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By C. Caballero, M. Rosales, C. León, A. Valencia, R. Fuentes, A. Moyano

Slopping is the formation of waves in the converter due to the gas injection by tuyeres. Those waves produce a premature wearing of the refractory lining of the reactor due to its great amplitude. The affected zones are the tuyere line (outlet gas from tuyeres) and the front of this line. In the present work, a theoretical and experimental study is made to develop a theory that determines the variables involved in slopping, characterizing the more important parameters of operation in the phenomenon of slopping. In addition, this theory will allow for determination of new technological alternatives of the blast injection permitting to depress the slopping phenomenon.

Jan 1, 2007

By W. R. McQuarry, M. E. Wilson

"The structural relations of the ore deposits of the Staclacona mine are of considerable interest, for they not only illustrate the effect of a change in competence of the wall-rock, but also the effect of either the convergence together of two faults, or a change in the clip of a fault, or both of these factors, on ore deposition.The mine is in claim M.L. 1818 near the eastern end of Pelletier lake and lies about 2 miles south of the town of Rouyn. The Company was organized in 1926 to explore claims in Rouyn, Dufresnoy, and Beauchastel townships, but attention was directed mainly to those in Rouyn. Underground work began in 1928 with the sinking of the main shaft to a depth of 300 feet. Except for 1930 and 1931, the mine has been in operation continuously since that time. Production, which began in 1936, up to the end of 1946 has amounted to 1,381,422 tons of ore from which gold and silver having a total value of $7,861,860 were recovered. The average grade of the ore milled in 1946 was $6.68.GEOLOGYThe rocks in which the Stadacona ore deposits occur are mainly volcanics of the (Keewatin) Abitibi series intruded here and there by numerous dykes, sills, or masses of diorite. Single dykes of olivine diabase and lamprophyre are also present in the property and are intersected in the mine workings. The volcanic rocks are part of a wide belt of northward dipping lavas and pyroclastic rocks, having a thickness of over 16,000 feet, that extend from the east-west trending belt of Timiskaming sediments on the south northward to the Horne Creek fault and form the south limb of a large syncline. The volcanic rocks within the property consist of numerous, east-west trending, northward dipping flows of andesite and a few flows of rhyolite interbedded with rhyolite ruff and agglomerate. The angle of dip throughout most of the property is 60° to 80°N., but in the main cross-cut on the 850- and 975-foot levels stratification in rhyolite tuff was noted dipping 35°N. The tuff at this point lies above an intrusive mass of diorite and it is probable that the change in dip results from the way in which the tuff and agglomerate have been thrust aside by the intrusive."

Jan 1, 1954

"Canada Centre for Mineral and Energy Technology (CANMET)Natural Resources CanadaMining and Mineral Sciences LaboratoriesA. Address and Contact Information555 Booth StreetOttawa, Ontario, Canada, KIA OGlWebsite: http://www.nrcan.gc.ca/Contact: Philippe Dauphin, Manager, Business DevelopmentTel.: (613) 947-0798Fax: (613) 947-0984E-mail: pdauphin@NRCan.gc.caB. Type and Size of FacilityScope of facilitiesCrushing from minus 4 in. to 10 mesh; grinding - rod, ball, vibration, SAG and impact mills; classification- screening, cycloning, mechanical, hydraulic and dry centrifugal classifiers; froth flotation - automated, column, and frothless flotation; gravity separation- wet and dry; magnetic separation - high gradient, high and low intensity, wet and dry; electrostatic separation; heavy-media separation; calcining; cyanidation; thickening; filtration; drying - fluid bed and freeze drying; pelletizing; microwave.SpecialtiesMineral beneficiation research and development; flotation of sulphides - flowsheet improvement, selectivity, reagent selection; novel flotation techniques; analysis of thiosalts formation; use of mineral processing techniques for recycling.Specialized equipmentHigh gradient magnetic separation, Denver XRF on-stream analyzer, automated flotation cell.Complementary support servicesElectron microprobe; SEM; STEM; X-ray diffraction; particle size analyzer; mineralogical and analytical chemistry services; physical chemistry; hydrometallurgy; pyrometallurgy; engineering and economic evaluation; mechanical shops; technical information services and library integrated with the National Library System of the National Research Council."

