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By K. M. Mayhew, G. D. Barr, T. M. McCoy, C. T. Knilans

"Teck Resources Limited (“Teck”) has developed and extensively tested on a continuous basis the CESL Technology hydrometallurgical process for treating copper and nickel sulphide concentrates, including bulk copper-nickel concentrates. Copper, nickel and cobalt are leached efficiently into solution, utilizing CESL process conditions. Total precious metals including gold, silver, platinum and palladium are recovered from the residue stream via sulphur flotation. This paper describes the CESL Technology testwork on a bulk copper-nickel concentrate derived from Twin Metals Minnesota?s (TMM) deposits within the Duluth complex and evaluates the economic benefits (increased cash flow, increased revenue certainty) and investment criteria (capital cost, payback and cash flow) of incorporating CESL Technology into the staged development of TMM?s deposits.INTRODUCTION Mineral Processing and the Role of Hydromet in the Duluth Complex The Duluth Complex in northern Minnesota, United States (US), represents one of the largest undeveloped accumulations of copper, nickel, gold, and platinum group metals (PGMs) in the world, ranking second in copper and PMs and third in accumulation of nickel. The figure below identifies some of the larger known deposits within the Complex (see Figure 1). Copper, nickel, PM and PGM mineralization within the Duluth Complex is hosted by mafic to ultramafic intrusive rocks that are part of the overall intrusive complex.One of the mineral processing challenges of Cu-Ni-PM-PGM deposits in this Complex is the complicated, polymetallic nature of the mineralization1: copper occurs primarily as chalcopyrite and cubanite with minor occurrence of talnakhite; nickel occurs as pentlandite and refractory nickel oxide/silicates; iron sulphides are present as both pyrrhotite and troilite; and PMs/PGMs occur in both the sulphide matrix as well as discrete minerals. An additional challenge for the Duluth Complex is the ratio between copper and nickel; in most of the identified deposits, copper grade is three to four times greater than the nickel grade, which precludes the production of a simple bulk concentrate due to the lack of a traditional smelting market for a bulk concentrate of this character."

Jan 1, 2017

By H. Oterdoom, S. Pilger, T. P. Bui, J. Rotarius

"Most FeNi furnaces used to rely on post-combustion and off-gas cooling inside the furnace to eliminate the produced CO gas, and control the off gas temperature. As furnace load, capacity, and thus gas volumes increased over the years, this led to increased instabilities that can cause problems in controlling the operation. Some of the large capacity furnaces nowadays work with partial or full combustion outside the furnace, more similar to the steel industry. Forced combustion with or without enriched air and other additions can support in controlling post-combustion, stabilizing and even reducing off gas amounts, and affecting composition. This paper presents some of the possibilities and advantages of having a specially designed post-combustion system for the FeNi laterite industry, but that could also be applied to other processes as well.Large Scale Furnaces In the FeNi industry, the Rotary Kiln Electric Furnace (RKEF) process is still going strong in spite of continuous hope that hydrometallurgical processes will one day make the RKEF plant obsolete. Within the pyrometallurgical plants there is a continuous trend for larger scale furnaces. The development for a number of furnaces that were started before 1985 and increased capacity by “natural growth” is given in Figure 1. Natural growth refers to the development of the plants that after having mastered a certain level of operation, were ready for a higher load that could be installed either with a new furnace on the same site, or during a revamp. The advantages of natural growth are numerous, for example: •,Deep knowledge of the ore and its’ behavior, no need for testing, and little risk of surprises. •,Mining, laboratory, equipment, etc. is all proven technology for the conditions on site. •,Starting a furnace with increased capacity is a re-start, not a green-field commissioning. •,Typically, when increasing the production capacity of an existing plant, not the entire plant is commissioned for the first time, but only a part. In the FeNi laterite industry for example, the kilns may already have had the capacity to provide enough material."

Jan 1, 2017

By K. Miao, W. Mu, M. Sharma, A. Haas, N. Dogan

"The ever increasing demand for cleaner steels with low inclusion content has highlighted the limits of our current knowledge for controlling and predicting inclusion agglomeration and removal during liquid steel processing. Key knowledge gaps in this area result from the complex nature of the problems associated with measuring and visualizing the phenomena studied. Confocal scanning laser microscope (CSLM) allows for continuous in situ observation of micron-size samples in real time, at high resolution, under conditions relevant to the steelmaking process. This paper summarizes some of recent CSLM applications in our laboratory to illustrate the methods of analyzing transient behavior. The reaction between inclusions and slag is given as an example. The dissolution rate of calcium aluminate inclusions in CaO-SiO2-Al2O3 slags has been studied at elevated temperatures: 1500, 1550 and 1600°C as well as thermodynamic/kinetic analysis. It is found that total dissolution time decreased with increasing temperature. The rate limiting steps are discussed. It is shown that the diffusion through a product layer is responsible for dissolution at 1500°C. At higher temperature, dissolution is most likely controlled by both boundary layer diffusion and chemical reaction at the slag-inclusion interface. In this paper, the evidence for and against the theory will be critically examined and repercussions of the theory to steel refining processes will be discussed.INTRODUCTION Inclusion formation during liquid steel refining is an unavoidable consequence of current ladle steelmaking processes. The nature and quantity of the inclusions formed in steel is critical in steelmaking, as it affects both productivity through clogging, and downstream physical properties of the steel. It is therefore crucial to better understand and control the formation, agglomeration and dissolution behaviour of inclusions in a slag in order to improve the removability of inclusions from liquid steel. Most research (Sandhage & Yurek, 1988; Sandhage & Yurek, 1990a; Sandhuge & Yurek, 1990b; Sandhuge, 1991) relevant to the kinetics of inclusion removal has been obtained by using a technique where simulated inclusion material (ceramic rods) is dipped in slag and the dissolution rate is measured. While much has been learned using this approach, the difference in scale from bulk materials to inclusions is likely to have a significant bearing on the dissolution kinetics of inclusions in a slag and will certainly result in a very different influence of capillary effects. Further, the data obtained using an indirect (dip test) procedure relies on a comparison of the initial and final conditions of a sample rather than in-situ observation which can be achieved in a confocal microscope in real time."

