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By Michael J. Sapko, Ellsworth R. Spencer, Frank J. Perzak

"The fire resistance of several mine conveyor belts is evaluated using a new belt-flammability apparatus developed by the U.S. Bureau of Mines. The test apparatus, experimental details and a calculated flammability index (FI) are described.The FI values are useful for ranking the fir e resistance of mine conveyor belts. Values are determined using parameters readily measured with thermocouples, high-temperature flow probes and a methane-oxygen torch, all of which are components of the Bureau's new test apparatus. The FI varies directly with the flame-spread rate and the rate of heat release during burning and varies inversely with the critical (minimum) ignitor energy output.The fire-resistance ranking of nine different belt types using this moderately scaled apparatus is compared with available full-scale data on belt fires. This comparison shows that the ranking based on the FI is consistent with the full-scale data.IntroductionFull-scale fire hazard evaluations of mine conveyor belts are not easily related to the properties usually measured in small-scale flammability tests. The inadequacy of small-scale belt fire tests has been demonstrated in works by Mitchell, Warner and Reinke.Mitchell and Warner showed that certain neoprene (NP) and polyvinyl chloride (PVC) belts, which had been approved by the Code of Federal Regulations 30 CFR 18.65, were nevertheless capable of propagating flame over their entire length when full-scale fire conditions were simulated. Comparable results were also observed by Reinke at the Tremonia experimental mine in Dortmund, West Germany, where all belts burned in full-scale tests even though they passed the small-scale tests. Only by reducing the severity of the full-scale test could these fire-resistant belts be grouped on a pass-fail basis."

Jan 1, 1982

By G. M. Ritcey, M. Silver

"The processing of uranium ores produces tailings that could constitute environmental problems. At most operations the tailings are dumped into a designated area, with the ultimate acid drainage occurring if sulphides are present, together with the release of metal constituents to the rivers and streams. If the chemical reactions occurring within the tailings could be predicted, perhaps methods could be developed to either increase or decrease 'the rates of reaction. One such study has been in progress at CANMET during the past three years. The paper describes the use of Iysimeters containing low-grade and complex uranium tailings to determine the effects and interactions of bacteria, sulphides and solvent extraction organics on the release of radionuclides and on acid production. A simulated rain cycle nine-fold the normal was used and the Iysimeters were subjected to timed intervals of light and darkness. As a result, the tests simulated a 25-year period.IntroductionAlthough Canadians derive major benefits from uranium, there are environmental and health consequences, not yet fully understood, from the associated mining and milling operations. A major project at CANMET (Canada Centre for Mineral and Energ y Technology) has the ultimate goal of ensuring that any adverse effects on man and environment, now or in the future, resulting from the processing of uranium should be acceptably low. The magnitude of the task was exacerbated by the fact that the increased demand for electrical energy and the resultant increased prices for uranium oxide during the 1970s led to a rapid expansion in the industry. Annual world demand for uranium was expected to increase 12-15 fold in the next quarter century, with annual requirements of between 200,000 and 300,000 metric tonnes anticipated by the year 2000. Currently, the demand is low and the prices for the oxide have decreased."

Jan 1, 1982

By D. R. Rice

"The Smoky Valley Common Operation is managed and 50 percent owned by Echo Bay Mine' s Round Mountain Gold Corporation. The other partners with 25 percent each are Homestake Mining Company and Case Pomeroy. The operation in central Nevada includes an open pit, 3-stage open-circuit crushing train and heap leaching on asphalt pads. Presently, about 18,000 tons per day of 0.039 troy ounce gold per ton are transferred to the leach pads, and a similar tonnage of leach residue is transferred to a waste dump. One million tons of ore are being leached at any one time.Gold and silver cyanide are adsorbed from pregnant leach solution on activated coconut shell carbon granules. Pressure stripping desorbs values from loaded carbon to electrowinning solution.Three electrowinning cells are operated in parallel. Each contains six cathodes. Each cathode includes about 40 troy ounces (2.7 pounds) of Number 2 medium coarse steel wool. The wetted area of each cathode is about 24 by 30 inches. Solution flow is 2 to 3 gallons per minute per electrowinning cell. Average current flow is 25 amperes per cathode. The voltage is controlled in the range of 3 to 4 volts to maintain desired amperage.Twice a week two cathodes are pulled from each cell and drained. Each cathode is split into four portions. These are put in a steel pan coated with WD-40 and dried overnight.Each dried cathode portion is put into a paper sack. Each group of four sacks corresponding to a cathode is weighed together. The typical weight ratio of loaded cathode wool to new cathodes is 9 or 10 to 1. To each sack is added 35 troy ounces of silica, 45 troy ounces of anhydrous borax, 35 troy ounces of nitre, and 5 troy ounces of fluorspar. The sacks are taped shut."

