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By Freddy Syvertsen, Ali Riza Tarakcilar, Engin Tan, Derya Dispinar

"It has been shown that the disturbance of the advancing liquid front in the mould cavity may lead to surface entrained defects known as bifilms. These defects can deteriorate the mechanical properties significantly. The developments in the simulation of castings aid many casters. It is quick and economical. Therefore in this work, the aim was targeted to optimise the mould filling of a tensile test pattern design that is used for aluminium alloys. Several different designs, gatings and runner systems were investigated with Vulcan Casting Simulation Software. In addition to the achievement of non-turbulent and quiescent mould filling; other parameters such as temperature profile, porosity and feeding were investigated to optimise the process.IntroductionConsiderable effort has gone into understanding and controlling defects that are formed in aluminium and its alloys during casting. The conventional approach was the elimination of porosity by eliminating hydrogen in the melt simply due to the following reaction:"

Jan 1, 2012

By Raj Mutharasan

The phenomena of gas-molten metal reactions for the production of metal matrix composites consist typically of a combination of one or more gas transport steps and a liquid gas reaction step. Reaction products include such strength enhancers, grain refiners, or high thermal conductivity phases as TiC, AIN, SIC, Si3N4, TiN in aluminum alloys. Nitrides, carbides and oxides can be produced at various volume fractions and in fairly fine sizes (500 am to 5 um) in laboratory melts by Reactive Gas Injection method (RGI). Gas injection methodology to produce the reinforcements is attractive because it can potentially be scaled to production scales in excess of 10,000 kg/h. For continuous production, the reactant molten metal can be continuously fed into the .crucible where the reactive gas is injected. The molten metal phase reactant may also be involved in a controlling transport step, depending on its concentration and viscosity. It is well known that the reaction product reinforcement size and shape of these phases have significant impact on the physical, mechanical and thermal properties. The current state of knowledge is unable to predict the kinetics and growth of solid reaction products obtained. The primary goal is to develop a fundamental framework for the understanding and prediction of the particle size in such reaction systems. In addition, the role of gas transport, liquid hydrodynamics and decomposition are important issues. A reaction-transport model is being developed using a reaction, transport, and thermodynamic framework, both at macro and at atomistic level to assess gas - liquid interactions.

Jan 1, 1996

By Kathryn A. Mrotek

The textural growth patterns of nodules from two areas in the North Pacific and the South Pacific are characterized by mottled, columnar and compact-type zones. Amorphous material (mainly iron and manganese hydrox-ides) is a botryoidal-forming phase in the mottled and columnar zones. Crystalline material (platy crystals of birnessite and crystallites of todo-rokite) is found primarily in the mottled zones on botryoidal structures or as long-protruding structures growing onto that portion of the nodule in contact with the underlying sediments. The long-protruding mottled zones contain little or no biogenic debris, suggesting that these zones grew un-interruptedly within the underlying sediments. The coalition of spheroidal knobs comprising some of the nodules also suggests a relatively long residing time within the sediments. It appears that crystalline material (the usual host to associated valuable metals) forms in a quiet environment and as a result of direct nodule association with the underlying sediments.

Jan 1, 1982

By Vahid Rastegar

"Characterization of the microstructure and revealing dendrites in the microstructure and also measuring the dendrites arm spacing and the distribution of silicon were studied in various pieces of compacted graphite cast irons with 0.17, 0.185, 0.2, 0.22 and 0.24 percent of mischmetal. Black-white and color metallography (quantitative and qualitative) were carried out on the various steps of the cast samples. Distribution of silicon was studied quantitatively using spot analysis with scanning electron microscopy. Furthermore, effects of two variables (cooling rate and mischmetal percentage) on dendrites arm spacing were investigated.In order to color metallography, the samples were plunged into a boiling solution of 18% KOH, 9% NaOH and 9% picric acid in distilled water. It was inferred that the microstructure coloration varies according to the sequence: green-->red-->yellow-->blue-->dark brown->light brown as the silicon content decreases. After observing dendrites, dendrites arm spacing was measured. In this method, it seems to be possible to predict the mechanical properties of compacted graphite cast irons by knowing dendrites arm spacing and without any destructive testing. After studying the two variables, it was concluded that dendrites arm spacing decreases as the amount of mischmetal increases and it increases as the cooling rate increases.IntroductionIn general, detecting of primary austenite dendrites is not possible in cast irons due to their solidification system. Observing the dendrites in the room temperature is possible only in those gray cast irons that contain type D graphite. With collecting data of dendrites arm spacing (DAS) measurements, it could be possible to achieve the mechanical properties of cast irons without any destructive testing. In this research by applying a particular method, primary austenite dendrites and also distribution of silicon in the microstructure has been observed."

