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By D. J. Bowen

"The Great Dyke extends for 540 krn along strike, to unknown depth, and varies in width from 3 krn to 11 krn. Rb/Sr age determinations gives values of approximately 2470 Ma.The Dyke consists of a variety of mafic and ultramafic rocks, many altered to serpentinites. These include, from top to bottom, successions of gabbro/norites, pyroxenites, peridotiteslharzburgites, and dunites/picrites.The layers dip in from either margin, steepest at the edges (20°) and flattening toward the central sections. Four separate complexes are present. From north to south these are termed the Musengezi, Hartley, Selukwe and Wedza Complexes, and are described as 'boat-shaped' or 'pig-troughed'. All are similar in petrological sequences. Physiographically, the Dyke is spectacular in the north, where as a mountain range it meets the Zarnbezi Escarpment. Elsewhere in the central parts there is little surface expression and wide open treeless vleis. Dyke rocks cut through granite and schist belt terrain and are termed 'The Magnesia Belt'.Vast mineral resources exist. These include chrome, asbestos, platinoids, nickel, copper and gold. Up to eleven chrome seams numbered from top to bottom occur in the lower ultramafic sequences. Seams are narrow at 10 em to 30 em but of high grade. The platinum occurs 10 m to 40 m below the norite/pyroxenite contact.A 60 m wide zone of Light Sulfide Mineralization (LSM) of less than 1070 sulfides extends from the lower gabbronorites into the upper pyroxenites. In this LSM, four enriched zones carry up to 5% sulfides. The most widespread is termed the Main Sulfide Zone (MSZ), below which is No. 2, No.3 and No.4 Sulfide Zones. The MSZ carrying pyrite, pyrrhotite and chalcopyrite is a multielement ore with components of PGE (pt-Pd-Rh), nickel, copper and cobalt, and gold and silver.Extensive exploration programs have been carried out and the intention is to begin large-scale mining. However, with Russia supplying metals to the western markets, South Africa's cutback on production, and an end to the Cold War, delays have arisen."

Jan 1, 1994

By Iain Sommerville, Hugh Mountford, Dawid D. Smith, Claude Dube, Brett Hixson

JW Aluminum use lean and Six Sigma techniques to continuously improve their target of reliable, repeatable and reproducible (3R) manufacturing. Six Sigma’s second stage gate, known as "Measure" involves identification and qualifying appropriate measuring systems. Metal quality (inclusions) are known in the industry to be an important element in 3R casting. The measurement of inclusions at JW Aluminum historically depended on outside vendors. In order to establish real time inclusion measurement ability within JW Aluminum, inclusion measurement systems in the marketplace were investigated. The qualification of a MetalVision MV20/20 ultrasonic inclusion analyzer are discussed as well as the subsequent application of the system in melting and casting improvement projects.

Jan 1, 2015

By L. Vollert

"The application of pneumatically-assisted fluidized bed flotation, specifically the ERIEZ HydroFloatTM technology, has found widespread use in non-sulphide processing (particularly phosphate, potash and coal) for the recovery of coarse particles. In gold processing, centrifugal gravity circuits and flash flotation cells are typically employed for the recovery of coarse and near-size liberated gold which tends to accumulate in recycled grinding streams due to bypass to the classifying cyclone underflow streams owing to the higher specific gravity of these gold particles. Early removal of this gold from the grinding circuits contributes toward the reduction of downstream processing losses as a result of overgrinding and particle shape deformation in the case of flotation processing, longer leach residence times in the case of extractive processing, and surface occlusions in the case of both flotation and extractive processing. Furthermore, recovery to bullion attracts higher payment terms by way of comparison to concentrate sales in the case of copper-gold concentrators. This paper assesses the application of pneumatically assisted fluidized bed flotation for the recovery of coarse liberated gold through the analysis of piloting data generated from the operation of a continuously operated 16 inch ERIEZ HydroFloatTM unit treating a sized coarse grinding circuit stream. The paper presents the stage recovery by size performance of the ERIEZ HydroFloatTM unit together with quantitative gold deportment analysis to demonstrate the efficiency with which gold was recovered during this pilot campaign and then compared to more conventional processing units – centrifugal gravity and conventional flotation.INTRODUCTION Newcrest Mining Limited (NML) has identified that an opportunity exists for improving the recovery of coarse composite particles at its current operations, both as a means for improving overall recovery and as an opportunity for early gangue rejection. As such, Newcrest Mining Limited has taken an interest in the application of pneumatically-assisted, fluidized-bed flotation i.e. ERIEZ HydroFloatTM technology. This interest dates back to 2011 with sighter testwork carried out on their Australian-held ore bodies (Kohmuench et al, 2013). Newcrest continues to assess ERIEZ HydroFloatTM potential for coarse composite recovery and, in the case of the topic of this paper, coarse gold recovery based on examples in the literature which demonstrate the efficiency of this technology in this regard (Carmona Franco et al., (2015); Miller et al., (2016); and Kohmuench et al, 2013)."

