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By Ehsan Khajeh

In this study, the permeabilities of Al-15.5wt%Cu and Al-19.5wt%Cu have been determined by solving the full Navier-Stokes equations on 3D geometries of interdendritic channels obtained by X-ray microtomography (XMT). The samples for XMT were sectioned from different positions in directionally solidified cylinders in order to obtain a variety of microstructures for each composition. The flow has been solved using a 2nd-order accurate Finite Volume Method (FVM) approach. The effect of employing uniform or unstructured mesh on the calculated permeability has been studied. The Marching-cube triangulation method was necessary to extract accurate surfaces for unstructured volume meshing. Calculated values of permeability for this range of solid fractions show partial agreement with previous experiments. Observed deviations are attributed to the difficulties of experimental permeability measurements.

Jan 1, 2009

By T. Johnson, B. Q. Li

"Electromagnetic stirring has found a wide application in metals processing for the benefit of obtaining refined solidification microstructures. This paper presents an experimental study on the melt flow and turbulent behavior in an electromagnetically stirred Woods metal pool. The experimental setup consists of metal bath unit equipped with temperature control to allow both cooling and heating, velocity probe positioning unit and data and signal acquisition and processing unit. The whole measuring system is under the control of an IBM personal computer. Velocity measurements are made using the incorporated magnet probes, which are calibrated using a turntable. The measured results showing the effect of the coil positions, coil arrangements and the applied currents on the melt flow are presented. Both mean flow and turbulence quantities are discussed.1. IntroductionElectromagnetic stirring is widely practiced in the metals industry for melt mixing and for casting microstructure refinement. Industrial examples are taken from induction furnaces where the electromagnetic forces are applied to generate desired melt mixing and also various types of electromagnetic stirrers used in various stages of steel and/or aluminum casting processes to produce fine grain solidification microstructure or to eliminate undesired defects such as TCG (twinned-columnar-grain) structure. For ultrahigh purity aluminum or high strength aluminum alloys containing zirconium or lithium, grain refinement can be difficult with the conventional technique, and electromagnetic stirring provides a particularly powerful means to obtain the refined solidification microstructure [1]. A fundamental understanding of the melt flow and the turbulence characteristics in these magnetically-driven flow systems is of significant engineering importance to both process design and product quality improvement.There exists extensive literature on the magnetically-driven melt flows in material processing systems. Nakanish. et al. [2] were perhaps among the early investigators to mathematically and physically model the magnetically-driven flow phenomena in molten metal systems. Subsequent theoretical and experimental work by Tarapore and Evans [3, 4], Szekely and Chang [5], Hunt and Moore [6] and Szekely and El-Kaddah [7] has contributed very significantly to our understanding of magnetically-driven flow in inductively stirred melts. They have developed mathematical models for the electromagnetic field and turbulent flow in induction furnace and validated the models by either laboratory experiments or direct measurements in the industrial-scale induction furnaces."

