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By R. Carrier

"There has been a continuous evolution with the use of pre-cast concrete elements in the construction of aluminum smelters. In 1990, Phase I of Alouette was built using cast-in-place concrete exclusively. Whereas, other AP 30 technology plants such as Hillside 2 in the mid-1990s used pre-cast concrete beams with cast-in-place floors. Mozal 2, in 2002, used pre-cast concrete beams with pre-cast partial-slab operating floors. Alouette Phase II went further. Not only were the potroom building beams and floors pre-cast, but the entire pot support system, insulating walls and basement jersey walls were pre-cast. Once the techniques for bending and welding the reinforcement bars and the design for attaching electrical insulating plates to the concrete was perfected, the challenge for the project remained only in the logistics of transporting the pieces to site and simple erection. The overall impact on the project was dramatic. Using prefabricated concrete not only allowed advancement of the schedule, but totally eliminated formwork, re-bar installation, and form removal activities along with the handling of all the materials involved with these activities. With the elimination of these labour and material-intensive portions of the job, exposure to work injuries was dramatically reduced. The most prevalent activity for lost time accidents is during the rough work associated with concrete formwork, placing concrete and form removal. Another area where prefabricated elements were successfully used on Alouette Phase II was for the insulating walls enclosing the pot area, known as the ""claustra walls"". Usually these walls are constructed in-situ using mortar and breeze block. Success was also achieved with prefabrication of the perimetric walls that are installed at the lower floor of the potroom. A big advantage of using prefabricated concrete in the electrolysis area is in assuring electrical isolation for the operating floors. Poured concrete requires a meticulous clean-up effort before commissioning to establish the electrically ""floating"" characteristics of the operating floors. Poured concrete results in ""wash"", stray wood,"

Jan 1, 2006

By D. W. Zandee

"IntroductionHaving mined an economic mineral bearing rock which is of insufficient grade to warrant direct smelting, upgrading or beneficiation is required to make it an economically viable ore. The first step in effecting the concentration process is comminution or sequential breaking of the rock to allow liberation and subsequent recovery of the desired mineral particles. Desirably the ore could be broken down to the point where the valuable mineral is completely liberated to maximize the chance of recovering as much of it and in as pure a form as possible. The number of energy intensive stages of breakage required to attain this goal depends on many physical characteristics of the ore such as hardness, friability, toughness, grain size, existing fracture planes and particle shapes.Commonly the distinct stages are primary, secondary and often tertiary crushing and finally grinding. To increase the efficiency of each stage of size reduction, pre-treatment sizing is common.Crusher feed is commonly scalped of large pieces or screened for reduction crushers and classified for secondary grindingcircuits.Although crushing and screening is employed for many different products, this chapter reviews current practice in larger tonnage metalliferous ore treatment plants.Current practice is to use large gyratory or jaw crushers for primary crushing and some sort of gyrating or cone crushers for additional stages of reduction. For autogenous or semiautogenous grinding circuits only the primary crushing stage is necessary, the balance of the work being performed in the grinding stage. For conventional grinding circuits using ball mills or combinations of rod and ball mills, secondary, tertiary and even quaternary crushing stages are normally required.Older type crushers such as stamp mills, double rolls, sledging mills and hammermills are no longer common but are used for small tonnage special processes.Important to efficient crushing are a variety of sizing devices such as grizzlies and vibrating screens. Products at different stages must be stored to give surge capacity and allow controlled feeding rates through mechanical and gravity feeders. These storage piles, bins and feeders as well as crushers and screens are commonly integrated into a total facility by means of conveyor systems. Most often these are endless rubber belts driven by simple or multiple drive mechanisms usually consisting of electric motors and speed reducers."

