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By Francisco Zenteno

Dado que la operación aurífera de Pierina representa uno de los costos operativos más competitivos del mundo, la minera Barrick Misquichilca trata de proporcionar un grato ambiente de trabajo para su personal, estimulando la creatividad y la polifuncionalidad en sus empleados. Por ello, nace el proyecto SIP2000 donde optimiza el sistema de información para el mantenimiento preventivo de la planta de procesos en la mina Pierina. El proyecto comprende el desarrollo de tres fases: La primera fase comprende la definición de los principales equipos críticos que podrían afectar a la producción, asímismo la implementación y estandarización de redes de comunicación entre equipos críticos para finalmente desarrollar interfaces HMI que supervisen variables relativas a Mantenimiento. La segunda fase, integra todos los sistemas de supervisión y control de planta con los sistemas de seguimiento “online” de Mantenimiento (fase 1), desarrollando un solo sistema de tratamiento y análisis de información de planta; y la tercera fase comprende la instalación y el desarrollo de aplicaciones basadas en tecnologías Cliente/Servidor con base SQL, que finalmente proporcionan la información y los medios para realizar consultas que optimizan el seguimiento y toma de decisiones relacionado al mantenimiento preventivo/predictivo.

Jul 17, 2000

By J. F. Lupo

Leaching operations combine both metallurgical and hydraulic processes to extract metals from the ore heap. In the design of leaching operations, metallurgical tests and simple hydraulic tests are often conducted to define operational parameters such as leach cycle time, application rate, lift height, and effective leach area. While metallurgical constraints are often the primary focus on leach facility design, the hydraulic factors are also critical to the overall success of the operation. Some of the hydraulic factors that are known to impact solution flow through heaps include: • Ore physical and hydraulic properties, • Variation in ore properties under heap loading, • Ore mineralogy and its susceptibility to chemical and/or mechanical degradation, and • Heterogeneities within the heap. This paper presents a discussion on hydraulic factors that may impact the effectiveness of leaching operations. In addition, methods are presented which may be used to assess flow conditions within active and inactive heaps.

Jan 1, 2000

By S. Maurhofer

The Uetliberg Tunnel in Switzerland is the longest tunnel in Zurich?s new Western Bypass Expressway, connecting the Birmensdorf bypass in the west with the existing Zurich-Chur national motorway in the east. Thus the tunnel links the Zurich-West motorway interchange with the Zurich-South interchange (shown in Figure 1). The Uetliberg Tunnel project comprises two parallel tubes, each about 4.4 km long. The two tunnel tubes are connected every 300 m by a transverse walkway and every 900 m by a transverse roadway (Figure 2). The SOS niches are spaced 150 m apart. Portal stations with machinery rooms are located at the west and east portals. The tunnel falls with a gradient of 1.6% from the west portal at Wannenboden to the east portal at Gänziloo. The Project costs are about CHF 1.12 billion. The carcass construction started in March 2001. The Opening of the Uetliberg Tunnel is planed in spring 2009.

By T. A. Muhlare

The use of electrolyte additives to smoothen cathode deposits during copper deposition is practised worldwide. These additives absorb on the cathode surface and take part in the electrochemical crystallization process. However, these additives also affect the quality of the cathodes when they are inadequately controlled. Electrolyte additives used by Palabora are glue, thiourea, Avitone and chloride. Their effects were determined on cathode quality, the size of the current density region that gives the desired compact morphology, and current efficiency. This was done in a small-scale cell. Small cells have different hydrodynamics from industrial-scale cells, which makes it difficult to simulate the operation of industrial cells in a laboratory. The approach used here was to use a rotating cylinder cathode to attain controlled hydrodynamics. The rotation speed was chosen to give a diffusion layer thickness that is similar to that of an industrial-scale cell. It was shown that even fairly small changes in the additive levels can significantly affect the cathode morphology, and the current density range over which this morphology can be obtained. Keywords Copper, electrorefining, glue, thiourea, avitone and chloride.