Jan 1, 1998

By Mei Yang, Wei Gao, Jian Yang, Qingcai Liu, Wenchang Xi

"TiO2 has been loaded on cordierite porous ceramic to prepare the SCR catalyst carrier by using both APCVD and sol-gel technology. In APCVD method, TiC14 and O 2 were used as reaction precursor. TiC14 was gasified by using N2 as carrier gas which was controlled to 500sccm. Its reaction temperature and reaction time were limited to 773K and 30min respectively. The physical properties, SEM and SEM-EDX of the TiO2-cordierite carrier and the properties of SCR catalysts prepared by these carriers have been tested. The tests showed that TiO2 loaded by APCVD method were of graininess shape and even accumulation. The loading rate of TiO2 and the specific area of carrier sample were increased 114% and 21 % respectively comparing with sol-gel technology. In the result of sol-gel method, the maximal difference of Ti content was 66.92%, while the result of APCVD method was 18.89%. It demonstrated that TiO2 was uniformly attached with the cordierite ceramic by using APCVD method, which would ensure more active ingredients well loaded on the Ti02-cordierite carrier. This difference made the denitrification ratio of catalyst prepared by APCVD method was 8.1 % higher than that of catalyst prepared by sol-gel method.IntroductionIn recent years, the emission of NOx, which were caused by coal-fired power plants, has gotten more and more attention. SCR (selective catalytic reduction) is the most effective technology to DeNOx [ll. The core technology of it is the catalyst. The SCR catalyst usually uses Ti02 as the carrier, and V2O 5 as the active component [2, 3] . However, the thermal stability and mechanical properties of TiO2 carrier are unstable, which would influence the performances of the catalyst. The commercial catalyst generally uses WO3 or MoO3 to promote its heat stability at present [4-7] Besides, TiO2 is expensive. Compared with TiO2, the cordierite is of good thermal stability and lower price. So loading Ti02 on cordierite porous ceramic as carrier to produce SCR catalyst is of good prospects [S, 91 • Currently, TiO2 is usually loaded on cordierite by the sol-gel method. But some research has shown that the sol-gel method easily reduced the loading performances of TiO2, such as distribution, combination, etc. APCVD (atmospheric pressure chemical vapor deposition) has many advantages to preparing TiO2 films, such as high bonding strength, fast reaction rate and so on [l0-13l_ In this paper, TiO2 has been loaded on cordierite porous ceramic to prepare the SCR catalyst carrier by using both APCVD and sol-gel methods. The properties of the carriers prepared by the two processes have also been compared."

Jan 1, 2011

By Renato G. Bautista

"The chemistry of the separation of metals from each other and from the other undesirable components involve multiple simultaneous chemical reactions. In the case of leaching, the heterogeneous chemical reactions between the solid and the liquid phase may be limited to a few reactions. In the homogeneous liquid phase, the number of simultaneous chemical reactions could be double or triple that of the number of heterogeneous reactions. The rate of dissolution becomes very dependent on the changing concentrations of the significant chemical species taking part in the multiple reactions in both the heterogenous and homogeneous phase. The rate expression developed for the process must take into account the mechanism of chemical reactions in order to best represent the actual process. This paper also examine the role of mass transfer with chemical reaction in the develpoment of the rate equations for dissolution, liquid-liquid extraction, membrane separation, precipitation, and electrodeposition.IntroductionThe understanding and the elucidation of the mechanism of the rate phenomena for a specific chemical reaction system is of prime importance in the development of a successful chemical process. The development of successful emerging technologies for metals separation will depend on the accurate interpretation of the intrinsic chemical reaction kinetics and the rate of mass transfer of the desired metal species during its separation from the undesirable chemical species. This is the case whether the process application is for separation, concentration, and /or purification.The chemical processes that will be examined in this presentation will include leaching, solvent extraction, membrane separation, precipitation, and electrodeposition."

Jan 1, 1996

By L. A. Bertram, F. J. Zanner

"The goal of this paper is to present a tool to simulate transient melting of the electrode tip. This capability is needed to develop and test furnace control algorithms since experimental determination is difficult and expensive. Simulation incorporates parameters (including arc voltage, arc current, electrode gap and furnace pressure) from previous quasi steady experiments with 460 mm diameter Inconel 718 electrodes.Cathode heating rates (determined by classical as well as experimental arc models) are linked to these independent variables. After radiative loss adjustments to the heating, transient one dimensional melting is computed. IntroductionThe vacuum arc remelting (VAR) process attempts to improve the physical and chemical homogeneity of a static-cast electrode by remelting and solidification in a quasisteady manner. To achieve steadiness of furnace operation requires automatic controls based on inputs measuring physically relevant state variables of the process. Previous industrial scale VAR studies (1,2,3) involving stainless steels, superalloys, and other alloys have provided a basis on which control strategies of some generality can be proposed (4). Of these measurements, the data for Inconel 718 is the most complete, so discussion in this paper is restricted to this alloy.Studies of the In 718 alloy subjected to the VAR process have established that melt rate M (kg/hr) depends not only on the melt current 1m (kA) supplied to the furnace, but also on ambient gas pressure of CO, PCO (micron), and electrode gap ge (mm) as well (1):"

