Search Documents

By M. Somppi, Z. Yamak

"Gold producers invest significant effort in mining, processing, and creating an intermediate gold doré product. Nonetheless, equal effort should be extended to the final handling and processing of the doré bar, and managing the high-purity gold produced at the fine-gold toll refiner. This detailed attention to bullion handling and refining provides rigor and confidence that the mine site is achieving, through fair and controlled methodology, the most appropriate value for the final product. With the above in mind, the following study explores the importance of preparing a set of site best-practices for bullion handling and specifically, detailing the peculiarities of sampling methodologies and the impact on assays.INTRODUCTION Gold and silver handling practices are common place at mine sites and refineries. The practices include but are not limited to smelting, ingot casting, weighing practices, and secure transportation. Proper handling and processing of the bullion material ensures that the mine site is achieving the true value of the final product. Various handling aspects can critically impact the perceived value of the bullion. A few of these particulars include weight tracking, scale recertification and calibration, refining and melting practices, melt temperature measurement, sampling, pouring, bar cleaning, furnace technology and crucible selection, and assaying. Nevertheless, this report discusses and focuses on the importance of proper sampling and molten-metal temperature measurement and their potential impact on the final doré bar value. Refining or re-melting operations achieve a proper measure of the precious metal content of its bullion when the sample accurately represents the whole bar. At first this task appears seemly straightforward, however, taking a representative sample can be challenging and is also one of the most important tasks for valuing gold during the settlement stage at the precious metal refinery. Various bullion sampling methodologies exist; including: dip sampling, granulation, drilling, cutting, and vacuum pin sampling. The Royal Canadian Mint (2009) indicated in their technical review of refinery operations that pin sampling is one of the best methods for cases where representative sampling and accuracy are required, e.g. to determine the payable metal content. Pin sampling consists of inserting a sealed glass vacuum tube (Figure 1) into the molten metal; when the molten metal contacts a purposely-designed weak portion of the glass, the seal breaks and the metal is suctioned into the hollow centre (Figure 2)."

Jan 1, 2018

By S. Espley, T. Nyabeze, D. Beneteau

"Many mentorship programs are available to Canadian mining industry employees. Some are company-led initiatives, whereas others are provided through educational institutions or nonprofit organizations. In 2016, a national survey was launched to gain insight into perceptions of what mentorship is, learn about available programs, and collate experiences with formal and informal mentorship opportunities. This paper outlines survey findings and delivers recommendations to industry for consideration in employee mentorship programs. In addition, mining industry leaders share their mentor/mentee perspectives. The intent of this paper is to bring awareness of best practices that can help employees grow and develop in their profession.RÉSUMÉ Les employés de l’industrie minière canadienne ont accès à de nombreux programmes d’encadrement. Certains sont des initiatives menées par les sociétés, d’autres sont proposées par le biais d’établissements d’enseignement ou d’organismes à but non lucratif. En 2016, une enquête à l’échelle nationale a été lancée en vue d’obtenir des informations quant à la perception de ce qu’est réellement l’encadrement, de découvrir les programmes proposés et de comparer les expériences aux possibilités d’encadrement, officielles ou non. Cet article présente les résultats de cette enquête et fournit des recommandations à l’intention de l’industrie afin qu’elle les prenne en compte dans ses programmes d’encadrement des employés. En outre, des chefs de file de l’industrie minière partagent leurs points de vue conseillers/protégés. L’intention de cet article est de sensibiliser les employés aux meilleures pratiques, ce qui les aidera à évoluer et à se développer dans leur profession. INTRODUCTIONThis paper about mentorship in the mining industry is based on voluntary responses to a cold survey, written and circulated by the authors. In 2016, a link to an online mentorship survey was circulated to males and females in the mining industry with the belief that mentorship programs should be available to everyone. The link was delivered via the authors’ personal networks in mining, the CIM Reporter, Women in Mining (WIM) email blasts, LinkedIn, and Facebook. This paper summarizes the answers to the survey questions. The paper is a follow up to one by the same authors (Nyabeze, Espley, & Beneteau, 2010), which was written to gain insight into why women join and stay in the mining industry, and to learn why the overall representation of women is low."

