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By Yannis Faitakis, Simon Bergeron

"This paper describes the implementation of model-based predictive control (MPC) on a vacuum heat exchange network at Alcan's Jonquière Complex. The plant produces alumina from bauxite ore using the Bayer Process.The MPC system was commissioned in 2000, by Alcan personnel and an Advanced Control Engineer from Matrikon. The application has achieved an uptime of about 97%.The benefits were:• Energy savings : 0.5% - live steam reduction• Reduced variation: standard deviation of key temperatures reduced by 50%• Plant throughput increase: via the automated use of surge tanks• Decreased supervision time: by plant operations• Faster and easier diagnosis of problems and plant constraintsThe benefits were higher than expected with a payback time around 12 months.The purpose of the vacuum heat exchange network is to recover energy from a hot stream (pregnant liquor) by transferring it to a cold stream (spent liquor). The system is very tightly coupled, and the main constraints of the multivariable control system are: • to control the many tank levels involved in the process (8 tanks)• to maximize the temperature of the heated streams (spent liquor)• to prevent cooled streams (pregnant liquor) from cooling to below a minimum temperatureThe system includes 9 manipulated, 14 controlled and 2 feedforward variables.The advanced control implementation runs under an expert system environment and provides added flexibility to the overall control strategy."

Jan 1, 2003

By Sandra K. Zacharias

Brass, a deliberate alloy of copper and zinc, has been known since before Roman times. There are two main methods of making brass: (1) Cementation or calamine process - crushed zinc ore (calamine, ZnC03 , or calcined calamine, ZnO), is mixed with charcoal and small pieces of metallic copper and heated to about 900°C in a closed crucible, (2) Alloying - metallic copper and zinc are melted together in a reverberatory furnace. According to most modern authorities (e.g. Smith and Forbes 1955), the calamine process was the only one used in western Europe prior to the 18th century. At that time, the alloying technique began to take over, because metallic zinc was successfully produced on a large scale for the first time. Previously, this had been a problem because zinc vapourizes at 906°C or about the same temperature at which it can be reduced from its ore. Thus, some means had to be devised to collect and condense the zinc vapour (Tylecote 1976). Metallic zinc was known, however, earlier than the 18th century A.O. Several early finds have been made, including a rolled sheet of metallic zinc found in excavations at the Athens Agora dating to the 3rd to 2nd century B. C. (Farnsworth et al. 1949). The Chinese were producing zinc by at least the 10th century A. D. and, by the 17th century, Chinese zinc ingots were being imported into Europe by the Dutch East India Company (Needham 1974). Metallic zinc is also mentioned in several European documentary sources from the 16th century (e.g. Paracelsus, Agricola). This study traces the changes in Western brass making methods from Classical to Renaissance times by examining documentary and archaeological evidence.

Jan 1, 1999

By Ralph Harris, Xia Qi, Frank Komsic

"Gold cyanidation kinetics which are often limited in commercial operations by the rate of oxygen dissolution from gas bubbles into the slurry, are discussed. Emerging technologies for improving the rate of oxygen dissolution are compared and the gas efficiency, energy use and operating performance of inverted cones and a device based on a jet diffuser are examined. The effect of solids loading is also reviewed and a relationship between operating parameters and the kilograms oxygen dissolved per kilowatt-hour is presented.Inverted cones are shown to create slurry settling problems at high gas flow rates and surface tension lowering agents are shown not to greatly improve the overall rates of oxygen dissolution.The novel jet diffuser technology operates at a range of gas to liquid ratios that improves its energy use over conventional technology and the performance of a number of designs are discussed.Gas efficiencies as high as 35% were observed with the novel diffusers at 40 cm diffuser immersion and are expected to increase at greater immersions. Energy use of 1.8 kg 02 I kWh were estimated for prototype full size diffusers operating at 100 cm immersion. Energy use of 3.S kg 02 /kWh is conservatively expected at 600 cm immersion.IntroductionGold ExtractionGold that can not be recovered by gravity separation can be recovered by either the Merrill-Crow process or the newer carbon in pulp (CIP) or carbon in leach (CIL) processes 1. Reductions in operating costs and improvements in gold recovery are central mill operating strategies. The present paper examines the potential for improvement that can be achieved in the gold cyanidation step of gold recovery. This paper introduces a number of emerging technologies and provides a basis for comparison of the performance. It shows that the basis for comparison of a particular technology depends on the type of gold extraction circuit employed and the type of reactants employed."

