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By Kafui Nyavor

Acid mine drainage (AMD) is presently the biggest single environmental problem facing the mining industry. New and expanding metal mines in most parts of the world have to demonstrate their ability to contain this problem to obtain operating permits. Conventional methods of controlling acid mine drainage have primarily been limited to collecting the drainage and neutralizing with alkaline materials which do not provide a permanent solution to the AMD problem. Since acid mine drainage results from the oxidation of sulfides in the presence of oxygen, water and iron-oxidizing bacteria, controlling any of these three factors contributing to pyrite oxidation provides a potential at-source remedy for reducing or preventing acid mine drainage formation. Physical properties such as hydrophobicity also play an important role in the attachment of bacteria, adsorption of oxygen, water, and other ions that subsequently lead to the oxidation of pyrite. In this communication, the suppression of pyrite oxidation by treatment with fatty acid amines (FAA) was investigated. The FAA treated pyrite samples were tested at various conditions of temperature and pressure. At an elevated oxygen pressure of 500 psi and a temperature of 600 C, less than 0.2% oxidation was obtained for the FAA treated pyrite samples, while over 1.2% oxidation was obtained for the untreated samples in 10 hours of oxidation time. Accelerated column oxidation tests at ambient condition showed that FAA mated samples reduced pyrite oxidation by at least 75% in 81 days.

Jan 1, 1994

By L. Z. Villanueva

An investigation and evaluation has been performed to determine the potential utilization of electron beam irradiation technology for sulfur oxides removal from reduced-S02-strength metallurgical gases from copper smelters. These off-gases, though too weak to be converted to usable, concentrated: sulfuric acid by conventional means, are characterized by SO2 content higher than 2,000 ppm and a complex chemical composition, including high oxygen content and its generation occurring in a cyclical, fluctuating pattern. This work was based on information supplied by principal smelter companies in Chile. A laboratory facility with flow rate of 20 Nm3/h and equipped with an electron accelerator of beam energy 8.00 keV, has been used for testing. Influence on SO2 removal efficiency of operational parameters such as gas temperature, water vapor content, ammonia feed ratio and irradiation dose was established. The main conclusion of this work, from experimental laboratory tests as well as engineering studies, is that the Electron Beam Process (EBDS) is a cost-effective, simple and appropriate chemical process means for emission abatement. EBDS can, on a site-specific basis, adequately augment SO2 removal to upgrade overall abatement as required and in an optimal manner.

Jan 1, 1999

By Pengfu Tan

Lead blast-furnace bullion cools to near its freezing point in an operation known as copper drossing or hot drossing usually contains 0.02-0.06% copper. The removal of this copper is usually carried out in a batch operation known as sulfur drossing. Sulfur is stirred into the bullion at temperatures near its freezing point, and the dross of copper and lead sulfides that floats to the surface is skimmed off manually. A thermodynamic model has been developed to simulate the copper drossing. The phase diagram of Pb-Cu-S system has been calculated, and the effects of the process parameters, such as temperature, copper content, and sulfur content, on the drossing process have been simulated and discussed.

Jan 1, 2006

By K. Fukushima, K. Baba, H. Kurokawa, M. Yamagiwa

"The Toyo smelter has expanded its anode production capacity from 126,500 to 239,000 t/year by introducing technical oxygen into blast air for flash and converter furnaces and improving smelting facilities. Significant efforts were made in the expansion not to increase the number of workers, which mean development of some automation systems for the copper converters and anode casting wheel. The efforts have resulted in the above-mentioned increase in productivity and a saving of production cost as well as a decrease in the number of workers for the anode casting operation.IntroductionThe Toyo smelter has been performing a highly stable and pollution free operation since its commencement in 1971 (1). Its distinctive features are the on-line control by process computer (2) and the high productivity without trouble. But owing to the so-called oil crisis in 1979, we were faced with a sharp increase in production cost. To decrease the production cost, some measures for saving of energy were planned and carried out, such as conversion from oil to coal in a flash furnace (3), the heat recovery from converter slag and the introduction of technical oxygen in blast air with the intention of energy saving as much as possible.The first increase in production capacity and some savings of production cost were attained in 1982 by the introduction of technical oxygen in blast air for the flash furnace without major modification of the furnace as shown in Table I. The capacity of an oxygen plant is 7,800 Nm3/H as 90% O2 . Part of oxygen from the plant is also supplied to tuyeres of copper converters through an oxygen holding tank with a volume of 830 m3 at 7 kg/cm2-G."

