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By J. Day, Matthew X. Yao, Lijue Xue

Hardfacing overlays are commonly applied on the shroud Z-section of turbine blades for enhanced wear resistance. Among various processes that are used to apply the hardfacing overlays, the plasma transferred arc (PTA) welding process offers several advantages including lower heat input, less base material dilution, rapid process time, and reduced operating cost associated with the capability to apply materials in the powder form. The development of a robust PTA process is crucial for overlay performance and repeatability, particularly in the aerospace industry where a quality intensive manufacturing environment prevails. For this reason, the Taguchi method of experimental design was selected to develop a test plan. A 4-factor 3-level (L9) orthogonal array (OA) was used in the experiment. The L9 OA allows for a more detailed (3 level) investigation of critical process parameters, namely plasma gas flow rate, traverse speed, powder feed rate, and arc current. Two hardfacing materials, Stellite 694 and Tribaloy T-800, both Co-based wear resistant alloys, were investigated by deposition onto a cast IN738 Ni-based superalloy substrate. Performance measurements of the hardfacing deposits included deposit hardness, substrate hardness, deposit density (porosity), degree of cracking/inclusions, and a quantified visual inspection. The procedure resulted in optimized PTA hardfacing parameters for both Stellite 694 and Tribaloy T-800 on IN738 turbine blade material.

Jan 1, 2004

By A. Gillis

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

Jan 1, 1965

By A. Putz, F. Vincent, A. R. Laplante

"This paper briefly reviews some of the gravity research done at McGill University and current Canadian operating practices, with emphasis on results of interest for operators. The following topics are addressed: security, economics, predicting recovery, circuit optimization, unit selection and final upgrading. Emphasis is placed on the Knelson Concentrator.The topic of security and economics are addressed jointly, in terms of the place of the gravity circuit in the mill flowsheet. Actual plant experience is drawn upon to identify potential problems and actual solutions.Predicting primary recovery is linked with a characterization of the ore, the choice of a circuit, and the fraction of the bleed used. Factors such as feed preparation, preliminary upgrading, fraction of recycle treated, ability to recover fines and location of the bleed are discussed.Final upgrading is achieved almost only by tabling and smelting. This can lead to fine gold recovery problems when more effective units are used upstream. Alternatives are discussed.IntroductionResearch on gold recovery by gravity over the past eight years has associated McGill University with a number of gold producers. This paper attempts to review the information gathered from a practical perspective. Some of the information was generated in McGill University's labs, some gathered at plant site, and some was shared by operators."

Jan 1, 1994

By Gilles Bonin

Structures and serpentinization patterns in the Thetford Mines peridotites are important characteristics indicating the necessary geological conditions which led to the development of chrysotile orebodies in Early Ordovician limes. These structures and serpentinization patterns are reviewed in this paper using the geology of LAB Chrysotile orebodies as a model. Structural aspects include parallel and transverse faults, parallel and transverse granite slabs, and orebodies, some of which trend clearly north-westward parallel to the accretionarymovement. Serpentinization patterns in the peridotite belt, particularly in the harzburgite, include primary pervasive mass serpentinization and secondary complete serpentinization. Listwaenites layers appeared along some faults and along some granite slabs as a result of hydrothermal alteration of the serpentine, following the emplacement of the devonian plutons to the south. These plutons as we/1 as other important lineaments, align with the structural pattern of Thetford Mines ophiolites. It is believed that these plutons are part of a heavy magma tic corridor resembling the Pilote-Mont-Louis corridor in the Gaspe (Doyon and Berger, 1997), and the Buchans' structure in Newfoundland (Hutchinson, 1984), both intersecting the Brompton-Baie Verte line.