Jan 1, 1996

By James R. Lang

The Xietongmen deposit is located 350 km west of Lhasa, Tibet. It is a new, high-grade porphyry copper-gold discovery and the first deposit to be systematically explored by a western company in southern Tibet. In 2005, Continental Minerals Corporation drilled 21,332 m of core in 63 holes and demonstrated excellent lateral and vertical continuity of high-grade copper-gold mineralization over an area 750 m by up to 350 m in size which remains open in all lateral directions. Drill intersections repeatedly yield grades >1% Cu equivalent (based on gold and copper prices) and include 308.5 m at 0.87% Cu and 1.25 g/T Au (1.60 CuEQ%), and 315.6 metres at 0.61% Cu and 1.11 g/T Au (1.26 CuEQ%). Extensive drilling in 2006 will expand and delineate the deposit, and metallurgical, engineering, environmental and socio-economic evaluations will begin. Xietongmen is hosted by volcanic and intrusive rocks of the Gangdese belt, a magmatic arc active between 120 and 30 Ma along the southern margin of Eurasia. Pervasive alteration is dominated by a well-mineralized K-feldspar and biotite assemblage, and by a more peripheral sericitic assemblage also with strong chalcopyrite. Major vein stages include chalcopyrite-bearing quartz, biotite, magnetite and pyrite-pyrrhotite types.

May 1, 2006

By Michael Harley, E. Guy Charlesworth

"Abstract - Bedding-parallel thrust-hosted gold veins are developed in the Sabie-Pilgrim's Rest goldfield, eastern Transvaal, South Africa. The reefs display a complex history characterized by temporally and spatially overlapping events of similar mineralization and deformation. Recognition of the episodic reactivation of these low angle (5° to 10°) thrust faults implicates high fluid pressures (equalling or exceeding lithostatic pressures). Geochemical constraints limit the amount of fluid-rock interaction and the occurrence of transgressive mineralization within the Archaean granitoid basement suggests that the high pressure fluids originated at depth beneath the Transvaal Basin.Similarities exist between gold deposits of Sabie-Pilgrim's Rest and Telfer, Western Australia as well as Passagem de Mariana, Minas Gerais, Brazil. All deposits are sub-parallel to the enclosing bedding which is shallowly inclined. Furthermore, they are also hosted by contractional deformational structures and are clearly epigenetic in origin."

Jan 1, 1994

By Michel Robert

"In 1974, Copperfields Mining Corporation and Soquem formed a new company, Niobec Inc, to bring the niobium deposit of the St-Honore carbonatite into production.St-Honore is located in the Saguenay area, near the cities of Chicoutimi and Arvida, and about one hundred and forty (140) miles north of Quebec. The discovery of the carbonatite complex was made in the fall of 1967 as a result of an airborne radiometric survey in search of uranium. The detailed exploration of the carbonatite indicated two niobium-bearing formations besides the original discovery of a rare earths zone. During the following years, the niobium formations were defined by diamond drilling and a decline was driven down to obtain adequate samples for metallurgical evaluation. In 1974, after seven hundred (700) bench scale tests, eleven (11) months of pilot plant 2nd a worldwide market research, a joint decision was made to initiate the development of a fifteen hundred (1500) T.P.D. mine and mill, under the management of Teck Corporation. The construction of the facilities were completed in early 1976 both on time and within budget. Niobec is now the only north american and the world second largest producer of Niobium concentrate.The process used at Niobec was developed from the pilot plant programs and later modified by the mill personnel. A simplified flowsheet for this process is shown on the slide. Briefly, run of mine ore is crushed to minus 5/8"" and fed to a rod mill, ball mill, and screens circuit where the ore is ground to 92% passing 65 mesh. The ore is deslimed in two stages of cycloning, and the final cyclone overflow at 85% minus 11 microns goes to waste. The cyclone underflow is conditioned prior to flotation of a carbonate-apatite concentrate. This concentrate is cleaned twice and then pumped to tails. The carbonate rougher and cleaner tails are cycloned in two stages to change the process; water and then sent to the pyrochlore rougher flotation. The rougher concentrate is cleaned five times. This is followed by pyrite flotation to remove sulfur, leaching with hydrochloric acid to remove phosphorus and dyed to less than 0.1% moisture before being sent to packaging."

