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By Chr. Kersch

This project further develops supercritlcal fluid extraction as an industrial soil remediation process. Heavy metals are removed from sand using CO2, The effect of the type of complexing ligands, pressure and water content on the extraction efficiency is investigated.

Jan 1, 1999

By Carlos Antonio da Silva

Steel refining reactors based on chemical heating are being used as an alternative to ladle furnaces. They show a high degree of flexibility in respect to heating rate in addition to carrying out refining reactions such as de-S, inclusion removal, alloying etc. IR-UT and CAS-DB are examples of such reactors. Their performance is dependent upon geometrical characteristics as well as operational conditions which determine the flow field inside the vessel. A physical model of the IR-UT process of the Companhia Siderurgica de Tubarao, steel plant located in Serra, Espirito Santo, Brazil, was developed to assess the features of the flow field and its influence on the metallurgical behavior. Results of the physical model were used to optimize the process parameters in the industrial unit.

Jan 1, 2003

By J. J. Moore

The application of plasma technology to process metallurgy is briefly discussed. Experiments involving in-flight reduction of minerals (taconite, chromite, in particular) with a solid-based carbon reductant are described. The resultant metallic and slag product analysis is discussed with respect to thermodynamic and kinetic considerations.

Jan 1, 1985

By Kent D. Peaslee

When supersonic oxygen jetting is used in electric furnace steelmaking, the lance jet axis is typically inclined at larger angles to the vertical than is used in basic oxygen steelmaking. The supersonic jet is important not only for refining the steel, but for sustaining the foamy slag in the electric furnace. Physical modeling was carried out using a room temperature, two-dimensional slice apparatus in which mercury represented the metal and water-glycerol the slag. High speed video photography with image analysis was used to study the effects of the angle of inclination on the slag/metal bath. Mathematical modeling using FLUENT provided a method of predicting flow patterns and the trajectories of drops injected at various points in the flowfield. A one-half scale water model of the system, in which lance heights, angles, and flowrates simulated those encountered in steelmaking operations, was used to provide a better understanding of some aspects of the oxygen blowing process in electric furnace steelmaking.

Jan 1, 1994

By Carlos Ortiz

The Huelva Flash Smelting Furnace was commissioned in September 1975. The Smelter and the Acid Plant were expanded in 1995 to their present capacity of 300,000 tpa new copper equivalent and one million tonnes of concentrate per year. During these years of operational experience, most of the initial practices have been reviewed, process control has drastically improved and main process equipment has been modernised. The fourth Flash Furnace campaign lasted 9 years (1995-2004) during which 8 million tonnes of concentrate were smelted. Increasing sulphur content in concentrates and new environmental requirements imply new challenges for smelters to keep production and operation costs down. This paper is an overview of the modifications and improvements carried out in the 2007 general shutdown in Smelter and Acid Plants. Al

Jan 1, 2008

"Injection technology has been an important subject from the early days of ladle metallurgy until the present. During the last decade, there have not been many publications in the area of injection technology. It is the author's opinion that with the challenge to find new solutions especially to environmental and energy related problems as well as better understanding of phenomenas from computer modelling, a new era of inventive injection technology developments is at hand. This is illustrated in the article with examples from six different areas where MEFOS is or have recently carried out R&D work related to issues from the injection technology field. IntroductionThe boom in injection technologies came with the introduction of ladle metallurgy treatment during the '70s and '80s. Since then, the theories and principles have been thoroughly laid down by a number of scientists and also published at several early SCANINJECT conferences.Not many new technologies/applications have been presented during the last ten years. This might lead one to believe that everything is known and done. Those, like MEFOS, who are challenged to find technological solutions to a number of environmental problems and energy saving issues in the pyrometallurgical field are, however, continuously faced with the task of developing new injection technologies.Especially, the call for sustainable technologies to solve environmental problems is a challenge for metallurgists all over the world and it will surely induce a revival of injection technologies. So, in order to encourage all injection experts, let us share some new experiences and let us encourage each other's creativity to solve some of the demands of the future society.The following show some examples of technologies under development, or recently tested."