Jan 1, 1989

"6.1. Mineralogical Techniques ApplicableTo the Platinum-Group Elements6.1.1. IntroductionThe named platinum-group minerals (PGM) usually occur as grains smaller than about 200 microns and, even when present as larger grains as in nuggets, these are often complex multimineral intergrowths. Therefore, the PGM must be examined by microscopic techniques and, because all named PGM are opaque, they are suitable for microscopic study by reflected light. Special techniques for concentrating PGM and preparing suitable polished sections are detailed in Chapter 5. Another characteristic of the PGM is that the majority have very high reflectance at 589 nm, i.e., over 450Jo, but they range from about 38 to 74%. In contrast, micro-indentation hardness has a wider range from - 60 to - 3,000 kg I mm, and the PGM range from brittle to malleable.The small grain-size of PGM imposes certain limitations, or complications, on the usual mineralogical determinative methods of reflectance, micro-indentation hardness and X-ray diffraction. In addition, certain combinations of elements in some PGM render electron-probe analyses difficult. The usefulness and shortcoming of these methods, as applied specifically to the PGM, are discussed in the following sections. These are not, however, meant to be exhaustive descriptions of the techniques, which are fully described in other texts.6.1.2. Micro-Indentation HardnessDetermination of the Vickers Hardness Number (VHN) is discussed in detail in recent publications, such as Bowie and Simpson (1977) and Craig and Vaughan (1981). In addition, the recommendations of the Commission on Ore Microscopy (COM) of the International Mineralogical Association (IMA) are given by Criddle (1980). The usual small grain-size of the PGM, however, precludes the widespread use of this technique and very few PGM have, in fact, had their VHN determined at the COM-recommended standard load of 100 gf (cf. Cabri, 1981b, in Chapter 7). Examination of VHN data reported in the literature reveals that the few PGM whose microindentation hardness has been measured have incomplete VHN data, measured with loads other than 100 gf (Chapter 7). The small grain-size may also result in unreliable VHN data because, even though the correct load may have been applied, a thin grain will give erroneous data due to the matrix, or the grain may even shatter or pop out of the section. On the other hand, micro-indentations may give useful qualitative diagnostic clues. Moncheite, for example, shows fractures near the indentation (Chapter 7, Plate 1). In other cases, intergrown PGM produce different-sized indentations: e.g., froodite-michenerite-gold in Cabri (1972); isoferroplatinumtulameenite in Cabri et al. (1973); michenerite-moncheite in Cabri and Laflamme (1976) and Chapter 7, Plate 1; altaitemichenerite- testibiopalladite in Hudson eta/. (1978) and Plate 1, Chapter 7."

Jan 1, 1979

By A. F. Brock

Introduction During the past ten years, shaft sinking has been going on continuously at Inco and new shafts and shaft extensions have been sunk under a broad diversity of conditions. The Murray mine and the Stobie section of the Frood-Stobie mine have?been opened and a main hoisting and supply shaft has been sunk at each of these mines; No. 2 shaft at Murray was sunk initially from surface to 1,960 feet and is now being extended; No. 7 shaft at Stobie was sunk from surface to 3,105 feet. No. 2 shaft at Garson has been extended from 2,200 feet to 3,200 feet in depth. At Levack, No. 2 shaft is being extended from 1,860 feet to 2,850 feet for ore hoisting from the 2,650 lev el. At Creighton, No. 6 shaft, collared on 52 level, was sunk 1,740 feet to a total depth of 5,563 feet below surface. It is the deepest Inco working. At Creighton, also, No. 7 shaft is being sunk from surface to the 30 level to handle the ore from caving operations. Ail Inco main hoisting and supply shafts sunk during the past twenty years have been vertical rectangular shafts equipped with two cages and two ore skips. The cages are standard and interchangeable for all shafts except Garson No. 2; they are single-deck, 13 ft. 4 in. by 5 ft. 2 in. inside and are designed to carry a maximum material load of 16,000 lb. The man load is 48 men. Skip capacities at the several shafts vary from 8 to 15 tons. Forty-two hundred feet bas been established as the standard vertical lift, and the permanent hoisting equipment at each shaft is designed for eventual hoisting from that depth.

