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By F. Charette

Instrumentation has been developed that can monitor the strain applied to a D-Bolt up to 7.5% elongation. The technology far exceeds the limit for foil resistance strain gauges. In the laboratory the instrumentation has provided insight into the fundamental behaviour of the D-Bolt following yield. Currently the instrumentation is undergoing field trials at a number of Canadian Mines. Discussion on field results is provided with regards to significance, reliability and temperature effects.

Aug 1, 2013

By O. -J. Siljan

"Refractory materials are an integral part of aluminium production. One special feature of aluminium making is the prominent role of sodium in all parts of the production process. This presence of sodium inflicts stresses on the refractory materials through reactions and may cause severe damages to the refractory linings. The present paper address possible reactions between sodium and refractories in anode bake furnaces, electrolytic pots and casting furnaces. The discussions presented in the paper points to the importance of selecting materials with excellent alkali resistance in all parts of the aluminium making process, although alkali resistance is not the sole parameter to determine refractory life-time. ""Acid"", i.e. silica-rich alumino-silicate refractories are shown to be the best materials for aluminium electrolysis cell potlinings, whereas high- alumina refractories based on minerals like andalusite seems to be the preferred choice for anode bake furnaces as well as cast house furnaces."

Jan 1, 2004

By M. E. Austin

Many numerical models for the tubular solid oxide fuel cell (SOFC) exist, with various degrees of sophistication. However, the question of what physics must be modelled, and what can be neglected has not been resolved. A parametric model is proposed and analyzed to quantify the influence of thermal phenomena such as reaction heat generation, cathode channel convective cooling, and thermal radiation with participating media. Currently, a three-dimensional model is used to simulate the conditions of an anode supported cell in the centre of a tube bundle. The interconnect and nickel foam spacers that bridge adjacent cells in series and parallel, respectively, are neglected thus enabling a domain consisting of a 45o azimuthal section of the tube. The conservation equations for mass, energy, and species transport are solved using commercial computational fluid dynamics software, and radiation heat transfer is also modelled using a Discrete Ordinates method. Finally, temperature-dependent material properties and reaction rates are used. The model predicts lower overall temperatures than models that do not include radiative heat exchange and more moderate temperature gradients than those that ignore participating media radiation. Further, different regimes are identified, from convection dominated heat transfer to radiation dominated heat transfer. The results can be used to aid in the selection of appropriate models for a given fuel cell operating regime.

Jan 1, 2005

By Deborah A. McCombe

"One of the cornerstones of NI43-101 Standards of Disclosure for Mineral Projects is the technical report. The purpose of the report is to provide a summary of the scientific and technical information concerning mineral exploration, development, and production activities on a mineral property that is material to an issuer. The reports must be prepared in accordance with NI43101 and Form 43-101F1 Technical Report and the information must be current as of the date of the filing of the technical report. As these reports provide important information to the investing public, qualified persons preparing these reports should, as much as possible, write in plain, simple language that can be easily read and understood by people who are not geoscientists or engineers. So let’s review some of the common deficiencies with technical reports. Non-current technical report Some of the factors you should consider when determining if your previously filed technical report is still current are as follows: •,Is there new technical information on the property, such as drilling, assays, metallurgical testwork? •,Have you made changes to key assumptions, parameters relating to mineral resources or mineral reserves, or economic analysis? If you have completed the previously recommended work, are your recommendations still current? Similarly, are your report recommendations consistent with what you are telling your shareholders or disclosing in the use of proceeds in your offering documents? For example, if the recommendations in the report consist of further exploration and metallurgical test-work prior to completing a preliminary feasibility study and you have completed the proposed work and are now raising money for a final feasibility study, the report is probably not current."

