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By M. T. Ernett

Significant amounts of arsenic are often present in effluents arising from the mining of sulfide ores for the extraction of metals such as copper, gold, lead and zinc. The arsenic is usually removed from the process effluent by co-precipitation with iron because of its common occurence in the mined ore bodies and the excellent adsorptive property of the precipitated hydrous ferric oxide compound. There has been controversy, however, over the long-term stability of the arsenic-bearing ferrihydrite which is produced. This paper presents the results of laboratory studies which indicate that the cations of calcium, magnesium, zinc, cadmium and lead, increase the pH range of effective arsenic adsorption in the Fe-As precipitate from 4-7 to 4-9. The increase in the pH range is similar for all of the added cations investigated. Sulphate ions are shown to have a minimal effect on the residual dissolved arsenate concentration. Silicate ions reduce the adsorptive capacity of ferrihydrite if they are present before the arsenic is adsorbed.

Jan 1, 1994

By Hideki Yamamoto

A new technology to convert fluoride gas (C2H2F4 : R-134a) contained in the exhaust gases from semiconductor manufacturing plants and refrigerators directly into a harmless substance have been established, thus, presenting a new concept for the disposal of fluoride gases such as CFCs that are associated with the global warming. Experimental results verify that chemical reactions with metal compounds can take place at substantially lower temperatures of 700- 800K as compared with combustion treatment temperatures of 1200-1500K. The reaction product is mainly metal fluoride, which chemically is a harmless material. Furthermore, this process is compact, easily controlled, safe and has low running costs. This paper deals with a new chemical reaction method for the harmless disposal of gases effecting the global warming.

Jan 1, 2003

By Basak Anameric

Pig iron nugget process was developed by Kobe Steel as an environmentally friendlier, economical alternative to traditional blast furnace process. The process aimed to produce highly metallized, slag free pig iron nuggets throughout a single stage heat treatment, utilizing coal as a reducing ? carburizing agent. The objective of this work was to determine whether the pig iron nuggets produced at the laboratory conditions had comparable physical and chemical properties with the blast furnace pig iron. The physical and chemical properties of the pig iron nuggets were determined utilizing x-ray fluorescence spectroscopy, x-ray diffraction, optical microscopy, scanning electron microscopy, energy dispersive spectroscopy and apparent density measurements. The pig iron nuggets had similar chemical composition and apparent density values (6.7 ? 7 g/cm3) with blast furnace pig iron and they had microstructures similar to low carbon white cast iron. These properties make them a competitive alternative to blast furnace pig iron.

Jan 1, 2006

By C. F. Ferron

A process has been developed to treat the copper gold ores from the Guelb Moghrein mine in Mauritania. The process consists of pressure leaching the sulphide concentrate, neutralising with the oxide ore, recovery of copper by SX/EW and of gold by cyanidation of the autoclave residue. This paper focuses on the pressure leaching step, and presents data from bench and pilot plant test programs. In particular, attention is drawn to the effects of temperature, grind size, neutralisation, retention time and solution recycle on the kinetics of copper dissolution from various flotation concentrates. Likely leach mechanisms are briefly discussed.

Jan 1, 2000

By Animesh Jha

The carbothermic reduction of chalcopyrite has been studied in the temperature range 1073 to 1273K in presence of lime. The role of lime during the reduction process is explained and the phase equilibria leading to the metallisation of copper and iron are discussed. The effect of coal and carbon monoxide on the reduction process have been studied and the rate governing steps are identified. This investigation also cites examples of possible mechanisms of physical separation of metallic Cu from iron during the reduction process.

