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By S. Eckert, G. Gerbeth, K. Timmel, B. Willers, T. Wondrak, N. Shevchenko, M. Röder

The quality of the produced steel in the continuous casting process is significantly governed by the melt flow in the mold. However, direct flow measurements in liquid metals are still rather scarce. In order to investigate these flow phenomena, three experimental facilities operating with low melting liquid metals were installed at Helmholtz-Zentrum Dresden-Rossendorf (HZDR). The melt flow in the models is measured by the Ultrasonic Doppler Velocimetry (UDV) or the Contactless Inductive Flow Tomography (CIFT), multi-phase flows can be visualized by X-ray imaging. The obtained measurement results are primarily used for validation of numerical models. In this paper we will investigate the fluid flow in the mold and the behavior of the surface of the liquid metal using flow measurements by UDV and surface profile measurement by a laser scanner, respectively. Strong fluctuations and deviations of the free surface were observed in case of a static magnetic field

Jan 1, 2016

By A. C. Mollison

In November of 1983 a fire inside the autoclave caused the curtailment of operation of the Kidd Creek pressure leaching facility. Subsequent repairs and recommissioning of the autoclave in 1984 allowed Kidd Creek to increase its production of zinc as originally planned. This paper describes the operation of this process from 1984 to 1988 and details major mechanical work carried out on the vessel in 1.988:

Jan 1, 1990

By Larry M. Southwick

There is much ongoing work in research and development of new processes for the recovery and recycling of met.a.ls and other materials from various waste and scrap streams. Commercialization of such new technologies requires the bringing together and successful execution of a considerable effort involving a variety of activities. These include process conceptualization, research and development, detailed design and construction, and then plant startup and operation. Processes evolve through all of these steps by engineering due diligence, making objective and critical analyses of results, and troubleshooting processing steps to, hopefully, arrive at a sequence that has the best chance to succeed operationally and economically. After a summary review of the above steps, several processes will be described in more detail that provide mostly successful examples of the above procedures. Finally, some observations will be made on areas that will become critical in the near future to the success of new processes for wastes and residues.

Jan 1, 2000

By J. Murdoch Mackenzie

Two commercial nickel solvent extraction plants treating laterite leach solutions and using LIX®84-I have been operated in Australia. These circuits employ similar extraction chemistry but differ in their leaching and stripping operations. An alternative process involving elements of both can be conceived. The preparation of the feed solution to solvent extraction plays an important role in nickel extraction using LIX®84-I and the special features of manganese removal and cobalt oxidation in the preparation of the PLS are discussed. This paper compares these three circuit configurations with special reference to the extraction and reductive stripping of cobalt, the transfer of zinc and copper to the strip aqueous, ammonia transfer and sulfur transfer. The potential degradation of the organic and remediation using re-oximation is discussed. Keywords: Nickel, Solvent Extraction, Oxime

Jan 1, 2004

By J. A. Holmes

Due to varying and complex mineralogy, the flotation tailings from the Chingola Concentrator have, for some years, contained upwards of 0.4% acid soluble copper. In 1968, an investigation was initiated, to determine a method for recovering this acid soluble copper. This initial investigation concluded with a recommendation to install a leach-solvent extraction-electrowinning plant at Chingola, to treat up to 900 000 tonnes of material per month, for an additional copper production of some 4 500 tonnes per month. The process consists basically of six stages :- Materials reclamation handling and preparation, acid leaching in air agitated pachucas, solid-liquid separation by countercurrent washing in thickeners, solution concentration and purification by solvent extraction, copper recovery by electrowinning, and residue neutralisation and disposal. This paper describes the development of the main parameters for design of each of the six sections, and gives details of the final plant design. Problems encountered in commissioning and initial operations are commented on, particularly insofar as they indicated any errors or misjudgements in the design. The choice of materials of construction is commented on in some detail.

Jan 1, 1976

By Feng Chen, Lirong Chen, Yufeng Guo, Wenjie Weng, Tao Jiang

"In this paper, the carbonthermal reduction behavior and the influencing factors of Panzhihua ilmenite under the condition of carbon-burdened were systematically investigated. The results show that the ilmenite forms into titanium nitride during the reduction process at 1200 °C under the condition of carbon-burdened. Carbon-burdened is beneficial to the reduction of iron oxide, but less favorable for the growth of iron grain.IntroductionThe titanium ferrous resources are very rich in Panzhihua-xichang area, accounting for about 38.85% of the world's proved reserves [1]. However, TiO2 grade of this kind of ilmenite is low and calcium magnesium content is high, it generally requires preconcentration to titanium-rich material—titanium slag or synthetic rutile.Chlorination process is an advanced method for production of titanium dioxide, which should takes high quality titanium-rich material with low content of calcium and magnesium as raw materials (the content of MgO and CaO are less than 1.0%). Ilmenite in Panxi area, however, contains high calcium and magnesium; it is not suitable as a raw material for chloride process. Methods of producing titanium-rich materials which have been applied in industry are electric smelting, various acid leaching and reduction rust [2-5]. There still exist some problems such as CaO and MgO removed not thoroughly, low resource utilization, high energy consumption and environmental pollution."

