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By G. Gabra

"A process of leaching niobium oxide from pyrochlore concentrate using hydrofluoric acid is described. Variables such as acid concentration, temperature, reaction time, solid/acid ratio, agitation speed and particle size are correlated to the recovery of niobium oxide.The relatively low activation energy (1,86 Kcal/mole) and the dependence of reaction rate on agitation suggest that the process is diffusion controlled. The optimum conditions for extracting niobium oxide from the leach solution, using either methyl isobutyl ketone or tributyl phosphate have been determined.IntroductionMost of the commercial production of niobium and tantalum has been derived from the treatment of columbite - tantalite minerals.In recent years (1960) , pyrochlore mineral has been found to be an alternate source of niobium . This mineral varies widely in composition and contains in addition to the main elements of calcium , sodium and niobium, some tantalum, fluorine, rare earth elements, titanium, alkali an d alkaline earth elements.It is well known that the province of Quebec possesses several pyrochlore niobium deposits totalling approximately 151 million ton s at an average 0.45% niobium oxide(1). One of the deposits, the St-Honor carbonatite, was brought into production by Niobec Inc. in 1976. Flotation o f this material produces a concentrate of about 60% Nb205(2).In view of an expanding niobium market in recent years and the presence of large niobium deposits in the province, a research and development program was initiated at the Centre de Recherches Miner ales to evaluate known processes for the separation of niobium and tantalum from each other as well as their purification . Some work has also been undertaken at the CRM to develop an improved extraction process. T his work will be the subject of further communication s."

Jan 1, 1985

By D. T. White

Pressure acid leaching of nickel laterite ores typically involves the production of an intermediate product that is releached and refined to pure nickel and cobalt products. BHP Billiton is developing the Ravensthorpe Nickel Project to produce up to 50,000 t/y of nickel via a mixed hydroxide intermediate, which will be refined at its Queensland Nickel (QNI) Yabulu Refinery near Townsville, Queensland. The hydroxide precipitation flowsheet has been adapted to process high magnesium ores through an atmospheric leach stage, eliminate iron(III) as jarosite and oxidise iron(II) during neutralisation. The neutralisation conditions are controlled to precipitate aluminium, chromium and silicon, and to ensure good solid-liquid separation. Soluble impurities such as magnesium are purged with the tailings stream and will be managed over the long term by crystallisation in evaporation ponds.

Jan 1, 2006

By Stephen C. Tadolini

"The use of a torque wrench to establish the amount of actual load developed on an expansion anchor bofting system dates back to work completed in the early 1950s. The advent of ultrasonic measurement systems and hydraulic torque wrenches has made it possible for the U.S. Bureau of Mines to perform torque-tension measurements in the laboratory and the field much more accurately. The results indicate that the amount of initial boft preload may be overestimated by amounts in excess of 45% of the expected load using torque wrenches. This inaccuracy is primarily due to the friction that occurs between the bearing plate and the head of the boft. These parameters become extremely important when the support system is being used to prevent joint members from slipping relative to each other or when the boft acts as a heavy spring to clamp two or more sections together. Methods to overcome the frictional losses are presented in conjunction with a laboratory method to determine the actual torque-tension ratios for expansion anchor and combination bolting systems.IntroductionMechanically anchored roof bolts have been widely used in the mining industry since their introduction in 1947. Estimates made in 1989 indicate that out of 85 million fixtures, approximately 49 million bolting fixtures still use applied tension to complete the reinforcement necessary to maintain stable openings. Nearly 85 million bolts are used yearly. The most widely used bolt is the resin-anchored headed rebar, followed by standard mechanical roof bolts, specialty bolts (mechanically anchored, resin enhanced fixtures) , and combination bolts . Po st-tensioned resin rebars, combination systems, and friction stabilizers make up the remaining 10% of the units used (Fig. I).For mechanical, combination, and tension rebar bolts, the bolt tension is the primary means of reinforcing the roof, but in many cases, because of poor installation procedures, the bolts are ineffective. Mine operators recognize the importance of proper installation procedures. Long-term bolt tension measurements are required in the Code of Federal Regulations (CFR)In each bolting cycle, the actual torque or tension of the first tensioned bolt installed with each drill head shall be measured immediately after it is installed. Thereafter, for each drill head used, at least one roof bolt out of every four installed shall be measured for actual torque or tension. If the actual torque or tension of any roof bolts measured is not within the range specified in the roof control plan, corrective action shall be taken."

