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By Gui-fang ZHANG, Zhe SHI, Lei GAO

Secondary V-recycling slag, an industrial waste containing high gallium is being dumped continuously, which causes the loss of gallium. Thus, the alkali fusion process was employed to recover gallium from this slag. The effects factors on extraction of gallium such as roasting temperature, roasting time, alkali fusion agent concentration and CaO concentration were investigated in the paper. The experimental results indicated that excessive roasting temperature and roasting time is unfavorable to the recovery rate of gallium. The appropriate roasting temperature and duration are 1000 and 2 hours, respectively; The appropriate proportioning of Na2CO3: NaOH is 2:1 when the concentration of alkali fusion agent weighs 0.4 times the mass of the slag; In order to remove SiO2 from the leaching liquor, CaO should be used as an additive in the roasting process. The appropriate concentration of CaO should weigh 0.2 times the mass of the slag. Employing these optimal alkali fusion conditions in the roasting process, gallium recovery is above 90%

Jan 1, 2015

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 Matthew John M. Krane

"The macrosegregation patterns and convective behavior of a Pb-5wt%Sb-35wt%Sn alloy are studied using new numerical treatments of solid particle motion and of transport phenomena occurring during the solidification of ternary metal systems. At this composition, the solidification which occurs while the local liquid composition is in the (Pb)-(SbSn) binary eutectic trough has a significant effect on these phenomena. The effects of this solidification path on fluid flow and macrosegregation are compared to the more familiar binary alloy patterns and the effect of solid particle transport is evaluated. The final predictions of macrosegregation are compared to measured composition profiles. IntroductionThe macroscopic maldistribution of alloy constituents during solidification, commonly called macrosegregation, is a defect which occurs in real metal processing systems. This nonuniformity of species distribution, especially when it forms a high composition gradient or a poor distribution of secondary phases, can lead to areas of high stress concentration, which contribute to cracking during extrusion or forging of wrought alloys or when an as-cast piece is severely loaded in service [1, 2]. Macrosegregation studies in binary systems have become quite common since the introduction of single-domain numerical models which feature one set of conservation equations and boundary conditions for an entire, fixed computational domain containing solid, liquid and multiphase regions. A complete review up to 1995 has been presented by Prescott and Incropera [3]. However, most commercial alloys generally have more than two species in amounts significant enough to affect the convective flows which lead to macrosegregation and other defects. The formation of secondary solid phases, including eutectic and peritectic reactions, also may occur in commercial metal alloys and should be treated using appropriate thermodynamic models."

Jan 1, 1999

By T. Ueno

Naoshima Smelter & Refinery of Mitsubishi Materials Crop. commissioned a new Mitsubishi continuous copper smelter in May 1991. Process offgas volume of the conventional reverberatory furnace line, one of the previous smelters having been shut down, was very large and thus two acid plants had been operated. It was expected that the offgas volume would, be reduced at the new smelter to about a half of the sum of those from previous two smelters and the sulfur dioxide strength would be increased. So various alternatives were studied to minimize the operation cost. And it was decided to utilize both of the plants with minor modifications by diluting the gas either with air or with dilute gases. The acid plants now receive off gases from the new copper smelter, a sintering machine of a lead smelter and a decomposer of waste acid. The paper discusses plant design, operation, improvements and modifications realized in relation with the retrofitting of the copper smelter.

Jan 1, 1992

By F. R. A. Jorgenson

The ignition of chalcopyrite and pyrite was studied using laminar flow furnace and thermal analysis techniques which were supported by XRD and optical microscopic examination of the products. In air, chalcopyrite and pyrite ignited at temperatures of 400-500'C and 500-600?C respectively. The phase assemblages predicted from thermodynamic analyses were compared with those found by experiment, and the onset of ignition was correlated against changes in the phase compositions. Pyrite and chalcopyrite ignited when pyrrhotite and intermediate solid solution formed thus opening up the structure and allowing ready access of oxygen.