Jan 1, 2012

By R. Padilla

In most of the Chilean copper and gold concentrates, arsenic is present mainly as enargite, Cu3AsS4, which at the conventional roasting or smelting temperatures decomposes liberating arsenic as gaseous compounds. The objective of this investigation was to study the decomposition reaction of enargite in an inert atmosphere in the range of 500 °C - 750°C. The results obtained indicated that the decomposition begins at about 525 °C. Two distinct regions in the temperature dependence of the decomposition rate were observed: a low temperature region between 525 °C to 650°C and a high temperature region between 650 °C to 725 °C. The X-ray diffraction analysis suggests that the decomposition of enargite occurs through the formation of intermediate tenantite, according to the following sequential reactions: 4Cu3AsS4(s) ? Cu12 As4S13(s)+ 3/2S2(g) Cu12 AS4S13(s) ? 6Cu2S(s) + 2As2S3(g) + 1/2S2(g) The decomposition kinetics was analyzed by using the model for a topochemical reaction of spherical particles: 1-(1-X) 1/3 = kt, which represented well the data. Apparent activation energies of 113 kJ/mol and 60.5 kJ/mol were found for the low and high temperature regions, respectively.

Jan 1, 1999

By Kenji Morinaga, Hiromichi Takebe

"Ge-S binary glasses in the range 57 to 90 at %S at 0.5 to 3 at %S intervals were prepared by a conventional melting technique using fused quartz ampoules as melting containers. Impurities contaminated during preparation process are evaluated by IR spectroscopy. The causes of impurity contaminations are discussed. Density data in a systematic series of Ge-S glasses is demonstrated. IntroductionSulfide glasses are of particular interest for new laser and nonlinear optical materials in the near-infrared and infrared regions [1]. Sulfide glasses have the features of low-phonon-energy and high refractive index with moderate rare-earth ion solubility. The low-phonon-energy is favorable for the reduction of nonradiative rate for the emission of rare-earth ions. The high refractive index results in a high radiative-rate and in a high third-order nonlinearity. However, impurities may degrade the superior optical properties of sulfide glasses.In this work Ge-S glasses were prepared by a conventional melting technique. Impurities contaminated during the preparation process are evaluated and their causes are discussed for future improvements. The measured densities of Ge-S glass samples were compared with the results of previous studies [2], [3]. Ge-S glasses have some favorable properties for practical .applications including non-toxicity, good thermal and chemical stabilities."

Jan 1, 2000

By Jitka Jandová

In this study, hydrometallurgical processing of waste ZnO flue dust arising during zinc removal from galvanized low-alloy steel sheets was investigated on a laboratory-scale to obtain electrolytic zinc. The flue dust was separated from flue gases, generated during heating waste galvanized steel sheets in an electric furnace under air atmosphere at temperatures of about 1000oC. The dust, comprising tetragonal ZnO and insignificant amounts of SiO2, was contaminated by Fe, Mn, Pb, Al, Mg, Pb, Cu and Ca. The dust was leached in 0.5 and 1.0M H2SO4 and/or in 20 and 30% NaOH at different temperatures and different liquid-to-solid ratios to determine the optimum conditions leading to the highest possible selectivity of leaching and efficiency of Zn extraction in minimum time. The subsequent electrowinning process was performed with refined zinc sulphate leach liquors and/or with untreated zinc caustic solutions. Zinc sulphate leach liquors were purified using a combination of a hydrolytic pH-controlled precipitation, cementation and carbon refining. Effects of operational variables on Zn electrowinning have been studied for both sulphate and caustic electrolytes. The conventional plate-plate electrowinning cell has been explored in this study. Comparison of results obtained for both zinc electrowinning from acid sulphate and alkaline solutions is presented contribution.

