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By Somayeh Dashti, Ehsan Vahidi, Fereshteh Rashchi

"The main goals in zinc electrowinning process are decreasing of power consumption and increasing of current efficiency. In this study, the electrowinning of zinc in the presence of different additives in electrolyte were established and Arabic Gum, Gelatine, sodium lauryl sulphate and l-hexyl-3-methylimidazolium hydrogen sulfate in the five levels using Taguchi method was examined. In our previous researches, using orthogonal array, effect of zinc electrowinning parameters such as anode type, current density, sulphuric acid concentration, temperature and zinc ion concentration was studied and the optimized conditions for zinc electrowinning was obtained. Anode composition: Pb-Ag 0.5%-Sn2%-Sb1%, current density (A/m2):500, acid concentration (g/1):165, temperature: 60°C, zinc ion concentration (g/1):70. The main goals in zinc electrowinning process are decreasing of power consumption and increasing of current efficiency. ln this research, the effect of four additives: Gum Arabic, Gelatine, sodium lauryl sulphate and an organic material in the four levels with Taguchi method was examined. ln fact the effect of electrolyte environment and determining the best electrolyte under the optimized conditions is the main aim of this study.IntroductionDue to its low cost and abundance, zinc is widely used in the production of brass, galvanized steel, sacrificed anodes and primary and secondary batteries [I]. Some 80% of world primary zinc production is derived via roast-leach-electrowinning processes [2-4]. In the electrowinning process to both improve final product quality and current efficiency the leachate should be purified [5].To produce zinc a current method is to extractit from acidic zinc sulphate solutions by electrolysis with aluminum cathodes and insoluble lead-based anodes [6]. Though the electrolytic processing of zinc has been performed for many years, there are still current efficiency problems in the cathodic process. These low efficiencies (88- 93%) have a serious impact on the costs associated with the energy consumption. On the other hand, these low efficiencies increase energy consumption and decrease the quality of the surface morphology [7- 8]."

Jan 1, 2012

By Clara María Lamus Molina

The following minerals found in the residual black sands from gold mining in El Bagre Antioquia (Colombia) were identified as having major economic interest: Ilmenite (FeTiO3), with an average of 49% of TiO2, frequently altered presenting crowns; lamellaes of rutile and alteration textures; titanomagnetite with up to 25% of TiO2; magnetite (Fe3O4) in individual grains or associated with others minerals as hematite and ferromagnesian silicates rutile (TiO2) with considerable quantities of Nb2O5(0.1-3.7%Wt); zircon (ZrSiO4) with 66%Wt of ZrO2 and monazite with an average of 63.43%Wt of REE, this frequently associated to xenotime and thorite forming textures as little drops. Analysis in EPMA and SEM/EDS showed percentages of minor elements and traces, thereby clearly establishing the applications of these minerals in diverse industries. Furthermore, a detailed granumetric study of the different minerals and textural relationships among them also allowed for establishing the basis for possible processing and exploitation.

Jan 1, 2006

By S. F. Cheng

Among the many extraordinary features of the rare earths are their magnetic and magnetoelastic properties. The rare earths, e.g. Tb, Dy, Nd, Sm, are known worldwide for their large magnetocrystalline anisotropy and magnetization, which has led to the importance of magnetic rare earths as vital ingredients of modem permanent magnets. In this paper, we focus on the strain dependence of these giant effects which gives rise to huge magnetostrictions, magnetomechanical couplings, and ?E effects. Magnetostrictions greater than 10-3 have been measured at temperatures as high as 500 K. At low temperatures magnetostrictions reaches -1%. ?E effects - 10. No other solid state material has matched these values. A proper balance of magnetic anisotropy and magnetostriction, plus a proper choice of crystal axes lead to alloys which can switch large quantities of energy between the internal (magnetic) and external (mechanical) states with the application of small triggering magnetic fields. In addition to the traditional use of these materials in transduction, they are particularly valuable for smart systems where reliability and robustness are needed such as active structure stiffening and active vibration control.

