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By Yuki Tsunazawa, Sho Fukui, Chiharu Tokoro

"A milling process is one of the important unit processes in mineral processing. In the milling process, the control of particle size distribution is necessary for the later physical separation process. Since the milling process is strongly affected by the equipment designs, operation conditions and raw materials, the control for particle size distribution of milling products is mainly based on empirical rules. Recently, the discrete element method (DEM) has been widely used as an effective tool to investigate the behavior of grinding media. Although the behavior of grinding media can be accurately simulated, it is not well-established the way to predict particle size distribution after milling by the DEM simulation.The objective of this study was to develop a new method to predict particle size distribution in ball milling using the DEM simulation. To predict particle size reduction, a correlation between experiments and the simulation was investigated in various operation conditions, that is, wide range of the rotation speed and the filling ratio of grinding media. In experiments, after lime stone was ground, the average and variance of particle size distribution were evaluated using some kinds of distribution equations. In the DEM simulation, direct simulation of particle disintegration in milling process is generally very difficult because of huge computational load. Therefore, collision energy between grinding media balls orgrinding media ball and wall was used as a factor of particle disintegration.As a result, a good correlation between experiments and simulation was obtained. In addition, the particle size distribution in ball milling could be predicted using this correlation. Therefore, these results indicated that the use of the correlation between experiments and the DEM simulation was an effective approach of predicting the particle size distribution in milling process."

Jan 1, 2016

By K. Barbetti, J. Avraamides

"The processing of gold ores with high silver contents can provide operational challenges, such as high cyanide consumption, retardation of gold leaching and competition during adsorption stages of carbon-in-pulp/leach/column (CIP/CIL/CIC) circuits. In particular, the silver, which is about 1.5% of the value of gold, competes with gold during carbon adsorption due to its higher concentration in many Ag-Au ores, potentially leading to gold solution losses. Fresh and partially fouled (barren and regenerated) activated carbons were evaluated at various Ag:Au ratios and total metal concentrations with regard to the adsorption kinetics and equilibrium loadings. Conventional Freundlich isotherms were found to be highly inaccurate for predicting equilibrium loadings in the competitive adsorption environment. An integrated model, which incorporates competitive adsorption kinetics with a modified competitive adsorption isotherm model has been developed and validated using plant and laboratory data. The model performance and some of its salient features will be discussed.INTRODUCTIONThe processing of gold ores with high silver contents can present a range of operational challenges, such as high cyanide consumption, retardation of gold leaching and competition in carbon adsorption circuits. Silver is often present at significantly higher concentrations than gold in many gold-silver ores and competes with gold in carbon adsorption circuits, limiting the gold loading rate and capacity, resulting in gold solution losses and reduced gold recovery.Curtin University’s Gold Technology Group has evaluated fresh and partially fouled (barren and regenerated) activated carbons at various Ag:Au ratios and total metal concentrations to determine the adsorption kinetics and equilibrium loadings for gold and silver. Conventional Freundlich isotherms were found to be highly inaccurate for predicting equilibrium loadings in the presence of both gold and silver.An integrated model, which incorporates competitive adsorption kinetics with a modified competitive adsorption isotherm model has been developed and validated using plant and laboratory data. This paper describes the model performance and some of its salient features."

Jan 1, 2016

By D. Sediako

Excessive residual stress in Al engine blocks may result in cylinder distortion which reduces engine operating efficiency. As such, neutron diffraction was used to measure residual strain along the Fe liners and Al, in the hoop, radial and axial orientations with respect to the cylinder axis, at the cylinder interbore region. Residual stresses were subsequently calculated using generalized Hooke's law and related to the microstructure along the cylinder bridge. The results suggest that the residual stresses in the Al interbore region are tensile and increased with depth in the axial direction of the cylinder. The increase in residual stress at the bottom of the cylinder coincides with a finer and more uniform microstructure in this region of the cylinder. The refinement in microstructure at the bottom of the cylinder likely increased alloy strength, thereby decreasing this section's susceptibility to distortion. This study successfully quantified the residual stress profiles in a heat treated engine block and related the stress profiles to an as-cast engine block.