Jan 1, 1986

By A. Gillis

"In order to obtain the equipment necessary to automate the equipment it was decided that the Department of Mines and Milltronics would jointly survey the circuit. This survey involved a metallurgical study by the Department of Mines and Milltronics took sound recordings during manual operation, checking in circuit bottle necks and determining the number of sensors that could be applied.The conveyer is driven by 2 PIV drives, each has a variable speed of 3/ 1. The cross conveyer that feeds directly into the rod mill feed chute will contain an automatic sampler and will eliminate the necessity of stopping the belt feeders to take samples. At present, hourly samples are taken from this point and the circuit is upset and cycling results.The Adequate scale is very close to the rod mill to totalize and thereby give a continuous indication and the second purpose is to take a signal from it and control the solution addition to the rod mill.A pneumatic positioner was obtained and put on the scale which produces a 3 tp 15 psi signal which is proportional to the actual tonnage going across the scale. This signal was fed to a bias loader which was mounted on the control panel. From there the operator can set the amount of solution that is wanted by the rod mill. No matter what the feed rate is, the signal coming from the bias loader will follow it automatically. This in turn goes to the pneumatic solution valve (1 ½” ) and the solution goes in with the feed to the rod mill. This is only part of the solution required for dilution since the rest of it is used as a force jet for the feed to the rod mill."

Jan 1, 1965

By Jerry Z. Lu

Belt conveyor design involves the evaluation of belt tensions, drive selection, pulley configuration and other technical issues. The conveyor belt tensions vary with conveyor layout, drive pulley configuration, belt selection, and idler selection. The decisions for the belt conveyor construction always take all technical, commercial and maintenance issues into consideration. A good conveyor design shall provide required operational features and at the same time be cost effective. The common issues for an engineer to face during belt conveyor design include: (1) Conveyor drive selection ? drive with fluid couplings or variable frequency drives; (2) Drive system configurations - single pulley large drives or dual pulley smaller drives, if intermediate tripper booster drives shall be applied, what power ratio should be adopted for a multi-drive conveyor; (3) Gear reducers ? shaft mount drives, right angle gear reducers or parallel gear reducers; (4) Drive pulley lagging - ceramic lagging or rubber lagging; If ceramic lagging, what type should be used. (5) Conveyor speed variation ? If conveyors run at variable speeds, faster speed/lower percentage loading or slower speed/higher percentage loading. In many cases the decision maker find themselves in a dilemma ? technical benefits vs. financial benefits, capital cost vs. operational cost, and capital and operational cost vs. maintenance effort. Although many conveyor design topics above have been discussed in numerous technical papers and design reference books, management executives and inexperienced engineers may be confused and feel lost. The consultation of people around them may lead to different opinions since experiences tend to vary, making the decision making process complicated. The purpose of this paper is to simplify these complicated issues and provide useful guidelines for belt conveyor design. This paper focuses more on providing simple and practical answers and solutions instead of discussing each topic academically and theoretically in depth.

