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By Jochen Petersen, Diane Taggart

"At an average of 90.3% (for the period of 1 January 2009 to 30 September 2011), Zincor’s zinc recovery was well below the industry standard of 96%. The losses through the residues, in particular the iron residue, were the biggest contributors to the overall zinc loss. It was believed that this loss could be decreased with the implementation of seed recycling. A plant trial was run to test the implementation of a seed recycle. The rate of seed addition through recycle was increased over a 4-week period. The presence of seed decreased the insoluble zinc loss by providing additional surface area for iron to precipitate onto, and reducing coating of unleached neutralising agent. The soluble zinc loss was also decreased at low and moderate seed recycle volumes. The improvement was attributed to agglomeration growth of the recycled particles, which improves the dewatering characteristics of the precipitate. In contrast, the soluble zinc loss increased at high seed recycle rates. This result was attributed to particle crowding and a low wash ratio.INTRODUCTION The Zincor refinery, which closed in December 2011, was situated just outside of Springs in the Gauteng Province of South Africa and employed the conventional Roast-Leach-Electrowin process, which accounts for 75 to 80% of the annual primary zinc production in the world. The refinery fed up to 220 000 t/a of zinc sulphide concentrate. The major portion of the raw material was sourced in Southern Africa from the Rosh Pinah and Black Mountain mines. Between 20 000 and 40 000 t/a of material was imported to make up the deficit and to improve the grade of the feed material. The iron contained in the zinc concentrates, at an average of 6.03% (for the period of 1 January 2009 to 30 September 2011), resulted in the formation of zinc ferrite during roasting, which is insoluble under atmospheric leach conditions. At Zincor, most of the zinc ferrite was dissolved in the residue treatment plant at elevated temperature and high acid strength. The leach liquor from this aggressive leach contained between 15 to 30 g/L of iron, mostly in the ferric form, and was known as the hot iron solution (HIS). The presence of iron in the liquor had an adverse effect on the zinc operation, particularly on the current efficiency in the electrowinning circuit. Therefore the iron needed complete removal."

Jan 1, 2016

By H. Al-Kazzaz

The 2-mm butt joints of ZE41A-T5 sand castings were laser welded using 1.6 mm EZ33A-T5 filler wire and a continuous wave Nd:YAG system at a power of 4 kW, surface defocusing and various welding speeds, Compared with the base metal, the fusion zone showed significant grain refinement due to high cooling rate, No grain coarsening was observed in the heat affected zone (HAZ). The porosity area percentage and total solidification crack length in the fusion zone (FZ) were reduced as the welding speed increased from 4 to 7 m/min, Fusion zone area, total penetration depth, and weld width decreased with increased welding speed, The hardness in the FZ was similar to or higher than the base metal after a natural aging of about one year, but there was a drop in the hardness of the HAZ, The HAZ width decreased with increasing the welding speed, Tensile test showed that a joint efficiency of approximately 75 ? 90 % was obtained.

Jan 1, 2005

By Eric Bain Wasmund, Lance Christodoulou, Julio Jairo Carmona Franco, María Fernanda Castillo, Jose Concha

"A number of technologies are in practice for selectively removing coarse gold from conventional grinding circuits. These circuits are often designed so that the grinding mill output is size classified, with large (or high density) particles being removed before the tails are returned to the mill. Because of the high relative SG of gold, and the fact that some forms of gold such as free gold do not break apart during conventional grinding, coarse gold can accumulate in the circulating load, and eventually be lost.Eriez has developed a flotation cell that uses fluidized water to enhance flotation of coarse particles. More than 40 units have been sold in industrial minerals, and we are now exploring applications for the HydroFloat® in the gold industry.Mineros S.A currently produces approximately 120,000 oz of gold per year by gravity concentrating alluvial gold ore with a mean particle size of 330 microns, followed by further concentration using a Falcon separator. A 400 mm diameter pilot-scale HydroFloat® was added to the tails of the Falcon to test whether additional gold could be captured. Enrichments of 50-600 times and recoveries normally in excess of 95% were achieved. This allowed direct smelting of the gold concentrate. Metallurgical results and operating parameters such as water addition and power will be discussed during the presentation.This result opens the possibility that the HydroFloat® could be used directly in the grinding circuit, for removing coarse gold in the circulating load. This work also shows the possibility that the HydroFloat® can produce a throwaway tail, which will reduce the size of the circulating load stream and the grinding requirements of the circuit."

