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By Eduardo Juncal, Jorge Alberto Soares Tenorio, Jose Roberto de Oliveira, Denise Crocce Romano Espinosal

"Steel industry has been expanding every year, consequently there has been an increase in waste generation in this area. Thus, companies in this sector are finding it difficult to give a correct destination of waste. For example, only in a basic oxygen furnace (BOF) converter are generated about l8kg of dust per ton of steel. The aim of this work was the characterization of dust generated in the BOF converter. The characterization was performed by chemical analysis (titration for iron and its oxides and Inductively Coupled Plasma Atomic Emission Spectroscopy for other elements), scanning electron microscopy, size analysis using Mastersizer 2000 equipment and X-ray diffraction. It was observed that dust is composed mainly iron in form of magnetite, metallic iron and wustite with approximately 99% of the particle size below 100 µm.IntroductionToday, steel is a important metal for the world. It can be produced for two routes, blast furnace/ basic oxygen furnace (BOF) converter and electric arc furnace (EAF) [1].First route, the iron is produced from the reduction of iron ore and coke for fuel injection and! or natural gas for a production of pig iron in blast furnace. The pig iron is sent until BOF converter to perform the blowing of oxygen to obtain the steel. In the second route, the steel is produced using scraps or direct reduced iron (DR!) using electric arc.During steel production are generated a lot of wastes like slag, sludges, scraps and dust [2]. Only in the first six months of201O, world steel production totaled 706 million tons [3]. According to Watson and Wang [4], some 10 to 20 kg of dust is generated per tonne of liquid steel produced. Thus, the reuse of these wastes can be a great to companies, because it reduces the amount of raw material to be extracted and reducing disposal costs [5,6]."

Jan 1, 2012

By Xavier Kleber, Aude Lamontagne, Veronique Massardier, Daniele Mari

"The thermoelectric power (TEP) technique was used to determine with high accuracy the strain ageing kinetics in heavily cold drawn pearlitic steel. Because of the very high sensitivity of the TEP to solute atoms, this technique allowed the strain ageing to be followed from the very first moments. The kinetics were followed during isothermal ageings performed between 20°C and 200°C for different strains. In order to avoid any ageing at room temperature, the samples were kept at -80°C immediately after cold drawing. TEP evolution versus strain highlights cementite decomposition occurring during cold drawing. During the ageing, a redistribution of the dissolved carbon atoms in ferrite occurred. The TEP increase with the ageing time was attributed to the departure of carbon atoms from ferrite (segregation to dislocations and/or carbide precipitation). The kinetics were analysed using the Johnson-Mehl-Avrami-Kolmogorov approach which enabled to determine activation energies associated with carbon atoms redistribution.IntroductionHeavily cold drawn pearlitic steel wires are commonly used as structural materials for their high strength and their acceptable ductility. However, several previous studies highlight the microstructural destabilization of pearlite mainly due to cementite decomposition during the drawing process, which induces changes of mechanical properties [1, 2]. This phenomenon was detected by several experimental techniques such as Mossbauer spectroscopy [3, 4, 5], themomagnetic analyses [6, 7], TEM [8, 9, 10] or atom probe tomography [9, 10, 11]. Nevertheless, the mechanism of cementite decomposition is still unclear. Several hypotheses were proposed in the literature. The first hypothesis relies on a strong interaction energy between carbon atoms and dislocations involving higher binding energy than that between carbon atoms and iron atoms in cementite [3]. The second hypothesis is the increase of the free energy of the interface between cementite and ferrite due to the fragmentation of cementite during deformation (Gibbs-Thomson effect) [8]. Some authors even suggest that the dissolution of cementite occur during a post-deformation ageing [12, 13]. It is worth"

Jan 1, 2013

By Xinli Wang, Matthew Andriese, Jiann-Yang Hwang, Zhiwei Peng, Byoung-Gon Kim

"The microwave dielectric properties of silicon dioxide at frequencies of 915 and 2450 MHz were characterized in the temperature range of 24 to approximately 1000 °C using the cavity perturbation technique. It is shown that the relative dielectric constant of silicon dioxide at both frequencies remains almost unchanged below 500 °C, above which there is a slight increase of 2%. The relative dielectric loss factor of silicon dioxide exhibits a strong temperature dependence above 500 °C and increases by approximately 7 and 5 times at 915 and 2450 MHz, respectively. The substantial increase in the relative dielectric loss factor is mainly attributed to the enhanced dielectric polarization and accelerated electrical transport in silicon dioxide at elevated temperatures.IntroductionSilicon dioxide (Si02) is usually considered a microwave transparent material due to its poor absorption capability at room temperature [1]. This characteristic has led to various applications of silicon dioxide in microwave processing of materials and communication. For instance, Si02 has been used to produce sample holders for microwave heating and substrates for electronic devices [2,3]. These applications generally require the material to withstand high temperatures under microwave irradiation. This indicates that microwave absorption capabilities of silicon dioxide at elevated temperatures are also important for its utilization.The microwave absorption capability of Si02 can be determined based on dielectric characterization (permittivity measurement) of the material at commonly used microwave frequencies, 915 and 2450 MHz, in a broad temperature range. To date, however, no detailed work on the dielectric properties (permittivity) of silicon dioxide at high temperatures has been reported. The present work is aimed to study the dielectric properties of silicon dioxide from room temperature to approximately 1000 °C at 915 and 2450 MHz. The results show that the permittivity of silicon dioxide has a strong temperature dependence above 500 °C, suggesting a substantial increase in its microwave absorption capability."

