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By D. E. Woolley

The rate of reduction of iron oxide from calcia-silica-alumina slag by carbon in liquid iron has been measured over the temperature range 1400-1600°C by monitoring the rate of carbon monoxide (CO) evolution. Slags containing ferric iron have been used in order to study the reduction of both ferric and ferrous cations. Results show that ferric iron is reduced before ferrous iron, so that the ferrous iron concentration increases initially. It is also shown that the rate constant, k, decreases at low reaction rates, or, equivalently, at low concentrations. The authors conclude that the reaction occurs in two periods. During the first period, ferric iron is reduced to ferrous iron. During the second period, ferrous iron is reduced to metallic iron, and the rate-limiting step during the second period is the mass transfer of ferrous cations in the slag phase to the slag-metal interface.

Jan 1, 1998

By P .. R. Ammann

A two-stage pyrometallurgical process has been developed for the recovery of copper (and other non-ferrous metals) from copper smelter slags. All types of slags, including highly oxidized, converter-type slags, are cleaned in an electric furnace which employs mechanical mixers to promote magnetite reduction and copper extraction at high rates. In a 10-ton pilot furnace, it has been demonstrated that slags can be cleaned to 0.2-0.3 per cent copper with economically acceptable usage of raw materials and energy; copper is recovered as a high-grade matte. Pilot plant data have been scaled up to a commercial furnace and engineering designs have been made for a furnace to treat 60 tons per hour of slag from a Noranda Reactor and the associated converters. Plans are being formulated for the construction of a prototype slag cleaning furnace.

Jan 1, 1976

By Lamar S. Todd

The direct production of metal from a sphalerite concentrate is an attractive route for primary zinc. A series of operations and conditions have been selected to efficiently cause the following overall exothermic reaction. The process uses a continuous circulation of molten copper for material and energy transfer between the unit operations. Sulfide concentrate is reduced with an excess of superheated copper to make a copper alloy and white metal. The alloy is stripped of volatile metals under vacuum and some metals can be separately condensed. The residual copper and the white metal are fed into a copper converter to be blown with oxygen for desulfurizing and the superheated copper is recycled. The paper will include a detailed material flow sheet for the process, discussion of the operating conditions of the individual units, behavior of minor elements, and zinc quality.

Jan 1, 1999

By Florian Kongoli

Non-ferrous smelting slags .can contain magnesia, which substantially increases the liquidus temperature. One option to counter this increase is to flux with calcia. In this work, experimental liquidus measurements including new measurements on industrial slags have been compared with a FACT-based thermodynamic model, which predicts the liquidus surface of multi-component iron silicate smelting slags containing both magnesia and calcia. The predictions, which agree well with experimental results, are summarized in both isothermal and non-isothermal diagrams to give a quantitative description of the liquidus surface.

Jan 1, 1998

By Kuniaki Murase

Cadmium telluride (CdTe) semiconductor has been well investigated as a CdS/CdTe heterojunction solar cell material since its band gap is suitable for energy conversion from sunlight into electricity. In this paper a new electrochemical processing of thin-layered CdTe using basic aqueous electrolytes is reviewed from the standpoint of thermodynamics using a potential-pH diagram. The cathodic electrodeposition of the stoichiometric CdTe with a flat surface morphology took place at more positive potentials than that of the Nernst potential for the bulk-Cd deposition and at more negative potentials than that for the hulk-To. In this potential region deviation from the stoichiometric composition of eleetrodeposited CdTe was controllable by the Cd(II)/Te(IV) concentration ratio, pH, or concentration of complexing agent for Cd2+ ions of the electrolytes, The deposition behaviors for ammoniacal media were well accounted for by the potential-pH diagram of the Cd-Te-NH3-H2O system devised by a combination of those of the Cd-NH3-H20 and the Te-H2O systems, Diagrams for other complexing agents, ethylenediamine and diethylenetriamine, were also constructed to investigate and discuss the electrodeposition conditions regarding the corresponding media.