Jan 1, 2017

By Sadough vanini Ali

The silicon anisotropic wet chemical etching technique is widely employed for fabricating various microelectromechanical system (MEMS) structures for advantages such as simple etching equipment and its capability to fabricate special microstructures. In this paper, we consider a complete theoretical derivation of the analytical solution based on geometrical and kinetic aspects of step flow on any surface and with a mathematical method we derive new equation for calculating the microscopic etch rates of surface atoms for a new range of concentrations and temperatures. Furthermore, a novel equation is presented for the calculation of the microscopic activation energies for some typical surface atoms and a new comparison of activation energies between some atoms is made that divides atoms into three categories. The results demonstrate agreement with the experimental results.

Oct 1, 2011

By T. Shariff

Titanium alloys have found increasingly wide range of applications in aerospace, chemical, medical, sporting, power generation, oil and gas extraction industries mainly due to the low density, high mechanical property characteristics, biocompatibility, and excellent corrosion resistance. In the manufacturing routes of their finished products, welding has been a key technique used and always been a main concern requiring the stringent compliance to the well defined process. Conventionally, gas tungstenarc (TIG), gas metal-arc (MG), plasma arc, and electron beam welding processes have been used to weld titanium alloys. Nowadays, laser beam welding has provided great challenging applications for titanium alloys due to the low and precise heat input, deep and narrow fusion zone, small heataffected zone, low thermal distortion and high productivity. At the NRC Institute for Aerospace Research, some R&D work has been undertaken for titanium alloys using laser beam welding process. These investigations have mainly concentrated on optimizing the welding process as well as understanding the fundamental process-structure-property relationships. In this invited keynote presentation, the research progresses obtained and the main issues encountered in laser welding of titanium alloys will be briefly summarized.

Jan 1, 2011

By Kevin P. Plucknett, Z. Memarrashidi

"In the current work, factors influencing the corrosion mechanisms of TiC and Ti(C,N) based cermets are reviewed. Cermets were typically prepared with 30 vol.% of metal binder, in the form of various in-situ reaction-formed Ni3Al alloys. Commercial WC-Co hardmetals were also examined as baseline materials. The assessment of corrosion involved a variety of electrochemical measurements, including open circuit potential and potentiodynamic polarisation. The corrosion potential and current density were determined, following Tafel extrapolation, allowing estimation of the corrosion rates. Post-corrosion characterisation involved scanning electron microscopy analysis and associated energy dispersive X-ray spectroscopy of the sample surfaces. It is demonstrated that the primary corrosion mechanism for this type of cermet is dissolution of the metallic phase during oxidation attack, and thus this response can be expected to increase with the amount of binder in the cermet, although degradation can be subtly affected by composition (i.e. alloy composition, C:N ratio, impurities in the ceramic phase, etc.) and test procedure (i.e. aerated vs. de-aerated electrolytes). It was observed that addition of N content into the ceramic phase is beneficial to the corrosion characteristics of TiC based cermets, through significant refinement in the grain size of the hard phase. Similarly, elimination of impurities, such as W in selected TiC powders, also improves the corrosion resistance.INTRODUCTION Cermets are prepared using the combination of a hard, high elastic modulus ceramic phase with a ductile, high toughness metallic binder. This pairing of hard and ductile components ensures wide application of cermets in demanding wear environments. These materials are consequently used industrially in both bulk and coating form. The most common example of such a composite system is based on the use of tungsten carbide with a cobalt-based binder (WC-Co), which has been widely examined over the past 80 years. However, while WC-Co has been shown to exhibit an excellent combination of high strength and wear resistance, the corrosion and high temperature properties of this material are relatively poor. In addition, WC-Co possesses a high density (~13–14 g/cm3), which makes it a less desirable option when the component mass is a design factor (i.e. use in aerospace). In particular, the aqueous corrosion response of WC-Co limits its use in wear environments where combined corrosive degradation may occur (i.e. tribo-corrosion scenarios). Alternate cermet systems are therefore being actively developed due to these performance limitations."