Jan 1, 1989

By I. Gaballah

Decontamination of synthetic solutions of PbC12 containing 10, 100 and 1000 ppm of lead, using chemically treated barks had been studied. The percentage of !cad cations' removal from solutions depends upon the pH and the initial concentration. About 99 % of the initial lead content can be removed at pH of about 3.5, 5.5 and 6.5 for initial concentrations of 10, 100 and 1000 ppm respectively. The maximum retention capacity of the treated bark is about 83 mg of lead per gram of modified bark. Bark loaded with lead had been analyzed by Infra Red spectroscopy. It seems that lead reacts with hydroxyl groups of the phenolic constituents of the bark. On the other hand, the removal of a lead cation by the bark leads to the release of two H+. This seems to show that the removal of lead could be interpreted as an ion exchange with hydrogen belonging to the hydroxyl groups of the modified bark.

Jan 1, 1994

By V. Montenegro

Smelting of copper concentrates in Teniente Converter produces highly oxidized slag, containing from 4 to 10 % Cu and from 15 to 25 % of Fe304. Copper recovery requires magnetite reduction at a level of 5%, determining the degree of cuprous oxide co-reduction and the liberation of copper matte inclusions. The rate of slag reduction is controlled by the mass transfer to the reaction interface. Slag stirring affects the rate of reduction and enhances coalescence of mechanically entrained copper matte inclusions. Slag reduction and sedimentation in the AC electric furnace is a commonly used method of slag cleaning. Utilization of DC electric furnace creates beneficial conditions introducing slag electrolysis additionally to chemical reductions with carbon of coke and electrodes. Application of external magnetic field, interacting with a direct current in an electric furnace, induces magnetohydrodynamic phenomena, such as intensive stirring and electromagnetic buoyancy force acting on inclusions. Laboratory scale research in simulated DC electric furnace with a superimposed magnetic field showed a significant acceleration of the rate of slag reduction and copper removal. Continuous measurement of gas flow and composition allowed for determination of the reduction rate along the time. Application of external magnetic field in the reduction of the industrial slag in a crucible simulated DC electric furnace results such as the increase of the reduction rate from 2 to 3 times, compared with the identical conditions in the AC electric furnace. Interaction of non- homogeneous electric field with crossed permanent magnetic field induces vigorous slag stirring, enhance mass transfer and accelerate the rate of the slag reduction. Additional participations of the slag electrolysis in the magnetite and cuprous oxide reduction as well as the acceleration of the settling of the inclusions by the electromagnetic buoyancy force affect the slag cleaning intensification.

Jan 1, 2003

By V. Montenegro

Smelting of copper concentrates in Teniente Converter produces highly oxidized slag, containing from 4 to 10 % Cu and from 15 to 25 % of Fe304. Copper recovery requires magnetite reduction at a level of 5%, determining the degree of cuprous oxide co-reduction and the liberation of copper matte inclusions. The rate of slag reduction is controlled by the mass transfer to the reaction interface. Slag stirring affects the rate of reduction and enhances coalescence of mechanically entrained copper matte inclusions. Slag reduction and sedimentation in the AC electric furnace is a commonly used method of slag cleaning. Utilization of DC electric furnace creates beneficial conditions introducing slag electrolysis additionally to chemical reductions with carbon of coke and electrodes. Application of external magnetic field, interacting with a direct current in an electric furnace, induces magnetohydrodynamic phenomena, such as intensive stirring and electromagnetic buoyancy force acting on inclusions. Laboratory scale research in simulated DC electric furnace with a superimposed magnetic field showed a significant acceleration of the rate of slag reduction and copper removal. Continuous measurement of gas flow and composition allowed for determination of the reduction rate along the time. Application of external magnetic field in the reduction of the industrial slag in a crucible simulated DC electric furnace results such as the increase of the reduction rate from 2 to 3 times, compared with the identical conditions in the AC electric furnace. Interaction of non-homogeneous electric field with crossed permanent magnetic field induces vigorous slag stirring, enhance mass transfer and accelerate the rate of the slag reduction. Additional participations of the slag electrolysis in the magnetite and cuprous oxide reduction as well as the acceleration of the settling of the inclusions by the electromagnetic buoyancy force affect the slag cleaning intensification.

