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Proposed by outstanding electrochemist and electrometallurgist Prof. Raphael Agladze (191 1- 1989), process of copper and manganese co-electrowinning was enhanced to the pre- electrowinning stages: low,temperature co-leaching of copper and manganese containing materials, and to high-temperature co-roasting of the same materials with consecutive leaching. The report presents results of experimental investigations of the processes mentioned above, as well as results of thermodynamic investigations of co-roasting processes, and co- leaching processes computer modeling.

Jan 1, 1997

By V. M. Paretsky

The basic work conducted by Prof. A.Yazawa has demonstrated that in order to ensure single-stage white metal production by autogenous smelting of copper sulfide raw materials, it is most favorable to use highly basic slags, in particular oxide systems CaO-FeO-Fe2O3-Sio2. he special studies have been conducted in the Gintsvetmet Institute to investigate the composition and structure of slags produced on a semi-commercial scale when testing the KFP and FBP processes for white metal smelting, as well as the slag obtained in a full-scale KFP furnace at the Almalyk copper smelter. The investigations conducted have demonstrated why production of high-grade matte or white metal is associated with lower loss of copper in slag in a series: silicate slag I silicate-calcium slag I ferrite-calcium slag.

Jan 1, 2003

By F. Kongoli

Viscosity is an important parameter of copper smelting and converting processes. It affects the settling of matte or metal droplets in the slag, distribution of elements etc. Despite this importance, confusion exists on the viscosity of copper smelting slags as a result of disagreements found among the measured viscosity data of several authors especially in the slags of high ferric iron content and close to magnetite precipitation. In this work a critical review of the existing data on the viscosity of copper smelting slags has been first carried out and the effect of oxygen potential on the viscosity of copper smelting slags has been clarified through a coupled quantification of viscosity and liquidus temperature. The confusion in the literature has been clarified and the importance of the relation between the viscosity and the liquidus temperature is discussed.

Jan 1, 2003

By R. Boom, Y. V. Meteleva-Fischer, B. Kraaijveld, H. Kuntzel

"Segregation of impurities during refining of metallurgical grade silicon (MG-Si) is an option to produce solar grade silicon (SG-Si). Directional solidification is a last step in production of SG-Si effective for removal of metallic impurities. The possibility is investigated to use metallic impurities originally present in MG-Si for removing boron and phosphorus. MG-Si has been treated using two methods: 1) alloying with calcium and 2) refining with Na2O-CaO-SiO2 slag, both by controlled cooling. The microstructure of silicon and the impurities distribution have been studied before and after the treatments. Using EPMA phosphorus and boron have been detected in 1-2 wt% concentration range in several intermetallic compounds in grain boundaries after both treatments. This observation points to a different possible mechanism of silicon refining from boron and phosphorus. Controlled cooling improves migration of phosphorus and boron to the silicide phases in grain boundaries, which can be removed by acid leaching treatment.2. IntroductionStandards for silicon solar cells and growing demand on “green” energy require economical and efficient route to the production of solar grade silicon. Refining of cheap metallurgical grade silicon is one of the promising options, where application of existing metallurgical approaches can result in cost-efficient production on industrial scale. Focus in refining is on impurities, which are most difficult to remove: B, P, Al, Ti, due to their large segregation coefficient in silicon and low vapour pressure [1]. Moreover, more environmentally friendly technology in comparison to the traditional Siemens process [2] will be in accordance with societal needs. Based on properties of common impurities in metallurgical grade silicon, alloying refining and slag refining are suggested as competitive techniques having potential effect on removal of impurities harmful for conversion of solar energy [3, 4]. Alloying with Ca followed by acid leaching was found to be effective for removal of Fe and Ti from silicon [5] and to enhance also removal of boron [6] and phosphorus [7, 8]. In the work of Inoue et al. [8] drastically increasing removal of phosphorus from silicon has been observed with an increase of Ca content and a thermodynamics-based explanation was provided. Since phosphorus has been found to condense in the secondary precipitate mainly composed of CaSi2, it can be removed together with iron and titanium by consecutive acid leaching treatment. Slag refining is one of the metallurgical methods proposed to be effective for refining of metallurgical grade silicon from boron [9, 10]. Slags with additions of the following oxides to silica have shown positive effect on removal of boron: CaO [11-13], Na2O [11,14]. Mechanism of slag refining from boron is based on oxidation of boron followed by its incorporation in the slag network [9,11]; the same mechanism is suggested for refining from phosphorus taking into account that oxides of boron and phosphorus are known as network-formers [15]."

