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By Robert E. McIvor

"The design/optimization of the pump and cyclones to maximize grinding circuit efficiency first requires a concise understanding of, and clearly defined specifications for, desired grinding circuit performance. Subsequently, the pump and cyclone performances that provide the desired grinding circuit performance can be defined. Once the performance requirements of each process unit are determined, selection of physical equipment parameters that will deliver those performances can be carried out.The Functional Performance Equation shows that there are two distinct efficiencies in closed circuit ball milling. One of these, “Circuit Classification System Efficiency” (CSE), is the fraction of “coarse” material inside the ball mill upon which grinding energy is deliberately expended, versus the remaining fraction of “fines” or finished size material inside the mill, upon which grinding energy is wasted (on over-grinding). The role of the pump and cyclones is to maximize CSE, which is the desired grinding circuit performance. The obtainable target CSE for any given circuit can be estimated, for example, by referring to a plant data base of CSE’s. Design/optimization guidelines then allow us to specify the pump and cyclone performances that will achieve the target CSE.This paper outlines the step-by-step, systematic method of pump and cyclone selection which maximizes CSE. Numerous examples of its successful application are provided.THE FUNCTIONAL PERFORMANCE EQUATIONObservation of the feed and product size distributions going into and discharging from the mill in grinding circuits with low versus high circulating load ratios initially led to the definition of “Circuit Classification System Efficiency” (or CSE, McIvor, 1988a), and subsequently the discovery of the Functional Performance Equation (McIvor, 1988b; McIvor et al, 1992). The CSE is the fraction or percentage of “coarse” (usually in reference to the plus P80) size material inside the mill, versus “fines” or product size material finer than the circuit P80. It can be readily calculated by taking the average of the percentage of said coarse material in the mill feed and mill discharge streams. As this also represents the percentage of the mill energy expended on targeted, coarse size material, it is directly proportional to overall grinding circuit efficiency and production rate. This is all clearly expressed in the Functional Performance Equation for ball milling circuits, for which the derivation has often been presented (e.g. McIvor, 2006)."

Jan 1, 2011

By Marco A. Vera

"This paper investigates the froth function in flotation and the associated upgrading process. Flotation literature has revealed that one of the main functions of the froth phase is the cleaning of bubble-particle aggregates by rejection of entrained material. The cleaning and transport processes across the froth phase exert straining forces on these aggregates on their way up to the froth surface. These forces will impact on the recovery of bubble-particle aggregates.The grade at the top of the froth (TOF) is a parameter related to the quality of particles collected by bubbles in the pulp zone (true flotation). It has recently been demonstrated that TOF corresponds to the maximum practically attainable grade described by the recovery-grade (or enrichment ratio) curve. TOF lumps all the processes experienced by the bubble-particle aggregates before reaching the launder concentrate. This paper describes a methodology for quantifying flotation performance by means of the top of the froth sample - a touch of froth.INTRODUCTIONFroth flotation may be the most important mineral processing technique, but its theory is complex and is not completely understood even though many aspects have been studied and reviewed (Teague, 1998; Wills, 1992).Two distinct particulate systems prevail in the flotation process: a pulp phase and a froth phase (Figure 1). The pulp zone had been studied extensively; however, it is only recently that techniques to measure the froth zone performance have been developed (Contini et al., 1988; Falutsu and Dobby, 1992; Feteris et al., 1987; Seaman, 2002; Vera et al., 1999b).Flotation involves a number of mass transfer processes, occurring in the pulp phase and the froth phase. The formation of the froth and its subsequent removal are considered to be two important steps of the process. Phenomena that occur in the froth phase are known to affect flotation performance significantly (Cutting et al., 1981).Because the froth has a high free surface energy (as a result of the extensive interfacial surface between liquid and air), it appears thermodynamically unstable. The foaming is a dynamic balance, as new bubbles are added continuously from the pulp, while others disappear from the top. Under steady-state conditions, the volumes of added and subtracted air are equal (Booth, 1953)."

