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By E. P. Wiechrnann, C. M. Castro, G. A. Vidal, F. A. Muñoz

Different authors and publications indicate that Optibar Segmented Intercell Bars cause a remarkable distortion in the distribution of the current in a cell group. However, these results were based in inaccurate computer based models and do not represent the technology. During the last trimester of 2010, a 92 cells circuit from Barrick Zaldívar EW plant was implemented with Optibar Segmented Intercell Bars. The technology was incorporated progressively without disrupting the plant production. Depending on operational conditions, this led to a 2 to 4% current efficiency increase and 3 to 5% specific energy consumption reduction. By October 2011, 40,000 tons of copper will be produced with the technology.

Jan 1, 2011

By D. Kong, A. Klyashtorin, L. McGilp, I. Wilson

This work reports on applying iron oxide coated sands media in an experimental permeable reactive barrier to remove uranium species from uranium containing water. A field experiment was conducted at the legacy Gunnar uranium mine & mill site that was abandoned in the 1960s with limited to no decommissioning. The flooded Gunnar mine pit presently contains about 3.2 million m3 of water contaminated by dissolved U (1.2 mg/l), Ra-226 (0.4 Bq/l), and minor concentrations of other contaminants (As, Se, etc.). The water is seeping over the pit rim into Lake Athabasca posing environmental and health concerns. Iron oxide coated sands can be used to immobilize uranium species through an adsorption process. Methods for preparation of hydrous ferric oxide sorbents and their supported forms onto silica sands are described. Fourier transform infrared spectroscopy (FTIR), and powder X-ray diffraction (pXRD) were used to characterize the physical-chemical properties of the sorbent. The monolayer uranium uptake capacity (Qm) was estimated through the Langmuir adsorption isotherm. Adsorption kinetic experiments were performed in a lab environment before moving to a field trial. Based on these lab results and the input on field-scale appropriate geometries, a pilot permeable reactive barrier was fabricated and a field test conducted near the Gunnar pit in June 2019. This pilot test provided technical data and information needed for designing a full-scale permeable barrier based on the iron oxide coated sands, which may be applied for in-situ water treatment at Gunnar and other legacy uranium sites.

Jan 1, 2020

By Imane Benhamed, Jaouher Diouani, Laurent Cassayre, Florent Bourgeois, Carine Julcour-Lebigue, Université de Carthage

The attrition-leaching process aims at improving leaching performance when formation of passivation layers at the surface of leached particles is a severe limiting factor, as discussed recently by Julcour and coworkers (Julcour et al., 2015). This paper proposes a geochemistry-based modelling scheme for deriving the window of possible operating conditions for the attrition-leaching process to match the properties of the processed ore. The rationale is that the attrition-leaching process maintains the surface of reacting particles in an unpassivated state by continuous mechanical removal of surface leach layers, so that the process reactions can be modelled from thermodynamic equilibria throughout the duration of the process. The strength of the proposed modelling approach is that it bridges the gap between the properties of the ore and the process operating conditions. The present paper exemplifies the proposed process modelling route for derivation of the attrition-leaching process operating conditions in the context of the leaching of silicate ores, matching model predictions against controlled laboratory experiments. It is shown how thermodynamic modelling, when used in conjunction with a solid knowledge of the phases present in the system, can assist with deciding upon suitable process operating conditions. As an example, this firstprinciple modelling approach predicted that steel grinding medium would be converted into siderite (FeCO3) under a wide range of operating conditions, which led to questioning this initial choice of grinding medium for the attrition-leaching process under mineral carbonation conditions. It is emphasised that the same approach could be applied to ores of greater economic significance.