Jan 1, 2003

By Keizo Uematsu, Satoshi Tanaka, Zenji Kato, Nozomu Uchida

"A novel technique is developed and applied to evaluate the binder segregated at the· surface of granule. Compressive strength of each granule was measured directly with a micro-compressive instrument. The relation between compressive characteristics and the amount of binder was discussed quantitatively.IntroductionCharacterization of granules is essential in the production of ceramics, since they govern the structure of green compact and thus the structures and properties of ceramics. However, there is no research to clarify the relation between the strength of granules and structure of granules, especially of binder segregation at granule surface. We develop a novel technique to determine the binder concentration in the granules by the iodine method. In this study, we measure yield strength of granules directly and discuss the relevance between compressive characteristics and the concentration of binder.ExperimentalGranules were prepared by spray-drying of aqueous slurry of commercial alumina (AL160-SG1. Showa Denko, Tokyo, Japan) and PVA (PVA 105 Kurare, Japan). PVA. concentration in granules was 1.1, 1.5 and 2.3 wt%. The inlet and outer air temperatures were 200 and 95 °C , respectively. Iodine-potassium iodide solution was prepared by dissolving iodine (0.15mol) and potassium iodide (0.15mol) in diluted water (50ml). A saturated boric acid solution was prepared by mixing boric acid powder with a diluted water."

Jan 1, 2000

By Terry C. Cheng

The Akita Hematite Process is currently the only hydrometallurgical iron removal process producing saleable iron by-products in the zinc industry. In this study, McGill University and Akita Zinc Co. have worked together into elucidating the basic precipitation chemistry of the process from the standpoints of hematite product quality and prevailing precipitation kinetics. This work determined that hematite is produced under the applied conditions (T = 195?200oC,PO2 = 103?414 kPa) directly without prior formation of basic ferric sulphate and transformation of the latter to hematite as thought originally. The rate-limiting step responsible for the long retention time (~180 min) was found to be either the re-dissolution of ferrous sulphate according to the batch reactor studies, or the slow hydrolysis of the remaining ferric sulphate according to the continuous reactor studies. Another interesting contrast between the batch and continuous reactor data was the degree of sulphur contamination (1.5 vs. 3.8%, respectively) and the specific surface area of the product (10 vs. 30 m2/g, respectively). These differences in addition to the co-precipitation of SO4-containing phases such as jarosites, alunite, and anhydrite were attributed to the significantly higher supersaturation level prevailing in the industrial continuous autoclaves that yields highly aggregated sub-micron hematite crystallites contaminated with chemisorbed sulphate ions.

Jan 1, 2003

By J. P. Ibáñez

The uptake of copper from extremely dilute aqueous solutions by alginate in the form of protonated dry alginate beads was investigated. Barium was used to cross link the alginate forming the beads. The effect of various experimental parameters such as pH and metal ions concentration on the uptake of copper were studied. The uptake was strongly dependent on the Cu-bearing solution pH up to a value of 4.5. A removal of 100% o was achieved when the initial concentration of copper was as low as 8.0 mg/L. The maximum uptake, i, e., the loading capacity, was found to be 167 mg of copper per g of beads. The mechanism governing the removal of copper was found to be ion exchange between protons of the alginate beads and cupric ions of the solution. For this ion exchange process a molar ratio, d[H+]/d[Cu2+], of 2.0 was determined. EPMA-EDX analysis of the Cu-loaded beads showed a uniform distribution of the ions throughout the structure of the alginate, regardless the solution pH. This may suggest that this sorbent material is a porous ion exchanger having high permeability and capacity. The uptake of copper and of the heavy metals cadmium and zinc by this sorbent is compared.

Jan 1, 1999

By Chuan-fu Zhang

The fibrous precursor can be obtained by coordination precipitation process, using oxalate, cobalt chloride and ammonia. XRD pattern of precursor precipitated at pH=9.0 is different from that of ß-CoC2O4?2H2O precipitated at pH=1.0 which indicates that the precursor powders are one type of cobalt complex. According to the results of element analysis and IR spectra, it can be inferred that the composition of the precursor is [Co(NH3)x]C2O4?H2O(x=1.2?..6) formed by the coordination reaction at pH=9.00 in the Co(II)-C2O42--NH3-NH4+-H2O system. It?s found that the fibrous cobalt powders greatly inherited the morphologies of the precursors. Many factors could affect the formation of the fibrous cobalt precursor powders, such as the initial Co2+concentration, pH value and so on. The SEM images show how they influence the morphologies of the precursor powders. By adding proper surfactant, the dispersion of the precursor powders would be improved. At last, the final product-fibrous cobalt powders which are about 0.3~0.5min size and 40~60 in aspect ratio were produced by thermal decomposition of fibrous cobalt complex at 400~500°C in the weak reducing atmosphere.