Jan 1, 2018

By R. Holmestad, M. Gazizov, S. Wenner, R. Kaibyshev, J. K. Sunde

"Mechanical properties and microstructure of an Al-4.7Cu-0.74Mg-0.51Si-0.48Mn-0.10Cr-0.09Ti-0.02Fe (wt. %) alloy subjected to various thermomechanical processing (TMP) have been investigated and compared to conventional ageing at 170°C (designated T6). Three TMP routes involving cold deformation of solution treated samples were tested. These were (i) 3%-stretching (T8-3%), (ii) equal-channel angular pressing (ECAP) to true strain (e) of ~1 (T8-1) and (iii) ECAP to e~2 (T8-2), all with subsequent ageing at 170°C for 0-96 h. At peak age conditions, both yield stress, ultimate tensile strength and elongation-to-fracture decreased for the T8-3% state as compared to the T6 condition. Intermediate ECAP (T8-1 and T8-2) lead to significant increase in maximum yield stress, ultimate tensile strength and elongation-to-fracture. The changes in mechanical properties were related to microstructure evolution, encompassing changes in grain sizes, dislocation densities, precipitate morphology and phase fractions, which were characterised using transmission electron microscopy. Relations between TMP, precipitation behavior and contributions to different strengthening mechanisms are evaluated.INTRODUCTION Al-Cu-Mg-Si alloys are widely used as structural materials in aerospace industry due to their attractive combination of high specific strength, good fracture toughness and enhanced creep resistance. These properties are largely due to the formation of a large number of nano-sized metastable precipitates during artificial ageing (Polmear, 2006; Eskin, 2003; Gazizov, Dubina, Zhemchuzhnikova, & Kaibyshev, 2015). The precipitation behaviour in these alloys is complicated and depends among other things on Cu concentration and the Mg:Si ratio (Wolverton, 2001; Chakrabarti, & Laughlin, 2004). In general, the precipitation sequence has been presented in a prior study (Eskin, 2003) as follows:"

Jan 1, 2018

By E. Barnard, J. Tero, J. Rajala, N. Avenido, M. Fullam, A. Nashitati, S. Mbalamba

"The Otjikoto mining and milling complex is 90% owned by B2Gold Corporation, and began commercial operation on February 28, 2015. The milling circuit operates at a throughput 3.3 million tonnes per annum, with an average reserve gold grade of 1.28 g/t. The ore is high in Gravity Recoverable Gold (GRG), which varies between 73-91%, depending on ore type. Overall gold recovery since start-up is 98.2%, with about 63.5 % coming from the gravity circuit as doré. 2016 cash operating costs, and all in sustaining cost (“AISC”) were $361 and $604 per ounce, respectively.During design, three ore types were tested for GRG content, and based on the high GRG value of all three ore types, the decision was made to treat the full ball mill circulating load by gravity. Once operating, the gravity circuit performance was characterized by performing a detailed gravity audit, which included the ore, cyclone classification, Knelson concentrators, and the Consep Acacia intensive leach system. The deeper ores contain significant pyrrhotite, and this created some unusual challenges that had to be overcome. This paper presents the gravity circuit design process, the circuit commissioning, and the audit results and ongoing improvements.IntroductionHeadquartered in Vancouver, Canada, B2Gold Corp. was founded in 2007. Currently, B2Gold has five operating mines, and numerous exploration projects in various countries, including Nicaragua, the Philippines, Namibia, Mali and Burkina Faso. The Otjikoto Mine is located in the north-central part of the Republic of Namibia. It is situated approximately 300 kilometers north of Windhoek, the country’s capital, within the Province of Otjozondjupa. The Otjikoto mining and milling complex is 90% owned by B2Gold Corporation, and began commercial operation on February 28, 2015. The milling circuit operates at a throughput 3.3 million tonnes per annum. During design, a large emphasis was placed on gravity recovery, as the Otjikoto ores are unusually high in Gravity Recoverable Gold (GRG)."

Jan 1, 2018

"HPGRs operate in a wide array of applications in mining and minerals. These range from relatively coarse crushing of copper and gold ores at one end of the spectrum to the processing of fine iron ore pellet feed and fine industrial mineral products at the other. Traditionally these circuits involve the treatment of relatively moist materials in pre-grinding circuits; using single stage HPGRs in open circuit or as a closed circuit operation with screening or partial product recycle. More recently, HPGR is increasingly deployed in dry grinding in combination with air classification. The high throughput demonstrated by larger HPGRs has stretched the application towards coarser size reduction duties for a number of new projects. At the same time, the basic principle of inter-particle crushing for generating a product with a high fines proportion gives ground to investigate applying the technology further towards finished product duties. The advantages that HPGR brings are clear. Multi Stage grinding enables energy efficient size reduction across more of the comminution circuit. Primary HPGR serves for a coarse grinding duty, whereas a secondary HPGR is geared towards generating a fine product for downstream processing or even a finished product. This publication summarizes some of the features of staged HPGR circuits and discusses some examples of operating and projected applications.INTRODUCTION In most HPGR applications, the grinding units are used as a single process stage, either in open circuit, such as for pebble crushing [Rose 2002, Westermeyer 2000, Van der Meer 2015] or in closed circuit with classification [Van der Meer 2009, 2012] or product recycling [Van der Meer 2010]. Where a higher plant capacity is required, the HPGRs are commonly installed in multiple lines in a parallel arrangement [Parker 2005, Koski 201, Vanderbeek 2006]. HPGRs can take a wide range of feed size distributions, and grind this down to a product with a high fines content. In general view, there is a limit on the size reduction range that even an HPGR can provide. Grinding down from a very coarse ore (e.g. 70-100 mm) to a very fine product (e.g. 100 microns range) is stretching the ability of a single stage HPGR circuit. Fine grinding generally requires a classification stage that returns the classifier oversize to the head of the HPGR circuit. From one point of view, it can be demonstrated that when recycling a large proportion of fines and middlings back to the HPGR feed results in an effective feed with an overrepresentation of middlings and fines, which will eventually reduce the grinding efficiency and consequently result in an increased recirculation mass flow [Van der Meer 2014]. From another point of view the large recycling mass puts a strain or even a limit on the capacity of present-day conveyor capacity."

