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By John Snowberger III, J. Brent Hiskey

The electrochemical dissolution of super alloys containing different amounts of rhenium was investigated. The initial part of the investigation focused on the anodic dissolution of rhenium from second-generation (3% Re) and third-generation (6% Re) nickel based alloys. Exploratory electrochemical tests were conducted to evaluate solution chemistries and to establish fundamental dissolution behavior of the alloys. These included rotating disc electrode (RDE) cyclic voltammetry, linear sweep voltammetry, and chronoamperometry tests. Electrolytes comprising sulfuric acid, hydrochloric acid, and ammonium sulfate were examined. Of these, a 0.1 M HCl solution proved to be extremely effective for electrochemical dissolution of samples of CMSX-4, CMSX-10, and SC-180 alloys. This paper discusses in detail the electrochemical behavior of these alloys.

Jan 1, 2014

By Masatsugu Morimitsu, Tian Zhang

"This paper presents a novel anode for oxygen evolution in acidic aqueous solutions to produce non-ferrous metals by electrowinning. The method to prepare the anode was thermal decomposition of a precursor solution, and the obtained anode consisted of Ru02-based oxide catalytic layers formed on a titanium substrate, in which the catalytic layer contains nano-oxide particles as the active component. The oxygen evolution potential was lower than amorphous lr02-Ta20s coated titanium anodes so that the cell voltage of electrowinning was further reduced with the amorphous Ru02-based electrode.IntroductionElectrowinning (EW) is used to produce high purity of non-ferrous metals, and the primary metal production of copper, zinc, nickel, and cobalt by EW consumes huge electric energy worldwide, which tends to increase with increasing demand of such metals. The reduction of electric energy consumption is a significant issue for electrowinning industry, which means that the cell voltage reduction is needed to realize more energy-efficient EW processes. Another issue is also indicated from environmental perspectives; i.e., an improvement in EW plant environment by eliminating hazardous byproducts and wastes. Such byproducts and wastes include lead oxide, manganese oxide, and acid mist.We have been developing the anodes for energy-efficient and environmentally friendly electrowinning processes [ 1-11]. The development has been successfully done with the invention of the smart anode, MSA TM (Morimitsu Smart Anode) [ 1-5], which has low polarization for the main reaction and high polarization for the side reaction, in which the main reaction is oxygen or chlorine evolution, while the side reaction is the anodic deposition of each or both of lead oxide, manganese oxide, and cobalt oxide. The anode consists of a valve metal substrate coated with amorphous or less crystalline oxide catalytic layers. One of the typical examples of such oxides is amorphous lr02-Ta20s, and the substrate is normally titanium plate or mesh. The most important point of the oxide is that the amorphization or less crystallinity induce the increase in the active surface area only to the main reaction, not to the side reaction, thereby the polarization of the main reaction being reduced.In this paper, we present the smart anode consisting of RuO2-based catalyst formed on titanium substrates for oxygen evolution in electrowinning. The preparation, characterization, and polarization behaviors of the anodes are shown, and the cell voltage data for zinc or copper electrowinning using the anodes are also presented."

Jan 1, 2012

By Moo Eob Choi

The reduction of iron oxide particles by hydrogen is one of the most widely investigated gas-solid reactions. The search for new methods for producing iron by the direct reduction of iron oxide has resulted in a large number of exhaustive studies of the various aspects of this reaction. However, previous studies have largely been done with either pellets or lump ores. Little has been published on the hydrogen reduction of very fine concentrate particles smaller than 37 µm (-400 mesh). The kinetics of hydrogen reduction of fine iron oxide concentrates were investigated in the temperature range of 900 - 1300°C.

Jan 1, 2006

By Ray D. Peterson, Annette Revet

The optimization of secondary aluminum furnaces is critical to the efficient operation of a recycling facility. Since all metal loss occurs in the drosses, physical and chemical analyses of these by-products are valuable diagnostic tools. Dross analyses can provide information concerning total furnace metal recovery efficiency as well as identifying areas for potential improvements. A complete dross analysis is a labor-intensive process that requires significant care both in sampling and performing the analytical techniques. Experiments can be done at a bench- or plant-scale depending on the facilities available. This paper outlines the benefits and information that can be generated through dross studies. Furthermore, several analytical methods are discussed as well as the special requirements needed to gain accurate results. Experimental data from industrial studies is provided to demonstrate the use of dross evaluations for ~ace optimization.