Jan 1, 2017

By A. Dolatmoradi

Nanocrystalline structure formations produced by severe plastic deformation in Fe-0.15C with initial ferritic-pearlitic and IF steel with ferritic microstructures have been studied through microstructural observation and microhardness measurements. It was found that the nanocrystalline region first forms near the surface of samples due to localized severe deformation. It was also observed that the nanocrystallization rate of Fe-0.15C and IF steels and the deformed layer thickness in these two materials are different with similar milling conditions. The crystallite size and structural evolution of the samples during milling was studied by employing XRD and SEM.

Jan 1, 2010

By T. P. Johnson, A. Vathavooran

"Conventional mining operations can produce a wide range of wastes containing gold and other precious metals but which are less suitable for processing by traditional methods. There are also types of ore that do not fit easily into a traditional processing flowsheet, e.g. because the refractory nature of their minerology or the combination of valuable metals is less suitable for traditional processes. Nevertheless, these potential sources of valuable metals remain unexploited resources that have attracted growing interest in the metals and mining industries over recent years. The challenge is therefore to develop and use alternative processing methods that have the flexibility of operation to cope with a wide variety of material types and tonnages, whilst providing high recoveries for valuable metals. Tetronics’ DC plasma smelting technology achieves industry-leading recovery rates for precious metals from a wide range of input materials and initial precious metal concentrations, whilst generating an inert slag-based material as a by-product (even when starting from a hazardous waste input material), approved within the EU for use in construction applications. This paper describes how this technology can be used as a key part of an overall process for the recovery of precious metals from these interesting materials.INTRODUCTION The extraction of gold from its ores by various forms of cyanide leaching has been practised by the mining industry for over a century (Minerals Council of Australia, 2005) and it remains the primary extraction method in a wide range of mining operations. The ability of cyanide to extract gold efficiently and quickly from lower grade ores without extensive additional processing, coupled with well-known methods to recycle the cyanide for re-use within the process mean it is often both the most economically preferable and environmentally acceptable method for recovering gold. As a result, 88% of all gold produced from mines in the USA in 2014 was recovered via leaching of open heaps or dumps (UGGS, 2016). Nevertheless, there are occasions where certain combinations of mineralogy and other circumstances reduce the effectiveness of cyanidation techniques, so that ever more elaborate additional processing steps are required, with inevitable increases in operating costs (Swash, 1988). In these circumstances, which are likely to be more common in future as ore qualities diminish, other methods of extraction may offer better alternatives. Whilst much less commonly used for Au extraction at present, pyrometallurgical methods are amongst the longest-established of these alternative approaches and merit serious consideration in such cases."

Jan 1, 2017

"The successful commissioning and ramp up of the Albion Process™ at the GPM Gold Project relied on the successful scaling up of the process from batch and continuous pilot plant campaigns (Voigt et al., 2015). Critical information about reaction kinetics and residence time, grind size and pulp density were determined at the laboratory scale and successfully applied to the commercial scale. A limitation of small scale testwork, is that some parameters cannot be measured reliably and scaling up is a function of the physical size of the equipment which isn’t possible to test with laboratory scale equipment. Oxygen mass transfer rate is one such parameter since this is a complex interaction of many factors including slurry temperature, solution and slurry chemistry, slurry viscosity, agitator type, dimensions and power, oxygen bubble residence time, oxygen purity, tank geometry and oxygen injection technique. Oxygen generation represents an important operating cost for the Albion Process™. Pivotal to the Albion Process™ operating economically at atmospheric pressure is the capability to efficiently transfer oxygen while utilising as much oxygen injected to the process as possible. To respond to this Glencore Technology developed the HyperSpargeTM supersonic gas injector. This paper compares the HyperSparge™ against other sparging techniques to quantify the benefits of oxygen injection via a supersonic gas jet on scale up of the oxygen mass transfer system. The paper then examines plant survey data from the GPM Gold Project to demonstrate the very high oxygen utilisation that can be achieved with a correctly designed oxygen mass transfer system.INTRODUCTION One of the main challenges in chemical reactor design is the scale-up of processes from the laboratory to industrial scale. Processes which cannot be faithfully simulated with an experiment at the laboratory scale face challenges due to the physical dimensions and complexity of full scale operation. One example of this is the design of oxygen mass transfer systems in atmospheric oxidative leaching circuits such as the Albion Process™. A number of constraints associated with the use of laboratory scale equipment to design full scale circuits are involved in gas mass transfer processes in agitated slurries such as the Albion Process. Chiefly, typical laboratory and pilot size equipment lacks the required volume to provide useful design data without relying on empirical correlations: the specific agitator power input is artificially high, the bubble residence time in the vessel is artificially low, the oxygen partial pressure at the base of the vessel is artificially low and the oxygen delivery method may differ significantly to the industrial process. Further, the dynamic nature of the process introduces additional impacts on gas mass transfer, including the presence of solids, recycle streams and minor elements, plus the variances within the reality of a process plant such as disruptions or variance of feed quality."