Jan 1, 2001

By Pierre Giasson

"Les avantages de l'électricitéLe thème de la réunion 1982 de l'ICM District No. 2: "" Le défi des années 80 pour l'industrie minière de la Côte-Nord"" exprime trè s bien la réalité . En effet, la récession économique qui touche présentement tout le monde industrialisé, frappe de façon particulièrement sévère le marché du fer et de l'acier. Il est donc primordial pour les industries minières de la CôteNord de minimiser leurs coûts de production. Comme on sait, une bonne part des coûts de production est directement reliée à la consommation d'énergie.Si on retourne en arrière de quelques années, les prix des produits pétroliers étaient beaucoup moins élevé s que maintenant . Par exemple: A Philadelphie, en janvier 1930, le prix de l'huile no. 6 (bunker C) était de 1.22$ le baril. En 1940, le prix mondial du pétrole brut se situait aux environs de 1.80$ le baril et augmentait très lentement jusqu'en 1973. A la mi-octobre 1973, l'organisation des pays exportateurs de pétrole (O.P.E.P.) surprend le reste du monde en annonçant que le prix du brut grimpe à S.12$ le baril. .. on connaît la suite.On sait qu'au point de vue énergétique, le nord du Québec est l'une des régions les plus avantagées au monde. Malgré le fait que notre climat soit plutôt défavorable, nous sommes assurés d'une alimentation électrique à toute fin pratique éternelle, contrairement aux autres régions du globe. En effet, l' hydro-électricité ne représente que 2.S070 de toute l'électricité produite dans le monde.Une bonne partie de l'énergie consommée dans les industries minières de la Côte-Nord est utilisée pour produire la vapeur. Or, il y a plusieurs avantages à produire de la vapeur à partir de l'électricité:1. Le prix d'achat d'une chaudière électrique peut être moins de la moitié de celui d'une chaudière à carburant fo ssile.2. Le prix de l'électricité est plus bas que celu i des autres sources d'énergie disponibles dans notre région.3. Hydro-Québec offre un programme spéci al de subventions et un prix garanti de l'électricité, inférieur de 10070 à celui de tout autre combustible (1982).4. Souvent il est possible d'utiliser l'énergie hors pointe à un coût minime.S. L'espace requis pour un chaudière électrique est beaucoup moindre. Par exemple: une chaudière d'une capacité de 120000 Ibs/hre ne demande que SO pi? de plancher, c'est-à-dire un cercle de 8 pieds de diamètre comparativement à environ 600 à 700 pi2 pour une chaudière au ma zout.6. Aucun espace n'est requis pour l'entreposage du carburant.7. Aucun espace n'est requis pour la cheminée.8. Il n' y a que très peu de pièce s mécaniques, donc ces chaudières demandent très peu d 'entretien .9. Les chaudières électriques ne génèrent aucune pollution, donc on n'a pas besoin d'équipement coûteux de contrôle de la pollution.10. Ces chaudières sont extrêmement rapides. En effet, on peut passer de zéro à la production maximum en moins d'une heure si la chaudière est froide et en quelques secondes seulement si la chaudière est à sa température d'opération.11. L'efficacité de ces appareils est au moins de 9S% par rapport à 80-8S% pour les chaudières au ma zout. De plus, cette efficacité demeure la même quel que soit le niveau de production de la chaudière. Il faut faire attention ici: les manufacturiers proposent des rendements de 99% et plus, mais ceci ne tient compte que des pertes de chaleur à travers l'enveloppe, et de l'énergie nécessaire au fonctionnement de la pompe de circulation. Il faut ajouter à cela l'énergie perdue à cause de la vidange qui varie selon le type de chaudière et selon la qualité de l'eau d'alimentation.12. Ajoutons simplement que ces appareils sont très facile à opérer du fait qu'il n'y a aucun système complexe à manipuler.Cependant, il y a un inconvénient non négligeable à utiliser l'électricité comme source d'énergie: comme on ne peut pas emmagasiner l'énergie électrique, nous sommes à la merci du fournisseur."