Jan 1, 2000

By Neal Schwartz, Robert De Saro, Richard Rosenthal, Ed Kear

"A Stack Melter has been installed and is currently operating at Lexington Die Casting. The Stack Melter consists of a 1 meter (3 foot) diameter refractory tube, 2 meters (7 feet) high. Specification ingots are continuously fed to the top of the melter and piled to nearly the top. A burner fires through the scrap which melts the lower portion and preheats the upper portion. As the lower portion is melted, it is drawn out and the upper preheated scrap falls to a lower level where it in tum melts. The molten metal is fed to one of two holding furnaces for eventual delivery to a casting machine.The Stack Melter's energy use is approximately 2900 joules/g (1,250 Btu/lbm), resulting in an overall energy savings of about 58%. This energy savings is brought about primarily because the flue gases preheat the scrap and the flue gas temperature is dropped to well under 528°C (1000°F)."

Jan 1, 2000

By Malcolm J. Harrison

The problems associated with the flow control of abrasive slurries and solids laden fluids creates reliability problems in many mining operations. Conventional valves such as pinch, knife gate and plug types cannot always function reliably in such harsh operating environments. Due to the technological advances in the hard coating industry, ball valves can now be produced with internal surfaces protected from the erosive effects of these applications. Pressures well in excess of the capability of conventional 1000 kPa working pressure valves can now be handled reliably. The significant advantages of minimizing down-time and lowering maintenance costs can now be realized with metal seated ball valves.

Jan 1, 1999

By E. S. Geskin

"This paper is concerned with the construction of a formal technique for the selection of a metallurgical technology. Exergy consumption is used as the criterion of process efficiency. Different items of the exergy balance are considered and techniques for the reduction of exergy consumption are determined. The selected techniques of exergy saving enable us to identify processes which should be used at different stages of steelmaking. The combination of the selected processes enables us to suggest a technology for conversion of iron ore into steel products. The selection of this technology narrows the range of further search of metallurgical processes. The paper shows that qualitative thermodynamic analysis can be used as the first step in the design of metallurgical processes. IntroductionThe existing processes for making, shaping and treating of steel enable us to convert the available iron bearing ores into marketable steel products. However, the energy cost of metal production is much higher than thermodynamically required, while the metal properties are much lower than thermodynamically available. Increasing cost and declining availability of energy and raw meterials make the creation of new steelmaking technologies imperative. In recent years, the number of novel processes for the making, refining, and shaping of steel have been suggested and tested. Some found a practical application. However, the tested technologies make up a small portion of the physically available routes for the conversion of iron ore into a marketable product. It is also not evident that the optimal routes have been tested and that the selected technologies are the best among those tested.Although the development of new metallurgical technologies must be based on the experimental and practical information, the number of the alternative routes for the making, shaping and treating of steel, as well as the cost of examining each single route, make necessary the use of analytical techniques for the evaluation of the possible ways of process development."

Jan 1, 1988

By Lei Zhang, Shining Chen, Lina Wang, Pu Liu, Benquan Fu, Jiannyang Hwang

A three-dimensional (3D) electrode reactor combined with Fenton reagent was used for advanced treatment of coking wastewater from secondary biological treatment. Effects of some key factors on total organic carbon (TOC) removal rate were investigated, and the results were compared with those of the common three-dimensional electrode reactor. Experimental results showed that TOC removal rate could reach 51.7%, when optimal operating conditions were as follows: initial pH value 3.5, H2O2 dosage 17.6mmol/L, reaction time 90min and FeSO4·7H2O dosage 3.5mmol/L. Analytical results from UV absorption spectra indicated that the organic substances in the coking wastewater were well degraded by this system, which provided good experimental basis for the practical application of this process in the treatment of coking wastewater. This can be meaningful for the treatment of other kinds of wastewater.