Nov 1, 2011

By M. P. Amsden

"Ecstall Mining Limited, a subsidiary of Texasgulf, Inc., Operates the Kidd Creek Mine, Concentrator and Zinc Plant at Timmins, Ontario. Two different ore types are mined and milled to produce concentrates of copper, zinc, lead and tin. The ores are processed at the Concentrator in three separate individual milling circuits, each with the capacity to treat up to 3500 tons per day. Two circuits treat copper-zinc ore 1t an average combined rate of 6500 tons per day and the third circuit treats 3500 tons per day of silver-lead zinc ore. Conventional crushing, grinding and flotation procedures are followed. The purpose of this paper is to describe Ecstall's experience with rubber mill linings in the grinding circuits.CrushingBoth ores are crushed to minus 6 inches at the Mine and delivered by rail to the Concentrator where they are reduced by secondary and tertiary crushing to minus 5/8 inch.GrindingThe crushed ores are prepared for selective flotation by grinding with rod mills and two stages of ball milling. flotation circuit middling products are reground in regrind mills prior to further treatment. A typical flowsheet of one of the grinding circuits is shown in Figure 1.All the grinding units are Allis-Chalmers Mills. The rod mills are 10 1/2 feet diameter by 16 feet long. Both the primary and secondary ball mills are 12 feet diameter by 18 feet long and all regrind mills are 6 feet diameter by 12 feet long. The primary mills are charged with 1 13/16 inch forged balls. Secondary mills are charged with 1 1/2 inch forged balls and the regrind mills are charged with 1 inch forged balls. All cyclones are Kreb units. The primary cyclones are Dl5B hydrocyclones, the secondary cyclones are D6B hydrocyclones and all regrind cyclones are D6B hydrocyclones."

Jan 1, 1974

By Marcel Vallée

"Abstract-In recent years, several unsavory events in international mineral exploration, as well as several widely publicized project difficulties and failures have occurred. The report Setting New Standards has "raised the bar" and proclaimed a "commitment to continuous improvement... and change." We need to evolve from our "generally accepted" practices to more effective quality assurance policies, guidelines and standards. Several steps will be required to support the work of the "qualified persons" now wholly entrusted with technical and professional matters:• adopt a mineral development model and objectives appropriate to orient the selection of workmethods and verification procedures suitable to increase the profitability of these activities;• review the definitions and implications of the terms practice, guideline and standard;• review three quality assurance systems with emphasis on commitment of company management and complementary emphasis on systematic quality policies, plans and manuals (ISO 9000), continuous improvement through "profound knowledge" (Deming, 1986), and self-appraisal of continuous improvement and client satisfaction using the Qualimeter Guide (Québec Society for Quality);• determine, from the objectives of the mineral development model proposed and the problems often encountered, the requirements of resource/reserve estimation and the production feasibility study. To regain investors’ confidence and improve the returns from mineral development activities, an explicit commitment to quality by the board of directors and the management of every company is required.A number of mining companies have gained ISO 9002 certification for their operations but exploration companies should start by developing and implementing quality assurance guidelines and standards based on the ISO 9001 pattern, without achieving actual ISO certification in the short term. Both professional associations and industry organizations must be involved in the process of developing the required quality and continuous improvement guidelines and standards."

Jan 1, 1998

By Bing Li, Kai Liu, Yongcheng. Zhao

With the ongoing development of copper smelting technology, the improvement of environmental emission control and achieving an automated continuous copper pyrometallurgical process have become the key development goals for copper smelting. The double bottom blowing continuous copper smelting process combine bottom blowing smelting (SKS) and bottom blowing converting (BCC) process and fire refining as “three-connected furnaces” arrangement is a pyrometallurgical process independently developed by China’s ENFI which can continuously produce copper from raw material through to anodes. This technology can improve energy efficiency and reduce environmental emissions for the overall copper smelting and converting process. This paper discusses the engineering characteristics and production practice of the SDIC Jincheng Metallurgical Project, which operates SKS smelting and BCC converting process with “three-connected furnace” arrangement for the first time in the world. Advanced engineering concepts and tools were used to optimize the configuration during the project engineering stage. The operation shows that the process has good environmental performance, reduced energy consumption and high level of automation, which is a new choice for copper continuous smelting process. INTRODUCTION One of the most important developing trends for the overall copper smelting process is to develop a continuous operation. Continuous copper smelting can maximise energy efficiency in copper concentrate and make full use of the rich heat treatment system. Cold charge and a part of low-heat-generating materials, which are processing with additional equipment in traditional copper smelting process, can be processed with rich reaction heat in continuous copper smelting and converting process to achieve good economic benefits. Yuan and Wang (2017) noted that SKS+BCC copper smelting process can reduce the secondary SO2 emissions compared with discontinuous copper smelting process, which required transportation of melted matte by matte ladle and may cause secondary pollution. The continuous copper smelting process can also reduce the generation of intermediate cold materials.