Jan 1, 2012

By Guo Chen, Yifeng Shi, Xiaobiao Shang, Nanshang Shen, Bangqi Zhang, Jinhui Peng, Junruo Chen

"The energy is introduced directly into the volume of the honeycomb ceramic regenerator due to the complex interaction of microwaves with minerals in microwave gas heating system. A three-dimensional numerical model is developed to simulate the electromagnetic field by solving Maxwell's equations using finite-difference time-domain method. Computational result is presented for the microwave power absorption of the regenerator. Effects of the dielectric constant and the effective loss factor on the microwave power absorption in the regenerator are studied as well. Numerical results show that the heating pattern strongly depends on the dielectric property of the regenerator. The demonstration of the model of electromagnetic field distribution can be applied effectively and efficiently to optimize the fundamental parameters in the microwave heating processing.IntroductionIn recent years, microwave energy has been utilized in many fields, such as food processing, chemical engineering and mineral processing [l]. In contrast to conventional heating, where heat is transferred from a surface to the interior, microwave energy is introduced directly into the volume of minerals due to the complex interaction of the microwave with the mineral. Based on volumetric heating effects, microwave heating has several advantages such as pollution free, rapid heating technique, internal heating, high efficiency over conventional heating [ 1-4]."

Jan 1, 2013

By S. Viswanathan, Q. Han, A. S. Sabau

"In spite of recent advances in the mathematical modeling of fluid dynamics for materials processing applications, no significant advances have been made in the numerical discretization of these equations. In this work, the application of two-step projection methods for the numerical simulation of interdendritic flows is discussed. Unlike previous methods, the methods presented here are constructed for the exact equations which are characterized by variable density and volumetric fraction of the liquid. The drag terms, which describe the momentum loss due to the flow around and through the dendrite structures, are treated implicitly. Numerical examples for shrinkage-induced flow during solidification of an Al-4.5% Cu alloy bar is used to illustrate the effectiveness of the proposed algorithm.IntroductionLiquid contraction during solidification plays an important role in the formation of casting defects such as shrinkage voids, microporosity, and macrosegregation. Owing to their importance, the study of transport processes during solidification have received considerable attention during the past years [1, 2]. By the use of volume-averaging techniques, the mass and momentum equations for flow through a stationary dendritic structure were derived [3]. By using the volume-averaging techniques for multi-phase systems, two-phase transport equations for solidification problems were derived [4]."

