Search Documents

By Elbasher M. E. Ahmed, Indresan Govender

"A mechanistic model of axial charge segregation in rotating drums is presented. We show that granular material composed of different frictional properties diffuse into axial bands as a consequence of concentration fluctuations in the free surface layer that is caused by friction-limited mobility. A Bagnoldian stress assumption ensures an asymmetric free surface profile thereby providing the essential ingredients for the evolution of axial bands and the subsequent band coarsening observed in the literature. The formulation is sensitive to the boundary conditions of tumbling mills, including particle size and density, mill speed, inter-particle bulk friction, end wall friction and drum geometry (length and diameter).INTRODUCTIONA mechanism to fully describe the axial segregation of charge in a rotating drum remains elusive to the mineral processing industry. With regard to low aspect ratio mills (like ball mills), current thinking favours the use of closed circuit mills with correspondingly low residence times to offset the completely random contact probabilities between particles and balls (Wills & Napier-Munn, 2006). Conical end caps are argued to exploit the centrifugal force to achieve a regular gradation of ball size along the mill with larger sizes at the feed end and smaller ones closer to the discharge. However; segregation along the length has been observed in the absence of conical end caps (Oyama, 1939; Levine, 1999): In these investigations, sufficient differences in the particle’s mechanical properties (particle size, density, shape, surface roughness) was enough to successfully achieve axial segregation. Figure 1 shows the segregation of a bimodal distribution (by size) into bands of larger (darker colour) and smaller (lighter colour) particles."

Jan 1, 2016

By S. Mamonov, V. ?shikhin

"The purpose of work was the significant increase of copper recovery from slag at a concentrating plant. Analysis of study of slag phase composition showed the perspective of a slow slag cooling method due to its recrystallization and transition of primary copper minerals to secondary.Copper content in base slag varied between 0.71 and 0.96%. The study of a degree of copper minerals release of the slowly cooled slag in comparison with a yielding slag showed that in a flotation size grade –0.071 mm of yielding slag the weight ratio of released copper minerals grains is 58.95% against 86.73% in samples of slowly cooled slag. The process flotation sheet consists of three main, one control and two cleaner flotation operations with aftergrinding of middling products. A reagent mode was differed from a factory one by decreasing the slurry pH from 11–12 to 8–9. This paper shows research results of the slurry alkalinity impact on technological indexes of beneficiation (flotation).Industrial testing of a resulted batch of slowly cooled slag at “SUMZ” concentrating plant showed the efficiency of such processing: copper recovery to a copper concentrate increased by 15–19%.INTRODUCTIONIntensive development of mining and metallurgy industries within a 250-year period in the Ural region led to forming of approximately 315 man-made mineral formations at the territory of the Sverdlovsk region. The region contain over 32.5 billion tons of barren rocks and out of balance ores, over 1.5 billion tons of tailings, over 115 million tons of slimes, and over 100 million tons of metallurgical slag (Demin et al., 2000). Latters, at average, contain 407 thousand tons of copper, 2519 thousand tons of zinc, 7 tons of gold, and 150 tons of silver (Rudoy et al., 2011). Wastes generated in mining processing and metallurgical sector of economy contain not only thousands tons of copper and zinc, but cause significant damage to the environment where they are located. The reduction of negative impact of anthropogenic wastes on the environment as well as the storage volume reduction of valuable metals from dump slags is possible by improving the efficiency of the melting and further flotation of slags formed during this process."

