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By Mao Chen, Tim Evans, Zhixing Zhao, Weidong Zhang, Baojun Zhao, Dongqing Wang

High temperature softening behaviours of iron blast furnace feeds (sinter, lump and pellet) have been determined under conditions simulated to the blast furnace. The industrial samples were packed with sandwich structure (coke / ore / coke) in graphite crucibles and 30 CO / 70 Ar gas mixture was blowing directly through the bottom of the crucibles. The displacement and temperature were continuously recorded simultaneously to construct the softening curves. Separated quenching experiments were also carried out at selected temperatures under the same gas atmosphere. The temperatures were selected corresponding to the turning points of the softening curves. The phase assemblages and composition of each phase in quenched samples were analysed by Electron Probe X-ray Microanalysis (EPMA). The proportion of the liquid formed at temperature was obtained from the backscattered electron images. The deformation characteristics of these complex multi-phase materials are shown to be related directly to the phase assemblages of the samples and the microstructures. FactSage was also used to assist the predictions of liquid / solid fractions and their compositions.

Jan 1, 2015

By Wei Yin, Bin Xu, Qian Li, Yongbin Yang, Tao Jiang

Copper anode slime is an increasingly significant resource for precious metals such as Au, Ag and Pd. The extraction of Au, Ag and Pd from decopperized anode slime by different pretreatments and different lixiviants including cyanide, chloride, thiourea and thiosulfate have been investigated. When oxidizing roasting pretreatment was carried out under the conditions of roasting time 120min and temperature 625 ℃, the removal ratios of S and Sb could reach 82.18% and 98.52%, respectively. And the following alkaline leaching of calcine could result in the dissolution of 46.40% Cu and 98.48% Pb. The optima leaching ratios of Au, Ag and Pd reached 99.48%, 97.69%, 94.79% by cyanide leaching, and 95.01%, 79.84%, 96.59% by chloride leaching, and about 95.21%, 95.66%, 48.79% by thiourea/thiosulfate leaching.

Jan 1, 2015

By Susumu Okabe

Top blow injection has been applied to continuous copper smelting and converting by Mitsubishi Materials Corporation since 1974. In this process, injected feeds are captured by and dispersed in the molten bath immediately and effectively, and the reaction is enhanced by the agitation of the bath. The continuous motion of the molten bath, however, may cause severe damage of furnace lining materials, if the injection is not controlled and the furnace is not designed properly. In order to suppress refractory wear, especially at the bath line, surface wave of the molten bath should be moderated. A cold model study was carried out with water bath in a cylindrical vessel and the physical model was derived which correlates the oscillation of gas jet impingement on the bath surface and the surface wave. It was found that a half of the proper frequency of the gas jet impingement coincides the proper frequency of the surface wave.

Jan 1, 1998

By S. Kang, D. G. C. Robertson

Slag cleaning furnaces require extensive wall cooling because they involve the use of a superheated slag bath. This is in direct contrast to smelting furnaces, where the wall is usually (but not always) protected by "banks" of solid charge. In order to understand the heat transfer and flow in slag cleaning furnaces a number of model studies have been carried out using molten wax to simulate the slag. Wax is a good model fluid because, like slag, it has a high Prandtl number. Wax models cannot simulate the behavior close to the electrodes (DC arc or AC submerged), but they can and do give a good simulation of the flow and heat transfer at the wall. An understanding of these phenomena is of great importance for the design of cooling panels in the walls of the furnace. Since superheated molten slag will eventually wear away any refractory bricks over time, the wall cooling must be designed to form a frozen layer of slag, referred to as a "freeze lining". The heat flux density (Q/A) required to do this is given by Q/A = h* ?T, where h is the heat transfer coefficient in the slag phase at the wall, and Li T is the superheat (bulk slag temperature - liquidus temperature). Both Q/A and h vary greatly with position and both are usually a maximum at the slag line. In the experimental work, molten wax baths were heated by block heaters to provide similar energy densities to those encountered in commercial slag cleaning furnaces. This procedure was considered to be valid since most of the electrical energy into a furnace bath is dissipated as heat. Gas stirring was used to simulate the gas evolved at the electrode in real furnaces - the quantity of this gas could be estimated from a knowledge of electrode consumption. The similarity criterion was equal gas flow per unit area of surface, in model and prototype. Heat transfer coefficients were measured in the models as a function of power density, gas stirring, superheat, etc., and could be related to the full-scale operations by the use of dimensional analysis.

