Search Documents

By Mike Johnson, Niels Verbaan, David Dreisinger

The Search Minerals Foxtrot project in Labrador is a surface deposit enriched in the highly sought after heavy rare earth elements. Early metallurgical work investigated beneficiation of the rare earth content of the Foxtrot resource using flotation, gravity separation and magnetic separation. The concentrate was then processed by acid baking and water leaching to produce a REE leachate for purification and recovery. The Search Minerals Direct Extraction Process was developed through bypassing the beneficiation process and directly acid treating a coarse crushed ore material prior to water leaching. The result is a simple, low risk technical process for direct recovery. Concurrently, the treatment of the water leach solution was modified to produce a high grade (98.9% total rare earth oxide) product for refining.

Jan 1, 2016

By Mitsutaka Hino

The contents of gangue minerals, such as A1203, P205, crystalline water and so forth in the iron ore imported to Japan tend to increase year by year, Though the increments of such gangue contents are approximately 0.1-0.2 mass%, some problems for the blast furnace operation in ironmaking process have already been reported, In order to clarify the mechanism of harmful effect caused by the small increment of gangue minerals, mainly A1203, on the blast furnace operation, the dripping behavior of FetO-CaO-SiO2-AI2O3-MgO slag from the iron funnel, which simulated the micro-porosity in sinter ore, has been observed with the wide range of basicity, Al2O3, FetO and Mgo contents. The effect of MgO on the dripping behavior of slag has been summarized in this paper, It was found that the addition of 2mass% MgO resulted in large increase of hold-up on the most of the conditions. When FetO content was less than 20mass% and the basicity was lower than 0.8, MgO lowered the hold-up even if the slag contained 10mass% Al2O3. Every slag hold-up showed the minimum at the basicity of less than unity on the conditions of constant FetO and A1203 contents. This trend became remarkable when the slag contained 2 mass% MgO.

Jan 1, 2003

By Jewel Andrew Gomes

Arsenic is considered as one of the toxic materials being controlled by Environmental Protection Agencies in several developed and developing countries. It is found in the nature as constituents of the soil, minerals and also in various organic forms. It enters the air, water, and land from wind-blown dust and gets into water from runoff, leaching, soil erosion and anthropogenically from chemicals used for wood preservation, insecticides, medicine, military purpose, pigments, and electronic circuitries. There are several techniques available for removal of Arsenic, such as coagulation/filtration, lime softening, ion exchange, reverse osmosis, nanofiltration, wet chemical, and electrochemical. Electrocoagulation has been found as one of the most efficient techniques to remove inorganic arsenic with more than 99% efficiency. In this paper, we present our work on electrochemical treatment of both the inorganic and organic arsenic from water using various sacrificial electrode materials, i.e., iron, aluminum, copper, and combination of them. The floc produced by this method has been also characterized using XRD, SEM/EDS, FTIR, and cyclic voltammetry.

Jan 1, 2010

By Shadia J. Ikhmayies

Nanocrystalline CdS:In thin films with particle size in the range (3-36 nm) were produced by the spray pyrolysis technique on glass substrates. The films were characterized by investigating their X-ray diffractograms (XRD), scanning electron microscope images (SEM), transmittance curves and photoluminescence (PL) spectra. The size of the nanocrystallites was estimated from XRD difractograms and then from the hyperbolic band model and the bandgap energies of the nano- particles, which were calculated from the positions of the minima in the first derivative curve of the absorbance. Fine-structured PL spectra confirmed the nanocrystalline nature of the films.

Jan 1, 2010

By Preston C. Holloway

Transformational roasting involves the heating of a material along with specific additives to induce mineralogical changes in the starting material. By controlling the chemical composition, roasting atmosphere, temperature and time of reaction, the mineral transformations induced during roasting can be engineered to control the distribution of valuable, or harmful, metals and to produce new mineral assemblages that are more amenable to conventional methods of metals recovery or to environmentally safe disposal. To date, this type of process has only been applied to the recovery of a limited number of metals, but current research is looking to expand the application of these techniques to the recovery of metals from a wider range of materials. An introduction to these techniques is presented along with preliminary results from their application to metals recovery from zinc bearing wastes, such as zinc ferrite leach residues and carbon steel electric arc furnace dust.

Jan 1, 2006

By Chuanlin Fan

The process of flotation separation and recycling of spent potlining (SPL) was described. On the basis of the laboratory investigations, the effects of influencing factors in froth flotation process, such as grain size, flotation agent dosage, pH value, pulp density, and dissolved components concentration, etc, were carefully studied. And the influence on environment of the process was also discussed. It was found that flotation separation can be used as an environment-friendly method for treatment of SPL residue. Carbon and other compounds (include cryolite, sodium fluoride, calcium fluoride and diaoyudaonite, etc.) from SPL were separated and recycled as flotation products respectively.

