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By J. Leon-Torres, D. M. Stefanescu, P. A. Curreri, S. Sen

"Experiments were performed under terrestrial gravity (lg) and during parabolic flights (10·2 g) to study the solidification and macrosegregation patterns of Al-Cu alloys. Alloys having 2% and 5% Cu were solidified against a chill at two different cooling rates. Microscopic and Electron Microprobe characterization was used to produce rnicrostructural and macrosegregation maps.In all cases positive segregation occurred next to the chill because of the shrinkage flow, as expected. This positive segregation was higher in the low-g samples, apparently because of the higher heat transfer coefficient.A 2-D computational model was used to explain the experimental results. The continuum formulation was employed to describe the macroscopic transports of mass, energy, and momentum, associated with the solidification phenomena, for a two-phase system. The model considers that liquid flow is driven by thermal and solutal buoyancy, and by solidification shrinkage. The solidification event was divided into two stages. In the first one, the liquid containing freely moving equiaxed grains was described through the relative viscosity concept. In the second stage, when a fixed dendritic network was formed after dendritic coherency, the mushy zone was treated as a porous medium.The macrosegregation maps and the cooling curves obtained during experiments were used for validation of the solidification and segregation model. The model can explain the solidification and macrosegregation patterns and the differences between low- and high-gravity results."

Jan 1, 1999

By Yoshinao Kobayashi

he removal of oxygen from titanium and zirconium is important for use in application because it significantly affects the mechanical and physical properties such as ductility and toughness. However, thermodynamic properties of oxygen in molten titanium and zirconium have not been clarified and the effective deoxidation process of molten titanium and zirconium has not been established. In this study, the standard Gibbs energy of reaction of oxygen and yttrium in molten titanium and zirconium have been measured by a chemical equilibrium technique. Molten titanium, zirconium, and their alloys with aluminum were equilibrated with a Y2O3, A12O3, or Zr02 pellet in a cold crucible. The results are summarized as follows:

Jan 1, 2000

By Herbert H. Kellogg

A model of the ISF is described. which reproduces with accuracy the "normal" operation of three industrial furnaces. The model, written in Fortran, is based on detailed heat and material balances, and the concept that the ascending gases reach equilibrium with zinc oxide and with the water-gas shift reaction. "Solution loss" of carbon in the lower shaft, and partial reoxidation of zinc vapor in the upper shaft are also essential features. For prediction of furnace behavior under altered operating conditions (blast rate, temperature, moisture content, oxygen enrichment, or injection of oil or coal through the tuyeres) the model modifies the heat loss, temperature of slag and bullion, amount of reoxidation in the upper shaft and the condenser efficiency to reflect the altered operating parameters. Model predictions for such operating conditions are in reasonable agreement with plant experience.

Jan 1, 1990

By J. D. Miller

Air-sparged hydrocyclone (ASH) flotation is a high-capacity flotation technology originally developed in the Department of Metallurgical Engineering at the University of Utah for processing mineral resources. However, the technology has been found to be useful in industrial waste processing, in the recycle of secondary resources, and in remediation of environmental problems. For example, areas in which the ASH technology is expected to have potential application include cleaning of waste coal fines, air stripping to remove volatile organics from drinking and process water, water disinfection by ozone or chlorine sparging, dispersed oil removal from water, and contaminated soil remediation. Recently, the ASH has been studied extensively for deinking flotation in the wastepaper recycling industry and has been shown to have excellent efficiency/capacity. In fact, a 20-million-dollar plant has been in operation since June 1992. The ASH technology can provide a specific capacity hundreds of times more than that which can be achieved with conventional flotation equipment and in certain instances is expected to provide superior separation efficiencies when compared to other technologies. The design and principles of ASH flotation are described. Experimental data for fine coal flotation, volatile organics stripping, and deinking flotation for paper recycle are presented and discussed. Finally, other potential areas of application for environmental technology are considered.