Jan 1, 2016

By G. D. Just

"Extensive mechanization of underground mining operations, improvements in blasting technology and the development of simulation models for systems evaluation has now made it feasible to optimize rock fragmentation and materials handling operations. Methods of achieving these objectives are described in this paper, with particular emphasis on the need to obtain precise field data measurements. Techniques are illustrated with reference to the sub-level open stoping system of mine production. IntroductionThe primary objective to be achieved in any mining system is to deliver a specified grade of ore to the mineral processing plant at a planned delivery rate and at the minimum total mining cost. Design and management of such a system is complicated by the large number of unit operations and the often unknown inter- relationships between the different unit processes. This particularly applies in underground mines, where planning restrictions and unit costs are much greater than in comparable tonnage sur face mining operations. These difficulties can often be resolved by the application of judgment based on extensive experience, but the costly trial -and-error methods required for new technology discourage innovation.Most modern medium- and large-scale mines are now extensively mechanized. Consequently, the performance of each unit operation by individual items of equipment should be predictable for a given set of conditions. An essential prerequisite is that quantitative performance data are available from field measurements. Such information can then be used to optimize the design and management of the complete mining system to achieve the minimum tot al mining cost. One of the most significant factors influencing all unit costs is the degree of rock fragmentation. The importance of this variable is indicated by the fact that opt imization of rock fragmentation implies minimization of tot al mining system costs."

Jan 1, 1980

By A. Ockewitz, A. Trondl, D. -Z. Sun

"Numerical simulation of extrusion processes offers an efficient method for tool design and optimization of geometries and properties of extruded parts. However, until now there are few systematic investigations about influences of material model and different parameters e.g. for friction and thermal processes on calculated local and global responses. Since extrusion processes are essentially influenced by friction between billet and extrusion tools, new friction tests were performed in this work to develop a reliable friction model. Compression and torsion tests were performed at different temperatures and velocities to calibrate the material model for extrusion simulations. Extrusion processes for circular rods and U-profiles were conducted at TU Berlin with backward and forward extrusion for different extrusion ratios, billet temperatures, product velocities and cooling conditions. This work focuses on numerical simulations of the extrusion tests with the FE code HyperXtrude. Based on the calculated distributions of local strain, strain rate and temperature the recrystallized volume fraction and grain sizes were calculated with empirical models and compared with the experimental results from optical micrographs and EBSD scans. The calculated total and friction forces and temperatures were compared with the experimental results and the deviations between experiment and simulation were analyzed.INTRODUCTION Extruded aluminum components are widely used in vehicle constructions due to light weight and manufacturing consideration. Local mechanical properties in the components are inhomogeneous as a consequence of the spatial distribution of microstructure which is influenced by numerous factors like material composition, temperature, tool design, friction, extrusion ratio and speed during the extrusion process. For the optimization of the extrusion process with regard to all these factors numerical simulation can be an essential tool. Based on results of finite element simulations of the extrusion process the microstructure in the extruded components can be predicted and then the resulting mechanical properties can be numerically determined instead of by costly trial and error methods. The aim of the work presented in this paper is the development of a numerical method for the simulation of extrusion processes with modeling of microstructure."

Jan 1, 2018

Who is CIBC? ? Canadian Imperial Bank of Commerce (?CIBC?) is a leading North American financial institution. ? Total Assets: US$315 billion ? Market Capitalization: US$29 billion ? CIBC comprises three strategic business lines: ? CIBC Retail Bank ? CIBC Wealth Management ? CIBC Wholesale Bank ? CIBC Wholesale Bank is a leading North American investment bank with niche capabilities in Asia, Australia & Europe. ? 1,000 + employees around the world ? Product range includes: Mergers & Acquisitions advisory and financing, Equity and Debt issues, Merchant Banking and Strategic Lending ? CIBC is ranked as the #1 investment bank in Canada across most of its key products and industries ? #1 Equity Underwriter in Canada ? #1 Mergers & Acquisitions Advisor in Canada

