Search Documents

By Nobuhiro Oguma, Yuji Mizuta, Hideya Sato, Shigehiko Iwahori

"Recyclable materials containing copper and precious metals have been treated at the Mitsubishi Process in Naoshima. In 2003, a new incinerating and melting plant (pre-treatment plant) for waste materials, such as shredder residue of automobile and scrapped appliance, was constructed. All of produced slag/metal mixture is treated at the Mitsubishi Process, and which results in the significant increase of recyclable materials treatment. The combination of two processes has realized a highly efficient and environmentally friendly system for recycling valuable metals in the waste which used to be sent to a landfill. Naoshima continues to make efforts to achieve the highly efficient operations of the two processes, and plans to increase the treatment of recyclable materials further. This paper summarizes the recent operations and the various improvements implemented in the pre-treatment plant.IntroductionRecyclable materials containing valuable metals such as copper and precious metals have been treated at the Mitsubishi Continuous Copper Smelting and Converting Process (Mitsubishi Process) since the start-up in 1991. In the early stages, recyclable materials consisting mainly of metal scrap were charged into the process and the treatment had been increased steadily. In order to promote the recycling business, treatment of various kinds of materials including printed circuit boards was started. However, the treatment hit the ceiling due to a limitation of furnace boiler capacity, since they contained large amounts of combustible materials. In addition, severe corrosion of boiler tubes was caused by halogen contained in recyclable materials."

Jan 1, 2012

By Jun Sugiyama, Hiroyuki Sano, Toshiharu Fujisawa, Hideki Takeuchi, Chikabiuni Yamauchi

"The solid .state electrotransport (SSE) is one of the most promising methods for the elimination of gaseous impurities from chemically active metals, such as rare earth metals. . In the present work, the SSE process was applied for the oxygen removal from praseodymium. The SSE factors, such as effective valence, were measured under the various temperatures, electric field intensities and initial oxygen contents, and the effects of those conditions on the SSE process were discussed. Furthermore, the solubility of oxygen in .solid praseodyillium was also measured·, by using the SSE method and metal-oxide equilibrium method.IntroductionWhen a direct current is passed through a solid alloy, not only electrons but also solute atoms are transported as charge carriers toward the anode or cathode. This phenomenon is referred to as an electrotransport or electromigration. The solid state electrotransport (SSE) is the application technique, based on this principle, to the pUrification of the solid metallic materials.Rare earth metals are used for various functional materials, such as magnetic, optical or electronic materials, therefore their high purity metals are required [l ,2]. However, rare earth metals are chemically active and have a strong affinity with gaseous elements (e.g. oxygen, nitrogen, hydrogen and carbon). In many cases, eliminating operations of gaseous elements have not been always made commercially, because these impurity elements could not be eliminated by usual treatments applied to the purification of ·common metals. As an alternative method, authors have proposed the· application of the SSE process to the elimination of gaseous impurities from rare earth metals. Investigations have been carried out on the yttrium-oxygen and neodymium-oxygen systems and the results were already reported[3,4]."

Jan 1, 2000

By Francis Vanbellen

Umicore Precious Metals Refining operates an integrated precious metals smelting and refining plant in Hoboken, Belgium. Once a smelter and refiner of complex concentrates, the plant today?s feed consists exclusively of industrial and consumer recycled products, making it the world?s largest recycling facility for precious metals. Unlike the fairy tale of the Frog Prince, it took much more than a princess? kiss to successfully realize this makeover. A completely renewed plant has been built over the past decade. The most visible technological innovation was the commissioning of the Pb-Cu smelter. Its flexibility towards very different types of feed makes it perfectly suited as main entry to the Hoboken flow sheet. A new Cu-leaching & electro winning plant and precious metals refinery make up the Precious Metals Operations (PMO) whose targets are fast throughput and maximized yields for gold, silver and the platinum group metals. The Base Metals Operations (BMO), flexibly process the by-products from the PMO, valorizing ?impurities? like indium, tellurium, selenium and others. Off gas and waste water treatments ensure compliance with strict environmental standards. Precious metals recycling is an art that goes beyond mastering a unique flow sheet. Umicore Precious Metals Refining offers a complete recycling service, taking care of sampling and assaying, metals management and logistics. The quality of this integral service is recognized through the attribution of ISO certifications for our operational activities, sampling and the environmental care. And it?s an art that follows Michelangelo?s experience: ?Art is 5% of inspiration and 95% of transpiration.?