Jan 1, 2000

By C. J. Simensen, R. Østhus, H. J. Roven, K. G. Skorpen, H. Kalager

"This work encompasses co-extrusion of alloy Al4.5Mg at the core and rapidly solidified Al4.5Mg1Ag forming the surface layer. The goal is to produce a multi-material by co-extrusion having a relatively hard surface as compared to a softer core. At the same time, work hardening in both alloys is expected to be significant due to Mg in solid solution. Precipitation hardening at 160°C is studied by applying solution heat treatments at 560°C. The hardness increased from 80 to 130 VH in the surface material after 236 h. Surprisingly, the Al4.5Mg alloy also shows pronounced aging at this temperature, i.e. from 70 to 90 VH. The relatively high solution heat treatment temperature introduces grain growth in the core, but this is insignificant for the RS surface alloy. Blisters forms at the surface and cracks follows large portions of the interface. However, the tensile ductility is significant in all conditions due to very pronounced work hardening, i.e. for the as co-extruded, T6, under- and over-aged. The elongation at fracture ranges between 40–45% and the tensile strengths 240–275 MPa. The tensile properties increase linearly with the thickness of the RS alloy, i.e. following the rule of mixtures.INTRODUCTION Al-Mg alloys in 5xxx-series are classified as non-heat treatable wrought alloys (Polmear, StJohn, Nie, & Ma, 2017). The formation of the binary ß-Al8Mg5 does not give a substantial increase in the strength of the alloys (Mondolfo, 1976). When a third element like Ag, Cu or Zn are added, G.P.?zones are formed at low temperatures and intermediate, partial coherent phases are nucleated somewhat higher temperatures and finally a ternary, equilibrium phase is formed (Auld, 1968; Cousland & Tate, 1986; Mondolfo, 1976). Both the formation of G.P.?zones and intermediate phases increase the hardness and strength of the materials. An intermediate, hexagonal T´?phase is formed in Al-5 wt%Mg-1wt%Ag, and finally the equilibrium, cubic phase (Al,Ag)9Mg5 is nucleated (Cousland & Tate, 1986; Mondolfo, 1976)."

Jan 1, 2018

By L. M. Nolan

Chemical Mechanical polishing, or CMP, has four components in the polishing interface; namely the polishing pad, the polishing fluid, the abrasives in the fluid, and the surface being polished. Understanding the way that load is transferred between these components is key to understanding and predicting wafer polishing. Numerous models of CMP and the different load sharing arrangements which occur between these four components have been proposed. These include models by Luo and Dornfield (1) and Fu, Chandra and colleagues (2). Other models focus on just one or two loading arrangements, such as `hydroplaning' when all load is transmitted by the liquid in the case of Runnels and Eyman (3). In this work, we consider four possible combinations of load transfer from pad to wafer in CMP. These combinations are listed below in Table 1 and are illustrated schematically in Figure 1. It is important to note the role of scale in this process; the illustrations in Figure 1 are drawn to scale from actual profilometer scans obtained over a length of 5 with particles of 150 nm in diameter. Table 1 - Load Transfer Combinations Load Regime Illustration Wafer - Fluid - Pad Figure la Wafer - Particles/Fluid - Pad Figure lb Wafer - Particles - Pad Figure lc Wafer-Pad Figure ld The interest in load-sharing between the system components is because some configurations are anticipated to achieve higher polishing rates than others. For instance, in hydroplaning, or hydrodynamic lubrication, the lateral force exerted on the polished surface by the particles can be no higher than the fluid shear force developed in the gap between the pad and wafer. This is not expected to generate high rates of material removal from the surface (4). For contact that is largely between the pad and the wafer, such as the regime depicted in Figure ld, the lateral load is transmitted to the wafer by the pad and is hence limited by the pad's low rigidity. This regime is not expected to generate high material removal rates either. The highest levels of material removal are expected from regimes where the mechanical load exerted on the system is transmitted by the particles, in combination with either the fluid or the pad. Under what circumstances does the polishing regime change from one to another? What must occur in order to initiate or terminate contact between the system components? This is an ongoing question in the field of tribology, and has traditionally been viewed in terms of the pressure and velocity applied to the system, the thickness of the fluid film between the two surfaces, and the roughness of those surfaces (4). In this paper, we propose a new mechanism ? that the load on the particles may be sufficient to totally embed them in the polishing pad, at which point they are no longer able to transmit load and polish the wafer surface. This is illustrated schematically in Figure 1(d).

