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By J. W. Senn

A magnesium alloy modeled after commercial alloy WE54 was thermomechanically processed and characterized to understand the mechanisms by which its texture can be randomized, as reported by Ball and Prangnell [1]. Samples were deformed in plane strain compression to prescribed strain levels at temperatures high enough to prevent cracking and then recrystallized. The deformation texture is very similar to that observed after plane strain compression (e.g., rolling) of other Mg alloys, such as common AZ31. However, the texture can radically evolve during recrystallization. Annealing above the precipitate solvus temperature results in a nearly random recrystallization texture where the initially strong basal texture is completely eliminated. Annealing below the solvus temperature produces a recrystallized texture similar to conventional Mg alloys, i.e., a weakened basal texture. If this same material is then annealed above the solvus to promote grain growth, a randomized texture evolves, which is similar that of samples simply recrystallized above the solvus. It is hypothesized that a sort of preferred growth mechanism, whereby grains with random orientation grow faster than those with the original basal texture, contributes significantly to the texture randomization observed in wrought magnesium alloys containing rare earth elements.

Jan 1, 2006

By Th. Hassel

The application of magnesium as an absorbable biomaterial demanded the consideration of the alloy composition, the mechanical properties and the corrosion a special adapted material development in terms of the human biological system. Magnesium for technical applications mostly comprised alloying elements up to 10 wt%. Thereby often metals (e.g. rare earth and aluminum) with high toxic potentials are used to optimize the mechanical properties. To minimize toxic reactions during the degradation of a absorbable magnesium alloy, the Mg-Ca system is being selected and investigated because both elements belong to the mineral nutrients. Rods and small tubes are produced by extrusion of gravity die casting billets (Ca-content 0.4 to 4.0wt%). The positive grain fining influence of calcium and its improvement of the corrosion behavior are additional advantages. The microstructure, the mechanical properties and the corrosion attitude are investigated. The results show that an optimal composition of micro alloyed Mg-Ca and ideally processing parameters lead to 16% strain and a tensile strength up to 185MPa. Electrochemical investigations and measurements of the hydrogen production demonstrate the influence of the Ca-content to the corrosion behavior of the investigated alloys.

Jan 1, 2006

By R. Krentz, P. D. Cordingley

The nickel-cobalt sulphides produced from limonitic laterite ores by Moa Nickel S.A. in Cuba are refined at the Corefco nickel-cobalt refinery in Canada. Major changes to the refining process were required when the Moa sulphide feed, with its unusually high cobalt content, was introduced in the early 1990's. In the period 1994 to 2005 the production capacity of the refinery has increased dramatically to match increases at Moa, and significant process improvements incorporated. The process flowsheet consists of the original ammonia leach process, optimized for cobalt chemistry and overall leaching capacity. Extraction of metal values is followed by the unique nickel-cobalt separation technology, in which most of the cobalt is separated from the ammoniacal nickel sulphate leach solution by precipitation as a nickel-cobalt hexammine salt. This salt is refined from a Co:Ni ratio of 1:1 to over 10,000:1 by selectively leaching nickel, redissolution and recrystallization in ammonium sulphate solution. Nickel and cobalt are recovered using the well-known Sherritt hydrogen reduction technology. This paper reviews the chemistry described above, examines some of the changes in operating conditions made over the years and highlights some of the recent physical changes made to the refinery.

Jan 1, 2005

By K. Karan

Oxygen reduction reaction in PEM fuel cell cathodes involves participation of three reactants - oxygen, hydrogen ions, and electrons. Electrochemical reaction in the catalyst layer is, therefore, influenced by how these species are transported to the reaction site. The two-phase boundary locations at which percolating networks of ionically conducting electrolyte and electronically conducting Pt/C meet are feasible reaction sites. The electrolyte phase also provides pathway for the transport of dissolved oxygen. Most of the 3-D models describe the catalyst layer as an ultra-thin layer, thereby, losing useful information on the distribution of electrochemical reaction rate. In this paper, we extend our previous work on 2-D cross-the-channel modeling of PEMFC cathode based on agglomerate catalyst layer. In particular, we take a closer look at the influence of proton conductivity on the reaction rate distribution in the catalyst layer. As well, we re-examine the role of anisotropic transport coefficient of the porous transport layer (PTL), commonly known as the gas diffusion layer, on the current density distribution under the channel and the rib of the flow-field plates. Results from both a 2¬D and a 3-D models will be presented.