Jan 1, 2013

By Samson Adeosun, Sanmbo Balogun, David Esezobor

"In a typical year, approximately 1.7 million tons of residues and wastes are expected from Ajaokuta integrated steel plant, Nigeria. They will be generated mainly from sinter plant, blast furnace (BF), and basic oxygen furnace (BOF) operations and during rolling and finishing. The residues and wastes include slag, dust, sludge and slurries from gas cleaning, waste water, mill scales and other associated scraps. In this paper concepts for the utilization of residues and wastes in Ajaokuta Steel Plant where no reclamation routines have been provided for in the first and second phases of its project implementation is designed. The paper analyses the sources of the iron oxide wastes and evaluates the quantities expected from the main production facilities of the plant which include the two 312 m2 capacity sintering machines, the two 2000 m3 blast furnaces and two 130-T BOF (of the 2nd phase expansion of the Steel Plant). A reclamation routine designed for Ajaokuta residues and wastes is presented.IntroductionIn the steel industry, approximately 550kg of residues per ton of crude steel arise from the production processes and from pollution control facilities [1- 4]. These residues consist of slag, dusts and sludge, mill scale, spent pickle liquor, and other iron bearing materials. The main by – products generated in the steel industry are listed in Table I.Although major progress has been made in the recycling and use of some of these residues, particularly flue dust, blast furnace and steel making slag, yet a significant quantity are land filled or stockpiled. These unsightly stockpiles occupy valuable real estate and may become a source of environmental pollution if not otherwise disposed. In any case, the dumping option has become quite costly. For instance, one ton of iron ore costs between 28 and 34 US dollar, whereas as much as $20 per ton of steel produced is required to meet environmental compliance obligation in the USA [5, 6]."

Jan 1, 2008

By Wander. L. Vasconcelos, Virgínia. S. T. Ciminelli, Angela. M. F. Guimarães

"The present work was aimed at synthesizing nanostructured hybrid materials derived from the functionalization of smectite clays with ligands containing thiol (-SH) groups for application in cadmium adsorption processes. An in nature Brazilian bentonite was investigated. The modification route was based on the grafting reaction between hydroxyl groups present on clay surface and the hydrolyzable alkoxy group of the (3-mercaptopropyl)trimethoxysilane in dry toluene under reflux. The present work showed that the proposed modification route was effective for the grafting of the thiol groups in the clay structure. The thiol-functionalized bentonite samples showed average binding capacities 160% higher with respect to Cd2+ to those obtained with the ungrafted material. These results support a mechanism of adsorption involving primarily ion complexation by the thiol groups (specific) instead of cation exchange (unspecific). The proposed modification processes are suggested for the preparation of novel adsorbent materials with controlled selectivity and specificity and therefore with good potential for separation and pre-concentration purposes.IntroductionMany efforts have recently been devoted to the design and preparation of inorganic-organic nanomaterials because of their potential application in novel functional materials. The intercalation of organic species within the spaces between interlayers of inorganic layered crystals provides nanostructures consisting of alternating layers of inorganic and organic compound. The intercalation reactions occur by insertion of mobile guest species (neutral, molecules, or ions) into the accessible crystallographic-defined vacant sites located between the layers (interlayer spacing) of the layered host structure [1}.Silane coupling agents, used widely for the modification of silica surfaces, have also been employed more recently for modification of layered silicates [2,3,4,5]. Modification with organosilane involves grafting reactions by establishing covalent bonds between the reactive groups of the layer, normally hydroxyl groups, and silane molecules. These reactions can be restricted to the external surface (the basal spacing remains unchanged) or to the interlayer surface, in which case an interlayer expansion occurs. The resulting material can be defined as a hybrid material or, more specifically, functionalized inorganic layered material [1]."