Jan 1, 2016

By R. Shamsodini, A. Poor Zaeif Doost, H. Haji Amin Shirazi, M. R. Garmsiri

"With columns being installed in rougher section at Miduk Copper Complex, the rougher feed mainly reports to rougher-scavenger cells. To evaluate the efficiency of regrinding circuit, we conducted flotation experiments on samples of the feed and the products of the regrinding circuit. The grade difference of these products at 85% recovery was considered as the efficiency index. Results show that, with weight recovery of the rougher-scavengers the efficiency of the circuit increases. Exclusion of the rougher-scavenger concentrate from the feed to the regrinding circuit, resulted in an increase in the efficiency index from 10.12 to 17.6%.INTRODUCTIONThe flotation circuit at Miduk Copper Complex consists of five flotation columns as roughers and ten mechanical cells as rougher-scavengers. According to design criteria, 75% of the final product was expected to be produced by the rougher columns, while most of the feed consisting of liberated valuable particles is introduced into rougher-scavengers. To liberate locked particles, the rougher-scavengers concentrate is introduced into the regrinding circuit (see Figure 1 below). The regrind mill is in reversed closed circuit with a secondary hydrocyclones cluster, and the cyclone overflow is introduced into three parallel cleaner columns. Cleaners concentrate reports to concentrate thickener and the column tailings is introduced into six mechanical cleaner-scavenger cells. The cleaner-scavengers concentrate reports to the regrind circuit(Figure 1)."

Jan 1, 2012

By E. Wright

"INTRODUCTIONThe Ruttan Mine is located twenty-two km east of Leaf Rapids in northwestern Manitoba. The copper-zinc exhalative massive sulphide deposit is comprised of a series of individual and interconnected en echelon lenses which strike east 20 degrees north and dip south 70 degrees. The mine has been owned and operated by the Hudson Bay Mining & Smelting Company since July 1987. Sherritt Gordon Mines Limited began mining the orebody in 1973 from an open pit, but production has been entirely from underground since 1980. HistoryDuring the progression from open pit to underground mining, it was recognized that manual methods of ore reserve calculation were inadequate for responding to changing metal prices and evaluating alternative mine plans. The mine planning system that was developed is described in the paper, ""Computerization of Ore Reserves and Mine Planning Functions at Ruttan Mine"", presented by B.C.W. Haystead at the 1984CIM Annual General Meeting. At that time, programs for core logging, diamond drill hole plotting, grade interpolation, ore outline digitizing, and reporting had been developed by the Systems Department for use on Sherritt's UNIVAC 1100 mainframe computer. Telecommunications linked terminals at the Ruttan coreshack and office to the UNIVAC in Fort Saskatchewan, Alberta. The same mine planning system was also used at a second property.Operation of the mine planning system was expensive, and it was evident that increased use required a costly upgrading of the UNIVAC in order to maintain an acceptable service level to all users. The system was re-evaluated,' and it was concluded that: core logging was not easily adaptable to a new property, nor flexible enough for exploration; plotting, grade interpolation, and digitizing required considerable manual effort; and that the UNIVAC operating system was difficult to learn.It was recommended that a study should determine if: core logging could be redesigned and/or implemented on a microcomputer; interactive graphics be used to reduce the effort for functions requiring visual interpretation; and the creation of input processors would assist users in setting up parameters for guiding the programs."

Jan 1, 1989

By Feng Xue, Mi Xujun, Peng Lijun, Yin Xiangqian, Liu Dongmei, Xie Haofeng, Huang Guojie, Yang Zhen

