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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 S. M. Chentouf, M. Jahazi, N. Bombardier, T. Belhadj

The main limiting factor in the commercial expansion of superplastic forming (SPF) of thin sheet aluminum alloys is the extent of cavitation phenomenon that takes place during the processing. The severity of the cavitation process is mainly dependent on the uniformity of deformation (i.e. level of local thinning) during processing. In the present paper, correlations are made between thickness variations in several formed sheets and the characteristics of the cavities observed in the material. The 1.4 mm thick 5083 aluminum alloy sheets were hot pre-formed at around 450°C for 4 min and then air-cooled. Opto-digital and Scanning Electron Microscopy were used to examine the microstructure and analyse the cavities. Also, grain size measurements were carried out for different location in the SPF formed piece. The surface and volume fractions of the cavities were measured with the aid of metallography image processing (MIPTM) on as-polished samples prior to etching. The results are analyzed in terms of the influence of applied strain and microstructure conditions on the propensity to cavitation of the alloy.

Jan 1, 2015

By S. Usui, Y. Shinohara, C. Tokoro, K. Horiuchi, S. Owada

Process optimization of heating and physical separation for Cobalt (Co) recycling from spent lithium ion battery (LIB) was investigated. LiCoO2 in spent LIB was transformed to LixCoO2 which was more easily decomposed than LiCoO2 by heating. Coexisting materials of aluminum and carbon, and sealed atmosphere of the LIB promoted LixCoO2 decomposition. In an atmosphere of Argon, 95 % of LixCoO2 in the spent LIB was decomposed to 76 % of Co oxide and 19 % of Co metal in 10 min at 823 K; a lower temperature than the theoretical value for LiCoO2. The Co oxide and Co metal exhibited magnetic properties and could be recovered by wet magnetic separation. Furthermore, slow heating was effective for grain growth of Co oxide and Co metal. At 2 K/min rate of heating, average grain size of Co oxide and Co metal were 239 µm and 28 µm respectively, whereas at 30 K/min they were 190 µm and 15 µm respectively. Therefore, separation efficiency for Co recovery by wet magnetic separation was increased when spent LIB was slowly heated at 2 K/min.

Jan 1, 2015

By Liu Yulin, Zhao Yi, Tan Qi, Liu Lei

"Hydrotalcite is one kind of layered double hydroxides, and has special crystal chemical characteristics. Due to its good thermal stability, hydrotalcite used as the PVC heat stablier has attracted scientists’ attention. In this study, nano-hydrotalcite was synthesized by the method of mechanochemistry/crystallization, using brucite, Al(OH)3 and Na2CO3 as raw materials, and added into PVC to investigate the effect of hydrotalcite on thermal stability of composites. The synthesis mechanism was suggested by virtue of XRD, FE-SEM, FT-IR. It has been indicated that at the first of dry milling process, the parical sizes of brucite and Al(OH)3 decrease, while specific surface areas of them increase by the action of mechanical force, until produced amorphous particles. In the process of wet milling, metal ions in the amorphous body, which has high surface energy, can easily react with H2O, and produce the precursor of Mg6Al2(OH)18•4.5H2O, which has the same crystal structure as hydrotalcite. Under the hydrothermal condition, anions of OH- in the interlamination of precursor are exchanged by CO32- in the solution and nano-hydrotalcite is generated at last. The thermal stability was characterized by Congo red method. The results have revealed that hydrotalcite is one kind of long-term heat stabilizer, and residual stability time increase with the rise of added hydrotalcite amounts.INTRODUCTIONHydrotalcite, one kind of anionic clays, has been attracted a great interest for researchers because of their unexpected physical and chemical properties. The general formula is Mg6Al2(OH)16CO3·4H2O, where Mg2+ and Al3+ occupy octahedral positions in the brucite-like layers, and CO32- is an interlayer anion (Hoyo, 2007). Hydrotalcite is widely used in the fields of chemical engineering, materials engineering, environmental protection, medicine, and so forth, owing to its unique capability of adsorbability, ion exchange and thermal stability (Rozov, Berner, & Taviot-Gueho, 2010; Iwasaki, Yoshii, & Nakamura, 2012; Ay, Zümreoglu-Karan, & Temel, 2011; Cavani, Trifiro, & Vaccari, 1991; Li & Duan, 2005; Lin, Wang, & Evans, 2006). As a result, the study on synthesis and application of hydrotalcite has received considerable attentions."

