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By Yong Kuk Park

The horizontal cold chamber die casting process can produce a wide range of near-net shape, non-ferrous castings with small dimensional variation, excellent surface finish and very complex geometries. However, top quality die castings can be achieved only when optimal performance of the cold chamber and plunger is maintained during the molten metal injection phase of the process. Cold chambers (shot sleeves) are known to deteriorate fast and sometimes fail catastrophically because of poor design. Catastrophic fracture and wear due to deformation are leading causes to degrade quality, increase downtime and thereby decrease productivity and profitability. Therefore, a systematic approach to minimize irregular and adverse conditions which prevent an intended injection profile, is highly desirable. To eliminate them, design criteria for shot sleeves were developed using analytical tools and available experimental data. The correlation between design and mechanical failures of shot sleeves was shown by the data obtained from the die casting industry. Also, the relationship between die casting process parameters and deterioration/ failure mechanisms were carefully evaluated.

Jan 1, 1996

By W. D. Cho

Fast dissolution of nonmetallic inclusions such as alumina particles in molten slags has been required in secondary steelmaking -ladle and tundish - to minimize the amount and the size of nonmetallic inclusions in steel products. In the present work, the dissolution behavior of alumina particles in molten CaO-A12O3 and CaO-A12O3-SiO2 slags at the temperatures between 1450 and 1550°C have been investigated in terms of kinetics and mechanism. Alumina particles were added directly into the slags and the variation of the particle size with time was determined using optical and electron microscopies. The conventional types of slag for ladle and tundish were included in the dissolution study. The effects of Al2O3, Siq, CaF2 and MgO contents on the dissolution rate of alumina particles have also been determined. The diffusion boundary layer between alumina particle and bulk slag phase has been observed and analyzed using SEM and EDS. Based on the analysis of kinetic data and the boundary layer, the dissolution mechanism has been discussed.

Jan 1, 2002

By Brajendra Mishra, Mark L. Strauss, Gerard P. Martins

Nearly the entire worldwide production of europium is recovered, as a minor constituent, from mining bastnäsite, monazite ore, or ion absorbing clays. However, this research indicates a process to recycle europium from waste lamp phosphors as a strategy meet the demand for europium. In this process, waste fluorescent lamp powder is retorted, sieved, leached, and precipitated to produce a mixed europium/yttrium rare earth oxide (REO). Europium is separated from yttrium by selectively reducing Eu(III) to Eu(II) using zinc powder and precipitating europium (II) sulfate from solution using sulfuric acid. Screening experiments were conducted observe the effect of pulp density, precipitation time, entrance pH, and stoichiometric ratio sulfate upon the grade and recovery of europium (II) sulfate. The best conditions to maximize grade and recovery of europium (II) sulfate were a 1 h precipitation time, 10 the stoichiometric ratio of sulfate, 100 g/L mixed REO, and the entrance pH equal to 3. The maximum grade of europium sulfate was 95.93%, and the maximum recovery was 73.32%.

Mar 1, 2018

By T. Goda, H. Kiuchi, M. Iguchi

"IntroductionThe utilization of silver in the electronic industry has been increasing in recent years. It is desirable that valuable metals are recovered from the used scraps of these industrial goods. Condensor chips, for example, contain silver, palladium, and Ag-Pd alloy. The dissolution behavior of silver was studied assuming that scraps such as used condensor chips in which Ag-Pd paste is used are subjected to wet treatment.ExperimentalIn this study the powder, granules, and flakes of silver were used in these nitric acid leaching experiments. The nitric acid solution was agitated in a glass reactor with a magnetic stirrer and heated to the required temperature. The experiment was started by putting the silver sample in the solution. After the leaching, the solution was filtered and the concentration of silver in the filtrate was analyzed by ICP.ResultsIn dilute nitric acid of less than 5 N, silver powder dissolved easily with increase in the concentration of nitric acid and temperature. However, the more intensive the stirring of the solution was, the lower the dissolution quantity became. Fig. 1"