The Age-hardening Cu-Cr alloys are extensively used in integrated circuit lead frame, railway contact wire, resistance welding electrode and continuous casting mold copper plate, owing to having an excellent combination of high electrical or thermal conductivity and high strength. High temperature performance is very important during the service process. Effect of Magnesium and Zirconium on softening behavior of Cr-Cr alloy are investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). During the softening process in the Cu-Cr alloy, the recrystallization process, grain growth and Cr precipitates coarsening are observed. The addition of Mg or Zr to the Cu-Cr alloy, the resistance to elevated temperature can be significantly improved, owing to being restrained the growth of the precipitates by segregating along precipitates surface. INTRODUCTION Age-hardening Cu-Cr system alloys can be widely uesed in many fileds such as electrodes for spot welding (Hatakeyama et al., 2008; Cheng, Shen & Yu, 2013; Zhou et al., 2016; Chbihi, Sauvage & Blavette, 2012), intergrated circuit lead frame (Hatakeyama et al., 2008; Cheng, Shen & Yu, 2013; Zhou et al., 2016; Liu et al., 2006; Pang et al., Xia et al., 2012; Wang et al., 2009; Huang et al., 2003; Cheng, Yu & Shen, 2014; Zhang et al., 2016; Li et al., 2007) and railway contact wire (Cheng, Shen & Yu, 2013; Zhou et al., 2016; Chbihi, Sauvage & Blavette, 2012; Liu et al., 2006; Pang et al., Xia et al., 2012; Wang et al., 2009; Huang et al., 2003), because it has high strength, good electrical and thermal conductivity. The precipitation behavior of binary or ternary Cu-Cr alloys had been investigated by many researchers (Chbihi, Sauvage & Blavette, 2012; Peng et al., 2017; Batra et al., 2002). In addition, to obtain additional mechanical properties without much deterioration in electrical conductivity, trace addition of alloying elements like Zr, Ag, rare metals (Y and Ce) and Mg are added into Cu-Cr alloy. The addition Mg to Cu-Cr alloy accelerated the process of precipitates nucleation and restrained the growth of the precipitates by segregating along precipitates surface during aging, which enhanced the stability of the deformation microstructure and improved the mechanical properties of the alloy (Zhao et al., 2018). Additional zirconium in Cu-Cr alloy enhances the strength by the decrease in inter-precipitate spacing of Cr precipitates and the formation of Cu5Zr phase (Chihiro, Ryoichi & Kazue, 2008). Owing to the decrease in inter-precipitation spacing of Cr precipitates and to the Ag-atom-drag effect on dislocation motion, the addition of Ag can increase in strength, stress relaxation resistance and without much deterioration in electrical conductivity (Chihiro, Ryoichi & Kazue, 2008). The enhance in strength and electrical conductivity of the Cu-Cr-Zr alloy by adding Ce and Y elements are attributed to removing oxygen and sulfur from as-cast alloy (Li et al., 2006). However, the effect of Mg or Zr element on microstructure and properties of Cu-Cr alloy during the softening process are not clear. Therefore, Microstructure evolution and properties of a Cu-Cr systems alloy were investigated in detail by OM and TEM. The Relationship between microstructure and properties of Cu-Cr systems alloy was also discussed.

Jan 1, 2019

By Peter Godbehere, Christian Desroches, Viken Baboudjian

"Noranda Copper Smelting and Refining is a unit of Noranda Metallurgy Inc., comprising the Home smelter in Rouyn-Noranda, Quebec and the C.C.R. Refinery in Montreal East. The Home smelter provides custom smelting services for a wide variety of copper and precious metal bearing concentrates and recyclable materials, producing over 200 000 tonnes of anodes and 450 000 tonnes of sulphuric acid annually. The C.C.R. Refinery has an annual production of 360 000 tonnes of copper cathode, and is a major refiner of precious metals.Over the past twenty years, Noranda Copper has developed innovative processes and operating techniques to treat the ever increasing complexity of primary feed materials, while improving the quality of its final products, working conditions and reducing environmental emissions.This paper presents an overview of the operating practices of Noranda Copper with particular emphasis on the impact of impurities in the smelting and refining processes.IntroductionThe treatment of custom materials has been practiced by Noranda Copper since commencement of operations at the Home smelter in 1927 and the CCR refinery in 1931. Copper concentrates from a wide variety of regional, North American and overseas producers account for the bulk of the 800 000 tonnes treated annually, although recyclable and secondaries have increased in importance as feed sources in the past two decades. The geographical disadvantage of the Horne smelter compared with most custom smelters located on tidewater has provided an important incentive for Noranda Copper to develop the necessary technology and operating practices at its smelter and refinery to treat high value complex concentrates and other feeds containing significant concentrations of bismuth, antimony, arsenic, lead, tellurium, mercury, etc."