Jan 1, 2003

By Deni Côte, Marcel Vallée

"The Guide to the Evaluation of Gold Deposits reviews the successive evaluation steps in the domains of geology, engineering, and economics. The Guide analyzes, in a systemic perspective, the sequence of exploration, development, and evaluation work required to bring a mineral deposit to production. The aim is to identify the metal/mineralization losses and ore dilution that each work step contributes to the evaluation and mining process. The procedure allows one to maximize the income and profits of a mining operation, and to reduce the risks of financial losses tied to investment decisions in the mining sector. For greater efficiency, the criteria of reserve estimation and classification should be integrated with the evaluation steps and methods. At earlier stages of deposit development, when quantitative knowledge is available mainly on the geological axis, the term ""delimited mineral deposit"" should be used. The term ""reserve"" should be used only in an operating mine or in a mining project, when information in the geological, engineering, and economic domains is adequate to ensure technical and financial feasibility. ""Reserves"" are by definition ""mining reserves"". Each category of proven/probable reserves and measured/indicated deposits should be subdivided into two classes to express better the many steps of mineral valuation. The category of ""possible reserves"" shall be replaced by that of ""inferred mineralization"". This system, derived from the Australasian Code, can easily be integrated into current practices of the exploration and mining industry within a short timeframe. The proposal to develop the use of the margins of error of the estimates at a confidence level of90% should be viewed in a longer timeframe. Establishing the precision of the mineral inventories and distinguishing between categories and classes by means of the margin of error will require more work and a longer break-in period.SOMMAIRELe ""Guide d’évaluation des gisements d'or"" analyse, dans une approche systémique, les travaux d'évaluation et de mise en valeur des gisements minéraux dans l'axe de la géologie, dans l'axée l'ingénierie et dans I ‘axe de l'économique. L’objectif est d'identifier la contribution aux pertes de métal et à la dilution du minerai des diverses étapes de l'évaluation et de l'exploitation du gisement. Ceci aid erra à maximiser les revenus et les profits, et ainsi, à réduire les risques départe financière que comportent les décisions d'investissements dans le secteur minier. Pour atteindre ces objectifs, iI est essentiel de relier les critères d'inventorie et de classification des réserves aux méthodes d'évaluation des gisements. Aux stades antérieurs du développement minéral, lorsque les connaissances quantitatives ne s'étendent qu’à l'axe géologique, le terme ""gisement délimite"" sera utilisé. Le terme ""réserve"" ne sera utilisé que dans une mine en exploitation au dans un projet minier, lorsque l'information dans les axes de la géologie, de l'ingénierie et de l'économique sera appropriée pour en garantir la faisabilité technique et économique. Chaque catégories des réserves, prouvée et probable sera subdivisée en deux classes pour mieux qualifier les niveaux d'évaluation du projet. La catégorie actuelle des réserves possibles sera remplacée par celle des ""minéralisations inférées"". Plusieurs essais démontrent que le système propose, qui s'inspire du Code australasien, peut facilement et rapidement s'intégrer dans les pratiques de l'industrie. II pourrait également contribuer à une standardisation des méthodes et des nomenclatures à l'échelle internationale. La proposition d'utiliser les marges d'erreur des estimes au niveau de confiance de90%pour caractériser les estimations se situe dans une plus longue perspective. Cette application demandera des développement méthodologiques additionnels ainsi qu'une période de rodage."

Jan 1, 1992

By Nirmal Weerasekara

Mill liners serve the dual purpose of protecting the shell from wear and transferring the rotary motion of the mill to an effective grinding action. As the liners wear, the efficiency of energy transfer changes, so there is balance between liner profile for wear and for milling efficiency. A tool that can simultaneously predict the evolution of the liner profile and the associated change in milling efficiency should prove most useful in optimal liner design. This paper presents such an approach, based on measured 3D liner profile data informing 3D DEM simulations of charge motion and liner wear modelling.

