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By Bowang Xiao

Recently more and more attentions are paid to high pressure hydrogen quenching (HPHQ) for its advantages such as environmental friendliness, low distortion, etc, compared to oil and water quenching. In HPHQ process, heat transfer coefficient (HTC) usually varies from part surface to surface because of the intense variation of gas velocity around the part. This article studies the effect of HTC distribution on part distortion after HPHQ and shows that finite element simulations considering HTC distribution predict different distortion from these without considering HTC distribution. It is also pointed out in this article that HTC distribution can be optimized by adjusting part orientation and HPHQ condition so that part distortion is minimized.

Jan 1, 2010

By S. Eck

In previous work the influence of the casting speed on the flow field and the shape of the solidification front in an industrial 0.82 x 0.25 x 0.8 m³ bronze caster had been investigated. Both numerical and experimental model represented 1:1 the real caster geometry. A comparison of the results of both numerical and experimental models for the flow during the casting process showed a good agreement in the qualitative velocity fields (flow direction and vortex formation). This work represents a parameter study of the numerical model with variations of the turbulence conditions at the inlet in order to clarify their influence on the flow field in the caster. In order to find the best boundary condition at the inlet, the numerical calculations for water have been compared with the measured flow fields in the water model. The new boundary conditions were then applied to the numerical model of the bronze casting process.

Jan 1, 2009

By K. Osseo-Asare

"The molecular structural and solution chemical characteristics that underlie the surface activity of solvent extraction reagents are highlighted, with particular emphasis on the tendency towards reverse micelle and microemulsion formation. The physicochemical factors that lead to microemulsion-enhanced solvent extraction with chelating extractants are elucidated. Membrane-based contactor systems are described which are uniquely suited for enhanced solvent extraction with microemulsions. The possibility of combining solvent extraction with microemulsion-mediated materials synthesis is discussed. IntroductionThe discovery of new selective extractants has resulted in major breakthroughs which have helped to establish solvent extraction as a versatile separation technology (1-3). A complementary strategy towards new process development is to seek new ways of using the available reagents. This paper explores this second approach. From a molecular structural standpoint, an extractant may be viewed in terms of two components: a polar functional group and a hydrocarbon radical. In the conventional view of solvent extraction, this molecular structure serves two main purposes: The polar functional group provides the binding sites for complexation of metal ions, while the organic group is needed to render the resulting metal-extractant complex organic-soluble. But are these the only properties of the organic and the polar groups that are relevant to the solvent extraction process?In this paper, attention is directed to the fact that solvent extraction reagents possess the molecular structures of amphiphiIes; that is, they are characterized by the presence of spatially separated hydrophilic and hydrophobic groups on the same molecule. A case is made for the view that this amphiphilicity offers interesting opportunities to develop new separation processes which collectively may be described as enhanced solvent extraction (4-6)."

Jan 1, 1996

By C. M. F. Vieira

This work has as its objective to characterize ceramic bodies for vitrified tiles elaborated with the mixture of nepheline-syenite flux and kaolinitic clay. Formulations were prepared with 0, 30 and 50 wt.% of nepheline-syenite incorporated in a kaolinitic clay. To determine the physical and mechanical properties such as dry bulk density, linear shrinkage, water absorption and flexural rupture strength, specimens were prepared by 30 MPa uniaxial pressure-molding and then fired in a laboratory furnace at 1150oC. The microstructure of the fired ceramics was evaluated by scanning electron microscopy. The results indicated that the nepheline-syenite improved the evaluated properties of the clay and attended the specifications of vitrified ceramic tiles.

Jan 1, 2010

By A. S. Usmani

The flow associated with the pouring of molten metal into moulds has been modelled on the basis of certain simplifying assumptions. A finite element based Navier-Stokes equation solver has been used to analyse the flow. The velocities obtained from the Navier-Stokes equation solver are used to advect a pseudo-concentration function for modelling the fluid front. A simple problem with a known analytical solution is solved first to test the model. Subsequently, several more examples with varied geometrical configurations are modelled, including one with curved flow boundaries.