Jan 1, 2017

By E. J. Marcotte

"INTRODUCTIONThe Upper Canada Mine is located at Dobie, approximately ten miles east of Kirkland Lake, Ontario.The mill contains Upper Canada's cyanide circuit and Upper Beaver's flotation circuit. The combined capacity is 590 tons per day consisting of 415 t.p.d. of Upper Canada gold ore and 175 t.p.d. of Upper Beaver copper-gold ore.The Upper Beaver ore is trucked five miles to the Upper Canada mine site.Crushing:The crushing circuit consists of primary, secondary and tertiary crushing employing one C .A. C. 15 in. x 24 in. Superior jaw crusher, one 4 ft. x 8 ft. Tyler-Niagara double deck screen, one 3 ft. Symons standard cone crusher and one 3 ft. Symons shorthead cone crusher.The -2 in. product from the jaw crusher is fed to the double deck screen. The+ 5/ 8 in. passes over the top deck to the 3 ft. standard cone crusher; the+ 3/ 16 in. material passes over the lower deck to the shorthead cone crusher. The - 3 / 16 in. material pas sing through the lower deck of screens is the product to the mill.The screens used prior to the installation of rubber screen cloths were: one 4 ft. x 4 ft. section with 3/ 4 in. square openings and one 4 ft. x 4 ft. section with 5/ 8 in. square openings on the top deck; two 4 ft. x 4 ft. sections with openings of 3/16 in. x 4 1/2 in. slot on the lower deck. The fine screens were positioned so that the 4 1/ 2 in. slots were parallel to the flow of feed.The crushing circuit is operated on a three shift per day basis by one operator per shift."

Jan 1, 1968

"INTRODUCTIONThe Department of Energy, Mines and Resources has recently developed two automatic controls for use in the cyanidation circuits of Canadian gold mills. These controls are the alkalinity probe and the Continuous Cyanide Titrator both of which are discussed in the paper ""Instrumentation in the Cyanide Process"".(1)In May 1966 these process controls and associated recording equipment were installed in the Bralorne mill by two Scientific Officers from the Department. The object was to determine if the equipment was amenable and applicable to this particular circuit. The purpose of this paper is to discuss the performance of the equipment over a test period of 4 months.CONCLUSIONSThe results of test work to date indicates that both the Conductivity Probe and the Continuous Cyanide Titrator would be an as set to the operation of the Bralorne mill.The conclusions are generalized as follows:-(1) At a milling rate of 100, 000 tons per year the expected reductionin reagent consumption would give a direct saving of 37, 660 lbs of lime@$0.030 per lb and 15, 790 lbs of sodium cyanide@ $0.175 per lb. Such cost savings would pay for the equipment and installation costs within a 30 month period"