Jan 1, 1989

By Kuniaki Murase

Cadmium telluride (CdTe) semiconductor has been well investigated as a CdS/CdTe heterojunction solar cell material since its band gap is suitable for energy conversion from sunlight into electricity. In this paper a new electrochemical processing of thin-layered CdTe using basic aqueous electrolytes is reviewed from the standpoint of thermodynamics using a potential-pH diagram. The cathodic electrodeposition of the stoichiometric CdTe with a flat surface morphology took place at more positive potentials than that of the Nernst potential for the bulk-Cd deposition and at more negative potentials than that for the hulk-To. In this potential region deviation from the stoichiometric composition of eleetrodeposited CdTe was controllable by the Cd(II)/Te(IV) concentration ratio, pH, or concentration of complexing agent for Cd2+ ions of the electrolytes, The deposition behaviors for ammoniacal media were well accounted for by the potential-pH diagram of the Cd-Te-NH3-H2O system devised by a combination of those of the Cd-NH3-H20 and the Te-H2O systems, Diagrams for other complexing agents, ethylenediamine and diethylenetriamine, were also constructed to investigate and discuss the electrodeposition conditions regarding the corresponding media.

Jan 1, 2003

By Yuanbo Zhang, Zhixiong You, Guanghui Li, Peidan Wen, Tao Jiang

Sn-bearing iron ore containing small amount of Zn, Pb and As is one of the typical complex polymetallic ores in China. This kind of ore is not extensively utilized due to the complicated relationships between iron and other associated nonferrous metal minerals. Excessive contents of these elements would adversely affect the metallurgical operation as well as the quality of steel products. In this study, reduction behavior of Sn was detailedly investigated using H2 or mixed H2/CO as reductant. The results revealed Sn volatilization was improved in the presence of H2 than individual CO/CO2 atmosphere. Simultaneous volatilization of these elements was realized by roasting under weak H2/CO reducing potential, and metallization reduction was advantageous for further Zn volitilization. A metallic pellet (DRI) with Fe metallization greater than 90%, residual Sn, Zn, Pb and As content of 0.054%, 0.012%, 0.0045% and 0.09% was prepared via a simulated reducing gas of coal gasification.

Jan 1, 2015

By D. E. Woolley

The rate of reduction of iron oxide from calcia-silica-alumina slag by carbon in liquid iron has been measured over the temperature range 1400-1600°C by monitoring the rate of carbon monoxide (CO) evolution. Slags containing ferric iron have been used in order to study the reduction of both ferric and ferrous cations. Results show that ferric iron is reduced before ferrous iron, so that the ferrous iron concentration increases initially. It is also shown that the rate constant, k, decreases at low reaction rates, or, equivalently, at low concentrations. The authors conclude that the reaction occurs in two periods. During the first period, ferric iron is reduced to ferrous iron. During the second period, ferrous iron is reduced to metallic iron, and the rate-limiting step during the second period is the mass transfer of ferrous cations in the slag phase to the slag-metal interface.

Jan 1, 1998

By F. J. J. van Loo, A. A. Kodentsov, J. A. van Beek, M. R. Rijnders

"A periodic layered morphology of the reaction zone has been observed in several annealed solid/solid diffusion couples, including metal/metal and metal/ceramic couples. This morphology is characterized by a regular array of alternating layers, which are either single-phase layers or bands of particles embedded in an intermetallic matrix phase. A description of several systems showing periodic layer formation is given. It is shown that the periodic layered structure with the single phase layers and the one with the bands of particles have a different mechanism of formation.IntroductionSolid state reactions in ternary systems can produce a variety of reaction zone morphologies if there are two or more reaction products. Three types of morphology have been described in detail: 1) simple layered; 2) isolated precipitates in a singlephase layer; 3) interpenetrating columnar (lamellar) or interwoven structure. Understanding the factors that govern the formation of different morphologies is of importance in many fields of engineering. For solid state displacement reactions the conditions governing the formation of these morphologies are well understood [1-4]. For example, the development of a layered or aggregate reaction zone depends on the relative diffusivities of the components through the reaction products.This paper is concerned with the periodic layered morphology which has been observed in various solid state systems. We consider this to be a fourth type of reaction layer morphology. Two manifestations of periodic layered morphology may be distinguished. One form consists of regularly spaced layers of particles of one reaction product embedded in a matrix phase (another reaction product). The other form consists of single-phase layers embedded in a matrix phase. It will be shown that each manifestation has its own mechanism of formation. In section A we consider a system (Ag/Ti-foil/Si) in which periodic layer formation will be explained as a special case of the Liesegang phenomenon. In section B we consider systems where the periodic layered structure has a different origin."