Jan 1, 1992

By Thomas P. Battle

Ilmenite (iron titanate) is the source of over 90% of all the titanium produced in the world today. At some point during production of titanium dioxide or titanium metal the iron impurity must be removed. Too often it becomes a waste instead of a product. DuPont and MINPRO have developed a solid-state process which separates the iron and titanium components of ilmenite into different high-purity powders, which can be separated using conventional mineral processing techniques. The main reactor in this process is a unique high-temperature ball mill, where the iron segregates from the ilmenite lattice with the assistance of catalytic quantities of He\. The results of lab, pilot plant, theoretical, and scale-up studies are presented and discussed.

Jan 1, 1996

By Joël P. T. Kapusta

Although Peirce-Smith converting remains the workhorse in matte converting, the copper and nickel industries are still confronted with production hindrances such as tuyere blockage, excessive refractory wear and limits in the oxygen enrichment levels of the blast air. The knowledge acquired on high-pressure gas injection technology as well as the invention of the concentric tuyere for steelmaking led to the development of the Air Liquide Shrouded Injector (ALSI) technology for copper and nickel converting. Following a technology demonstration in 1997-98 with four shrouded injectors installed in a Peirce-Smith converter, Falconbridge Limited implemented ALSI Technology on a commercial scale in May 1999 as an integral part of its new Slag Make Converter at Sudbury, Ontario, Canada. The paper presents the various aspects of commissioning ALSI Technology, as well as the operating changes and injector design modifications over the five years the shrouded injectors have been in operation.

Jan 1, 2005

By Minji Jun

Leaching of the surface-coated metals from waste acrylonitrile butadiene styrene plastics (WABSP) has been investigated in the ammoniacal solution. The ammoniacal leaching of WABSP (typically containing 4.1 wt% Cu, 1.3 wt% Ni, 0.03 wt% Cr) efficiently dissolved copper and nickel, leaving unleached chromium as fine particles. The results indicate that the anions of different buffer media for metals leaching follow the order: CO3 2− > Cl− > SO4 2−. A declined leaching with high NH4OH–(NH4)2CO3 ratio (8:1) and a steep rise in extraction with high pulp in solution revealed the influence of anion (CO3 2−) and cation (Cu2+) present in the system. The leaching performed in carbonate solution by maintaining 5.0 M total NH3 concentration as NH4OH–(NH4)2CO3 ratio, 4:1; pulp density, 200 g/L; agitation speed, 400 rpm; temperature, 20 °C and time, 120 min yielded the maximum extraction (>99%) of copper and nickel. The study reveals a plausible recovery of the surface-coated metals from the WABSP without altering the properties of polymer material that can be recycled separatel

By Guomin Jiang

Potassium ferrate is an excellent multifunctional reagent for wastewater treatment, but its preparation is crucial. The improved hypochlorite oxidation method was used to prepare potassium ferrate in this study. Iron nitrate, the preferred iron source, was added into hypochlorite solution and then the stabilization agent was added during the purification process of product. The influence of available chlorine content, iron molecular proportion, reaction temperature and reaction time on potassium ferrate preparation was investigated. The optimal condition for potassium ferrate preparation is 15% of available chlorine content , 0.6 of iron molecular proportion , 30i of reaction temperature , 45min of reaction time. The yield of potassium ferrate is about 67% with high purity (> 99%). The structure and performances of the product was characterized by XRD, EDX, SEM, TG and IR and the results show that the prepared product is consistent with the properties of potassium ferrate(VI).

