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By Go-Gi Lee, Jae-Young Jung, Myung-Duk Seo, Hyun-Na Bae, Seon-Hyo Kim

"Bubbles form at the anode during the electrowinning of magnesium and cause hydrodynamic acceleration and electrical field disturbance. A three-dimensional computational model was developed to investigate the effects of the geometry of the electrochemical chamber and the size distribution of bubbles on the fluid flow in the pilot plant. The results are validated by measurements of the surface characteristics of molten salt and the bubbles formed. Fluid flow at the surface was recorded with a high speed camera, and the distribution of bubble size is determined by inspecting the video images frame by frame. The measured size distribution of the bubbles is entered into the computer simulation of a multi-phase flow. A sloped roof is installed above the electrodes, to enhance the flow of the molten salt, thus resulting in higher current efficiency, lower energy consumption, and higher quality of magnesium metal.IntroductionTitanium's excellent properties of low density, high specific strength, high temperature strength, and exceptional resistance to corrosion are highly beneficial to diverse applications including aerospace, automotive, construction, and medical implants. Although the Kroll process[l] and Hunter process have been used for the extraction of titanium in the 20th century, their complicated engineering stages and high production cost, have led to further research into new processes such as FCC Cambridge, Armstrong and TiRO. Despite these intense research efforts, no process has yet been developed that is more economical than the Kroll process, by which most of the global commercial titanium is still being produced."

Jan 1, 2011

By Yuzura Sato

Viscosity has been measured for various molten binary alloys of nickel with iron, cobalt and chromium in order to clarify the behavior of viscous flow of molten nickel alloys. The entire concentration range for iron and cobalt and 0-67at% of chromium content were studied. The measurement method was an oscillating cup viscometry using an alumina crucible that was precisely machined. The temperature was up to about I 880K for all the measurements. The results represented good Arrhenian relationship although some measurements included overcooled temperatures. The isothermal viscosities increased monotonously with an addition of iron and chromium into nickel. The addition of cobalt increased after stationariness. The isothermal viscosities showed concave curves. Activation energies increased monotonously by adding all the elements into nickel. These phenomena were considered to be related to the thermodynamic properties 'such as the heat of mixing and the structures of mixture melts.

Jan 1, 2003

By Chen Song

In the experiments of purifying the solution of chlorine leaching from nickel concentrate with N235, the effects of organic phase composition on purifying efficiency have been studied. From the results obtained, the optimal organic phase composition is found to be 25%N235+12%isomerous alcohol +63%sulfonic kerosene (VIV) and the saturated content of cobalt in organic phase is7.95 g*dm3. And then the serial experiment is carried out. The results show that at the given organic phase composition, the purified solution contains p(Ni) >200 gm dm3, p(Ni)l p(Co) >50000 and the contents of Cu, Fe, Mn, Zn meet the technical criterion of standard nickel electrolyte. The cobalt chloride solution contains p(Co) >I10 g L-1, p(Co) lp(Ni)>50000 and the enrichment of cobalt has been achieved.

Jan 1, 2006

By R. G. Reddy

Nickel solubilities in spent pickling solutions (i.e. HF-HNO3-H2O solutions ) were measured as a function of HF and HNO3 acid concentrations. The chemical analysis of the industrial pickling solutions and sludges were made. The stable phases observed in the sludges are FeF3?3H2O, and ( FeCr ) F3?3H2O. Pure Ni, and stainless steel type 316 were used in this study. The results showed that the solubility of Ni increased with increase in concentrations of HF in pickling solution at a fixed concentration of HNO3: An excellent agreement between the experimental solubility data and the theoretical data was obtained. X-ray diffraction analysis showed that the solid solubility product formed is mainly NiF2?4H2O compound.

Jan 1, 1992

By Jiang Diao, Xuan Liu, Tao Zhang, Bing Xie

In the present study, the oxidation process of vanadium and chromium bearing hot metal was investigated by using CaO-FetO-SiO2 slags at 1653K in MoSi2 furnace. The results indicated that both the vanadium distribution LV and chromium distribution LCr were of the orders of 2.2~2.4 with the basicity range of 1.32~1.78 and FeO weight percent range of 28%~45%. Both LV and LCr decreased with increasing basicity and decreasing FeO weight percent. The phosphorus distribution LP was of the order of 1.34~1.56. However, LP increased with increasing basicity and decreasing FeO weight percent. The oxidation ratio values of V and Cr in hot metal were above 84% and the values of P were nearly 50%. In other words, it means the addition of CaO in vanadium slag provided a certain ability of dephosphorization along with keeping high oxidation ratios of V and Cr.

