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The 108th Annual General Meeting of The South African Institute of Mining and Metallurgy was held at The Country Club, Johannesburg, Napier Road, Auckland Park on Thursday, 11 August, 2005. Welcome The President extended a special welcome to the guests and representatives of our sister institutes and other associations, also to recipients of awards, senior members of industry, Honorary Life Fellows, past-presidents, our members and other guests, among them the following: Dr Con Fauconnier, President, Chamber of Mines of South Africa Prof. Jay Barton, President, The Geological Society of South Africa V. Townshend, President, Institute of Certificated Mechanical and Electric Engineering, South Africa M. Livingstone-Blevins, President, Institute of Certificated Mechanical and Electrical Engineers, South Africa Prof. B. Lacquet, President, South African Institute of Electrical Engineers Dr F. Malan, President, South African National Institute of Rock Engineering

Jan 1, 2005

By George H. Holmes

The water situation in Nevada mineral and related industries is described in this report. It contains information on the sources and adequacy of supply to current operators, requirements and uses, quality and costs, geography, hydrography, precipitation and evaporation characteristics, and Nevada water laws. Also, information is given on the water requirements of one public utility powerplant, and the source and consumption of water in four major cities. Water distribution at 24 operations is shown on schematic waterflow diagrams. The mineral industries of Nevada in 1962 used 8.6 billion gallons of new' water and reused 3.8 billion gallons for a total usage of 12.4 billion gallons. The copper industry was the major water user. The 1962 value of all mineral production in Nevada was $85.5 million. The large amount of water required to maintain thin high production is obtained principally from ground-water sources in alluvial valleys and the permeable rock formations of some mountain ranges. Some water is also obtained from perennial streams and springs. Sources of water utilized by existing industry ire near most mineral industry operations; however, seven companies are forced to pipe water distances ranging from 2 to 8 miles. Although water supplies of presently operating companies are adequate at most operations, several companies resort to large-scale reuse of water as a matter of conservation and economics. Acquisition of water by new operators is possible but takes considerable negotiation. Water rights, surface and underground, are controlled by the State. The quality of the water is satisfactory for most purposes. Analyses of 19 samples, listed in the appendix, show the range in water quality at various plants throughout the State. Costs of delivering new water to current operations range from 2 to 26 cents per 1,000 gallons with an average of 10 cents per 1,000 gallons for power and maintenance. No firm costs for recirculating water were available; estimated costs range from 1.5 to 2.5 cents per 1,000 gallons. The mineral-product value of the entire Nevada mineral industry in 1962 was equivalent to $10 per 1,000 gallons of new water and $26 per 1,000 gallons consumed. Projection of the 1962 water requirements of the Nevada mineral industry indicates that the demand For new water will increase from 8.6 billion gallons in 1962 to 11.9 billion gallons in 1980, a 43-percent increase. Water requirements in the year 2000 are estimated as 14.8 billion gallons, an increase over 1962 water demand of 78-percent.

Jan 1, 1966

By R. Gunda

Due to the rapidly increasing production rates and deepening of mine working areas, there is a drastic rise in the number of thermal issues to be addressed for maintaining a safe mine environment. As high temperatures and humidity in underground mines could affect the health and performance of workers, and ultimately the production rate, it is necessary to provide a properly controlled safe environment. The backfilling of stopes in metal, non-metal mines results in different thermophysical properties for the hanging, side and foot walls, modeling of which is not provided by any existing mine climate simulation software. This paper presents the modeling of such a single stope using the MULTIFLUX (MF) software, developed at University of Nevada, Reno. A special case is presented in this paper, where a case study from the Homestake mine in the US with a drift and ramp connected to a stope with high Virgin Rock Temperature (VRT) and various spot heat sources is modeled in MULTIFLUX and CLIMSIM, and the results are compared against each other. Another case is presented in which the stope of the previous cases is modeled with walls, each having a different set of thermophysical properties. These results are compared with the former results to analyze the effect of anisotropic properties.

Jan 1, 2011

By Manish Uttarwar, Rajendra Yerpude

India is the third largest producer of coal and the fourth largest in terms of coal reserves in the world. However, new research quite ironically projects that despite the continuing growth in domestic coal production, the country’s exploding economic growth will position it to be the biggest coal importer by 2020. India’s inability to meet the domestic coal demand is mainly attributed to low rate of production, increasing stripping ratio, non use of appropriate technology etc. of coal mining operations here. Presently Indian surface mines which have to shoulder the onerous responsibility of augmenting the coal extraction rate at an even brisker pace are mulling bigger, better and more efficient operations ensuring commensurate rise in stripping work as well. This mammoth task can be accomplished only by deploying smart technologies. In this perspective, cast blasting of overburden emerges on the horizon as a promising alternative for enhancement of the production and productivity of Indian open-pit coal mines.