Jan 1, 2015

By J. H. H. Chamberlin

"In the Introduction the author briefly discusses the company history as it relates to the development of its contracts with the Japanese steel mills. The main part of the text describes how Coleman Collieries Limited approached the problem of mining coal profitably in thick, steeply inclined seams. For many years a basic room-andpillar system was worked by conventional methods. Main roadways were driven on strike across the mineable area. These roadways acted as haulage routes for coal, materials and men. Rooms were developed to the rise of the main haulage route by pairs of men using air-operated hand picks. As these rooms advanced the miners would lay and extend a sheetiron chute down which mined coal would gravitate to a controlled loading point, where it was loaded into trains of mine cars. Connecting roadways or ""OFFS"" were driven at predetermined intervals between adjacent rooms, forming pil1ars or blocks. Extraction of the blocks followed on a line conducive to good strata control some distance behind the developing rooms. A need for higher productivity, expansion of the operations and a scarcity of qualified miners resulted in the company deciding to mechanize its underground mines. Joy 6 CM continuous miners and 10 SC shuttle cars were selected as being machines that could reasonably negotiate the problems associated with the pitching seam. The equipment, nonetheless, has definite limitations and Coleman therefore developed a modified version of the room-and-pi11ar system such that the miners and cars could work on cross pitch. In the area described, main roadways were driven to the rise on an average gradient of 12 degrees. Panels, which consisted of two parallel roads with interconnecting cross-cuts, were then developed on strike to a boundary point. Blocks formed in the development of the panels were subsequently extracted on retreat. Problems associated with each phase of the operation are thoroughly discussed, together with roadway support methods and equipment used for the conveyance of coal and materials."

Jan 1, 1972

By G. M. Hutt

Introduction The major development of industrial minerals in Manitoba has been in building materials. 'The building-stone industry is developed far beyond the needs of the Province, and the well known Tyndall limestone is marketed over a wide area throughout the other provinces to Canada. Similarly, gypsum and gypsum products are produced in excess of local requirements and are exported to adjacent provinces. The crushed-stone, sand and gravel, limestone, and lime industries are sufficiently developed to supply the needs of the Province and, notably in the case of lime and lime-stone, there is a surplus for export to the adjacent provinces and to the United States. The manufacture of common brick is well established, but for face-brick and other clay products the Province is dependent largely on importations. Production of silica-sand will increase as Canadian markets become available through recognition of the utility value of the Black Island sand as foundry-sand and for other purposes. There is some possibility of the export of feldspar, of lithium ore and concentrates, and perhaps of salt. A considerable part of the Province has not been seriously prospected for industrial minerals and it may be expected that, as time goes on, other deposits of non-metallic minerals will be discovered and opened up, especially as the prairie provinces become more industrialized. At the present time, there is some activity in the southern part of the Province based on gas and oil indications. Whatever may be the outcome of this work, it should yield valuable information concerning the geological structure of the area.

