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By G. Deschenes

"This literature survey discusses the recovery of gold from thiourea solutions. An overview of techniques used and general comments on the basic cyanidation methods are presented. The chemistry and mechanisms of cementation, activated carbon, resins, electrowinning, solvent extraction and pressure reduction are examined. Conclusions and recommendations give orientation for future research and development activities in this field.RésuméCette revue littéraire traite de la récupération de I ‘or des solutions de thiourée. Elle fait un survol de I ‘ensemble des techniques utilisées tout en introduisant des commentaires généraux sur la méthode classique qu'est la cyanuration. La cémentation, Ie charbon active, les résines, l'électroextraction, I ‘extraction par solvant et la réduction sous pression sont les méthodes analysées tout en considérant leur caractère chimique respectif ainsi que les mécanismes qui y sont rattaches. Des conclusions sont tirées et différentes recommandations sont suggérées pour orienter la recherche dans ce domaine."

Jan 1, 1986

By Changmiao Liu, Dong Dong

"Magnesite is a major mineral resource in China, whose output and export are massive and quite important to the world. Flotation performances of eight anionic collectors on magnesite were studied to find the proper ones. Micro-flotation results indicated that collectors of HOl, SDBS and AEP had outstanding flotation performances on magnesite, with the recovery ratio all reaching above 90% in a wide range of alkaline pulp. Solution chemistry calculation, Zeta potential and FTIR measurements were employed to reveal the interaction mechanism between anionic collectors and magnesite surfaces. Solution chemistry analysis indicated that the main active components of HOl, SDBS and AEP were anions and association complex anions in alkaline pulp. Magnesite surface was negatively charged in the alkaline pulp. The active sites on magnesite surface were mainly the components of MgOH-, Mg (OH)2, and MgCO3 when the pulp pH was over 8. Anionic components of HOl, SDBS and AEP reacted with Mg in magnesite surface to make the insoluble anionic salts. And the chemical adsorption was confirmed by the FTIR measurement evidences.INTRODUCTIONAs an important industrial mineral, magnesite has been widely applied in metallurgy, building materials, chemical industry, agro-pasturage and other fields (Hu et al., 2006). It is a major mineral resource in China with abundant reserves. Its output and export are massive and quite important to the world. Liaoning province is rich in magnesite, whose reserves and production both come first in China. So far the proven reserves have reached 2.91 billion tons, accounting for more than 90% of total reserves in China, and more than 25% in the world (Li et al., 2012).Magnesite ores in Liaoning province mainly contain crystalline magnesite, and the gangue minerals of quartz, dolomite, talc, tremolite, chlorite and carbonaceous materials. Some ores also contain a little pyrite, chalcopyrite, hematite and apatite. Most of the ores must be preprocessed to separate the useful parts from the large amount of gangue minerals, so that their value and industrial application can be enlarged and promoted.Flotation is commonly used to process the magnesite ores, and the conventional flotation methods include anionic and cationic flotation. In the former, gangue minerals of silicates were separated by using amine type cationic collectors. After the impurity minerals were removed, high qualified magnesite concentration could be gained. For the cationic flotation method, it had some drawbacks of lower recovery ratio and poor performance in the lower temperature pulp (Li et al., 1995)."

Jan 1, 2016

By S. P. Narayan

The hot deformation behavior of Pure Mg and Mg-0.29Ce alloy were studied by isothermal hot compression tests in the temperature range of 250 - 500°C and strain rate range of 10-3 - 102 s-1 in a computer-controlled 50kN servo hydraulic universal testing machine (UTM). The results show that the flow stress of Mg pure and Mg-0.29Ce alloy increases with strain rate and decreases after a peak value, indicating dynamic recovery and recrystallization. Process efficiency was increased by nearly 10 to 12% by addition of Ce in Mg. Mg pure exhibits instability zones between 250-275°C at 10 ? 102 s-1 and 400¬500°C at 101 ? 102 s-1 temperatures and strain rates respectively, rest is the safe deformation zone. Wherein, Mg-0.29 Ce exhibits two low efficiency zones from 250 ? 300°C at 10-2? 10° s-1, 400 ? 500°C at 101 ? 102s-1 and high efficiency zone at 450 ? 500°C at 10-3? 10-1s-1. 4D process maps were generated for the above said alloys which illustrate contours of power dissipation and instability in the 3D space of strain rate, temperature and strain.

