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By K. Bruce Hodgins

The North American mining industry faces challenging emissions regulations in coming years with the introduction of new standards for off-road diesel engines. In order to remain competitive, industry stakeholders must invest in new technologies that are economically and environmentally sustainable. Westport Innovations Inc., of Vancouver B.C. has developed high pressure direct injection (HPDI) technology that allows diesel engines to run primarily on natural gas with no intrusive engine modifications, reduced emissions of NOx, PM, and CO2, with no loss in performance. This is accomplished through late-cycle high-pressure injection of natural gas directly into a diesel engine combustion chamber. The natural gas is injected at the end of the compression stroke. A small amount of diesel fuel is injected first to initiate combustion, followed by the main natural gas fuel injection. The diesel cycle and its operating characteristics are fully retained including high combustion efficiency, low speed torque, high-power output, no engine knock and fast response to load changes. Natural gas has not been an attractive fuel alternative in mining operations due to reduced performance associated with spark ignition engines and the added weight and space required for compressed natural gas tanks. However, liquefied natural gas (LNG) can be stored in a similar manner and volume to diesel fuel by virtue of its increased energy density over compressed natural gas. Cummins, Inc. of Columbus, Indiana and Westport have formed a joint venture, Cummins Westport Inc. (CWI), under which agreement the HPDI technology is being applied to a Cummins QSK engine series for high horsepower applications such as mine haul trucking. CWI, along with Komatsu Mining Systems, ENRG Fuels, Placer Dome, and Cortez Joint Venture are performing a feasibility study for the development and demonstration of an LNGfueled HPDI QSK engine in a large mine haul truck. The goal would be to demonstrate low emissions consistent with EPA ?Blue Sky? standards, high efficiency based on HPDI technology and good economics resulting from the high fuel consumption of 2,000+ hp trucks.

May 1, 2002

By S. Tuttle, R. Sisson

"Suncor Energy Inc. has proposed a 2.2 billion dollar expansion to the current oil sands operation, which will more than double the productive capability of the facility. As part of the application for this expansion, a comprehensive closure plan had to be developed and filed.Closure planning includes a systematic evaluation of the area to be developed, the development activities planned, the goals and objectives of the corporation in re-establishing landforms and ecosystems at the same time as running an effective operation. As early as is practical during the mine development, surface contouring is completed, soil is reconstructed, and vegetation, surface drainage and wetlands are re-established. Once active reclamation is complete and vegetation has been re-established, Suncor monitors maturation of landscapes and ecosystems to provide the submission basis for reclamation certification"

Jan 1, 1999

By J. P. Sancho, L. F. Verdeja, J. I. Verdeja

"This paper analyzes the present state of the different processes competing to keep their market shares within the future iron and steel business sector.The continuous transformations in the steel making process are also studied here. These transformations have happened especially during the two last decades obviously favouring steel price, properties, quality and environmental compatibility in the new millennium. IntroductionIn the early 1980s, world steel production reached a historic figure; specifically in 1982, the amount was 645 Mt (Verdeja et al., 1993). This might have been one of the reasons why the United States, Japan and the European Community drew up a declaration of principles after which the leading industries and sectors in the following century’s development would be: advanced materials, also known by the very diffuse term of new materials; information technologies; and biotechnology (Eager, 1998).On the threshold of the 21st century, it can be inferred that information technologies (computers and telecommunications) have progressed spectacularly. Nevertheless, there have been downsides too; technology develops so quickly that after a few months the products are obsolete. Environmental problems may also appear in a few years due to storing so many useless devices. At the same time, the achievements of biotechnology did not meet the optimistic forecasts made in the early 1980s.On the other hand, it is also curious that some solutions for the environmental problems generated by star technologies of the new millennium, such as computers and biotechnology, are closely linked to the iron and steel industry. For example, blast furnaces in Germany and Japan are prepared for burning residua by introducing polymer materials from computers and other electronic prepared devices through their tuyeres, while cement tube furnaces can destroy any organic residua from different origins."

