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By Jafar Safarian, Merete Tangstad, Leiv Kolbeinsen

"Silicon and its binary alloys have several applications in metallurgical, chemical, photovoltaic and semiconductor industries. Silicon goes to its liquid state within its production, refining and when it is alloyed with other elements. Therefore, the characterization of silicon melts thermodynamics is important and useful. The liquidus and activities in several silicon binary systems have been recently calculated by the application of two liquidus constants, which were established using the experimentally determined liquidus data. In the present study, the thermodynamic properties of six silicon binary melts, which are simple eutectics, are calculated by analytical approaches. In this case, the changes in the partial and integral Gibbs free energies and enthalpies of mixing are calculated and compared with the experimental data in literature. The enthalpies are calculated by two methods and the calculation results are compared to the data from the literature. It is shown that thermodynamic properties of silicon binary melts can be accurately predicted without the use of complicated thermodynamic software.IntroductionSilicon and its alloys have several industrial applications. Silicon is used for making aluminium-silicon alloys to produce cast parts, mainly for automotive industry. Silicon in the form of ferro-silicon is used to deoxidize and alloy steel and cast iron. The photovoltaic (PV) industry has had a rapid growth in the recent years and silicon is the dominant material used for the fabrication of solar cells. Silicon is primarily produced through carbothermic reduction of quartz in electric arc furnaces and the produced metallurgical grade silicon (MG-Si) contains around 1 wt% impurities. It is further refined to produce solar grade silicon (SoG-Si) with above 99.9999 wt% Si to fulfil the chemical requirement for PV application. Since molten silicon is processed all along the metallurgical route, obtaining fundamental thermodynamics knowledge about silicon melts is valuable for the related industries."

Jan 1, 2012

By W. G. Davenport

Smelting oxidizes Cu-Fe-S concentrate to matte. Converting oxidizes this matte to metallic copper. Smelting and converting are, therefore, part of the same oxidation process. It would seem natural, then, that smelting and converting should be combined to produce metallic copper in one step. This would: (a) maximize S02 capture by restricting S02 emission to a single, continuous source (b) minimize industrial oxygen and fuel requirements (c) minimize cost. This chapter discusses one step, direct-to-copper flash smelting as it is practiced in 2000. It then uses. the matrices of this book to determine: (a) the industrial oxygen and oil requirements of direct-to copper flash smelting (b) the distribution of Cu between metal and slag during direct-to-copper flash smelting. It concludes that direct-to-copper flash smelting: (a) captures?S02 efficiently from its single continuous stream of SO2 off gas (b) minimizes oxygen/oil consumption but: (c) sends -114 of its Cu-in-feed to slag.

Jan 1, 2001

By Simon N. Lekakh, D. G. C. Robertson

A new integrated CFD-combined reactors approach is proposed for the description of processes in metallurgical vessels. CFD simulations were used to obtain the melt flow pattern in the vessels (ladle, tundish, and continuous caster mold). From these simulations, the characteristic curves were derived: (i) the residence time distribution curves (RTD) for flow-through systems (at tundish exit or at dendrite coherency surface in the mold) and (ii) the mixing curves for closed systems (ladle). In the next step, the melt flow was represented in a “combined reactors” system consisting of a combination of unit reactors (Plug Flow, Mixer, and Recirculated Volume). An inverse simulation was used to define the volumes of the reactor units and the melt flow rates between them by fitting to the characteristic curves from both methods (CFD and combined reactors). The suggested approach is demonstrated for multiple designs of Ar-stirred ladles, tundish, and SEN. This methodology can be used to enhance traditional post-processing CFD analysis and also as a tool for on-line process control.

Jan 1, 2014

By C. Damiani

The Chuquicamata smelter, operating since 1952, has gone through several developing stages which have been characterized by the addition of peak technology for copper concentrate smelting (Teniente converter and Outokumpu flash furnace) with an intensive use of technical oxygen, which has permit-ted to partially discontinue the reverberatory furnace utilization. This paper shows the main indicators and operational practices at present, as well as those concerning maintenance aspects. Finally, the most relevant topics related to the future development of the smelter are mentioned with special remarks on the Decontamination Plan, which allows US to keep the high level of production, reducing the emission of contaminants according to the legal requirements in force.