Jan 1, 1978

By G. Castillo, G. Thies, C. Bissue

"Newmont’s Phoenix mine began gold production in 2006 and has since experienced difficulties in reaching design throughput due to variability in ore hardness. In 2010, a debottlenecking study was conducted, generating multiple options to increase throughput of the existing Phoenix Mill through a series of phased expansions. An option was selected in early 2011 to increase the current concentrator capacity by approximately 25% through two phases. The first phase of the project was the installation of a secondary crushing and screening circuit in order to reduce SAG feed size from a P80 of 6 inches to 2 inches. The second phase focuses on downstream unit operations in the concentrator aiming to relieve existing bottlenecks such as flotation. This paper analyzes the design, commissioning, and operation of a recently installed SAG Pre-crush circuit (Phase 1). The design discussion will focus on concept development, flowsheet design, design criteria, process models, design limitations, and control philosophy. Discussion on the integration of operating data and flowsheet into design during engineering will be presented. Actual operating data of major equipment is gathered from the commissioning and operation of the circuit and compared to the initial design models. Conclusions will be drawn on equipment design factors used during engineering, and the success of model integration into operation. The paper concludes on the successes of the project and where improvements can be made during design.INTRODUCTIONThe Phoenix mine is located within 25 miles of the town of Battle Mountain, Nevada. The mill processes copper, silver, and gold ore. Production started in 2006 and has since struggled to reach the designed tonnage of 33,600 stpd due to the variability in ore hardness. In production year 2010-2011, the Phoenix mill average daily throughput of 33,000 stpd. In 2008, a larger primary crusher (FLS 60/89 gyratory crusher) was installed to operate in parallel with the originally supplied primary crusher (Metso 50/65 gyratory crusher), in order to provide additional capacity upfront in the circuit so that the primary crushing circuit could keep up with the mill.In 2010, a mill debottlenecking study was completed to assess the various options that could be implemented to increase the current mill capacity. The study was completed in late 2010 and contained four tonnages that Phoenix could achieve through various expansion scenarios. A single option was selected in early 2011 to increase the mill capacity from 33,000 stpd to 48,000 stpd. The selected option looked at a four phased expansion that would increase the capacity of the Phoenix mill and address the mill’s current bottlenecks:"

Jan 1, 2013

By A. M. Krzanowski, T. S. Golosinski

"This paper presents results of a study undertaken to determinethe feasibility of mining plains overburdens with bucket wheel excavators. Based on extensive geotechnical testing of overburdens under study, the relations between material geotechnical properties and its cuttability were defined. The properties with the highest correlations to the cuttability werethen used to develop the material diggability classification. This classification may be used for identification of overburdens and coals mineable by bucket wheel excavators.IntroductionLow cost of mining and high productivity can be achieved when mining unconsolidated soils and soft rocks with bucket wheel excavators. As a result this mining equipment will likely be introduced into plains coal mines. At present there are plans to use a bucketwheel excavator (BWE) in at least one mine by the end of this decade. Unfortunately, the performance of a BWE deteriorates rapidly with the increasing strength of mined material. To avoid costly misapplication, material diggability must be defined in advance of an application (i.e. the force required at the cutting edges of BWE buckets must be quantified). Correct definition of material diggability permits reliable selection of a BWE, or may indicate unsuitability of this equipment for a particular application.The reported studyu i was undertaken to investigate the diggability of typical prairie overburdens and thus provide a guidance for likely future applications of bucketwheel equipment. Investigations concentrated on the parts of overburden most likely to create problems for a BWE mining. These are defined in Table 1. At present, thin layers of the two investigated materials (samples K and L) are mined by a BWE in an oil sand mine, after being loosened by blasting."

