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By Richard S. Kunter

Artech Recovery Systems, Inc has developed a low pressure and temperature? leach process called the "Cashman Process" to extract metals from arsenical flue dusts and residues and fix the arsenic in an environmentally stable form as ferric arsenate (scorodite). The process was pilot tested at Hazen Research in an integrated plant including continuous recycle from August 1989 to October 1989 during which several tons of flue dust were processed. Based on this pilot program, the process was deemed technically feasible and produced commercially salable products. Residues from this pilot program were subjected to a long-term stability test jointly designed by PTI environmental services and the USEPA. The process, its versatility, and the nature of the products is discussed in some detail.

Jan 1, 1992

By Yoshinao Kobayashi

he removal of oxygen from titanium and zirconium is important for use in application because it significantly affects the mechanical and physical properties such as ductility and toughness. However, thermodynamic properties of oxygen in molten titanium and zirconium have not been clarified and the effective deoxidation process of molten titanium and zirconium has not been established. In this study, the standard Gibbs energy of reaction of oxygen and yttrium in molten titanium and zirconium have been measured by a chemical equilibrium technique. Molten titanium, zirconium, and their alloys with aluminum were equilibrated with a Y2O3, A12O3, or Zr02 pellet in a cold crucible. The results are summarized as follows:

Jan 1, 2000

By F. Rivard, L. Rao, P. Carabin

"Advances in thermal plasma torches have resulted in this technology becoming a commercially viable solution for chemical and metallurgical processes. The main advantages of plasma are its ability to control process chemistry and to build small footprint reactors due to its high energy density and reactivity of the free radicals that are produced. This paper focuses on thermal plasmas produced by DC torches and their applications for waste treatment, production of high purity metals, and nanomaterials. Both transferred and non-transferred torches have been used as either a source of heat or as a reagent in various industrial processes. Retrofitting plasma torches in place of fuel oil burners lead to lower operating costs, capital cost and greenhouse gas emissions.INTRODUCTIONPlasma technology has become an ideal solution for many industrial chemical, metallurgical and mechanical processes [!]. Thermal plasma powered systems are typical used for their unique characteristics such as high energy densities, high temperatures, small installation sizes, rapid start-up and shutdown features, controlled process chemistry and use of electrical energy as a heating source resulting in decoupling the heat source from the oxygen flow rate [2]. Depending on the nature of the main plasma forming gas used, thermal plasma systems offer a high temperature heating source coupled with a highly reactive plasma plume rich in free radicals and ions which promote otherwise hard to drive chemical reactions, as well as high heat transfer rates."

Jan 1, 2013

By Dietmar Eifler, Benjamin Jost, Marcus Klein

This paper focuses on the ductile cast iron EN-GJS-600 which is often used for components of combustion engines. Under service conditions, those components are mechanically loaded at different temperatures. Therefore, this investigation targets at the fatigue behavior of EN-GJS-600 at ambient and elevated temperatures. Light and scanning electron microscopic investigations were done to characterize the sphericity of the graphite as well as the ferrite, pearlite and graphite fraction. At elevated temperatures, the consideration of dynamic strain ageing effects is of major importance. In total strain increase, temperature increase and constant total strain amplitude tests, the plastic strain amplitude, the stress amplitude, the change in temperature and the change in electrical resistance were measured. The measured values depend on plastic deformation processes in the bulk of the specimens and at the interfaces between matrix and graphite. The fatigue behavior of EN-GJS-600 is dominated by cyclic hardening processes. The physically based fatigue life calculation “PHYBALSIT” (SIT = strain increase test) was developed for total strain controlled fatigue tests. Only one temperature increase test is necessary to determine the temperature interval of pronounced dynamic strain ageing effects