Jan 1, 2011

By Denir Paganini Nascimento

O efeito da convecção forçada foi estudado na micro e macroestrutura de lingotes de silício grau metalúrgico obtidos pela solidificação unidirecional a partir da extração de calor por uma base refrigerada em contato com o fundo do cadinho com o banho líquido. Um disco sob rotação foi imerso no silício líquido para promover a convecção forçada. Em lingotes de 100 mm, esta convecção aumenta de 8 para 80 mm o comprimento de uma região de grãos colunares claramente alinhados e livre de intermetálicos, indicando um aumento da macrossegregação. Um modelo de transferência de calor e massa indica que o aumento de transporte de soluto causado pela convecção forçada diminui o super-resfriamento constitucional e, consequentemente, aumenta a estabilidade da interface sólido-líquido plana, sem células ou dendritas. A ausência de células e dendritas pode ter contribuído para a maior macrossegregação de impurezas observada sob efeito de convecção forçada.

Oct 30, 2017

By Bruno Vidal de Almeida

A campanha dos refratários à base de carbono aplicados como revestimento de trabalho de diversos equipamentos siderúrgicos depende da soma de diversos fatores como resistência à corrosão, resistência à oxidação do carbono, estabilidade termomecânica, entre outros. Durante a etapa de aquecimento inicial de revestimentos refratários novos ocorre a oxidação prematura do carbono presente no revestimento refratário, reduzindo a vida útil do revestimento precocemente. Para reduzir a oxidação precoce do carbono foi desenvolvido um novo coating cerâmico que atua como uma eficiente barreira física, reduzindo o contato do oxigênio da atmosfera de aquecimento com o carbono presente no refratário. O coating desenvolvido possui uma fase ligante com pega química ativada termicamente e possui como carga refratária um composto sílico-aluminoso com elevada estabilidade térmica. Os resultados laboratoriais de avaliação de desempenho revelaram que com a aplicação do novo coating desenvolvido reduz-se a oxidação prematura do carbono em até 77% e elevase a vida útil do revestimento em alguns casos em até 15%. O coating desenvolvido revelou possuir excelente desempenho quanto a proteção do refratário MgO-C contra a oxidação do carbono que ocorre durante a etapa de aquecimento de equipamentos com refratários novos, comprovando sua aplicabilidade em diversos equipamentos siderúrgicos que possuem revestimentos refratários à base de carbono.

Aug 17, 2017

By L Reynolds

Oceana Gold (New Zealand) Limited (OceanaGold) has commenced mining operations at the Globe-Progress mine in the Reefton Goldfield, an area that historically produced 2.1 million ounces of gold from underground quartz lode deposits. During the construction phase of the operation, advanced exploration programmes targeting near-mine prospects commenced. The focus of this ongoing exploration is the discovery of near surface, refractory gold deposits that are amenable to open-pit mining methods and treatment through the Globe-Progress process plant.   One such discovery is the Supreme deposit, located along strike approximately 3 kilometres to the south of the Globe-Progress mine. The Supreme area was tested extensively with diamond drilling in 2006, defining a deposit with similar mineralisation styles and grade to the Globe-Progress deposit. The mineralisation comprises a central core of gold-bearing quartz veins, locally containing visible gold, surrounded by a more extensive halo of refractory, disseminated gold associated with an arsenopyrite-pyrite sulphide mineral assemblage. Three subparallel mineralised structures host the mineralisation. These structures are highly oblique to the country rock orientations, extending approximately 250 metres along a northeast-southwest strike and at least 220 metres down-dip, with an average thickness of 12 metres and moderate dip to the southeast. Records of historical workings indicate that mineralisation extends further down-dip and remains open at depth. 5175 ounces of gold were mined historically at the Supreme deposit. OceanaGold have defined an Inferred Resource for the Supreme deposit of 0.84 million tonnes at 1.46 grams per tonne for a total of 40 000 ounces (at a 0.8 grams per tonne cut-off). Higher-grade zones of mineralisation exist within the deposit and further drilling is planned to test the extent, continuity and geological controls of the mineralised structures.

