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By James Lett

The role of pre-conditioning in a caving operation has multiple benefits, ranging from assisting with improved caveability, normalising fragmentation and improving draw point hang-up frequency. At Newcrest Mining’s Cadia Operations, both the Ridgeway Deeps block cave the Cadia East Panel Cave have utilised pre-conditioning using hydraulic fracturing. Seismic response data inside and outside the pre-conditioned volume show the benefit of treating the full caving block. Cadia East has further developed pre-conditioning to mitigate developing seismic hazards associated with major structures (fault-slip events) and managing mine-wide seismic hazards in new caving operations where the potential for large damaging seismic events exists due to high stresses and hard competent rockmasses. A case study reviewing the impact of pre-conditioning to mitigate seismic hazard associated with fault slip is presented. Cadia East operation undertook a targeted hydraulic fracturing program and reduced the overall number of large events as an example of the benefits of pre-conditioning. This paper will review the application of Hydraulic Fracturing at Cadia and discuss the geotechnical and seismological parameters of seismic events that occur within and outside of pre-conditioned rockmass volumes to demonstrate the benefits that Hydraulic Fracturing bring to future caving operations.

Apr 26, 2022

By Robert A. Westman

The INRED process has been developed step by step by Boliden since 1972 at MEFOS, the Foundation for Metallurgical Research, at Lulea in Sweden. The demonstration - plant is number five in this series. The purpose of this plant, which has a nominal capacity of 60,000 tonnes per year of hot metal is to: 1) prove the process on a sufficiently large scale to provide the basis for construction of production plants, 2) test various kinds of raw materials on behalf of licensees, 3) train operators of the first production plant, 4) develop the process further for special applications.

Jan 1, 1983

By Alafara A. Baba, Yakubu A. Dallatu, Kehinde I. Omoniyi, Shemang Y. Chindo, Edith B. Agbaji

As a result of the rise in global demand for pure copper, there is urgent need to consider the processing of low-grade chalcopyrite ores. Ammoniacal leaching solutions have been reported as an effective and efficient leachant for the dissolution of chalcopyrite. This work reports different parameters that influence the leaching kinetics of a Nigerian chalcopyrite-rich siderite ore obtained from Wase Local Government Area, Plateau State, Nigeria, and assayed as 11.30 wt% of Cu. At the optimum leaching conditions (0.4 mol/L NH3-( NH4)2SO4 leachant concentration; 75 °C reaction temperature; 45 μm particle size), the extent of chalcopyrite ore dissolution reached 87.4% within 120 min. The dissolution rate was affirmed to conform to the diffusion control mechanism with the activation energy, Ea, of 38.84 kJ/mol and a reaction order of 0.661 for the leachant concentration being established. The leaching mechanism was affirmed by characterizing the raw ore and the leached product by XRD and SEM-EDS analysis. Ascertaining optimal leaching conditions for copper using alkaline leachant is advantageous from the environment and economic points of view.

Jan 6, 2023

By R. C. Timberlake

In the past three years there has been a great amount of attention given to phosphates world wide, and in particular to the Florida Phosphate Industry. I would like to relate some of the most recent history of the industry and give you a personal outlook for the future. Phosphate rock has been produced in Florida since its discovery on the Peace River in the 1880's. Through 1976, approximately 720 million ST of rock had been mined from Florida reserves, and it is my opinion that there are at least 1.2 billion tons remaining which are consolidated, accessible and can reasonably be expected to be permitted for mining. Over half the 1.2 billion tons will be deeper, more scattered, leaner and will produce lower grade rock than the Bone Valley of Central Florida has tradition-ally produced. In 1973, '74, '75 and '76 the Florida Phosphate Industry produced 32.6, 34.0, 38.2 and (38.0) (P) million ST of phosphate rock respectively. This rock was produced by ten mining companies, Agrico, Borden, Brewster Phosphates, Gardinier, Grace, IMC, Mobil, Occidental, Swift, and USS Agri-Chem; mines are located -17 in Polk County, one in Hillsborough County and two in Hamilton County, Florida. Phosphate rock is used by local companies in Florida primarily to produce phosphoric acid from which DAP and TSP is manufactured. Florida acid producers use about 15 million STPY in acid plants in Florida, and another 7.5 million STPY is consumed by acid producers in plants on and near the Mississippi River. Somewhat

Jan 1, 1977

By James A. Bloom

To operate the Morris Fork Preparation Plant with a closed water circuit has been an elusive goal for Union Carbide. The benefits of a closed circuit have never been questioned. The removal of fine solids from washery water makes possible the recirculation and reuse of the water. Heavy media drag tanks and other separating machines perform better and more consistently with washery essentially free of fine solids. Finally, the production of a clarified effluent makes unnecessary the sludge ponds usually associated with a coal preparation plant. Why then do I say elusive? Because, since plant design was completed in 1970 we have been in hot pursuit of an ever-growing fine solids problem. In four years the minus 28 mesh material in the plant feed has nearly doubled. The replacement of conventional sections with continuous mining machines has led to a lowering in size and quality of product from the mine. In addition, increasing emphasis underground on roadway clean-up has contributed to the fines problem.

