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By Eduardo Macedo Junior

O presente trabalho descreve o desenvolvimento de uma nova especificação para a Linha de zincagem numero 3 (LZC#3) da Companhia siderúrgica nacional (CSN), de grande demanda e aceitação, alta produtividade e foco nos requisitos do cliente que tangem qualidade superficial e características metalúrgicas (resistência mecânica) em aços para atendimento do mercado Norte-americano. Este novo produto tem como característica o ciclo de recozimento com velocidade alta para obtenção de microestrutura 100% encruada na saída do equipamento e limites de escoamento e resistência acima de 500 MPa. A combinação dessas características do produto junto com as características do processo tornou a especificação “ASTM-A653MSS80CL1” um grande desafio para garantir qualidade superficial sem comprometer as propriedades mecânicas especificadas assim como a integridade do equipamento. O baixo custo de produção associado a alta produtividade desse produto fazem da especificação “ASTM-A653M-SS80CL1” um produto de extrema importância para a estratégia adotada pela CSN, mantendo dessa maneira sua competitividade no mercado Norte-americano e garantindo capacidade máxima de produção do seu equipamento em tempos de retração do mercado interno.

Aug 17, 2017

By S. G. Dixit, A. K. Biswas

The flotation and adsorption behavior of ilmenite, monazite and zircon have been studied with sodium oleate as the collector and pH as the principal variable. The maxima in the flotation and adsorption properties of any of the above minerals fall within similar pH ranges. The bell shaped pH versus adsorption magnitude (r) curve is explained on the basis of collector concentration (Co and the concentration of hydroxyl ion (COH-) acting as the depressant. An equation of the type: 1 =KiCor~K2 Coh-/Coi-is proposed to account for the experimental data. The beach sand deposits along the sea coast in Southern India contain ilmenite, monazite, zircon, rutile and sillimanite as valuable minerals while quartz, garnet, shells and traces of hornblende form the gangue. A typical composition of the deposits is reported to be as follows:' Ilmenite 75%, Zircon 4-6%, Rutile 3-4%, Monazite 2 - 4%, Garnet 2 - 5% and the rest 8 -10%. Selective flotation of beach sand constituents has been reported by many workers.2-4 The fatty acid soaps have been invariably used as collectors. It is seen that all the valuable constituents of the beach sand are efficiently floated by soap collectors such as sodium oleate. In order to selectively float the beach sand constituents, it is necessary to use some depressants such as sodium silicate.3 The physicochemical parameters that govern the flotation of these minerals are yet to be studied in detail. In the present article, the findings on the parallel studies on the flotation and adsorption of the systems — ilmenite-sodium oleate, monazite-sodium oleate and zircon-sodium oleate — are being reported. In these correlative studies on adsorption and flotation of beach sand minerals, ilmenite (FeTiO3), monazite (Ce, Dy, Nd) PO4 and zircon (ZrSiO,) have been selected because they represent three important

Jan 1, 1970

By Belisario Pérez

Con el objetivo de lograr cero accidentes en las empresas minero-metalúrgicas de la división minera Breca, se fortaleció la gestión de incidentes mediante la incorporación de los eventos de alto potencial (EAP). En el periodo del 2012-2018, en gran medida gracias a la gestión de los EAP, se logró una reducción del 91% del índice de frecuencia de accidentes incapacitantes y del 100% en el número de accidentes fatales. El presente trabajo detalla dicho modelo de gestión, que puede servir para mejorar el desempeño de seguridad de otras empresas minero-metalúrgicas en el país, contribuir a la reducción de accidentes en el sector y lograr así el objetivo de cero accidentes.

Sep 20, 2019

By Michael C. Newbury

For thousands of years gold has been not only a commodity, valued for its comparative scarceness, immutability and homogeneity but also a medium of exchange which has no nationality. Approximately 90% of the gold produced is still accessible in the world, although some of it in museums, galleries, jewellery and dental work is not immediately available for circulation. The majority is held as bars by central banks for their reserves; the balance circulates as coinage or bullion held for investment. The value is further enhanced by the political aspect that gold cannot be debased as paper currency can and, therefore, it always becomes an investment refuge. It has always been possible to buy and sell gold at a price which is readily established by reference to bullion's weight and purity; and it is this fact which makes a loan denominated in gold, rather than one in currency, a viable alternative means of finance. The purpose of this paper is to discuss some general aspects of what is considered to be one of the more effective and presently popular methods of financing the development of a gold mine - the gold loan. This is not intended to discuss all the minute details which must be uniquely designed to fit each individual situation, but rather to provide general guidelines. You will all be aware of the traditional sequence whereby companies primarily finance exploration work by the raising of equity through the sale of shares to the public or by that unique Canadian form.