Jan 1, 2012

By M. Pineau, G. A. Monteith, M. Laliberte, G. Houlachi

Conventional physico-chemical treatment methods, either hydroxide or sulfide precipitation, can hardly achieve a high removal of selenium from the liquid effluents which can be generated in some metallurgical operations. In weak acid solutions, selenium exists mainly as anionic species (selenite Se03-2 and selenate SeCV2) which, therefore, cannot precipitate as metal hydroxide or metal sulfide compounds. At the same time, neither selenite nor selenate form stable precipitates with the common cations (Ca, Mg, Fe, etc.) that are typically used in water treatment. At Noranda Inc., CEZinc Division in Valleyfield, Canada, the introduction of new discharge requirements for effluent toxicity initiated a R&D program which resulted in the full-scale implementation of a new treatment method for selenium removal. The goal of this paper is to present this new method which is now being patented by CEZinc. The process chemistry will be presented along with pilot-scale developments and full-scale operational results.

Jan 1, 2000

By Beatriz Ribeiro Nogueira, Vijaya Kumar Rangari, Esperidiana A. B. Moura, Anne Chinellat, Arifa Parveen, Angel Visentim Ortiz

"Composite consisting of ethylene vinyl alcohol (EVOH) with short piassava fibers were prepared by extrusion process and their thermal and morphological behavior were investigated. The EVOH reinforced with 5 and 10 % of pi as sa va (Attaleafunifera Mart) fiber particle, based on the percentage weight ratio (wt %), untreated and treated with a commercial silane coupling agent, were prepared and the influence of fiber loading and the effect of chemical treatment on their thermal and morphological behavior were evaluated by SEM, DSC and TG analyses. Melt flow index (MFI) of the composites have been determined to evaluate the effects of fiber reinforcement on dynamic viscoelastic melt of the EVOH. In addition, piassava fibers characterization by SEM, FTIR, and organic and inorganic composition have also been carried out. The SEM results of the composites showed surface micrographs without microvoids and a good distribution, dispersion and compatibility between the fillers and the EVOH matrix. Concerning the piassava fibers characterization, the results showed that piassava has higher lignin content than cellulose and hemicelluloses, and around 0.7 % of ash with 52 % of silica (Si02). This high concentration of silica is consistent with the SEM analysis of the fiber that showed a large amount of ""silica rings"" encrusted on their surface.IntroductionLately, great worldwide interest has arisen in developing new technologies that enable the use of products with less environmental impact. Effort has been put into seeking natural modifier applications, particularly regarding the use of natural fibers. Special attention has been given to the use of natural vegetable fibers, because of the huge variety of species available. Such vegetable fibers are usually referred to as lignocellulosic materials [1]. This work evaluated the effects of piassava (Attalea funifera Mart.) fiber incorporation in an ethylene and vinyl alcohol copolymer (EVOH). The EVOH belongs to a family of copolymers with excellent gas barrier properties and resistance to organic compounds, which allow its application in different segments, from food packaging to gas tanks. However, EVOH is very sensitive to moisture, and in conditions of high humidity its gas barrier properties, thermal and mechanical properties are affected."

Jan 1, 2012

By D. Valic

In 1997, 9.2 million tonnes of mined, recoverable copper was produced, of which, 1.8 million tonnes or 19.4% was produced by leaching, solvent extraction and electrowinning. The amount of copper produced by this method grew faster than those attained from concentrate smelting, signifying the growing importance of this low-cost production method. Statistical experimental design, unlike traditional approaches, allows for proper distribution of experiments within the boundaries of factors being studied such that the number of experiments required to develop a sound relationship between the factors and a response is minimized. In the past, very little use has been made of statistical experimental design in copper electrowinning studies. Traditional one- variable-at-a-time approaches are widely employed for this purpose. The present study employs a factorial experimental design to relate current efficiency with current density (180 and 300 A/m2), copper concentration (25 and 65 gL), and temperature (40 and 60 °C). Pure synthetic electrolyte with a constant acid concentration of 180 g/L was used throughout the study. The designed study produced a linear relationship where the independent variables of current density, copper concentration, and temperature, and their interactions, were found statistically significant. It was shown that current efficiency could not solely be used as a predictor of copper cathode quality. The quality of the deposit is difficult to be incorporated into a model or relation. It was determined that other measures, such as cathode morphology and crystal structure should be considered. This was done through XRD and SEM analysis.

