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By G. J. Heferen, A. Pranowo, N. J. Aslin, P. O. Eriksson

Glencore Technology (GT) has over four decades experience supplying stainless steel cathode plates (“cathode plates”) to the electro-refining and electro-winning industry. Cathode plates are typically the single biggest capital investment in a refinery. Refineries may view cathode plates as fixed asset or consumables depending on their operational characteristics. This paper examines the issue of cathode plate life and the strategies and philosophies used by different plants in the management of their cathode plate asset. Some plants operate with their original plates after more than 20 years. Others accept high turnover and regular maintenance as normal operating practice. Reference data are provided on plate life for various operating plants including benchmark plants achieving best-practice plate life and operating cost. The role of the electrode handling equipment on cathode plate longevity is also examined, including latest developments in Cathode Stripping Machine, robotic copper stripping, and full-automation production cranes. The ability to identify and manage the population of plates in service is also critical for maximising plate life and minimising its overall operating cost. This paper discusses a novel and unique RFID system for tracking and managing cathode plate inventory. INTRODUCTION Permanent cathode plates The adoption of permanent stainless steel cathode electrodes in the electro-refining of copper was the most significant process development since the first commercial electro-refineries were built in the late 19th century. It provided significant improvement over the labour intensive and complicated starter sheet system. Copper grows over the permanent cathode blade for a number of days before being stripped, and the permanent cathode can be returned straight back to cells for the next cathode cycle. Glencore Technology (formerly Mount Isa Mines (MIM), then Xstrata Technology) has been manufacturing permanent stainless steel cathode plates from the late 1970s with the birth of ISA PROCESS™, and the Kidd process that came one decade later. Invented and commercialised by Mount Isa Mines, the ISA PROCESS™ was first implemented into Copper Refineries Limited (CRL), Townsville, in 1978. The KIDD PROCESS by Falconbridge evolved in the 1980s and was first implemented into the Kidd Creek Tankhouse, both operations converting from traditional copper starter sheets.

Jan 1, 2019

By Washington Luiz Mafra

Every year the conventional direct reduction processes ? Midrex and HYL III ? increased their market share in the world steel production, even though they are only economically feasible in countries where natural gas is available at competitive prices. In this context, the new Midrex projects are based on large reactors (Megamod - 1.5 to 1.8 Mt/y of DRI), reduction temperatures of the metallic burden up to 850oC, with bustle gas temperatures between 960oC e 1050oC. Thus, the requirements of metallic burden performance, as well as the evaluating methods, usually based on ISO standards, need to be reviewed. It is well known that the standards usually applied to quality evaluation do not reflect the performance of metallic burden inside the reactors. This paper describes the different methods of evaluating the disintegration under reduction of DR pellets based on ISO 11257 standard. This is the most important method used by pellet producers and customers for evaluating DR feedstocks. The different methodologies tested to evaluate the disintegration under reduction had varying results, evidencing the relevance of the method and the quality of the pellet. Nevertheless, validating the method in an industrial reactor is still fundamental.

May 1, 2007

By Boyd Davis, Brook Zaback

"Among the first published papers from Prof. Torstein Utigard was work on imaging the aluminum electrolysis process and in-situ measurements of aluminum in cryolite melts. He and Prof. Jim Toguri used an x-ray radiographic technique to measure interfacial tension of aluminum drops. Publications using this equipment for aluminum electrolysis spanned from 1985 to 2006. As well, other methods were used to better understand electrolysis in molten salts, including hot-stage microscopy, direct observations from above the bath and water modeling techniques. For chloride systems (for magnesium and lithium), it is possible to see side-on the electrolysis using a quartz cell. In honour of Prof. Utigard’s contribution to this field, this paper presents a summary of work on visualization of molten salt electrolysis, including work done at the authors’ labs and others around the world. The paper will summarize key findings and their possible impact on molten salt electrolysis."