Jan 1, 1999

By Yiling Zhang, Paul A. Salvador, Gregory S. Rohrer

"Photocatalysis utilizes solar energy to produce hydrogen by splitting H2O. When a thin film of photocatalyst TiO2 is supported on a ferroelectric BiFeO3 substrate (band gap ~2.5 eV), the TiO2/BiFeO3 heterostructure is capable of photochemically reducing Ag+ to Ag0 in aqueous solutions under blue light with enhanced efficiency. The observation of spatially selective silver patterns on surface of the heterostructure after reaction suggests that photogenerated electrons and holes in ferroelectric BiFeO3 are driven in opposite directions to reduce their chance of recombination. Comparisons of the amounts of reduced silver on TiO2 film grains with distinct phases/orientations show that the reactivity is mildly preferential on anatase TiO2 phase and does not strongly depend on crystallographic orientation of BiFeO3.IntroductionTitania (TiO2) is capable of photocatalytically converting H2O to hydrogen and oxygen under the irradiation of ultraviolet light. [1, 2] One of the limiting factors for titania to be used as an effective photocatalyst is its band gap. Because the absorption edges of rutile and anatase titania are at 3.0 eV and 3.2 eV, respectively, they can only absorb light in the UV portion of the spectrum, which is about 3% of the available solar energy. [3-5] This limitation has motivated attempts to modify the absorption edge of titania so that it can absorb visible light.One strategy is to substitute a portion of the titanium and/or the oxygen with other atoms. There are numerous reports on visible light absorption of titania by doping and co-doping of Cr, V, Mo, Sb, Fe, N, S, C, and F. [6-34] Another strategy is to add an adsorbed molecular species that absorb visible light and donate an electron or hole to the titania, such as organic dyes [33, 35, 36] and Ce3+/Ce4+. [37, 38]The strategy in the present work takes the approach of depositing a pure titania thin film on a visible light absorbing substrate BiFeO3 to induce visible light activity of the heterostructure. BiFeO3 is a semiconductor with a band gap of about 2.5 eV [39-41] and is photocatalytically active in visible light. [42, 43] It is also ferroelectric with spontaneous polarization along pseudo-cubic <111> directions of 6.1 µC cm-2. [44] The spontaneous polarization gives rise to internal electric fields that drive photogenerated charge carriers, namely electrons and holes, in opposite directions to reduce their chance of recombination. [45-47] Additionally, the separation of electrons and holes leads to the spatial separation of reduction and oxidation half reactions so that the back reaction of intermediates is also suppressed. Such charge carrier separation has been reported in TiO2/BaTiO3 heterostructures with UV light illumination. [48-51] The TiO2/BiFeO3 heterostructures in this work combine both advantages of the relatively narrow band gap and the internal fields in BiFeO3 to enhance the overall photocatalytic activity."

Jan 1, 2014

By V. I. Lakshmanan, R. Roy

"TiO2 is used in paints, plastics, rubber, paper, inks, textiles and other miscellaneous applications. The demand for the pigment grade Ti02 is growing at 3.0%/year on average and this invites the development of innovative and cost effective processes. The current processes are not designed to recycle the reagents and thereby discharge the effluents into the environment, causing an environmental concern.During this study, synthesis of TiO2 from an ilmenite concentrate was investigated using an innovative atmospheric mixed-chloride leach process. The solution purification was carried out using solvent extraction in two stages. In the first stage iron removal was carried out and in the second stage titanium was extracted. The strip solution obtained from the second stage solvent extraction contained the purified titanium and from this stream pigment grade Ti02 was recovered. The barren solution was used for reagent recovery and the regenerated leach liquor was recycled."

Jan 1, 2011

By I. Gaballah

Decontamination of synthetic solutions of PbC12 containing 10, 100 and 1000 ppm of lead, using chemically treated barks had been studied. The percentage of !cad cations&apos; removal from solutions depends upon the pH and the initial concentration. About 99 % of the initial lead content can be removed at pH of about 3.5, 5.5 and 6.5 for initial concentrations of 10, 100 and 1000 ppm respectively. The maximum retention capacity of the treated bark is about 83 mg of lead per gram of modified bark. Bark loaded with lead had been analyzed by Infra Red spectroscopy. It seems that lead reacts with hydroxyl groups of the phenolic constituents of the bark. On the other hand, the removal of a lead cation by the bark leads to the release of two H+. This seems to show that the removal of lead could be interpreted as an ion exchange with hydrogen belonging to the hydroxyl groups of the modified bark.

Jan 1, 1994

By W. G. Davenport

A flash furnace can be run many different ways. It can, for example, be operated with: (a) highly 02"enriched, ambient temperature blast and no fossil fuel (b) considerable fossil fuel and hot, slightly Or enriched blast. It can also produce different grades of matte. With all these possibilities, the flash furnace operator can benefit from any technique that will indicate the &apos;best&apos; way to operate his furnace. One such technique is Excel&apos;s &apos;Solver&apos;optimizationroutine#. This chapter shows how our matrices and Excers optimization.abllity can be used to optimize a flash furnace operation. The chapter sets three optimization goals: (a) minimum industrial oxygen + oil cost, $ per tonne of concentrate (b) maximum smelting rate, tonnes of concentrate per hour (c) maximum profit, $ per hour.