Jan 1, 1992

By M. Zamalloa

Slag foaming is an important phenomenon in many metallurgical processes. It creates large surface areas for multi-phase reactions to take place. In other applications, it protects electrodes and improves the energy efficiency by reducing radiation from hot surfaces. However, it may also be a source of serious disturbances. To control and optimize the use of slag foams, an extensive knowledge of the factors controlling the foam formation and stability is required. Slag foaming experiments were carried out using synthetic FeO-CaO-Si02 slags at temperatures ranging from 1200 to 1350 "C. A data acquisition system was used to continuously measure the foam height, gas flow rate, bubble frequency and temperature. The experimental results show that the gas injection rate has a strong effect on the behaviour of slag foams. At high flow rates and rapid bubbling, unstable foams with short decay times were created. The addition of P20, favours the foam formation and stability by lowering the surface tension of the slag. The average foam life increases with decreasing basicity (CaO/Si02). It is proposed that this is attributed to the increase of the surface viscosity due to surface adsorption of a thin film of silica, retarding the drainage of the liquid films.

Jan 1, 1992

By Lifeng Zhang

The transport of fluid, heat and particles (bubbles and solid inclusions) in flowing molten steel is investigated in steel refining ladles, the continuous casting tundish, continuous casting mold and strand, and steel ingot casting processes. Inclusion removal from the molten steel by flow transport and bubble flotation, and inclusion growth by collision and diffusion are discussed. Removal of impurity elements such as [C] and [O] during steel refining are reported.

Jan 1, 2006

By Wenliang Cao, Jidong Li, Mingjie Zhang, Yiyong Wang

In CaC12-CaF 2 System, we studied the electrode process and discharge mechanism of preparation of Al-Ca alloys by fused salt electrolysis with CaO as raw material. The change of back electromotive force after adding CaO was measured by continuous pulse oscillograph method and the discharge process mechanism was also investigated by cyclic voltammetry. The finial results indicate that back electromotive force decreases by 0.6V after CaO of 1 % is added and there was a peak of oxidation current ahead of the potential at which the negative chlorine ions precipitated. According to thermodynamic calculation, it was determined that current peak was caused by the CO2 produced by 0 2 - ionic discharge due to CaO addition.

Jan 1, 2014

By E. A. Werner, A. Pichler, A. Spalek, G. Reisner, P. Stiaszny

"Interstitial free (IF) sheet steels are used for complex shaped parts because of their excellent formability. If a deep drawn part is subjected· to a impact deformation at low temperature brittle fracture of the part may occur. This phenomenon\ is called secondary work embrittlement (SWE). One possibility to characterize this material/structural behavior is the drop-weight test. The result of .this .test is a temperature at and below which a crack can initiated in a deep drawn part under the investigated set of parameters. This paper addresses the influence of the preforming process on the sus- . . ceptibili.ty of IF steels to SWE.IntroductionInterstiiial:free (IF-) steels are frequently used in the automotive industry for complex· shaped p·arts because of their excellent deep drawability. The microstructure of the steel consists of a highly ductile ferritic matrix with embedded precipitates of nitrides and/or carbides. Brittle fracture can occur in deep drawn parts, if they are subjected to a high speed deformation at lo""w temperature. This phenomenon is called ~econdary Work gmbrittlement (SWE) [1-11]. Up to now there are no standardized testing procedures available to quantify the sensibility of IF-sheet steel to SWE. Neveitheless, a reasonable testing procedure which allows to quantify the tendency of a predeformed part to SWE is necessary for further material development. A commonly used test method is the drop-weight test performed at low temperatures. In such ·tests a cone-like drop weight expands a deep drawn cylindrical cup [l-3, 6, 8, 9, 11]. From this expansion experiment the temperature is determined at and below which a brittle crack can be initiated in the deep drawn cup under the investigated impact test parameters. The highest measured temperature at which a deep drawn cup fails by brittle fracture is called frack appearances !emperature (CAPT). The lower the value of the CAPT the lower is the sensibility of a deep drawn part of IF-sheet steel to SWE. This paper aims to clarify the role of the preforming process on the impact behavior of an IF steel. For this purpose a numerical analysis of the deep drawing process and cup expansion tests are conducted."