Jan 1, 2015

By John J. Jonas, Hong Qin

Cylindrical samples of pure titanium were subjected to uniaxial compression at room temperature, leading to the formation of three generations of twins. Many primary contraction twins were observed as the initial texture was favourable for their formation. Numerous secondary extension twins formed within the primary contraction twins and some tertiary contraction twins within the secondary extension twins. The orientations of these three generations of twins were determined by electron backscatter diffraction techniques and their associated Schmid factors (SFs) were calculated. The formation of the twin variants selected in each generation and the absence of certain potential variants are accounted for by rotating the twinning displacement gradient tensor expressed in the twin system reference frame into the crystallographic reference frame of the relevant neighbouring grain. The presence of the observed primary, secondary and tertiary twins is explained in terms of the ease of imposing the required accommodation strains on the neighbouring grains. By contrast, certain first, second and third generation potential high SF twins were absent because their formation would have required accommodation by the most difficult deformation mode: pyramidal glide.

Jan 1, 2015

By Alessandro Navarra, Roberto Parra, Boyd Davis, Frank Mucciardi

A smelter scheduling algorithm has been developed, which allocates the oxygen production between the smelting furnace and the converter aisle, so as to maximize copper throughput. The algorithm is intended for daily operation planning, controlling the sequencing of the converter cycles, and the oxygen drawn by these cycles. In some cases, it may be worthwhile to decrease converter oxygen allocation in favour of the smelting furnaces. Thus, a better utilization of the oxygen plant can increase primary copper throughput by several percentage points. This principle is demonstrated through sample computations. The approach presented in this paper can be incorporated into smelter management software.

Jan 1, 2015

By M. L. F. Paullo, S. Cristian Mejia, D. Roehl

"Rock fracture simulation most often presents non-linear behaviour due to loss of material integrity and strain concentration in the fracture zone. These strains generate local instabilities that propagate to the global system of equilibrium equations, generating convergence problems of the numerical solution. Often, in such cases, analyses in the post-critical regime are unfeasible. To overcome the numerical difficulties associated with problems of stiffness loss in the post-critical regime control methods, also called continuation methods, are employed. Among them are the arc-length method, the energy control method and the indirect displacement control method. These methods are employed in conjunction with a Newton- Raphson scheme for the solution of non-linear systems of equations. However, depending on the system instability, convergence in not guaranteed even with very small increments. In the present work these control techniques are investigated in combination with cohesive elements to simulate rock fracture. The constitutive model employed with the cohesive elements represents stiffness degradation through a damage law, which leads to serious convergence difficulties as reported in the literature. Here the continuation methods mentioned are applied to a Mode I rock fracture problem and to hydraulic fracture simulations. The effectiveness of the different continuation methods is compared.INTRODUCTIONThe process of rock fracture induced by the fluid pressure is called hydraulic fracturing. The propagation of a hydraulic fracture is a complex process, which is basically defined by the mechanical deformation of the rock, the fluid flow within the fracture and the fracture propagation itself (Mokryakov, 2011). In the works of Bendezu et al. (2013), Chen (2012) and Carrier et al. (2012), vertical hydraulic fracture propagation is modeled by cohesive elements with traction-separation law. The softening behavior of rock in post-critical regime is demonstrated by experimental testing and is characterized mainly by high strains and low stresses (Crowder and Bawden, 2004). This nonlinear behaviour can arise due to material nonlinearity, such as micro-cracking and damage, leading to softening behaviour (Chandrakant, S.D., 2012). The cohesive fracture model considers in its formulation the softening behaviour that most rocks present in post-critical regime with propagation criteria."

Jan 1, 2015

By J. C. Gilbert

"IntroductionTHE PURPOSE of this paper is to discuss in a general way the heavy oil situation in Western Canada, and particularly to acquaint those in the oil industry who have not participated in the heavy oil end of the business with past and current developments. The author has covered •briefly the location of the heavy •and asphalt-base oil fields, their geology, current drilling and production practice, the location of the •refineries capable of handling heavy crude, their products and markets, and the problems and future prospects of the industry.Location and Description of FieldsThe term heavy oil is generally used to denote crude of 20.9° gravity and under. Since the products from heavy oil are also to a lesser extent obtained from asphalt-base crudes of higher gravity, some mention will be made here of the latter; but in general the emphasis of the paper is on heavy oil as such.In the order of their production to date, the heavy oil fields and those light oil fields which produce asphalt-base crudes are : Lloydminster, Taber, Vermilion, Conrad, Princess, and Wainwright.The Lloydminster oil field has not only produced most of the heavy oil, but also is currently the largest producer, supplying at the present time about 80 per cent of the heavy and asphalt-base crudes produced in Western Canada."