Jan 1, 1987

Recovery of Rhenium from Mineral Raw Materials of Kazakhstan

Sep 13, 2010

By Tiago Ramos Ribeiro

A redução do ferro é a etapa da produção de aço que mais consome energia e emite CO2. Os processos de redução direta são uma alternativa ao tradicional alto forno devido ao uso de H2 no gás de redução e consequente menor emissão de CO2. Existem duas tecnologias principais, Midrex e Energiron (ou Hyl) que representam 80% da produção mundial de ferro esponja. Uma revisão das patentes publicadas por estas duas empresas foi realizada e foi possível descrever o funcionamento dos processos, os desenvolvimentos ao longo dos anos e evidenciar as diferenças. Ambos os processos são baseados em fornos de cuba onde os gases de redução fluem em contracorrente ao minério aquecendo-o e reduzindo o ferro. Os gases de redução são gerados pela reforma catalítica de metano. A reforma no processo Midrex é realizada principalmente pela reação com CO2, e no processo Energiron com H2O. Há uma versão sem um reformador separado, o processo Energiron ZR. Neste processo o gás natural é injetado conjuntamente com H2O e CO2 no reator de redução e o ferro recém reduzido funciona como catalizador das reações de reforma.

Aug 16, 2017

The value of water is defined by its marginal utility. Challenges arise where the marginal utility is difficult to estimate. Therefore, when two or more interested parties wish to access water and they cannot use commensurate units for marginal utility; other means of value comparison must be sought. It is asserted here that sustainability principles can be used to guide this valuation if this is supported by a transparent decision framework. This paper proposes that the ICMM sustainable development principles provide appropriate guidance. In addition, a generic framework for decision making is suggested as a complement. Indicators of water management are recognised widely as an integral part of the accountability of minerals companies towards meeting sustainability goals. Less widely recognised are the ways in which sustainability principles can be used to guide decisions on water management which demonstrate growing awareness of its value. This paper illustrates the use of this logic in water issues associated with global sustainability challenges. It then goes on to demonstrate, using examples, that these links exist at all levels of the minerals industry and that indicators of this type are potentially as powerful as those currently being used. The reason for this is that the path from cause to effect is transparent and direct.

Jan 1, 2006

By Z. D. Hora

Commercial production of barite commenced in British Columbia in 1940; shipments have been recorded from ten deposits, of which four are particularly significant: The Brisco, Silver Giant, Parson, and Mineral King mines. Parr of the barite production is a by-product of base metal deposits in which barite is a major gangue mineral. About one hundred occurrences are known. COMMERCIAL production of barite in British Columbia dates back to 1940. Production volumes rose and fell and reached 39,900 tonnes in 1972. The main producer is Mountain Minerals Limited . There are two principal areas of barite deposits in British Columbia: ( I) The southeast part of the province along the Rocky Mountain Trench , which is the source of all production to date. (2) Stratabound occurrences in northeast British Columbia in the Gataga-Ketchika rivers and Muncho Lake areas which are not yet developed. Of the approximately one hundred reported barite occurrences, only ten have recorded commercial shipments, some of insignificant amount. So far, four deposits have proved to be important producers: Brisco, Silver Giant, Parson and Mineral King. The Mineral King property is situated near the confluence of Toby and Jumbo Creeks, 35 km southwest of lnvermere. The lead-zinc-copper-iron-barite deposits, as described by Fyles (1959, 1962), replace Proterozoic Mount Nelson dolomites of the Purcell system on the limb in the trough of a complex, tight syncline. The mine operated from 1954 to 1967 and 2,097,900 tonnes of baritic ore that was processed for base metal concentrates and also produced 22,680 tonnes of by-product barite. Since 1970, some 136,000 tonnes of barite have been recovered from the old tailings pond. The deposit is now considered depleted. The Silver Giant mine is located 10 km northwest of Spillimacheen. Barite and lead-zinc sulphides replace Cambrian Jubilee limestone near their contact with the overlying Ordovician McKay slate. Mineralization is located in the nose of an overturned plunging anticline. Between 1951 and 1957 800,000 tonnes of baritic ore were processed for lead and zinc concentrate. After 1959 barite was also produced , first from open pit, and later from reworked tailings. Up to 1979 production of barite totalled approximately 180,000 tonnes. Two other producing mines in the area are descri bed by G.R. Manson (this volume). Large, bedded stratabound barite deposits are reported from northeastern British Columbia. Six major shale-hosted Industrial Minerals in Canada lead-zinc-barite occurrences are known in the Devonian Gunsteel Formation. These are: Driftpi le Creek, Mount Alcock, Cirque, Pie, Fluke and Elf. In addition, numerous occurrences of strati form blebby or nodular barite and locally massive white crystalline barite are known from the Driftpi le Creek and Ak ie River districts in Gunsteel shale and from the Kechika, Road River and Ware map areas from Silurian siltstone . The size of these deposits is impressive; the baritic horizon at Mount Alcock is reported to be 25 to 30 m thick , and dri ll ing results from the Cirque deposit indicate reserves of 30 mi llion tonnes of baritic lead-zi nc-si lver ore. Similar bedded barite deposits are also reported from Midway area, near the Yukon border.