Jan 1, 2001

By Metehan Erdogan, Orhan Gökçe Göksu, Ishak Karakaya

"An experiment (mixture) design was created to optimize the process parameters of the electrochemical reduction of CaW04 to W in molten CaCl2-NaCl eutectic mixture. Temperature, applied voltage and the length of Kanthal wire winding of the CaW04 pellets were selected as the process parameters that were allowed to vary between the predetermined minimum and maximum values. The rates of the electrochemical reductions were interpreted from the variations of current and total charge vs. time graphs under different conditions. The analysis pointed out that 640°C and 2.81 V resulted in the fastest reduction. Itwas seen that the effect of Kanthal wire winding on the output current was less pronounced when compared to the other two parameters.IntroductionFFC Cambridge Process [1] has been applied to a number of metal oxides in laboratory experiments to produce metals. In nearly all of these studies, the electrolysis temperature was around 900°C, the electrolyte was pure CaCl2 or CaCl2 containing salt solutions and the anode was graphite. However, it was recently shown that the electrochemical reduction process of metal oxides in CaCl2 containing electrolytes at the mentioned high temperatures was not suitable for tungsten production [2], It was reported that as soon as WO3 contacts CaCl2, the following reaction occurs:"

Jan 1, 2012

By K. C. Liddell

"Cu/Ni multilayers exhibiting giant magnetoresistance were deposited from a single electrolyte under stepped potentiostatic control. To enable transport measurements to be made without remounting the multilayer film, we developed a novel method that involved plating on a thin metallic basal layer atop a rigid non-conducting Si substrate. Rotating ring-disk electrode techniques were used to monitor the composition and thickness of individual plated layers. Transmission electron microscopy confirmed that the interfaces between adjacent layers were sharp and that the structure of the layers was uniform throughout the film. Atomic force microscopy images indicated that the film's surface was smooth and free of defects.ELECTRODEPOSITION OF THIN MULTILAYER MAGNETIC MATERIALSI. IntroductionElectrodeposition of compositionally modulated films will in all likelihood continue to be used to produce the read heads for stored magnetic data. However, the next generation of head materials will require both improved sensitivity and reduced film thickness. Certain multi layers consisting of thin alternating ferromagnetic and nonmagnetic layers exhibit giant magneto resistance and consequently are promising candidates for read head applications. We have successfully made multilayer films with giant magnetoresistance that have total thicknesses as low as 25 nm, approximately 120 times thinner than the thinnest similar films reported in the literature. This paper describes early results from our work on electrodeposition and characterization of Cu/Ni multilayers, a model system with enhanced magnetic and mechanical properties, including the GMR effect. The structure and composition of the multilayers were determined using TEM, AFM, and electrochemical methods, and their magnetoresistance was measured by the standard four-probe technique. A novel method developed in this work enabled the transport properties of the ultrathin films to be measured reliably without the need to dissolve the cathode or handle the films. To provide a context for these results, short accounts of other work on giant magnetoresistance and multilayer electrodeposition are also included."

Jan 1, 1997

By Lin Li, Wen Shi, Hua Wang

"Specimens of the ultra-low carbon bake hardening steel were soaked for 1 min to 5 min, and then cooled by water quenching. The internal friction experiments were carried out to detect the spectra of the specimens. Results show that Snoek peaks are present in all the specimens, however, an obvious Snoek-Koster peak is found only in the 5 min-annealed specimen. Besides, tensile results indicate that the bake hardening values increase with the annealing time prolonging from 1 min to 3 min, but decrease as the annealing time prolongs further to 5 min. The solute distributions in the specimens were characterized by three dimensional atom probe. Some segregated C and V are found in the 1 min-annealed specimen, and the C and V contents decrease as annealing time prolongs to 5 min.1. IntroductionAs an excellent member of automotive body panel materials, various types of bake hardening (BH) steels have been developed since 1980s. Bake hardening property, as one of the most important mechanical properties, has been studied by many researchers [ 1-5]. As is known, BH phenomenon is generally controlled by the interaction between solute C and dislocations. The Snoek peak of internal friction (IF) is very popular in the investigation of solute C [6-9]. However, result of internal friction cannot suggest the distribution pattern of solute C as well as its influence on BH phenomenon.Three dimensional atom probe (3DAP) can diagnose solute element atoms as well as nano-sized precipitates, and it is the only instrument that currently can identify the identities of individual atoms in a material and measure their spatial coordinates with the resolution close to 0.3 nm [10]. There have been a number of studies about using 3DAP to detect solute elements as well as nanometer sized precipitates [11-19]. For example, Hono et al. [16] used 3DAP to determine the solute elements in an age-hardened Mg-Ca-Zn alloy, and they also obtained the distribution patterns of the observed elements."