Jan 1, 1952

By A. S. Dawson

Introduction The purpose of this paper is to discuss, in a general way, the application of geological principles in the exploration for, and development of, deposits of industrial minerals. Mention of geological factors pertaining co specific minerals will be by way of illustration only. Since many prospectors are little acquainted with the geological setting and mode of occurrence of deposits of these minerals, some prospecting possibilities in the field will be pointed out. Geology is a tried and proven tool in the search for and exploitation of metalliferous deposits and of oil and gas fields, but, so far at least as Canada is concerned, only very rarely has a directed, intensive search been made for deposits of industrial minerals. Examples might be cited, however, where, in other countries, such investigations have yielded rich rewards. Thus, development of the vitally important potash deposits of New Mexico was the result of a deliberately planned programme of geological investigation, first by United States Government agencies, and later by private interests. War or the threat of war, or peace-time industrial expansion, can render concentrated exploration for specific minerals desirable or even essential. Such exploration is, primarily, a geological problem. Admittedly, there is in general less scope for the application of geology in the search for, and development of, deposits of industrial minerals than of metalliferous minerals, oil, etc. Where the latter are concerned; the objective of exploration is to find a material that is valuable, within broad limits, no matter where it is located or how it occurs. The unit value of the material is limited only by the amount of the valuable constituent in the formation- its possible upper limit is tremendously high. On the other hand, many industrial minerals constitute in themselves 90 per cent or more of the formation- their amount cannot increase and their unit value is commonly low. Moreover, for commercial exploitation, the deposit must, in general, be reasonably close to markets or to plant or other facilities for processing the raw material, since, owing to its low value, this cannot be transported any great distance. As a consequence, intensive geological search for and investigation of such deposits has been restricted to industrialized areas. Obviously, however, it is good insurance for any operator to understand the geological background of his deposit, particularly in the case of new developments.

Jan 1, 1949

By B. Tonn, F. Kröger

"The continued development in engine technology is leading to an augmentation in power density which steadily elevates the requirements for thermally and thermo-mechanically highly loaded components such as cylinder heads and pistons. Due to these high performance requirements conventionally applied Al-Si alloys have reached their application limits, since their mechanical properties deteriorate quickly under the influence of heat. Improved applicability is given by Al-Cu-based casting alloys which have a superior high-temperature strength than Al-Si alloys. Since Al-Cu alloys exhibit insufficient casting characteristics, especially regarding hot tearing susceptibility and increased tendency for porosity, it is currently not possible to cast geometrically complex components in robust permanent mold casting processes. The further development of Al-Cu alloys is aimed at finding an optimum between improved castability while high-temperature strength and thermal conductivity are not deteriorated. It is known that a high amount of eutectic reduces the hot tearing susceptibility of an alloy, but it reduces thermal conductivity at the same time. In this paper it will be presented how the conflicting objectives – improved high-temperature strength, good thermal conductivity and reduced hot tearing susceptibility – can be brought together to develop an optimized Al-Cu alloy for application in permanent mold casting.INTRODUCTION At the beginning of the 21st century car, engine blocks were primarily made of gray cast iron (GJL). Less than half a decade later, the choice of material had shifted towards lightweight materials. Ever since, the car engine manufacturing is dominated by aluminum-based alloys. The weight of car engine blocks could thus be reduced by around 50% due to the lower specific weight of aluminum alloys compared to gray cast iron. Furthermore, the high thermal conductivity of aluminum alloys allowed a reduction of complex cooling channel systems and thereby promoted the advancement of this material group. The further development in engine technology leads to an augmentation in power density which elevates the requirements for thermally and thermo-mechanically highly loaded components. For example, in diesel-powered car engines the upper required limits can reach an ignition pressure as high as 230 bar and gas temperatures of up to 1000°C. Thereby, thermal loads can cause high alternating thermal stresses (Grzincic, 2003) which can effectively be reduced by providing high thermal conductivity."

