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By Jose Alberto Gonzalez, Said Sharif Mahboob, Jeffrey L. Shepherd

"During the industrial electrowinning of zinc, uneven growth can cause short-circuits and make the deposits more sensitive to the presence of impurities that can significantly impact current efficiency. To produce levelled zinc deposits, additives such as glue, licorice and sodium silicate are often added to the electrolyte. Even in the presence of additives, uneven zinc growth still takes place because of the combination of hydrodynamic and electrolysis conditions in the cell house. Recent advancements in imaging spectroscopy and scaling analysis have opened an avenue to further study the effects of additives on zinc growth morphology. In this study, Atomic Force Microscopy (AFM) and scaling analysis have been used to monitor zinc growth characteristics including roughness, periodicity, aspect ratios and growth mechanisms as a function of electrolyte composition as well as deposition time. Zinc was electrodeposited from an industrial electrolyte containing a host of additives onto an aluminum cathode with a platinum wire serving as the anode. AFM images of the samples were collected to obtain 3D topographical information on which scaling analysis was performed to extract details on root-mean-squared (rms) roughness, periodicity (grain size), aspect ratio of surface features and growth mechanism. This analysis provided information on the mechanism by which the previously mentioned variables can impact short term growth and also provided a prediction of expected growth at long deposition times.INTRODUCTIONElectrowinning is one of the final stages in the industrial production of zinc metal. It is during this process where dissolved zinc ions undergo electro-reduction from an acidic electrolyte onto an aluminum cathode and are later recovered by stripping the zinc metal from the substrate. However, due to the nature of zinc growth as well as the various operating conditions, zinc deposition may occur unevenly, sometimes causing short-circuits that can cause electrode damage and reduced zinc production."

Jan 1, 2016

By Wei Huang, Anh V. Nguyen

"Potash flotation is an industrially proven success of flotation of soluble salts, but its collector adsorption mechanism remains elusive. In this paper, specific ion effects in NaCl-KCl flotation with carboxylate collectors were investigated. Flotation recovery and contact angle were determined as a function of brine composition of NaCl and KCl. The experimental results have shown that wettability of KCl and flotation of the soluble salts with laurate collectors were dependent on brine ion composition. Specifically, adding Na+ to brines decreased hydrophobicity of KCl crystals and their flotation recovery. Both KCl and NaCl could be floated with laurate collectors. However, flotation of NaCl was greatly enhanced by adding K+ to brine whereas flotation of KCl was significantly suppressed by the presence of Na ions. The decrease in KCl recovery upon adding Na+ is attributed to the counter-ion binding in the pulp. The flotation recovery enhancement of NaCl in the presence of K+ is explained by two effects: 1) increasing K+ concentration leads to a better dispersion of collector colloids in the pulp and 2) K+ enhances the collector adsorption at NaCl crystal surfaces. The water affinity matching rule can explain the specific ion binding behaviors and supported by the SFG spectroscopic results.INTRODUCTIONPotassium is an important fertilizer. Its primary source comes from potash ores, which are a mixture of sylvite (KCl), halite (NaCl) and many other complex double salts such as carnallite (KCl·MgCl·6H2O), alkali nitrates such as KNO3 and NaNO3, and sulfates-langbeinite (2MgSO4·K2SO4) with water-insoluble minerals such as clay and carbonate minerals. Previously, these salts were recovered with a lengthy hot leaching method, with further crystallization of potassium salts from saturated saline solutions. Selective flotation has been preferred since 1940s. Various collector adsorption mechanisms have been proposed soon after the industrial introduction of potash flotation. These include the formation of the insoluble compound model (Halbich, 1933; Singewald, 1961), an ion exchange model (Fuerstenau and Fuerstenau, 1956), a heat of solution model (Rogers, 1957), the surface hydration model (Schubert, 1988), the surface charge model (Roman, 1966; Miller et al., 1992), the interfacial water structure model (Hancer and Miller, 2000) and the colloid adsorption model (Leja, 1983; Burdukova and Laskowski, 2009). Most of the early exercises attempting to propose a unified rule on collector adsorption mechanisms can be seen as heroic endeavors due to the consideration of a vast number of salts in the pulp including alkali halides, nitrates, and sulfates, even the practically insoluble heavy earth metals. Additionally, several types of surfactants with different polarization features and alkyl chain length have been employed. As for the recent models, due probably to the preferential application of long chain amines as collectors in industrial potash flotation, most researchers are only devoted to collectors with low polarization features like amines and sulfonates (Hancer and Miller, 2000; Du et al., 2014). Collector adsorption mechanisms are therefore proposed based largely on a neglect of carboxylates as collectors. However, carboxylates remain an important collector type in soluble salt flotation systems where both salt minerals can be floated using anionic collectors and cationic collectors. Fatty acid type collectors are still one of the widely used collectors for soluble salt flotation and also one of the first to be applied on an industrial scale for the separation of potash ore (Hernáinz et al., 2003; Titkov, 2004). Here we examine some recent models that are relevant to our study to reveal a long neglected specific ion binding effects in potash flotation."