Jan 1, 1975

By Bryce T. Tripp

Utah's abundant industrial rock-and-mineral resources support a relatively small but important sector of the State's economy. In 1983, six of the top 10 nonfuel mineral commodities (by value) were industrial commodities. Portland cement was ranked fourth, potash fifth, halite sixth, phosphate seventh, construction sand and gravel eighth, and lime tenth. Portland cement was produced by three operators, principally from the Jurassic Twin Creek Limestone. Potash was produced by three companies from Pennsylvanian beds in the Paradox Basin, surface brine of the Great Salt Lake, and subsurface brines of the Great Salt Lake Desert. Halite was produced by eight operators, primarily from surface brine of the Great Salt Lake. Additional production came from salt beds in the Jurassic Arapien Shale, solution mining of the Pennsylvanian Paradox Formation of the Hermosa Group, and subsurface brines of the Paradox Basin. Phosphate was mined by one company from the Permian Meade Peak Phosphatic Shale Member of the Park City Formation. Construction sand and gravel were produced by dozens of operators, primarily from Quaternary Lake Bonneville beach and nearshore deposits. Lime was produced by four operators from Paleozoic formations in the Basin and Range physiographic province of Utah. The future production of these and other industrial commodities, though individually uncertain, is expected to increase gradually as a group. Factors favorable for the future of the industrial commodities industry in Utah include large to almost unlimited resources for the major commodities, a healthy projected population growth, an abundant local supply of relatively inexpensive energy from coal and natural gas, and a favorable corporate tax structure and business climate.

Jan 1, 1987

By N. T. Lowe

The National Institute for Occupational Safety and Health (NIOSH), Spokane Research Laboratory (SRL), investigated a means to evaluate the potential impact of surface conditions above underground mines on emergency response activities. Recent events have highlighted the need to conduct critical emergency operations on the surface above underground work areas. Accessibility and usability of the surface, such as the ability to drill holes or deploy seismic monitoring or through the earth communications systems, are an important consideration for emergency response planning. This paper identifies critical surface conditions such as: surface waters, valley fill, highways, railroads and significant structures that must be considered in emergency response planning and in the conduct of emergency operations as they relate specifically to the seismic detection of trapped underground miners. Results of case studies indicate a need to consider the impact surface conditions may have on emergency response capabilities.

Jan 1, 2009

By Kirk P. Kinart

The mid to late 1980s saw a modern day global gold rush that largely focused on the mature mining countries of the United States, Canada and Australia. This gold rush led to a large number of new discoveries in these countries and phenomenal growth rates in annual gold production. For a variety of reasons, however, gold exploration and development activity appears to have peaked in these countries. The drive for mineral investment is, instead, growing in lesser explored countries (LEC). LECs, particularly those of Latin America, are currently enjoying greatly increased attention from North American mining companies. They are becoming major consumers of mineral investment capital and are important markets for exploration and mining skills. Through sole ownership, joint ventures and subsidiary companies, Battle Mountain Gold now operates or controls gold mines in the United States, Chile, Bolivia and Australia. And it has been or is an active participant in gold exploration or development projects in seven other countries, six of which classify as LECs. In selecting new country entries and opportunities for mineral investment, there are several factors to be considered and parties to be satisfied - shareholders, corporate management, financial institutions and host country governments. This article, though, focuses on some of the more practical concerns of the exploration unit as a whole and the exploration geologist in particular. The exploration unit's "new country" concerns primarily relate to exploration potential, ownership security, quality and availability of data and the ability to operate efficiently. The following material reviews each of these concerns and how they impact the new country entry decision, exploration strategy, chances of success and human experience.