Jan 1, 1999

By A. P. Paiva

Studies focused on the recovery of precious metals by solvent extraction have recently increased. either to devise suitable solvents or to clarify the involved extraction mechanisms and kinetics. In this work, a comparison of the performance exhibited by triphenylphosphine (TPP), bis-(penty1thio)-ethane (BPTE) and triisobutylphosphine sulfide CI"I'BPS) in the extraction of silver from acidic chloride media is carried out. Extraction and stripping isotherms involving the three extractants are presented together with the results obtained on the selectivity of silver extraction against high contents of iron, copper and lead. Attempts to clarify the mechanism of silver extraction by TIBPS were performed by studying the distribution coefficient dependence on ligand and chloride concentrations. The effect of temperature on extraction and stripping is also considered. The interfacial tension for the system, measured with different concentrations of extractant in the organic phase, is analysed.

Jan 1, 1994

By Xinghui Meng

The recovery of platinum and palladium from automotive catalysts has been investigated by leaching in iodide solutions with oxidants including oxygen and iodine in an autoclave. An ammonium salt was presented in a neutral leaching solution as a key leaching reagent to achieve high recoveries of the platinum group metals (PGM). The effect of temperature, and concentrations of oxidants and of ammonium salt on the recovery of PGM was examined. Under the experimental conditions studied, the recovery of platinum and palladium was found to be greater than 95%. An economical assessment of this process has also been examined and discussed.

Jan 1, 1995

By B. Sereda

As it is known the creation and development of new titanic alloys has been problematic up to now. They can be used in aircraft and vehicle construction, shipbuilding and as materials for keeping static loadings in high-temperature environments. In this work the synthesis of various titan aluminides is investigated. Mathematical model of structurization process was done. On the base of retrieved model the mechanisms of structurization in systems Ti + Al and Ti + 3Al was determined. Experimental researches were done at two different modes: burning and thermal spontaneous ignition. The method of retrieving compacted products combusted in SHS conditions (SHS-compacting) was used to gain these intermetallic compounds. The physical and thermal characteristics of technological process and their influence on structurization, homogeneity of structure and porosity of titan aluminides have been simulated and researched. It is established that the SHS-compactizing technology is fully capable of supervising the process of structurizations with the whole complex of advantages and can be applied for receiving qualitative titan aluminides with the set of chemical-physical properties.

Jan 1, 2010

By Ibrahim Yusufoglu, Cem Kahruman, Mert Zoraga

In this study, a strontium sulfate mineral (celestite) was converted to strontium oxalate in solutions containing ammonium oxalate as a reactant. The experiments were carried out under isothermal conditions. The effects of stirring speed, ammonium oxalate concentration, particle size and temperature on the conversion rate were investigated. During the conversion process, definite volumes of solutions were taken from the reactor after different reaction times for the determination of sulfate ions using ICPOES. Fractional conversions of strontium sulfate were determined at different times and fractional conversion vs time diagrams were generated. It was found that the conversion of strontium sulfate was increased by increasing the ammonium oxalate concentration and temperature in addition to decreasing the particle size. The effect of stirring speed was negligible on the reaction rate. It was observed that above 328 K, a protective layer of strontium oxalate was formed on the strontium sulfate particles. X-ray Powder Diffraction technique was used for characterization of solid substances.

Jan 1, 2014

By Junji Shibata

Waste solution from the Ni non-electric plating process contains 4.0 kg/m3 Ni, 0.1 kglm3 Fe, 0.0 I kg/m3 Zn, 48 kg/m3 S042-, 98 kg/m3 HP032-and 31 kg/m3 laetic acid as a typical composition. Solvent extraction, cementation, ion exchange resin and precipitation methods are possible to use for the treatment of this kind of solution. In this study, solvent extraction of Ni was investigated using two kinds of extractants to clarify the relation between extraction percent and pH for various extractant mixtures. As Ni ion has an octahedral structure with ligands, the synergistic effect for Ni extraction is considered to take place in solvent extraction using two types of extractants. The investigation of the synergistic effect for Ni extraction was carried out in case of various extractant systems.