Jan 1, 2011

By M. E. Moraes Castanho de Almeida, A. Ribeiro Cotri

Recovery of cobalt to produce high grade cobalt sulfate from cobalt concentrate by leaching and solvent extraction was investigated. The PLS typically contains Co 10g/l, Mg 2g/l, Fe < 10ppm, Mn < 200ppm, insolubles <100ppm and is extracted with 20wt% Cyanex??272. The typical strip solution contains Co 60g/l, Mg 0.03g/l, and was sent to the current process for the production of cobalt sulfate heptahydrate. The cobalt yield of the plant with two extraction steps was 92%, with three steps was 97% and with four steps 99%. The extraction stage used the concept of "scrubbing" in a countercurrent system. In the first stage of extraction pH was 4.8, and in the last stage of extraction pH 5.5 to promote the exchange of magnesium in the organic with cobalt contained in the PLS. Following the extraction, when using two scrubbing stages, Co/Mg selectivity between of 2,000-3,000 was obtained, and with three scrubbing stages, selectivity was greater than 6,000. The desired selectivity was reached when using a scrubbing configuration with O/A ratio of 10:1. The typical cobalt sulfate heptahydrate had the following composition: Co 20wt%, Mg < 0.01wt%, Fe < 5ppm, Mn < 0.01wt%, Cu < 0.01wt%, Zn < 0.01wt%.

Jan 1, 2014

By James W. Cameron

DESPITE the fact that, after oxygen and silicon, aluminum is the most abundant and widely distributed element in the earth&apos;s crust, it is, commercially, a modern metal. Attempts were made by Sir Humphrey Davy and other chemists to decompose alumina, the oxide, into its elements, but with unsatisfactory results, and it was not until 1827 that Wohler succeeded for the first time in isolating the metal in pure form. Some thirty years later, commercial production of aluminum was started in a plant near Alais, France, using a process developed by Deville which was a modification of that of Wohler. It was not, however, until around 1886 that possibilities of low-cost production were realized. Hall and Heroult discovered, independently, the now famous process for extraction of aluminum by the electrolysis of alumina (Al,O,) dissolved in fused cryolite. This discovery, with its subsequent effect in reducing the price of the metal, was perhaps the greatest single factor contributing to the remarkable growth of the aluminum industry. But only in the years following the Great War did aluminum begin to attain equal importance in many fields with other non-ferrous metals. Numerous factors, political and economic, in the past decade have had a profound effect on the industrial history of the metal. At present, systematic substitution of aluminum for other base-metals is proceeding at a rapid rate in such countries as Germany and Italy with a view towards &apos;economic self-sufficiency&apos;. Quite naturally, ?the economic depression started extensive research and experiment in various industries in an attempt to improve efficiencies and lower costs. Partial answers have been found in the extended use of aluminum and its alloys. Even against the background of tremendous technological advance that has marked the past fifty years, the rise of the aluminum industry must necessarily stand out conspicuously.

Jan 1, 1939

By L. Tikasz

The primary purpose of ore hauling model studies is to capture the variability of the ore delivery ? stockpiling process in order to improve the estimation of equipment capacities and achievable throughputs. The operation of a mine-to-site ore delivery system is the subject of a number of challenges. Typically, ore is hauled by a given combination of trucks, conveyors and trains. In addition, ore loading, ore transferring to another means of delivery, stockpiling, reclaiming, and further deliveries involve many other types of equipment. The concurrent operation of all these units is scheduled; nevertheless, they are subject to planned maintenance and random breakdowns. To support our engineering design work on ore hauling operation, discrete event type models were built for each specific task. Then, due to recurring demands, an ore hauling library was gradually compiled. The now available model library allows fast and efficient simulation of various mine-to-site hauling arrangement, adaptable to various mining and mine construction operations (e.g. bauxite, iron ore, copper ore and coal).

