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Current AG and SAG mill circuits have continued the trend to larger, fewer mills. These large mills place a significant additional load on the discharge systems and it has become imperative that the designs of these mill discharge systems are evaluated carefully to ensure maximum efficiency and have the capacity to be able to handle the increased mill discharge volumes. The current generation of multiphysics modeling tools allow a detailed analysis of AG and SAG mill discharge performance. The combination of Discrete Element Method modeling and Computational Fluid Dynamics allows the designer to model in detail all aspects of a mill discharge performance. This includes a detailed description of the build-up of solids and slurry in a mill discharge, the recycle of material back into the mill through the grates, the relative wear rates and the occurrence of overloading at the pinch points. These tools allow intelligent decisions to be made regarding the type of discharge arrangement, pan lifter geometry, and discharge cone design, so as to ensure that the discharge is capable of handling the duties required for a specific installation. This paper details the current state of the art in these modeling tools, and provides an overview of some recent applications.

Jan 1, 2012

By Chuck Edwards

"Milling operations in northern Saskatchewan’s Athabasca Basin have produced uranium continuously since 1975. Over that period, the Athabasca Basin has been one of the world’s premier uranium camps, yielding more than 660 million lb of U3O8. In this paper, the author describes former and current milling operations and discusses why and how the milling process has changed and developed over the past 35 years. The author’s considerations for the future of uranium extraction in the Athabasca Basin close out the paper.INTRODUCTIONThe roughly oval Athabasca Basin in northern Saskatchewan occupies nearly one third of the surface area of the Saskatchewan Shield. Its sandstone-like deposits lie unconformably on the older basement. The basin hosts many high-grade unconformity-type uranium deposits(Saskatchewan Energy and Resources, 2010) for which the Athabasca Basin is world famous. Uranium production in the Athabasca Basin has come from four mills. In the order of startup these are Rabbit Lake, Cluff Lake, Key Lake and McClean Lake. General data (AREVA, 2010; Cameco, 2010; Denison 2010) for each mill are shown in Table 1."

Jan 1, 2011

By Michael Young, Peter Allum, Mingwei Gao

"Tough economical conditions and high grade but fine-grained ore processing have forced the mining industry to look for more efficient processes. Isa Mill Technology for ultra-fine and fine grinding is one such process employed at several mining operations in Australia including Mount Isa Mines Limited in Australia. Mount Isa Mines is a business unit of MIM Holdings Limited. MIM is an Australian-based international mining and mineral processing company with around 8000 employees worldwide. Major products include copper, gold, zinc-lead-silver, coal and technology sales.The Isa Mill is a horizontal stirred mill with sizes up to 3 m3 chamber net volume and 1 120 kW installed motor. It was jointly invented by Mount Isa Mines of Australia and Netzsch Feinmahltecknik GmbH of Germany for ultra-fine and fine grinding duties in the minerals industry. Isa Mill operations started in 1994 at the Mount Isa Mines Leadzinc Concentrator and then at MIM’s McArthur River Mine in 1995. These Isa Mills have been used to liberate sphalerite and galena at Mount Isa and silica at McArthur River by grinding to less than 7 micron.This paper discusses the Isa Mill Technology and reports on the metallurgical performance of the Isa Mills at Mount Isa Mines, including work done over the last 9 years to improve mill design, process efficiency and maintenance, which has resulted in the current state-of-the-art Isa Mill Technology.INTRODUCTIONThe current leadzinc deposits at Mount Isa Mines (George Fisher, Hilton and Isa) have an average grade of 10.5% zinc, 7.2% lead and 165g/t silver. Fine grinding, in particular in the zinc retreatment circuit requiring a milled product P80 of 7 micron, is essential to treat the ores from the Mount Isa Mines deposits. Every one micron size reduction in the zinc retreatment circuit below a P80 of 10 micron improves the overall plant zinc recovery by 1%, resulting in an increase in revenue of about 1 million dollars per annum."

