Search Documents

By Sridhar Krishnan

This paper presents the results of a comprehensive pre-production pile testing programme for the US$ 800 million 1400MW Coal-Fired Jimah Power Plant Project in Negeri Sembilan, Malaysia. The testing programme included high-strain dynamic testing and fully instrumented static axial and lateral load testing of driven prestressed concrete piles and bored cast-in-place piles. A highlight of the testing programme was the pioneering use of the Global Strain Extensometer (GloStrExt) Method, a deformation monitoring system that uses advanced pneumatically- or hydraulically-anchored extensometers and a novel analytical technique to monitor loads and displacements down the shaft and at the toe of driven prestressed concrete piles. The experience with the testing programme for the Jimah Project also demonstrates the possibility of achieving notable breakthroughs, not only in the monitoring, evaluation and reporting of pile foundation behaviour dynamics but also in our understanding of the mechanisms that underpin such behaviour. These significant gains are undeniably a direct result of the committed and co-operative relationship among the project owner, design/builder, specialist piling subcontractors, pile suppliers and pile instrumentation and testing specialists.

Jan 1, 2006

By E. Dzingayi

Keywords: Pyrometallurgy, furnace, Bindura, nickel The smelter at Bindura Nickel Corporation processes concentrates from its own mines and other external sources. Concentrates are dried, smelted, and converted to a desulphurised matte (leach alloy) for further processing at the refinery. The smelter comprises a drying plant, submerged arc electric furnace, electrostatic precipitator, and three Peirce-Smith type converters capable of treating 150 000 tonnes of concentrates per year. Concentrates are dried in a rotary coal-fired kiln, blended with fluxes, and smelted in a six-in-line submerged-arc 15MW electric furnace. Slag is tapped and granulated for disposal, and matte is tapped at regular intervals for blowing in Peirce-Smith converters. The paper details the 37-year history of the smelter, including furnace rebuilds and operating parameters as they have evolved in response to changing feed compositions. Special challenges, particularly relating to the treatment of high talc concentrates, are also described.

Jan 1, 2006

By D Crequer

Land rehabilitation at Golden Cross is reviewed, 8 years after mine closure in 1997/98, from the perspectives of a Peer Reviewer (land rehabilitation) and a Regional Council Officer (Resource Consents compliance). Land rehabilitation items we discuss include: management of restored pastures, native plantings (on-site riparian and block plantings and off-site environmental riparian enhancement plantings), wetlands (on-site tailings lake and sediment ponds littoral zone plantings, and basement of the open pit; and off-site wetlands enhancement plantings), pine plantations on-site and on surrounding land, stabilization of the Tailings Lake Embankment (landslide) and Open Pit capping, capping of acid-mine-rock, stability of discharge channels, buildings and amenities, public access for recreation, educational uses, and future management of the site. Pest control has helped to conserve the rare and endangered HochstetterÆs (Leiopelma hochstetteri) and ArcheyÆs (L. archeyi) frogs, and a regionally significant stand of rare swamp maire (Syzygium maire) has been conserved and fenced.

Jan 1, 2006

By A. N. Lasseigne

Hydrogenation behavior of the NaAlH4 intermetallics is investigated utilizing thermoelectric power and magnetic analyses. Using both thermoelectric power and magnetic susceptibility measurements on these intermetallics allows for confirmation and further insight into hydrogen's role in altering the material's electronic structure. The electronic and magnetic property correlations will indicate the direction for further alloy development to optimize hydrogen storage.

Jan 1, 2006

By K. Yoshida

Recently, light magnesium alloy with superior heat radiating ability has been attracting attention in various fields. However cold plastic working of the alloy is very difficult and hot working necessary. Furthermore, the magnesium of products with complicated shapes is difficult, the processing cost is high, and the applicability of the alloy is limited. In this study, a technique for obtaining fine wires and tubes by cold drawing is examined to obtain wires and tubes with high strength, quality and surface morphology, while decreasing production cost. In addition, the shearing strain of magnesium alloy wires and tubes drawn under various drawing conditions was calculated by FEM analysis. It was clarified that cold drawing of magnesium alloy is possible. It was also demonstrated that greater reduction of the cross-sectional area could be realized during cold wire and tube drawing by optimizing the drawing conditions.