Jan 1, 2010

By R. L. Eadie, J. L. Luo

The effect of plastic deformation on near-neutral pH stress corrosion cracking (SCC) also known as environmentally assisted cracking was studied by cracking rate measurements. All the tests were conducted in a synthetic near-neutral pH solution. The traditional potential drop tests using compact toughness (C-T) specimens with 2-3 mm long pre-cracks showed varying plastic deformation by rolling would increase the material's susceptibility to SCC. This was confirmed by cyclic loading tests using double notched flat tensile specimens with 200-300 µm long pre-cracks which gave the same results that the specimen with large scale plastic deformation by tensile loading had a relatively faster crack growth rate than that with only small scale plastic deformation.

Jan 1, 2005

By J. G. Ross

A DESCRIPTION of the block-caving system of mining as practised at the King mine of Asbestos Corporation, Limited, Thetford Mines, Que., was presented. at the Annual Meeting of the Institute held in Quebec city, in April, 1934. The paper was published in the Transactions of the Institute for 1934. There has now been recovered, by this method, one million tons of ore, and a review of experience indicates that the method was well planned and has been executed smoothly. In approaching the problem of selecting the type of mining best adapted to this deposit, the method had to be one which would be low in cost, use no wood, and not disturb the surface immediately bounding the ore-body on two sides. Prior to 1931, block-caving had been considered but rejected, as it en-tailed disturbance of the surface area which lay within a 45° angle of the lowest contemplated workings, if the practice of such mines as Ray, Miami, Inspiration, and Morency, where this type of mining has been used extensively, was followed. At these properties there have been mined large tannages at outstanding low costs, but an extensive surface area has been disturbed in each case. In some instances, townsites in the mining area have had to be abandoned, and dwellings, not considered worth moving, have been allowed to fall into the depression. A study was made of the principles involved in the various types of block-caving, the existing information on ground movement, subsidence, etc., also being carefully analysed. Toward the end of 1931, a plan was conceived whereby the country adjoining ground being caved might be held permanently in place and undisturbed. The success of such a scheme was essential to the application of block-caving at the King mine on account of property boundaries, the Quebec Central Railway right-of-way, and expense of moving buildings. Study of existing data on caving and movement of rock, caused by sub-surface excavations of sufficient unsupported area to result in failure of the backs, indicated, in practically every instance, that such movements followed certain definite laws of mechanics.

Jan 1, 1936

By Samuel Nunoo

Gibraltar Mine is an open pit copper-molybdenum mine in central British Columbia. The stability and potential failure modes of pit walls in the Granite Pit are controlled by the orientations of joints and faults. The structural geology also has an impact on as-mined bench geometries. Geotechnical mapping and surveying were conducted using stereo photographs and photogrammetry software. Detailed digital terrain models were constructed to determine the pit wall geometry and the locations and orientations of larger structural features. The pit wall geometry is compared to conventional survey results and the mapped structures are compared to results from a nearby geotechnical borehole.