Jan 1, 2000

By Ramana G. Reddy

In the past, many lead-containing slags and wastes were stored in piles or landfills. However, shortages of landfill space as well as increased public, concern about the toxic nature of disposing lead containing industrial wastes in landfills have led to review of disposal methods. Several lead wastes are processed to provide commercial products. They are used on-site in land reclamation projects. or are processed and sold as a by-product. These by-products contain nutrient elements needed for plants or animals and also may contain heavy? metal contaminants such as As, Cr. Cu, Zn and Ph. Use of such by-products containing unacceptable levels of these contaminants could cause plant and animal toxicity. In this paper. role of viscosity in conversion of lead slag wastes into commercial products containing ,low content of lead and other, heavy metals is presented. Effects of slag viscosity on the velocity of movement of metal' and matte prills through themolten slag layer in the melting furnace is discussed. Current and emerging slag cleaning technology, foamed, granulated and pelletized slag technologies are reviewed.

Jan 1, 1995

By John Frederick Colloghon, O&apos

Bulong remains the only hydrometallurgical process plant in the world that recovers nickel and cobalt directly from high pressure acid leach (HPAL) laterite leach liquors without need for precipitation of an intermediate product (e.g. sulphide, hydroxide or carbonate). Direct solvent extraction (DSX) of both nickel and cobalt in combination with electrowinning of nickel has been operation at Bulong since early 1999. Focus in the first years has been on ramp-up and resolution of commissioning problems. More recently the focus has been on de-bottlenecking and process optimisation. A number of significant process problems have been resolved, the most difficult being the formation of gypsum in the nickel solvent extraction circuit. Sound control of process chemistry is essential to ensure the production of high quality nickel and cobalt products at the lowest possible cost. This paper describes the numerous changes and enhancements to the process chemistry and plant equipment at Bulong and discusses the importance of ore leach chemistry on downstream impurity metal removal. Potential additional enhancements to further reduce unit costs are also presented.

Jan 1, 2004

By G. Riverin, C. Simard, W. D. Stevens

"An on-line technique to measure the efficiency of decoating I delacquering processes is being developed by Alcan' s Arvida R & D Centre. Decoating processes are used to remove moisture and coatings from shredded coated material such as Used Beverage Containers (UBC) before melting. Complete removal has been demonstrated to maximize metal recovery. Quantifying the weight of carbon and organic residue adhering to the shred surfaces is very difficult to measure directly, as the material can be highly folded. The technique developed indirectly measures the residue remaining by analysing the concentration of CO evolved in the decoater end zone exhaust gas.A commercial CEMS (Continuous Emission Monitoring System) incorporating an infrared type CO gas analyser was modified for on-line process exhaust gas analysis. Both pilot and plant trials had demonstrated that the CO concentration measured was inversely proportional to the efficiency of the organic removal achieved. As the quality of coated purchased scrap can be highly variable in moisture and organic content, continuous measurement should permit adjusting the feed rate and other decoater process parameters to the quality of decoating required."

Jan 1, 2000

By Larry Southwick

In the early 1940's, the Caron ammonia ? ammonia carbonate leach process was used to produce nickel from Mayari ores at the Nicaro plant in Oriente Province, Cuba. While plant operation was generally successful, it was not broadly economical and was shut down. The plant was later restarted in the 1950's and a number of investigations initiated to resolve the more serious operational and performance issues. Processing steps studied included iron reduction (chemistry ? nickel and iron, reductant, equipment), ore variability (homogeneity and consistency of mineral concentrations, serpentine vs. laterite), leach solution strength, nickel recovery (temperature ? reduction and leaching, reoxidation) and a variety of other topics. These studies and their findings will be discussed. Caron himself obtained good results on these ores in the laboratory. They could not be duplicated in the field, the reasons for which will be reviewed. (Note: the ore looked like garden dirt; charcoal made from palm trees was one of the reductants attempted; and ammonia was the leach solution. Mixing the three, so to speak, was to yield nickel.)