Jan 1, 2018

By Jean-Christophe Ehrström, Fanny Mas

"A specific test set-up has been developed to study at the lab-scale the high-temperature behavior of aluminium alloys in conditions close to those experienced by thick plates during hot-rolling. A particular attention is paid to reproducing both the stress triaxiality and strain fields that exist in plate during rolling. In addition to standard ductility measurements by means of secondary tensile tests (STT), multi-step plane strain compression (PSC) tests have been performed to mimic hot-rolling pass schedules. Tool and sample geometries were adapted to allow low h/a ratios (h= average specimen thickness, a= tool width) and thus guarantee depressive stress conditions at the center of the specimen during most of the test. Such conditions resulting in porosity opening can then be used to investigate the impact of rolling conditions on damage evolution. The mechanical testing was combined with post-mortem high-resolution ultrasonic scans allowing to detect small amounts of damage and quantify its evolution as a function of processing parameters such as strain and temperature. The test set-up was validated on two 2050-type AlCuLi alloys with different susceptibilities to high temperature embrittlement.INTRODUCTION Aluminium thick plates are widely used in the aerospace industry, mainly as semi-products to be machined for internal structure parts of wings (spars, ribs) and fuselage (frame). The conversion route of such products always involves a hot-rolling step, the conditions of which (temperature, speed, pass schedule) have to be optimized to maximize both mechanical properties and final plate quality. This goal cannot always be efficiently achieved by full-scale industrial trials as (a) cost limits the number of possible test conditions and (b) it is often difficult to change one parameter alone. That is why there is a need for laboratory-scale tests able to mimic the rolling process in terms of temperature, strain rate, stress triaxiality and deformation. Most laboratory hot-rolling mills do not adequately simulate industrial processing routes, especially in terms of heat loss, deformation speed and rolling geometry (maximum roll gap vs. work roll diameter). Concerning thick plate, it is of interest to achieve both similar deformation and L/h ratio (L=arc of contact, h=mean gauge) per pass as the industrial schedule because they are simultaneously involved in damage evolution and void closure during hot forming processes (Saby, 2014)."

Jan 1, 2018

By Eiichi Sato, Koichi Kitazono, Hiroshi Masuda, Kenta Higane

"The present study investigated the low-temperature creep mechanisms in ultrafine-grained (UFG) aluminum manufactured by accumulative roll bonding. UFG aluminum with grain size 0.39 µm showed steady state creep even at room temperature under low stresses as confirmed by the creep curves in the strain rate–strain plot. The low-temperature behavior was divided into four regions by three distinctive stresses, sI, sII and sIII: sI (=45 MPa) is denoted as the micro-yielding stress with which dislocations start movement, sII (=85 MPa) the dislocation-multiplication stress above which dislocations multiply with creep deformation, and sIII (=171 MPa) the conventional yield stress above which macroscopic plastic strain is generated. During low-temperature creep, below sI, negligible plastic strain is generated. Between sI and sII, creep deformation with stress exponent 2.5 occurred, which is accommodated by dislocation absorption into grain boundary and grain boundary sliding, similarly to the low-temperature creep of HCP metals. Between sII and sIII, creep deformation with stress exponent 7.0 occurred, whose mechanism is similar to the low-temperature creep of coarse-grained aluminum. Above sIII, power-law breakdown occurred.INTRODUCTIONIt is well understood that the creep deformation brings about at high homologous temperatures (T/Tm) of >0.4, where Tmis the melting point, with diffusion processes. Recently, the importance of aluminum is increasing for cryogenic temperature parts such as a metallic liner or a cap in high pressure-hydrogen vessels, and the presence of creep behavior in aluminum at room temperature has become recognized (Matsunaga, 2013;Kassner, 2015).In HCP metals and alloys, especially intitanium, steady-state creep behavior appears at room temperature with apparent activation energy of1/10 of that for self-diffusion(Neeraj, 2000; Matsunaga, 2009).On the other hand, Kassner (2015) claims that aluminum shows creep behavior at room temperature with apparent activation energy of 4/5of that forself-diffusion, but never reaches the steady state. We should note that it is derived from the data obtained from short-term creep tests of few hour, and Matsunaga (2013) already claimed the presence of steady state in room temperature creep in aluminum with activation energy of 1/5of that for self-diffusion.The mechanisms for low temperature creep are considered different between HCP and FCC metals: in HCP metals, grain boundary sliding is observed and is thought to accommodate piled-up dislocations at grain boundaries through absorbing them. The so-called slip-induced grain boundary sliding occurs with low number of activated slip systems(Matsunaga,2009).On the other hand, in FCC metals, many activated slip systems bring about work hardening with dislocation cell structure formation. In the initial stage of creep, it results in primary creep (Kassner, 2015), but Matsunaga (2013) claimed that once the annihilating of a cross-slipped dislocation to another reaches balance, steady state is established. It has been, however, strongly required to show more convincing experimental verification for the presence of steady state in FCC metals at low temperature."