Jan 1, 2011

By H. J. B. Couto, J. G. S. Puelles, M. L. Torem, R. H. Rojas, A. G. Merma

Understanding the limits of fine particle flotation is fundamental to achieving a significant and selective separation. Conventional flotation processes are not suitable to treat these particles because of their low collision efficiency. This problem can be overcome by decreasing the bubble size or by increasing the apparent particle size. However it is worth noting that the use of small bubbles or micro bubbles also involves some disadvantages such as their low momentum resulting in a slower process comparing with conventional flotation. Electroflotation is an attractive alternative for treating fine particles with small bubbles less than 100 µm, generated by the electrolysis of water. In this sense, this study assesses the effect of current density and pH on bubble size in a binary electroflotation cell. An increase in the bubble generation rate was reported with an increase in current density. In addition, at acid pH values, the size of oxygen bubbles increased and conversely decreased at basic pH values; this may be due to the electrostatic attraction between the oxygen bubbles and the anode resulting in a greater nucleation time. An opposite trend was observed with the hydrogen bubbles. These results are in agreement with their electrokinetic studies, which reported that at acid conditions the bubble surface may be positively charged for both the hydrogen and the oxygen bubbles. Finally the bubble size was slightly affected by the electrolyte concentration, resulting in smaller diameter bubbles at higher concentrations.

Jan 1, 2016

By Jin Li

The tensile properties and microstructure of AZ91 Mg alloy before and after equal channel angular extrusion (ECAE), and the fracture behavior during tensile testing for as-extrusion and ECAE AZ91 were investigated. The alloy was performed ECAE from one to eight passes at 498K. The elongation decreased with the pass number increasing after ECAE. Grains were refined, partial coarse ß-Mg17Al12 phase fell to pieces, fine ß-Mg17Al12 precipitated in the AZ91 Mg alloy after ECAE. During tensile test the a-Mg/ ß-Mg17Al12, a-Mg/Al8Mn5 interface and the grain boundaries in a-Mg matrix acted as the crack initiation sources. The frequency of micro-cracks at the a-Mg/ß-Mg17Al12 interfaces and grain boundaries increased after ECAE, which accelerated the growth and coalescence of the micro-cracks during tensile test and resulted in the decrease of elongation of AZ91 Mg alloy by ECAE.

Jan 1, 2006

By H. Perez, A. Lavoie, V. Prévost, P. Létourneau, P. Lind

The Home smelter is a custom copper smelter located in Rouyn-Noranda, Quebec. In 2005, the smelter produced 145,000 t of copper containing 807,000 oz of gold, 20,388,000 oz of silver in addition to 515,000 t of sulphuric acid. Recently, a flexible flow sheet has been developed incorporating the intermittent use of the Noranda Continuous Converter allowing for the increasing or decreasing of production based on market conditions, while attaining 90% or greater sulphur fixation regardless of operating mode. For 2006, the smelter is operating in full production mode and production is expected to be approximately 185,000 tm of copper. Mechanical modifications, process changes, metallurgical concepts, minor element treatments, and operational techniques that have allowed the smelter to develop this flexibility are presented. Current efforts to increase the productivity of the converter aisle and anode furnaces as well as improvements being made to address fugitive emissions are also discussed.

Jan 1, 2007

By Hervé Toubon, Matthieu Davrinche, Jim Corman, Mamane Bello Boubacar Kinassa, Pierre Amadieu

Orano Mining maintains a significant level of Innovation and Development Research for its sites in Canada, Niger, Kazakhstan, Mongolia, and France. This effort is formalized within the six major thematic programs below, which include more than one hundred affiliated R&D projects:  Geological understanding, tools and methods for exploration  ISR technology (geology, modeling, mining development tools)  Mining technology (SABRE)  Ore treatment and processing (in particular via our Centre for Innovation for extractive metallurgy, CIME)  Environment (radiochemistry, modeling, tools and methods for remediation)  Digital Mine (sensors, transmission, database, and data modeling) This paper describes the main actions of these six programs, their stakes, and their progress. There is no single path leading to innovation but fostering an innovative context and a structured project approach are essential ingredients to successful development and industrial deployment. As a result, Orano Mining has, over the years, developed a disciplined methodology for R&D portfolio and project management. This methodology, presented here, targets a reduction in time to implementation while valuing both the expertise and the work in project mode.