Jan 1, 2008

By Guodong Lai, Shixing Wang, Lijuan Chu, Jinhui Peng, Zebiao Zhang

"The beneficiation of poor manganese ores containing phosphate gangue is very difficult by conventional processes, because of the similarities in the physico-chemical properties of the constituent minerals. The shaking table gravity concentration process and concentrated strong acid selective intensified leaching process were used for dephosphorisation of Yunnan manganese ore. The leaching process was effective. The effects of intensified leaching time, solid-liquid ratio and particle size were investigated. The relevant leaching factors were optimized as -0.125+0.088 mm particle size with 68% nitric acid for 24 h when using a solid-liquid ratio of 1:1 at room temperature and atmospheric pressure. Under these conditions, the P/Mn ratio was reduced from 0.0107 to 0.0056, and the grade of manganese was increased from 12.32% to 42.76%. The dissolution of manganese during leaching was negligible.IntroductionManganese and its compounds are widely used in the iron and steel industry as deoxidation and desulfurization agents and as alloying additives [1-2]. Because of the increase in demand, low grade refractory manganese ores are becoming a new source. Many Chinese manganese ores are high in phosphorus, which cannot be used directly for metallurgical purposes. This occurs because phosphorus enters into the metal phase during smelting and its presence sharply deteriorates the mechanical properties of the metal [3-4].Kanungo and Sant [3] investigated the dephosphorization of phosphorus-rich manganese ores by selective leaching with dilute hydrochloric acid. They observed that leaching with dilute hydrochloric acid (0.1-0.6M) could reduce the phosphorus contents to the specified limit of 0.12%. Ye [5] investigated dephosphorization of high-phosphorus manganese ore of the Huayuan type. Using high intensity magnetic separation, roasting and leaching with acid for dephosphorization, as used in the industry, a 40.15% manganese concentrate with a P/Mn ratio of 0.0037 was obtained. Yimin [6] investigated magnetic separation followed by inverse flotation of high-phosphorus manganese ore, and found that the P/Mn ratio could be reduced from 0.046 to 0.002."

Jan 1, 2012

By C. Carreno, A. D. Gonzalez Escarcega, M. A. Neri, A. Martinez –Villafane, O. Cobarrubias-Alvarado

"Waspaloy is a superalloy used to manufacture some aeronautical parts subjected to high temperatures and stresses. During thermo-mechanical processing cracks are generated, causing some parts to be rejected. In order to determine the causes of these cracks, this alloy was characterized using techniques such as chemical analysis, optical microscopy, scanning electron microscopy, and EDX analysis. Heterogeneous grain sizes in the microstructure cause a non-uniform strain distribution in these parts, creating cracks in zones with different grain sizes.IntroductionNickel-base superalloys are important materials for high-temperature service applications. The manufacture of components from these materials is typically based on solidification or powder-metallurgy processes [1]. Solidification techniques comprise either the direct casting of parts or the casting of ingots which subsequently undergo a series of thermo-mechanical-processing steps to refine the microstructure. During solidification, microsegregation is usually unavoidable. The primary solidification product is a disordered nickel solid solution with an fee crystal structure (?). In many alloys, the material which solidifies last is a mixture of ã and an ordered fee phase (? '). In prototypical nickel-base superalloys, the ?'-phase is Ni3(Al,Ti) [2-3].Waspaloy is a superalloy that is used in demanding high-temperature environments in which good creep and fatigue resistance are required. One of the most common applications of Waspaloy is for turbine engine rings. To ensure the required mechanical properties, the rings are usually forged and heat treated (Figure 1). Two distinct types of microstructures are usually found to be attractive for such applications: a) A microstructure with a grain size of ASTM 10 to 14 for tensile strength, ductility, and resistance to crack nucleation in low-cycle fatigue; or b) A microstructure with a grain size of ASTM 4 to 8 required for creep strength and resistance to crack propagation [4]. Because it is impossible to refine the grain size through heat treatment, a skillfully designed forging process is crucial for the control of the grain size and, hence the properties of the forged ring [5-6]."