Jan 1, 2002

By Phil Thwaites

"The mining industry uses many types of mineral and metallurgical plants to produce saleable product from ore mined. Plant design history has left current operations with a mixture of manual operation and various forms of automated process controls. Consequently, we typically see high variability in the continuous operations together with a shortfall in the attainment of full capacity, or higher utilization of consumables.At a level of best practice, “Operational Performance Excellence” focuses on process control, using automation and control systems to deliver process optimization. This more sophisticated delivery is a great deal more difficult than the first stage of equipment selection / installation. It includes the appropriate selection of the right instrumentation, control system, key process knowledge, individuals with a solid control engineering background/experience, and the essential backing/ support of the operations management team together leading to higher value delivery. Robust solutions can be realized, considerably minimizing process variation, thus leading to process optimization. This approach results in an easier, efficient and safer process while providing considerable returns for the plant owners.How variable are your processes, and do you maintain optimized process performance with dedicated resources, modern instrumentation, ‘best practice’ control systems and performance monitoring tools? In this lecture, these questions and their possible answers are discussed.357"

Jan 1, 2013

By Ron Board

"Probably the only thing that can he said about conveyor belt scales without fear of contradiction is that they have been responsible for as much or more puzzlement, argument and frustration than almost any other piece of equipment commonly found in ore processing facilities. To be sure, there are certainly a good number of satisfactory installations, some of these having been achieved through forethought and careful consideration in the early stages of plant design, while others seem to owl their success to what seems to be little more than good luck or white witchcraft; and it might also appear that black witchcraft or other gremlins are solely responsible for the poor performance of many belt scales that enjoy well-designed installations with apparently good operating conditions.This paper is intended to acquaint users with the major operational reasons why belt scales seem so fickle (and downright ornery too), and establish some reasonably simple test standards against which the performance of scale hardware can be measured. Then it shall be shown how the design flexibility of electronic scale systems can offer particular advantages in overcoming some of these everyday problems in a practical way, and without undue inconvenience to plant operations."

Jan 1, 1975

By Lian-Jin Tao

With fast development of China modernization, road construction obtains great achievement. However, in the construction process of highway, especially the high-grade highway in mountainous area, there are many unavoidable high cut slopes. Specifications for Design of Highway Subgrades, China, prescribe that the design scheme of slope with height more than 30m should be compared with bridge scheme and tunnel scheme economically. In spite of the existing guidelines, it is still quite common to see many high slopes due to engineering geological conditions, highway line shape, cost and issues related to traditional design ideas. Actually the traditional way with ?high backfill, the high cut? for mountainous highways seriously damages the original ecological environment and groundwater system, especially to those area with weak ecology, where the damage is unrecoverable. It is quite common practice to use artificial vegetation for cut slope virescence, however it still has problems such as low ratio of survivor, high maintenance cost and lack of species diversity. Now people are more and more aware of the importance of ecological environment, it becomes urgent to decrease the damage to ecological environment after ensuring the stability of high slopes. With the aim to reduce ecological damage, we proposed a new design approach which is ecological environment friendly by decreasing cut slope height with steep excavation scheme. This approach requires that (1) the geological condition is good, and the rockmass can be sTable itself; (2) excavation should not badly damage the rock, which means blasting must be controled by using buffer blasting, smooth blasting and pre-splitting blasting; (3) if local geological condition is not very good, excavation should have intervals for one bench, the advised space is 20m; (4) to ensure the slope stability in construction process, the cut slope should be reinforced more strongly than usual and in time. Finally, the deformation of the slope and the working condition of the reinforcement structure should be monitored to ensure the slope stability. The new design is used to a roadside cut slope of provincial trunk highway S223 in Guangdong Province. Based on intensive geological investigation and borehole tests, it is found that the slope rock mass is intact and sound, and the rock strength is quite high. Results from numerical modeling by UDEC reveal that compared with the traditional design scheme with 90.23m high slope, the steep scheme with only 23.46m high is characterized by its relatively large deformation and stress concentration, however the influenced area only appears at the upper slope and tends to sTable. With cable reinforcement, the stability of slope excavated steeply can be guaranteed. Deformation of the slope and the cable force are monitored in details in the period of construction, which show that the deformation of the slope decreases gradually and the final deformation is very small, and the cable tensions change small after the cables were tensioned. It is optimistically estimated that the steep slope should be sTable during operation. Comparison analysis between the steep scheme and the common scheme affirms that the steep excavation is better than the traditional scheme in terms of ecological environmental effect, slope height, the excavated amount, the excavated quantity of slope surface, engineering cost. It is concluded that if geological condition permits, the steep cut scheme should be used with better benefits.