Jan 1, 2016

By Stephen Mullowney

Outline ? Setting the stage ? Deal activity ? Q1 2013 update ? Key deal sectors ? Deals by geography ? Outlook for 2013 Key Observations 2012 ? Major retreat in M&A activity ? Glencore-Xstrata deal dwarfs all other deals ? Gold & copper dominate deal activity

May 1, 2013

"INTRODUCTION Secondary mine ventilation has been hamstrung by the availability of fans that satisfy many competing operational factors. The sometimes legislated requirement of adequate volume to the working face, the minimisation of excavation required to fit the selected secondary fan and the power requirements of various operational phases has, in the past, not been satisfied with just one system. The new system being introduced overcomes all these competing requirements in one simple unit with an added bonus of being very durable without loss of performance when wear occurs on the impeller. Existing Operational Situation Several studies (e.g., CIPEC, 2005; LCG Energy Management Group, 2009) have found that between 42% and 49% of mining energy costs are associated with mine ventilation, depending on the type of mine and the equipment used. If we then look at the general breakdown of installed power of the secondary fan to primary vent fans, the ratio is around 2:1. Thus the total energy costs of the secondary ventilation represents about 25% of the overall mining energy costs. It is of interest to note that the cost of running a typical two stage axial vs the cost of purchasing and general maintenance cost of the same fan over a 10 year period, the breakdown will be conservatively in the order of 40:1.The currently available secondary ventilation axial fan have one duty curve at any given time. Generally this can be changed manually within the motor power parameters but requires a minor outage and removal of the fan to do the pitch adjustments. As the bag vent ducts grow longer, the supplied air reduces to a point where inadequate air is supplied to the working face. This is exacerbated by underground equipment putting additional resistance in the heading and further reducing the supplied air at the working face. This shortfall is normally corrected by the installation of an additional fan in the system to overcome losses in the bag system but comes at a cost of production as the heading needs to be shutdown to install the second fan. This also means that the heading is supplied with excessive air on the shorter runs with a wastage of fan power."

Jan 1, 2019

By T S. Cochrane

A variety of practical tests have been tried in the mining industry to determine the support properties of mine roof bolts. Such tests include torsion wrench readings, hammer blow tests and the use of plates with built-in tension indicators. This paper gives some details of pull tests with a hydraulic jack, as carried out in coal mines of western Canada. M A~Y criteria exist for establishing the efficiency of roof bolting, and the one adopted de-pends on the nature of the problem and on the individual leanings of the investigators. Consequently, sufficient studies have not been made from a common viewpoint or under similar geological and techno-logical conditions to compare these methods of evaluation. However, regardless of whether certain tests provide sufficient factual data to form a basis for theoretical research on bolting or not, many of these tests can and do provide a positive means of judging the suitability of chosen roof bolting techniques and equipment under definite geological conditions.

