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By W. G. Scott

IT IS APPROPRIATE that your Institute should have chosen, for its 1956 Annual General Meeting, the Capital City of a province which is making such rapid advances in mining. The railway industry is proud to be playing an active role in this development, expenditures on equipment and railway construction in the Province of Quebec alone in recent years being in ?excess of a quarter of a billion dollars. In looking up some background material for this address I ran across a definition of a mine by Mark Twain, the great American humorist, which I thought might amuse you. He said that a mine was "a hole in the ground owned by a liar". I am sure that if he were alive to witness the enormous value attached to Canada's mineral resources today he would quickly change his definition. Canada's postwar record of mining development has been staggering in its variety and enormity. Historically, only the ?construction of our transcontinental rail ways outranks the largest of three of these development projects - the aluminum undertaking at Kitimat; the Quebec-Labrador iron ore deposits ; and the petroleum and natural gas developments in Wes tern Canada.

Jan 1, 1956

By B. Arlyuk

The complex system has been developed for long-term assessment of world prices and sale volume of primary aluminium when using the analytical model of the market and market supply forecasts as well as economy development in the Western countries characterized by the industrial production indices as correct data of Western World aluminium consumption are absent, The important part of this system is the model developed for forecasting the degree of capacities utilization of smelters and refineries depending on the price level, The model contains a statistic part corresponding to the capacities distribution by the production cost, and a dynamic part determining the deviation from the static depending on the price variation dynamics, The developed complex system has been identified by the actual data of the world prices of smelter grade alumina and primary aluminium, conservation and reactivation of refineries and smelters in the Western countries within the period from 1992 to 2003. The system was used for primary aluminium and alumina price forecasts till 2020.

Jan 1, 2004

By Michael S. Moats, Prashant Bagri

"In recent years with increasing concerns about energy consumption in hydrometallurgical processing, there is an ongoing attempt to use Catalytic Titanium Anodes (CTAs) for copper electrowinning. For this work, anodes with IrO2 - Ta2O5 coatings were prepared in the laboratory with the same total coating loading but varying the number of layers by changing the speed of withdrawal in dip coating. A second set of CTAs were fabricated on niobium, Ti Grade 1, Ti Grade 7 and Ti Grade 36 metal substrates. All the anodes prepared in the laboratory were characterized using standard electrochemical techniques and subjected to accelerated life testing. It was found that the coating would not adhere to the niobium substrate, the grade of titanium had a minimal to no effect on the life of the anode, and it is observed that as the coating speed slows, there is an increase in the electrochemically active surface area of the coating which seems to directly contribute to an increase in the Tafel slope of the anodes. There was inconclusive evidence on the effect of coating speed on anode lifetime.INTRODUCTIONLarge scale hydrometallurgical extraction of copper has become widely practiced over the last 40+ years. The hydrometallurgical route entails leaching, solvent extraction and electrowinning. With the increasing desire to process refractory sulphides like enargite and chalcopyrite through the hydrometallurgical route, use of hydro-processing of copper is expected to remain high.In conventional electrowinning, copper is deposited on the cathode and an inert anode is used for oxygen evolution. Presently, the most common anode material is rolled lead-calcium-tin and the cathode is 316L stainless steel (Robinson et al., 2013). This lead alloy is fairly inexpensive and is robust, providing lifetimes typically of 4+ years. The main drawbacks of lead alloys are their relatively high oxygen evolution overpotential, the need for cobalt in the electrolyte to reduce their corrosion, the contamination of cathode product by lead, and the generation of harzardous by-products (Hiskey, 1999)."

Jan 1, 2016

By T. Lu

Microwaves have considerable potential as an energy source in both mineral processing and metals extraction. In this research, the utilization of microwave radiation for the heating of a gibbsite type bauxite ore was investigated. Firstly, thermogravimetric studies were performed in order to characterize the dewatering processes of the ore. Secondly, both the real and the imaginary permittivities, which are the fundamental properties that determine the interaction of microwaves with any given material, were measured for the bauxite ore as a function of temperature. The changes in the permittivities were shown to be related to the dewatering processes. Subsequently, the effects of operating variables such as processing time, sample mass, particle size, microwave power, sample bulk density and carbon and magnetite additions on the sample temperature in a microwave field were studied. The results showed that under suitable conditions the bauxite ore could be readily heated. Therefore, there is considerable potential for the application of microwaves for the heating of bauxite ores.