May 1, 2010

By L G. White

During 1958, prospecting parties working for the Mackenzie Syndicate in the Flat River area of the Mackenzie mountains, Northwest Territories, identified tungsten mineralization and located the property now being developed by the Canada Tungsten Mining Corporation Ltd. Scheelite mineralization, associated with pyrrhotite and minor chalcopyrite, occurs in lime silicate skarn replacement zones within a limestone-chert-argillite series intruded by granitic dykes originating from the ? main batholithic mass underlying the sedimentary beds. The results of surface outcrop sampling and 15,000 feet of grid-pattern diamond drilling have been combined to outline an orebody estimated to contain 1.32 million tons, grading 2.51 per cent WO after applying a 10 per cent dilution factor for mining purposes. T HE property of Canada Tungsten Mining Corporation Ltd. is located in the upper Flat River area of the Mackenzie mountains, Northwest Territories. Skarn-type replacement deposits containing scheelite mineralization are .situated between elevations of 4,500 and 5,500 feet above sea level along the east flank of the mountain range forming the boundary between the Yukon Territory and the Northwest Territories. The nearest supply center for the area is Watson Lake, Yukon Territory, located at Milepost 635 on the Alaska Highway.

Jan 1, 1963

By M. J. Nicol, T. Moyo

Ammoniacal solutions are an effective lixiviant for the oxidative dissolution of some mineral sulphides. A detailed study of the anodic dissolution of chalcopyrite in ammonium sulphate-ammonium hydroxide solutions has been carried out using cyclic voltammetry, chrono-amperometry and rest potential measurements. The role of the copper(II)/copper(I) redox couple in the oxidation process has been evaluated. Rest potentials have been found not to be affected by oxygen but to increase with an increase in initial copper(II) concentration. Pseudo-steady-state anodic current densities measured in the absence of copper(II) ions at the rest potentials obtained in the presence of copper(II) ions increase with increasing concentration of copper(II) ions, confirming the positive effect of copper(II) ions on the rate of dissolution of the mineral. Cyclic voltametric and chrono-amperometric data show that in the absence of initial copper(II) ions, the rate of dissolution in the presence of dissolved oxygen is significantly lower. These results confirm that the effective oxidant for the mineral under the conditions of the study is copper(II) and not dissolved oxygen. Coulometric measurements have been used to establish the stoichiometry of the anodic reaction at different potentials.

Jan 1, 2014

By Zhao-shu Sun, Mao-lin Li, Rui Cui

"Fankou Mine produced pyrite concentrate (PC) from the tailings by rougher and scavenger flotation before 2010, with the averaged S grade of 40.54% at recovery of 79.34%. The economic value of PC increases with its purity. When the S grade of PC feed to sulfuric acid plant is over 47%, the pyrite cinder can reach a high Fe grade of 62% which can be directly sold as iron concentrate. On this background, engineers in Fankou Mine set the PC with S grade of 47% as target.The direct way to reach that goal was to clean the rough PC Lots of cleaner flotation tests were conducted and the balanced strategy was to produce two ranks PC with the S grade of 47% and 38% at the recovery of 44.20% and 36.17%, respectively. The dual-product flowsheet was successfully industrialized in 2010. In order to further improve the quality of PC, gravity separation was introduced into the flowsheet. The numerical simulation and tests were performed to evaluate the beneficiation and classification performance of hydrocyclone as it treated the rough PC. It was shown that the underflow of hydrocyclone could addressed the S grade of 47%, and the finer size overflow could also be enriched to PC with S grade of 47% by flotation, due to the contained pyrite with well liberation. That is to say, with the ingenious addition of hydrocyclone to treat the rough PC, single PC with S grade of 47% could be achieved. The new flotation-gravity separation flowsheet was commissioned to produce the high quality PC at the end of 2013. The averaged S grade is 47.20% at recovery of 82.26% in 2014. The two steps flowsheet improvement maximizes the enterprise benefits and leads to simple utilization of Fe in pyrite in downstream industry."

Jan 1, 2016

By C. W. Davis

AN inclined shaft is usually more difficult to sink than a vertical shaft, yet it is often chosen because of the subsequent saving in cross-cuts required to reach an inclined ore body. This paper briefly discusses the factors which led to the choice of an incline and then describes the operations involved in the preparatory work and in the sinking. These operations included a programme of mining out the underground facilities and installing the structures required for a hoist-room, cable-raise, waste-pass, ore pass, two sets of skip dumps, and a collar station equipped with counterbalanced drop-rails. The shaft was sunk 1,000 feet and four stations were cut, each with loading pockets. As the sinking progressed, the rock changed from hard porphyries and dense cherts to blocky limestones and earthy rubble. These conditions called for a change in methods and it is to the red it of the shaft-sinking crew that they overcame the new difficulties as the shaft progressed, while maintaining a satisfactory monthly advance. The section mined out was nine feet six inches by seventeen feet overall. This gave room for three compartments: two skip compartments four feet three inches by five feet nine inches inside the timber, to handle two-ton skips, and a manway three feet six inches by five feet nine inches. The sinking began on December 16th, 1941, and was completed on February 15th, 1943.