Jan 1, 2011

By D. B. Dreisinger

The zinc pressure leach process developed by Sherritt Gordon, Ltd. permits the direct leaching of sulphide concentrates according to the overall reaction, ZnS +H,zS04 +402.+ZnS04+H20 +S0 The kinetics of the leach are affected by three rate controlling steps; ( l) oxygen mass transfer from the gas to the leach solution, (2) homogeneous oxidation of ferric ion to ferric ion by dissolved 011.ygen and (3) ferric ion leaching of zinc sulphide in the presence of a sulphur dispersing detergent (lignin sulphonic acid). Fundamental studies have been conducted to identify the factors that influence the kinetics of each individual rate controlling step. Oxygen mass transfer studies have been directed toward optimization of the agitator configuration for solids mixing and gas pumping from the atmosphere above the leach slurry. The rate of ferrous oxidation by molecular oxygen and the rate of zinc sulphide leaching by ferric ion have been studied over a wide range of temperature and solution compositions. The study of zinc sulphide leaching by ferric ion was supplemented by a series of interfacial tension measurements in the liquid sulphur - zinc sulphate solution system. The various kinetic studies have been summarized in terms of the importance of each rate to the performance of the process.

Jan 1, 1990

By Fiseha Tesfaye, Pekka Taskinen, Daniel Lindberg

Due to increasing complexities of raw materials for base metals production the conventional pyrometallurgical processes are challenged. To make the appropriate modifications, thorough evaluations of the thermal stabilities of phases and phase assemblages which are commonly encountered in these processes are essential. In this work, phase relations and thermal stabilities of equilibrium phases in the Cu-Ni-S system have been reviewed. The calculated phase diagram of Cu-Ni system has been validated. At T < 630 K, in the Ni-rich corner, large scatter in data has been observed and discussed in detail. The other binary systems, Cu-S and Ni-S, have been also critically reviewed together with the ternary Cu-Ni-S system. The reviews were focused on compiling and discussing phase relations and thermal stabilities of the selected systems in the pyrometallurgical processes of Cu and Ni productions.

Jan 1, 2016

By Shengqi Chen

The reduction smelting of nickel laterites produces slag, consisting principally of the chemical components MgO, "FeO", SiO2, and A12O3, and ferro-nickel alloy. Despite the fact that the phase equilibria for the ternary MgO-"FeO"-SiO2 up to 1500°C is well established limited experimental data are available in the MgO-"FeO"-SiO2-Al2O3 system, which is relevant to commercial operation of the process. A methodology has been developed for the experimental investigation of the liquidus temperatures for the multi-component system MgO-"FeO"-SiO2-Al2O3-Cr2O3 in equilibrium with metallic iron. Experiments have been carried out using high temperature equilibration, quenching, followed by electron probe X-ray microanalysis (EPMA). Liquidus temperatures have been determined in the silica primary phase field in the composition ranges directly relevant to the Cerro Matoso S.A. ferro-nickel smelting slag. Liquidus isotherms have been determined for temperatures between 1450 to 1600°C. The study enables the liquidus to be described for a range of MgO/FeO ratios. It was found that liquidus temperatures in the silica primary phase field decrease significantly with the addition of AI2O3. Keywords: Liquidus temperature, ferro-nickel, pyrometallurgy, smelting

Jan 1, 2004

By Vinicius Alves Gomes, Jean Igor Margem, Frederico Muylaert Margem, Sergio Neves Monteiro, Marina Rangel Margem

The interface between the matrix and the reinforcing fiber plays an important role in the efficiency by which an applied load is transmitted through the composite structure. The shear stress at the fiber/matrix interface can be associated with this load transference and, consequently, affects the composite strength. In the present work, pullout tests were used to evaluate the interfacial shear stress of malva fiber in epoxy matrix composites. A small critical length was found for the malva fiber embedded in epoxy, which corresponds to a relatively weak fiber/matrix bond and lower interfacial strength.