Jan 1, 2003

By T. Norvell, R. Gosine, S. O’Young

"This paper describes the use of dynamic scheduling and discrete event control to provide coordinated control of multiple automated vehicles. This work has been carried out within ongoing research into multi-robot coordination developed around the underground mining scenario. Demonstrations using scaled laboratory models of underground mines illustrate the potential for this technology for full-scale implementation for mine-wide automation. IntroductionIn the past decade, the mining industry has been improving the efficiency of underground mining operations. Robotics and automation have demonstrated the potential to further reduce costs. Tele-operation of underground vehicles from above ground and autonomous navigation have reduced travel delays and allowed for single operator control of multiple vehicles (Bloomquist and Hinton, 2001). Other recent projects include the automation of the digging process as well as the drilling and blasting operations. Infrastructureless guidance systems are also being developed (Bloomquist and Hinton, 2001).Mine-wide automation requires significant developments at two levels: (1) the development of mining robots capable of performing tasks either autonomously or semiautonomously; and (2) the development of methods for automating operations at a systems level. This paper focusses on the latter, and describes a general framework for the coordination of multiple mobile robots in an unstructured or semi-structured environment."

Jan 1, 2003

By Christoph Mueller

Broad band mine communication traditionally is characterized mainly by individual solutions, which have in common their long development phases and their high cost for development, operation and service. The use of Ethernet and the TCP/IP family of standardized protocols provide an uniquely price efficient combination of high bandwidth open networking, universal use and accessibility of price efficient development tools, especially because it forms the technical infrastructure for the worldwide Internet. TCP/IP and Ethernet assures reliable networking however it is not able to guarantee the latency timing of forwarding network information. Therefore, the network design requires strict load limitation and application level traffic control especially if moving equipment has to be manually remotely controlled via the network. The paper discusses the technologies the application of Ethernet and WLAN in underground mining environments.

May 1, 2006

By Klaus Tietz, Hamish Adam, John Selby, Ian Glazier, Brian Sinfield

"Room-temperature tunable diode laser (TDL) analyzers are gaining in acceptance for highly critical safety monitoring applications in a variety of industries. This paper describes the testing, evaluation and deployment of a laser-based hydrogen cyanide monitoring system at the Campbell Complex of Goldcorp’s Red Lake Gold Mines in Balmertown, Ontario, Canada.A trial, single channel installation was followed by a staged multi-channel installation. Unexpected technical issues with the multi-channel installation were addressed and resolved.INTRODUCTIONLaser-based gas detection has several advantages over existing gas detection techniques (Ballangrud, 1993; Silver, 1992; Bomse, 1995; Table 1). For practical purposes, lasers generate light at a single wavelength. Room temperature tunable diode lasers (TDL) emit light in the near infrared (NIR) part of the electro-magnetic spectrum. Many gases of interest, including HCN, NH3 and others, absorb energy in the near infrared (NIR). Each gas has a unique absorption signature, or spectrum, made up of a large number of individual “absorption lines”. A TDL can be tuned to select a single absorption line of a target gas, which does not overlap with absorption lines from any other gases. Therefore, laser gas sensing is selective and does not suffer from interference from other gases. The single-wavelength nature of laser light also means that laser gas analysers have a linear response over a wide dynamic range.Tunable Diode Lasers (TDL) generate only a few mW of power. However, all this power is concentrated at one wavelength, the wavelength where gas absorption occurs, resulting in high signal-to-noise ratios and short response times, typically of about 1 or 2 seconds (Ballangrud, 1993). This also means that long path lengths can be used, enabling accurate measurements of very low concentrations, even with weakly absorbing gases. Tunable Diode Lasers provide all the advantages of other semiconductor devices: they are small, solid-state devices, operate at room temperature, and have long-term reliability (over 15 years). Currently, they can be obtained for any wavelength throughout the NIR (700nm to 2000nm). Because many gases absorb in the NIR, the technique is widely applicable."