Jan 1, 1945

By Willie van Niekerk

As mining projects get larger and more complex there is a need to examine the use of project management techniques developed for large construction projects in order to ensure completion of the project on time and budget. In recent years the construction/civil industry has sought new methods to ensure that multimillion dollar projects involving multiple contractors, working in an increasingly legislated work environment, are delivered to the clients satisfaction. The paper describes these methods, which range from program management to systems and tools to gather all project information such as schedule and cost, and relates how these can be applied to large international mining projects. The paper also describes the benefits that an independent project manager can bring to a client or owner?s team by setting up the relevant organization and controls together with the appropriate contract and procurement strategy.

May 1, 2009

By T. Grammatikopoulos, A. Jordens, C. Gunning

"Exploration activity for rare earth element (REE) deposits (i.e., alkaline complexes, carbonatites) has increased significantly in the last decade. A number of deposits have been evaluated around the globe. However, new mines have not been commenced in the last few years with the exception of Mount Weld (Lynas) and Mountain Pass (Molycorp).Resource estimation of REE can follow similar guidelines to other metal projects. However, the inherent mineralogical characteristics of the REE deposits, despite their complex nature, have been generally overlooked by many exploration companies. These include variability of the ore, liberation and association of the REE minerals, and grain size, all of which can affect the processing of the ore. Each deposit appears to be different in terms of matrix and REM (rare earth minerals). Light REE bearing minerals such as allanite, monazite, bastnaesite, synchysite, and HREE bearing minerals such as fergusonite and xenotime can vary widely in composition, grain size and association (e.g., carbonates or hard silicates). On the other hand, although not really REM, zircon, Zr-silicates, titanite, fluorite, apatite, and in some cases many other common silicate minerals can carry trace to significant concentrations of REE.The evaluation of REE deposits should include an appropriate mineralogical characterization in order to quantify the REM, distribution, liberation and association by quantitative mineralogical techniques (i.e., QEMSCAN, MLA, TIMA and others); chemistry of the REM by electron probe micro analysis (EPMA), Laser Ablation ICP-MS or ToF SIMS.These techniques provide valuable data for geological purposes such as: defining quantitatively, the variability and distribution of the REM; differentiating between LREE and HREE zones to delineate ore; and metallurgical purposes to predict minerals/REE behaviour during processing. The lack of a comprehensive mineralogical characterization often leads to the wrong processing path and ultimately affects the elemental/mineral recovery."

Jan 1, 2016

By Raymond S. Suglo

Increasing depths of mining coupled with the mechanization of most underground mining operations have led to growing complexities in the mine environments with the production of large amounts of gaseous and particulate contaminants. Over 100,000 lives have been lost due methane gas and dust explosions in coal mine workings in both the US and Canada since 1900 when the methane concentrations exceeded stipulated levels in some workings. There is therefore the need to constantly assess and evaluate the performance of the existing mine ventilation systems to maintain safe and acceptable mine environmental conditions in workings to meet the requirements of federal, state or provincial laws. This paper uses the results of continuous monitoring of methane concentrations conducted in selected development headings in coal mines in North America to assess the effectiveness of existing auxiliary ventilation systems in the control of methane gas concentrations in the headings. The results show that the average quantities of fresh air required to dilute, disperse and remove methane concentrations within set levels of one minute varied from 5.43 m3/s in Heading #11 (Condition 2) to 27.97 m3/s in Heading #10 (Condition 1) and this represented about 12 to 26% of the quantities required to dilute methane concentrations to safe levels within one minute under Condition 1 and 32 to 139% under Condition 2. The average dilution times in the headings studied were less than 8 minutes. The forcing efficiencies of the auxiliary systems in the headings studied ranged from poor to excellent implying that the auxiliary ventilation systems were capable of controlling the methane concentrations below statutory levels but may not be able to cope with large and unusual methane concentrations in the headings. This study is important to prevent methane gas and coal dust explosions in coal mines and thus avoid any loss of lives and property.