Jan 1, 2012

By M. A. Creaney

"The Construction Group is responsible for the construction of all of Placer Dome’s major projects and contributes to the development of most major feasibility studies. This group includes an international collection of Placer Dome people who have built mines in Papua New Guinea, Australia, Chile, the United States and Canada. This paper outlines the changing role of the Construction Group from the early days of single projects to today, when several projects are in various phases from feasibility to construction. The projects’ total annual budgets have from time to time exceeded one billion dollars. IntroductionAs the competition increases globally between the major gold mining companies, the impetus continues to build mines at the lowest cost with the shortest construction schedule. Placer Dome has more than met that challenge by building mines around the world at a pace that was not contemplated 15 or 20 years ago. Since 1960, Placer Dome has built 30 mines and expansions at a cost of nearly 4.5 billion dollars.In the last six years alone, Placer Dome has built 14 mines and expansions, worth 2.6 billion dollars. The company’s success is due primarily to Experience, Innovation, People and Standards.The diversity between projects, let alone the pace, has been a challenge. Placer Dome has built mines around the world in a variety of extreme climates and distinctive cultures. The construction experience gained from these projects has allowed Placer Dome to develop an extensive knowledge and data base making it easier to “fast track” projects.Through the years Placer Dome has developed a human resource base. It now has an experienced and adaptable core team of people able to set up construction projects and build mines anywhere in the world. By developing standards and systems to support the projects they can act as soon as a new project is approved, and complete the projects quickly and effectively. The result is that Placer Dome now has the construction expertise to build its own mines, giving them the competitive advantage that allows them to design and construct a mine in the least time at the lowest capital cost. This was demonstrated in March 1997 with the completion of the construction of two new mines in 12 months."

Jan 1, 1998

By G. A. Gamble

"The inlet air velocity profile of any surface mine ventilation fan is an important factor when designing the connecting ductwork from the mine shaft collar to the fan. Deficient fan performance can be the result of ductwork that adds unnecessary pressure loss and/or adversely influences the fan inlet air conditions (velocity profile). The need for optimized inlet air conditions begins with discussing the process of performance testing during the development of the fan performance curve. Additional discussions include design of the shaft collar connection and the connecting ductwork. A preferred design of ductwork for parallel fan installations will be illustrated.INTRODUCTIONThe inlet air velocity profile of any surface installed mine ventilation fan is one of the most important factors to consider when designing the connecting ductwork from the mine shaft collar to the fan. Oftentimes deficient fan performance can be traced to poorly designed ductwork that adds unnecessary pressure loss and/or adversely influences the fan inlet air conditions (velocity profile). Such designs may lead to added power requirement, excessive vibration and noise, and reduced fan performance.Understanding the need for optimized inlet air conditions begins with discussing the process utilized when factory testing takes place during the development of the fan performance curve.Additional discussions include design considerations for the shaft collar connection, the connecting ductwork, and fan inlet. Illustrations of cost savings and pressure losses will be included for audience consideration. The design of ductwork for parallel fan installations on the surface is another issue that requires consideration. A preferred method will be illustrated.The selection of accessory components, such as self-closing doors, can also add to the potential for reduced fan performance. Several components will be discussed.An elementary presentation of the Air Movement and Control Association (AMCA) Standard 201 “Fans and Systems” will be included to provide background for those audience members that want additional technical explanations of the need for a uniform inlet air velocity profile at the fan inlet."

Jan 1, 2019

By J. Keith Haddock

"Introduction The Coal Valley Mine is operated by Luscar Stereo (1977) Ltd. with the Alberta Energy Company having a minority interest. The mine produces 2.0 million tonnes of bituminous thermal coal per year. Deliveries include 1.5 million tonnes to Ontario Hydro and 0.5 million tonnes to the export market via bulk handling facilities on the west coast near Vancouver, B.C. There are a number of mining methods utilized at the mine including open-pit by truck and shovel, strip mining with large draglines and stripping with scrapers. The mine is located 100 km south of Edson, Alberta. Geology The coal measures are concentrated within a 210-metre int~rval of the Paleocene section. The coal seams were originally named by the mining companies in the earliest days of development of the area and these names continue to be used today. Of the five main seams, only three are presently economic to mine based on quality, thickness and depth of cover. These are the Val d'Or, Upper Silkstone and Mynheer. The Coal Valley Mine is located in the structurally deformed foothills area of Alberta and the structure of each mining area is therefore very complex. The general bedding strike is 305 degrees azimuth but major thrust faulting and folding has extensively deformed the natural seams as a closer examination will show. The Mynheer Seam, located at the base of the coal measures, ranges in thickness from 5 m to 10 m and has numerous bentonite and shale partings. Because of inherent geological features, the Mynheer Seam has been subdivided into two zones, the Mynheer 'A' and the Mynheer 'B', and the mining of coal in these zones has necessitated the utilization of distinctly different mining methods. The structural regime of the Mynheer 'A' zone consists of an overturned asymmetrical anticline crest containing a steeply dipping major thrust fault which has raised the seam above the present topographic level. Further extensive shearing and rotation of the coal has resulted in the coal taking a 'pod' shape. The Mynheer 'B' Zone is a continuation to the southeast along strike from the Mynheer 'A' Zone. The bedding dips to the southwest at an average of 12 degrees and is interrupted at the south end by a transverse fault and to the north by its outcrop at the surface."