Jan 1, 2002

By R. Heikkilä

Fluent information exchange between different work phases, software and systems used in infra construction is a key for successful execution of infra construction projects. Open and publicly available information formats with the determined data models aim to facilitate the interoperability between different software and systems developed by competitive vendors. While building and construction industry has developed and used IFC format for years, infrastructure sector has just recently started to target clear efforts on the development of open information formats for infra construction processes. In the paper, a new Inframodel3 extension just developed in Finland and based on the LandXML1.2 international standard is to be introduced. The aim of the Inframodel3 was set to meet the requirements of information transfer needed especially between BIM based design software, measurement systems and 3-D machine control systems used in road, railway and watercourse construction projects. Some test results are reported and evaluated in the paper. In the field of bridge engineering, the IFC format and IFC Bridge extension have been tested and evaluated in Finland. The results from the experiments show and verify as well the applicability of these open formats to the information exchange requirements in bridge engineering. The current limits for open information transfer of these formats are shown. The active co-operation with the International Building SMART Organization has led to the achieved status and position for both the Inframodel3 and IFC Bridge formats and hence the continuing international support provided by Building SMART.

Aug 1, 2013

By Gary S. Anderson

Rajant Corporation is the global leader in mining communications systems implemented a vision to develop a wireless network that is rapidly deployed, self-powered and managed, for portable or fixed configurations ? Mobile, Portable, Self-Powered, Secure and High Bandwidth. The network configures itself allowing for very rapid deployment without the time delay and personnel typically required for set-up and configuration. Rajant?s proprietary technology ?InstaMesh®? is incorporated in a device called a BreadCrumb®. Rajant has filed several patent applications on its proprietary technology and has received trademark protection on its brand names. The BreadCrumb® uses technology which allows mining, military and first responders to easily establish internet connections at remote sites or situations where existing internet communications has been disrupted. The BreadCrumb® products are standards-based Wi-Fi 802.11 a/b/g compliant, ruggedized, lightweight, portable; self-meshing and the system can be established by just turning on several of the BreadCrumb® units. The Rajant Network has evolved in the ?One Network? philosophy and has been deployed by both the military and homeland defense organizations. With multiple radios, transmitting on multiple frequencies as the same time, bandwidth is doubled, the speed of the network is enhanced, management is simplified, and manageability is made easier. Rajant has partnered with world class integrators and partners, including ten CAT dealers, a world-wide mining technology company, a mining and construction software company and leading technology innovators in mining automation and operations. Recently, Rajant provided a significant network to Rio Tinto?s Iron Ore of Canada Mine in Labrador City, Newfoundland, Canada, Kennecott Utah Copper Mine, and is currently the wireless standard at Peabody Energy and several mines in Australia. These networks range from 20-250 BreadCrumbs®. The result is a meshed mobile broadband network capable of operating in a vast open pit active mining space. Simultaneous applications currently running on these BreadCrumb® networks in the mining sector consist of Caterpillar?s VIMS?s, CAESultra grade control and Aquila Drill Management Systems, Carlson Grade Control systems, Jigsaw Technologies and Modular Mining fleet management system, Ground Probe Radar, an Automatic Train Operation and various video and VoIP applications. All vendor applications have been turned off and all applications are running on Rajant?s ?One Network?.

May 1, 2010

By Faan Bornman

"Reeves and Platt1 stated that dense medium separation is one of the most complex unit processes in mineral processing today particularly if cyclones are used. It is also the most efficient gravity concentrating process available to process engineers. The complexity of the process and large number of design and operating variables means that the process has largely remained more an art than a science. Dense medium separation is well established in the diamond, coal and iron ore industries but is gaining popularity as a pre-concentration step in other industries. The maintenance issues are addressed that will affect the efficiency of the operation.INTRODUCTION The purpose of the dense medium separation (DMS) process is to separate the valuable material from the waste based on gravity differences. However, the specific gravity difference between the two fractions must be large enough to achieve high efficiencies. Heavy particles sink through the dense liquid and light particles float. DMS is also used for the pre-concentration of minerals before further downstream processes like communition, in order to minimise the treatment costs. Examples are the pre-concentration of diamond ores or metalliferous ores like nickel, copper and cobalt. Dense medium separation is also used to upgrade the material to meet different market specifications, for example in coal and iron ore applications. A typical dense medium separation process for a diamond application is shown in Figure 1."