Jan 1, 2012

By S. K. Varma, Miriam Regalado, Daniel Salas, Erica Corral, Erika Esquivel

"Age hardenable 2014 aluminum alloys and composites containing 0.10 and 0.15 volume fractions of alumina particles (VFAP) have been solutionized at 540 and 550°C for up to 20 hours. The solutionized samples, heat treated for 5 and 20 hours, have been subjected to room temperature rolling until cracking develops. The work hardening curves have been compared to determine the effect of solutionizing time on the rolling characteristics from both hardness and the microstructural evolution points of view. Solutionizing at two different temperatures results in differences in the extent to which the composites can be rolled until fracture. The microstructural characterization by TEM has been performed to understand the room temperature rolling behavior.IntroductionThe effect of solutionizing on the age hardening response of 6061 and 2014 aluminum alloys and composites reinforced with 0.10, 0.15 and 0.20 volume fractions of alumina particles (VFAP) have been reported in the literature [1-4]. A comparison of the monolith and composites indicates that particles promote the aging process through differences in the microstructures in solutionized condition. The first effect of solutionizing is to produce a grain growth process which follows a grain growth law (square of grain diameter as a function of solutionizing time). It appears that it is possible for vacancies to be emitted during grain growth period as they try to minimize the total grain boundary surface area by increasing their diameter. This may be common to both the monolith and the composites. However, the second effect must be exclusively considered for the composites. The particles generate dislocations during the solutionizing process due to the differences in the values of the coefficient of thermal expansion (CTE) between the particles and aluminum base metal. It has been determined [1] that the dislocation density increases with increase in solutionizing time in the composites of 6061 aluminum alloys reinforced with 0.10, 0.15 and 0.20 VFAP. The improved bonding between particles and matrix can give rise to additional generation of dislocations due to curvature effects [1] with the result that the dislocation density continues to increase with increase in solutionizing time even after the CTE effect is considered to have been stabilized."

Jan 1, 1998

By M. J. Soria-Aguilar, F. R. Carrillo-Pedroza, S. Preciado-Nuñez

"Dust originated from the Iron Blast Furnace (BF) and the Basic Oxygen Furnace (BOF) containing alkalis and zinc are not completely recycled because due affects the process efficiency. These types of dust represents an economical lost as a consequence of values contents of iron and carbon. Several processes in aqueous media have been developed to treat the steelmaking dust. This work presents a laboratory study for reduce zinc and alkali containing in BF and BOF dust, using different acid and alkaline solutions and oxidants as ozone. The results obtained show that the elimination of zinc and alkalis can vary from 5 % to 80 % depending on the treatment conditions (the solution, the oxidant and the temperature). The dust obtained from this treatment can to be recycling to the steelmaking processes to recovery iron and carbon values.IntroductionEach one of the steel making industry processes generate several sub-products and residues containing useful units of iron, carbon and other elements that are or could be recycled to the productive process. Some of those sub products are the dust from the gas cleaning system of the blast furnace and the dust from BOF reductive process; such dusts are sent to the sedimentary lagoons. The dust represent a lost of 2 % of the total iron and coal mineral’s content feed to the process.The typical iron, carbon and zinc content of the blast furnace dust is approximately 40, 24 and 0.3 % and the content of the BOF dust are 50, 15 and 0.9 % weight respectively, with physics - chemical characteristics that became them susceptible to be agglomerated and feed to the blast furnace. But the high content of zinc does not allow recycling it into the process. At the blast furnace the presence of zinc propitiate the formation of film in the furnace wall; these elements are vaporized in the low section of the cube of the furnace and they are dragged by the gases to the top and condensed again at the cube. Part of these condensed materials strongly adheres to the furnace cover harming it and reducing the empty space of that section, causing eventually a severe perturbation of the ascendant gas flux [1]."

Jan 1, 2008

By R. Boussaa, Y. Fautrelle, K. Zaidat, O. Budenkova, B. Saadi, X-D. Wang, L. Hachani, H. Ben Hadid

"Comparison of experimental data obtained in a benchmark experiment of solidification of a Sn-3%wt.Pb ingot and numerical results of two-dimensional and three-dimensional simulations of the process is presented. The benchmark experiment consisted in solidifying a rectangular ingot of Sn-3%wt.Pb alloy using two heat exchangers. Conditions of solidification were thoroughly controlled due to six thermocouples embedded into each heat exchanger. Due to another array of thermocouples the evolution of the temperature field at a lateral wall of the crucible was registered during the whole experiment. A treatment of the temperature data provided an estimation of the velocity field in the experiment. Post-mortem analyses of the sample provided the pattern of macrostructure of the sample and qualitative segregations pattern. 2D and 3D numerical solidification models are developed to give the distribution of the solute in a solidified sample.IntroductionConvection, either natural or forced, plays a very important role during the solidification. Its intensity and flow pattern affect heat and mass transfer and, consequently, macrostructure and segregation in a solidified ingot [1-4]. The effect of buoyancy convection during solidification has been studied in many laboratory-scale experiments [5-6]. Due to these experiments a general comprehension of formation of various defects in the ingot has been achieved. However, mentioned studies were not consistent since alloys, solidification conditions and configurations were every time chosen arbitrary. That is why the role of each parameter characterizing solidification process remains unclear. Moreover, the question of reproducibility of defects under the same solidification conditions still exists. In addition, most of the experiments suffer from the insufficient knowledge of control parameters that makes difficult their use for validation of models for solidification. These parameters serve as boundary conditions for numerical modeling and their incomplete description leads unavoidably to the errors in simulations. This situation motivated us to develop a setup for benchmark solidification experiments and to perform a set of the solidification experiments which we reported in [7]. Here we presented a comparison between results obtained in a benchmark experiment of solidification of Sn-3%wtPb ingot and its numerical modeling, which was performed in two-dimensional and three-dimensional configurations."