Jan 1, 1993

By Brett Schug, Caelen Anderson, Sohail Nazari, Carlos Cristoffanini

"The Haile gold mine in South Carolina is increasing the automation level of its processing plant in order to improve operational stability. One step toward this goal is the application of a digital twin concept to provide virtual instruments. Haile has engaged Andritz to implement virtual instruments at its grinding area hydrocyclones and at its tailing thickener underflow pump. These virtual instruments provide density values in a traditionally difficult location for reliable slurry density measurement. The digital twin is a first-principles integrated design engineering with advanced simulation (IDEAS) simulation model, connected in real time to the control system. Results have been promising, with the virtual instrument values matching the physical instrument under normal operating conditions and showing better prediction under upset conditions. Haile plans to use the virtual instruments as optional process control parameters.OceanaGold’s Haile gold mine is located near Kershaw, SC, about 80 km (50 miles) southeast of Charlotte, NC. This location was first mined in 1827 and has produced gold through several operating periods since then, including a heap leaching operation from 1985 through 1992. In October 2015, OceanaGold acquired Romarco Minerals, the previous owner of the Haile operation.The current operation began in 2017 as an openpit mine with additional underground resources. The nameplate throughput is 5,760 t/d (6,350 stpd) ore, and 2017 production was 3,345 kg (118,000 oz) gold, with 3,968 to 4,384 kg (140,000 to 155,000 oz) gold expected in 2018. Proven and probable reserves exceed 85 t (3 million oz) gold at a grade of 2 g/t (0.06 oz/st) gold. The process, as shown in Fig. 1, includes a primary jaw crusher, comminution with a semiautogonous grinding (SAG) mill and ball mill circuit, flash flotation, rougher flotation, regrinding, pre-aeration, carbon-inleach leaching, carbon elution and regeneration, cyanide recovery, electrowinning and refining. The Haile operation’s inaugural gold pour took place Jan. 20, 2017. Mine life is expected through the year 2030."

Dec 1, 2018

The Mining Foundation of the Southwest (MFSW), located in Tucson, AZ, will hold its 16th annual American Mining Hall of Fame Awards Banquet Saturday, Dec. 5,1998. The Hall of Fame recognizes outstanding contributions to the mining industry by selected individuals and industry partners. Each year, one living award recipient and up to two mining history honorees are chosen by the , Hall of Fame Committee and the Board of Governors of the Mining Foundation. In 1989, the Mining Foundation initiated a Medal of Merit to recognize outstanding individual, technical and professional contributions to the mineral industry. In 1995, an award was created to recognize contributions made by companies and organizations in partnership with the mining industry. This year's inductee, guest of honor and featured speaker will be Charles G. Preble, president and chief executive officer of Southern Peru Copper Corp. He is being recognized for outstanding performance as an executive of an American company operating under difficult circumstances in a foreign country. The Hall of Fame will induct H. Myles Jacob, former chairman and CEO of Inspiration Copper Co., for innovation and farsightedness in matters pivotal to the cop- per industry of his time. In addition, John Cromwell Lincoln, former president and chairman of Bagdad Mining Co., will be inducted for his outstanding contributions to the American mining industry. These contributions include metallurgical research and development of the Bagdad Mine as well as pioneering innovation in the electrical industry. Medals of Merit will be awarded to David N. Skillings, editor and publisher of Skillings Mining Re- view, for his dedication and support of mining interests. J. Ruben Velasco Rodriguez will also receive a Medal of Merit. He is economic geologist, professor and former secretary of the board of directors and secretary general of Compania Minera de Cananea. His medal is for fostering excellent relations between Mexico and the , United States in mining geology and management and for advancing the professional development of others in the field of earth science. An Industry Partnership Award will be presented to Stephen Bechtel and the Bechtel Corp. in recognition of Bechtel's 100th anniversary and the company's outstanding service to the mining industry. The banquet will be held at the The Westin LaPaloma in Tucson beginning with cocktails at 6:30 p.m. Tickets are available from Clare A. Roscoe, manager, Mining Foundation of the Southwest 520-577-7519, fax 520-577-7073.

