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By Steve Cole

"The economic and strategic importance of PGE bearing deposits is fuelling renewed exploration and development efforts in the precious metals mining sector.This paper presents a review of the various techniques used in the processing of PGE bearing ores, from primary benificiation to processing routes for the different flowsheets that have been developed amongst current producers. Recent innovations such as preconcentration of ore using gravity separation, recent trends in flotation circuit design and the development of hydrometallurgical routes for the direct treatment of flotation concentrates without the need for smelting will be discussed. Data from recent projects will be presented to illustrate common characteristics of PGE ores and concentrates.INTRODUCTIONThe six platinum-group elements (PGE): ruthenium, rhodium, palladium, osmium, iridium and platinum, together with gold and silver, are considered to be ""precious"" metals. The recent spike in platinum and palladium prices coupled with the projected increase in demand for the metals has fuelled a spate of exploration and new projects in the PGE sector. Historically primary producers of PGE metals have controlled the flow of information relating to the mining and processing of these ores into the public domain. Very little published information relating to individual operations and processes is available in comparison to the abundant literature relating to other metals.The purpose of this paper is to provide a general overview of the issues relating to the processing of PGE ores. Each topic discussed could easily be the topic of a paper or book and so in many cases only the surface of the topic will be scratched. An attempt has therefore been made to provide as many references as possible.This paper discusses the classification and location of PGE ores, the mineralogical factors that affect recovery of PGE's, methods currently used for recovering PGE's and process trends in PGE metallurgy."

Jan 1, 2002

By N. A. Beier, N. Slingerland

"Oil sands tailings impoundments rank among the largest (spatially) in the world, covering a total of approximately 220 km2 of northern Alberta, Canada. A preliminary geomorphic design for an oil sands tailings storage facility (TSF) landform was completed with the goal of eventual closure and delicensing in mind. This paper outlines methods identified during the design process that streamline closure when implemented early in the mine planning and TSF design stages. With most oil sands TSFs currently in active operation (and some still in the planning stages), geotechnical engineers and mine planners have the opportunity to make operational and design decisions, such as those outlined herein, that are likely to improve the geotechnical and environmental performance of the landform post closure. ¦ KEYWORDS Alberta, Athabasca oil sands (AOS), Landform design, Reclamation, Sand dam, Tailings storage facility (TSF) RÉSUMÉ Les bassins d’accumulation des résidus issus des sables bitumineux font partie des plus grands (en termes d’espace) au monde, et couvrent au total environ 220 km2 dans le nord de l’Alberta, au Canada. Une conception géomorphologique préliminaire a été réalisée pour le modelé d’une installa¬tion de stockage des résidus (ISR) issus des sables bitumineux en gardant à l’esprit la fermeture et le retrait de permis à terme. Cet article présente les méthodes identifiées pendant le processus de conception qui simplifient la fermeture lorsqu’elles sont mises en oeuvre dès les premières étapes de planification de la mine et de conception de l’ISR. La plupart des ISR issus des sables bitumineux se trouvent dans des exploitations actives (dont certaines en sont encore aux étapes de planification), aussi les ingénieurs géo¬techniques et les planificateurs miniers ont la possibilité de prendre des décisions en termes d’exploita¬tion et de conception, telles que celles présentées ici, qui pourraient améliorer la performance géotechnique et environnementale de la phase suivant la fermeture du modelé. ¦ MOTS CLÉS Alberta, assainissement, barrage de sable, conception du modelé, installation de stockage des résidus (ISR), sables bitumineux de l’Athabasca (SBA)INTRODUCTION The Athabasca oil sands (AOS) underlie 140,200 km2 of land in northeastern Alberta, Canada. Oil sands located within 100 m of the original surface account for 4,800 km2 of the total area and are considered to be economically mineable (Figure 1; ERCB, 2009). Bitumen, the thick, tar-like substance contained in the AOS, is extracted through open-pit mining and in-situ methods. During mining, the overburden is first removed as waste and the sandy, bitumi¬nous ore (“oil sand”) is transported to processing facilities via conveyor belts and 400 t trucks. Warm and hot water, as well as process aides such as caustic soda, are mixed with the oil sand, creating a slurry from which bitumen is mobilized and extracted. The resulting slurry waste product is called “tailings” and contains mineral solids, process water, and small proportions of unrecovered bitumen (Masliyah, Zhou, Xu, Czarnecki, & Hamza, 2004; Sobkowicz & Morgenstern, 2009)."