Jan 1, 2003

By Kenneth S. Coley, Michael Pomeroy, Elaine Chen

Recent work on modeling of BOF steelmaking is reviewed, highlighting the critical aspects of each approach. It is concluded that the most successful models should be based on a deep understanding of the mechanisms and kinetics of the critical reactions. The importance of the decarburization mechanism is discussed with particular reference to its role in droplet swelling or bloating which has a profound influence on the droplet residence time in the slag. Conditions which cause bloating are discussed and the rate determining step is proposed to be primarily nucleation of CO bubbles inside the metal droplet with some influence from growth by reaction at the bubble/metal interface. The discrepancy in the super-saturation ratio required for classical nucleation is discussed and an approach using a surface tension modifying parameter is illustrated. Finally, the role of CO nucleation in controlling the driving force for dephosphorization is discussed.

Jan 1, 2014

By A. Dutta, B. Devulapalli, A. Mukhopadhyay, E. W. Grald

"Computational Fluid Dynamics (CFO) has matured over the past two decades as an analysis tool for conducting virtual experiments with significant time and cost savings. It complements and reduces physical testing. CFO has penetrated the diverse materials industry in much the same way as Computer Aided Design (CAD) did more than a decade ago. As the basic numerical algorithms used in CFO have steadily improved, so have the reliability, consistency and user-friendliness improved significantly, too. Other recent trends have also contributed to the rapid growth and widespread adoption of CFO. In this presentation, CFO applications from several materials processing industries will be presented using case studies. Emphasis will be on metals, glass and semiconductor applications.IntroductionThe term materials processing covers a diverse array of industrial applications and products today. From the continuous casting of steel, to the deposition of semiconductor materials atom by atom, to the extrusion of molten polymers, materials processing applications span an incredible range of length scale, process times, pressures, temperatures and velocities. The properties of the materials themselves, in terms of density, viscosity, thermal conductivity, etc., can be complex functions of temperature, shear rate, chemical composition and time. And the processing equipment may be very complicated in geometric shape.Computational fluid dynamics (CFD), the technique of solving the governing equations of fluid motion and other related phenomena using a computer, has enjoyed widespread and rapid growth, which started in the aerospace and automotive industries. More recently, CFD has also been successfully applied to a great many materials processing problems, in spite of the challenges described in the previous paragraph. The reasons for the growing usage of CFD in materials processing are many. Using CFD to test design options and reduce the number of physical prototypes can decrease the time and cost associated with new product and process development. CFD gives insight and provides detailed predictions of operating conditions in lieu of difficult, intrusive and often expensive experimental methods. CFD can be used as an aid to scale-up processes from lab or pilot scale to full production. Troubleshooting the performance of existing equipment is often carried out with the help of CFD. Determining how an existing piece of process equipment will operate under new conditions, or with new input ,materials, is also a common task for CFD."

Jan 1, 2004

By A. S. Rao

In the original roast-leach-electrowin (RLE) circuit at the Chambishi Cobalt Plant, commissioned in 1978, the separation of nickel and zinc from cobalt in aqueous streams was achieved by successive stages of precipitation using lime. However, this technique was not able to meet the increasingly stringent metal quality requirements of customers whilst maintaining acceptable process recoveries. Intensive process development work was carried out and, in July 1988, an ion exchange circuit for nickel removal was commissioned using DOW XFS 4195 resin and for the first time Z.C.C.M. produced high purity cobalt metal containing less than 0.10% nickel. Following further work, a solvent extraction circuit for zinc removal, using DZEHPA, was commissioned in February 1991 in order to enhance cobalt recovery by reducing co-precipitated cobalt losses. This paper outlines the process development, design, commissioning and subsequent operation of these nickel ion exchange and zinc solvent extraction circuits.

Jan 1, 1993

By Richard W. Lawrence

Leaching of copper from sulfide minerals using biooxidation offers a potential route for copper recovery. Oxidation of . sulfide sulfur can proceed either; to sulfate or to elemental sulfur depending on mineralogy and process conditions. The advances in commercial application of biooxidation for sulfidic gold ores has made available operating and cost data which allow the derivation of conceptual costs for copper ore processing for comparison with conventional processing routes. Although costs for copper biooxidation generally remain high relative to conventional smelting, application might be competitive in specific cases. Biooxidation becomes more competitive in the general case if the cost ofS02 emissions in pyrometallurgical processing were to be internalized to a greater degree than currently required. This paper describes the technical aspects of biological processing of copper sulfide ores and concentrates, specifically with respect to the fate of sulfur. The environmental and economic implications of the biooxidation route are discussed in relation to conventional processing.