May 1, 2009

By Ed Beswick

Resource Update Drilling Program ? Pre-feasibility ? Exploration Metallurgy Program ? Grindability ? Metallurgical Optimization ? Hydrometallurgical Options Preliminary Mine Development Design Environmental Permitting Infrastructure Development

May 1, 2008

By David D. Davidson

Commodities remain hot for the time being, but for how much longer? The bulls point to global economic growth lead by China?s insatiable demand for raw materials. To further emphasis the bullish view they point to the emergence of India for follow through demand. The bears remain convinced China?s growth is unsustainable and with higher interest rates and high oil prices, the United States economy is poised to slow. Both groups can make a convincing argument and both will be proven right in the fullness of time. Profitability and balance sheet strength for the mining industry has rarely been better. Is this a time to be bold or cautious? In this paper, the author will address the dilemma facing today?s management as they pursue growth and try to minimize risk.

Apr 1, 2005

By A. N. Veltmeyer

"INTRODUCTIONTeck-Corona Operating Corporation's David Bell Mine is located 35 Km east of Marathon, Ontario. In conjunction with its 1000 tonne per day gold concentrator, the company operates an effluent treatment plant for the treatment of mill, mine and site effluents prior to environmental discharge. This paper provides a brief overview of treatment strategies and methods, employed to detoxify final effluent.WATER MANAGEMENTThe tailings impoundment basin, located 3 Km south of the plant site, provides storage capacity for all process effluents and site run-off. Basin supernatant (reclaim water) is recirculated to the plant for reuse as process water, in order to minimize fresh water consumption. As site run-off and limited fresh water intake exceed natural losses due to evaporation, reclaim water in excess of process requirements is passed through the effluent treatment (ET) facility to control tailings basin level by providing regulated discharge of environmentally acceptable effluent. (Figure 1)PASSIVE TREATMENTTo reduce treatment costs and burden on the ET facility, reclaim water is fed to the plant to take maximum advantage of natural destruction processes occurring in the tailings basin.These include: volatilizationphotodecompositionbiological oxidation and precipitationstorm water dilutionConcentrator recovery techniques (Figure 2) are directed toward maximizing gold recovery while limiting the addition and extraction of contaminants requiring disposal and eventual treatment.Currently ore ground to 90% -200 mesh is pre-aerated at pH 9.0 with lime for 18 hours prior to 30 hours cyanidation at pH 9.5 with low cyanide ion excess (70 ppm).Pre-aeration passivates cyanicides prior to cyanide contact. This reduces cyanide consumption and the formation of cyanide complexes. In conjunction with recovery requirements low pH is maintained to retard the dissolution of stibnite into its antimony and sulfide components."