Jan 1, 2009

By Benjamin Cebrian

Traditional dilution control systems range from computer modeling, use of physical markers on the field as polypipes to a technology that marks some control points where displacement is measured. The latter includes walking over a muckpile which is prohibited by some mining companies as a safety measure. The new technology presented in this paper is a patented system that is installed on board excavators (backhoe or front shovel types). Several control points are set along ore/waste contacts and their position is uploaded on the corresponding shovel. The operator proceeds on mucking until he is alerted when reaching any of the several control points previously located in the blast patterns and that have moved with the muckpile. A case study is presented at a high grade copper mine, were unique 3D shapes are showing as a result of using an on-board excavator dilution control system. Both ore-loss or dilution cost of opportunities are analyzed.

By David Crouthamel, Raymond Henn

"The need to fill the void space or annulus created between an excavated tunnel or shaft and the final lining system has long been a requirement in underground construction. Most of those types of voids are created as a result of employing the two pass tunneling lining method. Filling of this void is called backfilling. For many years the materials used as backfill were primarily reinforced and non-reinforced concrete, sanded grout, neat cement grout, or blown-in sand/pea gravel. However, in the past 20 years the use of cellular grouts/cellular concrete as the backfill material has greatly increased. Most cellular grout is made of a mixture of water, Portland cement (with or without the addition of fly ash), a foaming agent and admixtures such as a water-reducer or superplasticizer.It is the authors’ preference to use the term cellular grout as opposed to cellular concrete since by ACI Concrete Terminology an ACI Standard (ACI CT 13), concrete contains aggregates. Normally cellular grout does not contain sand (finite aggregate), but almost never contain course aggregates.The authors believe there are several reasons for this increased use of cellular grout as backfill, such as:• The increase utilization of the various trenchless tunneling methods. Tunnels constructed using trenchless method tend to be smaller in size, excavated diameter or cross sectional area. Making man-entry for placing backfill from inside the secondary liner, utilizing pre-installed grout posts, more difficult if not impossible. It is these workspace restrictions that are the drivers as to when to utilize grout ports installed during the pipe/liner fabrication versus grout delivery pipes installed within the void/annulus space.• The ability of cellular backfills to be pumped and flow longer distances.• The unit weight of cellular grouts can be controlled by mix design and generally can range from 560 Kg/m3 (35 lbs/CF) to 1040 Kg/m3 (65 lbs/CF)."

Jan 12, 2017

By Reed Thorne

To many people, rescue from elevated, sometimes vertical, locations brings about thoughts of heroism mixed with brawn and self-sacrifice. Images are conjured of cliff rescues where the technical effort is hanging from a few seemingly small nylon ropes hundreds of feet above the ground. Such is the vertical realm of technical rope rescue. This is a technical field in which the author serves professionally as battalion chief of (rope) operations for a northern Arizona fire district, and as a private sector instructor to mines in the United States and Canada.

Jan 1, 1996

By H. Do, R. Yoon

Mineral flotation is effective over a relatively narrow particle size range of approximately 10 to 100 µm. If the upper particle size limit can be increased, however, a run-of-mine ore may be coarse ground, and only the middlings are ground further to achieve required grades. This will result in significant energy savings and increased throughput. In this communication, methods of increasing the upper particle size limit will be discussed on the basis of a flotation model that can predict flotation from both hydrodynamic and surface chemical parameters. An example of increasing flotation recovery by control of a chemistry parameter is given.