Jan 1, 2006

By Francis Vanbellen

Umicore Precious Metals Refining operates an integrated precious metals smelting and refining plant in Hoboken, Belgium. Once a smelter and refiner of complex concentrates, the plant today?s feed consists exclusively of industrial and consumer recycled products, making it the world?s largest recycling facility for precious metals. Unlike the fairy tale of the Frog Prince, it took much more than a princess? kiss to successfully realize this makeover. A completely renewed plant has been built over the past decade. The most visible technological innovation was the commissioning of the Pb-Cu smelter. Its flexibility towards very different types of feed makes it perfectly suited as main entry to the Hoboken flow sheet. A new Cu-leaching & electro winning plant and precious metals refinery make up the Precious Metals Operations (PMO) whose targets are fast throughput and maximized yields for gold, silver and the platinum group metals. The Base Metals Operations (BMO), flexibly process the by-products from the PMO, valorizing ?impurities? like indium, tellurium, selenium and others. Off gas and waste water treatments ensure compliance with strict environmental standards. Precious metals recycling is an art that goes beyond mastering a unique flow sheet. Umicore Precious Metals Refining offers a complete recycling service, taking care of sampling and assaying, metals management and logistics. The quality of this integral service is recognized through the attribution of ISO certifications for our operational activities, sampling and the environmental care. And it?s an art that follows Michelangelo?s experience: ?Art is 5% of inspiration and 95% of transpiration.?

Jan 1, 2006

By Takeshi Yoshikawa, Kazuki Morita, Kunitoshi Matsunaga

"In metallurgical grade silicon (MG-Si), most impurities mainly exist at the grain boundaries and distribute in silicon grains at extremely small contents. Grain boundary phases in MG-Si transform into liquid above the eutectic temperature, and migrate towards high temperature regions when heated under a temperature gradient. With the migration of all liquid phases in MG-Si to the surface, the impurity contents will be decreased less than their solubilities in principle.In the present work, the fundamental research was conducted to discuss the possibility for purification using the liquid phase migration technique. The purification limit was estimated by thermodynamic calculations, and metallic impurities were estimated to be effectively removed except for Fe and Al. The migration behavior of the liquid phase in the synthesized silicon substrate was investigated by unidirectional heating under infrared radiation at 1523-1548 K, and the proceeding of migration was confirmed. The migration velocity was 1.4--2.0xl0-7 mis, and found to be controlled by the liquid phase diffusion.IntroductionPhotovoltaic energy is one of promising energy resources in a sustainable society because of its inexhaustibility and cleanliness. Although the production and installation of solar cells have increased significantly during the last decade, the cost of solar cell installation is still high. To enable the widespread use of photovoltaics and for the photovoltaic electricity price to reach grid parity, a low-cost and abundant feedstock of solar grade silicon (SOG-Si) is essential. Recently, a modified Siemens process and a fluidized bed reactor process were developed to address the cost and energy issues associated with the conventional Siemens process. However, their cost reduction potential is limited because of the large energy consumption needed to convert silicon into gaseous compounds. Purification of silicon through metallurgical routes offers a promising way for producing SOG-Si from metallurgical grade silicon (MG-Si), because it enhances productivity and can also lower the process costs. Although several metallurgical processes such as directional solidification [l ], vacuum refining [2-4] and plasma oxidation [5-7], have been developed, processing times and refining efficiencies still have to be optimized."

Jan 1, 2013

By Francis Vanbellen

Umicore Precious Metals Refining operates an integrated precious metals smelting and refining plant in Hoboken, Belgium. Once a smelter and refiner of complex concentrates, the plant today?s feed consists exclusively of industrial and consumer recycled products, making it the world?s largest recycling facility for precious metals. Unlike the fairy tale of the Frog Prince, it took much more than a princess? kiss to successfully realize this makeover. A completely renewed plant has been built over the past decade. The most visible technological innovation was the commissioning of the Pb-Cu smelter. Its flexibility towards very different types of feed makes it perfectly suited as main entry to the Hoboken flow sheet. A new Cu-leaching & electro winning plant and precious metals refinery make up the Precious Metals Operations (PMO) whose targets are fast throughput and maximized yields for gold, silver and the platinum group metals. The Base Metals Operations (BMO), flexibly process the by-products from the PMO, valorizing ?impurities? like indium, tellurium, selenium and others. Off gas and waste water treatments ensure compliance with strict environmental standards. Precious metals recycling is an art that goes beyond mastering a unique flow sheet. Umicore Precious Metals Refining offers a complete recycling service, taking care of sampling and assaying, metals management and logistics. The quality of this integral service is recognized through the attribution of ISO certifications for our operational activities, sampling and the environmental care. And it?s an art that follows Michelangelo?s experience: ?Art is 5% of inspiration and 95% of transpiration.?

