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To determine the optimal circuit configuration for gravity gold recovery consideration should be given to a range of factors in addition to the efficiency of the gravity circuit, including capital costs, ease of operation and impact on comminution. The most common gravity gold circuits utilise a centrifugal concentrator treating a portion of the hydrocyclone underflow. This paper will examine this option and alternative circuit configurations to illustrate the effect of various gravity circuit feed and tailings configurations on the equipment sizing, capital costs, operating costs, water balance, comminution efficiency and gravity gold recovery. The optimum circuit configuration can provide reduced capital and operating costs, maximise gravity gold recovery and improve comminution efficiency.

Jan 1, 2011

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 René Dufour

Jusqu?à son acquisition par MM René Dufour et Alain Robin en 1994, les claims miniers et les droits de surface de la propriété étaient détenus depuis 1953 par la société Québec Columbium, une filiale de la socité américaine Kennecott Copper qui y a réalisé d?importants travaux miniers. En 1995 la compagnie NIOCAN inc. fut incorporée; ses actions furent inscrites à la bourse de Montréal en 1997, et à la bourse de Toronto en décembre 1999. Jusqu?à maintenant, NIOCAN a investi plus de 7 millions de dollars dans le développement de sa propriété minière de niobium située à quelques 40 kilomètres au nord-ouest de Montréal. Le haut rendement économique des deux gisements principaux que compte exploiter la compagnie, le S-60 et le HWM-2, a été établie par des études de faisabilité effectuées par le consortium Met-Chem/SNC-Lavalin. La mission que s?est donnée NIOCAN inc. consiste à mettre en production ses deux gisements et à devenir ainsi productrice de ferroniobium dans les plus brefs délais. Figure 2 Le projet est présentement à un stade avancé d?obtention du certificat d?autorisation du ministère de l?Environnement. À plus long terme, la compagnie compte aussi exploiter les sous-produits de ses gisements (apatite, forsterite, magnétite, calcaire et terres rares).

May 1, 2003

By J. Erik Scheel

Overview ? About Hard Creek Nickel ? Turnagain property ? Proposed power line ? Recent Preliminary Assessment ? Favourable economics ? Property Geology ? Mineralization and metallurgical characteristics of major lithologies ? Development of the acNi (ammonimum-citrate H2O2) technique ? Overview of necessary steps ? Results of the technique ? Conclusions

May 1, 2008

By R. Kong, X. W. Zhang

"High pressure (up to 50 MPa) isotropic compression tests were performed on marble, gneiss and sandstone specimens, of which represents the typical rocks, to investigate isotropic compression deformation characterization at room temperature. Experimental data with respect to volume change in loading and unloading are presented. An apparent volume change inflection point (sensitive stress) was observed at a lower pressure range for porous sandstone, indicating that the elastic-plastic behaviour arising in the isotropic compression stage, but for tight crystalline rock, the sensitive stress is much higher, not probed prior to 50 MPa. The irrecoverable volumetric strain in the unloading can be seen for sandstone as well. The anisotropic deformation was discussed in terms of the axial and radial strain measurement. It was found that essential features of mechanical anisotropy are the irreversible in deformation range. The deformation feature in the isotropic compression tests is a very complex issue due to the factors concerning the stress history, unloading in sampling and in-situ stress. INTRODUCTIONThe isotropic or hydrostatic compression condition that stress is compressive and has the same magnitude for all direction, which is expressed as s1=s2=s3 in principal stress space. A yield locus of soils subjected to the isotropic and anisotropic compression was widely known, for instance Cam Clay model, which forms a closure cap model. However, the similar isotropic compression yield curves for rocks, especially for hard rock, was not established due to the geo-stress in the rock mass is much less than the socalled isotropic yield stress. And hence, the previous experimental studies on the hard rock have been made tend to on the stress-strain-strength relationship (Handin & Hager, 1957; Edmond & Paterson, 1972; Menéndez et al., 1996). Perhaps the yield curves related to an increasing in the hydrostatic pressure is not forced to construct for hard rocks, undoubtedly, the deformation data in this processing is valuable to assess the bulk module (Fabre & Gustkiewicz, 1997), anisotropy (Niandou et al., 1997), field stress (Hakala et al., 2007). Furthermore, many rocks store much elastic volume strain energy link to the hydrostatic pressure exerted, following a deviator stress applying, to drive the unstable brittle fracture for hard rock. Latter was studied to interpret the incentive of rock burst. However, volume change characteristic in the isotropic compression behaviour have been scarcely studied experimentally to our knowledge, less application related to the fracture in hard rock as well. The mechanical behaviour in the isotropic compression of hard rock is notably affected by the original structure anisotropy, stress history and stress condition before sampling, all of which need reasonably assess. It is also a useful understanding to study isotropic compression that elastic and plastic volume change in the isotropic loading and unloading, and the micro crack evolution throughout it."