Jan 1, 2018

By S. McPhail, D. Richardson, G. J. Simandl, C. Akam, S. Paradis, M. Yakimoski, A. Teucher, Y. Cui, F. Ferri

Historically, extracting dissolved solids from formation water was economically motivated. Today, main drivers are environmental benefits and regulations, as large volumes of water needed for hydraulic fracturing require treatment before reuse or disposal. The concentration of dissolved solids in flowback water increases with each use and may require treatment prior to disposal. Element recovery from produced water is not profitable unless market conditions are favourable, recoverable elements are abundant, and economical recovery methods are established. Sale of recovered materials could offset recycling and disposal costs. This paper describes markets for Cl, Na, Ca, K, Sr, Mg, Br, Ba, I, B, and Li, and their concentrations in produced water from oil and gas wells in British Columbia. It recommends revising sampling protocol for produced water.

Jan 1, 2018

By C. Pichler, C. Benigni, J. Antrekowitsch

"The recycling of steel mill dust results in zinc oxides which are sold to the primary industry in or-der to recover zinc in its metallic form. Due to the contained impurities - chlorine and fluorine - these sec-ondary oxides are usually charged into the roaster together with primary concentrates. Appearing problems in this furnace limit the application of secondary materials. Based on the zinc amount, a direct leaching, assumed that a low halide concentration is present, would be possible. To use the zinc solution directly in the electrowinning stage, the concentration of impurities, first of all iron, is limited. Iron can be found in secondary zinc oxides due to carry over during the recycling process. In order to reduce the iron content in the solution, the leaching has to be pH-controlled. This leads to a limited number of simple purification steps before the solution enters the electrolysis. Various trials were performed to evaluate the influence of temperature, time and sulphuric acid concentration on the iron dissolution. This paper deals with the results and also focuses on other impurities such as halides. Additionally, the soda washing process, usually done with secondary zinc oxides to remove most of the halides, and the challenges within this step are discussed.INTRODUCTION Recycling of steel mill dust, which is the main zinc containing residue, in the Waelz process dis-plays the common method worldwide. The product of the process is a secondary zinc oxide which is con-taminated with different elements like lead, iron and halides due to mechanical carry over or evaporation. Depending on the feeding material the concentration of each element in the dust is varying. The zinc con-tent of the product, also called Waelz oxide, lies around 65–68%. Based on these values it presents an al-ternative to the primary concentrate for the production of metallic zinc. The contained halides limit the direct utilization in the leaching stage and therefore have to be reduced. State of the art is a soda washing process but also solvent extraction gives a possibility to remove chlorine and fluorine but the desired con-centration for the electrolysis is hardly reachable (Antrekowitsch et al., 2016) Iron is present as an undesirable component of such secondary zinc oxides due to carry over. During the hot acidic leaching of the secondary concentrate, iron is dissolved too. Based on the higher electrical potential iron has to be removed before the zinc solution enters the electrowinning stage. It is usually removed by precipitation as goethite, hematite or jarosite, which is the common precipitation residue (Ismael et al., 2003)."

Jan 1, 2017

By A. Scheltema Beduin, H. Oterdoom, A. Haaks, C. Kempe, A. Liedtke

"For the Kazchrome DC Ferrochrome plant, SMS-group specifically designed an electrode column that would minimize downtime. Special features include the possibility for on load electrode jointing, on load slipping, and back-slipping. Electrode consumption is strongly related to furnace load and impedance, and is very low at high loads, which makes the graphite electrode an alternative to consider even in AC applications. The electrode could also be applied in other DC applications, as for example TiO2 slag, the novel Conroast process, or (twin) DC FeNi furnaces, and could possibly be installed during bigger shut downs. This paper will describe some of the design considerations and operational performance data on this novel column in the FeCr industry that could also be of interest for the FeNi or PGM industry if these would continue to develop towards DC technology.INTRODUCTION Every DC furnace has a cathode and an anode. The anode applied is commonly known as the Concast design, though the original design was by ABB who handed it over to Concast, subsidiary of the SMS-group. Some well-known DC furnaces outside the steel industry where the Concast bottom has been installed are listed in Table 1 as well as a few other key design features.Sidewall cooling and some other data have been left out for reasons of space, and being a lesser relevant design feature to this paper. HES stands for Hollow Electrode System, in which feed is charged through an electrode. Table 1 is built up chronologically according to first start-up date. Below comments are given to briefly explain some of the columns in Table 1: •,“Arm” in the “Cathode” column means that the design of the cathode holding and regulating mechanism consists of an electrode arm as depicted in Figure 1. •,Charging is relevant as some operations started with HES charging, whereas recently most new operations have started without HES but only charging chutes, of which at least some are close to the electrode and possibly others installed closer to the sidewall. •,“Dome” in the “Roof” column means that the design of the roof involves a center piece that can be exchanged if worn. •,The optimal roof design still seems to be a topic of debate, where no design is without problems."