Jan 1, 2019

By M. N. Bassim, W. W. Tennese

"Concepts of linear elastic fracture mechanics were applied to study two cases of failure, namely an equalizing beam from a tandem rear axle of a highway tractor unit and the main beam of a flat bed trailer. In the first case, the presence of a crack, initiated by stress corrosion cracking followed by significant fatigue crack propagation produced a state of stress which was sufficient to produce brittle failure. Calculation of the fatigue life agreed with the number of cycles that the structure experienced before final fracture. In the second case, it was demonstrated that a combination of low temperature and high loading rate was sufficient to cause brittle fracture.IntroductionFailure analysis of engineering components has generally been carried out without the benefit of fracture mechanics. It is generally understood that real structures inevitably contain internal or surface flaws which under an applied load, may propagate to fracture. Fracture mechanics relates the applied stresses to the crack size in specified geometries. Since its introduction approximately thirty years ago, fracture mechanics has evolved as a design philosophy which can be used to develop fracture-safe designs. It can be also applied in analysis of failures, to ascertain if sound design and fabrication methods have been used."

Jan 1, 1985

By A. Warczok

Smelting slags contain payable metals in a dissolved form and as mechanically entrained matte or metallic inclusions in the size range from 2 to 1000 µm. Slag cleaning requires reduction of magnetite and metal oxides and sedimentation of inclusions. Slag cleaning in an electric furnace is carried out in batch or semi-continuous mode. The strong trend for continuous slag cleaning generates the basic question about the optimal geometry of the electric furnace. Results of combined CFD, potential distribution and heat transfer modeling allowed for the determination of the fluid flow pattern and the temperature distribution in a classical, circular electric furnace as well as in a rectangular furnace. For the rectangular furnace, various length/width ratios and position of electrodes have been simulated. Analysis of key phenomena pointed out the advantages of the rectangular electric furnace over the circular furnace, particularly for continuous slag cleaning. Phenomena that have been analyzed were mass transfer, the rate of slag reduction, coalescence and settling of inclusions, all on the basis of the calculated slag flow pattern and the temperature distribution.

Jan 1, 2007

By Arthur Grounds

Historical In the course of a paper which is necessarily limited in length, such as the present one, it is obviously impossible to describe in detail the history, development, and present position of coal preparation in Western Europe. Great Britain has been blessed with large deposits of excellent coal of nearly every type, ranging from the high-grade anthracites of South Wales, which are characterised by their very low ash and volatile con-tents, to the superb coking coals of South Wales and Durham -probably the finest in the world -with their low ash and sulphur contents, the latter constituent often well be-low l per cent. Gas coals abound in Lancashire and Yorkshire, while coals from the East Midlands, Northumberland, and Scotland are excellent for steam-raising and other industrial purposes. The excellent quality of these various coals has, in years gone by, ensured ready .sales abroad and it is not surprising, therefore; that methods of coal preparation were largely developed on the Continent in an endeavour to upgrade the inferior fuels found there, so that the prepared product could compete with British coals on the European market.

Jan 1, 1951

By Éric Poulin, Simon Gariépy, Mario Paredes Malca

"While the design of a control strategy depends on the available process knowledge, its implementation depends on the available process information. On-line chemical analyzers are today widely spread in the mineral processing industry. A real-time concentration measurement of chemical components is valuable information that could bring control strategies to whole new levels. However, the use of these measures rarely reaches anything more than process monitoring. The reason is simple: the on-line chemical measurements quality is most of the time insufficient to be directly included in control strategies. The choice is then made to let the critical eye of the engineer or the operator appreciates the measurements before making any decision based on it.Data reconciliation through mass balance is a technique today widely used in the mineral processing industry to increase the accuracy and the reliability of plant data, mainly for accounting and survey analysis purposes. Real-time data reconciliation of on-line measurements appears as a natural coupling of technologies that could bring new process optimization trends. Once overcome the technical difficulties, full valorization of the instrumentation investment could be reached.This paper presents the application of real-time data reconciliation for process control and performance monitoring. It proposes a general approach, discusses challenges and illustrates concepts with industry experiences."