Jan 1, 2007

By Christopher Mark

The first International Conference on Ground Control in Mining opened with the topic of pillar design. Two classic papers were presented, one by Bieniwski and the other by Wilson. Unfortunately, the two methods were so radically different from each other that it was nearly impossible to reconcile them. Adding to the confusion were the many other pillar strength formulas (such as the Salamon-Munro, the Holland-Gaddy, and the Obert-Duvall, just to name a few) that were also available. Little wonder that discussions of pillar design in those days often ended with anguished cries of “but which formula is the right one?” The past 25 years have seen substantial progress in the science of coal pillar design. Indeed, one testament to the improvement is the relative scarcity of papers on the topic at recent Conferences. Two factors have been largely responsible for the progress that has been made. The first has been the collection of large data bases of actual case histories of pillar performance in a variety of settings, from shallow room-and-pillar mines through deep cover longwalls. These have made possible the development of empirical design procedures that are closely linked to real world experience. The second important factor is the development of sophisticated computer models that can accurately simulate pillar behavior and roof/pillar/floor interactions. Together, these two lines of research have led to a new understanding of pillar mechanics that identifies three modes of pillar failure: • Sudden, massive collapse, accompanied by airblast, for slender pillars (width/height<4) • Squeezing, or slow, non-violent failure, for most room and pillar applications (4<w/h<10) • Entry failure or bumps for deep cover and longwall applications (w/h>10) It is particularly satisfying that the insights gained from numerical models broadly support those obtained from the empirical studies. While far less controversial than in the past, pillar design problems continue to arise. One recent example is pillar design for highwall mining. NIOSH has just released a software package, called ARMPS-HWM, which employs a number of modern pillar design concepts. Since highwall mining web pillars are long and slender, the greatest danger is that of a sudden collapse. ARMPS-HWM suggests two possible prevention strategies, one which

By J. W. Wang

This article first explains the mechanism of forming strength in the Jet grouting reinforced foundation, and points out the function of cement hydrates and clay minerals in clayey soil, the reinforced body with the character of long-term growth of strength. Secondly, regarding the strength and the deformation characteristics of compound foundation, the article points out that the stress-strain curve of the jet grouting pile is approximate to hyperbolic curve. Finally, the article cites three examples of application in the construction of the metallurgical industry.

Jan 1, 2010

By C. J. Badenhorst

Oxides of sulphur are corrosive and are produced when sulphur-containing fuels are burned. Sulphur dioxide (SO2) is a colourless gas with a characteristic, irritating, pungent odour. Exposure routes to the human body are mainly through inhalation and skin and/or eye contact. Symptoms of exposure to SO2 may include irritation of the eyes, nose, and throat; rhinorrhea (discharge of thin nasal mucous); choking; cough; and reflex bronchoconstriction. To protect employees against the ill health effects of SO2 exposure, they are often required to make use of respiratory protection whenever entering areas were the SO2 levels exceed the statutory limits. The use of respiratory protective equipment should always be a last resort and should be considered only after other control measures have failed to reduce occupational exposure levels to below the occupational exposure limit or whilst other control measures are being investigated or implemented. Whenever the use of respiratory protection equipment is considered, it should always be used as part of a comprehensive respiratory protection plan. It is also extremely important that all potentially exposed persons are adequately and comprehensively informed and trained.

Jan 1, 2007

By William H. Schiffbauer

The Bureau of Mines has developed a passive encoder for range knobs, a device that automates the task of obtaining the range settings from devices or instruments to be input to microcomputers. It is easily constructed and installed and will not disrupt the device to which it is being attached. It consists of a custom knob and a small printed circuit board that has light-emitting diodes and magnetic reed switches attached. A ribbon cable connects it to a microcomputer. This encoder eliminates one source of human error in an automated process.

Jan 1, 1983

By Lifeng Zhang

The transport of fluid, heat ,and particles (bubbles and solid inclusions) in flowing molten steel is investigated in steel refining ladles, the continuous casting tundish, continuous casting mold and strand, and steel ingot casting processes. The two-equation k-?? model is used to simulate the turbulence. Multiphase fluid flow is numerically simulated with a Lagrangian-Eulerian approach, an Eularian-Eulerian approach and the Volume Of Fluid (VOF) method. The simulation can predict inclusion trajectories, inclusion removal fraction, free surface waves and other phenomena, which can be used to optimize these important metallurgical operations.

Jan 1, 2006

By M. C. Villeneuve

A numerical modelling approach was developed to explicitly simulate geomechanical characteristics of intact rock: mineralogy, grain size and fabric. The approach involved creating a representative constitutive model for each of three common rock-forming minerals: mica, quartz and feldspar. The constitutive models developed are valid within the low confinement realm of excavation boundaries, where tensile fracture processes dominate. The mineral types were assigned to numerical elements, which were associated with each other through an algorithm created in a finite difference model, FLAC 2D (Itasca 2007a), to simulate real crystal geometries and orientations. The numerical models were used in a parametric investigation of the geomechanical characteristics and compared with published observations of the rock yielding process in laboratory testing. This approach has allowed the explicit grain-scale investigation of the impact of geomechanical characteristics on rock yielding at low confinement, leading to an improved mechanistic understanding of excavation-scale rock yielding processes at excavation boundaries.