Jan 1, 1967

By D. Paul Bishop, Kevin P. Plucknett, Hung-wei Liu

"Spark plasma sintering (SPS) process has been evaluated for producing the commercially pure (CP) Ti, TiAl and a TiAl-B4C composite. Comparisons were made between the materials in terms of the sintered density, resultant hardness and microstructures. In the present work, the titanium aluminide powders (Ti-48Al, producing a mixture of y-TiAl/a2-Ti3Al) were synthesised „in-house? using a simple reaction-sintering and mechanical attrition approach. This allowed various size distributions to be generated. The powders were then blended with a fine boron carbide (B4C) powder (up to 6 wt.%), and the resulting mixtures were consolidated using spark plasma sintering (SPS) under vacuum in graphite dies. An applied stress of 50 MPa was used for all SPS runs. The SPS parameters were varied in terms of the ultimate sintering temperature (up to 1300°C) and hold time (up to 10 minutes) for each material. It is demonstrated that high densities can be achieved this approach (exceeding 95% of theoretical, with optimised samples close to full density). Microstructural characterisation was conducted using optical microscopy, scanning electron microscopy, and X-ray diffraction. The B4C additions were seen to partially react with the TiAl to form reinforcements, such as TiCx and TiBx. Preliminary mechanical property assessment will also be briefly discussed.INTRODUCTION Titanium- and titanium aluminide-based alloys possess many unique properties, such as excellent corrosion resistance and high temperature strength, respectively (Cardarelli, 2001; Leyens & Peters, 2003). Compared to many other competing materials (e.g. stainless steel or Ni-based alloys), Ti- and TiAl-based alloys also have relatively low densities (~4.5 and ~3.9-4.1 g/cm3, respectively), which is critical for performance in aviation and automobile applications. However, the manufacturing cost is high, due to the expensive raw Ti material and difficulties in machining. TiAl-based alloys are particularly difficult to produce because of their limited ductility (Lütjering & Williams, 2007). To overcome those problems, powder metallurgy (PM) technologies have shown great potential as near-net shape processes for Ti- and TiAl-based alloys. The general PM process largely avoids laborious post-machining and minimises material use. In industrial production, the PM approach has been successfully utilised to manufacture aluminium- and iron-based alloys (Huo & Heath, 2008)."

Jan 1, 2017

By A-A. Bogno, M. Rappaz, J. Valloton, H. Henein

"Rapid solidification of Al-Cu droplets of eutectic composition was carried out using Impulse Atomization in an argon atmosphere, to study the microstructures forming at different cooling rates and undercoolings. Two distinct morphologies were observed within the investigated Al-33wt%Cu droplets microstructures: (i) A regular lamellar morphology and (ii) an undulated morphology. The volume fraction of each type of morphology was measured as a function of the droplet size and the nucleation undercooling was deduced using the hypercooling limit equation. The scale of the microstructures was determined through measurements of inter-lamellar spacing across and along the growth direction. Growth velocity and undercooling were deduced using Jackson and Hunt (1966) eutectic growth theory. Finally, mechanical properties were estimated through micro-hardness analysis using a Vickers hardness tester, revealing exceptional properties for an aluminum-copper alloy. Indeed, the hardness values, increasing with growth rate and undercooling, were 3 times higher than the values obtained in hypo-eutectic Al-Cu alloys.INTRODUCTION Eutectic alloys are very attractive due to their good fluidity allowing ready shaping of parts in casting processes as well as in thermal spray deposition. In addition, they yield microstructures with high mechanical properties, by the virtue of their scale/size which is defined by the solidification parameters and the thermodynamic and thermophysical properties of the given alloy. Therefore, it is important to understand the relationship between the microstructures and the solidification parameters of eutectic alloys in order to control their solidification path and mechanical properties. The latter could be improved by either adding an appropriate strengthening component to a base eutectic material (Böyük, MaraslI, Kaya, ÇadIrlI, & Keslioglu, 2009) or by refining the microstructures for more effective dislocation pinning (Campbell & Campbell, 2003). Tailoring the microstructure can also be beneficial to chemical (Freitas, Osório, Spinelli, & Garcia, 2014; Osório, Freire, Caram, & Garcia, 2012) or electrical (Kaya, 2012) properties of the material. Eutectic-type microstructures, usually formed from liquid (eutectic transformation) or solid (eutectoid transformation), are made up of two or more different phases, generally of lamellar or fibrous (rod like) morphologies (Kurz & Fisher, 1998). In general, a binary eutectic structure can be regular (when both phases are non-faceted) or irregular (one of the two phases is faceted), the two solid phases having roughly the composition of the liquid from which they are formed."