Jan 1, 1997

By E. Burgos Cruz

The behaviour of S, N and P during refining of Fe-18 wt%Cr-10 wt%Ni with calcium carbide was investigated. The effects of the initial contents of C and N in the metal phase, as well as the supply method of calcium carbide to the melt on the removal degrees of S and P were evaluated. Heats were carried out at 1873K, in MgO crucibles, using a laboratory induction furnace. It was observed that simultaneously with S and P, N and O have also participated in the reactions. It seems that, in fact, O governs the behaviour of the other elements dissolved in the melt and that N is had to the removal of P with calcium carbide. It was also noticed that high C content in the metal phase have not altered the dephosphorization and desuffirization degrees, but that the supply of calcium carbide done by injection led to a lower dephosphorization degree than the one obtained by dumping it.

Jan 1, 1995

By A. Iván, Patiño C. Francisco, Flores B. Javier, Peréz L. Miguel, Hernandez A. Juan, Trapála P. Norma, Salinas R. Eleazar, Rivera L. Isauro, G. Flores, U. Mizraim

"Tills work is related with the production of tiles using wastes from mining and metallurgical industry of Hidalgo State, as raw material. These wastes present a majority particle size (60 %), minor than 53 m (mesh 270, in Tyler Series) with the following composition; 70.01 % wt. of Si02, 12.82 % wt. of Ah03, 3.80 % wt. of Fe, 0.70 % wt. of Mn, 3.98 % wt. ofK20, 3.34 % wt. of CaO, 2.50 % wt. ofNa20, 0.04 % wt. of Zn, 0.026 % wt. of Pb, 56 grams per ton of Ag and 0.6 grams per ton of Au. In this work, the partial results and experimental conditions for the preparation of some composites to produce tiles are shown. The composite that offers the best results in productions of tiles was that with 66.67 % wt. of mining waste, 26.67 % wt. of red mud and 6.67 % wt. of black mud.IntroductionTo now, mining activities carried out during more than 457 years in Hidalgo State, Mexico; has lead a great volume of wastes; which can be classified into different types, having among the more common; Acid mining water, solid transport water, elements in radical form, abandoned minerals without processing and processing minerals wastes known as burrows, being these the most abundant in the region counting with an approximated volume of 110 million of tons, presenting a fine particle size that can affect population health during windy epochs [1 -4].Form metallurgical point of view, is well known that a fundamental characterization study it is necessary to know the viability of reusing or recycling of these wastes. According this, these residues can also be considered as raw materials in other economical activities, due its Si, Fe, AI, Ca, Na and P oxides contents, its mineralogy and the distribution of chemical elements in the primary and secondary phases [1,2,5,6]."

Jan 1, 2012

By A. F. Kaczmarek

Cerro Negro is an undeveloped ore body located at the Cerro Verde mine near Arequipa, Peru. The mineable reserve contains 70 Mt of oxide ore grading 0.532% copper. Mineralization is hosted in three distinct rock types: tourmaline breccia, crackle breccia and granodiorite. Rock type effects copper recovery and acid consumption. The paper describes Cyprus' testwork philosophy and the resulting four-phase metallurgical program used to define the commercial leaching parameters. Copper recovery and acid consumption were monitored as functions of crush size, heap height, irrigation rate and acidulation conditions. Single lift, on-off and permanent multi-lift heaps were considered. Leach cycle times were based on incremental copper extraction and acid consumption rates, with added constraints imposed by operational requirements. The optimum leach system involves an on-off pad using tertiary crushed ore acidulated with 20 kg/t acid and stacked to a height of 6.5 m. The active leach cycle is 82 days at an irrigation rate of 0.26 l/min/m2. Under these conditions copper recovery is expected to average 81% over the life of the mine.

Jan 1, 1999

By J. Méndez-Nonell

The thermodynamic and chemical properties of SrSO4 and SrS in a gaseous flow of CO and CO2 at high temperature are discussed. The thermodynamic analysis of the system was made using data from the literature. The results obtained from the thermodynamic analysis were experimentally verified using the thermogravimetric technique. The experimental results suggest the formation of a complex compound between SrO and SrSO4. It was also found a change in the chemical mechanism of the process between SrSO4 and CO-CO2 and in the chemical mechanism of the process between SrS and pure CO2.