Jan 1, 2017

By P. J. Mehrfert

"Recovery of mineralized coarse particles is notoriously low in conventional concentrators that treat copper porphyry ores. The application of coarse particle flotation techniques has the potential to achieve comparable metallurgical performance at significantly coarser primary grind sizings. ALS Metallurgy has been conducting both internal research and commercial test programs to investigate the potential of Eriez HydroFloatTM technology on copper sulphide ores. Test data indicates that significant improvements in the recovery of copper sulphide bearing particles between 200µm to 850µm can be achieved using Hydrofloat technology compared to conventional flotation techniques. This paper summarizes the results from a selection of test programs that includes recovery by size data from both conventional flotation and HydroFloatTM tests. An explanation of the apparatus and test procedure will be given. Mineralogical analyses of the test products and characteristics that limit metallurgical performance will be discussed.Description of Apparatus and Test ProtocolThe HydroFloatTM laboratory cell is a clear plastic column with an internal diameter of 14 cm. Water and air are introduced to the cell through a circular manifold located in the lower portion of the cell. The cell has a conical bottom which directs slurry to a pinch valve that controls the discharge of tailings. Feed solids are introduced to the upper portion of the cell in slurry form. The cell is operated in a manner such that the manifold water creates a teeter bed zone of suspended solids in the middle portion of the cell. Tailings exit the bottom of the cell at a high pulp density, and most of the introduced water overflows the top of the column and is collected in a launder. Particles with a hydrophobic surface may attach to air bubbles that percolate through the teeter bed, rendering them sufficiently buoyant to be transported to the overflow launder.Three significant features of this arrangement enhance the potential to recover coarse, low grade particles by flotation techniques. Firstly, the hindered settling conditions created by the rising column of water allow coarse particles to become buoyant once attached to a modest sized air bubble. Secondly, the flow conditions within the cell are relatively quiescent compared to a conventional flotation cell that utilizes an agitator. This allows particles that have limited hydrophobic portions of their surface, due to a low content of exposed sulphide mineral, to maintain a somewhat fragile attachment to air bubbles long enough for successful recovery to the overflow. Finally, the absence of a froth phase at the top of the cell allows particles attached to air bubbles to immediately exit the vessel, reducing the potential to drop back into the pulp phase as bubbles burst or coalesce."

Jan 1, 2017

By O. G. Olvera

"Refractory sulfidic ores consist of materials in which gold occurs finely disseminated within metallic sulfides or forming solid solutions, with pyrite and arsenopyrite being the two sulfides most commonly associated with gold. Typical cyanide operations show poor performance and require oxidative pretreatments to increase gold recovery. Pretreatment alternatives include roasting, pre-aeration, acidic and alkaline high pressure oxidation, and bacterial oxidation. The presence of arsenic, however, introduces a serious disadvantage to the use of roasting and bacterial leaching, while high pressure oxidation involves high capital costs. This work focuses on evaluating the effect of the addition of a carbon resin as a sulfur collector on the oxidation of different arsenopyrite concentrates under atmospheric tank leaching (ATL) conditions. The addition of the resin improved the oxidation of sulfides and favored the formation of elemental sulfur over the generation of sulfate. The use of AF5 in ATL resulted in higher gold recoveries under standard cyanide carbon-in-leach and thiosulfate leaching.INTRODUCTION Refractory sulfidic ores consist of materials in which gold occurs finely disseminated within metallic sulfides or forming solid solutions, with pyrite and arsenopyrite being the two sulfides most commonly associated with gold. Gold is not readily accessible to solutions in these types of ores and typical cyanide operations show poor performance, thus making the use of oxidative pretreatments a requirement to increase gold recovery. Pretreatment alternatives include roasting, pre-aeration, acidic and alkaline high pressure oxidation, and bacterial oxidation. The presence of arsenic, however, introduces a serious disadvantage to the use of roasting and bacterial leaching, while high pressure oxidation involves high capital costs. The use of carbonaceous materials to enhance the dissolution of sulfides is not novel, and leaching additives such as coal, activated carbon and carbon powder have been considered for the improvement of bioleaching, atmospheric leaching, and pressure oxidation leaching processes. However, this type of technology has been focused mainly on the recovery of copper from copper concentrates containing chalcopyrite with less attention paid to other sulfides."

