed by conventional carbon-in-leach gold recovery. We laboratory tested a variety of Getchell ores to determine the effects on gold recovery of conventional factors such as grind size and retention time, as well as the influence of factors such as ore variability and preliminary carbonate destruction. Because the mill is currently operating, we were able to directly compare certain laboratory predictions with operational results.

Jan 1, 1999