Jan 1, 2015

By Jay. M. Khodadadi, Josef Štetina, František Kavicka

"With the aid of the proper original numerical model of solidification the instruction for preparation of input parameters for numerical simulation of technological processes, with change of the phase or structure, will be presented. A method of calculation analysis of influence of therrpophysical properties of materials entering the system of casting-mould-cores environment, and also of boundary conditions on the required simulation accuracy will be suggested. For the cast material, the influence of heat .conductivity, specific heat capacity, density and latent heat of phase transformation also has been analysed. For metallic or non-metallic moulding material"" the influence of the see main parameters has been analysed and, furthermore, their combination, influence of thermal conductivity, and of heat storage. The order of influence of all quoted parameters of a casting and moulding material was established. For example heat conductivity in the liquid state is on the last place. From the boundary conditions the -most important influence on the total solidification time and · on the mechanism of forming of temperature field has the ·boundary condition on the casting mould boundary, then follows the boundary condition on the level of a molten metal. The negligible influence has the boundary condition on the mould frame and on the bottom.IntroductionThe original and universal mathematical model of solidification, cooling and heating has been set up and checked, in order to be capable of analysing a one- to three-dimensional steady or unsteady temperature field of the casting-mould-environment system and, namely, of the system as a whole or its arbitrary parts, during any industrial technological process whose individual processes could be solidification, cooling, heating, refrigeration and others, in any sequence or singly. The model enables the simulation of traditional and also non-traditional technologies of casting in foundries, metallurgical plants, forging operations, heat treatment processes, etc. If solidification is not the matter, the metal part of the system need not be called the casting but a component, a block, a forging and the like."

Jan 1, 2000

By Z. R. Llanos

This paper presents a review of industrial and experimental processes for the recovery of molybdenum, vanadium, nickel, cobalt and aluminum from spent hydrotreating or hydrodesulfurization catalysts. Numerous processes have been developed in a laboratory and pilot scale. However, worldwide, there are only four well established commercial facilities currently in operation. The installed capacity of these facilities exceeds the availability of spent catalysts and may be sufficient to assimilate future increases of spent catalysts. Despite liability risks; significant quantities of spent catalysts are still being landfilled. Changing regulations that may affect the future handling and disposal of spent catalysts are also reviewed.

Jan 1, 1995

By D. de la Villa

From 1989 to 1992 Rio Tinto Minera has developed and implemented a productivity program in its Huelva Plant, including Smelter, Acid Plant and Electrorefinery. This Plan was designed in order to increase productivity, reduce emissions and produce a better quality of cathodes. This paper describes investments and operating improvements involved in this project, focusing on Smelter and Acid Plants, and comments the results obtained so far.

Jan 1, 1993

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 M. R. Barkhudarov

Semi-solid metal can be formed into useful products of near net shape and high quality. Use of this method has been limited, however, because of the difficulty of working with metal in the semi-solid state, which has strong shear rate, temperature and time-dependent properties. In this paper we describe a thixotropic model and apply it to the problem of small metal droplets impacting on a flat plate.

Jan 1, 1997

By E. M. Weenink

A proposed alternative to the conventional zinc extraction processes is the flash reduction of zinc calcines. As part of an overall study of this process, the kinetics of single zinc oxide pellets were investigated. Pellets, compacted from Outokumpu zinc calcine (60.9% zinc, 9.6% iron), were suspended in a flow of CO/CO, mixtures and reduced at temperatures between 1000 and 1200°C and atmospheric pressure. The pellet weight loss with time was recorded and analyzed. It was found that the reduction of calcine pellets (0.9 cm height and 1.36 cm diameter) was controlled by chemical reaction. This paper includes an analysis of the experimental results of two previous investigations of ZnO reduction.

Jan 1, 1992

By A. A. Bustos

Four Air Liquide Shrouded Injectors (ALSI ) were installed and operated for over one year in a Peirce-Smith converter at the Falconbridge nickel smelter in Falconbridge, Ontario, Canada. A shrouded injector consists of an inner pipe and an annulus, through which high oxygen enriched air and nitrogen flow, respectively The nitrogen cools the injector and protects the refractory in the vicinity of the injector tip, allowing for substantial increases in oxygen flow rates to the converting reactions. Several injector designs were tested to study the effect of changes in the cross-sectional area and changes in the entrance geometry of the annulus. An optimum design would minimize the injection pressure required for a given flow rate to achieve choked flow conditions at the tip of the injector. The operation of the ALSI was simple and did not require any special care or maintenance, either between blows or between converter cycles. In particular, the shrouded injectors did not require punching, as is the case with conventional tuyeres. In terms of refractory performance, the ALSI, operating at 30-40 % oxygen enrichment, were superior or equal to the conventional tuyeres, which operated at 21-23% oxygen. The results of the demonstration program led Falconbridge Limited to implement the ALSI technology on a commercial scale The paper presents the demonstration program results in terms of gas flow rates, accretion formation, punchless operation and refractory wear.

