Search Documents

By James E. Rider

"Fractures in mine hoist drumshafts are rare. We know of no previously reported attempts to repair a fractured drumshaft; any feasible method would involve welding and the associated problems of distortion, crack formation and strength.In June 1984, a fracture was discovered in the drumshaft of the production hoist in the Teck Corporation, Lamaque Division Mine at Val d'Or, Quebec. Delivery time on a new shaft would have been at least six months. The shaft was repaired in ten days and the total out -of-service time was four weeks.This paper describes why the shaft failed, how it was repaired, and the special alignment procedures employed during re-installation to minimize stresses in the repaired area.IntroductionThe performance of a mine hoist drumshaft is absolutely critical to mine operation. An inoperable drumshaft means no hoist, which in turn means no production or mine operation.Fractures in mine hoist drumshafts are rare. Previously when they have occurred, no one has seriously considered attempting a repair because of problems involved. Any feasible method would involve welding, which raises several major problems - namely, metallurgical, alignment, and strength.In July 1984 this very situation occurred at the Teck Corporation, Lamaque Division Mine in Val d'Or, Quebec.It was recognized that a new shaft would take at least 6 months' fabrication and delivery time. However, having had some experience at repairing broken shafts in other machines under similarly desperate circumstances, and after due consideration, it was concluded that by applying the correct techniques and engaging the right expertise, it would be possible to perform a repair and have the mine back in operation within a month.Thanks to outstanding efforts by all, the repair was accomplished in ten days and total out-of-service-time was only four weeks. The causes of the failure were determined and the calculated stress levels confirmed by strain gauge measurement during operation.The success of this project was achieved by adhering rigorously to fundamental management and engineering principles."

Jan 1, 1988

By R. Flood

"Oil has been discovered off Newfoundland in a number of locations on the Grand Banks, the most notable and exciting being in 1979 when Hibernia was discovered. This discovery has brought new challenges to the province as well as to all of Canada. During the seven years"" since its discovery, both industry and governments have attempted to define its parameters and to find the most efficient and economical way to develop the field.A number of studies have been completed during the interval and in 1985, Mobil Canada Ltd. and partners stated that they would prefer to develop the field by using a concrete Gravity-Based Structure (GBS). IntroductionHibernia is located in an environmental climate much more severe than that of any previously developed oil field. The wind and wave conditions are similar to those of the North Sea, but unlike the North Sea, any structure on the Grand Banks would have to contend with ice floes and icebergs. Decisions had to be made on whether fixed structures could be put in place that would withstand the pressures of the ice and the impact of an iceberg, or whether structures that could be removed when such impacts were imminent would be used.Early studies in 1981, determined that it was possible to build a concrete Gravity-Based Structure which could withstand the impact of the largest icebergs that are anticipated to float in that area of the banks.Additional studies increased the knowledge of icebergs: their patterns and size, and verified the original conclusions that Concrete Gravity-Based platforms would provide a practical solution."

Jan 1, 1988

By O. Matwijenko

"1. IntroductionThe Falconbridge Owl Creek open pit gold mine is located 17 km northeast of Timmins and 2.5 km west of the Kidd Creek metallurgical site. Diamond drilling first commenced in 1964 with open pit production commencing in 1982. Other operations within close proximity are the Canamax-Pamour Bell Creek Mine and the Falconbridge Hoyle Pond Mine.Since 1982, 1,216,000 tonnes assaying 4.5 g/t have been processed in six concentrators. This paper summarizes the metallurgy achieved with special emphasis on some of the unique problems encountered in the processing of this refractory ore.2. GeologyThe Owl Creek deposit, located 3 km north of the Porcupine-Destor fault is in easterly trending carbonaceously altered volcanic and sedimentary rocks. The deposit strikes east and dips steeply north.The ore body can be best described as a wedge shaped sandwich of volcanic basalt between the surrounding sedimentary greywacke. The north and south volcanic-sedimentary interfaces are marked by graphitic zones. The south graphitic contact is more continuous with its thickness varying from 5 m to 20 m as compared to 0.5 m to 3 m to the north. Quartz veins occur throughout the deposit with a predominant vein running along the south contact where it is characterized by numerous graphitic inclusions. Some veins carrying gold values intrude into the sediments in the north. With depth the sedimentary and volcanic zones taper while the quartz-graphitic zones appear to become more dominant."