Jan 1, 1950

By Magella Pelletier

"IntroductionDepuis une vingtaine d'année, les nombreux travaux de géochimie effectués par l'industrie privée et les milieux gouvemementaux ont permis:• de découvrir de nombreuses zones minéralisées a valeur économique;• d'identifier et de vérifier certains patrons de dispersion géochimique au-dessu s de secteurs minéralises déjà connus;• de favoriser le développernent des techniques analytiques;• de forcer le développement d'une mise en carte des résultats d'analyse, qui soit plus adéquat afin de permettre une meilleure interprétation géochimique.L'une de ces cartes géochimiques qui permet le mieux de mettre en valeur les données analytiques et qui fut instaurée au debut des années 80, est la carte d'interprétation géochimique par pondération.Cette carte numérique semi-quantitative, qui est construite à partir des données de base et de l'importance des éléments indicateurs pour une substance donnée, permet d'identifier et de définir des zones possédants de fortes probabilités pour la recherché de sources minéralisées."

Jan 1, 1987

By Marvin E. Lane

Viburnum, located in the foothills of the Ozarks in south-east Missouri, is the site of a modern lead mining and milling operation. Two mines are currently producing a total of 5,000 tons per day and a third mine is in the final development stage, with full production scheduled for late this year (1964). These mines will supply the tonnage required to keep the Viburnum mill operating at a full capacity of 7,000 tons per day for many years. The efficient underground mining operation is completely trackless. Drill jumbos are used to break the ore in a room and pillar method of mining. Transloaders, or St. Joe shovels, and trucks do the loading and hauling. The Viburnum mill has a world-wide reputation as a most efficient operation. This is due to the extensive use of automatic process controls, and labour saving materials handling facilities. Introduction THE St. Joseph Lead Co., has operated lead mines in southeast Missouri for 100 years. These operations have been confined largely to the area called the

Jan 1, 1964

By E. T. Turner

Introduction 1n assembling material for this paper on Wood Refuse Burning 1 turned first to the records of our early studies of the problem in order to learn how and why certain basic decisions were arrived at and also how it came about that the completed central steam plant differed so much from the original plans. It may be of interest, therefore, to outline the engineering problems as they presented themselves in the early part of 1948, and to indicate the economies involved. Although the principle of using wood refuse as boiler fuel instead of burning it to waste was quite sound, and in fact the practice had been in use for a long time in the boilers of many lumber companies, there was some guesswork as far as Hollinger was concerned in deciding how best to handle the large quantities of wood refuse involved and as to the type of boiler equipment necessary to .burn it efficiently. These problems will be examined first. Hollinger Boiler Equipment in 1948 Hollinger had four separate boiler houses, at Main, No. II, and No. 19 shafts, and a small unit at the compressor plant for heating purposes. Main and No. Il boiler houses operated all the year round; No. 19 and the compressor plant only in the winter. At Main there were four 36-year-old HRT boilers with total available h.p. of 500, at No. II, three 30-year-old HRT boilers with 195 available h.p., and at No. 19 two old field-type locomotive boilers capable of producing 95 h.p.

Jan 1, 1951

By Roger J. Higgins

Papua New Guinea is a country on the cusp of development, struggling to find a balance between the demands of national and regional growth, landowner expectations and the maintenance of cultural identity. Ok Tedi Mining Limited is the single largest contributor to PNG?s economy, representing about 10 percent of the country?s GDP. OTML is demonstrating that business and country risk can be managed through effective, respectful partnerships with local communities. OTML?s relationships with the communities of PNG?s Western Province are multifaceted. Communities have borne the brunt of the mine?s environmental impact, yet have benefited enormously from the development that the mine has brought. Importantly, the PNG economy is now the ultimate beneficiary of more than four-fifths of the dividends from the mine, the majority of which are held in trust for long-term sustainable development projects. The paper describes how OTML works with the Western Province communities to create a secure operating environment that recognizes the people?s aspirations for development and self-determination.

May 1, 2002

By V. Gangrade

Recirculation is the major concern associated with the utilization of booster fans. In controlled recirculation, a portion of the return air is purposely mixed with the intake air and the mixture is directed towards a working district, while the air quantity and gas concentrations in the air are closely monitored and managed. The objectives of this study were to determine the gas concentration in intake and return airways during controlled recirculation, and to determine the recirculation fraction for multiple headings. Experiments were conducted in a laboratory model to determine the effect of controlled recirculation on the quality of air circulated through the working faces. Preliminary results showed that recirculation is beneficial to ventilation planning because it reduces the build-up of air contaminants at the working faces and reduces the overall power consumptions. The experimental results were used to quantify the recirculation fraction and to calibrate ventilation models of the laboratory model. These models are used to simulate the controlled recirculation and to predict the gas concentrations in multiple headings.