Jan 1, 2007

By Dogan Paktunc, Larry J. Hulbert, Robert C. Carne, D. Conrad Grégoire

Abstract -A thin layer of stratiform Ni-Zn-PGE sulfide mineralization of sedimentary-diagenetic origin was deposited during the Middle to Upper Devonian in the euxinic "Nick basin". The mineralized unit (2:3 cm thick), which seems to have been developed over the entire sedimentary basin of >80 km2, consists of pyrite, vaesite (NiSi), and sphalerite. The average grade of the mineralization is about 5.3% Ni, 0.73% Zn, ?770 ppb (PGE+Au), and up to 61 ppm Re. Anomalous Se, As, Mo, P, Ba and U are present. A minimum of 0.90 x 106 tonnes of Ni were deposited in the basin (based on a bed thickness of 3 cm) during the Devonian. The unique metal association, extensive lateral distribution, persistent metal grade, mineralogical makeup, and stratigraphic control demonstrate that this is a new deposit type and a new geological environment for Ni and PGE +Au. The sulfide layer occurs at the base of a Phosphatic Chert Member which is underlain by a distinctive marker unit consisting of concretionary limestone structures. The limestone spheroids may represent a vent-specific carbonate facies developed adjacent to faults that emanated nutrient­ rich hydrothermal discharges just prior to the main mineralizing event. The suite of elements associated with the Nick mineralization suggests that the ore-forming metals were originally bound to organic matter derived from decaying marine organisms. Discharge of hot brines bearing organic­ matter-bound metals took place along numerous conduits within basin faults that are now manifest as bitumen veins. Our syndiagenetic model proposes that these fluids were discharged laterally from the conduits into the unconsolidated bottom sediment (ooze). The introduction of this metalliferous fluid, rich in organic matter, stimulated biological activity and bacterial reduction of its contained S04 to sulfide. Hot, dense, laterally migrating hydrothermal fluid precipitated thin sulfide-rich 1arninae within bottom sediment. Published thermodynamic studies suggest that the diagnostic vaesite­ pyrite assemblage crystallized at approximately 138°C. The ?34:S values range from -14.7 o/oo to-10.0 o/oo and are up to 34 o/00 lighter than locally surrounding sulfides and age-equivalent mineralized strata elsewhere in the Selwyn Basin. The ?13:C values of calcite in the footwall of the mineralized unit ( -12 o/00 to -6 o/00) are isotopically much lighter than regional values. The lighter isotopic character is attributed to the hydrothermal discharge of fluids enriched in organic compounds. Although geochemical profiles of the lower Earn Group sediments that host the Nick mineralization reveal that these black shales are not distinctive, the unusual Ni, Zn, PGE, U, Ba, and P elemental associations and their anomalous concentrations in stream sediments can be used to explore for this deposit type.

Jan 1, 1992

By S. Southall, F. McCaffrey, F. Stober, M. Darini

Electrode Columns are commonly used in electric furnaces to deliver current and regulate furnace power to the smelting or melting process. Hatch has developed an innovative patent-pending system for lowering ("slipping") and/or raising ("back-slipping") the electrodes through an electrode column, without requiring the release of any clamping devices. All clamping forces are applied by springs. Unlike systems employing hydraulically applied clamping forces, (e.g., water bladders) the spring system is failsafe. Its inherent simplicity virtually eliminates the need for maintenance. The Hatch system is particularly applicable to Soderberg electrodes, and comprises two axially movable slipping clamps and a stationary power clamp, each of which apply a distributed, radial clamping force to the electrode. The magnitudes of the slipping sleeves' clamping forces and sequencing of their axial movements are selected such that the slipping clamps, in conjunction with the weight of the electrode, provide slipping or back slipping without release of any clamping force.

