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By John Folinsbee, Brian Danyliw, Tony Y. Chong

"Control of fugitive dust has become increasingly important in the mining industry both from a health and safety and environmental standpoint. Mining operations in particular have required improved fugitive dust control due to recent lowering of the allowable airborne silica concentration to which workers can be exposed. Experience has now proven that the implementation of a surfactant based chemical dust suppression system can enhance existing mechanical dust control methods resulting in much more efficient control of fugitive dust.The Porcupine Joint Venture (Dome Mine) utilizes dry secondary crushing and screening that makes it particularly prone to fugitive dust emissions. A variety of potential dust control systems were evaluated and this led to the installation of a surfactant based water spray system to augment the existing mechanical dust collection systems.A great deal was learned through the implementation of this system. This paper describes the entire process, from testing, system design and installation, through optimization and standardization of operation. In addition a variety of problems were identified, and innovative solutions were provided. Also, the metallurgical impacts on down stream processing are highlighted. Finally, a full discussion of overall results including a discussion of the relationship between silica and total dust concentrations is included."

Jan 1, 2005

By G. K. Mann

Fragmentation analysis of blast or crushed rock material is a time-consuming and costly process. During the last two decades, the mining industry has been investigating image-based analysis systems as an alternative to generate fragmentation results. Many image-based techniques and commercial products have emerged during the last few years, and the mining industry has recently begun using these tools for real-time estimation of size distributions. Some existing systems require manual image editing to add or delete edges (or net) before executing the fragmentation analysis routine. This manual procedure may take hours of time for each image analyzed. Reliable and robust image segmentation should be able to handle a wide range of rock textures and sizes under a variety of lighting conditions. This paper describes a novel software application, which has the capability to autonomously capture images and analyze them to generate the particle size distribution. The system can also process a batch of images captured during a fixed duration of time and produce the overall particle size distribution. The new method has different layers of segmentation modules, which allows the system to operate under a wide range of rock textures and lighting conditions. A new grey-level slicing technique is developed which can perform under a range of illuminating conditions. The Canny-based edge detection technique is used to segment rocks appearing in dark regions.

Jan 1, 2006

By Frank B. Amon

Highland Valley Copper had to make some significant changes in the way it was working in order to counter the effects of ever-increasing costs and decreasing metal prices. A mine/mill optimization plan started in 1997 introduced new technologies and management approaches that resulted in a dramatic drop in cash breakeven costs. The changes involved employee training, added authority and responsibility for staff, better communications, and a consistent approach to setting and achieving property-wide goals. The net effect was to change the culture of the organization from one that was fragmented and focussed on local objectives to one that is cohesive and has common goals. These changes have allowed the mine to remain in business during a protracted period of low metal prices, and have positioned the mine favourably to benefit even more from any future increase in prices.

May 1, 2004

By Leslie F. Sawatsky

Each potential oil sands developer deals with the question of optional sources of raw water to supply large water demands that range from 50 to 80 million cubic metres per year for each of six existing and planned developments. The Athabasca River currently supplies nearly all of the water to the existing mines via conventional bank intakes, which has resulted in some concern over the effects of reduced river flows. This paper describes the various water supply options, and the likely scenario for future oil sands water supply projects. Various water supply options have been suggested including Athabasca River water via infiltration galleries, groundwater, combined Athabasca River water and alluvial groundwater using wells (i.e. bank filtration systems), diversion of tributary rivers, utilization of large lakes in the region and pumping from other large rivers in the region. Investigations show that the size of river catchment needed to support raw water usage by a typical oil sands mines exceeds 5,000 km2 eliminating all tributary rivers that are located in the oil sands region except those rivers with large drainage areas like Firebag and MacKay Rivers. Lakes cannot be used as a source of supply due to large water deficits for smaller lakes and the large cost of sourcing water from a lake as large as Lake Athabasca. A groundwater source alone would not likely meet the large water demands. River intakes on the Athabasca River will likely continue to be the most practical water supply option for oil sands mines north of Fort McMurray, although various types of Athabasca River intakes are possible. Existing intake systems include screened riverbank intakes, forebay intakes, and river bottom intakes. Infiltration galleries are not feasible for most sites, though some bank-filtration-type systems using high capacity wells may be an option if there is sufficient thickness of high-permeability alluvium at a suitable location in the Athabasca River valley.