Jan 1, 2010

By Tetsuya Uda

Our recent achievements of rare earth separation technique[1,2] and new process idea for rare earth magnet recycling[3] are reviewed, (1) Binary chloride mixtures of rare earths were separated by a new selective reduction-vacuum distillation process. According to our experimental results, apparent separation factors were 8.1 for the Pr-Nd chloride mixture and 570 for the Nd-Sm chloride mixture. These values are much higher than conventional solvent extraction methods. (2) A study of recycling process of magnet sludge was carried out. The rare earths in the neodymium magnet sludge were extracted by chlorination with FeCI2, An activated carbon was used as a de-oxidation reagent Metallic iron in the sludge was not chlorinated because the iron monochloride is not stable, The extracted rare earth chlorides were easily separated from Fe-alloy and the excess of FeCh by vacuum distillation, 96 % of neodymium and 94 % of dysprosium in the sludge were extraeted into chloride phase, By the vacuum distillation, a mixture of neodymium and dysprosium trichlorides of 99.2 % purity was recovered, On the other hand, the rare earth chlorides can be converted to the corresponding oxides by a pyrohydrolysis reaction accompanied by a formation of HCl gas, The HCI gas can chlorinate metallic iron to FeCh, Therefore, a new recycling process for rare earth magnet waste can be realized as a chlorine circulation type process. During the process, only carbon and water are consumed and there are no toxic pollutants, Moreover, the obtained rare earth oxide can be directly used as raw material in the conventional oxide electrolysis process,

Jan 1, 2003

By Xiao Caimei

The method of Substance Flow Analysis (SFA) provides a helpful tool for the study of the industrial metabolism of a certain metal within a regional level, such as copper, lead etc. In this paper the flows and inventory of cobalt in China, 2008, were traced with the STAF model, and the situations of production, fabrication and manufacturing, use and waste management in China were introduced. The result revealed that the resource of cobalt in China was so poor that a large amount of cobalt material or cobalt products needed to be imported, and there was lack of recycling of cobalt resources.0

Jan 1, 2010

By Clara María Lamus Molina

The following minerals found in the residual black sands from gold mining in El Bagre Antioquia (Colombia) were identified as having major economic interest: Ilmenite (FeTiO3), with an average of 49% of TiO2, frequently altered presenting crowns; lamellaes of rutile and alteration textures; titanomagnetite with up to 25% of TiO2; magnetite (Fe3O4) in individual grains or associated with others minerals as hematite and ferromagnesian silicates rutile (TiO2) with considerable quantities of Nb2O5(0.1-3.7%Wt); zircon (ZrSiO4) with 66%Wt of ZrO2 and monazite with an average of 63.43%Wt of REE, this frequently associated to xenotime and thorite forming textures as little drops. Analysis in EPMA and SEM/EDS showed percentages of minor elements and traces, thereby clearly establishing the applications of these minerals in diverse industries. Furthermore, a detailed granumetric study of the different minerals and textural relationships among them also allowed for establishing the basis for possible processing and exploitation.

Jan 1, 2006

By B. G. Thomas

"Mathematical process models can be applied in several different ways to serve industry by inducing beneficial changes to process operation. This paper attempts to summarize the different uses, types, and attributes of these models, and to offer some ideas to consider when developing, using, and reporting on them. Process models range from empirical to mechanistic in nature and vary in complexity from simple analytical solutions to coupled, 3-D transient numerical simulations. They are classified here according to the way in which they are implemented in practice, viz. fully-online models, semi-online models, off-line models, and literature models. The purpose of the model should dictate how choices are made during its development. Ways to validate and compare the model with experiments are suggested. Examples are taken in the context of the author's experience in modeling the continuous casting of steel.IntroductionThe objective of this paper is to provide a partial introduction for this symposium by discussing some basic aspects of the application of mathematical process models in industry. Essentially, the aim is to explore how process models are used to benefit industry, and to offer some general comments and suggestions, based on the experience of the author, on how models can best meet this goal.This work is concerned with process models, which consist of systems of mathematical equations and constants that are solved on a computer to make quantitative predictions about some aspect(s) of the process. The specific variables required as input data and generated as output data are important features of the model. The equations often derive from a numerical solution to one or more differential equations and their boundary conditions. The model also includes the constants, which represent material properties, empirical relationships, and other knowledge about the process, and usually require considerable effort to obtain. Thus, general purpose commercial software packages, (ie. finite-element or finite-difference based codes), are not models in this context. They are useful tools, however, serving as frameworks for the development of process models."