Jan 1, 2005

By Arthur Notman

In view of the alarm expressed in many quarters over the increased production of copper to come from Canada and Africa in the future, it is of interest to study the history of the principal producing districts of the world and to attempt to forecast the future part to be played by them. Tables 1 and 2 record the world production and that of the United States, together with their respective rates of increase, both in percentage and actual amounts. The important point in this record is the decline in rates of increase for both the world and the United States, but more particularly in that of the latter, since 1881. The increase for the United States in the last decade is less than that for any decade since 1881, and is only 20 per cent of that for the decade 1911-20. The increase for the world is less than that for the two preceding decades, and is only about 65 per cent of the war decade 1911-20. Referring to Table 1, the decade 1871to1880 showed an increase of 32.l per cent in the world's production, which was the low until the last decade, ending 1930, which shows an increase of only 24.5 per cent. These decades both represent periods of economic stress following wars. In the first case the recovery was very sharp, the percentage increase in 1881-90 reaching a high of 86.4 per cent. It would seem dangerous, however, to assume that a similar high will be reached in the next ten years, because of the severity of the depression brought about by the Great War and the probability of its influence extending well into the next decade.

Jan 1, 1931

By K. Szczesny

This paper considers the integration of uncertain real-time logistics data for reactive construction scheduling. In order to manage a construction project efficiently, an accurate schedule representing the current project progress is inevitable. The quality and up-to-dateness of such a schedule depends on the availability of real-time data. Typically, real-time logistics data contain information about the availability of material, equipment and personnel as well as delivery dates and site conditions. The accuracy and inherent uncertainty depends on the location where the real-time data was acquired. Currently, the integration of such data into a construction schedule is a very time-consuming, manual and, thus, errorprone process. Therefore, this paper proposes a methodology that enables an automatic integration of such uncertain data into construction schedules. By integrating uncertainties into the existing schedule their impacts on the construction work can be evaluated. For this, discrete event simulation is applied. In order to model uncertain input parameters for simulation models this methodology applies the fuzzy sets theory. In combination with alpha-cut sampling technique, discrete model input parameters are obtained. By applying reactive scheduling with several discrete event simulation experiments, the results can be used to modify construction schedules according to agreed timeframes and costs. In order to demonstrate and validate the presented approach an example is conducted.

Aug 1, 2013

By Eiichi Sato, Koichi Kitazono, Hiroshi Masuda, Kenta Higane

"The present study investigated the low-temperature creep mechanisms in ultrafine-grained (UFG) aluminum manufactured by accumulative roll bonding. UFG aluminum with grain size 0.39 µm showed steady state creep even at room temperature under low stresses as confirmed by the creep curves in the strain rate–strain plot. The low-temperature behavior was divided into four regions by three distinctive stresses, sI, sII and sIII: sI (=45 MPa) is denoted as the micro-yielding stress with which dislocations start movement, sII (=85 MPa) the dislocation-multiplication stress above which dislocations multiply with creep deformation, and sIII (=171 MPa) the conventional yield stress above which macroscopic plastic strain is generated. During low-temperature creep, below sI, negligible plastic strain is generated. Between sI and sII, creep deformation with stress exponent 2.5 occurred, which is accommodated by dislocation absorption into grain boundary and grain boundary sliding, similarly to the low-temperature creep of HCP metals. Between sII and sIII, creep deformation with stress exponent 7.0 occurred, whose mechanism is similar to the low-temperature creep of coarse-grained aluminum. Above sIII, power-law breakdown occurred.INTRODUCTIONIt is well understood that the creep deformation brings about at high homologous temperatures (T/Tm) of >0.4, where Tmis the melting point, with diffusion processes. Recently, the importance of aluminum is increasing for cryogenic temperature parts such as a metallic liner or a cap in high pressure-hydrogen vessels, and the presence of creep behavior in aluminum at room temperature has become recognized (Matsunaga, 2013;Kassner, 2015).In HCP metals and alloys, especially intitanium, steady-state creep behavior appears at room temperature with apparent activation energy of1/10 of that for self-diffusion(Neeraj, 2000; Matsunaga, 2009).On the other hand, Kassner (2015) claims that aluminum shows creep behavior at room temperature with apparent activation energy of 4/5of that forself-diffusion, but never reaches the steady state. We should note that it is derived from the data obtained from short-term creep tests of few hour, and Matsunaga (2013) already claimed the presence of steady state in room temperature creep in aluminum with activation energy of 1/5of that for self-diffusion.The mechanisms for low temperature creep are considered different between HCP and FCC metals: in HCP metals, grain boundary sliding is observed and is thought to accommodate piled-up dislocations at grain boundaries through absorbing them. The so-called slip-induced grain boundary sliding occurs with low number of activated slip systems(Matsunaga,2009).On the other hand, in FCC metals, many activated slip systems bring about work hardening with dislocation cell structure formation. In the initial stage of creep, it results in primary creep (Kassner, 2015), but Matsunaga (2013) claimed that once the annihilating of a cross-slipped dislocation to another reaches balance, steady state is established. It has been, however, strongly required to show more convincing experimental verification for the presence of steady state in FCC metals at low temperature."