Jan 1, 2014

By F. M. Makarinsky

"SynopsisThe Kanichee open pit mine and milling complex is situated approximately four air miles north-west of Ternagami, Northern Ontario, in Strathy Township. Mining and milling production commenced in January 1974.Milling throughput currently is at a rated capacity of 500 tons per day, seven days per week. A bulk nickel-copper sulphide concentrate is produced, and is trucked daily to the smelter at Falconbridge Nickel Mines Limited, Falconbridge, Ontario, some 120 road miles from Kanichee. Concentrate grades produced are in the order of 4.0% Ni and 8.0% Cu, with corresponding recoveries of 68-70% nickel and 86-90% copper. Stage additions of 100% guar-gurn solution reagent to the flotation cells for depression of talcose minerals, proved to be the major break-through for optimizing metallurgical performance.2. HistoryThe present Kanichee Mining property is known to old-timers in the Temagami area as the former Cuniptau Mine. Several attempts were made in the mid '30's and 40's to extract the ore at a profit, but each effort resulted in failure.In 1933-36, Cuniptau Mines Development Co. Limited, later called Cuniptau Mines Limited, sank a 245-foot vertical shaft and completed 2,200 feet of lateral work on the 100-140 and the 225 foot levels. Fifteen tons of ore were sent for testwork to the Mines Branch, Ottawa, Ontario.Cuniptau Mines Limited, in 1936, milled some 3,000 tons, and the resulting concentrate was put through a pilot smelter situated on the present mine site. Metallurgically, the smelting results were not encouraging, primarily due to the high melting point of the talcose minerals in the concentrate. From the period 1937-48, minor exploration work was done by Ontario Mining Corporation, Ontario Nickel Mines Limited, and Trebor Mines Limited. During the period 1948-49, 128 diamond drill holes, totalling 40,900 feet were evaluated by Trebor Mines Limited. In 1961, the name was changed to Ajax Minerals Limited, during 1968, five diamond drill holes were sunk, totalling 1,700 feet. Since that period the property has remained idle."

Jan 1, 1975

Operationalizing the Ruggie Framework in a Mining Context Ruggie?s 3 Pillars: The State?s duty to Protect Policies, regulation, adjudication The Corporation?s responsibility to respect Acting with due diligence to avoid infringing Addressing adverse impacts when involved in abuses Access to Remedy ??even the most concerted efforts cannot prevent all abuse.?

May 1, 2013

By Tom Gaines, G. S. Brant, J. G. Debanne

"AbstractThe Bonnie Glen oil field, one of Canada's largest, lies about fifty miles southwest of Edmonton, Alberta. One hundred and thirty-eight wells have been completed in this field since its discovery in January, 1952. Five different procedures have been used in completing the producing wells.The reservoir is an Upper Devonian biohermal reef with good porosity and uniformly high permeability. The top of the reef is quite flat but the flanks slope at angles approaching 20 degrees from the horizontal. The reservoir has a gas cap with a maximum thickness of 400 feet, an oil column of 300 feet, and a :porcus aquifer of over 300 feet. The reservoir pressure is now 2,400 pounds per square inch gauge at datum ( -4100 M.S.L.).Because of the high permeability and the high •pressure, lost circulation and resultant blowouts are a particular hazard in drilling at Bonnie :Glen field. To reduce the dangers of blowouts, it is general practice to run casing to the top of the reef. If the reef is encountered 'high' it was usual practice to run a liner and perforate for completion. Wells penetrating the •reef below the gas/oil interface were either completed in open hole or through casing perforated opposite the oil pay, with the former method more frequently used. Eight wells were completed by the Humble-Otis permanent-type completion, and recently five high wells were completed open hole with the gas •cap exposed. This latter completion, 'tubing submergence', has proved highly satisfactory thus far.The open-hole type of completion is cheaper than the liner perforation method and results in better well performance. More experimentation and data are needed before the tubing submergence method can be recommended unqualifiedly. but all evidence thus far favours its use in reef reservoirs."