Jan 1, 2006

By S. C. Grand, T. J. Auping, K. Born

Process control, environmental monitoring, budgeting and accounting are based on process data. Without appropriate tools for data analysis, the process data could remain unused and wasted. This paper demonstrates how data reconciliation can be used as a tool to develop closed mass balances. Mass balances are the initial step in plant optimisation (technical, economical or environmental). From mass balances, fundamental process models can be developed. These balances link process parameters (e.g., feed materials) to process performance (e.g., recovery of valuable elements). Some of these models could find their way into simulators useful to plant operators. Classical regression methods regularly fail when they are applied to complex non-linear problems involving a large number of variables. Alternatively, multiparametrical regression analysis can be successfully applied with the aid of neural networks based on reconciled data. Both methods have been applied to plant data originating from the hydrometallurgical zinc plant at Ruhr-Zink, which in this paper serves as a case study. Very promising and useful results were obtained from this study.

Jan 1, 2000

By Michael J. Nicol

One of the preferred methods for the recovery of gold from refractory gold ores and concentrates involves pressure oxidation in acidic solutions. The main refractory gold-containing minerals are pyrite and arsenopyrite and there is evidence that the presence of even small amounts of chloride can inhibit the oxidation of these minerals and also substantially reduce the recovery of gold. In this paper, the results of a study of the anodic (oxidation) and cathodic (reduction) behaviour of pyrite electrodes in acidic sulfate solutions containing ferric ions at different chloride concentrations and temperatures up to 200oC and pressures of 2000KPa are presented. The electrochemical studies have been complemented by pressure oxidation experiments on a refractory gold concentrate. Results have shown that, as the chloride concentration increases, the anodic reactivity of pyrite is largely unaffected but the rate of the cathodic reduction of iron(III) decreases. The rate of oxidation of a sulfide concentrate and the recovery of gold by cyanidation of the residues decreases at high concentrations of chloride.

Jan 1, 2003

By Xiaorong Liu

Interfacial emulsion generated in copper solvent extraction is an inhomogeneous O/W emulsion that consists of organic phase, aqueous phase and solid particles. In order to determine what kind of components in organic phase promotes the emulsion, the organic phase separated from the interfacial crud provided by Dexing Copper Mine in Jiangxi, China was analyzed for its components by combined gas chromatography-mass spectroscopy. It was found that many kinds of emphiphiles containing such hydrophilic groups as carbonyl, carboxyl, or acylamine existed in organic phase, most of which were originated from the reagent degradation. Conclusively, Lix984N would degrade gradually during a long-term contact with the acidic aqueous feed and strip reagents. Lix84 and nonylphenol, as effective components of Lix984N, degraded almost completely after long-term recycling. As a result, the effective components of Lix984N were far lower in concentration than the dense-aromatic impurities derived from the diluent and the degradation products in total. The degradation of Lix984N would deteriorate solvent extraction, disengagement performance and result in more serious interfacial emulsion.

Jan 1, 2006

By Y. F. Jia

Arsenic constitutes a major contaminant for the hydrometallurgical industry. Its removal and immobilization from process effluents typically involves lime neutralization and co-precipitation with ferric iron (Fe (III)/As(V)>3). Alternatively, precipitation of scorodite (FeAsO4?2H2O (cr)) may be applied to arsenic fixation. The mechanism of arsenic fixation in the former process has been suggested to be surface adsorption. Unequivocal characterization of these products is difficult because of their amorphous nature hence a variety of methods need to be applied including the particularly powerful method, extended x-ray absorption fine structure (EXAFS) spectroscopy. In this study, we have investigated the preparation of arsenate-adsorbed ferrihydrite with the purpose to compare its structure to that of Fe(III)-As(V) co-precipitates and scorodite (both amorphous and crystalline). Furthermore the solubilities of these Fe(III)-As(V) solids are measured as a function of pH. Their structures are elucidated and correlated to their solubilities and thereby the application of these findings to the practice of arsenic removal and disposal is assessed.

