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By Olga Slavkina

A new technology of bacterial leaching by means of the Thiobacillus ferrooxidance bacteria is proposed. The equations of reactions that describe of the first and the second stage of bacterial leaching of sulfide raw materials containing non-ferrous metals are given. The theory is analyzed and the technology of processing of some complicated substandard concentrate containing copper and zinc is proposed. The main technological operations including a two-stage bacterial leaching and stages of copper and zinc recovery in the form of marketable product are described. The results of the experimental validation of the main technological parameters of the first stage are given. The main possibilities of a more complete zinc and copper recovery at the second stage of bacterial leaching are discussed in comparison with single-stage leaching process.

Jan 1, 2003

By Tapio Ahokainen

Commercial modeling software and increasingly efficient computers enable today computational fluid dynamics (CFD) to be used as a tool for a more comprehensive understanding of the flash smelting and flash converting processes. CFD modeling can be used for design purposes in many technological areas, but some relevant physical and chemical phenomena are still missing in the commercial CFD solver packages. Therefore, Outokumpu has developed several subroutines for solvers to describe analytically the phenomena in the flash smelting environment. CFD sub-models of the copper concentrate and matte combustion, the particle-particle-wall interactions and for more accurate radiation properties of the gas-particle suspension are needed to ensure reliability of numerical simulations on the flash smelting and converting vessels. Several basic combustion phenomena can be modeled with a number of commercial solver packages, but own models for combustion must be included in the case of sulfides as the feed. Mathematical models for copper concentrate and solid matte combustion have been developed during the last decade. They calculate compositions of the particles and temperature, based on extensive experimental research work in laboratory scale furnaces with validated kinetic parameters and temperature measurements of reacting particles. Inside and near the concentrate burner, the standard particle tracking methods do not include the particle-particle interactions and the particle-wall interaction is too much simplified to describe properly the particle collisions with the distribution cone. Therefore, additional models for the particle-particle as well as particle-wall interactions have been written and implemented. For thermal radiation, models for the emissivity of a gas mixture and for calculating the particle absorption and scattering coefficients have been developed and tested. In addition, the advanced radiation model can be used i.e. in the enhanced simulation of off-gas cooling in the heat recovery boiler area of the flash smelter.

Jan 1, 2006

By B. R. Baldock

The converting of high-grade nickel matte for production of low-sulphur matte or nickel metal is a process which has eluded metallurgists in the past because of the limitations of conventional converting furnaces. The high temperatures required and the refractory nature of nickel oxide has prevented practical success in a process which has been known to be theoretically feasible for a long time. The Ausmelt top submerged lancing system is capable of operating under close control of the smelting conditions. High temperatures and both rapid oxidation and rapid reduction can be achieved. These features have provided the basis for successful pilot plant trials of the desulphurisation of high-grade matte from the Kalgoorlie Nickel Smelter. Sulphur level in product was lowered from 20 to 25% to as low as 0.2%, with iron levels in matte in the range of 1.0 to 3.5%. The theoretical background of matte desulphurisation is surveyed and the pilot plant operations described. The implications of the results in relation to commercial plants and possible refinery operations are summarised.