Jan 1, 1996

By E. T. White

The population balance is one of the basic relations for a:n:aIysing particulate minera1 processing operations. It is an exact relation. The principles of the population balance are reviewed and applications in the minerals industry discussed.

Jan 1, 1996

By G. Haesebroek

In L969 Metallurgie Hoboken-Overpelt started an industrial plant for the separation of iron and zinc from a concentrated CoCL2 solution. Iron and zinc are extracted in column contactors by a solvent containing 12 vol % of tertiary amines in xylene. The extracted metals are stripped from the pregnant organic phase by precipitation with a NaOH solution at pH LL. In this paper an overview is given of the industrial process. In order to overcome some drawbacks of this process (low flash point of the diluent, reagent consumption, batchwise stripping) an alternative solvent extraction process has been examined. In this alternative process, iron and zinc are extracted with an or¬ganic phase containing 50 vol % of TBP in Escaid 110. The pregnant solvent is stripped with water in conventional mixer settlers. Despite the ability of this process to overcome most of the inconveniences due to the use of tertiary amines, it suffers from the poor stability of TBP in concentrated chloride solutions, resulting in unavoidable and inacceptable precipitation phenomena in the stripping section.

Jan 1, 1988

By M. Moinpour, E. Liao, C. Y. Aw, D. J. Brown, P. W. Cheung

"Currently, silicon-based insulated-gate field-effect devices are being widely developed as the basic structural elements in a new generation of chemical microsensors. In this paper, we discuss some of the process considerations related to the fabrication of the Chemically Sensitive Field-Effect Transistor (CHEMFET). This ion-sensitive CHEMFET (or ISFET as it is often called) can be used for pH measurements (i.e., as a pH sensor) when the gate insulator of the electrolyte/insulator interface is made of Si3N4 obtained by the LPCVD method. Effects of processing parameters such as the Si3N4 deposition rate, gas composition, total flow rate, annealing treatment, etc. on Si/Si02, Si/Si3N4 and Si/Si02/Si3N4 structures are discussed in relation to the CHEMFET fabrication. Their effects on the electrical characteristics and chemical response of the sensor are also examined. Capacitance-Voltage (C-V) measurements and ESCA analysis have been used to interpret the results. The Si3N4/Si02 double dialectric layer provides improved ion blocking for the gate insulator in electrolyte solutions with enhanced pH sensitivity over time. The stability and performance of the fabricated CHEMFET sensors were tested by measuring the pH sensitivity in various storage conditions. The SEM analysis was used to evaluate the hydration effect at the ISFET's gate insulator with respect to different storage conditions.IntroductionThere has been a continuous interest in the development and fabrication of various chemical microsensors for chemical and biomedical applications over the last fifteen years. The application of semiconductor (particularly silicon) technology to the area of sensor fabrication has led to an emergence of a new generation of miniaturized, microelectronic, solid-state chemical sensors. There are numerous clinical situations where continuous monitoring of body electrolytes concentrations such as Na+, K+, Ca+2 , etc. and blood gases (pH, Po2 , and PC02) would be essential for the effective diagnosis and management of patients under critical conditions. Solid- state microsensors can be used for direct and continuous in vivo measurement of the above parameters in most instances."

Jan 1, 1988

By L. J. Lutz

The U.S. Bureau of Mines has developed an electrorefining process to recover Ni, Co, Cr, and other metals from mixed and contaminated superalloy scrap. The superalloy scrap is cleaned then directly electrodeposited as a Ni -Co deposit. The process recovers approximately 90 pct of the Ni-Co available from the scrap as a 99t pct pure Ni-Co alloy. During electrorefining the electrolyte undergoes a purification process which results in Cr and other refractory metals reporting to the purification residue. Operating data is given for a 3-L compartmented electrolytic cell. Techniques for the removal of Fe, Cr, and trace impurities from the recycled electrolyte are outlined. The economics of a facility producing 15 mt/d of a Ni-Co alloy are also discussed.