Jan 1, 1986

By K. Sarveswara Rao

The present paper firstly describes some recent trends from literature on energy management via process intensification to arrive at sustainable technologies for aqueous processing of minerals, metals and materials. Secondly, the energy saving measures practiced in leaching, solid-solution separation, solution purification, metal and material winning and environmental aspects have been discussed. The emerging importance of interdisciplinary nature of hydrometallurgy for practical applications is also highlighted. With the above background, the present paper describes an overview of energy conservation and autoclave processes with a special reference to hydrometallurgical research activities of our Laboratory.

Jan 1, 2008

By G. A. Irons, D. Colbert

Several electric arc furnace (EAF) shops have increased the zinc and lead grades of EAF dust by reinjecting it into their furnaces; however, the kinetics of this operation are poorly understood. To understand the kinetics, EAF dust was injected into 70 kg heats of iron or steel in an induction furnace. Supplemental additions of carbon and oxygen to overcome the heat load on the system were also investigated. In all cases, the dust was chemically transformed, and the zinc content increased from 16% Zn to 60 - 80% Zn. About 50% of the zinc in the EAF dust dissolved in the iron or steel. The zinc oxide in the dust is thought to be reduced by carbon and the zinc vapour subsequently dissolved in the iron. A kinetic model for the dissolution process is proposed, and the implications for EAF dust recycling are discussed.

Jan 1, 2000

By Rolando Campos

Until 1970, the Caletones Smelter of CODELCO-CHILE, División El Teniente, operated under the conventional pyrometallurgical process used by most of copper smelters. The annual copper production varied around 165.000 tons. The failure in the commissioning of the "oxygen smelting" technology in Peirce- Smith converters (1970-1972), forced further introduction of transcendental changes in the Caletones smelter operating scheme. Implemented technological innovations were based on wide studies and research works performed by División El Teniente. This paper presents a summary of technological modifications introduced, their impact on production and energetic performances, and short and medium terms improvement plans.

Jan 1, 1993

By G. Lissens

In this work the electrochemical combustion of dissolved organic species in a single compartment cell containing a titanium mesh cathode and a boron doped diamond anode has been studied, The organic molecules involved were complexing agents such as EDTA (ethylenediaminetetraacetic acid) or NTA (nitrilotriacetic acid) used in metal plating shops and bright nickel plating bath additives, From batch experiments, it is shown that complete decomplexing of EDTA and NIA is feasible. Complete TOC (Total Organic Carbon) removal from solutions containing 0.01 M EDTA, 0.02 M NTA and bright nickel plating bath additives could also be achieved. Recycling experiments show that decomplexing of EDTA and NTA solutions can be obtained at an average electrical energy input of ~20kWh.kg-1 of complexing agent. Decomplexing rates of respectively 3.l3 mmol.Ah-1 for EDTA and NTA have been obtained, The Instantaneous Current Efficiency (ICE) was 71% for EDTA and 95% by NTA, Simultaneous recovery of Cu from a 0.01 M Cu-EDTA solution has also been evaluated. A solution (1.8 dm3) containing 0.01 M EDTA and 528 ppm of Cu was treated in a single compartment cell at a current density of 2 A.dm-2. 73% of the TOC could be removed and a final copper concentration of 8 ppm was obtained.