Jan 1, 2019

By Giles St. Pierre

"The purpose of this paper is to report in a general way on the use of the Portaspec X Ray Spectrograph.At Manitou Barvue, we are milling two types of ores, copper and zinc. The control assay practice was to take grab samples at 4 hour intervals. These samples were dried in the mill, then taken over to the Assay Office where two operators would process them. Three hours later results were available at almost the same time as the operator was ready to take his set of grabs again, leaving no time for adjustments, if any were needed.After a reduction of personnel, there were no assays available on night shift. This practice was slow and inadequate, and a new way of doing control assays was investigated.After investigation the Portaspec was found suitable for the type of operation that we had in mind. The Portaspec is a conventional dispersive type of X Ray spectrograph. The instrument consists of three parts:The Power Supply The Spectrographic Head The Digital ScalerIn our case, where dried powder samples are analyzed, the instrument was provided with a two sample holder using one for the standard and the other for the sample. The operation of the instrment does not require any degree of skill or knowledge of chemistry or spectrography.Previous to buying the instrument, six sets of six to ten samples were sent to the supplier along with the assay for each sample. These samples were Cu. HDS., Cu. Conc., Cu. tls, - Zn. HDS., Zn. Conc., Zn. tls. A definite pattern was observed. For example - six Cu. HDS. samples ranging from .40 to .90 gave 10400 counts for the lowest to 16.040 counts for the highest. The number of counts were then plotted to give percentages."

Jan 1, 1971

By T. McCallum, B. Wellbrook, T. Ratnaweera

Leaching of copper (Cu) concentrates produces elevated concentrations of Cu and acid, which makes solvent extraction (SX) processing more challenging. Maintaining extraction targets can be more difficult with higher pregnant leach solution (PLS) grades, and variability of PLS Cu and acid can lead to increased chemical iron transfer. Diluting concentrate leach feeds with an existing heap leach inventory makes SX processing easier. However, considerations about how much to dilute and where to distribute the flow into the SX configuration must be carefully evaluated, given their impact on metallurgical performance. In this paper, characteristics of a concentrate leach feed are discussed, along with considerations for processing by SX. Also reviewed are pilot plant results of concentrate leach distribution into SX and plans for commercial testing. INTRODUCTION Hydrometallurgical processing of copper concentrates continues to gain interest from the industry. Treatment by smelting and electrorefining continues to dominate, accounting for ~80% of global copper production, but is faced with its own challenges (Li et al, 2017). The case for increased hydrometallurgical processing has been discussed as high grade ore deposits are diminishing, capital costs for smelting are high, and the environmental aspects present challenges for sustainable practice. The hydromet copper industry is also turning a corner as easily leachable copper oxide deposits are depleting, and excess SX-EW capacity exists in certain regions. The transition to hydrometallurgical processing of copper concentrates will take a bit of effort as leaching of copper sulfides is difficult and byproduct credits must be considered. Various POX leaching processes have been studied and proposed to the industry as viable practices. Of the many processes, commercial use has been practiced with the Mount Gordon Copper Process, total and partial pressure oxidation by Freeport-McMoRan at their Bagdad and Morenci, Arizona complexes, the Sepon Copper Process in Laos, and the bioleach BIOCOP™ process in Chile (Dreisinger, 2016).