Jan 1, 2009

By Joël P. T. Kapusta, Romeo U. Pagador, Noparut Wachgama, Chumnoom Khuankla

"Thai Copper Industries (TCI) is a custom copper smelter and refinery in Rayong, Thailand, with an annual capacity of 165,000 tons of cathodes. It employs the El Teniente Technology as the primary smelting reactor to produce white metal from copper concentrates. The white metal is further treated in Hoboken Siphon Converters to produce blister copper then refined in anode furnaces before being cast into anodes for electro-refining in the on-site tankhouse.Thai Copper Industries is the first copper smelter to install and successfully operate on a commercial scale with the Air Liquide Shrouded Injection (ALSI™) Technology in the Hokoben converters with sonic injection of oxygen enriched air and nitrogen for cooling of the injector tip areas. Following commissioning and the establishment of operating practices, the performance of the Hoboken converters with ALSI™ Technology produced outstanding results. The unique combination of an El Teniente and Hoboken siphon converters, both of which are bath smelting operations, offers very high blowing and oxygen efficiencies. As a consequence, reverts recycling was accelerated with minimal build up on the mouth, end-plates or even below the siphon that is typical in Hoboken converters.These outstanding results in the Hoboken Siphon Converters with ALSI™ Technology helped the TCI Plant reach a production of about 75% of its capacity within four months despite the fact that the TCI staff is quite young and its converter know-how and experience are not yet fully developed."

Jan 1, 2009

By Qiang Zhang

Hybrid composites are fabricated by adding two reinforcements into matrix materials so that the expected excellent properties can be achieved through the combined advantages of short fibers, and different size particles (micron or submicron), which provide a high degree of design freedom. In this paper, hybrid preforms were produced with the different size reinforcement of the Al2O3 particles and short fibers. The Al-Si alloy-based hybrid composites were fabricated by preform-squeezing casting route. The structure and performance of composite materials were studied with the Transmission Electron Microscopy (TEM), and Scanning Electron Microscopy (SEM). The results show that the reinforcements, both particles and fibers, distribute homogeneously in the matrix materials, and the properties of composites are found to improve in comparison with the matrix Al-Si alloy.

Jan 1, 2009

By Vladimiros G. Papangelakis

During the past five years, chemical modelling work at the University of Toronto has elucidated the role of soluble magnesium on the autoclave acidity and has demonstrated why feeds rich in magnesium, and other divalent metals, require more than the stoichiometric requirements in acid to produce a leaching performance comparable to that of low magnesium feeds. This understanding has allowed the calculation of acid additions to the pressure acid leach (PAL) on a less empirical basis. Optimizing acid additions to the PAL confers savings in neutralization costs, ensures high productivity and minimises corrosion problems. Hence, our picture of the solution chemistry inside the autoclave during the PAL process has been substantially improved and is reviewed here. Experimental techniques based on solubility and direct acidity measurements that support the theoretical predictions are presented. Concepts of chemical modelling of electrolyte systems at high temperature and software issues are also discussed. Finally, a better understanding of the solution chemistry at temperature has led to better kinetics models because all metal dissolution and precipitation reactions are acid driven and controlled. . Therefore, reactor modelling efforts by our group are also presented and a reactor model with very good performance, as compared to pilot-plant data, is also made here. Finally, in spite of the above success in PAL solution chemistry and reactor modelling, significant challenges lie ahead in theoretical data gaps and instrumentation; these are also discussed in this paper. Keywords: Laterites, process modelling, pressure acid leach, solution chemistry, chemical modelling, reactor simulation

Jan 1, 2004

By Jiann-Yang Hwang

Microwave heating has been proved an effective method to rapidly heat iron oxide. This offers an opportunity to apply microwave heating in the steelmaking process. The reduction reaction of iron oxide is traditionally achieved at high temperature with reducing gases such as H2 and CO generated from various sources, including coke, coal, and natural gas. This study investigates the differences in iron oxide reduction using conventional and microwave heating under H2 and CO atmospheres. A special microwave thermal gravimetric device was designed and built to facilitate the investigation. With this device, iron oxides can be heated by electric resistance heating, microwave heating, or a combination of methods. The incoming CO and/or H2 also can be preheated to simulate a potential utilization of recovered heat. The iron oxide weight and temperature can be monitored during an entire reduction period. A series of reduction experiments have been conducted. The results are presented and discussed.