Jan 1, 1955

By Ngonidzashe Chimwani, David Glasser, Diane Hildebrandt

"Milling circuits play an important role in achieving the desired product; tonnage, size distribution and properties, since they are directly linked to the comminution energy consumption for the whole process. A grinding model with a mathematical simulation was developed for an open milling circuit with a scalped feed from a hydro-cyclone. The circuit was optimized by determining the optimal conditions in terms of energy consumption which would produce a floatable product having a desired size range (i.e. -75 +9 µm) for a platinum-bearing ore. The simulation results showed an operating region comprising the best combination of the ball filling and mill speed to achieve the highest production of a floatable size class, with the minimum energy consumption.INTRODUCTIONBall milling is usually conducted in closed circuits in order to achieve a desired product size without material overgrinding. The technological importance of optimising milling circuits cannot be overemphasised (Toneva and Peukert, 2007). Previous work has brought significant insights into the benefits of modelling milling circuits (Austin et al., 1984; King, 2012; Toneva and Peukert, 2007). However, the ability to model these circuits is dependent on the performance of the classifiers and the fidelity of the grinding mill model used compared to the actual circuit (Toneva and Peukert, 2007). Austin et al. (1984) identified five types of milling circuits as shown in Figure 1 namely; the grinding circuits employing mill in an open circuit, normal closed circuit, reverse closed circuit, open circuit with scalped feed, and, the combined closed circuit. Depending on the presence of the first classifier, the second, or both as well as their corresponding loops (streams), the combined circuit (e) can reduce to; an open (d), a normal closed (b), an open circuit with scalped feed (c) or a reverse closed circuit (a). In the case of an open circuit, the mill is operated without being directly influenced by a classifier. The normal closed circuit does not have the first classifier and therefore the make-up feed is the actual feed stream. Conversely, the reverse closed circuit keeps only the first classifier. The open circuited with scalped feed has only the first classifier but does not have the second one. The overflow stream from the classifier is mixed with the mill product to form the final product for the downstream process."

Jan 1, 2016

By S. Kodama, G. Sasaki, K. Matsugi, K. Sugio, Y. B. Choi

"Pure aluminum (Al) matrix composites with changing the volume fraction of TiB2 particle content from 10 to 30% was fabricated by spark plasma sintering (SPS) process. Then the microstructure, density, dispersibility and thermal conductivity of the composites was estimated. As increasing TiB2 content, the dispersibility of particles and the density of the composites degraded slightly. And, the effect of the dispersibility of TiB2 particles on the thermal conductivity was quite little. The thermal conductivity of the composites was less than the theoretical value calculated by Maxwell-Eucken equation considering the effect of the density. It is due the influence of the interface heat transfer rate, because these composites have many small sized particles and have high interface density.INTRODUCTION Recently, metal matrix composites (MMCs) have been used widely in electric / electronic components, architectural materials, transportation equipment, aerospace and a precision instruments, because it’s superior properties have been greatly watched. Demand of MMC for industrial use has been increasing gradually. Furthermore, multifunction properties are required for the composites strongly. By integrating the dissimilar materials, the composites have various properties that we cannot get from monolithic materials. On the other hand, the response to the thermal management is required for materials, recently, and the need for the structural material controlling the thermal conductivity has been increasing. Especially, superior thermal conductivity and good mechanical properties from room temperature to high temperature are required for heat sink and heat exchanger at the same time. In late years, a study on the composites combining carbon materials and aluminum and copper has been developing, and actually the composites with high thermal conductivity which is not provided in the conventional materials is developed. On the other hand, non-oxide ceramics particles such as SiC and AlN, TiB2 have good thermal conductivity. Particularly, as TiB2 has good electrical conductivity, TiB2 containing MMCs is expected as innovative materials used as electric/ electronic components. Furthermore, as TiB2 has low density, high melting point, low thermal expansion and good deformation resistance, the development of high performance composites with multi-functional properties is expected. As thermal conductivity of pure Al and TiB2 are 225 and 66.4 W/mK, respectively, it is expected that the degradation of thermal conductivity by adding dispersant in Al matrix is suppressed. The authors have carried out a thermal conductivity, electrical conductivity, mechanical properties of 20 vol.% TiB2 dispersed Al composites (Sugio, 2016, Sasaki, 2016). In this study, the influence of quantity of addition of TiB2 on microstructure, thermal conductivity was studied minutely."

Jan 1, 2018

By Patrick Moore

In 1971 the government of British Columbia issued a permit for the Island Copper Mine to commence disposal of 33,000 tons per day of mine tailings into Rupert Inlet, a marine fjord on the northwest coast of Vancouver Island. There was considerable controversy surrounding the development, public hearings were held, and as a requirement of the permit the company was obliged to carry out a comprehensive environmental monitoring program. The results of this program provide a thorough assessment of the environmental impact of submarine tailings disposal over the 24-year life of the mine. Following closure in December, 1995, the monitoring program continued for three years to determine the extent of marine ecosystem recovery and re-colonization. It is apparent from the findings of the monitoring program that the mine tailings were dispersed more widely than was originally predicted. It is also clear that widespread heavy metal contamination has not materialized. In retrospect it appears that submarine tailings disposal has resulted in far less severe environmental impacts than if the alternative of land disposal had been adopted. This review highlights significant aspects of public policy decision-making, design of environmental monitoring programs, and questions of interpretation of monitoring program data.