Jan 1, 2000

By D. P. Cook, M. I. Bloch, J. A. Dantzig

"In this article, we describe a combined experimental and computational program to study the filling of automotive wheels during low pressure die casting. Experiments are performed by placing thermocouples into the mold walls of a production caster for the Ford F 113 wheel to measure the temperature profiles in the die during processing, and to infer the filling pattern. Computational models are also developed using a 36° section of the wheel pattern, taken directly from CAD data files. We use these models to simulate the filling and heat transfer processes. Comparison between experimental and computational results are presented, demonstrating the viability of this procedure.IntroductionAutomotive companies are using increasing amounts of aluminum in production vehicles: While the main driving force is improved fuel economy through weight reduction, replacing steel wheels by aluminum also offers the potential for improved vehicle performance by reducing unsprung mass. For these reasons, many new vehicles are now supplied with cast aluminum alloy wheels, and the aftermarket for these wheels continues to grow.The most common production process for these wheels is low pressure die casting. The process is subject to numerous defects, including microporosity, cold shuts, cold folds, misruns and inclusions. Scrap rates at the caster of the order of 10% are not uncommon. Many wheels also have large production runs, into the hundreds of thousands of wheels per year. Thus, the cost savings from even small reductions in scrap rate have the potential to be quite significant.Most of the defects are associated with the filling and solidification processes in the mold. The molds are air cooled, and the placement and sizing of cooling passages is currently as much art as science. The ultimate goal of this project is to improve that situation, by implementing simulation procedures that enable engineering design methods to be used in die and process specification."

Jan 1, 2000

By D. S. Barr

The Freeport McMoRan chlorination circuit is comprised of four related processes: ore chlorination, gas scrubbing, chlorine supply and excess hypochlorite removal ("hypo kill"). Each of these processes are described, and related to the pertinent mineralogic components in the carbonaceous ore feed to the plant. The chlorination system in use at Jerritt Canyon to passivate forms of preg-robbing organic carbon has proven to be a cost effective and efficient means to recover gold from low sulfide carbonaceous refractory ores, where gold may not be specifically associated with either the sulfides or the carbon.

Jan 1, 1987

By Y. Ide, K. Kishitake

It is expected that an Al-Cr-N composite nitride film may have a higher resistance to oxidation at elevated temperatures than the well-known Ti-Al-N films. The formation conditions of Al-Cr-N films by a de reactive sputtering method and their properties were studied in this study. The films characterized with respect to their high temperature properties such as chemical composition, crystal structure, microhardness, wear and· friction. The crystal structure of the Al-Cr-N films changed from hexagonal phase to cubic phase with an increase in Cr content in the films. The resistivity to thermal oxidation of the Al-Cr-N films is superior to that of usual TI-Al-N films. A half of the friction coefficient in the Al-Cr-N film was obtained comparing with that in the ordinary TI-Al-N film at room temperature and the wear rate of Al-Cr-N film was 2 order smaller than that of TI-Al-N film. The Al-Cr-N films show a small friction coefficient at 500°C and then they are recognized to have good tribological characteristics.

Jan 1, 2000

By C. J. Parradies

During injection into a die, semi-solid metal alloys exhibit a shear-rate, history-dependent flow response. Simulating the injection of a thixotropic material requires that empirically determined boundary conditions and viscosity are specified as a function of both temperature and shear rate history. Experiments were performed using an industrial die casting machine that was instrumented with sensors to measure the pressure and temperature during the injection of a semi-solid aluminum alloy through a tube. This benchmark experiment was used to develop a simulation of the die casting process that could then be applied to more complex die geometries. The results of the experiments were analyzed using the exact, steady state solution for a power law fluid and simulations accounting for slipping at the boundary between the semi-solid metal and the die. Results indicated that the no-slip condition cannot be used to simulate the velocity boundary condition, because the measured pressure is much lower than that predicted by the models. An estimated apparent slip coefficient was introduced to account for the reduced pressure. During some of the experiments, a sudden drop in the measured pressured, prior to decreasing the ram velocity, coincided with observations of segregation in the form of concentric rings visible on the polished surface of cross-sections cut from material remaining in the tube.