Jan 1, 2019

By M. A. Nadar

Harsh and dynamic construction sites are generally equipped with cranes in order to rapidly and conveniently move heavy loads from one location to the other. If not properly inspected and managed, this operation can be very hazardous and lead to accidents. As such, a reliable and self-contained monitoring system that can update construction and safety personnel about the status of the crane, the weight of the load lifted, the location of the boom with respect to nearby buildings and other tower cranes, and the weather conditions under which the crane is operating, is deemed necessary. This can lead to significant time and cost savings as well as safety and productivity improvement due to the accuracy and immediacy of relevant on-site crane information delivery. This paper takes the initial steps and presents research targeted at evaluating the capability of wireless sensor networks (WSN) for monitoring tower crane operations in construction environments. A reliable long range WSN system is implemented and information is obtained from various special-purpose sensors (temperature, wind, proximity, etc.) mounted on special motes that relay data to and from each other and a central hub. The latter continuously monitors and manages network performance and relays incoming data to the host application. This application, in turn, displays the received data, and maps it onto a user-friendly visualization scheme, triggering alarms when a set of pre-programmed rules and safety conditions are crossed. The components of the proposed system have been tested through proof of concept experiments and preliminary results highlighted the potential of WSN systems for improving monitoring of tower cranes and reducing related accidents on construction sites, especially in Lebanon and the Middle East region where safety precautions are usually not properly implemented.

Aug 1, 2013

By Jean-Francois Magnan

"The old conventional process to produce lithium raw material dates from 1954 (CA patent #504477A). This process produces low purity lithium carbonate (Li2CO3) only. To obtain battery-grade carbonate, another polishing process is needed. To further obtain lithium hydroxide, another chemical conversion process is needed. That is why historically, the value of lithium hydroxide has always been higher than that of the lithium carbonate precursor. With the old conventional process, the low quality lithium carbonate is precipitated from a lithium sulfate solution (Li2SO4) by adding soda ash (sodium carbonate and its impurities). The resulting reaction produces significant quantities of sodium sulfate (salt cake) as a by-product with amounts larger than the impure Li2CO3 recovered with part of the soda impurities. When this conventional process was invented, the salt cake by-product was not an issue: it was discarded in a river near the plant. This practice cannot be done today in North America. While looking to find a solution for salt cake, electrolytic salt splitting of Na2SO4 into NaOH and dilute sulfuric acid appears as a technically feasible solution to get a rid of the salt cake. However, the sodium sulfate salt splitting process has difficulties to economically compete with the chlor-alkali process, which produces millions of tons of NaOH from sodium chloride (NaCl) every year.In contrast, the process developed by Nemaska to directly produce LiOH by Li2SO4 salt splitting not only solves the environmental problems related to the conventional process to produce lithium carbonate raw material, it also produces very high purity lithium hydroxide monohydrate directly at very competitive OPEX cost in comparison with industry peers (Figure 1). It also drastically reduces the amount of reagent and the direct greenhouse gas emissions."

Jan 1, 2016

By James A. Deeks

"Motor failures and equipment bearing failures are responsible for reduced productivity.With the introduction of computers and data acquisition systems, users are now able to monitor, report and trend deteriorating conditions and take corrective action before a critical shutdown occurs.This paper discusses the monitoring and trend analysis of' motors, and motor and equipment bearings. With today's digital electronics technology users are now able to monitor their equipment, detect deteriorating or abnormal conditions quickly, alarm the condition locally and or remotely, and decide if immediate corrective action is necessary or if it can be delayed until the end of a work Shift. All of this can be done long before any damage is done to the equipment.Monitoring Trend AnalysisIt is no longer necessary to compromise in selecting products, since state-of-the-art designs allow the adjustment in such small increments that the users are able to detect minute changes in a system's performance.Monitoring and trending of motors and equipment bearings is now available in economical packages which can be expanded as a system grows. Simply select the information you need, set the parameters, choose the scan time, and decide on the degree of reporting.Buffer storage of short-term monitoring of a number of analogue channels permit the user to view the recent history of motor data such as: motor average load, unbalance, motor current, ground fault, reserve thermal capacity, plus all of the settings of the protective device.A decision can be made to freeze the stored information after the motor stops or after the motor starts. Then the user is able to recall the conditions and diagnose the performance and the cause of the abnormal condition. Typical scan times range from ¼ second to 5 seconds ."