May 1, 2004

By Dale Dean, Bill Hancock, Raul Mondragon, Carlos Aguilar, Chris Martin

"In 1942, commercial mining operations began in what is now the Lucky Friday Ag/Pb/Zn mine in Idaho’s Silver Valley. Wholly owned since 1962 by Hecla Mining Company, the mine has produced more than 145 million ounces of silver and has been a mainstay producer in Idaho’s Silver Valley for over 70 years.However, by the early 21st century, the mill had fallen, technologically, seriously behind the rest of the industry. Accordingly, starting in 2005, the current mill management team set to revitalizing the milling operation. This paper will describe how the mill was systematically evaluated and the aging infrastructure replaced with more current technology. Driven by internal mill review studies supported by QEMSCAN mineralogical balancing, the mill has in recent years been through waves of upgrading – from the installation of new mechanical and column flotation equipment to the introduction of on-stream analysis, a technology well-accepted around most of the industry but alien to this technologically conservative mining district.The experience at Lucky Friday is a testament to the need for ongoing structured mill optimisation and technology upgrading in established mining operations. This paper will describe engineering experiences associated with upgrading equipment in an operating mill, contained in a confined building. Experiences in teaching the team new ways of operating a mill, and finally the metallurgical rewards that have been reaped will be described.INTRODUCTIONMining in Idaho’s Silver ValleyIdaho’s Silver Valley is a 64-km long valley flanked by the US Northern Rocky mountains, seldom more the 3-km wide, and stretching across much of Idaho’s northern panhandle, roughly 150 km south of the Canadian border. Mining has been continuously active in the area for more than 140 years, during which time, the Silver Valley has become one of the richest silver producing districts in the world, and as of 1985 had out-produced the 500 years of production from the famed Potosi district in Bolivia. Since 1885, almost 100 deposits have been discovered and worked in the district (Chapman, 2000)."

Jan 1, 2011

By K. U. Kainer, A. Stark, D. Tolnai, M. Hehenberger, C. L. Mendis, N. Schell, N. Hort

Samples of an as extruded Mg-6Zn-0.6Zr-0.4Ag-0.2-Ca (wt.%) alloy was compressed at room temperature and at 250°C. The in situ deformation tests were performed at the P07 (HEMS) beamline of PETRA III, DESY, with a modified DIL 805 A/D dilatometer with to Kapton windows on the sides and the induction coil opened for the beam to transmit the sample. The deformation rate was 10-3 s-1 the samples were deformed to failure. The diffraction patterns were recorded every 3 s with a Perkin Elmer 1621 Flat Panel Detector. The results reveal that different deformation mechanisms are activated during compression at a given strain value. At room temperature twinning is the dominant deformation mechanism, while at elevated temperature dynamic recrystallization occurs while the contribution of twinning to deformation is significantly reduced. The compressed samples were further investigated with conventional metallography and SEM-EBSD to determine the volume fraction, the type of twinning and the strain retained within the grains. The parallel testing of pure Mg samples under the same conditions allows comparison of the compression behaviour of the ZKQX alloy with Mg.

Jan 1, 2014

By Tony Lipiec, Chris Fleming, Larry Urbanoski

In 2009, the Canadian Mineral Processors (CMP) became aware that Canadian securities regulators were amending the contents of National Instrument 43-101. NI 43-101 is a set of regulations which establish how ore resources and reserves are presented to the investing public. The documents produced under NI 43-101 are central to the ability of many companies to raise financing for their projects. With the increase of metallurgical complexity, and decrease of head grades encountered in new deposits, the role of the Qualified Person (QP) in determining process performance has become increasingly critical in determining the classification category of resources and reserves. Given the challenges confronted by those involved in defining the concentration and extraction of minerals and metals, there is a need to provide support to these QPs. To address these concerns, the CMP established a sub-committee in 2010 to create a set of guideline documents to assist the QP involved in process matters as to what should be included at the various levels of study supporting the establishment of resources and reserves in NI 43- 101. The results of the sub-committee work are presented and the considerations in the writing of the documents are discussed.