Jan 1, 1995

By W. Evans, T. Steis

"Sulphide ores under certain circumstances will react with explosives to generate an autocatalytic chemical reaction. This reaction is exothermic and results in the production of large volumes of poisonous gases and creates an unsafe, unstable condition with the possibility of a low energy deflagration or even a detonation of the loaded hole. This paper outlines the conditions that need to exist for such a reaction to take place and the precautions necessary to minimize or eliminate the problem in areas of reactive ore. A special case study involving a northern Ontario mine will be detailed.IntroductionOne of North America's leading underground gold producer's processes over 6500 tonnes of ore per day from an orebody containing high concentrations of sulphides. After six years of problem free operation, the mine experienced two serious reactions in two months between the sulphides and AMEX II, the ammonium nitrate and fuel oil explosive it uses."

Jan 1, 1995

By Alan B. Morrow, William A. Poe

"Minerals processing operations are constantly challenged with improving production rates, yields, energy efficiency and process stability. Advanced Process Control has proven to be an effective tool for improving operations by capturing the full process capabilities consistently. However, the velocity of applying the technology as well as the sustainment of these significant benefits has been hampered by the usability of the software and adaptability of the applications.Some of the new technology developments that improve the usability and adaptability of advanced process control include:• modern and intuitive user interfaces,• customizable models to support unique process behavior,• fast and flexible OPC connection tools,• automated model building,• integration with first principles dynamic models and• improved performance monitoring.This paper will briefly discuss the new technology developments that have improved the usability and adaptability of advanced process control and how this can affect minerals processing operations.In today’s environment, Minerals Processing plant managers continuously face new challenges and requirements including:• higher energy efficiency,• increased run lengths,• reduced product quality variability,• reduced emissions,• higher availability, and• lower operating costsOperating a unit to meet these challenges in real time is not easy for operators and conventional process control systems. However, innovatively using existing technologies in Minerals Processing plants can improve operations on a minute by minute basis and reap significant benefits.Advanced Process Control (APC) can extract the maximum performance benefits from existing equipment while respecting plant operating constraints. Expensive capital projects to upgrade equipment are not always necessary. Advanced Process Control can deliver significant economic benefits by maintaining the plant at its most profitable point as conditions change."

Jan 1, 2016

By F. Urekar, R. B. Pankhurst

"Air spaces and air gaps in an explosives column are known to allow greater distribution and cushioning of explosive energy from the rock mass. This energy distribution is enhanced if the explosives ' gases can be confined in the borehole for as long as possible by plugging and stemming above the air space.Power Plug is an inflatable plug which can seal a borehole at any point to separate the stemming from an air gap and explosive toe load.IntroductionThis paper will discussion-going work by C-I -L Inc. and operators of two open pit mines to study the results of using Power Plugs:I. Pit wall stability - the authors have found the Power Plug effective for wall control blasting in open pit mines.2. Selective mining of coal seams - the authors work shows the Power Plug allows mining selective coal seams by predrilling underseam waste wedges.Pit Wall StabilityWall stability in an open pit mine is essential for safety. Good wall stability can be achieved with wall control blasting techniques which cushion the effect s of the explosives charge by decoupling the charges from the borehole wall. The usual method of decoupling a charge in a large-diameter rotary borehole is to load the explosives in tubes (Fig .I) . We now believe the air deck system is effective in sea ling a borehole above the explosive charge to create an air deck within the borehole which will cushion the blast.In a linear decoupled charge, an air annulus surrounds the explosives charge and cushions the effects of detonation genera ted gases on the pit wall. In an air deck, i.e. with the hole plugged at the collar, the gases genera ted by an explosive toe load are sealed in the empty borehole column. After a period of time, these trapped gases produce radial cracking between holes along the entire length of the borehole.It is common practice to employ de coupled explosive charge columns in the borehole to limit blast damage to surrounding rock. The exact mechanism of energy transfer in such blasts, however, is not well understood. Interruption of the continuous explosive column in a borehole by means of stemming, or air decks, may also be viewed as another form of decoupled blast. Decoupling of the explosive charge from the borehole wall affects both explosive energy release and explosion pressure developed in the borehole."

