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A line of nine self-aspirating W emco cells, part of the Rougher circuit at Division Salvador, Codelco Chile, was retrofitted to allow operation with forced air. Each cell could be operated self-aspirated or with compressed air supplied through a 4-inch line equipped with a mass flow meter. Gas dispersion was characterized for the two modes of operation. Metallurgical performance was compared under self-aspirated conditions and with different gas profiles under forced air conditions. Cell characterization demonstrated that with forced-air the cells could not evenly distribute air across the cell volume. Bubble size increased with gas velocity, as expected, with no difference between self-aspirated and forced-air operation. A systematic increase in bubble size down the bank was found. Cumulative bubble surface area flux down the bank showed no major differences between surveys. However, grade-recovery curves revealed that the highest recoveries were invariably obtained with forced air operation. Plotting concentrate mass recovery vs. enrichment ratio showed that the line performance could be controlled over a wider range when forced air was used.

Jan 1, 2007

By T Nakamura, M. Itoh

Most of the used cathode ray tube (CRT) glass in Japan, which contains lead oxide, was exported and recycled in overseas factories of new CRTs. However, domestic treatment and recycling of waste CRT glass has become necessary because overseas CRT factories have shut down and exports of CRT glass have stopped. Some of the waste CRT glass recycled domestically is charged in lead blast furnaces instead of silica flux, because there is no local reproduction route for glass that contains lead. However, the mass of CRT glass that can be treated in this manner is limited because of its high silica content. Consequently, additional treatment methods for waste CRT glass are required so that more can be used as a lead smelting material. In this study, waste CRT glass was treated with hydrofluoric acid to dissolve the silica contained in the glass, and the dissolved lead was recovered by precipitation. Lead metal was recovered by electrodeposition from the prepared hexafluorosilicic acid solution.

Jan 1, 2011

By Philippe V. Scheers

Polycrystalline gold, glassy carbon and gold-activated glassy carbon electrodes were compared for the production of hydrogen peroxide by the cathodic reduction of dissolved oxygen. Gold was deposited on glassy carbon by sputtering with a sputter coater and by electrodeposition from a diluted KAuCl4 solution using short potential steps. The sputtered gold particles were not adherent enough, but there were no adhesion problems with the electrodeposited gold particles. The gold coverage of the glassy carbon surface could be varied by applying a different number of potential steps. The overpotential for the electroreduction of oxygen to hydrogen peroxide decreases with increasing gold coverage of the glassy carbon surface, and for gold coverages exceeding about 16 %, the overpotential is close to that observed on polycrystalline gold.

Oct 1, 2003

By M. Fujikawa

The Kamioka Zinc Smelter was converted from the jarosite process to the goethite process in the year 2000. The reasons for the conversion of the process were that the silica content of the raw material increased and the iron content decreased. The silica easily turns to a gel in sulfuric acid solutions and this causes the solid-liquid separation characteristics to deteriorate. The basic behavior of silica in sulfuric acid solution was investigated and it was found that the goethite process is the most suitable to effectively separate and remove silica from solution. Furthermore, Fe has the capability to remove elements such as Ge that have an adverse effect on zinc electrolysis. This means that, when the Fe content of the raw material decreased, the impurity removal capability also decreased and there was a risk of a build-up of impurities in the process. Iron precipitates in many forms in sulfuric acid solutions. The capability to remove elements such as Ge differs depending on the compound precipitated. Goethite has a higher capability than jarosite to remove elements such as Ge. In this report, the results of applying the process established by investigations of the basic behavior of Fe, silica and Ge in the zinc refining plant are presented.