Jan 1, 1993

By B. Farouk, D. Apelian

"A numerical model has been developed to predict the temperature history of particles injected in a low pressure d.c. plasma jet. The temperature and velocity fields of the plasma jet are predicted as a free jet by solving the parabolized compressible Navier-Stokes equations using a spatial marching scheme. Particle trojectories and heat transfer characteristics are calculated using the predicted plasma jet temperature and velocity fields. Correction factors have been introduced to take into account non-continuum effects encountered in the low pressure environment. The plasma jet profiles as well as the particle/plasma interactions under different jet pressure ratios (from underexpanded to overexpanded) have been investigated.I. IntroductionIn the plasma spraying process a d.c. plasma jet is used as a heat source to melt and accelerate powder particles which subsequently impinge and solidify on a given substrate. During low pressure plasma deposition (LPPD) prooess, the plasma jet is expanded into a low pressure environment (40-80 Corr) which results in high plasma jet velocities with Mach numbers ranging from 2 to 3. Previous efforts to predict heat transfer and fluid flow in plasmas have made use of incompressible flow formulation employing turbulence models [1-3] for atmospheric plasma spraying. However, these theoretical calculations have been limited to the subsonic flow regime; hence, the compressibility effects and viscous heat dissipation were neglected. In the LPPD process, the plasma jet is operated at the supersonic flow regime, therefore, the compressibility effects and viscous heat dissipation are no longer negligible. This is the main motivation of this work.In addition, production of high quality dense deposits requires that a large fraction of the injected particles be in a molten state when they impact the substrate. An additional motivation for this work is that it is important to understand the plasma/particle heat and momentum transfer since these phenomena dictate both the particle thermal history and particle trajectory.Early computational works in supersonic nozzle field flow [4,5,6] consisted of patching methods that divided the flow field into an invisoid free stream and a viscous boundary and. mixing layers. Each was analyzed independently and coupled through appropriate boundary conditions. Later schemes [7,8] involved solving time-dependent, compressible Navier-Stokes equations over the entire computational domain. These schemes show a great promise in predicting flows with complex structure, and where the viscous effects became prevalent."

Jan 1, 1986

By J. L. Jambor

Previous crystal-structure determination of magnesian annabergite (Ni,MgMAsO4)2 8H2O indicated that ordering of Ni and Mg occurs in non-equivalent octahedral sites; such ordering supports the possibility of miscibility gaps on the Ni3(AsO4)2 8H2O -MgiAs04)2 8H2O. (annabergite-hornesite) join. In a predecessor study based on analyses of natural specimens, it was proposed that solid solution is incomplete both for annabergite-hornesite and annabergite-erythrite [Co, (AsO4)2 8H2O]. In the current study, syntheses by use of a slow-addition technique and aging of the precipitates indicated that the annabergite-erythrite solid solution is complete, and that no miscibility gap is present on the annabergite-hornesite join to at least 58 mol % Mg. Thus, interpretation of the compositions of these phases in oxidized mill-tailings impoundments can be done with the normal precautions for homogeneity, and without the added concern of the possible presence of miscibility gaps in the ternary system.

Jan 1, 1995

By D. N. Wilson

The potential risks of working with lead have been recognised for centuries, but it is only with the development of sensitive measuring techniques in relatively recent years that it has been possible to establish effective approaches for the monitoring and control of lead exposure. This paper examines the principal control measures employed today - lead in air and lead in blood - and reviews the evolution of numerical standards, with particular reference to the latest understanding of health effects. In addition to lead, a large number of other metals are commonly encountered when producing lead and zinc - both primary and secondary - and the health effects of many of these are discussed. Modern hygiene practices and technologies, which have proved successful in reducing worker exposures, are reviewed. The paper concludes with a look at how exposure standards are likely to change in the near to medium future

Jan 1, 2000

By O. A. Bascur

Applying the latest information technologies in mining and metallurgical complexes has become a serious challenge to management and technical teams. Emerging component design is changing the way the user relates to the desktop. Connectivity between mining and metallurgical process operations and their business systems has become a reality. Expanded use of plant information on the desktop is a standard tool for revenue improvement, cost reduction and adherence to production constraints. The industrial component desktop support access to information for continuous improvement and innovation by staff personnel and engineers. Collaboration between groups enables the implementation of an overall process effectiveness index based on losses due to equipment availability, production recovery and quality rate. The integration of information from mining, mineral processing and metallurgical performance monitoring increases production efficiency, even when many elements cannot be measured directly. Three case studies of large mining/metallurgical complexes are highlighted.