Jan 1, 1987

By Martin Nevens

"In 1998, the Iron Ore Company of Canada initiated an aggressive program to improve the performance of its Carol Lake Concentrator located in Labrador City, Newfoundland. This program was termed the Concentrator Upgrade Program. The Concentrator Upgrade Program was a group of initiatives developed with the common goal of improving the overall process and operations of the IOCC Carol Lake Concentrator. The main goal of the program was to increase the annual production capacity of the concentrator from 18.0 million tomes to 21.6 million tomes. This gain in capacity was to be done mainly through improvements in process iron recovery. The target iron recovery value was 80+% versus a historical value of 70%. This improvement in iron recovery would translate to a natural weight recovery improvement from 44% to 50%.The Concentrator Upgrade Program provided the first opportunity in 30 years to make fimdamental changes to the concentrator flowsheet. To accomplish this, several pilot plants were built to evaluate new circuits. AAer 2 years, a new flowsheet was selected for the primary gravity separation circuit and the magnetite circuit. The centrepiece of the new flowsheet was the introduction of Hindered Settling Separators to the metallurgical process.The Concentrator Upgrade Program has since proceeded into detailed engineering and, as of February 2001, construction. The first one of IOCC’s 3 primary AG Mills (Mill 11) has been converted to the new flowsheet at the time of writing and is in the throes of commissioning. This paper will review the flowsheet development program in the pilot plant for the gravity separation circuit and examine the overall benefits to the operation of the IOCC Carol Lake Concentrator."

Jan 1, 2002

By R. E. Jones

"INTRODUCTIONCominco Limited, one of the free world's largest producers of lead and zinc having majority ownership in Pine Point Mines Ltd., operates a mining and concentrating complex on the south shore of Great Slave Lake in the Northwest Territories. The mine was developed in 1963-64 and commenced operation late in 1964 with the direct shipping of high grade ore. The concentrator started production in November 1965 at a design throughput rate of 5,000 T.P.D.In 1968, the Company acquired the mining rights to a large ore body located to the east of the Pine Point claims and subsequently an expansion program at the concentrator raised the throughput rate to 8,000 T.P.D. The expansion included a third grinding circuit and additional flotation capacity. The flotation capacity took the form of a completely separate circuit from the existing flotation plant. In 1972, the zinc flotation circuits were modified to include two additional stages of cleaning. This change concluded the ""Pre-Consolidation Flotation"" circuit at Pine Point.In considering these modernization programs of the flotation section of the concentrator, the philosophy was to utilize the largest available machine having proven and modern technological changes. With the advent of the large capacity machines available in the late 1970's, it was considered a suitable time to revamp the entire flotation circuit at Pine Point in 1979. The Circuit Consolidation Project was developed to meet this requirement."

Jan 1, 1982

By Paul J. Cascone

This paper will discuss the science behind the development of a unique gold alloy for dental prosthetic applications. The alloy (GOLDTECH BIO2000) contains 99.7% gold providing unquestioned biocompatibility and unsurpassed esthetics. The topics discussed are: (1) How the alloy meets the functional requirements of a porcelain-fused-to-metal dental alloy. (2) How the alloy color affects the esthetics of the restoration and why the color of gold is best. (3) Overcoming the intrinsic malleability of gold when grinding the alloy surface. (4) Preventing the oxide color from interfering with the alloy esthetics. (5) Attaining excellent porcelain adhesion. (6) How the design of the restoration allows for the production of single and multiple unit restorations. Gold 2003