Jan 1, 2006

By B. Tougas

Recycling of titanium represents an important economic activity due to high cost of the material and the amount of returns of machined parts which represent the bulk of finished titanium products (typical "buy to fly" of 10 in the aeronautic industry). In the present work, the metallurgical quality of 76 mm in diameter and 20 cm ingots poured in coated graphite mold will be assessed against the nature and condition of application of 4 coatings namely aluminum oxide, yttrium oxide, zirconium oxide and zirconium oxide with 4% aluminum oxide. The metallurgical quality has been evaluated in terms of alpha case thickness, microstructure and composition. Microhardness from surface will be assessed against casting conditions. Least square regression analysis have been use to optimize casting conditions.

Jan 1, 2011

By George A. Guess

The making of contracts for the purchase of ores is a business which the metallurgist usually understands better than the miner. Companies in the custom ore business often employ an ore buyer who is aware of the class of ore which the smelter needs, and is thoroughly conversant with the business. The miner on the other hand makes ore contracts but seldom, and it is often only after a settlement has been made that he realizes the meaning of the terms of the contract under which he has sold his ores. He has expectations usually greatly in excess of the amount 'net proceeds' shown at the bottom of the settlement sheet. Seldom does the occasional shipper really know his contract. A somewhat similar parallel is to be found in insurance policies. We all have insurance policies; we never know the conditions contained in them until after the fire. The clauses in the policy are for the protection of the Insurance Company. An Insurance Company has no friends.

Jan 1, 1926

By A. Zarei-Hanzaki, O. Golmahalleh, S. M. H. Hosseini, H. Azizi-Alizamini

The main importance of acicular ferrite microstructures arises from their desired combination of mechanical properties in comparison with the bainite and ferrite-pearlite microstructures. Several factors affect the microstructural transition from bainite microstructure into the acicular ferrite one. As is well established any factor corrupting the prior austenitc grain boundaries nucleation potential, such as the thin layer of allotriomorph ferrite and the austenitc deformation inhomogenities may promote the acicular ferrite formation instead of bainite. Accordingly, this study deals with the effects of the aforementioned features on the acicular ferrite formation in low carbon microalloyed steel. The results indicate that the formation of strain-induced ferrite at the prior austenite grain boundaries accompanied by deformation inhomogenities in the austenite grains change the effectiveness of allotriomorph ferrite on acicular ferrite formation from active to inert one.

Jan 1, 2004

By S. Jordanov

The nature of processes that take place on top of copper bearing grains during the suppression of copper acid drainage from mine tailings was studied on a grain model. Cyclic voltammetry (C.V.) was employed as an experimental technique suitable for indirect measuring of copper leaching. Experiments were done in sulfuric acid (pH=2) at electrodes that progressively approach the real situation during acid main drainage, starting with Cu-metal, then with CuO and finally with CuO covered with CaSO4. Oxidation was found to be the only process that takes place on metallic copper electrode anodically polarized up to 2 V vs. Cu/CuSO4 reference electrode. Dissolution is intensive and reaches up to 50 mA.cm-2. When the same was repeated, but on CuO electrode, anodic currents were some 4 times lower than on the bare metallic surface. This indicates that the electrode material is not completely oxidized to copper(II)oxide and the Cu(O) or Cu(I) residues are oxidized during the anodic polarization. This explains the diminished dissolution. Dissolution is further restricted at electrodes covered with CaSO4. It is some 20 times lower than on the bare oxide electrode. When the second layer of CaSO4 was applied, anodic currents were another 15 times lower. Total decrease of anodic currents when transition is made from Cu-metal to CuO covered with 2 layers of CaSO4 reaches up to 7.500 times. C.V. measurements produced a proof that mechanical blockage is the way how lime prevents leaching of copper bearing grains in immobilization experiments referred elsewhere.

Jan 1, 2007

By M. H. Kotze, V. Yahorava

A gold-selective ion exchange resin, containing tributylamine groups, was developed by Mintek for the recovery of gold from cyanide leach solutions. The Dow Chemical Company and, more recently, Purolite commercialized the production of this gold selective resin for use in the gold mining industry, and it is marketed as Dow XZ-91419.00 and Purolite A194 respectively. A novel application of this resin is the selective recovery and separation of AuCl4 - f rom p latinum group metals (PGMs) in chloride and nitrate solutions. The current paper describes potential benefits of this type of resin for selective recovery and upgrading of gold from low grade chloride or nitrate waste streams, and the possibility of gold separation from PGMs during their refining in chloride media.