Jan 1, 2006

By Gianni Bartolacci, Patrice Nadeau, Szatvanyi. Gerard, Carl Duchesne, Claude Chrétien

"Combustion is used throughout the mineral processing industry to produce steam in boilers, to dry concentrates in rotary dryers, and to apply heat treatments in pyrometallurgical furnaces. Tight combustion control is very important in latter type of furnace since the combustion conditions directly affect final ore quality. However, achieving tight combustion control is not straightforward since most of the flames encountered in industry are turbulent non-premixed flames, they are affected by several unmeasured disturbances and are often produced by burning several types of fuel simultaneously, some of them coming from other parts of the plant. A novel method is proposed in this paper to improve process and product quality control as well as to optimize the combustion conditions based on digital flame color images. Multivariate Image Analysis and Regression is to used extract the flame color characteristics from images to predict the solids discharge temperature of an industrial rotary kiln. It is shown that this method yield extremely good 10 minutes ahead forecast of the temperature and should lead to a substantial reduction in product quality variability as well as in fuel consumption.INTRODUCTIONFuel-fired furnaces are often used in the mineral processing industry for various purposes, such as for the production of steam (utility boiler), in conjunction with rotary dryers to dry mineral concentrates or in pyrometallurgical processes for induration, roasting, and so forth. These furnaces are necessary in the supply chain from the mine to the metals, but their operating costs are constantly rising due to the fluctuations in fuel prices. Moreover, these processes are now targeted by the Kyoto Protocol since they are energy intensive and they produce significant amounts of CO2 and other pollutants such CO, NOx and SO2. To achieve both a reduction in operating costs (i.e. fuel consumption) and in pollutant emissions while maintaining or improving product quality, one needs to have a very good control of the combustion process."

Jan 1, 2005

By D. Wolfe, R. Cleminson

"The Aurora North mine has been operating for more than ten years, and is the source of over half of Syncrude’s bitumen production. The hydrotransport systems at Aurora experience high rates of wear, and mission lengths on current slurry pumps are nominally 1,500-2,000 hours. Recent work has enabled a better understanding of the significant adverse effect of large particle impingement damage to impeller vane leading edges - which is the known life determining issue for Aurora hydrotransport pumps. A new pump design has been developed and installed at Aurora, incorporating significantly increased impeller diameter and pumping vane lengths. The new pumps are expected to triple Aurora’s previous mission length for hydrotransport pumps. Part II of this paper will share actual hydraulic and wear performance observed in the first several months of operation, and draw comparisons relative to what was expected for these pumps in design / development.INTRODUCTION Slurry Pumps are Critical Equipment at Syncrude Slurry pumps are a key component in Syncrude’s operations. In a typical Aurora application, each 5000 HP pump stage helps move over 8,000 dry tonnes per hour of oil sand, plus an equal volume of process water that has been added to create the slurry. The average impeller life in oil sand hydrotransport service at Aurora has been nominally 1,500 to 2,000 hours, or 12 to 16 million tonnes of oil sand pumped. Generally, the slurry pump application at Aurora has proven very difficult to improve due to the unique combination of high sand abrasivity, 125 mm (5”) large particle top size (lumps), and high flow rate relative to basic pump size; a factor that results in unduly high impeller vane leading edge speeds for the service conditions."

Jan 1, 2014

By I. R. Jonasson, R. W. Boyle

"Current interest in the distribution of mercury in the natural environment comes from quite different, though not unrelated, sources. Mercury has long been an important metal in many industries and has, therefore, been much sought after by mining interests. The presence of mercury traces in the various media of the natural environment, namely soil, rock, air, water and vegetation, is exploited by geochemists not only to find mercury and polymetallic ore deposits, but also to find most other types of economic metal mineralization. More recently, however, mercury has caught the attention of health authorities and environmental scientists who are becoming increasingly concerned over the hazards of mercury wastes and the danger these present to the environment and to man. It is now apparent that the trace quantities of mercury, considered so important and helpful to exploration geologists, can be concentrated in the biosphere to such levels as to present considerable problems for ecologists. This article summarizes most of the available data on mercury contents in materials of geological interest and presents average normal values for rocks, ores, minerals, soils, sediments, waters and plants. The geoch.emical cycle for mercury in nature is presented and the mechanisms of mercury migration around the cycle are discussed."