Jan 1, 2015

By Aichun Dou

Au-Sb alloy sample in which the total amount of Cu and Ni is below 25% (wt. %). In practice, Cu and Ni were difficult to be dissolved in sulphuric acid solution by oxidative leaching under the atmospheric pressure conditions, because of the lower concentration of Cu and Ni in the sample. In this paper, pressure oxidation leaching in sulphuric acid system (POLS) followed by hydrochloric acid leaching (HAL) was employed to remove impurities in the Au-Sb alloy. The effects of variables in POLS on leaching ratios of different metals were investigated in detail. Under the optimal conditions: the concentration of H2SO4 is 1.5 mol/L, liquid-solid ratio is 7:1, the amount of oxidizer is 1.2 times of the theoretical amount, leaching time is 4h and leaching temperature is 427K, the leaching ratios of copper and nickel reached up to 99%, antimony, lead and silver were not dissolved in dilute sulphuric acid solution. The residue from POLS was then treated with hydrochloric acid solution in fixed conditions, the leaching ratio of antimony reached over 92%, the grade of gold in the ultima residue was enriched up to 66%.

Jan 1, 2016

By M. Ramprecht, M. Wu, A. Kharicha, A. Ludwig, H. Holzgruber

"The influence of the frequency of AC power supply on the magneto-hydrodynamic during the electroslag remelting process is studied. The focus is on the electrodynamic field and its resulting mechanical effects on the flow and liquid interfaces. The possible influence of the electrochemistry on the droplet formation is qualitatively discussed.IntroductionThe electroslag remelting (ESR) process is a secondary melting technique which can be used for a variety of metals and alloys, provided appropriate fluxes (slags) and melting parameters are employed. The ESR process is presently operating mostly with AC current of about 50 Hz. However for reasons primarily of inductive losses in the electric circuit, furnaces for ingots larger than 1 m, use or are projected to use current of very low frequency (< 5 Hz). Effects of lower frequencies (2.5-5Hz) on macrostructure and non-metallic inclusions were recently studied by Chang [1]. Most of investigations were performed either with DC power or with AC of 50-60 Hz [2-4]."

Jan 1, 2012

By R. T. Jr. Faria, H. Vargas, R. Toledo, S. Cosin, V. P. Souza

"With the purpose of decrease environmental impact, caused by industrial residues (just discarded in the environment) and clay extraction in the ceramic industry, sanitary ware wastes were incorporated into clay. In contrast, it is important to evaluate not only the technological essays but also gases emissions in the ceramic firing process. The pollutant gases emitted in ceramic with residues can be in much larger concentrations than that in a pure clay ceramic firing or, on the other hand, can decrease the pollutant gas concentrations. With the aid of thermal analyses and photo acoustical techniques it was observed that sanitary ware waste can reduce the C02 emission. The gas emissions were shown as in function of firing temperature from 300 DC to 1100 DC. In order to analyze phase transformations during the firing process, clay samples and wastes were both analyzed by x-rays fluorescent chemical analysis and x-rays diffraction.IntroductionResearch works on the structural and physical changes that wastes, mainly industrially produced, cause to the final ceramic product has been rapidly expanding in these last two decades. See, for instance references in [1]. In spite of these examples of a continuous effort to incorporate wastes into clay ceramic motivated by technical and economical advantages, environmental issues are still a matter of concern. However, the gas emission due to the clay firing process and its related atmospheric pollution may be enhanced as a consequence of an incorporated waste [2]. It is known that the firing of clay ceramics in conventional furnaces using fuels such as wood, charcoal, heavy oil and natural gas generates appreciable amounts of gaseous components, mainly carbon dioxide (CO2), carbon monoxide (CO) and methane (CH4). Additionally to the atmospheric pollution, these gas sets could be harmful to the human health and can corrode equipments [3,4]."

Jan 1, 2012

By Milton Syamujulu

In 2004, KCM Nkana Smelter commissioned a 1200 tonne per day flash dryer and associated dry concentrate transport and injection system on the existing Teniente Modified converter (CT) unit. The aim was to upgrade the existing smelting unit, increase copper output and improve energy efficiency. This paper reviews the design, installation and commissioning phases of the introduction of this new technology and also discusses the initial two years of operating results for both the flash dryer and injection system at Nkana.