Jan 1, 1999

By Yuanbo Zhang

Zinc leach residues produced by hydrometallurgical zinc plants contain many valuable elements (zinc, iron, lead, gallium, indium silver, etc), while they have not been utilized effectively hitherto. In this paper, a new process of flotation-reduction roasting-magnetic separation to recover these valuable elements from zinc leach residues is developed on a basis of mineralogy investigations of them. The results show that silver concentrate with grade of 4321.6 g/t and recovery of 80.69% have been obtained, using 1750 g/t Na2S as conditioner, 750 g/t ammonium dibutyl dithiophosphate and SN-9 (assistant collector) as combined collector and 100 g/t terpenic oil as frother, if zinc leach residues with 523 g/t silver are floated at pH = 5.0. When the flotation tailings are subjected to reduction roasting at 1100? for 2 h, the volatilizations of zinc, lead and indium are over 96%. After roasted products are treated by wet-grinding and magnetic separation, the grade of gallium and gallium in the concentrates achieved respectively reaches 1805 g/t and 1536g/t, and the recovery of them is high to 94.67% and 93.20%, respectively.

Jan 1, 2006

By Nicholas S. Lynn

"A new process has been developed to bioleach refractory gold ores to expose the precious metal values using Thiobacillus ferrooxidans bacteria.The ore is hosted in a limestone rock with secondary replacement of carbonaceous and pyritic minerals. Crushing, stacking, bioleaching, rinsing and neutralization have been completed in a 45-day total time cycle. The use of sulfuric acid operation, and concentrated Thiobacillus ferrooxidans population allows the short bioleaching cycle.The ore is then processed using conventional Carbon-In-Leach Cyanide recovery techniques.ABSTRACT ONLY"

Jan 1, 1997

By J. Brent Hiskey

Recently basic concepts of semiconductor electrochemistry and solid-state electronic structure theory have been applied to the dissolution of mineral electrodes. In this paper, fundamental aspects of semiconductor electro- chemistry and interfacial charge-transfer processes are reviewed. Information regarding the electronic and semiconductor properties of chalcopyrite is summarized. The electrochemical response of chalcopyrite in acidic solution is analyzed in terms of initial dissolution processes. The initial charge- transfer reaction involves the consumption of holes. It has been shorn that Fermi level pinning is consistent with observed electrochemical and dissolution behavior. Semiconductor electrochemistry has proved helpful in explaining the formation of intermediate surface films produced during the initial stages of chalcopyrite dissolution

Jan 1, 1993

By K. Ono

A new process for extraction of titanium metal from its oxide is demonstrated. In this process, row material to be reduced is titanium oxide synthesized from ilmenite. The reducing agent is the Ca+CaCI2 two-phase mixture. TItanium is elaborated in the medium consisted of liquid Ca, Caq and solid TI02 at the temperature range 1200 to l300K by means of mixing mechanically the ingredients in the reactor into a smooth paste. Fluidity of the feed which enables continuous scheme depends on the CaCl2 content. The oxygen level of the reduced titanium is the range 500 to 1000 mass ppm varying with the operational conditions. The Ca+CaCI2 reducing agent is taken out from the electrolysis of CaC12 at 11401(, and this CaCl2 is produced by aqueous chemistry conversion using Cl2 gas recycled from the electrolysis.