Jan 1, 1989

By J. G. Strasser

"There has been considerable output over the last three decades from the social sciences concerning man and his working environment. In the mining industry at large, however, authoritarian, hierarchical control systems remain the norm, and it can be argued that something less than optimum effectiveness in terms of both productivity and worker satisfaction has resulted.Recently (/975), Campbell Chibougamau Mines Ltd. devised a most interesting organization and incentive system that links the underground production of a standard ton of mined output at controlled grade to an incentive payment scheme. A parallel scheme in the mill complex is based on maximizing recovery of copper and gold from available feed. A key part of both minsystems is the formation of groups who have considerable autonomy, particularly when compared to the still prevalent traditional mining industry relationships between the worker and supervisory levels.This paper traces the development of Campbell Chibougamau's system . Attention is drawn to qualitative and quantitative measures of the success of the method through the commentary of those miners involved in the scheme, and by reference to the favourable records on productivity, absenteeism, safety, turnover and grievance activity.IntroductionPyramidal or hierarchical management control systems, coupled to piece-work incentive schemes, predominate throughout Canada's underground mining industry. Although specific details of such systems vary from site to site, they , are generally understood and accepted as fact by the majority of the work force.Normally, a front-line supervisor (shift boss) directs a number of workmen and assigns them to tasks and working locations commensurate with their abilities, knowledge, training and skills. This front -line supervisor may direct or supervise from as few as 12 to as many as 75 or more workmen. He issues orders according to his assigned production objectives and ensures that these directions are fulfilled in accordance with standard mine practice . Several shift bosses are usually directed by a mine foreman or mine captain. The mine captains report to a general foreman or directly to the mine superintendent or his assistant, depending on the size and scope of the operation."

Jan 1, 1981

By David M. R. Stone

Underground mining in the gold industry is gaining popularity in Nevada, and with it the use of cemented rockfill is becoming mainstream. Even with today?s high metal prices, however, mining companies are very sensitive to the margins they realize, and are constantly looking for ways to reduce costs or improve efficiencies. Given that the backfill is one of the largest cost centers in underground mining, mines are constantly under pressure to reduce backfill costs. This paper will present an overview of the factors that impact cemented rockfill quality in Nevada mines based on the authors many years of consulting experience. Cemented rockfill quality can be linked directly to binder consumption, hence programs aimed at improving quality generally result in lower binder costs, better performance in the fill (hence less dilution), and improved safety. The paper will conclude with the key elements of a comprehensive program of backfill quality assessments and backfill QA programs. Comparative laboratory and minesite data from a number of operating and proposed mines will be presented.

May 1, 2007

By Bruno Bussière

Le drainage minier acide (DMA) provenant de la circulation des eaux à travers les rejets miniers sulfureux est sans doute le principal problème environnemental auquel est confrontée l?industrie minière. Afin de prévenir les problèmes environnementaux reliés au DMA, on doit restreindre la présence de l?une et/ou de l?autre des principales composantes menant à la production d?acide, soit l?eau, l?air et les sulfures. Pour ce faire, différentes techniques ont été proposées au cours des dernières années, dont la désulfuration environnementale et les couvertures avec effets de barrière capillaire (CEBC). Dans ce papier, on propose d?utiliser ces deux techniques en combinaison. Ainsi, on produirait un rejet désulfuré à l?usine de traitement qui pourrait, par la suite, être utilisé comme matériau pour la couche de rétention d?eau de la CEBC. Dans un premier temps, on présente les résultats d?une étude de laboratoire qui montre qu?il est possible de désulfurer les rejets de concentrateur à l?aide de la flottation non sélective jusqu?à l?obtention d?un résidu non générateur d?acide. Par la suite, des essais en colonne ont permis de démontrer qu?il est possible de limiter la production de DMA d?un résidu sulfureux à l?aide d?une CEBC dont la couche fine est constituée de résidus désulfurés. Des prédictions théoriques estiment même que la présence de sulfures résiduels dans la fraction désulfurée utilisée comme matériau pour la rétention d?eau peut avoir un effet bénéfique en réduisant la migration d?oxygène. En effet, les sulfures contenus dans la couche de rétention d?eau peuvent consommer l?oxygène qui tente de migrer vers le bas et, ainsi, réduire les flux d?oxygène qui atteignent les rejets réactifs.

