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By Antoine Allanore, Guillaume Lambotte, Bradley R. Nakanishi

Current industrial methods used for rare earth element (REE) extraction involve: 1) ore enrichment, 2) separation of rare earth oxides (REOs), 3) chlorination or hydrofluorination, and 4) individual electrowinning of REEs from a molten halide electrolyte. The complexity of REE extraction is inherited from their electronic configuration. Recently, molten oxide electrolysis (MOE) has been used to produce reactive metals directly from their oxides, e.g. titanium. As a single-step alternative to processes 3) and 4), or laboratory has investigated rare earth extraction by MOE. A key challenge is to find a molten electrolyte more stable than REOs. One possibility is to use binaries of REOs directly as a solvent. We have, therefore, developed two experimental approaches for studying molten REOs at temperatures exceeding 2200oC. The present work reports the most recent experimental results obtained with La2O3-Y2O3. Those promising results demonstrate potential for operating with molten REOs and refine the underlying materials challenge for electrodes to enable metal recovery.

Jan 1, 2015

By A. J. van der Zeeuw

The use of SME 529 in the extraction of copper from acidic liquors and of copper and nickel from ammoniacal solutions, is illustrated with results of laboratory and bench scale mixer/settler experiments. Special features of SME 529 are its high loading capacity and the ability to keep the complexes dissolved in the organic phase up to quite high concentrations.

Jan 1, 1976

By Bart Blanpain, Muxing Guo, Bin Yang, Fei Wang

An experimental investigation of the precipitation behavior of the Dy2O3 containing slag during cooling was carried out in this work. The slag with composition 45 wt% SiO2—49 wt% CaO—6 wt% Dy2O3 was equilibrated at 1673, 1773 and 1873 K for 24 h in an argon atmosphere, and then quenched in water to determine the phase relations. The composition and microstructure of the equilibrated phases of the systems were determined by EPMA/WDS. The precipitation behavior of the REEs containing phases during cooling was studied by using an in-situ confocal scanning laser microscope (CLSM) observation technique combined with an infrared imaging furnace heating (IIF). Data resulting from this work aims to support further investigation on separation of rare earths from metallurgical slags.

Mar 1, 2018

By D. Tait, M. A. Halim, V. I. Lakshmanan, R. Sridhar

Rare earth elements (REEs), nickel and cobalt find their use in developing strategic materials and their demand is consistently increasing in the world while the extractable ores of these metals are gradually depleting. Process Research ORTECH Inc. (PRO) has developed innovative mixed chloride leaching processes for the recovery of REEs from alumino-silicate ores, and nickel and cobalt from laterite ores. The addition of magnesium chloride in hydrochloric acid enhances the activity of the hydrogen ion by orders of magnitude, which permit rapid leaching rates at moderate temperature and atmospheric pressure, along with high metal recovery. Innovative solvent extraction process steps are used for the separation of these metals from pregnant leach solutions. PRO’s processes also produce value added by-product of high purity iron oxide and recycle chloride lixiviant to the leaching stage. This paper describes the leaching and separation reaction mechanisms and potential process flowsheets.

Mar 1, 2017

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 L. G. Wiseman

The raw materials processed, highlights of technology used, and products produced at INCO's Copper Cliff Nickel Refinery in Ontario, Canada, are described in this paper. INCO's Bessemer matte separation process yields various nickel and copper products and intermediates. The latter presents the main supply of raw materials for the Refinery. Key features in the Refinery are Top Blown Rotary Converters and the INCO Pressure Carbonyl (IPC) process. Process improvements made since the commissioning of the Refinery in 1973 are also discussed. The Refinery produces a variety of nickel products, including nickel powders. Residue after carbonylation presents an important intermediate enriched in precious metals and cobalt that serves as feed to downstream operations for recovery of the residue's metal values. Also discussed are detection, measurement and control procedures which ensure safe operation.

Jan 1, 1988

By Lamar S. Todd

The direct production of metal from a sphalerite concentrate is an attractive route for primary zinc. A series of operations and conditions have been selected to efficiently cause the following overall exothermic reaction. The process uses a continuous circulation of molten copper for material and energy transfer between the unit operations. Sulfide concentrate is reduced with an excess of superheated copper to make a copper alloy and white metal. The alloy is stripped of volatile metals under vacuum and some metals can be separately condensed. The residual copper and the white metal are fed into a copper converter to be blown with oxygen for desulfurizing and the superheated copper is recycled. The paper will include a detailed material flow sheet for the process, discussion of the operating conditions of the individual units, behavior of minor elements, and zinc quality.