Aug 1, 2013

By Anne-Marie Dagenais

Un recouvrement de type couverture à effets de barrière capillaire (CEBC) a été mis en place en 1988-1999 sur le parc à résidus de l?ancien site minier Lorraine situé au Témiscamingue. Depuis sa construction, la CEBC fait l?objet d?un programme d?auscultation et de suivi qui vise à évaluer son comportement hydrique et sa capacité à limiter le DMA. Des essais de consommation d?oxygène ponctuels ont également été réalisés sur le site afin de mesurer directement le flux d?oxygène traversant la couverture. Les résultats provenant des relevés de teneur en eau volumique et de succion, pour les années 1999 à 2001, montrent que les effets de barrière capillaire sont présents et que la couche de rétention d?eau demeure dans un état près de la saturation pour l?ensemble de la couverture. Les flux d?oxygène calculés à partir des mesures mensuelles sont en général inférieurs à 10 g/m2an, soit en deçà des valeurs de design de 20 à 40 g/m2an. Les essais de consommation d?oxygène réalisés sur la CEBC donnent également des flux d?oxygène du même ordre de grandeur. Les résultats obtenus de ces différentes méthodes d?évaluation concordent, et ils confirment l?efficacité de la CEBC à inhiber le flux d?oxygène et à contrôler le DMA.

Nov 1, 2002

By L. Rao, P. Carabin

"Advances in thermal plasma torches have resulted in this technology becoming a commercially viable solution for chemical and metallurgical processes. The main advantages of plasma are its ability to control process chemistry and to build small footprint reactors due to its high energy density and reactivity of the free radicals that are produced. This paper focuses on thermal plasmas produced by DC torches and their applications for waste treatment, production of high purity metals, and nanomaterials. Both transferred and non-transferred torches have been used as either a source of heat or as a reagent in various industrial processes. INTRODUCTIONPlasma technology has become an ideal solution for many industrial chemical, metallurgical and mechanical processes (Venkataramani, 2002). Thermal plasma powered systems are typical used for their unique characteristics such as high energy densities, high temperatures, small installation sizes, rapid startup and shutdown features, controlled process chemistry and use of electrical energy as a heating source resulting in decoupling the heat source from the oxygen flow rate (Heberlein et al., 2007). Depending on the nature of the main plasma forming gas used, thermal plasma systems offer a high temperature heating source coupled with a highly reactive plasma plume rich in free radicals and ions which promote otherwise hard to drive chemical reactions, as well as high heat transfer rates.Industrial plasmas can be broadly classified as thermal plasmas and non thermal plasmas. Thermal plasmas are atmospheric pressure plasmas characterized by local thermodynamic equilibrium (Boulos et al., 1994). Thermal plasmas are typically established between any two current conducting electrodes separated by an insulator. A plasma forming gas is blown between the two conducting electrodes resulting in a high temperature plasma plume. A plasma torch generates and maintains an electrically conducting gas column between the two electrodes; a cathode (negative electrode) and an anode (positive electrode) (Camacho, 1988). If both electrodes are housed in a single housing, resulting in an arc enclosed inside the plasma torch, then such plasma generating torches are termed as non-transferred (NT) plasma torches, whereas, if the second electrode is external to the torch, creating an arc transferred between the cathode and the working piece, then such plasma torches are termed as transferred (T) plasma torches. Depending on the source of the electricity which can be either direct current (DC), alternating current (AC) at main network frequency or at radio frequency (RF), the plasma torches are classified as DC, AC or RF plasma torches (Venkataramani, 2002)."