Jan 1, 1993

By R. E. Sundell, S. M. Correa

"A mathematical model is developed for the fluid flow in tungsten-inert gas weld pools. The fluid is taken to be incompressible, viscous, electrically conducting, and confined within a pool of specified shape. The flow is driven by surface-tension gradient (thermocapillary), electromagnetic, and buoyancy forces generally in this order of importance. Analysis indicates that the electromagnetic field may be calculated a priori and so decoupled from the nonlinear fluid mechanics and heat-transfer problem. The resulting set of equations is solved numerically by a line relaxation process. Computational errors caused by truncation in finite-difference schemes and by inadequate grid distributions are considered. The model is used to study several cases of differing heat and current input to the pool with and without surfactant-induced thermocapillary forces. The principal conclusions are that the thermocapillary flow, when present, is dominant with surface velocities on the order of 1 m/s. The heat transfer, as deduced from isotherms within the pool, is crucially dependent on the flow. Also, flow velocities and weld-pool surface temperatures were measuredand agree well with the model.2. IntroductionThe requirements of improved control and of automation in the TIG (tungsten-inert gas) welding process have led to the development of mathematical models for the heat transfer to the workpiece. It is now widely recognized that the fluid flow in weld pools sufficiently distorts the conduction heat transfer pattern to warrant inclusion in a process model. The experiments of Woods and Milner (1), among others, demonstrated that TIG weld pools could be driven by the electromagnetic J x B body forces present, J being the current distribution and B the induced magnetic field. Atthey (2) calculated that in typical pools the buoyancy force was about an order of magnitude less important - despite the large temperature gradients present - and neglected it in a computational study of the magnetohydrodynamic (MHD) flow. This work also reviewed many earlier studies of MHD flow caused by a source of current at a fluid surface, including analytical studies by Shercliffe (3), Sozou (4), and Sozou and Pickering (5), and a numerical study by Andrews and Craine (6). These works establish the importance of the electromagnetic force in the weld-pool flow."

Jan 1, 1986

By Sylwia Zymankowska-Kumon, Rafal Danko, Józef Danko, Mariusz Holtzer

"Burning of ceramic materials is carried out at temperatures 900+ 1300°C, in dependence of the required functional properties. The Faculty of Foundry Engineering together with the Faculty of Material Engineering and Ceramics developed the technology of production of burned ceramic materials with using spent moulding and core sands. The mentioned above waste materials of the foundry industry fulfilled -in plastic masses intended for obtaining ceramic materials -the role of the addition weakening clay raw materials. The laboratory investigations were fully verified by the results of industrial tests. It should be pointed out that none negative effects were observed at the stage of mixing raw materials and preparation of plastic masses. The measurements of exhaust gases emissions performed during burning the products containing spent moulding sands as well as during the normal production did not exhibit any significant differences, which could have indicated the harmful impact on the natural environment.IntroductionSands are used by the foundry industry to make metal casting molds and are a mixture of silica sand, bentonite clay and carbonaceous additives or resins. During the casting process, the molten metal cause thermal decomposition of carbonaceous additives or resins, which results in the formation of potentially hazardous organics, that are emitted to the atmosphere and condense in the molding sand. Each year the U.S. foundry industry landfills about 10 million tones of sand because it is no longer suitable to make metal casting molds. A large high-silica sand content in spent foundry sands (SFSs) generates rational premises for their reuse in other than foundry practice fields. Efforts to divert the SFSs from landfills and encourage their beneficial use in manufactured soils, geotechnical applications, the construction industry (road construction, highway construction), the building materials industry (cement, bricks, limestone manufacture), in the filling of mining cavities or in landfill construction (roads on landfills, permanent covers) are make [1-7]."

Jan 1, 2013

By S. Seetharaman

A mathematical model has been developed to evaluate the viscosities of melts at high temperatures. The viscous flow in liquid is described by the equation, {n = Aexp(AG*/RT)} based on the absolute reaction rate theory. The Gibbs energy of activation,{ AG* } is considered to be a function of the temperature as well as the composition of the melt. The model has been applied successfully to various metallic and slag systems from unary to quaternary. On the basis of this model, a relationship has been suggested to relate the Gibbs activation energy of viscosity to the Gibbs energy of mixing in binary metallic melts. The viscosities predicted from available thermodynamic data in the case of a number of binary metallic systems using this correlation show satisfactory agreement with the reported experimental values.

Jan 1, 1994

By N. M. S. Balbinot, A. L. Rodríguez, C. M. Mahlmann, R. de C. de S. Schneider

The use of sunflower oil co-products it was studied for production thermoplastic composites. Thermoplastic composites have been processed in polyethylene matrices of virgin linear low density polyethylene (LLDP) or recycled. Samples have been formulated with 10% mass fraction of sunflower bran, seed coat and mixture of bran and seed coat. The material characterization has been achieved by mechanical tensile test and Shore D hardness and by density physical testing. The results have demonstrated better properties to thermoplastic composites with sunflower seed coat.

Jan 1, 2008

By Claassen J. O.