Jan 1, 1992

By Gerhard W. Heinrich, Gerald V. Schroeder, Daniel A. Murphy, Daniel F. Suarez, Jamie B. Beauchamp

"Washwater 'Finger' sprays were installed and tested in the copper/nickel separation circuit at Strathcona Mill to improve flotation capacities and related metallurgical performances. The new spray design features submerged sideways introduction of wash water into the flotation froth through nozzles at the end of vertical pipes which are suspended from a header above the froth. This maximizes the effective cross sectional area of flotation vessels while maintaining effective froth cleaning and a desirably high density of the concentrate slurry. The plant tests gave increases of copper concentrate production rates of 17% to 20% for conventional cells and 16% to 20% in column flotation at target grades of 29% to 30% copper and of less than 0.5% nickel. Basic considerations and concepts of tests and evaluation procedures are described.IntroductionMeeting flotation concentrate grade targets at maximum production rates and recoveries is a challenge all too familiar to operators of base metal ore concentrators. Frothwashing is an option to improve grade/recovery performance by minimizing entrainment of impurities into the concentrate, which is commonly known since the sixties (Kaya & Laplante, 1989). It has been recommended for the flotation of sulphides and industrial minerals alike (Kaya & Laplante, 1989; Miller, 1969; Heinrich, 1989) and has found its ultimate application in flotation columns (Finch & Dobby, 1990). The washwater addition in a flotation column is most evenly distributed over the column's cross-sectional area thus ensuring almost complete displacement of feed water from the froth by a countercurrent washwater flow -provided, a positive bias is maintained. Therefore, flotation columns are ideal for cleaning flotation. However, there is usually less room for boosting the concentrate production capacity by increasing airflow or slurry level then with conventional cells because of the smaller cross-sectional area available."

Jan 1, 1994

By A. Khan, C. Ciriello, W. Oliveira

"The purpose of this paper is to demonstrate the value of Operational Readiness (OR) in the successful delivery of capital projects. OR can be captured using several technical and practical definitions:• To ensure that the capital project being delivered is capable of an effective start up, ramp-up as planned and a sustainable productive operation.• To function as intended when started, with the appropriate people able to run it.• To increase the value in delivering the product/service through established systems, processes and procedures, while simultaneously minimize risk to both the project and the business.Historically, mining and metallurgical capital projects concentrate efforts on cost and scheduling during the implementation and design phases. The completion and subsequent handover of the operational unit is the main objective.When reviewing the mining and metallurgical industry’s capital projects, it seems many poor results and errors in terms of project design and ramp-up are self-inflicted, with the project neglecting to account for key aspects of the future operational plant. Interestingly, if the problems for the future plant occur during project implementation, they can be prevented during the project phase. It is required to connect the operational knowledge with the project in order to ensure an effective start up and operation.The benefits of OR will be shown to be applicable not only to mining capital projects but also to sustaining and business transformation projects. The paper also includes industrial examples showing both proper and improper use of OR techniques.The paper will cover 3 main areas of Operational Readiness: the OR model, OR related risk elements (i.e., risks associated specifically with the improper execution of OR) and conclude with OR specific case studies."