Jan 1, 2011

By Andy Fortin, André Vien, Christophe Bouché, Jeff McKay

"The technology and equipment design of the Twenty-first Century permit us to exploit low-grade ore bodies with milled tonnages reaching 300,000 tpd. Because of their substantial operational costs (energy, wear parts, etc) and precarious economic situations, the operations of today must maximize their metallurgical performance.The implementation of an Expert System becomes a logical avenue to pursue in view of increasing plant performance.Many operations, following the implementation of an Expert System, meet the objectives they determined before its integration; such as increased tonnage, stability, decreased costs, etc. However, they often cannot develop the full potential of the system due to certain factors that have been neglected or omitted during the implementation of the system.Three main elements have been identified during the implementation phase at INMET Mining Troilus Concentrator: 1- Instrumentation & Control 2- Software 3- Integration. Even though they have been clearly identified, these elements are often neglected due to lack of resources or lack of comprehension on the part of the operations personnel. This document will demonstrate, based upon our experience at Troilus and that of Metso Minerals, that we can identify and handle many factors which influence the profitability of the Expert System, for both short and long-term process control improvements.INTRODUCTIONThe Inmet Troilus Mine is an open pit mine, situated 175 km north of Chibougamau in the province of Québec, Canada. The mill, which started production in November of 1996, was originally designed to treat a gold – copper ore at a rate of 10,000 tpd.In early 1998, the mine plan called for a pit pushback and decreasing head grades for the following two years. With the price of gold nearing decade lows, the Troilus project was facing a major economical setback. There was a sense of urgency to reduce operating costs below the market price of gold. The mill team presented a project to management calling for an increase in mill throughput while minimizing capital expenditures and operating costs. This idea was supported by the existing mine plan, which called for a mine cut-off of 0.7 g/t Au and stockpiling low grade 0.5 g/t material for future milling."

Jan 1, 2003

Stress induced, gravity-assisted failure processes typically dominate long before stress levels approach the strength of the intact rock (at approximately smax > 0.4UCS where smax = 3s1 ? s3 and UCS is the Unconfined Compressive Strength of the intact rock (Martin et al. 1999)). Under these conditions, discontinuities typically become clamped and the failure process becomes brittle. This brittle failure process is dominated by new stress induced fractures growing subparallel to the excavation boundary. While it is possible to identify areas with the potential for brittle failure, for example, using the general assumption that brittle failure will occur in areas at right angles to the major principal stress (Hoek et al., 1995), when the threshold smax > 0.4UCS is reached in areas around the tunnel boundary, or elastic modelling and the Hoek-Brown brittle parameters proposed by Martin et al., (1999) (i.e. m? 0 and s ? 0.11), amongst others, recent observations discussed by Everitt & Lajtai (2004), and Kaiser (2005; 2006) suggest that brittle failure processes are enhanced when structural features such as joints, weakness zones, bedding planes or foliations are preferentially orientated around the excavation boundary creating stress raisers which in turn facilitate the stress-driven rock mass disintegration process (e.g., as illustrated by Everitt & Lajtai (2004) on Figure 1b). Such weaknesses induce stress heterogeneities that thus promote tensile-spalling failure processes (Diederichs 2000). The observations suggest that stress induced damage can occur ?prematurely? depending on the orientation of micro and macro structures in situations where the known stress conditions should not yet initiate brittle failure processes. In general, when structural features (micro and/or macro), especially foliations, are present in a rock mass, the strength is effectively reduced, largely due to tensile strength heterogeneity in areas depending on the orientation of the structural features with respect to the excavation boundary. As a result, stress induced damage could occur in areas not normally considered due to the influence of anisotropy (Figure 1).

May 1, 2009

By Eugen Gluck, Gus Van Weert, Peter Kondos

"Microwaves have the capability to heat up sulphides, especially clusters of particles of approx. 1 mm. Some sulphides absorb microwaves more readily than others. Molybdenite is especially effective in this regard, possibly due to its flaky nature and/or electrical conductivity. Even where it occurs in low concentrations in a deposit, individual rocks may be ore grade due to the high monetary value of MoS2. Such rocks often result from crushing mined veinlets or stockwork, or are contained in the cutoff grade fraction of ROM. Machine segregation of rocks high in MoS2 by infrared sensors after microwaving could therefore advantageously be used to upgrade lower grade ore between Mine and Mill. This would reduce the size of the latter, and thus its CAPEX and OPEX. Such upgrading could also yield shipping ore for a distant Mill, or extend ore reserves.Barrick Gold Corp. has been supporting the development of MW/IR sulphide sorting for the past three years. The results of MW/IR sorting work on molybdenite and other (pyritic) ore samples from a variety of sources are being presented here.INTRODUCTIONThis paper looks at mechanized, i.e. machine ore sorting technologies currently available and under development, and what conditions would be needed for the potential application of such ore sorting to sulphide mining and milling. Current machine sorting involves no-contact sensing technology for rocks, and signal processing after sensing to activate airblast segregation of certain rocks, normally the smallest mass to keep compressed air costs down.The forerunner of modern sorting is probably magnetic separation, which utilizes an inherent property of certain ores to divert it into mag and non-mags fractions. Radiometric ore sorters, which have been applied successfully for decades in the pre-concentration of uranium ores (Wotruba and Riedel, 2006) initiated modern sorting. In the 90’s, sensor-based machine sorting became a viable means of increasing the overall economic recovery of a resource. This technology became driven by the availability of low cost computing equipment and the concurrent development of algorithms, and by the availability of extremely fast response sensors and air actuators, allowing the sorting equipment to run faster, dropping the cost per tonne. It has been in industrial minerals processing that rock sorting has been most widely adopted, not really surprising. Liberation occurs on a different scale than in the base metal industry. Most industrial minerals are mined from massive deposits, requiring (in the past) no upgrading. Many of these operations now run into product contamination problems, which ore sorting can solve. One illustration: in Finland, a quarry is separating limestone from dolomite at 500 tonnes / hour, with individual rocks weighing up to 15 kg. Many of these industrial minerals operations have stockpiles of earlier discarded below-quality rocks, now being reprocessed with the help of ore sorting. The economics of this are very favourable, going from zero or negative value (stockpiles can not be left when closing the mine) to full product value for at least a portion of the stockpile. This suggests that in the future the economics of overburden sorting could become attractive under the right circumstances and such treatment could well become an integral part of open pit mine development."