Nov 1, 2002

By W. T. Martson

ABSTRACT Sooner or later, every producing mine faces the question of fill. This paper invites consideration of mill tailings as an economical, efficient, and quantitatively adequate source of such fill. Some of the advantages, disadvantages, methods of utilization, and methods of treating mill tailings for sand recovery are covered. ADVANTAGES AND DISADVANTAGES OF SAND FILL DISREGARDING economic com-promise, that material which supports the greatest applied load with the least compression is the best choice for fill. Table I, reproduced from U. S. Bureau of Mines Bulletin 60, is offered as evidence of the adequacy of hydraulically placed sand. Table II gives the results of tests made in an effort to determine the reason for the difference between load hearing qualities of dry-placed and hydraulically-placed sand. From these, it would appear that hydraulic placing gives a denser initial packing, with corresponding higher, and faster development of, load bearing qualities. Assuming this to be true, then if sand from mill tailings can be placed underground economically, it is the superior fill material. Table III summarizes cost data available. The most cursory glance through the available references (2, 5, 6, 7, 8, 9) will show .that the major benefit from the adoption of sand fill is a decrease in the non-productive fill ?cycle of a working place. This, it is estimated, increases the output of an individual stope by from 25 to 50 per cent. The advantage of reducing the number of required working places for a constant daily production is obvious.

Jan 1, 1951

By George H. Hope, Steve Ciccone

"The Red Dog Mine is both the largest known zinc reserve and the largest zinc producer in the world. The mine started in 1989, and by 1999 had increased production from approximately 300,000 tonnes per year (t/yr) of zinc concentrate to in excess of 900,000 t/yr. The VIP Mill Optimization Project further increased zinc concentrate production to 1.1M t/yr while improving both product quality and zinc recovery. The Mill Optimization project also addressed a number of issues related to risk reduction: power generation capacity, water treatment capacity and concentrate thickening. The project was faced with numerous challenges, the most daunting of which was the schedule. This US$105M project was executed, from conception to completion, inside of two years. Less than nine months elapsed from concept to delivery of materials and equipment to site. The project also faced a 100-day ice-free shipping window, the challenges of construction in an Arctic environment, and an extremely tight labour market for qualified craft personnel. These challenges were successfully addressed with several innovative approaches to project execution, including an Alliance contracting arrangement between the owner, engineer and contractor; full integration of the team; construction of modules in Anchorage; and fast-track engineering, procurement and construction.INTRODUCTIONThe Red Dog Mine, which began operations in 1989, is located above the Arctic Circle in Northwest Alaska, approximately 145 km north of Kotzebue (Figure 1). An 80-km road connects the mine site to the DeLong Mountain Transportation System (DMTS) port site. Red Dog is the largest known zinc deposit in the world, with known reserves totalling 94.5M tonnes, and is the largest zinc producer with a concentrate production rate of more than 1.1M t/yr.Open-pit mining is by typical drill, blast and load operation using moderately sized mining equipment. Ore is processed through conventional crushing, grinding, and flotation to produce separate lead and zinc concentrates. Filtered zinc and lead concentrates are trucked year-round to the DMTS port site, where they are stored in two A-frame buildings, 330 and 440 m long. A lightering barge system is used to transfer concentrate from the shallow water load-out to deep-sea vessels anchored approximately two miles offshore. Shipping is limited to a 100-day, ice-free window beginning in early July."

Jan 1, 2003

By B. J. Clauzier

"The Falconbridge Limited approach to employing communication equipment is first, to determine what is required in a given situation, second, to evaluate the possible alternatives, third, to select the most suitable hardware and, fourth, to determine what modifications, if any, are required to ensure not only successful implementation but continued low-cost reliability. Two examples are examined.The first situation required remote video monitoring of an acid loadout station. Several alternatives for linking to theremote site were investigated, including hard-wired, slow-scan and microwave. A comparison of these alternatives is shown and an appraisal of the performance of the selected microwave link is presented.The second situation required direct voice contact between the two members of an underground tram crew. Alternative solutions are described and an evaluation of the selected system- SHF portable radios - is presented.ObjectivesIn general, projects must have four main objectives: (1) to improve the safety of its operations; (2) to reduce its operating and capital costs; (3) to increase the efficiency of its work force; and (4) to increase its productivity. ScopeCommunication, when used wisely, can be a good tool to achieve these objectives. Projects can be kept simple using existing technology and adapting it to a particular task. To ensure the success of the project, it was necessary: to determine the project objectives; to evaluate the possible alternatives; to select the most suitable hardware; to adapt the hardware to the application, if required; and not to provide more than is necessary.Application at FalconbridgeTo illustrate this approach, two examples of actual installations at the Sudbury Operations are presented, sulphuric acid loadout, and the Falconbridge Mine haulage system."