May 1, 2001

By J. Chenier, M. Boissoneault, D. Ducharme, R. Schonewille

The operation of Falconbridge's Sudbury nickel smelter has undergone significant change since the production was consolidated to a single electric furnace in 1994. In the late 1990's a capital program of about $100 MM (Cdn) was undertaken to expand and modernize the smelter. This project, known as Smelter 2000, was mainly driven by the need to process the new concentrate produced at Falconbridge's Raglan operation in northern Quebec. Included in the scope of the project was the installation of dry concentrate handling facilities, modifications to the roaster feed preparation system, installation of a matte granulation system and modification of one of the converters. Improvements to in-plant hygiene were also an important part of the Smelter 2000 project. Over the past 5 years much has been learned about the challenges in treating two significantly different concentrates. More recently, the introduction of a third concentrate from Falconbridge's new Montcalm operation near Timmins, Ontario has added another dimension to the operation. This paper will describe how the main challenges from the past 7 years have been overcome and discuss the path forward for the Sudbury Smelter Business Unit.

Jan 1, 2005

By J. Scrimgeour

"The word ""instrumentation"" has expanded from its original meaning, which in engineering perhaps referred to measuring apparatus alone. In its broadest form, it now includes sensors, display instrumentation, standard pack-aged controllers and, most recently, the use of stored program computers for on-line process control. The paper traces the evolution, in tutorial form, of the successive application of mechanization, measurement instrumentation, automatic control, central operating systems, programmed control, process computer control, direct digital control and, finally, hierarchies of computers used for process control and corporate management as a fully integrated business system. In the field of industrial minerals, the cement industry has seen the most widespread acceptance of these techniques. Computer control has been accepted as the way of life for the blending of chemical materials and for on-line control of the cement kiln. Accordingly, the cement application is selected for further presentation in the paper. This illustrates the trend progressing from control of single loops on process variables toward the objective of total control of the product quality. The economic justification for instrumentation, centralized control, automatic control and computer control is .discussed with reference to savings in fuel, maintenance, operating labour, depreciation, power and product quality improvements."

Jan 1, 1967

By J. J. Jonas, G. R. Stewart, A. M. Elwazri

Two important parameters for dynamic recrystallization can be derived from the changes in the strain hardening rate: the critical strain for initiation of dynamic recrystallization and the point of maximum softening. In this work, these values are determined from the flow stress-strain data obtained in continuous compression testing in the range 900-1100°C. The resulting strains are used to calculate a kinetic model of dynamic recrystallization for two materials: 304 austenitic stainless steel and a hypereutectoid plain carbon steel. The mechanical parameters used to define the proposed model are confirmed with quantitative metallographic analysis of the recrystallized microstructure.

Jan 1, 2004

By Y. W. Pan, Y. R. Liu

The disturbed natural rock mass tends to equilibrium state accompanying with non-equilibrium evolution process which has significant influence on the long-term stability of engineering structure. The deformation development in the non-equilibrium evolution is determined by two intrinsic processes, trend to equilibrium and damage development, which can be illustrated by evolution of excavated tunnel. Thus the creep and damage must be taken into account in study of non-equilibrium evolution process. Within Rice’s irreversible thermodynamics with internal state variable (ISV), the conjugate force function which equals to zero is a convex surface which divide the stress space into two parts, called equilibrium and nonequilibrium stress space respectively. The concept of effective stress of non-equilibrium has been proposed, in which the stress difference (d - d ) are the effective driving forces of non-equilibrium evolution process with hardening and damage effective. The formulations of inelastic strain rate and energy dissipation rate have been recast in the form of effective stresses. The inelastic complementary energy (ICE) is proposed to measure intensity of non-equilibrium evolution of material system. The specific equations of conjugated forces and kinetic equations of internal state variables are presented. The ICE and rate of energy dissipation are all calculated to be used to evaluate long-term stability of geo-engineering. The results show that rate of energy dissipation may be more convenience and flexible than ICE for internal state variable constitutive equation of rock mass.