Jan 1, 1991

By Matt Manson

?? Current Exploration and Assessment ?? Overview of Potential Development ?? Infrastructure ?? Opportunities and Challenges ?? Renard? 1-10 kimberlite pipes and ?Lynx-Hibou? kimberlite dyke system within ?Foxtrot? property ?? 50/50 Joint Venture between Ashton (a subsidiary of Stornoway) and SOQUEM ?? Discovered 2001-2003 ?? Québec is routinely assessed as one of the top mining jurisdictions in the world ?? Agnico-Eagle Mines Ltd. Is Stornoway?s largest shareholder and a leading mine developer in Québec

May 1, 2008

By A. P. Sasmito

It is well known that underground miners are exposed to one of the most dangerous working environments on earth. As mine delve deeper, the geological factor, mine position and climate condition as well as heat generation from mining machine give rise to the mine operating temperature. This, in turn, has an adverse effect on the environment and thus leads to higher operating costs. Careful estimation and design of air flow rate, spray system, cooling load and additional ventilation auxiliary equipment are of importance to ensure safety, comfort and productivity whilst maintaining low operating cost. A computational fluid dynamics simulation approach is employed to examine underground mine ventilation in a 36 m cul-de-sac of tunnel of coal mine. The model predictions in the turbulent range were validated by comparison with published data. Different turbulence models were tested to select one that yields adequate accuracy and is computationally efficient. Effects of the following parameters are evaluated: tunnel geometry, air flow rate and inlet air temperature. The objective of the simulation is to arrive at an optimal strategy for ventilation and thermal comfort at low cost.

Aug 1, 2013

By Rick Steen, Weldon Read, Morrism Tracy T.

Edging for starter sheet blanks used in conventional copper refineries has always been problematic for getting the edging to seal and adhere to the titanium material used for the blank so that copper is prevented from plating under the edging and cause undo problems in getting the copper sheets to separate from the blanks. A method was developed at the Amarillo Copper Refinery utilizing an injection molding process that better adheres the edging material to the titanium that makes the harvesting of starter sheets much easier to the point that robots are now used to strip with and which holds up very well to the unforgiving physical nature of the electroplating process. It is believed that this technology could be successfully utilized for permanent cathodes as well. INTRODUCTION ASARCO LLC (Asarco) was organized in 1899 as the American Smelting and Refining Company. Originally a consolidation of several lead-silver smelting companies, it evolved over the years into an integrated producer of primary non-ferrous metals, including copper, lead and zinc and associated co- products (Marcosson, 1949). Grupo México, S.A.B. de C.V acquired Asarco in 1999. Today, Asarco is a vertically integrated producer of primary refined copper and associated co-products such as gold, silver, molybdenum, selenium and tellurium. Asarco operates three open-pit mines and mills and two solvent extraction-electrowinning (SX-EW) plants all in Arizona plus a copper smelter in Arizona and a copper refinery in Texas. Figure 1 illustrates how the copper metal comes out of the ground at the mine and ends up as a refined product at the refinery. The copper refinery in Texas is known as the Amarillo Copper Refinery (ACR) and is located in Amarillo, Texas. It was built in 1975 to replace 3 other aging refineries and was designed to produce 550,000 tons (500,000 MT) of refined copper per year using conventional starter sheet technology. At the time it was commissioned it was the largest tankhouse in the world at just under 1/2 miles long under one roof.