Jan 1, 2020

By G. Lafont

Aug 1, 2013

By Farzad Mohammadi, David Kratochvil, Patrick Littlejohn

"With more rigorous regulations being enacted in the mining industry, a need exists for cost effective and environmentally compliant technologies to remove selenium from mine impacted waters to ultra-low concentrations. Existing selenium treatment methods have high life cycle costs, introduce risks of acute fish toxicity, and produce biological waste residues that represent future liabilities. Furthermore, achieving selenium discharge limits of less than 4 ppb is a challenge for existing technologies. Selen-IX™ is a technology developed by BioteQ that selectively removes selenium from mine impacted waters to less than 1 ppb. The technology is purely physico-chemical and takes advantage of the basic principles of ion exchange and electrochemistry. Unlike conventional electrocoagulation that removes suspended solids and breaks emulsions or oxidizes heavy metals, the electrochemical process employed by Selen-IX™ relies on creating conditions where iron acts as a highly effective reducing reagent transforming selenium from a dissolved species into elemental selenium bound in a solid phase. The iron-selenium by-product of Selen-IX™ is an inorganic, non-hazardous and chemically stable solid. Due to their high iron content, the solids produced by Selen-IX™ are of interest to the steel making industry as a low cost feedstock. This offtake potential can not only reduce the life cycle cost of selenium removal by reducing disposal costs but more importantly, eliminate the risk of future environmental liabilities. In this paper, the basics of Selen-IX™ technology are presented along with results of successful piloting on streams from coal and copper-gold deposits.INTRODUCTIONVarious contaminants are released into mining wastewater during the extraction and processing of metals. One such contaminant is selenium. A naturally occurring element found in rocks and minerals, mining activities accelerate its release into the environment. Selenium in trace quantities is essential to all life forms but at higher concentrations it can be harmful, especially to aquatic life where selenium bioaccumulation can lead to reproductive deficiencies."

Jan 1, 2016

By R. Roufail

Mineral liberation is accomplished by comminution and is the first step towards achieving successful downstream processes such as flotation or leaching. In metal mining, one of the most effective comminution methods that is used to grind particles below 10 microns is stirred milling. In this paper the study of particle breakage mode vs. mill operating parameters is addressed. Stirred mills' grinding action is mainly attrition, but operation can be manipulated to include breakage by compression or impact loading. Macro and micro analysis of particle breakage and grinding mechanisms are correlated. Macro analyses convey information that relates grinding mechanism to particle size and shape. It is speculated that the breakage mechanism in the horizontal stirred mills is massive fracture for the coarsest particles and attrition (abrasion) close to the grinding limit where the size reduction ratio approaches 1.0. For micro analysis, the particle breakage mode has a direct impact on fracture type either transgranular or intergranular. Intergranular particle breakage leads to higher mineral liberation compared to transgranular breakage. Similar minerals would have more homogeneous properties that convey a stronger bond compared to dissimilar, heterogeneous mineral bonds. Transgranular fracture requires higher energy than inter granular fracture; trans granular fracture toughness of pure single phase mineral is about 10-14 % higher than the intergranular fracture toughness. This communication presents the results of an investigation to assess how operating conditions can affect trans- vs. inter-granular breakage.

Jan 1, 2009

By P. Homola, M. Karlík, M. Slámová

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

Jan 1, 2018

By Fulchand Shende

Around the world many potash mines experience brine inflow problems. The presence of brine in underground excavations may induce structural and stability problems. A study has been carried out to simulate the effect of brine on the performance of pillar support. The testing program consisted of loading potash specimens in a creep frame, and simulating inflows by continuously pumping brine into an experimental cell. Brine temperatures and load conditions were varied to simulate several mining and inflow conditions. Specimens were fitted with acoustic emission transducers to monitor energy emissions during an eight-hour test duration. Samples of brine were also collected to provide K+ and Na+ concentration data necessary for an accurate assessment of the dissolution process. Test results indicated that dissolution rates are highly dependent on brine temperature and load conditions. Loads approaching 50% UCS tend to generate very high rates of energy emissions, often leading to the failure of the simulated pillars. This study demonstrated that acoustic emission could be effectively used for predicting the performance of pillars when exposed to inflow brine.