Jan 1, 2015

By L. B. Kilius

The composite cathode system based on Ce0.9Gdo.1O2_,5 electrolyte with a painted cathode was used for an intermediate temperature (500-700°C) solid oxide fuel cell. This cathode system was chosen due to its excellent thermal expansion match to the electrolyte, its relatively high conductivity (115 S cm-1 at 700°C), and its low activation energy for oxygen reduction (99 kJ/mol). It was found that the decrease of sintering temperature of the composite cathode system produces a significant decrease in charge transfer resistances to a level of 0.25 SI cm2. The conductivity measurements of porous samples produced values between 40 and 88 S/cm for porosities of 30-40%.

Jan 1, 2005

By G. G. Manekar

MOIL Limited (formerly Manganese Ore India Limited), a Government Enterprise, under the Ministry of Steel, Government of India, produces about 1.1 million tonnes (T) of manganese ore annually from three opencast and seven underground mines. The underground operations are mining using an overhand cut and fill method. The orebody is too narrow for the use of larger equipment and the poor to fair rock mass quality limits the size of stable excavations. Prior to the 1990s underground support consisted primarily of timber square sets in tandem with timber chocks and props. As mine production requirements increased throughout the 1990s led to larger opening sizes and more modern support practices. Research was conducted on ground support design based on rock classification and empirical techniques for designing ground support. Based on the findings and field trials, the Company adopted full column cement grouted cable bolts for back support. Instrumented field trials, using extensometers and load cells on the cable support confirmed the support effectiveness. Stope design was based on two and three dimensional stress modeling which resulted in a significant increase in stope dimensions. The rock mechanics studies for safe stope design were carried out using numerical modeling tool in two and three dimensions for the analysis of stresses. Based on the findings, the safe stope geometry with new stoping parameters was introduced. The earlier stope length of 30 mtrs were changed to 60 mtrs with in situ rib pillar at the cross cuts and in situ post pillars to be left-out in the stope. This leads the formation of of panel comprising of three stopes, for production, supporting and filling. For mechanical handling of ROM in stopes Side Discharge Loaders (SDL) were introduced. The above changes have improved the face productivity from 2?3.5 T with manual operation and 9 T with SDL. The above rapid mining operations has improved the stope productivity but reduced the stope life from 6 to 3 years. For the improvement of the stope availability, further studies were conducted by numerical modeling of stress analysis. The related studies confirmed that with the existing supporting system and proper instrumentation, level interval could be increased up to 45 mtrs from the existing 30 mtrs at deeper levels. At present below 12th Level interval is 45 m at Balaghat Mine. For future mechanization program for introduction of Single Boomers, LPDT, Cutting Machines etc for the development headings rock mechanics studies are underway. The paper provides details of rock mechanics studies that were carried out to study efficacy of the cable bolt support, safe stoping parameters and increased level interval for the improvements in safety, production and productivity at Balaghat Mine.

Aug 1, 2013

By Juan Asalgado

The JORC and NI43-101 codes impose that mineralized material has a reasonable prospect of economical extraction to be classified as Mineral Resource. For deposits close to surface and amenable to open pit mining, it is easy to show reasonable prospect of economic extraction running a Lerch-Grossman optimization. The Lerch-Grossman pit provides a transparent and repeatable way of separating the Mineral Resource (within the pit) from the remainder of the mineral inventory (outside the pit). Deposits amenable to underground mining are more challenging because of the variety of the underground methods. AMEC developed a stand-alone software package that outlines the material which has reasonable prospect of economic extraction for open stoping, block caving, sublevel caving and room and pillar. The software takes a block model file in ASCII and exports a 3D surface outlining the part of the mineralization that has a reasonable prospect of economic extraction, and which the Qualified Person can smooth out manually if required.

Oct 1, 2009