Jan 1, 2017

By Xiaowen (Wendy) Ma, Hans Liang, Xiaoying Chen, David Way

"The mineralogical characteristics of the process streams provide key indicators to the potential improvement in the metallurgical performance. Therefore, the process mineralogy and diagnostic metallurgy have been widely used as a tool to assist the metallurgists at the operating plants. The challenge of this study was then how to characterize the diagnostic flowsheet of the minerals of interest in the process streams across the flotation circuit. The investigation from this study indicates that the minerals chematic flowsheet can visibly demonstrate the sources that caused the gold losses during the mineral processing.In this paper, we present studies of the flotation process stream samples, representing the feeds, intermediate products, final concentrate and final tails, which were produced from the flotation concentrators of Mt Carlton mine in Queensland, Australia. This study was focused on characterizing the process streams and learns how the gold in the process streams was associated with other sulphide minerals and host minerals on a size by size basis. The automatic QEMSCAN/MLA Particle Mineral Analysis (PMA) and Trace Mineral Search (TMS) were applied to identify the minerals and to detect the gold in the sized fractions of process streams. The Laser Ablation ICP-MS (LA) spot analysis, QEMSCAN EDS spot analysis and electron microprobe spot analysis were employed to identify and quantify there fractory gold concentrations in the sulphide minerals, like pyrite, and the elemental concentrations of visible gold grains. The diagnostic flowsheet of gold recoveries by the process streams, by mineral association classes and by the particle sizes were generated and discussed."

Jan 1, 2017

By Z. Ren, M. Tomlinson, E. Asselin

"Organic carbon blinding is a common, yet often partial, solution to the reduction of preg-robbing. A quantitative method to assess the extent of adsorption of a given blinding agent is presented herein. The adsorption of several blinding reagents on various carbon samples is quantified using electrochemical impedance spectroscopy (EIS). EIS results showed that kerosene is more strongly adsorbed on carbon than sodium lauryl sulphate (SLS), while SLS can hinder the charge transfer process of the oxygen reduction reaction on the carbon surface more effectively. The effectiveness of SLS is pronounced when its concentration is higher than 100 ppm. Raman spectra are presented for selected carbon samples: as the area ratio of the disordered peak to the graphitic peak increases, blinding agent adsorption increases.INTRODUCTION The presence of naturally occurring constituents in gold ores may adversely affect the extraction of gold in cyanide leaching since the gold cyanide complex, Au(CN)2–, can be adsorbed by these constituents (M. Adams & Fleming, 1989; Afenya, 1991; Miller, Wan, & Díaz, 2005). Such ores are known as “preg-robbing”. Preg-robbing behavior may arise from natural carbonaceous materials in the ore (M. Adams & Burger, 1998). In the past decades, a number of pre-treating methods have been developed for refractory carbonaceous ores (Arriagada & Osseo-Asare, 1984; Beer, 1994; Dunne et al., 2007; Jiang, Liu, Xiao, & Yang, 2012; Kohr, 1997; Kulpa & Brierley, 1993; Menne, 1992; Menne & Revy, 1994; Moyes & Houllis, 2010; Petrie, Craw, & Ryan, 2005; Simmons, 1996). The method known as blinding is one of the most effective and economical pre-treatment methods (M. D. Adams & Burger, 1998; Albert, 1923; Darrow, 1924; McQuiston & Shoemaker, 1975; Van den Berg, 2000). Blinding, also referred to as blanking or passivation, uses a chemical reagent to passivate the preg-robbing carbon by selective absorption or wetting (Bas, Altinkaya, Yazici, & Deveci, 2012; Brierley & Kulpa Jr, 1993; Dunne et al., 2012; Van den Berg, 2000; Yang, Qian, Song, & Dong, 2013; Yen, Amankwah, & Choi, 2008; Zhou, Jiang, & Choi, 2014). Organic reagents, which selectively adsorb on the surfaces of activated carbon and “smother” the surface, have been used for blinding carbonaceous matter in gold ores prior to cyanidation. Two comprehensive studies by Abotsi and Osseo-Asare and Adams and Burger have been published on this topic (Abotsi & Osseo-Asare, 1986; M. D. Adams & Burger, 1998)."

Jan 1, 2017

By C. Piribauer, E. Feichtenhofer, A. McEneaney

"As part of a major diversification project, RHI AG, through its plant in Drogheda Ireland, has developed a Caustic Calcined Magnesium Oxide (CCM) for use in the Cobalt (Co) & Nickel (Ni) hydrometallurgical extraction industry. In the course of the project, the company investigated the chemical and physical properties of a number of different Magnesia’s used in Co & Ni hydrometallurgy applications and has been able to determine the important parameters for a successful Magnesia for this application. A number of live plant trials have confirmed the results of this testwork and the company is now proceeding to produce this product in commercial quantities at Premier Periclase Ltd., the RHI AG plant in Drogheda, Ireland. This paper will outline the development work conducted by the company and highlight the important chemical and physical properties that make a successful CCM. Much of the research was conducted at the RHI Technology Centre in Leoben, Austria. In addition, a number of external laboratory studies were conducted on behalf of RHI AG. The result of this work has allowed the company to develop a Magnesia product with optimised properties for use in the Cobalt and Nickel hydrometallurgical extraction process.INTRODUCTION Premier Periclase is part of RHI AG, a globally operating supplier of refractory products, systems and services, headquartered in Vienna, Austria. The company produces Magnesia from seawater at its plant in Drogheda, Ireland. While the main focus is on production of refractory grade Dead Burned Magnesia for the steel industry, the plant also produces a number of different grades of Caustic Calcined Magnesia as well as Magnesium Hydroxide products. As part of a major project to diversify the company’s product base, the use of CCM in the Cobalt (Co) & Nickel (Ni) hydrometallurgical extraction industry was investigated. One of the company’s highly reactive grades of Caustic Calcined Magnesia was found to be particularly suitable for this application. In an effort to understand what makes a successful Magnesia for hydrometallurgy the chemical and physical properties of different Magnesia’s used in Co & Ni hydrometallurgy were investigated. This paper and conference presentation outlines the findings of this process."