Jan 1, 1993

By A. A. Bustos

A model was developed to simulate the blow-by-blow operation of the converting process. From the weights, compositions and temperatures of all converter feeds the model calculates the composition and tonnage of both converter matte and slag as well as bath temperature at the end of each blow. The development of the model and its application to the converter aisle operation are described. There is good agreement between model predictions and observed results. At the present time the model is being used to investigate different converting schemes and their effect on pay metal recoveries, slag chemistry and temperature of the bath. Future work involves the use of the simulation model as a process control tool for the converting operation.

Jan 1, 1988

By K A. Pericieous

"Magnetic fields have many actual applications in the metals processing industry. Externally applied magnetic fields give rise to electromagnetic (Lorentz) forces formed by the cross product JxB, between the induced current density J and the magnetic field density B. When the metal is in liquid form, the Lorentz force generates motion in the fluid which in applications of practical interest becomes turbulent. In modelling terms, the Lorentz force appears as a source in the momentum equations. In addition, the induced current generates heat (Joule heating) in the metal that is in proportion to J2, with a corresponding source of heat in the energy equation. Whether as heat or as a force, these effects represent action at a distance - a most useful attribute when dealing with hot metal. The Lorentz force is used to stir solidifying alloys, pump liquid metal in conduits, dampen the flow in the meniscus of a continuous caster, levitate metal drops, induce artificial gravity conditions in suspensions or contain liquid metal. Elsewhere, the Lorentz force may be a by-product of some other operation, so leading to wave excitation in aluminium electrolysis cells, or altering the shape of the weld pool in arc welding. Joule heating is most commonly used with applied AC fields, to melt metal in induction furnaces.The author and his colleagues have been involved in the modelling of most of these processes in the past decade. Modelling is not however straightforward, since most of the examples mentioned represent genuine multi-physics challenges. There is a strong coupling between the flow field and electromagnetic field. The addition of a dynamically varying metal free surface and the moving solidus front means the flow, heat and electromagnetic fields need to be computed simultaneously. In situations involving metal containment, the metal free surface position is governed by the interplay of gravity, Lorentz force, surface tension and fluid inertia. Since all the interesting effects often happen in thin boundary layers at the surface due to the skin effect, mesh generation and mesh control during the computation become non trivial problems that need to be addressed. This paper presents a review of numerical methods used to model droplet levitation, semi-levitation melting and cold crucible induction melting of metals. The first method is based on spectral collocation techniques and the second is the traditional FV approach. Steps taken to validate the computations and typical transient results are also given."

Jan 1, 2001

By S. M. I Kytö, J .. K. Mäkinen, K. Saarhelo

"At the Outokumpu Oy Harjavalta Copper Smelter the control philosophy of the flash smelting process has been changed from the slow feed-back control to feed-forward control. This is important as the fluctuations in the flash smelting furnace matte grade and slag temperature are desired to be minimized.The system is based on a specially designed automatic sampling device and the Outokumpu Courier 20 on-stream X-ray fluorescence analyzer. A microcomputer-based Analyzer Operator Station (AOP) controls the system and calculates the process parameters for the furnace from the analyzed chemical composition and other existing data.A considerable reduction in the deviation of the matte grade and slag temperature has been gained. This has resulted in conservation of energy and refractories, lower copper losses and higher through-put in the flash smelting furnace and converters.1.0 IntroductionThe flash smelting technology for copper concentrates was developed at the Outokumpu Oy Harjavalta Smelter soon after the World War II. The incentive for this development was shortness and high price of any form of energy. The fact that smelting can be carried out autogenously, without external energy by utilizing the latent heat of sulfide combustion was known decades before, but Outokumpu Oy was the first company to take the advantage of this knowledge in practical operation. A further advantage of this technology was that the SO2 containing gases suited well for sulfuric acid production, thus minimizing the detrimental effects on the environment (1).The very heart of the flash smelting process is the reaction shaft of the flash smelting furnace (see Appendix I). Heating up of the dried feed mixture, dissociation of several compounds, ignition and oxidation of the feed take place very intensively in the reaction shaft during 2 - 3 seconds, which the fine grained particles reside in the reaction shaft. A very accurate control of the amounts of the feed materials as well as of oxidizing gases, fuel, etc. is of primary importance."