Jan 1, 1934

By The Staff

FOR forty years cyanide men have been intensively engaged on the treatment of sulpho-telluride ores. So far as we know, the processes used today were-with the important exception of the concentration plus high-lime process at the Victor mill (1915)-in use, or had been tried, in the earl y years of the century. Roasting, bromocyanide, ordinary cyanide, table and vanner concentration, floating and treating the concentrate, roasting con-centrates prior to treatment, etc., all were used at Kalgoorlie in 1904 or earlier. Flotation, followed by shipment of the concentrate to the Golden Cycle mill, was the practice at the Vindicator mine, Cripple Creek, for some years prior to 1917. Similar practice was employed in the Portland Independence mill at Victor, Colorado, and was lacer superseded by the table concentration, high-lime cyanide treatment of rails of the older Portland Victor mill. During all this time, an immense amount of research was being clone on these ores by the staffs of numberless companies. Conclusions were drawn and mills built. But if the results of one per cent of this research were ever published in sufficient detail for intelligent use by others, the Lake Shore staff has been unable to discover them, or does not recall having clone so. Government laboratories-as for instance chose of the Mines Branch, Ottawa, in or about 1927-have touched upon certain methods in their publications, but they simply have not had the time to finish the job. The paper by W. E. Johnston, Tellurides-Problem or Alibi? (E. & M.]., Aug., 1933), aroused wide interest and comment. It published conclusions, some right and some wrong, and gave the evidence adduced by the author i:n support thereof. Conclusions published without supporting evidence are to most of us worse than no conclusions at all. We suggest chat, if even one-tenth of the operators had published full, detailed results of their laboratory work, ad vance in the treatment of sulpho-telluride ores would have been very much accelerated. Therefore, we venture to inflict upon the Institute a compendium of the results of laboratory work performed during the past few years at the Lake Shore mill. It is really a summary of the more interesting results to date, prepared by the mill staff for their own use and benefit. But we hope chat the discussion under any heading is so detailed chat it will be intelligible to anyone interested in that phase of the subject.

Jan 1, 1936

By Milton C. Graves, Marcos Zentilli

"Gold has been reported from most geological environments in Nova Scotia; however, virtually all production (circa 2,000, 000 troy ounces; circa 60 tonnes) has come from that part of the province to the south of the Glooscap Fault which is underlain by Lower Paleozoic rocks of the Meguma Group. Over fifty concordant sets of quartz-carbonate-arsenopyrite veins have seen production. The host rocks are greenschist-grade equivalents of Cambro-Ordovician flyschoid quartz wackes and shales folded and metamorphosed during the Devonian Acadian Orogeny. The veins were emplaced under conditions of greenschist-grade regional metamorphism and under the same conditions of tectonic stress that later resulted in the regional folds and penetrative, axial-plane slaty cleavage. Rapid filling of hydraulic fractures caused by excess metamorphic pore fluid pressure under Acadian tectonic stress conditions can account for the geometry and paragenesis of these veins.The ultimate source for gold deposits in most greenschist-grade domains remains in doubt, but these domains seem to have had ample gold within them available for mobilization. The work done, to date, on the gold geology of Nova Scotia suggests that regional greenschist metamorphism was an effective mobilizer and a potential concentrator of Au, As, W, Fe and S from these vast reservoirs.In rocks of pre-Acadian age north of the Glooscap Fault, gold occurs as an important accessory in volcanogenic massive sulphide ore, as a minor constituent in other types of basemetal concentrations and in one small concordant group of quartz veins.The post-Acadian metallogenetic domain, which overlies and overprints the two older domains, contains small amounts of gold in many mineralizing environments. Veins, with stibnite and gold, cross-cut crystalline rocks. Disseminated gold is present in basal conglomerates of post-tectonic molasse. Gold has been a by-product of Mississippi Valley-type Pb-Zn-Ba-Sr deposits in Lower Carboniferous sedimentary rocks and has been reported with Pb-Zn-Ba-F in veins which cross-cut Lower Carboniferous and older rocks. Small post-glacial placers have also seen minor production."