Jan 1, 1993

By Yuanbo Zhang, Zhaokun Tang, Mingjun Rao, Guanghui Li

The ballability of hematite ore with addition of a certain amount of pulverized anthracite and the induration features of anthracite–containing hematite pellets were studied. The results indicate that adding a certain proportion of anthracite can improve the quality of green pellets as well as the roasting performance of roasted pellets. The suitable mass dosage of anthracite is 1.0%–1.5%. Under the conditions of roasting temperature 1280 oC–1350 oC and roasting time 15 min–20 min, the compressive strength of roasted pellets is found to be more than 2500 N/P. Compared with hematite pellets in the absence of anthracite, the proper induration temperature is diminished by 20 oC, whereas optimal induration temperature range expands by 50 oC, and induration time is shortened by 5 min–10 min. Adding anthracite is an effective measure to improve the pelletization of hematite.

Jan 1, 2015

By Hee Dong Jang

Crystalline metal oxide nanoparticles such as lithium cobalt oxide (LiCoO2) and indium tin oxide (ITO) were synthesized from sprayed droplets of aqueous precursor solution by flame spray pyrolysis. Complete thermal decomposition of the aerosol precursors was obtained at high flame temperature. Molar concentrations of the precursor solution, and the flow rate of combustion gas such as hydrogen, oxygen and air were varied to control particle size, size distribution and crystal structure. The crystalline nanoparticles synthesized were nearly spherical, and their average primary particle diameters ranged from 11 to 35 nm for LiCoO2 and from 8 to 15 nm for ITO.

Jan 1, 2006

By James A. Sommers

Hydrolysis of NbC15 is used to recover oxide values for ceramic and metals production. Reaction of NbC15 with water is rapid, exothermic and vigorous, yielding a gelatinous slurry. In contrast, dissolution of NbC15 in 12 N HCl is endothermic, resulting in a clear yellow solution. Such solutions can be de-hydrochlorinated by controlled contact with air, to precipitate a tantalum¬rich solids, depleting the liquid of its tantalum content. In this way, cheap, useful Nb-Ta partial separation is achieved. The separation is based upon differential oxide-chloride stability. Nb2O5 with <200 ppm Ta/Nb has obtained from starting levels of 2000 ppm. Observations are made on the different types of hydrolysis.

Jan 1, 1992

By V. Ramachandran

Under the Resource Conservation and Recovery ACT (RCRA), generators of listed or characteristic hazardous wastes must find satisfactory means for disposal. of wastes. Initially, for many this meant landfills and deep-well injection. Until recently, mining and metallurgical by-products have largely been exempt from RCRA, but now are coming under its jurisdiction. With the increasing closures of landfills, companies in the U.S. such as electroplaters, miners, metallurgical plants and others are turning to recycling as an alternative to treat their wastes. While the cost of recycling has been challenging, the long-term economics prove attractive because recycling interrupts the cradle- to-grave responsibility for the waste generator. The present paper describes the recycling of hazardous wastes at ENCYCLE/TEXAS. Encycle extracts marketable metals from metal-bearing sludges and wastewater using hydrometallurgical processes borrowed from the mining and metallurgical industry.

Jan 1, 1994

By V. I. Lakshmanan

"Historically flowsheets are developed for efficient separation of metals for economic recovery. With increasing emphasis on reduction, reuse and recycle (3Rs) efficient methods are sought to recover values from a variety of feeds where cost of collection, transportation, local consumer behaviour and regulatory guidelines dictate the development of economically viable flowsheets. Innovative understanding of potential market applications can provide means to develop value added end products. The paper with examples will discuss the use of innovative-separation technologies to obtain value added end use materials from secondary sources.IntroductionFlowsheets are developed for the efficient separation of materials of value for economic recovery. However with increasing societal pressures and regulatory initiatives for stricter environmental guidelines, there is strong need to provide focus to recover materials efficiently and economically in an environmentally accepted manner. North American industries are increasingly caught between demands for high technology value added products and responsibility for environment. An aspect that is receiving increasing attention is Design for Environment'. This incorporates a system wide approach for product design and incorporates environmentally preferable features such as recyclability, disassembly, maintainability, reusability and use of safe materials as part of a product's design objectives.The present paper with case histories will address innovative flowsheet development to convert wastes into recyclables value added products or for minimising generation of waste materials. Case HistoriesProcess for Separating Fibres from Composite Materials 1In the automotive industry, sheet molded compound (SMC) is used to produce panels, bumpers and the like. During the manufacture and at the end of life, considerable waste materials are generated which are potentially recyclable. Fibre reinforced plastics where fibre substrate impregnated with thermosetting resin, find applications in several manufacturing processes and are potentially recyclable at the end of life."