Jan 1, 2019

By D. H. Wilton, C. I. Godwin, A. J. Sinclair

"A computer-based drill core logging system used to examine computer-based drill core logging system used to examine copper mineralization hosted in volcaniclastic rocks at the Sustut deposit, in north-central British Columbia, has many advantages over conventional logging. A relatively simple format for recording geological information allows complex, but significant, geologic parameters to be recorded consistently, accurately and quickly. This allows graphical presentations and statistical interpretation of the data that lead to rapid and detailed analyses of the control and distribution of copper mineralization at the Sustut deposit.Ore mineralization is concentrated in lens-shaped bodies and is zoned from native copper cores through chalcocite, bornite and chalcopyrite to a margin containing pyrite. Chalcocite, the principal mineral, occurs mainly in volcaniclastic agglomerate characterized by a specific grain size, a narrow range of matrix and fragment proportions, and a specific sorting.IntroductionWe report here a case history of the practical application of a detailed computer-based drill core logging system applied to the Sustut copper deposit of Falconbridge Nickel Mines Ltd. The Sustut deposit, containing a few tens of millions of tons of ore grading slightly more than one per cent copper (Church, 1975), is in north-central British Columbia about 875 km north of Vancouver. The deposit is contained in volcaniclastic sedimentary rocks of the Upper Triassic Moosevale Formation, which is within the upper part of the Takla Group (Monger and Church, 1977) of basic volcanic and associated sedimentary rocks. Takla rocks occur along the eastern fringe of the Intermontane Belt in the Canadian Cordillera (Sutherland Brown et al., 1971). The deposit consists of concentrations of copper sulphides, native copper and pyrite within pods and lenses parallel to bedding in the host sedimentary rocks. These sheet-like deposits exhibit a mineral zoning from pyrite at the fringes successively through chalcopyrite, bornite and chalcocite to native copper at the core (Wilton, 1978; Wilton and Sinclair, 1979)."

Jan 1, 1980

By John C. Loretto

"The paper identifies two of the main problems encountered in recent hydrometallurgical plants for the recovery of gold and silver: firstly, the plant recovery is lower than anticipated from the testwork; secondly, the metallurgical accounting figures cannot be reconciled.The principal reasons for the plant recovery being lower than the testwork are discussed, together with solutions that can minimize these problems both during the design stage and during the plant operation after the problems have manifest themselves.The reasons for the difficulties in metallurgical accounting are analyzed by reviewing the various components of the plant figures. Recommended solutions are given for minimizing this problem and the realities of obtaining accurate figures are discussed.IntroductionThe start-up over the last few years of new hydrometallurgical plants for the recovery of gold and silver has brought to the surface again a number of problems. Most of the problems have existed for some time and they manifest themselves mainly in two ways. Firstly, the plant results do not agree with the metallurgical testwork figures; secondly, the metallurgical accounting figures do not balance.Metallurgical TestworkThe plant results not agreeing with testwork figures are mainly due to:a) testwork samples not representative of the eventual plant feed;b) misinterpretation or misunderstanding of testwork ;c) plant losses;d) plant design not allowing testwork results to be achieved;e) operating deficiencies."

Jan 1, 1982

By Yan Germain, Université Laval, Bernard Dallaire, Jocelyn Bouchard, Peter Radziszewski, Gilles LeBlanc, Michelle Levesque, Nicolas Tremblay

"The comminution process is estimated to be only 1% efficient, resulting in waste energy dissipated as heat, noise, and vibration. Energy recovery from grinding circuits has not been implemented mainly because recovering heat from the surface of the grinding mill or from mill slurry can impede operation, increase maintenance requirements, and prolong plant shutdown time (and production). However, currently very little information is available in the public domain regarding the amount of waste energy and that potentially recoverable in the grinding circuit of a mineral processing plant. Availability of such information could drive innovation and improve decision-making regarding opportunities for waste energy recovery. The Canadian Mining Innovation Council (CMIC) has initiated a study with CanmetMINING and mining industry partners to develop a model to map the energy flows in grinding circuits and to quantify the potential for energy recovery. The paper outlines the underlying fundamentals and data requirements for use in the model and then focuses on quantifying the energy recovery potential of the semi-autogenous grinding and ball mill circuits at the Agnico Eagle Goldex Division. Results show that most of the electrical energy (over 75%) is used to heat the slurry, leaving only a relatively small amount of it to achieve mechanical work (~9%). INTRODUCTIONCanmetMINING commissioned a study in 2013 to better understand the barriers for adoption of new technologies in the mining industry (MNP, 2013). The conclusions highlighted the importance of enhancing industry/regulator engagement and communication to raise awareness and improve the industry’s comfort level with new technologies.In November 2014, the Green Mining Innovation Advisory Committee (GMIAC) held a workshop to explore the possibility of accelerating the uptake of green mining technologies by bringing together key stakeholders among the mining value chain to address industry priorities. Participants included representatives from mining companies and associations, academia, provincial governments and federal departments and organizations. Two key priority areas emerged at the workshop: i) energy saving, and ii) water management."