Jan 1, 2012

By Ruixiang Wang, Jinhui Li, Youjun Xiao, Daoling Xiong, Hao Chen

"Leaching solution prepared from spent battery materials contains large quantities of valuable metals, such as Cu, Ni, Co, Mn and Fe. Therefore, recovery of valuable metals from acidic polymetallic aqueous solutions is of great importance for every plant. In this work, a method is introduced of recovery of Ni, Co and Mn from polymetallic solution prepared by leaching spent battery material. The basic concept includes copper was removed through replacement by iron powder followed by iron precipitation in goethite method. The experimental results show that Cu can be removed 99% at least through replacement by Fe powder, and the removal of Fe can achieve 99% by goethite method. At the same time, the loss of Ni, Co and Mn are about 2%, 3 % and 2%, respectively. The process of differential removal of metals can be selected as the treatment alternative that combines simplicity, efficiency and reliability with low capital and maintenance costs. The purified solution which only contains Ni, Co and Mn can be used to prepare NixCoyMnz ternary system precursor.1 IntroductionNickel and Cobalt are very important metals which are applied in many fields, such as energy material and support material for some new material field. The world demands for such metals is progressively increasing, while raw resources are being depleted and with the constraints raised by the Law and related legislation assigned to protect the environment from hazardous wastes in the world. Nowadays study on reutilization of waste materials has great significance for achieving secondary resources recycling and preventing environmental pollution. There are many hydrometallurgy methods applied for dealing with these wastes, while they usually contain large quantities of valuable metals, such as Cu, Co, Mn and Ni, as well as impurities, such as Fe, Zn, and etc. Therefore, proper treatment of these leaching solutions prior to their discharge is of great importance, so that the contained valuable metals can be recovered.Separation and extraction of metals from leaching solution can use some methods through solvent extraction[l,2], ion exchange[3,4], precipitation with sulfide[ 5] or alkali[ 6] and electrolytic recovery[?]. Among the appropriate treatment alternatives, replacement and differential precipitation is the most attractive treatment that combines simplicity, efficiency and reliability with low capital and maintenance costs."

Jan 1, 2011

By Judy Che, Steven Ceccio, Gretar Tryggvason

"A detailed understanding of drop deformation and solidification is essential for quantitative predictions of geometry and properties of parts made by ballistic particle manufacturing processes. Axisymmetric results of towers built by the deposition of multiple drops are presented. In these computations, fluid flow, heat transfer, and phase change are fully coupled throughout the drop deformation and solidification process. The solution method is based on a single set of conservation equations written for all phases simultaneously. The phase boundaries are treated as imbedded interfaces by adding the appropriate source terms to the conservation equations. A parameter study demonstrates the effect of Weber number, Peclet number, and drop deposition frequency on the final shape of the structure. Numerical results show that most successful method of building uniform towers is when two conditions are met. First, each drop solidifies at the same time in the deformation cycle. Second, the cooling rate is slow enough to allow for good adhesion between drops. The ability to predict the final shape of deposited drops will greatly reduce the amount of experimentation necessary to select the desired set parameters for any artifact.IntroductionMaterial deposition techniques based on layering small molten metal drops holds the promise to build small, coherent three-dimensional structures. In this process, numerous 20-100 µm diameter drops are deposited onto a substrate with a low impact velocity (on the order of 5 mis). Both the momentum and trajectory of each drop are controlled precisely to build up complex parts. This material layering technique differs from processes such as spray forming and splat quenching which involve high impact velocities (on the order of 100 mis) and high frequency deposition with little control over individual drop placement. This process of layering small drops can produce parts with near net shape accuracy, while spray forming produces slabs of material which must then be worked to make a usable part. The ability to computationally predict final drop shape and cooling rate has the advantage of allowing the user to select parameters to produce parts with desired shape and mechanical properties. However, the development of such predictive methods requires a thorough understanding of both drop deformation and solidification"