Jan 1, 2006

By C. Isaac Garcia, Sihai Jiao, Anthony J. DeArdo

"A practical model based on the Hill analysis has been developed to calculate the Lankford value of interstitial free (IF) steels and its distribution in different rolling directions, by considering only a few selected texture components. The Texture Intensity Ratio (TIR), i.e. (111 ) /(100), was used in the model to describe texture. By using the new TIR parameter, the texture-based prediction models can be used more easily to predict the Lankford value in a rather straightforward way.IntroductionThe deep drawing capacity of sheet steels is generally indicated by the Lankford value, which is mainly determined by the texture in steels1. Traditionally, various models derived from the Taylor model are employed to calculate the Lankford value from the texture2-4. In such models, the plastic deformation of steel is assumed to be the result of the slip of dislocations in certain slip systems, i.e., by either pencil glide or restraint glide. The slip direction is the <111> direction. In the case of pencil glide, the slip is thought to be possible in all crystal planes with the <111> crystal direction. Assuming the material is elongated in the X1-direction by d n and compressed in the X2 and x3-direction by qd n and (l-q)d n, respectively, corresponding to a deformation tensor"

Jan 1, 2001

By Jorge Alberto Soares Tenório

Household zinc based batteries contain some heavy metals such as zinc, manganese and mercury. There is a large effort from manufacturers in order to eliminate the last one. As a municipal waste, the disposal of batteries has become an increasing worry. The aim of the present work was to characterize dry batteries scraps, and establish a flowsheet for their processing. This was done using unit operations of mineral processing and parameters and yields of each stage have been defined. Such procedures have been chosen due to their low cost. The operations were hammer mill grinding, size separation, magnetic separation and specific weight separation in water. The characterization step was done through chemical analysis and x-ray difiactometry. After size classification, it was verified that 76.6% of the total amount of zinc was over 1.70mm. This fiaction was constituted basically of zinc and some coarse pieces from the steel body, paper and plastics. This fraction was submitted to magnetic separation followed by specific weight separation in water. A visual examination showed that during the grinding process, graphite was concentrated in the finer fractions. Manganese concentration in the fractions over 6,35mm was less than 2%. This means that there was low contamination by the paste in this fraction. It was due to the entrapment of the paste by steel scraps (from the body) and zinc (from the cup) during grinding.

Jan 1, 1999

By Bingchen Chen, Zhitong Sui, Junwei Ma

"In the blast furnace slag, titanium disseminated in various mineral phases Titanium could be concentrated mainly in perovskite, which could be selectively precipitated and grown by optimizing the operation factors like the slag composition, temperature of heat treatment and additive agents. This study aims at establishing the titanium slag mineralogy and its distribution in the treated slag and the as-received slag, as well as the methods of perovskite separation. After heat treatment, the grain size was grown from 5 - 20µm to 80 - 200µm, the distribution of Ti02 in perovskite was increased from 48% to 81 %, the morphology was changed from snow-shaped grain to coarsening dendrites or equiaxed crystals. A concentrate were produced by gravity separation analyzing 35.25% Ti02 with a recovery of 68.28% and a tailing analyzing 9.53% Ti02 , and a possibility of flotation upgrading was discussed. I INTRODUCTION CHINA is rich in mineral resources of titanium, 92.4% of which is vanadium-titanium bearing magnetite. About 53% titanium were in iron concentrate after mineral processing, by which the blast furnace slag containing about 25% TiO2 were produced[11 • The content of TiO2 in such slag is too low to separate titanium dioxide, and it is also too high to produce slag cement[21. It has been accumulated to 50 million tons so far, which is still increasing at a rate of 3 million tons per year, and results in a waste of titanium resources and pollution of environment. Due to the dispersed distribution of titanium component in various mineral phases, very fine grain(<10µm) and complex interfacial combination, it is very difficult to recovery titanium component from the slag by traditional separating technique. In this paper, a novel technique to recovery titanium from the waste slags was proposed [3H4l, on which three continuous processes were involved: selective concentrating, selective growing and selective separating. Perovskite was designed as a titanium-rich phase, in which the most titanium was concentrated promptly, then perovskite could be selectively grown and coarsened by optimizing the heat treatment and the appropriate additives [ 5l[6l. The grain size of perovskite phase was larger than 80 µm, and the crystals appeared as coarsening dendrites or equiaxial grains like lump."