Oct 1, 2003

By Barun Gorain, Andy Stradling

"The traditional metallurgical scale-up techniques for flotation plants are based on lumped flotation rate constants, dimensionless hydrodynamic numbers and the use of safety factors. Once the plant has been designed, the flotation principles that govern scale-up play almost no role in the optimisation of the circuit to meet its metallurgical targets. This deficiency can potentially lead to a plant design incapable of meeting its targets, especially when circuits incorporate large flotation cells. This paper demonstrates the application of the k = PSbRf model in providing a suitable framework for flotation modelling, scale-up and circuit optimisation, thus presenting an integrated approach to the problem. Studies were conducted at Teck Cominco’s Red Dog concentrator to characterise cell hydrodynamics, gas dispersion properties, fioth flow behaviour, entrainment and ore floatability to obtain the key data necessary to develop a model for the flotation circuit. The findings of these studies are presented in this paper, which provide valuable insights into the modelling and optimisation of the Red Dog flotation circuit.INTRODUCTIONThe traditional methodology for flotation scale-up and plant design is based on the rule-of-thumb with safety factors, dimensionless hydrodynamic group similitude considerations, etc. With the recent trend towards larger flotation cells with volumes of 150 m3 and greater in concentrators, the problem of scale-up has become even more acute. The scale-up factors that may have been tolerated on smaller cells are not applicable to larger cells. The transportation of froth in these large cells adds further complexity to the problem. Arbiter et al. (1980) foresaw this problem and pointed out that if scale-up were attempted by rule-of-thumb and trial-and-error, then the probability of failure would increase with scale. This problem is confounded by the fact that the design and scale-up considerations used for a new flotation circuit play almost no role in optimisation of the circuit to meet its metallurgical target. This results in a plant design incapable of meeting its metallurgical targets. There have been several instances where new concentrators have required significant circuit modifications and additional capacity to achieve design targets."

Jan 1, 2002

By Sami Hindstrom, Travis Orser, John Starkey

"A great deal of effort has been expended in the last 11 years by the authors and others to identify the correct power required to grind ore in a SAG mill, by developing ore hardness variability functions for the ore body to be mined. This paper describes the next step in the SAG design process, which is choosing a SAG mill to accomplish the required specified design performance.At the test work stage, each ore hardness data point is a unique and discreet bit of information that represents the energy required to grind the ore represented by that sample at optimum SAG conditions. When the design criteria are set, it is now considered necessary that the required power draw in the mill chosen be provided at optimum conditions as well.Based on actual 3-ft diameter pilot plant results, we can now show that the grinding efficiency and throughput drop when the optimum load limit is exceeded. Future work is expected to show a similar reduction in efficiency when exceeding optimum speed. Providing specified power by exceeding these optimum conditions is not adequate and leads to a lower cost but underperforming SAG mill.It is possible in some cases to modify a SAG circuit to force it to perform better, but this often takes time, much effort and costly modifications. In most cases the capital spent on a properly sized SAG mill may prevent production losses that would be many times greater over the extended start up period. This is the direct result of choosing the proper SAG mill at the start.INTRODUCTIONThe sequential steps required for the design of any grinding circuit, have changed dramatically in the last seven years. Previously, it was considered necessary to do six foot diameter SAG mill pilot plant tests on representative samples of minus six inch ore (F80), in order to understand design requirements. It can now be shown that this method is costly and not likely to produce the desired result because it is difficult to recover six-inch material from deep within a new mine. The representative nature of the sample is often compromised when the sample is selected."