Jan 1, 1988

By Robert B. Parsons

"This article is based on a paper presented by Jim Scott at the 1988 annual convention of the Prospectors and Developers Association of Canada. The paper suggests a number of factors that might be taken into account in negotiating royalty terms.IntroductionRoyal ties are a part of mining life in Canada. They are used by many kinds of individuals in many kind s of situations. Prospectors commonly take royalty interests back when they transfer claims to development companies. Mining companies disposing of undeveloped (or sometimes even developed) properties are often paid at least in part by royalties. Royalties are even used by institutional investors with no other connection with the resource industry.Such different royalty holders have different investment goals, different cash flow requirements, and different risk / return preferences. These differences have given rise to a number of different royalty type s. These types range from the simplest cents-per-ton royalty (where the operator pays a royalty at a fixed rate per ton milled) to net smelter return or ""NSR"" royalties (where the royalty is based on a percentage of the operator's NSR) all the way to net profit interest or ""NPI"" royalties (where the royalty is based on the operator's bottom-line net profit),The fundamental difference between the many royalty types is in the risk/ return relationship. The cents-per-ton royalty, for example, is relatively risk-free. Of the many economic factors which affect a mine, the only one which will affect the royalty holder is the amount of ore physically milled. On the other hand, the potential for significant gains under a cents-per-ton royalty is also very limited. The royalty holder will not share in any increases in the market price of the end product or any cost reductions achieved by the producer."

Jan 1, 1988

By Jean-Yve Tremblay, Michel Prud'homme

"Industrial minerals include a group of more than fifty minerals which are marketed into almost all the sectors of industry; they are the backbone of many manufacturing industries. Table I shows major end-uses for industrial minerals in manufacturing sectors. At Energy, Mines and Resources, industrial minerals are divided in three major categories: (I) agro chemicals and chemicals, (2) construction mineral s, and (3) ceramics and specialty minerals. A listing of the major groups of minerals is shown in Table 2. Agro-chemicals and chemicals are sold on the basis of their chemical content and purity. Construction minerals or structural minerals are distinguished by their performance as low cost and bulky commodities. Ceramics and specialty minerals are performance-specific and are sold for their property on imparting functions on end-products. Industrial minerals have unique characteristics that are useful in many stages of processing; from crushed size to micronized fillers a single mineral ca n serve a broad range of industries because of its intrinsic properties."

Jan 1, 1988

By W. H. Hodgson, A. R. Preston

"Improved rail production techniques provide new options for the rail user. Steelmaking improvements offer tighter composition control, lower oxide and sulphide counts, greater control of segregates and freedom from hydrogen problem s. New ultrasonic, laser and eddy current equipment gives printout information on surf ace flatness, straightness and internal condition. These have come along at a time when dramatic changes have occurred on the rail heat treatment scene. Rails can now be deep hardened on or offline in ways which should eventually result in a complete rewrite of the world's specifications. Rails of simple composition can be produced in the hardness range 2801400 BHN as required. The rail user can choose the hardness within this range according to requirement without the necessity for any step changes in the process routes.It is suggested that this is the pattern f or the next decade.IntroductionRails have been the subject of very slow improvement over many years but developments gathered momentum in the early seventies. Recent improvements in quality and properties have provided dramatic increases in rail life under the more severe service situations. Rail profile grinding, lubrication and other track improvements have greatly added to expectations of even longer life. All of this, coupled to even newer mill heat treatment developments, tilt both technical and economic advantages away from tradition to the point where specifications will need to be rewritten so that railroads can take full advantage of these new products."

Jan 1, 1988

By Robert B. Parsons

"One of the disadvantages of the federal government's idea of ""taxation by consultation"" is that it seems to take longer to enact new legislation. The proposed new rules for taxing automobile benefits is one example. Here is a ball which has been batted around between government and the public several times and still has not come down to earth. Fasten your seatbelts, there may be more to come. IntroductionThe draft legislation released on April 13 contains the details of the government's current proposals on car expenses and benefits. They differ significantly from the last announced position. Finance Minister Wilson has indicated that the release in draft form will provide an opportunity for the Commons Standing Committee on Finance and Economic Affairs (the Blenkarn committee) and other interested persons to comment before the legislation is introduced in Parliament. Accordingly, there may yet be revisions.Notwithstanding the prospect of further changes, the proposed rules generally come into force in 1988. While taxpayers may welcome some of these changes, particularly the increase in the tax-exempt allowance, many must be frustrated that, at this late date, the rules for the current taxation year are not yet finalized."