Jan 1, 2015

By Ross W. Smith

Microorganisms are increasingly finding use in mineral processing and hydrometallurgy both for the enhancement of mineral engineering operations and for the remediation of mineral industry wastes. Some of the applications, such as biologically assisted leaching of sulfide ores and biooxidation of refractory sulfide gold ores, are established commercial processes. Others, such as the use of organisms for the removal of heavy metal ions from dilute aqueous streams, are nearing commercial application. Other uses of microorganisms are potentially possible. These include use of microorganisms in leaching non-sulfide ores, the flocculation or flotation of minerals and remediation of toxic chemicals discharged from mineral engineering operations.

Jan 1, 1993

By Liow Jong-Leng

A survey of the interactions of large gas bubbles formed from top and bottom injection of gases into melts was carried out. Spherical cap bubbles were found not to produce much splash when they break through the bath free surface except for that formed by plunging of the-spout at its edges. In contrast, the bursting of balloons produces cavities which give rise to liquid jets being ejected from the bath free surface. The position of the balloons relative to the bath free surface is an important parameter in the formation of the liquid jet. It is found that the interactions of multiple bubbles close to the free surface is important in determining the splash behaviour of gas injected systems.

Jan 1, 1996

By Shu-cai Zhou

"To understand the solidification behavior of austenitic heat-resistant stainless steel (TP34 7) in rotary electromagnetic-field, the influence of electromagnetic stirring in mold (M-EMS) on solidification structure of TP34 7 heat resistant steel in a round billet continuous casting was investigated based on industrial experiments. The results indicate that the excellent billet solidification structure of TP34 7 heat resistant steel can be obtained with appropriate electromagnetic stirring parameters. The solidification structure of TP34 7 heat resistant steel can be remarkably refmed, central porosity and shrinkage cavity can be remarkably decreased and equiaxed grains zone widens was enlarged. The industrial trials verify that the stirring intensity of TP34 7 heat resistant austenitic stainless steel should be higher comparing with plain carbon steel. Due to a higher viscosity, rotating speed of molten stainless steel was 20-30% lower than that of molten carbon steel in the same magnetic flux density.IntroductionIn recent years, the development of ultra super critical (USC) plants is accelerated by the demands of environment protection and energy saving, and USC plants with steam temperature and pressure conditions in excess of 593°C and 24.lMPa respectively were constructed. To achieve the goal, it is important to develop new materials with excellent high temperature strength, superior resistance to oxidation and corrosion at high temperature. Besides, their cost must be low enough to meet the requirement of plants [ 1]. TP34 7H steel is promising austenitic heat-resistant steel, which is used as superheater/reheater tube material and is extensively used for high temperature components and fossil-fired power plants, and suitable to be used in USC boilers plant. This kind steel contains with about 0. 7%Nb and it keeps higher allowable stress and creep rupture strength than TP304 and TP321H [1-2]. TP347H has conventionally been produced by ingot casting followed by forging and rolling. Recently, in order to decrease the production cost, challenging trials to produce these types of alloys by a continuous casting (CC) process have been attempted. However, the solidification structure of austenitic stainless steel is one of the key issues that attract more attention. Due to the low thermal conductivity of TP347H heat resistant stainless steel (much smaller than that of plain carbon steel), pronounced defects during continuous casting of austenitic heat-resistant steel such as coarse columnar, center porosity and coarse bridging, greatly influence mechanical properties of fmished products.A widely used technique in metallurgy is the inductive drive of molten metals using rotational or traveling magnetic fields. Recently, rotary electromagnetic stirring (EMS) has been applied to reducing various defects and improving increase the solidification structure of the metals in the continuous casting of steel, Al-based alloys and Mg-based alloys [3-8]. Electromagnetic stirring of plain carbon and low alloy steel in the continuous casting bloom and slab is well established for improving the quality of cast products [9-11] and is widely used in industry. However, very few literatures on electromagnetic casting of heat resistant stainless steel have reported. In this work, an industrial plant trial was performed to clarify the effect ofM-EMS on the macroscopic quality ofTP347heat resistant steel billet, in which the regularity and mechanism of the influence of EMS on solidification casting billet were discussed."

Jan 1, 2014