Jan 1, 2016

By J S. Kermeen

This paper deals with drilling and blasting techniques at the Phoenix mine, near Grand F1nks, B.C., which is now operated by The Granby Mining Company Ltd. The difficulties of open-pit mining through former underground workings are unique to this operation. Rock types are related to drilling conditions, and the methods used, or contemplated, to overcome the several difficulties are outlined. The equipment used is also mentioned. Finally, blasting techniques and costs are reviewed. Introduction T HE Granby Mining Company operates on open-pit copper mine and concentrator at the site of the original Phoenix mine, near Grand Forks in south-central British Columbia. The pit is a side-hill cut measuring approximately 1,000 by 2,000 ft., and covering a vertical range of from 4,550 to 4,950 feet above sea level. The mill is currently operating at 1,900 tons per day. A 4.5 to 1.0 waste to ore ratio necessitates the removal of some 15,000 tons of ore and waste per working day. Mining conditions at Phoenix are extraordinary in that all the ore zones currently being

Jan 1, 1965

By Dougla McDonald, Richard Poulin

"Most mine managers in Canada today will agree that one of the keys to mining efficiency and productivity is their human resources. A5 a result, many mines develop some sort of incentive designed to tap their employees' capabilities to the fullest extent. Historically, the most common plans used have been ""piece-rate"" plans, where individual or small groups of miners are paid a financial bonus based on some measure of their productivity. Recently, however, incentive plans that take a more team-based approach have been developed in some Canadian mines. One such plan will be defined in this paper, and its popularity in the industry today discussed.Gainsharing PlansThere are two primary components to a gainsharing plan. The first is a cash incentive, which is paid to all employees and based on factors that are highly correlated with employee productivity, and key to the profitability of the mine. For example, the typical gainsharing cash incentive is based on the cost/unit of metal produced. Management (in consultation with employees in some cases) will establish the budgeted cost per tonne, and any savings in this amount is shared between the company and the employees. The second is a management philosophy and associated communication network, which is designed to foster an environment that encourages information exchanges, communication, participation, and trust between employees and management. The typical gainsharing communication network consists of two tiers of committees. The first, operational committees, include all employees working in the same department or departments which frequently interact. The employees meet monthly with management personnel to discuss problems encountered and brainstorm for solutions. In most cases, these committees will nominate a person in the group to structure the meeting to maximize its efficiency. The second, the screening committee, is a single group consisting of representatives from the various operational groups, whose primary job is to ensure that the plan is effective, and the objectives and results generated by the plan remain consistent with the mine objectives. In short, gainsharing plans tell employees that their bonus depends upon performance and then gives them the opportunity and incentive to affect that performance. The opportunity is provided by a communication network and positive management practices, and the incentive comes in the form of ""intrinsic"" rewards of participation and the ""extrinsic"" rewards of the bonus payments. Figure I will clarify the relationship between the intrinsic and extrinsic rewards."

Jan 1, 1995

By D. Shen, J. Cheung

Variable reactance arc control by the SPLC (Smart Predictive Line Controller) has been installed at many different mining sites and steel processing plants around the world. Since its first installation 18 years ago, many advances have been made to both the technology, and to its integration with furnace processes and plant operations. The SPLC has helped to improve electric arc furnace stability by reducing electrode movement while maintaining flat line arc power. Stable furnace operation at higher average power increases productivity. This paper summarizes the progression of electro-technology at Hatch since the 1970s, including fixed and variable reactance, digital electrode regulation, and fast variable speed hydraulics for Soderberg electrode, as demonstrated and benchmarked through projects and lessons learned over the years.