Jan 1, 2017

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 C. Tissot, R. Palmer

"Due to the low concentrations of gold, direct measurement of gold concentration in ore on belt has not been seriously considered to now. Pre-concentration or sorting strategies have largely consisted of particle sorting based on secondary characteristics such as colour, which can be successful in select cases. CSIRO has produced sample measurement results using gamma activation analysis of ~300 gm samples with accuracies of around 30 ppb at best. With this encouragement, a feasibility study into gold ore measurement on belt for the purpose of sorting pods of gold ore has been undertaken. The study described here included, prototype design options with existing industrial Linacs, extensive Monte Carlo modelling of measurement sensitivity and shielding, further sample measurement, a study of the interaction of target measurement accuracy and sorting efficiency, and a rough estimation of potential economic benefit. The projected model sensitivity of around 0.1-0.15 ppm (1 standard deviation) in 10 seconds for 1 ppm average feed result in good bulk sorting performance and intriguing economic potential.INTRODUCTION Pre-concentration or sorting strategies for gold ores have largely consisted of particle sorting based on secondary characteristics such as colour or density, which can be successful in select cases (Klein, 2010). No method is available to measure gold content for sorting in particles or even in bulk on belt, principally due to the low concentrations of gold present. In fact, in many cases it is difficult to do rapid bulk grade measurements of base metal ores with concentrations many orders of magnitude higher. By a fortunate quirk of nature gold is particularly amenable to gamma activation analysis (GAA). CSIRO has performed extensive work in GAA of samples of crushed ore (Tickner, 2017). This has resulted in the Photon AssayTM technique that is currently being commercialised through the CSIRO spinoff company Chrysos. The technique relies on the recent availability of industrial high intensity X-ray sources such as Linacs which are currently being used in industry for security, medical and sterilisation applications. This development has led to CRC ORE funding a feasibility study to determine whether on-belt measurement of gold concentration is possible at a rate and accuracy sufficient to be useful for bulk sorting, where pods of ore are diverted rather than individual rocks. The study in the first instance is based on Monte Carlo modelling that has successfully predicted the performance of the sample based gold measurements. As well as the measurement feasibility consideration was also given to the likely heterogeneity of gold ores and hence the degree to which useful separation could be achieved. This is then tied to a back of the envelope evaluation of the order of magnitude economics of bulk sorting in an example deposit."

Jan 1, 2017

By D. Warkentin, T. Yeomans, R. Tavakoli, A. Nacu

"One of the most successful commercial methods of extracting gold from ores involves solubilizing gold as a gold cyanide complex, followed by adsorption of the complex onto activated carbon. The gold cyanide is subsequently eluted from the carbon to produce a concentrated gold solution suitable for electrowinning to recover the precious metals. Stripped carbon is treated in a kiln under a flowing steam atmosphere to reactivate its surface, allowing it to be reused. The aim of this study was to investigate the gold elution using a mixture of sodium hydroxide and isopropyl alcohol in both batch and continuous tests, with the eluates being electrowon on carbon foam cathodes. The effects of various factors, including alcohol content and sodium cyanide addition were studied. The addition of alcohol considerably improved gold elution kinetics, while the presence of sodium cyanide did not have a significant impact on either elution efficiency or kinetics. In all cases, efficient electrolysis was shown to be an important factor in maintaining effective carbon circuit operation.INTRODUCTION Gold dissolved as Au(CN)2- complex during cyanidation is recovered either by cementation with zinc powder, also known as the Merrill-Crowe process, or by adsorption into activated carbon through Carbon-in-Pulp (CIP) or Carbon-in-Leach (CIL) processes. Activated carbon loaded with gold is then eluted and gold is subsequently recovered by electrochemical methods. Conventional elution processes such as atmospheric and pressurized Zadra processes, involve stripping with a cyanide (0.1–0.2% NaCN) and sodium hydroxide solution (1–2% NaOH) at high temperature (90–140°C) over long elution times of 8 to 72 hours. In the Anglo American Research Laboratories (ARL) elution process, the acid-washed loaded carbon is pretreated with a strong sodium cyanide and sodium hydroxide solution (1–5% NaCN and 1–2% NaOH), followed by elution with water at 110–130°C. Solvent-assisted elution processes have also been reported, such methods use varying concentrations of alcohols (methanol, ethanol and isopropanol), ketones, or glycols to enhance atmospheric elutions at temperatures up to 95°C (Muir et al., 1985; Ubaldini et al., 2006; Espiell et al., 2008; Soleimani & Kaghazchi, 2008). The present work investigates the efficiency of isopropanol in the gold elution process, as well as the methodology of evaluating gold stripping processes in the lab setting"