Jan 1, 1988

"This paper describes some of the methods and equipment used for fine milling of minerals, and gives particular attention to the Vibro Energy system.In addition, the paper describes a specific application in the gold mining industry. This is the 200 tpd plant built by Anglo American Corporation at the President Brand Mine in South Africa in 1985, now a division of Freegold. This plant treats a gold bearing pyrite flotation concentrate which is finely ground to 15 microns prior to cyanidation and carbon-in-pulp (CIP). l .0 INTRODUCTIONFree milling gold ores are those that yield acceptable dissolution and recovery of the gold following grinding to what can be described as normal fineness, frequently between 50% and 90% passing 74 microns.Increasingly, gold metallurgists are faced with ores that are refractory. The traditiona1 treatment route for refractory gal d ores and concentrates has been by roasting, but for environmental reasons this is becoming less acceptable, or in some areas of the world, totally unacceptable. New methods of treating refractory gold ores are being developed and applied in practice. These new methods include pressure and biological oxidation. Higher gold liberation can also be attained by increasing the fineness of grind, although with conventional systems there are economic limits to this.In flowsheet development and test programs on new deposits, a standard procedure is to establish the relationship between the grind and subsequent go 1 d extraction. The normal situation is that gold extraction increases as the ore, or concentrate, is ground finer. Typically, this relationship is as shown in Fig. l, where the incremental additional extraction is very small once an optimum, or economic, grind has been achieved. This generally app1ies whether the material is free milling or refractory. The limits to grinding are set by the type of equipment which is commonly in use, usually ball mills. These mills have the obvious advantage of high capacity, however, they are increasingly inefficient as finer grinds are required. In general, ball mills are used to reduce ore to some agreed percentage passing 74, or possibly 53 microns."

Jan 1, 1988

By A. Piche, J. Nantel

"This paper describes the recent developments in Canada toward the establishment of a Canadian Centre for Mining Automation and Robotics, at McGill University and École Polytechnique in Montreal. The role of the Mining Association of Canada (MA C) and of the National Advisory Committee on Mining Automation will also be reviewed. IntroductionIn order to remain competitive, the mining industry must increase its productivity and reduce its costs. In the last two decades, this objective has been achieved through mechanization. From now on, any further improvement in productivity will be gained through increasingly more automated mining equipment.Recent international developments following the Versailles Economic Summit in June 1982, having given rise in Canada, to a renewed interest in applications of robotics and automation to mining.The mineral industry in Canada is at a crossroads. Competition in emerging from everywhere: lower grade ore bodies, increasing distances between viable mines and markets, third world massive production of certain commodities, substitution of "" space age"" materials (ceramics, plastics, composites, etc.) for metals.On the positive side, it is generally believed that present mineral commodities, i.e. base metal, gold, iron, industrial mineral s, etc ., will continue to be in high demand for centuries to come despite substitution. New applications for conventional metals will be found and the enhancement of certain properties of these conventional metals mean continued demand. For some mineral commodities, there will never exist an y substitute."

Jan 1, 1988

By Robert B. Parsons

"It is generally felt that flow-through shares face a bleak future under the set of tax rules proposed in the federal government's tax reform white paper. Industry and government circles are beginning to give thought to alternatives to flow through as a mechanism for facilitating equity financing in the exploration industry. Despite suggestions that grants and tax credits may someday be on the table, industry is sticking to its position that there is no substitute for flow-through. Alternatives toFlow-throughProposals in the federal government's tax reform white paper have cast significant doubt on the ability of the mining industry to raise risk capital after 1989by way of flow-through shares. There is serious concern that introduction of the ""cumulative net investment loss"" (CNIL) rules, the phase-out of the mining explorati0! 1 depletion allowance (MEDA), and the Increased capital gains inclusion (750/0 versus 50%, at present) will make the economics of flow-through so unattractive after 1989 that these shares will hold little appeal to most investors. The question might be raised, then, as to what alternatives exist by way of tax or other government assistance that could help the exploration sector.The purpose of this paper is to survey the types of government incentives that could be of some value to explorationists and to the mining industry in general. For the past several years, flow-through has been in the spotlight insofar as incentives to the exploration industry are concerned. Other potentially useful and attractive incentives have been partially hidden in the shadow of flow-through. These incentives, in certain circumstances, can be of considerable benefit, and should not be ignored."