Jan 1, 2005

By W. E. Selnes

Introduction In 1938, a survey conducted by the Ontario Mining Association revealed a rather startling fact. Injuries incurred in chute pulling were more numerous than those from any other single cause. This report prompted Mr. W. B. Paton, then Inspector of Mines for Manitoba, to make a similar survey of the mines of his Province. It indicated that, in Manitoba mines, chute accidents ranked second only to those from falls off roofs and sides. Why has the mining industry been so slow to recognize the dangers of chute pulling? A partial answer may be the lack of any systematic classification of accidents according to their real cause. The result has been to attribute to other causes injuries which were a direct outcome of chute pulling, and, indeed, has made it difficult to analyze accidents in the industry as a whole. Perhaps, too, because chutes are generally located in the comparative safety? of the drifts, there has been a tendency to consider the occupation as not very hazardous. Not until enough statistics were obtained on this particular task could it be appraised correctly. The Mining Association's survey has been most helpful, and latterly the industry has done a great deal toward analyzing the causes of chute accidents and toward determining an effective means of overcoming them. Much, however, remains to be done. An effort will be made in this paper to outline methods which have been found successful in materially reducing the number of injuries. Qualifications of the Chute Puller First of all it must be realized that chute-pulling is a specialized occupation. The men require proper training for the job, just as in other mining operations. Care must, therefore, be taken to choose persons whose qualifications fit them for the job. Chute-pulling is an integral part of the general mining operation and cannot be considered as isolated from the tasks of other workers. One of the essential qualifications of a chute-puller is a sufficient knowledge of mining operations to appreciate the effect his work will have on the safety of others in the vicinity. He must take the necessary precautions, by verbal warnings, by placing barricades and signs, or by personally guarding the chutes, to prevent accidents to fellow workers.

Jan 1, 1947

Accurately modeling and predicting long term mill throughput is one of the challenges facing metallurgists, geologists and mine engineers in their quest to consistently deliver accurate life of mine business plans. Batu Hijau has systematically improved long and short term mill throughput predictions since feasibility and commissioning in 1999. This has been achieved through a combination of ongoing improvement to the geology ore hardness and grade characterisation model, drill and blast optimisation and, by application of these data to model mill throughput. Batu Hijau has demonstrated the ability to consistently estimate long term mill throughput within ±2% accuracy. Aside from reliably predicting expected production rates with the existing plant configuration, this predictive ability provides a solid foundation for identifying operating and design criteria for short term grinding circuit optimisation and future expansions. This paper discusses ongoing throughput prediction model development at Batu Hijau based on geo-metallurgical characterisation. Also discussed are tools used for day to day production performance management. This includes on line "Mine to Mill" variable monitoring to improve operations parameter ecision making and performance assessment.

Nov 1, 2011

By F. Wirfiyata

"Accurately modeling and predicting long term mill throughput is one of the challenges facing metallurgists, geologists and mine engineers in their quest to consistently deliver accurate life of mine business plans.Batu Hijau has systematically improved long and short term mill throughput predictions since feasibility and commissioning in 1999. This has been achieved through a combination of ongoing improvement to the geology ore hardness and grade characterisation model, drill and blast optimisation and, by application of these data to model mill throughput.Batu Hijau has demonstrated the ability to consistently estimate long term mill throughput within ±2% accuracy. Aside from reliably predicting expected production rates with the existing plant configuration, this predictive ability provides a solid foundation for identifying operating and design criteria for short term grinding circuit optimisation and future expansions.This paper discusses ongoing throughput prediction model development at Batu Hijau based on geo-metallurgical characterisation. Also discussed are tools used for day to day production performance management. This includes on line ""Mine to Mill"" variable monitoring to improve operations parameter decision making and performance assessment."