Jan 1, 2018

By A. G. Eccles

Western Mines' milling circuit produces three concentrates (copper, lead and zinc), with the tailings being disposed of at the bottom of Buttle Lake. In view of the mine's location and the method of tailing disposal, a comprehensive pollution control program has been in effect since start-up. Changes -in the ore over the past few years have required the use of increasing quantities of sodium cyanide in order to effect a good copper-lead separation. This led to the use of alkaline chlorination for destruction of ?residual cyanide and precipitation of dissolved copper contained in the tailing effluent. The development of Western Mines' alkaline chlorination plant is discussed in detail, including initial test work and the evolution of procedures leading to the present operation. The current monitoring program is also reviewed.

Jan 1, 1977

By H. Jung

The microstructures and grain sizes of nanocrystalline Co and Co-1.1 wt % P alloys were characterized by X-ray diffraction. The corrosion properties of as-deposited and annealed Co-l.l wt % P alloys and pure nanocrystalline Co were studied in a deaerated 0.1M H2SO4 solution using electrochemical measurements and XPS surface analysis. Potentiodynamic polarization testing and impedance measurements revealed that an addition of P to pure nanocrystalline Co improved the anodic-corrosion resistance, however, this enhanced corrosion resistance was compromised by the heat treatment process at 350 and 800°C. The corroded surface of annealed nanocrystalline Co-1.1 wt % P at 350°C exhibited a more porous P-enriched layer compared with the as-deposited case. A sample annealed at 800°C corroded uniformly showing second-phase precipitates. The enhanced corrosion resistance of as-deposited nanocrystalline Co-1.1 wt % P was attributed to the elemental P on the surface that acted to hinder the anodic dissolution kinetics of surface Co following an initial selective dissolution of Co. However, at a higher anodic overpotential region, the superior corrosion resistance of Co-l.l wt% P alloys did not last because of the formation of a non-protective surface film consisting of mainly hypophosphite and phosphate as well as elemental P.

Jan 1, 2005

By Damien Gaboury

"Two practical methods for correlating two or more diamond-drill core intersections, using a stereographic projection software are presented. The first may be used to establish if two or more vein intersections are correlative, based on their core angles and diamond-drillhole attitudes. The second method allows prediction of main vein attitudes from numerous intersections, based on a spherical density contouring projection. The methods are suitable for: (1) correlating veins in complex orebodies; (2) ascertaining lateral continuity of ore for reserve estimations; (3) demonstrating the hidden complexity of an orebody; and (4) correlating and interpreting various planar elements.IntroductionModern mineral exploration relies on diamond- drill core data and on the ability of geologists to interpret them. Drill core generally yields unoriented information, unless an expensive orientation device is used. As a consequence, strike and dip of planar elements such as lithological contacts or mineralized veins cannot be determined easily. This is particularly true for blind deposits (covered by thick overburden) and complex orebodies, where field data cannot support drilling interpretations. Such a problem has been addressed previously using two and three diamond drillholes and several solutions were proposed based on trigonometry, and geometric and stereographic projections (Mead, 1921; Wisser, 1932; Fischer, 1941; Stein, 1941; Bucher, 1943; Gilluly, 1944; Addie, 1962; Mills, 1963; Lyons, 1964). However, these solutions are time consuming and not relevant to present day computerized data plots."