Jan 1, 1999

By Kuniaki Murase, Tetsuji Hirato, Yasuhiro Awakura

"Electrodeposition of CdTe was studied using aqueous ammonia-alkaline electrolytic baths in which Cd11-and Te1V-ions are dissolving as Cd11(NH3)/+ and Te1vol-ions, respectively. Ca-thodic polarization curves of the baths suggest the presence of strong interaction between the Cd11-and Te1V-ions; electrodeposition of tellurium is inhibited by the presence of Cd(NH3)/+ ions. The interaction makes it possible to electrodeposit CdTe films with stoichiometric composition. Polycrystalline CdTe thin film of about 1 µm thickness was electrodeposited at 343 K from ammonia-alkaline solutions (pH= 10.7) containing TeO32-(<20 mmol dm-3) and Cd(NH3)/+ ( < 60 mmol dm-3) ions. Increasing Cd(NH3)/42+/TeO32- mole ratio or decreasing total concentration of ammonia/ammonium-ion gave flat and smooth crystalline CdTe deposits at constant cathode potential-0.70 to -0.30 V vs SHE at 343 K.IntroductionCadmium telluride (CdTe) is well-known as a compound semiconductor whose band gap, i.e. 1.44 eV, is suitable for solar energy conversion with a photovoltaic cell. Various methods, such as CVD (chemical vapor deposition) and electrodeposition, of preparing CdTe thin films for solar cells have been investigated.Acidic sulfate solutions with a pH of 1-2 are usually employed for CdTe processing by electrodeposition.1-3) The electrodeposition of compound semiconductors is usually achieved (i) at a higher cathode potential than the redox potential of less-noble species, can in this case, and (ii) under the condition of diffusion-limiting current of a more noble species, Te1Y.4) There-fore, a suitable CdII/TeIV concentration ratio in the acidic electrolytic baths, resulting in the deposition of stoichiometric CdTe, is determined by the diffusion-limiting current density of TeIV- reduction, i.e. the concentration of HTeIVO2+ · Since the solubility ofTe1v species HTeIVO2+ in the acidic solutions is quite low, the rate at which CdTe is deposited from the acidic solutions is extremely slow."

Jan 1, 1998

By Hector Henao

To provide thermodynamic data for converting the nickel matte to liquid nickel, an experimental study was conducted in the phase equilibrium between the Ni-S alloy and the CaO-Ah03 based slag melted in a MgO crucible at 1873 K under controlled Pso2 of 10.1 kPa and pO;, in a range between 2.5x,IO,2 and 10.1 Pa by using CO-C02-S0Z gas mixtures. The content of nickel in the slag at POz of 10.1 Pa, above which solid NiO is expected to precipitate in the equilibrium state, was found to be 4.1 mass% and the contents of sulfur and oxygen in the nickel melt were 0.4 and 0.2 mass%, respectively. It was clarified that increase in the temperature reduces the solubility of nickel in the slag and the contents of sulfur and oxygen in the alloy. The distribution of minor elements such as gold, silver, copper, cobalt, iron, arsenic and antimony between the Ni-S alloy and the CaO-AI20) based slag was also studied. The distribution ratios of iron and cobalt, defined by (%X in slag)/[%X in alloy] where X is the minor element, are larger values than that of nickel, while those of copper, silver and antimony are similar to that of nickel. The distribution ratios of arsenic and gold are lower than that of nickel in the higher range of oxygen partial&apos; pressure.

Jan 1, 2003

By Hector Henao

To provide thermodynamic data for converting the nickel matte to liquid nickel, an experimental study was conducted in the phase equilibrium between the Ni-S alloy and the CaO-Al2O3 based slag melted in a MgO crucible at 1873 K under controlled Pso2 of 10.1 kPa and Po2 in a range between 2.5x 10-and 10.1 Pa by using CO-CO2-SO2 gas mixtures. The content of nickel in the slag at Po, of 10.1 Pa, above which solid NiO is expected to precipitate in the equilibrium state, was found to be 4, I mass% and the contents of sulfur and oxygen in the nickel melt were 0.4 and 02 mass%, respectively. ft was clarified that increase in the temperature reduces the solubility of nickel in the slag and the contents of sulfur and oxygen in the alloy, The distribution of minor elements such as gold, silver, copper, cobalt, iron, arsenic and antimony between the Ni-S alloy and the CaO-Al2O3 based slag was also studied. The distribution ratios of iron and cobalt, defined by (%X in slag)/[%X in alloy] where X is the minor element, are larger values than that of nickel, while those of copper, silver and antimony are similar to that of nickel. The distribution ratios of arsenic and gold are lower than that of nickel in the higher range of oxygen partial pressure.