Aug 1, 2013

By G. J. Simandl

"Since the 1980s, China has become the predominant producer of REEs. Recently, it introduced REE export quotas and this started a world-scale REE exploration rush. REE resources are concentrated in carbonatite-related deposits, peralkaline igneous rocks, pegmatites, REE ± P veins, ion adsorption clays, placers, and some deep ocean sediments. REEs could also be derived as a by-product of phosphate fertilizer, U processing, Ti-Zr-bearing placers, and exploitation of Olympic Dam-type sub-type of IOCG deposits. The ideal REE development target would be located in a politically stable jurisdiction such as Canada. REE grade and tonnage, mineralogy, and permissive metallurgy are some of the key technical factors that could be used to screen projects. INTRODUCTIONAccording to the International Union of Pure and Applied Chemistry (IUPAC), the term “rare earth elements” (REEs) encompasses yttrium (Y), scandium (Sc), and the lanthanide series: lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). This definition is used throughout this paper.REEs are subdivided into light (LREE) and heavy (HREE) categories. LREEs include, Sc, La, Ce, Pr, Nd, Sm, Eu, and Gd and HREE include Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y. Promethium (Pm) does not occur in nature. Concentrations of individual LREEs in the upper crust of the Earth are comparable to those of base metals. Even the least abundant REE (Lu) is about 200 times more abundant than gold.The production of REEs, reported in the form of oxides (REOs), for 2011 is estimated at 140 000 t (Figure 1a). Although high technology industries can substitute several REEs with other materials, these substitutes are typically more expensive or less effective than the REEs they replace. A number of countries, including the United States, consider several REEs essential for national security, their economy, and a general reduction in green house gas emissions. The forecasted demand for individual LREOs is much higher than that of HREOs (Figure 2). Dy, Eu, Tb, Nd, and Y are essential for the US economy and subject to predicted supply disruptions (U.S. Department of Energy, 2010)."

Jan 1, 2012

By A. G. Spencer

"The horsepower required to drive large grinding mills has increased dramatically during the past ten years. Limitations on the amount of power which may be transmitted by a single gear and pinion have resulted in the application of multimotor drives, with consequent loadsharing problems. It has also sparked the development of some entirely new drive concepts. In addition, the severe demands made upon the electrical system during the acceleration period have required that the selection of motors and electrical system design be closely coordinated. Moreover, the installation of such large process units results in downtime being very costly. The equipment selected and the plant maintenance philosophy must therefore be such as to minimize the risk of unscheduled downtime."

Jan 1, 1972

By C. Gosselin, M. Rheault, M. Benoit, Y. Bouroubi, V. Sarago

The last three decades have seen significant mining development in northern regions of Canada, where the freeze and thaw cycle of permafrost and the corresponding surface subsidence and heave represent a significant challenge to the design and maintenance of infrastructures. Identifying areas at risk is of great assistance to reduce the impact of this issue. Over the past ten years, Synthetic Aperture Radar Interferometry (InSAR) has been widely used to monitor ground surface deformation. With this technique, changes in phase between two SAR acquisitions are used to detect centimeter to millimeter surface displacements over a large area and with high spatial resolution. InSAR can be used as a tool to assist the siting and design of new infrastructure as well as highlighting the risk to existing structures in areas of unstable terrain. This paper presents the results of a project carried out by Effigis, which made use of SAR interferometry in the context of monitoring terrain and infrastructure stability in a northern mining environment that is affected by permafrost seasonal and long term changes. TerraSAR-X images acquired during two periods, August to November 2012 and March to October 2013, were used to measure the deformations and/or movement of ground surface, infrastructure and stockpiles caused by seasonal changes in permafrost extent in and around a mining site located in Nunavik, Quebec. The results showed that spatial and temporal distributions of surface displacements are in accordance with scientific and terrain knowledge. Some displacements were observed in loose soil areas while, as expected, none were detected in bedrock and rock outcrop areas. The areas most affected by active layer changes showed surface subsidence in the thaw settlement period. This study confirms that SAR interferometry has a great potential for operational applications related to risks induced by surface deformation in mining environments. It shows that this technique can be used to produce reliable maps of surface movement and monitor the vertical displacement of important infrastructure.