Jan 1, 2007

By R G. Barker

This paper reviews the annual status of the New Zealand mining industry (metallic minerals and coal) including key aspects such as mineral production, mineral exploration expenditure, commodity price trends, key industry players, market activity and other significant commercial factors.   Strong commodity prices during 2006 have been underpinned by a number of key factors including US dollar weakness and emerging market demand, particularly from countries such as China and India. In real terms commodity prices have recovered significantly since 2002 and are currently at 20-year highs.   New Zealand exploration spending on metallic minerals (predominantly gold) is at a 15 year high driven by rising global commodity prices. New Zealand gold production in 2006 was about 340,000 oz and is expected to grow in 2007 as new mines at Frasers and Globe-Progress (Oceania Gold) and Favona (Newmont) come on stream. Gold production broadly lags 10 years behind exploration spending and exploration activity over the last five years remains well below that seen in the early 1980Æs. Expenditure on coal exploration shows a similar trend with strong growth from a low base over the last five years, reaching over $11 M in 2006. Total coal production in 2006 was 5.9 Mt, an increase of 10% on 2005 with imports from Indonesia adding a further $1.1 Mt.   Newmont and Oceana Gold are by far the largest public gold mining companies operating in New Zealand, although only Oceana Gold maintains a presence on the local stock exchange. Other metals explorers with New Zealand projects include a range of public-listed Juniors (market capitalisation less than NZ$50m) domiciled largely in New Zealand, Australia and/or Canada. Capital-raising on public markets directed towards New Zealand exploration is estimated at around NZ$12 M for 2006, the bulk of this coming via Glass EarthÆs NZ$10 M IPO on the NZAX in October.   The New Zealand Coal sector is dominated by the state-owned enterprise Solid Energy with around 80% market share by production. Other domestic coal competition remains limited, and includes the L&M Group, Pike River Coal, Eastern Corporation, and New Vale (acquired by Solid Energy in 2007). Pricing parity comes mainly from imported coal and global thermal coal prices have remained strong during 2006 at around US$45-55/t, driven by continued expansion in Chinese demand. Coking coal prices have eased 16% since 2005 to around US$98/t in 2007.   Although recent increases in exploration spending suggest a renaissance in the New Zealand minerals sector, long-run trends indicate that we have simply rebounded from a low base over the last five years and much work is still to be done to stimulate further growth in the mining industry to maintain minerals production at current levels. Key industry challenges include marketing exploration opportunities to local and overseas investors, building a critical mass of NZX-listed explorers and providing an internationally competitive environment to attract further capital and expertise.

Jan 1, 2007

By Thomas M. Barczak

Roof support technology for longwall tailgates has changed dramatically during the past decade. Filling tailgates with conventional wood cribs is becoming the exception rather than the rule. Modern engineered timber support systems and a host of other alternative support products provide far greater capacity as well as stiffer response, thereby allowing the supports to resist roof movement with much less displacement than the soft wood cribbing used in the past. For these reasons, these products can provide superior roof control. In addition, the material handling requirements for support installation have now become a major consideration in the support design and selection process. Products such as conventional wood cribbing that require piece-meal construction of bulky, heavy components have diminished, while prop-type supports and products that can be installed with machinery and pumpable support technologies have grown in use resulting in fewer injuries to mine workers. Now, the opportunity exists to provide the safest, most cost effective support system, through engineering design rather than by trial and error and to optimize the use of the support system chosen. Yet this is rarely done. The key to accomplishing this task is to understand the interaction of the support system with the ground conditions at the installation site. A major focus of the paper is to conceptualize the support and interaction through the use of a ground reaction curve which relates the support resistance to the convergence of the longwall tailgate. The goal of any roof support design is to control the ground deformations and maintain the structural integrity of damaged or broken ground to the extent possible to provide a stable mine opening. In general, deformations will be a function of the stress environment and inherent strength of the surrounding rock mass. However, if the deformations are intimately linked to the stress changes such that the deformation can be controlled by the load resistance or reinforcement provided by a roof support system, then the loading behavior can be described as load-controlled. Conversely, if the deformation occurs irrespective of the installed support (assuming practical limitations), then the loading behavior is described as displacement-controlled. In this case, the deformation can be considered irresistible from a practical standpoint. In this context, the nature of the loading has significant consequences on the support design requirements. Finally, examples using the NIOSH Support Technology Optimization Program (STOP) to develop design criteria using ground reaction data from underground studies and ways to include uncontrolled convergence as part of the design criteria for standing roof supports will also be discussed.