Jan 1, 2006

By Luis M. González, Guzmánm Guillermo D., Davis Juan C.

"The Teniente converter (CT) of the Ventanas Smelter and Refinery of Codelco-Chile has two tuyeres for dry concentrate injection directly into the melt.The diluted phase injection system can feed 15 to 20 kg of concentrate for 1 kg of air, which creates a very abrasive solid/gas phase. The tuyeres commonly used lasted for about 3.5 days due to the accelerated decay of the shell, and 1.5 hours were necessary for the replacement of new ones in the reactor.Tests were carried out with common shell tuyeres with a tungsten based welding cover, and a life span of 28 days was reached, increasing the Teniente converter operational continuity between 1.5 to 2 %."

Jan 1, 2009

By Akihide Nagao

The behavior of impurity hydrogen that is contained in starting material or picked up during processing has been little investigated up to now. The hydrogen microprint technique is applied to determine the microscopic location of impurity hydrogen during deformation in aluminum without hydrogen charging. Three kinds of pure aluminum of 99.99% are prepared, in which hydrogen content is varied by changing the atmosphere when they are melted and heat-treated. After rolling, tensile specimens with a gage size of 4 x 4 rnm and 0.5 mm in thickness are stamped out from these three kinds of aluminum sheets. These specimens are covered with a liquid nuclear emulsion of silver bromide crystals, stretched by 5,10 and 15 percent plastic strain or fractured, developed and fixed. SEM micrographs reveal a number of silver particles on the slip lines and on the grain boundaries. Also shown is that the more hydrogen present in the specimen, the more silver grains appear on the slip limes and on the grain boundaries. Consequently, it is concluded that impurity hydrogen is transported to the surface with gliding dislocations during deformation.

Jan 1, 1998

By Suleyman Tekeli, Serdar Salman, Bulent Aktas

"The effect of La2O3 content up to 15 wt% on phase stability, sintering and microstructure of cubic zirconia (8YSZ) was investigated. XRD results showed that the specimens containing up to 15 wt% La2O3 were composed of only cubic structure. Also, the specimens doped up to 5 wt% La2O3 revealed no La2O3 peaks, indicating that La2O3 was completely solubilized in the cubic structure. However, when> 5 wt% La2O3 was added, the peak of La2Zr2O7 compound emerged, showing that the overdoped La2O3 was not solubilized in the 8YSZ matrix. The lattice parameter of the 8YSZ slightly decreased with the increasing La2O3 content up to 1 wt% but further increase in the La203 amount resulted in an increased lattice parameter. The comparison of grain size of the 8YSZ specimens with various La2O3 content showed that grain size slightly increased with the increasing La2O3 content up to 1 wt% but further increase in the La2O3 amount resulted in a decreased grain size.IntroductionAt atmospheric pressures, three polymorphic forms of Zr02 are stable at different temperatures i.e. monoclinic, tetragonal and cubic. A high-pressure orthorhombic form of Zr02 has also been reported[l]. The successful production of pure Zr02 bodies is not possible all the time due to the large volume expansion associated with the martensitic tetragonal-monoclinic transformation. This fact restricts the applications of zirconia, in spite of its excellent mechanical and thermal properties. However, the stabilization of the high temperature polymorphs at room temperature as stable phases is made possible by addition of suitable dopants. Fully stabilized cubic Zr02 and partially stabilized tetragonal Zr02 show interesting properties and are widely used as ionic conductors, coatings and gas sensors in solid oxide fuel cells and structural applications[2]. Most frequently used dopants include Y203, CaO, MgO and Ce02, although other oxides, such as those of rare earth elements, can also act as stabilizers of the high temperature structures. The incorporation of aliovalent cations to the lattice, forming substitutional solid solutions, allows to control the concentration of anionic vacancies in the structure. This aspect is particularly important in designing ionic conductors[3], and is also determinant in the stabilization process[ 4]. The process of stabilization with larger ionic radii dopants is rationalized by the crystal chemistry model[ 5], that describes the dopant cations as typical stabilizer when they have larger ionic size, lower charged state and higher ionicity than Zr4+ The ionic radius of Zr4+ is 0.84 Å and that for La3+ is 1.016 Å [6]."