Jan 1, 2016

By L. C. Kitchener, K. Vollenwyoer

"This paper describes the development of an automated, 70-ton capacity, underground electric trolley truck at Inco Ltd. The purpose of the project is to provide a high capacity and high productivity haulage system to suit continuous loader applications in existing mining horizons where conveyor belt application is not immediately practical. IntroductionWith the start o f a program by Inco in mid-1983 to develop a continuous loader for bulk mining of our hardrock orebodies, the need for a rapid ore transportation system was recognized to match the increased extraction rates planned. Two methods were investigated, truck haulage and conveyor belt. As a result, a conveyor belt system has since been designed and installed with a continuous loader at Stobie Mine and an electric truck has been designed, fabricated and assembled, with shop testing underway. This paper deal s with the latter project. BackgroundMany existing mining horizons which could utilize continuous loaders do not have the straight runs required for conveyor belts. In these situations, truck haulage would be the only alternative of the other transportation methods that would be practical. In order to match the high productivity potential of the continuous loader, however, a more efficient trucking system is required than would be available with conventional diesel powered trucks or with electric truck designs commercially available, or under development. A higher capacity truck and an automated operation is necessary so that the application of additional units to suit increasing haulage distances matches loader output without reducing over-all productivity because of the need for additional operators.A first effort to work with a major electrical manufacturer was unsuccessful and resulted in a project delay of almost one year. In November 1984, an investigation into the concept was reinstigated with UTDC, and an agreement to start design was reached in April 1985."

Jan 1, 1988

By P. M. Solozhenkin, O. I. Ibragimova, I. P. Solozhenkin

Molecular models of complexes of poorly studied bismuth, gold, and arsenic mineral clusters and reagents were created for use in collector activity forecasting using Chem Bio 3D and ChemOffice2005, with optimization by MM2. The density functional theory approach was used to determine HOMO, LUMO, SOMO, and total energies, atomic charges, and s, p, d- populations for various compounds. The structure-based virtual screening (SBVS) and docking technique was proposed to reduce the vast number of compounds to a more manageable number for selection of potential flotation candidates. The prognosis of collector activity evaluation (PCAE) strategy was proposed as a consistent approach to estimate the interaction between a collector and a mineral cluster as the difference between the total energy and sum of cluster energy and collector energy to search the analogue of butyl xanthate. The negative relationship between PCAE and flotability was shown. The combinations of dialkylamino sulfhydryl collectors can be considered as prospective reagents for gold-bearing sulfide ore flotation. These results were confirmed by experimental data in ore flotation. The increase in recovery of gold and bismuth with the aid of a combination of reagents has been established and additional cyanidation of tailings has been avoided.