By H. Rozovsky

"AbstractThis paper discusses the methods of handling air in a large asbestos mill presently being completed at the Jeffrey mine of the Canadian Johns-Manville Company in Asbestos, Quebec.The mill, being the largest single asbestos producer in the world and capable of handling over 14,000 tons of ore per day, requires vast quantities of air. A minimum of 2,500.000 c.f.m. is required or about 10 tons of air for each ton of ore milled.Short descriptions of the process and systems requiring this air are given, followed by details of the fans and filters which make up the heart of the mill.This 'draw through' system, located on the top or 12th floor, is an automatically .controlled volume-pressure system creating the required suction to draw .air throughout the mill building and its numerous air systems.The dry mechanical method of milling develops enormous quantities of airborne dust and fibre. A section of this paper is devoted to a description of the multiplicity of dust systems within a system to control, filter, and remove this dust.Finally, the paper describes the method of returning the filtered air to the• working floors or to the outside, with some notes on heat, humidity and dust counts.IntroductionGeneralTHE discussions in this paper deal only with operations where air movement is involved. No attempt is made to delve into production methods.The Jeffrey mine of the Canadian Johns-Manville Company, located about 100 miles east of Montreal, is the largest single asbestos producer in the world, being responsible for over half of Canadian asbestos fibre production."

Jan 1, 1955

By Jeremiah Cohn, Rachel L. Bauer, Catherine E. Johnson

Water is frequently used in explosive applications to increase explosive performance and reduce air overpressure. Water tamping can enhance cutting abilities of shaped charges in demolition and increase impulse of kicking or breaching charges. In explosive disposal, water is used to suppress air overpressure and reduce noise. Despite its widespread use, the specific effect of water placement, whether in front of or behind the explosive, has not been studied. This work evaluates the directional effects of water placement on blast performance using 400-gram sheet explosive charges in five configurations: no water (control), rear-only water (tamped), front-only water (pushed), water on both sides (confined), and a thin front-and-rear water layer (low mass confined) to assess reduced mass effects. Water was sealed in plastic bags and held in position with custom 3D-printed cages to ensure consistent geometry and contact. A modified ballistic pendulum consisting of a hanging steel W-beam was used to evaluate impulse transfer, with high-speed video capturing swing velocity. Air overpressure was recorded using a seismograph microphone. Rear-only water (tamping) increased beam swing velocity by 69% over the control while confinement with water on both sides increased performance by 12% at a 2:1 water-to-explosive ratio and by 50% at 4:1, though it still underperformed the tamped-only configuration. Pushed water alone did not increase beam momentum and reduced tamping effectiveness by 19% when combined. Seismograph microphone data showed that pushed and low mass confined water configurations produced some of the highest air overpressure levels (up to 139.2 dB), while tamped and control charges produced lower levels (~134–136 dB), suggesting that pushed water may amplify, rather than mitigate, air shock transmission. These findings show that water placement has a strong directional influence on blast dynamics: water behind a charge enhances energy transfer to the target, while water in front provides limited or potentially counterproductive mitigation. This study advances understanding of water–explosive interactions and will lead to more effective charge designs for breaching, disposal, and demolition.

Jan 26, 2026

By Zoltan F. Oszter

The design of belt conveyors is a well-known procedure and related formulae can be found in any handbook dealing with materials handling. Belting and conveying equipment manufacturer's catalogues and design manuals offer a wide range of detailed information which can be applied to most of our conveying problems. The aim of this paper, however, is to investigate the design of a specific type of belt conveyor, namely the long horizontal, or nearly horizontal, type. (The undulating type, with moderate lifts and drops, can also be included in this category.) Most of the long overland conveyors carrying ore from pit to processing plant, or those carrying over-burden to the disposal area, fit this description. A critical appraisal will show that reasonably accurate results can be obtained when tl1e familiar horse-power formulae are applied to this type of conveyor. The progress and new developments in the design of belt conveyors, which have resulted from the extensive research done in the past decade, will also be explored.

Jan 1, 1962

By Anand Raman, Steve Dixon

"Industry practice for defining acid consumption is based on column tests. Freeport-McMoRan (FCX) has adopted a practice of leach operation using a defined pH or gpl acid in the raffinate based on the column test program. The acid consumption can be easily calculated using the leach operating parameters of SX-EW efficiency, lift height, bulk density, irrigation rate, primary leach cycle time, acid cure dose and acid concentration in the raffinate. The column leach test results and a column to heap efficiency factor are used to define the copper extraction. The maximum acid consumption will occur when zero acid is contained in the raffinate. The term Net Extracted Value (NEV) is to define the maximum extracted value relative to acid consumed.This paper presents the operating logic and method used to calculate acid consumption based on column tests and operating parameters.INTRODUCTIONIndustry practice for defining acid consumption is based on column tests. This may result in lower economic value if the tests are not designed to account for operating variables. A test program is described to assist in defining lift height and the influence of gangue on solution chemistry. A simple spreadsheet is presented that will use the leach operating parameters of SXEW efficiency, lift height, bulk density, irrigation rate, primary leach cycle time, acid cure dose and acid concentration in the raffinate to calculate the acid consumption for a proposed operation.A review of current leach operations solution chemistry will help to define acid consumption. This is recommended for all current leach operations.DISCUSSIONThe current practice at Freeport-McMoRan (FCX) is the use of column test results to define operating parameters. The monitoring of operational solution chemistry and copper production addresses any changes needed in operational parameters. This practice maximizes the value extracted from each tonne of ore leached."