Jan 1, 1982

By Francis W. Gray

Introduction Extensive undersea coal-mining has developed on both the east and west coasts of Canada, and at this time some four million tons, or 25 per cent of the total output of Canadian coal, representing a pit-mouth value of $14,000,000 per annum, is coming from coal seams lying under the sea. Of the coal now being mined in Nova Scotia, 55 per cent comes from under the sea, and this proportion is likely to increase. The Province of Nova Scotia is at this date receiving in royalties paid upon coal ?removed from undersea areas a sum exceeding $400,000 per annum. The subject is, therefore, one of special interest to the Mining Society of Nova Scotia and the Canadian Institute of Mining & Metallurgy, and while this paper will deal chiefly with undersea coal-mining in Nova Scotia, an attempt has been made to summarize the development of mining practice in the winning of undersea coal in other parts of the world, with the hope that such a recital may assist in the assessment of local problems. The connection between the mining of coal under the sea and an insular or maritime geography is obvious in regard to Great Britain, Japan, Vancouver Island, Australia, and Cape Breton Island, and also in regard to the curious conformation of Chile; the tendency towards growth of a mercantile marine and naval eminence is equally obvious where coal is mined at tidewater. But, there is the further and less favourable significance that the mining of coal under the sea is associated with poverty rather than with abundance of coal reserves.

Jan 1, 1927

By Zachary Mayer

Agenda ? Kidd Mine ? Background ? Problem & Opportunity ? Challenges associated to depth - Production Rates - Productive Work Time - Operational Delays - Transfer Levels - Mucking Time - Impact on Hoist ? LHD Automation ? Sandvik AutoMine Lite ? Expected Benefits Kidd Mine - Background ? Located in Northern Ontario, Canada ? Underground base metal mine operating since 1966 ? Total 148 Mt mined (2.31% Cu, 6.08% Zn, 75 gpt Ag) ? 2.35 Mt/Y from stopes as deep as 9500 ft (2.9km) below surface ? Mining method: blasthole open stoping ? Mine/Mill: 1263 employees and contractors ? 2012 National John T. Ryan Safety Award

Aug 1, 2013

By Rodrigo Toro, Mario Delisle, Claudio Zamora

"The mining market is researching innovative methods to train the workforce for mining which is normally extremely difficult to get. Thus, the dynamic simulation-based technologies become an essential pillar to educate and train the inexperienced staff at the pace required by this industry. Even if Operator Training Simulator (OTS) systems are commonly used in most of industries, knowledge transmitted to operators are unfortunately not ""capitalized"" in general. The OTS systems are usually delivered as a single hardware and software platform and very little as a full service long-term.In this article, an integrated solution to increase the efficiency of the operators is proposed. This solution is based on the combination of dynamic simulation, processes knowledge, virtual reality and the knowledge capitalization through the creation of simulation scenarios and e-learning. The Codelco Ministro Hales plant simulation project for a copper concentrator plant is presented as a real life example.IntroductionDynamic and real-time process simulation have proven to be a must in the development of greenfield projects, providing mechanisms to design and test controls design, interlocks, start-up, shut down sequences and operator training, among others (see (McMillan, 2006) for further details). Early adopters of this technology were utility power plants; in the petrochemical industry have become a standard, and in the mining industry the use of dynamic simulations is growing, especially in new projects and training of operations personnel for the adoption of best practices and new technologies, see (Nikkhah & Anderson, 2001) and (Toro, Ortiz, & Yutronic, 2012).This paper outlines a solution that utilizes dynamic simulations as the base of an integrated platform for operational effectiveness, which takes into account the current scenario of new mining projects and operations, where high turn over rates and needs of specialized workforce have given a special value to this kind of technologies."