Jan 1, 1989

By Nieves Iglesias

The removal of the refractoriness of a gold bearing pyrite- arsenopyrite ore is studied. Flotation concentrates were prepared and leached with a dilute acidic ferric sulfate solution. The elemental sulfur film which forms on arsenopyrite in the oxidation process is not responsible for the low rate of the arsenic dissolution observed. A positive effect on the leaching rate is observed when Ag' is added. This pretreatment eliminates the refractory nature of concentrates.

Jan 1, 1993

By Paul E. Queneau

The QS (Queneau-Schuhmann) copper converter is a gently sloped, stepped, horizontal kiln-type tilting reactor in which desired bath oxygen activity, compositional and temperature gradients are created by countercurrent flow of matte and slag phases through a series of controlled bubble plume, mixer-settler configurations. Flow of gas and slag is normally concurrent. Copper sulfide concentrates are top-fed, employing oxygen flash burners. Oxygen and oxygen-carbonaceous fuel mixtures are bottom-blown into the smelting bath through judiciously located, independently regulated submerged injectors. Composition and mass flow rates of injector inputs are controlled to produce bubble plumes of desired character, without jetting through and out of the bath. The mixer-settler pattern can be reinforced if desired by employment of suspended shallow baffles. State-of-the-art instrumentation provides timely information required to govern key process variables. The outstanding capabilities of the QS converter for coppermaking have now been indicated by the current success of industrial QSL (Queneau-Schuhmann-Lurgi) leadmaking reactors. Modified converter designs are employed for leadmaking, nickelmaking and steelmaking.

Jan 1, 1993

By Michael B. Mooiman, David J. Kinneberg, Philippe Cettou, Leo W. Simpson, Pierre Ramoni

"The demand for high purity precious metals began with certain industrial applications having uncompromising requirements for quality and performance. As industrial uses proliferated and as the jewelry industry became increasingly sophisticated, the demand for high purity gold has reached the point where 99.99% is now the standard in the marketplace. A similar evolution is expected for other precious metals.In this paper, we examine both the production and use of high purity precious metals, specifically gold, silver, platinum and palladium. After defining what is meant by ""high purity"", we discuss the various analytical techniques used for measuring impurity concentrations. Next, we review process strategies employed by extractive metallurgists to produce high purity precious metals. Lastly, we describe some of the principal applications for high purity materials including thick films, thin films, bonding wire, thermocouples and jewelry manufacture.Precious metals have unique physical properties that, despite their expense (and the ever-continuing search for more economical alternatives), make substitution difficult if not impossible. These physical properties are dramatically affected by small concentrations of certain impurities. As long as manufacturers continue to demand quality and performance, there will be a need for high purity precious metals.IntroductionIn the precious metals industry, the qualifier ""high purity"" describes any specification over and above commodity grade. High purity specifications delineate lower limits on overall metal purity or upper limits on individual impurities or both. Sometimes, if these special requirements become commonplace, either because of improved refining technology or because of market pressures, yesterday's ""high purity"" material becomes tomorrow's commodity. This transition is now occurring with gold bullion and probably will soon occur with platinum and palladium as industrial use of these materials grows."

Jan 1, 1998

By M. F. El-Demerdash

The activity distribution diagrams for different species in aqueous systems are developed. Computational method may be considered as an extension of the Activity-Term method introduced by the authors to construct EH-pH diagrams. In the Activity-Term method, all activities of different species are evaluated before deciding the most stable one. In the present study, a factor is assumed to allow for the conservation of the element. At any point, the total concentration of all species should contain only the input m moles of the element (elements) considered. This approach is applied to Zn-, 5-, and Zn-S-H2O and activity distribution diagrams are plotted as a function of pH, at different potential levels and at different temperatures.

Jan 1, 1990