Jan 1, 2012

By Karl J. C. Harries

"1.1. WHAT ARE AGREEMENTS AND HOW ARE THEY FORMED?In order to have an agreement, at common law, there must be an offer, acceptance of that offer, and consideration passing between the parties. In addition, the material terms (i.e. the basics or substance) of the agreement must be discernible, preferably by means of documentation. Although these concepts may appear simple and straightforward, the law relating to them is voluminous and complex. Some brief comments are worthwhile.• Offer/acceptance: Both offer and acceptance should be in writing, but they need not be. The actions, conversations, and/or correspondence of the parties may constitute either or both of them. Notwithstanding, the local law or practice of a jurisdiction will impose some specific requirements for certain types of agreements. If these requirements are not met, the agreement may be unenforceable. For example, Ontario’s Mining Act requires transfers of unpatented mining claims to be evidenced in writing and recorded.1• Consideration: Consideration is usually thought of as being money, but it can be virtually anything, even “the premises” (i.e. the mutual covenants or promises contained in the agreement itself). In addition, if one party, relying upon the offer of another, does something to his detriment, then the doing of the act can be considered to be an acceptance of the offer and, under the legal concept of “detrimental reliance”, can also be consideration. Whether or not detrimental reliance exists will depend upon the circumstances of each case.2• Material terms: The requirement that the material terms of an agreement must be discernible does not mean that all of the terms of an agreement must be documented or even have been considered, just the basic or material ones. In addition, it will be up to a judge to decide what is material – not necessarily the parties. In order to establish the material terms, a Court may look at all relevant documentation and may hear oral evidence. It will resist “writing the agreement”"

Jan 1, 2003

By W. M. Goodwin

The gold district of northwestern Quebec, though it has attracted such widespread attention during the past year, is still in the prospect stage throughout, and one must preface any remarks about it with the plain statement that its capacity to produce gold commercially is still subject to proof. However, this proof may be forthcoming any day, and from widely separated localities. Consequently it is of interest to note some of the features of the region and of the prospects now being developed. First I shall note the relation of this mining development to the province of Quebec and to the Dominion; then will follow a brief resume of the known geological facts; and finally I shall describe briefly some of the more advanced prospects developed during the past twelve-month. Those that have followed closely the fortunes of the new gold-field will find little that is new in what follows, but it may serve a useful purpose for others by bringing together scattered items of information and presenting them as a whole. GOLD MINING AND AGRICULTURE First let us consider the gold belt in its relation to the province of Quebec. Apart from the world-renowned asbestos camp south of the St. Lawrence, it is the only mineral development of major importance the province has experienced. It is the first important development in the province&apos;s vast area of Precambrian rocks, most of which remains as yet totally unexplored and unprospected. The relative importance of this first mining camp in northern Quebec cannot as yet be gauged, but it is bound to stimulate an active interest in the other mineral-bearing areas now known to exist, and in the vast unexplored spaces.

Jan 1, 1924

By H. Hamza

Efficient and effective management of extraction process tailings is an essential ingredient for the continued success and development of Alberta&apos;s vast oil sands resources. Open-pit oil sands operations north of Fort McMurray recover bitumen from flotation circuits. Process tailings are managed in carefully engineered and monitored external tailings management facilities and in below-grade mine pits. In order to support reduction of production costs and improve upon established tailings management practices, CANMET has been working with the oil sands industry in a collaborative framework to assess the potential to integrate thickened tailings into oil sands extraction process flowsheets. Albian Sands has commercialized the process while others, including Syncrude Canada Ltd., continue to evaluate the suitability of the process for their operations. This paper provides an update on R&D work undertaken in recent years to assess and develop the potential of thickened tailings technology for the open-pit oil sands operators of northern Alberta. The aim of this work was to explore opportunities to optimize process efficiency and environmental sustainability by improving water and energy conservation and develop more alternatives for tailings management and reclamation.