Jan 1, 2000

By Itsuki Uehara, Hiroyuki T. Takeshita, Tetsuo Sakai, Nobuhiro Kuriyama, Hideaki Tanaka

"AB5 type hydrogen storage alloys (A: rare earths, B: transition metals) are extensively applied to a negative electrode of a nickel metal hydride (Ni-MH) rechargeable battery for portable electric equipments, electric vehicles, hybrid vehicles etc. Performance of a hydrogen storage alloy electrode is affected by various factors, microstructure and surface composition of the alloy and structure of the electrode as well as composition of the alloy. Control of those factors enables us to commercialize the Ni-MH battery in various field.IntroductionA Nickel-metal hydride (Ni-MH) battery has been extensively developed because of (1) good compatibility with a nickel cadmium (Ni-Cd) battery, (2) high energy density (1.5-2 times higher per unit volume than a Ni-Cd battery) and high dischargeability, and (3) low environmental pollution. The charge/ discharge reactions can be written as [l, 2,3]:(+) Ni(OH)2+OH- = NiOOH+H2O+e· (E=+0.490V NHE),(-) l/6LaNi5+H2O+e-· = 1/6LaNi5H6+OH- (E=-0.828V NHE),where E° is a standard potential of an electrode vs. normal hydrogen electrode (NHE). Because of the above advantages of a Ni-MH battery, the battery have been widely used as a power source of portable computers, cellular phones, electric vehicles (Toyota ""LAV4L EV"", Honda ""EV Plus"" etc.) etc. Some hybride vehicles (Toyota ""Prius"" and Honda ""INSIGHT"") and fuel cell vhehicles (Toyota ""FCEV"") are power-assisted by a high-power Ni-MH battery. In 1999, the production of Ni-MH batteries reached 870 million cells in Japan. Most of commercialized NiMH batteries are incorporated with rare-earth-based AB5-type hydrogen storage alloy as a negative_ electrode. The production of rare-earth-based alloy is estimated to be approximately 8000 tons.The battery performances of the Ni-MH battery, for example, capacity, durability (cycle life), dischargeability (kinetics) and selfdischarge, ate closely related to the metal hydride· (MH) electrode, especially, the hydrogen storage alloy in the electrode. Substitution of alloy components, heat treatment, and surface treatment in order to change surface and bulk structure of hydrogen storage alloys have been examined by us and many reseachers in order to improve the performances of MH electrodes. This paper is a review of our and their efforts to improve performances of MH electrodes."

Jan 1, 2000

By Jr. Foot

The Bureau of Mines, U.S. Department of the Interior, investigated flotation methods for recovering fluorite and byproduct beryllium from the Fish Creek deposit of Nevada. The preferred method includes (l) fluorite rougher and cleaner flotation, (2) de sliming at 20 micrometers, (3) muscovite flotation, (4) silicate flotation, (5) hypochlorite wash of silicate concentrate, and (6) beryllium rougher and cleaner flotation from the silicate concentrate, Laboratory results showed that over 94 pct of. the fluorite was recovered in a concentrate containing 96 pct CaFz. Beryllium flotation produced .concentrates .containing in excess of 5 pct BeO with recoveries over 70 pct. A 1.00-lb/h continuous flotation unit was constructed to demonstrate this procedure,

Jan 1, 1985

By Marisa Di Sabatino, Michael Phan Knudson, Mari Juel, Eivind Øvrelid

"A p-type Czochralski silicon ingot doped with boron was characterized for resistivity, minority carrier lifetime, interstitial oxygen, and metallic impurities. Analyses show a peak in resistivity and a dip in lifetime both occur 5 cm from the top of the ingot crown. This peak in resistivity deviates from the expected trend based on Scheil's equation for boron distribution. High concentration of interstitial oxygen in this area suggests that other oxygen-related defects, such as thermal donors and precipitates, may also be present here, and the observed peak in resistivity and dip in lifetime could be attributed to such defects. The low lifetime of 15-30 µs at minority carrier density of 7.5 x 1014 cm-3 is likely due to copper contamination.IntroductionSolar energy resources vastly exceed all other alternative energy resources, ensuring that solar power must play a crucial role in the evolving energy market. The economic viability of solar power in competition with other energy resources depends upon finding efficient, cost-effective, reliable, and controlled methods for solar cell production. In this regard, minimizing waste (such as material with unsuitable electrical properties that hinder solar cell performance) is a vital component of making solar cell manufacturing cost-effective. Impurities affect electrical properties of solar cell silicon in different ways (i.e. [1, 2, 3, 4, 5, 6]). In this work we focus on the role of oxygen and metallic impurities. Understanding oxygen impurities in silicon is critical to solar cell development because oxygen has been attributed with influencing critical electrical properties including resistivity and minority carrier lifetime and thereby potentially hindering solar cell performance or rendering material unsuitable for solar cells.[1, 2] Furthermore, oxygen is a common impurity in the standard type of solar cell silicon, Czochralski (CZ) silicon, due to diffusion of oxygen from the silica crucible into the melt during crystallization. [7] This study investigates the effects oxygen impurities have on the electrical properties of p-type CZ silicon."