Jan 1, 1984

By Steve Lalancette

Centre Jardin Lac Pelletier (CJLP) has been a leading actor in the revitalisation of closed mining sites in northern Québec for over 20 years. Over that period, CJLP developed a cost-efficient technique that transforms sterile mining residue into a substrate able to support a resilient ecosystem. Using a unique mix of organic matter, fertilisers and selected plant species, this technique rapidly builds a microorganic fauna and a layer of humus that will sustain the creation of vegetation coverage. The coverage is composed of over 13 different plant species, each having a unique role in the development of a resilient ecosystem, from soil stabilisation to nitrogen fixing. Considerably less expensive than traditional methods using civil engineering techniques, it does not require the use of heavy machinery or the spread of topsoil. This technique has been successfully used to restore over 20 sites in Québec such as Joutel, Yvan Vézina and Louvicourt. It is a proven technique that has passed the test of actual implementation. The presentation will review the biological, production and economic aspects of the technique through the revitalisation of the Joutel site.

May 1, 2011

By M. King Hubbert

In 1856 Henry Darcy described in an appendix to his book, Les Fontaines Publiques de la Ville de Dijon, a series of experiments on the downward flow of water through filter sands, whereby it was established that the rate of flow is given by the equation: q= - K(h2- h2)/I1 in which q is the volume of water crossing unit area in unit time, I is the thickness of the sand, h1 and h2 the heights above a reference level of the water in manometers terminated above and below the sand, respectively, and K a factor of proportionality. This relationship, appropriately, soon became known as Darcy's law. Subsequently many separate attempts have been made to give Darcy's empirical expression a more general physical fornzulation, with the result that .so many mutually inconsistent expressions of what is purported to he Darcy's law have appeared in published literature that sight has often been lost of Darcy's own work and of its significance. In the present paper, therefore, it shall be our purpose to reinform ourselves upon what Darcy himself did, and then to determine the meaning of his results when expressed explicitly in terms of the pertinent physical variables involved. This will be done first by the empirical method used by Darcy himself, and then by direct derivation from the Navier-Stokes equation of motion of viscous fluids. We find in this manner that: q = (N4(p/p)[g - (l/p) gradPI = WE, is a physical expression for Darcy's law, which is valid for liquids generally, and for gases at pressures higher than about 20 atmospheres. Here N is a shape factor and d a characteristic length of the pore structure of the solid, p and IL are the density and viscosity of the fluid, a = (Nd2)(pip) is the volume conductivity of the system, and E = [g - (l/p) grad p] is the impelling force per unit mass acting upon the fluid. It is found also that Darcy's law is valid only for flow velocities such that the inertial forces are negligible as compared with those arising from viscosity. In general, three-dimensional space there exist two superposed physical fields: a field of force of charucteristic vector E, and a field of flow of vector q. The force field is more general than the flow field since it has values in all space capable of being occupied by the fluid. So long as the fluid density is constant or is a function of the pressure only, curl E = 0, E = - grad F where F = gz + dp/p The field of flow, independently of the force field, must satisfy the conservation of mom, leading to the equation of continuity div pq = — f ap/at , where f is the porosity, und t is the time. For steady rnotion ap/at = 0. and div pq = 0 .

Jan 1, 1957

Indigenous brown coals, which provide a readily available primary energy source, have played a significant part in the industrial development of Victoria. The deposits located in the Latrobe Valley compare in extent with other major deposits of brown coal in the world. Smaller but valuable deposits occur at Stradbroke, Gelliondale, Anglesea and Bacchus Marsh. Extensive drilling, aided by geophysical surveys, and detailed analyses of coal samples, have enabled the extent and quality of these Tertiary deposits to be Defined.