Jan 1, 1985

By M. R. Henzinger, W. Schubert

"The quality of the backfill applied at a shield driven tunnel is of significant importance failure of the lining. The used material also affects the interplay between support and excavation behaviour.In this research the state of the actual bedding situation is investigated by an analytical approach, laboratory tests and numerical simulations. The numerical simulation using continuum methods have shown shortcomings. These shortcomings regarding the instability of large strain simulations restrict the possibility to reproduce the relocation of the backfilling material. The performed scaled model tests have shown that the regripping process of a double shielded tunnel boring machine affects the soil failure within the gap. With the analytical results the influence of the wall friction can be predicted. Therefore the angle of the failure surface can be determined. The results have shown that the wall friction significantly increases the failure angle. INTRODUCTIONFor tunnel boring machines (TBM) with single (SM) or double (DSM) shield, precast liningsegments are used as rock support. These segmental linings are installed within the protection of the TBM shield. In order to reduce the friction while advancing, the shield diameter is smaller than the diameter of the cutter head and therefore also smaller than the excavation boundary. The difference depends on the expected radial convergences. Since the lining segments are mounted within the shield the steering gap between the shield and the excavation boundary increases and is hereinafter called annular gap.In the process of tunneling in hard rock, the annular gap is usually filled with fine grained and closely graded gravel, termed as pea gravel. The backfilling process starts as soon as possible after the shield tail passes the lining. Due to the operational procedure within the working area of a TBM, a fully backfilled annular gap might not be established after every ring closure. This leads to an unfavorable distribution of the pea gravel leaving the segmental lining partially without bedding. Segmental linings can develop sufficient resistance only when properly bedded."

Jan 1, 2015

By L Gill

The four basic types of electric motors -squirrel-cage, wound rotor, synchronous and D.C. -are de-scribed, with particular reference to speed-torque characteristics. The three classifications of squirrel-cage motors, C.E.M.A. B, C and D, are compared, and methods of selection for specific drives are outlined. Wound rotor and synchronous motors are covered from the viewpoint of construction details, methods of operation and control required. The application of these motors to crushers, conveyors and ball mills is described and reasons for their selection are given. The application of D.C. motors to haulage equipment and mine hoist drives is included, and the basic principles of a variable voltage drive are illustrated. Efforts have been made through-out to provide specific examples of motor selection, with particular reference to the mining industry. THIS paper will attempt to answer the question -"which motor should be used for a specific drive?" Although it is impossible to cover the complete subject of electric motor application here, we hope to give some idea of the types of motors available and why certain types are used on specific applications.

Jan 1, 1963

By Michael Loken, April Montera

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

Jan 1, 2016

By Ning Yu

There are about 1.341 trillion tons (t) of proven coal reserves in China, of which 279.58 billion t are available for mine well construction basis. Thick coal seams are 44% of the reserves. The production of thick coal seams exploitation is over 45% of the total coal production. Full-seam mining and fully-mechanized mining for large mining height is the technology development direction of thick and extra thick seam mining. It is also the important way to achieve efficient and intensive mining with the characteristics of high production, high mechanization, high efficiency and low energy consumption, etc. Complete set of technology and equipment of fully-mechanized top caving for large mining height of full-seam (7m) mining and extra thick seam ( 14-20m) has been gradually mature and for demonstration application by the joint research of government, enterprises, universities, scientific research organizations and users. It has solved some technical problems of coal face for large mining height (over 7m) such as the coal wall spalling control, stability of support, wall rock coupling, cooperation work of mining and caving, full roadway support for super large section, end support, equipment matching of coal shearers, hydraulic support and scraper conveyor. It has developed key equipments including powerful hydraulic support of fully-mechanized mining and fully-mechanized top caving for large mining height, electrically-driven coal shearer with high speed and reliability, scraper and belt conveyer with big capacity, soft-start and high reliability, automatic control system of coal face with the core of electric-hydraulic control, bolting drill boom large section coal roadway shearer, heavy auxiliary transport equipment. The operation rates of fully-mechanized top caving equipment for full-seam and large mining height are 94% and 92.1%, and recovery ratios are 93.6% and 88.9% respectively. The annual raw coal production of single work face is over 10 Mt. The automation and intelligentization level have been clearly improved. The exploitation of thick and extra thick coal seam that is safe and efficient has been achieved in China.