Jan 1, 2006

By Corby G. Anderson

Laboratory testing, interpretation and application of metallurgical technologies can be tedious, time consuming and costly. This paper outlines the use of proven statistical design of experimentation software for rapid optimization of laboratory testing and operating plants with limited representative sample utilization. This results in less costly required testing, a more thorough understanding of results and the ability to simultaneously optimize several variables and outcomes at once. At the Center for Advanced Mineral and Metallurgical Processing, this testing methodology has been used successfully in many metallurgical development and plant optimization projects thereby confirming its real world utility and application. Accordingly, several applied examples in flotation and hydrometallurgy will be outlined in this paper. This will include flotation testing of a copper gold ore, flotation testing of a copper, cobalt and gold ore, optimization of an industrial hydrometallurgical jarosite circuit and optimization of industrial nitrogen species catalyzed pressure leaching of a copper enargite concentrate.

Jan 1, 2006

Leadership challenges for mine management over the next decade will be primarily about doing more with less labour. This will require a greater focus on people leadership and management, reducing uncertainty by evening out employment peaks and troughs, understanding and addressing our demographic destiny and its implications whilst identifying and holding onto our mission critical employees, managing creativity and accepting diversity whilst providing flexibility in employment for work-life balance. Greater emphasis will also be required on the non-technical social skills of complex interactions with community and education providers and finally a greater emphasis on forecasting and planning for the provision of future skills needs. Skills needs will become an ever increasing priority in risk management as retention starts with attraction and remember: SATISFACTION = REALITY                                EXPECTATIONS These are the challenges and opportunities for leadership and mine management of the 21st century to assist in better meeting and maintaining our human resources needs and thus contributing to the sustainability of the sector in Australasia.

Jan 1, 2006

By T. L. Baum

External oxidation during in-line heat treatment of TRIP steels can cause problems for the subsequent coating process. This research aims to elucidate the kinetic rates of internal oxidation, external oxidation and decarburization and their interdependence under different gas atmospheres and temperatures. A rolled steel sample chemistry of 0.14 wt.% C, 1.8 wt% Mn, 0.6 wt.% Si and 1 wt.% Al is used as a case study. Thermogravimetric techniques are used to examine the net mass change in a sample during heat treatment and the results show an initial mass decrease and later an increase for particular partial pressures of H2O. SEM-EDS, optical microscopy and glancing-angle x-ray are used to quantify the microstructure. The cross-section of the samples have 4 distinct zones: (i) an external scale, rich in fayalite, (ii) an internally oxidized region with Al, Si and Mn oxides in an Fe matrix, (iii) a decarburized steel region, characterized by large ferrite grains and low carbon content, and (iv) a relatively unaffected steel core with a structure similar to the starting material.

Jan 1, 2006

A single aggregate mix design was developed based on a slag/Portland binder blend and crusher sand. The primary design criterion, after performance, was the fluidity of the shotcrete and concrete product to ensure compatibility with existing manufacturing and shotcrete equipment as well as the pipeline transport system Cullinan Diamond Mine was investigating. Initial work had determined an optimum slag/Portland to aggregate ratio while retaining a water to slag/Portland binder ratio of approximately 0.4 to maintain the flowability of the product. A super-plasticizer was used to further increase the flowability of the product as opposed to increasing the water content. Finally a polypropylene reinforcement fibre was included in the wet shotcrete product to improve the energy absorption characteristics of the shotcrete. Previous work on the strength development of the slag/Portland based shotcretes and concretes suggests that strength class based on the EN 206 specification is C40/50 while the toughness classification based on the EFNARC plate test is c, or greater than 1000 joules1. Typically, Cullinan Diamond Mine wanted a shotcrete with a uniaxial compressive cube strength of 45 MPa and an energy absorption, based on the EFNARC plate test, in excess of 700 joules. This is an EN 206 strength class of C36/45 requiring a uniaxial compressive core strength of 30.5 MPa and a toughness classification of b1. In addition to the shotcrete development, Cullinan Diamond Mine required concrete products with a compressive strength range of between 25 and 60 Mpa for differing construction operations underground to be manufactured from the same mix design and raw materials as for the shotcrete. Finally, Cullinan Diamond Mine carries out extensive dry shotcrete operations and an investigation into the possibility of using the single aggregate mix design for dry shotcreting was also entered into. This paper presents data that indicates that, under the terms of reference, a wet and dry shotcrete and concrete product appears to be possible from a single aggregate less than 6.7 mm in size, and that a slag/Portland binder is suitable for use as the hydraulic binder in all the products, and that the necessary performance parameters of strength and energy absorption can be achieved.