Jan 1, 1995

By Joner Oliveira Alves

The aim of this work was to study the use of steelmaking slag as raw material to the production of rock wool and glass wool. Firstly, the chemical composition of the slag was analyzed. These results were used to infer the amount of additives to assemble the charge for the experiments. A laboratory-scale electric furnace was used to melt the mixtures used as charge. The melt material were turned into a water filled recipient, this process was performed in order to impose a fast freezing that is a characteristic of mineral wool production. Finally, with the rest of the melt material it was performed the Herty Viscosity Test. Samples of the produced material were characterized by different analyses. The results found in this research may lead to a technological innovation, because they indicate that the use of steelmaking slag to produce rock wool and glass wool is possible.

Jan 1, 2009

By Jilai Xue

Fe-Ni alloys can be used as raw material in making stainless steel. Laterite nickel ore is one of mineral resources for producing nickel alloys. In this work, the laterite ore after dehydration at 800 °C and the anthracite as reducing agent were mixed for pre-reduction at 900 °C, and then reduced to form Fe-Ni alloys at 1550-1620 °C through carbon-thermal reduction process. A high Ni-content alloy component in the metallurgical mixture can be formed through pre-reduction. Better separation of the resulting metals from the slag is found with lower Ni-content alloys produced or higher temperatures during reduction. An effective processing of Fe-Ni alloys needs further understanding of the process fundamentals and optimizing of the process parameters.

Jan 1, 2010

By Magdelinka Padenkova-Yaneva, Emilia Christova Kostakeva

"One of the methods for waste treatment is composting during which as a result of controlled biological decomposition of organic waste in aerobic conditions harmless materials are received. Composting takes place in suitably designed premises which ensure the optimal conditions for biochemical decomposition of the waste. A usual way to process composting is the spreading of the waste on a base made from reinforced concrete.In the paper the phases and basic technical features of the process of composting, the requirements and properties of the base and the ways of protection of concrete base against corrosion are revealed. Technical decisions for a specific construction site in Bulgaria are shown and the advantage of achieving durability of the concrete constructions in the plant while achieving simultaneous environment protection from pollution is discussed.IntroductionComposting is the process of controlled biochemical decomposition of vegetable and animal organic waste in aerobic conditions as a result of which harmless materials are obtained. The latter have better stability and are rich in humus substances which are useful for agricultural crops and can be used for restoring the soil fertility [1, 2, 3, 4].In modern waste treatment plants a composting technology is adopted in which the waste is spread on a concrete base as piles with certain dimensions [1, 3]. These piles are periodically stirred or air is blown through them in order to ensure the quantity of oxygen required for the process of aerobic decomposition of the organic matter. The fluids and gases formed in the course of the composting are take away in order not to pollute the environment – air, water, and soils. For this purpose the base on which the waste is spread must satisfy certain requirements, and the gases must be taken away and rendered harmless in order to protect the atmospheric air from pollution. This paper discusses the need for protecting the concrete base from corrosion and characterizes the stages and main parameters of the composting process and the possibilities for primary and secondary protection of the concrete base from corrosion. Specific technical decisions applied in a composting facility in the area of the town of Plovdiv are presented."

Jan 1, 2008

By Alexandre Bonan

This paper reports the results of a kinetic study on the oxidation of free cyanide and Cu-cyanide complex ions with HO,. The variables and respective ranges studied were the following: [CN] total =10 - 500 mg/l; pH=10-11; (H2O2/CN) mole ratio = 1- 3; (Cu/CN) mole ratio = 0.10 - 0.25. The results were interpreted by a semi-empirical model that incorporates the useful oxidation reactions and the parallel alkaline decomposition of H2O2