Aug 1, 2013

By J. C. Li, Y. Zou, L. He

"The effect of rock joints is significant in characterizing dynamic behaviors of discontinuous rock masses. To reveal the relation between the transmission coefficient and the contact situation of the joint surface, an experimental study on stress wave propagation across an artificial rock joint was carried out using a modified Split Hopkinson Pressure Bar (SHPB) apparatus. All the bars and specimens were norite cored from the same site, and one surface of the specimen which contacted to the transmitted bar was sawn with a number of notches to simulate the artificial rough joint. According to a wave separation method, two strain gauges were mounted on each pressure bar at a specific spacing, then the incident, reflected and transmitted waves across the joints were obtained from the test data. It was found that the contact situation of the rock joint surface makes a different on the wave propagation. Finally comparisons of the transmission coefficients with different contact area ratios and different joint thicknesses were made respectively. The results show the effects of contact area ratio and thickness of joints on wave transmission.INTRODUCTIONJoints affect the dynamic mechanical behaviors of the rock masses significantly. When propagates across the rock masses, wave usually attenuates in amplitude and frequency due to the presence of the joint as a discontinuous interface in the rock masses. Rock joints are the main factor that affects the behaviors and properties of rock masses. Many researchers have focused on the mechanical properties of rock joints under quasi-static conditions. Nowadays, the effect of joint dynamic properties on wave propagation across rock masses is gradually taken into account in theoretical and numerical studies.The effective contact area, joint roughness, and properties of the asperities and filling materials have been found to influence the normal stiffness of joints (Bandis et al. 1983). As suggested by the International Society for Rock Mechanics (ISRM), the roughness of the discontinuities can be generally characterized by large-scale “waviness” and small-scale “unevenness” (Brown 1981). Many researchers focused on the roughness of rock joints that affects the mechanical properties of rock masses and wave propagation. For example, Brown and Scholz (1985, 1986) presented theoretically and verified experimentally a closure model of contact between two random nominally flat elastic surfaces, which showed that the joint closure property depended both on the surface topography and material properties. Pyrak-Nolte et al. (1997) presented the quantitative aperture data for three-dimensional interconnected fracture networks, which were imbedded in intact opaque rock samples several centimeters in length, using x-ray computerized tomographic (CT) imaging. Fardin et al. (2001) systematically investigated the effect of scale on the surface roughness of rock joints and concluded that samples should be equal to or larger than the stationary limit for surface roughness to be accurately characterized on a laboratory scale or in the field. Zhao et al. (2006) conducted excellent ultrasonic tests across intact cement mortar specimens, singlefracture specimens, and two-fracture specimens."

Jan 1, 2015

By J. Satur

In copper mineral processing, pyrite coexisting with copper sulfide minerals like chalcopyrite is separated by flotation as tailings and its oxidation in tailing dams causes the formation of acid mine drainage. This paper proposes carriermicroencapsulation (CME) as a new method for suppressing pyrite flotability, as well as its oxidation. In this method, an organic carrier combined with Ti is used to form a thin Ti02 layer on pyrite, which gives a hydrophilic property and acts as a protective coating against oxidation. To form the coating, a ground pyrite sample was treated with Ti-catechol complex solution under various conditions. Bubble pick-up experiments and flotation experiments showed that the treatment of pyrite with Ticatechol complex changed the hydrophobic nature of pyrite into hydrophilic even in the presence of xanthate as a flotation collector. Oxidation testing of the CME-treated pyrite by 0.02 kmol m-3 HN03 showed that Fe release was suppressed by the CME treatment with respect to the control. This is assumed to be due to the formation of Ti02 coating on the pyrite surface. The effect of CME treatment on chalcopyrite wettability is also discussed.