Aug 1, 2013

By W. J. Li, L. Kong, G. L. Li, X. M. Xi, J. Qiu

"A novel hydrothermal method was applied to prepare the precursor of LiMn2O4 using pre-treated electrolytic manganese dioxide (EMD) and lithium hydroxide as the main raw materials. The precursor was subjected to heat treatment between 400 and 900ºC to obtain spinel Li1.05Mn1.95O4 and Li1.035Co0.035Mn1.930O4 positive materials for lithium ion batteries. The structure and morphology of the obtained powder materials were studied in detail by means of X-ray diffraction (XRD) and scanning electron microscope (SEM). It is found that the precursor has an amorphous structure and a high reactivity, which is easily transferred to spinel structure during heat treatment, obtaining a positive material with an uniform structure and good performances. The XRD patterns reveal that single phase spinel Li1.05Mn1.95O4 can be obtained from the precursor after heat treatment at 600°C in air. The final Li-rich Li1.05Mn1.95O4 product obtained showed a well-defined stable spinel structure and distinctive crystal faces with particle size between 200 and 300 nm. The as-prepared Co-doped spinel sample exhibited a excellent electrochemical performance with an initial discharge capacity of 113.0 mAh/g and 93.8% of its original value was retained after 100 charge-discharge cycling at 0.5 C.INTRODUCTIONThe increasing demand for portable electronic devices and hybrid or full electric vehicles is driving the development of cheap, efficient, compact lightweight and environmental friendly rechargeable batteries systems (Chung et al., 2002; Scrosati, 1995). Lithium ion secondary batteries have satisfied this demand to a greater degree than other battery systems. The cathode material plays a critical role in the performance of Li-ion batteries. The high cost and toxicity of cobalt compounds for the cathode material of LiCoO2 has prompted a search for alternative materials. LiMn2O4-based spinels offer a potentially attractive alternative to LiCoO2, due to its abundance, low price, ease of preparation, environmentally friendly characteristics, better thermal stability, and its effortless recycling (Tarascon et al., 1991; Yabuuchi and Ohzuku, 2003; Amatucci et al., 1999; Tsai et al., 2003). Some achievements have been created to meet the requirements (Guo et al., 2010; Kang et al., 2005; Park et al., 2008; Takahashi et al., 2006; Lee et al., 2001; Yoshio et al., 2001; Arumugam et al., 2008). However, the largest obstacle encountered in the practical applications of LiMn2O4 is its fast capacity fading during long term cycling, which is due to Jahn-Teller distortion of the [MnO6] framework, the electrolyte decomposition at high potentials and manganese dissolution into the electrolyte (Fey et al., 2003). The electrochemical performance of LiMn2O4 is also strongly dependent on its morphological properties, such as crystallinity, phase purity, surface area, grain shape and particle size distribution, etc. All these morphological properties are closely related to the material synthetic routines and heat treatment processes (Huang et al., 2000; Myung et al., 2000; Takada et al., 1998)."

Jan 1, 2012

By G. T. Lapidus, J. Trejo-Gallardo

A phenomenological model is presented for leaching silver from silver sulfide contained in mineral particles with ammoniacal thiosulfate solutions of copper in stirred reactors. Experimental results were used to adjust the kinetic parameters of the model, such as the reaction order and velocity. The incorporation of the cuprous sulfide-silver sulfide equilibrium at the reaction interface allowed the prediction of the conversion limits for different reagent concentrations. The information obtained from the reactor model was later integrated into a heap leaching simulation, whose results adequately describe tendencies observed in column tests, with respect to variations in copper and thiosulfate concentrations. Comp

Jan 1, 2005

By H. Vendette, N. R. Dando, A. Moras

The thorough analysis of results obtained from different testing campaigns performed on an alumina dry-scrubber pilot installation treating aluminum potline offgases, suggests a clear relationship between the emissions of gaseous fluoride and the fluoride saturation level of the alumina. The integration of this relationship into the development of a new generation of alumina dry scrubber represents an intriguing challenge regarding the design of more efficient air pollution control equipment. An innovative scheme challenging conventional industry practices was proposed. From theoretical simulations, the reduction in fluoride emissions can potentially be reduced by as much as 50% in the summer season. To validate this innovative approach, Solios in partnership with Alcoa Primary Metals, modified one of the Aluminerie de Deschambault's systems by adding new temporary equipment on the operating units and subjecting it to several test campaigns. This article presents the first results obtained in testing this new and innovative approach on alumina dry scrubbers used to capture fluoride emissions coming from aluminum electrolysis potlines.

Jan 1, 2006

By J. Béland

"Three stages, each characterized by a particular sedimentation, magmatism, mineralization and deformation, are recognized in the geological history of Gaspe. The first stage led to the formation of the Taconian orogen, the second to that of the Acadian orogen and the third stage to the accumulation of a post-orogenic cover. The Taconian orogen includes volcanic and detrital rocks of Late Precambrian or Cambrian and Lower to Middle Ordovician ages in which ultrabasic intrusions have been emplaced. Folding is severe. Mineralization is of the Cr-Ni-Cu type, related to the igneous facies.The rocks constituting the Acadian orogen include two distinctive sequences corresponding to two successive sub-stages. The second substage began in Early Devonian time with the first pulses of the Acadian orogeny. The rocks of the first substage grade southward from a nearly platformal sequence to an assemblage implying less stability and spotty volcanism. The second substage was one of synorogenic deposition of elastic rocks, first in a marine environment and later under terrestrial conditions. Granitic intrusions, surrounded by aureoles of skarn and hornfels in which Cu-Pb-Zn mineralization is found, accompanied the Acadian deformation. The second-stage"