May 1, 2009

By Vishwajeet Ahuja, Benoit Jones

"INTRODUCTION Shotcrete lining forms an integral part of conventional tunneling and is widely applied for underground excavations. Early strength gain of the shotcrete is a crucial aspect for ground support and safety of operatives. Strength requirements are dependent on various factors such as lining thickness, ground type, excavation size and tunnel depth. The early strength gain is typically monitored using destructive tests, such as needle penetration, stud driving or coring samples for uniaxial compressive strength testing in the laboratory. Being destructive, these tests cannot be directly performed onto the lining without causing damage that must be repaired, which is a particular problem for permanent linings. For this reason and to avoid the need for operatives to work near to exposed ground and/or fresh shotcrete, these destructive tests are often performed on panels, which are sprayed at the same time as the tunnel lining. All current testing methods are also very local, testing only a small part of the lining or a panel, which may not be representative because the temperature history could be significantly different. Therefore, these tests do not provide an accurate or complete picture of the lining strength gain. New testing methods that are non-destructive and can scan the whole lining remotely would be extremely desirable. This paper describes a new method, using thermal imaging techniques, that achieves these aims. It also discusses the real-time on-site application of the method, providing insight into the experience gained and conclusions derived. Shotcrete Shotcrete used for tunnel linings requires immediate strength development. The strength development is a direct result of the hydration reaction of cementitious materials present in it. A progressive sequence of the hydration reaction changes it from a solid suspension (typically referred to as fresh concrete) to a solid skeleton with a porous network and thereafter, into a solid with predominantly discontinuous pores (Byfors 1980). In the case of shotcrete, early strength is needed to support the self-weight and then continuing early age strength gain is required to begin to support ground loads. These strength requirements, along with other workability needs, are met by careful concrete mix design, the use of admixtures, such as accelerator and superplasticizer (BS EN 934-5 2007), and supplementary cementitious materials, such as silica fume."

Jan 1, 2016

By Verya Nasri

The proposed Second Avenue Subway Project in New York City is approximately 8.5 miles long, up to a depth of 120 feet beneath grade and runs the length of the eastern side of the island of Manhattan from Harlem in the north to the financial district in the south. It will reduce overcrowding and delays on the existing parallel line, improving travel for both city and suburban commuters, and upgrading access to mass transit for residents of the East Side of Manhattan. This subway line will have 16 new stations providing transfers to the existing Metro-North commuter rail service and to New York City Transit subway lines and bus services. The first phase of construction includes two TBM rock tunnels 2.4 miles long and two new large and shallow rock cavern stations with clear span openings ranging from 70 to 100 feet and length in excess of 1000 feet with 615 feet center platform, coupled with low rock cover ranging from 20 feet to 40 feet. The design methodology for these large and shallow rock caverns consists of using well known empirical methods for initial estimate of support requirements and then two and three dimensional continuum and discontinuum analyses for verification of the selected excavation sequence and support system. This paper describes the analysis and design methodologies used for the two large and shallow rock caverns with insight into how to overcome the design complexities and construction challenges of the urban underground.

Jan 1, 2008

By Michael Allen, Paul Worsey

In underground blasting, the pull of the initial cut is the limiting factor for the success of the rest of the round. By improving the pull of the first cut, a critical step is made towards improving the entire round. This project attempted to optimize a burn cut’s effective pull by varying the depths of the relief holes in the burn. The effect of varying the depths of the relief holes was investigated, including depths longer than that of the cut’s charged holes. The overall objective was to consistently achieve greater pull than in a standard burn, using an identical amount of explosives. Increased pull results in savings of both time and cost in underground heading advance.

Jan 1, 2015

By J. F. Childs

Montana consists of an Archean crystalline basement overlain by Proterozoic through Cenozoic sedimentary rocks. Igneous rocks range in age from Archean to Pleistocene; the most voluminous magmatism and volcanism occurred during the Late Cretaceous and early Tertiary. The state can be divided into three tectonic provinces whose deformational styles are a function of different bedrock responses to Late Cretaceous-early Eocene compressional tectonism. Several long-lived structural zones have been periodically reactivated since the Precambrian, and were the sites of recurrent magmatism. Regional gold distributions are strongly influenced by the tectonic provinces and structural zones. Lode gold systems in Montana occur in diverse geologic settings resulting from a complex interaction between structure, magmatism, and sedimentary depositional processes. Reserves or resources are known for 19 significant lode gold systems, and additional unannounced discoveries have been made recently. Mineralization ranges in age from Archean to Tertiary. The influence of long-lived structures is apparent at both the regional and deposit scale, and in some cases multiple mineralizing events have been superimposed upon one another. Most Montana gold systems have a direct spatial and genetic association with Late Cretaceous through Oligocene igneous rocks. However, the importance of sedimentary rocks and associated depositional processes should not be underestimated.