Jan 1, 2013

By M. A. Neri

A lead-free solder alloy Sn-57.5Bi-0.5Ag has been developed by mechanical alloying and foundry processes, and has great potential as a lead-free solder system, to low temperature applications. The mechanical alloying powders show a microstructure different to the microstructure obtained by the foundry process for the same alloy. Its melting point of 142°C is slightly higher than that of eutectic tin- bismuth solder. Examination of the microstructure revealed that eutectic microstructure is refined by the mechanical alloying process Ag additions. The lamellar structure of tin-bismuth gradually disappeared with the process of mechanical alloying, while intermetallic compounds AgaSn phase was formed. The Cu-Sn intermetallic compound layer formed at solder-copper interface is the Cu6Sn5 phase. Keywords: Lead-free solder, Microstructure. Mechanical alloying

Jan 1, 2003

By Nobuhiro Shinihara, Makio Naito, Keizo Uematsu, Tadashi Horta, Hiroya Abe, Masataro Okumiya

"A significant variation of strength was noted in silicon nitride ceramics made through the powder compaction processing with minor processing changes. The relevance of the fracture strength to the microstructure was examined in these ceramics. In the examination of microstructure, the ceramics were made into thinned specimens, and their internal structures were observed with an optical microscope in the transmission mode. This technique can distinguish a difference in microstructure associated with the minor processing changes. The strength of all ceramics examined in this experiment was qualitatively correlated with the -pore size distribution in the specimens. Clearly, the elimination of these detrimental defects will enhance the reliability of ceramics.IntroductionIn ceramics made through powder processing, a variation of properties is often encountered [l ,2]. This brings a major problem on producing reliable and cost-effective ceramics. The variation is often ascribed to the changes in the characteristics of defects. However, there is no clear evidence f\)r this explanation due to the lack of an adequate tool for identifying the defects determining the properties. Details of the origin of the variation have still been poorly understood.A new technique is very promising for clarifying the origin of the variation [3,4]. This has very high potential in detecting minor differences in structure for .engineering ceramics. With this technique, ceramics are made transparent with its thinning down to about 50 µ m and their internal structures are observed with various types of optical microscopes in the transmission mode. The characteristics of the defects determined through this approach were found to be directly related to the strength of the ceramics [4-6].The objective of this study is to clarify the ongm of fracture strength of silicon nitride ceramics. This material is representative of high performance ceramics, and the origin is of great practical interest. For this study, silicon nitride ceramics with minor changes in processing condition were prepared. Specific feature focused in this study is the difference of large pore structure determined with the new technique and its relevance to the strength of the silicon nitride ceramics."

Jan 1, 2000

By Zhen Zhang, Jiang Diao, Xuan Liu, Tao Zhang, Bing Xie, Hong-Yi Li

Extracting vanadium from vanadium containing hot metal by LD process has been proven an effective solution for the utilization of vanadium-titanium magnetite ore, but the systematic analyses of vanadium extraction rate and mechanism by basic slag are seldom reported. In this study, mathematical model of vanadium transfer from metal to slag was formulated and the rates of vanadium extraction of hot metal with basic slag were investigated. The results indicated that the apparent vanadium extraction rate constant, kp, were in the range of 1.33~9.07×10-4g/(cm3·s). And the rate constant was increased with the increase of final slag basicity, reaction temperature and stirring gas flow. The apparent of mass transfer parameter decreases significantly from 0.13 cm3/ s to 0 cm3/ s in 20min, and the data changed as negative due to the decrease of slag oxidation and recovery of vanadium from slag to metal.