Jan 1, 2017

By Masahiro Eguchi, Giuseppe Granata, Chiharu Tokoro, Hiroki Fukuda, Yuichiro Toba, Shungo Hobo

"Currently, large amounts of wastewater containing boron are discharged from industries like coal-fired power plants. Although coagulation-sedimentation is widely employed for their treatment, only a little consideration has been given to its mechanism. An additional problem is that the produced sludge has poor solid-liquid separation. This study is focusing on coagulation-sedimentation using magnesium, examining the mechanism and improving the solid-liquid separation. First, the co-precipitation with magnesium hydroxide was conducted against high-concentration boron wastewater with 500 mg/dm3as B. Second, in order to improve the solid-liquid separation by maintaining high reactivity, low-crystalline magnesium oxide was synthesized from magnesium carbonate by calcination at 400–700°C. It was tested as an adsorbent of boron and compared to co-precipitation with magnesium hydroxide. Co-precipitation showed high removal capacity. X-ray diffraction (XRD) of the sludge revealed the presence of other compounds besides magnesium hydroxide. This result suggests that other processes play a role other than simple adsorption on to magnesium hydroxide, and provides a plausible explanation for the observed high separability. As for the adsorption, the synthesized magnesium oxide immobilized as much or more amount of boron than co-precipitation. Furthermore, the results of fourier transform infrared spectroscopy (FT-IR) suggested the residual magnesium carbonate improved solid-liquid separability due to its poor solubility.INTRODUCTIONBoron is used in various industrial applications. In glass industry, the addition of a little amount of boron into glass products can enhance heat-resistance and chemical-resistance. Semi-conductor industry also employs boron as dopant for silicon. From these industries, large amounts of wastewater containing boron have been discharged. Additionally, coal-fired power plants have been recently discharging highly concentrated boron wastewater because the amount of boron contained in coal has been increasing due to a gradual decrease of the quality of coal. Since boron is partially proved to be toxic for animals, plants, and human beings (WHO, 1998),the guideline of the World Health Organization limit the boron concentration in drinking water to 2.4 mg/dm3(WHO, 2009).Because boron does not precipitate from solutions by simply changing the pH, the removal could be carried by operations such as adsorption or ion exchange. However, since ion exchange is an expensive operation with relatively low capacity, it is not suitable to treat the large amounts of wastewater produced by heavy industries like the coal-fired power plants. Therefore, coagulation-sedimentation method is still widely used as a suitable alternative way."

Jan 1, 2017

By L. Lorio, B. Hilscher, P. Nayak, N. Yoon

"Mining has been a staple to technological advancement ever since the dawn of time. By harnessing the different physical and chemical properties that each mining commodity brings to the table, more and more innovation is developed and manufactured. As these non-renewable resources continue to be extracted, the industry as a whole faces a challenge in finding the next economical deposit as well as declining grade at the current operations. By means of pre-concentration, ore sorting aims to separate the barren material from the valuable ore to reduce energy consumption and tailings generation, while increasing the feed grade, concentrate grade, mill recovery, and revenue. In addition, ore sorting allows the modification of deposit geometallurgy in order to allow the creation of an optimal mill feed. This paper evaluates the applicability and challenges of ore sorting by utilizing the results from four different mines, and reviews them in detail. The mines include one underground and three open pit mines that are precious metal operations. In order to understand the applicability of ore sorting in these operations, initial rock-by-rock test results and different types of assays (atomic adsorption [AA], inductively coupled plasma [ICP], and fire assay) are utilized. Using the assay results, the grade recovery curves for ore sorting are generated and they are further improved by using and developing an ore sorting algorithm, which is discussed in this paper. The application and evaluation of ore sorting in greenfield and brownfield properties will also be discussed. The state of the art ore sorting technologies for both rock-by-rock and bulk sorting are also reviewed in this paper. The future technologies on the horizon, including different combinations of sensors, are explained. The sorting technologies include X-ray transmission (XRT), X-ray fluorescence (XRF), colour, infrared, electromagnetic, and laser induced breakdown spectroscopy (LIBS)."

Jan 1, 2017

"In response to mine head grades declining and orebodies becoming more complex, Glencore Technology has developed an alternative method for recovering economic minerals once leached into solution, rather than relying on conventional flowsheet options. The method involves the precipitation and separation of base metals from solution with limestone or lime. The final grade of these precipitate is not usually high enough to attract favourable terms of sale due to dilution from gypsum and sulphate salts. A set of operating conditions have been developed to allow the separation of the base metal precipitate from gypsum by exploiting the difference in particle size. A high-grade oxide product can be easily separated from the gypsum stream at very low cost. This process was originally developed by Glencore for zinc and copper systems. This paper reports on the successful application to nickel and cobalt, and this process has significant advantages over the incumbent precipitation process utilising magnesia.INTRODUCTION During evaluation of transitional and oxide zinc ore deposits during the 1990’s, Noranda Inc. (now Glencore) developed a sulphate based ore leach process to extract zinc into solution. For flowsheet development, conventional schemes dictated that once the zinc was dissolved in an acidified solution it was recovered by means of purification or solvent extraction followed by electrowinning and casting to produce zinc ingots. The deposits Noranda evaluated were high grade but had a relatively short mine life (10 years) and economic analysis showed that the projects couldn’t sustain the investment of a full zinc refinery. Compounding this problem was the lack of power supply infrastructure and the high power cost in the region. Noranda then evaluated alternative means of recovering zinc from solution. Laboratory testwork showed that a high-grade zinc precipitate (+50 wt% Zn) could be produced as an oxide, carbonate or sulphide by contacting acidified zinc sulphate solution with a number of reagents including soda ash, sodium hydroxide, and sodium hydrogen sulphide. Economic evaluation showed that the cost of the reagents are prohibitive, especially when the final product is still a metal intermediate (ZnO, ZnCO3 or ZnS). Noranda then continued to focus on fine zinc oxide precipitation for supply into the automotive tyre industry as this product would attract favourable terms of sale as a premium on Special High Grade (SHG) zinc."