Jan 1, 2006

By Yoshiyuki Matsui

As one of the factors of frequent troubles on iron-making blast in recent years, increased size of the blast furnace and high-productivity operation are pointed out. Consequently, great importance is attached to deadman shape and solid flow at the lower part of furnace. In the present study, firstly, the blast furnace raceway formation under the intensive coal injection by measurement of micro wave reflection gunned through a tuyere is discussed. As the flow rate of coke as the momentum of coke into raceway decreases by combustion of coal injected into tuyeres, the depth of raceway defined as the maximum position of micro wave reflection is easy to contract. It is expected that this new technology could detect the raceway collapse phenomena in short time and that the stability of raceway in coal injection is different from that in all coke operation. Secondly, the reduced stockline surface profile was measured by the reflection intensity of microwave struck from the furnace top after blow-off with stockline reduced, and investigation was made on the countermeasures for changes in the raceway depth and furnace body profile during operation. As a result, it has been clarified that flow-down of coke into the lower part of blast furnace and inflow into the raceway are greatly subject to the existence of deadman which is the packed structure of the lower part of furnace, and further, they are closely related to dynamic behavior of the raceway, and affect changes of the furnace body profile.

Jan 1, 2006

By G. Chambovet

Applied geophysical methods such as the surface seismic method have been applied for many years and in many places, mainly for oil exploration and to a lesser extent for mineral deposits? exploration in sedimentary basins. The seismic method fundamental is based on the variations of acoustic impedance in a layered earth model and such variations at each main geological interface create reflected waves that are processed and imaged in order to output a clear picture of the subsurface structure. The geology of South Africa was historically, and even until recently, considered as unfit for seismic exploration and the mines were always reluctant to spend any portions of their exploration budgets on these techniques. Hard rocks and high P-waves velocities were creating quite a hopeless model for any mine geologist or geophysicist (if any), unsuitable for the proper use of seismic waves to image their subsurface problems. Boreholes were considered the only reliable tool to derive a geological image of the mine structural features and were linked sometimes with surface methods such as aero-magnetism. The obvious flaw of this methodology was the inability to derive a continuous image from a discrete set of measurement points. Surface 3D seismic is the tool that gives a reliable solution from the initial model extracted from the boreholes, as even the aero-magnetism mapping gives a flat image, unable to show any depth correlation from well to well. The first 3D surface seismic surveys were recorded in the early Nineties only for the gold mines of the Witwatersrand, after a series of serious new shaft sinking failures. The wrong geological locations of these shafts resulted in financial loss of several hundred million rands. The era of3D seismic just started in South Africa and till 1997, all seismic done in the country was for gold exploration with geological target depths close to the oil exploration average depth of investigation. A very important breakthrough was reached when the depth accuracy of the seismic image was tested in real scale as the stopes were surveyed. An error of amplitude of 20 m was usual when true depth was compared with the seismic image predicted depth and shape. This accuracy, completely unknown in oil exploration, started to gain supporters of seismic methods in the mining community but the cash problems and the concentration/disappearance of gold mines in the late Nineties, led to the belief that seismic would be just a very short exploration activity for the mining sector. ort exploration activity for the mining sector. But starting in 1998 with Impala, a tremendous and continuous 3D surface seismic activity occurred in the platinum mining sector. The seismic world got used to new terms such a Merensky and UG2, which have replaced the VCR and black reef. If the primary expectation of platinum surface 3D seismic was to determine and ascertain new shaft locations, as for the gold mines, the quality of seismic data led the mine geologists to require smaller and smaller imaging of geological objects. In addition to the main structural image, small faults, potholes, and shear zone were common expectations of platinum seismic. In a constant velocity environment, what saved the day was the sharp density contrast between the PGM reef and the embedding geology. A good contrast of impedance exists in the whole Bushveld and is sufficient to have enough reflected waves from the PGM main layers to build a high quality seismic image of the subsurface. Recent advances in technology have led in less than 10years to major improvements in the seismic acquisition by using high frequency vibrating seismic sources, but also in processing and interpretation. With these latest improvements, seismic can detect objects of 7.5 m size, either fault throws, flexures, etc. The PGM formations of the Eastern limb of the Bushveld Complex are now accessible for seismic imaging, with cost per square kilometre comparable to the borehole cost of the same surface unit. The economically acceptable seismic surveys can be used for UG2 structural imaging up to a depth of 210 m below surface. Linked with borehole information, 3D seismic today offers a wide range of information for mine development: structural imaging, small fault detection, pothole and shear zone identification. All users of 3D seismic have also used this technique as a tool in the process to qualify their mineral reserves and especially from the category ?inferred? to the category ?measured?. Junior mining companies, in the feasibility stage of their projects, are also quite eager to use seismic as a reserve certification tool, when they present financial statements to future potential investors. Junior mining companies, in the feasibility stage of their projects, are also quite eager to use seismic as a reserve certification tool, when they present financial statements to future potential investors. The current high demand on platinum, pushes the seismic towards new technologies to be implemented in order to improve the final image. Using surface and borehole seismic together or acquiring seismic surveys with multi-component receivers have been just introduced in South Africa. In less than 10 years, surface seismic by adapting its methods to the special case of the Bushveld, became a mandatory step in mine development and ore resources evaluation. As part of the ?seismic? world we are proud to be a major player the ?surge? of platinum exploration and production in these last years and we will certainly increase our synergy with the mine sectors in the exciting coming years.