Jan 1, 2015

By Yuki Tsunazawa, Shuji Owada, Sho Fukui, Chiharu Tokoro

"Since the amount of e-waste has been rapidly increasing all over the world, there is a desire to develop the effective recycling process. E-waste has various kinds of electronic components with valuable and/or hazardous materials. Recycling of them is an important subject from the viewpoint of both the recovery of valuable materials and waste treatment. In common with all mineral processing, the comminution of e-waste is a key process because the liberation states after comminution determine the overall efficiency of metal recovery. Since some of useful critical metals are concentrated in a specific component, a special and selective grinding is expected to be effective. However, the knowledge about the mechanism and the effectiveness of the selective grinding is still limited and unclear.To better comprehend the mechanism, in this study, the investigation of comminution process using the particle-based simulation was conducted. Especially, this study focused on the comminution performance of printed circuit boards (PCBs), which are major components of e-waste. The behavior of PCBs and airflow in a drum typed agitation mill having flexible chains was simulated by the discrete element method (DEM) coupled with computational fluid dynamics (CFD). To model the shape of PCBs, the particle based rigid body model was introduced into the DEM. Since this model could not directly simulate the breakage phenomena, collision energy was calculated to qualitatively evaluate the comminution performance. In addition, the simulation results were compared with the experimental comminution tests using simulant PCBs where some capacitors were solder-mounted. These results indicated that comminution performance was affected by the rotation speed of the agitator. It was also demonstrated that the comminution performance was qualitatively evaluated using the particle-based simulation and this particle-based simulation made it possible to investigate the mechanism of e-waste comminution."

Jan 1, 2016

"Pilot plants for pressure hydrometallurgy represent special design and project execution challenges. Over the past twenty years, Zeton has designed and fabricated a variety of world-class pressure hydrometallurgical pilot-plant facilities for the nickel industry, and this paper discusses design considerations and strategies related to such projects. Project execution methods are also discussed, and guidance is given for the selection of materials of construction and for the selection of appropriate pressure and temperature design points for pressure hydrometallurgical pilot equipment. The paper concludes with a discussion of the need for process similarity with future commercial operations and the realities of pilot-scale equipment.INTRODUCTION The process technology developer or owner and the designer/fabricator of a new pilot-plant facility are faced with some difficult technical choices even after the decision to build a dedicated plant has been taken. A pilot-plant project is usually on the critical path of a large commercial project involving investments many multiples greater than the capital cost of the pilot plant. Schedule savings in the design, manufacture, and commissioning of the pilot plant or in a rapid completion of the experimental program can be disproportionately beneficial to the overall development project. However, inappropriate shortcuts resulting in major oversights can be disproportionately problematic. A number of considerations and suggestions for both the project execution approach and the process engineering design of pressure hydrometallurgical pilot-plant facilities are presented as a guide for potential owners and operators of new pilot-plant equipment and facilities. These suggestions are particularly applicable to the nickel industry, where the majority of our firm’s prior hydrometallurgical experience was obtained. This paper is an update to an earlier publication (Martin, 2004), offering an opportunity for a new generation of metallurgists and engineers to learn the specialist requirements of pilot- and demonstration-scale plant design, which are key functions in the development and commercialization of new processes."