Jan 1, 1988

By K. Barr, F. Grenier, J. Hettinger

"To reach the Hemlo Gold Inc. objective of becoming the lowest cost, safest Canadian gold producer while causing no environmental damage, management embarked from its inception on a strategy to build an organization which would foster employee involvement wherever possible. This paper describes the organizational structure and how various innovative concepts have been implemented.BACKGROUNDThe Golden Giant Mine in the Hemlo area of North Western Ontario is owned by Hemlo Gold Mines Inc. 50.1% is controlled by Noranda. The mine commenced operations in March 1985 at a modest production rate. After it reaches full production by the end of 1988, with completion of underground development work, the mine is expected to operate at 3000 t/d and produce in excess of 300,000 ounces of gold per annum. This makes it one of the three largest producing gold mines in North America.Two other companies, Lac Minerals and Teck-Corona, operate mines on either side of the Golden Giant Mine. Noranda Geco Division is located 55 kilometers to the north at Manitouwadge. The majority of Hemlo Gold's 270 employees live in Manitouwadge where a mix of accommodation was constructed and made available for purchase by employees. Bus transportation is provided to and from the workplace with modern coaches. The housing and transportation policies were implemented prior to start-up and designed to help attract and maintain good employees.As shown in Figure 1, the operation is divided into five operating and support departments with each reflecting a high degree of departmental control and responsibility. For example, the mill department is responsible for all aspects directly relating to the milling complex including safety, operation, mechanical maintenance, assaying, instrumentation, and environmental control. Similarly, the mine department is responsible for all phases of operation, mine engineering, geology, and maintenance of underground mobile equipment. The plant department is responsible for maintenance of hoisting plants and conveyances, underground stationary equipment, all site electrical services, surface buildings, housing and yard maintenance. Efforts are made at every level of the organization, from departmental organization to individual job assignments, to ensure responsibilities are clear and that they encompass complete functions."

Jan 1, 1988

By M. Leroux, C. J. Martin, S. R. Rao, J. A. Finch

"The effect of nitrogen on the flotation separation of sulphides from complex ores from Brunswick Mining and Smelting (New Brunswick) and Mattabi Mines (Ontario) was investigated. The most significant finding was enhanced pyrite floatability after as little as 3 minutes nitrogen conditioning. This was used in a novel sphalerite/pyrite separation process developed on the Brunswick ore. After aeration and Cu/Pb bulk flotation in air using xanthate the slurry was nitrogen conditioned, xanthate added and the pyrite floated in nitrogen. As an example up to 70% pyrite recovery with about 20% sphalerite recovery was achieved. Sphalerite was recovered from the pyrite tailings and the pyrite concentrate by copper-activation, raising the pH to 10 and floating in air. About 65-70% recovery at 35-40% Zn grade was achieved compared to 25% Zn grade by the conventional route. The process offers a promising alternative to current practice which seeks to depress pyrite at all stages. A possible mechanism of the effect of nitrogen is presented. INTRODUCTIONUse of gases other than air in froth flotation has been reported from time to time. [Podobnik and Shirley, 1982; Lin and Metzer, 1975]. Of all the gases, nitrogen would appear to hold the greatest practical promise because of its easy availability and chemical inertness. It is used in froth flotation in chalcopyrite-molybdenite separation [Redfearn, 1983]. The use of nitrogen in polysulphide chalcopyrite. this case is mainly to reduce the oxidation of a compound (Nokes reagent) used as a depressant for There is no reported use of nitrogen in the flotation of other sulphide minerals."