Jan 1, 2003

By S. Viswanathan, A. S. Sabau

"Dimensional changes between a pattern die and its corresponding investment casting part occur as a result of complex phenomena such as thermal expansion/contraction and hot deformation (elastic, plastic, and creep) during the processing of the pattern material (wax), mold material (shell) and solidifying alloy. Determining the pattern tooling dimensions is crucial to the dimensional control of the investment casting process. To date, computational methodologies have not been applied to the prediction of dimensional changes in investment castings.This paper deals with the evaluation of wax pattern dimensions, which is one important factor in determining pattern tooling dimensions in investment casting. Cerita 29-51, an industrial wax, is considered in this study. The wax pattern dimensions are determined by considering its thermo physical and thermomechanical properties, restraint of geometrical features by the metal die, and process parameters such as dwell time, platen temperature, injection pressure, and injection temperature.IntroductionThe investment casting process involves making a disposable wax pattern by injecting wax into a metal mold, building a ceramic shell mold around the wax pattern by the application of a series of ceramic coatings to the wax pattern, dewaxing the ceramic shell mold, and casting the alloy into the shell mold. Dimensional changes between the pattern tooling and its corresponding cast part occur as a result of thermal expansion, shrinkage, hot deformation, and creep of the pattern .material (wax), mold material (shell), and solidifying alloy during the processing [1]."

Jan 1, 2001

By M. M. Kim

As-electrogalvanized coatings of pure Zn, Zn-11% Fe, and Zn-18% Fe coatings were characterized in terms of initial crystal structure and surface morphology. Samples were then subjected to heat treatments simulating the paint bake cycle of automobile manufacturers. Surface morphology changes were correlated with the process variables, and crystallo.graphic changes were interpreted by mapping heat treatment routes on the Fe-Zn phase diagram. The morphology of pure zinc electrogalvanized coatings with heat treatment from platelets to smeared platelets. The zn-11% Fe coating changes with heat treatment from tetrahedral nodules to a mixture of round and tetrahedral nodules, with the Zn-:18% Fe coating always having round nodules. Regarding crystal structure, a critical transformation time can be defined at any selected temperature, below which the crystal structure does not change. This temperature is related to iron content.

Jan 1, 1990

By Xu Weimin

The existing copper electrorefining tankhouse of Jinchuan Nonferrous Metals Complex (JNC) was commissioned in 1986 for refining blister copper anodes. Blister copper is produced by reverberating chalcocite separated from converter high grade nickel-copper matter by means of flotation. Special chemical analysis of the anodes shows, a composition of 93.02 - 95.72 % copper, 3.0 - 4.96 % nickel and 0.5 - 1.23 % sulfur. The wide range of composition makes the electrorefining process fairly different from others throughout the world. The initial nickel content of 20 ppm and sulfur 40 ppm or more in copper cathodes are reduced to 8.5 ppm and 11 ppm respectively. Since 1986 the tankhouse has undergone significant evolutionary modifications and implementations to ameliorate cathodes quality desirably. The important fact is that the N-additive was utilized through many studies and pilot and field trials successfully. While our primary purpose is to improve chemical quality of the cathodes, tankhouse capacity is increased considerably and the process is perfected satisfactorily. The tankhouse is described with special emphasis on JINCHUAN PROCESS. The upgrading of our product by the utilization of the N-additive is highlighted. The other aspects of the tankhouse including spent electrolyte treatment and by product nickel sulfate manufacturing are briefed as well. Key words: JINCHUAN PROCESS, anode, cathode, electrolyte, electrorefining, N-additive.

