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By Nobuaki Sato

The electrical conductivity, k, of pure and sodium doped sulfur melts was measured with and without ultrasonic waves at temperatures ranging from 140 to 340° C by the two probe method using an ultra high resistance meter. The II: value of the pure sulfur melt with irradiation jumped at around 170°C by an order of 102 after which it monotonically increased from 10-5 to 10-4 (omega) 1cm-4 with an increase of the temperature. The addition of the sodium metal to the sulfur melt was found to cause a larger jumping in the II: value. The II: value increased with the increase of Na proportion in the melt. For a 10 mol% Na doped sulfur melt it was as high as max. ~30 (omega) 1cm-1 above 180°C under the irradiation of ultrasonics.

Jan 1, 2003

By Stein Tore Johansen

Some ferro-silicon fumaces have heat-recovery equipment. Here, the recovery of electric energy from the off-gases can be increased by increasing the off-gas temperature. This is easily done by reducing the amount of air which usually is mixed into the off-gas to cool the gas mixture. If the off-gas becomes too hot problems with severe fouling or clogging of the gas channels? close to the fumace is observed~ The result is irregular stops to clean the off-gas channels. The paper focuses on the nature? of the clogging phenomena and some of the ways to avoid clogging. A detailed experimental study was carried out at the Elkem Thamshavn Plant. Theoretical studies were performed to understand the particle deposition, turbulent multiphase fluid flow and off gas combustion in the off-gas channels. The study has resulted in reduced clogging.

Jan 1, 1992

By Stein Tore Johansen

Some ferro-silicon furnaces have heat-recovery equipment. Here, the recovery of electric energy from the off-gases can be increased by increasing the off-gas temperature. This is easily done by reducing the amount of air which usually is mixed into the?off?gas to cool the gas mixture. If the off-gas becomes too hot problems with severe fouling or clogging of the gas channels close to the furnace is observed. The result is irregular stops to clean the off-gas channels. The paper focuses on the nature of the clogging phenomena and some of the ways to avoid clogging. A detailed experimental study was carried out at the Elkem Thamshavn Plant. Theoretical studies were performed to understand the particle deposition, turbulent multiphase fluid flow and off gas combustion in the off-gas channels. The study has resulted in reduced clogging.

Jan 1, 1992

By Nobuaki Sato

The electrical conductivity, k, of pure and sodium doped sulfur melts was measured with and without ultrasonic waves at temperatures ranging from 140 to 340'C by the two probe method using an ultra high resistance meter. The k value of the pure sulfur melt with irradiation jumped at around 170°C by an order of 102 after which it mouutuniocally increased from 10-5 to10-4 A' 1 cm-1 with an increase of the temperature. The addition of the sodium metal to the sulfur melt was found to cause a larger jumping in the K value. The k value increased with the increase of Na proportion in the melt. For a 10mol% Na doped sulfur melt it was as high as max ~30 A 1cm -1 above 180 C under the irradiation of of ultrasconics.

Jan 1, 2003

By L. A. Neumeier

The Bureau of Mines, U.S. Department of the Interior, is investigating the feasibility of partitioning complex sulfide minerals to simpler sulfide .phases by sulfldation reactions. Such partitioning can afford opportunity to improve selective extraction of mineral constituents of value. This report describes initial research involving sulfidation partitioning of chalcopyrite concentrates. Small chalcopyrite samples were sulfidized with elemental sulfur in glass capsules sealed after evacuating and backfilling with helium, by heating for 1 to 24 h at specific temperatures in the range of 250° to 500° C. which extends from below to above the boiling point of sulfur (-445° C). Above the boiling point of sulfur, the overall reaction with adequate sulfur (13.9 wt pct of CuFeS2) is 5CuFeS2 + 4S g ? Cu5FeS6 + 4FeS2.