Jan 1, 2015

By G. K. Ruhlandt, C. W. Kim

"A 3-D Finite Element Method program called ""SOLCAST"" has been developed to simulate the casting solidification process. Using the temperature recovery method to evaluate the latent heat of fusion and applying a new combination of the time integration scheme, SOLCAST reduces the computational time significantly compared to an existing commercial FEM program, and produces accurate results comparable to experimental casting results. Prediction of casting shrinkage porosity for A390 aluminum alloy will also be discussed. To make this FEM program useful for foundry engineers, this program was connected to a commercial pre- and post-processor.IntroductionBecause of recently increased competition, foundrymen must produce high quality castings more economically. Therefore, casting solidification analysis prior to casting production is an attractive way to reduce costs and development time.Although the actual casting solidification process is a very complicated phenomena, foundrymen could predict where shrinkage defects would occur based on a transient conduction heat transfer analysis that includes the liberation of latent heat. A numerical analysis is generally required to solve the heat diffusion equation with the latent heat diffusion term, because casting shapes are very complicated and pure materials are rarely used.Different numerical methods have been applied to the casting solidification analysis 1. Among them, a finite difference method 2 and a finite element method (FEM)3 are most commonly used.Each simulation method has one or more basic difficulties which are different for each method. These difficulties are:(1) Modeling casting shapes on a computer.(2) Time consuming computation.(3) Uncertain material properties."

Jan 1, 1986

By S. Moussa

The formation of boron-doped nickel aluminides Ni3AI, (76 at. % Ni) from elemental powders by reaction synthesis using reactive sintering was studied. The process involves the mixing of elemental powders of nickel and aluminium with various wt % of boron up to 1 wt % boron. Nickel and Aluminium powders were mixed in the correct proportion to form the intended boron-doped nickel aluminide intermetallic. XRD, SEMI EDS, Image analysis and Archimedes principle; were used to study the effect of Boron addition on the final microstructure, bulk density, average grain size of as reactively-sintered nickel aluminides (boron-doped), compared with no boron addition. The results showed that at greater boron content than 0.3 wt %, a two-phase non-equilibrium microstructure of consisting of NiAI phase in NiJAI matrix was formed that have been primarily retained even after heat treatment for 5 hours at 1000 °C. Boron was present in solid-solution within both the NiAI and the Ni3AI (in greater amounts) phases.

Jan 1, 2001

By K. Robinson

Following the longest Smelter campaign in BCL?s history it was planned to completely rebuild the flash smelting furnace in 1987. This was the fourth major overhaul and the most extensive so far attempted. Detailed planning took place over several year$ preceding the shutdown and implementation was completed in 54 days. The key to minimising shutdown time was the method designed for installation of the new uptake shaft and reaction shaft. Major repair work was also undertaken in the waste heat boiler and electric furnaces. Both of these activities had an impact on the critical path of the flash smelting furnace overhaul.

Jan 1, 1993

By Maurizio Marezio Bertini

Successful treatment of contaminated sediments was achieved by sparging either 0.5 M NaOH solutions or distilled water with an SO2/O2 gas mixture. Metals such as Cu, Pb, Cr and Cd were successfully removed in a relatively short time. The effect of temperature and pH was investigated. Higher temperatures produced faster and higher recoveries with Pb and Cr more affected to temperature increase than Cu and Cd. The removal of copper, up to 50% percent, was achieved in alkaline solutions through the formation of copper sulfite complexes. The complete removal of metals such as Cu, Pb, Cr and Cd required that part of the treatment be carried out in acidic solutions. A preliminary cost analysis was carried out.

Jan 1, 2003

By Junwei Han, Wenqing Qin, Dawei Wang, Fen Jiao, Wei Liu

The removal of iron impurity from zinc calcine was studied by magnetization roasting and magnetic separation. The effects of roasting temperature, magnetic intensity, ore grinding, and leaching pretreatment on iron grade and recovery were investigated. The results indicated that iron recovery increased with the increase of roasting temperature or magnetic intensity, while iron grade was always less than 22%, depending on the fact that the magnetite were not liberated completely. The good liberation was difficult to be achieved by ore grinding but was easier by acid leaching, since the magnetite grains were very fine. After the leaching pretreatment, the recovery of 76.31% with iron grade of 53.24% was obtained by one roughing and cleaning. The SEM/EDS analysis showed that a part of sphalerite, zinc ferrite and other gangues were mixed into the iron concentrate, while some of fine magnetite was reported to the tailing.

Jan 1, 2016

The U.S. Bureau of Mines investigated CaF2-assisted H2SO4 leaching to extract Mn from domestic silicate manganese resources. A pyroxmangite ((Mn,Fe)Sio3) ore containing, in pct, 34 Mn, 23 Si, 3 Ca, and 1 Fe was leached at 90° C for 3 h in a solution containing, in g/L, 12 Mn, 140 H2SO4, 130 (NH4)2SO4, and 5 CaFz. Manganese extraction of 92 pct was achieved. Manganese of greater than 99 pct purity was prepared by electrolyzing the purified pregnant solution at a current density of 50 mA/cm2. The current efficiency was 65 pct.