Jan 1, 1993

By Ronald Erdmann

Today the BOF filter dusts and sludges are mainly dumped due to their zinc contents. By typically ranging from 2 to 5 % they prevent the filter dusts and sludges from beeing recycled via the blast furnace route. Based on the different discharge kinetics of Iron and zinc during the main blowing period In a bottom stirred BOF a simple and efficient system for recovery allow zinc fractions has been developed. The obtained material Is suitable for recycling without nsc of shell formation In the blast furnace. Different subsequent development steps have been performed. By starling with a very simple lime dependent model the sludge from the BOF off gas cleaning system was collected in two different sludge channel systems. This model based an the fact that most of the scrap based zinc Is discharged from the melt within the first eight to ten minutes of the BOF process. To Improve the system a spectroscope zinc sensor was Installed at the hot section of the off gas cleaning system to get more reliable informations on the actual zinc concentation of the BOF dust. By use of the system up to 50 % of the BOF sludge can be recycled.

Jan 1, 1995

By Rodney J. Ishak

The reduction of Mn3O4 to MnO has been investigated in a thermobalance apparatus, The charge was composed of manganese ore (decomposed by heating/calcination or pre-reduction to mainly Mn3O4) and coke. The material was charged to a crucible, which was suspended in the balance. CO-gas was distributed through a grid in the bottom of the crucible. Two sizes of ores were used; 2.4-4.8 mm and 6,7-9.5 mm. Coke particles were in the size range 4.8-6.7 mm. Experiments were conducted in the 900-1100°C temperature range. The composition of the product gas was monitored continuously. External mass transport between bulk gas and particle surface does not seem to limit the rate of reduction. Assuming that both diffusion through product layer and chemical reaction at the interface between MnO and Mn)04 are rate controlling, the data was tried both in a shrinking core model and in a grain model using regression. The grain model gives the best physical description of the process, because the reactant is in fact a porous medium. With this model the effective diffusivity was calculated to be in the 1.5-6.10.5 m2/s range. The pore size was mainly between 0.1 and 10 um,

Jan 1, 2003

By M. Sakamoto, S. Karaswa, Y. Yoneoka, Y. Ohmizo

"The Annaka Refinery has been processing leach residue by Waelz process for 17 years. Recently, the quantity of the leach residue has increased due to a decline in the quality ~f zinc concentrate. Meanwhile, negative factors (e.g. deterioration of water balance due to improved electrolytic power consumption rate) have increased· in the processing of the leach residue.We have implemented various measures in responses to this situation, while striving to increase ·processing capacity and achieve stable operation. AS we have largely completed our assessment of the efficacy of these measures, we report on our recent process improvements.IntroductionWe have been treating leach residue by the Waelz kiln process since 1981. At that time, treatment of only 50,000 tons of leach residue per year was anticipated. However, subsequent process improvements have revised this figure up to 75,000 to 80,000 tons per year.However, today's increased Fe zinc concentrate grade has resulted in increased amounts of leach residue. In addition, improvements have reduced electrolytic power consumption rate of zinc electrolysis, limiting the amount of water that can be used in ·the zinc refining processes and for deaning leach residue. Consequently, we encounter an increasing number of problems and factors adversely affecting leach residue treatment, including increases in water-soluble Zn (WsZn) and. S (S04) in leach residue.To solve these problems, we have taken several measures to ensure long-term continuous operation and treatment of this increased · amount of leach residue. This paper discusses these measures."