Jan 1, 2006

By T. G. P. Vasquez

The elimination of metal ions from aqueous solutions by biosorption plays an important role in water pollution control. Heavy metals are hazardous to the aquatic ecosystem and pose possible human health risk. Beside the toxic and harmful effects to organisms living in water heavy metals also accumulate throughout the food chain and may affect human beings. Conventional methods for removing metals from aqueous solutions before they are disposed of include chemical precipitation and sludge separation, chemical oxidation or reduction, ion exchange, reverse osmosis, electrochemical treatment, and evaporation. Alternative processing methods are being considered more seriously. Sorption and/or complexation of dissolved metals species based on the chemical activity of biomass, known as biosorption, is the base of the new technology for metal removal and recovery. Different types of biomass (dead and alive) have been investigated for biosorption of heavy metals ions. In the present work, the cadmium biosorption capacity and bioflotation of Rhodococcus opacus were studied. The adsorption capacity of biomass was investigated by batch experiments, the influences of some variables like pH and ion concentration were evaluated and the experimental data obtained for each metal were evaluated and fitted using adsorption and kinetic models. The bioflotation process showed that R. opacus has excellent features as collector and foaming agent after metal biosorption. Around 90% of cadmium uptake by the biomass was achieved by bioflotation.

Jan 1, 2006

By R Vleggaar

In addressing a short-term operational need for the relocation of a tailings storage facility reclaim pond, a mine has achieved a host of water management objectives. Through effective planning and adoption of a strategic æwhole of mine lifeÆ approach, the mine has achieved significant environmental, social and economic benefits. A review of all water management aspects across the site identified a host of other interrelated water issues and concerns which, if dealt with individually, would prove too costly for individual operational departments. When considered as a whole, however, the issues became opportunities and provided the stimulus for integration of the site water management system. The development of site water and solute balance models provided the tool by which a number of water management options/strategies could be evaluated. The conceptual design and costing of the proposed water infrastructure further facilitated the evaluation of the multiple benefits to be gained from each option. A business case could then be made to mine management for the preferred option. The recommended water management strategy finally recommended to the mine not only provided a tailings storage facility (TSF) reclaim pond, but also provided for:increased wastewater recovery from the TSF, the capture of all waste rock dump run-off, additional water harvesting from local creeks, increased wastewater reuse, improved environmental water management, infrastructure that could be used by the local community after mine closure, and overall cost savings. This paper illustrates how effective water management planning can provide both short-term economic and environmental benefits, as well as long-term social benefits.