Jan 1, 2016

By L. Cáceres, G. Leinenweber, P. Bustamante

"Given the severe scarcity of fresh water sources in Northern Chile the use of seawater has become the only alternative to allow mining expansion. This option however poses several technological challenges as a result of the high concentration of natural salts that promote various forms of metal corrosion. Therefore the steel piping protection has been a constant challenge for design engineers responsible for solving the problems of corrosion. Known protection alternatives are varied and expensive, a few of them are rubber coatings, protection based centrifuged concrete, extra wall thickness of pipes in combination with corrosion inhibitors, extra wall thickness of pipes without using corrosion inhibitors, and the use of highly corrosion resistant steel materials.In this framework the aim was to study the corrosion kinetics of carbon steel pipe API 5L X70 under electrochemical and weight loss testing. The test conditions include a range of seawater velocities between 0.2 to 3.0 m/s.For electrochemical experiments the API 5L X70 steel specimen was a 4 mm diameter disk embedded in an 8 mm diameter Teflon rod and exposed to seawater. Duplicated coupons were placed in a standard test apparatus that was built according to the standard ASTM D 2688 – 94.The main results were: a) corrosion mechanism explained in terms of the counterparts partial processes which are the hydrogen evolution and oxygen reduction reaction; b) for the test specimen a corrosion band like feature that suggest a lateral dispersion of aggressive solutions from corrosion pits; c) a range of corrosion rates between 1 and 1.96 mm/year for flow rates between 0.2 and 3.0 m/s; and d) a convenient inhibitor dose between 20–25 mg/L for optimum inhibition efficiency to obtain a maximum value of 80% for corrosion efficiency."

Jan 1, 2016

By Greg M. Hollyer

The search for minerals in the future will be dominated by deeper exploration and the need to accurately target ?blind? deposits as more and more of the ?easy? near surface targets are exhausted. In this context, key technologies are emerging for deep exploration both in grassroots and minesite exploration, including the Titan 24 Deep Penetrating geophysical technology. Introduced in 2001, this technology has grown rapidly into an accepted approach for exploration in a variety of geologic environments, including brownfield environments where discovering additional reserves would most quickly benefit companies. Titan 24 belongs to a new class of sophisticated Distributed Acquisition Systems (DAS) which record high-volume, high-quality data simultaneously at multiple receiver stations. This data is then processed digitally, modeled using specialized inverse modeling software, and interpreted according to geologic and other parameters. The result is a robust, high-quality, high-volume data sets which provide a basis for improved imaging to depth. In this paper, the Titan 24 distributed technology is discussed. Illustrations of the vast improvement to overall exploration are showcased through results in several case studies. These include examples from two gold deposits, a porphyry deposit and a minesite. These examples show the range of applicability of the technology and the ability to effectively image mineralization, lithology, structure and alteration to depth as an aid to understanding prospective mineral deposits and targeting drills more accurately.

May 1, 2008

By Carol Odell

This paper was prepared as a brief for Prospectors and Developers Association of Canada (PDAC) to guide input at a series of round tables carried out by the Federal Government in response to the 38th Standing Committee on Foreign Affairs and International Trade (SCFAIT) report, on ?Mining in Developing Countries and Corporate Social Responsibility?. This document mandate is to provide background information, analysis and recommendations on the practice of Canadian exploration and mining companies abroad. This research was based on 11 case studies of Canadian companies which have experienced conflicts or controversies overseas. All case studies were assembled through an extensive literature review of publicly available documentation and communications with representatives of the mining companies to assist in deepening the insights into the drivers of the conflicts and the needs of Canadian companies in similar situations. The case studies include both exploration and mining operations. Our analysis begins with the identification of general and case specific drivers of conflict/controversy in each case study. Company names are kept confidential and only anonymous results are presented. We make ample use of simple flow charts and schematic diagrams to explain how contextual drivers and aggravators and company drivers and mitigators play varied and interrelated roles in conflicts. The diagrams also illustrate the cumulative analysis of drivers including the linkages among drivers/aggravators/mitigators across different domains (social, governance, NGO/media and company). Finally, we discuss needs of companies and propose recommendations for addressing social responsibility and human rights concerns.

May 1, 2007

By D. W. Bennett, J. B. Hadaway

The operation at Phu Kham commenced design and construction in early 2006 and was commissioned in May 2008. This paper will examine and discuss the project from the inception of flow sheet development and equipment selection, equipment design and manufacture, construction, commissioning and ramp up to full production. The paper will touch on the strategies employed to achieve a short schedule and the efficient use of capital, but with the main emphasis on the grinding circuit. Various challenges during the early years of operation will be discussed including the effect of ore characteristics, including competency, on the performance of the grinding circuit. Actions to overcome these challenges and to enhance performance will also be discussed. Finally, current and future plans to improve the performance of the grinding circuit and the overall plant will be summarised.