Jan 1, 2003

By Patricia A. Wells

In the remelting of scrap, the ultimate goal is to produce clean aluminum while minimizing metal losses. Recently, it has become more difficult to make significant recovery improvements in Reynolds' Reclamation Plants since metal recoveries were nearing the theoretical maximum. In an effort to gain a better understanding of the factors impacting Reynolds remelting process, a series of experiments using a Taguchi-type design was performed. Specifically, the critical variables and interactions affecting metal recovery of shredded, delacquered Used Beverage Containers (UBC) melted in a side-well reverbatory furnace were examined. This furnace was equipped with plunger-style puddlers and metal circulation. Both delacquecing and melting processes operated continuously with downtime only for necessary mechanical repairs. The experimental design consisted of an orthogonal array with eight trials, each using nominal 500;000 lb shred charge volumes. Final recovery results included molten output and metal easily recovered from dross generated during the test.

Jan 1, 1995

Mineralogical and metallurgical scoping testwork were carried out to investigate the production of separate, marketable gold and platinum concentrates. The study utilized a flotation concentrate assaying approximately 5 wt% gold and 5 grams per tonne platinum. The gold-platinum mineralization was recovered from a placer deposit. Optical microscopy and scanning electron microscopy with energy dispersive x-ray analysis identified gold as zoned Au- Ag and Au-Ag-Cu alloys. Platinum primarily occurred as weakly zoned, variably magnetic Pt- Pd-Fe alloys. A combination of gravity and magnetic separations resulted in a gold concentrate grading 86.9 wt% Au (and 9.lwt% Ag) and a separate platinum concentrate grading 400 g/t Pt with recoveries of 94.5% and 96.7%, respectively. Magnetohydrostatic separation (MHS) using the Magstream 200 Separator indicated promising results.

Jan 1, 1994

By Dale W. Collins

The disposal of arsenic from copper operations possess various health, environmental and processing problems. There are basically two areas of concern. The first being the disposal or treatment of smelter flue dusts and the second the removal of arsenic from refinery electrolytes. A number of treatment options have been proposed including the addition of soluble arsenic wastes to copper heap and dump leaching solutions. This approach will allow arsenic to be reintroduced to the ore via Solvent Extraction (SX) raffinate associated with hydrometallurgical operations. Knowledge of the attenuation behavior and mechanism during leaching is important in determining the long term stability of arsenic and the success of this approach. Parameters, such as uptake capacity, pH, particle size and solution chemistry have been investigated. Arsenic attenuation has been examined using column leaching with experiments employing both continuous flow and pulsed additions of As(V). In the initial stages of leaching, the attenuation of arsenic appears to depend on the pH and iron concentration in the effluent. Arsenic stability in the copper oxide ore has been examined with rinses of progressively lower pH.

Jan 1, 1994

By Nagy El-Kaddah

"One of the emerging technologies for the production of ultra-clean metals is electromagnetic filtration. The theory and the mechanism of electromagnetic separation of inclusions from molten metal are briefly reviewed along with basic electromagnetic separation systems. This paper focuses on inclusion removal in the induced current separators, with specific reference to a new separator developed at the University of Alabama. A simple analytical model is presented for the analysis of particle separation in such a system. The role of the applied magnetic field on inclusion removal will be discussed. It is shown that particle velocity increases exponentially with increasing magnetic field strength. At moderate field strengths, the velocity of 50 to 100 u. inclusions· are an order of magnitude larger than those achieved by buoyancy. The separator developed at the University of Alabama is described together with experimental results of laboratory and large scale experiments on purification of molten aluminum. These results demonstrate the capability of the system for producing super-clean metals.IntroductionThe nature of extraction, refining and processing of metals is such that oxides and other non-metallic particles will always be present. This is due to the highly reactive nature of metals with oxygen and other non-metallic elements. The presence of these type inclusions in metals, even in minute amounts, can seriously flaw the reliability and performance of the final product. They not only reduce the strength and the stiffness of the metal/1/, they are the reason behind many of manufacturing defects such as porosity in castings, surface and internal cracks in continuously cast ingots and rolled products, etc., which act to cause premature failure of manufactured parts. In fact, for critical applications such as turbine blades, there is virtually no tolerance for inclusions above ten microns in size /2/. Therefore, removal of inclusions from the liquid metal is an essential processing step.The demand for cleaner metals has brought major changes in the technology and practice of metal refining and casting. Inclusion removal from the melt is currently achieved by passing the melt through a series of melt treatment systems, including induction stirring furnaces, argon-stirred ladle, and ceramic foam and deep-bed filters /3,4/. These systems are generally capable of removing all inclusion particles above 50 microns in diameter, which meets current cleanliness requirements for most applications. However, they may not be able to meet the projected cleanliness levels for critical applications due to kinetic and operational limitations of these systems in removing smaller particles /5/."