Jan 1, 2014

By M. Sokoto, H. Hata, K. Nishina, K. Haiki

Fluoride ions in zinc electrolyte cause corrosion to aluminum cathode plates at zinc electrowinning process, so we have developed an iron compound as a fluoride ion adsorbent used in zinc sulfate solution. The iron compound is synthesized from FeC13 solution with a small amount of sulfate ion by neutralizing reaction with Na2CO3 solution. The fluoride ions adsorbed on the surface of the iron compound are desorbed in alkaline solution and the iron compound can be reuse as a fluoride ion adsorbent. Moreover, if adsorption capacity of the iron compound decreases, it can be dissolved in HCl solution and re-synthesized.

Jan 1, 2008

By K. D. A. Whaley

Abstract -The Captain North Extension deposit consists of five sulfide lenses hosted in cherty and chloritic metasediment that is bounded by quartz-eye rhyolite and laminated rhyolite . Lens 2 consists of sphalerite and galena with silver-rich tetrahedrite in chert. Lens 3 contains massive pyrite, with chalcopyrite and minor gold, gradational to minor pyrite in a chloritic metasediment . The other lenses are unexplored. The sulfides occur as beds, fracture infills, and disseminated grains. Reserves are estimated at 207 555 tonnes grading 7.38% Zn, 2.76% Pb, and 91.81 g/t Ag. The deposit is isoclinally folded, dips steeply west, plunges 50 degrees south, and is faulted out to the north, where drag folding has reversed the plunge. Minor cross-faults contain talc and sericite. High sphalerite but low pyrite abundances result in poor responses to standard electromagnetic techniques. Lens 3, which contains more pyrite than Lens 2, responds better to induced polarization and allows detection. Geochemical anomalies are found in a nearby swamp and stream, but an impervious till cover inhibits the development of soil anomalies.

Jan 1, 1992

Real Time Monitoring of Cemented Paste Backfill Introduction Methods ?how to instrument a Long Hole stope Key Results from 2 case studies: barricade pressures and displacement, in-stope pressures Importance of Real Time Monitoring How binder, rise rate, cement content affect fence pressures

May 1, 2010

By Fulchand Shende

Around the world many potash mines experience brine inflow problems. The presence of brine in underground excavations may induce structural and stability problems. A study has been carried out to simulate the effect of brine on the performance of pillar support. The testing program consisted of loading potash specimens in a creep frame, and simulating inflows by continuously pumping brine into an experimental cell. Brine temperatures and load conditions were varied to simulate several mining and inflow conditions. Specimens were fitted with acoustic emission transducers to monitor energy emissions during an eight-hour test duration. Samples of brine were also collected to provide K+ and Na+ concentration data necessary for an accurate assessment of the dissolution process. Test results indicated that dissolution rates are highly dependent on brine temperature and load conditions. Loads approaching 50% UCS tend to generate very high rates of energy emissions, often leading to the failure of the simulated pillars. This study demonstrated that acoustic emission could be effectively used for predicting the performance of pillars when exposed to inflow brine.

May 1, 2001

By J. Satur

In copper mineral processing, pyrite coexisting with copper sulfide minerals like chalcopyrite is separated by flotation as tailings and its oxidation in tailing dams causes the formation of acid mine drainage. This paper proposes carriermicroencapsulation (CME) as a new method for suppressing pyrite flotability, as well as its oxidation. In this method, an organic carrier combined with Ti is used to form a thin Ti02 layer on pyrite, which gives a hydrophilic property and acts as a protective coating against oxidation. To form the coating, a ground pyrite sample was treated with Ti-catechol complex solution under various conditions. Bubble pick-up experiments and flotation experiments showed that the treatment of pyrite with Ticatechol complex changed the hydrophobic nature of pyrite into hydrophilic even in the presence of xanthate as a flotation collector. Oxidation testing of the CME-treated pyrite by 0.02 kmol m-3 HN03 showed that Fe release was suppressed by the CME treatment with respect to the control. This is assumed to be due to the formation of Ti02 coating on the pyrite surface. The effect of CME treatment on chalcopyrite wettability is also discussed.