Jan 1, 1988

By J. A. Finch, G. Labonté

"A long-standing objective has been to obtain interpretable measurements of the oxidation-reduction potential in mineral slurries. For this purpose several sensing electrodes (black platinum wire, platinum foil and spiral, gold foil and spiral, and sulphide minerals such as chalcopyrite and galena) were investigated to determine their response to the presence of sulphide minerals in the pulp, and to the addition of reagents commonly used in flotation. The observed discrepancies between the electrodes may be explained using a combination of the classical mixed potential model for complex solutions and the probability of contact between the mineral particles and the sensing electrode. It is shown from laboratory testwork that gold spirals are preferred over platinum electrodes. Finally, some of the practical aspects of using the electrochemical measurements in a plant environment are discussed.IntroductonThe interpretation of flotation of sulphide minerals in terms of electrochemical (electron transfer) processes has brought new possibilities for process control of selective flotation. Investigations on massive and compacted particulate bed electrodes have shown that the flotation of a given mineral in the presence of a collector can be controlled by the potential induced on the mineral surface. Also, phenomena such as collector less (self-induced) flotation, activation by heavy metal ions, and natural selectivity sustained by galvanic coupling during flotation might also be controlled by electrochemical means.The technique for measuring electrochemical potential in slurries is an adaptation of that used for solutions. The measurement of the oxidation-reduction potential of a solution (ORP , Redox, Eh) is usually carried out by immersing a noble metal electrode (platinum, gold or silver) and a non-polarizable reference electrode: Standard Hydrogen Electrode (SHE), Standard Calomel Electrode (SCE), or silver/silver chloride (Ag/AgCl) in the solution. (The abbreviation Eh implies the SHE is the reference electrode.) The potential difference between the two electrodes is measured using a high impedance electrometer. ASTM standard D 1498-76 (revised 1981)(1) covers the practical details of such measurements; however, it does not deal with their meaning either in complex solutions or in mineral slurries ."

Jan 1, 1988

By O. J. C. Runnalls

"Canada became the world's largest uranium producer in 1984. That leadership position is likely to be maintained for many years into the future because of a firm production base, many undeveloped known deposits with commercial promise, and a large geologicalpotential for new discoveries.There are some uncertainties on the horizon, principally because of restrictive actions in process within the U.S.A., which are aimed at preserving a deteriorating domestic uranium industry. Should such actions result in import restrictions, for example, there would be a negative effect on foreign producers at least in the short term. Canada may avoid such difficulties under a tentative U.S.-Canada free-trade agreement where restrictions on the import of Canadian uranium into the United States would be eliminated. Over the longer term, demand for Canada's uranium resources will grow because of the foreseen growth in the world's installed nuclear power capacity. IntroductionSince the phenomenon of nuclear fission was discovered in 1938, the utilization of uranium has grown substantially. Initially, the principal use for uranium was in the production of nuclear weapons. However, once civilian nuclear power reactors began to be built in the 1950s, an increasing fraction of uranium output was directed to the production of fuel elements for use in electricity generating stations.The cumulative uranium production by those countries in the World Outside Centrally-Planned-Economies Areas, WOCA, during the period 1938 to 1985 exceeded 800 000 tonnes of uranium. Some 60% of that was mined in the United States and Canada, as indicated in Figure 1. In 1986, nearly 80% of WOCA output came from five countries, Canada, United States, South Africa, Australia, and Namibia, as indicated in Table 1 and illustrated in Figure 2.During the past decade the world annual consumption of nuclear energy has more than tripled (Fig. 3). As of December 31, 1986, the world total of nuclear power reactors had reached 394 with a total net capacity of 270 GWe. The thermal output from nuclear power plants in 1985 exceeded 60% of the energy contained in all of the oil produced that year in the Middle East. Thus, nuclear power has already become an important component in the world energy supply picture."

Jan 1, 1988

"INTRODUCTIONThe Kidd Creek Concentrator is located 28 kilometers east of the city of Timmins, Ontario. Two types of ore are treated; 'A' type, a copper-zinc-low silver ore producing copper and zinc concentrates, and 'C' type, a copper-lead-zinc-high silver ore producing copper, lead and zinc concentrates.The ore is processed at a combined rate of 12,400 metric tonnes per day through four parallel grinding and flotation divisions. Three divisions treat the 'A' type ore and the fourth treats the 'C' ore. Each division is fed from its own fine ore bin.This paper reviews the grinding section with specific emphasis on grinding media consumption and the factors affecting it as related to 'A' type ore. At Kidd Creek there was an awareness that grinding media consumption varied on a weekly and monthly basis. The reasons for this variation was usually attributed to ore hardness as evidenced by short term variations in the circuit feedrate and head assays. However, there has been a diversity of opinion published in recent years regarding the factors contributing to steel consumption. This initiated a study of historical Kidd Creek operating data, from the period 1970 to 1986 inclusive, to determine the effect of various operating parameters on media consumption. The results of the study could then be used as a baseline for future media consumption testwork."