Jan 1, 2006

By Christophe Thiébaut

Keywords: Pyrochemistry, Salts Treatment, Distillation The pyrochemical purification of metal generates spent salts. When this metal is an actinide such as plutonium, the slags cannot be discarded and are thus disposed in nuclear facility. In order to handle with these slags, the decision has been taken to reduce stored quantities. The development of a pyrochemical treatment is in progress in the CEA Valduc centre. The feed salt, typically composed of various Pu and Am species contained into monovalent or divalent chloride matrix, is first oxidized to convert the actinides into oxides. Then the chlorides are separated from the actinide oxides by vacuum distillation. Temperatures higher than 750°C for monochloride salts mixture NaCl/KCl and higher than 1100°C for divalent CaCl2 base salts, are required to produce an industrial flow of vaporization. Inactive qualification of the process for NaCl/KCl base salt has been carried out with lanthanide surrogates. Then, a pilot equipment, called distillator has been designed and built for production-scale distillation of NaCl/KCl and CaCl2 oxidized plutonium salts. Industrial flows of vaporization have been obtained with this pilot equipment : about 4 g/cm²/h for NaCl/KCl at 800?900°C and 1 Pa, and more than 1,5 g/cm²/h for CaCl2 base salts between 1000?1200°C at 0.1 Pa. The last step, now in progress, is the integration of the distillator into a glove box.

Jan 1, 2005

By H. Yin, T. Emi

"Advantages of gas/flux injection technology as materialized in the main stay unit processes for steelmaking are depicted covering hot metal pretreatment through secondary refining. Current status of micro-kinetic issues involved in the injection technology are reviewed including gas-in- metal, gas-in-slag, flux-in-metal, metal-in-flux and three-phase dispersion systems with reference to macro-kinetics. Key problems are briefly addressed to further develop injection technology for steelmaking processes.1. FROM PAST TO PRESENTApplication of gas injection to steel industry started in early 1950's when inert gas bubbling via stopper rod, lance, or porous refractory plug was practiced to make the temperature of steel melt in ladle uniform The gas bubbling in ladle was then extended to slightly removing hydrogen ti'om the steel melt tapped from Electric Arc Furnace (EAF) and Basic Open Hearth Furnace (BOH) when vacuum processing facilities were not popular. Later, oxygen gas injection via calorized steel pipe into molten steel bath in BOH Furnace was also put into operation to promote the decarburization to increase the productivity of the process. This line of development has been made in parallel with more profound processes, i.e, top blowing Basic Oxygen Furnace (BOF) for primary steelmaking and side blowing Argon Oxygen Oecarburization (AOD) vessel for decarburizing stainless steels.On the other hand, injection of fluxes into steel bath was first industrialized in Germany in 1960's, Primary objective was to desulfurize steel melt in ladle by injecting CaC2 or CaCrCaO mixture via lance under neutral slag cover with good success. Difficulties in injecting fluxes without clogging and rippling at a desired flux/gas ratio, and durability of injection lance were resolved in due time to bring forth many injection facilities to flourish for versatile refining operation. Top injection of fluxes from main oxygen lance to BOF was also industrialized as LDAC to promote early slag formation. A new process then emerged which injects oxygen gas and fluxes together through concentric annular tuyere, installed at the bottom of the BOE into steel melt. This process, developed in Germany [Oxygen Bottom Maxhutte (OBM)] and brought into maturity in USA (Q-BOP) and Japan in a large scale operation, became the predecessor of the combined blowing (top and bottom blown) BOF which dominates modern steelmaking."

Jan 1, 1996

Sm-Co alloy is a kind of magnetic material with high power and has been applied in modern industry widely. In this study, the wet chemical co-precipitation was developed for synthesis of the Sm-Co alloy oxide precursor. The thermodynamic analysis of the studied system was done to clarify the solution behavior theoretically based on the thermodynamic equilibrium and simultaneous equilibrium. Then, the experiments were done to address the various effects on the wet chemical process, including solution pH, reactant concentration, dispersant, reaction temperature and time, etc. It is found that by precise control of the process, the Sm-Co alloy oxide precursor was synthesized with fine crystallization and special size & size distribution.

