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By Y. Y. Sheng

Plume flows created by gas injection into liquid metals have been studied extensively, however the dynamics of bubbles within the plume have not received adequate attention, particularly for large, irregular bubbles, characteristic of the processing of liquid metals. The present model uses a combined Eulerian-Lagrangian approach in which an estimated void fraction distribution is used to calculate the liquid flow field with a conventional Eulerian scheme. The trajectories of bubbles are then computed in a Lagrangian manner using the estimated flow field, and experimentally measured information on bubble drag coefficients', lateral migration due to lateral lift forces and interaction with turbulent eddies, and variation in bubble size due to break-up. Turbulence in the two-phase zone is modeled with a modified k-e model with extra source terms to account for the second phase which have been recently determined by the present authors. The computed void fraction and turbulent liquid flow field distributions are in good agreement with experimental measurements.

Jan 1, 1993

By T. Ikeda, M. Maeda, K. Mita

Galvanized steel sheet is the major product for the automobile industry. Therefore, automotive recycling results in zinc-containing scrap that should be remelted in EAFs. Naturally, the EAF dust is a very important source of zinc for zinc recycling processes. The thermodynamic properties of the Fe-Zn intermetallic compounds formed on the surface of galvanized steel sheet should be clarified to make clear the evaporation mechanism of zinc; however, there are few reports on these compounds because of difficulties in their synthesis. There are various intermetallic compounds in the Fe-Zn system. We synthesized them at about 673K. A specimen was examined chemically and X-ray diffraction was applied to ensure the formation of intermetallic compounds. Material containing two phases was placed in a Knudsen type effusion cell and the mass spectrum studied to evaluate the vapor pressure of zinc. The thermodynamic property of intermetallics was then evaluated through measured intensity.

Jan 1, 2000

By T. J. White

A synthetic Mineral Immobilization Technology (SMITE) has been developed for stabilizing municipal and hazardous waste incinerator ash. Tailored additives are introduced to the ash in a' first stage that pre-stabilizes all the toxic metal components in non-volatile forms. and in a second pyrometallurgical stage, these are converted to insoluble mineral analogues. It has been found that a combination of apatitie. spinal, anhydrite and monazite can immobilize all the ash components at high waste loading and high density. Typically the stabilized products contain in excess of 50 wt% ash and have densities of 2.5- 3.0 g.cc-1. Toxicity Characteristic Leach Procedure (TCLP) testing has demonstrated that the products well satisfy regulatory requirements. The cost of production and disposal of SMITE waste forms in 2-5 less expensive than. convential methods of solidification/stabilization. This paper will describe the principles of SMITE design for ash stabilization, outline the fabrication procedure, and present comprehensive microstructural and chemical data to validate waste form performance.

Jan 1, 1996

By U. M. Mutnti

In order to meet the stringent market requirements for high purity cobalt, ZCCM commissioned the VIR plant in December 1982. The plant comprises a 4.1 tonne/heat vacuum induction furnace with a rated annual capacity of 2,500 MT of barstock. In the VIR furnace, molten cobalt is held under vacuum at 1600°C resulting in the removal of more volatile impurity elements by distillation. Operations todate have demonstrated that Pb, Zn and Cd have good distillation rates in excess of 95%, leading to cobalt containing 1 ppm or less of the above elements. Removal of other impurities such as Se, Bi is about 65% with the finished product still assaying around 1 ppm of each of these elements. Vacuum refining of cobalt offers an economic route for producing higher grades of cobalt from the type of concentrates and treatment processes available within ZCCM. The consistency of VIR cobalt quality has been confirmed by ZCCM and some of its alloy customers.

Jan 1, 1988

By Peter Brown

The present work involves the study of Chemical Vapor Deposition (CVD) of silicon carbide from the methyltrichlorosilane (MTS) - hydrogen system. A computer program, SOLGASMIX has been employed to calculate the equilibrium compositions of the gaseous and condensed phases in the MTS - H2 system. The results indicate the range of parameters such as temperature, pressure and species concentrations, required to deposit the single phase Sic under thermodynamic equilibrium conditions. A mathematical model for describing the transport phenomena and the rate of deposition of Sic onto a thin rod in a vertically-oriented hot-walled CVD reactor has been developed. Exper iments were conducted using the same operating conditions as those used in the model in order to validate the mathematical predictions. The predicted rates of deposition were found to be in good agreement with those obtained experimentally. The model can be used to study the effects of various operating parameters on the rate of Sic deposition on a fiber.