Jan 1, 2015

By V. Prodanovic, M. Militzer

Production of advanced linepipe steels with strength levels of 685MPa (100ksi) and higher requires excellent control of runout table cooling to produce the desired final fine-grained microstructures, which may include acicular ferrite. Cooling is exerted on the runout table by applying water jets onto the hot surface of the strip and heat is removed from the steel by forced convective boiling. The associated boiling mechanisms are complex and include film, transition and nucleate boiling. A pilot-scale runout table test rig has been built to systematically study boiling heat transfer from a moving steel plate by employing industrial scale headers. Experiments were conducted using test plates moving at speeds between 0.3 m/s and 1.4 m/s. The plates were cooled down from 850°C to temperatures below saturation by a single water jet supplied through an industrial size circular nozzle. Based on these experiments heat fluxes were determined and further used to develop improved runout table cooling models.

Jan 1, 2005

By J. Yue

The particle breakage kinetics, product size and size distribution, as well as grinding limit for quartz suspensions in a horizontal stirred mill are investigated. Results of grinding studies on quartz suspensions in a horizontal stirred mill confirm "first-order" particle breakage rates. A comparison of equation fits reveal that the product size distribution from stirred mill is best represented by the Rosin-Rammler equation when compared to the Gaudin-Shuhmann equation, but results fit poorly as particle size below five microns. A method of determining breakage rates versus particle size is demonstrated which shows that the 10% top size fraction is most appropriate for the determination of specific breakage rates. The method is used to demonstrate the relationship between particle breakage rate and particle size. As the feed particle size becomes smaller, the size reduction ratio decreases and approaches a grinding limit which depends on the effective stresses created in the mill.

May 1, 2004

The original JKMRC AG/SAG mill model was developed over 30 years ago and has been upgraded a number of times since then, with the current published version being the Variable Rates model that is now over 15 years old. Since this model was developed further enhancements have been derived, some of which are applied in-house and some which have yet to be incorporated. The published and the commercially available model in JKSimMet is currently undergoing a comprehensive overhaul with a vastly extended data base for model evolution and validation. Improvements developed within the AMIRA P9 project, in-house development and a number of collaborative projects, are being incorporated into the upgraded model structure. Enhanced capabilities will include: power-based breakage rates scaling; a far wider mill filling range (from 10% to 40%) that exhibits peak in throughput as mill filling increases; higher ball loads; improved pebble discharge function; improved slurry discharge function incorporating important mill design and operational influences; and the new size dependent breakage function. The model will also be able to accommodate some influence of liner design and multi-component ores (blends of hard and soft components). This upgrade is still a work in progress but substantial changes have been made to date. This paper presents some of the new improvements and their influence on the predictive capability of the model.