Jan 1, 2016

By J. Cayouette, C. Bolduc, P. Blatter

"The LaRonde mill was commissioned in 1988 and began treating ore from the Penna shaft in 2000. The mill has been expanded to accommodate 7,500 t/day, but ramped down to 6,000 t/day since the deep extension began. The process recovers gold, silver, and base metals. In 2008, the Goldex plant began trucking gold-pyrite concentrate to a treatment plant feeding pulp to the LaRonde mill, increasing gold output by 40,000 oz. In 2009, the high-grade Lapa ore processing facilities were annexed to the LaRonde plant, increasing gold output by 120,000 oz. This paper outlines the metallurgical considerations related to the treatment of different ore types.RÉSUMÉ Le concentrateur de la mine LaRonde a été mis en service en 1988 et a commencé à traiter le minerai du puits Penna en 2000. La capacité du concentrateur a augmenté afin de permettre le traitement de 7 500 tonnes de minerai par jour, capacité qui est retombée à 6 000 tonnes par jour (tpj) depuis le début de l’extension en profondeur de la mine. Ce procédé permet de récupérer de l’or, de l’argent et des métaux communs. En 2008, l’usine de traitement Goldex a commencé à transporter par camion du concentré de pyrite et d’or vers une usine de traitement alimentant en pulpe le concentrateur de LaRonde, augmentant ainsi la production d’or de 40 000 onces. En 2009, les installations de traitement du minerai à haute teneur de Lapa ont été annexées à l’usine de traitement de LaRonde, augmentant la production d’or de 120 000 onces. Cet article passe en revue les considérations métallurgiques liées au traitement de différents types de minerai."

Jan 1, 2017

By Gabriel Voicu, Marc Bardoux, Ross Stevenson, Nuno Machado, Jean Lafrance

"Abstract - Paleoproterozoic gold is found in two different volcano-sedimentary sequences and intrusive bodies separated by 600 km within the Guiana Shield. The 2148 Ma St-Élie granite intruded volcanic-arc sequences of the Paramaca Group, whereas the 2096 Ma Omai stock penetrated backarc/ island-arc sequences of the Barama-Mazaruni Group. Positive ?Nd values suggest that both suites lack Archean crustal contaminants, which is consistent with an origin in an oceanic arc setting.The St-Élie deposit is characterized by quartz-dominant vein systems with minor metallic minerals, represented chiefly by pyrrhotite and pyrite. Biotite, calcite, and chlorite are the main gangue minerals. The alteration haloes at St-Élie feature a strong potassic zone, which is absent at Omai. The ore-controlling structures are ductile and the vein emplacement is related mainly to contemporaneous, high-angle ductile shear zones. The St-Élie deposit formed at temperatures >350°C. The stable isotopes values are compatible with a magmatic or metamorphic source.The Omai deposit is characterized by quartz-dominant vein systems with minor metallic minerals, represented mainly by pyrite. Ankerite, scheelite, albite, and chlorite are common gangue minerals. The vein emplacement is syn- to post-deformation and it is related mainly to brittle shear zones with low-angle, stockwork networks and breccia zones. The Omai deposit formed in a temperature range between 250°C and 170°C, much lower than the St-Élie deposit. The stable isotope values are compatible with mixing between deep-seated fluids of metamorphic or magmatic origin with surface- derived fluids.These differences between St-Élie and Omai are interpreted in terms of their depth of formation. Alteration patterns, structural elements, and paragenetic assemblages indicate that the gold at St-Élie was most probably emplaced at a mesozonal depth, whereas the Omai setting yields evidence for epizonal conditions."

Jan 1, 1999

By Jean-Luc Beaudoin

"In addition to the actual energy consumed, billing is dependent on the peak load and the power factor. The lower the power factor goes, the higher will be the penalty the consumer pays. The principles of a power factor regulator, the two ways of improving the power factor and methods for calculating the capacitor values required will be described.The rate structure of the utility company is founded on three cornerstones: the energy consumed during a given period of time and two penalties imposed when the power factor is low or the power demand is high. Even though the normal consumption of a customer might be 10 kW, with a peak demand of 20 kW only once a month, the wiring and associated equipment at the input to the customer's plant will have to accommodate this peak demand. The power company has no means of forecasting these demands and cannot therefore provide the additional equipment necessary. So it exacts a penalty, and the customer must take all possible steps to avoid these peak power demands. This can be accomplished by using an automatic peak load regulator which will selectively disconnect the loads which are not essential in the operation of a plant .The principles of such a controller will be described.Principles of power factor regulatorsThe operating principles of a power factor regulator will now be described. It might be asked why the power factor of an electrical installation in a mine, or a factory, should be corrected at all, but there is a simple answer. In addition to the actual energy consumed, the billing is dependent on the peak load and the power factor. The lower the power factor goes, the higher will be the penalty the consumer pays."