Jan 1, 2015

By Adrian Daniel

"Dating back to 1934, Con Mine is located directly south to the city of Yellowknife in the NWT, Canada. With mill operations ceasing in 2004, a challenging surface remediation situation resulted which required the treatment of close to 40,000 m3 of Arsenic impacted material.Through much of the period of 1941 to 1970, Con Mine treated their refractory arsenopyrite ore through the use of an Edwards Heath roaster. With mounting environmental pressure and through Canadian governmental studies during 1950 to 1970, attention was directed to the Arsenic Trioxide material being collected by two Doyle scrubbers on the Con’s roaster stack. In 1970, the roaster was decommissioned leaving the resulting Arsenic material in two containment areas on surface.As a result of Con Mine entering into remediation in 2004, the Con’s autoclave, commissioned in 1992, was dedicated to the immobilization of high impacted Arsenic material through the combination of excess Iron under high temperature and oxygen overpressure. Examined, herein, is the history and chemistry of the Con Mine autoclave as well as the two stages of chemistry for the Water Treatment Plant used to remove arsenic, heavy metals and WAD cyanide from tailings water. Simplified capping plans of the tailing containment areas and a high arsenic impacted area are also presented.INTRODUCTION TO CON MINECon Mine (Con) is situated just south of the City of Yellowknife in the North West Territories (NWT) Canada and is bounded locally by Yellowknife Bay (North Extension of Great Slave Lake) to the east and Kam Lake to the west (Figure 6). The discovery of gold at Con was made in 1934 and mineral rights were acquired by Consolidated Mining and Smelting Limited (Cominco) and Falconbridge soon thereafter. Nerco Minerals Limited (Nerco) took control in 1986 and in 1993, was subsequently sold to, Miramar Mining Corporation which in turn was purchased by friendly takeover involving Newmont Mining in November 2007 as a result of acquiring the Miramar’s Hope Bay project. Con’s underground operations ceased in September 2003 and have since entered into the remediation of the site. The current surface lease holdings are about 340 Hectares (Table 1) which sits on top of the Archean-aged Yellowknife Greenstone Belt."

Jan 1, 2009

By H. Lachmund, R. Bruckhaus

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

Jan 1, 2005

By P. J. Gron

"The Samatosum Project is a base and precious metal deposit located in south central British Columbia. A dilute ore reserve of 766, 682 tonnes grading an average 1.1% copper, 3.0% zinc, 1.4% lead, 833 gram per tonne silver and 1.6 gram per tonne gold is available. The base metals occur as tetrahedrite, chalcopyrite, sphalerite and galena. Virtually all of the silver and gold are associated with the tetrahedrite.The mill is operated at a rate of 21 tonnes per hour. Sulphur dioxide is used as a zinc depressant in the grinding circuit. Production of a Cu/Pb/Ag concentrate is accomplished by conventional flotation. This concentrate is then separated into Cu-Ag and Pb concentrates through a reverse flotation circuit utilizing sulphur dioxide, starch and sulphuric acid as lead depressants.The tailings from the Cu/Pb/Ag circuit are treated with copper sulphate to activate the zinc. Production of a zinc concentrate is accomplished by conventional flotation. Dewatering of the concentrates to 6% moisture is done with a LAROX filter press.Tailings effluent is treated with lime and sodium sulphide to precipitate out the heavy metals. The resulting sludge is treated in OYNASAND sand filtration units to produce a quality effluent."

Jan 1, 1990

By Nn Li

Energy consumption in commercial buildings has been increasing rapidly in the past decade. The knowledge of future energy consumption can bring significant value to commercial building energy management. For example, prediction of energy consumption decomposition helps analyze the energy consumption patterns and efficiencies as well as waste, and identify the prime targets for energy conservation. Moreover, prediction of temporal energy consumption enables building managers to plan out the energy usage over time, shift energy usage to off-peak periods, and make more effective energy purchase plans. This paper proposes a novel model for predicting heating, ventilation and air conditioning (HVAC) energy consumption in commercial buildings. The model simulates energy behaviors of HVAC systems in commercial buildings, and interacts with a multiagent systems (MAS) based framework for energy consumption prediction. Prediction is done on a daily, weekly and monthly basis. Ground truth energy consumption data is collected from a test bed office building over 267 consecutive days, and is compared to predicted energy consumption for the same period. Results show that the prediction can match 92.6 to 98.2% of total HVAC energy consumption with coefficient of variation of the root mean square error (CV-RMSE) values of 7.8 to 22.2%. Ventilation energy consumption can be predicted at high accuracies (over 99%) and low variations (CV-RMSE values of 3.1 to 16.3%), while cooling energy consumption accounts for majority of inaccuracies and variations in total energy consumption prediction.