Jan 1, 2012

By Jorge Alberto Soares Tenório, Denise Crocce Romano Espinosa, Viviane Tavares Moraes

"The development of mobile phone technology has increased the replacement of outdated equipments for more modern models, transforming disposal of such devices into a serious environmental problem. Recycling appears as an attractive alternative to minimize the environmental impact of disposing such large quantities. Recycling can be accomplished by treating the printed circuit boards of used mobile phones by using the same techniques used in ore treatments with hammer mill; magnetic separation, electrostatic separation and grain size range. Before performing the recycling process a PCB characterization was performed to identify the fraction with the higher metals concentration/content. This study demonstrated that the electrostatic separation was not the best metals concentration of PCB aiming the recycling, while the non-magnetic residue had presented a more significant metal concentration. Furthermore, after the magnetic separation was possible to separate the following metals: iron and nickel.IntroductionPortable electronic devices have gained increasing acceptance over the last decades. Mobile phones sales in Brazil, for instance, have reached 104 million in 2007, and 128 million in 2008. It is estimated that, around the world, 100 million mobiles are thrown away every year, either because of loss of functionality or because newer models are launched in the market [1,2, 3]. Printed circuit boards in mobile phones are made of many materials, with approximately 83% in weight being metals and fiber-glass, and the balance being plastics pl. Several metals can be recovered from the electronics waste, such as copper, tin, iron, lead, nickel, titanium, aluminium as well as some precious metals such as gold, silver and palladium [4, 5, 6, 7, 8]. Concurrent with the increasing world demand for copper, there average metal content in ores has been decreasing. Economically interesting copper mines used to have 4% metal content, whereas presently, such content is around 1%, i.e., for every 1 ton of ore extracted, only 10 kg are copper [9, 10]. Approximately 33% of printed circuit boards (PCBs) composition is copper, that is, for every 1 ton of PCBs waste, 330 kg are copper [1]. Research in recycling PCB waste focuses on mechanical, electrometallurgy, pyrometallurgical and hydrometallurgical processes [3, 8]. Collecting and recycling obsoletes electro-electronic equipments is very important these days, in order to, not just preserve the non renewable natural resources but also to keep the environment and the population safe from the pollution caused by the toxic materials and heavy metals present in this kind of waste."

Jan 1, 2011

By Ejike Emmanuel, Nwoye Chukwuka, Ogwuegbu Martin, Asuwaji Ayuk, Onyedika Gerald

"Microwave pre-treatment of cassiterite ore prior to leaching was carried out in an attempt to obtain high grade of Sn02 and to conserve the total energy expended during processing. Microwave treatment was selected due to the presence of associated minerals which behaves differently to microwave energy. Studies in this work showed that microwave pretreatment of cassiterite ore can be applied to increase the recovery of tin oxide within 5 minutes of leaching. Microwave treatment of the ore resulted in mineral liberation at all particle sizes. Tin oxide was separated from the major impurities via leaching in potassium hydroxide solution and precipitation, resulting in 98% Sn02 at pH 7.IntroductionIn the nineties, the available techniques used for ore processing and analysis in Nigeria was the solution methods of either alkaline fusion or acid digestion [1,2]. A process in which cassiterite is made acid soluble by reduction to SnO2 , which stabilizes by glass formation and the tin was extracted by leaching the glass with sulphuric acid, followed by electrowinning was reported [3,4]. In another study, Baba et al [5] studied the dissolution kinetics of a Nigerian casiterite ore in hydrochloric acid solution. The effects of acid concentration,temperature, particle size and stirring speed were examined. It was found that the dissolution rates of cassiterite depends on hydrogen ion concentration, H+, stirring speed and ore particle dimensions. These were believed to report low data due to incomplete solubilization of the ore minerals in aqeous medium [6]. Analytical chemists have used microwave heating devices routinely for the dissolution of metals, minerals and various chemical products in chemical analysis [7,8]. It offers faster heating rate and consequently faster dissolution rate than conventional heating. The principle of the dissolution of analytical samples has been applied to the leaching of various minerals contained in an ore or concentrate sample. Some researchers [9, 10] conducted microwave assisted leaching of laterite ores containing oxides of nickel, cobalt, and iron. The metals of these mineral components were converted into their chlorides by microwave heating (1200 W, 2450 MHz, Nz atmosphere) a mixture of the ore and ammonium chloride between l 77°C and 312° C for 4-5 min, followed by water leaching at 80° C for 30 min. Nickel and cobalt extractions were 70% and 85%, and respectively, and are comparable with roasting at 300°C in a conventional rotary kiln for 2 hours."