May 1, 2001

By S. A. Bunk, E. C. Eccleston, J. J. Amsden

Fluidized bed technology has been widely applied to mineral and metallurgical processes. Over the years, modeling of fluidization technology has progressed to a level at which basic design parameters can usually be defined based on empirical correlations. In addition, scale-up considerations have become better understood, and significant advances have been made in the area of computer simulation. Despite these advances, fluidization is a complex phenomenon, and modeling tools remain limited in their ability to simultaneously model both fluidization and chemical process parameters. As a result, almost all mineral and metallurgical applications of fluidized bed technology require pilot testing prior commercial scale design. This paper outlines pilot plant testing requirements and process development considerations for development of low technical risk commercial designs.

Jan 1, 2011

By J. W. Coetzee, H. E. Deist

Carbon-in-pulp (CIP) and Carbon-in-leach (CIL) processes are used extensively in the gold mining sector to recover aurocyanide from solution. This paper discusses the modelling of these operations, using various simplifying assumptions, in order to simulate the effect of changing operating conditions on the dynamics of the system. It is assumed that the adsorption and leaching rates are a function of concentration difference between the source phase and recipient phase. The simulation was set up using Matlab's Simulink interface. Plant variables are solved using a medium scale Newtonian search algorithm in Matlab, where the differences between the actual and predicted plant outputs are minimized on a continuous time-line.

Jan 1, 2005

By E. Ghali, A. D. Bas

"Treatment of oxide, e.g. roasted gold ores has received relatively less attention than sulphidic ones and recently, handling of oxide gold ores is becoming essential. In this study, the influence of roasted gold ore (RGO) slurry (at 35% solid ratio) on the electrochemical dissolution of gold has been examined using pure gold and iron oxide minerals (hematite, maghemite, and magnetite) as disc electrodes by zeroresistance ammeter mode either in one or two separate containers. The presence of slurry decreased galvanic currents, i.e. corrosion rates due to the release and increase in the amount of soluble and/or insoluble species that could retard further the anodic behaviour of gold. Higher galvanic currents were observed in two separate containers than that in one container indicating the primary importance of galvanic interactions. SEM-EDS results observed iron hydro/oxide coatings on gold surface in case of magnetite test. However, in case of RGO electrode it is not a perfect passivation, although somewhat decreasing trend was observed on gold dissolution. These findings have revealed that passivation is not only a laboratory phenomenon, but also it could be responsible for the slowdown of gold dissolution in industrial practice.INTRODUCTIONThe cyanidation of gold is an electrochemical corrosion process thus; the dissolution of gold can readily be studied by electrochemical techniques. The outcome/summary of previous electrochemical studies of gold leaching can partially be summarized as follows: Filmer (1982) and Lorenzen and van Deventer (1992) reported the negative effect of pyrite and pyrrhotite on gold leaching due to the galvanic interactions; Aghamirian and Yen (2005) studied gold galvanic corrosion in presence of sulphide mineral electrodes only in one cell using zero-resistance ammeter (ZRA) mode; Dai and Jeffrey (2006) discussed, individually, the anodic and cathodic behaviours between gold and sulphide minerals, and Azizi et al. (2010, 2011) used a bed reactor to examine the influence of sulphide minerals on gold dissolution in one and two separate cells. Accordingly, a slowdown in gold leaching has generally been attributed to the passivation phenomenon, although the indication of this phenomenon is still an undergoing debate. For instance, Mrkusic and Paynter (1970) identified the passivation as the film formation of dissolved species from calcine, Crundwell (2014) explained passivation, in the case of corrosion of metals, as the formation of a layer which is composed of a new chemical species on the mineral surface and this layer inhibits or blocks further reactions. He suggested that passivation is related to the oxidation of the metal, and the formation of a passive layer that retards the rate of dissolution by several orders of magnitude. Consequently, galvanic interactions, passivation phenomena, or combinations of them are considered significant electrochemical factors affecting gold dissolution (van Deventer, Reuter, Lorenzen, & Hoff, 1990; Azizi, Petre, & Larachi, 2012). It is important to note that generalizing the influence of a mineral/metal on gold dissolution may not be correct in all cases, since contrary behaviours/results (for pyrite) have been observed (Aghamirian & Yen, 2005). Therefore, electrochemical study of gold is still a subject of research and need to be examined further in detail."