May 1, 2002

By O. Hyvärinen

Outokumpu has developed a new chloride leaching process called HydroCopper®. In this process copper sulfide concentrates are leached at atmospheric pressure in concentrated sodium chloride solution using cupric ions as the oxidant. Copper is recovered from the purified leach solution by precipitating cuprous oxide, which is then reduced to pure copper and further melted and cast directly into copper products. The key reactants: sodium hydroxide, hydrogen and chlorine are generated from the spent sodium chloride using chlor-alkali technology. An important feature in the HydroCopperTM process is that the gold contained in copper concentrates is leached as chloride complexes and recovered from solution by activated carbon. Conditions for the leaching of gold-bearing pyrite can also be achieved in the chloride system by optimizing the redox conditions. This paper deals with the basic factors affecting gold leaching from copper sulfide concentrates. Opportunities for the recovery of refractory gold associated with arsenopyrite and pyrite will also be discussed.

Jan 1, 2005

By A. T. Robles, L. Buckingham

"When certain gold ores containing pyrite, graphite, humates and fumates or other organic compounds which are possibly adsorbed on clay minerals are treated with aqueous solution of alkali metal cyanide, the aurocyanide complex which forms is adsorbed by these ""pregrobbing"" species in the ore. Dissolution of gold proceeds until chemical equilibrium is attained between the cyanide complex adsorbed by the ore and in solution.Sodium lauryl sulfate (SLS) may be used to decrease the adsorptive activity of the prerobbing species in the ore. It has successfully improved recovery at Holt-McDermott Mine and is highly biodegradable.INTRODUCTION Precious metal-bearing ores containing preg-robbing species are poorly amenable to standard cyanidation techniques. The ""preg-robbing"" impurities with which they are associated tend to adsorb the gold cyanide complexes and carry them through the circuit to the tailings. Also, gold may be associated with these impurities in the ore and not be leached by the cyanide complexing agents used in conventional cyanidation techniques.Methods for dealing with the problem of preg-robbinq impurities in gold ores are:Carbon-in-Leach (CIL), in which granular activated carbon is added to compete with preg-robbing species for the gold cyanide complexes. This process can improve gold recovery in mildly preg-robbing ores especially when fine carbons with very high activities are used. However, with severely graphitic ore, the carbon associated with the rock may outperform the granular activated charcoal.Chemical Oxidation, in which the ore is subjected to preliminary chemical oxidation techniques to oxidize carbonaceous materials using such diverse reagents including ozone, sodium hypochlorite, calcium hypochlorite, chlorine gas, permanganates, perchlorates, chlorates and oxygen prior to subjecting the oxidized ore to standard cyanidation treatment to extract gold. This is generally a costly method and will not prove economical on a low-grade ore."

Jan 1, 1992

By Y. Luo

The rock breakage process in drilling is a main source of noise in roof bolting operations, especially when hard rocks are encountered. Proper control of drilling operation can provide an opportunity to improve energy efficiency of drilling and to reduce noise and heat generated from bit-rock friction. Drilling tests have been conducted in laboratory settings to confirm this noise-reduction strategy. Preliminary results show that the drilling parameters, penetration and rotational rates can be controlled to achieve in a desirable range in drilling medium hard rock. Based on the theoretical and experimental studies, rational drilling control strategy is developed for noise control while maintaining a safe and productive roof bolting operation. Applying this strategy in underground roof bolting operation, the noise exposure of roof bolter operators will be significantly reduced.