Jan 1, 2005

By D. M. Wyslouzil

The fundamentals of dissolving silver and silver minerals are discussed in the following sections: 1) Basic chemical reactions in the silver system 2) Leaching of pure silver minerals 3) Leaching of silver-bearing ores 4) Description of processes The basic chemical reactions of silver are an important guide to the mineral processor or the extractive metallurgist, particularly for systems in which complex formations are balanced against solubilities. The competition of other cations for free ligands can shift the equilibrium to the detriment of silver. Solubilities of pure silver minerals in specific solvents may not be a good indication of the solubility of silver minerals in ores. The abundance of silver minerals which usually appear in a typical ore precludes the selection of a single method that would result in the best extraction of silver from all minerals in the ore. Frequently, the recovery of silver from host minerals requires a destructive pretreatment such as intensive leaching, oxidation with or without elevated temperature and oxygen pressure, or roasting. The transformation of the host or the silver minerals does not always result in a leachable species? and this requires additional treatment before the precious metal can be recovered.

Jan 1, 1990

By M. J. Collins

Direct pressure leaching of zinc sulphide concentrates was started? commercially in October 1980. Continuing research and development studies at Sherritt and feasibility studies for a number of clients have defined various pressure leach configurations for integrattons with existing roast- 1 each operations and for grass roots plants. Existing and potential applications of zinc pressure leaching are discussed.

Jan 1, 1990

By Wenshan Zhang

Three important methods of removing Fe in hydrometallurgy of zinc, manganese, copper, nickel, cobalt and etc are described, including neutralized hydrolysis method, jarosite method and goethite method. The reactions, technical requirements and thermodynamic analysis during Fe removal process are also discussed in this paper.

Jan 1, 2006

By Dale A. Zuck

Recovery of aluminum metal from drosses? is a major factor in the recyclability success story enjoyed by the United States aluminum industry. Today's modern dross processor uses the latest technology to maximize metal recovery at the lowest cost while complying with all environmental laws and regulations. Most dross processors, however, pay little attention to the resulting saltcake, the end residual of dross recyCling, and rely on landfills for .disposition of this material.. The alternative is to recycle the saltcake, but the success of this technology is dependent on the development of reliable outlets for each of the saltcake constituents. This paper discusses the evolution of an aluminum dross oxide processing technology that ,produces an economically attractive source of alumina for the production of portland cement.

Jan 1, 1995

By Finlay Campbell

Nickel laterite pressure acid leach plants and reduction roast plants have had a checkered history in their engineering, construction, startup and operational reliability. Many potential projects have been the subject of detailed studies over the last thirty to forty years but relatively few have advanced to commercial production. Four reduction roast plants are currently operating, an additional one was partially constructed but never completed, and another was started up in 1974 and shut down after 12 years operation. Three acid leach plants have been built and commissioned in the last five years, trying to follow the example of the Moa Nickel plant in Cuba. An additional acid leach plant project is currently on hold, following limited construction work, its future subject to review by the owner because of potential cost over-runs. This paper attempts to discuss difficulties that may be encountered as a project is developed and will address factors which may affect production ramp-up schedule, long term production performance and overall production success. Comparisons are made with ramp-up performance at other large metallurgical plants that employ some comparable unit operations. Keywords: Caron, PAL, nickel laterite ore, ramp-up, reliability, process development, equipment design, step-out, commissioning, startup.

Jan 1, 2004

By Zhuokun Cao

Manufacture of aluminum foams still suffer from nonuniformity and poor reproductively for there is lack of basic knowledge of foaming process. In this paper, carbon fibers are used as novel stabilizing additive for aluminum foams, and the structure evolution of aluminum foams with different fiber content was studied. A laser rangefinder was used to detect the expansion rate of different al foams. Al foam samples are solidified at different foaming time to determine its relative density and cell size distribution. Results indicate that the cell size of foams linearly increases with the decrease of density, and the slope of the line is influenced by fiber content. The relationship between expansion ratio, density and cell size of the foams is discussed. It is concluded that the density of resulting foam is influenced by the rate of gravity driven drainage, and its cell size is determined by expansion ratio and foaming time.

Jan 1, 2010

By Sergio Neves Monteiro

The efficiency by which an applied load is transmitted through the composite structure depends on the strength of the interface between the matrix and the second phase. In fiber reinforced composites, the interfacial shear stress plays a major role in the composite capacity to support the applied load. This interfacial stress can be obtained by means of pullout tests using the fiber embedded to a certain length in a socket of the matrix material. In the present work, pullout tests were performed to evaluate the interfacial shear stress of ramie, a relatively strong natural fiber, reinforcing polyester matrix composites. The general result permitted to calculate a critical length for the ramie fiber embedded in polyester resin. From this critical length, the value of the interfacial shear stress was calculated. An interpretation of this result together with SEM observation displayed a relatively weak bond between the ramie fiber and the polyester matrix.

Jan 1, 2010