Jan 1, 2007

By M. A. Vos

"Cretaceous sands and clays underlie an area of approximately 5,000 km2 in Northern Ontario, southwest of James Bay. The deltaic deposits occur as a wedge of continental sediments to the north of an east-trending fault scarp referred to as the Precambrian Escarpment. They rest on older sedimentary formations of the Moose River Basin (Jurassic, Devonian) and are covered by glacial tills and marine sediments of the Quaternary period. Outcrops are restricted to occasional exposure in the deeply incised riverbeds.In 1975 and 1978, drill programs sponsored by the Ontario Government provided new information on the extent and quality of the deposits. Fourteen holes at approximately 12-km intervals were drilled to a maximum depth of 189 m by reversed- circulation chip drill methods. Some core was obtained as well. Analytical results show that the thickness of Cretaceous deposits exceeds 100m in several instances. Abundant kaolinitic clay and quartz sand of glass-grade quality, both unique materials in Ontario, are available in an area where hydroelectricity and lignite resources combine to enhance the energy outlook.IntroductionThe presence of refractory clay in deeply incised riverbeds in Northern Ontario was known to geologists travelling the rivers as early as 1875. Robert Bell (1877) reports outcrops of clay and lignite on Coal Brook, a tributary of the Missinaibi River. E.B. Borron in 1880 collected a sample of clay from the bed of the Missinaibi River which H.H. Croft of the University of Toronto considered to be ""nearly if not quite, equal to the Cornish clay used in the manufacture of English porcelain"" (Keele, 1920, p. 42). The Cretaceous age of the clay, sand and lignite deposits was determined with the help of plant remains collected by Keele. He referred to the deposits as the Mattagami series, which later became the Mattagami Formation."

Jan 1, 1982

By H. Lachmund, R. Bruckhaus

At Dillinger Hüttenwerke/Germany steel production of grades for linepipe applications especially for sour service has a long tradition. The BOF process after replacement of the vessels is optimized by a newly developed lime addition model and variations in lance tip geometry. Equipped with three state-of-the-art VOD tank degassers metallurgical requirements of lowest contents of e. g. sulphur, nitrogen and hydrogen can be achieved. Three continuous casting machines of vertical bending type with solid core even improve already high levels of cleanliness. The vertical part corresponds to the metallurgical length of 12 to 15 m and therefore assures a maximum of cleanliness after solidification before bending. Slab thickness up to 400 mm can be produced with model controlled dynamic soft reduction. The accurate alignments of the casters assure minimized segregation and microporosity. Surface and internal cracks can be avoided by special cooling, bending and straightening strategies.

Jan 1, 2005

"The Society for Mining, Metallurgy, and Exploration (SME) Inc. developed a guide of minimum standards for reporting exploration results, mineral resources, and mineral reserves for the purpose of informing the general public. The SME Guide has been adopted by the Society.History1. In 1988, at the request of members of the Society for Mining, Metallurgy, and Exploration (SME), Inc., the President of SME formed Working Party #79, Ore Reserve Definition, with the mission to develop guidelines for the public reporting of exploration results, resources, and reserves. A Subcommittee was appointed by the Working Party to draft these guidelines and submit recommendations to SME. The Subcommittee's recommendations were published by SME in the April 1991 issue of ""Mining Engineering"", and as a document entitled ""A Guide for Reporting Exploration Information, Resources, and Reserves"" (the SME Guide) in January 1992. Work continued on an ad-hoc basis until 1996, when Working Party #79 was renamed the SME Resources and Reserves Committee and became a standing committee.In 1994, the Council of Mining and Metallurgical Institutions (CMMI) started a concerted international effort to create a set of international definitions for reporting mineral resources and mineral reserves. An ad-hoc International Definitions Group was formed, with representatives from mining and metallurgical institutions from the United States (SME), Australia (AusIMM), Canada (CIM), the United Kingdom (IMM) and South Africa (SAIMM). A major breakthrough came on October 18, 1997 when the CMMI International Definitions Group met in Denver, Colorado and reached a provisional agreement (the Denver Accord) on definitions of mineral resources and mineral reserves. Concurrently, and since 1992, the United Nations Economic Commission for Europe (UN-ECE) was developing an international framework classification for mineral resources and mineral reserves. Starting in October 1998, joint meetings were held in Geneva between the CMMI International Definitions Group and the UN-ECE Task Force, resulting in agreement to incorporate the CMMI definitions into the UN framework classification."