Jan 1, 1996

By Jean P. Murray

The extractive metallurgical industry is a major consumer of high-temperature process heat. It is, consequently, a major contributor of C02 emissions and other greenhouse gases derived from the combustion of fossil fuels for heat and electricity generation, or from the process itself. These emissions can be substantially reduced by replacing fossil fuels with solar energy as the source of process heat. Concentrated solar radiation can supply a large amount of thermal energy to endothermic reactions at temperatures exceeding 2000 K. Another potential for C02 emission reduction exists as well. Thermodynamically, the total amount of energy required for metal production at any given temperature is the enthalpy change of the reaction, AH. Of this total, an amount equal to the Gibbs free energy AG must be supplied as high quality energy in the form of electrical work or by using a reducing agent. Many conventional metallurgical electrolytic processes and reducing furnaces are unable to add only the thermodynamically required electricaVchemical energy due to process inefficiencies. Electrical work in excess of AG for the reaction may be used to supply process heat, or excess chemical reducing agent burned to supply process heat. Besides the thermodynamic and economic drawback, this inefficiency results in excess C02 emissions derived from the combustion of fossil fuels. With these practices, energy becomes an important cost element of the metal produced. Highly-concentrated solar energy has the demonstrated potential to separate these two forms of process energies, allowing the addition of only the thermodynamically required high-quality energy while high-temperature solar process heat is provided to the reactor. Examples of metal oxide reduction processes that have been studied experimentally in solar furnaces include the production of Fe, Al, AI/Si alloy, Mg, Zn, Tic, Sic, CaC2, TIN, Si3N4, and AIN by carbothermic reduction of their oxides, and the high-temperature solar- electrothermal reduction of ZnO.

Jan 1, 1999

By Boyd Davis, Vladimiros Papangelakis, Joshua LaMarre, Jan de Bakker

"HCl leaching using molten salt hydrates has the potential to improve the extraction of nickel from laterite ores. However, as in other HCl leaching applications, recovery of HCl is key to process economics. Spray pyrohydrolysis, which is used in current chloride-based flowsheets, is associated with a high energy cost. The authors have developed a proposed laterite leach circuit using an alternative HCl recovery route. The leach circuit envisions a leach by concentrated (33%) HCl in an MgCl2 molten salt hydrate (MSH) or brine medium, followed by Ni/Co recovery and iron precipitation. Magnesium and chloride are precipitated from solution as magnesium hydroxychloride; this hydroxychloride is thermally decomposed to produce HCl gas. The proposed flowsheet employs a chloride leach circuit with simpler equipment and lower energy cost than in the conventional practice of pyrohydrolysis. Laboratory work investigated key aspects of the flowsheet, including precipitation of magnesium hydroxychlorides and their composition; magnesium hydroxychloride thermal decomposition; and iron control.Introduction As sulphide nickel ores become harder to mine and more complex to process, laterite ores will increase in importance. Laterite ore deposits can be divided into two main mineralogies. Limonite ores consist mostly of hydrated iron oxide, FeOOH, with 1-3% nickel substituting for the iron. Saprolite ores consist of iron-magnesium silicates, (Fe, Mg)2Si04, again with some nickel substituting for the metal ions. Limonite ores can be treated using the HP AL (High Pressure Acid Leach) process, in which the ore is reacted with sulphuric acid at high temperature in an autoclave. HP AL, however, cannot in general be used to treat saprolite ores because the magnesium enters solution and consumes sulphuric acid, which results in excessive spending on lixiviant. It is therefore desirable to find a hydrometallurgical process specifically for saprolite ores that can provide better results than the treatment options currently available."