Jan 1, 2001

By Alexandre Monteiro

Alumina precursor powders can be precipitated from aqueous solutions, using hydrothermal decomposition of urea to deliver base homogeneously to the system. Primary particles agglomerate early in the process, generating a wide size distribution. The presence of a polymeric surfactant such as polyacrylate can suppress or delay agglomeration, reducing particle size and narrowing the size distribution. The stabilization of commercially available a-Alp03 powder with polyacrylate was studied, investigating the effects of polyacrylate molecular weight, ionic strength and temperature. The effect of aluminum concentration, polyacrylate molecular weight and urea concentration on the precipitation of alumina precursors in a sulfate- urea system in the presence of polyacrylate/polyacrylic acid was then studied. The hydrolysis kinetics were followed, and particle sizes were determined. Precipitates were further characterized using energy dispersive spectroscopy. The particle characteristics are discussed in terms of the process conditions.

Jan 1, 1994

By C. Flores

A novel process using solid metals for the direct reduction of more noble metal ions from solvent extraction organics has been developed. Base metals recovery has been the principal focus of investigations to date but feasibility tests have now also been made on galvanically stripping selected precious metals. In this study gold (III) was loaded from an aqueous HAuCI4 .3H20 solution into a mixed organic 40 vol.% TBP, 10 vol. % D2EHPA in kerosene. The direct precipitation of metallic gold from the loaded organic phase using zinc powder and iron, aluminum and copper slabs at 70 °C was successfully demonstrated. The gold reduction rates were relatively fast even though the conductivity of the organic solutions is very low. The reaction rates were studied as a function of the variables zinc particulate size, oxygen and nitrogen atmosphere, water content in the organic phase, organic ratios and temperature. The gold morphology was usually powdery or dendritic in nature but continuous films were obtained in some instances. Activation energies were calculated and possible reaction mechanisms are discussed. In general, the results obtained were very promising and showed that gold can be successfully cemented from selected organic solvents by galvanic stripping using less noble solid metal reductants.

Jan 1, 1995

By C. Landolt

Inco's Copper Cliff Smelter Complex produces some 11 5,000 tonnes per year of nickel and 120,000 tonnes per year of copper. The Smelter flowsheet has changed a number of times over the years. The most recent changes were effected in the mid-1980's in response to new realities in metal markets and heightened awareness about the workplace environment. By 1994, the flowsheet will undergo yet another metamorphosis as part of Inco's SO2 Abatement Program. The paper discusses the improvements implemented during the 1980's and projects the processing in the Smelter through 1994.

Jan 1, 1993

By Di Yang

The influence of high density (104 -105 A/cm2) electric current pulses (70 us duration) and continuous DC (~103 A/cm2) on the flow stress and ductility in tension of a high carbon steel wire were determined at 204°, 427° and 649°C. Electropulsing (100 pulses per second) with an effective current density of 100-200 A/cm2 gave a 10% enhancement in the uniform elongation of the wire at 204°C, but had no effect at 427°C and 649°C. In contrast, continuous DC either had no significant effect on the ductility or gave a decrease. The electropulsing per se decreased the flow stress only slightly at 204° and 427°C, but gave a significant decrease at 649°C. Continuous DC increased the flow stress at all three temperatures. The present results along with those by others suggest that the enhanced ductility by electropulsing and the reduction in flow stress may be further increased by raising the effective current density through increases in either the pulsing frequency, maximum current density of each pulse or pulse duration. This could conceivably increase the reduction per pass during wire drawing or the number of passes between anneals.

Jan 1, 2001

By Shadia J. Ikhmayies

SnO2:F/CdS:In bilayers were produced by the spray pyrolysis technique on glass substrates. The structures were characterized by recording and investigating their transmittance curves, I-V plots, X-ray difractograms (XRD) and by observing their scanning electron microscope (SEM) images. From the I-V plots it was found that the SnO2:F forms an ohmic or quasi-ohmic contact with CdS:In. XRD patterns show the polycrystalline nature of the films and show that there is a small shift in the position of the (200) line of SnO2:F without the appearance of new peaks. The morphology of the structures are compared with those of SnO2:F alone and CdS:In alone on glass substrates.

Jan 1, 2009