Jan 1, 1997

By Valentine A. Chanturiya

A model for development of electric discharges between particles of sulfide minerals (pyrite) under the action of high-voltage nanosecond pulses is proposed. It is shown that through discharges in a layer of pyrite particles lead to energy concentration in small contact regions between particles; the concentrated energy is sufficiently high for local disintegration of mineral complexes.

Jan 1, 2009

By Hani Henein

"Heat transfer between droplets/particles and a gas phase plays an important role in the transport of numerous materials processing operations. These include rapid solidification operations such as gas atomization and spray forming, as well as chemical systems such flash furnaces. Chemical reaction rates and solidification are dependent on the rate of gas-particle or gasdroplet heat transport. Using a heat transport model validated using single fluid atomization of molten droplets; the effect of process variables on heat losses from droplets was examined. In this work, the effect of type of gas, droplet size, gas temperature, gas-droplet relative velocity on the heat transport from AA606 l droplets was examined. The most critical of these process variables to heat transfer is identified and will be presented.IntroductionIn materials processing, droplets are often encountered and used in processing a wide range of liquids and slurries. The small size of the droplet enables high reaction rates or high solidification rates in many systems. In order to capitalize on these high rates of transport processes, sprays are· also developed to maximize throughput. The design of these sprays, however, does not account for the transport steps and rate limiting mechanisms at the droplet surface. Rather, spray design focuses on maximizing the break-up of a stream or slurry into small size droplets or controlling the spread of the spray. Spray systems in industrial use typically generate droplets of wide size distribution leading to a wide range of reaction times for each of the droplets. Often the generation of a spray involves a number of coupled phenomena such as stream break-up, droplet-gas transport, droplet size distribution and spray geometry. Using gas generated sprays, it is not possible to identify how individual process variables contribute and control each of these coupled phenomena. While many mathematical models have been developed of sprays and they attempt to simulate coupled droplet transport, they do not provide insight into the contributions of different mechanisms in heat transfer. This is primarily because the basic fundamental heat transport between droplet and gas cannot be isolated from other gas spray phenomena experimentally such as two-way thermal coupling [l]. Thus, experimental validation of heart transfer of large and complex industrial spray models is not carried out. Hence, the validity of spray models remains in question and the approach required to optimize spray processes cannot be clearly identified"

Jan 1, 2004

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 Henry Hu, Alfred Yu

"A numerical model has been developed to simulate heat and mass transfer phenomena occurring during a novel magnesium reduction process-the vertical retort technology. The model was based on the control - volume finite difference approach. Simulations were run to determine the effect of various processing parameters on magnesium reduction cycle time. The model predicted temperature distributions, heating curves, recovery ratio of magnesium, and total process times. The predictions were used to optimize the magnesium reduction process including dimensions of the retort, geometries of the reactant compounds, and productivities. The results indicate that the implementation of the optimized processing parameters significantly decreases the reduction time, and consequently increases the production rate as well as lowers the energy consumption.IntroductionMagnesium consumption has been growing considerably in the past decade [1]. Of the total magnesium production, 30% is produced by the thermal reduction (Pidgeon) process, and it is anticipated to be still the main technology for producing magnesium in future [2]. One of the advantages of the Pidgeon process is that it is capable of producing high purity magnesium demanded by both the automotive and aerospace industries. However, the inefficiency of heat and mass transfer taking place in the horizontal Pidgeon reduction process results in low productivity, high energy consumption, labor-intensive operation, large floor space and high capital investment. This limits the production scale of a horizontal Pidgeon reduction process [3].Vertical reduction processTo overcome the shortcomings of the horizontal magnesium reduction process, a novel vertical magnesium reduction process [3] for large-scale production has been developed, in which heat and mass transfer in the retort is enhanced. The new process shortens reduction time, reduces energy consumption and increases productivity. The vertical reduction system is comprised of a vertically-placed retort, a heating furnace and a vacuum system. A section of the vertical retort is illustrated in Figure 1. Since the retort is set vertically, instead of horizontally, the entire procedure of loading the reactants material in the new process is different from the one for the horizontal reduction process."