Jan 1, 2004

By F. L. Thompson

MAN has been using lubricants of one type or another for at least four thousand years, and probably for a much longer period. We have learned from the inner wall of the tomb of Tehuti-Hetep, on which is a decoration illustrating the method of moving a great stone statue, that as early as 1650 B.C. lubricants were used to facilitate the movement of heavy loads. The Egyptians had available nearly every animal oil and fat, as well as at least thirteen vegetable oils, of our time, all used for food products and in the arts. Examination of the deposit on the axle of a chariot from an Egyptian tomb of 1400 B.C. showed it to consist of animal fat, quartz, sand, iron, and compounds of aluminium and lime-indicating a manufactured lime-soap grease made with lime-soap and possibly tallow. This would not be a bad lubricant for the axles of chariots which had to travel over sandy soil in hot weather. As to the method of grease application, it is remarkable that, from the time wheels were first used in the far distant past up to the present day, no one has ever thought it necessary to design a seal to keep the lubricant in and the dirt out. While time certainly marches on, we have today, in waggons throughout the world, exactly the same form of lubrication as was used in the earliest chariots. From the early days of the chariot until shortly before 1800 A.D. (when the steam engine was introduced), the main heavy equipment required for mining purposes, for machines of war, etc., was made of wood. The bearings were rough, but usually they had metal in the lower half. Light machinery was made of bronze, brass, or iron. Large clearances and poor alignment, plus the fact that speeds were much below present-day demands, combined to provide conditions that were quite satisfactorily met by the lubricants available. These were often produced locally by the machine operator. In northern countries, lard oil, prepared from the fat of hogs, was the universal lubricant employed in machine shop, as a belt and leather dressing, and for cutting operations. Sperm oils were used for light machinery, whereas beef and mutton tallow were more generally employed for the largest bearings. For the early steam cylinders, a slug of heated beef tallow was injected wherever the cylinders gruntingly complained of a lack of lubricant. Southern countries, however, resorted to the use of vegetable oils-olive, cocoanut, etc.

Jan 1, 1940

By K. Cybulski

Coal dust explosions still remain the main hazard in the coal mining sector, notwithstanding their relatively wide recognition compared to other hazards and the development of effective methods of prevention. Coal dust explosions are still the cause of numerous catastrophes, often leading to fatalities. Fortunately, they rarely occur, and it is for this reason that their hazardous impact is often underestimated. This problem in Poland is being exclusively solved by the Central Mining Institute, Experimental Mine Barbara. Here, basic research on the phenomenon of coal dust explosions and prevention methods is carried out, as well as investigations into the causes and circumstances of past accidents. After 15 years of no coal dust explosion accidents in Poland (1987?2002), a few coal dust explosions have recently occurred, with tragic consequences. These events have taken place not only in hard coal mines, where the presence of dangerous coal dust is the result of common production cycle, and safety measures against coal dust explosions are subject to specific regulations, but also in coal-fired power plants. This is of special concern because prior to 1987, such accidents had been been reported only for coal mines and not for coal-fired power plants. In recent years, two dust explosions occurred in Polish power facilities: the Dolna Odra and Turow power plants. In both cases, coal dust explosions occurred in the fuel supply system, but biomass dust was also involved. The explosions caused significant damage to the systems and buildings. This paper gives description and schematics of the regions of catastrophic coal dust explosions that have occurred in recent years in Poland, as well as the results of post-accident investigations, presenting the coal dust explosion hazard at the accident scene The results specify in detail the state of safety measures against coal dust explosions in light of the relevant regulations in force, including amount of deposited coal dust, content of incombustible matter in coal dust, free moisture content in coal dust, state of coal dust explosion safety zones, and state of explosion barriers. The conclusions from the site inspection and post-accident investigations presented enable us to determine locations of explosion initiation, probable ignition sources, range of explosion flames, and explosion barrier performance. A complete elimination of coal dust explosion hazard at the site of dust deposition is practically impossible to achieve. Similarly, a total elimination of ignition source, which may be related to the occurrence of other natural hazards, equipment malfunction or human errors, is impossible. The examples of tragic events that took place in Polish coal mines and coal-fired power plants highlight shortcomings and mistakes made in terms of assessment and prevention measures taken against the coal dust explosion hazard.