Jan 1, 2017

By M. Nusheh, C. Bumby, A-H. Puichaud

"Vanadium-bearing titanomagnetite ironsand deposits occur along a 480 km stretch of the west coast of New Zealand. In the present study, the leaching behaviour of NZ ironsand was investigated in hydrochloric acid (2–10 M) solution at 50–80°C for 2 h. The resulting leaching liquors exhibited Fe/V ratios in the range 150–180. The distribution of trace element contaminants between solution and solid residue was investigated, and processing conditions have been determined for rapid and efficient dissolution of Fe, Ti and V into the leaching solution. In addition, mineralogical analysis of raw ironsand and leached residues was performed in order to study the leaching mechanism. Samples were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy (EDX), X-ray fluorescence spectroscopy, qualitative and quantitative X-ray diffraction and inductively coupled plasma mass spectrometry (ICP). Results indicate that the dominant dissolution process follows shrinking particle mechanism. However, ironsand particles containing ex-solution lamellae exhibited a different leaching behaviour compared to homogenous titanomagnetite particles.INTRODUCTION Titanomagnetite ironsand (blacksand) forms Quaternary onshore beach and dune deposits and offshore marine deposits (Figure 1) along 480 km of coastline from Kaipara Harbour south to Wanganui on the west coast of the North Island (Christie, 2016). It attracted the attention of scientists from the earliest times (Galbreath, 1998). The principal minerals in ironsand are titanomagnetite (TTM), ilmenite, quartz and ferromagnesian minerals such as augite, hornblende, diopside, and olivine with smaller amounts of rutile and apatite (Mauk, 2016).Several large ironsand deposits have been discovered and exploited since the late 1960’s. The Waikato North Head and Taharoa mines are currently operating and they have a 2015 measured resource of 400 million tonnes in total and provide over 2 million tonnes of concentrate per year by simple cost effective magnetic separation process (Christie, 2016; Christie & Brathwaite, 1997). The concentrate contains not only 7–8% TiO2 and 56–60% SFe, but also 0.3–0.6% V2O5, is both a valuable titanium mineral and a source of vanadium. All the production is used for steelmaking industries. The other potential for utilizing more of this resource without requirement of integration into an iron and steel producing plant is to develop a hydrometallurgical route with advantages of higher efficiency along with lower emissions. Currently, there is no existing commercial process capable of extracting all three of these elements as industrial-grade commodity products. Acid leaching of TTM concentrate with higher degrees of recovery and selectivity is a key step in any possible hydrometallurgical route."

Jan 1, 2017

By Lauri Pesonen

"Although electrical energy use at copper smelters is typically about 15-20% of operational costs, it is something which is not very often analyzed and discussed at a detail level in technical papers and presentations. This paper aims to list different equipment configurations per smelter area and estimate their electrical energy consumptions versus unit of material processed. In addition chosen smelting technology and oxygen enrichment rates affect the overall electricity consumption and therefore some overall guidance is provided for efficiency gains.INTRODUCTION In principle, processing plants, such as copper smelters, require electrical and chemical energy together with some degree of human input to process input materials into desirable output form like metallic copper. From the standpoint of metallurgical plant designers, the thermodynamics of smelting, when it comes to releasing and conserving thermal energy, is sufficiently understood and frequently discussed in the literature in detail, but judging from the quantity of publications, the way how we exactly utilize electrical energy is not. This article is meant to illustrate how electrical energy consumption is distributed among different process units and equipment types at copper smelters using various smelting technologies. In general, typically about 15-20% of operational costs are related to electricity and at locations with high electricity prices the potential savings can be quite significant for the overall profitability of the plant operations. In today’s tight profit margin environment any potential savings are more than welcome. The purpose here is not to promote any certain copper smelting technology, but to open a discussion on how and where we use electrical energy, and how the overall energy use could be lowered with the implementation of newest electric power saving designs and solutions. Using the principles outlined in this article, it should be fairly easy and straightforward to replicate the calculations and even improve them wherever it is seen necessary for the greater benefit for us all in this industry"