Jan 1, 1979

With the evolution rate of technologies, earthmoving equipment users are establishing vision statements for their operation out to and in some cases beyond 2000. Autonomous systems are receiving a lot of 'press' - and rightly so, as they hold a potential for achieving quantum leaps in productivity and cost gains. Caterpillar feels that it is important that the infrastructure of on-board systems are understood and can be utilised more in the near term to `grow' a user up to the stage of autonomous operation.

Jan 1, 1997

By L. Prosser, A. Iannacchione, G. Esterhuizen

The potential for roof falls in underground mines remains a clear and present danger for mine workers. An investigation of ground conditions in nearly 50% of the nation’s underground stone mines found that the state of roof stability is primarily determined in a limited and subjective manner. These large opening mines, with roof heights typically of 7 m or more, make physical observation difficult. Although some mines use monitoring techniques to gain additional information on roof stability, this practice is usually short-term and localized to address ground conditions in a particular section or part of the mine. A methodology to assess the risk for a roof fall is proposed in a preliminary fashion based on engineering judgment acquired from extensive underground stone mine experience and examination of related literature. The proposed method utilizes an observational technique to identify the risk of roof falls in three categories. Case study scenarios provide a realistic picture of model implementation. Providing the mine level decision maker with an accurate assessment tool to ascertain the level of risk related to ground conditions is expected to reduce mine worker injuries and fatalities. Moreover, the presences of danger can be overcome with a clear picture of quantified ground conditions.

By L. Prosser, A. Iannacchione, G. Esterhuizen

The potential for roof falls in underground mines remains a clear and present danger for mine workers. An investigation of ground conditions in nearly 50% of the nation’s underground stone mines found that the state of roof stability is primarily determined in a limited and subjective manner. These large opening mines, with roof heights typically of 7 m or more, make physical observation difficult. Although some mines use monitoring techniques to gain additional information on roof stability, this practice is usually short-term and localized to address ground conditions in a particular section or part of the mine. A methodology to assess the risk for a roof fall is proposed in a preliminary fashion based on engineering judgment acquired from extensive underground stone mine experience and examination of related literature. The proposed method utilizes an observational technique to identify the risk of roof falls in three categories. Case study scenarios provide a realistic picture of model implementation. Providing the mine level decision maker with an accurate assessment tool to ascertain the level of risk related to ground conditions is expected to reduce mine worker injuries and fatalities. Moreover, the presences of danger can be overcome with a clear picture of quantified ground conditions.

Jan 1, 2006

By Julio Cezar de Sousa Zorzi

Aços com teor de Mn entre 15% e 30% apresentam ductilidade excepcionalmente alta para sua elevada resistência mecânica, devido à ocorrência de transformação de fases (efeito TRIP) e/ou à formação de maclas de deformação (efeito TWIP) na microestrutura predominantemente austenítica. A adição de Mn ajuda a manter a austenita até a temperatura ambiente, evitando a sua decomposição após o recozimento aplicado depois da laminação a frio. O objetivo desse estudo foi avaliar o efeito da temperatura de recozimento na microestrutura e nos valores de propriedades mecânicas de um aço com 17% de Mn, por meio de simulações piloto das etapas de processamento industrial utilizando dilatômetro e simulador termomecânico do Centro de Pesquisa da Usiminas. Observou-se que o aumento na temperatura de encharque durante o ciclo térmico de recozimento contínuo promoveu a reversão completa da martensita a’ para austenita. Além disso, a alteração desse parâmetro praticamente não afetou o limite de resistência e o alongamento total do aço, embora tenha reduzido significativamente o limite de escoamento.