Jan 1, 1996

By KNona C. Liddell

"Many metal recovery processes involve heterogeneous reactions in porous media accompanied by fluid flow and mass transfer. Modeling such systems is difficult because of the number of rate processes involved and is complicated even further by effects due to the structure of the porous medium. Data on even bulk properties of the medium are often severely limited or unavailable. For many such systems, a cell model may provide an attractive alternative to models based on transport mechanisms in a differential volume. A cell model requires less input data and is computationally efficient. Identical residence time distributions can be obtained with models of both types, and both allow conversion and concentration profiles and histories to be calculated. The formulation and properties of cell models for metals recovery are described in detail.INTRODUCTIONSubsurface mineral leaching, metal ion recovery and environmental remediation are significant modeling challenges. They involve one-, two-, or three-dimensional reactive flow in multi reaction open systems. Dissolution, adsorption, and ion exchange occur at reactive mineral surfaces, and these heterogeneous reactions are accompanied by acid-base, complexation, and redox reactions in the solution phase.Two approaches have been taken to reactive flow problems in geologic media: mixing cell and transport models. Mixing cell models, the subject of this review, are based on a network of connected cells, each with a specified number of input and output streams. Mixing cells are assumed to have no internal solute concentration gradients, that is, each cell behaves like a well-stirred tank. Gradients are represented by step changes between connected cells; this results in a model that is spatially discretized at the outset. Different methods of discretizing the model equations are considered more fully below. Although this is not strictly necessary, it has usually been assumed in subsurface flow applications that all cells in the network have the same volume and identical initial properties."

Jan 1, 1996

By Yan Beygelzimer, Alexander Spuskanyuk, Victor Varyukhin

"The main idea of the report is that the yield surface can be presented as thick, ""foamed surface"" with dimensionality exceeding two. By other words, perhaps, the yield surface is fractal, i.e. it belongs to the class of geometric objects with fractional dimensionality. Apparently, fractal structure of the yield surface is determined by the fractal structure of natural materials. ""Cloud of internal stresses"" term is introduced to describe the stress distribution in representative volume element. Its plastic flow is determined by the interaction of this cloud with the thick yield surface. Thick yield surface and internal stress cloud concepts allow to determine an additional correlation between micro mechanical models of polycrystals and phenomenological theory of plasticity.1. IntroductionClassical plastic flow models are not satisfying the modem requirements. There are two main directions in their development. The first, mathematical, is connected with the development of the general theory of rheological relationships; the second, physical, is connected with the development of the representative volume element (RVE) models which are based on specific ideas about deformation mechanisms. Within the framework of the first direction, the macroscopic experimental data is formalized; the second approach deals with the generalization of physical research results for the different scale levels that are involved in plastic deformation.These approaches have advantages and disadvantages. In phenomenological theories, the advantages are the mathematical simplicity and laconic formulation of constitutive relations, which allows using them in practical calculations. However, the mathematical models of this class can not be considered as general, they are useful only for the description of limited range of deforming processes. On the other hand, physical theories that are based on the description of real plastic deformation mechanisms are very explanatory and predictive, but they lack mathematical simplicity. The above circumstances lead us to the necessity of compromise that can be found in determining the constitutive relations for RVE, which structure and parameters would bear the information about rnicrolevel and mesolevel phenomena. In this synthesis direction, the fundamental role belongs to [1,2], etc."

Jan 1, 2001

By Pragna N. H. Bhakta

The minerals industry is under political and economic pressure to reduce its processing wastes and minimize their impact on the environment: Recycling is one of the means by which the minerals Industry can reduce the quantities of effluents and residues that are discharged to the environment. The wise use of available resources is not only an environmental necessity but also an economic benefit as natural mineral resources are depleted and/or become more complex. The purpose of this paper is to review the technical and regulatory issues that will help shape the future of minerals recycling over the next ten years. Research and development to address technical issues will be discussed with emphasis on the Bureau of Mines recycling research program.

Jan 1, 1992

By F. A. Steward

Copper is one of the trace minerals essential to life. It is added, usually in the form of copper sulfate, to virtually all formulated feedstuffs and to dietary supplements fed to animals on forage. Over the past five years, an improved inorganic copper source trademarked Micronutrients TBCC™, has been developed, tested and commercially introduced. TBCC is a crystalline form of basic copper chloride. Synthesis is accomplished in a continuous neutralization I crystallization process. In current commercial production, the primary sources of copper currently used as feedstocks are the etching solutions used to manufacture electronic printed wiring boards. These solutions have traditionally been managed as hazardous wastes, but their use to manufacture TBCC™ exempts them from regulation as wastes under the "Use/Reuse" provisions of RCRA. Research conducted over five years at multiple universities has shown that animals are healthier when fed this source of copper and that vitamin losses in feed are reduced by its use.