Jan 1, 2012

By D. M. Ward, J. H. Ahrens

"The Fond-du-Lac uranium deposit was delineated primarily by percussion drilling and a small program of diamond drilling. Drillcore samples from three diamond drill holes as well as digitized gamma logs from percussion and diamond drill holes were utilized to define and implement an algorithm for the conversion of gamma-log data to equivalent-grade data. The procedures and detailed analysis for the provision of assay data for uranium reserve estimation are documented.IntroductionThe Fond-du-Lac uranium deposit is on the south shore of Lake Athabasca, approximately 2 km southeast o f Fond-du-Lac , northern Saskatchewan. It is on the northern rim o f the Athabasca sandstone basin.A train of mineralized glacial erratics was discovered in 1967 by Farnok, Limited by means of a helicopter-borne radiometric survey. In 1969, a program of diamond drilling by Famok was successful in locating in-situ mineralization in the Athabasca sandstone at the apex of the mineralized boulder train. Since 1974, exploration and development work have been performed under a joint-venture agreement between Eldorado Nuclear Limited and Famok Limited, with Eldorado acting as operator.From the discovery drill hole to the development of the gamma-log to equivalent-grade con version algorithm, the deposit had been tested by a total of 222 drill holes, 210 of which were percussion holes and 12 of which were diamond drill holes. The holes are generally vertical and collared at 10-metre centres on fences spaced 20 metres apart. The deposit is approximately 390 metres long, 10 to 40 metres wide and up to 45 metres deep, and is generally confined to the Athabasca sandstone. Uranium occurs as pitchblende, coffinite and uraniferou s goethite."

Jan 1, 1983

By B. M. Das, D. B. Cross

"In June 1983, the Computer Applications and Process Control Committee (CAPC) of the Canadian Institute of Mining and Metallurgy (CIM) circulated a questionnaire to coal mining, exploration and consulting companies in Canada to determine the industry's level of interest in holding a workshop-style meeting to introduce company personnel to ""state-of-the-art "" computer systems designed to carry out specific technical and management junctions. It was necessary to conduct the survey to determine the specific fields of application and the nature of training which are of most interest.Almost universally, the companies expressed interest in computer workshops and training for applications in the Canadian coal industry. The survey showed that all categories of personnel felt the need for some sort of training. Areas of specific interest identified were: exploration and geology, mine design, reserve calculations, coal mining technology, coal preparation, rock mechanics, ventilation, financial planning, and process simulation. The details of this survey together with an assessment of the significance of computer applications in the Canadian coal industry are presented in this paper."

Jan 1, 1986

By S. A. Kenzap

This paper provides an overview and discussion of key aspects of operating risk valuation in underground metal mining systems, with impact on project economics, using stochastic computer modelling in Discounted Cash Flow (DCF) analysis. Mine operating risk classification and assessment for ground, equipment and scheduling aspects are presented with an overview of available risk valuation tools that have been developed in engineering disciplines. The classification is organized by keeping in perspective the mine design needs and constraints, as well as the potential economic impact that operating problems can have on an underground development and production system. These sources of cost, revenue and time delays are tabulated to enable the hierarchization of potentially hazardous unplanned events occurring during the mining project life cycle. In complex technological systems, like the underground mining systems, the decision-making process involve a wide range of uncertainties, and often this is based on subjective and qualitative expert evaluations. Whether a qualitative or quantitative analysis is conducted, it is often the case that the probability of a certain project parameter value needs to be estimated. This requires use of methods and techniques to handle subjective, qualitative measures and to combine them with quantitative stochastic modelling in order to evaluate mine operations-related issues on DCF economic performance measure parameters. Links are established between decision making and the risk-based mine planning process for evaluation of design alternatives, with emphasis on the need of introducing flexibility in mine design. Finally, challenges of risk-based mine planning and design implementations are discussed and the call for an integrated risk-based real options systems valuation (ROV) ?in? projects analysis is made.