Jan 1, 1991

By Yuanbo Zhang, Yingming Chen, Zijian Su, Bingbing Liu, Jun Chen

Iron, tin-bearing tailings is a kind of hazardous solid waste generated from cassiterite dressing operation. It is difficult to utilize the tailings by present mineral processing methods due to the complex dissemination characteristics. In this study, a process of gas-based magnetizing roasting followed by magnetic separation was studied for separating and recovering iron from the tailings. The effects of roasting and magnetic separation parameters on the recovery of iron were systematically investigated. The optimum parameters were proposed as follows: CO/(CO+CO2) content of 5%, roasting temperature of 850 C, roasting time of 60 min, grinding particle size of 90% less than 45 μm and magnetic field intensity of 800 Gs. Under these conditions, the magnetic concentrate containing 68.5% Fe and 0.06% Sn was achieved, which can be used as high-quality raw materials for direct reduction iron production.

Jan 1, 2016

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 A. C. Wadhawan

In the present context of rapid industrialization, production of Lead-Zinc metals from low grade materials, residues and wastes can make substantial contribution to the supply of these metals in India. Recovery from secondary sources also plays an important role in conservation of mineral resources and lower power consumption. Conscious effort is therefore, required to increase the secondary metals which, besides saving in energy cost will also help in waste material management and keeping environment clean. The major thrust is, therefore, needed in this direction. During all these years, the Indian Lead- Zinc industry has made sustained efforts for recovery of metals from low grade ores and from metallurgical wastes and residues. The paper identifies the treatment of low grade ores by various technologies and techniques and the treatment of metallurgical residues and wastes generated during primary Lead and Zinc smelting in India. Some of the major achievements in past decade have also been elaborated in the paper. The strategies to be followed for continuing treatment of low grade ores and waste materials by adopting newer, environmental friendly technologies, in consonance with the rigid standards being adopted by most of the countries including India. have also been dealt with in the paper.

Jan 1, 1994

By In-Hyeok Choi

Currently, spent V2O5–WO3/TiO2 catalysts contribute significant amounts of solid waste following increasing levels of global demand. V2O5–WO3/ TiO2 catalysts usually consist of TiO2 anatase as a supporting oxide, vanadium as a catalytic agent, and other promoters such as tungsten, silicon, and calcium. Although vanadium is the main catalytic agent, a relatively high content of tungsten (WO3, 7–10 wt%) typically exists compared to vanadium (0.5–1.5 wt%). Considering the irreplaceable properties and industrial importance of tungsten, a feasible method for the recycling of spent V2O5–WO3/TiO2 catalyst should be established to utilize it as a secondary source. This paper presents a process to recover tungsten from spent V2O5–WO3/TiO2 catalyst. The processes proposed here involving roasting, decomposition using HCl, ammonia leaching, and crystallization. Within the process, ammonium paratungstate (71 wt% as WO3) is obtained as a final product. The total yield rate of tungsten from feedstock was found to be 96.3%.

By Masao Suzuki

Over 5 million cars are scrapped yearly in Japan. After dismantling. scrapped automobiles, they are put into a shredder for differential recovery of ferrous and nonferrous metals. The residue, which is called shredder dust, runs over 1.2 million tons per year. This paper reports a entire sequence of scrapping. cars. in Japan with the following sections: (1) production and scrapped car management, (2) material composition, (3) dismantling, (4) shredder plant, (5) differential recovery of metals including specific gravity separation and newly developed color separation.