Jan 1, 2009

By Hiroaki Sakurai

Using batch reactors equipped with CO and CO2 gas sensor, CO oxidation over Au catalysts in room air has been investigated and compared with Pt catalysts. For both Au and Pt catalysts, the logarithm plot of CO concentration data during initial 10 min are well fitted by straight line, which mean the first order dependence on the CO concentration between 10 and 10,000ppm. The rate constant value (k) over Au and Pt catalyst generally decrease with increasing initial CO concentration above 100ppm. The value decrease especially rapidly between 100ppm and 1,000ppm over Pt catalysts, which should be due to the strong adsorption of CO on Pt. The k value over Au catalyst has become ten times or more as large as the Pt catalysts at 1,000ppm. Already for the initial concentration of 100ppm CO, the strongly adsorbed CO on Pt metal has been clearly observed by FT-IR during the reaction over Pt/Al2O3. A part of the strongly adsorbed CO has been remained on Pt after the disappearance of gas phase CO, and has gradually changed to gas phase CO2. Such strongly adsorbed species on Au has never been observed on Au/TiO2 under the same reaction conditions. These features of Au catalysts are favorable for indoor air purification.

Oct 1, 2003

By D. Laguitton, D. Hodouin, V. K. Gupta, R. Spring

"The CANMET SPOC project aims at inducing progress in process evaluation and optimization by developing user oriented software based on state-of-the-art theory. The present work is the result of a joint effort by CANMET, Noranda Mines and Université Laval to develop two computer packages: one (RTD) to calculate the residence time distribution that best describes the material transport through the mill, the other (FINDBS) to estimate the rate of breakage and distribution function of the population balance model in a ball mill. The RTD package can handle data from various experimental methods (impulse or complex tracer feed, with or without recycling, etc...). The FINDBS package provides options for the functional description oj both model parameters Band S. The full detail of the methods and programs appears in a users guide. The program capabilities and several sample runs are presented.IntroductionSimulation of mineral dressing operations by computer has been largely contained within academic and research circles and has not yet gained a status of routine practice in the ore and coal industries. It is however a matter of time before process simulators are available on every process engineer's desk to assist process optimization tasks, flowsheet design and professional training. The CANMET SPOC project (Simulated Processing of Ore and Coal) was initiated in 1980 to assist the Canadian industry in integrating computer-based methodology for process evaluation and optimization(1). Software development, documentation and transfer is one of the main priorities of the project which will mature in 1985 by releasing a complete package of manuals and programs covering sampling, material balance computation, unit modelling, flowsheet simulation and optimization . This paper is a condensed description of a typical project element in its 1982-1983 state of development. The required methodology for ball-mill modelling and simulation was consolidated an d merged to other project elements during a joint study under contract financed by CANMET and Noranda Mines Ltd . The first part of the study dealt with documenting experimental methods and software for ball-mill computer simulation. Université Laval GRAAIM (Goupe de Recherche en Automatistion Appliquée à l'Industrie Minérale) acted as sub-contractor for this part of the study(16,17). A second part dealt with applying the model calibration techniques to a large industrial data base and is reported elsewhere(2,18,19)."