Aug 1, 2013

By A. Golabchi

Building Information Modeling (BIM) is an increasingly popular method for generating and managing facility information during the life cycle of a building, ranging from facility conceptualization, through design, construction and its operational life. Organizations involved in Facility Management (FM) have the opportunity to use BIM as a knowledge repository to document evolving facility information and to support decisions made by the facility managers during the operational life of a facility. This paper demonstrates the potential of using BIM to develop algorithms that automate decision making for FM applications. The potential of utilizing BIM as an analysis tool is demonstrated through the scenario of HVAC (Heating, Ventilation, and Air Conditioning) system failure in an operating facility. In case of a typical HVAC malfunction today, facility occupants record complaints in a ticketing database maintained by the FM organization. Upon receiving notification of HVAC system failure, facility inspectors visit the location to confirm the reported failure. Upon confirmation, facility managers review building plans and specifications to develop a detailed plan of action to repair any HVAC components suspected of damage. Based on the plan of action, inspectors visit the facility to inspect and, in case of damage, repair the appropriate HVAC system components. These FM practices ? as currently implemented across the industry ? are labor intensive, time consuming, and often rely on unreliable and outdated information. To address these shortcomings, the authors propose an alternative methodology of HVAC fault detection in operational buildings. The authors implement an algorithm that leverages complaint ticket data and automates BIM to determine potentially damaged HVAC system components. Based on the list of HVAC components suspected of damage, the algorithm develops a plan of action for the facility inspectors. Finally, the authors discuss the advantages of the proposed method as well as the challenges of implementing automated BIM-enabled decision making processes in the FM industry.

Aug 1, 2013

By T. R. Ellis

The valuation of mineral properties in the U.S. is only partially regulated. The regulations which have jurisdiction or impact appear to have such mainly as a consequence of unintended fallout, since the regulations were designed for other purposes. Court case history can also be important. The combined results are a mixture of bad and good, with important lessons to be learned. Since 1981, the Securities and Exchange Commission has prohibited U.S. listed companies from reporting quantitative estimates of mineralization and the value of mineralization, other than proven and probable reserves. This results in the minerals appraiser (valuator) working with a shortage of data in his everyday work, both on the subject property and in sales analysis. Between 1989 and 1995, all 50 states and essentially all federal agencies adopted the Uniform Standards of Professional Appraisal Practice (USPAP) for real property appraisals (valuations). The major national appraisal societies also require their members to abide by USPAP. A significant portion of minerals appraisals must now follow these standards. This paper will discuss the content of USPAP. It provides a very good framework for the valuation of a minerals property or a mine, both as real property and as a business. However, the credentialing standards for real property appraisers are now prohibitive for minerals appraisers.

Mar 1, 2002

By T. R. Ellis

"The valuation of mineral properties in the U.S. is only partially regulated. The regulations which have jurisdiction or impact appear to have such mainly as a consequence of unintended fallout, since the regulations were designed for other purposes. Court case history can also be important. The combined results are a mixture of bad and good, with important lessons to be learned.Since 1981, the Securities and ExchangeCommission has prohibited U.S. listed companies from reporting quantitative estimates of mineralization and the value of mineralization, other than proven and probable reserves. This results in the minerals appraiser (valuator) working with a shortage of data in his everyday work, both on the subject property and in sales analysis.Between 1989 and 1995, all 50 states and essentially all federal agencies adopted the Uniform Standards of Professional Appraisal Practice (USPAP) for real property appraisals (valuations). The major national appraisal societies also require their members to abide by USPAP. A significant portion of minerals appraisals must now follow these standards. This paper will discuss the content of USPAP. It provides a very good framework for the valuation of a minerals property or a mine, both as real property and as a business. However, the credentialing standards for real property appraisers are now prohibitive for minerals appraisers."