Jan 1, 2011

By Fuming Wang, Xin Lu, Hao Bai, Hebin Zhu

"In this study, CO2 emissions and carbon footprint of a typical steel works with integrated process and iron and steel industry in China was calculated and analyzed by a carbon footprint method based on the model of process CO2 emissions in iron and steel making. The carbon footprint of iron and steel industry from 1991 to 2010 in China showed a rapid increasing tendency. In 2008, the CO2 emissions of iron and steel industry in China was 1.289 billion tons, 19.71% of the national total CO2 emissions, and the corresponding carbon footprint was 159.13 million hm2 of green area. Carbon deficit of iron and steel industry also go up gradually if considering the carbon storage by green vegetation. Thus, the internal carbon reduction strategy, such as energy structure optimization and energy saving technology, was mainly encouraged for the sustainable development of iron and steel industry in China.IntroductionThe Global Warming resulting from the increase of Greenhouse Gases (GHGs), in particularly CO2, in the atmosphere has become the main reason of global climate change, and large emission reductions are required for sustainable development [ 1]. The iron and steel industry is the largest energy consuming manufacturing [2] in the world and the largest emitter of CO2 emissions. In 2005, it accounted for about 20% of global industrial energy use and 30% of energy and process CO2 emissions from industry [3]. In China, the crude steel has firmly been ranking at first of the world recent years and kept growing tendency year by year. With the production growth, the CO2 emissions of iron and steel industry also increased significantly and hence the steel industry has become one of the most sources of CO2 emission in China [4], which has attracted more and more attention to seek the carbon reduction strategies.Carbon footprint is an important and useful concept originating from Ecological Footprint, which was used efficiently to quantitatively analyze the impact of the human activities on ecological system, in particularly impact of the human energy activities [5]. In the view of Life Cycle, the carbon footprint is efficient to analyze the direct and indirect CO2 emission in the whole life of various products used in human activities. As to the iron and steel, the important materials and products in the human life, the carbon footprint analysis is quite necessary to evaluate the CO2 emission impact on the corresponding ecological system and global environmental."

Jan 1, 2013

By C. Beckennann, C. Y. Wang

"Computer simulations of structural and compositional development in equiaxed dendritic alloy solidification are performed using a recently developed multi phase model. The model not only accounts for the transport phenomena occurring on the macroscopic (system) scale, but includes also the grain nucleation and growth mechanisms taking place at various microscopic length scales. In this paper, a numerical technique consisting of a fully implicit control-volume based finite difference method and a multiple time step scheme is developed for accurate and efficient simulations of both micro- and macro-phenomena. Sample numerical results are presented to reveal the effects of liquid now and crystal sedimentation on segregation and the final grain size distribution. In particular, the importance of the interplay between the dendrite microstructure and multiphase now patterns is shown.IntroductionIn recent years, modeling of equiaxed dendritic solidification without convection has experienced considerable progress (1,2]. Nucleation and growth kinetic laws have been coupled with transient heat conduction calculations to determine the solidification microstructure. However, modeling of equiaxed dendritic solidification with melt convection and solid movement has not been attempted so far, largely because of the complications associated with the transport of free equiaxed crystals in the melt. The gravity-induced transport of free crystals is fundamental to the development and extent of the equiaxed zone and also greatly affects the columnar to equiaxed transition. Another possible effect of crystal sedimentation or floatation is to cause severe macrosegregation as well as structural inhomogeneities. The only study available in the literature that accounts for both liquid convection and solid transport is by Ni and Beckermann (3], but deals with globulitic structures (as opposed to dendritic)"