Jan 1, 1999

By K. Asokan, K. Subramanian

"Electrowinning of copper by monopolar cells require common anode and cathode busbar and crossbars to connect each electrode to the respective common busbar. On the other hand, the bipolar configuration warrants the end electrodes only to be connected to busbars; there is substantial reduction in copper requirement. In the present work, an electrowinning cell with bipolar electrodes and end electrodes, each having an area of 1000 cm2 was designed and operated. The bipolar electrode is made of mixed metal oxide coated titanium mesh welded to plain titanium sheet. Coated titanium mesh acts as anode and the plain titanium sheet acts as cathode. Environmentally unacceptable lead anode and the recurring loss of lead are done away with. Closer spacing of the electrodes, paves way for the application of higher current density leading to mass transfer enhancement. Performance of bipolar copper electrowinning cell is reported.1. IntroductionThe normally adopted practice in electrowinning of copper is the conventional monopolar configuration. In this practice, the individual electrodes act either as anode or cathode. Hence there is a need to connect every one of the electrodes to the common anode or cathode busbar and crossbars running across the top of the cell are necessary. The common busbar carries very high current which is divided among the individual crossbars and hence has to be thicker in relation to the current load of the cell. The drawback of the need to use common busbars of thicker cross section and the need to have crossbars are obviated in the bipolar configuration."

Jan 1, 2009

By M. Benavides

An experimental study is carried out With sulphide ore obtained from Bailadores-Venezuela as well as artificial concentrates. Concentrates of the minerals from froth flotation are fused to study equilibrium between the matte and slag phases. The first part of the work deals with obtaining a concentrate by flotation experiments with collective and selective reagents, with acceptable metallurgical recovery, studying the influence of different parameters in the process. The second part gives the results of the experimental investigation. on thermodynamic equilibrium in smelting which facilitates knowledge of the elemental processes, giving bases for the possibilities of reducing the loss of metal in slag.

Jan 1, 1983

By Pinakin Chaubal

An analysis of the blast furnace and the low-pressure shaft DR furnace is carried out by redefining the reaction zones. The concept of a characteristic reaction gas temperature (CRGT) is introduced and the two reactors are compared and contrasted using some recent process developments with an aim to develop a platform for further synergistic innovations.

Jan 1, 2006

By Kurt Svens

"As zinc consumption is gradually increasing all the time in the world, many zinc plants are looking for possible expansions. As the sulphuric acid market as well as the fertilizer market in many areas is saturated, the costs for the roasting-acid plant section of the zinc plant will create problems when making feasibility calculations for possible expansions. For solving the customers' situation, two proven zinc concentrate direct leaching technologies are available. A third one, which is possible, does not have any industrially proven applications in the zinc area.IntroductionTime to time, the zinc plants in the world scrutinize their operations with respect to their cost efficiency, the total zinc recovery and the near-by or far-away consumer markets, especially the for zinc and sulphuric acid. Their preliminary profitability calculations can show that a possible total expansion is not economical, when they are looking to expand the whole roasting/acid plant - leaching - solution purification - electrowinning - casting route, as the possible market price for the sulphuric acid is low or the sulphuric acid market is too far away. Based on these facts, their economical study often indicates that implementing a zinc concentrate direct leaching option could be more favourable. Regarding this situation, several aspects concerning three alternative direct leaching methods will be discussed, of which pressure leaching and the atmospheric leaching processes have several industrial applications in the zinc industry, as the ultrafine grinding - conventional leaching process at present has none. As iron is also dissolved during zinc concentrate direct leaching, iron removal processes generally used in the zinc industry are additionally discussed below."

Jan 1, 2012

By Kimio Itagaki

Thermodynamics and rate process fundamentals are two of the important principles involved in nonferrous production processes. The process configuration establishes whether thermodynamics or rate process behavior is most relevant in a particular application. In this paper, thermodynamic theory and rate process fundamentals are used to analyze the main characteristics of smelting and converting processes. The effect of increased oxygen potential .is examined with emphasis in view of the increased use of highly oxygen-enriched gas in modem smelting processes. Phase equilibrium and the distribution of minor elements between copper or nickel matte and FeOx-SO2- or FeOx-CaO-based slag are reviewed. The use of oxygen-rich gas has no serious effects on 'the recovery of valuable copper and silver in the matte phase, while the recovery of nickel and cobalt is adversely affected. The oxygen content in the gas also strongly affects the distribution behavior of arsenic, antimony and bismuth. Analysis of the rate processes occurring in the shaft of flash smelting, and converting furnaces by a 3-D computational fluid-dynamics model is also discussed. After being validated with experimental data collected in a large laboratory furnace, the computer model has been used to simulate the main features of an industrial flash converting operation. The results present quantitative features of the improved mixing of the particle-gas suspension and increased oxygen efficiency obtained with a distributor-cone burner compared with those with a single axial entry burner. The role of basic principles in the engineering analysis of high-intensity matte smelting processes is also discussed.