Jan 1, 1998

By NILAMADHABA SAHU, Gajanan U. Kapure, Pankaj Kumar, Sunil Kumar Tripathy

Chromite ore processing tailings and low-grade manganese ores are typically considered waste due to their limited or negligible utility, leading to environmental and storage concerns. Researchers globally have explored various methods to utilize or upgrade these wastes, particularly because dumping chromite ore has been linked to severe health issues through Cr(VI) leaching. Individually, these ores lack economic value, and there has not been research on simultaneously reducing both low-grade ores. In this study, the focus lies on smelting these ores together, aiming to create a precursor alloy for 200 series stainless steel scrap. Initial research indicated the potential for scrap formation, validated through lab experiments with varying coke rate, basicity, and holding time. The investigation discovered that smelting this combination could yield a metal product comprising 59% Fe, 24.93% Cr, 7.56% Mn, 0.62% Ni, and 0.93% Si. The optimum basicity was found to be 0.6 with 80% recovery. Notably, this process eliminates intermediate steps in 200 series stainless steel production, potentially reducing overall CO2 emissions. This proposed method represents a cleaner, sustainable approach to repurpose these two waste ores, projecting a net profit of USD 330 per ton.

Jan 10, 2024

By Danu Putra, Budi Sulistianto, Tri Karian, Mohammad Nur Heriawan

Stope layout optimization is an important feature of underground mining that maximizes the economic value of the project while taking mining limits into account. The large number of parameters and constraints makes it difficult to obtain the optimum condition. Several algorithms have been created to address these problems using a variety of methods. However, the circulating method has not explicitly included stope dimension stability analysis, resulting in a solution that is not stability-proven, which can result in a suboptimal solution. This study integrates the Mathews stability graph into the stope optimization algorithm so that the optimized stope layout considers stability conditions directly through an assessment of the available geomechanical data within the block model. The proposed algorithm is validated through a case study of a synthetic block model created by considering variations in grade and the geomechanical conditions of the rock. Furthermore, several scenarios are created to compare the performance of the algorithm that applies variations in stope sizes with the common case study of stope sizes that remain fixed. A more detailed assessment is also conducted on each final stope layout wall to ensure the successful application of stability analysis in the proposed algorithm through back analysis on the Mathews stability graph. The optimization results show that all walls in the final stope layout fall into the stable condition. Also, the proposed algorithm is also capable of maintaining the project’s economic value. Ultimately, the proposed algorithm can be deemed applicable and suitable for use in the initial stages of mining as a comprehensive assessment of the optimal stope layout, taking into account the stability conditions of the stope.

May 22, 2024

By Rollien R. Wells

The Bureau of Mines was created in 1910 by an act of Congress and subsequently directed to: "...conduct inquiries and scientific and technologic investigations concerning mining, and the preparation, treatment, and utilization of mineral substances with a view to improving health conditions, and increasing safety, efficiency, economic development, and conserving resources through the prevention of waste ..." Under this broad charter, the Bureau's responsibilities have changed and grown from an almost exclusive concern with coal and coal mine safety to the present emphasis on a full spectrum of mineral producing and consuming problems. In the past 30 years, the domestic consumption of coal, oil, gas, metals, and industrial minerals has more than quadrupled, in parallel with the rapid and enormous growth in industrial production. Of the scores of metals and nonmetals essential to the Nation's progress and security, many are scarce and difficult to wrest from domestic sources. Reserves of some ores are dwindling. Available ore resources are becoming leaner and more difficult to treat. In recognition of this many faceted problem, the Bureau has engaged in a continuing quest for new and improved technology to enable economic exploitation of marginal minerals and fuels, to find substitutes for minerals in short supply, and to create better materials to meet the expanding and diverse requirements of the growing economy. The current central concern of the Bureau is focused on meeting projected fuel, metal, and mineral demands at the lowest real cost by recovery from available resources by new and improved technology that minimizes waste, hazards, and social and environmental problems.