Jan 1, 1999

By Xiao Long, Ting Wu, Lilong Zhu, Qian Wang, Shengping He

"During the continuous casting of peritectic steel slabs, mould fluxes with high crystallization capacity are usually chosen for improving slab surface quality. However, the lubrication condition of casting shell also could be deteriorated. Since precipitation of crystals within liquid slag film can change the composition and property of liquid slag over solid-liquid slag film interface region, its impacts on continuous casting process also are not clear. In order to clear this phenomenon, an experiment method was put forward, and mould fluxes for peritectic steel slabs continuous casting were selected and examined. The results reveal that after crystals have been separated, the crystallization capacity of leftover liquid slag increased with different levels, which could deteriorate the lubrication condition of casting shell and cause a series of problems. Thereby, mould fluxes with high crystallization capacity at beginning for heat transfer control and then weaker after crystallization should be considered in the future.IntroductionIn the continuous casting of peritectic steel slabs, contradiction between heat transfer control and slab shell lubrication by mould fluxes has been treated as a key problem for maintaining a smooth manufacturing process [ 1]. Strong and uneven horizontal heat flux over the meniscus region will cause uneven solidification of casting shell, especially for peritectic steel slab with enormous volume change caused by phase transition. All of those could cause surface defects like longitudinal crack [2-4]."

Jan 1, 2013

By László I. Kiss, Verena Mackowiak, Alexandre Perron, Dominic Toulouse, Alicia Liedtke, Sándor Poncsák

"Bubbles play a very important role in different metallurgical applications like for example in electrowinning. During heterogeneous nucleation, the maximal size of the bubbles growing at the nucleation sites as well as the nucleation frequency is determined by the so-called detachment condition. Detachment occurs when the external forces acting on the bubble exceed the retaining forces along the solid-gas-liquid triple interface line. The phenomenon depends strongly on the shape and orientation of the solid surface and on the nature and strength of the external buoyancy and drag forces. In the present study the detachment conditions of bubbles from downward facing horizontal and inclined plates were studied experimentally under the effect of gravitational and hydrodynamic forces. The results show the deformation of the bubbles under the effect of the external forces and the detachment conditions as function of the bubble volume.IntroductionIn heterogeneous nucleation bubbles are generated at the so-called nucleation sites along the solid-liquid interfaces. They continue to grow there and after they reached a certain size they detach from the solid surface and leave the nucleation site. This scenario is well known both in boiling and electrolysis. During the growth period a stable equilibrium exists between the forces that retain the bubble at the nucleation site and the forces that try to remove it. This equilibrium evolves with the increasing volume of the bubble to the point when the detachment forces overcome the retaining forces.The life of a single bubble generated by heterogeneous nucleation can be divided into two periods separated by the detachment - or in other words by the departure - of the bubble: first the growth at the nucleation site and then the movement away. The knowledge of the detachment conditions makes possible the determination of the maximal volume of the bubble at the nucleation site that, in tum, makes possible the determination of the nucleation frequency. This is why so many researches have been directed toward the clarification of the details of the bubble detachment in the past decades. The equilibrium between the attaching and separating forces depend on the presence of body, surface and flow induced forces in the liquid, on the geometry and orientation of solid surface, on the properties of the solid-liquidgas system etc."

Jan 1, 2004

By Batric Pesic

Solvent extraction of nickel and cobalt from the real leach solutions was studied by using a novel extraction system. The extraction system was a mixture of 2,6-bis-[5-n-nonylpyrazol-3¬y]] pyridine (BNPP) and dinonylnaphthalene sulfonic acid (DNSSA). The BNPP represents a novel molecule, which was designed and synthesized in our laboratory. Real solutions for the study were prepared by leaching of two different cobalt-nickel bearing concentrates, cobaltite [CoAsS] concentrate from Blackbird Mine, Idaho, and siegenite [(Ni,Co)3S4] concentrate from Missouri Lead-Belt. The major strength of the system was the selectivity of extraction toward nickel and cobalt from iron containing solutions. Other metals such as Mn, Mg, Ca, Al and As were not extracted. Due to the irreversibility of copper extraction, its removal from solution was required prior to the extraction of nickel and cobalt. Zinc was not as strongly extracted (i.e. its stripping was readily achieved) as was copper . Flowsheets for the recovery of nickel and cobalt were also developed.