Jan 1, 1963

By Michael Loken, April Montera

"The process of blending consistent and predictable feed for the roasters is critical to optimizing product quality and controlling production costs. To assist in this process, Online PGNAA Slurry Analyzers have been installed and evaluated at a Sudbury Ontario smelter. They are used to measure 100% of the full process stream to obtain elemental composition data in real time. This paper explains the application details at Sudbury and the benefits achieved from their Full Stream, Elemental Slurry Analyzers.INTRODUCTIONSudbury Integrated Nickel Operations (Sudbury INO), a Glencore Company consists of two underground nickel/copper mines in Sudbury, Nickel Rim South and, Fraser, along with the Strathcona mill and the Sudbury smelter. The facilities are spread throughout the 60 kilometer-long, oval-shaped geological formation known as the Sudbury Basin (Figure 1). The company has been mining nickel-copper ores in the Sudbury area since 1929. Nickel and copper are the primary focus of operations at Nickel Rim South and Fraser. Other base metals such as cobalt and precious metals are also produced."

Jan 1, 2016

By A. P. LeBis

This article attempts to relate the concept of utility to the risk involved when only a small number of projects (compared to their probability of occurrence) are accessible to a firm and to quantify utility when other financial and physical parameters are known.

Jan 1, 1978

By F. Habashi

"While bioleaching of pyrite concentrates has been successfully used in industry to liberate gold from the sulphide matrix for subsequent cyanidation, the same technology cannot be recommended for leaching chalcopyrite concentrates for copper recovery. It will be shown to be uneconomical and cannot compete with pressure leaching technology. Data on the pilot plants that were constructed for this purpose and were shut down will be given.INTRODUCTIONBacterial leaching has been successfully applied for heap leaching of low-grade copper ores (Habashi, 1978, 1999). One of the major operations is that at Bingham in Utah (Figure 1). The leach solution collected at the bottom of the heap is extracted by organic solvents and the strip solution is electrolyzed to get high purity copper. The process was extended to treat auriferous pyrite concentrates to liberate gold and render it amenable to cyanidation by a process known as BIOX (Marsden & House, 2006; Lunt & Briggs, 2005).BIOX plants currently or recently in operation are the following:??Ashanti Goldfields Company, Ghana. Designed with an initial capacity of treating 720 tonnes of concentrate per day, the Sansu plant has since been expanded and currently has four modules processing 960 tonnes per day in all. It is by far the largest biooxidation plant in the world. The capital cost of the plant totalled US $25 million (1994 terms) and the operating cost is currently US $17/tonne milled.??Fairview, South Africa. The plant at the Fairview mine in Barberton, which was the initial pilot plant, has been fully operational since 1986. It was originally designed to treat 10 tonnes/day of concentrate but with the success of the project this has been increased to 55 tonnes per day. With the purchase of Fairview by Avgold’s Eastern Transvaal Consolidated, Avgold concluded a licensing agreement with Gold Fields, formerly known as Gencor, entitling it to use the BIOX technology to treat itsconcentrate.??Saõ Bento, Brazil. A BIOX plant was recently in operation in Brazil at the Saõ Bento Mine where a pressure oxidation circuit is used to treat the refractory flotation concentrate. This plant has confirmed the viability of combining bio-oxidation with pressure oxidation as a cost-effective method ofincreasing capacity at an existing oxidation plant.??Wiluna, Australia. The plant at Wiluna Gold Mine, Western Australia, was commissioned in 1993. Although originally designed to treat 115 tonnes per day of concentrate this has subsequently been increased to 158.??Other plants at Tamboraque in Peru, Harbour Lights and at Youanami in Australia have been commissioned recently."

Jan 1, 2012

By L. Chunpongtong

The Athabasca oil sands mineable resource is located in northeastern Alberta, Canada. In oil sands mining, the ore zone is regulated to have a minimum mining thickness of 3 m and a cutoff grade of 7 wt.%. The current algorithm that is widely used to flag ore zones and waste zones tends to overestimate oil reserves and causes low-grade ore to be processed. This paper presents the development of a more complex algorithm that is more representative of the actual oil found during operations and that can prevent low-grade ore from being sent for processing.