Aug 1, 2013

By S. Razavialavi

In the planning phase of every construction project, layout of temporary facilities is a crucial task; site layout can affect safety, travel cost and time, construction productivity, and space utilization. However, site layout planning can be a complicated problem, due to the interdependency of influencing factors. Although interaction among activities is one of the major drivers of site layout planning, it has not been properly addressed in past research. In this study, simulation is presented as a promising tool to address this gap. The capability of simulation technology to model complex processes in construction projects makes use of simulation tools in site layout optimization problems effective, while existing methods are unable to perfectly model these problems, in some cases. Additionally, the advantages and challenges of implementing simulation are assessed and a generic framework for simulation application in site layout planning is proposed.

Aug 1, 2013

By Christopher Andreae

"Years before the present iron and steel works were established at Sydney, several thriving although short-lived iron work s operated in Nova Scotia. These furnaces reflected the general nineteenth-century North American experience with iron work s. At the beginning of the century, small furnaces struggled to supply local needs. Charcoal was the principle fuel and water powered most furnace equipment. By the end of the century, a few huge primary iron and steel work s dominated production for Nova Scotia and the rest of Canada.Two sites achieved prominence in the nineteenth-century Nova Scotia iron industry: Londonderry and Ferrona. Londonderry, the larger and longer-lasting of the two sites, is today a small village on the south flank of the Cobequid Mountains, about 30 km west of Truro. Prior to the establishment of an iron works in 1849, no community existed. At the peak of operation in the 1880s, however, over 2,600 people were located there. The second site, Ferrona, today is a mere crossroads on the map, about 10 km south of New Glasgow. Following the construction of a blast furnace there in 1892, a small village grew up around the furnace, but once the furnace was blown out in 1904, the population gradually drifted away.Early HistoryThe history of Nova Scotia&apos;s iron industry began in 1604 when Samuel Champlain became the first European to identify iron ore in the future province. Despite this early acknowledgment, iron was not smelted commercially in Nova Scotia for another two hundred years. Although primitive smelters of the period produced more iron than could be used locally, early settlers depended on imports of iron from Britain and the United States."

Jan 1, 1983

By John Crusius

? 3-year research program overview ? initial results- MainZone pit Waterline pit ? questions raised ? increasingly common in western N. America ? frequently low-pH waters with elevated concentrations of many metals ? water quality controls poorly understood ? some in U.S. are Superfund sites

May 1, 2002

By A. P. Page, G. E. Alexander, L. L. Sirois, A. A. Winer

A knowledge of the electrical surface characteristics of minerals is all-important in the choice of treatments to up-grade and beneficiate them. At their solid-liquid contacts, there are transfers of ionic species, which for insoluble oxide minerals are the H+ and OH-ions. The adsorption density of these ions can be detected by carrying out potentiometric titrations, and this paper describes the automation of such an apparatus. The details are discussed fully and the validity of the method is demonstrated by flotation tests.

Jan 1, 1969

By D. Bernard

Over the last decades, the wrought aluminum casting industry has made significant progress with regards to process consistency by the introduction of new technologies in the field of liquid metal processing and casting. These technologies, combined with the application of best practices, have led to increases in productivity as well as better process performances and product quality. The competition in the addedvalue aluminum products (by opposition to P1020 production) is, however, very strong and involves players that did not hold a major role five years ago but who are now exerting a strong competitive pressure on our industry even sometimes from far abroad. There are still technical and technological challenges remaining in the different areas of aluminum casting production, amongst which metal pre-treatment, furnace operations, in-line treatment and casting hold a predominant influence. The comprehension of the contribution of each individual process step to the entire process chain is a key element and must be considered in future process optimisations. This paper presents the technological position of the casting industry and tries to highlight areas where further progress can be made.