Jan 1, 2011

By Seppo Haapamaki

"Since it started production in 1970, Anderson Lake Mine has experienced several radical changes in mining methods as a result of the physical characteristics of the ore zone along with the need for improved productivity. This paper examines the transition from longhole open stoping to mechanized cut-and fill then to vertical crater retreat at Anderson Lake Mine. The reasons for the need to change mining methods is analyzed taking into consideration the impact of such criteria as improved productivity and ground conditions and how these criteria affected the over-all economic viability of the mine. IntroductionAnderson Lake Mine is one of five producing copper mines in the Snow Lake area and is situated approximately 3 km southeast of the townsite of Snow Lake (Fig. I).The mine production rate at Anderson Lake is 700 tpd and all ore is trucked from the mine to the mill located approximately 2.5 km from the mine site . The mine is serviced by a three-compartment shaft sunk to a depth of 3300 ft with level spacings at 175 ft and 150 ft intervals from the 600 ft level to the 3000 ft level. .The shaft was collared in 1965 and, a year later, the hoist and compressors were installed. By 1969, a crusher system had been built and actual production began in 1970. During 1978, production was suspended for the year to allow for 430 ft of shaft deepening."

Jan 1, 1988

Plan de l?exposé ?? Présentation du site de la mine Restigouche et du mandat confié à Genivar ??Dénoyage de la mine ??Processus d?enlèvement des boues au fond de la fosse ??Utilisation de Géotubes dans le procédé à l?usine de traitement des eaux.

Feb 1, 2008

By Norman O. Lotter

The problem of quantifying the full performance potential of an ore body in a concentrator, and how to configure a flowsheet to achieve that potential, either for a new operation or an existing one, is a strategic challenge. Modern flowsheeting technology that has been developed over the last twenty years has provided a suitable platform to achieve this. The integrated use of geology, compositional and quantitative mineralogy, sampling models, quality controls, and mineral processing, including flotation testing, has evolved into what is now called process mineralogy. Two specific tools have been developed and validated as standard methods in this toollbox. These are statistical benchmark surveying and high-confidence flotation testing. Both of these have borrowed from the sampling theories of Pierre Gy and from geostatistics. Additionally, they work on a replicate measurement and averaging basis, thus reducing the overall random error level. With this arrangement, one is in a position to characterize the ore from true samples and identify and quantify the economic minerals present in a manner that easily brings out the processing implications and likely grades and recoveries. In particular, the approach captures the variation in the ore body, which, if properly translated into the flowsheet design, minimizes the risk that unexpected responses will develop in the concentrator operations. A further advantage is that successful plant trials are now possible and practical. An overview of this approach is presented with two case studies.

Jan 1, 2011

By Carl Bertrand, Patrice Nadeau, Claude Bazin

"Rio Tinto Fer et Titane processes the ore extracted from the Lac Tio orebody to concentrate the hemo-ilmenite (FeO.TiO2-Fe2O3) mineral that is subsequently smelted to produce pig iron and titanium oxide slag. The ore is crushed, heat treated (roasted) and concentrated using dry magnetic separators. This paper describes a model to predict the magnetic susceptibility of the roasted ore and its behaviour in the magnetic separation plant. The model uses a classification of the ore as a function of the size and magnetic susceptibility of the particles. A subsequent division into mineral species allows the simulation of the magnetic separation process. The model is used to assess various operating options when process disturbances occur.INTRODUCTIONOre processing operations consist of ore size reduction followed by the recovery of valuable species in a concentrate that is subsequently sold for its minerals or metal content. The concentration processes are based on the physical and/or chemical properties of the minerals contained in the ore. Flotation is typically used to recover minerals of base metals such as copper, zinc, lead or nickel. Iron ore and other dense minerals are typically concentrated by gravity separation processes. Magnetic separation uses the magnetic properties of the minerals to concentrate magnetite and other minerals, to clean coal concentrate and to recycle ferrosilicon for dense separation processes (Brophy, 1985).Magnetic separators can be divided into low and high intensity separators and high gradient magnetic separators (Gillet, 2008). Most of the low gradient magnetic separators are built as rotary drums that are operated in wet or dry conditions. Dry magnetic drum separators are used by Rio Tinto Fer et Titane in Sorel-Tracy, Canada to concentrate hemo-ilmenite from the ore extracted at the Lac Tio Lake mine near Havre St-Pierre, Canada. The analysis of production data suggests that process improvement could be achieved by identifying key variables for the control of the magnetic separation circuit and/or by modification to the circuit flowsheet. The use of a process model was considered to be an effective approach to conduct a preliminary analysis of the circuit with a view toward process optimization. However, the literature contains few detailed studies dealing with the modelling of magnetic separation processes."