Jan 1, 1997

By Jannie S. J. van Deventer

Geopolymers are novel engineering materials with the potential to play a highly significant role in the transformation of the construction materials and building products industry in the push towards sustainable development. These materials are formed by activation of industrial aluminosilicate waste materials such as coal ash or blast furnace slag with alkaline solutions. Geopolymers derived from coal ash can exhibit superior mechanical properties and chemical stability when compared to ordinary Portland cement (OPC). The use of waste-based geopolymers can also result in significant (up to 90%) reduction in carbon dioxide emissions when used in cement replacement applications. In addition to the formation of conventional pre-cast products, these high performance mineral binders are ideally suited to use in the encapsulation of mine tailings, immobilization of heavy metals and back-filling of mines due to their chemical stability and resistance to acid attack. A key attribute of geopolymer technology is the robustness and versatility of the manufacturing process; it enables products to be tailor-made from a range of raw material sources (waste and/or virgin) with specific properties for a given application at a competitive cost. Despite these key technical and environmental attributes, it is the ability to add significant value to coal ash or and/ or metallurgical slag waste streams which drives the commercial development and uptake of the technology.

Jan 1, 2006

By Larry Hopkins

The molten metal circulation pump has become a staple for melting aluminum in reverberatory furnaces. The forced convection that is created in the melt efficiently provides circulation while dramatically improving melt rates, lowering fuel consumption, extending refractory life, and providing metallurgical homogeneity. Two metallurgical guidelines that are important to many casthouses are molten metal inclusion levels and hydrogen gas content. In order to improve molten metal quality, furnace and casting practices must 'manage these molten metal defects, Today specialized in-line degassing and filtration equipment is used downstream of the furnace to accomplish these tasks. In contrast, the molten metal gas injection pump has metallurgical contact time in the process for hours during the charging/homogenization cycle. The qualitative benefits of employing a gas injection pump to "pre-clean" are outlined and discussed against historical empirical information obtained with alternate methods. Further, a recent study quantifies the merits of this gas injection technique as an effective molten metal quality improvement tool. Specifically, the effects on inclusion level as determined by PoDFA?, gas content as determined by A1SCAN? sampling and alkali metal content as determined by spectrographic analysis are examined in relationship to various gas feed compositions and flow rates.

Jan 1, 1995

By E. Fregeau-Wu

The major obstacle in recycling steelmaking slags to the blast furnace is their phosphorus content. Removal of the phosphorus, which is primarily associated with the silicate and phosphate phases, would allow for greater recycle of these slags for their iron, manganese, and lime contents. Calculations show that separation of the silicates from the oxide phases would remove nearly 90% of the phosphorus from the slag. The variable grain size of the as-received slag made liberation by fine grinding difficult. Therefore, slow-cooling experiments were undertaken to improve the grain size distribution. The grain size distributions were determined using in-situ image analysis. The samples were ground to their apparent liberation size and high gradient magnetic separation was used to separate the magnetic oxides from the nonmagnetic silicates and phosphates. Liberation analysis and modeling was performed on selected separation products for discussion of benefication characteristics.

Jan 1, 1995

By Veena Sahajwalla

The cupola furnace is a coke-fueled shaft furnace used as a primary melting unit in iron foundries. Control of chemical composition of the iron tapped from the cupola is a key factor in productivity and quality control. In an effort to develop a control model for the cupola, a fundamental approach based on physical and chemical principles has been taken to describe the melting process. The behavior of oxidation of the solid charge in the stack of the cupola has been studied. Sulfidation of the charge materials by sulfur-bearing components released to the furnace gases from the coke has been described. Carburization of metal droplets of iron and of steel in separate molten streams has been characterized. Finally, reactions with alloying elements in the hearth (well) of the furnace have been defined. These reactions have been described in a computer-implemented model developed to predict the composition of the iron tapped from the cupola. The model has utilized the thermodynamics and kinetics of the oxidation, sulfidation, and carburization reactions, including temperature and physical aspects, in the various zones of the melting unit. The model predictions have been compared favorably with operating results.

Jan 1, 1992

By L. J. Friedman

Smelter operating and environmental requirements demand high on-stream time (high reliability) from the primary smelter sulfur retention device - the sulfuric ?acid plant. The key to reliable smelter sulfuric acid plant operation is the gas cooling and cleaning system. Problems in the gas cleaning system cause corrosion, plugging, equipment failure, etc - plant down time, in the contact section of the plant. The last fifteen years have seen major changes in gas cleaning system design _to the current standard of brick lined venturi scrubber, packed gas cooling tower with plate type liquor coolers and lead or plastic tube precipitators, The current? design offers improved' impurity scrubbing along with increased reliability. in addition, a number of alternate gas cleaning systems have been offered Chemetica LAB System; Monsanto DuPont D:Jna-Wave Syatem1 Lurgi venturi scrubber with lead star gas cooler. This paper will review the design and operating advantages, disadvantages, and risk of the standard gas cleaning system and compare it to the alternate systems. _