Jan 1, 2003

By Renaud Adams, Vladimir Salatic

"The El Mochito Mine located in Honduras, Central America, has produced lead, zinc and silver in concentrates since the 1950s. The paper discusses changes made in both lead and zinc circuits to reduce costs while maintaining production during the recent period of low metal prices.The intent of this paper is to show that sometimes thinking “outside the box” is beneficial for progress. Also, in striving for better metallurgical results we should not forget the basics of flotation. Sometimes the latest trends may not be applicable to the ore we are treating and may not meet the operating cost constraints.A major beneficial impact on El Mochito metallurgy was achieved when the overall grind was coarsened, eliminating the significant percentage of slimes. Switching from two parallel twostage grinding circuits to one circuit with three-stage series grinding has resulted in a significant reduction in power and steel consumption. With minor layout/reagent modifications, both lead and zinc circuits gained not only in retention time but as well in producing better grade products.Of course, the challenges are still there; they exist and only with the full support of operational data collection and metallurgical laboratory investigation success can come. That is why, we as professionals, can never stop in trying to make the most of what we have.INTRODUCTIONThe El Mochito Mine is owned by American Pacific Honduras S.A. de C.V. (AMPAC) a subsidiary of Breakwater Resources Ltd. Of Toronto, Canada. The mine is located in western Honduras, approximately 220 kilometers northwest of the capital city, Tegucigalpa and 90 kilometers south of the country’s second largest city, San Pedro Sula. The mine began operating in 1948 and to date has produced more than 19 million tonnes grading 240 g/t Ag, 3.5% Pb and 7.4% Zn. Production in 2005 was 700,190 tonnes grading 87 g/t Ag, 1.85% Pb and 6.61% Zn.Decreasing metal content in the ore followed by the lowest zinc price on the market in the last 15 years (see Figure 1) has reduced the cash flow and endangered to stop the operation."

Jan 1, 2007

By Terry Keough

Contents for discussion ?Current liner technology ?Innovation of magnetic products ?Development of magnetic wear liners ?Installation and change out method ?Uses and capabilities ?Internal wear liners ?Summary Vulcanized rubber ?Many of you are familiar with using vulcanized rubber to provide wear protection on mining equipment. For years, this was the standard for most mining equipment, and mines spent a lot of money fabricating and lining steel equipment.

May 1, 2010

By Mohammad Noaparast, Babak Fotoohi

"Due to certain advantages in (semi-)Autogenous-Ball mill circuits in most of the high-throughput ore grinding units of mineral processing plants, much attention is paid to optimize the mill performance. Despite the maturity of the grinding mill mechanical design, there had been made less attention to the efficiency of the grinding media in the past. In this research, the possibility of establishing a relationship between liner/lifter wear rate and variations in the composition of the iron ore (from Chadormalu mine) is investigated.Measurements and determination of liner/lifter wear rates and patterns concluded in recognition of critical liner segments exposed to much abrasion during the ore grinding. After metallurgical analysis of liner materials and correlation of wear rate with the ore composition, the homogeneity in the metallurgical microstructure of the alloyed steel (such as the uniform distribution and amounts of the constituent phases) was determined as the most influential factor in the response of the liner/lifter to the variations in the ore composition. Magnetite with greater abrasion index than hematite, in finer particles, is responsible for additional abrasion of liners; hematite with greater work index exists in the mill with larger particle sizes, thus it could produce wear on liner parts with less tolerance to impact as is the situation for martensitic steels.INTRODUCTIONThe mineralization in Chadormalu plutonic iron ore deposit is consisted of mostly magnetite, hematite, martite, apatite, quartz and carbonates. The average composition of the ore is presented in Table 1. In the processing circuit, the gyratory crushed ore reduced to 30 cm would finally be the feed to three similar 32’ semi-autogenous mills in parallel processing lines. The pulp in the mill would have the characteristics mentioned in Table 2. The quality of the mill output has its direct effect on the downstream processes either physically or chemically (e.g. in cycloning or flotation respectively). In order to take advantage of optimum performance for these circuits, a close control of the ore grinding conditions is necessary; because any shortages in throughput, liner/lifter damage or changes in ore composition could bring the unexpected casualties. In this work, it has been attempted to find (possibly) a reasonable relationship between variations in ore characteristics together with liner quality and the amount of wear rate in different liner/lifter segments of a semi-autigenous mill. Liner/lifter segments are supplied by three different domestic steel making companies. The alloy structure of the liners/lifters is made up of pearlitic chromoly steel."