Jan 1, 2017

"Real time analysis of conveyed bulk materials can be used to improve process performance by reducing variability and upgrading ore quality through selective removal of increments of flow that do not meet appropriate selection criteria. This paper focusses on proven Prompt Gamma Neutron Activation Analysis (PGNAA) and microwave transmission technologies used to representatively measure conveyed ore quality in real time so that meaningful decisions can be made between the mine and mill. This enables the effective removal by bulk diversion of small increments of conveyed flow such as waste, highly deleterious material or sub-economic material from the mill feed. Improved ore quality in plant feed optimises process performance, reduces processing costs and minimises tailings generation. Analysis is unaffected by particle size, dust, layering or segregation, mineralogy and belt speed. Technologies are explained and performance examples given from installations in copper and iron ore. The technology has been used successfully in bulk sorting for over twenty years typically using measured increments of a few minutes. Improvements in technology and calibration performance have resulted in accurate measurements over increments of thirty seconds and below.INTRODUCTION Ore quality variability exists on a number of scales. Block model grades represent a few hundred to many thousands of tonnes. Grade control at the mine occurs on a scale typically down to the size of a haul truck, which may be a few hundred tonnes. Highly variable ore quality is detrimental to process efficiency and effectiveness. Processing waste or low grade ore when higher quality feed is available represents a lost opportunity to generate higher revenues earlier in the operational life. Measuring ore quality accurately over short time increments during conveying enables small increments to be measured and diverted according to their quality. The paper explains the technology and benefits. Neutron irradiation techniques were considered potentially suitable for conveyed bauxite measurement by Beurton et al, 1995. Tran & Evans (2001) concluded there was no equivalent technology to Prompt Gamma Neutron Activation Analysis (PGNAA) in terms of material penetration power. PGNAA was evaluated by Nelson & Riddle (2003) for possible use in the phosphate industry and recommended its use for further characterisation of the mine’s various ore types to improve stockpile allocation and grade control. Cottle (2007) discussed test work for an iron sinter application and Delwig et al (2011) described the successful installation in 2009 and performance of PGNAA for base-to-acid ratio control in sinter feed with the analyser output used to control lime addition. Geoscan (PGNAA) works very well on iron ore and can “improve control over what is happening in the plant” and that comfort can be provided in knowing that the product is on-spec according to Minnett (2010). PGNAA is not yet used in the minerals sector for tariff purposes as has occurred since 2000 with Coalscan (PGNAA) in coal (Minnett, 2010)."

Jan 1, 2017

By Haruka Takeura, Tomoaki Murata, Kazunari Yoshida, Masato Adachi

"Pure magnesium is a material with high functionality, however, the cold drawing of this material is very difficult, that is why, until this day there are no optimal cold drawing conditions. Furthermore, cold drawing of pure magnesium wire shows a problem with internal defects that occurs under certain conditions. In this research, the aim is the suppression of internal defects, and final target is to create the optimal cold drawing conditions for pure magnesium wires. The first step is the investigation of the drawing limit by using 250°Cannealed wire. As a result, reduction of 10% per pass was chosen for stable wire drawing. However, in this case, it was found that internal defects occurred at total reduction of over 45% during drawing. Investigation of intermediate annealing conditions that can suppress internal defects, and influence on internal defect that the die half angle and reduction per pass. As a result, it was found that the drawing condition capable of suppressing internal defects most efficiently was 13% reduction drawing by using under 6°half angle die. Consequently, it’s possible to manufacture a cold fine drawn pure magnesium wire of 100µm, without defects in the center of the wire and hindering its mechanical properties.INTRODUCTIONMagnesium is a light and high functionality material that has high vibration absorbency, heat dissipation, electromagnetic wave-shielding and recycling efficiency (Conruy, 1989). However, proper cold wire drawing conditions haven’t been established, that is why warm or hot processing is commonly used (Oishi, Mori, &Kawabe, 2005). As a result, strength improvement of the wires is not possible, that is why the production of medical tools is disregarded. If it was possible to cold draw magnesium wires, the applications for material products would expand. Further, in wire drawing such difficult processing material, if appropriate processing conditions are not selected, defects will be generated inside the drawn wire."