Jan 1, 1972

By R. Clarkson

"The Yukon's numerous (185) placer gold mines are still a major social and economic force in this developing economy. Gold recovery at each of the various sluiceboxes is not optimized due to extremely difficult sampling logistics and a shortage of technical expertise and industrial research.At each of six operating placer mines, numerous sluicebox tailings samples were collected with hand held sample cutters and combined into large (2-7 cubic yards) duplicate samples. The entire sample volumes were screened and processed on a shaking table to determine gold losses. The existing and potential gold recoveries and recommended sluicebox design and operating parameters are presented.2 ACKNOWLEDGMENTSThe Project Manager gratefully acknowledges the following support for this placer research program:The funding received from the National Research Council's Industrial Research Program, the Canada/Yukon Economic Development Agreement and the Canada Center for Minerals and Energy Technology (CANMET): andThe technical advice provided by Tad Cienski (CANMET), Ron Johnson (KPMA), George Poling (University of B.C.) and Dan Walsh (University of Alaska).3 OBJECTIVESThe objectives of the Gold Recovery Project are to: evaluate gold losses with statistically based sampling programs; determine how to improve gold recovery; assist miners with the recommended technology and make this information available to the entire placer industry."

Jan 1, 1990

By Peter Radziszewski

"Comminition process costs, which typically represent an important contribution to mining operating costs, can themselves be divided roughly between energy and liner /charge wear. As such, developing the ability of predicting mill wear will allow a more accurate estimation of wear costs and therefore their control. In this paper and based on the possibility of estimating energy dissipated in impact and abrasion by using a discrete element charge motion model for mill charge motion simulation, media wear will be investigated principally as a function of three wear mechanisms : impact, abrasion and corrosion. Experimental results will be used to identify a total media wear model. Model results will be compared with real mill data from three operating Australian mines. These preliminary results show for the cases tested that the overall average error, as compared with the observed cases, is 0 % with a standard deviation of 66.1 %. Results from the Bond abrasion index tests, for the same cases investigated, give an overall error of 73 % and a standard deviation of 192.5 %. Further work is in progress to improve test procedure, validity and confidence.INTRODUCTIONComminition process costs, which typically represent an important contribution to mining operating costs, can themselves be divided roughly between energy and line / charge wear. In Greenfield situations where the estimation of operating costs is critical in determining project feasibility, the level of confidence in such estimates becomes quite important. With regards to media wear, the Bond abrasion test currently serves as the standard media wear prediction device. However, as shown [l, 21 test results once compared with actual wear rates can vary greatly. Figure 1 shows test results as compared with 15 cases. Average error over this data is 73 % with a standard deviation of 192.5 %. As such, developing the ability of more accurately predicting mill wear will allow greater confidence in wear cost estimation and therefore their control."

Jan 1, 2001

By M. B. McClenaghan

"Abstract - The Matheson area of northeastern Ontario is of great interest for mineral explo­ ration because of its geological similarities with the adjacent Timmins, Kirkland Lake and Larder Lake gold camps. Exploration in the area, however, is hampered by the presence of an extensive and thick cover of glacial sediments. For this reason, till geochemistry has be­ come an important exploration method. The Ontario Geological Survey&apos;s Black River -Matheson (BRiM) reconnaissance till sampling project, carried out between 1984 and 1988, was designed to aid exploration in the Matheson area by documenting the Quaternary stratigraphy and providing a database of till geochemistry. Till samples were collected by backhoe trenching of surface pits in areas of thin drift ( < 5 m) and by sonic overburden drilling in areas of thicker drift. This paper summarizes the results from the shallow till sampling component of the BRiM project.Two hundred and eighty-two surface samples were collected from Matheson Till, the youngest till sheet in the area, which was deposited during the Late Wisconsinan. For each sample, the non-magnetic heavy mineral (>3.3 S.G.) and fine (-250 mesh) till fractions were analyzed geochemically. In addition, visible gold grains were recovered by panning the heavy mineral fraction. Five areas that display multi-element anomalies in both till fractions warrant further investigation: (1) western Egan Township, overlying the Bradley Lake Syenite; (2) around and south of the Munro and Croesus mines, in Munro and Guibord townships; (3) central Garrison Township overlying the Garrison Stock; (4) south of Ore Car Lake in northern Thackeray Township; and (5) southeastern Harker Township. In these areas, Matheson Till has a local provenance and the bedrock sources for these anomalies are nearby in the up-ice (north­ northwest) direction. Due to the fine-grained nature of gold in bedrock deposits in the BRiM area, the small size of most gold grains recovered from till samples (<50 1-1m) and the variable distribution of gold in the heavy mineral concentrate and fine fractions, the fine fraction in addition to the more commonly used heavy mineral concentrate should be used for gold exploration.Surface till samples have been affected by weathering to a depth of s3 m. Weathered till is characterized by a very low carbonate content in the matrix fraction, the absence of sulfide grains in the heavy mineral concentrate and higher concentrations of copper, nickel and zinc in the fine fraction than in the heavy mineral concentrate. As a result of the weathered/ oxidized nature of the surface till samples, the fine fraction is a better sampling medium for base metal exploration."