Jan 1, 1989

By Hiroyuki. Fukuyama

The pseudo-binary phase diagram of the cuspidine (3CaO2?SiO2?CaF2) - CaF2 system has been studied by electron probe microanalysis (EPMA) and X-ray diffractometry (XRD). To prevent fluorine loss in the form of a HF gas by a reaction of CaF2 with water vapor at elevated temperatures, the equilibrium experiments were conducted with the sample hermetically sealed in a platinum tube. By employing this technique, it was successfully revealed that cuspidine exists as a stable phase and congruently melts at 1684 ± 1 K, and the cuspidine - CaF2 system presents a simple eutectic type of phase diagram, of which eutectic temperature has been estimated to be around 1540 K, corresponding to the composition of 40 mass% 3CaO?2SiO2 - 60 mass% CaF2?

Jan 1, 1999

By Yang Hong-ying, Yu Juan

Electrochemical behavior of natural chalcopyrite in electrolyte solution at pH value of 6.97 was studied by cyclic voltammetry, X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy. The results showed that the electrochemical processes occurred on electrode surface were controlled mainly by the growth of sulfur species at lower applied potentials (<0.35Vvs.SHE), and the oxidative dissolution of sulfur species and the hydroxylation of iron at higher applied potential (>0.45V). The EIS spectra of oxide product layers could be illustrated by the equivalent circuit of Re(QdlRct(QfRf)), and the degree of hydrophilicity for chalcopyrite was higher when the value of charge transfer resistance Rct. was greater. The optimum potential range for the floatation of chalcopyrite in collectorless solution at pH value of 6.97 was between OCP (0.165V) and 0.35V.`

Jan 1, 2015

By M. K. Mohan

Lead recovery from process solutions contributes not only to the conservation of resources but also clean environment. Zeolites are natural aluminosilicates, which finds applications as catalysts and in wastewater treatment. In the present investigation, studies were taken up on the processing of Pb from process solutions by zeolites. Effects of pH of the solution, time and type of zeolite viz. chabazite, mordenite, erionite and clinoptilolite on the removal of Pb from solutions was investigated. Rate of sorption was found to depend on the pH of the solution and about 99 pct. recovery was observed at pH 6. Optimal conditions were established for the maximum recovery of lead from process solutions. Possible sorption mechanisms were proposed. The calculated adsorption constants calculated from Langmuir and Freundlich equations showed that the adsorption of lead on chabazite was strong.

Jan 1, 1999

By Juan Patricio Ibáñez

Separation of arsenic and copper from Cu-As-H2S04 electrolytes by electrodialysis has been investigated at room temperature. The effects of current density and pH were studied. An arsenic-free copper solution was obtained for all the tested conditions. The transport efficiency for copper ions was found to be higher than 98% after 3 hours&apos; test. Transport of arsenic and copper through the ion exchange membranes was increased by increasing pH and current density. Solution pH was found to be a key parameter for the separation process, since it controls the speciation of the ions to be transported and the formation of unwanted precipitates which reduce the global efficiency of the electrodialysis process. The main conclusion is that electrodialysis is a promising technique to be used in separating and/or concentrating ions of interest in copper electrometallurgy.

Jan 1, 2003

By Junji Shibata

Some fundamental studies were carried out in order to produce composite powders comprising of two or three metal salts by using liquid-liquid extraction and to develop the control technology of the particle size. The combination of samarium and cobalt was selected as the two component composite powders. Both stripping and crystallization occurred at the same time by emulsifying the organic phase loading the two metals extracted with Versa tic Acid 10 and the aqueous solution containing oxalic acid. The effect of aqueous pH, oxalic acid concentration and agitation speed was examined on some properties such as crystallization percent, particle size and shape of each metal oxalate powders obtained in this process. The analysis by using EDX showed that the two metal oxalates were distributed uniformly at the same ratio as the organic phase composition.