Jan 1, 1996

By Lichao Ding, Jingbiao Fan, Yunnen Chen

"With the development of industrial production, more and more wastewater containing high concentration ammonia nitrogen was discharge into the environmemt, which caused serious harm to the environmemt. Treating the wastewater has great significance to protect water resources. Using air-stripping combined with oxidation to uptake high concentration of ammonia nitrogen wastewater. The influence of operating parameters was investigated. Experimental results revealed that pH of solution, aeration time and aeration strength showed heavy influence on ammonia nitrogen removal. Air-stripping combined with oxidation can be considered as an alternative approach for the removal of high concentration of ammonia nitrogen from practical metallurgical wastewater. When pH was 11, aeration time 20 min, aeration strength 1040 Lh-1, and oxidation with 10 % NaClO solution 10 min, the initial ammonia nitrogen 2130 mgr1 could reduce to 12 mgr1. Other items could also be removed to meet the ""Integrated wastewater discharge standard (GB8978-88)"".1. IntroductionThe rapid development of human activities has caused a worldwide increase of nitrogen in rivers, lakes and coastal waters. It leads to considerable eutrophication and an increase in the frequency of toxic algae blooms [1,2]. The concentrations of nitrogen in the water of China are pervading high [3]. The discharge of wastewater containing high concentration of ammonia nitrogen is one of the most important factors. Great efforts have been devoted to the removal of ammonia nitrogen from wastewater. Traditional methods include biological denitrication [ 4 ], chemical precipitation with magnesium ammonium phosphate [5], electrochemical conversion [6], air-stripping [7] and so on. Biological denitrication is the most common process in the treatment of ammonia nitrogen wastewater. But the process is only suitable for the removal of relatively low ammonia concentration due to the requirement of appropriate C/N ratio [8]. Chemical precipitation needs additional reagents, which may introduce new pollutants to water body. Electrochemical method often uses expensive metal or metal oxide as electrodes, and also consumes large quantity of energy [6].Although air-stripping makes use of stripping tower and consumes energy, it is very suitable for the removal of relatively high ammonia concentration. Different air-stripping conditions would appear different removal efficiency. And only air-stripping the effluent can not be attained the ""Integrated wastewater discharge standard (GB8978-88)"". In this study, we use air-stripping and oxidation to removal high concentration of ammonia nitrogen from simulated and real ammonia nitrogen wastewater."

Jan 1, 2011

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 Marcelo Mourao, Adolfo Pillihuaman, Alberto Nogueira, Cyro Takano