Jan 1, 2000

By Toshiro Kuji, Masakazu Fujita, Tetsuji Saito

"The magnetic properties of the magnetic materials were deeply dependent on the microstructures. In this study, the novel technique to produce the desired microstructures in a controlled manner was proposed. The technique consisted of the production of the amorphous alloys and the control of the crystallization process. The technique was applied to improve the magnetic properties of Nd-Fe-B permanent magnets. The microstructural control of the magnets exhibited the excellently high energy-products of higher than 430 kJm-1. The relationship between the magnetic properties and the microstructures of the Nd-Fe-B permanent magnets was discussed.IntroductionThe intrinsic properties of the materials are basically determined by the properties of the constituent elements or the compounds. However, it is often noticed the difference between the observed properties and the theoretical values expected from the intrinsic properties of the materials. This indicates that the observed properties of the materials are determined not only by the properties of the constituent elements. In other words, the observed properties of the materials are also strongly dependent on the morphology of materials. This means that the microstructural control may creates a great improvement of the properties of materials.In Nd-Fe-B permanent magnets, the superiority arises from the uniaxial intermetallic Nd2Fe14B compound which has a large saturation magnetization and a high anisotropy field [1,2]. The magnetic properties of the Nd-Fe-B permanent magnets are dependent on the microstructure, that is, the size, shape and degree of the crystallographic alignment of the Nd2Fe14B phase. Currently, the Nd-Fe-B permanent magnets have been produced by either sintering or melt-spinning [3,4]. In the sintered magnets, alignment of the Nd2Fe14B phase is achieved by the prior green compaction of the crushed ingot powders in an applied magnetic field [3]. In the melt-spinning approach, alignment of the Nd2Fe14B phase is achieved by hot deformation [5]. Amorphous melt-spun ribbons are comminuted and then are consolidated into bulk form by hot pressing before hot deformation. As-hot-pressed magnets have randomly oriented Nd2Fe1~ grains [6]. Subsequent die upsetting of as-hot-pressed magnets gives rise to the crystallographic alignment of the Nd2Fe14B phase."

Jan 1, 1998

By A. J. Paul

Traditionally, 16"/50 caliber projectile shells have been fabricated from forged steel. The Naval Surface Warfare Center (NAVSWC) has determined that cost savings of approximately 60% (-$4.7M/year) as well as improved shell fragmentation can be achieved by casting these shells from austempered ductile iron. One of the technical concerns arising out of this material substitution is the role of the casting process in controlling the quality of the cast shells. Optimizing the process through proper orientation of the mold, placement of chills, superheat, etc., can minimize shrinkage porosity and, consequently, flaw size. For this purpose, the mold filling and subsequent solidification of the projectiles was simulated using a 3-D, fully transient, coupled fluid flow and heat transfer model based on finite differences. Several casting orientations were investigated and the casting parameters were varied to optimize the process and minimize casting defects. A comprehensive software tool, which was developed using state-of- the-art visualization techniques, has been used to analyze the process of casting. Emphasis is placed on the use of this visualization tool as an aid to the foundry engineer for process optimization.

Jan 1, 1992

By M. E. Karabin, R. J. O'Malley

"A mathematical model of the roll casting process has been developed which predicts macro-variables, such as roll separating force, roll torque, and strip exit speed for a range of roll speeds. Continuum variables, such as interface pressure, interface shear stress, freeze-front shape, and internal temperature distribution are also predicted.The model consists of two independent segments: solidification and rolling. The solidification model is two-dimensional (thickness and rolling direction) and is capable of handling alloy solidification. The solidification model is employed until solidification through the thickness is complete, then the rolling solution is activated.The rolling model is a one-dimensional (rolling direction) mechanical solution based on the von Karman approach, coupled with a two-dimensional thermal solution. The flow stress is expressed as a function of the average through-thickness temperature of the strip.Experiments were performed using a laboratory roll caster to test and refine the model. Experimental strip exit temperatures were used as input to the model. Experimental and predicted roll torque and strip exit speea were forced into agreement at a single reference roll speed to obtain values for the coefficient of friction and the interfacial heat transfer coefficient. Using these values, good agreement was obtained between predicted and experimental torque and strip exit speed over the entire range of roll speeds examined."