Jan 1, 2003

By D. MOORE, A. REINSBAKKEN, A. J. Sinclair

The Gypo quartz vein lies near Oliver, British Columbia, and was quarried between 1955 and 1968 for decorative chips. The vein is one of many quartz veins hosted by the Late Jurassic Oliver Plutonic Complex, specifically by the porphyritic quartz monzonite phase of the pluton. The vein has a known length of 155m and a thickness of 46m. It strikes east-west and dips at 60 degrees to the south. Mineralogy is predominantly quartz with minor pyrite, muscovite, fluorite, calcite, apatite and manganese; trace amounts of chalcopyrite, pyrrh otite, marcasite and molybdenite also are present. Quartz in the vein is zoned. A thin grey quartz zone found near the margins of the vein fades gradually into white quartz, which comprises over 95% of the vein. Late-stage boxworks cut earlier mineralization, particularly fluorite, which occurs as pods in a zone fairly close to the hanging wall. Sulphide minerals are found in a centrally located zone in the quartz vein. The hanging wall of the Gypo veins is altered only slightly, but thefootwall is altered extensively to a greisen of muscovite and grey quartz. Evidence suggests that early in rhe vein development, the adjoining country rock was feldspathized. As grey quartz and muscovite was deposited, a period of intensive greisenization and fracturing occurred which so weakened the rock that a central block of greisenized country rock foundered. This provided the open space in which the vein was deposited.

Jan 1, 1984

By Friedrich Benthaus

"The natural and man-made realities on either side of the Atlantic are different. Therefore, a large part of the other side' s knowledge and experience cannot be transferred easily. In the following, the author will attempt to describe some of those developments in the German hard coal industry which may be of particular interest to readers on this side of the Atlantic.The area of the Federal Republic is quite small, especially if compared with a country as large as Canada. On a territory the size of the maritime provinces of New Brunswick and Nova Scotia, Germany holds coal reserves roughly corresponding to the total Canadian reserves. More than 20 billion tons of hard coal down to a depth of 1500 m, and more than 30 billion ton s of brown coal of lignite are technically and economically extractable acording to current technology.However, not only are Germany's coal resources more concentrated; the country is also densely populated, and there are dense networks of railroads and highways All components of the so-called infra-structure are available everywhere, be it electricity, any machinery or personnel. Public opinion is likely in favour of an increased utilization of coal.The coal industry is well developed through a long evolution covering centuries. As a consequence, there is an effective and intensive cooperation of numerous bodies and institutions concerned with coal mining, from government agencies including the inspectorate to suppliers, trade union s, producing companies, to jointly operated management and research organizations. In the Federal Republic, hard coal is mined in deep mines only, and lignite in general, only from open-cast pits. There is a complete organizational and geographic separation of hard and brown coal in Germany. Because the Federal Republic holds only insignificant mineral oil and very little natural gas deposits, coal is essentially the only and consequently the most valuable source of energy."

Jan 1, 1984

The paper will cover the basic reasons for alkaline leaching, a brief description of the circuit and the reasons for the flowsheet used. Changes made to the flowsheet, including the use of mechanical agitation of pachuca slurry, the use of oxygen and its effect on extraction, the use of lime and its effect on process economy, and the environment, will be described. A brief description of a unique semi-autogenous mill and future circuit changes will be included.