Jan 1, 2017

By S. Esfahani, M. Barati, Y. Kauwachi

"Heat recovery from slag has gained attention due to its high potential in lowering energy intensity of metal extraction processes. A direct method to recover the thermal energy of slag is to use countercurrent air flow that extracts the heat from falling droplets. Often, the solidified slag is aimed to be used as a substitute for Portland cement, thus high cooling rates are required to form an amorphous slag with sufficiently strong hydaulicity. Rapid cooling however involves using large gas flow rates that in turn lower the thermal efficiency of the process. This article presents a mathematical model that was developed to determine the optimum conditions in the heat recovery process and to investigate the effect of the air flow and granule diameter on the cooling rate of the droplets as well as the thermal efficiency of the heat recovery system. INTRODUCTIONMetallurgical slags are the largest by-product of high temperature materials refining and extraction processes. The total amount of metallurgical slag produced in the year 2008 has been estimated at up to 422 million tonnes containing up to 222 TWh/y (Barati and Esfahani, 2011) of thermal energy. Over the past four decades attempts have been made to recover this substantial amount of energy as heat, electricity, or fuel, while none of the proposed method has been commercialized yet.During slow cooling the slag tends to crystallize the constituents (CaO, SiO2, Al2O3, etc.) into a hard, heavy solid. In the past, over 90% (Bengt, 1983) of the molten waste was discharged onto heaps and allowed to cool slowly, then crushed and used in road construction or land filling or as coarse aggregate for concrete. However, later it was found if cooled rapidly, the slag can be used as a substitute for Portland cement. As a result, processes such as wet granulation were created in which molten slag is fragmented with water, forming amorphous (glassy) phases. Despite its effectiveness in producing a suitable material, heat would not be recovered through this process. Thus, dry granulation was introduced in 1930’s and was developed further in 1970 – 1980’s."

Jan 1, 2012

By K. S. Raja, B. McNall, B. Pesic

"High-level radioactive wastes are stored in large underground storage tanks made of low-carbon steel. The wastes consist of concentrated solutions of sodium nitrate (NaNO3) and sodium hydroxide (NaOH), and the radionuclides 137Cs, 99Tc, and 90Sr. The corroding steel microenvironment may produce localized reducing or oxidizing conditions that affect the solubilities of the species such as Tc(VII) and Tc(IV), which in turn modifies the kinetics of corrosion of the storage tank. To understand the influence of technetate ions on the corrosion of steel, electrochemical polarization studies of A 537 steel samples were carried out in 1 M NaNO3 + 0 .05 M S r(NO3)2 + 0.1 M NaOH with and without addition of HReO4 at different temperatures (24 – 85 °C). The concentration of HReO4 was varied from 0.014 – 0.04 M.INTRODUCTIONAqueous processing of spent nuclear materials generates a large amount of high-level radioactive wastes. The wastes are primarily salt solutions of sodium hydroxide and sodium nitrate which also contain fission products such as 137Cs, 99Tc, and 90Sr. Among the high level radioactive fission products, Tc-99 is of great importance because of its high concentration, long half-life (2.1 x 105 years), high solubility in geologic waters as technetate, and rapid diffusivity through the geologic systems. The solubility of technetate ions varies depending on the oxidizing conditions prevailing in the storage containers. High level radioactive wastes are stored in single shell or double shell tanks made of low carbon steels such as ASTM type A15, A516-70 and A537. Most of the available literature on corrosion of steel in simulated radio active waste environments pertains to nitrate induced stress corrosion cracking (Subramanian & Mickalonis, 2005). The corroding steel microenvironment may produce localized reducing or oxidizing conditions that affect the solubilities of the species such as Tc(VII) and Tc(IV). Corrosion of steel and formation of Fe(II) and Fe(III) will affect adsorption and reduction of Tc species. The radioactive species can irreversibly be sorbed on the steel surface by oxidation of Fe(II) to more stable Fe(III) and fixed as less soluble Tc(IV)/Fe(III). The solubility of Tc species is also affected by other factors such as dissolved oxygen, local pH, temperature etc. How the corrosion behavior of steel will be affected in the presence of Tc species is not clearly understood.Cartledge (Cartledge, 1960) demonstrated that passivation of iron can be achieved in the presence of oxygen along with suitable inhibitor ions/molecules of the general formula XO4 n-, such as pertechnetate (TcO4 -). The pertechnetate ion is univalent. Since it is derived from a strong acid, no buffering action can be expected from this ion. The redox potential of the reaction (1) is 0.738 VSHE (Pourbaix, 1974)."