Jan 1, 2006

By Rikiya Kamezawa, Rudiono, Manabu Takeuchi

"Schottky type solar cells based on phthalocyanine (Pc) thin films were fabricated, and their photovoltaic performance was investigated in various ambient atmospheres. Most of cells prepared in this study showed a good rectification and photovoltaic effects in the visible wavelength region. The introduction ofN02 gas into the measuring chamber was confirmed to increase the current both in dark and under light illumination. However, chemical reaction between the Al electrode and N02 formed some oxide and deteriorated the Schottky barrier, resulting in an increase in cell resistivity. SF 6 gas also showed similar effects on the cell performance.IntroductionPhthalocyanine is one of the typical organic semiconductors, which shows high photoconductive sensitivity in the visible to infrared region. Today, several kinds of metal phthalocyanines are used in electrophotographic photoreceptors. In addition, application of phthalocyanines to solar cells have also been trying by many workers [1, 2]. Many efforts have been made for improving performance of phthalocyanine solar cells by modification of device structure [3, 4], doping by dye or pigment [5, 6] and incorporation of metal clusters [7]. It is known that electrical conductivity in phthalocyanine is increased by adsorption ofNO2 [8, 9]. We tried to improve photovoltaic performance ofphthalocyanine solar cell by adsorption ofNO2. This paper describes the influence of N02 adsorption on the photovoltaic behavior of phthalocyanine solar cells."

Jan 1, 2000

By Laurentiu Nastac

"The importance of investigating solute redistribution during the unidirectional solidification of multi-component alloys is broadly discussed in the literature. A previously developed analytical model that was experimentally validated for Al-Cu, Sn- Bi and Fe-Si dilute binary alloy systems is used in this article to study in detail the solute redistribution, the liquid/solid interface stability based on an extended transient constitutional undercooling criterion and the size of the initial transient region during the unidirectional solidification of Ti-6-4 and Ti-17 alloys. A comparison between Ti-6-4 and Ti-17 alloy systems with respect to interface stability and the size of the initial transient region is also provided. The effective partition coefficients of the alloying elements in these alloys were determined based on specially designed experimental measurements.IntroductionThe importance of investigating solute redistribution during alloy solidification is broadly discussed in the literature [1-5]. One of the relevant applications of this study would be the mathematical modeling of equiaxed and columnar solidification of multicomponent alloys. This includes the instability of the solid/liquid interface. There are several mass and heat transfer processes that involve the calculation of solute redistribution during directional solidification such as industrial directional solidification processes, continuous casting, remelting processes, Czochralski crystal growth technique, floating zone techniques, etc."

Jan 1, 2012

By A. F. Otero

During the electrowinning (EW) of copper significant quantities of highly toxic vapors (acid mist) are produced due to the liberation of oxygen at the cathodes. Acid mist affects the health of operators, the environment and plant infrastructure. Acid mist can be decreased to acceptable levels by a combination of physical means (e.g. ventilation, plastic spheres over electrolyte) and chemical surfactants that decrease the surface tension of the electrolyte, modifying the way oxygen bubbles burst at the surface of the electrolyte. However, only few chemical surfactants are compatible with electrolytic applications, and they are not always used due to their high costs. This paper describes the application of a novel surfactant of natural origin (commercial name Mistop®) to suppress acid mist in copper EW process. Mistop® contains triterpenic saponins derived from the Chilean quillaja tree Quillaja saponaria Molina. The product is non-toxic, and poses no risks to the environment or to EW operators. Mistop® was tested at a laboratory, pilot plant and industrial scale in the world?s largest copper EW production plant at Radomiro Tomic (RT), CODELCO, Chile. At a Mistop® dosage of 8-9 ppm, acid mist decreased below the value accepted by Chilean regulations (< 0.5 mg/m3). At this dosage, Mistop® represents and economical alternative to chemical surfactants, and it is currently industrially used at RT.