Jan 1, 2005

By B. P. Simser, R. K. Brummer, A. Mortazavi, P. P. Andrieux

"A large-scale panel destress blast was fired at Brunswick mine in the fall of 1999 in order to reduce the ground stresses in a critically important neighbouring mining region. This work, sponsored by the Mining Division of CAMIRO and Brunswick mine, consisted in heavily choke-blasting — and subsequently leaving in place — a massive waste sulphide pillar in the southwest end of the 1000 m level. This paper describes the approach and design methodology used to try to maximize breakage in the rock mass in the area to destress, while minimizing damage to critical infrastructures in the vicinity. The loading operations, as well as the results of the blast — in terms of its field performances, as recorded by near-field blast vibration monitoring equipment, visual postblast assessments and measured impact on the regional stress field — are discussed as well. A brief comparison between the measured stress changes and inelastic numerical modelling of the test site is also presented.Un tir à grande échelle de relâchement des contraintes dans un pilier a été effectué à la mine Brunswick à la fin de l’automne 1999 dans le but de diminuer les contraintes de terrain dans une très importante zone de production adjascente. Ces travaux, financés par la division minière de CAMIRO et la mine Brunswick, consistaient à tirer violemment sans aucune face libre, et à laisser en place, un pilier de sulphures massifs au sud-ouest du niveau 1000 m. Cet article décrit l’approche et la démarche conceptuelle utilisées pour tenter de maximiser les fractures dans le pilier visé, tout en minimisant les dommages collatéraux à des infrastructures critiques se trouvant dans les environs immédiats. Les opérations de chargement des explosifs et les résultats du tir — en termes de ses performances, telles qu’évaluées par de l’équipement de monitoring rapproché des vibrations de tir, d’observations visuelles, et de son impact sur les contraintes de terrain locales — sont également discutés."

Jan 1, 2003

By D. Lindeman, R. M. Nendick

"From a technologist's point of view, there have been few fundamental 'breakthroughs' in the process of gold extraction since the turn of the century. However, the industry has made a great deal of progress in its response to the problems that have arisen: a changing demand for products, lower grade and more refractory ores, inflated labour and materials cost and the increasing control of governmental legislation. The trend in North America and South Africa to alleviate these problems has been to adopt a common policy to process larger tonnages of lowgrade ore through more efficient milling circuits. Here, however, is where the similarity ends.The purpose of this paper is to emphasise the different principles of practice employed by extraction plants in North America and South Africa to achieve the same common goal, namely gold bullion.2.0 INTRODUCTIONTwo very important aspects of extraction metallurgy for which the metallurgical engineer is responsible are plant design and plant commissioning.In North America and South Africa the importance of these aspects is due to the fact that both are related to the financial success of the project of which they form part. Good design is imperative if the capital invested in both the plant and the whole mining undertaking is to reap maximum profit. Furthermore, good design leads to a carefully planned and well executed start-up procedure resulting in bringing the plant into production on time, at designed efficiency and within budget.Due to the competent nature of the quartz pebble conglomerate and quartzite ore on the South African Witwatersrand, the characteristics of the ore type are not much different from one mine to the other. Thus a significant operating knowledge and experience has been built up over the years and there is considerably less risk in selecting a gold extraction process route."