Jan 1, 2011

"The Key Lake mill was commissioned in 1983 to process the two Key Lake ore deposits. With the depletion of these ore bodies in 1999, the plant was converted to mill the exceptionally rich McArthur River deposit located seventy eight kilometers northeast of the Key Lake mine site. This paper describes in detail the Key Lake milling process. The mill consists of a grinding circuit, a leachkounter current decantation circuit, a solvent extraction circuit, a yellowcake precipitatiodcalciner circuit, an ammonium sulphate crystallization circuit, and a waste treatment circuit. The paper also describes process changes to handle McArthur River ore, including the ore receiving stationLOCATIONThe Key Lake mill is located 78 kilometres south of the McArthur River mine. It is located at latitude 57' N in northern Saskatchewan, within the southern boundary of the Athabasca formation. The nearest town is Pine House, located 240 kilometres to the south. Access to the mine is by an all weather road and by a private airstrip.HISTORYAND DESCRIPTION OF OPERATIONThe Key Lake mill was commissioned in October 1983 to process ore from the Gaertner and Deilmann ore bodies. The mill was designed to produce twelve million pounds of uranium oxide (U308) a year from a feed grade of 2.4% U3O8.Following grinding, the uranium is leached in a two stage leach circuit using oxygen and sulphuric acid. An eight-thickener counter current decantation (CCD) circuit is used to separate the uranium bearing solution from the solid waste residue. The uranium is further purified in a solvent extraction circuit and then precipitated using ammonia. It is then calcined at 840' Celsius, and packaged into drums for shipping to refineries. There is a crystallization circuit to recover ammonium sulphate produced in the process and a waste treatment circuit."

Jan 1, 2001

1. Scope of project In South Australia, the Western Mining Corporation operates the underground copper and uranium mine Olympic Dam. The deposits concerned are enormous (approx. 570 million tons) and have been mined since 1988. At the end of 1996, Western Mining decided to increase the capacity of Olympic Dam from 85,000 t.p.a. to 200,000 t.p.a. Planning At this point, SIEMAG-GHH Mining Division was asked to carry out a study including the planning of the entire shaft hoisting operations and calculation of the investment and operating costs involved. With the assistance of Australian partners, the study was completed within a single month. The principal points of the study were as follows: ? Planning of the hoisting machinery for 1,375 tons per hour from the surge bin below ground to the discharge bunker above ground. ? Optimisation of the hoisting operation with regard to maximum availability and safety. ? Optimisation of the time schedule to minimise the financing costs of the investment. ? Statement of the investment and operating costs. ? Comparison of the technical data, design and availability of the planned machinery with reference plants. Construction of the plant Following acceptance of the study, the decision was taken within a few weeks to implement it. SIEMAG Transplan GmbH received the order to execute the entire shaft hoisting machinery on the basis of the study submitted. The decisive factors in placing the order were: ? Convincing study, adherence to schedule ? Reference to comparable plants elsewhere ? Reference with regard to availability.