Jan 1, 2006

By Lyn Jones, Mike Bratty, Rick Lawrence, David Kratochvil

"The treatment of water is required at many mining operations to remove metals and prevent the discharge of contaminated water to the environment. In other cases, water treatment is used to provide better quality water for recycle to the processing plant, or to process bleed streams in hydrometallurgical operations in order to prevent deterioration in metallurgical performance or process equipment. BioteQ Environmental Technologies Inc. has developed and commercialized the BioSulphide® Process which can provide an alternative for these treatment needs and which can also be used for profitable metal recovery, particularly in cases where conventional metal winning techniques are not economical. The BioSulphide® Process is a high rate anaerobic biotechnology for on-site production of H2S from sulphur species, although for smaller flows and metal loadings, the use of chemical sulphide reagent might be more cost effective. Both new projects and existing commercial operations, used for removal and/or recovery of copper, nickel, and zinc, and which range in sulphide generating capacity from 50 kg/day to 3.7 tonnes/day, are discussed. Particular focus is placed on the results of operations at the Raglan Mine in Northern Quebec where dissolved nickel is removed from contaminated water at a high efficiency through the precipitation of nickel sulphide. Plant effluent is discharged directly to the receiving environment and the high-grade nickel sulphide product is combined with the nickel flotation concentrate produced at the mine. The plant at Raglan will replace the existing conventional water treatment plant and will eliminate the need for on-site storage of treatment plant sludge.INTRODUCTIONThe BioSulphide® Process, which produces low cost H2S for use in selective metal precipitation, offers a low capital cost alternative which can operate efficiently and cost-effectively within a wide range of flows and solution grades. Since the technology can be used to recover metals from solutions with low flows and metal grades, the technology is also applicable to environmental applications for water treatment, with the sale of recovered metals providing an offset to treatment costs. For environmental control, the technology has a distinct advantage in being able to meet strict effluent discharge criteria due to the very low solubility of metal sulphides. To date, BioteQ Environmental Technologies has designed and constructed three plants for metal sulphide precipitation, with another three projects in the advanced development stage."

Jan 1, 2006

By Abhishek Lahiri

Titanium dioxide is extracted from titaniferous ores by chloride and sulfate processes. These two processes produce wastes in the forms of iron chloride, iron sulfate and rare earth oxides gangue, each of which has to go through a further treatment before it can be disposed safely, which may be expensive. The shortage of high-grade ores is also making the two conventional processes less efficient. In view of the above mentioned problems, an alternate beneficiation process of roasting titaniferous ores with soda ash is discussed. The advantage of this process is that, there is no production of wastes. The impurities present in the ore can be selectively separated after the roasting process. The roasting of titaniferous ores with soda ash was carried out between temperatures of 873K and1173K for several hours. The roasting process resulted in the formation of complex alkali compounds and various sodium titanate compounds, depending on the Na2CO3to ore ratio. The phases formed after roasting were characterized using the X-ray powder diffraction (XRD), X-ray florescence (XRF) and scanning electron microscopy (SEM) techniques. The phase equilibria in the Na-Ti-O system are evaluated and compared with the phases obtained after the roasting process. The effects of temperature and the proportion of sodium carbonate on titaniferous ores are also discussed. From the experimental data, the overall reaction kinetics and phases formed were analyzed to ascertain the mechanism of overall reaction and the rate-limiting steps.