Jan 1, 2014

By Victor F. Hollister

Elemental sulphur occurs as aformational sedimentary deposit in Upper Devonian Wabamun evaporites near Coronation, Alberta. The deposit developed in a stratigraphic jacies-change lrap; it is assumed that petroleum reacted with anhydrite to form sulphur, calcite, hydrogen sulphide and other reaction products. The deposit contains about 362,800 tonnes of sulphur and lies at a depth of 1200 m. The Coronation deposit is expected to be geologically typical of such other native sulphur deposits as may be found in Wabamun Group sediments. Widespread sour gas sulphur production f rom the Wabamun suggests the possibility that additional native sulphur deposits will ·be found.

Jan 1, 1984

By F. Bélanger, P. Fournier

"The Detour Lake Mine is located in northeastern, Ontario, approximately 300 kilometres northeast of Timmins and 185 kilometres by road northeast of Cochrane. The mill processes a free milling gold ore using both gravity circuit and leaching with a state-of-the-art carbon-in-pulp circuit. The grinding circuit is a conventional SABC circuit with a tonnage of 60,000 mtpd at 95 microns with the addition of pre-crushing upstream of the SAG mill. This paper will highlight the impact of a pre-detox thickener on the cyanide consumption in a gold leach/CIP circuit. While the pre-detox thickener was built with the intention to reduce the cyanide consumption, the opposite effect was observed when the thickener was put temporarily offline. It will show how the re-circulation of a dilute stream of cyanide into the grinding circuit, increases the overall slurry temperature and by the same effect, increases the dissolved copper concentration in the leaching circuit which subsequently increases the cyanide consumption.INTRODUCTION The processing plant is using a conventional gravity, cyanidation and carbon-in-pulp processing facility currently operating at approximately 60,000 mtpd. The comminution process is based on two parallel SABC lines, each fed from an individual reclaim tunnel. Cyclone overflow from the two ball mill circuits is directed to the pre-leach thickener. The thickener underflow is distributed to two (4) parallel leach trains of 5 tanks each, each leach train providing 29 hours of leaching retention time. After leaching, the gold in solution is recovered in a carrousel CIP circuit consisting of two (2) parallel leach trains. Tails from each CIP circuit are combined and sent to a pre-detox thickener to recover as much cyanide solution as is economically practical before being diluted and fed to a cyanide destruction system. The detoxified tailings are sent to the Tailing Management Area (TMA) for settling and retention. The excess water from the TMA is reclaimed and recycled back to the processing plant. The pre-detox thickener is designed to thicken the leach tails slurry to 64% solids with the overflow being recycled to the grinding circuit. It is estimated that the pre-detox thickener will recover 60% of the cyanide in the CIP discharge solution. It is also designed to reduce the SO2 consumption by diluting the thickener U/F to 50% solid using the tailing pond reclaim water which has very little cyanide content."

Jan 1, 2019

By R. E. Legg

This paper gives a brief outline of the mining and milling methods which will be used on the Stirling zinc-lead-copper ores by Stirling Mines, Limited, who have for the past two years been developing the Stirling mine in Richmond county, Nova Scotia, and who will bring the mine into production in November, 1929. No attempt has been made to give the paper a detailed technical character, for the main reason chat, since base-metal mining is something new in Nova Scotia, it is felt that a general description would be preferable before this Society, whose membership is mainly made up of chose engaged in the coal mining and associated industries. Furthermore, as both mining and milling operations will be governed to a certain degree by the experience gained after production commences, there are many points which cannot be definitely stated now. GEOLOGY Before discussing the mining methods, it is desirable to present a general picture of the geology and occurrence of the ore-bodies. The surface rocks in the vicinity of the mine consist of rhyolites of .pre-Cambrian age. These volcanic flows outcrop in very few places, usually along' the beds of creeks or on the shores of the numerous small lakes. Consequently, a detailed geological map is not available. The exploration work carried out to date has revealed a sheared zone extending through the volcanic flows for a distance of over 1,000 feet. Along this zone, there has been a replacement of the rhyolites by a carbonate rock for widths varying from 50 to 230 feet, and it is in this carbonate formation chat the mineralization at a later date took place.