Jan 1, 2017

By J. Zollinger, J. R. Kennedy, J. H. Park, D. Daloz

"In order to improve the properties of cast Ti-Al alloys to replace Ni-based superalloys past the low pressure stages of aircraft engines investigations into inoculation for grain refinement were carried out. Previous work showed isomorphic self-inoculation using Ti-Al-Nb particles was effective for grain refinement, however the relatively fast diffusion of Nb in Ti-Al make it difficult to observe the mechanism of nucleation. An alternative alloy was developed in the Ti-Ta system for isomorphic self-inoculation, maximizing the Ta content to improve the particles survivability in the melt. The powder processing produced comparatively small inoculant particles which dissolved, however larger particles were seen to survive solidification. The density difference between the inoculant particles and melt resulted in an inhomogeneous mixing of the particles and the melt with larger particles found near the outer edges of the ingots. Variations on particle size and interaction time between the inoculants and the melt resulted in the Ti-Ta inoculant reducing the as-cast equiaxed grain size by a factor of two compared to non-inoculated samples as well as increasing the equiaxed fraction in the ingot.INTRODUCTION Lightweight metals are of particular interest in aerospace applications. The hot sections of turbines are dominated by blades made of nickel based superalloys. Recently the GEnx turbine introduced TiAl blades in the last low pressure stage of the turbine to reduce weight and improve fuel efficiency (Kim & Dimiduk, 1991). In order to carry these benefits deeper into the turbine the high temperature (>800oC) properties of the alloys must be improved. Current grain refinement methods to improve properties rely on boron additions which may not be applicable for all blades as brittle precipitates may be formed during processing (McCullough, Levi, Mehrabian, & Hyman, 1991). A novel grain refinement process was previously introduced called “isomorphic self-inoculation” using Ti-Al-Nb particles to successfully grain refine TiAl (Kennedy, Zollinger, Bouzy, & Daloz, 2016). In order to better understand the mechanism of this process an investigation was carried out using the same process but with a Ti-Ta alloy which is more stable in the TiAl melt than the Ti-Al-Nb."

Jan 1, 2017

By A. Mazhary

"Although sensor-based ore sorting has gained significant attention recently, sorting gold deposits still face a high level of skepticism by gold mining companies. In order to shed some light on the matter, this article looks at two different gold deposits that were examined using X-ray Fluorescence, Electromagnetic and X-ray Transmission sensors. The heterogeneity of each sample is measured based on the assay results of each particle and is related to its sortability. Multivariate linear regression analysis was also performed on the XRF results to find potential proxy elements for detecting gold. The results from these deposits were varied and each sample showed different levels of sortability. While both X-ray sensors proved efficient for different deposits, the electromagnetic sensor failed to produce any promising results. Despite unsatisfactory result for one sample, this technology can have significant advantages in terms of lowering the operational costs and improving head grades and recoveries providing that the deposit is amenable to such separation methods. Therefore, it is important to mention that sensor-based ore sorting is ore and sensor dependent, and as a result, it cannot be applied and be beneficial to all deposits. Therefore, amenability tests are required in order to examine the potential for sensor-based ore sorting before one can reject the idea.INTRODUCTION Although sensor-based ore sorting has gained significant attention recently, sorting gold deposits still face a high level of skepticism by gold mining companies. Except for a few cases presented previously, no new case studies have been published. Previously, mines such as Kloof Gold Mine in South Africa used an optical sorter to sort their waste stockpile in 2003–2004 (Von Ketelhodt, 2009) and then again in 2009 (Von Ketelhodt, Falcon, & Falcon, 2011). More recently, Coeur Operations utilized an XRT sorter for their Kensington Mine in Alaska (Lasley, 2014) and also Anglo-American Platinum used an XRF sorter to pre-concentrate Platinum Group Metals through an algorithm that used chrome, copper and nickel as proxies (Rule, Fouchee, & Swart, 2015)."