Jan 1, 2016

By M. B. M. Monte, M. L. Torem, E. R. Pecanha, A. G. Merma

The recent literature has unveiled the potential use of microbial strains in mineral bioprocessing. This study presents the use of a Gram-positive bacterium (Bacillus subtilis) as bioreagent for hematite flotation. The bacterium presents the ability to modify the properties of mineral surface (electrophoretic mobility and hydrophobicity). It was studied the electrokinetic behavior of hematite particles, before and after the interaction with the bacterial cells. The results revealed a shift of the isoelectric point (IEP) of the hematite after interaction with bacterial cells, suggesting a chemical adsorption mechanism. Moreover, after bacterial conditioning, the zeta potential curve of hematite presented high values in the alkaline pH range. The hematite and the bacterial surfaces presented contact angle values around 27.4° and 41.0°, respectively. According to the results, the B. subtilis strain was capable of modifying the hematite surface, and after interaction the hematite surface presented a contact angle value around 46.0°. The flotation tests were carried out in a modified Hallimond tube. The experiments revealed a significant increase in hematite flotability using the Gram-positive strain as bioreagent. The tests pointed out a maximum recovery of hematite in the presence of 600 mg/L and pH 5. Therefore, the results from this study showed the potential use of the B. subtilis strain as a biocollector for hematite flotation, and its possible application in the mineral flotation industry.

Jan 1, 2016

By P. J. Oakley, W. M. Thomas, S. W. Kallee, D. G. Staines

A Friction stir welding (FSW) is now extensively used in aluminium industries for joining and material processing applications. The (FSW) technology has gained increasing interest and importance since its invention at TWI almost 15 years ago. The basic principle, recent applications and the continuing development of the FSW technology are described. The paper will introduce some of the variants of FSW, such as Dual-rotation, Twin-stir(TM), and the Stir-lock(TM) technique.

Jan 1, 2006

By Joseph B. de Hart

Two papers recently published on the subject of mine ventilation: "The Theory of Ventilation," by Douglas Hay. and "The True Effect of Natural Ventilation in Deep Mines," by Robert Clive, form the first and second reports respectively of the committee on the Ventilation of Mines appointed by the Midland Institute of Mining Engineers. The purpose of the present paper is to draw attention to these two papers and the discussion thereon. The theory of ventilation as taught in our schools is based on Atkinson's formula, which is a variation of Chezy's formula for the flow of water in pipes. The formula depends on two assumptions : 1. That air is an incompressible fluid within the limits ordinarily encountered, and; 2. That the pressure required to produce ventilation varies as the square of the rate of flow. The Atkinson formula has been assumed to hold good over the entire range of conditions met with in mines.

Jan 1, 1924

By A. Bendada, P. Servais, X. P. Maldague, C. Ibarra-Castanedo, C. Mohr

Infrared (IR) thermography is a nondestructive, non-contact and non-intrusive technique that allows the fast inspection of large and complex structures with limited accessibility. Pulsed thermography is particularly interesting for the inspection of aerospace materials such as composites given that, after submitting the specimen surface to a thermal front, the most common types of subsurface discontinuities (e.g. porosity, de laminations, dis bonds, fiber breakage and inclusions) can be detected with an IR camera as regions showing abnormal temperature patterns. We present first the case of an aircraft door with water ingress and surface repairs on its honey comb structure. We also highlight the advantages and limitations of thermography for the inspection of aircraft composite parts, such as edge flaps, rotor blades and speed breaks. Finally, we expose some results from a Kevlar® non-planar specimen with Teflon® inclusions at different depths and locations.

Jan 1, 2006

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