Jan 1, 1988

By K. J. Griffin, G. W. Rosval

"In our increasingly competitive market, attempts to improve productivity by increasing axle loads have placed more severe demands on rails. CP Rail thus requires stronger, tougher, and more wear-resistant rails from steel manufacturers. The choice of any rail steel is always a compromise between technical and economic factors. The technical assessment of a candidate rail consists of laboratory and field testing. Laboratory evaluation of rail steels cannot adequately model many service conditions and must, therefore, be supplemented by long-term field testing. The field testing conducted on CP Rail is the subject of this paper.Long-term, in-track, assessment of candidate rail steels begins with the selection and re-laying of a test curve representative of the intended service with both the candidate rail and a control rail steel (i.e. the present intermediate or premium rail standard). The wear performance of the candidate rail is evaluated, in relation to that of the control rail, using data obtained with a rail profilometer developed by the Research and Development Department of CP Rail. Qualitative observations are also periodically made to evaluate the relative susceptibilities of the two rail types to surface defect formation. Testing continues until stable metal loss patterns are achieved. Relative life predictions are then made and detailed monitoring of the test site is discontinued.CP Rail's in-track assessment program for premium rails has resulted in the establishment of a new CP Rail premium rail standard - low-alloy, head-hardened, rails have replaced high alloy rails. The wear/fatigue lives of these new premium rails exceed those of our previous standard by more than 50%, and they also exhibit excellent weldability. CP Rail will continue to evaluate new premium and intermediate strength rail products."

Jan 1, 1988

By J. E. Nesset

"This paper discusses the importance of considering residence time distribution (RTD) in the design of flotation and mixing circuits and in the analysis of operating problems. The experiences and successes of Brunswick Mining in this area are covered and include: the development of a practical RTD measurement technique using pulp conductivity, baffle installation to improve the RTD of existing process equipment, and the method in which RTD considerations have been used to design the newest flotation and conditioning operations. IntroductionThe use of residence time distributions (RTDs) in the design and analysis of unit operations is well understood by the chemical engineering profession in while mineral processing engineers have tended to rely on empirical and rule-of-thumb factors. For example, in scale up from laboratory and pilot test results to full size flotation plant design, empirical rule s are often used to establish residence time and number of cells in the bank. Coleman suggests a factor of at least 2, and up to 5 for gold ores, be applied to laboratory determined flotation times. This is further illustrated in Table I, taken from Denver equipment.The number of cells in series to achieve the required retention time while minimizing short-circuiting has generated a variety of conclusions (Table 2). Obviously there is less than complete agreement on the subject. Young notes that a clear difference of opinion has emerged and cites as extremes, (i) the publications of Outokumpum showing unimpaired recovery for its largest machines (38 m3) compared to equivalent retention times for numerous smaller machines, and (ii) the experiences of Eastern European countries where the practice is to install banks of 30 unit s or more, operating in series, often with unit retention times of only a fraction of a minute.The empirical factors used by engineers presumably account for other than tested feed conditions, inefficiencies in large continuous machines, inevitable day-to-day circuit disruptions, gradual equipment deterioration and any other safety factor the engineer feels compelled to incorporate. An understanding of RTD concepts and techniques should help the practicing mineral engineer to develop more soundly based factors. This paper relates the experiences of Brunswick Mining in using RTD techniques in the unit operations of flotation and mixing."