Jan 1, 1970

By Ivan Weber

Asking the question, “What do the world’s leading corporations and cutting-edge practitioners of sustainability put forth to guide a given mine site for planning and action toward ‘sustainability’?”, this paper explores the spectrum of methodologies and mindsets in available literature, then constructs an example for the large near-closure facility at Kennecott Utah Copper. Values, opportunities and constraints spring from physical, unutilized byproducts, from critical ecosystems and wildlife populations, from location relative to those ecosystems and proximate communities, and from the political will to perform adequate feasibility investigations. Patience, determination and thoroughness are imperative. Identifying most productive and, simultaneously, most protective and restorative, practical methods to approach ‘sustainability’ has become a central mission of industry and business, worldwide. A survey of recent international initiatives finds no single approach that establishes either a readily adaptable methodology or an appropriate set of ‘attention’ points, or agenda, to guide individual mining operations at specific locations toward the elusive but essential goal of ‘sustainable’ mining. Untying this convoluted knot of contending factors requires willingness to recognize and work within ecological constraints for community long-term needs. Occasionally, the task requires the sword of Alexander the Great. Through integration that is unflinchingly honest ethically, culturally, economically, ecologically and scientifically, fully cognizant of place and community at whatever scales are of greatest significance, and integrative of both problem-response and opportunity, we may envision a mineral extraction and beneficiation future that achieves the best, most nearly sustainable, results possible. Industrial ecology (IE), with its clear emphasis on community, ecosystems, and sustainable economic stimulation, presents a sufficiently broad and adaptable discipline to facilitate planning and management toward sustainable mining. The creation of sustainable jobs encapsulates IE’s analogy to the niche survival strategies of organisms in nature. Open to common-sense recognition of faults and opportunities at appropriate scales, IE is less a discipline or prescribed methodology than a mindset, willing to be rigorously scientific when science is imperative, but also willing to exercise “art” when creativity or community engagement are needed. IE is also capable of future-looking compassion for peoples and nature. Looking beyond what has occurred to date, the case of Kennecott Utah Copper provides ample illustration of possibilities for community economic development, environmental management, and significant initiatives beneficial at regional and planetary scales, to become recognizable as deserving of the label, ‘sustainable.’ Through what this researcher terms “whole mine, whole region, whole planet” thinking, strategies become visible and subject to serious consideration, presenting a path to best possible accomplishment in mining. Constituting a maximal broadening of mining’s “traditional” scope, the integrative approach proposed here is the ‘paradigm shift’ being made by many other industries around the world. In aggregate, these steps are the only hope for avoidance of environmental, social and economic risks that threaten to curtail resource development and impair mining companies’ ‘social license to operate.’

Jan 1, 2005

By Joseph Clare

It’s not the 1960s anymore. Upgrading wastewater pipelines in the current era demands the latest trenchless technology to minimize impacts. King County Wastewater Treatment Division in Seattle, Washington is designing a nearly mile long Direct Pipe® influent sewer combined with microtunneling to replace a 1960s era trunk sewer constructed along and within Coal Creek and its natural area. Trenchless installation using Direct Pipe® and microtunneling was chosen due to reduce impacts to residential neighborhoods, natural creek environments, and the constraints of topography

Jun 13, 2021

Mineral liberation data are routinely obtained for a wide variety of applications, including ore characterization and characterization of various metallurgical test products obtained in bench-scale laboratory testwork. Newmont Mining Corporation owns several properties in the Carlin Trend containing refractory gold ores. These ores are generally difficult to treat and have to undergo several processing stages for gold recovery. At Carlin?s Mill 5 operation, flotation is used to pre-concentrate some of these difficult ores to produce a sulfide concentrate to feed the roaster. It is of interest from a flotation perspective to be able to study the floatability of pyrite, arsenopyrite and arsenian pyrite, since these minerals all have different quantities of gold associated with them, and have to be recovered to ensure a successful separation has been achieved. In this paper, a detailed MLA study on several Carlin ores was undertaken on samples from flotation tests, using air or nitrogen as flotation gas, specifically to study the differences in floatability characteristics, which ultimately impacts overall gold recovery. I

Jan 1, 2009

By D. S. Bird

The Kennecott Utah Copper Modernization Project, initiated in 1986, was directed to provide an expansion and modernization of mining and process facilities at the property's Bingham Canyon Mine and ore concentrators. Major components in the project included installation of an in-pit ore crusher, transfer conveying system, and construction of a new copper ore concentrator with a design capacity basis of 70,000 tonnes/day. The Copperton Concentrator was commissioned in February 1988. A principal feature of the plant is the grinding circuit, comprised of three identical lines, each consisting of a 10.37 m (diameter) by 4.57 m (length) Semi-Autogenous Grinding (SAG) mill and two 5.54 m (diameter) by 8.62 m (length) ball mills. The SAG mills are driven by two variable-speed 9,000 kW DC motors coupled through a clutch-pinion gear-ring gear assembly. The ball mills are driven by 4,125 kW synchronous motors coupled through a typical clutch-pinion gear-ring gear system. The expansion and particularly the Copperton Concentrator performance was so successful that by early 1989, management began examining options to further expand production capacity. With regards to the concentrator, numerous alternatives were considered, ranging from installation of a grinding line similar to one of the existing lines, to a "super" line consisting of a 12.8 meter (diameter) SAG mill and a 20,000 kW motor with a capacity of 50,000 tonnes per day. The technical and economic analysis of the various scenarios indicated that one "large" 11.0 meter (diameter) by 4.88 meter (length) SAG mill with a production capacity of 32,000 tonnes per day and a 12,000 kW drive would be optimum. The key question to be answered in the project was whether to continue with the pinion-ring gear combination, or install a gearless drive. The following paper outlines many of the items that were evaluated in the mill selection process followed by actual plant performance, and a discussion of ongoing plant continuous improvement projects.