Jan 1, 2015

By T. E. Wakefield

"Final Galloway (stage) designs for vertical drill and blast shaft sinking projects evolve from complex thought patterns which integrate operational processes, systems and methods of communication, power supply, drilling, blasting, ventilating, mucking, supporting, surveying, dewatering, sealing, concrete lining and shaft furnishing. Attention to ergonomic design detail at the shaftsman / structure interface is at the heart of safe and successful multi-deck working platforms. For economy the end product must have a low mass to reduce suspension rope end loads to be able to use smaller suspension hoists and have lighter headframe structures, be robust to withstand concussion damage, be easily constructible on site, be maintainable in the shaft barrel, and comply with safety and legislated standards. This paper’s ambition is to describe a systematic design framework and sequenced thought process that delivers a product that is engineered with excellence, illustrated by making use of two designs that evolved during recent Galloway projects, one destined for a large diameter man/material shaft, the other for a ventilation shaft. The stage engineering iterative process starts with mapping permanent and sinking hoisting layouts, followed by laying out horizontal deck plans, mostly constrained by the permanent shaft purpose and configuration, whilst maximizing openings to enable muck to be removed rapidly for the best sinking cycles. Concurrently the designer needs to understand the chosen sinking methodologies in conjunction with crewing to determine the number of decks and fix their spacing. Insufficient access to move and line up formwork, set reinforcing rods and pour concrete in the confined spaces of the stage is an inherent major risk to be mitigated. An iterative and integrative process follows for the primary configuration which delves into increasing design detail, accommodating all other methodology influences, resulting in 3D layouts for further risk assessment, review and fine tuning by seasoned shaftsmen. INTRODUCTION Documented colliery shaft sinking practice from the late 1800’s makes reference to purpose built walling (bricked lining) cribs with floors suspended in sinking shafts, thereby allowing shaft lining to proceed concurrently with the excavation. Improvements were made by Sir William Galloway who introduced two decks supported at the corners by angle irons. The sinking stage, or Galloway, has developed substantially over time to be the in-barrel heart of the sinking operation, with overwhelming complexity for those who have to design one for the first time."

Jan 1, 2019

By T. H. Janes

"IntroductionSULPHUR is a constituent of many industrial products. It is part •of almost anything we eat, wear, or use. In fact, sulphur is so important that there has been an increasing tendency in recent years to measure industrial growth in terms of sulphur consumption.The uncertainty of obtaining adequate supplies •of elemental sulphur from the Frasch-mined domes. of Texas and Louisiana in the United States led all countries in 1950 to seek alternative sources of supply of this necessary element.Canadian industry has been supplied, for many years, with most of its sulphur requirements by United States Frasch-mined sulphur. World demand for this sulphur has necessitated the imposition of controls on its distribution, as production has not kept pace with demand. Until the third quarter of 1950, Canadian manufacturers of pulp and paper, heavy chemicals, explosives, and textiles •experienced little difficulty in obtaining their needs of elemental sulphur from the United States. However, at that time, low producers' stocks and declining reserves threatened to reduce shipments from producers, with the prospect of a continuing shortage for some time. These conditions, together with higher prices, stimulated the search for alternative sources of supply in Canada."