Aug 1, 2013

By Brian Hart, Stamen Dimov, Aparup Chattopadhyay, Barun K. Gorain

"A novel gold deportment technique has been developed for complex copper-gold and double refractory gold ores using state-of-the-art technology. Characterization of these ores is a challenging task due to low copper and gold grades in ores, presence of both primary and secondary copper sulfide phases and variable proportion of visible and invisible gold in different sulfides and iron oxide phases.Double refractory ores are mainly composed of silicates and carbonates with moderate clay and mica, and minor amounts of sulfides and organic carbonaceous matter. Gold mostly occurs as ""invisible gold"" (sub-microscopic gold) as solid solution or as colloidal-sized particles in different sulfides and other phases. The dominance of invisible gold and presence of highly preg-robbing and finely disseminated carbonaceous matter adversely affects gold recovery in flotation and leach circuits. Characterization of this carbonaceous matter, commonly known as TCM and quantification of gold associated within TCM, along with different sulfide and oxide phases is highly complex and challenging.Studies were initiated on various complex ore deposits and also on samples representing various process streams. This paper presents the development of a systematic approach to diagnostic metallurgy using state-of-the-art optical and automated mineralogy techniques, namely, micro-probe, dynamic SIMS and TOF-SIMS analysis for quantification of invisible and visible precious metal content in various species. The relevance of the mineralogy characterization to metallurgy will also be discussed in this paper."

Jan 1, 2016

By R. Ghomashchi

Wear, fatigue and corrosion are the most widely encountered modes of failure in materials used in engineering applications, including aero-gas turbines. Although wear is distinctly classified as adhesive, abrasive, erosive, fretting and so on, there are usually more than one wear mechanism involved in the failure of components in service because there are many systems and materials variables active in materials wear that makes it more difficult to study. This is further complicated by the discrepancies between the results of laboratory tests and field data. The present investigation was set up to examine the wear characteristics of M50 and T1 high-speed steels at both room and elevated temperatures to draw a thorough understanding of the wear behavior of this class of high-speed steels. This article focuses on the mechanical and microstructural characterization of wear for T1 and M50 high-speed steels using a pin-on-disk wear machine.

Jan 1, 2005

The uranium ore processed by the McClean Lake Operation is co-mineralized with niccolite, rammelsbergite and gersdorffite (nickel arsenides). During the strong acid leach process, the majority of the reduced arsenic is oxidized and liberated into the lixiviant solution as As+5. Following uranium extraction, the residual raffinate solution, enriched in As+5, reports to the tailings preparation process. In this process, Fe+3 is first added and mixed with raffinate (pH~1) to achieve a Fe+3/Astotal molar ratio of at least 3. This is followed by two stages of neutralization, using slaked lime to achieve a solution pH of 4, and approximately 7.5, respectively. Synchrotron based x-ray absorption techniques (XANES, EXAFS) applied to neutralized raffinate solids and tailings samples collected from the tailings management facility provide evidence that arsenic has been precipitated as a poorly crystalline form of the mineral scorodite (FeAsO4?2H2O).

Aug 1, 2010

By M. P. Rennick, D. M. Burton

Abstract -The Murray Brook massive sulfide deposit, which was the first geochemical discovery in the Bathurst camp, is one of the largest sulfide deposits in the area. The massive sulfides are hosted by quartzose metasedimentary rocks in the lower part of the Ordovician Tetagouche Group. This thick succession of sedimentary rocks is overlain conformably by felsic volcanic rocks, and is structurally overlain by mafic volcanic rocks. The massive-sulfide body is polydeformed, but primary metal zoning is still discernable and may permit future exploitation of discrete lead-zinc and copper zones. Although it was discovered in 1956, the deposit was not developed unti11989, when Murray Brook Resources commenced processing of gossan containing precious metals. Recovery of gold, silver, and mercury is accomplished by indoor vat leaching on a year-round basis.