Aug 1, 2013

By Paul Grady, Martin Froehling, Curtis Mohns, Eliab Roman

"Since the idea of processing rock to unlock the valuable minerals inside was put into practice, efforts to improve production began. Methods have been learned that allow for operation in environments and under circumstances where it would not have been possible until now. All existing operations have experienced at least some form of productivity improvement measures. The objective is simple: generate more product of better quality in less time and at lower unit cost. Since the year 2000, various modifications have been made at the Kemess Concentrator in efforts to improve productivity. The following is a discussion of these modifications and their contributions to the success of the operation.INTRODUCTIONThe Kemess South Mine, a major producer of gold and copper, is located in north-central British Columbia. Kemess was brought into production in May 1998 by Royal Oak Mines with a modern mill controlled by a fully integrated Foxboro IA DCS system and employing 134 people. On February 11, 2000 Northgate Exploration Limited (now Northgate Minerals Corporation) acquired Kemess Mine from receivership. Since acquisition in 2000, Kemess has seen many accomplishments, including the reduction of costs by 40% site wide.The mill has a nameplate capacity of approximately 56,000 tonnes per day which is processed through a Metso (Svedala) 60” x 89” Primary Gyratory Crusher and then conveyed by a 60” conveyor to a stockpile with 48 hours of total storage capacity. The nominal minus 6” rock from the stockpile is fed to two parallel grinding circuits (A & B). Each section consists of a 10.4 m F x 4.7 m SAG mill with dual drive motors (4,480 kW apiece) discharging onto a 2.4 m x 7.3 m Metso (Svedala) single deck vibrating screen to remove the coarse material for recycle to the SAG mill by a Continental 45º high angle sandwich conveyor. Screen undersize is pumped along with ball mill discharge to a cyclopac consisting of twelve Krebs 66 cm F cyclones to classify flotation feed to a size of approximately 65% minus 200 mesh. Cyclone underflow feeds a Metso (Svedala) 6.8 m F x 11.0 m ball mill, also with dual drive motors (4,480 kW apiece). The primary grinding circuit has 35,840 kW available for grinding."

Jan 1, 2005

By P. Homola, M. Karlík, M. Slámová

"Aluminum sheets (AA1199, AA8006, and AA5754) were processed by accumulative roll-bonding (ARB) in the temperature range from 20 to 350°C. The microstructure of the sheets was characterized by means of scanning and transmission electron microscopy and electron backscattered diffraction. Mechanical properties were monitored by hardness measurements and tensile tests. Increasing strain (number of ARB cycles) led to incremental development of lamellar microstructure with a decrease of the spacing between high-angle grain boundaries in the normal direction of sheets. ARB process produced an important increase of strength while maintaining thickness and relatively high ductility, without accenting of the anisotropy of mechanical properties of sheets. The level of hardening decreased with the processing temperature and at 300 and 350°C ARB caused even the softening of the material due to the recovery of the deformed microstructure or partial recrystallization during heating to ARB processing temperature.INTRODUCTION Accumulative Roll Bonding (ARB) is a technique of grain refinement by severe plastic deformation (SPD) proposed by Saito et al. (1999). One ARB cycle consists in sheet cutting, surface treatment, stacking of two pieces, heating (optional), and rolling with 50% reduction in thickness. Since the sheet thickness remains unchanged by this cycle, ARB processing can be repeated as many times as desired. The goal of ARB is to impose an extremely high plastic strain on the material, resulting in structural refinement and strength increase without changing specimen dimensions. After several cycles, ultra-fine grained (UFG) materials with high strength and relatively high ductility are produced. An advantage of this method is that it does not require any special equipment as other SPD methods such as equal channel angular pressing (ECAP) (Valiev & Langdon, 2006), high pressure torsion (HPT) (Valiev et al., 2000), or cyclic extrusion and compression (CEC) (Richert et al., 1999), but only a conventional rolling mill and so it is seen as an economically viable and industrially scalable processing route. ARB processing has been successfully applied to various kinds of metallic materials at room or elevated temperatures (Tsuji, 2005). Besides processing single metals and alloys, ARB has also been used for creating ultra-fine grained and nanograined metallic composites (Wu et al., 2010; Qu et al., 2014)."