The Zinc Corporation of South Africa Ltd. (Zincor) operates an integrated roast ? leach ? electrowinning circuit. The efficient removal and control of iron forms an integral part of the process. Zincor developed its own iron removal process (Zincor Process), which was recently shown to be unique with some similarities to the para-goethite iron removal process. Newly developed operating parameters for iron removal are in the process of being implemented. These include a change in the pH-profile and operating temperature, the recycling of seed material and the utilisation of an alternative neutralising agent to aid iron removal. Some of these actions, together with the implementation of a pre-neutralisation step, new filtration equipment and control systems in Zincor?s Residue Treatment Plant have significantly reduced zinc losses associated with iron in calcine and the iron residue produced. This enabled Zincor to take a step closer to world-class zinc recovery levels of around 96% for a similar type of operation.

Jan 1, 2003

By Derek Fray

Molten salts have been used for the extraction of metals since the 19th century but, recently, many interesting processes have been investigated using mixtures of molten salts and different cathodic materials. In several existing processes, the cation is simply discharged from melt but, in some cases, complications arise when the electrode potentials of the cations are relatively close. For example, the co-deposition of sodium with aluminium in the Hall-Heroult process is discussed in terms of electrode potentials of the components in the molten electrolyte. Similar considerations will also be given to the anodic reactions with respect to chlorine, oxygen, carbon dioxide or monoxide evolution from chloride-oxide melts. In some cases, the cathodic product interacts with the cathode to produce new and exciting products such as nanotubes from carbon or titanates and reduced titanium oxides from titanium dioxide. Depending on the electrode potentials, it is also possible to completely change the cathodic reaction from discharge of the cation in the salt to ionisation of the anions in the cathode. Examples are given of the reduction of metal oxides to produce metals, high technology alloys and nanomaterials and the cathodic refining of liquid metals.

Jan 1, 2006

By I. Gaballah

Spent hydrorefining catalysts may contain 4 to 6 % of COO and/or NiO, 8 to 16 % of Moo3 and up to 10 % V205 generally supported by alumina. Raw samples are roasted in order to eliminate carbon, sulfur and hydrocarbons contained in the spent catalysts. The roasting optimum temperature and time are 500 "C and 7 hours. Selective chlorination of roasted samples with Cl2 + air, Cl2 + N2 and Cl2 + CO is investigated in order to recover the valuable metals. Depending on the chlorination it is possible to recover more than 80 % of the Ni and Co about 95 % of the Mo and up to 80 % of vanadium compounds. Cobalt and nickel chlorides are obtained by leaching the chlorination residues' by acidified water. Molybdenum and vanadium chlorides and/or oxychlorides are obtained by selective condensation from the vapor phase. The chlorination of the catalyst support, Al2O3, can be limited to less than about 5 %. Besides the reaction temperature and time, the oxygen partial pressure of the chlorinating gas mixture appears to be the key factor for the reactions' selectivity.

Jan 1, 1993

By Jr. Robison

"Aluminothermic (""thermite"") smelting became commercial with the development of tonnage aluminum, and prospered producing metals and alloys with higher cleanliness, consistency and elemental control than competing technologies. We explore the scope of thermite smelting, and metallothermic smelting in general; the thermochemistry of the process; and its advantages and limitations as applied to industrial production. We review currently-produced products of thermite smelting in several forms and a wide range of heat sizes. As these products serve several industries, we relate the demands of those industries to the requirements imposed on the thermite process, leading to process dynamics and mechanisms to control/alter those dynamics. We review ways to lower the process costs by altering process stoichiometry, using other energy sources and utilizing less costly materials while considering effects on product quality and customer requirements. Finally, we examine overall emissions control and waste disposal.IntroductionAluminothermic smelting is the reduction of various oxides by aluminum to produce metals or alloys with varying levels of residual aluminum. One of the earliest uses of the process was the production of liquid iron to weld railroad rails, later modified in ""thermite grenades"" used to ""spike"" artillery pieces in World War II. Then during the 50's, 60's and 70's the growth of jet aircraft created a demand for new superalloys and titanium alloys, both requiring master alloys for efficient production. Aluminothermic smelting grew with the aerospace industry and with the expansion of microalloyed steels. It is very much a niche industry, dependent on the specialized demands of the specialty steel, superalloy and titanium industries. In this paper we introduce the characteristics of aluminothermic smelting, the scope of smelting operations, the markets served, and the environmental aspects of the process, as seen through the eyes of a company using aluminothermic smelting for over fifty years"