Jan 1, 1992

By G. Shen, W. R. Tyson

In most fracture toughness test standards, such as ASTM E 1290 and BS 7448, crack-tip opening displacement (CTOD) is measured by using three-point bend (SE(B)) or compact (C(T)) samples with deep cracks. The loading mode and crack depth in these tests sometimes are different from that of pipelines. Pipelines usually have shallow defects and experience tensile loading when the supporting ground moves. As a result, the CTOD measured by these samples is lower than that of pipeline in tension. Recent researches suggest using single-edge-notch tension (SE(T)) samples to measure fracture toughness for pipelines. In the present study, shallow and deep SE(T) samples under fixed grip loading were analyzed by using the finite element technique. An equation to relate the CTOD to the area of the load/plastic crack mouth opening displacement (CMOD) is proposed. With this equation, the CTOD of a SE(T) sample can be evaluated by measuring the area under the load/plastic CMOD curve of a SE(T) sample.

Jan 1, 2005

By A. Farzanegan, D. A. Lowther, A. R. Laplante

"Off-line optimization studies are often necessary to improve the efficiency of grinding circuits. These studies are primarily based on the mathematical modelling of processing units (e.g., ball mills and hydrocyclones) and computer simulations. To complete an optimization task, process engineers must possess skills and knowledge of different subtasks involved in such efforts, e.g., plant audit, laboratory tests, and data analysis. Such know-how can be in part provided by Knowledge-Based Systems (KBSs). One such system, being developed in C Language Integrated Production System (CLIPS), is presented here, with focus on the estimation of ball mill selection functions for the purpose of both diagnostic and simulation, and its use for the optimization of ball size. Some of the interpretation and diagnostic rules will be presented, as well as grinding kinetics and classification data likely to fire them.IntroductionSince the late eighties there has been a growing trend in applying Knowledge-Based Systems (KBSs) to mineral processing [Meech 1990, Bearman and Milne 1992). Table l lists some KBS (often referred to as expert systems) applications that have been used mainly as tools for improving on-line monitoring and control of grinding circuits. However, there has been fewer attempts to add the symbolic processing powers of KBSs to conventional off-line grinding simulators. Figure 1 shows a relatively standard procedure to perform an off-line optimization study [Napier-Munn and Lynch 1992]. In brief, a typical program includes taking representative samples from a number of streams, running laboratory tests on collected samples, estimating model parameters which describe physical processing units (e.g. ball mills and hydrocyclones) validating model predictions and using models for simulation trials. One inevitably needs to be familiar with concepts of process modelling and simulation as well as various computer programs to be able to complete all steps of the study. Much of this ""expertise"" can be captured by KBSs, given their inherent capabilities for symbolic knowledge representation and manipulation."

Jan 1, 1997

By A. J. Basu

Air quality in underground mining operations can fluctuate significantly during the working day, but until recently the only way to ensure a mine had sufficient air quality was to over-ventilate and, with significant delay in adjusting the volume or direction of the airflow, working conditions were tolerable but rarely ideal. Underground ventilation management systems have been considered to achieve improved energy efficiency since at least 1995 in Canada. However, Mine Ventilation Optimization, (MVO) and integrating it with Ventilation on Demand (VOD) is only becoming more of a reality in the last seven (7) years. A systems approach to MVO takes into account all the elements from the point the power is distributed into the ventilation fans through to the actual quality and quantity of fresh air to the working face. Opportunities exist throughout the system for energy savings but not all of them are cost-effective. Depending on the application, these opportunities can be easily realized by properly sizing, streamlining, maintaining and operating the ventilation system using premium mine proven energy efficient components throughout. Implementation of VOD is a key step in achieving the MVO objective. However, VOD is a concept, and it requires various tools, procedures, and strategies for cost-effective and operationally viable implementations. This paper provides a historical background in the development of VOD and provides a framework for proper and cost effective implementation. In addition, an optimized ventilation system will also allow increased airflow by reducing resistances and shock losses. This turn in would allow production target improvement, which could be an attractive objective compared to energy savings. Mine ventilation is the life support system of an underground mine, and contributes to sustainable development and corporate social responsibility goals assuring health and safety aspects of strategic planning. The proposed framework addresses implementing mine ventilation optimization integrating ventilation on demand as a vehicle for energy, health and safety improvement and overall productivity gains in the mining cycle efficiency while significantly reducing carbon footprint of a mine.