Jan 1, 1999

By Huanyu Zhang, Zhancheng Guo, Liqiang Fan, Huiqing Tang

"In this study, a simple process has been developed for zinc oxide recovery from RHF (rotary hearth furnace) secondary dust. The results have shown that a high dissolution efficiency of soluble zinc was achieved with water leach at ambient temperature with a liquid/solid ratio of 10/1 in 30min while 20% of the dust was left as solid residue. The rate of dissolution increased slowly after the dissolution efficiency reached 90%. The leaching process was found to be controlled by external diffusion. After separation, zinc was precipitated in leached liquor by introducing a precipitation agent of potassium hydroxide. The resulting solid was purified and dried at 393K. Zinc powder in the form of ZnO with purity of 98.5 mass% was obtained with an average size of 12.4µm.IntroductionThe RHF (rotary hearth furnace) direct reduction process is widely used in many iron and steel enterprises to deal with various metallurgical dusts [l]. The basic principle of this process is that first various metallurgical dusts (BF dust, EAF dust and so on) are pelletized with a coal reductant, and they are then subjected to a fast reduction using RHF after being dried. Highly metallic pellets are produced and at the same time, nonferrous elements such as Zn, Pb, K and Na are evaporated into the RHF flu gas as secondary dust. Zinc is listed by the Enviromnental Protection Agency as one of the 129 priority pollutants. Therefore, recovering zinc from the industrial wastes is important in terms of enviromnental protection [2-3]. On the other hand, nowadays China is in shortage of zinc resource and the annual output from metal recycle only accounts for some 13% of the total zinc resource. There are many ways proposed to recover zinc from various wastes [ 4-7]. The aim of this paper is to recover zinc oxide from RHF secondary dust by a method with water leach followed by caustic precipitation. This work investigated the influence of the leaching temperature and leaching liquid/solid ratio on the zinc recovery efficiency. The process consisted of three stages: (1) leaching with water; (2) liquor/residue separation; and (3) zinc precipitation in caustic milieu."

Jan 1, 2014

By Blas Melissari, Stavros A. Argyropoulos

"In this paper a computational approach was employed to estimate the melting of solid spheres immersed in different liquid metals and under different convective conditions. The spheres are made from the same material as the liquid metal. The SIMPLER algorithm was implemented using a three-dimensional system in Cartesian co-ordinates. Experimental validation of the dimensionless correlation was carried out in two fluids with vastly different Prandtl numbers. The dimensionless heat transfer coefficient (Nusselt number) is obtained as a function. of the Reynolds and Prandtl number.IntroductionThere is a paucity of dimensionless convective heat transfer correlations applicable to fluids like liquid metals. The existing correlations cover single Prandtl number metals [l] or at most two different Prandtl number metals [2]. A knowledge of heat transfer rates from particles at high flux levels has become increasingly important to the design of energy transfer systems. Melting of solid particles has been studied extensively as it relates to many engineering and environmental applications, such as materials processing, space applications, water resource and energy conversion. When objects are immersed in a fluid with a temperature higher than their melting point, they melt and produce molten material that then mixes with the surrounding fluid. These objects experience not only size variation but also changes in their shape. This observation is more pronounced when the melting occurs in a forced convective flow.Yuge performed pioneering experimental work on the heat transfer from a sphere to air under mixed convection [3]. He suggested procedures for predicting the Nusselt number. Hieber et al [4] studied the spherical system analytically, but their study was limited to flow with small Reynolds numbers. Many researchers studied the melting dynamics of ice spheres in water at different convective regimes. Aziz et al [5] and Hao et al [6] performed measurements of the heat transfer coefficient in the water system by measuring the melting time of ice spheres in forced convection. Hao et al [7] performed visualization studies of ice spheres melting in water under mixed convection regime. All of this groundbreaking work, however, did not involve the use of liquid metals"

Jan 1, 2004

By E. O. Stensholt

The Hybinette electrorefining process for production of cathode nickel was in use at Falconbridge Nikkelverk A/S, Norway, until 1975 when conversion to the new chlorine leach process was started. In 1978 the conversion to electrowinning had been completed, but further major improvements to the process have been made up to 1987. After a major expansion program in 1985 - 87 the refinery has a nickel capacity of 54 000 mt Ni/year. The main feed materials to the process are converter matte from the Falconbridge smelter in Sudbury, Ontario, Canada, and from the BCL smelter in Selebi-Phikwe, Botswana. A typical composition of the mixed feed to the refinery is: 40 - 45% Ni, 25 - 30% Cu, 20 - 22% S, 2 - 3% Fe and 1.0 - 1.5% Co. The matte is chlorine-leached in the first process step, nickel being dissolved selectively in a train of leach-cementation tanks. Essentially all copper and sulphur that was present in matte appears in the leach residue as CuS. In 1986 an autoclave treatment stage was added to the process to improve nickel extraction from the leach residue. The resulting strong nickel chloride solution is purified by the process steps (1) precipitation of iron and arsenic, (2) solvent extraction of cobalt and other minor elements and (3) precipitation of lead and the remaining impurities. The nickel solution is then fed to the tankhouse, where various nickel products are produced by electrowinning. The chlorine gas that is produced during the electrolysis is returned directly to the chlorine leaching tanks to dissolve more matte. After stripping from the loaded organic phase and solution purification cobalt is also produced by electrowinning. The copper sulphide leach residue, which contains some nickel, is dead- roasted in fluidized-bed roasters. The sulphur is recovered and sold as sulphuric acid. The calcine is leached in spent copper electrolyte, from which cathode copper is produced by electrowinning. Precious metals and the remaining base metals are recovered from the copper leach residue. The Falconbridge chlorine process is very versatile. It can accept a wide range of impurities in the feed and still produce metals of exceptional purity.