Jan 1, 1986

By Batric Pesic

Gold dissolution with bromine was studied by using the rotating disc technique. Geobram TM 3400 was used as a source of bromine. The parameters studied were: rotating speed, Geobrom 3400 concentration, pH, temperature, sulfuric and hydrochloric acid concentration, and the concentration of various cations (copper, iron, zinc, aluminum, manganese, potassium and sodium) and anions (chloride, bromide, sulfate, nitrate, and iodide) According to the Levich plot and activation energy, gold dissolution was controlled by a chemical reaction rate. Copper, iron, and manganese in their highest oxidation states, aluminum, zinc, sodium and potassium did not have any effect on gold dissolution rate. The presence of manganous ion dramatically decreased the gold dissolution rate. Kinetic performance of bromine, in the form of Geobram TM 3400, was compared with performance of cyanide and thiourea.

Jan 1, 1990

By Karl A. Gschneidner

Magnetic refrigeration was first used in the mid-1920's and new developments seem to have taken place about every 20 years, and this is especially true for the mid-1990's. The active magnetic regenerator magnetic refrigerator has the promise to become the first practical machine utilizing the magnetocaloric effect for cooling (and also heating). The basic principles are briefly discussed. Since the temperature lift for the magnetocaloric effect spans about 50 K, one will need to utilize several ferromagnets with different magnetic ordering temperatures in order to reach temperatures below ~250 K. The basic properties, behaviors, limitations, and new phenomena and knowledge are discussed.

Jan 1, 1997

By Toshitaka Ota, Hisao Suzuki, Minoru Takahashi

"Perovskite-type lead zinc niobate (PZN) exhibits excellent electrical properties such as high dielectric constant, high electrostrictive coefficient and superior piezoelectricity. Therefore, PZN ceramics are very promising for high performance electronic devices. However, perovskite phase PZN is not stable under the ambient atmosphere. Accordingly, it is very difficult to prepare single-phase perovskite PZN ceramics. In this study, A-site cation of lead was partially substituted for barium to stabilize the perovskite phase of the PZN (Ba-doped PZN) powder. In addition, molecular design of an alkoxide precursor was controlled for a low-temperature processing. As a result, molecular design to suppress the lead-volatilization during calcination was preferred for a low-temperature processing. Processing temperature for a single-phase perovskite was depended on the amount of barium dopant. Doping of20 mole% of barium resulted in the single phase perovskite at 900 °C. The temperature for the single phase perovskite of Ba-doped PZN powder, which depended upon the amount of Ba-doping, was lower than that of the powder prepared by the atmosphere controlled conventional powder processing at least by 150 °C.IntroductionFerroelectric thin films and powders with perovskite structure are of renewed interest for micro-electronic applications, including ferroelectric random access memory (FRAM), dynamic random access memory (DRAM), and thin-layer capacitors integrated onto a silicon wafer [1-3]. In addition, recent advancement in micro-machine requires a high performance micro-actuator [4]. A perovskite type relaxor of Pb(Zn113 Nb213)03 is one of the promising materials for a high performance capacitor and microactuator because of their high permittivity and electrostrictive coefficient [5]. Therefore, this paper focuses on the low temperature processing of Ba-doped PZN powders.Chemical solution deposition (CSD) from molecular-designed alkoxide precursor solution is one of the most promising techniques for processing high-performance powders and thin films because it offers precise control of compositions on a molecular scale as well as a low processing temperature [6]. However, chemical solution deposition of perovskite type PZN powders and ceramics are very difficult because of the formation of stable pyrochlore phases. Therefore in the past, PZN powders and single crystal have been prepared by the hydrothermal method or flux method as well as the partial substitution method of a A-site cation [7-10]. In this study, a suitable molecular design for a preparation of perovskite type Ba-doped PZN powders with a chemical solution deposition process is investigated as well as the effect of A-site cation substitution. Chemical solution deposition from molecular-designed alkoxide precursor solution is expected to decrease the amount of a A-site substitution and/or a crystallization temperature for a single phase perovskite. This paper describes ""the relation between molecular-design and processing temperatures for a single-phase perovskite of Ba-doped PZN powders in comparison with the conventional oxides mixing method."