Jan 1, 2012

By Jose Alberto Gonzalez, Said Sharif Mahboob, Jeffrey L. Shepherd

"During the industrial electrowinning of zinc, uneven growth can cause short-circuits and make the deposits more sensitive to the presence of impurities that can significantly impact current efficiency. To produce levelled zinc deposits, additives such as glue, licorice and sodium silicate are often added to the electrolyte. Even in the presence of additives, uneven zinc growth still takes place because of the combination of hydrodynamic and electrolysis conditions in the cell house. Recent advancements in imaging spectroscopy and scaling analysis have opened an avenue to further study the effects of additives on zinc growth morphology. In this study, Atomic Force Microscopy (AFM) and scaling analysis have been used to monitor zinc growth characteristics including roughness, periodicity, aspect ratios and growth mechanisms as a function of electrolyte composition as well as deposition time. Zinc was electrodeposited from an industrial electrolyte containing a host of additives onto an aluminum cathode with a platinum wire serving as the anode. AFM images of the samples were collected to obtain 3D topographical information on which scaling analysis was performed to extract details on root-mean-squared (rms) roughness, periodicity (grain size), aspect ratio of surface features and growth mechanism. This analysis provided information on the mechanism by which the previously mentioned variables can impact short term growth and also provided a prediction of expected growth at long deposition times.INTRODUCTIONElectrowinning is one of the final stages in the industrial production of zinc metal. It is during this process where dissolved zinc ions undergo electro-reduction from an acidic electrolyte onto an aluminum cathode and are later recovered by stripping the zinc metal from the substrate. However, due to the nature of zinc growth as well as the various operating conditions, zinc deposition may occur unevenly, sometimes causing short-circuits that can cause electrode damage and reduced zinc production."

Jan 1, 2016

By M. H. Kotze, V. Yahorava

A gold-selective ion exchange resin, containing tributylamine groups, was developed by Mintek for the recovery of gold from cyanide leach solutions. The Dow Chemical Company and, more recently, Purolite commercialized the production of this gold selective resin for use in the gold mining industry, and it is marketed as Dow XZ-91419.00 and Purolite A194 respectively. A novel application of this resin is the selective recovery and separation of AuCl4 - f rom p latinum group metals (PGMs) in chloride and nitrate solutions. The current paper describes potential benefits of this type of resin for selective recovery and upgrading of gold from low grade chloride or nitrate waste streams, and the possibility of gold separation from PGMs during their refining in chloride media.

Jan 1, 2014

By M. Sokoto, H. Hata, K. Nishina, K. Haiki

Fluoride ions in zinc electrolyte cause corrosion to aluminum cathode plates at zinc electrowinning process, so we have developed an iron compound as a fluoride ion adsorbent used in zinc sulfate solution. The iron compound is synthesized from FeC13 solution with a small amount of sulfate ion by neutralizing reaction with Na2CO3 solution. The fluoride ions adsorbed on the surface of the iron compound are desorbed in alkaline solution and the iron compound can be reuse as a fluoride ion adsorbent. Moreover, if adsorption capacity of the iron compound decreases, it can be dissolved in HCl solution and re-synthesized.

Jan 1, 2008

Real Time Monitoring of Cemented Paste Backfill Introduction Methods ?how to instrument a Long Hole stope Key Results from 2 case studies: barricade pressures and displacement, in-stope pressures Importance of Real Time Monitoring How binder, rise rate, cement content affect fence pressures

May 1, 2010

By J. Shibata, N. Murayama

"Rare earth elements are present in more than 100 minerals, of which monazite, bastnaesite and xenotime are typical. Rare earth elements have excellent chemical and physical properties for industrial use in functional materials such as phosphors, magnets, electronic components, abrasives and catalysts. China produces more than 90 % of the world’s rare earths, and Chinese trends significantly influence the demand and price of rare earths. From the viewpoint of resource securement, it is desirable to separate and recover rare earth elements from low-grade resources and wastes. Phosphate gypsum, which is a by-product of wet phosphoric acid manufacturing, contains low concentrations of rare earth elements. In this research, the separation and recovery of rare earth elements from phosphate gypsum were investigated. A series of recovery methods including washing of phosphate gypsum, leaching of the rare earth elements with sulfuric acid, adsorption and desorption of rare earth elements by using ion-exchange resin, and precipitation of rare earth oxalates were carried out. The separation of rare earth elements from Ca2+ simultaneously leached from phosphate gypsum was also investigated."