Jan 1, 1985

By Chr. Krause

Within the scope the collaborative research centre 599 (Medical University of Hanover, University of Veterinary Medicine Hanover, University of Hanover) the behaviour of the degradation of magnesium materials as implants are investigated by using animal experiments (rabbits). Thus extruded cylindrical pins from the magnesium alloys MgCa0.8%, WE43 and LAE 442 were implanted intramedullary in the tibiadiaphyses. The implantation duration was 3 and 6 month. After the explantation 3 point bending tests were carried out to investigate the possible changes of the mechanical properties. Clearly changes in dependence of the implantation duration could be determined. The three magnesium alloys show a decrease of the mechanical resistance with an increasing implantation time. To evaluate the degradation process, wich is the reason for the changes, micrographs and element analyses (EDX) have been accomplished after the 3 point bending tests. The micrographs show for all used magnesium alloys corroded surfaces but no preferred corrosion on the grain boundarys. The element analyses show beside a layer which is rich in calcium and phosphorus an agglomeration of rare earth elements in this layer. With these results a using of magnesium alloys as a material for implants can be announced.

Jan 1, 2006

By Tyler J. Irving

"In June, 2018 Lalor Mine experienced a catastrophic blade failure of its No. 2 main exhaust fan. Over the following weeks several key changes were made to the auxiliary ventilation system to allow for continued production while the exhaust fans were repaired. Issues encountered during the period of reduced ventilation, and how they were addressed, are analyzed. The suspected causes of the exhaust fan blade failure and how risk was mitigated during the reconstruction are discussed. Key findings and lessons learned are summarized.INTRODUCTIONLalor Mine, owned and operated by Hudbay is an underground zinc, gold, and copper mine located in northern Manitoba. The mine workings extend to a depth of 1090 metres below surface and is ventilated using a push-pull system. The mine exhausts through the main exhaust raise; equipped with two, 2,500 HP fans and upcasts through a portal located at the neighboring mine, Chisel North. Air is supplied to Lalor Mine through four intake fans: The Production Shaft Downcast (two, 250 HP), Lalor Downcast (one, 400 HP), and Chisel Downcast (one, 600 HP) fans (Figure 1). In June 2018, Lalor was scheduled to produce approximately 4,000 tpd.On June 20, 2018 at 2:52 pm Lalor Mine experienced a fault on the Variable Frequency Drive (VFD) for Exhaust Fan No. 1. Time would be needed to complete the necessary repairs. The No. 2 exhaust fan was ramped up from 525 rpm to 800 rpm, 90% of its capacity, in order to maintain underground ventilation. At 4:46 pm, approximately two hours after the rpm was increased, exhaust fan No. 2 experienced a catastrophic blade failure. The forces from the blade failure resulted in the top half of the fan housing being thrown 50 metres from where it was installed; with several large sections of fan blade being thrown further (Figure 2)."