Jan 1, 2015

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

The direct removal of lead ions from D2EHPA-kerosene using metallic zinc as the reducing agent was evaluated. The electrochemical process, called galvanic stripping, is a potential alternative stripping technique when standard chemical methods are not adequate. Four parameters found to be important in the rate of lead removal were studied in a factorially designed experiment. The variable evaluated included D2EHPA concentration, temperature, zinc surface area and solution agitation. Temperature and surface area were found to be the most significant, while agitation and D2EHPA concentration had less influence on the reaction. An activation energy of 22.5 Kcal/mole was calculated indicating a chemically-controlled process. The reaction was also sensitive to the concentration of oxygen in the system. The zinc required was considerably in excess of stoichiometry, possibly due to the dissolution and redeposition of lead: In general, the results were encouraging and demonstrated that lead impurities could be removed from D2EHPA using cementation type reactions.

Jan 1, 1995

By B. Farouk, Y. G. Kim, D. Apelian

"Continuous strip casting has received considerable attention in recent years due to its economic advantages with increased energy savings and the elimination of intermediate processing steps. A promising concept in strip casting is the twin-belt (Hazelett) process which incorporates two cooled continuously moving thin metal belts wrapped around pulleys which tension and drive the belts at a predetermined speed. Molten metal is introduced at the entry end of the caster through a tundish and feeding nozzle into the mold. The twin-belt process has been successfully used with non-ferrous metals such as aluminum, copper and brass, and is a prime candidate for strip casting of ferrous materials. A numerical model has been developed which predicts the interface locations, the temperature fields in the solid and liquid regions of the cast and the velocity fields of the liquid metal at the entrance region of the twin-belt caster. The process variables considered are the velocity and cooling conditions of the belt and the nozzle shape. A body fitted coordinate system is used to track the front locations and to solve .the Navier-Stokes equations in the liquid region. Results obtained can help design efficient casters for thin strip steel castings. The development of the numerical model is presented, and sample results are discussed. I. IntroductionContinuous strip casting of steel has attracted world-wide concerns in recent years due to its economic advantages with increased energy savings and the elimination of intermediate processing steps. New methods of thin strip casting of steel are developing. One of the promising concepts is the Hazelett process, which is being used in nonferrous applications. The process incorporates two continuously moving, intensely cooled, thin metal belts. Metal blocks linked together are sandwiched between the moving belts and form moving side mold walls.In this work, the freezing front position, the temperature field and the liquid region flow field will be analyzed for the strip casting of metal using the twin belt caster (the Hazelett process). Up to now almost all theoretical analyses undertaken of the continuous casting of metal [1-3] have used a heat conduction equation, assuming slug flow in the liquid region. The effect of convection in the liquid pool during continuous casting were first investigated by Szekely and Stanek [4]. They considered potential flow between the feed metal orifice and the liquidus front, and slug flow in the mushy and solid regions of a vertical static continuous casting process for steel. Viscous effects and natural convection affects were not included Kroeger and Ostrach [5] studied the effect of natural convection flow in the liquid pool during solidification for a pure metal."

Jan 1, 1986

By B. A. Paponetti

The following report discusses the bioleaching of chalcopyrite of italian origin catalyzed by Thiobacillus ferrooxidans. The developments vcr.ius time of the main .biochemical and chemical reactions involved in the production of soiuble and insoluble species were investigated focusing on the times at which they begin and bow long they last. The precipitates were characterized both in quantity and in quality relating the rate of the process to the precipitates fonnatiom. A material. balance has been made to verify the proposed mechanism.

Jan 1, 1991

By Mokka Rao, Asdrubal Serrano

"A mathematical model is developed which describes the movement of the minerals present where the vertical and angular velocities are related with the different operative parameters involved in the process of separation of silica from iron ore, which permit maximise the capacity of the spirals to obtain major productivity. The process is realised in two steps, of the rough dressing and other cleaning. Through the results obtained for chemical analysis of the final products of each spiral and the equation of movement of particles, it is proved the applicatibility and efficiency of mathematical model to operating parameters of the spiral. Moreover, it is determined though the recuperation of the final products of quality in the use spiral HC 1870 and HG 8/7. INTRODUCTIONThere is prospetive of increasing the production the iron ore in agreement with the demand of siderurgical proyects united with the external demand of quality 40 million tons per year. The Ferrominera de Orinoco Company is experimenting two types of modem spirals, Humprey (HC 1870) and Reichart (HG 8/7) which have limited capacity. For this reason this investigation designed a mathematical model with which larger units can be designed for increasing the capacity of the spiral."

Jan 1, 1999