Jan 1, 2018

By L. A. Wolff

"Second only to profitability (but not always), productivity is the most sought after measurement for any operation. Whether it is in mining, manufacturing, construction, etc. managers always strive to know how productive various plants are. Even the Federal Government publishes, on a monthly basis, the nation's factory productivity.Just what is productivity and how is it measured? This is an important topic that needs definition. There could be as many definitions as there are people who use it. In the mining industry, the problems of defining productivity would be analogous to the definition of equipment availability. Each mine uses its own definition to suit its needs. Webster's Dictionary primary definition for productivity is ""the quality or state of being productive,"" with productive defined as ""yielding or furnishing results"". This is a definition open to a broad spectrum of interpretation. A discussion of how productivity is currently used in the mining industry and an introduction to a potentially different approach to its measurement and meaning is outlined in this paper.Defining ProductivityTypically, mining companies track several productivity measurements. These are partial measurements and can include the following: tons per specific equipment class per hour, tons per man-hour, and tons per shift. None of these, however, track the over -all performance of an operation, that is, a unit of output per unit of input.For a mining operation, output can be defined as the ore for mill processing. Input includes the required components of production to get to the first step of processing.The Wesbter's Dictionary definition exposes a major fault with the popular conception of productivity. The critical issue of accountability is not addressed. Anyone can produce, but how effectively and efficiently are resources used? Quantifying an inclusive measurement is difficult. Statistics referring to an increase in productivity are often published. For example, the statement, ""gold productivity has increased by 10%"" has many potentially dangerous interpretations. One must ask, what does this statistic really mean? Did gold companies produce 10%” more gold? Were less manpower or equipment required to produce an equivalent amount of gold? Did ore grades increase resulting in more ounces of gold produced, etc. Obviously, production and productivity can have similar implied applications and meanings, but also two different, distinct meanings.To mitigate a problem like this, a standard needs to be developed within the mining industry. Because of varying ore grade, changing waste to ore ratios, different mining methods, etc. all of which have a direct impact on mining, development of a standard is difficult. Kendrick(1) discusses the use of Total Factor Productivity as a productivity measurement. Summarized, the total factor productivity measure is an indication of the change in efficiency in the use of basic labour and capital factors associated with an operation.This measurement has little meaning when calculated at a given point in time. It should be an on-going calculation, tracking an operation over a period of time, to evaluate trends. These trends can be used to determine if an operation's productivity is what it should be, and alert management to potential problems before they become major and adversely affect an operation."

Jan 1, 1990

By S. Gregory

Many gold treatment plants have sulphides and coarse particle gangue components that contain gold in their tailings (cyanide leach residues and flotation tailings). Coarse and very fine liberated gold may also be present in some tailings streams. Two issues usually govern the economics of recovering additional gold from gold occluded in sulphide and gangue particles. The liberation characteristics of the gold in the sulphide and coarse gangue (gold liberation versus grind size) is the first and most important of the two. If fine grinding can liberate a reasonable amount of the gold, then the next important issue is how effectively these two constituents can be concentrated. Flotation will achieve high sulphide recovery but is usually costly. Selectivity is also an issue because of entrainment. Continuous centrifugal gravity concentration offers a viable solution to the recovery of both sulphides and coarse gangue however selectivity is also likely to be a problem. The possibility of improving concentrate grade by using a Falcon B separator was investigated. This paper describes a program of test work carried out on a gold leach tailings using a laboratory Falcon '13' separator. The program involved three different bowl angles: 10, 12 and 14 degrees and two bowl speeds (giving 250 and 350G accelerations). A number of tests were also performed on samples that had free gold present to ascertain the size-by-size recovery of gold in these samples.

Jan 1, 2005

By Tim Martin, Dave Tahija

"In April, 2014, Hecla's Greens Creek mill, near Juneau, Alaska, switched from sulphuric acid to the use of dissolved carbon dioxide for lead flotation circuit pH control. The Greens Creek mine uses paste backfill, in which mill tailings are mixed with cement and used to fill mined areas. Some backfill inevitably becomes part of mill feed during subsequent mining cycles, resulting in high feed pH levels and increased dissolved calcium in the lead flotation circuit. Sulphuric acid is traditionally used to lower pH in such cases but it produces undesirable side effects, including poorer lead-zinc separation and unstable froth. The amount of sulphuric acid used at Greens Creek was limited due to these effects, resulting in higher than target pHs when feed backfill content was high. Dissolved carbon dioxide can be added without these limitations so pH levels have been under much better control since the switch. Additionally, lead-zinc separation and froth characteristics have significantly improved.IntroductionThe Greens Creek Mine, owned by Hecla Greens Creek Mining is an underground mine located on Admiralty Island near Juneau, Alaska, producing silver, gold, lead and zinc in the form of lead and zinc flotation concentrates and a gravity gold concentrate (McDonald, Morgen & Hancock, 2012). The lead and zinc concentrates are produced in conventional flotation circuits preceded by a graphite removal flotation step.The underground mine utilizes cemented paste backfill, of which a certain amount is inevitably re-mined in later mining cycles and returned to the mill, mixed with fresh ore. The Portland cement used in the paste backfill is highly basic so that, from the point of view of the mill, the net effect is to introduce a good deal of lime to run-of-mine mill feed, producing a very high natural pH. This high pH needs to be lowered to obtain good metallurgical results."

Jan 1, 2016