Jan 1, 1992

By C. Tan, A. Putz, P. Lacombe, R. Kemp, M. Kaya, B. J. Huls, A. R. Laplante

"This paper concentrates on the four recent plant trials/ applications of froth washing. Results showed that improved metallurgical performance can be achieved with wash water. Increased froth cleaning yielded better upgrading, and some cases slightly improved recovery. Froth sampling and salt tracer tests supported the findings of froth washing tests.At Falconbridge, Ni grade increased from l.47% to 2.15% and recovery from 85% to 87%. At Eastmaque, final Au grade increased from 2.3 to 2.7 oz/st at a slightly higher recovery. At Les Mines Selbaie, Cu grade increased from 24.5% to 25.S% and Zn grade from 54.5% to 56.l%. At Zinc Corp. of America, average Zn grade increased from 55% to 56. 8% at the same recovery for a 45-day period. A number of plants in Canada and the United States have evaluated and/or now practicing froth washing. Wash water has now proved itself in some plants over several months of operation.INTRODUCTIONFroth washing in mechanical flotation cells offers a number of metallurgical (i. e. increased grades and/or recoveries) and economical (i.e. decreased transportation and smelting & refining costs) benefits. Fundamental development work in laboratory and pilot scales performed at McGill yielded encouraging results. (Kaya and Laplante, 1988a and 1989a). Since laboratory and pilot flotation performance can differ from full-scale due to differences in hydrodynamics, kinetics, and froth characteristics (e.g. stability, loading etc.), plant trials were essential to prove the viability of this technology."

Jan 1, 1990

By J. Don Scott

Analytical predictions of the rate and magnitude of settlement of deposited oil sands tailings slurries generally overestimate how fast pore pressures will dissipate. Field deposits of nonsegregating tailings to mature fine tailings show continued high pore pressures near the surface which impede surface reclamation. In geotechnical analyses which predict the consolidation behavior of soft soils a finite strain theory is used. Effective stress-void ratio and void ratio-hydraulic conductivity relationships determined from laboratory large strain consolidation tests, are used in the finite strain predictions. This theory, however, cannot predict the full range of sedimentation, consolidation and pore pressure dissipation which occurs in large scale deposits of thixotropic tailings slurries. A new large strain consolidation model which assumes that the creep rate of the slurry exceeds the pore pressure dissipation rate is being investigated. This model is relevant for rapidly deposited, low permeability thixotropic slurries where the upwards drainage path increases by several meters a year, such as, in oil sand fine tailings ponds and nonsegregating tailings deposits. The model will be verified by analyzing the 10m high column of fine tailings at the University of Alberta which has been monitored for over 20 years and in which the excess pore pressures are still very high.

May 1, 2004

By Y. X. Zhao

This paper briefly describes the characteristics and induced factors of coal mining bumps based on the investigation of recent bumps accidents occurred in China. According to the theory of non-equilibrium thermodynamic and dissipate structure, the process of strain energy accumulation and dissipation in the ?Coal-Surrounding Rock? system (CSRS) is discussed during the preparation of coal bumps. In addition, a series of experiments are conducted to analyze the relationship between bump-prone property and micro-structural characteristics of coal. The process of coal bumps induced by propagation of fractures and deterioration of coal mass properties are also analyzed systematically.