Jan 1, 1988

By V. B. Telles, D. C. R. Espinosa, J. A. S. Tenório

"The purpose of this work was to study the reutilization of the steelmaking dust, derived from steel production in the electric arc furnace (EAF), in iron ore sintering process aiming zinc elimination. In each sintering process were collected sintered samples, these materials were analyzed by chemical analysis using atomic absorption spectrophotometry in order to determine the zinc content. Samples of not sintered mixtures were also characterized by chemical analysis aiming to determine the initial amounts of zinc, i.e. in order to check the zinc amounts present in the mixture before the sintering process. The comparation among the zinc contents of samples sintered and not sintered allowed to determine the elimination of zinc during the experiments. Results showed that the zinc elimination in the process is proportional to the ratio reducer/waste. The zinc removal was lower when the reducer/waste ratio was decreased.IntroductionThe electric arc furnace dust (EAFD) is a residue generated in the steelmaking process using electric arc furnace. Aproximately 30% of all steel produced (in the year 2009) was obtained through electric arc furance (EAF). In the United States of America the percentage of this process in the total crude steel production was about 62% in 2009, while in 2000 this percentage was only 47% [1].The iron ore sintering is a process that reuses wastes generated in metallurgical industries. However, the materials used must be physical and chemical characteristics compatible with the blast furnaces.The quantity of zinc, cadmium, chrome and other metals present in the EAFD depends on the quality of the scrap used to feed the EAF and the type of steel that it is been made [2,3]. The reuse of EAFD waste is interesting to steelmaking processes because of its iron content. However the presence of zinc inside a blast furnace is undesirable since the zinc oxide can be deposited on the blast furnace walls and in the drivers of gas output, interrupting the flow. Another part of the zinc oxide can form deposits on the refractory lining of the blast furnace [4,5]."

Jan 1, 2012

By Miaoyong Zhu, Sen Luo

"A two-dimensional CAFD model was developed for simulating the solute diffusion-controlled dentritic growth in the low Peclet number regime. Mass conservation and local equilibrium at the solid/liquid interface were solved to determine the growth velocity of interface with consideration of constitutional and curvature undercooling. The modified decentered square growth proposed by Wang et al was adopted to capture the first eight neighboring cells. The comparison between the classic Lipton-Glicksman-Kurz (LGK) analytical model for steady state tip variables and the simulated values showed that the present model was capable of quantitatively determining the dendritic growth, and the simulation tests demonstrated that the effects of the mesh anisotropy in growth kinetics and crystallographic orientation were eliminated. The numerical simulations were performed to the dendritic growth ofFe-0.6%C binary alloy in undercooled melt, and the results showed that the present model could predict the dendrite morphology with artificial growth orientation in acceptable level.IntroductionDuring the solidification of metals and alloys, the dendrite grows from the substance or the undercooling melt and solute redistributes between the dendrite and the interdendritic liquid. The solidification microstructure is close related to the phase and solute evenness and has a close linkage with the properties of final production.In the past few decades, various kinds of deterministic and stochastic models have been developed to predict the evolution of microstructures in solidification, with the fast development of computer power. Among these methods, Phase Field (PF) model [1, 2] has been known as one of the most adequate deterministic models for directly simulating the dendritic growth. However, there is a vital drawback that the PF method requires considerable computation time and is limited to simulate very small domains with a few dendrites [3]. On the other hand, stochastic models, such as Monte Carlo (MC) method [4, 5] and Cellular Automaton (CA) method [6-8], have been usually applied to predict the solidification microstructure evolution. Comparing with the MC method, the dendritic growth kinetics is explicitly integrated in the CA model, while the MC model doesn't. Therefore, the CA method is more reasonable to predict the dendritic growth during the solidification of melt."