Jan 1, 1988

By R. C. Lo, M. D. Scott

"This paper reviews tailings management at Highland Valley Copper, and outlines main features of its tailings storage facility enclosed between the H-H and L-L dams. Key management focusses are: energy efficiency, cost effectiveness, safety and integrity of the tailings impoundment, environmental protection, and reclamation after decommissioning. Main features of the tailings facility include: high international standards for seismic and flood design criteria, water management and water quality monitoring, operations and construction optimization, reclamation and decommissioning plan, and geotechnical challenges associated with the complex geology of the L-L tailings dam foundation.IntroductionHighland Valley Copper stores its tailings mainly in the Highland Valley tailings facility (ultimate capacity: 1.8 billion tonnes). Smaller tailings storage facilities were operated by predecessor companies: the Number One Pond, the Trojan Pond at Bethlehem and the Highmont Pond at the Highmont operation as well as backfilling the Heustis and Jersey lona Pits at Bethlehem. These areas are currently not in use, and are in the reclamation phase prior to decommissioning. This paper focusses on tailings management in the main facility. As indicated in Figure I, the facility includes three tailings dams: these are, going from east to west, the H-H, J-J and L-L Dam, named after the alignment alternatives in the initial feasibility studies. From 1970 to 1977 Canadian Bechtel Ltd. advised Highland Valley Copper's predecessor company Lornex, on tailings storage at the H-H and J-J Dams and on the L-L Dam. Since the completion of the L-L Starter Dam in 1977, Klohn Leonoff Ltd. has provided ongoing consultation and construction monitoring of the raising of the L-L and the H-H Dams. The J-J Dams is currently buried by deposited tailings. This paper reviews key tailings management focusses and main features of the tailings facility."

Jan 1, 1992

By G. P. Demopoulos

"The recovery and separation of platinum-group metals (PGM) from primary and secondary materials currently attracts a lot of interest due to the high value of the metals and their increasing demand for high-tech applications. Thus, the traditional refining processes are gradually replaced by newer more efficient separation techniques such as solvent extraction and ion exchange. In this paper the classical and modern refining techniques are reviewed and the pertinent solution chemistry dictating proper processing strategies in each case is discussed. The technological advantages of the modern separation methods are emphasized and reference to the recovery of PGM from primary as well as secondary materials is given. INTRODUCTIONDue to their outstanding physicochemical properties, such as catalytic activity, conductivity and corrosion/oxidation resistance, precious metals now find extensive usage outside of the traditional jewellery and investment industries. The increasing use of precious metals in such areas as electronics and catalysis, as well as their increasing high value, has led to a growing interest in their recovery and separation from primary and secondary materials.Quantitatively the demand of platinum metals in the western world by area of application is described in Table I. Platinum and palladium represent 90% of the total demand, Rh and Ru 8% and the remaining is taken by Ir and Os. In terms of value the following were the average prices (US$/oz) of the metals in the second half of 1986: 500 Pt, 125 Pd, 1200 Rh, 650 Os, 400 Ir and 80 Ru. Due to these prices, exploration, mining, reclamation and refining activity were very high in South Africa, the biggest producer of Pt metals in the world, as well as in other areas: United States (Stilwater deposit), Canada (Sudbury, Marathon and Lac des Isles, Ontario; Kenly Lake, Quebec, etc.), Australia, Europe and elsewhere"