Jan 1, 2002

By Daniel Hodouin, Claude Bazin

"A graphical method to assess the size reduction by grinding is presented and illustrated with data collected from laboratory grinding tests and industrial grinding circuits. The method lies between the graphical comparison of size distributions and the population balance model. The method is easy to apply and provides a quick way to compare grinding mill performances under various operating conditions and processed ores. The application of the method to industrial mills shows that a grinding mill operation could present an invariant behaviour that can be exploited for simulation purposes.INTRODUCTIONThe size reduction of particles by grinding has been studied for decades and several books were published on the subject. Most of the recent studies focus on the modelling of the ball, semiautogenous and autogenous grinding mills operation (Napier-Munn et al., 1996) because accurate simulators can be used for design, optimization and control. Although the development of realistic simulators is progressing, the trial and error method is still used by many operators to identify optimum operating conditions for a grinding machine.Laboratory tests allow the characterization of the material submitted to grinding and the analysis of various operating conditions, such as ball size or shape, mill speed and slurry concentration of solids, on particle size reduction. Similar tests can be conducted in a plant, but results are often difficult to analyze due to errors associated with sampling and sensor accuracy. This paper presents a graphical method to assess the degree of size reduction carried out by a grinding machine. The paper consists of three sections. The first section describes the method and the following sections illustrate the method with data taken from laboratory and industrial grinding machines."

Jan 1, 2004

By J. P. Cooney

Placer Dome is learning from experience in Latin America, Asia and Africa, as well as in North America, that contributing effectively to sustainable human progress in the areas of its operations presents unending challenges to think creatively, communicate effectively and remain culturally sensitive. People must be better off in terms of their economic circumstances, their social conditions and the quality of their natural environment not only during the life of the mines, but after mines close. Stakeholders, all those who are directly or indirectly affected by a mining project, should be able to participate in decisions which affect them. The development of sustainability strategies, the monitoring of sustainability performance and the implementation of sustainability programs are best done in partnerships with governments, communities, nongovernmental organizations and multilateral development institutions. Ultimately, the success, if not the survival of mining, will depend on our ability to get the sustainability equation correct.

Jan 1, 2000

By Michel Brissette

"To recover more valuable ore and considering the complexity of minerals, the needs to grind finer is increasing. To reach the desired fine grinding targets, using the existing grinding media size, the energy consumption is increasing exponentially. As already proved at this conference, small grinding media represents the best potential to improve grinding efficiency. How do the small grinding media perform in industrial grinding mills?The use of small grinding media in regrind mills proved that finer grinding can be achieved at lower energy consumption. In ball mills, smaller grinding media versus 25 mm media generate a power saving from 10% to 44%. In vertical stirred mills, the power saving increases from 20% to 60%. More potential savings have been identified.For the same operating conditions, how a vertical stirred mill is performing compared to ball milling? In regrind application, a vertical stirred mill with small media (5-12 mm Millpebs) will require at least 62% less energy than a ball mill charged with 25 mm grinding media.INTRODUCTIONIn some mining applications, fine grinding is needed to liberate further the valuable ore. The purpose of regrind mills is to achieve the last stage of grinding before final flotation stage: the cleaners. In part because of high prices of small grinding media as well as availability, the most widely used size of grinding media is 25 mm.When calculating the recommended ball top size from Bond’s formula (Bond, 1961), the size for regrind applications is much lower than 25 mm. Today, the barrier for small grinding media is broken. They are best suited in regrind application. The size of grinding media is one of the most important variables affecting the mill efficiency (McIvor, R., 1997; Nesset, J.E., Radziszewski, P., Hardie, C. & Leroux, D.P., 2006).Conventional ball milling was discarded for fine grinding because of its very poor energy efficiency (Zheng, J., Harris, C.C. & Somasundaran, P., 1994; Yan, D.S., Freeman, M. & Dunne, R., 1995). Therefore, new technologies as stirred mills were developed to grind finer more effectively. Three fundamental questions should be asked. What is the best fine grinding technology? What should be the best media size to use? Is it possible to grind finer by using less energy with the existing regrind equipment?"

Jan 1, 2009