Jan 1, 1996

By T. -M. Guo, M. J. Braun

"This paper presents an experimental and numerical study of melt flow near the solid-liquid interface and its effect on the interface curvature in a horizontal unidirectional solidification system with succinonitrile. Melt flow is introduced by increasing the ampoule channel thickness. Visualization techniques are employed to observe the flow field and the solid-liquid interface curvature. A numerical model is also developed to simulate the heat transfer, melt flow and phase change in the system. Quantitative information on the flow and temperature fields is generated. A good agreement is achieved between the experimental observations and model predictions. The results could be used for the study of the effect of the melt flow on interface morphology during solidification.IntroductionClassic unidirectional solidification experiments of transparent alloys are conducted with thin film samples sandwiched between two glass slides to investigate the development of interface morphology during solidification [1]. Samples with small channel thickness are usually used to suppress any melt flow due to natural convection and solidification in the channel would then be in the diffusive regime so that the solidification theory can be significantly simplified [2, 3]. Effects of melt flow, in particular due to natural convection, on solidification have also been studied extensively in those systems with large geometrical dimensions [4-6]. These studies indicate a strong effect of the melt flow on interface curvature during solidification [5, 6]. Only limited efforts were made to address the effect of the melt flow on interface morphology in horizontal unidirectional solidification, in particular for the cases when the channel thickness is not thin enough to suppress completely the natural convection [7]."

Jan 1, 2004

By László I. Kiss, Verena Mackowiak, Alexandre Perron, Dominic Toulouse, Alicia Liedtke, Sándor Poncsák

"Bubbles play a very important role in different metallurgical applications like for example in electrowinning. During heterogeneous nucleation, the maximal size of the bubbles growing at the nucleation sites as well as the nucleation frequency is determined by the so-called detachment condition. Detachment occurs when the external forces acting on the bubble exceed the retaining forces along the solid-gas-liquid triple interface line. The phenomenon depends strongly on the shape and orientation of the solid surface and on the nature and strength of the external buoyancy and drag forces. In the present study the detachment conditions of bubbles from downward facing horizontal and inclined plates were studied experimentally under the effect of gravitational and hydrodynamic forces. The results show the deformation of the bubbles under the effect of the external forces and the detachment conditions as function of the bubble volume.IntroductionIn heterogeneous nucleation bubbles are generated at the so-called nucleation sites along the solid-liquid interfaces. They continue to grow there and after they reached a certain size they detach from the solid surface and leave the nucleation site. This scenario is well known both in boiling and electrolysis. During the growth period a stable equilibrium exists between the forces that retain the bubble at the nucleation site and the forces that try to remove it. This equilibrium evolves with the increasing volume of the bubble to the point when the detachment forces overcome the retaining forces.The life of a single bubble generated by heterogeneous nucleation can be divided into two periods separated by the detachment - or in other words by the departure - of the bubble: first the growth at the nucleation site and then the movement away. The knowledge of the detachment conditions makes possible the determination of the maximal volume of the bubble at the nucleation site that, in tum, makes possible the determination of the nucleation frequency. This is why so many researches have been directed toward the clarification of the details of the bubble detachment in the past decades. The equilibrium between the attaching and separating forces depend on the presence of body, surface and flow induced forces in the liquid, on the geometry and orientation of solid surface, on the properties of the solid-liquidgas system etc."