Jan 1, 2017

By H. Saeedi Ali, A. J. Monhemius

"Anglo Asian Mining’s Gedabek mine is situated in the Lesser Caucasus mountains in Western Azerbaijan. The ore body is a complex copper-gold porphyry deposit, comprising intermixed oxidized, transition and sulphidic gold and copper-bearing ores. Gold in the sulphide ores is generally not refractory and is recoverable by cyanide leaching, but the secondary copper minerals, which are also cyanide soluble, lead to high cyanide consumptions. Ore processing at Gedabek is by agitation leaching for high grade ore (>1g Au/t) and heap leaching for lower grade ore. In order to cope with the high copper concentrations in the cyanide leach liquors, a unique combination of resin-in-pulp for selective gold extraction and SART processing for copper removal and cyanide recovery is used. In 2015, a flotation plant was added to treat the tailings from the agitation leach plant before the tails are sent to the tailings dam. This plant produces a copper sulphide flotation concentrate and also recovers some of the residual gold and silver in the tailings. Since February 2017, due to lower grades of gold and higher copper in the feed ore, the decision was taken to alter the flow sheet and to carry out flotation ahead of agitation leaching, to reduce the cyanide consumption during leaching by removing soluble copper minerals. The paper compares and contrasts the performance of the plant in the two configurations, namely, (i) leaching followed by flotation and (ii) flotation followed by leaching.INTRODUCTION In May 2009, Anglo Asian Mining started open pit mining for gold on its Gedabek property in the Lesser Caucasus Mountains in western Azerbaijan. Gedabek is situated on the highly mineralized Tethyan Belt that runs from the Himalayas to the Balkans. The ore body at Gedabek is a complex copper-gold porphyry deposit, comprising intermixed oxidized, transition and sulphidic gold-bearing ores. The sulphidic ores contain mainly pyrite and chalcopyrite, with some secondary copper sulphide minerals, such as bornite and chalcocite, and minor amounts of sphalerite, galena and tetrahedrite. Gold in the sulphide ores is generally not refractory and is recoverable by cyanide leaching, but the secondary copper minerals, which are also cyanide soluble, lead to high cyanide consumptions and passivation of free gold."

Jan 1, 2017

By M. Hekmati, M. R. Garmsiri, S. M. Hosseini

"SAG/AG mills have been most common choice in grinding circuits last decades. In the most cases, at the discharge of SAG/AG mills, a trommel screen is used that is equipped with baffles to provide appropriate residence time and improve separation efficiency. Using baffles, with the resultant maintenance requirements could lead to decrease in mill availability. In this research, an innovation in the structure of baffles of a trommel is presented. The results show that using new baffles led to 67% decrease in SAG mill downtime due to problems of baffles and 80% decrease in fine particles on recycle conveyor.INTRODUCTIONComminution is a vital operation in mineral processing circuits and it helps to achieve a certain level of fineness in the ore material. About 60-80 % of the overall energy used in mining is consumed in comminution, and this is the reason that much research has been performed in this field (Kochnev, 2008).During the last decades the configuration of grinding circuits has been changing due in large part to the decrease in the grade of mineral resources and the need for large scale, energy efficient processes. The previous configuration of conventional grinding circuits was based on parallel primary circuits (mostly using ball mill), such as the grinding circuit of Sarcheshmeh concentrator plant no.1 (Figure 1). The new configuration of grinding circuits is based on using SAG/AG mills, such as Shahrebabak concentrator plant (Figure 2), sometimes incorporating new technologies like the HPGR. Nowadays, application of new configuration of grinding circuits using large SAG/AG mills up to 40 feet (Allan, Major, Flintoff, Klein, & Mular, 2006), in the minerals industry is continuing increase due to the significant reduction in capital and operating costs, and increase in the plants throughput (Banisi & Hadizadeh, 2007)."