Jan 1, 2012

By Gjergj Dodbiba, Atsushi Shibayama, Toyohisa Fujita, Takashi Shikazumi, Yukio Kato, Kenji Murata

"A new crushing or liberation technique by means of underwater explosion is put forward. This technique is suitable for crushing and liberating various materials, for instance: the electric parts of the discarded portable telephone, CPU from mother-boards of PCs, steel from plastics tubes used as construction materials, waste constructed materials like panels, tungsten carbide scraps, as well as slitting the optical disk (e.g. DVDs), etc. The materials to be crushed are immersed in water and then the explosion is carried out by using only a small amount of explosive. The shock waves in combination with the generated bubbles are very effective in liberating the materials of different densities. It was observed that the metals crushed or liberated by using this technique were leached much faster when compared with the conventional crushing technique. This crushing method can be applied for liberation of many kinds of electric or mechanical tools. Introduction The explosive has been used since Nobel’s invention in 1866. The main practical application of explosion is in the large scale public works, such as dam construction, land development, tunnel, mining and dismantlement of building. The shock wave caused by explosion extremely can generate high pressure able to break the concrete and rock, and other materials. In this study, the crushing and liberation of waste materials was carried out by explosion in water. The idea was to use this technique as a pretreatment stage prior to recycling. The explosion in water can be used to crush hard materials, helping the liberation between different attached materials. The samples used in this experimental work are waste materials such as construction materials, hose, cemented carbide, cellular phone, lithium buttery, DVD-R, etc."

Jan 1, 2008

By G. Belardi

The purpose of the study was to check on the level of environmental contamination and to design a project for cleaning up the Abetina Mine area at Piancastagnaio (Grosseto, Italy). Contamination of this area had occurred during the mining and treatment of cinnabar (HgS) over a prolonged period. The aim of the project is to remove the sources of contamination or render them harmless. Mining of the Piancastagnaio deposit started in 1840, mercury metal being extracted from the ore by thermal treatment. Together with Spain, Italy was the first country to produce this metal and was the world leader in this field between 1936 and 1943. Though mercury production in the Monte Amiata region of Tuscany ceased in 1974 the ensuing environmental impact is very evident, taking the form of rusty old mining and processing works, plus waste tips which still contain considerable amount of mercury even after the ore had been subject to thermal extraction treatment. The research which has been conducted included mapping the area to identify the main sources of mercury and arsenic pollution, as well as the level of environmental contamination. Mercury and arsenic values in excess of 16,000 and 150 ppm respectively are encountered in the most highly-contaminated places. The cleanup project has been drawn up on the basis of the field and laboratory investigations. This provides for a combination of remediation measures on the land concerned, as well as in situ inertization of contaminating elements by means of mixtures of chemical compounds such as cyclosiloxanes. Due account has been taken of Italian and EU environmental regulations when establishing the measures for rendering the various polluting element innocuous. 'The efficacy of the inertization techniques has been checked by yield tests in acetic acid and carbon dioxide, reducing the Hg and As contents of the material in the untreated and treated states from maximum values of 7 mgll to minima close to zero.

Jan 1, 1996

By P. A. Metz

The Fairbanks mining district has produced in excess of 7.5 million troy ounces of placer gold and 250,000 troy ounces of lode gold since gold was discovered in the area in 1902. The Fairbanks mining district is in the northwestern part of the Yukon-Tanana Upland Schist Terrane, an area of approximately 240,000 square km that has produced in excess of 21 million troy ounces of placer gold. All lode gold production from the terrane has been from the Fairbanks mining district, and all of this production has come from high-grade gold-quartz polymetallic sulfide veins. Gold grains in the vein systems range in size from several microns to several millimeters. The veins are localized in a complex metamorphic rock assemblage which includes greenstones and felsic metavolcanic and volcaniclastic rocks, meta-exhalatives and metasediments. Gold occurs in the metamorphic host rocks in association with arsenopyrite and arsenic-antimony sulfides which occur in lenses and disseminations within the host rock. Gold grains occurring in the metamorphic host rocks range. in size from sub-micron to a few microns in diameter.