Jan 1, 2004

By S. G. Kumar

Experimental studies on high carbon steelmaking through LD Converter - Vacuum Arc Degassing - Bottom Pouring route to produce low oxygen steels were carried out. The results indicated that it is possible to produce steel with a total oxygen content of less than 15 ppm. Thermodynamic and mass balance calculations are made on low-carbon steels that are treated by a complex deoxidation practice based on primary deoxidation of aluminum, manganese and silicon additions; followed by secondary deoxidation of vacuum degassing with simultaneous additions of aluminum. The results showed that primary deoxidation is mainly due to aluminum and the effect of carbon under reduced pressures on deoxidation of molten steel that is already killed by aluminum is negligible. The effect of process parameters on total oxygen content of steel, like carbon content, slag composition and inert gas purging, are discussed.

Jan 1, 1994

By Yoshifumi Abe, Akinori Toraiwa

"Nippon Mining & Metals started a new copper anode slime treatment plant that processes slimes in a chloride media. The basic plan of the process was proposed by Mr. James E. Hoffmann and Nippon Mining & Metals modified and advanced to produce precious metals in acceptable qualities for the company. The process has a wet chlorination stage of decopperized slimes, a solvent extraction and a reduction stages of gold, a silver chloride reduction stage and separative reduction stage of its gold extraction raffinate. The new plant of this process started in 1997 and has been operated in good condition.IntroductionThe old anode slime treatment plant of Nippon Mining & Metals, located in it's Hitachi Refinery, processed anode slimes through a combination of pyrometarllurgical processing and electrorefining. There was a need to plan a future of the plant because the maintenance cost increased year by year and a new selenium registration was going to be applied to the plant. Some plans were discussed and the result was that the process proposed by Mr. Hoffmann was superior among them.Nippon Mining & Metals started 'to examine the process and the experimental result showed that the process had an ability to be its new process but further research should be necessary to produce precious metals in acceptable qualities. The final process flow has some modified and additional stages to be suitable for its requirement. Silver processing stage is quite changed. Gold extraction stage has a new step to polish gold loading DBC. Gold extraction raffinate treatment stage is advanced to be able to recover precious metals, selenium and tellurium, separately. Aeration under atmospheric pressure is employed in decopperizing stage.The basic design of the new plant started in 1995 and finished in 1997. The construction of the new plant began in April 1997 and finished in October. The plant has been operating well after the four months test operation."

Jan 1, 2000

By Tim B. Vander Wood

Standard methods of determining clay mineral powder aspect ratios involve manual scanning electron microscopy analyses of shadowed particles in order to measure both platelet thickness and diameter. We present a method whereby the diameters of platelets are quickly determined by automated scanning electron microscopy and their images are recorded and digitally transferred to a transmission electron microscope equipped for parallel electron energy loss spectroscopy. Thickness' of platelets whose diameters are known from the previous analyses are determined by measurement of the ratio of scattered and unscattered electrons in the beam after it has been transmitted through the platelet.

Jan 1, 1995

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 G. Van Weert

Refractory gold ores and auriferous concentrates containing silver tend to form refractory silver jarosites during pressure oxidation. Earlier work with pure Ag2S has shown that the addition of iodine species to the autoclave feed yields cyanide soluble iodargyrite (Agl) instead. Near complete silver extractions from the autoclave product were obtained at a I-/Ag+ ratio of 5 or more. This paper reports on the pressure oxidation and cyanide leaching of two industrial refractory (arseno) pyritic silver-bearing concentrates: 1. from Peru (sulphosalts) and 2. from the USA (pyrite, with acanthite occlusions). While using a I-/Ag+ mol ratio of only 1 in the feed, it has been possible to obtain 98 and 97% Ag extraction from the two autoclave products by cyanide leaching, respectively. This compares to 11 and 54% Ag extraction from the as-received concentrates and 4 and 15% Ag extraction, respectively, after pressure oxidation without KI present. The results of the testwork are discussed in terms of concentrate mineralogy and pressure oxidation conditions.

Jan 1, 1994