Jan 1, 1929

By A. B. C. Stothart

"IntroductionIn the past four years Ontario Mines have made great progress in the development of reliable mine conveyance safety dogs. History shows that, prior to 1945, a rope failure on a descending conveyance was usually followed by unsatisfactory safety dog operation.It is proposed in this paper to discuss briefly;The history of this development. Progressive .development of one type (E. Long).Free fall testing of safety dogs. Anti-trailing rope device.HistoryOn February 2nd., 1945, a hoisting rope broke at the Paymaster mine. The safety dogs proved ineffective and permitted the cage to crash through to the bottom of the shaft, with disastrous results.Following this accident, the Ontario Government appointed a Technical Committee to investigate The Safety of Hoisting Equipment and Hoisting Practice in Ontario Mines. This Committee consisted of Dr. C. R. Young (Chairman) and Professors T. R. Loudon, E. A. Allcut, V. G. Smith, and Lloyd M. Pidgeon. The Ontario Mining Association (at the request of the Ontario Government) also appointed a Committee consisting of Messrs. R. E. Dye, R. D. Parker, and R. L. Healy."

Jan 1, 1950

By S. W. Henley

"Shaft sinking design is typically driven by what has been successful in the past and the availability of sinking plant. This document considers a project where the sinking design and methodology is unconstrained by conventional thinking and removed from the commonly held belief that a sinking methodology should be developed from available winding plant. Schedule was a key driver for the Project and led to an alternative sinking design that aimed to optimise sinking advance rates by specifying new winders that compliment known sinking plant while providing improved safety, redundancy and flexibility within each part of the sinking cycle. KEYWORDS Consistent, Efficient, Flexible, Improved, Innovative, Optimise, Redundancy, Safety, Schedule INTRODUCTION The project is remotely located in the South Gobi region of Mongolia on a brownfield site and the scope of work included the concurrent blind sinking and concrete lining of two (2) ventilation shafts to an approximate depth of 1,150 m at a finished diameter of 10 m and 11 m respectively. All sinking and lining operations to be completed as in-line activities, (no lining whilst other activities are undertaken). The project was schedule driven with a completion date set for the first quarter (calendar) of 2021 and there were no restrictions imposed on the successful Contractor with respect to their equipment selection. Existing sinking plant already onsite from three previous shaft sinking operations would be made available to the Contractor if required on an as is where is basis Sustained advance rates in excess of 2.4 m per day would be required in order to achieve the completion milestone, therefore the design would have to include contingency and demanded flexibility to account for equipment down time. Previous shafts that had been sunk onsite have utilised a single double drum kibble (bucket) winder (hoist) with a single excavator loading on the shaft floor into a large capacity kibble (bucket). DESIGN Mucking The sinking design centred on the mucking cycle given that this is traditionally the most restrictive part of the sinking cycle and typically accounts for one third of the overall sinking cycle. The Vertical Shaft Mucker (VSM) and/or diesel excavator are commonly used plant for shaft sinking that were under consideration. The use of Cactus Grabs was not considered given the higher risk associated with grab ropes and hoist failures."

Jan 1, 2019

By L. Iacopetti, A. Calderara, M. Perego, P. Perrone, T. Furusawa

De Nora, a global leader in the development, manufacture and sale of all DSA® anodes based on titanium coated with mixed metal oxide (MMO) for electrochemical processes will present key advancements made to Self-Protected Anodes (SPA) for metal electrowinning. (DSA® is a registered trademark of Industrie De Nora S.p.A., Italy). In 2017 pre-commercial demonstration cells were operated in industrial environment. The program’s focus was to fully demonstrate the SPA anode’s superior mechanical and electrochemical robustness during normal and induced dendrite shorting occurrences while providing quality of plating in commercial operation. De Nora specialists focus on key components, in particular the engineering of the self-protection system, DSA® anodes and catalyst formulation capable to cope with high levels of pollutants while providing long service life in the meantime. Results of field trials confirmed the expected anode performance and enabled the selection of the most suitable “SPA” structure, based on resistive protective elements. Summarizing the economic benefits to copper electrowinning tankhouse operation with De Nora’s self- protected all DSA® anodes are; Double-digits power savings Cobalt-free electrolyte operations Minimal dendrite shorting damage incurred at the SPA anode Smoother, uniform cathode deposits with tangible improvement on current efficiency Tankhouse operations producing lead-free copper quality cathodes, in addition to elimination of lead waste for improved operator health and environment. INTRODUCTION De Nora’s engineered “Value Technology Package” (“VTP”) for electrowinning, consisting of our DSA® anodes coated with mixed metal oxide specifically formulated for copper electrowinning in conjunction with an advanced self-protected full titanium anode (“SPA”), underwent an intense field qualification program, inclusive of the behavior under massive short-circuits as part of the field investigation, with the goal to select and appoint the ultimate design configuration of “SPA”. Optimized wireless-based monitoring system was included in the field program, demonstrating good functionality for cell parameters monitoring and remote shorts detection.