Jan 1, 1989

By J. Clark

Erosion control during the mining cycle can be more effectively planned using Erosion and Sedimentation Control Plans (ESCPs). This raises the issue of who should develop an Erosion and Sedimentation Control Plan Guidance document (ESCPG) to standardize the content of ESCPs. A search for ESCPG documents in Canada revealed no examples for mine sites. In the U.S. there are a number of regulatory authorities who developed such documents for mine sites, including EPA. An ESCPG is expected to result in: (a) plans will be more standardized (b) more clarity and efficiency for those generating ESCPs; (c) assisting regulators tasked with reviewing/approving ESCPs; (d) providing guidance for the mine effluent permitting process relative to sediment control; (e) providing a basis for developing and including ESCPs in the Environmental Assessment (EA) phase and the mine economic assessment; (f) applying and optimizing ESCPs above the ?watersheds? of sediment ponds; (g) utilizing the ESCPG document for ?exploration? sites; (h) lowering the risk of adversely impacting water quality downstream of mining activities; (i) providing a methodology for determining the need for sedimentation pond(s) during the construction and production phases; and (j) providing a clear environmental sustainability message relative to sediment control if the mining industry takes the lead in developing an ESCPG. ESCPs will proactively create increased administrative (regulatory) efficiency in the EA and sub-EA reviews relative to erosion control and sediment release from mine sites. This also assists the new initiative in BC, One Project, One Process (OPOP) and synchronous permitting (a variation of concurrent permitting): as an example, enhanced erosion control planning at the EA phase then allows the synchronous permitting initiative to proceed efficiently, particularly for the mine permit (Ministry of Energy, Mines and Natural Gas) and effluent permit (Ministry of Environment). Approximately twenty more management plans (e.g. ARD/ML, explosive management, emergency response, hazardous waste, sediment pond operation, environmental effects, environmental sampling, etc.) may also be entered into the EA process to create increased efficiency, and then feed into the synchronous permitting effort. The BC OPOP initiative also adds support to the Canadian Federal ?One Project, One Review Process? approach. The ESCP and a sediment pond management plan will also address the Canadian Metal Mining Effluent Regulations requirement for all discharges from mine sites to meet a grab sample of 30 mg/L Total Suspended Solids.

Aug 1, 2013

By W. E. Cockfield

"The Stump Lake mining camp is in Nicola mining division of southern British Columbia. It lies about halfway between the cities of Kamloops and Merritt.The deposits at Stump Lake are among the earliest lode discoveries of British Columbia, many of the claims having been staked between 1882 and 1885. A considerable amount of work was done prior to 189Cl, after which very little was done until 1916. Since that time mining has been carried on at intervals, much of it on the same deposits, by a number of companies, including the Donahue Mines Corporation, the Planet Mines and Reduction Company, the Nicola Mines and Metals Company, the Consolidated Nicola Goldfields, Limited, and others. According to the British Columbia Department of Mines, total production from the area has been: gold, 8,520 oz.; silver, 259,413 oz.; copper, 40,822 lb.; lead, 2,208,859 lb.; and zinc, 367,869 lb. Most of the production has come from the Enterprise vein and a branch of the Enterprrsethe King William vein."

Jan 1, 1954

By Neil Westoll

Extensive Global Network ?Working together, AECOM provides clients with a unique blend of global reach, local knowledge, innovation and technical excellence. ?43,000+ team members worldwide ?450+ offices ?100+ countries ?6 continents The Changing Climate ?Climate change is ?official??IPCC 2007 ?Climate change will create instability, change and opportunities ?Companies that are resilient and adapt will survive and evolve ?CO2/GHG emissions will be curbed by legislation ?How will this affect the mining industry? ?How can the mining industry adapt to the new realities?