Jan 1, 2008

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

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

Jan 1, 2013

The Role of Mineral Processing in the Development of Cement with Low Carbon Emissions

Sep 13, 2010

By Michel Robert

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

Jan 1, 1978

By Gilberto Yanarico Apaza

"El presente texto señala las pautas necesarias para realizar una evaluación técnica integral de la influencia del collar de bolas para las operaciones de molienda, afectando al desgaste de los revestimientos de los molinos convencionales. Para la determinación del collar de bolas es necesario realizar los análisis granulométricos con la finalidad de obtener el F80 y el P80 de las muestras obtenidas en la alimentación y producto de los molinos, definir el índice de trabajo (Wi) y consumo de energía. Asimismo, se debe considerar el porcentaje de la velocidad crítica, las dimensiones de los molinos, la densidad de los medios de molienda (bolas), el porcentaje de la carga de bolas, las características geométricas de las bolas para molienda y el diámetro real de bolas, que influye de forma inversamente proporcional en la tasa específica del consumo observada."

Jul 1, 2015

By Shuvranshu K. Rout, Anup K. Mandal, Biswajit Das, Manos De

"To adopt new technology advancement in Steel Plant, there is a requirement of shifting of operation process from Coke Wet Quenching (CWQ) to Coke Dry Quenching (CDQ). New CDQ chamber foundation with deep basement and underground conveyor tunnel are to be constructed in an operating plant where heavy foundations and structures are located in close proximity. Furthermore, the existing CWQ system will be in operation during new underground construction and erection. Challenges to deep excavation of tunnel and chamber foundation consist of non-uniform ground condition, prevent washing out of soil from bottom of existing foundations, stability of existing nearby structures, presence of large number of underground utilities, ensuring safe underground workplace to construction resources engaged in new construction work along with project schedule and budget constraints. A combination methods involving use of soil nailing, soil grouting, contiguous bored pile and micro pile had been adopted for protection of excavation sides as well as existing structures. Each side of excavation in different stretches were analysed during design as well as construction stages. The use of combination of all techniques in a single brown field project in context of the nature of site constraints and safety issues made this a unique project.INTRODUCTIONSteel Industry is one of the backbones of industrial growth of any developing country like India. Due to increasing land prices most of the steel plants in India are expanding within their existing plant facilities. In addition to that, there is demand of adoption of new technology for future expansion projects to set new benchmarks with global standards.The property owner had earlier installed a Coke Wet Quenching (CWQ) for their Coke Plant. Now, there is a requirement from process department to proceed with Coke Dry Quenching (CDQ). To facilitate the CDQ within the existing CWQ which will be in operation is the main challenge for the property owner. The second challenge is the limited space for underground construction and subsequent equipment erection within the stipulated time frame.From a geotechnical prospective, the project team had uncertainty and reservations in their mind about the construction methodology. Therefore, the role of three “C”: ‘Consultant’-‘Client’- ‘Contractor’ and their combining brainstorming is essential to freeze a working plan for achieving the goal. In this paper, only the excavation support systems for underground foundation structures have been highlighted in the context of solving geotechnical problems."

Jan 1, 2017

By H. Walqui, G. Rajala, G. Suardini

The Empire mine began operations on 1963. Low grade Magnetite ore is processed to produce iron pellets for blast furnace feed. Three expansions were added to the original plant and several equipment upgrades have been completed to improve the plant performance as the ore characteristics have been changing through the life of the mine. Size reduction is carried out by two grinding stages, the first one using autogenous grinding and the second one using pebble mills. Pebble crushing is also used to break the critical size fraction and increases primary grinding capacity. This paper describes changes in the configuration of the grinding circuits that have helped increase plant throughput and reduce power consumption by more efficiently utilizing assets available. Understanding the different components of the size reduction circuits and plant sections has allowed shifting part of the load from one section of the plant to another without affecting plant throughput.

Jan 1, 2007