Jan 1, 1993

By Gábor Csicsovszki

We have developed a novel method - at the laboratory scale - comprising an ion-exchange separation and a membrane-electrolysis step for the purpose of zero-waste regeneration of spent HCl pickling liquors originating from hot-dip galvanizing of common steels. It is aimed at the parallel regeneration of HCl and iron. Experiments revealed that iron can be electrodeposited at high current efficiencies by maintaining the following conditions: 0.04-0.08 M HCl, 500-1000 A/m2, 20°C and stationary electrolyte in a conventional cell. Zinc in the solution did not disturb the deposition of iron, however it contaminated the product and it poisons the anion-exchange membrane required to tackle acidity during electrolysis. For a preliminary separation, anion-exchange tests were carried out to produce pure iron solutions. Beyond the equilibrium studies, column experiments were carried out showing that low flow rates of the loading solution and the ~1.5 M HCl eluent are essential for separation.

Jan 1, 2006

By Rosaire Emond

Le concept du forage horizontal a été développé voilà de nombreuses années. Différents types de plate-formes permettant le forage horizontal depuis une cheminée ont été conçus par divers manufacturiers ou opérateurs miniers. Entre autres, on connaît bien la griffe de montage Alimak à laquelle peut être fixée une plat-forme sur laquelle est montée une foreuse. En 1992, Ross-Finlay a développé sa propre plate-forme de forage qui à notre opinion améliore la flexibilité du concept du forage horizontal, en augmente la productivité et en diminue le coût d?ensemble tout en assurant une sécurité accrue des travailleurs. Tel que montré à la figure 1, la plate-forme employée à la Mine Kiena est composée d?un toit de protection contre les chutes d?objets et de deux passerelles de forage de forme carrée. Le toit et les passerelles sont fixées à une structure de 6.5 m de longueur équipée de deux assemblages de rouleaux (non montrés à la figure) permettant de faire glisser l?ensemble sur des rails Alimak. L?angle du toit et des passerelles peut être ajusté pour des cheminées dont le pendage varie de 65 degrés à 85 degrés.

Oct 1, 2001

By Henk van der Bijl, Sean Rogers, Eugene Sidorski, Alan Carpenter

The electrode column is the heart of the submerged arc furnace. Superior electrode performance provides improved furnace performance. This paper describes the main features of the electrode column that delivers superior performance in furnaces worldwide, developed by Pyromet. Pyromet?s electrode comprises the compact slipping device, lower electrode assembly, upper and lower mantles, self-adjusting electrode seal, paste heaters, and Pyromet?s patented innovative electrode breakage detection and length determination system. Pyromet?s slipping device features compact interlocking clamping rings, incorporating fail-safe spring-loaded design. The interlocked clamping rings distribute the clamping force over a larger area of the electrode casing, preventing damage. The slipping device assembly features a low maintenance modular design that allows rapid slipping cycle times, back slipping, and compatibility with Pyromet?s electrode breakage detection and length determination system. Pyromet?s lower electrode assembly consists of the contact shoes, pressure bellows, pressure ring and heat shields. The contact shoes and pressure ring are designed for long, trouble free operation whilst the pressure bellow configuration equalise contact pressure and current distribution. Furthermore, the contact shoes incorporate a self cleaning feature, ensuring optimum electrical contact. The segmented design offers easy maintenance. Pyromet?s clients experience less down time due to longer component life. Pyromet?s remote adjusted electrode seal assembly reduces the rope seal working temperature, increasing rope life. The self compensating rope seal clamping force ensures an effective seal as the rope wears. Pyromet?s electrode breakage detection and length determination system detects electrode breaks utilising Pyromet?s electrode holder and data processing system. The length measurement system controls electrode length, eliminating the occurrence of short electrodes. The length measurement system furthermore eliminates the need for manual electrode length measurement, reducing associated production losses during furnace burn downs.

Jan 1, 2007