Jan 1, 2017

By Y. Tanaka, M. Maeda, S. Suzuki, C. Tokoro, T. Kato, K. Muto

Boron (B) co-precipitation was investigated with ettringite to establish a cost efficient method of removing B from acid mine drainage. For 25 mg/L of B solution, most appropriate pH for B removal was pH 11.5. The most appropriate amount of reagent for B removal within Japanese effluent standard (10 mg/L) was B:Al:Ca:SO4 = 1:3:9:4.5, which corresponds to the composition of Ettringite (Al:Ca:SO4 = 2:6:3). The effect of silicate, carbonate and temperature on efficiency of B removal is important as groundwater and hot spring water are often contaminated. When silicate and carbonate are present, more Al and Ca salts are needed for B removal since some aluminum and calcium precipitate with silicate and carbonate as kaolinite and calcium carbonate. These precipitates do not contribute much to B removal. As the temperature raised, the most appropriate pH for B removal decreased. B removal became less efficient as monosulfate precipitated more rapidly as ettringite.

Jan 1, 2015

By J. P. Aiello

"INTRODUCTIONWhile this paper deals specifically with potential coal use at the Cold Lake Project of Esso Resources Canada Limited, a majority of the technical aspects of coal conversion could apply to any oil field and industrial boilers or stearn generators. In 1962, Imperial Oil Limited's production arm (the forerunner of Esso Resources), began examining methods of extracting bitumen from a 50 m thick layer of oil sand buried 450 m below the surface in the Cold Lake area. Almost two decades of research followed to develop an in situ oil sands recovery technology that made commercial production feasible.A $13 billion mega project that would have produced 22 000 m3/d (141 000 barrels/day) of synthetic crude oil (160 000 bpd of bitumen) was shelved in 1981, and ultimately replaced by a phased development strategy, involving smaller production units, to bring blended bitumen production on stream as markets and prices permit.The first two phases came into production in 1985. There are currently a total of six phases in production with four more in the construction stage. Each phase has 130to 140production wells (initially) and a central plant with water treatment, crude treatment and stearn generating facilities capable of producing 150 m3/d (9500 bpd of raw bitumen). The stearn generation section for each phase consists of three 180millionBtulhour oil fieldsteam generators.In its natural state, the bitumen is too thick to be recovered using conventional oil recovery techniques. At the Cold Lake Project, bitumen is recovered by a method called cyclic stearn stimulation. Water is pumped to the central plant where it is treated and heated to produce high pressure, high temperature steam. During the steam cycle, this steam is transported in insulated pipelines to the wells for injection into the oil sand formation. This cycle lasts from 30 to 50 days, heating the formation and causing the bitumen to flow. Following an initial flowback period, a surface based artificial lift system pumps the heated liquid bitumen, mixed with water and gas, out of the well and back to the central plant. The water and gas are separated from the bitumen, with the gas being used to provide some of the fuel for the stearn generators and the water being treated and recycled. Approximately 5% of the water cannot be recycled and is disposed of by injection into deep formations . The bitumen is blended with a diluent and shipped by pipeline to market."