May 1, 2009

By Y. Chunhua, L. Chunsheng, W. Sheng

"Countercurrent solvent extraction is the dominant industrial rare earth separation method. For the rare earth separation, with low separation factors and multiple components, designing and optimization plays an important role in reaching product quality and reducing separation plant costs. Based on the theory of countercurrent extraction, cost-efficient methods, such as third-outlet separation and hyperlinked extraction processing, have been introduced following computer simulation. The consumption and fixed investment of industrial practice are compared, by which advantages of the optimized rare earth separation process are indicated. INTRODUCTIONThe rare earths (RE) have outstanding optical, magnetic and electric properties in advanced material applications and have therefore received much international attention in recent years. Liquid-liquid extraction is the major industrial RE separation method and is widely used in the industry. Supported by the government and with collaboration from the institutions and enterprises, China has made great progress in RE separation, and has become the dominant supplier of separated RE products. Complicated by multiple elements and low separation factors, careful design of RE separation processes is vital for the quality and cost of production. The theory of separation is the key to basic of flowsheet design and industrial applications.BASIC SEPARATION PROCESS AND THEORYGeneral ProcessAcidic extractants such as P507, P204 and naphthenic acid, are the most popular extractants in modern RE separation industry. In the general separating process, the extractant is saponified with a base, then ion-exchanged with RE solutions, thereby to provide stable and high RE loading in the extractant to fulfill the requirement of production quantity and quality. The RE-loaded extractant is then countercurrently extracted and scrubbed with RE solutions and the RE element thereby is purified. After the countercurrent extraction process, the RE-loaded extractant is stripped with acid to obtain an aqueous RE product, and prepare the extractant for recycling (Xu, 1995)."

Jan 1, 2012

By C. H. Sleeman

"The Iron Ore Company of Canada constructed a beneficiation complex in Sept-Iles, Quebec, to concentrate and pelletize earthy red hematite iron ores from the Knob Lake area. The plants were scheduled for initial production during the first quarter of 1973.Many problems have been experienced to date. Difficulties in controlling the process, excessive mechanical failures, design deficiencies and manpower-staffing problems have caused an extended start-up. The problems are now essentially solved and, with the completion of some additional minor modifications, it is expected that the plants will be producing premium iron ore pellets at or near rated capacity within the next immediate period."

Jan 1, 1976

By D. Royston

In SAG mills fed with a variety of ore types, hard packing between the shell lifters can come and go depending on rock type and rock size distribution and the presence of a binder. Packing can appear in all sizes of SAG mills, and can be tenacious. High ball impact forces (depending on ball size) in larger mills may compact and encourage packing. Packing can have a negative impact on milling performance and a change in shell liner design may be required to remove it. However shell liner design changes need to be managed with care to ensure liner reliability. In smaller mills control of packing can extend shell plate wear-life and may help to maintain milling performance in fixed-speed mills through the liner wear-cycle.

Jan 1, 2012

By T. R. Kostecki, K. V. Jessu

"Roof bolts are subjected to axial stresses, shear stresses, or both. Axial and shear stresses were compared between roof bolts machined with two and three slots. Shear stresses perpendicular to and at an angle to the shear planes were evaluated by analyzing a three-slot instrumented roof bolt, performing laboratory tests on two- and three-slot roof bolts, and conducting in-situ test analyses. Threeslot bolts appear to provide a complete bending strain profile, requiring no prior knowledge of the estimated shear-plane orientation. Minimum displacements occur in roof bolts installed perpendicular to rather than at an angle to the shear planes.RÉSUMÉ Les boulons d’ancrage dans le toit d’une mine sont sujets à des contraintes axiales, des contraintes de cisaillement ou les deux. On a comparé les contraintes axiales et de cisaillement de boulons d’ancrage usinés avec deux ou trois fentes. Les contraintes de cisaillement perpendiculaires et à angle aux plans de cisaillement ont été évaluées en analysant un boulon d’ancrage de toit à trois fentes, en effectuant des essais en laboratoire sur des boulons d’ancrage de toit à deux et à trois fentes et en effectuant des analyses de tests in situ. Les boulons à trois fentes semblent fournir un profil complet de résistance aux contraintes de flexion, sans avoir besoin de connaître l’orientation estimée du plan de cisaillement. Des déplacements minimums ont lieu dans les boulons d’ancrage de toit installés perpendiculairement, plutôt qu’à un angle, aux plans de cisaillement."