Jan 1, 2017

By L. Tafaghodi, A. Hosseinpour

"Silicon is considered as the most appropriate semiconductor material for manufacturing solar cells because of its natural abundance and being nontoxic. The transferable knowledge and technology from the electronics industry and the long history of silicon-based semiconductors are also assisting the domination of silicon as the most common semiconductor material. Developing an environmentally and economically viable process for producing solar grade silicon has been one of the main challenges in the silicon industry in the past few years. Metallurgical refining processes have received significant attention because of their high productivity and low cost. Slag refining is one of the purification methods which is based on oxidation of the impurity elements, followed by its dissolution into a slag phase. This article presents a review of various slag refining processes that have been employed for purification of silicon and silicon alloys. SiO2, CaO, CaF2, CaCl2, Al2O3, MgO and Na2O are the major components of the slags used for silicon refining. These slags can be classified into three main categories including binary, ternary and quaternary slags.INTRODUCTION Silicon can be categorized into three different grades based on its application or purity: metallurgical grade silicon (MG-Si) with purity of ~98 %, solar grade silicon (SoG-Si) with purity of ~99.99999 % and semiconductor grade silicon (SeG-Si) which has the purity of 99.9999999 % (Johnston & Barati, 2010; Krystad, Tang, & Tranell, 2012; Tang, Øvrelid, Tranell, & Tangstad, 2009). Producing SeG-Si is carried out through an energy-intensive and complicated process named Siemens. This purification process is relatively slow and involves using toxic and corrosive reagents (e.g. Trichlorosilane). At present the majority of SoG-Si is produced via Siemens or Siemens-like processes and there is very limited production via processes dedicated to SoG-Si. Because of the difference in silicon specifications required in microelectronics and photovoltaic industry, and the cost and energy associated with the Siemens process, an interest has emerged to develop technologies dedicated to producing low cost SoG-Si (Istratov et al., 2003; Johnston, Khajavi, Li, Sokhanvaran, & Barati, 2012; Mitrašinovic, D'Souza, & Utigard, 2012; Wu et al., 2012)."

Jan 1, 2017

By M. B. Kime, A. T. Kaniki

"Grinding tests were conducted on an oxidized copper-cobalt ore using a pear-shaped ball mill. Twelve mono-sized ore fractions were prepared and wet ground batchwise. The mill was run for 0.5 to 30 min intervals. The shortest interval provided data more closely related to the breakage function (B) because less secondary breakage was hypothesized. Some selection function (S) and B parameters were determined. Remaining parameters were estimated using a population balance model simulator. To evaluate the kinetics model, an unsized ore sample was also milled. Predicted and measured particle size distributions (PSDs) agreed well, suggesting that S and B parameters can be used for continuous operation mass balances.RÉSUMÉ Des essais de broyage ont été menés sur un minerai oxydé de cuivre-cobalt à l’aide d’un broyeur à boulets piriforme. Douze fractions de minerai de dimension unique ont été préparés et broyés en voie humide en lots. Le broyeur était mis en route à des intervalles de 0,5 à 30 minutes. L’intervalle le plus court fournissait des données plus étroitement liées à la fonction d’abattage (B) car d’après l’hypothèse avancée, le besoin d’abattage secondaire était moindre. Certains paramètres de la fonction de sélection (S) et de B ont été déterminés ; les paramètres restants ont été estimés à l’aide d’un simulateur de modèle d’équilibre de population. Pour évaluer le modèle de cinétique, un échantillon de minerai non calibré a également été broyé. Les compositions granulométriques (PSD, de l’anglais particle size distributions) prévues et mesurées correspondaient bien, ce qui laisse penser que l’on peut se servir des paramètres S et B dans le cadre d’équilibrages massiques en fonctionnement continu. INTRODUCTIONSize reduction of solids is a very energy intensive and highly inefficient process. It consumes approximately 5% of the electricity produced worldwide (Rhodes, 1998), and more than 50% of the total energy used in mineral processing plants (Walkiewicz, Lindroth, & Clark, 1996). An increase in grinding efficiency can therefore result in significant reductions in operating costs. This often amounts to determining the optimal design configurations for milling an ore sample in a laboratory mill under standard conditions. Prior to optimizing the milling stage, the requirements for downstream processing in terms of particle size distribution (PSD) need to be understood because low liberation and overgrinding will lead to future problems. Once this is done, it is also important to clearly understand the breakage properties of the ore. The kinetics of size reduction in tumbling mills are often determined using two probabilistic functions: selection and breakage (Austin & Luckie, 1972). Knowledge of the selection and breakage functions also enables the prediction of the PSD for a given ore sample."

Jan 1, 2017

By J. Girard, V. Aubé, M. Barakate, S. Bellec, M. R. Eddahabi, Y. Chaik, M. Deshaies

"The activated carbon used in the carbon-in-leach (CIL) process to absorb gold is subject to breakage. This carbon breakage can be minimized, but it will always be necessary to deal with fine carbon particles, known as carbon fines. These fines contain a significant amount of gold and mining operations generally struggle with the treatment of this product. Since IAMGOLD’s Essakane mine is located in Burkina Faso, shipping carbon fines out of the country was not considered a viable solution due to the logistical burden and legal procedures in place. A benchmarking study demonstrated the complexity of treating carbon fines on site. IAMGOLD partnered with the host government to find an innovative approach to economically recover the gold locked in these fines. This paper describes the new circuits commissioned in July 2016 built to improve carbon fines collection, incinerate the carbon fines and leach the gold in the ashes produced by incineration. These new circuits successfully demonstrate that it is possible to extract more than 94% of the gold content in the carbon fines. This is profitable for the company as it improves the overall mill recovery rate by 1.0% to 1.5% and significantly decreases gold inventory build-up on site.INTRODUCTION The activated carbon used in the carbon-in-leach (CIL) to absorb gold is subject to breakage. This breakage can occur in the CIL tanks, the stripping circuit, the regeneration process or anywhere throughout the pumping and handling processes of carbon through the circuit. Fine carbon particles are invariably created and, because of their small size, present a large specific surface which favors gold absorption (Hilsher et al., 2014). At the very beginning of operations at Essakane, the carbon fines were recovered by means of a thickener and a filter press, but the circuit was undersized and inefficient. Subsequently, a decantation basin was used to settle the fines before the thickener. The settled fines were shovelled from the basin into bags. All these bags were stored in the backyard of the plant. The average tonnage of carbon fines recovered monthly was 23.5 tons with a gold grade at 1938 g/t."