Jan 1, 1984

TABAKOTO / SEGALA ? Annual gold production approximately 100,000 oz ? Debt free ? Unhedged ? Combined surface reserves 949,000 oz ? Combined 9 year life Tabakoto open pit reserve 568,000 oz (3.4m tonnes @ 5.26 g/t Au) Segala open pit reserve 381,000 oz (3.98m tonnes @ 2.98 g/t Au)

May 1, 2006

By Jean-Sébastien Kroll-Rabotin, Éric Climent, Florent Bourgeois

"Falcon concentrators are enhanced gravity separators designed for concentrating fine and ultrafine slurries. The Falcon UF model is unique in that it is dedicated to beneficiation of ultrafines, one key feature being that it does not make use of any fluidisation water. In a former study, we investigated the physical mechanisms that govern the transport of ultrafine particles (in the range 10 to 80 µm) inside Falcon UF concentrators, and concluded that separation efficiency is governed by differential settling. Initially, we derived and published a predictive model of the partition function under dilute conditions. The present paper proposes an extension of the initial model to concentrated ultrafine suspensions for application to industrial scenarios. The paper discusses how hindered settling has been added into the initial model to account for solid concentration effects. The modified model is tested against experiments carried out with a laboratory scale UF Falcon concentrator from dilute conditions up to 30 vol%. A good agreement between measurements and model predictions is obtained, which confirms that our hypotheses about the physics of separation inside a UF Falcon separator remain valid even at high concentrations.INTRODUCTIONThe Falcon concentrator is a fast spinning bowl that is fed at its centre of rotation. It uses centrifugal force to separate particles that are transported inside a thin liquid film that flows upward along the inclined wall of the bowl (McAlister and Armstrong, 1998). Due to differential settling, dense and coarse particles are concentrated inside the bowl whereas light and fine particles are rejected with the overflow stream. The fast rotation speed of the bowl yields high centrifugal force several hundred times the attraction of Earth. Despite the thinness of the liquid film (between 100 µm and 1 mm with a Falcon L40) where separation takes place, the Falcon concentrator can treat high flowrates (up to 30 L/min). At the bottom of the bowl, an impeller transmits the bowl rotation to the feed, which drains upward by centrifugal force as soon as it hits the base of the spinning bowl (Figure 1)."

Jan 1, 2011

The Stability Graph Method is widely used in Canadian underground hard rock mines for open stope support design and is frequently used in the mine planning phase to assess the viability of stope geometries and to determine maximum permissible spans. The Method is well accepted due to its simplicity and suitability to a wide range of mining methods requiring the use of sublevels to access and extract the mining blocks. While this Method is reliable in situations where the maximum induced tangential stress creates adequate compressive stress keeping the face in a state of confinement, the Method fails to reflect the effect of low confinement caused by lower compressive stresses and instances where tensile stresses are developed. In this paper, a new Rock Stress Factor, A?, an update to the original Rock Stress Factor, A, is proposed, which will reflect the impact of low confinement or overstress regime on critical face stability. Two case studies, based on two Canadian operating gold mine shows that using the new Rock Stress Factor A? to predict the stability of stope hanging-wall and footwall gives better agreement with the CMS survey results, compared with the prediction using the original rock stress factor.

May 1, 2011

By Tapiwa Chenje, Victor Olivas, Peter Radziszewski

"Ore breakage and grinding media wear have always been considered and determined separately in laboratory tests. However the two processes are linked with the ore broken down in any comminution device being responsible for the majority of the steel wear experienced. The Comminution Dynamics Laboratory (CDLab) successfully developed a test methodology that can more accurately predict grinding media wear in tumbling mills than the Bond Abrasion test. This paper looks at the possible application of the abrasive wear methodology to determine breakage parameters of the same ore used in the abrasion test. Results indicate that breakage parameters comparable to t10 can be determined using the Steel Wheel Abrasion Test (SWAT), while using significantly less ore than standard breakage tests.BACKGROUNDThe Rubber Wheel Abrasion Test (RWAT) is an internationally accepted and widely used method for determining the abrasion wear behavior of materials. The abrasion wheel test was developed to primarily utilize a steel wheel (Brinell, 1921). Haworth (1949) criticized using of the steel wheel by arguing that increasing the contact area size in the steel wheel test causes a change in the wear rate with time. He suggested that the use of a rubber wheel instead eliminates this problem, leading to the adoption of the RWAT which was standardized in ASTM G65 (2004).Radziszewski (2002), however, found that the use of the Steel Wheel Abrasion Test (SWAT) was more applicable for wear testing in the mining industry for two critical reasons. Firstly, the major cause of wear in a ball mill, the most frequently used comminution device, is ball-ore-ball contact and also ball-ore-liner which both are metal-ore-metal contact. Therefore, using the steel wheel has the advantage of providing a similar abrasive environment to the one that takes place in a real ball mill. Secondly, the SWAT creates the potential of running experiments at much higher force regimes that are closer to what happens in actual mills, unlike the RWAT which is a low stress test."