Jan 1, 2002

By Keith E. Forrester

This paper presents results of bench scale laboratory evaluation of a processes developed by FESI and Brookhaven National Laboratories for the extraction and recovery of Pb and other heavy metals from incinerator ash which was subsequently modified by FESI for the extraction and recovery of Pb from soils excavated from a FESI client scrap yard and battery breaking operation facility. The specific waste matrix presented within the paper is a battery acid contaminated surficial soil at 0" to 12" depth. The extraction method was found to be highly successful on the bench scale in generating a final post-extracted soil matrix which passed TCLP Pb regulatory limits and retained minimal Pb after aggressive extraction application. The paper findings at this time are brief, as a majority of the research results are currently being compiled and additional efforts are underway based upon initial screening findings.

Jan 1, 1995

By Bing Li, Miao Shen, Qiang Wang, Yuqi Chen

Electrochemical methods including cyclic voltammograms, square wave voltammograms, chronopotentiometry are applied to characterize the reduction potentials of Na+ and Li+ ions in LiCl-KCl melts. According to theoretical calculation, the reduction potential for Na+ is slightly more negative than Li+ in NaCl-LiCl-KCl melts at 450℃. However, by electrochemical measurements, the reduction potential of Na+ is slightly more positive than Li+ in the above melt and the potential difference between Na+ and Li+ reaches 0.16-0.2V on an inert W electrode in 1.0-2.0 wt% NaCl-LiCl-KCl melts. An active Pb electrode is used to improve the removal rate of Na+ from LiCl-KCl melts. The reduction potentials for both Na+ ions and Li+ ions on a Pb electrode shift to more positive values and the reduction currents become larger. After 6h electrolysis on a Pb electrode at -3.0V, the practical removal efficiency of Na+ ions reaches 90.12% and the reduced products contain metallic Na and Li with a Na/Li mass ratio of 4.25/1.

Jan 1, 2015

By Beatriz Ramírez

Xanthates are anionic collectors normally used in flotation devices to modify the hydrophobic surface of sulphide minerals. Xanthates are heteropolar compounds and in aqueous media they dissociate into ionic xanthate and alkali-metal ions; nevertheless their behaviour is not well understood yet. This work characterises the six reactions describing the decomposition of the ionic xanthate in aqueous media by analysing the set of spectra from a UV- Spectrophotometer. Results show the effect of pH on the stability of certain compounds which can be useful to explain the relationships among xanthates and the hidrophobicity of some surfaces (or ions dissolved).

Jan 1, 2006

By Abhishek Lahiri

Titanium dioxide is extracted from titaniferous ores by chloride and sulfate processes. These two processes produce wastes in the forms of iron chloride, iron sulfate and rare earth oxides gangue, each of which has to go through a further treatment before it can be disposed safely, which may be expensive. The shortage of high-grade ores is also making the two conventional processes less efficient. In view of the above mentioned problems, an alternate beneficiation process of roasting titaniferous ores with soda ash is discussed. The advantage of this process is that, there is no production of wastes. The impurities present in the ore can be selectively separated after the roasting process. The roasting of titaniferous ores with soda ash was carried out between temperatures of 873K and1173K for several hours. The roasting process resulted in the formation of complex alkali compounds and various sodium titanate compounds, depending on the Na2CO3to ore ratio. The phases formed after roasting were characterized using the X-ray powder diffraction (XRD), X-ray florescence (XRF) and scanning electron microscopy (SEM) techniques. The phase equilibria in the Na-Ti-O system are evaluated and compared with the phases obtained after the roasting process. The effects of temperature and the proportion of sodium carbonate on titaniferous ores are also discussed. From the experimental data, the overall reaction kinetics and phases formed were analyzed to ascertain the mechanism of overall reaction and the rate-limiting steps.