Jan 1, 2014

By John Loop, W. A. Gibbins, Donald D. Hogarth

"Introduction Background The Frobisher voyages of 1577 and 1578 were organized by the Cathay Company for the express purpose of finding and mining gold ore. Since publication of the Baffm expedition of Charles Francis Hallill, the location of Kodlunarn or Countess of Warwick Island, the headquarters of Frobisher's third (1578) voyage, and focal point of the largest Arctic voyage of all time, has been known to the world. Through Hall we also know the location of the Countess of Warwick Mine on Kodlunarn Island. However, the exact locations of the other mines are not known. Of the ""ore"" we know little. Pieces of the original ""black stone"", once as large as ""a half-penny loaf' have now disappeared altogether. Specimens collected at random from the repository of shipments in England and from loose rock on Kodlunarn Island were termed, respectively, ""hornblende pyroxenite"" and ""amphibolite"" and from a locale about 200 yards from Kodlunarn as (hornblende) ""pyroxenite""121. However, it is uncertain whether these specimens are representative of Kodlunarn or of the other mines, although Blackadar131 notes that, in the northern trench of Kodlunarn, biotite gneiss contains lenses and bands of amphibolite. The ""gold"" itself is even less well defined. It has long been accepted that gold was virtually absent in Frobisher's ore. The ""gold"" has been termed pyrite, biotite and both biotite and pyrite together. Even t h e word "" marquesset"" , which appears and reappears in contemporary descriptions, is nebulous and is defined as ""a stone participating in the nature of some metal, yet in so small quantity, that the metal cannot be melted from it"" (0.E.D., definition of 1616)."

Jan 1, 1999

By A. C. Hatton

Doped SrCoO3.8 was found to be a promising material for use as a cathode component in intermediate temperature SOFCs. In this work, strontium cobaltite ceramics doped with 10 mol% to 90 mol% samarium were synthesized using the glycine nitrate process in order to study the electrical conductivity and thermal expansion at temperatures of up to 800°C. As-synthesized powders were deagglomerated, pressed and sintered at temperatures ranging from 1100-1250°C. The effect of temperature and composition on electrical conductivity and thermal expansion are presented and discussed.

Jan 1, 2005

By S. Dallaire

"RÉSUMÉLes revêtements céramiques ont une moins grande visibilité que les revêtements métallurgiques. Ils ont cependant jour un role significatif dans noire développement technologique. Les procédés de revêtement ont permis de s'affranchir de barrières technologiques importantes dans le domaine de l'optique, de l'électronique, de l'usure, des hautes temperatures. L'introduction de nouvelles technologies ou la mise en service de nouveaux matériaux peut nécessiter l'adaptation de certain procédés actuels ou le recours a des procédés qui ont peu percé jusqu’ à maintenant.ABSTRACTApplications concerned with ceramic coatings are not as well known as those with metallic coatings. However, ceramic coatings have played a tremendous role in the development of technology. Ceramic coating processes made it possible to overcome technological barriers in the areas of optics, electronics, wear resistance and high temperature applications. Ceramic coatings can provide new properties to materials never considered for demanding applications. They can also open new frontiers and revitalize materials which are maturing or in decline."

Jan 1, 1990

By Jochen Petersen, Caroline Muzawazi

The technical feasibility of ammonia leaching of PGM bearing Platreef flotation concentrates was investigated as an alternative method for the recovery of base metals prior to precious metal recovery. The composition of the concentrates includes 2.02% Cu and 3.17% Ni, and the major base metal minerals are chalcopyrite and pentlandite. Optimal leaching conditions were initially established in shake flask experiments to be a solution containing 4 M NH4OH, 4 M (NH4)2CO3 and a pH range between 9 and 10. These were used as base case conditions in column and batch stirred tank reactor tests, where the effects of total ammonia concentration and operating temperature were explored further. At optimal conditions nearly 100% Cu and Ni extraction were obtained in the batch stirred tank reactor, and 95% Cu and 60% Ni extraction was obtained in columns. The activation energy for chalcopyrite and pentlandite was 36 kJ/mol and 16 kJ/mol, respectively, in both reactors, indicating different reaction pathways for the two minerals. Gas-liquid mass transfer appears to be the limiting reaction step in columns much more than in tanks, and the degree of ammonia loss to air is significant. This initial test work indicates the feasibility of using ammonia leaching for this and similar materials as an alternative route to conventional smelting and refining prior to PGM recovery, but a number of technical challenges still need to be overcome.