Jul 30, 2018

By José Wilmar Calderón-Hernández

Aços inoxidáveis supermartensíticos (AISM) são aços de matriz martensítica contendo baixos teores de carbono, abaixo de 0,03%. Eles vêm sendo utilizados na indústria de óleo e gás para aplicações específicas que exigem resistência mecânica aliada a moderada resistência à corrosão. Após serem temperados para a obtenção da estrutura martensítica, esses aços são submetidos a tratamento de revenimento para alívio de tensões e melhoria das propriedades de tenacidade e ductilidade. Durante o revenimento é esperada a ocorrência de mudanças microestruturais resultantes principalmente da precipitação de diferentes fases. Tais precipitados influenciam tanto as propriedades mecânicas finais quanto a resistência à corrosão desses aços. Nesta pesquisa foi avaliada a resistência à corrosão por pite de dois AISM do tipo 13Cr5Ni2Mo, um deles contendo Nb (0,11%), através de ensaios de polarização potenciodinâmica em soluções de 0,6M NaCl sem e com adições de 0,3M e 0,6M Na2SO4. Os resultados mostraram que a adição de Na2SO4 no eletrólito contendo NaCl inibe consideravelmente a corrosão por pite. Foi constatado também que o AISM contendo Nb apresenta maior resistência à corrosão por pite nos eletrólitos de misturas de cloreto e sulfato. Além disso, os resultados mostraram que o revenimento a 575°C melhora a resistência à corrosão por pite, comparativamente ao revenimento a 600°C. O melhor potencial de pite foi obtido para o aço ao Nb, revenido a 575°C por 2h, em eletrólito 0,6Na2SO4+0,6NaCl.

Jan 16, 2018

By James A. Martin

In relating geology and mineral resources to the nongeologist engaged in planning and zoning, a major hurdle to overcome is often the concept of natural resources. Statements listing such "resources" generally include and often may he limited to such items as "open space", "buildings of historical value", "forest and wilderness areas", and "sites of natural beauty" but seldom mention minerals even where they are of significant economic importance to the area. Unfortunately, mention of mineral resources is often limited to statements calling for tight controls on mining to prevent "ravaging of the land". While, the concept of sequential use involving mining is sometimes acknowledged, it is frequently done in such a manner that this approach is discouraged. In the conflict for land between urban development, recreational open space and mineral extraction, far too often the mineral industry will be the loser. In Missouri, there have long been continuing requests for geologic and resource data for planning purposes from city and county government and from Federal agencies for inclusion in the various river basin studies and Soil Conservation Service projects. These reports vary in detail from concise statements of the geology of an area to rather lengthy reports on mineral and water resources, bed rock and engineering geology characteristics. In most cases, these reports as written were directed to a geologically-oriented reader. Our initial approach to presenting geologic data to the land-use planner was in the area of engineering geology with attempts to show the limitations that bedrock and soil conditions can place on development. The first formal reports, engineering geology studies of urban areas, were released by the Missouri Geological Survey in