Aug 1, 2013

By Simon C. Dominy, Patrick R. Stephenson, Alwyn E. Annels

Abstract - The often complex, erratic, and localized nature of gold is a common feature of many vein-style gold deposits. This style of mineralization is often referred to as being nuggety or possessing a high-nugget effect. As a result of these complexities resource estimation is difficult and in general, only Exploration Results can be provided or an Inferred Mineral Resource estimated from surface drilling data alone. Underground development, further drilling, and probably bulk sampling will be required to delineate Indicated and Measured Resources. Tonnages can generally be estimated from diamond drill and development information with a reasonable degree of confidence. Grade is much more difficult to define with confidence because it is commonly highly erratic and discontinuous in nature. The dependency of higher confidence Resource categories on development information may create a Catch 22 situation, with funding for such development often depending on the prior definition of at least Indicated Resources. There are no easy solutions to these challenges posed by high-nugget effect deposits, and it is important when classifying and reporting not to downplay the uncertainties often associated with Mineral Resource and Ore Reserve estimates for such deposits. However, in common with all deposit types, if the principles that underpin the estimation, classification, and reporting procedures are borne in mind and common sense applied, most issues can be satisfactorily resolved. This paper discusses the classification and reporting of Mineral Resources for high-nugget effect gold vein deposits within the framework of the JORC Code (JORC, 1999).

Jan 1, 2001

By Jean-Marc Simard, Richard Genest

"La mine Agnico-Eagle, localisée près de Joutel, a été découverte en 1962 par le forage d'anomalies électromagnétiques. Exploitée à partir de 1974, elle a déjà produit près de 30 tonnes d’or à partir de 2 puits, le puits Eagle et le puits Telbel, distants de 1,3 km.Le gisement est situé entre le sommet du complexe volcanique de Joutel, à dominante felsique, et la base de l'ensemble sédimentaire de la rivière Harricana. Ces deux unités ont une extension régionale; elles sont orientées NW-SE avec une polarité NE et des pendages subverticaux. Une faille majeure, la faille Harricana, passe de façon subconcordante au contact de ces deux ensembles.La minéralisation aurifère, de 2 à 5 m d’épaisseur moyenne, est liée a une zone carbonatée, comprise entre des tufs felsiques, argilites et sédiments chimiques (éponte inferieure) et des argilites carbonatées (éponte supérieure). Le minerai est constitué habituellement de 20% de fine pyrite disséminée. L’or est en fines particules associées directement à ces grains de pyrite de texture cataclastique.Deux modelés ont été for mules jusqu' a présent pour expliquer la genèse du gisement: une thèse syngenetique (Barnett et a/.1982) et une thèse épigénétique (Wyman et al. 1986). Cette dernière apparalt comme la plus probable du fait de la présence de la minéralisation dans les zones cisaillées a carbonates secondaires et pyrite cataclastique."

Jan 1, 1990

By D. G. Dixon

A novel technology for leaching copper from primary copper concentrates has been developed at UBC. This patented technology takes advantage of the galvanic couple between pyrite and chalcopyrite to ensure rapid and complete oxidation of chalcopyrite under mild conditions in acidic iron sulfate solution, without the need for microbes, ultrafine grinding, or chemical additives such as chloride, nitrate, or surfactants. Copper recoveries of 98% or greater can be achieved at 80°C under atmospheric conditions in as little as 4 hours of residence time. The process is selective for chalcopyrite over pyrite, generates near-quantitative levels of elemental sulfur, and is fully compatible with conventional solvent extraction and electrowinning of LME Grade A copper cathodes. In this paper, the fundamentals of the Galvanox ? process are reviewed, and selected results of batch leaching tests on various concentrate samples are presented and discussed.

Jan 1, 2007