Jan 1, 1994

By Shenghui Guo, Ying Lei, Hao Niu, Huilong Luo, Jinhui Peng, Libo Zhang, Yu Li

"In this work, the combination of microwave drying (MWD) and heat pump drying (HPD) drying experiments were designed by response surface methodology (RSM) based on central composite design (CCD) using design expert software (Version 7.15), and the process parameters were optimized. The conditions given by software are: the MWD time is 4.6 or 4.4 min; the HPD time is 9.0 or 8.6 min; and the sample mass is 620 or 600 g. Under those conditions the moisture content is 1.0 10-2kg water/kg wet basis, and the effectiveness ratio is 0.70 kg water/kwh. The results of confirmatory experiments conducted under the optimized conditions show the combined drying have superiority of decrease of energy consumption and increase of handling capacity over the single MWD or HPD.1 IntroductionSilica sand is one of a silicate mineral with properties as hard, anti-friction and less reactive, commonly used as raw material for foundry and construction. The silica sand obtained from mineral dressing processes such as scrubbing, magnetic separation and flotation. Its moisture content is approximately 0.08~0.12 kg water/kg wet basis. The most common methods used for drying are solar drying and hot air drying. But these methods have some shortcomings: for example, the solar drying has longer process time due to low energy yield, [1] hot air drying has low-energy efficiency and a lengthy drying time. [2]Microwave is electromagnetic waves with frequency are 300MHz to 300GHz. The outstanding features of microwave heating are rapidity and selectivity. The water specific inductive capacity of 60~78 is much bigger than common materials, the moisture always quickly absorb electromagnetic wave and rapidly transfer to vapors. So, it can significant reduce the drying time. [3] Heat pumps (HPs) are devices for raising the temperature of low grade heat energy to a more useful level using a relatively small amount of high grade energy."

Jan 1, 2011

By Yunhua Gan, Xiaowen Chen, Meilong Hu, Haige Li, Yang Tong

Ethanol is a kind of renewable fuel, which can be produced from biomass and applied in many energy areas, such as motorcar. The combustion of ethanol in meso-scale is facing great challenges, such as great heat loss, poor stability, and low combustion efficiency. Electro-spraying technique is an effective method to atomize liquid ethanol due to its great advantage of monodisperse and uniform characteristics. In present study, electro-spraying was applied in liquid meso-scale combustor to produce very small droplet diameter and uniform droplet distribution. Experiments were carried out based on nozzle-ring-mesh electrode structure using pure liquid ethanol as fuel. Electro-spraying characteristics were measured by Phase Doppler Anemometer (PDA) under different nozzle voltages, ring electrode voltages, flow rates, and steel mesh positions. The results may be helpful to the design of new meso-scale electro-spraying combustor using renewable liquid fuel.

Mar 1, 2017

By A. S. Rao

In the original roast-leach-electrowin (RLE) circuit at the Chambishi Cobalt Plant, commissioned in 1978, the separation of nickel and zinc from cobalt in aqueous streams was achieved by successive stages of precipitation using lime. However, this technique was not able to meet the increasingly stringent metal quality requirements of customers whilst maintaining acceptable process recoveries. Intensive process development work was carried out and, in July 1988, an ion exchange circuit for nickel removal was commissioned using DOW XFS 4195 resin and for the first time Z.C.C.M. produced high purity cobalt metal containing less than 0.10% nickel. Following further work, a solvent extraction circuit for zinc removal, using DZEHPA, was commissioned in February 1991 in order to enhance cobalt recovery by reducing co-precipitated cobalt losses. This paper outlines the process development, design, commissioning and subsequent operation of these nickel ion exchange and zinc solvent extraction circuits.

Jan 1, 1993

By Kenneth S. Coley, Michael Pomeroy, Elaine Chen

Recent work on modeling of BOF steelmaking is reviewed, highlighting the critical aspects of each approach. It is concluded that the most successful models should be based on a deep understanding of the mechanisms and kinetics of the critical reactions. The importance of the decarburization mechanism is discussed with particular reference to its role in droplet swelling or bloating which has a profound influence on the droplet residence time in the slag. Conditions which cause bloating are discussed and the rate determining step is proposed to be primarily nucleation of CO bubbles inside the metal droplet with some influence from growth by reaction at the bubble/metal interface. The discrepancy in the super-saturation ratio required for classical nucleation is discussed and an approach using a surface tension modifying parameter is illustrated. Finally, the role of CO nucleation in controlling the driving force for dephosphorization is discussed.