Jan 1, 1992

By Mahesh C. Jha

Molybdenum, a major refractory metal, is widely used as an alloying element in steels and superalloys to improve their corrosion resistance, physical properties and mechanical strength, particularly at elevated temperatures. The current worldwide production and consumption is estimated at about 130,000 tons contained molybdenum per year. Molybdenum occurs in nature as molybdenite mineral and is recovered by a flotation process as a primary concentrate at molybdenum mines and as a byproduct concentrate at copper mines. The concentrate is roasted to a technical-grade molybdic oxide (tech oxide) in multiple-hearth roasters. About 80 percent of the tech oxide is sold, as such or after conversion to ferromolybdenum, for addition to iron and steel. The remainder is further refined to pure oxide and molybdate chemicals that are used in the manufacture of catalysts, specialty chemicals, molybdenum metal and superalloys. This paper discusses the various steps in the extractive metallurgy of molybdenum, from flotation of sulfide concentrate to reduction of pure oxide to molybdenum metal.

Nov 26, 1999

By Ray D. Peterson, Garry G. Blagg

"Molten aluminum is routinely transported hundreds of miles to customers in large ""over-the-road"" crucibles. This is especially common for aluminum recycling organizations handling scrap and by-products. Receiving the aluminum in a molten form can save the customer time and money since in-house melting costs and capital equipment can be avoided. Additionally, the alloy can be on specification and nearly ready to use for the casting operation.A number of transport crucible designs are currently in use. The specifics of each design are based on the needs of the customer, the equipment used at both the producer and the consumer, and over-the-road transportation constraints. Crucibles are designed to maximize carrying capacity, and refractory life while minimizing heat flow and dead weight. These conflicting demands place difficult design criteria on the design engineer.This paper will review the basic advantages and disadvantages associated with molten metal transport, give examples of the design restrictions and examine several types design of crucibles currently in use."

Jan 1, 2000

By Pekka Parvinen, Saija Luukkanen, Pentti Pirkonen, Väinö Hintikka, Hannu Sekki

In the study was developed a new method for the treatment soils contaminated by polychlorinated dibenzodioxin and dibenzofuran. The method is based on attrition of soil so that the contaminants absorbed on the particle surfaces are liberated with the fine fraction formed in the attrition process. Same the attrition process produces active surface which can absorb the free contaminants. Before starting the remediation process must be decided the limit value under which the residual concentration must lie. Then in the laboratory is performed an experiment in the base of which is determined the grain size level; material under which much be removed together with the contaminant. In the real sample has been found that after the attrition the limit value 0.5 ng/g (I-TEQ) is obtained when the fine under 0.1mm fraction (20% of the original soils amount) is removed together with the contaminants 96% (original level 10 ng/g; 100%).

Jan 1, 2008

By M. Pineau, G. A. Monteith, M. Laliberte, G. Houlachi

Conventional physico-chemical treatment methods, either hydroxide or sulfide precipitation, can hardly achieve a high removal of selenium from the liquid effluents which can be generated in some metallurgical operations. In weak acid solutions, selenium exists mainly as anionic species (selenite Se03-2 and selenate SeCV2) which, therefore, cannot precipitate as metal hydroxide or metal sulfide compounds. At the same time, neither selenite nor selenate form stable precipitates with the common cations (Ca, Mg, Fe, etc.) that are typically used in water treatment. At Noranda Inc., CEZinc Division in Valleyfield, Canada, the introduction of new discharge requirements for effluent toxicity initiated a R&D program which resulted in the full-scale implementation of a new treatment method for selenium removal. The goal of this paper is to present this new method which is now being patented by CEZinc. The process chemistry will be presented along with pilot-scale developments and full-scale operational results.

Jan 1, 2000

By H. Roberts, C. Hassall

The opening years of the new millennium will be characterised by the closure of many lead and zinc mines because of reserve depletion. However, weak commodity prices through the second half of the 1990s have slowed project evaluation and have made it difficult to raise finances for the development of new mines required to replace lost output and to meet increasing demand for metal in the future. Growth of lead and zinc demand will be determined by the pace of global economic activity, especially in the emerging economies. How rapidly demand grows will have a key bearing on the possible shortfall in mine output and the response of prices to the implied tightening of metal supplies early in the new millennium. These issues are the focus of a discussion of the critical lead and zinc supply developments which will unfold post 2000, taking into account project lead times and the role that recycled metal plays in meeting market demand.

Jan 1, 2000

By Ximena Massone

Chile is the most important copper producer in the world and the mining sector plays a key value in its economy. However, at present the country does not have a satisfactory set of regulations about closure and restoration of mining operations. In our country many mining operations will, in the near future, shut down their activities, therefore, it is of utmost importance to elaborate and enforce a set of regulations to prevent risks and to protect the environment. The present study is focused on reviewing and analyzing the existing national regulations about the closure of mining operations and preparing a comparative analysis with other international regulations of countries with mining experience. The final results of the study will be a legal proposal to regulate the closure of mining operations in Chile, aiming at minimizing the potential environmental adverse impact, internalizing the social costs by the relevant operators and defining all aspects of liability for the environmental damage.