Jan 1, 1994

By Nathanael Hudson, Ruel A. Overfelt, Sushil H. Bhavnani

"In the aerospace and automotive industries, complex shapes exist which require casting. The problem with these cast parts is the empiricism required to develop the casting process and the accompanying time and expense to develop that process.There has been an interest in using fluidized beds to allow molding sand to better encapsulate the complicated surface geometries of lost foam patterns. Fluidization coupled with a mixing jet helps to homogenize the sand through stirring and may improve the integrity of the casting.At issue is the hydrodynamics of the sand and air around the foam pattern. The commercial package PHOENlCSTM is used to simulate the flow around the pre-casting foam geometry. Employing a two fluid approach, each component is considered a fluid that interpenetrates the other phase. To this end, the kinetic theory of granular 'flow for the sand phase was incorporated into the re-compilable PHOENlCSTM code.The results of this study consist of time-averaged void fraction patterns, with voidage being defined as the fraction of air in the mixture, around the foam pattern submerged in a two-dimensional fluidized bed. The model was benchmarked against past fluidized bed experiments. In order to better understand the dependence of the void fraction pattern around the lost foam pattern, certain physical parameters are varied and the resultant void fraction maps are predicted with the model. Physical parameters such as the aspect ratio of length to width, the placement of the mixing jet, and different mixing jet velocities are varied to illustrate the dependence of the time-averaged void fraction on those variables.Results consistently indicate the presence of channeling around the lost foam pattern, with the extent of the channeling and void formation reliant to a greater degree upon the placement of the mixing jet, and to a lesser degree on mixing jet velocity and aspect ratio.The increase in radial position of the mixing jet from the bed centerline had the desirable effect of granting the churning benefits of a penetrating jet, while at the same time minimizing the formation of excess void fraction at the top of the pattern."

Jan 1, 2001

By H. Y. Sohn, Joshua E. Ramos, Moo Eob Choi

"A new technology for ironmaking based on direct gaseous reduction of iron ore concentrate is under development. This technology would drastically lower CO2 emission and reduce energy consumption by nearly 38% of the blast furnace requirements. Experiments were performed using iron oxide concentrate at 1150oC in a bench-scale facility, which was the highest temperature that could be reached in the facility. The reduction extent was determined at residence times of 3.5 - 5.5 seconds in which the reduction extent approached 43% with 0% excess H2 and 95% with 860% excess H2. Separate kinetics measurements showed that the rate is much faster at 1200 - 1400 oC. Experiments were also carried out using syngas (mixtures of H2 + CO). About 90% reduction in 3.5 seconds with 860% excess hydrogen contained in the syngas demonstrated sufficiently fast reduction for a suspension process and the feasibility of usingsyngas instead of pure hydrogen.IntroductionDespite the improvements in the modern blast furnace (BF) process, it suffers from many drawbacks. The process requires the feed in the form of sinters or pellets and high-grade coking coal. Thus, BF iron production is projected to decrease gradually [1]. The main factors for this are the environmental regulations [2] and the high capital investment cost.A large number of new ironmaking technologies have been developed or are under development [3]. Most of these processes, however, are not sufficiently intensive to replace the blast furnace because they cannot be operated at high temperatures due to the sticking and fusion of particles. Therefore, a new technology is under development for producing iron directly from fine concentrates by a gas-solid suspension technology, which would reduce energy consumption by about 38% of the amount required by the blast furnace and drastically lower environmental pollution, especially CO2 emission, from the steel industry."