Jan 1, 1992

By Serge Ouellet

Résumé Six modèles métriques de remblai cimenté en pâte (RCP) ont été suivis durant 120 jours par l?utilisation de deux méthodes géophysiques non-destructives : la résistivité et la micro-sismique. Les RCP étaient constitués de trois résidus miniers et de deux proportions de ciment (3% et 6% en poids). En parallèle, des cylindres de RCP étaient utilisés pour évaluer périodiquement l?UCS. La résistivité augmentait quasi-linéairement de 28 à 120 jours pour tous les RCP investigués. Des variations de résistivité selon le type de résidu et le pourcentage de ciment ont été observées. Une équation empirique a été dégagée entre l?UCS, la résistivité, le temps, la densité relative et le rapport eau/ciment (E/C). La mesure de la vitesse des ondes de cisaillement a permis de dégager une équation mathématique de type exponentielle qui relie la résistance mécanique sans correction préalable par les paramètres de la recette de RCP. La réalisation de ce projet avait pour but de dégager la meilleure approche non-destructive afin d?estimer la résistance mécanique des remblais en chantier minier. Sur la base des résultats obtenus, les deux méthodes utilisées ont donné des résultats probants afin d?estimer la résistance mécanique et les deux méthodes sont donc à même d?être utilisées en chantier souterrain. Abstract Six scale models of cemented paste backfill (CPB) were followed during a 120 days period using two nondestructive geophysical methods: resistivity and micro-seismic. CPB were made up of three mine tailings and two cement proportion (3% and 6% by weight). In parallel, CPB cylinders were used to periodically evaluate uniaxial compressive strength (UCS). Resistivity was increasing nearly in straight line from day 28 to day 120 for all CPB models. According to the tailing type and cement percentage, resistivity variations were observed. An empirical equation emerged from UCS, resistivity, time, specific gravity of tailings and, water/cement ratio. The use of shearwave velocity allowed to identify a mathematical exponential equation related to mechanical strength without prior correction of the CPB?s formula parameters. The purpose of this project was to identify the best non-destructive approach in order to evaluate the mechanical strength of backfill in a mine site. On the basis of those results, both methods gave conclusive results in order to estimate mechanical strength and both methods can be used in underground operations.

Feb 1, 2008

By Joseph Poplawski, Christian O’Keefe, Robert Maron

"Unique and difficult minerals processing measurement situations will be described and the application of passive array-based technology for performing these measurements will be illustrated. Examples of these situations include volume flow measurements in froth lines and flotation feed lines with entrained air, slurry lines with magnetite and other magnetic ore, slurry lines with abrasive or corrosive materials, high pressure lines, and slurry and non-slurry lines exhibiting scale buildup. Other situations include measurement of entrained air levels in pipes and in flotation columns. These measurements are achieved through CiDRA’s patented passive sonar array-based technology. This technology performs two independent measurements – flow rate and entrained air amounts. Two hardware implementations of this technology have resulted in a non-intrusive flow and entrained air meter which easily is installed on the outside of the pipe, and a submersible version for entrained air or gas holdup measurements which is used in flotation processes. Recent developments in extending this technology to solve other unique measurement problems such as valve movement confirmation will be covered.INTRODUCTIONThe minerals processing industry faces many unique and challenging process control conditions and environments. In terms of flow measurements, many of these situations are not being properly served by traditional flowmeters such as ultrasonic meters, magmeters, turbine meters, orifice plate meters, vortex flow meters, Coriolis flow meters, and venturi meters. A new class of flowmeters has been developed that solves these unique situations and flow measurement problems. This new class of flowmeter technology utilizes sonar-based processing algorithms and an array of passive sensors to measure not only flow, but also fluid composition. It does so accurately, reliably and without making contact with the fluid. These measurements are performed on practically any type of fluid within virtually any type of pipe.PRINCIPLE OF OPERATIONSonar array-based flowmeters are ideal for tracking and measuring the mean velocities of disturbances traveling in the axial direction of a pipe. These disturbances generally will convect with the flow, propagate in the pipe walls, or propagate in the fluid or slurry. First let us focus on the disturbances that convect with the flow. The disturbances that convect with the flow can be density variations, temperature variations or turbulent eddies. The overwhelming majority of industrial flows will have turbulent eddies convecting with the flow, thus providing an excellent means of measuring the flow rate as described below."

Jan 1, 2008