Jan 1, 2012

By Leonard L. Fischman

It is important to define "adequacy," and the most useful definition is a continuing availability of mineral materials under cost and other conditions which imply no significant burden on the achievement of otherwise attainable levels of consumption and well-being. For current decision making, it is sufficient to consider adequacy just to the end of the century, with some regard being given to then remaining mineral inventory. A comparison of cumulative demand projections to the year 2000 with already identified reserves ( economically recoverable amounts in known deposits) suggests little reason for concern with world adequacy of iron ore, aluminum, manganese, chromium or potash. Conservative estimates of "prospective" reserves (amounts producible at today's prices, but yet to be discovered) suggests that there are ample quantities of virtually all other mineral resources as well. A probable exception is oil and gas, of which there may be scant amounts remaining after the turn of the century. However, there is an evident sufficiency of substitute forms of energy, though it is difficult to see just where developing technology will take us. The critical questions have to do with the increasing dependence of the industrialized countries on external sources of supply , coupled with a new international politic s which complicates the problem of insuring timely development of, and access to, remaining deposits. In this context, Canada, a still mineral-rich nation, is in one of the more favorable positions.

Jan 1, 1977

By R. Drozd

"The Bui/moose Mine is in the northeast coal area of British Columbia, and less than $300 million was spent to bring this 2.3 million-tonnes-per-year metallurgical and thermal coal mine into production by November 1, 1983, one month ahead of schedule. The project is an unincorporated joint venture undertaking, with Teck-Bullmoose Coal Inc., a wholly-owned subsidiary of Teck Corporation, holding 51%, Lornex Mining Corporation holding 39%, and Nissho-lwai (Canada) Ltd. holding 10%. Bullmoose Operating Corporation will be the manager and operator of the project. This paper will broadly cover the history and exploration work on the property, the geology, open-pit mining plans and equipment, the preparation plant flowsheet from breaker station to clean coal silo, the 35 km highway truck haul, the railroad loadout system, manpower requirements, approvals and permits, and general financial arrangements. Introduction The Bullmoose Mine Project is located about 87 km by road south of Chetwynd, B.C. and consists of an open-pit coal mine, a plant facility in the Bullmoose Creek valley below the mine, and a separate rail loadout facility on the British Columbia Railway Branchline near the new town of Tumbler Ridge some 35 km by road to the east. The plant will be capable of producing a total of 2.3 million tonnes per year (mty) of washed metallurgical and thermal coal. Long-term metallurgical coal contracts for high-quality, medium-volatile, bituminous coal have been signed with nine Japanese buyers for 1.7 mty, and the balance of0.6 mty will be for thermal coal production. Plant construction began in the spring of 1982, and in May 1983, preproduction waste and overburden removal in the mine was started. The plant began tuning up in October and was fully operational by December 1983. Metallurgical coal began moving to the coast in unit trains during November, and first vessel loading at the Ridley Island port began in late December 1983."

Jan 1, 1985

By Hugh M. Roberts

DEVELOPMENT at Steep Rock lake has given rise to renewed interest in the geology of the iron ore deposits in the Lake Superior Region and has implications of no small moment bearing upon methods of exploration in the Precambrian Shield generally. Following upon the Regional Lake Superior meeting of the American Institute of Mining and Metallurgical Engineers in August, 1941, the authors prepared a paper on the Steep Rock deposits, which appeared in the A.I.M.E. publication, Mining Technology, for January, 1943. Between Januar7 and April, 1943, exploration at Steep Rock was continued by means o vertical, Mesabi-type churn-drill holes put down from the ice. This drilling has enlarged the tonnage of ore previously known and has disclosed further facts relating to the origin of the ore. The added evidence, we believe, goes to support the hypothesis that the deposits were formed by a process of replacement due to upward-moving, iron-bearing solutions which came in as igneous after-effects. Accordingly, in presenting the subject to the Canadian Institute of Mining and Metallurgy, it seems best not to change our first explanation, but to prefix the original paper with an interpretation of the results of the more recent explorations completed after its publication.