Jan 1, 2017

By K. R. Barnard, K. D. Marte, T. V. Gamarano

"The first commercial scale application of CSIRO’s direct solvent extraction (DSX) technology has been in operation at the Boleo project in Mexico since December, 2015. In this application, DSX is a synergistic solvent extraction system consisting of the extractants LIX 63 and Versatic 10 for recovery of cobalt and zinc from a solution background of manganese, magnesium, and calcium. Key operating parameters such as metal extraction, phase disengagement and extractant stability are summarized and discussed in this paper.INTRODUCTION Commissioning of the Boleo processing plant, located on Mexico’s Baja peninsula, began with the copper circuit starting in late 2014, with first copper cathode production achieved in January, 2015. The cobalt and zinc circuits began commissioning in December, 2015 with first zinc sulphate monohydrate (ZSM) and cobalt cathode production achieved in February and April, 2016 respectively. The Boleo project flow sheet and development has been described in detail in previous publications (Dreisinger, et al. 2005; Dreisinger, Baxter, & Molnar, 2006; Dreisinger, et al. 2008; Dreisinger, et al. 2009) and is summarized schematically in Figure 1. Boleo is a mixed oxide/sulphide Cu-Co-Zn-Mn high clay deposit that is processed in a whole ore, atmospheric, oxidative and reductive, sulphuric acid/seawater leach. Copper is recovered as cathode by conventional solvent extraction and electrowinning. Cobalt and zinc are recovered, from a solution background of manganese, magnesium, and calcium, by CSIRO’s synergistic solvent extraction technology Direct Solvent Extraction (DSX). Cobalt and zinc are bulk stripped from the DSX circuit and then further purified by phosphinic acid solvent extraction to produce zinc sulphate monohydrate granules via spray dried granulation and cobalt cathode rounds via divided cell electrowinning."

Jan 1, 2017

By T. Plikas, T. Porretta, M. Al-Dojayli, B. Pretorius, J. Woloshyn, H. Ghorbani

"Water-cooled ducts represent an integral part of high temperature off-gas systems in metallurgical processes. Typically, off-gas enters these ducts at significantly elevated temperatures; therefore, water cooling may be required to maintain the duct skin temperature within allowable design limits. These off-gases are typically of high mineral content that could lead to dust buildup, and there is a possibility of slag buildup / molten metal splashing. Therefore, dust cleaning provisions may be necessary in order to remove or minimize accretion on the duct wall, which could otherwise impact the water cooling and the system process efficiency. These ducts may have complex geometry and experience a wide range of loading, including gravity loads, water and gas pressures, cyclic thermal loading and dynamic impact forces. Consequently, the thermo-mechanical assessment of such water-cooled ducts is critical and requires consideration phenomena such as high temperature gradients, potential nucleate boiling, thermal ratcheting and fatigue failures. Such assessment is not comprehensively covered by design-by-rule design codes and guidelines due to its complexity. This paper presents a successful implementation example of design-by-analysis methodology to improve the design and extend the life of a water-cooled furnace transition duct using Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA).INTRODUCTION Water-cooling represents an important part of high temperature off-gas systems in metallurgical processes. Typical temperatures of the off-gas in the furnace uptake are in excess of 1400°C, and thus there is a need to maintain the water-cooled duct and jacket skin temperatures within their material allowable design limits. Water-cooled channels have been used effectively in arc furnace roof design (Sosonkin et al., 1972; Smolyarenko and Khainson, 1988) and other furnaces as well as in furnace fuming jackets (Scholey et al., 1994). The design of these systems was based on one-dimensional analysis to ensure sufficient cooling is available under extreme furnace conditions (Smolyarenko and Khainson, 1988; Scholey et al., 1994). With advancement in furnace and fuming system designs, water-cooled duct designs have become more complicated in geometry. Numerical techniques, such as three-dimensional fluid flow and heat transfer modeling, are therefore needed to more accurately calculate water velocity, temperature and convective heat transfer coefficients in the water-cooled channels (Haywood et al., 2002; Henning et al., 2010). This is of particular importance around geometric corners where stagnant water flow may lead to local nucleate boiling at the critical heat flux, causing hot spots (Bergman et al., 2011). High wall skin temperatures increase the risk of failures due to thermal stresses as well as increasing corrosion rates (Gelfi et al., 2012), leading to costly equipment downtime and potential safety risks."

Jan 1, 2017