Jan 1, 2011

By F. Dai

Due to difficulties associated with gripping in direct tension, indirect methods are commonly used to measure rock tensile strength. In this work, we adopt an innovative indirect tensile test method: Semi-Circular Bend (SCB) to measure the tensile/flexural strength of Laurentian granite (LG). The static tests are carried out with a servo-controlled material testing machine and the dynamic tests are conduced with a Split Hopkinson Pressure Bar (SHPB) system. Pulse shaping technique is adopted to achieve dynamic force equilibrium in SHPB to facilitate data regression. Finite element method is used to relate the failure load to the tensile strength. Strong rate dependence of the tensile strength is observed. The flexural strength is higher than the tensile strength measured using Brazilian Disc (BD). This difference is rationalized using the non-local theory. To further validate the method, a coupled Finite element/Discrete element method (Fem/Dem) in conjunction with the smeared crack model is utilized to simulate the fracture process during dynamic SCB tests. The resulting fracture patterns are qualitatively consistent with those from recovered samples. Both the experimental and numerical methods have validated the results and this new method is readily to be used for other rocks and other brittle materials.

May 1, 2009

By Y. L. Su, S. Vongpaisal, H. A. Smith

"It is extremely difficult for a mine's central control room operator to control peakpower demands and to maintain normal materials handling operations at the same time. An investigation of the Falconbridge Strathcona Mine 's central control room has revealed that there are more than eight thousand possible combinations of ""situations"" that can arise. For such a circumstance, an expert system can become a very valuable tool to assist the operator in taking the most appropriate and timely action.A forward chaining expert system module has been developed for this application. The module is based on Level 5 ObjectTM software. It is graphics oriented and user-friendly. Training requirement is minimal.ForewordThis paper has arisen out of work carried out by YLS Associates and Falconbridge Limited as part of a contract between Falconbridge and the Department of Energy, Mines and Resources, Government of Canada, on the application of expert systems in mining operations.IntroductionThe electrical bill charged to large consumers by Ontario Hydro is based upon two elements: demand and energy consumption. The demand is the peak kilowatt level that the consumer has required during a monthly period. It is not uncommon for the demand portion to be as much as one third of the monthly bill. Energy consumption is the total kilowatt-hour s (kWh) consumed during the period.Ways to reduce the energy consumption part of the electrical bill involve utilizing energy-efficient equipment and operating machines in off-peak hours when a lower energy rate is charged. Maintaining the peak power below a critical level may require that simultaneous usage of major pieces of equipment be avoided. A 3000 kW skip run at an inopportune time could cost a company an extra $30,000 in that month's power cost.Potential disadvantages associated with peak power control are lost production due to work stoppage and increased operating costs due to the need to employ extra personnel. Most companies find these matters relatively easy to deal with and with incentives provided by Ontario Hydro, actively pursue this facet of energy savings (Harju , 1991)."

Jan 1, 1993

By D. Wolfe, K. Reid, T. Nunn

"The Aurora North mine has been operating for more than ten years, and is the source of over half of Syncrude’s bitumen production. In order to minimize front-end rejects, and to allow for high throughput, the ore top size at Aurora has been set at a nominal 125 mm. These relatively large lumps have a significant effect on both pump performance and pipeline pressure gradient. Current design methods underestimate the solids de-rating effect of lumpy slurries in pumps, and do not accurately describe the distribution or magnitude of the lump effect on pipeline pressure gradient. Data from the Aurora hydrotransport systems has been compiled, to quantify the effect of lumps on the pump head ratio and pipeline pressure gradient, and how this effect changes as lump ablation occurs along the length of the pipeline. A model has been built, using a logarithmic curve, which predicts the effect of 125 mm lumps on pipeline pressure gradient as a function of velocity and the distance from the start of a hydrotransport pipeline. This model is applicable only to Aurora hydrotransport operation, but similar models could be developed for other operations using the same methods. Using accurate pipeline pressure gradients and pump head ratios when designing future hydrotransport pipeline systems will help improve their reliability and operability."