May 1, 2003

By R. A. Bergman

"Process descriptions are provided for the following ten plants that treat high-magnesia lateritic nickel ores (saprolite) by pyrometallurgical means: PT Aneka Tambang; Cerro Matoso S.A.; Falconbridge Dominicana C. por A.; Hyuga Smelting Company Ltd.; Larco (Societé Minière & Métallurgique de Larymna); Loma de Niquel; Le Nickel, SLN-Eramet; Nippon Yakin Kogyo Company Ltd.; Pacific Metals Company Ltd.; and PT Inco Indonesia.Flowsheets, equipment information,chemistry and production data have been compiledfor plants based on both information providedby the companies and on calculated massand energy balances.IntroductionNickel is of vital importance to modern society. Without it, we would not be able to enjoy many of the things that we take for granted, such as computers, airplanes and stainless steel appliances in our homes and workplaces, to mention a few.Nickel occurs in nature both as sulphide and oxide ores. Approximately 36% of the nickel reserves in the Western World occur as sulphide and 64% as oxide ores. Sulphide ores respond to concentration processes, whereas, oxide ores do not. Sulphide ores mined at 1% nickel can be readily concentrated to 10% nickel, whereas, oxide ores cannot be concentrated and therefore have to be processed as mined.Laterite ores are normally classified intotwo groups:1. The high-magnesia ores, saprolites or serpentines, are, as a rule, processed by smelting. The main reason for this is that the nickel replaces magnesium in the magnesium-silicate lattice. To be able to recover nickel, the lattice has to be destroyed. This can be achieved by smelting under reducing conditions.Acid leaching is also possible, but in this case, large amounts of MgSO4 or MgCl2 will be produced making it costly to regenerate the acid.2. The high-iron, low-magnesia ores are known as limonite. The nickel is relatively loosely bonded to goethite and hence can be recovered by selective reduction followed by ammonium-ammonium carbonate leaching. In recently developed processes, these ores are also being extracted by acid pressure leaching, with high Ni and Co recoveries.This paper focusses on the production of ferronickel and nickel matte from the highmagnesia ores."

Jan 1, 2003

By Bin Tang, Suping Yao

In the last decade, the copper industry in China has developed rapidly and attracted the world’s attention. The production capacity of refined copper has grown remarkably from 4.578 million tons in 2010 up to 9.029 million tons in 2018, accounting for about 40% of the global refined copper production. And now, China has become the biggest refined copper producer in the world. This paper summarizes the application of modern copper metallurgical technologies such as Outotec flash smelting/converting technology, Cyclone smelting technology, TSL (ISA/Ausmelt) smelting/converting technology, Jinfeng side blown smelting and Baiyin side blown smelting technology, Chifeng side blown smelting and continuous top blown converting technology, SKS bottom blowing technology, Dongying two-step smelting technology, copper electrorefining with high current density, etc. in China’s copper industry, analyzes and compares the characteristics of those technologies and presents the great efforts of China’s copper smelters in adapting to the increasingly strict emission standards and improving economic benefits of copper smelters. INTRODUCTION China has been the biggest refined copper producer in the world for many years. China produced million tons of refined copper in 2018, accounting for 40% of the copper smelting production in the world, and of which, roughly, 70% of the copper concentrate was imported, mainly from Chile, Peru and Australia. ICSG (International Copper Study Group, 2017) shows clearly the position of top 20 countries of copper production and copper mine production (Figures 1 and 2). Blast Furnaces, Reverb Furnaces and Electric Furnaces dominated China Copper Smelting for quite long time till 1980s. The first modern copper smelting technology (flash copper smelting) was introduced into China in 1980s, then followed by Noranda, Ausmelt and ISA. Since then, China copper smelting technology stepped into modern time. Since 2000, old processes (Blast Furnace, Reverb Furnaces and Electric Furnaces) were phased out and replaced by modern smelting technologies. China Copper Production has been increasing dramatically (Figure 3).