Jan 1, 2003

By Musa Karakus

Ceramic build-ups are synthetic mineral deposits formed in critical locations in or near the throats of inductor units in channel induction furnaces, the preferred melting and holding furnaces used in iron foundries. The build-ups are undesirable because they slow down melt circulation, increase power consumption and cost. and decrease the quality of the metal. This study involved the determination of the mineralogy of build-up samples and the quantitative measurement of phase abundance in those build-ups by cathodoluminescence microscopy. These undesirable deposits usually are hard and dense and contain variable amounts of entrained metallic iron. The non-metallic phases dominantly consist of oxides and silicates of several refractory elements, AI, Mg. Ca, Si, and Fe. Minor amounts of the sulfides of Ca. Mg, Fe and REE elements, especially Ce and La. and the oxides and silicates of Ce and La elements are locally present in the build-ups. The build-up samples were found to be ideally suited for study by cathodoluminescence, which has provided an easy means for rapid re-cognition of the phases present in the build-ups. The phase compositions were determined by electron microprobe analysis. The phases identified and their characteristic cathodoluminescence shown in the ceramic build-up samples were: spinel (bright green, blue-green, and red). forsterite (red and purple), periclase (dark reddish-brown, blue. and orange), corundum (red, blue, orange, and white), anorthite (yellow, yellow-green, blue, and blue-purple), hibonite or calcium hexaluminate (dark green), mullite (dull red-brown), gehlenite (deep blue), silica(dark brown, pink, purple, red. and blue), monticellite (light violet blue and light pale yellow-orange), silicon carbide (orange), oldhamite (bright yellow and orange). Ce-La silicate phases (purple), and glass (orange, dull red, and purple). Non-luminescent phases were: hercynite, Fe-oxides, Ce-La-oxides, Fe-sulfides, and metallic iron.

Jan 1, 1989

By T. P. R. de Jong

Dual energy X-ray transmission imaging is extensively applied for safety luggage inspection. Its advantages are its rapid scanning rate (25 to 100 cm/sec) at approximately I mm resolution and simultaneous thickness independent metal identification. This is especially advantageous for secondary scrap metal inspection and automatic sorting. Other applications include metal product inspection, bale control, and waste processing. Recent progress in development of an automatic on-line sorter for bulk solids is presented and discussed. Besides various non-metal applications (solid fuels, wastes etc.) it appeared particularly effective in light metal sorting. As inspection tool better control of difficult to monitor solid bulk streams, batteries, bales and other related metals becomes possible.

Jan 1, 2003

By Aarne Kopanen

In recent years, various renovations have been carried out in the production chain of the Outokumpu copper refinirg process. The anode casting shop, which is the final integral production section at the Harjavalta copper smelter built in its original form in 1945, was fourxl unsuitable for technical and capacity demads during longer periods of operation, and a new casting shop was built in 1974. The electrolytic copper refinery of Outokumpu Oy at Pori was built in 1941, and subsequently expanded in two stages. Even with its present limited scale of production it has been fom important to mechanize the main operations. This work was started in 1967 with the design and construction of the starting sheet machine connected with the cathode washing and unloading machine as a combined unit. Mechanized treatment of anodes has gained advantage particularly from the new design of a highly automated anode casting shop. In the further development of the mechanization a stripping machine for, starting sheets was designed and installed, starting operation in 1974.