Jan 1, 1976

By W. E. L. Minter

Discussion by R.W. Hutchinson Minter's excellent recent paper (1990) on the great paleoplacer gold deposits of the Witwatersrand and its subsequent discussion (Cheney, 1991) and reply (Minter, 1991) provide an informative, interesting and up-to-date review of the geology of these unique ores and some long enigmatic questions regarding their origin. Clearly summarized by Minter (1990) are the compelling sedimentologic and stratigraphic relationships indicating that the Central Rand Group conglomerates are ancient placers and documenting the fluvio-deltaic conditions of their transport and deposition. As Minter (1991) indicates, Cheney's discussion broadens Minter's 1990 coverage of the subject by considering higher and lower stratigraphic units and by adding detailed comments concerning recently published information about metamorphic and age relationships. Cheney's discussion and Minter's reply also readdress the old controversy of epigenetic hydrothermal vs. syndepositional placer origin for these deposits. This controversy has been resurrected by: • recent recognition of hydrothermally-altered granites (HAGS) in the older Archean basement rocks that lie unconformably beneath the Dominion Group rocks north and west of the Witwatersrand depository; • recognition of greenschist metamorphic assemblages in the Witwatersrand strata; and • the presence of interpreted epigenetic mineral assemblages and textures in some of the deposits. These relationships are briefly discussed by Cheney who suggests they may result from later, superimposed metamorphism and deformation and do not prove that the gold was introduced by epigenetic/metamorphogenic processes. In his paper, Minter (1990) cited the 1986 abstract of a subsequently published paper by Hutchinson and Viljoen (1988) who also considered many of these aspects and attempted to integrate them all in abroad genetic hypothesis. In addition, they emphasized the additional important problem of determining the source for the Witwatersrand gold. Although this issue was partially addressed by Reimer (1984), Mossman and Dyer (1985) and Reimer and Mossman (1990), the question has been generally under emphasized in earlier work and was, therefore, not stressed by Minter and Cheney. Reimer (1985) also emphasized the importance of weathering of the basin's Archean hinterland and its affects on Witwatersrand sedimentation. Since the epigenetic hydrothermal hypothesis was essentially discarded in favor of placerist origin, the gold source for these great deposits has generally been attributed to the weathering of lodes in greenstones or granites of the uplifted, older Archean hinterland to the north and west. However, Hutchinson & Viljoen (1988) present evidence that this explanation is inadequate, as well as data in support of an alternative explanation. They suggest that the gold and accompanying abundant, clearly detrital and auriferous pyrite in the conglomerate reefs were derived by erosional degradation of auriferous-pyritic exhalite previously deposited, by shallow marine discharge of hydrothermal fluids, along the fault-bound northwestern margins of the Witwatersrand depository. The auriferous-pyritic exhalites were generated by fluid-rock reactions in the subsurface, particularly in the highly-altered lavas of the Dominion Group but also in adjacent basement granitic rocks. The process envisaged is comparable to that observed in sea floor hydrothermal systems today, although, in this case, it occurred at the margin of a rapidly subsiding, shallow marine or continental basin. Important evidence for this explanation is the anomalous gold content of the ferruginous, shaley strata occurring throughout the Witwatersrand Supergroup and including the distinctive contorted bed that is an iron formation. These layers have been interpreted (Hutchinson and Viljoen, 1988 and 1990) to represent the more distal, finer-grained, mixed chemical/clastic sedimentary strata. Thus, they are the basinal equivalents of the proximal, auriferous-pyritic exhalites that were deposited along the basin's margin and subsequently reworked by sedimentary processes. This gold source explanation resolves many of the enigmatic questions regarding Witwatersrand geology and the reawakened controversy between proponents of hydrothermal and placerist genetic hypotheses. The theory invokes a hydrothermal origin for the gold in the basin-margin pyritic exhalites, thus explaining the visible hydrothermal characteristics (Figs. 1 and 2). It also provides compelling evidence for placer origin by encompassing all of the fluvio-deltaic processes of clastic sedimentary transport and deposition that are clearly summarized by Minter. These characteristics result from the degradational reworking of the pyritic exhalites along the depository's margins. Fluvial reworking, transport and deltaic redeposition of this detritus, along with additional detritus carried into the depository from the hinterland, then formed the conglomerate reefs. Other enigmatic aspects of Witwatersrand geology include: • the rarity of magnetite and ilmenite (the two most common heavy minerals in placer deposits) and the contrary abundance of leucoxene in the conglomerate reefs; • the presence of differing varieties of pyrite (authigenic, allogenic, compact and porous) all of which are auriferous; and • the presence of well-rounded pebbles, even cobbles, of pyrite that, in view of the brittleness of the mineral, could not have been transported great distances from a hinterland.

Jan 1, 1993

By J. M. Karpinski, F. P. White, R. L. Stone

By means of laboratory balling tests and a procedure for determining bentonite concentration in a green ball, the present study revealed that the bentonite savings by mulling concentrate and bentonite prior to balling was sufficient to warrant installation of a full-size unit in a pellet plant. On the basis of this work, a muller was put on stream at Bethlehem Steel Corp.'s Cornwall pellet plant in June 1969, and has operated continuously since then. Plant tests showed that the use of the muller resulted in bentonite savings of about 50% without any loss of green, dry, and fired ball quality. Virtually no maintenance problems have been encountered. This information is important to future pelletizing operations both from the standpoint of product quality and economics.

Jan 1, 1972

Kambalda Nickel Mines (KNM) currently have eight operating underground mines, three on care and maintenance and other orebodies at various stages of development. Each operation differs greatly in scale, ore grade, milling characteristics and cost structure. The optimum number of mines operating at any one time and their level of production, within the constraints of mill blending requirements and overall mill capacity, is the key to maximising profit in a climate of fluctuating nickel price. Cost models are developed for each mining operation which relate ore tonnes mined to total cost per pound of nickel produced from that mine. Aggregating the mine cost models provides a composite cost model for the entire operation. The cost models provide the operating levels necessary for each of the mines and hence Kambalda as a whole, to operate at the lowest cost per pound of nickel produced. However, lowest operating cost does not necessarily lead to maximum profit. The level of nickel price above operating cost can dictate maximum profit positions which are contrary to the lowest cost position. In addition, the decision to temporarily shutdown mines or reopen mines in response to nickel price movements comes at a cost. In considering the optimum operating position, the price of production capacity flexibility needs to be taken into account. This paper describes the process used to assess all these factors in arriving at the optimum operating position for Kambalda Nickel Mines for varying nickel prices. The same methodology can be used by corporate management in managing multiple mine sites as well as mine management managing multiple orebodies or stoping blocks for maximum profit.

Jan 1, 1995