Jan 1, 2019

By H. Powell

"This paper discusses how elemental analysis of conveyed bulk flows in real time using PGNAA (Prompt Gamma Neutron Activation Analysis) technology has resulted in significant improvements in advancing plant control in mineral processing operations. PGNAA through belt, full stream, continuous, multi-elemental, real time analysis technology is explained. Capabilities and limitations in plant operating environments are discussed including comparison with other real time, on-line technologies through review of published information available for on-conveyor minerals applications. Case studies include an iron ore and copper-gold company, both of which consider the technology an essential component in advanced plant control necessary in new process flow sheet designs, rather than an optimisation tool.INTRODUCTION Process operators rely on supply of a reasonable ore quality and consistency from the mine. Unfortunately neither the mining nor process operators have much control over the ore quality once it has been put into the crusher. Grade control typically stops once the material is designated as ore and the process plant operator needs to process it irrespective of quality. Plant control is most effective when technologies measure process streams directly and preferably in real time. Measuring sampling streams that are not representative of the primary flow will result in incorrect plant control decisions. Sampling coarse conveyed flows is expensive and impractical at many operations, however, this does not mean those flows cannot be measured. Investigations to find techniques suitable for real time elemental analysis have focussed on the application of known laboratory techniques to process streams. For conveyed applications, development of neutron irradiation techniques were most promising and early studies indicated potential success for bauxite measurement (Beurton et al, 1995). Tran & Evans (2001) concluded there was no equivalent technology to PGNAA in terms of material penetration power and that the technology was eminently suitable for basic industries such as cement. Nelson and Riddle (2003) evaluated PGNAA for possible use in the phosphate industry by using a unit installed in a cement plant to test performance on phosphate samples and ultimately recommended its use for further characterisation of the mine’s various ore types to improve stockpile allocation and grade control"

Jan 1, 2014

By John A. Wells, Leticia Conca, Kenneth G. Thomas

"Since about 2002 there has been significant capital cost escalation, not inflation, in the mining industry causing turmoil for successful project completion. Project capital costs have more than doubled and some cases tripled in this time period. This has rendered many projects to be economically challenged and in some cases not viable. In addition higher than expected operating costs have further adversely affected project metrics such as NPV and IRR. Capital cost increases for projects have been widely reported globally. This current paper reviews three items. Firstly, why such capital increases and the various components that make up capital estimates. Secondly, it looks at reasons why preliminary estimates, for example at scoping and pre-feasibility level, have been lower than the ultimate constructed costs. Such increases and differences in estimates have caused major problems for mine builders and have led to a general nervousness on the part of those providing project finance. Thirdly, what discipline is needed in project execution in an attempt to mitigate such capital increases. The paper will hopefully give a better understanding of the various issues and factors involved for those in the mining industry.INTRODUCTION The years 2012 and 2013 were a turbulent time for the mining industry. The European economic crisis, politics, metal price volatility and a wave of changes of CEO´s in some of the major mining companies all contributed to a challenging couple of years. Two issues stood out. First, the huge increases reported in the capital costs of projects, where increases of 100% - 300% were not uncommon and in some cases exceeded that during the first decade of the 21st century. Second, company write downs related to takeovers during the boom and the stabilization/correction in commodity prices. These have led to great uncertainty, made it difficult (or impossible) to raise project financing costs, contributed to the changes at CEO level and placed many projects either on hold or cancelled altogether. It is commonplace now to read of companies talking of reduced capital expenditure and making a complete review of their projects and operations to contain costs."

Jan 1, 2014

By Jacques Ouellet, Ferri Hassani

"Within the mining industry paste backfill technology has evolved over the last two decades. This technology aims at producing safe and cost effective backfill of high strength. When used as cemented backfill underground the usual practice in the mining operations was to consider the backfill as a component under the production engineer responsibility. With its growing use in various site conditions some problems were encountered. Over time the mechanical characteristics of paste backfill could deteriorate. Investigations on these problems brought an increased understanding of paste backfill chemistry. Effectively, paste backfill is produced with tailings slurry having sometimes very complex chemistry and mineralogy. The bonding agents can be sensitive to the chemistry of these slurries. Today, a new understanding of the complex chemical reactions involved in cementing paste backfill is derived from concrete research literature. Cemented paste backfill is a manufactured product and as thus all steps involved in its making must be looked at. Both the processing engineers and mining engineers need to be involved. The proposed paper will go over the various developments and new understanding gained over the years on paste backfill chemistry. The authors had the opportunity to work with various Canadian mines that implemented paste backfill in their operations. Chemical alterations case study will serve to illustrate the importance of a good understanding of cement and paste chemistry. The authors will then conclude on research orientations needed to bring a more efficient use of paste backfill technology. The crucial role of the processing engineers in the paste backfill manufacturing will be discussed.INTRODUCTIONPaste backfill is usually prepared from a mixture of solids and water containing at least 15% particles smaller than 20 microns with the addition of binders for mechanical strength. Historically, tailings had been classified to extract the fines and only the coarse part was placed underground as sand slurry. Paste fill was researched in the last three decades to enable mining operations to use all the tailings, including fines, in backfill. The outcome of the early studies showed that paste fill provides high strength but due to preparation complexities and transportation problems is expensive. A greater understanding of the transportation mechanisms and advances in dewatering technology in recent years has resulted in more practical use of paste backfill."