Jan 1, 1976

By B. L. Chulu

In the carbothermic reduction of lead sulfate to produce lead, the inclusion of soda ash (Na,CO,) in the charge provides for the control of sulfur dioxide in the effluent gas. An important mechanism in the process appears to be the carbothermic reduction of the sodium carbonate whereby sodium gas and carbon monoxide are produced. These intermediates then participate in the reduction of the lead sulfate to produce lead metal and stable sulfur species in the molten slag phase. In addition, there is some evidence that the presence of lead metal in the charge may also serve to increase the lead recovery in the process. These aspects were investigated by conducting laboratory-scale smelting tests with small charges (;3g), at 1173°K(9000C). Recovery did not exceed 74w% and the role of incipient lead metal in the charge could not be clearly assessed.

Jan 1, 1993

By M. Sizgoric

Certain types of mineralogical alteration due either to weathering or serpentinization, and the effects these transformations have on the flotation of nickel sulfide ores are discussed. These effects are generally deleterious due to: (a) the poor flotation properties of the alteration minerals (as in the case of tochilinite), (b) the nature of the alteration texture (as in the case of violarite), or (c) .close association of the alteration products with other undesirable minerals (such as nickeliferous smythite). Several examples from INCO Metals Company's mines and mineral prospects are given as illustration.

Jan 1, 1981

By Yuanbo Zhang, Zhixiong You, Daoxian Duan, Guanghui Li, Tao Jiang

"Manganese is mainly consumed by steel and battery industries. In recent years, it is essential to utilize the low-grade manganese oxide ores with total manganese grade below 25%, as the high quality manganese ore resources are becoming scarce with the rapid development of the steel industry. Conventional pyro-metallurgical processes for utilizing manganese oxide ores are characterized by high production cost and energy consumption, low productivity, serious environmental pollution, etc. In this study, reduction thermodynamic of MnO2 reduced by sulfur was firstly carried out. Then, a novel process of reduction roasting with sulfur followed by acid leaching was developed to recover manganese from the very low-grade manganese oxide ores. Effects of main factors, including temperature, reduction time and S/Mn mole ratio, were investigated, and a high leaching efficiency of Mn above 95% was obtained under optimal conditions.IntroductionHigh/middle-grade manganese oxide ores are generally used in the metallurgical industries, particularly in steel plants and ferro-alloy units. The consumption of metal manganese in the ferro-alloy industry accounts for 85- 90% of the total Mn demanded [1]. Therefore, high quality manganese ore resources are becoming scarce with the rapid development of steel industry. It is essential to make good use of large quantity of low-grade manganese ores (TMn < 25%) presently available."

Jan 1, 2012

By W. Gutmannsbauer

Thin films of TiO2 nanoparticles have been prepared by different reactive deposition methods, such as electron evaporation, ion plating and ion beam sputtering. Many properties especially the optical properties, are strongly related to the film morphology and surface roughness. Scanning force microscopy was employed to obtain information on the surface structure of as-deposited Ti(h thin films. The influence of the deposition conditions and the film thickness on the optical and structural properties has been investigated. The as-deposited films were found to be amorphous or polycrystalline with anatase structure.

Jan 1, 1995

By C. K. Gupta

The paper reports on the experimental work and results obtained in processing a xenotime concentrate. The rare earth resource concentrate has been treated by three different methods namely, hydrothermal leaching, alkali roasting and alkali pugging or baking. The recovery in hydrothermal leaching with caustic soda at 150-160°C has been 89%. En comparison, processes involving alkali roastings with soda ash at 850°C and with caustic soda at 500°C, and alkali pugging or baking with caustic soda at 200°C have given recovery values close to 100%

Jan 1, 1992

By D. L. Yopps

Platinum-group metal (PGM) flotation .. concentrate from the Stillwater Complex, MT, was subjected to biooxidation using Thiobacillus ferrooxidans in an effort to break down the sulfide minerals and liberate the ? associated PGM&apos;s for subsequent chemical leaching. Bacterial treatment oxidized up to 94 pct of the sulfide present, destroyed the PGM-bearing pentlandite [ (Ni,Fe),9Ss) mineralization, and dissolved most of the nickel in the concentrate. Results showed that increased sulfide oxidation during the biological stage led to improved PGH recovery in the subsequent. chemical leaching stage. cyanidation at 80° c proved to be the best chemical leachant tested. It removed 7.6 pct of the palladium, 94 pct of the rhodium, 97 pct of the gold, but only 34 pct of the platinum from the biooxidized concentrate.