May 1, 2009

By P. J. Le Roux

"Mining worldwide and definitely in South Africa, is constantly under pressure to reduce its cost structure so as to sustain profitability. In underground gold mines where an open stope mining method is employed, dilution often has a significant effect on the viability of sustaining profits. Target Mine practices Open Stope mining Method and it was found that in some open stopes dilution was in excess of 10%, which has a significant impact on the sustainability of the mine.Dilution in excess of 10% can result in the reduction of the recovered grade from 5,5 to 4,5 grams per ton (g/t). The reduction of 1 g/t in recovered grade results in a potential loss of about ZAR21 Million per month bases on a gold price of ZAR240 000 per kilogram. Based on Life of Mine projections the potential loss of income could be as much as ZAR3,3 Billion. A reduction in dilution would have the opposite effect. There are a number of factors which affect dilution of which falls of ground in open stopes is a major contributor. The falls of ground can be attributed to a number of factors such as beam failure as a result of a larger than normal expected roof area (hydraulic radius too large), poor ground conditions, and poor blasting. The cost of damage to or loss of trackless equipment as a direct result of the falls of ground in open stopes, is very significant. The review of financial figures has indicated that this could be as high as ZAR491 million. This combined with the added cost of transport, hoisting, secondary blasting, milling and plant treatment costs of ZAR293 results in an estimated opportunity loss of ZAR784 million.Currently there is a significant amount of data available in the mining industry which could be effectively used to develop suitable back analysis techniques but to date this has not been used effectively. If dilution can have such an impact on current and future mining ventures then the optimization of back analyses for the prediction of dilution in open stoping could assist significantly in the reduction of dilution in massive open stopes. Rockmass classifications, geotechnical information, blast techniques, blast design, the stress strain environment and hydraulic radius all have an effect on, or play a role in the evaluation of dilution. Each of these factors will be taken into consideration to ultimately determine a measurable or calculated percentage of dilution in massive open stopes.The amount of overbreak in an open stope can be determined by subtracting the planned stope volume in m3 from the actual measured final stope volume in m3, which is obtained from the CMS (cavity monitoring system). This is in turn divided by the planned stope volume in m3 to determine the percentage overbreak. The CMS wireframe is imported into the geological model and its grade re-evaluated. From this the actual percentage dilution for this open stope can be determined. The dilution obtained can result in a major reduction of recovered grade for the open stope, but can also increase the recovered grade. The latter is normally the exception rather than the rule.When analysing data from Target mine the following was achieved:• Using 11 years of data a method of measuring and predicting the percentage dilution in open stoping was developed. This took into account rock mass quality, stress-strain state, and the hangingwall hydraulic radius (size of stope hangingwall exposed).• Implementation of this prediction method resulted in a reduction in falls of ground in open stopes. The benefit of this was a reduction in the damage to mechanised equipment resulting from less falls of ground which had a positive effect on the profit margins of the mine. As a direct result the recovered grade from the open stopes increased due to the reduction in the amount of dilution.• A design criterion, Dilution Stress-Strain Index (DSSI), was developed which allows the user to calculate, with certainty, the stability of the open stope and determine if m"

Jan 1, 2015

By D. A. Riva

"The Line Creek Project is located in southeastern British Columbia, approximately 25 kilometres north of Sparwood. The design is to produce a total of2.7 million tonnes of coal annually. This is made up of1.4million tonnes of thermal coal and 1.3 million tonnes of metallurgical coal.Construction commenced in the spring of 1980 and mining operations began in July 1981. The thermal processing plant, maintenance and dry facilities, as well as extensive road and bridge construction, were completed in early 1982. A collective agreement was signed with the International Union of Operating Engineers, Local 115, in June 1981.The first unit train left Line Creek on February 18, 1982 with a load of thermal coal bound for the Ssangyong Corporation in Southern Korea. It was the start of a ten-year contract to supply 350,000 tonnes annually to fire their cement kilns. Additional contracts for 750,000 tonnes will fuel the boilers of Korea Electric Company&apos;s San Chon Po and Go-Jeong power stations. Metallurgical coal shipments are scheduled to leave the Roberts Bank port in Vancouver in April 1983.Tracking an introductory presentation given at the 1981 CIM Annual General Meeting in Calgary, this paper highlights the salient developments by which ""The Line Creek Project"" has progressed during the past year to the"" Line Creek Operation"". Line Creek has com e on stream as scheduled and will meet all contractual commitments pertaining to timing, volumes and quality for thermal coal. The first train load left the plant in mid-February, and the first boat load to Korea departed Roberts Bank in mid-April. Metallurgical coal deliveries will commence in April 1983."