Jan 1, 2000

By T. T. Natarajan, Nagy EI-Kaddah

"Numerical simulation of electromagnetic confinement systems generally requires large CPU time due to the strong coupling between the electromagnetic and the free boundary problems. The present paper examines the accuracy and the computational efficiency of the most common numerical schemes used in modeling such systems. Levitation melting was taken as a test case. In this study, a comparison was made between the finite element and surface integral methods for electromagnetic field calculations. The computational efficiency of Lagrange and the modified Hestenes methods for solving the free boundary problem were investigated. The convergence of the Lagrange method was found to be much faster than the modified Hestenes method. It was also found that finite element method not only gives accurate solutions, but faster convergence to the final equilibrium shape than the surface integral method. The applications and the limitations of these techniques in modeling electromagnetic confinement systems will be discussed.IntroductionIn recent years there has been a growing interest in the use of electromagnetic forces for confinement of molten metals as a means to eliminate molten metal contamination during melting and to improve surface quality of cast products. Continuous casting of metal without contact of a mold is now a reality, and is being commercially applied for casting of aluminum slabs /1/, and copper rods /2/. New applications of electromagnetic confinement in melting and casting include containerless melting (Magnetic Suspension Melting) /3/, edge containment in twin roll casting, and meniscus shape control in continuous casting of steel /4/.Modeling of confinement systems involves the determination of the electromagnetic field and the equilibrium shape. These two problems are strongly coupled due to the dependence of the field on the shape of the melt. While significant advances have been made in computational electromagnetics /5/, the application of developed computational techniques to electromagnetic confinement problems is not a simple task. The principal difficulty in using these methods is that the solution domain is not known a priori. due to coupling between the electromagnetic field and the free boundary problems. These two problems have to be solved simultaneously, leading to an iterative solution procedure. As a result, numerical simulation of electromagnetic confinement systems are computationally intensive with computational time at least an order of magnitude larger than the fixed domain problems."

Jan 1, 1994

By Thomas Gliick, Jianming Lu, David Dreisinger

"The recovery of manganese from the Boleo project of Baja Mining is via an acid oxidation and acid reduction process in seawater. Manganese as manganese dioxide is leached into solution as manganese sulphate with the addition of sulphur dioxide gas as a reductant and then precipitated as a manganese carbonate. The use of the manganese carbonate intermediate to produce electrolytic manganese metal (EMM) has been extensively studied. The manganese carbonate can be used in place of natural (MnC03) or reduced ores (MnO) of manganese as a feed to the EMM plant. Manganese carbonate can be dissolved in spent electrolyte from manganese plating, followed by purification using ammonium sulphide precipitation of minor elements and then electrowinning in a selenium free process. The results of small cell testing of manganese electrowinning are reported.IntroductionThe Boleo Project of Baja Mining is a greenfields development currently under construction approximately 5 km north of the town of Santa Rosalia, Baja California Sur, Mexico. The Boleo property is held by the Mexican company, Minera y Metalurgica del Boleo S.A. de C. V. (MMB). MMB is owned 70% by Baja Mining Corp. and 30% by a consortium of Korean companies consisting of KORES - Korea Resources Corporation, LS Nikko Copper, Hyundai Hysco, SK Networks and lljin Copper.The Boleo deposit has Measured and Indicated resources of264.7 million tonnes grading 1.50% copper equivalent (CuEq) & Inferred resources of 159.9 million tonnes grading 1.15% CuEq. The calculation of copper equivalent is based on a combination of metal prices and predicted metallurgical recoveries (Table I). The metallurgical recoveries have been confined by extensive bench and pilot plant testing. Proven and probable reserves are available at Boleo to provide for more than a 30 year mine life. Initially, 25 years of mine life and 23 years of process plant operation have been scheduled in the February 2010 Technical Report Update (www.sedar.com)"

Jan 1, 2012

By Tim Robinson, Michael S. Moats, Masatsugu Moritmitsu, Kathryn C. Sole, Lauri Palmu, Frank K. Crundwell

"Process technology and design trends for copper, zinc, and nickel electrowinning cellhouses include focusing on energy reduction, productivity, and acid mist abatement. Larger electrodes, longer cells, automation, and higher current densities are leading to more capital-effective designs. The latest cellhouse designs include installation of automated electrode-handling systems, thereby removing more operators from the cellhouse. These technology and design trends result in lower electrowinning operating costs and improved purity of electro won cathode.INTRODUCTIONTechnology transfer between similar industries is an important process in improving product quality and productivity, and reducing operating costs. The electrowinning (EW) recovery of base metals, such as zinc, copper and nickel, is no different. The zinc industry with its larger EW product-handling requirements as compared to nickel and copper, has been driven to automation technology and the use of larger equipment. This technology has been transferred to copper. Nickel has led development and application in large-scale anode and divided-cell technologies but, due to nickel being produced in multiple forms (not just cathode) and being a small part of the whole complex nickel process route, the quantities of electrowon nickel are small compared to copper and zinc. Copper process technology in acid mist abatement was recently transferred to nickel. The focus in copper EW has been on energy reduction and productivity."

Jan 1, 2012