Jan 1, 1995

By A. Bhargava, V. Nasri

Traditionally, secant piles have been utilized to provide temporary support during excavation for shafts and cut-and-cover tunnels. As an alternative, the secant piles can be included into the permanent structure, where they serve as the envelope sustaining the lateral loads and gravity of the permanent structure in addition to supporting the excavation during construction. This has several benets, such as shorter building times and lower excavation costs. Recent construction of an approach structure and an underground station as part of Montréal, Canada’s Réseau Express Métropolitain (REM), one of the biggest transit systems in North America, was completed with remarkable success using this. In this paper, a case study based on a project that employed secant piles as the permanent liner is presented. Techniques to guarantee a watertight construction with over a century of service life are described, along with a variety of structural and waterproong methods applied to create an economical design.

Jun 23, 2024

By X. Y. Yu, X. A. Wei, A. Zeng

"The flotation behaviors of diaspore and three kinds of silicate minerals - kaolinite, illite and pyrophyllite - using an organosilicon cationic surfactant as collector were investigated as functions of reagent concentration and pulp pH. The results show that the organosilicon cationic collector QAS122 is a suitable collector for the flotation of aluminosilicate minerals but has weak collecting ability with regard to diaspore, enabling the flotation separation of diaspore from silicate minerals using QAS122 as collector. The flotation of a bauxite ore was then studied in detail. Finally, a reverse flotation separation process was used to process a low-grade bauxite ore. It was concluded that use of the organosilicon cationic collector is effective. A concentrate with aluminum oxide (Al2O3) to silicon dioxide (SiO2) mass ratio, or A/S, of 9.67 was obtained from natural bauxite ore with A/S of 6.07 at pH of around 11. The Al2O3 recovery rate was 81.72 percent. IntroductionChina has abundant bauxite ore resources, but more than 98 percent of the bauxite ores are the diasporic type, with the characteristics of complex mineral composition, low aluminum oxide (Al2O3) to silicon dioxide (SiO2) mass ratio, or A/S, and difficulty of processing. The gangue minerals in bauxite ores are mainly kaolinite, pyrophyllite and illite, containing titanium and iron impurities (Zong et al., 2008). It is known that high-grade bauxite ore, with A/S greater than 8, can be processed directly by the Bayer process (Papanastassiou et al., 2002; Ma et al., 1996). However, Chinese diasporic ores have been processed mainly by the sintering process, which is environmentally damaging and energy intensive. Increasing the A/S of the diasporic ores using a flotation method is needed (Xia et al., 2010).Froth flotation is one of the most widely used processes to concentrate valuable minerals in beneficiation ores. It is particularly useful for separating finely ground ores from their associated gangue minerals. For diasporic bauxite ores, flotation is applied to obtain high-quality material for the Bayer process by increasing the A/S. Direct flotation has been shown to be an efficient method for the desilicating of diasporic bauxite ore (Wang et al., 2004; Xu et al., 2004), but reverse flotation has more advantages for this purpose, including less collector consumption, less foaming product and less effect on metallurgy (Liu et al., 2007; Hu et al., 2003; Hu, 2003; Luo et al., 2001)."

Jan 1, 2015

By Dan B. Kivari

A key operation of any milling circuit is grinding. Over the last two decades, large diameter semiautogenous grinding (SAG) mills have become the preferred primary grinding mills. The drive systems became more complex as the size of the mills became larger, during which time operating and design experience for SAG mill accumulated. Considerable reliance is now placed in power electronics to provide flexibility in SAG mill operation to meet the demands of lower operating costs. Most earlier SAG mills were designed to operate at fixed speeds. Present day SAG mills can operate at a fixed speed or variable speed through the use of an ac synchronous motor or dc motor. This flexibility, however, comes with an increase in capital and operating costs. Since the capital and operating costs of a project directly affect the project's rate of return, the selection of a SAG mill and its drive system should depend, in part, on the impact that the extra cost makes on the project. This impact can be measured by performing an economic analysis based on net present cost (NPC) calculations. Although the NPC calculation is an important factor in the grinding mill selection, other factors, such as reliability of mill drives and power source, are important elements in the decision making process. This article examines how the NPC calculation, plus reliability and power source, influence SAG mill selection.

Jan 1, 1992