Jan 1, 2017

By M. B. Kime

"A set of experimental batch leaching tests studied the effect of pH, time, temperature, and stirring speed on the relative Cu, Co, Ni, and Fe leaching yields of an oxidized copper-cobalt ore sample in an aqueous hydrochloric acid solution. The results were statistically analyzed and modelled using the structural equation modelling method. Models showed that Cu, Co, and Ni leaching yields were strong functions of the leaching time and leaching temperature, whereas the Fe leaching yield depended on the leaching temperature, stirring speed, and pH. Under optimum leaching conditions yields were 99.8% Cu, 82.4% Co, 91.3% Ni, and 30.6% Fe.RÉSUMÉ Une série d’essais expérimentaux de lixiviation en bâchée ont été menés pour étudier l’effet du pH, de la durée d’attaque, de la température et de la vitesse de brassage sur les rendements relatifs de lixiviation du cuivre (Cu), du cobalt (Co), du nickel (Ni) et du fer (Fe) d’un échantillon de minerai de cuivre-cobalt oxydé dans une solution aqueuse d’acide chlorhydrique. Les résultats ont été analysés et modélisés statistiquement à l’aide de la méthode de modélisation par équation structurelle (SEM, de l’anglais structural equation modelling). Les modèles ont montré que les rendements de lixiviation du Cu, du Co et du Ni dépendaient énormément de la durée d’attaque et de la température de la lixiviation ; le rendement de lixiviation du Fe, quant à lui, dépendait de la température de la lixiviation, de la vitesse de brassage et du pH. Dans des conditions optimales de lixiviation, les rendements étaient de 99,8 % pour le Cu, de 82,4 % pour le Co, de 91,3 % pour le Ni et de 30,6 % pour le Fe. INTRODUCTIONThe Katanga province in the Democratic Republic of Congo hosts the northwestern part of the Central African Copperbelt. This region abounds with large, rich deposits of sulfide and oxidized copper-cobalt ores. In general, the main valuable minerals present are malachite (CuCO3Cu(OH)2) and heterogenite (CoO(OH)). Common impurities found in heterogenite are Cu, Ni, Si, Al, Mn, and Fe. The substitution of Co by other cations (e.g., Cu, Ni, and Fe) has an influence on the crystallinity of heterogenite (Deliens, 1974). In general, well-crystallized varieties of heterogenite have lower impurity contents, whereas amorphous heterogenite types usually contain more impurities (Thys et al., 2009). Further, in heterogenite, Co can occur in the 2+ and 3+ oxidation states. The gangue generally consists of quartz (SiO2), talc (Mg3Si4O10(OH)2), kaolinite (SiO2·Al2O3·2H2O), limonite (Fe2O3·3H2O), and goethite (FeO(OH)). Oxidized copper-cobalt ores are often treated by hydrometallurgical methods, whereas sulfide ores are often treated by flotation or pyrometallurgy, depending on their grades. Hydrometallurgical methods typically entail selectively dissolving the metals of interest (Cu, Co, and Ni) in aqueous solutions (leaching), transferring the dissolved metals to an organic solution, and retransferring these to a second aqueous solution (solvent extraction). Copper and nickel are readily dissolved in an acidic aqueous media. In contrast, cobalt is difficult to dissolve, especially if it is present in the third oxidation state; however, this species becomes soluble after it is reduced to Co2+ (Mwema, Mpoyo, & Kafumbila, 2002; Kime & Makgoale, 2016)."

Jan 1, 2017

By Joey R. Kish, Shooka Mahboubi, Hatem S. Zurob, Gianluigi A. Botton

The kinetics of the Cr2O3-based scale oxidation and volatilization were studied in the presence of water vapour (H2O). A commercial Cr2O3-based scale forming Type 310S stainless steel was examined at the ambient pressure (0.1 MPa) and 550ºC in relatively low and high H2O containing environments of air- 10% H2O and air- 70% H2O, respectively. The increase in the partial pressure of H2O (pH2O) from 10% to 70% resulted in transition of the oxidation and volatilization kinetics from the parabolic rate law for air-10% H2O to the paralinear rate law for air-70% H2O. The kinetics transition was attributed to the increase in the Cr loss rate from the base scale after coupons exposure in air- 70% H2O. The significant role of the Mn alloying element in the base scale protectiveness was also discussed in the context of the Cr2O3-based scale stability.

Jan 1, 2017

By I. Caraconcea, M. Cousineau, S. Gariepy

"Several base metal plants operate in low grade/high tonnage conditions which impose strict cost control on all fronts for their operations to remain profitable. This leads to decisions regarding plant design, procurement, operations and maintenance that often favor cost minimization over value optimization. This may hinder the representativeness of the metal accounting systems while this should be a priority in a low margin environment. Such poor representativeness not only creates confusion in plant scheduling but can also hide suboptimal metallurgical performance. Furthermore, this situation can run undetected for a while since one dominant feature of a poor metal accounting system is its poor self-awareness. During their practice, authors have particularly identified measurement bias and reproducibility, as well as their impact on metal recoveries as areas of concern. These issues have not been extensively reviewed in the specific context of precious metals in base metal plants. Pragmatic solutions are proposed either at the design stage for a new project or to retrofit an actual operation. These solutions should be based on a business analysis that set a value of information matching the contribution of precious metals as well as the potential to use such information to act toward increasing plant profitability. Conclusions are that trade-offs are an inherent part of the design/audit/retrofit of any metal accounting system in any plant processing either base or precious metals. However, compromises must be evaluated on economic/technical ground.INTRODUCTION Every mineral processing plant must produce metal accounting reports (Morrison, 2008) where estimated saleable metal flows and inventories are published. These metal accounting reports are delivered to a variety of stakeholders who use them for internal management purposes (day-to-day plant production planning, plant operation optimization, capital spending, etc.) as well as for external management (royalty settlements, tolling agreements, etc.). Hence, there should be no doubt that state of the art metal accounting is instrumental for mining companies to reach and sustain high-quality corporate governance (Gaylard, Randolph, & Wortley, 2014). However, producing a metal accounting report involves much more than just printing it (Lachance, Leroux, & Gariépy, 2015a). The underlying metal accounting system (Figure 1) is responsible not only for the reliable production of the metal accounting reports but also for the quality of the outcome. As such, the crucial tasks of its design/audit/retrofit should neither be seen as ancillary nor be left as an afterthought."