Jan 1, 1969

While this paper is directed towards the ?Bellambie? type of rope attachment, the principles can be applied to any brand of rope fitting however, it is a only a broad outline and the specific installation and maintenance procedures can be obtained from the attachment supplier. The types of attachment to be discussed are:- ?Thimble Type rope cappel ?Wedge Type cappel ?WRC Rope Clamp ? (Rope Glands) ??Hoist and Balance Rope Sockets In each case, the assembly and stripping (disassembly) plus the basic maintenance procedures is briefly described. A guide for Risk Assessment is also included but because of his familiarity with the installation, the end-user is in the best position to draft the final version.

May 1, 2003

By G. D. Bateson

"The Low NOx/SOx (LNS) Burner is a technology which, in pilot-scale tests, significantly reduces acid rain-forming emissions from the burning of coal. The precursors of acid rain are nitrous oxides (NO) and sulphur dioxide (SO:;) . TransAlta is currently planning two demonstration projects.Esso Resources Canada and TransAlta are undertaking a project to demonstrate how coal can be burned cleanly for steam raising in heavy oil operations by using TransAlta's LNS Burner on a steam generator at Esso's Cold Lake Production Project. The $10.7 million project started up in mid-J990, with testing to be completed in mid-I99J. The province of Alberta and Western Economic Diversification Canada, along with other private industry, are contributing funding to the project.The other demonstration project that has been selected for funding under the United States Department of Energy's Innovative Clean Coal Technology Program is a retrofit of LNS Burners to a 33 MW cyclone unit at Southern Illinois Power Cooperative's Marion generating plant. The US$13.6 million project is scheduled for completion 18 months after final funding arrangements are made.TransAlta believes that these demonstrations will lead to the development of a commercial ""clean coal"" technology. Other demonstration projects being planned will further broaden the base of applications.IntroductionTransAlta has recognized an increasing concern worldwide for the environment, and in particular the acid rain problem. Increasing public concern and the need to meet either current or possibly more stringent emission regulations have prompted them to explore various emission reducing technologies - despite the low sulphur content of its coal.The flue gas desulphurization (FOD) and selective catalytic reduction (SCR) technology currently available to reduce sulphur and nitrous oxides from coal burning power plants is very costly. Having to incorporate FGD technology, or ""scrubbers"", greatly adds to the cost of producing power. Having to add such high costs to electric customers' bills is something TransAlta is striving to avoid.There are many research programs now underway which are evaluating ways to provide electricity from coal in a clean manner. TransAlta has been observing or participating in a variety of these programs. However, there is one new technology which the company has identified as having the potential to control acid rain causing emissions at a fraction of the cost of conventional systems. That technology is called Low NOx/SOx, Burner - or LNS Burner."

Jan 1, 1990

By Chris Yellowega

The construction and startup of a new mine is a daunting task. To successfully locate, design, build and startup an immense human endeavour like a new mine, takes perseverance, planning, dedication and significant capital. The application of capital requires a thorough evaluation of risk and where that risk is most properly limited to create the risk/return profile. One area of significant capital and thus, significant risk is the selection and maintenance of the very machinery needed to deliver the creation of investor wealth. Albian Sands Energy is the operator of the new Muskeg River Mine located north of Fort McMurray in Alberta?s oilsands. The Muskeg River Mine is owned by a joint venture of three companies: Shell Canada, Chevron Canada Ltd.and Western Oil Sands. The mine is designed to run 400,000 tons per day, 365 days per year. The mine conditions vary from material as hard and of similar consistency to pavement to underfoot conditions as soft as saturated sands. Water cannot be drained below surface conditions, shovel teeth can disappear in less than 24 hours and the primary business is often constructing large civil structures that have little to do with the delivery of ore. The mine starts with the deposit (if it doesn?t exist, nothing else matters), moves into the design, the feasibility study and the approval. The evaluation of risk and the strategies surrounding the control of that risk truly lie after these stages are complete. The strategy and execution stage is where risk is eliminated or accommodated. The point at which the investors money is being spent is the point at which the decisions made cannot be reversed. It is of absolute importance that the execution of the decisions are consistent with the strategy agreed to, lest the investors need to be asked for more money. The key sources of risk identified for the Muskeg River Mine were recruitment of trained and experienced personnel and the delivery of ore to maximize early (<2yr) cash flow. The Muskeg River Mine personnel determined that to minimize risk, personnel would be recruited to operate the mine equipment yet, the requirements for maintaining the equipment would best be held by the manufacturer. The strategy was to obtain the correct equipment for the operation of the mine and leverage the supplier?s expertise to ensure the mine wasn?t training a maintenance organization at the same time as a mining organization. In essence the key strategy for the mine start up and early operation was to leverage the equipment suppliers to maintain and repair the equipment. Albian Sands would maximize the utilization of Maintain And Repair Contract?s.