Jan 1, 2016

By B. McFadzean, J. Taguta

In order to recover minerals by flotation, the sub-processes of collector adsorption onto the valuable minerals followed by bubble-particle attachment should occur efficiently. This paper investigates both of these sub-processes for various thiol collectors and their mixtures onto base metal sulfide minerals. The aim of the work was to investigate whether there is a correlation between the strength of the collector interaction with the mineral and the subsequent bubble-particle attachment. The collector-mineral affinity was measured experimentally using an isothermal titration calorimeter in order to determine the molar enthalpy of adsorption for each collector-mineral system. The bubble-particle attachment was measured using a microflotation device which essentially determines the hydrophobicity of the mineral. Sodium ethyl xanthate (SEX) and sodium diethyl dithiocarbamate (DTC) and mixtures thereof were used as collectors with either single minerals or binary mixtures of pyrite and chalcopyrite, respectively. The adsorption enthalpies of the collectors were interpreted with reference to the chemical structure of the collector molecule and showed that the greater the positive inductive effect of the collector, which may be qualitatively related to their pKa, the greater their affinity for the mineral surface. In the microflotation studies, recoveries were strongly related to the alkyl chain length but there was no correlation between the enthalpies of adsorption and the flotation recoveries. When mixtures of collectors were used there was clear evidence of synergistic effects and in the case of DTC/xanthate mixtures it is possible that this synergism is related to a DTC promoted oxidation of xanthate to dixanthogen. When mixtures of pyrite and chalcopyrite were used the flotation recovery and enthalpy of adsorption of SEX onto the individual pyrite particles in the mixture increased substantially compared to the case of pyrite alone. Mechanisms are proposed to interpret these important observations.

Jan 1, 2016

By Tommee Larochelle, Henry Kasaini

"Simulation of rare earth element solvent extraction processes for plant design and optimization is complex, requires extensive bench scale and pilot scale testing, and is traditionally performed using proprietary algorithms. The complexity of simulation is mainly due to traditional simulation software solvent extraction modules not being designed to simulate rare earth separation processes because of the interaction between each element. This paper presents an alternative method for designing and optimizing rare earth element solvent extraction separation processes using METSIM to converge each stage of the battery individually until the full battery reached ultimate convergence. A feed-forward controller is used to control the organic to aqueous flow ratio feeding the solvent extraction modules. This method minimizes the complexity of simulating such processes by using inexpensive batch solvent extraction data, and allowing for rapid theoretical optimization, by varying the process configuration and parameters from a graphic interface instead of the traditional code-based interface of most proprietary models. Comparison of the model predictions to pilot plant data reveals that the method can be used to accurately model rare earth solvent extraction processes, as illustrated by its application in the development of Rare Element Resources innovative process.INTRODUCTIONThe Rare Earth Elements (REEs) consist of 16 metals, specifically the 15 lanthanide elements and yttrium, which is typically found in the same mineral deposits as the lanthanides. Scandium can be associated with the rare earth elements, but is usually only present in trace amounts, and therefore omitted. The term “rare earths” originates from an old term used to designate minerals (earths) and their believed scarcity upon their initial discovery. The rare earths designation is now considered a misnomer because it was demonstrated that the crustal abundance of some rare earth elements, such as cerium, is known to be higher than many common metals, such as copper. However, enriched deposits are fairly uncommon compared to other similarly abundant metals. The REEs are typically divided into groups commonly consisting of light rare earths (LREEs), medium rare earths (MREE), and heavy rare earths (HREEs). Light rare earth elements include lanthanum to neodymium, medium rare earths include samarium to gadolinium and the heavy rare earth elements include terbium to lutetium, and yttrium. The REEs exhibit similar chemical characteristics and are usually extracted from the ore and processed into a mixed rare earth concentrate. The rare earth concentrate requires further processing in order to separate the REEs from each other and produce a series of single element products."

Jan 1, 2016