Jan 1, 2019

By E. H. Kranck

Introduction Baffin Island is still too in-accessible to be of interest to the mining industry. However, twenty years ago few people dreamed of mining iron ?ore in Labrador. A journey by air to the most remote places in the Arctic is today no more remarkable than a trip to Europe, and the technical difficulties of mining minerals of high value are not insurmountable. Some ?observations concerning the geology and mineral possibilities of Baffin Island, the largest of the Arctic islands, may therefore interest the members of the Institute, in spite of problematic practical value of the subject. The following short account is mainly based on observations made during the Baird Expedition of the Arctic Institute of North America last summer 1950), and on information available from earlier expeditions. Early Work Baffin Island was one of the first parts of Canada to attract prospectors. Frobisher sent a shipload of rocks, which he believed contained precious metals, from Baffin Island to England. This attempt, however, was a failure and no further serious prospecting work has, so far as I know, been done. During the past few years geological mapping has been carried out by the Geological Survey of Canada (Fortier. Davison, 1949-1950) in the southern parts ?of the island, along the coast of Hudson strait. In 1942, Weeks mapped the coast from Pangnirtung to the head of Cumberland fiord, and Netteling river up to Netteling lake. In the northern parts of the island, only scattered observations have been made ?by Bell, Watkins, Baird, and others.

Jan 1, 1951

By F. A. Forward

"NINETEEN sixty-six is a year of unusual significance in our Institute and in our country. It marks two-thirds of a century of service by the Institute to the people of the mineral industry and two-thirds of the century that Sir Wilfred Laurier said ""belongs to Canada."" As we meet here today within the historic walls of Canada's oldest city, a city that looks back on three hundred and fifty years of progress, I am reminded that it is almost a third of a century ago -in April, 1934 -that here in Quebec I first attended an Annual General Meeting of the Institute. It occurred to me that it might be appropriate to examine briefly the change that the middle third of this century has brought in the affairs of the mineral industry and, with some trepidation, to consider the prospect for the third that lies ahead.Opinions differ as to the relative importance of factors that have been responsible for the expansion and growth of Canada in its first hundred years. Some will say that it has been due to the abundance and fertility of agricultural land, others to the early enterprise of the railroads, and financiers believe that the banking system has been a major factor; -the fisherman -the forester -the teacher -each has his own view. I suspect, however, that most of us here would subscribe to the thesis of T. A. Rickard -miner, author, imperialist -who wrote, a gene-ration ago, ""Trade follows the flag, but the flag follows the pick,"" and thus agree that the finest contribution to progress, to wealth, to extension of frontiers and to inter-national trade has been provided by the mineral industry."