Jan 1, 1995

By Ahmad-Bitar¸ Riyad N., Shadia J. Ikhmayies

"CdSi-xTex thin films with O<x<0.3 were prepared on glass substrates by the annealing of CdS:In thin films produced by the spray pyrolysis technique. The annealing was performed in nitrogen atmosphere at 400 --,C in the presence of Te vapor. The compositions of the films were determined by energy dispersive X-ray detection (EDAX) measurements. Scanning electron microscopy (SEM) was used to investigate the morphology of the films. The transmittance of the films was measured at room temperature in the wavelength range 400-1100 nm and used to produce the absorbance of the films. The first derivative of the absorbance was used to estimate the optical bandgap energy Eg by using the minima in the first derivative. The relation between the bandgap energy and the fraction x was found to fit with a parabola and bandgaps in the range 2.196: =Eg: =2.480 e V were obtained. Urbach tailing in the bandgap was also investigated.IntroductionPolycrystalline thin film CdS/CdTe solar cells are promising candidates for low cost and high efficiency photovoltaic applications. The fabrication process of these cells involves the deposition of a p-type CdTe absorber layer on top of an n-type CdS one which acts as a window. The efficiency of the solar cell is affected by the method of preparation of both layers [1, 2].Interdiffusion processes taking place at the CdS/CdTe interface have largely been realized to significantly affect the device performance [3] by changing the bandgap of both CdTe and CdS which modifies the spectral response of the solar cell [ 4]. The formation of a mixed crystal or a graded layer causes a reduction in the lattice mismatch at the CdS/CdTe junction [5] which is about 9% [ 6] and then a reduction in the number of interfacial states and recombination centers, thus enhancing the solar cell performance [7, 8]. A complete understanding of the properties of the intermixed layers CdSxTe1-x that usually constitutes the interfacial region in the CdS/CdTe solar cell is essential. According to our knowledge, a lot of research was devoted to the investigation of the diffusion of S into CdTe [3-5, 9]; but little on the direct investigation of the diffusion of Te into CdS [6]."

Jan 1, 2011

By Ramana. G. Reddy, Haoxing Yang

The electrodeposition of zinc from zinc oxide using urea and choline chloride mixture in a molar ratio 2:1 is investigated in different experimental variables, namely, the concentration of added [BMIM]HSO4, temperature, and applied cell voltage. The additive, [BMIM]HSO4, was determined to have beneficial effect on the current efficiency, energy consumed in the process and surface morphology of the deposits. The highest current efficiency (92.6%) and lowest energy consumption (2.92kWh/kg) was obtained for solution with 20mg/mL [BMIM]HSO4. The morphology showed the formation of absorbed additive layer on the cathode at higher concentration of additives. Experiments were conducted at different temperatures between 343K and 388K and at various applied cell voltages between 2.7V to 3.6V to determine the best experimental conditions. By varying temperature, highest current efficiency (91.3%) and lowest energy consumption (2.69 kWh/kg) was obtained at 373K. The electrodeposition process is enhanced between the applied voltage 3.0-3.3V by achieving lower energy consumption (2.75~3.06kWh/kg) and higher current efficiency (88.4~89.7%). SEM images showed grain size is significantly increased in higher applied voltages. While at higher temperatures, it seemed to generate particle growth as clusters at the outer deposit layer.

Jan 1, 2014

By Jong-Jip Kim, J. G. Byrne, W. Kim, In-Ok Shim, John E. Flinn

"Two rapid solidification processes for 304 stainless steel were studied: centrifugal atomization (CA) in a helium atmosphere and atomization by exposing argon-containing melt to vacuum (VGA). Positron annihilation and x-ray line broadening measurements of explosively consolidated monoliths were used to clarify microhardness measurements as a function of annealing temperature. Interesting differences in positron response between CA and VGA materials are ascribed to more carbide formation in the CA material than in the VGA material in the 600 0C range. In addition, hot isostatic pressing of the CA material was examined as to the relations between mechanical behavior, pore shape, and relative density. A variable stress concentration factor is introduced into the theory to allow for changing pore shape as relative density increases.IntroductionThere are many potential advantages of rapid solidification processing (RSP), such as a high degree of matrix supersaturation, finely dispersed microstructures, improved chemical homogeneity, and retention of metastable phases, which have been studied extensively. To consolidate rapidly solidified material which is in powder form into useful shapes often requires subjecting the material to elevated temperature for extended periods of time under mechanical forces, as in hot isostatic pressing or hot extrusion. In such cases, some of the characteristics of the rapid-cooling step can be strongly affected. An alternative is dynamic consolidation (1), for example by explosive forming, where the time frame at least is extremely short.In the present work, effects of the consolidation processes of hot isostatic pressing (HIP) and explosive forming in a die are examined. The particular material is 304 stainless steel. The characteristics of both RS and VGA 304 stainless-steel powders were described by Wright, Flinn, and Korth (2) earlier."

Jan 1, 1988

By F. G. Prado

The technology for the extraction of zinc from zinc residues, such as zinc ashes, drosses and metallurgical flue dusts, by way of ammonium chloride solutions is well established, at least at the laboratory and bench scale levels. (3, 4) Zinc is soluble in ammonium chloride solutions in the form of zinc diammine chloride. Its solubility depends upon the concentrations and temperatures employed. The procedure and the equipment required are simple, and they can be applied either to small or large operations. As a by-product, zinc diammine chloride is produced with extremely low impurities in quantities which are stoichiometrically proportional to the zinc removed. The technology has been applied experimentally to galvanized steel residues. The dezincing results, including removal performance, energy and reagents required, and by-products are summarily presented in this paper.

Jan 1, 1992