Jan 1, 1999

By J. L. Bill

The capacity of the Mount Isa Mimes Limited Copper Smelter was expanded in 1998 from 180,000 tomes per year of anode copper to 265,000 tpy. It is based on the innovative Copper ISASMELT technology, which currently treats concentrate at up to 184 tph. Increasing lance-air oxygen enrichment increased the ISASMELT furnace feed rate from 102 to 184 tph. The increased feed rate was achieved without any modifications to the ISASMELT furnace. The first refractory campaign following the upgrade lasted for two years. Future campaign lives of four years or more--without water cooling-are possible. Other Copper ISASMELT furnaces are operating in the U.S.A., Belgium, and India, with additional smelters under construction in China and Germany. In addition, Lead ISASMELT furnaces are operating in the U.K. and Malaysia. The paper discusses the performance of the MIM Copper ISASMELT furnace and the Copper Smelter since the expansion, including operating data and refractory performance.

Jan 1, 2002

By Toshiharu Hayashi

We prepared the water dispersed with Au particles ranging from 10 to 20 nm size by a novel wet chemical synthesis; generating seeds of Au cluster by adding a borane dimethylamine complex into chloroaureic acid (gold salt) solution, and then growing simultaneously with aminoalcohol included in the solution. As-prepared Au nano-particles with chemical surface modification were found to have some attractive performances, i.e., showing a high dispersiveness in an aqueous solution in a long time, sintering nano-particles at low temperature, and having low resistivity in the film prepared from nano-particles. In the case that smaller Au nano-particles were removed from as-prepared colloid, especially, Au thin film formed on the surface of Si plate showed the excellent value of 7.0x10-6ohm cm (reference peculiar resistance: 2.35x10-6 ohm cm).The sintering temperature was dependent on the elimination of 2-aminoethanol that modified on the surface of Au nano-particles.

Jan 1, 2006

By L. Y. Zhang

The current status of metal hydride alloys for NiMH batteries was systematically reviewed. Extensive application-oriented research and development has successfully made the NiMH battery an important part, with growing potential, among rechargeable batteries. The rare earth based metal hydrides (AB5) have been considered the best alloy material for use in the negative electrode in NiMH batteries. However, being in demand for high performance electronic markets, the still young NiMH industry is facing serious technical challenges in developing better products. Among all the efforts to respond to the challenges, advanced AF3, alloys are in great demand: the capacity enhancement race requires new or improved alloys possessing higher volumetric capacity; price competition mandates MH materials with low cost; high performance under severe service environments calls for alloys with high corrosion resistance when subjected to electrochemical cycling; and finally, high power service requires the negative electrode to deliver current at high rates.

Jan 1, 1997

By Yoshio Waseda

A laser flash method has been applied to obtain the thermal diffusivity values of Zr55Al10Ni5Cu30 alloy in the liquid, glassy, crystallized and supercooled liquid states. The electrical resistivity of this particular alloy was measured in the glassy, and crystallized states by a direct current four probe technique. A specific heat of Zr55Al10Ni5Cu30 alloy was also determined by a differential scanning calorimeter in the glassy state. On the other hand, thermal diffusivity values for two alloys of Zr60Al15Ni25 and Zr65Al7.5Cu27.5 were measured in the crystallized and liquid states. The thermal diffusivity values of three Zr-based alloys in the liquid state are summarized in the linear equations with positive temperature dependency and it is noted that the lower the thermal diffusivity values of Zr-based alloys at liquidus temperature, the lower the critical cooling rate to obtain metallic glass phase becomes. The thermal diffusivity values of Zr-based alloys were compared with those of Pd-based alloy case. These results suggest that thermal diffusivity of alloy liquids might be an indicator of the glass-forming ability of Zr-based and Pd-based alloys.

Jan 1, 2006

By W. L. Dalmijn, E. A. Schokker, N. Fraunholcz, P. C. Rem

Many processes developed for the mechanical processing of Automotive Shredder Residue (ASR) suffer from high processing costs. We offer a distinct concept for low-cost mechanical processing still allowing high value-added recycling of the recovered materials. The basic idea behind this approach is to produce saleable pre-concentrates at the lowest possible costs that can be further processed in existing separation facilities. Our process includes screening, size reduction and magnetic separation. Preliminary studies showed that fibers in ASR are magnetic due to adhering rust particles allowing separation into a fiber fraction and a non-magnetic rigid fraction by high-intensity magnetic separation. The fiber fraction is most suited for thermal processing. The rigid fraction mainly consists of plastics and rubbers with up to 10 wt.-% of non-ferrous metals, some inert material and copper wires. This fraction is very well suited for mechanical processing by, e.g., sink-float separation in existing metal separation plants. The non-metal fraction can be processed further to recover the plastics and rubbers. The process proposed in this study is expected to be substantially cheaper than full thermal processing. In addition, as it mainly relies on existing separation facilities, it can be applied in the short term.