Jan 1, 1991

By E. T. White

The population balance is one of the basic relations for a:n:aIysing particulate minera1 processing operations. It is an exact relation. The principles of the population balance are reviewed and applications in the minerals industry discussed.

Jan 1, 1996

By Wenbin Liu

A novel route for rapid synthesis of ultrafine WC-Co cemented carbides with homogeneous binder phase distribution is reported. The composite powder is produced by in situ reduction-carbonization reactions by using WO2.9, Co3O4 and carbon black as raw powders. The reaction equilibrium and phase stability are studied by thermodynamic calculations. The WC-Co composite powder is condensed by spark plasma sintering (SPS) to obtain the cemented carbides bulk. The sintering temperature is lower than that in the conventional sintering methods by 1500C, while the sintering time is remarkably reduced by 3-5 times. The high performances of the hardness and the fracture toughness are obtained. The experimental results confirm that the present processing scheme of in situ reduction-carbonization reactions and subsequent SPS sintering is an efficient way to prepare WC-Co cemented carbides, and is apparently superior to the conventional long-period techniques of preparing composite powder and cemented carbides bulk.

Jan 1, 2008

By Vincent Menard

The purpose of the present work is to demonstrate the removal of manganese from a neutral leach zinc-rich solution ([Zn] =150 g/L) at 80°C by oxidative precipitation using a gas mixture of sulphur dioxide (SO2) and oxygen (O2). In order to determine the optimum conditions for manganese removal, several bench-scale semi-batch experiments were performed, where the effects of ORP and gas mixing were investigated. These tests showed that SO2/O2 is a fast and effective oxidant for removing manganese down to ppm level as long as the appropriate ORP is attained/maintained and gas transfer kinetics are optimized.

Jan 1, 2006

By P. A. Davidson, D. J. Short

"In this paper we describe a 'non-contact' electromagnetic nozzle suitable for sprayforming and gas atomization processes. In such processes there is a need to control the flow rate and diameter of the liquid metal jet whilst minimising contamination of the stream. This can be achieved using an electromagnetic valve, which partially levitates the jet in freespace, using a segmented cylinder surrounded by an induction coil. This valve will significantly enhance the quality of the titanium alloys and nickel-based superalloys used in sprayforming and gas atomization. This paper describes the design and test of a laboratory prototype valve based on experiments performed with liquid tin.1. Introduction In many industries there is an increasing need for clean, high quality metals and alloys based on titanium and nickel. Two important processes are: 1) Spray deposition which allows the liquid metal to be converted to a near-net shape, thus alleviating the need for subsequent forging and extensive machining and; 2) Powder production of titanium by gas atomisation.In centrifugal spray deposition of titanium (see figure 1) the metal is induction melted in a cold crucible. The crucible consists of a number of water-cooled segments, which allows the high frequency magnetic field of the coil to pass through the crucible, and into the melt. The charge is melted by the induced eddy currents. Locally at the crucible walls the liquid metal solidifies, and is contained within a. 'skull' of its own solid, thus reducing contamination from the crucible wall. Once melted the metal is poured through an electrically heated graphite nozzle and into the spray forming chamber. The principal limitation of the process to-date, however, is that it currently uses a graphite and /or ceramic nozzle to direct the flow of liquid metal to the atomizing disk and as such there is considerable risk of nozzle erosion with inevitable effects in terms of contamination of the melt stream and variability in flow conditions. In this research programme we develop a. non-contact electromagnetic nozzle, which will totally eliminate refractories and/or ceramic materials from the melting and casting process. This will greatly enhance the technological capabilities of sprayforming and gas atomization processes."

Jan 1, 1999