Jan 1, 1952

By I. Vazaios, M. S. Diederichs, N. Vlachopoulos

"As rock engineering moves from continuum to more discontinuum approaches for modeling, the engineer must make decisions regarding the degree of complexity to simulate for a given application, balancing the level of structural detail within the rockmass model with computational cost and result accuracy. It is important to consider that model does not need to include all the existent fractures and that representative geometrical properties for a given rock mass volume can be defined including only major structural entities.Within this paper, the scale-dependency associated with the geometrical properties of fractured rock is investigated utilizing a Synthetic Rockmass (SRM) approach with a view to characterize such ground to aid in the design of geotechnical works. In terms of process, the concept of the Representative Elementary Volume (REV) is used to determine the equivalent structural properties of the rockmass in order to justify the applicability of far-field behaviour of such ground. A large size Discrete Fracture Network (DFN) measuring 60m x 60m x 60m has been generated using the structural data obtained from LiDAR scanning of the Brockville Tunnel, Ontario, Canada. A number of DFN samples of varying sizes are extracted from the master network, generated using MoFrac, in order to be used as a the basis of the structural analysis of the rockmass. Volumetric measurements for the density and the intensity of jointing are employed in order to approximate the geometrical REV for the networks.In this paper a complete methodology of how to generate a DFN from LiDAR data and its analysis in order to determine the size of a geometrical REV is demonstrated. For the specific rockmass found in the area of the Brockville Tunnel, a geometrical REV measuring 3.5m x 3.5m x 7m is established. The results are generally in good agreement with the in-situ observations."

Jan 1, 2015

By Ralph V. Stewart

"The asbestos orebody is contained within ultrabasic rocks of Precambrian age, being located in the continuous permafrost zone of the Quebec Ungava Peninsula, some 300 miles north of the tree line at approximate latitude 61'49' and longitude 73°58'.The asbestos deposit is at the western tip of a folded ultrabasic sill complex which trends northeast and covers an elliptical area 4.5 miles wide by 15 miles long. Locally. the asbestos occurs in. a completely serpentinized dunite rock. The principal rock types in the vicinity of the ore-body originally consisted of dunite, peridotite and pyroxenite, all of which have experienced at least two periods of alteration, so that no fresh rock now remains.The main ore zone in the open pit is approximately one quarter mile in length, 150 to 200 feet in width, and plunges at 25 to 30 degrees in a northeast direction below surface, to a vertical depth of at least 1,200 feet, Consider¬able tectonic activity resulted in favourable structural conditions which culminated in the formation of the ore zone in its present form.The deposit consists principally of cross-fibre ""gash type"" veins which vary in length from several inches to several feet. The principal fibre vein direction is parallel to the dip of the enclosing serpentinized dunite and sill complex.Some of the problems encountered during diamond drill¬ing in permafrost are briefly discussed."

Jan 1, 1976

By M. F. Lopez, A. J. Mattus, S. B. Magid, D. B. Mobbs

"The use of Caro's acid as a replacement for hydrogen peroxide for the oxidation of vanadium prior to solvent extraction resulted in a 56% reduction in oxidant usage when compared on an equivalent hydrogen peroxide basis. Comparative oxidation tests, using two actual uranium mill raffinates, resulted in premature precipitation of an amorphous ferric vanadate when hydrogen peroxide was used to oxidize one of the raffinates containing a high iron to vanadium ratio. The use of Caro's acid eliminated the precipitation problem, thereby permitting the adjustment of the raffinate pH to a higher, more favourable level prior to solvent extraction.Potentiometric characterization of the raffinates revealed that vanadium is responsible for the inefficiency of hydrogen peroxide compared with Caro's acid, with the oxidation efficiency of iron being the same for both oxidants. A limiting potential between 720 and 740 mV was observed when using hydrogen peroxide, while, when using Care's acid, potentials approaching 1200 mV were achievable.A four-stage, countercurrent extraction performed on the oxidized raffinates did not reveal any operational problems. The extraction efficiency and the extraction coefficient were found to be higher when Caro's acid was used as the oxidant, as opposed to hydrogen peroxide.IntroductionMost vanadium is recovered as a by-product of some other process: leaching of Carnotite uranium ores, oil fly ash, phosphate rock or chromite processing. The major source of vanadium has been from uranium mills incorporating acid leaching of Carnotite ore s at elevated temperatures and pressures. The by-product recovery of vanadium from uranium ores of the Uravan Mineral Belt, located in the Colorado Plateau , is a common occurrence when vanadium recovery is economically viable."