Jan 1, 2017

By Jian Li, Robbie McDonald, David Robinson

"The pressure oxidation of sulfide minerals at temperatures above 200°C enables the extraction of base metals, improves the extractability of gold from refractory ores, enables solubilisation of PGEs and can be used to hydrothermally upgrade base metal-containing feeds. Fundamental studies reveal that the solution chemistry (and mineralogy of the solids) during pressure oxidation can be manipulated with outcomes that include (1) increased leaching rates, (2) lower oxygen requirements and (3) the formation of chemically more stable residues. This paper presents examples describing how these outcomes might be achieved based upon fundamental investigations.INTRODUCTION The application of pressure oxidation to the processing of gold ores and concentrates dates back several decades and continues to be the process of choice at operations such as Pueblo Viejo (pyritic gold) which host the largest autoclave of its kind in the world (Barrick Gold Corporation, 2016). Commercial application to the processing of base metals and PGMs resides with long established processes such as the Sherritt process, ore specific applications such as by Noril’sk, at Sepon etc. or has not proceeded to date beyond pilot scale testing (e.g. Phelps Dodge, CESL, Activox, Platsol). Recently there has been significant interest in hydrothermal upgrading options for concentrates including the NONOX and Toowong processes (Rohner et al., 2016; Weidenbach et al., 2016). The latter options suggest directions where sound knowledge of the underlying fundamentals enables novel outcomes and efficiencies to be obtained. It comes as no surprise that investigations similar to those underpinning these developing processes can be traced back several decades. It is not the subject of this paper to provide a historical perspective of the relevant autoclave chemistries but rather, to present some potential opportunities suggested by studies in our laboratories. Topics to be discussed in this paper include (1) control of metal extraction rates, (2) control of iron-residue composition and (3) control of sulfur oxidation and hence acid generation and oxygen requirements. The work described will focus upon the pressure oxidation of a nickel concentrate."

Jan 1, 2017

By M. Kumral, E. Dilhuydy, B. Ozdemir

"In-pit crushing and conveyor (IPCC) systems have become increasingly popular in the mining industry as an alternative to truck-and-shovel systems. Deciding whether to haul waste rock by truck or IPCC represents an important gap to be investigated in semi-mobile IPCC systems. A cost analysis is presented to evaluate the feasibility of crushing and conveying waste material in IPCC systems, along with sensitivity and risk assessments through Monte Carlo simulation. Although the capital expenditure is higher, results showed waste crushing will be feasible in deep pits and over long mine life and haul distances.RÉSUMÉ La popularité des systèmes de concassage et de transport dans la fosse minière (IPCC, de l’anglais In-pit crushing and conveyor) n’a cessé de croître dans l’industrie minière ; ils constituent en effet une option intéressante de remplacement des systèmes par camions et pelles mécaniques. Le choix entre le transport des stériles par camions ou par IPCC est encore difficile à faire et devra faire l’objet d’une étude approfondie au niveau des systèmes d’IPCC semi-mobiles. Une analyse des coûts est présentée pour évaluer la faisabilité du concassage et du transport des stériles par les systèmes d’IPCC, de même que des évaluations de la sensibilité et des risques par le biais de la simulation de Monte Carlo. Si les dépenses en immobilisations s’avèrent être plus élevées, les résultats ont cependant montré que le concassage des stériles sera envisageable dans des fosses profondes ainsi que sur une longue durée de vie et de longues distances de transport. INTRODUCTIONThe mining industry is currently facing many challenges such as low commodity prices, increasing environmental concerns and regulations, lower grades, deeper mines, and greater waste-rock quantities. As a result, the profitability of mining operations has decreased, with many mines stopping or suspending operations, and many new projects being postponed. Mining companies have therefore focused on improvements and innovations to increase the cost effectiveness of operations, for example, increasing production capacity to take advantage of the economies of scale (Crowson, 2003) and decreasing the unit operation cost. Changes in production capacity force mining companies to evaluate alternative material handling systems.During the past few decades and within material handling systems, significant improvements have been made to truck performance and capacity. Consequently, operating expenditures (OPEX) associated with fuel and maintenance have risen swiftly. In a mining operation, truck hauling systems now represent 40–50% of the capital cost and approximately 45% of the OPEX (Tutton & Streck, 2009). Additionally, material transportation costs are expected to increase due to longer haul distances arising from deeper and larger mines (Fleet et al., 2015). Finally, large fluctuations in fuel prices result in high risks associated with truck OPEX. According to the United States Energy Information Administration (2015), the cost of crude oil—the largest component of the retail price of diesel fuel—increased from US$24.31/barrel in 1986 to US$46.92/barrel in 2016, peaking at US$151.72/barrel in 2008 (Macrotrends, 2016)."