Jan 1, 2012

"SART technology is a useful tool for improving the economics of gold recovery from certain types of complex gold ores. SART liberates cyanide consumed by base metals such as copper, zinc and nickel, and enables the newly freed cyanide to be recycled to precious metals leaching while producing high-grade base metal sulphide concentrates for sale. The benefits of SART include the reduction in cyanide consumption, avoidance of cyanide destruction costs, minimization of risks of environmental non-compliance due to residues of cyanide destruction reporting to mine effluents, and generation of extra revenue from the sale of base metal concentrates. Concerns with SART typically include uncertainties around capital and operating costs and proper integration of SART into the overall metallurgical flowsheet. This paper presents two case studies addressing these concerns. The first involves actual costs of the full scale SART integrated into a gold heap leach operation and treating up to 500 m3/hr of leach solution at a mine in Mexico. The second involves field pilot testing and a preliminary cost estimate for integrating SART into a silver mine in Peru using Merrill Crowe.INTRODUCTION One of the current trends in the gold industry globally is the increasing importance of complex polymetallic gold deposits as discoveries of large Carlin type gold deposits become increasingly rare (Sceresini, 2005). The presence of cyanide soluble copper and zinc in complex gold deposits necessitates changes in traditional gold extraction metallurgical flowsheets. One of the tools available to the industry to help deal with interferences of cyanide-soluble base metals in gold extraction is the SART (sulphidization-acidification-recycling-thickening) process. SART breaks the weak acid dissociable (WAD) base metal-cyanide complexes, precipitates the metals as high-grade sulphide concentrates and makes the freed cyanide available for recycle. Although SART is a commercially available technology, it is still relatively new to the industry. Fewer than ten (10) full scale plants have been constructed in the past couple of decades. Some of these SART plants are small, most are located at remote sites, and the majority have not operated on a continuous basis. This has resulted in a general lack of information in the industry about the true costs, operability and metallurgical performance of SART. BQE Water has been involved in the design, construction, commissioning and operation of large scale SART plants in Mexico, Turkey and Chile and has conducted field testing programs as part of the technical assessment of SART integration into various metallurgical circuits. Having built and operated numerous plants utilizing selective sulphide precipitation of heavy metals, BQE Water has gained unique insight into the design and control of the sulphidization stage of SART to minimize costs and ensure high efficiency in cyanide recovery."

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 A. P. E. Dirige

The stability design of cemented backfills is normally conducted using conventional approaches. Analytical or numerical models, backed by trial-and-error methods, are the primary means used to describe or predict the support performance of backfills during mining. The stability of paste backfill free-standing faces is a major concern due to potential consequences to production, ore dilution and safety. Available analytical or mathematical models are developed based on assumptions of the failure modes that may occur when vertical fill faces are exposed during adjacent mining. Numerical modeling serves to provide an understanding of backfill strength and deformation behaviour. Such approaches offer inherent limitations and generally result in conservative designs. In this paper, centrifuge physical modeling was conducted not only for performance evaluation studies, including stability analysis, but to develop an understanding of the strength and deformation behaviour of paste backfill exposed faces when the adjacent ore zone is removed. The failure mode and mechanics of failure observed in the centrifuge model of a given prototype situation are discussed in detail. Centrifuge model results were compared to numerical modeling and it was concluded that a sliding block failure mechanism that resembles a circular slip appears to be the predominant failure mode.

Aug 1, 2013

By D. A. MacFadyen, J. J. Brummer, C. C. Pegg

"The first record of a kimberlite found in Canada (1946) was the identification of thin dykes intersected while drilling for gold in Michaud Township, Ontario.Sampling of the Munro Esker (1964) in the Kirkland Lake area, Ontario, by the Geological Survey of Canada identified the occurrence of detrital grains of pyrope garnets along a length of 35 km of the 113 km tested. A search for the source of the garnets resulted in the identification (1968) of a narrow subsurface kimberlite dyke in the Upper Canada Mine. This discovery resulted in a staking rush. Unfortunately, subsequent work did not identify the source of the kimberlite indicator minerals.During 1978 the Ontario Geological Survey started a multi-discipline study of 29 townships (2560 krn2) in the Kirkland Lake area, to encourage exploration for gold, base metals, and kimberlites. Back-hoe sampling (1979 to 1982), where the overburden was thin, and reverse circulation drilling, in areas of thicker drift, yielded samples of the till. These were analyzed for several elements and a mineralogical identification of the heavy minerals was completed. Pyrope and chrome diopside grains were identified.Studies of the Pleistocene geology indicated only the most recent direction (167 degrees) of ice advance (Matheson) and the associated deposits, out of a possible three advances known to occur in the general region straddling the Ontario-Quebec boundary, is present in the immediate area of Kirkland Lake. Contouring the distribution of pyrope grains (1990) showed a concentration centered over an area of 616 km2 extending down-ice from Gauthier Township. This included a smaller area containing chrome diopside grains. Kimberlite boulders were identified (1981) in gravel pits on the Munro and Misema River Eskers located within this anomalous area. The next step would be to use the airborne geophysical data to locate the kimberlite pipes which yielded the indicator minerals and boulders. The source area is likely to be in the northern half of the Ontario Geological Survey study area."