Jan 1, 2002

By Randolph R. Dreher, Michael L. Schreder

"In recent years, FFE Minerals has designed, installed and commissioned several large grinding mill circuits. This paper discusses the issues related to the erection and commissioning of large grinding mill circuits. The three circuits discussed are Collahuasi in Chile, Minera Los Pelambres in Chile, and Century Zinc in Australia. These circuits include large SAG and ball mills with both gear and gearless drive arrangements, as well as, both trunnion and shell supported mills. Aspects of these features are discussed with respect to their impact on installation and commissioning. While the normal challenges of mill erection and start-up were experienced, there were also a few unexpected challenges encountered partly due to the large scale of the equipment. An overview of the equipment and design ratings of these circuits is also provided.COLLAHUASIOverviewThe Collahuasi mills were started-up in November of 1998. The site is located in the Andes Mountains at an elevation of 4300 meters. The grinding circuit includes two lines featuring one SAG mill and one ball mill for each line. The circuit features a recycle conveyor around the SAG mills with provision for adding a pebble crusher in the future. The design tonnage of the grinding plant is 60,000 MTPD with an ore BWI of 10.5 kWh/MT.The SAG mills are 32’ x 15’ (1 3’ EGL) with 10,800 HP drives. The drive arrangements are dual pinion through pneumatic clutches. The mills are driven by low speed synchronous motors with CCV variable speed drives. The SAG mills are trunnion supported and use hydrostatic lubrication. Feed to the SAG mills is via a rock-box type feed chute on a cart. The mills discharge on to trommel screens with a bucket wheel to remove the oversize.The ball mills are 22’ x 36.5’ (36’ EGL) with 12,500 HP drives. The drive arrangements are dual pinion through pneumatic clutches. The fixed speed mills are driven by low speed synchronous motors with GE Quadramatic load sharing drives. The ball mills are shell-supported and feature multi-pad bearings with hydrodynamic lubrication. The mills are fed via a rubber lined sump box with feed spout on a cart. The ball mills also discharge on to trommel screens. Twenty-six inch (26”) diameter hydrocyclones are in closed circuit with the ball mills."

Jan 1, 2001

By Steve Wilson, Bern Klein, Jeff Drozdiak, Stefan Nadolski, Andrew Bamber

"In the adaptation of high pressure grinding rolls (HPGRs) to hard-rock mining applications, circuit development has mainly focused on placing HPGRs in the role of tertiary crusher in the preparation of ball mill feed. In order to take advantage of the potential energy benefits associated with HPGR and stirred mill grinding technologies, work was done to investigate the potential of and resultant energy benefits of placing the HPGR in series with a high speed stirred mill in replacement of the conventional cone crusher / ball mill arrangement. The proposed circuit was designed to operate with two stages of HPGR grinding followed by high speed stirred milling.Using a pilot-scale HPGR unit inline with a 20 liter stirred mill, the design criteria, circuit arrangement and consequent comminution energy requirements for a circuit processing copper sulphide ore from Teck Resources’s Mesaba Copper project were determined. These results were then compared to two other circuits, an HPGR / ball mill circuit and a conventional crusher / ball mill circuit processing the same ore.The testwork indicated at a proof-of-concept level that the HPGR / stirred mill circuit could potentially be appropriate for this duty and further work on the concept is merited. While the results indicate that the HPGR component of the circuit was more energy efficient than conventional cone crushing, the energy efficiency of the stirred mill was found to be lower than that of a comparable ball mill undertaking the same duty. However, increased energy efficiency of the stirred mill portion of the circuit is possible with further optimization and further work on the concept is indicated."

Jan 1, 2010