"The self-reduction is an alternative and promising process for production of pig iron because offers decisive benefits such as enhancing the reaction kinetic with decrease in fuel consumption and C02 emissions. The self-reduction mixture of iron ore fines, carbonaceous reducer and additives for slag forming components, without agglomeration, was tested in a laboratory rotary kiln. The additives for slag were defined for presenting two different estimated liquidus temperatures (1623 Kand 1773 K) to verify the effect of these temperatures on the iron-carbon nuggets coalescence process. These mixtures were tested at 1673 and 1773 Kin an experimental rotary kiln. After reduction-melting and coalescence processes the samples were disaggregated and the iron nuggets were classified by size. It was considered that nuggets larger than 7,93mm would be a good reference for coalescence index. Low liquidus temperature slag presented 37% of this larger fraction against only 13.5% for high liquidus temperature one. The low liquidus temperature slag would facilitate contact between the particles of iron-carbon in a rotary kiln, enhancing the coalescence.IntroductionThe slag composition usually depends on the reducer ash composition, the ore gangue, the binder composition and any fluxing material [l], and the mechanism of carbon transportation in slag that contains iron oxide reducible by carbon can be explained by the oxide reduction and the metal carburization. During carbon transportation, the carburized particle is transported to slag-metal interphases by the gravity effect, being assimilated by the metallic phase [2]. When the slag's iron oxide comes in contact with the solid carbon, it is immediately reduced, forming Fe particles and CO bubbles as it is shown in the figure l(a). The Fe particles are carburized by carbon particles; they are liquefied simultaneously in the carbon-slag interphase. The Fe-C liquid particles are transported from the slag-carbon interphase to iron-slag interphase as a result of slag flow, based on the surface tension difference (Marangoni effect), figure l(b). The Fe-C liquid particles coalesce on the iron surface and the carbon is immediately diffused in the iron as it is shown in figure l(c). The reduced iron is carburized continuously by repeated sequences [3]."

Jan 1, 2013

By T. Johnson, B. Q. Li

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

Jan 1, 1998

Studies of electric pulse (EP) disintegration were conducted on ores of disseminated precious minerals, &apos;on platinum-bearing chromitites of the Konder Complex, Russia, on diamond-bearing impactites of the Popigai meteoritic crater, Russia, and on and diamond-bearing metamorphic rocks of Northern Kazakhstan. It was shown that EP disintegration ~s a technology that achieves ideal liberation of disseminated minerals, and is a new efficient method to study accessory minerals.

Jan 1, 1991

By Tsutomu Yamamura

The electrolytic reduction mechanism of rare-earth chlorides such as LaCl3, CeCl3, NdCl3, ` SmCl3 and DyCl3 in alkali chloride baths has been investigated in NaCl, KCI and eutectic LiCI- KCI by means of electrochemical transient methods. The thermodynamic behaviors of rare-earth containing species have been discussed in the frame of Electrode potential - P02- diagram. Low current efficiency found in the case of Nd electro-winning has been attributed to the dissolution of Nd into the bath. The analyses of electrochemical measurement required the elucidation of the effects of the factors such as under-potential deposition, metal dissolution, moisture and oxygen partial pressure.

Jan 1, 2003

By Zhihao Yue, Honglie Shen, Yahui Teng, Ye Jiang

"In this paper, manganous nitrate [Mn(NO3)z] was used to assist the etching of silicon wafer in hydrofluoric acid (HF) for the antireflective application, and alumina (Al2O3) layer was deposited on the surface of the etched sample by atomic layer deposition method for further antireflection. The surface morphological and compositional studies of these samples were performed by scanning electron microscopy attached with an energy-dispersive X-ray spectrometer. The surface reflectance measurements were carried out using UV-Vis-NIR spectrophotometer. Binary structures of pyramids and nanopores were obtained by etching the alkaline textured monocrystalline silicon wafer in HF and Mn(NO3)z mixed solution for not more than 15 min. But excessive increase of etching time of up to 30 min resulted in the whole destruction of pyramids. The average reflectances of the 5-min-etched sample before and after being coated with 75-nm-thick Al2O3 layer are 4.62% and 3.47% in the range of 200-1000 nm, respectively.1. IntroductionAs we know, the reflectance of silicon wafer after being sliced is so high that the maximal photoelectric conversion efficiency of silicon based solar cells is limited. Therefore, alkaline texturization process was used for silicon solar cell in industrial production. But the reflectance of this alkaline textured wafer is still greater than 10% and this process can only be used for monocrystalline silicon solar cell."

Jan 1, 2013

By Hiroshi Hashimoto

For the application of sodium carbonate slag treatment to product high purity copper on an industrial scale, the counter-flow batch process that reduces the amount of utilized slag is proposed from the viewpoint of the post-treatment of slag. Based on the distribution ratios of several impurities between the slag and molten copper determined previously, the effectiveness of this process is discussed using a mathematical model and confirmed experimentally. According to the model, the slag consumption to remove Sb to a required level in case of the counter-flow batch process with 3 reactors is calculated to be around 30 % of that in the case of an ordinary batch process, where pure sodium carbonate is used as a slag at every stage.