Jan 1, 2001

By Gregor Kücher

Lack of basic knowledge on the semi-direct recycling methods for hard metals hinders the application on an industrial scale. However, advantages like reduced expenses and lower environmental impact draw interest at future potentials. Consequently, this report aims to offer insight into the influence of varying bulky hard metal substrates during their lixiviation in acidic media with an oxidant. The statistical software Modde 11 assisted in the development of a design of experiments (DOE) for evaluation of the impact of average grain size, binder and tantalum carbide (TaC) content on the leaching characteristics. The other experimental parameters were constant. Among them were temperature, solution concentration and quantity, duration and substrate surface exposed to liquid volume. Eventually, prediction plots and factors of the computed model equation describe the effects of varying substrate qualities on leached binder metal and selectivity.

By M. Jahazi, P. P. Bhattacharjee, K. Chadha

The present work investigated the effect of strain reversal during high pressure torsion on the evolution of microstructure, texture and hardness properties of two different materials with different dynamic recovery behavior, namely, high purity (99%) Aluminum (2N-Al) and Aluminum-Magnesium (Al-2.5%Mg) alloy. In the two aluminum alloys subjected to different routes, the evolution of the ultrafine structure followed same trend. At lower strain level, sub grains with prominent LAGBs network were observed and at higher strains, ultrafine equiaxed grains separated by HAGBs were observed throughout the disk. The texture evolution in monotonically and strain reversal processed 2N-Al and Al-2.5%Mg showed presence of typical torsion texture components at different strain levels. The strength of the components was observed to follow different trends depending on the processing routes.

Jan 1, 2015

By Gervais Soucy, François Quesnel, Pierre Hovington, Wen Zhu, Karim Zaghib, Jocelyn Veilleux

The properties of lithium titanates anodes in Li-ion batteries are highly dependent on their secondary constituents. While their main phase is usually constituted of Li4Ti5O12, significant quantity of lithium titanates compounds of various stoichiometry are often present, due to either the processing, usage or aging of the material. These may go underreported, as many of these spectrums overlap or display low signal in X-ray diffraction (XRD). Samples of nanosized lithium titanates synthetized by inductive plasma were characterized by XRD and scanning electron microscopy (SEM), as they provide a regular yet typical crystallite size and shape including multiple phases. A Rietveld refinement was developed to extract the composition of these samples. Mass balance through further annealing and differential scanning calorimetry (DSC) enthalpy measurements from phase transformations were also used as identification and validation techniques.

Jan 1, 2015

By Ximeng Zhu

In the transpassive region, about 0.4 to 0.8 V (SCE), aggressive oxidation of pyrite occurred. The reaction products in this region were Fe(III) oxide, sulfate ion and partially oxidized sulfur intermediates. The growth kinetics of the reaction product film, resulting from transpassive oxidation of pyrite were studied using chronoamperometry measurement with both stationary and rotating disk electrodes. The effect of electrode rotation speed, solution pH and temperature were examined. Potentiostatic measurements were well correlated by a paralinear rate equation, suggesting the formation of an intermediate passive film, associated with the simultaneous dissolution of the outer layer of the film. Activation energies of 66.17 kJ/mole (15.83 kcal/mole) and 38.67 kJ/mole (9.25 kcal/mole) were obtained for associated parabolic and linear rate constants respectively, at an applied potential of 0.6 V.

Jan 1, 1993

By J. Grogan

Leaching of galvanized steel coatings allows the steel substrate to be used as a zinc-free scrap source to steel and iron furnaces. In this study the behaviors of sulfuric acid leaching solutions are investigated. The ranked significance of the variables are shown to be acid concentration > temperature > zinc concentration. Examination of the leaching mechanism finds the rate-limiting step to be the cathodic hydrogen reduction reaction. This rate is not only influenced by acid concentration, but also by the hydrogen reduction exchange current density. Dezincing leaching rates are improved by taking advantage of the higher exchange current density of the iron substrate versus the zinc coating. This is accomplished in practice by increasing the exposed interfacial zinc:iron surface area through shredding. Also, a leach control mechanism is proposed through online monitoring of the zinc-iron couple mixed potential.