Jan 1, 2012

By Fridrik J. Kristjansson, Stephen R. Hicock

"Three varieties of till are recognized in the Beardmore-Geraldton area: local lodgement till, nonlocal carbonate till, and local supraglacial till. The local lodgement till unit is examined in detail for the first time in this paper. It is the best potential overburden exploration medium for gold and other metals because its particles were locally-derived and deposited subglacially, probably within a few kilometres downglacier (southwestward) from their sources, and have not been diluted by distantly-derived glacialdebris. Both local tills are richer in gold and other metals, relative to nonlocal carbonate till. Local lodgement till rests on bedrock and was encountered frequently at or near the surface in thin drift/bedrock terrain (a widespread terrain type within the west half of the study area), and commonly at the base of boreholes in thick till terrain.INTRODUCTIONDrift prospecting in areas of glaciated terrain has been well documented (in a variety of journal publications and symposium volumes; e.g . Strobel and Faure 1987; MacDonald and Mills 1988) and has proven valuable especially where overburden thicknesses hinder traditional exploration techniques. Drift prospecting techniques may well prove valuable in the Beardmore Geraldton area. This applies especially to the Wildgoose Lake Turkey Lake area where a thick and laterally extensive sheet of nonlocal carbonate till has impeded conventional mineral exploration programs (Fig. I; note the lack of gold occurrences around Wildgoose Lake).Till in .particular has been cited as the best prospecting medium among the various types of glacial sediment (e.g. Shilts 1984). Three end member till varieties are recognized in the study area: (I) local lodgement till which rests directly on bedrock; (2) non local carbonate till; and (3) local supraglacial till which occurs predominatly within, or just downglacier of, upland areas where it commonly mantles the other till varieties. Previous authors have documented how the non local carbonate till hinders gold exploration (Geddes and Kristjansson 1986; Karrow and Geddes 1987; Kristjansson 1986; Hicock 1986, 1987a, b, 1988; Kristjansson and Thorieifson 1987; Thorleifson and Kristjansson 1987, 1988a, b) and why the local supraglacial till may be a good unit for prospecting (Hicock 1986). One detailed surficial geology map sheet of the area has been published (Kristjansson et al., 1988) and others are in preparation. Closs and Sado (1981) reported on the geochemistry of soils and glacial sediments in the west half of the study area. This paper documents the local lodgement till unit and demonstrates why it is the best overburden unit to use for drift prospecting."

Jan 1, 1989

By Z. Bibak, S. Banisi, A. Ghasemi, E. Nematollahi

"The major importance of liners in grinding is their role in providing an appropriate trajectory for the charge. Since it is not possible to study the charge movement by direct observation in operating industrial mills, this task is accomplished by physical (laboratory), and/or, mathematical (software) methods. Because of the high cost and a longer time required for a physical analysis, mathematical simulations have become more common. Simulation of the effect of liner shape on the charge movement has provided a means to select a proper design based on the operational objectives and conditions. Furthermore, the liner shape changes due to wear and impact during operation, which will influence the charge trajectory. This adds more of an incentive to use simulation. These changes in liner could be predicted through liner profile measurements during operation and/or simulation. In this research, an inhouse developed DEM software called KMPCDEM © was used to simulate the charge movement in industrial plant SAG mills. A geometrical method of implementing the shell liners on SAG mills at the Sarcheshmeh (9.75×4.87 m) and the Gole-E-Ghohar (9×2.05 m) operations facilitated the software simulation. Point by point implementation of the measurements of liner profiles of these mills enabled the study to trend the change in the charge movement as the liners wear. Comparison of the simulation to a laboratory mill (1 m diameter) showed that the difference between the measured and predicted charge impact point, shoulder angle and toe angle were 6, 4 and 3°, respectively.INTRODUCTIONComminution is the most energy intensive operation constituting the major portion of operating and capital costs of a mineral processing plant. In the last decade, a vast number of research was aimed at studying various aspects of grinding with the aim of performance improvements (Davis, 1919; Mishra & Rajamani, 1990; kalala, Breetzke, & Moys, 2008). Mill liners transfer the input power to the charge and play a significant role in affecting the motion of the charge (Mclvor, 1983; Mishra & Rajamani, 1990; Radziszewski, 1997; Van Nierop, Glover, Hinde, & Moys, 2001; kalala et al., 2008). Lifters are usually used with mill liners to extend their life and to enhance the grinding and impact breakage efficiency. Mill lifters are used to raise the grinding media and ore to transfer the energy from the mill to the load (Rezaeizadeh, Fooladi, Powell, & Weerasekara, 2010)."