Jan 1, 1987

By Edgar Peek

Lixiviant regeneration is by definition a precondition for any hydrometallurgical process. In chloride hydrometallurgy either HCl or Cl2 has to be regenerated in order to establish an economically viable metallurgical process. One such regeneration process is widely used with steel pickling where HC1 is regenerated through the thermal decomposition of ferrous chloride in either spray roasters or fluid bed pyrohydrolyzers. This standard HC1 regeneration process deserves to be considered as a potential separation process, since thermodynamic calculations show that a fluid bed pyrohydrolyzer can function as a ferrous-nonferrous separator. Several nonferrous,metals such as zinc, lead and cadmium can be volatilized as a chloride under ferrous chloride pyrohydrolysis conditions. If such a nonferrous metal volatilization could be achieved in the case of slurry feeding of "contaminated" iron oxides, then this would increase the Fe/H2O ratio of the (process) feed and thus save on fuel per ton of iron, while yielding a marketable iron oxide product. Previous test work on synthetic materials revealed that the near-complete separation of zinc, lead and cadmium from iron oxide was possible in a pyrohydrolytic atmosphere, even if zinc was present as zinc ferrite (more than 99.5%). This investigation, which was carried out in a tube furnace at 1100 K has now been extended to treat synthetic zinc minerals and also franklinite ore. For the latter, it was found that 85% zinc volatilization could be achieved in 4 hours at 1300 K. It is postulated that complete zinc volatilization could not be attained due to the formation and/or presence of gahnite and hardystonite, which might be stable in HCl/H2O atmospheres at 1100 K. The effect of adding small amounts of calcium chloride to react with gahnite and hardystonite to give zinc chloride and both calcium aluminates and silicates is being discussed. Test work on slurry feeding of this complex ore in a recently constructed 4-inch diameter fluid bed pilot unit has been planned for the near future.

Jan 1, 1995

By Roger Altman

The solubility of copper in primary spinel crystals encountered in reverberatory slag samples has been determined by electron microprobe analysis. These spinels, which ranged in composition from 22% A12O3 to pure magnetite, contained small quantities of dissolved copper (0-0.4%). Based on literature data it was estimated that the solubility limit of copper in solid magnetite is no greater than about 1% at 1200°C and about 2% at 1250°C. However, it was found that practically every spinel crystal examined contained significant amounts of matte inclusions. Further examination of converter slag revealed large quantities of irregularly shaped precipitated magnetite crystals which contained a large proportion of copper inclusions. Additional experimentation showed that the total copper content in reverberatory slag samples was greater than the sum of the estimated en- trained plus dissolved matte in the slag. This difference is believed to be significant and is due to the presence of matte inclusions in the spinel crystals. In the present reverberatory slag samples these inclusions accounted for about 1/2 of the amount of sulfide directly entrained in the slag.

Jan 1, 1976

By Natasa Mitevska

In order to ensure the minimal copper concentration in the reverb furnace slag, the graphical optimization method is used and the optimal slag composition of the reverberatory furnaces No.1 and No.2 in the RTB BOR, Copper Smelter and Refinery (Serbia) is obtained: (Si02) .. 38.0%; (FeO) .. 40.0%; (Fe3O4) = 5.0%; (CaO) = 5.0%; (Al2O3) .. 6.0%. Keywords: Optimization, Reverb Furnace Slag, Graphical Method