Jan 1, 1982

By Ross I. Kelly

Carbonate rocks are widespread throughout Ontario and provide raw material for more uses than perhaps any other rock type. The principal carbonate rocks that are used by industry in Ontario are Paleozoic era limestone and dolostone. Limestone is a sedimentary rock that is composed mainly of the mineral calcite (CaCO,) while dolostone, also a sedimentary rock, is composed mostly of dolomite [CaMg (CO,),l. The majority of the province's limestone and dolostone extraction occurs from Paleozoic era rocks located in southern Ontario. Calcite and dolomite are also found in Precambrian marbles, calcite veins and carbonatites, however, utilization of these rocks by industry has been less common. Calcite and dolomite-rich rocks are utilized for a wide variety of uses including raw materials for cement and lime manufacture, chemical and metallurgical stone, fillers and construction aggregates (Derry, Michener, Booth and Wahl and OGS 1989a). For some uses chemical and physical requirements are very important. In the manufacture of glass, for instance, the chemical requirements of source materials are very important and very stringent. In other uses physical criteria such as whiteness may be more important. Although carbonate rocks are quite plentiful within the province, deposits that contain high concentrations of calcite or dolomite are somewhat limited. For that reason, this paper focuses on deposits that are known to, or may contain, a high percentage of calcite and/or dolomite. The paper emphasizes potential sedimentary limestone and dolostone resources, as these are the carbonate rocks most commonly utilized by industry in Ontario.

Jan 1, 2001

By J. C. Thornley

Service failures of seemingly conventional galvanized bolts, in normal operation, on transmission towers in New Brunswick have been found to be the result of hydrogen cracking. In both these cases, similar failures elsewhere can be avoided by suitable clauses in the purchase specifications. In the first case described, the manufacturing procedure was responsible for strengthening and embrittling a standard, soft, constructional steel. In this case, a fracture mechanics analysis predicted critical crack depths for final fracture very similar to those found in practice. This case reveals an apparent cooperative connection between hydrogen embrittlement and strain ageing in plain carbon steels. In the second case described, the steel was simply a high strength steel which should not have been made into galvanized bolts.

Jan 1, 1979

By S. Rivard

"This paper demonstrates the selection of grinding circuit technology for a number of recent projects including discussion of the key drivers and the role of energy efficiency. Decreasing head grades combined with a strong and sustained increase in operating costs has forced miners to examine increased project size, increased equipment capacity and efficiency improvements in order to reduce their unit operating costs and improve overall project economics. Comminution energy consumption, safety and capital cost considerations play a critical role in the success of projects. This paper presents some key guidelines for a successful and cost effective comminution circuit design and includes a case study on three projects, outlining the issues and the drivers which led to the ultimate circuit selection and the critical role that energy efficiency played.IntroductionComminution circuits for minerals processing are selected based on their suitability and efficiency in reducing run-of-mine ore to the desired feed size for the downstream process. The input material (ore) properties and downstream process requirements are the key determinants and there are standard approaches for each circumstance.The minerals processing industry has been a fast adaptor of efficiency improvements based on increasing capacity of equipment (e.g. trucks, crushers, mills, pumps) but less successful in adapting radically new technologies that disrupt incumbent flowsheets or processes.The installed power of grinding mills has increased linearly over the past 25 years (Meka & Lane, 2010) and pumps and classification equipment have kept pace. The autogenous grinding (AG) and semi- autogenous grinding (SAG) mills displaced stage crushing as a dominant method of coarse rock breakage in many applications causing crusher manufactures to increase the capacity of cone crushers to meet the competitive demand.Examples of new comminution technology in the 20th and 21st centuries are the development and adoption of cyclone classification in the 1940s (Newtech, 2016), AG milling in the late 1950s, vertical grinding mills in the 1980s, high pressure grinding rolls (HPGRs) also in the 1980s and ultrafine milling technology in the 1990s (Meka & Lane, 2010)."

Jan 1, 2017