Jan 1, 2003

By Takayuki Ichikawa

Hydrogen storage properties of ballmilled mixtures composed of the hydrogenated nano-structured carbon (CnanoHx) and lithium hydride (LiH) were examined by thermal and optical spectroscopic analyses. LiH needs higher temperature than 600°C for hydrogen desorption even under vacuum condition, while CnanoHx, which was mechanochemically synthesized from graphite powder by ballmilling under hydrogen atmosphere, reveals hydrogen and hydrocarbons desorption in wide temperature range from 300 to 800°C. Nevertheless, the composite of CnanoHxand LiH prepared by ballmilling desorbs hydrogen in relatively lower temperature range from 150 to 450°C. These phenomena indicate that the thermally liberated hydrocarbon radicals immediately react with LiH and release hydrogen instead of hydrocarbons emission, because CnanoHx contains hydrocarbon groups at the edge of nano-meter sized graphenes, which are recognized as IR active C-H stretching mode, and LiH is well-known as an ionic crystal. Furthermore, it is of interest that a nanostructural feature persists in this composite even after annealing at 350°C, which shows excellent cycle properties as hydrogen storage media.

Jan 1, 2006

By Roberto Parra

The wear and corrosion phenomena in the furnace lining of the ferrous and non ferrous pyrometallurgical processes are complex problems where chemical, interfacial and mechanical phenomena are presents. The characteristics of the processes determine the conditions to which these materials are submitted, where the thermal conditions reached during the operation is one of the most important parameter. Assuming that all the degradation phenomena are thermal activated, the rate of the different steps of the wear mechanism will depend on the thermal field in the lining. In view to apply the independent physicochemical knowledge of degradation mechanisms to the analysis and design of furnace lining the methodology of the Nodal Wear Model (NWM) was done. It combines the mathematical modelling of the heat transfer in the lining with the physicochemical control equation for the wear-corrosion phenomena. The NWM has been applied to different examples: theoretical analysis, laboratory scale test and industrial applications. We present in this paper the theoretical background of the model and two examples of applications: the sole of an electric furnace and the earth of a blast furnace.

Jan 1, 2006

By Rainer Köster, Tobias Wagner, Markus Delay, Fritz Hartmann Frimmel, Wolfgang Ferstl, Wolfgang Höll

"The mobilization of contaminants from industrial residues like ashes from municipal solid waste incinerators in case of leaching is investigated world wide. In classical leach tests only soluble species are considered. In addition the geochemical behaviour of residues has to be completed by assessing the mobilization via colloidal particles. This transport is well known from natural aquatic systems. Quantification of aquatic colloids is associated with considerable difficulties, because they are often found in low concentrations and in a size distribution where small particles with diameters below 0.1 µm predominate. In the past years, the Laser-induced Breakdown Detection (LIBD) has been developed as a novel sensitive method for quantifying colloids. Column leaching experiments with directly coupled LIBD were used to quantify the release of heavy metals and colloids out of bottom ashes. Some typical colloid bound heavy metal concentrations in the leachate are in some cases exceeding the limits defined by German authorities. The LIBD with a flow-through cell allowed to assign absolute values to colloid size and concentration."

Jan 1, 2008

By M. M. Salari Rad

An investigation of gold distribution in the mill products of Sar Cheshmeh beneficiation plant demonstrates that on average 44% of the gold is routinely recovered as a by-product in the copper concentrate, and the remaining is lost to the tailing. In order to evaluate the causes of gold losses, the distribution and mode of gold occurrence in the Sar Cheshmeh ore and mill products were studied. Searching for gold within samples and within individual grains of sulphide minerals was carried out by SEM in the backscattered electron mode and SIMS, respectively. The mineralogical distribution of gold revealed by microbeam techniques were combined with the results of relevant metallurgical experiments including, sizing, heavy liquid separation, and diagnostic leaching tests, and the nature and location of gold in the ore and mill products were determined. The combined results of the experimental approaches pursued suggest that while there are some gold in solid solution and/or -colloidal size within sulphides of the Sar Cheshmeh ores, "visible" gold is the principal form of gold occurrence at Sar Cheshmeh.