Jan 1, 2019

By C. Karpuz, Y. S. Istanbulluoglu

This paper describes the results of convergence measurements conducted about five years for the re-use gate roadways at OAL lignite mine in Turkey. Double lignite seams separated with a marn layer, are mined with long-wall retreating mining system at the mine. Rib pillar has been abandoned and gate roadways were planned to be packed for the re-use of full extraction. Various packing systems have been attempted, namely three rows of woodenchock, one row of wooden chock plus concrete wall and concrete wall only. The re-use of maingate roadways packed with wooden chock yielded 62% of closure. Lastly developed concrete packing of 3 meters wide and specially developed support set composed of three friction props and a cap, which is a modification of yieldable set, have successfully maintained the main and tail gate roadways stability with a total vertical convergence of 32%. Good correlation has been established between pack stiffness and floor heave as well as maingate and tailgate convergences. The elimination of rib pillars by re-use of gate roadways increased the coal recovery by 20% and decreased the development/production ratio from 0.065 m3/ton to0.022 m3/ton.

Jan 1, 1997

By M. J. MONEA

Canada's only economic high-swelling bentonite deposit is mined in Wilcox, Saskatchewan, by A vonlea Mineral Industries Limited. The bentonite resulted from devitrified and altered volcanic ash released during the Laramide Orogeny. Volcanic ash was deposited in a pre-Cretaceous basin that was formed by salt solution collapse structures. Sedimentary rocks in the Wilcox area belong to the Snakebite Member of the Upper Cretaceous Bearpaw Formation. Bentonite beds are 61 cm, 46 cm and 30 cm thick; these are separated by 365 cm and 182 cm of shale respectively. Saskatchewan bentonite is used primarily in the oil well industry.

Jan 1, 1984

By R. E. Ray

"As real estate for new development in urban settings becomes scarce, commercial high rises are being constructed above open passenger rail tracks and vehicular roadways. Rail and roadway overbuilds are treated as tunnels requiring emergency ventilation systems for train or automobile and truck fires. The value of floor space in residential and office towers poses challenges to engineers responsible for designing fan rooms and shafts for tunnel ventilation systems within the towers. This paper describes a case study of the unique incorporation of tunnel ventilation fan plants in the overbuild structure of a passenger railyard and an adjacent roadway.INTRODUCTIONTunnel ventilation systems are required for passenger rail and transit (subway) tunnels by the NFPA 130 Standard for Fixed Guideway Transit and Passenger Rail Systems, and the NFPA 502 Standard for Road Tunnels, Bridges, and Other Limited Access Highways requires tunnel ventilation systems for vehicular (road) tunnels. Passenger rail and transit (subway) tunnels are typically ventilated with a series of shafts placed longitudinally along the tunnels to provide piston relief for normal train operations and emergency ventilation of train fires utilizing reversible axial flow fans. The shafts are incorporated in dedicated ventilation buildings that house the tunnel ventilation fans and starters, switchgear to power the fans and other equipment and systems in the building, Programmable Logic Controllers (PLCs) to control fan operation with Supervisory Control and Data Acquisition (SCADA) software, and HVAC fans and ductwork to ventilate the spaces in the building. These ventilation buildings may also provide access to the tunnels below with ingress/egress stairs for use by first responders and firefighters entering the tunnels and train or transit system passengers exiting the tunnels in an emergency. A photograph of a passenger rail ventilation building that encompasses four tunnels is shown in Figure 1."

Jan 1, 2019

By Hamidreza Soltanzadeh

The injection of CO2 into a reservoir or aquifer can potentially result in deformation, induced fracturing and fault reactivation in the injection zone and/or the rocks that surround it. This paper reviews the data collection and geomechanical analyses performed to assess these potential hazards for the Heartland Area Redwater Project (HARP), in which CO2 sequestration is being considered in a carbonate (Leduc Formation) reef. A three-dimensional mechanical earth model (3D MEM) was developed using available geophysical log data from several wells. The geomechanical response to CO2 injection was studied using a finite element numerical model based on the 3D MEM and pore pressure distributions predicted using a reservoir simulator. The modeling results suggest that the potential for induced fracturing and fault reactivation is low and the maximum predicted ground surface heave is less than 2 cm. Sensitivity analyses conducted with a 2D geomechanical model that was extracted from the 3D model confirm that this conclusion holds true even when a reasonable measure of uncertainty in rock mechanical properties, ambient pore pressures and horizontal stress magnitudes is accounted for.