Jan 1, 2009

By D. Q. Cang, G. Duan, H. X. Li, H. Bai

"Life cycle assessment (LCA) is a valid environmental evaluation method and enterprise environmental management tool used in industrial ecology areas. In this paper LCA was newly used to evaluate the environmental impact of manufacturing of alumina by Bayer process in china from two aspects of logistics and energy flow, GaBi software acted as analysis tools with evaluation model established, and several environmental impact assessment criteria were selected based on the actually typical date of Bayer alumina producing process. Evaluation results show that alumina manufacturing by the Bayer process has a great impact on the global warming and human health of respiration, even roasting process gives rise to the greatest impact of winter fog index. Scenario analysis proposed ways of reducing environmental load caused by Bayer process including: (1) the economic and efficient use of mineral processing technology; (2) optimization of energy use, saving power consumption or the use of new more economical source of energy; (3) actively promote the use of innovated technology and equipment in alumina manufacturing and waste such as red mud utilization process.1 IntroductionSince 2002, China is already the world's biggest producer of aluminium, in 2007, China aluminum production has accounted for above 1/3 all over the world, 2009 for 13 million tons and to the end of 2010, China aluminum production is expected increased to be over 15 million ton [1,2,3]. While as the raw material for producing aluminum the alumina production in china has up to 19.46 million tons of the world's total quarter in 2007, by the end of 2009 China alumina production has achieve to 23.78 million tons [4,5]. China has rich bauxite resources with proven reserves about 23 million tons, but the great majority of china bauxite is hard monohydrate diaspore type with low ratio of aluminium silicon, high impurity content and poor aluminum dissolution performance, that cause high energy consumption, long and complex process, high production costs and heavy environment load[6,7]. Before most used alumina production was sintering process rather than Bayer method in china, over the past decade Bayer method has been widely applied instead of sintering process or combination both forming joint process, premise is improving bauxite quality by mineral processing or adding imported rich bauxite mineral[6,8]. In general each ton production of alumina needs bauxite 1.6~2.20t, limestone 0.7~1.7t, soda 0.250kg, fresh water 12.30 cubic meters, in addition to consume large amounts of energy, and emission waste water over 8.0 cubic meters, dust 2.3~5.7 kg, red mud 0.8-1.5 tons. In china Red mud yield nearly 30.0 million tons every year, accumulated stock is approximately 0.2 billion tons, by 2015 accumulative total red mud is expected to reach 0.35 billion tons [9-13].We know aluminium industry and alumina production have produced large waste, make large energy consumption and its environmental impact could not be ignored. Expecting to optimize production processes and achieve resource recycling for this industrial process the proper environmental assessment is very necessary. Currently Life Cycle Assessment (LCA) is generally recognized as the approved tool to achieve the purpose. The essence of LCA tool is to examine, identify and evaluate a kind of materials, product, process, or a system of environmental impact in their whole life cycle. The life cycle of materials or products includes whole process from raw materials obtained to the final disposal, or more ideal with original or other forms of the whole process of recycling [14-17]."

Jan 1, 2011

By K A. Pericieous

"Magnetic fields have many actual applications in the metals processing industry. Externally applied magnetic fields give rise to electromagnetic (Lorentz) forces formed by the cross product JxB, between the induced current density J and the magnetic field density B. When the metal is in liquid form, the Lorentz force generates motion in the fluid which in applications of practical interest becomes turbulent. In modelling terms, the Lorentz force appears as a source in the momentum equations. In addition, the induced current generates heat (Joule heating) in the metal that is in proportion to J2, with a corresponding source of heat in the energy equation. Whether as heat or as a force, these effects represent action at a distance - a most useful attribute when dealing with hot metal. The Lorentz force is used to stir solidifying alloys, pump liquid metal in conduits, dampen the flow in the meniscus of a continuous caster, levitate metal drops, induce artificial gravity conditions in suspensions or contain liquid metal. Elsewhere, the Lorentz force may be a by-product of some other operation, so leading to wave excitation in aluminium electrolysis cells, or altering the shape of the weld pool in arc welding. Joule heating is most commonly used with applied AC fields, to melt metal in induction furnaces.The author and his colleagues have been involved in the modelling of most of these processes in the past decade. Modelling is not however straightforward, since most of the examples mentioned represent genuine multi-physics challenges. There is a strong coupling between the flow field and electromagnetic field. The addition of a dynamically varying metal free surface and the moving solidus front means the flow, heat and electromagnetic fields need to be computed simultaneously. In situations involving metal containment, the metal free surface position is governed by the interplay of gravity, Lorentz force, surface tension and fluid inertia. Since all the interesting effects often happen in thin boundary layers at the surface due to the skin effect, mesh generation and mesh control during the computation become non trivial problems that need to be addressed. This paper presents a review of numerical methods used to model droplet levitation, semi-levitation melting and cold crucible induction melting of metals. The first method is based on spectral collocation techniques and the second is the traditional FV approach. Steps taken to validate the computations and typical transient results are also given."