Jan 1, 2001

By J. M. D. Wilson

An analytical program using a combination of SEM-based image analysis techniques is developed for automated modal analysis of ores containing silicate and other gangue minerals. Previous knowledge, gathered by means of either optical microscopy, X-ray diffraction, SEM, or electron microprobe analysis is used to establish discrimination criteria in the image analysis program. The program initially discriminates minerals on the basis of their relative grey values in a backscattered electron image. For those minerals which have overlapping grey levels the minerals are identified by the program using energy dispersive X-ray spectrometry with X-ray counting for twelve or more elements. This technique is useful to quantify ores in which the gangue minerals are numerous. Two cases of application are presented.

Jan 1, 1999

By John J. J. Chen, Barry J. Welch

"The production of primary aluminium can potentially lead to metal that, with minimum treatment, meets a high purity standard. Smelters that can achieve a significant proportion of their production in this manner have a competitive edge which is of growing importance as the use grows for such items as compact discs and the like. Superimposed on the desire to produce high quality metal are stringent environmental requirements that the industry must adhere to. The environmental legislation focuses on fluoride emissions and the approach adopted is towards a zero waste management philosophy. The fluoride recycling process does, however, result in volatile impurities being captured and recycled to the cell. Aluminium has an extremely high reduction potential and this results in a significant proportion of the recycled impurities being reduced at the electrolyte metal interface and thus contaminating the metal. This paper reviews sources of impurities and the impact of the operating procedures adopted on metal treatment.IntroductionSeveral factors have contributed to the immense growth in the aluminium smelting industry. Initially the ready availability of hydro electricity provided a primary reduction energy source for the production of the light-weight metal. Because of its unique properties and innovation in the industry there has been a continued exploitation of its unique properties, especially at the high purity end of the metal. The industry has shown considerably versatility and innovation in adapting to the ever increasing demands of quality and purity. It is however a competitive industry and the ability to produce high purity grade metal (>99.9% pure) gives a competitive edge. Emerging markets such as for CD ROM disc production etc, will keep the quality demand stringent.While the industry has met the continuing demands for metal quality, it has also had to respond to stringent environmental requirements for emissions from the production plant. Like all extractive metallurgical processes carbon dioxide is an inevitable reaction byproduct. However, the volatilization and hydrolysis of the solvent electrolyte leads to fluoride emissions that are potentially harmful. Accordingly, the industry has adopted essentially a zero non-process waste management approach. All cell emissions, including reducible impurities, are recycled back to the cell. This has had a significant influence on the metal treatment processes."

Jan 1, 1996

By J. Vander Linden, R. De Ketelaere, M. Verhaege

In this paper, results are presented concerning the search to implement Supported Liquid Membrane (SLM) technology for the recovery of copper from electroplating effluents. Acid copper electroplating rinse solutions or effluents resulting from the post-treatment of, for example, cyanide-containing copper electroplating baths all contain copper (2+) in the lower concentration levels. A thorough study of the influence of the individual parameters and of their combined impact on mass transfer in small scale laboratory SLM modules has been performed, enabling to set forward the appropriate operating conditions for a pilot plant installation. The pilot plant, containing two SLM modules. of 18 m2 of surface area, has been tested extensively, including short and long term runs, with real process solutions. It was demonstrated that this installation is able to treat 40 l/h of acid copper sulphate rinse solutions· containing 500 ppm of copper. The final copper concentration in the effluent can be reduced to a few ppm while copper metal is recovered by electrolysis of the concentrate. This technology is also applicable to the treatment of solutions with low copper content of origins other than plating shops, such as tailings from copper plants or mine waters.

Jan 1, 2000