Jan 1, 2003

By Gabriel Riveros, Ariel Balocchi, Andrzej Warczok, Daniel Smith

Blister copper from converting of copper matte is processed by fire refining prior to electrorefining. The fire refining consists of two steps: copper oxidation with impurities slagging and copper reduction. The classical batch process is carried out in vascular or reverberatory furnaces called anode furnaces. A new process for continuous copper fire refining has been proposed. The copper flows through two reactors in cascade, where is oxidized and reduced. The flow of a liquid copper through a ceramic packed bed increases the surface area and the rate of oxidation as well as the rate of reduction in the packed bed of charcoal. Mathematical modelling allowed for the design of a laboratory scale demonstration installation and industrial-pilot installation in Hernan Videla Lira Smelter (Paipote). The results have demonstrated the process feasibility and flexibility in operation.

Jan 1, 2009

By Eric J. Grimsey

Steady state Excel models for a copper flash smelter and an iron blast furnace are used to enhance the teaching of pyrometallurgical smelting principles within a fourth year level process engineering unit delivered at the Western Australian School of Mines. A lecture/workshop approach has been adopted in which student teams undertake process simulation assignments that illustrate the multifaceted responses of process outputs to variation of inputs, the objectives being to reinforce their understanding of smelting principles. The approach has proven to be popular with students, as evidenced by the consistently high ratings the unit has received through student feedback. This paper provides an overview of the teaching approach and process models used.

Jan 1, 2014

By I. U. Onyenanu, C. E. Ilochonwu, E. I. Nwonye, C. O. Nwajagu

This work shows how pure silica was derived directly from rice husks ash (RHA) in different temperatures for reduction to Silicon (Si). The processes to form Si materials are usually complex, costly and energy-intensive. The silica in the ash undergoes structural transformations depending on the conditions of combustion. A high purity silica was produced at 650oC after burning the rice husk (RH) for up to 7 hours. The purity of the silica was determined by dissolving the RHA with alkali solution to form sodium silicate solution of pH 11.0. This was added to hydrochloric acid of pH 1.5 which lowered the pH of the solution to 4.0 to form silica gels. The silica gels produced were washed and dried to powder and then characterized using XRD and EDX techniques. This study was done to reduce energy waste and environmental pollution in Nigeria as silica is used to develop many materials.

Jan 1, 2015

By Juan Ruiz-Ornelas, Yousef Mohassab, Ricardo Morales-Estrella, Hong Yong Sohn, Noemi Ortiz-Lara

The effect of mechanical activation on the reduction kinetics of magnetite concentrate by hydrogen was studied. The magnetite concentrate was milled for 8 h using a planetary mill. After the milling process, the average particle size was reduced from 14 to 4.4 m resulting in a lattice microstrain of 0.30. Thermogravimetric experiments were conducted to focus on the chemical reaction as the rate controlling factor by eliminating external mass transfer effects and using a thin layer of particles to remove interstitial diffusion resistance. The onset temperature of reduction was decreased due to the mechanical activation, and the degree of conversion was decreased by sintering of particles which was confirmed by SEM analyses. In view of the results, a reaction rate expression is discussed from which the activation energy is calculated.

Jan 1, 2016

By D. Georgiou

Direct sulphuric acid leaching of nickeliferous limonites is the process of choice to recover nickel and cobalt from equatorially located lateritic ores. These ores are rich-in-iron (-45 wt%) existing in the form of goethite enriched with nickel. The merit of this process is due to its high nickel selectivity because of simultaneous iron separation and acid regeneration. Under acid leaching conditions (-250 to 270°C) iron follows an acid dissolution-hydrolytic precipitation path yielding a very low concentration level depending on temperature and acidity of the final leach liquor. The primary precipitation product of iron is hematite which also forms as a scale on reactor internals along with co-existing aluminum. In this paper, an overview of the behaviour of iron solid products under process conditions is made. The evolution of goethite to hematite transformation, as well as the role of iron in reactor scale production, are studied using SEM/EDX characterization techniques.