May 1, 2003

By Q. Shi, Q. Feng

"The influence mechanism of chlorite on the flotation of pyrrhotite was investigated through flotation tests, Zeta potential measurements, optical microscope photos, solution ion measurements and absorption measurements. It is observed that, the addition of chlorite influences the flotation of pyrrhotite seriously. The IEP (isoelectric point) of pyrrhotite and chlorite is 7.6 and 4.3 respectively, in the condition of slight alkalinity, both pyrrhotite and chlorite are negatively charged, and the hetero-aggregation will not occur. With the existence of oxygen in solution, the iron ions are dissolved from pyrrhotite surface because of the oxidation of pyrrhotite during pulp conditioning. The dissolved iron ions adsorb onto the surface of chlorite in the forms of iron hydroxyl and iron hydroxide, and the adsorption results in the opposite charge of chlorite surface. As a result, the hetero-aggregation between pyrrhotite and chlorite occurs. The adsorption of chlorite changes the surface property of pyrrhotite and restricts the adsorption of amyl xanthate onto pyrrhotite surface, and then decreases the flotability of pyrrhotite.INTRODUCTIONIn sulfide ores processing, magnesium silicate bearing gangue minerals often report to the concentrate causing downstream processing problems as well as increased smelting costs. Talc,chlorite and serpentine are gangue minerals commonly encountered in complex sulfide ores (Engel, Middlebrook, & Jameson, 1997; Pietrobon et al., 1997; Witney & Yan, 1997; Chen, Grano, Sobieraj, & Ralston, 1999a, 1999b; Bremmell, Fornasiero & Ralston, 2005; Senior & Thomas, 2005; Wang, Somasundaran, & Nagaraj, 2005; WieseHarris & Bradshaw, 2007). All of them are characterized with uniform crystal structures consisting of silicon-oxygen tetrahedron and magnesium-oxygen octahedron. The magnesium-oxygen octahedron layers are broken during the liberation of serpentine to expose the magnesium-oxygen bonds with strong ionicity and hydration, which results in natural hydrophilicity of serpentine. In water, the hydroxyl on serpentine surface ruptures and dissolves into the aqueous phase while the Mg2+ remains, resulting in surface positive charge (Tao, 2012). As serpentine has a positive potential at alkaline condition, it is therefore likely that it will attach through electrostatic attraction to the negatively charged mineral surface and reduce both the flotation rate and recovery of target minerals (Lu et al., 2011). For talc, characterized as good natural hydrophobicity, the liberation comes from the interlaminar fracture to remain molecular bonds on surface with weak hydration. Being naturally hydrophobic, talc easily reports to flotation concentrates, thus reducing concentrate grade (Shortridge, Harris, Bradshaw, & Koopal, 2000; Beattie, Huynh, Kaggwa, & Ralston, 2006). Meanwhile, both molecular bonds and magnesium-oxygen bonds are exposed on chlorite surface when liberation occurs, resulting in moderate natural hydrophobicity between serpentine and talc (Tao, 2012). And thus the mechanisms of influence of chlorite on sulfide ores are more difficult to study."