Jan 1, 2014

By E. Wasmund

"Sandfire’s DeGrussa Copper-Gold operation in West Australia is a new high grade copper sulfide mine, which includes a 1.5 Mtpa concentrator which was completed in 2013.Early after commissioning, it was identified that the flotation capacity in the all-mechanical cleaner circuit was not sufficient. In order to improve recovery, the tail from the cleaner scavenger was sent back to feed the rougher scavengers. Test-work was done on-site to evaluate the possibility of using a flotation column as a pre-cleaner. A CavTube™ sparging system was selected, which is especially effective for fine ore particle flotation. Test-work was conducted at site using a 150 mm diameter unit, and then confirmed on a 500 mm diameter unit. A 4250 mm diameter full scale unit was installed in Q4 2014 and commissioned in Q1 2015. This unit gave some significant advantages including a reduction in re-grinding requirements, elimination of a circulating load and increase in the recovery of copper in the cleaner circuit and overall circuit.In this presentation, the benefits of columns and cavitation sparging for floating fine particles and rejecting fine entrained gangue will be explained. Also, the results from a lab unit and a pilot unit will be compared against the results of the full-scale unit. The paper will demonstrate the scalability of flotation columns, and which phenomena and scale-up criteria must be considered to be successful. Finally, some general observations will be made about the importance of columns in copper cleaning circuits.IntroductionSandfire Resources’ DeGrussa copper-gold concentrator is located approximately 900 km north-north-east of Perth in Western Australia. The project area landscape is scrubby mulga lands with few notable features. The climate is arid with high temperature and heavy summer downpours."

Jan 1, 2016

By Fidelis T. Suorineni

Rockbursts are a major hazard in deep hard rock underground mining and tunneling. To date a significant number of rockbursts still defy conventional explanations. A review of rockburst case histories in the literature has shown that pillars and tabular excavations under shear loading are prone to rockbursting in situations where they are least expected under conventional knowledge of rockburst causes. Despite the evidence of the effects of shear loading on underground infrastructure, and the frequency of their occurrence, little is known about how this loading mechanism causes such large magnitude events and extensive damage. In this paper analytical and numerical modeling are used to understand the behaviour of pillars and tabular excavations under shear loading. The numerical modelling results show that pillars under shear loading are less confined than their equivalents in loaded in pure compression in the same geologic environment, and are therefore more brittle and weak. For tabular excavations under shear loading, the behaviour depends on whether such excavations are continuous, co-planar or offset with rock bridges. Analytical results based on slit theory show releasable potential energy in tabular excavations increases nonlinearly with excavation half-span. The study results are important for the safe and economic extraction of orebodies under shear loading.

May 1, 2011

By Robert B. Parsons

"Exploration and development of mineral resources in developing countries by Canadian-based multinational mining companies is becoming increasingly common. One problem being encountered is that the objectives of the governments of developing countries can differ from those of developed countries. These objectives are not always consistent with maximizing returns from the projects, which can create conflicts between the mining company's responsibility to its shareholders and the desire to be a good corporate citizen. This article discusses how a mining tax regime can be designed to make the social goals of a government consistent with the economic goals of the company.IntroductionAt the recent International Seminar on Mining Taxation organized by CIM and the United Nations there was considerable discussion about the role of international mining companies operating in developing countries. Not surprisingly, given the diversity of backgrounds of individuals attending the Seminar, there were different opinions about what this role should be.Government PositionRepresentatives of governments pointed out the strong desires of their countries for technology, high-level technical training of their workforce, increased employment, and development of social infrastructure. They pointed out that, to a large extent, these objectives could be more efficiently met by mining companies operating in the country than by the governments themselves. For example, a multinational mining company (""MMC"") would have extensive knowledge of the various technologies available, and would have performed a detailed evaluation of the mineral resources before choosing the most cost-efficient technology for that project. They would, therefore be in an ideal position to assist the country in importing and developing such technology. Similarly, the company could provide opportunities for hands-on training, both at the technical and managerial levels, which would otherwise be unavailable to the government."

Jan 1, 1991