Jun 1, 2012

By Stephen G. Mlot

The evaluation of mineral projects involves the identification, mitigation and management of significant uncertainty. Benchmarking is an essential and effective way of increasing confidence and reducing uncertainty associated with input parameters and assumptions. Comprehensive and detailed benchmarking will ensure ?best practice? technologies, methods and systems have been considered and that the appropriate practices can be identified and incorporated into the project. In conjunction with the involvement of experienced industry practitioners, benchmarking is best employed throughout project evaluation to enable early identification of ?errors?, producing more accurate and predictable outcomes. Considerable time and effort is required to gather data and information, which should be benchmarked by the project evaluation team. There is a history of mining projects underperforming, on production, on costs and on return to the investors. The quality of mine plans and feasibility studies, and the quality of the input data is being questioned in many ways. Benchmarking assists sound project evaluation practices, by providing a database of actual results, to validate project inputs and outcomes, ensuring they are realistic and achievable. Benchmarking also provides unbiased, statistical support as the basis for sound investment decision making and ensures well considered decisions are made resulting in a more efficient study process. The evaluation of the quality of projects which are the subject of transactions also benefits from the use of real data obtained from a benchmarking database. Vendors are quick to highlight the benefits of their projects, and conceal the flaws, inflating the value. Buyers will want to quantify the potential of a project through the due diligence process relying on actual results from benchmarking. For the reasons broadly outlined above, benchmarking should be considered as an essential component of effective Project Evaluation.

Aug 1, 2013

By Erik Richer La Fleche

LEGAL RISKS LEGAL RISKS ARE COUNTRY RATHER THAN PROJECT RISKS OTHER COUNTRY RISKS ARE POLITICAL AND MACRO-ECONOMIC RISKS COUNTRY RISKS ARE EXAMINED AFTER PROJECT RISKS COUNTRY RISKS COUNTRY RISKS INCLUDE: WAR AND ARMED CONFLICT TERRORISM AND SABOTAGE CURRENCY INCONVERTIBILTY AND TRANSFER NATIONALIZATION AND CREEPING EXPROPRIATION GOVERNMENTAL BREACH AND REPUDIATION OF CONTRACT CHANGE OF GOVERNMENT CORRUPTION COUNTRY RISKS FIRST NATIONS AND LANDOWNER CLAIMS LABOUR UNREST SINGLE CAUSE ACTIVISTS REGULATORY AND BUREAUCRATIC DELAYS CONFLICT BETWEEN GOVERNMENT LEVELS ETHIC AND RELIGIOUS TENSIONS INTERNATIONAL SANCTIONS TAXATION CHANGES CHANGES IN LAW

May 1, 2013

By D. W. Ginsberg, D. Cieplinski

"The lifetime cost of a material handling system, or any mine system, can be reduced through the application of quality engineering. Dynamic simulation is a powerful tool that can be used to enhance the experience and ingenuity of the design team. It cannot only de-bottleneck the system to improve system productivity, but also define critical design criteria to eliminate over-design and reduce capital cost. Eliminating over-design also reduces operating costs by lowering component replacement costs and by ensuring all parts of the system operate at a higher utilization and efficiency. IntroductionA mine owner’s profitability is improved when a mine is developed at the lowest lifetime cost. This cost relates not only to capital and operating costs, but also, to a great extent, on the efficiency and reliability of the operation. These factors are tied directly to the quality of the engineering which depends on the experience of the engineers involved, and their ability to apply known system information in a rational and constructive manner.It is becoming apparent that it is increasingly more difficult to deliver the quality of engineering expected and needed to provide attractive lifetime costs using traditional design methods. Historically, system information has been evaluated based on a limited amount of information to which global rules-of-thumb and the engineer’s personal experience were applied to develop design criteria. However, market forces are dictating that more system parameters be defined and that they be defined more accurately so that the most economical system can be developed. This increase in the volume of information and the need for more accurate predictions is straining, if not already exceeding, the ability of engineers to apply simple global rules of- thumb and to combine all the information in a rational, comprehensive and representative set of design criteria. Furthermore, as proposed system production rates increase beyond established industry practice, the extrapolation of the engineer’s experience becomes more difficult and increases the risk in the proposed design."