Jan 1, 1994

By Linli Wu, Guangchun Yao

"The influence of deformation on the properties of short-carbon-fiber reinforced 2024 alloy matrix composites was investigated in this study. It was found that the distribution of carbon fibers changed from the random state before deformation to the ordered state that carbon fibers arranged along the direction of rolling and extruding after deformation. Under the temperature range in control, the increase of rolling and extruding temperature would benefit to improve strength and elongation of composites, but was not conductive to improve the hardness of composites. With the increment of total deformation, all the strength and the hardness of composites became greater, nevertheless the elongation decreased. After being rolled and extruded, the strength and the hardness of composites were all bigger than those of composites before being rolled and extruded; moreover, the strength of extruded 2024 alloy matrix composites was higher than that of rolled 2024 alloy matrix composites under the same heat treatment conditions.IntroductionCarbon fibers have been reckoned as very important reinforcements due to the high specific strength, specific modulus, high thermal and electric conductivity, low expansion coefficient and good self-lubricant properties [1-4]. Light metal composites reinforced with carbon fibers, such as carbon fibers in an aluminum matrix, are widely used and studied. Some studies have concentrated on the interfacial characteristic of CF/Al composites in order to search for the way of improving the bonding between carbon fibers and the matrix alloy [5-8], and on the influence of the carbon fiber percent composition in the composites [9-11]. Some researchers began to take interest in the deforming characteristic and failure behavior of carbon fiber reinforced metal matrix composites [12-16]. However, the same with other metal materials, most of CF/AI composites were prepared by some single processes, such as powder metallurgy, extrusion casting and vacuum press infiltration, which caused that the composites products could not be manufactured directly. In order to cover the shortage of the mentioned above processes and get composites products with perfect mechanical properties and dimensional accuracy, the composites should be reworked by rolling, extruding or forging process. Compared with research about manufacturing process, the correlative investigation on the reworking of CF/Al composites was much less evidently, which restricted the application and the further development of CF/Al composites."

Jan 1, 2012

By Grigore Matei

The thermodynamic properties of CuzS-FeS system are important not only in the ease of copper smelting but also in the case of general pyro-metallurgy. However there arc not many reported activity data In this study, activities of FeS and CU2S in the Cu2S-FeS system were calculated using the Darken's method from the activity data of the Cu2S-FeS-Sb2S3 systems measured by the transportation method at 1050°C. The activities of Cu2S and FeS in the Cu2S-FeS system showed negative deviation from the ideal behaviour and satisfied the relation of the Gibbs-Duhem equation.

Jan 1, 2003

By C. L. Lin

Transformation of linear grade distribution to volumetric grade distribution has been used to estimate the actual mineral liberation during wet, batch, ball mill grinding of a copper ore. The degree of liberation based on the multicomponent-multisize grinding liberation model using volumetric grade is lower than the apparent degree of liberation estimated from using King's linear intercept model.

Jan 1, 1987

By Wang Shuchan, Zhang Zimu, Zhang Dianhua, Liu Yan, Zhang Ting-an, Zhao Qiuyue, Lv Chao

Rare earth extraction tank has many adverse effects like big floor space and high production accumulation during industrial production. Current researches usually focus on changing the device structure without making a breakthrough towards gravity clarification. This paper attempts to achieve this goal by using both the action of clarification by gravity and clarification by stirring. Because many physical parameters affect the clarification and separation rates, the density, viscosity and surface tension of the two phases were determined at different temperatures and different concentration of aqueous solution. The innovation of this research involves adopting the Karl-Fischer method to investigate water content in oil phase during the stirred separation process. In this paper, the separation effect of different physical parameters was studied and the dimensional equation between water content and the physical parameters was established by combining with the experimental data.

Jan 1, 2014

By A. A. EI-Geassy

High-grade iron ore fines rejected from the DRI plants (>96%Fe2O3) were isothermally reduced in 30-60%CO/H2 gas mixtures at 973-1273K. The freshly reduced reaction products were then subsequently carburised in either Hz/CO or H2/CO/S mixtures at 823-1 073K for 30-120 min. The thermogarvimetric technique was used to follow up both of reduction and carburisation reactions as a function of time. The carburised samples were characterized by X-ray and Mossbauer techniques. Chemical and carbon analyses were also applied. The influence of temperature and gas composition on the reduction behavior was investigated. The calculated values of apparent activation energy, application of gas-solid mathematical formulations were correlated with the microstructures to predict the reduetion mechanism. The influenee of carburization time, temperature, CO contents in H2/CO or H2/CO/S were investigated. A conversion extent of Fe to Fe3C was taken as a measurable index for the efficiency of carburization rcaction under the different experimental conditions.