Jan 1, 1988

By M. Remillard, M. Garon, D. Hodouin, M. Therien

"Nineteen streams in the copper and zinc flotation units of the concentrator of the Matagami Division of Noranda Inc. have been sampled f or particle size distributions, chemical assays, and gold and silver contents in each particle size interval. The data are upgraded by the mass balance package BILMA T. These results, in conjunction with microprobe analyses, are used to quantify the silver losses in the copper cleaning flotation stages and to determine how over-all silver and three silver-bearing minerals are recovered in the plant final products. RESUMEDix-neuf produits des circuits de flottation du cuivre et du zinc de la division Matagami de Noranda Inc. ont été échantillonnés pour leur distribution granulométrique, leurs analyses chimiques et Ie contenu d'argent et d'or des fractions granulométriques. Le bilan métallurgique a été obtenu à l'aide du programme BILMA T. Ces résultats, couples avec une étude minéralogique a fa microsonde, sont utilisés pour quantifier les pertes argentières aux diverses étapes de nettoyage du circuit de cuivre et pour déterminer la répartition de l'argent et des trois minéraux argentifères dans les produits finals de l'usine."

Jan 1, 1988

By Nural Kuyucak, Bohumil Volesky

"Extensive screening revealed a seaweed (alga) biomass type which in its non-living state possesses a very high cobalt sequestering capacity comparable to that of activated carbon and the ion-exchange resin currently used in the cobalt production process. Performance of the new bio-sorbent material was studied by examining its equilibrium metal uptake isotherms generated under different solution conditions such as initial cobalt concentration pH, temperature, and the presence of selected cations and anions. The rate of cobalt uptake was determined, which is a crucial parameter for recovery process design. Almost all cobalt sorbed can also be desorbed with a solution of CaCI2. The bio-sorbent material can be used repeatedly in the sorption-desorption cobalt concentration process. IntroductionIt has been well documented that certain types of microbial biomass, living or non-living, possess a high potential to sequester and accumulate inorganic ions present in aqueous solutions. Metal concentration by microbial biomass from a solution is termed bio-sorption. This phenomenon is quite complex and includes adsorption of metals onto the surface of a microorganism and/or into the cellular structure in combination with ion-exchange, complexation, and/or micro-precipitation. Bio-sorption is generally considered to be a rapid physical/chemical process. The cell wall structure is porous and allows metal ions, as well as large organic nutrient molecules, to pass freely through. Polysaccharides of the cell wall could provide binding amino, carboxyl, phosphate and sulphate groups. In addition to these functional binding groups, polysaccharides often have ion-exchange properties. Sometimes, bivalent cations, such as Ca2+ or Mg2+, help the formation of ionic bond bridges between the negatively charged cell surfaces and positively charged cations in the solution, Proteins in the cell wall could offer functional groups and also offer peptide bonds to bind ions. Interactions between metal and the cell wall components are responsible for the sequestering of metals by way of bio-sorption. Many metals feature a complex solution chemistry and it is not always possible to determine what ionic species are actually present in the solution. The equilibria involved are dependent on pH, concentration, the anions present and other factors. The transport system for the ions are sometimes dependent on both temperature and energy. Biosorbent material could also be regenerated for multiple reuse."

Jan 1, 1988

By P. R. Richardson

"Milling is the weak link in the process chain of many mineral operations. While this activity accounts for only a relatively small proportion of the direct costs of most mineral processing complexes, there are intangible and indirect costs associated with milling which are extremely large. For example, significant opportunity costs are associated with the relatively low yields which characterize this stage of the process.There are changes abroad in the world which I believe are going to cause us to reformulate the whole concept of milling. Increased competition in mineral markets are going to force managers to look anew at the high mineral values reporting to tailings which are a high opportunity cost for many operations. Tailings recovery plants are not the ultimate solution to this problem. Greater environmental concerns are going to increase the costs associated with tailings disposal and force the mining industry to look for other ways to dispose of waste products. Technology changes currently underway in manufacturing and other process industries, such as the automated 'lights-out' plant are going to be brought into this industry, and the changes will be dramatic.These are major long term changes which probably seem rather remote to many managers and professionals in existing operations which are faced with much more mundane challenges arising from day-to-day operations. However, I believe that milling is increasingly a 'lean and keen' operation involving fewer and fewer people, but who are increasingly skilled and professional. Traditional cost management approaches are no longer adequate and the industry has to take a new look at the nature of cost reduction in this core activity. This stage in the mineral process provides opportunities for value creation leading to a significant unit cost advantage for the corporations willing to adopt a total cost approach."

Jan 1, 1988