Jan 1, 1997

By P. Langlois, G. Labonté, J. J. Barrett, J. Holmes

"The Voisey’s Bay mill processes a high-grade pentlandite and chalcopyrite ore in a largely pyrrhotite/troilite matrix. From 1994 to 1997, circuit development focused on making a 14% nickel concentrate. When flowsheet development resumed in 2001, the target grade was raised to 20% ni. initially triethylene tetramine and sulfite pyrrhotite depressants were used in a lime circuit, but by recycling process water and the contained thiosalts, the required nickel grade was made without depressants. construction of the mill was fast-tracked, with start-up in september 2005. ramp-up was faster than other recent nickel installations, with tonnage being limited by concentrate dewatering due to higher-thanexpected ore grades.RÉSUMÉ l’usine de traitement de Voisey’s Bay traite un minerai à teneur élevée en pentlandite et chalcopyrite dans une matrice formée surtout de pyrrhotite/troïlite. De 1994 à 1997, le développement du circuit ciblait la production d’un concentré à 14 % de nickel. lorsque le développement du schéma de traitement a été repris en 2001, la teneur cible a été élevée à 20 % de ni. initialement les déprimants triéthylènetétramine et sulfite de la pyrrhotite étaient utilisés dans un circuit à la chaux; cependant, en recyclant l’eau du procédé et les sulfosels qui y sont contenus, la teneur en nickel a été atteinte sans utilisation de déprimants. la construction de l’usine de traitement a été accélérée et elle a démarré en septembre 2005. la mise en opération a été plus rapide que pour d’autres installations récentes de nickel; le tonnage traité étant limité par le séchage du concentré en raison des teneurs de minerai plus élevées que prévu."

Jan 1, 2017

By Tony Szwilski

Using Unity 3D as a collaborative multi-user virtual on-line environment, an interactive virtual underground mine platform (IVUMP) is being developed to provide on-line access to mine safety preparedness training with a focus on mine emergency response exercises (MEREs). Communication and information flow among MERE participants and their actions can be monitored, recorded and evaluated. A mine ventilation simulation utility VFIRE is being incorporated to enhance the realism and interactive nature of the ?in-world? exercises as well as extend its functionality to include training in real-time ventilation and fire control.

Aug 1, 2013

By Hajime Miki, Gde Pandhe Wisnu Suyantara, Tsuyoshi Hirajima, A. M. Elmahdy, Keiko Sasaki