Jan 1, 2014

By Biao Zhou, Qian Li, Kuo-Chih Chou, Yi-Long Liang, Jie-Yu Zhang, Qun Luo

"In this work, the phase transformational behaviors and microstructural characteristics of 60Si2CrVAT spring steel were systematically investigated as a function of applied cooling rates in the range of 0.l-10°C/s. A quenching deformation dilatometer was used to austenize and quench. The dilatometric curves between length changes and temperature of samples suggest three characteristic stages could be identified as different ranges of cooling rates, which meets well with metallographic examination and the measured hardness results. As the cooling rate increases, the structure transformed from pearlite, granular bainite to finally martensite. The F + P and B zones are completely overlapping in continuous cooling transformation (CCI) curve, which indicates that this steel is difficult to become single bainite and shows good hardenability.IntroductionThe 60Si2CrVAT, a high-carbon low ally super-high strength steel developed from the ?OCT 60C2XFA and 60Si2MnA, is often used for coil spring of heavy vehicles and high-speed railway by hot deformation or cold deformation [1-3]. The addition of Si improves relaxation resistance significantly, through the refinement of tempered carbides as the result of the retardation of E -carbide conversion to cementite during tempering. Due to its deleterious effects on decarburization and toughness, the maxinJum content of Si has limited to 1.5 or 2.0% [4-5]. Additionally, V and Cr can improve sag resistance due to the precipitation of fine carbonitrides during hot rolling [6-7]. To best of our knowledge, the strengthening by precipitation of alloy carbides of Cr and V often referred to secondary hardening [8]."

Jan 1, 2013

By Nieves Iglesias

The removal of the refractoriness of a gold bearing pyrite- arsenopyrite ore is studied. Flotation concentrates were prepared and leached with a dilute acidic ferric sulfate solution. The elemental sulfur film which forms on arsenopyrite in the oxidation process is not responsible for the low rate of the arsenic dissolution observed. A positive effect on the leaching rate is observed when Ag' is added. This pretreatment eliminates the refractory nature of concentrates.

Jan 1, 1993

By Ajit Kumar Jaiswal

"Electric Arc Furnace (EAF) being a power-intensive equipment, EAF based industries are highly dependent on scarce electric energy. This is the reason Government of India is highly concerned about this and laid emphasis on the conservation of electric energy.This paper highlights factors contributing to reduction in specific electric energy consumption in EAF and suggests measures not only for power saving, but also for productivity improvement. To name a few, these are proper sealing of furnace, introduction of oxy-fuel burners, foamy slag practice, increased usage of hot metal/DRI, post-combustion of CO gas for preheating of scrap, improved selection & design criteria of electrics, power demand management, and process automation. Few cases also have been cited, where the above measures have helped in reaping significant benefits.IntroductionFor a long time, Government of India had focused on increase in energy supply, in particular, through electricity generation. Now the emphasis of Government of India has shifted from electricity generation to its conservation for following two reasons:??Power plants have become very cost-intensive??By saving energy, more of it can be delivered at lower cost to the consumersPower generating units, transmission & distribution agencies as well as consumers all have roles to play in the area of energy conservation. By energy conservation, we mean curtailing energy requirement by reducing energy wastages and taking up measures to improve energy efficiency of electric equipment/appliances. In almost all cases, this would be economically beneficial.India’s cost-effective energy conservation potential has been estimated by the Planning Commission at 23 per cent of total commercial energy generated ?1?. A national movement for energy conservation can significantly reduce the need for fresh investment in energy supply systems in coming years. It is imperative that we make all-out effort to realize this potential. Whether a household or a factory, a small shop or a large commercial building, a farmer or an office worker, every user can and must make this effort for his own benefit and for the nation’s benefit as well."

Jan 1, 2009