Jan 1, 2007

By Andreas Zielonka

To meet the increasing demands of the quality and long term stability of technical systems also the applied materials have to full fill higher standards. This is of special importance where the function of a whole system depends on the reliability of the used materials for example for connector systems in automotive, computer and other electronic equipment?s. In most cases for connector systems electro deposited top layers are applied. To improve the quality of the applied layers new electro deposited systems are developed. One important field of research are the development of composite materials as dispersion coatings and multilayer systems. Multilayers are systems with a high number of single inter-layers of different metals or alloys with the wide chance of the alloy composition. As gold is one of the most important contact material for high quality connector systems it is used as basis for the development of multilayer systems. For the electrodeposition of multilayers two different methods can be applied, the single and the dual plating process. As in the dual plating process two different electrolytes are used, the single plating process allows the formation of multilayers from one electrolyte. In the presented research results cobalt and nickel are used besides gold for the formation of the multilayers. The properties of the layers can be influenced in a wide range by the change of electrolyte composition and the process parameters as current density, current waveform, temperature, hydro-dynamic conditions at the electrode surface and by the number and thickness of the inter layers of the deposited materials. The paper describes the fundamentals of the electro deposition of multilayer systems. For the investigation of the properties of the multilayers different techniques are applied. One of the most important parameter are the thickness of the total layer and of the applied sublayers. The thickness of the sublayers can be varied between a few nanometers up to micrometers. The wear resistance, the contact resistance and the plug-in forces are measured as these parameters are important for the technical application of such layers. For the description of the structure composition and surface properties the sample where also investigated by scanning electron microscopy (SEM), energy dispersive x-ray-analyses (EDX) and glow discharge optical spectroscopy (GDOS). The paper shows that the deposition of gold based multilayers is possible and that the properties of such systems can be varied in a wide range what opens new fields of applications of such materials.

Oct 1, 2003

By M. Fafard, D. Picard, J. -F. Bilodeau, G. Soucy

To simulate adequately the behaviour of a Hall-Heroult electrolysis cell, a finite element model must take into account the properties of each material. However, it has some lacking knowledge on the mechanical behaviour of materials, like the long-term visco-elastic (creep/relaxation) behaviour of cathode. A three-dimensional model is then proposed in this paper and will be ready to be implemented in the finite element code FESh++. The model was developed using the three-dimensional model based on thermodynamic of irreversible processes where the choice of the internal variables is based on a phenomenological approach. All parameters of the model are represented by constant constitutive tensors and the temperature and chemical dependencies are taking into account through scalar functions multiplying the constant constitutive tensor. The goal of the first part of this project was to determine the parameters of the threedimensional visco-elastic model at the reference state (virgin material at ambient temperature) of three different cathode materials. This paper presents the theoretical model and the results of creep tests at ambient temperature for the semi-graphitic carbon cathode.