Jan 1, 1995

By T. Gunawansa, T. L. Alford, Zhao Zhao, A. R. Lanz, N. David Theodore

Many sustainability issues arise during the manufacturing processes that are currently used for solar cells. Solar energy is a renewable energy source that is independent of the earth’s resources, and it is therefore important for the development of more sustainable technologies. Microwave annealing (MW) has been proposed as a technically feasible fabrication scheme for large area silicon solar cells. Apart from that, microwave annealing has been demonstrated to be a promising alternative for repairing damage and electrically activating dopants in ion-implanted semiconductors for integrated circuit manufacturing. A microwave oven is cheaper than conventional furnace systems. In addition, microwave heating is much more efficient than conventional furnace heating, as heating is directly produced inside the material. This minimizes the loss of energy due to heating of the ambient. There is a need for more efficient processing techniques. In this study, microwave annealing is used as an alternative to the current postimplantation processing. Arsenic-doped silicon was microwave annealed (with an aluminacoated silicon carbide susceptor) to activate dopant atoms and to repair damage that was caused by ion implantation. Sheet resistance and Hall effect measurements were used to assess the extent of dopant activation. Rutherford backscattering spectrometry (RBS) with ion channeling was conducted to determine the extent of recrystallization. The dopant activation and recrystallization resulting from microwave annealing is compared with that resulting from conventional rapid thermal annealing (RTA) with the same heating profile. The results show that when compared to RTA, susceptor-assisted microwave annealing results in better dopant activation for shorter anneal times under the same heating conditions.

Jan 1, 2015

By Edgar Blanco

At the Deer Trail Mine, interest in recovering noble metals from oxide ore and tailings oxide ore with 6.0/1.0 g/t Au and 200/140 g/t Ag respectively has led to metallurgic studies focused on finding an adequate treatment for these materials. Using cyanide leaching, the silver/gold recoveries from oxide ore and oxide tailings were 39%/95% and 36%/96%, respectively. Since these recoveries were less than spectacular for silver, it was decided to explore a non-cyanide leaching process that would extract silver and gold better. Based on previous research the possibility of using aqua regia in combination with sulfuric acid was evaluated. On a laboratory scale, variables such as mineralogical composition, concentration of reagents, dissolved oxygen, reaction time, pH and temperature were evaluated. Under optimal conditions it was possible to achieve >65% silver recovery and >85% gold recovery for both oxide ore and tailings.

Jan 1, 2009

By Julie M. Melluish

The metallurgical response of the Point Leamington deposit has been studied. Two series of bench tests were conducted and various ore samples and flotation products were examined using image analysis techniques. The majority of sphalerite and chalcopyrite grains in this texturally complex ore were found to be smaller than 10 micrometres. Copper recoveries were low with losses mainly as fine inclusions in pyrite. Sphalerite recoveries were somewhat better due to a generally coarser habit. Gold and silver recoveries were also low and only solid solution silver was identified in the ore. The deposit shows poor economic prospects unless additional tonnage of high grade zinc ore can be delineated.

Jan 1, 1989

By C. F. Ferron

A process has been developed to treat the copper gold ores from the Guelb Moghrein mine in Mauritania. The process consists of pressure leaching the sulphide concentrate, neutralising with the oxide ore, recovery of copper by SX/EW and of gold by cyanidation of the autoclave residue. This paper focuses on the pressure leaching step, and presents data from bench and pilot plant test programs. In particular, attention is drawn to the effects of temperature, grind size, neutralisation, retention time and solution recycle on the kinetics of copper dissolution from various flotation concentrates. Likely leach mechanisms are briefly discussed.

Jan 1, 2000

By Itavahn Alves da Silva, Jose Dimas de Arruda, Amanda Aparecida Fátima Arruda, da Silva de Souza, Carlos Antonio da Silva, Varadarajan Seshadri, Samuel

The knowledge of the flow field inside a continuous casting mold is essential to improve operational efficiency of the process and also to achieve better inclusion control. Physical modeling, PIV technique and CFD have been employed to assess the velocity distribution in the metal- slag interface region in a slab mold. The analysis of results shows how higher casting velocity and lower immersion depth of submerged nozzle can lead to higher turbulence in the slag-metal interface. The effects of density difference between slag and metal and interfacial tension between the phases have been highlighted.

Jan 1, 2016

By Ho Jung Heo

The proper control of slag composition is a dominant factor affecting yield of iron as well as dephosphorization efficiency in an electric arc furnace (EAF) operation. Moreover, thermophysical properties of slags such as viscosity are strongly affected by the changes in slag composition. Slag foaming, which is also a function of viscosity, is directly connected with the yield of iron and thus optimum slag chemistry are highly required in view of thermodynamics and physical properties. Therefore, we analyzed the slag composition in commercial melt shop (70 ton EAF) with the aim of higher yield of iron as well as higher dephosphorization during EAF process.