By M. Potesser

After the primary or secondary lead production the bullion lead is remelted and charged into a vessel with following refining process. The removing of arsenic, antimony and tin takes place by salt slags or oxidizing gases like air or pure oxygen. Due to the increasing lead price, Messer Austria GmbH in cooperation with the institute of Nonferrous Metallurgy at the University of Leoben have developed a new process named OXIPOT for the refining of tin, arsenic and antimony. The OXIPOT process is in principle based on purging technology with a ceramic or steel purging device. This leads to an increased retention time of the refining products due to the deeper bath level and an optimized specific reaction volume concerning the bubble size. This paper describes the process, pilot plant, and thermodynamic calculations for the optimization concerning the selectivity of element removal.

Jan 1, 2008

By Dorothée Proffit

Characterization of solids containing cyanides is carried out according to recommendations and standard guidelines. Most of these procedures are based on the analysis of leachates collected either on site or after leaching in the laboratory of samples. Unfortunately, these sole results are often insufficient to identify the source of the pollution. To provide &apos;a more complete characterization of polluted solids, optical and electron microscopy, XRD, Mossbauer spectroscopy, and transmission infrared spectroscopy were combined to analyze leachates and raw or ground samples. This combination of techniques allows the determination of the kind of cyanoferrate complexes are present in the solid state, different from insoluble Prussian Blue, since they do not have the same extraction&apos; behavior. The use of all these techniques to characterize solid samples combined ,to the usual analysis of solutions gives a better understanding of &apos; the cyanide behavior.

Jan 1, 1998

By J. A. Sekhar

Solidification processing/casting is increasingly being adopted as the preferred manufacturing technique for the fabrication of net shaped complex geometry components. Modeling of solidification processes is important both for design purposes as well as for understanding the physics of morphological evolution of the solidification microstructure. A fundamental aspect of such modeling involves the precise understanding? of heat transfer through the two phase solid/liquid region. A scheme to do this will be presented where the nonlinearity of the fraction liquid with change in temperature can be incorporated into the numerical calculations. The importance of properly accounting for the non-linear mushy zone will be discussed. Typical processes like squeeze casting and electromagnetic stirring will be discussed to illustrate how precise modeling of the solid/liquid region can aid in the calculation of accurate heat transfer coefficients for these processes.

Jan 1, 1990

By Xun Zhang, ZhiLong ZHAO, Lifeng Zhang, Huiqing Tang

A two-dimensional gas-solid model has been developed for examination of the blast furnace (BF) performance under hot charge operation. Simulation conditions were obtained from the actual operation conditions of the BF with inner volume of 2500 m3 and molten iron output of 6250 ton hot metal (THM) per day. The simulation results indicate that hot charge operation could change the thermal state of the BF in the region above cohesive zone (CZ) and has little influence on the thermal state of CZ zone and the region below CZ; it could intensify both the indirect reduction of the ore and the gasification of the coke in the region above the CZ. The optimum temperature for hot charge operation is 750 K, under which, a coke rate reduction of 25 kg/THM could be obtained.

Mar 1, 2017

By Claudio Toro, Alex Moyano, Rodrigo Díaz, Hugo Jara, Carlos Caballero, Pedro Morales, Leandro Guzmán

"During 2007, Codelco-Chile carried out industrial tests to validate the Continuous Converting Process in the Teniente Converter of the Codelco Norte smelter.For planning and starting up the tests, a predictive, analytical and dynamic model was developed to support operational decisions. The dynamic model was developed using the METSIM® platform and dynamic data exchange (DDE) to operate smoothly with MS Excel®. The main feature of this real-time model was the on/off-line ability to work and gather data from either the smelter’s PI system® or database, and simulate the operation with or without scheduled events and controls.The main model development aspects, which include thermodynamics, metallurgical and kinetic considerations, slag-type and on-line mass and heat balances of the process, as well as the successful validation of the model, are presented and discussed in the present paper."

Jan 1, 2009