Jan 1, 2003

By Guo Jun

In this study, BaTiO3 ultrafine particles surface-modified with stearic acid were synthesized by the hydrothermal method in a system of BaCl2-TiCl4-NaOH. The effects of NaOH/TiCl4 molar ratio, Ba/Ti ratio and time on structure and morphology of BaTiO3 ultrafine particles were investigated experimentally. The formation mechanism of different crystalline BaTiO3 particles was discussed, and it is considered that in a hydrothermal system, the main factors determining BaTiO3 crystalline are H+ replacement of Ba2+ causing H+ deficiency and anatase growth units involving in crystal growth, which clogs the axial channel for Ba2+ transference. By means of increasing the alkalinity of system and barium content, H+ deficiency and involvement of anatase growth units in crystal growth could be effectively controlled. The results show that when molar ratio of NaOH to TiCl4 is 9 and ratio of Ba to Ti 1.5, and time 8 hours, high purity tetragonal BaTiO3 ultrafine particles with a narrow grain-size distribution and nonpolar surface are obtained at 240oC. The particles have excellent flowability, which is ascribed that the surface polarity of barium titanium powder modified with stearic acid is changed and the interaction between the particles is weakened.

Jan 1, 2006

By Ilkka V. Kojo

This paper gives an overview of the primary copper smelting business during the years of flash Smelting in the light of various projects taking into account the sustainability of copper production. Also the future challenges of copper smelting are addressed with special emphasis on the environment. Flash Smelting connected with either Peirce-Smith converting or Flash Converting offers the most economical and environmentally friendly alternatives for the smelting of normal and lean copper concentrates. For rich copper concentrates the feasibility of Outokumpu Direct Blister Flash smelting is, understandably, beyond compare. When the total investment costs for building a smelter and acid plant are considered, it is clear that Flash Smelting is the more feasible option compared to bath smelting. Reduction of equipment and operating cost is further achieved by the LUREC-process developed by Outokumpu Technology for operating plants with SO2-contents up to 25 % by volume. As an example the Kennecott-Outokumpu Flash Converting Furnace (FCF) has been in operation at Kennecott Utah Copper for 10 years and has achieved excellent results both environmentally and production vice. The FCF treats the entire output of the Kennecott Flash Smelting Furnace and has excess converting capacity. Furnace life, initially projected at two to three years, is now projected to be more than 5 years. It is likely the life will be essentially the same as a well-operated Flash Smelting furnace.

Jan 1, 2006

By C. O. Bounds

The magnetic properties of (NdDy)15Fe78B6 sintered magnets have been evaluated using powder prepared by Inert gas atomization. The atomized powder had a particle size distribution from 1 to approximate 1000 microns. The as atomized powders have been sieved into, coarse, intermediate, and fine fractions; magnetic properties were evaluated for the as produced powder and each fraction. A B, of 11.7 kG, a Hci of 11.0 kOe and a BHmax of 32.5 MGOe was -obtained on a sintered magnet made from the as-atomized powder. The magnet made from coarse powder exhibited a slightly higher B, of 12.1 kG, while that from fine powder showed a decrease in B, to 11.2 kG. Hydrogen decrepitation has been utilized to study its effect on the magnetic properties. Finally, cast ingots with a definite columnar structure have also been used to compare the magnetic properties of magnets of the same nominal, composition but of different alloy preparation process. Hydrogen decrepitation does not appear to improve the magnetic properties of magnets made from thin cast ingots. However, it does show a significant improvement in the Hci of magnets made from the atomized powders. Possible causes for the differences in the magnetic properties on magnets made from each process have been discussed in the paper.

Jan 1, 1992

By Esperidiana A. B. Moura, Michelle Gomes, Cordelia M. F. Escanhoela, Francisco R. V. Diaz, Angel Ortiz, Rene R. Oliveira

"This work evaluates changes in morphological, mechanical and thermo-mechanical properties of electron-beam irradiated HDPE/nanoclay and HDPE/Piassava fiber/nanoclay. Material samples irradiated with 100 and 200 kGy using a 1.5 Me V electron beam accelerator (room temperature, presence of air) were submitted to tensile, flexural, and HDT tests. MFI, SEM and XRD analyses were carried out. Correlation between properties was discussed. Results showed that incorporation of piassava (Attalea funifera Mart) fiber and nanoclay, followed by irradiation represented significant gain in thermo-mechanical properties. Changes in surface morphology and reduction in MFI were observed. In conclusion, it may be claimed that the incorporation of piassava fiber in small size particles and nanoclay in the HDPE followed by electron-beam irradiation effectively improved the polymer properties and led to materials with superior properties suitable for several industrial applications.1. IntroductionIn recent years, the preference for using natural fibers instead of synthetic ones in polymer composites has been growing significantly. In Brazil, due to the great diversity of woody and fibrous plants of our forests, a vast potential of natural fibers is found, presenting good mechanical strength properties, chemical and biological stability, fire resistance, abrasion resistance, shear strength and lightness, among other which may contribute to the development of new materials for different applications such as automotive, aerospace, construction, food segment, cosmetics and others [ 1]."

Jan 1, 2013