Jan 1, 1992

By Vince Newberry

Alcan Rolled Products at Oswego, New York, commissioned Recycle II during May of 1995. Recycle II is an advanced technology UBC recycling facility designed to meet the most stringent environmental standards enforced to date in the United States, particularly with respect to NO, and particulate emissions. This paper addresses the exacting requirements and strategies of Alcan's Recycle II project andThorpe Technologies' design considerations and solutions for the supply of environmentally favorable melting furnace and delacquering systems. The furnaces are equipped with low NOx regenerative burners and furnace pressure and hearth gas flow controls designed specifically for processing the hearth gases through baghouses. The delacquering system is a new generation Apros concurrent flow unit designed for low NOx emissions.

Jan 1, 1995

By Michael S. Moats, Daniel Kim, Shijie Wang

"The behavior and deportment of lead, arsenic, antimony and bismuth are critical in producing high quality cathode by copper electrorefining. A critical review of research related to these elements is presented along with a comparison to industrial data, where appropriate. These elements exist predominantly in the anode as complex oxides along die grain boundaries. Upon dissolution, Group 15 elements report both to the electrolyte and slimes while lead essentially enters the slimes. The deportment of the Group 15 elements appears to be influenced by several chemical interactions which are discussed. The effect of these elements on floating slimes and anode passivation is reviewed. Under normal electrorefining conditions, lead, antimony and bismuth are thought to enter the cathode through the encapsulation of slime particles. The literature indicates that arsenic enters the cathode predominately by electrolyte entrainment. Finally, areas for future research regarding these elements are presented.IntroductionControlling lead, arsenic, antimony and bismuth is critically important for the production of high quality cathode in copper electrorefining. The reasons for this are twofold. First, ASTM Grade 1 Cathode specifications [1] for these elements are low, as listed in Table 1. Second, they can affect the efficiency of the electrorefining process (e.g., through passivation, current efficiency, slime processing)."

Jan 1, 2012

By Shadia J. Ikhmayies

The SnO2/CdS/CdTe thin film solar cells were fabricated on glass substrates by using the spray pyrolysis (SP) technique for the deposition of the SnO2 and CdS layers and vacuum evaporation for the CdTe layer. The transmittance curves were used to investigate the interdiffusion in the two interfacial regions SnO2/CdS and CdS/CdTe by taking the first derivative of the absorbance as a function of wavelength. The appearance of new bandgaps around the bandgaps of SnO2:F, CdS:In and CdTe layers is a strong evidence on the interdiffusion in the two interfacial regions and/or the formation of quantum dots.

Jan 1, 2010

By C. G. Bastos Andrade, F. R. Valenzuela Diaz, S. M. Toffoli

The modification of structural clays by chemical processes is a common method. It usually uses strong inorganic acid attacks, aiming at improving the clay’s properties and applications. Among the applications are its use in clay-polymer nanocomposites, cosmetics, medicines, and bleaching clays. Tests using acid attack to modified Brazilian bentonites were successfully performed and, resulted in significant improvement in the clay properties. This paper discusses the use of a Brazilian bentonite modified by acid attack as bleaching clay. The treated bentonite samples were characterized by XRF, specific surface area (BET) and SEM/EDS. The treated clay exhibited improved bleaching capacity for Brazilian nut oil and other Amazonian oils.

Mar 1, 2018

By Anne Kvithyld

Silicon solar cells, that convert the energy of sunlight into electric energy, are attractive sources of energy. In the production line wafers of solar cells are sliced from a multicrystaline ingot solidified unidirectionally. Recycling scrap from top and sides of such ingots is addressed. SiC and Si3N4 inclusions are a major problem. Scrap from Scan Wafer ASA is melted in a high vacuum furnace at around 1500ºC. The filters, from commercial producers, are C and SiC with 10, 20 and 30 ppi. Characterisation of inclusions before and after filtration, and in the filter itself, is performed by microscopy. Dissolution of silicon in acid and counting of the un-dissolved inclusions is also carried out. In the filter Si3N4 needles and SiC inclusions were identified. The amount of these inclusions in the filtered silicon is much less than in the input. In conclusion, filtration using SiC and C filters in vacuum system in argon atmosphere removes SiC and Si3N4 inclusions from solar cell scrap. Flow of metal through the filters is not a problem. These results are promising with scale-up to industrial application in mind.

Jan 1, 2006