Jan 1, 1983

By H. W. Kasaini, E. Bourricaudy, T. Larochelle

Rare Element Resources Inc., a U.S. based company, has developed a three-stage process for producing a +98% mixed REO powder from hard rock feedstock (-48 mesh, 2.9-4.8% REO) consisting of bastnaesite and ancylite minerals. Firstly, the whole ore is digested in chloride media at low temperature in counter-current flow mode. Secondly, the rare earths (REEs) are selectively precipitated as oxalates directly from an impure pregnant leach solution (PLS). Finally, significant amounts of free acid and water are recovered from the REE-depleted filtrate and subsequently recycled within the process. Excess heat from the oxalate calcination process is captured and reused in the plant. Due to the low leach temperature (45 ºC) and moderate acid dosage (240-297 kg/t, HCl), rare earth oxides (REOs) are preferentially leached out of fine solids leaving most of the base metals (Ba, Fe, and Al ) in the residue. Selective recovery of REEs from the PLS is achieved by mixing dilute oxalic acid (33% H2C2O4) and PLS at elevated temperature (85-95 ºC). The REEs plus thorium are precipitated as oxalates (REE2 (C2O4).xH2O) while the base metals are left behind in the barren filtrate. Multiple batch and pilot test results have confirmed that 50-80% of the oxalic acid can be recovered from the REE-depleted PLS through low-temperature crystallization (10-15 ºC). Typical leach efficiencies of critical rare earths at 45 ºC range from 85-99% (average 93%) while oxalate precipitation at high temperature increases the crystal size of RE oxalates (>450 microns, d80) thereby improving filtration. The economic benefits of this process include elimination of flotation and magnetic separation Capex and driving hydrometallurgical Opex down to $6- 7/kg, REO produced. As part of a comprehensive risk mitigation strategy, Rare Element Resources Inc has operated multiple pilot plants at SGS in Lakefield, Ontario, Canada to optimize counter-current leaching (CCL), REE oxalate precipitation (OXP), and thorium removal circuits. This paper presents pilot testing data from CCL and REE OXP circuits.

Jan 1, 2016

By W. R. Hargrave

"Mining OperationsOre will be mined by open pit techniques. Because of the high grade of the deposit and the low strip ratio, mining rates are small relative to most other open pit operations.The ore deposit is located in the valley of the main fork of Red Dog Creek. The bulk of the deposit is located on the southwestern flank of the creek, but mineralization does traverse the creek in both the north and east directions.Erosion has exposed the orebody in a number of locations, and has resulted in oxidation of the mineralization closer to the surface. Although much of this oxide material is very high grade, it leaches readily and, at least in the initial phases of the operation, will be stockpiled and not treated in the concentrator.During construction, 2.3 million mt. (2.5 million st.) of overburden and waste will be stripped from the orebody to expose ore for initial operations. Competent non-mineralized waste will be used to build roads and waste dumps, but the bulk of material removed consists of oxide or ice-rich soils and weathered rock which is not suitable for construction.The annual ore mining rate will be 1.9 million mt. (21. million st.). The strip ratio will start off at 1.2 to 1, falling to 1.0 to 1 by year 5 and ultimately to 0.8 to 1.Bench heights are set at 7.6 m (25 ft). Pit slopes will vary depending on the material present in the wall. The slope, through competent waste and the sulphide package, was set at 45 degrees. This is flattened to 26 degrees (i.e. 2: 1) through overburden and Upper Kivalina shales. The Kivalina Shales are an ice-rich shale whose carbonate matrix has been leached out and which exhibits little or no strength as it thaws. In addition, a 100 ft containment berm will be left in the wall below overburden and Kivalina."

Jan 1, 1989

By Greg Yuriy

Over the past two decades, Vale Canada has used discrete-event simulation in a key role to support many underground mining studies. Traditionally, general purpose simulation software was developed for manufacturing and service applications. Not until recently have Mine Designers and Simulation Specialists been able to model the dynamics of underground mining scenarios without extensive manipulation of the inherent tools and entities contained within these simulation environments. This paper discusses Vale Canada?s past experiences with a variety of simulation software, describing model development methods and highlighting some of the lessons learned. The paper concludes with a review of recently considered software and provides a framework of desired attributes/functions for modeling mining scenarios.

Aug 1, 2013