Jan 1, 2006

By James Wang

In July 2003, The Office of Hydrogen, Fuel Cells and Infrastructure Technologies of the Department of Energy (DOE) Office of Energy Efficiency and Renewable Energy solicited Grand Challenge Proposals to establish three Centers of Excellence in hydrogen storage developments for reversible metal hydrides, non-reversible chemical hydrides and carbon storage materials, respectively. The program mission is to research and develop cost-effective, on-board hydrogen storage systems that enable a minimum range of 300 miles within the weight and volume constraints of the vehicle. Currently, no hydrogen storage technology available can meet the DOE cost and performance targets. In April 2004, Sandia National Laboratories was selected by DOE to lead the Metal Hydride Center of Excellence with partners from 5 other national laboratories. We will present the organization and recent accomplishments of the Metal Hydride Center which is confident to accomplish DOE/FreedomCAR and Fuels Partnership objectives for 2010 in hydrogen storage for vehicular transportation applications.

Jan 1, 2006

By Robert D. Boiler, Bill Wilkie

"There is a wide choice of different types of woven filter media for hundreds of different filtration applications. Factors such as type of fiber, synthetic polymers used, weave style, fabric finishes and fabrication techniques all play an important part in selecting the best choice for a specific type of filter and process application. The purpose of this paper is to offer some basic knowledge of these factors and how they can impact the performance of a filter, the life of the media and the overall cost of operation through case studies of actual plant filtration applications.IntroductionThe use of woven filter cloth in liquid/solid separation applications is generally well known. Woven filter cloth, by the nature of the weaving process, offers unique consistency and repeatability when compared to some other filter media such as needled felts, papers, sintered structures and knitted cloth. This unique consistency and repeatability is particularly applicable to woven filter cloth produced using monofilament fibers. These fibers are consistent in shape and form the basis for a woven cloth with predictable pore size and throughput characteristics. Woven filter cloth can be used in most wet filtration applications. Typical examples are the separation of chemical and pharmaceutical solids from process liquors, waste stream solids capture, liquid foods clarification, mining separations, and polymer filtration.EnvironmentOne of the first considerations is the environmental demand of the given process. Though it is tempting to look immediately at the particles in a filtration process, it is often better to consider some of the more basic needs of the system. There are numerous materials available, both synthetic and wire cloth. Each has its own unique set of properties."

Jan 1, 2012

By M. L. Free

Electrowinning is directly impacted by many parameters that include electrolyte composition, voltage, current density, contact resistance, temperature, electrode spacing, and fluid flow as well as many other interrelated factors. The effects of these parameters are primarily related to thermodynamics, mass transport, and electrochemical kinetics. In this study thermodynamic, mass transport, and electrochemical kinetic equations are simultaneously solved to determine the effects of such parameters on electrowinning current efficiency, power consumption, electrodeposit morphology, and electrodeposit distribution. Modeling predictions will be compared with experimental results.

Jan 1, 2006

By Alexander A. Knminskii

Polymorphism of BaR2F8 compounds is analyzed, and some peculiarities of obtaining monoclinic low-temperature (3-BaR2F8 crystals (R=Y, Ho-Yb) and orthorhombic high¬temperature a-ßaR2F8 crystals (R=Yb, Lu) by the Bridgman-Stockbarger growth technique are discussed. We pay a special attention to BaYb2F8:Er3+ crystals, which are able to generate both 2:µm SE using the new four-level operating scheme (4F9/2?4I11/2 laser channel) and 2- and 3-µm SE by means of the cascade scheme (4F92?+4I11/2?+4I31/2). This 2-µm generation of Er3+ ions has an advantage over similar SE of Ho3+ and Tm3+ ions (especially under diode laser pumping), that is important in designing the medicine and ecology laser. We report on orthorhombic BaR2F8 crystals with the ordered structure, a new crystalline materials for generating Ln3+ ions. The growth conditions are determined and orthorhombic BaLu2F8 crystals of several cm3 in volume doped with Ce3+, Nd3+, Ho3+, Er3+, and Tm3+ ions are obtained for the first time. Spectroscopic and laser characteristics of these crystals are discussed for Nd3+-and Era+-doped samples serving as representative examples. In particular, low-threshold stimulated emission was excited in 4F3/2?+4I11/2 channel of Nd3+ ions in the BaLu2F8. Room-temperature generation was obtained also at -1.317 µm wavelength for Nd3+ and at ~2.8 µm (several lines) for Era+ ions in this new laser crystalline host with a threshold of about 20 J.

Jan 1, 1997