Jan 1, 1989

By Y. Thibault, L. Morin, R. Cameron, D. Gould

"There are an estimated 50 to 100 million dry metric tonnes of low-grade nickeliferous pyrrhotite tailings in the Sudbury area alone, with an average nickel grade ~0.8% (plus cobalt). Pyrrhotite is a highly reactive sulphide mineral that has the potential to generate acidity; consequently, it is stored in large tailings ponds that require perpetual treatment to avoid the production of acidic drainage. Re-processing this material using bioleaching technologies has the potential to recover valuable metals, while reducing the toxicity, reactivity, and acid generating potential of the remaining residues. CanmetMINING is currently developing a stirred-tank bioleaching process to recovery nickel and cobalt from pyrrhotite-rich tailings. Stirred-tank experiments have been conducted with one tailings sample over a range of pH and temperature conditions, resulting in 80 to 90% and 70 to 80% leaching of nickel and cobalt respectively in 10 days.INTRODUCTION Sulphide tailings may represent a significant financial liability for mining companies as these wastes may produce acidic drainage under some disposal conditions. As a result, the companies must post financial bonds large enough to ensure there are sufficient funds for perpetual management of these wastes. At the same time, there are billions of dollars in metals incorporated into these mining wastes waiting to become valorized. Many sulphide tailings are amendable to bacterial oxidation for metal extraction. Re-processing of tailings using bacterial leaching has the potential to recover valuable metals from waste; and reduce the toxicity, the reactivity, and the acid generating potential of the remaining residue. By reprocessing these wastes there is an opportunity to significantly reduce liabilities and financial assurance bonds, while recovering metal values. There are an estimated 50 to 100 million dry metric tonnes of low-grade nickeliferous pyrrhotite-rich tailings in the Sudbury area alone with an average nickel grade ~0.8% (Peek et al., 2011) plus cobalt and copper. Pyrrhotite is separated from pentlandite concentrates by magnetic separation and flotation. It is already finely ground and has often been segregated from other tailings material, making „mining? relatively inexpensive. This represents roughly (> $100/ton) in contained value, with negligible mining costs. This paper reports on the development of a stirred-tank bioleaching process for recovering nickel and cobalt from pyrrhoitite-rich tailings, which is currently underway at Canmet MINING."

Jan 1, 2017

By K. van Netten, T. P. Ernst

"Froth flotation has been used successfully for about a century in the beneficiation of both coal and mineral particles. With the on-going trend towards lower feed grades, however, there is a need to transform this technology in ways that can deliver ultrafast separations, with strong selectivity, and recovery, covering a broader size range. It should be recognised that the hydrophobic effect, with its highly selective and long-range interactions, will most likely underpin any new technology. We identified the separation of the concentrate from the tailings as the rate determining step of conventional flotation technology. This limitation was then addressed by developing a novel flotation technology, insuring the formation of a concentrate that could be separated more rapidly from the tailings. We introduced a novel binder medium, a highly concentrated water in oil emulsion, to act as the focal point for hydrophobic adhesion, effectively replacing the air bubbles used in conventional flotation. The hydrophobic particles adhere to and become embedded within the binder, forming saturated agglomerates that float upwards. Moreover, by forming these large and resilient agglomerates, the product can be quickly dewatered over a screen and separated almost immediately from the tailings. Remarkably, this new binder permits residence times in the order of a few seconds under batch conditions. This paper examines the performance of the technology as a function of the oil wt% added to the slurry. The paper also examines the performance of the technology as a function of the particle size, showing a decline as the particle size exceeds 0.50 mm.INTRODUCTIONFroth flotation involves the collision and adhesion of hydrophobic particles to rising air bubbles, the carrying of those particles from the bubbly-pulp zone into a froth zone, and subsequent drainage and migration of the pulp to achieve the final concentrate (Wills, 2006). Within a Jameson Cell the feed slurry and air bubbles are brought into intense contact within the active area of the downcomer, achieving rapid kinetics of hydrophobic particle adhesion to the air bubbles (Harbort et al., 1994). However, once the bubble laden product and tailings emerge from the downcomer there is the need for separation of the concentrate from the tailings, an inherently slower process. In other devices such as mechanical cells the initial kinetics of particle adhesion are far slower, relying on the turbulent eddies throughout the cell, while in a column the kinetics rely upon an even slower process of bubble interception with suspended and settling particles (Gorain, 2007). However, in all cases the driving force for segregating the bubbles from the tailings, and the drainage of the froth are inherently the same. We do note, however, recent advances by Galvin and co-workers in achieving so-called Fast Flotation, utilizing a system of inclined channels to dramatically increase the segregation rate of bubbles from the tailings, permitting much higher gas and feed fluxes to be applied, achieving up to a ten-fold throughput advantage (Dickinson et al., 2014). Any further improvement within the existing flotation paradigm would require the introduction of centrifugal forces, but this would also require the formation of much finer bubbles than is typically used given the tendency of relatively large bubbles to reach a limiting slip velocity due to deformations and increased drag. Across all flotation devices we argue the rate determining step remains the segregation of the bubbles from the tailings."

Jan 1, 2016