Jan 1, 1987

By William B. Hetherington

Communities are the foundation upon which the whole structure of society rests and upon which the nation builds its hope for the future. They are not established to serve any one particular generation, nor any one element or group, but should be erected to render a lasting service to all who are to follow. They play a very vital and important role in the lives and welfare of the people, in their industrial, business, and social relations, and in the economy of the nation, of which they are the fundamental assets. Communities and civic governments are destined to be vital factors in the national welfare in the days that are to come. Any improvement in national or world conditions must have its origin within the communities. Any attempt at solution of the community problem must give some consideration to the fundamental elements which exist in every community, and to the underlying principles, and ways of life and thought, upon which community life is based. The community is, in its essence, a number of people living and working more or less closely together, sharing common rights, privileges, conveniences, and comforts, which would be impossible for the individual to obtain for himself by his own efforts alone, or in any other way than by the mutual exchange of persona! services and resources. In this way, men have increased the returns from their labour and commerce, have raised the standard of their living, with better social, educational, and recreational facilities, and enjoy a greater personal security.

Jan 1, 1943

By R. Venugopal, Saxena. V. K., U. Sankrityayan

"There is a dire need of a technology which can break the mineral interfaces to enhance liberation with minimum energy consumption in mineral beneficiation processes. Understanding of mineral crystal system and interfaces is essential to develop such methodology. So, this study is carried out to find out the role of mineral crystallography in milling and liberation. Data related of mineral crystallography, Vickers Hardness Number, Bond Work Index and beneficiation processes were collected from literature and detailed statistical analysis has been carried out to establish a correlation among these parameters. It was found that atomic weight and cell parameters shown statistically significant relationship with Vickers Hardness Number of minerals, which controls the milling characteristics of ores. Liberation characteristics of five different kinds of ores were analyzed considering the types of interfaces between valuable and gangue minerals. It was found that phase interfaces play vita role in liberation and coarser liberation can be achieved in the minerals of incoherent crystal systems like manganese and zinc ores. Study of this subject can help us to understand the effect of stress wave propagation in solids and its effect on crystal interfaces. It can also help us to design a technology of future to break the mineral interfaces.INTRODUCTIONCommunition is energy intensive mineral processing operation and consumes up to 2% of the total electric power generated in the world. Energy consumption due to comminution is increasing every year as there is growing needs to exploit lower grade ore bodies and process rejects (Blazy et al., 1994; DOE, 2005). Low grade ores require crushing and grinding to liberate the valuable minerals which are further separated from gangues by various beneficiation methods like gravity separation, floatation, leaching etc. Currently, comminution methods are selected based on the reduction ratio and energy consumption but effect of grinding methods on subsequent processing methods specially on liberation also need to be studied to optimize the entire beneficiation process. Most of the attempts made in past to minimize the energy consumption in milling to enhance the mineral liberation were focused on compression mechanism, chemical additives, thermal treatment, microwave treatment and electric disintegration (Kilpelm and Austin, 1982; Norgate and Weller et al, 1994; Bearman et al., 1997; Kumar et al., 2010; Wang el al., 2011; Singh et al., 2012). But the role of mineral crystallography on milling and liberation behavior of minerals not fully explored yet."