Jan 1, 2006

By John O. Marsden

The past fifteen years have seen a number of important developments in copper hydrometallurgy, including the commercial application of biological heap leaching of secondary (chalcocite-dominant) copper ores, the commercial demonstration of chalcopyrite concentrate leaching technology using pressure leaching and biological processes, and the application of novel configurations of solution extraction circuits. Significant emphasis is now being placed on the development of effective stockpile leaching practices for primary ores (chalcopyrite and bornite-dominant mineralization). Some of these developments have been highly successful, and will pave the way for further development and commercialization. Others have been less successful. These developments are reviewed in the context of the metal price cycle and trends for the future are identified

Jan 1, 2006

Accurate geometric models of orebodies establish the framework for reliable mineral resource estimates that provide a basis for further exploration and mine planning, as well as for financial models that ultimately determine the economic viability of a deposit. Traditional, explicit geometric modelling techniques that are utilised for resource modelling by the general mining software packages, such as MineSight«, involve manually digitising interpreted ore outlines that must be carefully linked to create valid geometric solid models. An alternative, implicit modelling method, employed by LeapfrogTM software relies on a fast method of global interpolation, which offers several advantages over traditional modelling techniques. Although previous case studies have documented the relative efficiencies of the two approaches, the accuracy of the two methods has not been previously quantified and compared. This study quantifies the accuracy of solid models created using explicit and implicit methods, and compares the differences between the models. Solid models of the Doris Hinge vein gold deposit (located in the Hope Bay district, Nunavut, Canada) are constructed from preliminary and follow-up drilling data using both modelling techniques. The accuracies of the solid models generated using preliminary drilling data are determined by measuring the 3D distance between the surface of the models and the actual contact location defined by the follow-up drilling data. Additional comparisons based on volume, cross-sectional area and surface differences were made between both phase 1 solid models and solid models constructed from phase 2 drilling information. The overall results of this study find that the MineSight« and LeapfrogTM solid model accuracies are virtually the same, and that their volume, cross-sectional area, and surface differences are comparable. This study concludes that the implicit modelling technique generates accurate solid models that can be used in place of explicit models as ore shells for resource estimation in certain circumstances.

Jan 1, 2006

By Z. Trojanová

Mg micropowders generated by gas atomisation of a magnesium melt with argon were mixed and ball milled with ceramic nanoparticles prepared by laser-induced gas phase reaction. The materials were then hot extruded. Specimens were deformed in tensile as well as compression tests at temperatures between 20 and 300 °C at a constant initial strain rate. The flow stress is significantly influenced by the test temperature. The yield stress decreases with temperature. This decrease and the flat character of the stressstrain curves at elevated temperatures indicate possible contributions of softening processes. The materials studied exhibit high-damping characteristics. The results are analysed and possible mechanisms are discussed.

Jan 1, 2006

By A. C. Neiva

An energy-dispersive x-ray fluorescence spectrometer was assembled with the aim of analysing alloys and corrosion products of artistic, ethnological and archaeological pieces. The spectrometer is semiportable and consists basically of an 60kV/1.5mA X-ray tube with W anode and a Si-drift X-ray detector with Peltier cooling, with no need of liquid nitrogen. It was used for the analysis of the alloys and occasional corrosion products of several metallic pre-Hispanic pieces of the Museum of Ethnology and Archaeology of the University of São Paulo. Special care was taken to account for the contribution of spurious radiation from both the Pb primary collimator and the Zr detector collimator. The main components of most alloys were Au, Ag and Cu, but Pb, Ca, Fe and other elements were also identified. The characterization of the alloys and corrosion products is important for the subsequent conservation of the collection.

Jan 1, 2006

By D. Seo, P. Au, X. Husang, D. Nagy

The production of single crystal (SX) turbine blades represents the current stateof- the-art in Ni-based superalloy design. With complex casting processes and alloy composition modifications, SX superalloys exhibit superior high temperature mechanical properties to their polycrystalline counterparts. Stresses and plastic deformation can occur in SX nickel-base superalloy engine components at various stages during their manufacture and use. For examples, stresses are created during initial solidification and also during solid state processing such as shot peening, grit blasting, blending, electrodischarge machining and welding. Stresses may also be created during service due to random events such as foreign object impacts. Subsequent exposure of SX to high temperatures during solution heat treatment and brazing repair can result in recrystallization which has been shown to be detrimental to both creep rupture strength and fatigue performance of the components. It is therefore the objective of this paper to understand the recrystallization behavior of two SX superalloys, PWA 1484 and 1483, subjected to pre-stressing and subsequent heat treatments.

Jan 1, 2006