Jan 1, 2006

By Kristie D. Tarr

Ideally, in situ monitoring would supply the input data for numerical modeling of backfill material property requirements. However, clue to production requirements and costs of conducting field tests, input data are often based on small-scale laboratory tests. The size of test samples is known to play an important role in the laboratory assessment of the behaviour of geotechnical materials, including backfill. There are observed differences between the mechanical properties of laboratory-scale samples and those of in situ materials, and these are generally attributed to the differences in scale. Various scaling factors have been proposed for converting laboratory observations to anticipated in situ conditions for soil and rock materials. With regard to mine backfill, very limited studies exist which have involved the effects of sample size on material properties. The literature indicates that reported backfill strength data are based on a variety of test sample sizes and in some cases, specimen geometries. Carefully determined laboratory scale effects could play an important role in estimating the potential backfill behaviour in the field, especially when developing new backfill systems. Laboratory studies were conducted with sample diameters ranging from 50 to 300 mm. Scale factors relating specimen size to strength were developed wherever possible, and are presented in this paper

May 1, 2008

By O. Hyvärinen

Outokumpu has developed a new chloride leaching process called HydroCopper®. In this process copper sulfide concentrates are leached at atmospheric pressure in concentrated sodium chloride solution using cupric ions as the oxidant. Copper is recovered from the purified leach solution by precipitating cuprous oxide, which is then reduced to pure copper and further melted and cast directly into copper products. The key reactants: sodium hydroxide, hydrogen and chlorine are generated from the spent sodium chloride using chlor-alkali technology. An important feature in the HydroCopperTM process is that the gold contained in copper concentrates is leached as chloride complexes and recovered from solution by activated carbon. Conditions for the leaching of gold-bearing pyrite can also be achieved in the chloride system by optimizing the redox conditions. This paper deals with the basic factors affecting gold leaching from copper sulfide concentrates. Opportunities for the recovery of refractory gold associated with arsenopyrite and pyrite will also be discussed.

Jan 1, 2005

By D. Perednis

Fuel cells with thin samaria-doped ceria (SDC) electrolyte films deposited onto an anode support using spray pyrolysis were fabricated. The SDC films were deposited onto porous NiO-YSZ substrates at deposition temperatures between 400°C and 450°C. The influence of process parameters such as deposition temperature, flow rate, type of salt and salt concentration on the quality of the film was studied. A smooth dense film was successfully deposited using the precursor cerium ammonium nitrate and samarium nitrate dissolved in butyl carbitol (33.3 vol.%), 2-methoxy-l-propanol (33.3 vol.%), and ethanol (33.3 vol.%) solvent mixture. A deposition rate of 125 nm/h was achieved.

Jan 1, 2005

By Jaeheon Lee

"Biooxidation of gold ores or concentrates could be a very attractive alternative to pressure oxidation (POX) or roasting to liberate the gold grains from various sulfides. Crushed heap bioleaching was successful in US and many operations using tank bioleaching of gold concentrate are currently running around the world. Many parameters need to be considered during the project of sulfidic refractory gold ore process. Capital and operation costs are among the most important ones. Run-of-mine heap biooxidation could be very inexpensive and the smaller the crush size (particle size), the more expensive the capital and operating costs for biooxidation application are expected. The capital cost of biooxidation could be a fraction of the cost for building POX plant or roaster and the operating cost could be 1/3 of POX or roasting depending on the method utilized. A new biooxidation process, Sand Farming, is introduced as an alternative to POX and tank biooxidation process. A relatively coarser particle size (P80 = 650 µm) of the process benefits the low cost of grinding against the conventional grinding size (P80 = 75 µm) for other options. The cost of Sand Farming is less than 40% of that of pressure oxidation with comparable gold recovery from the downstream process. This paper will review the laboratory scale testwork for various biooxidation process of sulfidic refractory gold ores and concentrates and provide the economic evaluation showing the biooxidation could be the most economic method without much sacrificing the overall gold recovery. INTRODUCTIONThe decreased availability and lower grade of raw materials has motivated industries to consider recovering values utilizing low cost process options. The process may treat high grade concentrates or submill grade ores that cannot be processed economically by conventional milling-flotation or leaching. Sulfidic refractory gold ores/concentrates have been economically processed by roasting, pressure oxidation, and biooxidation in stirred tank reactor. The process selection is based on a series of studies including multi-year long ore characterization and metallurgical investigations."

Jan 1, 2016