Jan 1, 2016

By John Hughes

1. De Beers, Diamonds and Canada 1.1. De Beers was founded long ago (1888, the same time that Canada became a country) in a rural mining village in South Africa. Today, we employ 22,000 people across 19 countries and have 14 mines including open pits, shafts, beach-sands and seabed. 1.2. Last year our sales were US$5.7 billion and our total production amounted to 47 million carats which means a 40% global market share. For the Kyoto buffs in the audience, the company consumes 66 million cubic metres of water per annum, 210 million litres of hydrocarbon fuel and 1,600 GWh of electricity. Stats are good, but aren?t as expressive as a movie. This one is 2 minutes long, which is quicker than I could elaborate. (Video 1 - 2 minutes) 2. De Beers in Botswana is the leading source of diamonds 2.1 Today Botswana is the Jewell in the Crown. There are three big open pits that enjoy economies of scale that make them the lowest cost producers. Last year 60 million tonnes of overburden and 30 million tonnes of ore were moved in Botswana alone. Botswana produced 31 million carats, compared to 14 million carats in South Africa and 2 million very high quality carats inn Namibia. 3. Diamond Mines provide feedstock? ?.to jewellery stores

Apr 1, 2005

By Nirmal Weerasekara, Lian X. Liu, The University of Queensland, Weiguo Xie, Benjamin Bonfils, Ping Yu

A mill model structure based on the population mass balance framework incorporating breakage characteristics, slurry and solids transport, product classification and discharge and energy consumption was reported in XXVII IMPC and named the Generic Tumbling Mill Model Structure Version I (GTMMS I). In this work, a new 4D (four dimensional) appearance function sub-model based on the experimental results of the JK Rotary Breakage Tester (JK RBT) was developed to describe the breakage characteristics and was applied to this new model structure. The newly developed 4D appearance function model has fewer fitting parameters and is more generic in nature. Most importantly, it is applicable to both high and low energy impact breakage. It is therefore much more versatile in comparison to the existing JKMRC t10- tn appearance function and the size-dependent JK M-p-q t10-tn appearance function. In addition, the Discrete Element Method (DEM) energy distribution model was integrated into the new model structure. With DEM results providing energy distribution information inside the mill directly, the selection function and the back-calculation method used in the existing JKSimMet modelling method are not needed in this model structure. With the above two revolutionary innovations, the previous model structure was upgraded to the Generic Tumbling Mill Model Structure Version II (GTMMS II). Furthermore, the new model structure is dynamic in nature with time-stepping technique for non-steady-state simulation. A case of the dynamic grinding of a SAG mill was studied to validate the GTMMS II. The model simulation results agreed well with the plant data. With the newly developed 4D appearance function model, the incorporation of DEM energy distribution and transport function, the GTMMS II is an important step forward towards mechanistic modelling of tumbling mills.

Jan 1, 2016

By Gary Pattrick

A new class of spongy Au catalysts is studied for the selective catalytic reduction of NOx by propene under leanburn conditions. The spongy catalyst is an unsupported powdered Au that consists of micrometer particles (~5 microns) that have nanometer scale (~10 nm) internal skeletal structures. The effects of alloying 1 ? 50 atom % platinum group metals (M= Pt, Pd, Rh) and 5 wt% first row transition metals (M = Ti, Mn, Fe, Co) were studied. Even low additions of PGMs (1 at.%) cause significant shifts to lower temperature regions of activity and the largest shift is obtained for Rh. For Rh this is interpreted as a strong synergistic interaction between Rh and Au. Possibly related to the Rh effect, Co is the only other metal studied that lowers the temperature of NOx reduction. The other first row transition metals inhibit the reduction reaction.

Oct 1, 2003