Jan 1, 1982

By V. G. Minenko, A. L. Samusev

For efficient leaching of gold from sulfide ores and the oxidation of sulfides into sulfates, it is necessary to introduce a substantial amount of oxidant - atomic oxygen, hydrogen peroxide, ozone, potassium or sodium hypochlorite. In this paper, hypochlorite electrochemical treatment is proposed as an effective method of intensification of refractory ore leaching. The objective of the study is to increase the gold recovery from refractory ores with the application of chlorinated solutions that are modified by chemical or electrochemical treatment. The advantages of the use of the modified chlorinated solutions instead of cyanide for gold-sulfide leaching are considered to be the following: a high concentration of the oxidizing agent (hypochlorite ions) in solution helps to achieve a high speed of gold dissolution in the form of chloride complexes; the possibility to produce hydrochloric acid solutions that may be used for the recovering gold by electrolysis; the possibility of the processing of carbonaceous, arsenic-bearing and others kinds of refractory gold ores. The mechanism of the interaction of the modified chlorine solutions with gold-bearing sulfides (pyrite and arsenopyrite) was investigated. The efficiency of the application of chemical and electrochemical leaching method was proved. The main factor that limits the rate of gold dissolution is a high concentration of sulfate ions (SO4 2-) formed in the solution by the oxidation of sulfide minerals. The optimal parameters of chemical and electrochemical leaching method and effective ways to remove sulfate ions were determined. The method helps to increase the level of the gold recovery up to 87% from refractory ores. The intensification of leaching by chemical and electrochemical treatment opens up opportunities for the creation of modern efficient and environmentally-friendly technologies that may be applied for gold extraction from refractory gold ores.

Jan 1, 2016

By Rodnei Graça, Jorge Silva Bettencourt, Lena Virgínia Soares Monteiro, Baruch Spiro, Tolentino Flávio De Oliveira

Abstract - The Vazante Mine is located in the Vazante District, the largest zinc district in Brazil. The Vazante deposit consists dominantly of an unusual willemitic ore. Small sulfide bodies are tectonically imbricated with the willemitic ore, within the Vazante shear zone. Structural styles of deformation and petrographic and isotopic evidence indicate that willemitic mineralization and deformation occurred synchronously during the Neo-Proterozoic. Various generations of hydrothermal veins and hydraulic breccias may pre-date, accompany and overprint the mineralization. Ore-formation temperatures are deduced from stable isotope geothermometry and mineral chemistry of both sulfide bodies and willemitic ore. Temperatures during the main stage of mineralization range from 206°C to 294°C (willemitic ore) and 317°C (sulfides), and reflect the prevailing metamorphic conditions within the shear zone. The fluid from which the gangue minerals of the sulfide bodies precipitated (at 250°C) had an oxygen isotopic average value of ?18O = +19.4‰. This value appears to reflect the interaction of metamorphic fluid with the carbonate rocks of the Vazante formation. At 250°C, the fluid in equilibrium with the vein mineral phases and willemitic ore assemblage exhibits a uniform oxygen isotopic composition, with an average value of ?18O = +11.5‰. The positive linear covariance of ?18O and ?13C ratios of the carbonates is most likely due to the mixing of metamorphic and meteoric fluids. The ?34S values of sulfides indicate a direct crustal origin for the sulfur. It is suggested that the sulfur is largely derived from pre-existing sulfide bodies and has been transported by metamorphic fluids. The willemitic ore may have originated from the precipitation of metal in sulfur- poor fluids under oxidized conditions, within the Vazante shear zone.

Jan 1, 1999