Jan 1, 2017

By N. Ahern, L. Manoukian

"Cyanide is a leaching agent for precious metals commonly used in gold ore processing. Cyanide exists in various forms (including free, complexed as weak or strong complexes, and as ions such as cyanate and thiocyanate), so its detection, speciation and analysis in processing or environmental samples can be complex. This paper will review best practices for cyanide sampling and preservation in the field, interferences and pretreatment methods required prior to sample analysis and analytical methods that are used for cyanide species. Titrimetric, flow injection ligand exchange, spectrophotometric, colorimetric, potentiometric, amperometric, and chromatography techniques will be discussed and their chemistries, detection limits, advantages and limitations will be described.INTRODUCTION Cyanide is well known to be an extremely toxic species. Accurate cyanide measurement in effluent from mines is critical from an environmental perspective. Its measurement is also an important control parameter in the recovery of gold using cyanidation. Cyanide chemistry is diverse and complex, and cyanide analysis can be challenging as a result of and because of limitations in understanding of analytical methods. Various chemical mechanisms can form or destroy cyanide, and the sample matrix or preservation chemicals can also affect analytical results. These interferences make the collection of reliable cyanide measurements challenging and can start as soon as the sample is collected, during laboratory pre-treatment and during analysis. This paper reviews different methods of cyanide measurement. The basic chemistry of cyanide, best practices for sampling and preservation, as well as various methods of analysis will be discussed.CHEMISTRY The complexity of cyanide chemistry is well known (Beck, 1987; Delgado, Botz, Bucknam, Milasovljevic, & Staley, 2008; Botz, Milosavljevic, & Ward, 2013) and is attributed to the ability of cyanide to undergo: •,Volatilization •,Precipitation •,Adsorption •,Complexation with metals •,Oxidation to cyanate, ammonia, or cyanogen chloride •,Reaction with sulfur or sulfide minerals to form thiocyanate •,Redox reactions leading to the formation of cyanogen and cyanate •,Redox reactions (of some cyano complexes) •,Photochemical reactions (of some cyano complexes)"

Jan 1, 2017

By Joo Hyun Park, Hyun-Sik Park

"Gold is one of the most valuable and precious metals. But, the extraction efficiency of gold from natural resources is very low and labor-intensive due to very low concentration of gold, i.e.,1–5 ppm, which means that gold extraction processes produce extensive amounts of tailings. The gold content in printed circuit boards (PCB) from waste mobile phones is about 100 to 400 ppm, which is enormously greater than the concentration found in natural ores. Consequently, processes for recycling waste PCB and gold mine tailings become of increasing importance to maintain a sustainable society. As processing these waste materials by pyrometallurgical methods has become more economically attractive, understanding the thermodynamic behavior of gold in smelting slags under oxidizing and reducing conditions has become increasingly important. Therefore, in this study, the effects of slag chemistry, oxygen potential and temperature on gold solubility in smelting slags are discussed. From the results presented, the predominant species of gold is strongly dependent on the basicity of slag. Furthermore, more basic slags showed higher solubility of gold at a given oxygen partial pressure, and more oxidizing atmospheres enhanced the dissolution of gold to the molten slag phase. As a consequence, careful control of the slag composition during pyro-processing of gold-containing waste materials is required to maximize gold recovery. INTRODUCTIONGold has good physicochemical properties. Thus, it plays an increasingly important role in industrial applications. For example, over 300 tons of gold are used annually in electronic components (Hageluken &Corti, 2010).However, 75% of all gold ever produced has been extracted since 1910 and gold reserves in the world are becoming rapidly depleted (Louis & Pluchery, 2012).The cost of gold production and its price in the market have increased rapidly during last 20 years as shown in Figure 1, and interest in the recycling of gold-containing materials has naturally increased.The wastes from electronic equipment (e-wastes) contain large amounts of precious metals compared to their own respective ores, and therefore such wastes may be considered as a secondary source of valuable metals. For instance, the concentration of gold in natural ore is commonly 0.5–15 g/ton-ore (0.5–15 ppm), while its concentration in electronic circuit boards is over 10 times higher, typically being about 150 ppm in expansion cards and over 10,000 ppm in central processing units(Barbieri et al., 2010).Also, gold mine tailings are discharged after the flotation process as slurry form then stored near the operating plants (approx. 100 ton per day in one Korean gold mine). Gold mine tailings contain gold at about 1–2 g/ton. This is the reason why Au-containing materials such as e-wastes and mining wastes are highly important sources of gold (Yamasue et al., 2009)."

Jan 1, 2017

By Pingchao Ke, Zhihong Liu

Fe(III)-As(V) precipitates were synthesized from the Fe(II)-As(V)-SO42--H2O system at 90°C in initial Fe(II)/As(V) molar ratios of 4.0 and 5.0, respectively. The synthesis were carried out by introducing oxygen gas into the system to oxidize Fe(II) ions into Fe (III) ions, and at the same time, adding aqueous sodium carbonate solution into the system to neutralize the acid released by the hydrolysis reactions, with the purpose of keeping the pH constant at 1.5±0.05. The precipitates obtained were characterized by XRD, chemical composition analysis, SEM, XPS, and Raman spectrum. The results indicated that the particles in the precipitates were in the morphology of irregular aggregation with their sizes in the range of about 1–4 µm. The precipitates consisted of scorodite, ferric arsenate and amorphous hydrated ferric oxide, of which amorphous hydrated ferric oxide formulated as Fe(OH)x(SO42-)y. The characteristic XPS peaks of Fe-AsO43- and Fe-O in the precipitates located at 711.8 and 713.3 eV, separately, and the existence of amorphous hydrated ferric oxide led to two series of shake off lines developed over the end of high binding energy of Fe2p XPS. The precipitates were stable in TCLP tests at pH 4.93 for 60 hours with the arsenic concentrations in the leaching solutions being 0.27 mg/L and 0.59 mg/L for the precipitates prepared in the initial Fe(II)/As(V) molar ratios of 4.0 and 5.0, respectively. The tests for the long-term stability of the precipitates were carried out by leaching them for 40 days at 25°C under various media in the pH range from 9.50 to 10.57, and the results showed that the precipitates synthesized in this study were much more stable than those by previous researchers.

Jan 1, 2017