Jan 1, 2016

By O. Alonso-Gonzalez, F. Nava-Alonso, A. Uribe-Salas, R. Pérez-Garibay, C. Jimenez-Velasco

A current problem in gold production is the presence of copper minerals which dissolve during conventional cyanidation practice. The dissolved copper causes several problems in the different stages of the process. This issue is the base for copper elimination/recovery methods such as the Sulphidization, Acidification, Recycling, and Thickening (SART) process, which is currently used in gold production plants around the world. Even though the process is well established, new challenges appear as the composition of the solution varies from ore to ore, in some circumstances affecting the performance of the SART process. This work presents a thermodynamic study and experimental tests performed to understand the role of the initial copper concentration and sulfur addition, on the efficiency of the copper removal. For a constant cyanide concentration, an increase in the initial copper concentration causes a decrease in copper removal; high sulfur/copper molar ratios favor copper removal. We demonstrated that the cuprous sulfide formed from solutions with high ionic strength, presents better sedimentation rates than solutions with less ionic strength. For solutions with low sedimentation rates, the use of some pretreatment is necessary to facilitate the sedimentation such as addition of flocculants, particle recirculation and the used ultrasonic pretreatment.

Jan 1, 2014

By J. P. Wiser

THIS paper discusses testing and quality control of milled asbestos fibre. It has been composed with the intention of: (I) Summarizing past, present and probable future methods of testing and classifying the various grades of commercial asbestos produced by the Quebec asbestos industry. (2) Acquainting those unfamiliar with the methods used for evaluating, testing and controlling the grading and the quality of Quebec chrysotile asbestos fibres with some of the physical and chemical procedures currently used for that purpose. (3) Discussing some of the complications facing the producers, such as variations in the orebody and special requirements of asbestos manufacturers. ( 4) Detailing some of the present quality control methods. SUMMARY OF PAST, PRESENT AND PROBABLE FUTURE TESTING METHODS Past During the first years of production of commercial asbestos in the Province of Quebec, fibre testing and quality control were based principally on dry screen analysis and visual inspection. These methods were gradually expanded during the period from 18, 90 to 1932. In 1932, standardization

Jan 1, 1962

By Adam Jordens

Along with gravity separation and froth flotation, magnetic separation is one of the most common techniques for separating minerals. Minerals are separated by a magnetic force that is dependent on a combination of the applied magnetic field, the magnetic field gradient and the magnetic properties of the minerals themselves. Minerals may be classified as diamagnetic, paramagnetic or ferromagnetic based on the way they interact in a magnetic field. The magnetic susceptibility of a material may be determined by using a vibrating sample magnetometer to determine the magnetic moment of the material in an applied magnetic field and then converting this measured moment into the material?s magnetic susceptibility. In the case of rare earth minerals, magnetic separation is commonly used to remove ferromagnetic iron-bearing gangue minerals and to concentrate paramagnetic valuable minerals such as monazite and xenotime. These magnetic separation steps are frequently preceded by a gravity separation step as many iron oxides and rare earth minerals have specific gravities that are much larger than those of typical gangue minerals. By varying the magnetic field intensity it may be possible to use magnetic separation to selectively separate the paramagnetic and ferromagnetic minerals that report to the concentrate after gravity separation. Test work on a Canadian rare earth ore has shown that a gravity concentration step using a Knelson concentrator was able to selectively concentrate heavy magnetic minerals as evidenced by increased recoveries, relative to the Knelson tailings and fresh feed, after processing through a wet variable intensity magnetic separator. Mass pull to the Knelson concentrate was 4.5 % and the magnetic recovery of this concentrate, at 0.94 T, was approximately 40 % higher than the magnetic recovery from the Knelson tailings (70 % versus 30 %). The products of the wet high intensity magnetic separation were also analysed using a vibrating sample magnetometer to determine the magnetic susceptibilities of the various concentrate and tailings products.

Aug 1, 2013

By A. G. Roach

IT IS generally stated that the gold ores of Nova Scotia are free-milling, and for the most part this is true. However, there is a certain proportion of the gold finely disseminated throughout the sulphides, notably arsenopyrite, and this gold is definitely not recoverable as &apos;free-milling&apos; gold by amalgamation. The proportion of free-milling gold to total gold seems to vary widely in different localities in the Province and is lowest in deposits of the fissure-vein type. The problem of recovery of these relatively recalcitrant values is usually one of economics, in some plac.es a simple gravity concentrate being of such low tenor that its extraction and subsequent disposal will not bear the costs involved. In other cases, such a high percentage of values escapes from the mortars and plates that concentration is definitely indicated. The size of the mining operation is also an important factor. In the large majority of cases, however, some concentrating step is warranted, even if the resulting concentrate is stock-piled until sufficient has accumulated to justify further treatment.

Jan 1, 1940