Jan 1, 1998

By F. S. Su, P. Z. Pan, X. T. Feng, F. Yan, W. W. Ji

"This paper aims to simulate the spalling failure behavior in hard rock based on a self-developed numerical model, i.e. a rock discontinuous cellular automaton (RDCA). A crack initiation and propagation criterion is proposed based on the plastic strain, which is used to link the continuity and discontinuity during the failure process. The discontinuities of rock, such as cracks and other internal boundaries, are represented by discontinuous displacement functions, i.e. tip enrichment and step enrichment. The partition of unity is used to improve integral precision of the elements intersected internal boundaries, which is traced by a level set method. Arbitrary crack geometries can be conveniently represented and it does not require any remeshing in the modeling of crack initiation, propagation and coalescence. Numerical modeling of excavation in hard rock using RDCA is conducted. The spalling failure process of hard rock induced by excavation is well simulated. The depth and shape of hard rock spalling failure are good agreement with in situ observation.INTRODUCTIONThe excavation in rock mass is more and more popular. At the same time, the disasters, such as rock burst, rock spalling and falling etc, induced by excavation are quite prominent. Numerical modeling is an important way to help us understand the failure mechanism of rocks. Many numerical methods have been used to simulate the excavation of rock mass. For example, the finite element method (FEM) (Karakus and Fowell, 2003), the discrete element method (DEM)(Cundall and Strack, 1979, Labra et al., 2008), Finite difference method (FDM)(Zhu et al., 2009), Element Free Galerkin Method (Belytschko et al., 1994), Discontinuous displacement analysis (DDA) (Shi, 1988) and Boundary element method (BEM) (Katsikadelis, 2002, Chen and Hong, 1992) are commonly found in the stability analysis of excavation in rocks. In the modeling of crack propagation or excavation, most of these methods are tedious since the internal boundaries have to be consistent with the element boundaries. And in many cases, the remesh has to be conducted. In recent years, people are interested in particular types of FEMs, such as the extended finite-element method (XFEM), the particle discretization scheme finite-element method(PDS-FEM(Hori et al., 2005, Oguni et al., 2009)), the combined finite-discrete element method (FEM/DEM) (Munjiza and Wiley, 2004, Cai, 2008) and spectral-element method(Gharti et al., 2012) etc."

Jan 1, 2015

By S. Masambi, S. M. Bradshaw, C. Dorfling

The presence of iron in base metal leach solutions complicates nickel and copper recovery processes. Leach solutions are commonly purified by precipitating iron as hematite, jarosite or goethite. Fast oxidation of ferrous to ferric is an important step to remove iron by precipitation at low pH values. This study reviews the ferrous oxidation mechanism and reaction rates in chloride media using molecular oxygen. This work contributes to the development of a better understanding of iron precipitation processing steps, which continues to be an important matter in hydrometallurgy. The specific objectives were to investigate (1) the effect of key process variables (acid concentration, copper concentration, and temperature) on the rate and extent of ferrous oxidation by dissolved oxygen and (2) the oxidation mechanism by varying chloride and hydrogen ion concentrations separately. Batch oxidation tests were performed using synthetic chloride solutions containing 45 g/L Fe and 3 g/L Ni at 50 and 80°C, dissolved Cu concentrations (0.3 to 3 g/L) and HCl concentrations (2 to 4.6 M). Regression analysis indicated that the significance of the effect of different variables on the extent of oxidation achieved after five hours decreased in the following order: HCl concentration > Cu concentration > temperature. Increasing the HCl concentration from 4 M to 4.6 M caused the degree of oxidation achieved after two hours to increase from 58.3% to 98.1%. The catalytic effect of dissolved copper on ferrous oxidation was more significant at low acid concentrations. Experimental data suggest that rapid oxidation of ferrous is possible at high HCl concentrations for two main reasons. First, the formation of ferrous chloride complexes allows ferrous oxidation to proceed without the formation of superoxide as an intermediate product (the rate limiting step in dilute acid solutions). Second, the formation of ferric chloride complexes stabilises the oxidation product.

Jan 1, 2016