Jan 1, 2006

By H. C. L. Reemeyer

One of the fundamental trade-offs for copper concentrators is between grinding circuit product size and copper recovery. The capital and operating cost savings and throughput increases for a coarser grind should be evaluated against potential recovery reductions. Other benefits of coarser grinds, such as GHG emissions reductions and favourable effects on tailings and water management should also be considered. This paper assesses the formation of laboratory and pilot test programs, design of process flowsheets, equipment selection, and evaluation methods to determine the most appropriate and economical grind size for a given deposit. The paper will include an evaluation of case studies. INTRODUCTION The majority of the world’s mined copper comes from sulphide deposits, which are mostly processed using crushing, grinding, flotation and dewatering flowsheets to produce copper-bearing concentrates for smelting. Ores must be ground to a sufficiently fine size to achieve an acceptable level of liberation to allow both high recovery of copper and valuable by-product minerals while efficiently rejecting gangue to tailings. Therefore, a key design parameter in process plant design is the grind size of the flotation feed. Copper concentrators use a variety of grind size targets that depend on various factors, including ore mineralogy and the grain sizes of valuable and gangue minerals; the sensitivity of valuable mineral recoveries in the rougher flotation stages to grind size, ore hardness; electricity costs; and mining vs. processing throughput constraints. Typically, copper and by-product recovery increase as grind size is reduced, which can improve revenue, but finer grinds increase power and grinding media operating costs and may have implications for tailings management. This paper explores the trade-offs that should be assessed in determining the optimum grind size, and to answer the question if coarser grinds are worthwhile. METALLURGICAL AND FLOWSHEET FACTORS Recovery-by-size behaviour of sulphide-bearing particles In base metals sulphide flotation, it is typical that flotation recoveries vary by particle size. Metal sulphide particles rendered hydrophobic by collector in intermediate size ranges (e.g. 10 to 100 um) usually show very high recoveries, often approaching 100%. Recovery usually falls away in finer size fractions (<10 um) as fine particles have little inertia and can move around bubbles without colliding and attaching to them. Coarser particles (>100 um) are susceptible to particle-bubble detachment and dropback (Jameson, 2019).

Jan 1, 2019

By T. Mulpeter, G. Deschênes

Sadiola Gold Mine is an open pit operation located in Mali and owned by Anglogold Ashanti Ltd, Iamgold Corporation and the State of Mali. A conventional cyanidation process (cyanidation/CIP) treats 15,000 tpd (of a mixture of oxide and sulphide ores) at an average grade of 3 g/t Au. In 2002, the increasing tonnage of sulphides caused an increase in production costs and a decrease in gold extraction (from 95% to 70-76%). Because of the short retention time of the leach circuit (18 hours) and the refractory nature of the sulphides, gold leaching kinetics are critical. A laboratory investigation was initiated to evaluate actual plant practice and identify a means of improving the gold leaching rate. The study was conducted on a "soft" sulphide gold sample containing 4.96 g/t Au, 0.4 g/t Ag, 2.5% pyrite, 1.2% arsenopyrite, and 0.2% pyrrhotite with a P80 of 74microns. Pre-leaching significantly influenced the gold leaching rate. A short pre-leach (2 hours) performed at pH 8, a DO of 8 ppm, and with 300 g/t lead nitrate added at the start or the end, produced the preferred conditions. Pre-leaching for more than 2 hours was detrimental to gold extraction. The cyanide concentration had to be maintained at 450 ppm NaCN to reach a maximum gold extraction within the retention time of the circuit. A maximum extraction of 81.3% Au was obtained in 20 hours (leach residue at 0.97 g/t Au). A high level of dissolved oxygen in the pre-leach was not of any benefit. Extension of gold leaching beyond 20 hours indicated that all leachable gold had been extracted by that time. Plant modifications were made to allow leaching of oxides and sulphides in separate circuits. Treatment of oxide ores is now performed at a higher rate. Sulphides are processed at a lower throughput, with 300 g/t lead nitrate, to allow a retention time of 22 hours. Combined throughput remains the same, and total gold recovery has increased from 76% to 80% for an additional gold production of 16,000 ounces per year.

Jan 1, 2005