Jan 1, 2003

By D. Lui, B. G. Thomas, B. Ho

"Results from mathematical models and plant experiments are combined to quantify the effect of transverse depressions and oscillation marks on heat transfer in the continuous casting mold. A heat transfer model has been developed to calculate transient heat conduction within the solidifying steel, coupled with the steady-state heat conduction with the continuous casting mold wall. The model features a detailed treatment of the interfacial gap between the shell and mold, including mass and momentum balances on the solid and liquid powder layers. The model predicts the solidified shell thickness down the mold, temperature in the mold and shell, thickness of the resolidified and liquid powder layers, heat flux distribution down the mold, mold water temperature rise, ideal taper of the mold walls, and other related phenomena. The important effect of non-uniform distribution of superheat is incorporated using the results from previous 3-D turbulent fluid flow calculations within the liquid cavity. Results from plant experiments confirm that transverse surface depressions and oscillation marks form at the meniscus and move down the mold. Measurements of mold thermocouple temperatures and breakout shell thickness were used to calibrate the models. The results indicate that the surface depressions and oscillation marks are filled with mold flux, but still have a significant effect on decreasing heat transfer. The predicted mold temperature fluctuations are consistent with measurements. If the depressions become filled with air, their effect is greatly increased. These results should be useful in the difficult task of interpreting transient mold thermocouple signals for on-line quality monitoring.IntroductionMany different types of intermittent surface defects on steel slabs arise during initial solidification in the mold of the. continuous casting machine. These defects include deep oscillation marks, surface depressions, and cracks. They may lead to quality problems, such as slivers, in the final rolled product. In severe cases, breakouts may occur, where liquid steel bursts through a thin section of the shell and drains over the casting machine below the mold."

Jan 1, 1997

By E. V. Redin, B. A. Dubrovsky, E. V. Knyazev, A. I. Starikov

"Ti-V magnetite is one of the most abundant composite ore resources in the world. This ore cannot be fully processed via blast furnace technology because of high content of Ti02. According to the investigations carried out in the USA and Japan ITmk3 RHF (Rotary Hearth Furnace) technology is a breakthrough in Ironmaking. Reduction, melting and slag removal can be achieved in just 10 min. The main objective of the investigation is to establish optimum operation conditions for the production of iron nuggets from Ti-V magnetite ore via the ITmk3 by means of the lab scale testing. Samples of ore from the Maly Kuybas deposit (Southern Ural), carbon reductant and fluxes were chemically analyzed. Green pellets were processed via a lab chamber furnace to simulate RHF conditions. The nuggets and slag were chemically analyzed. This preliminary test work provides valuable information which may be used for large-scale testing in a commercially sized RHF.IntroductionThe ITmk3 process upon which this paper focuses was developed by Kobe Steel in its research facilities [l]. After pilot testing at Kobe Steel's Kakogava Works in 1999-2004 the pilot demonstration plant was built and operations were successfully carried out by Mesabi Nugget joint venture in 2002-2004. Steel Dynamics put into operation the commercial plant at the Mesabi Nugget site in Hoyt Lakes (Minnesota) in 2010. Results were consistent with nugget characteristics confirming ITmk3' s flexibility with respect to raw material inputs. At the same time, no research in the field of nugget from the Ti-V magnetite bearing ore with high content of Ti02 and Alz03 has been done. It is well known, if a lot of Ti02 and Alz03 enter the blast furnace, slag becomes viscous. The viscous slag is obstacle for stable operation of the blast furnace. Besides, high content of Alz03 raises the melting temperature of gangue minerals disturbing the coalescence of reduced iron to the nuggets."

Jan 1, 2013

By Toshiyuki Kozuka

CdTe metal composite semi-conducting material has high potential in good performance of energy conversion efficiency for solar cell and there is much room for improvement of the performance by developing a process of making a thin CdTe film. In this paper, the imposition of intense magnetic field on CdTe electro-depositing surface is proposed, which is one of the possibilities for improving the energy conversion efficiency. In the experiment, cryogen-free super-conducting magnet up to 5T was used and CdTe film was deposited electrically in -o.nv vs. SHE The electrolyte was Cd and Te ammonia alkali solution with controlled temperature in the acrylic cell of 70mm diameter. Electro-deposition behavior of CdTe has affected by the imposition of the intense magnetic field due to microscopic convection in the vicinity of the depositing surface. Electro-deposited surface of CdTe becomes smooth due to microscopic convection around the surface, and the crystallization behavior is also affected, where crystallization temperature and the grain size is changed by the imposition of intense magnetic field.

Jan 1, 2003