Jan 1, 1992

By G. Azimi, C. A. Ang, F. Zhang

"Nickel recovery from laterite ores generates large amounts of solid and liquid wastes. This is primarily due to the low concentration of Ni (about 1.4 wt%) in the feed ore to the High-Pressure-Acid-Leaching (HPAL) process. It is known that the HPAL residue contains a high concentration of hematite, a commercially important source of iron in the steelmaking industry. However, the balance is natroalunite, containing sulfur, which is a detrimental element in the steelmaking process. Hence, to make the HPAL residue a suitable feed for steelmaking, natroalunite must be removed. The current work is focused on: 1) a thorough characterization of the HPAL residue obtained from Vale, and 2) a systematic investigation of an alkaline leach process to remove natroalunite. The characterization results indicated that there are about 83 and 12 wt% hematite and natroalunite in the HPAL residue, respectively. The leaching results indicate that sodium hydroxide is the best leaching agent, which results in 55 wt% reduction in the sulfur content. The results of this work enable the conversion of an otherwise waste product into a useful feedstock for steelmaking. Furthermore, this project could potentially have significant environmental benefits by reducing the amount of residue produced during the HPAL process.INTRODUCTION Conventionally, crude steel has been obtained by reducing iron ore containing oxides such as hematite (Fe2O3), magnetite (Fe3O4), and wüstite (FeO) in a blast furnace with coke. The product is then refined in a basic oxygen furnace to produce steel with useful properties (McGannon, 1969; Turkdogan, 1978). Steel has been sought for its desirable properties and its application is widespread throughout modern civilizations. Surpassing the growth rate of other materials, the annual demand of steel has increased at a compound growth rate of 5% over the last 20 years (Baddoo, 2008). The global demand for steel was reported to be 1501 Mt in 2016 and demand is expected to double by 2050 (Cullen, Allwood, & Bambach, 2012; World Steel Association, 2016). In recent years, to meet the rapid growth of demand, secondary resources for iron have been identified as strategic sources of iron (Das, Kumar, & Ramachandrarao, 2000; Li, Sun, Bai, & Li, 2010; Matschullat et al., 2000). The residue produced from high-pressure acid leaching (HPAL) of laterite ore has been identified as one of the important secondary sources of iron (McDonald & Whittington, 2008). Laterite ore represents 60% of the world’s nickel resources and accounts for approximately 40-50% of the world annual nickel production (U.S. Geological Survey, 2016). Therefore, the amount of iron residue produced by the process is substantial and its utilization will produce both economic and environmental benefits."

Jan 1, 2017

By W. K. Chan, R. Lahaie

"The Suncor Oil Sands Mine located north of Fort McMurray, Alberta, produces about 80000 m' per day of tailings waste which must be disposed of economically in an environmentally acceptable manner. To date, this has been accomplished by impounding the high water content tailings wastes behind large dykes, many of which approach 100 m in height .The dykes are constructed using suitable overburden material stripped prior to the mining of the oil sands feed and/ or the coarse sandy fraction of the tailings waste itself. Although the above is common practice at many mining operations, the large volumes handled and the resultant costs require designs to be meticulously fine-tuned toward the optimum. As a result, considerable effort is expended on planning, designing and construction, and performance monitoring. The lack of precedent experience (Suncor pioneered oil sands mining), coupled with the realities of long, harsh winters and a variety of troublesome site conditions and construction materials, has led to some very unique dyke construction.This paper overviews current tailings disposal plans as welt as some of the key issues related to the design, construction and performance of these large dykes."