Jan 1, 1943

By C. T. Harper, B. J. Fryer, R. P. Taylor

"IntroductionThe Maurice Bay deposit is one of a number of uranium deposits that have been found in recent years in the Athabasca Basin of northern Saskatchewan (Tremblay, 1982). This deposit, along with the others, belongs to the unconformity type deposits (Beck, 1977). They are, for the most part, polymetallic, being characterized by a suite of metals which include U, Ni, Co, Cu, Pb, Zn, Mn, V, Ag, Au, Pt-group elements, S, As, Bi, Se, Te, and Mo, some of which, besides U, are present in economic concentrations (Amok, 1974; Ruzicka, 1975; Tapaninen, 1976; Hoeve and Sibbald, 1978; Dahlkamp, 1978). The Maurice Bay deposit was known to be a small low grade deposit in which the ore was essentially monomineralic, consisting mainly of pitchblende (Harper, 1978). However, the occurrence of trace amounts of some of the elements common in the larger polymetallic ore bodies (e.g. Key Lake, Cluff Lake D) was anticipated. Thus a lithogeochemical sampling project was undertaken in 1979 across part of the Maurice Bay deposit (Harper, 1979). Major oxides (SiO2, Al2O3, FeO, Fe2O, MgO, CaO, K2O, Na2O, MnO, P2O5, and TiO2) and a group of the most common trace metals (U, Ni, Co, Cu, Pb, As, Au, V, and Se) were analyzed to determine whether any elemental patterns (halos or depletions) could be detected which would reduce the number of pathfinder elements needed for exploration purposes. In addition to the above metals, Th was also checked because some conglomerate strata in the Maurice Bay area are known to be thorium-enriched (Harper, 1978). Only the trace metal distributions will be discussed in detail in this report.General GeologyThe Maurice Bay area is underlain by three major groups of rocks, the White Lake metamorphic complex, an unnamed granodiorite complex, and the Athabasca Group, described previously (Fig. 1; Harper, 1979). Table 1 summarizes the stratigraphic features as deduced by geological mapping and the examination of drill cores."

Jan 1, 1986

By Han Xing, Cui Jianzhong, Qin Ke, Shao Bo, Zhang Haitao

In this paper, a new approach that uses hot-top DC casting process to producing multi-alloy ingots is present. The different type and size of composite and coated ingots (4045/3004/4045 three-layer composite ingots with section 630mm by 1500mm and 4045/3003 coasted ingot with F140mm/F110mm in diameter) are cast by this approach. The macro-morphologies and microstructures of the composite ingots, the temperature distribution and the element distribution in the interface zone were investigated, also and the interface bonding strength was measured. Results show that the solid supporting layer formed on the cooling plates plays a key role in the casting process of composite ingots. The solid supporting layer can prevent the blending of two melts by resisting the impact of alloy melt, which ensures the stable casting process and casting high quality composite ingots, because the contact height is increased using hot-top DC casting. In addition, fabrication and properties of 4045/3004/4045 three-layer composite ingots with section 630mm by 1500mm are reported in detail.

Jan 1, 2015

By W C. Shakespeare

The Ontario Committee on Taxation is making a comprehensive study of taxation in the Province of Ontario, and in this connection has received representations concerning mining taxation from a number of interested parties. Some of the more important recommendations on mining taxation are reviewed in this article. Introduction FOLLOWING the appointment of the Federal Royal Commission on Taxation, the Ontario Government, effective in November, 1962, appointed the Ontario Committee on Taxation to review taxes and revenues available to the Province of Ontario and its local governments, to co-operate with the Royal Commission on Taxation and with any other bodies of enquiry appointed by other provincial governments, and to make such recommendations as it sees fit to the Prime Minister of Ontario and the Executive Council. The members of the Committee are: MR. L. J. SMITH, F.C.A., Toronto, (Chairman) MR. ERIC HARDY, Toronto DR. R. CRAIG MCIVOR, F.R.S.C., Hamilton MR. CARL A. POLLOCK, Kitchener MR. R. BREDIN STAPELLS, Q.C., and Toronto. Like its Federal counterpart, the Royal Commission on Taxation, the Ontario Committee has held public hearings, has received written

Jan 1, 1965

By Jack Craft

Local Environment Atmospheric conditions (or lack thereof) Drilling fluids are impractical Cuttings removal is a major concern Heat dissipation is a major concern Some tried-and-true mechanisms need air to function properly Gravity Low gravity means low downforce Microgravity means even less downforce Regolith Local dust may be highly abrasive Packaging for Spaceflight System mass is highly constrained The drill must fit within the spacecraft?s launch envelope Power is constrained