Jan 1, 2014

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 Z. Zhao, B. Li

"Fractures are the key channels for fluid flow and mass transport in fractured rocks of low/negligible matrix permeability. In single rock fractures, surface roughness causes fluid flow in tortuous paths, and reduces the overall fracture conductance. A number of empirical models have been proposed to relate the reduced hydraulic aperture to the mechanical aperture due to surface roughness, which were revisited and compared. Using two of those relationships between hydraulic apertures and mechanical apertures, we studied the influences of local surface roughness of fractures on fluid flow and solute transport processes at the macroscopic scales of fracture networks. The results show that fracture roughness can affect the flow rates and residence time to varying extent, mainly depending on the empirical models between hydraulic apertures and mechanical apertures. However, fracture roughness has negligible influences on the general patterns of fluid flow (channeling) and solute migration (e.g., travel paths and shape of breakthrough curves). This is because the connectivity of a fracture network is mainly determined by other geometrical parameters (fracture positions, orientations, and lengths), rather than roughness or apertures. INTRODUCTIONIn fractured crystalline rocks of low or negligible matrix permeability, fluid flow and contaminant migration mainly occur within the connected fractures. An understanding of fluid flow and contaminant migration in fractured rocks is a crucial issue in many deep underground projects, e.g. underground repositories for radioactive waste, CO2 sequestration, enhanced geothermal systems, oil and gas production, etc. Rock fractures are typically rough-walled, and surface roughness appears to have first order control on the mechanical and hydraulic behavior of single rock fractures (Boutt et al., 2006).It is well known that the mechanical aperture of a rock fracture is usually larger than its hydraulic aperture, due to fracture surface roughness (Tsang and Witherspoon, 1983). However, for naturally fractured rocks including numerous discontinuities, the effects of this reduced hydraulic aperture in local fractures on macroscopic fluid flow and solute transport in complex fracture systems still remain unclear. Many previous studies assumed identical hydraulic and mechanical apertures in discrete fracture network models for simplicity (Min et al., 2004; Zhao et al., 2011). Therefore, the main objective of this study is to evaluate the influences of local surface roughness of fractures on fluid flow and solute transport processes at the macroscopic scales of fracture networks, by employing the empirical models that relate the hydraulic aperture to the mechanical aperture."

Jan 1, 2015

By N. Kacira

"Canada's largest known chromite deposit occurs in a layered intrusion in the Bird River area of Manitoba. However, numerically most of the chromite occurrences are in the Appalachians. Few, apparently minor, occurrences are also known in the Cordillera.In the Appalachians, chromite occurs as lenses and pods in dunite; they are of ""podiform"" type. The individual concentrations vary in size from a few pounds to tens of thousands of tons. Locally, chromite concentrations form discontinuous zones extending several hundred feet along strike and presumably down dip, therefore resembling boudinaged layers. Chromite layering and lineation are commonly concordant to those of the host rocks.The Appalachian chromite occurrences are thought to have been formed by fractional crystallization and perhaps also by liquid immiscibility. Their present shape and distribution are largely the result of deformation mostly prior to complete solidification of their host rocks. Therefore, the attitude of layering, foliation, lineation and other features related to deformation provide valuable guides in predicting the probable distribution of chromite, and hence are helpful in exploration.Chromites fulfilling the requirements for metallurgical, refractory and chemical grades occur in the Appalachians. Although the Appalachian deposits are similar in size and grade to some of the chromite deposits being mined elsewhere, they are unlikely to be economic, at present, in the higher wage Canadian environment. However, in case of shortages in chromite ore supply which may result, among other reasons, from increasing tendency to further processing in the producing countries, the Appalachian occurrences may become sources of ore. Such eventual shortages combined with relative abundance of electricity in Canada and recent innovations in oxide ore reduction technology may hasten the time when ferrochrome manufacture based on local chromite sources becomes economically viable."

Jan 1, 1982