"Seawater has been reported to depress molybdenite in a copper-molybdenum (Cu-Mo) flotation process at high pH due to the precipitation of Mg(OH)2. Meanwhile, to improve mineral recoveries, collectors are usually added into the flotation cells, thus adding the complexity to the mechanism of bubble-particle interactions involved in Cu-Mo flotation. Therefore, understanding the interaction mechanism in seawater flotation and in the presence of collectors is important to explain the minerals depression. The present work investigated the effect of kerosene on the bubble collision and attachment to pure chalcopyrite and molybdenite surfaces in MgCl2 solution as one of the seawater major components at pH 6 and 11. Mineral surfaces were characterized using atomic force microscopy (AFM). In addition, minerals floatability in the same system were tested in a column flotation. The study of bubble-particle interactions shows that following several collisions, bubble could displace the intervening liquid layer on the mineral surfaces, forming a three-phase contact (TPC). A TPC formed more rapidly in the presence of emulsified kerosene in a 0.01 M MgCl2 solution at pH 6 for both minerals. The reason is kerosene increased the surfaces hydrophobicity and destabilized the intervening liquid layer on the surfaces. Moreover, the average time required to form a TPC was shorter on molybdenite surface. This can be attributed to the effect of adsorbed kerosene on molybdenite surface and molybdenite surface roughness.INTRODUCTIONIn froth flotation, bubbles are used to separate hydrophobic mineral particles from hydrophilic particles. In this process, bubble-particle interactions (i.e., collisions, attachment, and detachment) are crucial with regard to mineral recoveries. The effectiveness of froth flotation depends on the formation of stable aggregates between the hydrophobic particles and the bubbles, allowing the bubble to carry the particles to the froth layer. To form such aggregates, the bubbles and particles must collide, and the intervening liquid layer must be drained below the liquid layer critical thickness, forming a stable threephase contact (TPC) (Ralston & Dukhin, 1999). Particles detachment may take place if the particles still have sufficient kinetic energy and the TPC is not formed. Previous studies of bubble-particle interaction in electrolyte solutions have been conducted using atomic force microscopy (AFM) (Assemi, Nguyen, & Miller, 2008), and by approaching the bubble using mica plate (Pushkarova & Horn, 2008), however, these studies did not focus on the bubble-particle collisions. Bubble collisions and attachment to hydrophobic (Teflon) and hydrophilic (glass) surfaces in a a-terpineol solution have been investigated by Krasowka et al. (2003)."

Jan 1, 2016

By C. Dupuis, P. Waite, S. Leboeuf

Casthouses throughout the aluminium industry commonly use chlorine gas as a fluxing agent for furnace and in-line treatment of molten aluminium alloys. Its positive impact on the removal of alkali elements and non-metallic inclusions is well known. Nevertheless, the elimination of its use is highly desirable due to the safety and environmental risks associated with storage and handling. Over the past decade, the aluminium industry has significantly reduced its chlorine consumption. This has been achieved by maximizing the chlorine gas utilization efficiency during metal processing, and by the chlorine replacement for crucible and furnace metal treatment applications. Operation of sealed in-line treatment units without chlorine is now possible, but with lower or inconsistent removal efficiency penalties for alkali and inclusions respectively. This paper reviews the progress made at Arvida Research and Development Centre regarding the reduction of chlorine and the development of an alternative to chlorine for in-line metal treatment without penalizing the metallurgical performance.

Jan 1, 2006

By M. J. King, D. A. Van den berg, R. Fukuzawa

"Mercury bearing ore bodies are often treated for the production of copper, lead, zinc, gold, and silver. The mercury deports either to tailings or is collected during various stages of the extraction process. This paper reviews the relationship between various mercury collection processes and the subsequent management of the mercury by-product or waste. It focuses on mercury removal sequestration including cementation, sulphide precipitation, bulk neutralization, and carbon adsorption. Long term mercury management strategies including third-party stabilization, stabilized mercury co-disposal, secure storage, and mercury recycle are also evaluated. INTRODUCTIONMercury is produced in North America as a by-product of non-ferrous metals processing and from recycling of products such as dental amalgam, fluorescent lamps, and thermometers. Its toxicity is recognized to have significant negative impacts on the environment and human health. As a result, many countries are adopting regulations limiting mercury use and its uncontrolled release.The European Union banned mercury exports in 2011 and the United States will do so in 2013. The export bans aim to prevent mercury use in developing countries for activities such as artisanal small scale gold mining. However, by-product mercury production from the non-ferrous metals industries continues.These factors contribute to an oversupply of mercury and the need to find suitable treatment methods for the long term management and storage of mercury and mercury bearing materials."