Jan 1, 1999

By Laila A. Guirguis

Impurities are removed from crude phosphoric acid (57.75% P2O5) with a mixture of low and high molecular weight alcohols, one of which is hydrophilic and the other is hydrophobic i.e. methanol and hexanol. In a single stage, the phosphate values segregate to the high molecular weight alcohol fraction and the impurities segregate to the low molecular weight alcohol fraction. The optimum ratio for the extraction is found to be 0.5 part methanol, one part impure acid and four parts hexanol where an extraction percent of more than 95% is achieved. Re-extraction of the phosphate value from the solvent is obtained by 6% phosphoric acid and the different factors affecting the re-extraction process have been studied. Finally, the purified acid is concentrated under reduced pressure and passed through activated carbon column, whereas the alcohols are re-circulated. The produced phosphoric acid was found to be in good match with the international specifications of food grade quality acid. A technological flow sheet is elucidated.

Jan 1, 2006

By Luiz R. P. De Andrade Lima

This paper presents a mathematical model for the oxide copper ore heap leaching process. The data used in the model include physical-chemical, .geometrical and operational data, as: leachable metals ore contents, .flow rate and acid concentration, parameters of passivity, ore size distribution, the average residence time of the solution in the heap, height, irrigated area and weight of ore in the heap. In this model the heap is divided into horizontal and plane layers of constant area. The flow of the liquid in the heap is considered unidirectional and the solid-fluid reaction model is considered under diffusive control. The average residence time of the solution into the heap and the apparent effective diffusivity of the acid through the ore particles have .a significant influence on the rate of the copper extraction and its concentration in the pregnant solution; therefore these parameters are used in the model calibration. When this algorithm was applied to a laboratory test, the results showed that the model is adequate to predict the process performance.

Jan 1, 1999

By Bruce W. Downing

MagPower has developed methods to control the detrimental formation of hydrogen that occurs in electrochemical reactions in numerous commercial applications such as the Magnesium-Air Fuel Cell, electrowinning, zinc alkaline batteries, hydrogen embrittlement, waste water/ metal recycling and coolants. The company?s approach to an alternative energy source is the development of an environmentally friendly non-toxic alternative power source that generates electricity through a combination of magnesium, oxygen and a saltwater electrolyte with MagPower?s patent pending hydrogen inhibitors. The magnesium-air technology has never reached the commercial stage due to its limiting power output caused by hydrogen generation. MagPowerhas solved this problem and has patents pending on its intellectual property; the Hydrogen Inhibitors and has developed several consumer power units for a variety of applications through licensing agreements. The company has also shown that the inhibitors have an impact on zinc electrowinning through laboratory test work where current efficiency was improved. This will significantly reduce power consumption and increase the efficiency of the electrowinning process, as well as reduce the potential acid mist hazards associated with electrowinning.

Jan 1, 2003

By V. L. Stolyarova

As part of an effort to develop the fluoride electrolysis route for the production of rare earth metals and alloys, a study of the thermodynamic properties of DyF3 has been carried out by Knudsen cell mass spectrometry. A quadrupole mass spectrometer QMS 420 was used in conjunction with the Knudsen cell arrangement. The experiments were carried out in the temperature range 1280-1440 K. Vaporization was carried out from platinum, molybdenum and tantalum cells. The Dy*, DyF+, DyF2+ fragment ions and the DyF3 parent ion were identified in the mass spectrum of the DyF3 vapour. The DyF, vapour pressure was obtained by the complete isothermal vaporizadon method as well as the ion current comparison method, and the enthalpy of sublimation of DyF3 was evaluated. From the DyF3 vapour pressure data obtained at different temperatures, the enthalpies of formation of DyF3 in the gaseous as well as condensed phases have been evaluated. The experimental data are compared with the thermodynamic information available in literature.

Jan 1, 1995