Jan 1, 2003

By D. Tahija

The Getchell Mine produces gold from a geologically complex ore bearing high concentrations of arsenic and carbonate minerals. The mill treats the ore using high temperature aqueous oxidation in autoclaves, followed by conventional carbon-in-leach gold recovery. We laboratory tested a variety of Getchell ores to determine the effects on gold recovery of conventional factors such as grind size and retention time, as well as the influence of factors such as ore variability and preliminary carbonate destruction. Because the mill is currently operating, we were able to directly compare certain laboratory predictions with operational results.

Jan 1, 1999

By Grigore Matei

The thermodynamic properties of CU2S-FeS system are important not only in the case of copper smelting but also in the case of general pyro-mctallurgy, However there are not many reported activity data In this study, activities of FeS and CU2S in the CU2S-FeS system were calculated using the Darken's method from the activity data of the CU2S-FeS-Sb2SJ systems measured by the transportation method at 10S0°C. The activities of CU2S and FeS in the CU2S-FeS system showed negative deviation from the ideal behaviour and satisfied the relation of the Gibbs-Duhem equation,

Jan 1, 2003

By N. El-Kaddah, V. L. Acoff, M. Arenas

"Control of the weld penetration, weld pool shape and temperature field in arc welding is critical to achieve the desired microstructure and mechanical properties in the resultant welds. This is particularly important in welding gamma titanium aluminides (y-TiAl) where the weld pool is relatively shallow and the temperature gradient in the heat-affected zone is quite steep. This paper investigates theoretically and experimentally the evolution of the shape of the weld pool for stationary gas tungsten arc welds in y-TiAl alloys. A mathematical model has been developed for predicting the electric current flow, the resultant electromagnetic forces in the metal, and the transient development of the temperature and velocity fields in the molten pool generated by a spatially variable heat flux at the arc-striking zone. The governing equations were solved numerically using the control volume technique. Welding experiments were carried out to determine the shape of the weld pool and the extent of the heat affected zone at different welding times for model validation. The numerical predictions were found to be in reasonable agreement with measurements. It is suggested that the model presented in this paper is likely to provide the information needed for predicting the microstructure and mechanical properties of y-TiAl welds. IntroductionIn recent years, there has been considerable interest in the welding of gamma titanium aluminides as a means of manufacturing high-temperature, high-performance components for turbine and automobile engines. These alloys are highly reactive, and must be welded in vacuum or inert gas atmosphere, rendering electron beam, and inert gas tungsten arc welding (GTA) to be the only suitable welding techniques for joining these materials [1-3]. The GTA welding is especially attractive because of its flexibility and relative cost-effectiveness. However, previous studies on the weldability and weld properties of these alloys using this process revealed a decrease in the mechanical properties in the fusion zone [4]. This is generally attributed to the change of the original duplex structure to a dendritic structure amplified by the shallowness of weld spot. Quantifying the effect of arc operating parameters on the geometry and temperature profile of the welding pool prior cooling is the first step for controlling the fusion zone microstructure and mechanical properties."

Jan 1, 1999

By Mick O'Meara

Metal Organic Chemical Vapour Deposition (MOCVD) is used in the production of computer circuit boards and metal shapes in nickel, gold, copper, cobalt, etc. All varieties of .MOCVD use the decomposition of a vapour of organometallic compounds to produce different forms of ultra-pure metals, or alloys. CVD Manufacturing's proprietary MOCVD process has been adapted and developed to produce commercially ultra-pure metal shapes, metal powders, and metal foams. Therefore, it is a purification process. The typical process has three steps. First, a volatile metal organic compound is produced from volumetrically contaminated metals, metal oxides, etc. Typical feed materials are metal powders, ores, concentrates, or a slurry of metals and contaminants. Secondly, the volatile. metal organic compound is purified by fractional distillation. Thirdly, the purified metal organic compound is decomposed into different forms of ultra-pure metals, such as net shapes, powders, or metal foams. A mixture of metals can be purified either by the selective production of volatile materials, or a separation can be achieved during the second step, in the fractional distillation stage. The purification and recycling of metals by the MOCVD process will be discussed, particularly with regard to nickel, aluminum, gold, the platinum group and other metals.

Jan 1, 2000