Jan 1, 2013

By P. D. R. Maltby

"1. INTRODUCTIONMy talk today will discuss a new development in the thickening of slurries and clarification of waste water - the Enviro-Clear thickener. Several industrial installations of the thickener have been made in North America in the following applications:1.,water clarification in sugar beet processing plants.2.,separation of pregnant liquors from solid wastes following acid leaching in uranium mills3.,clarification of waste water from coal treatment plants as described in a paper in the June 1975 transactions of the SME entitled ""Application and Utilization of the Enviro Clear Thickener in a U.S. Steel Coal Preparation Plant"" by A.A. Terchnik, D.T. King and J.S. Anderson.2. HISTORYThe application of the Enviro-Clear thickener can be traced back to the filing of U.S. Patent 3523889 in 1970 by the inventor F. Eis. The claims of this patent are shown in Slide 1.The new concept was developed for sugar beet processing by the Spreckels Division of Amstar Corporation, and several such thickeners have subsequently been installed in various sugar beet plants. The Enviro-Clear Co. or New York took over the world-wide manufacturing and marketing of the thickener. Experience in the sugar beet industry indicated that the Enviro-Clear thickener volume requirements could be reduced to as low as one tenth that of a conventional type thickener. Various coal samples were supplied by U.S. Steel Research Laboratories for testing. The tests indicated that feed rate loadings of 3 gpm/ft.2 could be obtained by the Enviro-Clear thickener. Such results led to several industrial applications in the coal industry. Subsequently other branches of the mineral processing industry have come to learn of the possibilities of using this thickener. Slide 2 shows a list of commercial Enviro-Clear installations at the end of 1975."

Jan 1, 1976

By R. Dahlke, J. A. Finch

A campaign was undertaken during the greater part of 2001 at Noranda’s Brunswick mine concentrator to investigate the role of gas (air) superficial rate (Jg) distribution to the cells in the final Zn cleaning stage (bank of seven cells), i.e. the Jg profile. Three profiles were tested: “balanced” (each cell with same Jg), “increasing” (from cell 1 to 7 proportionally), and “decreasing,” along with an “as found” profile in a parallel control bank. The experimental design allowed for two confounding factors, changes in ore type and circulating load. The increasing profile consistently gave the best metallurgy (down-the-bank grade / recovery). The reason for improved performance was the response of the first cells in the bank where the increasing profile gave the highest selectivity of sphalerite against nonsulphide gangue (NSG). The other profiles gave lower selectivity and higher zinc recovery in the first cells, which combined to reduce overall bank performance. The higher selectivity with the Increasing profile is attributed to the low gas rate in the first cells reducing water recovery and hence limiting entrainment of NSG. The increasing profile was subsequently configured for all four stages in the zinc cleaner circuit.

Jan 1, 2004

By Linda Duncan, Trevor Yeomans, Chris Potorieko, Michael Fullam

"NVI Mining’s Myra Falls Operation is a 4,000 mtpd copper/zinc flotation circuit with by product gold of ~28,000 ounces per year. Gold recovery has historically averaged 40-55%, however, a portion of this was recovered in the zinc concentrate and received poor payment. Two Knelson CD-30 Concentrators have been operating in the grinding circuit since 1992, with gravity recovery averaging about 2-5% over that time period.The Myra Falls gravity circuit was one of the very first hard rock mining installations operating in the world with automated Knelsons. The mine has employed a unique and unusual upgrading method for the Knelson concentrate that had never been evaluated as to its efficiency. Recent Gravity Recoverable Gold Testing by McGill University, and mathematical modelling of the Gravity Circuit by Knelson Gravity Solutions indicated the gravity circuit was not living up to its potential. Myra Falls Personnel changed the upgrade system-operating regime, and a complete gravity audit of the grinding circuit was carried out, with the results confirming the initial suspicions. Gravity recovery increased from 5% to 15%, with overall gold recovery improving by 5%.INTRODUCTIONNVI Mining operates a 4000 tpd mine and mill complex on Vancouver Island. The milling circuit consists of open circuit rod milling, closed circuit ball milling, gravity recovery, copper flotation, zinc flotation, and tails disposal. There are two milling circuits, “A” circuit, and “B” circuit."

Jan 1, 2006