Jan 1, 2012

By C. DeLong

"The Mt. Milligan porphyry copper-gold deposits are in central British Columbia, 155 km northwest of Prince George. Mineralized outcrops and float were discovered in the Mount Milligan area by prospecting. The most recent discoveries, which utilized lithogeochemistry, were in 1983. Areas containing the outcrops and float then were investigated by geological mapping, soil and lithogeochemical sampling, ground and airborne geophysical surveys, trenching and diamond drilling. This work led to the discovery of the Mt. Milligan Main deposit in 1987 and the Southern Star deposit in 1989. Extensive diamond drilling continued until 1991 and delineated a measured and indicated resource of 299 million tonnes grading 0.45 g/t Au and 0.22 % Cu from the combined deposits.The Mt. Milligan deposits lie within the Early Mesozoic Quesnel Terrane and are hosted by porphyritic monzonite stocks and adjacent volcanic rocks of the Takla Group. The Mt. Milligan Main deposit is centred around the MBX stock and Rainbow dike, and the Southern Star deposit around the Southern Star stock.Potassic alteration is extensive within the stocks and in volcanic rocks adjacent to the MBX stock and Rainbow dike. Propylitic alteration surrounds the potassic alteration and decreases in intensuy away from the stocks. Mineralization consists mostly of pyrite, chalcopyrite, lesser magnetite, and minor bornite, molybdenite and gold.Mineralogical zoning is well-developed within the deposits. A biotite-rich subzone forms the core of the potassic alteration zone and hosts most of the copper and gold. Numerous polymetallic veins lie within the propylitic alteration zone just beyond the limit of porphyry-style copper-gold mineralization."

Jan 1, 1995

By N. W. Xu, C. Sha, F. Dai, Y. G. Zhu, B. Li

Underground caverns stability and excavatability of rock masses are of significance in geotechnical engineering, in both design and construction stages. Risks associated with underground group caverns of Houziyan hydropower station in southwestern China are growing as a result of continuous excavation-induced unloading. To improve our understanding of the underground caverns instability and resolve the complex subsurface conditions of the highly fractured rock mass, a high resolution microseismic monitoring system was established in the deep underground caverns, pursuing the relationship between the measured data about microseismic activity and excavation damage zones of surrounding rock mass. Through analyzing the tempo-spatial distribution of microseismic activity, excavation damage zones and potential risk regions in underground caverns were identified. Furthermore, the correlation between microseismic activity and pre-existing geological structures, as well as traditional monitoring was analyzed. In order to validate the correlation between seismicity and potential slip surface of underground caverns, a model was implemented into numerical code to further evaluate the deformation and stability of surrounding rock mass. The monitoring results demonstrate that microseismic events mainly occur at high stress concentration regions, which coincides with the results obtained from numerical analysis. Therefore, the comprehensive method incorporating microseismic monitoring and numerical analysis, as well as traditional monitoring and filed observation has been proven to be very promising in deformation and even instability prediction of surrounding rock mass in underground caverns subject to delineation of potential slip surfaces and excavation damage zones.

Jan 1, 2015

By M. Walawalkar, C. K. Nichol, G. Azimi

Rare earth elements (REEs) are essential to the production of technologically advanced products, including wind turbines, electric and hybrid cars, automotive catalytic convertors, hand held electronic devices, and military defense systems. Their application in environmentally beneficial technologies puts them at a high priority for ameliorating environmental concerns. Because of their increasingly high demand and limiting resources, it is highly beneficial to find new sources for them. The present study is focused on leaching REEs from a phosphate based fertilizer by-product, known as phosphogypsum (PG). Global estimated world production of PG is about 240 million tonnes that is stored in the form of wet stacks adjacent to fertilizer production facilities, occupying vast amounts of land. PG also contains trace metals, which are detrimental to the environment, and hence it is crucial to monitor these stacks. We obtained our PG sample from Agrium Inc. (a fertilizer manufacturing company in Canada). We performed a comprehensive characterization of the PG sample and found that it predominantly contains Y, La, Ce, Nd, and Sm. For leaching purposes, we used hydrometallurgical acid leaching techniques. We investigated three acids over a range of operating conditions such as acid concentration, temperature, solid-to-liquid ratio, and residence time. We achieved an average leaching of 81% with hydrochloric acid as leachant using operating conditions that can be easily replicated in industrial settings. If our process is implemented, not only will it reduce the size of the existing PG stacks (mitigating their environmental risks), but also enable the development of new innovative routes for extracting REEs, making countries like Canada less vulnerable to supply disruptions.

Jan 1, 2016