Jan 1, 2000

By Norbert L. Piret

From the copper smelter operation a various outputs are to exert negative impacts on the environment. Particularly, emissions like SO2 and dusts, solid wastes like contaminated gypsum and arsenic sludge, effluents and heated cooling water are generated. Most countries have sitipulated an environmental legislation to provide the framework for an efficient environmental management. As part of the planning activities for x major greenfield copper smelter, the Following elaborations are required and were drawn up. -The Environmental Impact Assessment which is the first step of environmental management and mandatory for every new project. - The Environmental Monitoring Plan, which describes the monitoring procedures for the main impacts identified and assessed. -The Environmental Management Plan, which deals with the minimization of environmental impacts, and the methods of its implementation.

Jan 1, 1996

By D. C. Foguel, J. L. R. Bravo

For several years, Caraiba Metais S.A. (CMSA) had to stock the arsenic sludge generated from the electrolyte purification process of its tankhouse. The amount stocked · reached approximately 3,500 tonnes, as the effects of its recycling during the smelting process and consequently in the sulfuric acid plant were unknown. Besides, it had as limiting factors the high content of arsenic in the copper concentrates supplied by foreign countries as well as the reduced capacity of the tankhouse's purification plant. The choice for selling the mentioned residue, which generally contains more than 50% of Cu, was attractive, but the environmental policies and regulations had not allowed this option. Other alternatives, such as the production of bicupric arsenic by means of a solvent extraction process or arsenic trioxide, were considered but the economic feasibility was not attractive due to the absence of a domestic market and a poor international market. After a study of the arsenic partition in the metallurgical process, it was verified that the residue could be recycled without causing any operational problems or damage to the environment. To make this possible, the capacity of the purification plant was increased and the way of removing the arsenic sludge from the cells was modified from manual to mechanical, therefore avoiding the direct contact of the workers with this poisonous substance. Moreover, procedures for recycling in the smelter were established and tolerance limits were set for both the smelter and the sulfuric acid plant. The main amount of arsenic to be recycled is released with the smelting furnace off-gas, which is washed during the purification stage of the sulfuric acid plant. The acid water, rich in arsenic, is then treated in the waste plant and the arsenic, in its stabilized condition, is confined in an appropriate area.

Jan 1, 2000

By C. A. Pickles

At the present time, pyrometallurgical processes are employed for the recovery of lead from battery scrap. These processes have serious pollution problems, primarily due to the emfssion of sulphur dioxide and airborne lead in the form of dust and fume. In addition it is necessary to dispose of solid wastes and liquid effluents which contain lead and in some cases sodium sulfide-containing compounds. In this work an improved process was investigated for the recovery of lead from battery residue. This involved pelletization of the residue with sodium carbonate and moisture. Then, the pellets were melted without carbon and the .sodium sulphate salt was removed. Subsequently, the molten lead oxide was reduced with carbon. This process minimizes the sulphur dioxide emissions and leads to very low sulfide contents of the sodium sulfate salt

Jan 1, 1992

A comprehensive numerical capability for the analysis of Thermal Spray (TS) systems consisting of a three-dimensional compressible, turbulent flow Navier-Stokes model and a multi-phase particle flow model in Lagrangian formulation, was developed. This capability is validated for a set of flow conditions typical for TS. The developed methodology is used for analysis of the JP-5000 TS gun gas and coating powder flow conditions. Modeling and analysis of particle/turbulent eddies interaction is performed. Details of gas flow field, particle temperature, and particle velocity histories, and particle temperature, velocity profiles in the system are presented. For the validation of numerical analysis, the computed results are compared with available experimental measurements. The flow phenomena for different flow parameters are analyzed and explained as the results of gas dynamics and heat and momentum transfer between the gas and particle phases. This methodology can be used for process control and reliability improvement, and has the potential to significantly improve TS gun performance through control of its parameters.

Jan 1, 1996