Jan 1, 1988

By D. C. Crothers

"What is new in air compressors? A good deal - the designers have been keeping pace with technical developments in related fields and also contributing new techniques of their own. Plant reliability no longer requires bulky slow-speed machines. Even the reciprocating machines, which still provide the most efficient method of compressing air, have been greatly reduced in size and installation cost for a given capacity rating. New materials and fabrication techniques are being used, by most manufacturers, to produce less costly plants in total. Many packaged plants are available, which generally means a more complete assembly for shipment. This type of construction offers savings in handling and erection costs at the site. A warning is in order, however - the extent of packaging in any given plant should be investigated carefully to determine what is included and just what field costs can be realized. A suggested specification has been offered for consideration when studying comparative costs. Rotating machines intrigue many because of their potential as regard fewer wearing parts, higher speeds and hence smaller units, utilizing less expensive drivers, and lack of contamination of the compressed air by lubricants. The inherent shortcomings of these machines - lower •efficiency and capacity control - have been much improved lately, and this type of plant is now becoming quite popular. Noise control, of much concern to everyone, is another development that has received considerable attention.Systems for efficient capacity control and continuous monitoring of compressor operation offer additional reliability and low-cost operation of the modern compressed air plant. Accessory equipment and its effect on over-all plant operation is also considered."

Jan 1, 1972

By Z. S. Abisheva

The Zhezkazgan copper sulfide ore deposit in Kazakhstan contains both rhenium and the rare osmium isotope "osmium-187" (187Os) in the high isotopic purity of 99.4 ± 0.2%. This isotope is believed to have originated as a result of the disintegration of one of the rhenium isotopes, according to the reaction: 187Re75 ?> 1870576 + B- + v~ (where B is a 13-particle, v~ is a 3-disintegration antineutrino). The distribution of osmium and rhenium in metallurgical byproducts produced during the recovery of copper from these ores has been studied and process flowsheets for the processing of rhenium and osmium-containing byproducts have been developed.

Jan 1, 2007

By Eduardo R. Rodrigues, Ankur Narang, Roberto Federico Ausas, U. T. Mello, Jose Maria Segura Serra, M. R. Lakshmikantha, Ignacio Carol, Kamal C. Das

"Modeling of big faults or weak planes of strong and weak discontinuities is of major importance to assess the Geomechanical behaviour of mining/civil tunnel, reservoirs etc. For modelling fractures in Geomechanics, prior art has been limited to Interface Elements which suffer from numerical instability and where faults are required to be aligned with element edges. In this paper, we consider comparative study on finite elements for capturing strong discontinuities by means of elemental (EFEM) and nodal enrichments (XFEM) for Geomechanical applications. For general fracture scenarios, Oliver et al. (2008) have demonstrated advantages of EFEM over XFEM for including: (a) ease of modeling in any standard finite element code due to the possibility of static condensation, (b) higher accuracy in some cases for coarse meshes, and, (c) a reduced computational cost. However, there has been no work that considers cohesive fractures in Geomechanics. We present a numerical analysis based on a linear constitutive model and linear triangular elements for the bulk and a linear constitutive behaviour for the fault for a representative set of fault planes in a circular tunnel made in rock mass. In the numerical examples we consider both well-traced and bad-traced meshes. We focus on traction profile analysis for both EFEM and XFEM, since that is crucial to understand the cohesive fracture behaviour specially rock joint. Therefore in each case, shear, normal and stress ratio are compared across the two methods along the fault plane. This is the first such work that compares XFEM and EFEM behaviour for Geomechanics problems.For the considered class of problems and the sharp penalization approach without regularizations adopted, it can be observed that accuracy and robustness of EFEM may strongly depend on the fault orientation with respect to the element edges, while, XFEM is independent of fault alignment with element edges. It has been also observed that, with mesh refinement model, stress oscillation completely removed with XFEM however EFEM fails to provide oscillation free results with finer mesh in case bad-traced model. We also performed error analysis and found that in case of bad-traced mesh the average error in the XFEM is 84% smaller than of EFEM and for XFEM the error goes to zero with increasing mesh resolution, while for EFEM the error increases with mesh resolution. Thus, we experimentally demonstrate that, XFEM performs better than EFEM in terms of accuracy and rate of convergence with marginal increase in computational cost. This work hence provides novel insights on the application of XFEM and EFEM in Geomechanics."

Jan 1, 2015