Jan 1, 1979

By J. Cui, Z. Meng, W. Zhao

"The decomposition of rare earth concentrates containing bastnasite and monazite by alkali solutions has been investigated. A slurry of the rare earth concentrate and the alkali solutions was calcined at different temperatures. The impacts of calcination temperature on the decomposition of rare earth minerals, the oxidation of cerium, the deportment of fluorine and phosphorous, and the adaptability of the method to the different grades of rare earth concentrate were all studied. A possible technique for comprehensive recovery is proposed in which the chemical elements such as rare earth, fluorine, phosphorus, calcium, iron and thorium could be recycled or recovered. INTRODUCTIONThe liquid alkali decomposition method is an important technique for the decomposition of mixed rare earth concentrates. The technique is relatively clean compared with the sulfuric acid roasting method. However, its operation is intermittent rather than continuous. The two-step solid-liquid reaction and the subsequent water washing make it not very suitable for mass production and application. An important reason for the disadvantage is that an additional process of ""calcium removal by acid leaching"" is needed for the technique. The content of calcium in Baotou rare earth concentrates is usually 6-12%. The requirement of the current technique is that the content of calcium should be reduced to about 0.2% after the calcium removal process. Otherwise, the decomposition and leaching of rare earth will be affected. Therefore, calcium removal by acid leaching is a necessity before the alkali decomposition process is carried out. Research on different alkali decomposition techniques has been conducted with prior calcium removal by acid leaching (Xu, 1995; Yu, 1993; Han, Li, Chang, Liu & Xu, 1985). There have been some investigations of direct decomposition of the bastnasite (Feng, Pan & Li, 1998; Zhao, Zhang, Yang & Liu, 2002)and monazite (Sun, Li, Li, Su, Zhao & Liu, 1998; Zhou, 2005) by alkali-liquid, however, all studies were carried out in solid-liquid reaction system, and continuous calcination studies have not been reported.This paper investigates the process of direct decomposition of Baotou rare earth concentrates by continuous calcination with concentrated alkali. Using the rotary tubular electric furnace, the mixture of rare earth concentrate and concentrated alkali solution were decomposed continuously. Satisfactory decomposition results were achieved. A method for clean processing and comprehensive resource recovery from Baotou rare earth concentrates is proposed."

Jan 1, 2012

By M. C. Bluteau, G. P. Demopoulos

Arsenic reports in the effluents of many non-ferrous metallurgical operations. The production of scorodite, a crystalline ferric arsenate, is considered as an attractive option for the fixation of arsenic from aqueous effluents. However, scorodite solubility and long-term stability in the pH region of interest for tailings disposal have not been thoroughly investigated. In this study the long-term stability of scorodite in the pH 5 to 9 region and the mechanism of scorodite dissolution were studied. Construction of eh-pH diagrams indicated that scorodite stability is highly dependant on the nature (stability) of co-existing iron-hydroxide/oxyhydroxide. It was also found that when scorodite dissolves, a ferrihydrite phase having very small particles size (nano-scale) forms and that the growth and crystallization of this material are delayed by the presence of arsenate even under accelerated (75°C) ageing conditions. Around neutral pH and ambiant temperature (22°C) scorodite seems to reach an equilibrium with ferrihydrite after 48 weeks yielding soluble arsenic concentrations < 5 ppm.

Jan 1, 2004

By H. C. Cooke

This paper will discuss two comparatively unrelated subjects; first, a general review of the advances made at the more important properties in the last year; and second, a statement of the conditions controlling the deposition of the copper ores in the Rouyn area, as determined by last summer&apos;s field work. FIRST PART Development has been very rapid since I stood before the Institute one year ago to discuss this same subject. Then, there were many properties on which gold had been discovered, any of which might develop into a mine. Further work has eliminated the most of them as possible mines, or at least has shown that before they can attain that status further discoveries must be made on them. Then, all gold veins held forth much the same promise; now the indications are that one particular type of gold vein is of greater prospective value than others. Then, all eyes were turned toward gold as the metal of prime economic importance; now copper has taken the centre of the stage, and gold is distinctly in the background.

Jan 1, 1926