Jan 1, 2000

By Jeaneth S. Benedetto

The physical and chemical processes developed for recovery of uranium and phosphor from phosphoro-uraniferous ore bodies consists of three basic steps: concentration of the phosphate bearing uranium by flotation, chemical dissolution of the concentrate by wet phosphoric acid and extraction of uranium by solvent. In this process two products are obtained: 1) uranium and 2) phosphoric acid. The purpose of this work was to develop technological know-how of phosphoric acid purification though an extraction of P2O5 by solvents. It was investigated by two lines of research. In the first one the uranium was extracted before the phosphoric acid purification. In the second, the phosphoric acid was extracted before uranium recovery. The comparison of the two processes is shown in this paper. Experimental work was developed on a laboratory scale to select and optimize the process variables. After the laboratory study, the research of extraction and stripping was continued on a pilot scale in pulsed perforated-plate columns in order to investigate the main operational and process conditions. The first phosphoric acid extraction experiments showed good results using a raffinate sample obtained from the uranium extraction process. It was possible to obtain a high purity phosphoric acid.

Jan 1, 2003

By N. Lohja

Metallurgical industries are generally big producers of solid residues of various kinds. In contrast with the past where environmental sensibilities were not so elevated and the accumulated mass of these residues were not considerable, these days the solid residues are everywhere scrutinized among others in term of their harmful environmental impact and as possible materials for valuable elements extraction or secondary utilisation. As a case study, the present paper gives an overview of the solid residues discharged by the metallurgical industry in Albania for the last tens of years. The results of two monitoring study on the solid residues of copper, iron and ferrochromium producing industries are also summarized. The first deals with the origin, quantities and chemical composition of these residues and the second one with the impact of harmful ingredients of these residues in the environment. Some methods for the processing of these solid residues are also proposed in order to ensure a clean environment and to make not just possible but also economically viable their secondary utilisation. This work is part of a bigger cooperation project among local institutions and foreign expert companies such as Flogen Technologies Inc and other in various countries that will not only monitor the situation but will also develop appropriate technologies for treatment of these specific residues.

Jan 1, 2006

By R. Upadhyaya

Aluminium alloy matrix cast composites have been synthesised by incorporating fine graphite powders (0.5 - 20 µm size) and chopped carbon fibres (6.5 pm P). 3-6 mm length) by liquid metallurgy technique. Incorporation of these second phase materials exceeding 6-8 wt% invariably resulted in agglomeration of the dispersoids and sometimes leading to even total rejection. It was found that small additions of mischmetal (1-3 wt%) during dispersion resulted in better incorporation without much agglomeration of the dispersoid as evident from the macro and micro structures of the composites. Further, the additions of mischmetal increased the volume of the effective incorporation of the dispersoid even to the extent 50- 60%. The mischmetal addition results in a significant increase in the power factor of the stirrer motor indicating an apparent increase in the viscosity of the system. The higher viscosity of the melt increase the shear transmission conditions within the melt during stirring thereby breaking the agglomerates of the dispersoids. The increased viscosity of the melt seems to be due to the formation rare earth - aluminium inter metallics precipitation, as observed in the metallographic studies, thereby making the process a "pseudorheocasting? technique. A provisional patent has been filed based on this work.

Jan 1, 1989

By Tracy Morris, Weldon Read, Luis Navarro

"Bismuth is a recognized contaminant in the electrolytic refining of copper that can render many cathodes to be outside ASTM standards and unsuitable for copper rod and other downstream products if not carefully controlled. This paper portrays the performance of Molecular Recognition Technology (MRT) for bismuth removal at the Amarillo Copper Refinery (ACR) and describes how the highly selectivity gel has been successfully used to achieve good bismuth removal and how many pit falls and draw backs have been overcome.IntroductionASARCO operates one of the largest copper refineries in the world at Amarillo, Texas. The main feed for this refinery is produced at the Hayden smelter in Arizona. During the operation of this smelter a variety of metals are carried as impurities in the copper anodes because of the diversity of concentrates and residue products used as raw materials in the smelter feed mix. Even though the impurities are concentrated enough to be detected at the smelter, it is difficult to remove them completely. A simple way to control impurities at the smelter is to minimize the addition of material with a high concentration of impurities to the charge in order to reduce the output of this metal species. All this leads us to have a ""refinery problem"" [1,2,3]."

Jan 1, 2012