Jan 1, 2013

By B. Q. Li, S. P. Song

"Numerical models are developed to represent complex electromagnetic, free surface deformation and fluid flow phenomena in floating zone refining processes with radio frequency inductive heating. The computational methodology is based on the coupled finite/boundary element method for the electromagnetic field distribution and the Galerkin finite element method for magnetically driven fluid flow and free surface profiles of the molten zone. With the models, the complex transport and free surface phenomena in a floating zone system can be studied as a function of various operating conditions including applied current, frequency, inductor position and shape, surface tension, floating zone diameter and height. Results show that the equilibrium shape is sensitive to the height of the molten zone and that the free surface shapes can have a significant effect on the melt flow in the molten zone. Our extensive simulations also suggest that to ensure accurate results, the same mesh should be used, whenever possible, for both the electromagnetic forces and fluid flow calculations.1. IntroductionThe floating zone processes have been widely used in the materials industry to grow ultra-pure rare earth metal or semiconductor single crystals for sensor or electronic applications that have a tough demand on purity. Developed based on the principle of magnetic melting/levitation, the processes possess a main advantage that the molten zone is supported in air by the electromagnetic forces generated by the coil (see Figure 1), and therefore is free from contamination from a container. Consequently, the final products made from the floating zone processes have higher inherent purity than those by other techniques [1-4].Complex physical phenomena occur in the floating zone processing of materials. These include free surface deformation, magnetically-driven melt flow, which may be turbulent or mildly turbulent [5] depending on the applied conditions, and solidification. Thermal stresses also develop in the single crystals, which are affected by the flow and temperature field and which can have direct implications to qualities of single crystals [6]. An understanding of the fundamentals governing these physical phenomena can be of critical value in elucidating the physics that controls the properties of the metal or semiconductor crystals being produced, thereby providing a rational basis for process improvement and quality control."

Jan 1, 1997

By David E. Hardt

"One of the critical variables to be controlled during arc welding is the size or geometry of the weld pool. The measurement of pool geometry has become an increasingly important problem with the advance of welding automation and control, and this paper addresses that problem. The basic concept of pool size estimation via measurement of pool dynamics is presented. The theory underlying this concept is discussed and is followed by a review of the current work in this area. It is concluded that pool dynamics can be characterized by natural frequencies of oscillation, for stationary welds, and that these can be measured by appropriate signal processing performed on the arc voltage. However, it appears that only full penetration welds show a strong correlation between weld size and natural frequency. Also, the extension of these results to the realistic case of moving welds has yet to be considered in detail. Nonetheless, this method of in-process measurement for real-time weld process control is still quite attractive where applicable since it can be accomplished simply by modifying the arc current schedule and by signal processing of the arc voltage.INTRODUCTUIONThe study of welding process control has been dominated by research into methods of in processing sensing of the weld pool geometry. While it has been shown feasible to measure the topside pool geometry using video methods [1,2], the penetration or backside bead width have remained elusive quantities. This is particularly true if a topside sensor location is required.The concept of using weld pool motion as a pool geometry sensing method was proposed by Hardt et al. [3] and later demonstrated by Hardt and Zacksenhouse [5] and Richardson and Renwick [6]. The concept is based on the fluid dynamics of a pool constrained by a solid container and by significant surface tension forces (i.e. a small shallow pool, not a ""pond"" or ""lake""). Such a pool, if subjected to external forces, will exhibit a surface motion is a function of that force, the properties of the fluid, the surface tension, and the shape of the container. Thus, if this motion can be excited and measured, and the relationship to the pool geometry determined, a means of sensing pool shape will exist."

Jan 1, 1986

By B. W. Lightfoot, Neill F. Arthur

"The AusIron process is a new development of the well established Ausmelt bath smelting technology(l). The development of this technology has been tied to the South Australian Steel and Energy (SASE) project which brings dedicated coal and iron resources together with this new technology. SASE is a joint venture between Ausmelt (40%), Meekathara Minerals (40%) and the South Australian Government through Mines and Energy South Australia (MESA) (20%). It will use a multiple lance furnace to process iron ore using steaming coal for both fuel and reductant.It is intended to build the simplest plant economically possible. Refinements such as preheating and prereduction of the ore are compatible with the technology but are not expected to be necessary in the first generation plant.The joint venture is negotiating with suitable partners for funding of the project through to commercial implementation at a target scale of2.5 mt/a of pig iron.ObjectivesAusIron aims to produce pig iron directly from steaming coal and from any of a variety of iron sources in a simple furnace system with a minimum of pre-processing of either coal or iron ore. Preheating and prereduction of ore are compatible with the technology but may not be necessary. The immediate aim is not to be the technology that uses the least quantity of coal to produce iron metal but rather the technology that uses the least number of dollars to produce metal.The chemistry of iron making is well known, probably better known than that of smelting of any other metal. Iron has been made for thousands of years and it is possible to make iron from charcoal and ore in a simple blast furnace the size of a beer barrel. The focus is therefore not making iron but rather making it more cheaply than it is made by current technologies. Large blast furnaces now set the standard and new technologies must perform better if they are to gain market share. It is still the cost of iron, energy units and capital going into these mega blast furnaces which ultimately set the market price for pig iron."

Jan 1, 1996