May 1, 2013

By T. Kerr, C. Mattich, J. Wilson

"In refractory gold concentrates, gold is occluded in sulphide minerals preventing efficient cyanide leaching. Hence, roasting is used to oxidize sulphur and organic carbon, the latter being necessary to minimize recovery loss through the preg-robbing effect. In 2009, Outotec commissioned the circulating fluidized bed roaster at Syama gold mine in Mali. Since 2013 Resolute and Outotec have been implementing improvements to the roaster performance with the capacity increasing from 8000 t/month in 2013 to above 13,000 t/month in 2016, while achieving a residual sulphide sulphur and organic carbon contents of below 0.1 wt.% and 0.4 wt.%, respectively. Thus a gold recovery in the CIL of above 90% is attained. In 2016, Outotec audited the Syama roaster. The analysis resulted in the Low Carbon Roaster (LCR) upgrade concept which (i) allows re-processing of calcine dust from the spray cooler and ESP after pelletization and (ii) allows the roasting of a further fine-organic carbon rich feed, i.e. de-slime circuit tailings. The LCR upgrade aims to reduce organic carbon to <0.2 wt.% and increase roaster-leaching gold recovery by >3%. Project development included extensive testwork. The LCR process is expected to become operational during FY 2019.INTRODUCTION Double refractory sulphide ores exhibit the characteristics of gold locked within pyrite grains, in the presence of preg-robbing natural (organic) carbon. Hence, to achieve high recovery during subsequent processing steps, i.e. cyanide leaching, oxidation of sulphide sulphur is required, producing a porous calcine by way of a roasting step. This allows for the gold contained within the pyrite grains to be accessible during cyanide leaching. Furthermore, it is necessary to oxidize the organic carbon. Oxidizing the organic carbon is essential as gold recovery loss occurs as a result of gold-cyanide complexes being adsorbed on organic carbon, this phenomenon is termed as preg-robbing (Miller et al., 2016). The gold absorbed on the organic carbon is lost, reporting to the tailings stream. Hence, the aforementioned oxidation of sulphide sulphur and organic carbon is the process goal. Nonetheless, the latter must occur at a controlled temperature which is concentrate/ ore specific, since the pores of the produced calcine should not sinter, as this makes the gold contained in the calcine less accessible during leaching, leading to gold recovery loss. The tight temperature control requirement is a decisive factor in the choice of a Circulating Fluidized Bed (CFB) as the roasting reactor, due to the excellent mixing characteristics of the CFB which results in temperature homogeneity of (+/-10°C). Roasting of double refractory ores, as described above, can be included in the flowsheet after comminution and grinding, a process termed as whole ore roasting, or by including a flotation circuit termed as concentrate roasting. Roasting the flotation concentrate results in less solid flow, increased sulphide sulphur grade and organic carbon content resulting in a higher heating value and higher gold content. A typical composition of the Syama ore and concentrate is given in Table 1. Ore average values presented correspond to the period 2015, while concentrate values are typical for the flotation performance throughout the period 2012–2015."

Jan 1, 2017

By R. Elliott, C. A. Pickles, J. Peacey

As the nickel sulfide ore deposits become decreasingly viable as a source of nickel metal, increasing attention is being paid to the exploitation of the nickeliferous laterite ores. Attempts to produce a high grade ferronickel concentrate from these ores by pyrometallurgical methods face several challenges, in particular the selective recovery of the highly disseminated nickel from the reduced ore. The current work explores strategies for maximizing the size of ferronickel particles formed in order to improve the selective recovery of the ferronickel by magnetic separation. The effect of various coal, elemental sulphur, pyrite and sodium sulphate additions on ferronickel particle formation and size at 1000°C have been investigated. It has been observed that increased coal additions leads to a moderate improvement in the size of the ferronickel particles, while the presence of any sulphur bearing reagent leads to a significant increase in particle size. The retention of sulphur in the reduced material has also been studied, showing sodium sulphate has the highest retention, followed by pyrite and then elemental sulphur. An inverse trend was observed in the efficiency of sulphur retention on the basis of residual mass of sulphur per unit mass of reagent added.

Jan 1, 2015