Jan 1, 2013

By Mikio Kobayashi

Extraction of valuable metals from sulfide ores continues to be a very important, process and so the strict control of discharge of harmful metals in effluents from refineries becomes more important in the future. The recovery methods for heavy metals have been developed. Some metals such as Se and As are still difficult to be removed to very low concentration, although the techniques for recovery and removal for many kinds of heavy metals have already been developed. Especially, in case of Se the recovery system from water with low concentration has not be developed yet, although the WHO decided Se to be harmful for human beings and then the discharge control is under obligation now. In general Se exists as selenite ion and/or selenate ion in aqueous phase and selenite ion is able to be recovered by coprecipitation with ferric hydroxide or by reduction to solid selenium by general reductants. Selenate ion, however, has a strong resistance to conventional treatments. Therefore the new technique for the recovery of Se from water including selenate ion has to be developed. In this presentation the new approach for removal of selenate ion using the reaction in which ferrous ion is oxidized to ferric ion is presented. Selenate ion is reduced to selenite ion during the reaction and then to solid selenium, while ferrous ion is oxidized to ferric ion. The coexistence of activated carbon is very useful to increase the reaction rate. The use of iron powder is also effective and very useful for reducing gel-like precipitates mainly consisted of ferric hydroxide. The concentration of the residual selenate ion is probably under 0.1 ppm after recovering Se by the mentioned-above approach. In addition to the mechanisms of these reactions, the effects of pH, coexistent positive and negative ions, and reaction temperature are also presented. Furthermore the investigation of the behavior of selenosulfate is presented.

Jan 1, 1998

By Jeff M. Kuhn

A new solvent extraction process for the removal of halides from zinc sulphate solution was tested in pilot plants at both a 0.1-L/min scale and at a 3-L/min scale. Teck Cominco?s process is called the HalogonTM process, for which patents are pending. Mixer-settlers were used for the 0.1-L/min pilot scale and two BATEMAN pulsed columns for the higher rates. Pilot testing was performed with commercial zinc sulphate solutions containing variable amounts of chloride and fluoride. Sulphate extraction was also controlled and deleterious halides were loaded and stripped into a form suitable for disposal. The engineering aspects and economics of this solvent extraction process for halide removal are also reported.

Jan 1, 2003

By T. Kozuka, K. Sassa, S. Asai

"A new atomization process is developed. The principle of this process is completely different from that of conventional processes. This process uses electromagnetic energy induced by direct electric current and direct magnetic field instead of kinetic energy produced by fluid impingement or disk rotation.Experimental work of this process was carried out using pure tin, and it was found that the crucial factor for a stable operation is the contact state of molten metal with the electrode. In order to control the condition, a delay time controlling unit was developed and combined with this process. It is noticed that this controller works well to produce uniformly sized particles.A linear relation between the impulse and the momentum of atomized particles is found by use of experimental data and is explained by theoretical analysis.IntroductionIn atomization processes prevailing in metal powder technology, kinetic energy is currently employed for atomizing molten metal. That is, molten metal is broken into small particles by other fluid (e.g. water, argon gas, etc) or by impinged upon a rotating solid disk. This splashing process is always accompanied with uncertain factors for shape and size of the particles. The diameter distribution of products, therefore, comparatively spreads over a wide range. From another standpoint, the restriction of atmosphere is inevitable in some of these processes. As a pulverizing technology, the process which can produce uniformly sized particles and permits the choice of atmosphere is strongly desired.On the other hand, a great attention has been paid to the spray casting process as a new near net shape casting. In this process, a small size spraying device is favorable."

Jan 1, 1988