Jan 1, 2001

By N. B. Gray, A. E. Guerra, D. E. Morton

"The formation of splash in pyrometallurgical operations that involve the injection of gases into a liquid has been the subject of a number of studies over the last few decades. Given the complexity of the phenomena, there have been some advances in understanding the microscale formation of splash but the ability to accurately predict the amount and character of the splash formed is still in its infancy. First, the macroscale mechanisms for splash formation is very varied. Second, the timescales for splash formation are very small, usually less than 100 milliseconds, making experiments elucidating the formation of splash difficult and costly. Work at the GKW CRC has shown that the microscale mechanism of splash formation is primarily is due to the Kelvin-Helmholtz instability. Substantial progress has been made in understanding the behaviour of large bubbles in effecting splash formation and a simple model has been developed to estimate the behaviour of splash formed from a top submerged lance. Direct numerical computation of splash formation using the GKMAC codes developed at the Centre has been successful in simulating the impact of liquid drops onto a liquid bath.IntroductionInjection of gases into melts is used in the metallurgical industry to promote mixing to ensure acceptable heat and mass transfer rates, conveying solids for alloying, provide efficient contact for gas-melt reactions, and as a reactant. High gas injection rates bring about the formation of splash and slop. Extensive splash formation leads to loss of valuable product, creation of safety hazards, formation of accretion on refractory lining and exhaust ducts, and increased load on dust removal equipment. Many operators and researchers have claimed that splash formation is the limiting factor in many gas injected processes. The problems listed above lead to loss of production and increased maintenance, adding to the cost of processing base metals. Over the last five years, the GKW CRC has been studying the formation of splash from a number of sources. They include the impingment of drops on liquids[ l·2.31, slopping of bath liquidI4.51, breakup of gas bubbles at the liquid-gas interfacel61, shearing of liquids by gases[7·81, and impact of packets of fluids on solidsl81. Theoretically, the extreme deformation of fluid shape and the influence of surface tension makes the simulation of flow resulting from only a drop impacting on a liquid surface a very challenging computational fluid dynamics problem. Recently, we have been successful in simulating the formation of the Rayleigh jet resulting from a drop impact showing the effect of drop Froude number on the shape of the Rayleigh jet."

Jan 1, 1996

By Payman Roonasi

Having knowledge of mechanism of magnetite formation is essential in a number of industrial processes including magnetite synthesis and corrosion of iron. In this study, magnetite nanoparticle was synthesized via two different ways; coprecipitation of iron (II) and (III) and oxidation of ferrous hydroxide. The samples were characterized using X-ray diffraction (XRD), Mid-Far IR spectroscopy, scanning electron microscopy (SEM), chemical analysis for determination of Fe II/Fe III ratio and ICP-MS for iron isotopic ratio (56Fe/54Fe) measurement. Since fractionation of iron isotopes depends on reaction rate and bonding strength, interpretation of the isotopic data with respect to the possible mechanisms is discussed. No fractionation of iron isotopes was observed for the magnetite synthesized by coprecipitation, whilst magnetite formed from ferrous hydroxide showed higher abundance of 54Fe compared to 56Fe in the beginning of reaction, implying the significance of the following reaction:

Jan 1, 2009

By Hongyang Cao

The iron constituents selectively separated from the modified copper slags by magnetic separation and flotation.were studied. The results of magnetic separation for modified copper smelting slags show that the grinding size, current intensity and dispersant agent had great influence on grade, and recovery ratio of TFe in preparation concentrate; The results of flotation for magnetic concentrate show that the positive flotation of sodium oleate negatively upgrade the grade of magnetic concentrate, but the reverse flotation of lauryl amine and soluble starch are effective. The grade of TFe can reach 54% and the recovery ratio can reach about 90% in magnetic concentrate, when the grinding size is 45.8µm and the current intensity is 2.5A. The optimal effect is obtained by using lauryl amine as collector and soluble starch as depressant to reverse flotate magnetic concentrate, and the grade of TFe is upgraded 2.37%.

Jan 1, 2009