Jan 1, 2003

By Masayuki Kudoh, Tohru Maruyama, Yohichi. Ito

When hypo-peritectic carbon steel is quenched during unidirectional solidification, the region of fine columnar grain is observed. It is classified into two coexisting phases. One is coexisting phases of liquid, delta and gamma in the upper part of the region, and the other is coexisting phases of delta and gamma in the lower part of the region. To form the coexisting part of the three phases means that solidification in this experiment proceeds in non-equilibrium state. The size of the narrow side of one fine columnar grain coincides with the arm spacing of a primary dendrite and this result is the same as the hyper-peritectic carbon steel. However, the boundary of the fine grain in the hypo-peritectic carbon steel is formed in different location from that of the hyper-peritectic carbon steel. The former is formed in the skeleton of the dendrite, while the latter is formed in the interspacing of the dendrite. The region of the fine grain changes suddenly to that of the coarse grain when the delta phase in the coexisting part of two phases disappears completely. Therefore, the delta phase in the hypo-peritectic carbon steel might prevent the growth of gamma grain. In order to recognize it, ferrite formers such as Mo, V and Ni are added in the sample. Then, the longitudinal length of the fine columnar grain extends in the sequence of the no addition, Mo, V and Nb.

Jan 1, 2000

By K. G. Wang, M. E. Glicksman, P. Crawford

"We formulate the mathematical solution to late-stage multi particle diffusion in finite systems. The transition from finite system behavior to that for an infinite system is established. Large-scale simulations are reported regarding the dynamics of phase coarsening. Even in the case of a small volume fraction (Vv = 10-4), the particle size distribution is broader than that for the well-known Lifshitz-Slyozov limit at zero volume fraction. We also report the first simulation studies of extremely low volume fraction, for which corresponding experiments, as well as other simulations, do not exist at present for comparison. However, in the case of moderate volume fractions (Vv = 0.1), the fiucutations in the volumetric growth rate of particles are extracted from our simulations. These simulations provide additional insight into the statistical nature of diffusion interactions, including multiparticle stochastics during microstructural evolution.IntroductionPredicting microstructure evolution in alloys remains one of the cornerstones of materials science. Phase coarsening is a common process in microstrucural evolution that leads to a decrease in the excess total interfacial energy of the system. The system typically consists of separate and identifiable units, or domains, such as second-phase particles distributed in a matrix. During phase coarsening, larger particles grow at the expense of small particles. Over time, this ""competition"" results in an increase in the average size of the particle population, and in a concomitant decrease in the number of particles.Particle size and microstructure of many cast alloys depend on similar coarsening processes. Indeed, properties of these materials, such as strength, toughness, ductility, and electrical conductivity, depend on the material's average particle size and particle size distribution (PSD). Understanding and controlling microstructures in two-phase systems are clearly of widespread technological importance."

Jan 1, 2001

By Marcos Aurélio S. Costa, Nilton F. Nagem, Andreia B. Henriques, Herman S. Mansur, Alexandra A. P. Mansur, Antonio E. C. Peres, Valeria G. Silva

The superfine material generated in the Bayer process was used in one innovatively way as a precursor to geopolymerization techniques because of the presence of Gibbsite. Gibbsite can play a role in system adjustment because of the SiO2/Al2O3 ratio. Furthermore in the geopolymeric system it was studied the influenceof the additives such as kaolin, metakaolin and sodium trisilicate in an alkaline media. Others conditions to form the geopolymer were also evaluated such as solid/liquid ratio, SiO2/Al2O3 ratio and total alkaline. The raw materials and geopolymeric products were characterized by several techniques e.g. XRD, DSC, FTIR and SEM. Through the FTIR technique it was observed an increase in intensity and bandwidth in the region centered at 1010 cm-1, which is related to the asymmetric vibration Si(Al)-O, this is an indicating of the possible geopolymer formation This broadening of the band promotes a relative disappearance (overlapping) peaks at 965 and 935 cm-1 associated with raw material (ESPDust).

Jan 1, 2015