Jan 1, 1966

By B. Chambers, M. Yunovich

"Corrosion monitoring is commonly used in a variety of industries as a means of effective corrosion control programs to extend the life of the asset and ensure safe operation of the facilities. The majority of the monitoring tools have limitations and tradeoffs – e.g., sacrificing the longevity of the probe for higher measurement resolution. Linear polarization resistance (LPR) probes have the advantage of providing the operator with accurate, real-time corrosion rate data; however, the probes can only be deployed in conditions where the measured environment possesses certain minimal conductivity. In many instances, utilization of LPR probes in conditions with intermittent wetting (for example, conditions where the temperature fluctuates above and below the dew point) presents a challenge. To address this limitation, a special-design cooled corrosion probe has been developed, commercialized and integrated into the distributed control system in the plants. In addition to high-accuracy measurement of corrosion rates, the probe allows for monitoring of pitting corrosion. The most innovative feature of the probe is the cooling circuit, which brings the temperature of the sensors below the dew point, forcing precipitation of moisture and thus permitting corrosion measurements. Additionally, the probe was found to be well-suited for monitoring corrosion in crude distillation unit (CDU) overhead space, where condensation of hydrochloric acid may take place at relatively high temperatures, which would require relatively moderate amount of cooling to be imparted to the probe sensors. This paper presents laboratory-based data from a test simulating CDU refinery environment. A case study is presented to demonstrate how the cooling probe can be effectively used in the plants for corrosion monitoring.INTRODUCTIONConventional corrosion-monitoring techniques such as weight-loss coupons to assess corrosion damage are commonly used in plants1. However, the use of coupons is not only labor-intensive, but also does not deliver real-time corrosion data, thus effectively serving as a “backwards-looking” monitoring tool. Linear polarization resistance (LPR) probes have the advantage of providing the operator with accurate, real-time corrosion rate data; however, the probes can only be deployed in conditions where the measured environment possesses certain minimal conductivity."

Jan 1, 2012

By B. Yamamoto, D. Post, J. De Leon, A. Meike

"This paper describes the theory, design, building, and testing of the passive magnetic bearing stabilizing system which is the core of the passive magnetic bearing system. The stabilizing system is made up of two large magnetic disks opposing themselves with a stabilizing disk in the center which allows the system to self-locate in a null position without the need for external power sources or sensors. When outside forces act upon the stabilizer, the magnetic fields interact with the stabilizing plate to return the system to its null position. Collaboration between two industry leaders has allowed an actual prototype to be built and tested providing real data to prove out the theory.INTRODUCTIONMagnetic bearing/stabilizer systems have many advantages over conventional mechanical bearing systems. These include near-zero drag losses and no need for lubrication since the rotating elements make no mechanical contact with the stationary elements of the bearing system. However all magnetic bearing systems must contend with a constraint known as Earnshaw’s Theorem in the early 1800’s, this theorem asserts the impossibility of constructing a stable, non-contacting, electrostatic or magnetostatic levitation system using only fixed charges or fixed magnetic poles, such as those produced by permanent magnets. Because of the constraint imposed by Earnshaw’s Theorem virtually all present-day commercial magnetic bearing systems are of the “active” type. That is, they employ electromagnets that are powered by amplifiers the inputs to which come from sensors embedded in the bearing system. These sensors are a part of a feedback loop that operates to keep the levitated rotating parts of the bearing stable and centered. The resulting complexity means that active magnetic bearings are expensive, require periodic maintenance, and continuously consume electrical power to energize their amplifiers and their electromagnets.Passive magnetic bearings are, of course, also subject to the constraints imposed by Earnshaw’s Theorem but they solve this problem in a straightforward and simple way, with only “passive” elements that take advantage of a loophole implicit in the derivation of Earnshaw’s Theorem. This loophole is that Earnshaw’s Theorem as derived applies only to static systems, i.e. an assembly of stationary permanent magnets arranged so as to levitate an object containing other permanent magnets. The theorem can be overcome if dynamic effects are taken into account. In active magnetic bearings the “dynamic effects” involve the afore-mentioned sensors, amplifiers, and electromagnets."

Jan 1, 2012

By J. F. Henderson

Stable mining operations commenced in the Northwest Territories in 1933. Pitchblende from Great Bear lake and gold from the Yellowknife district are the main minerals produced. The value of pitchblende products produced from 1933 to 1941 was nearly $6; 000; 000; data on subsequent production are not available. The first gold was produced from the Con mine at Yellowknife in 1938. Other properties that later came into production include the Negus; Slave Lake; Thompson Lundmark; and Ptarmigan mines. The annual gold production reached $3; 862; 000 in 1942 but due to the war and consequent labour shortage fell to $333; 218 in 1945. The only producing mines at present (May; 1947) are the Con and Negus; but several promising properties are under development; including that of Giant Yellowknife Gold Mines where large tonnages of ore are being blocked out. With the reopening of former producing mines and new production from properties now being developed; gold production should rapidly increase and exceed its former peak within the next few years.

Jan 1, 1954