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By Takao Oishi, Go Ohara, Toru Kitazaki, Masahiro Tanaka

"The High Pressure Acid Leach (HPAL) plant for nickel-cobalt mixed sulphide production at Coral Bay Nickel Corporation (CBNC) in the Philippines has been in operation since 2005 with a capacity of 10,000 t/year of nickel. Subsequent to the commissioning of the second plant in 2008, the production capacity increased to 22,000 t/year of nickel (Llerin et al., 2011). CBNC’s annual nickel production reached more than 24,000 tons of nickel in 2014. The concepts to achieve this capacity are the high availability and the reciprocally flexible operation of both plants. The availability depends on some factors, such as the control of impurities in the process and the equipment condition, to mention a few. In the HPAL process, it is not only the autoclave operating conditions that affect nickel extraction but also the impurities in the ore greatly influence it. The major element in the ore is iron and most of this iron is precipitated as Fe2O3, while the rest remains as Fe2+ or Fe3+ sulphate in solution. These ions in solution reduce the availability, so it is important to control the formation of iron ions by controlling the impurities in feed ore as well as the HPAL conditions. This paper presents the general HPAL process and the behaviour of impurities, focusing on iron behaviour in the HPAL process.INTRODUCTIONCoral Bay Nickel Corporation ProfileCoral Bay Nickel Corporation (CBNC) was founded on April 2002, as a joint venture of four companies; namely, Mitsui Corporation (18%), Sojitz Corporation (18%), Nickel Asia Corporation (10%) and Sumitomo Metal Mining Corporation (SMM) with a controlling stake of 54%. Aside from its capital share, Nickel Asia Corporation also supplies the ore and limestone for the High Pressure Acid Leach (HPAL) plant located in Rio Tuba, Philippines, as shown in Figure 1 (Tsuchida, 2008). The objective of the CBNC project is to produce 22,000 t/year (original design) of nickel and 1,500 t/year of cobalt, as sulphide, by the treatment of nickel laterite ore which is a low grade nickel oxide ore in the Philippines (Mines and Geosciences Bureau, 2014). The sulphide product has been exported as a raw material to the SMM Nickel Refinery in Japan for 30 years. The product of this plant, a mixed (Ni/Co) sulphide, is shipped to the SMM’s Nickel Refinery in Niihama, Japan. SMM Corporation provides the technology and management personnel to the plant. SMM Corporation also supplies the sulphuric acid, which is the main reagent for the HPAL process."

Jan 1, 2016

By A. Haldar

The major problem encountered in the casting of hypereutectic Al-Si alloys is the stoppage of flow below the rigidity level of solid fraction. In this study, the flow stoppage mechanism was studied using three Al-Si alloys with 14%, 18% and 22% silicon. The horizontal foam patterns used were 12.50 mm (0.50 inch) wide with two section thicknesses 12.50 mm (0.50 inch) and 6.25 mm (0.25 inch) with a common sprue. The primary silicon distribution along the length of the casting was studied to determine the mechanism of flow stoppage. It was found that the surface of the flow tip of Al-14%Si alloy was smooth with a few undulations. As the silicon level increased, undulations at the flow tip increased. The number and size of undulations were maximum for the Al-22%Si alloy. Microstructural analysis using optical image analyzer revealed that the flow tip consisted mainly of eutectic silicon in the aluminum matrix and a few primary silicon crystals (PSC). The PSC were in the interlocked condition few centimeters behind the flow tip. It was also found that the gap between the flow tip and the PSC concentrated area increased with an increase in silicon level. Phase characterization was done with SEM-EDX to identify the precipitating phases.

Jan 1, 2007

By G. A. Pinsky, Pickard M. K

"IntroductionTWO METHODS of mucking have been used in sinking C shaft, the five-compartment production shaft of the Yellowknife property of Giant Yellowknife Gold Mines, Limited:(a) Band mucking during the original sinking in 1949 and 1950 (l); and(b) Mechanical mucking with the Cryderman shaft mucker during the recent deepening in 1954.This paper briefly describes the recent deepening and compares the performance figures of the two sinking operations.PlanningProduction planning in 1952 showed that it would be advisable to deepen C shaft in 1954 to provide for three new production levels and the installation of an underground crusher. To complete the required shaft work it would be necessary for a shaft crew to deepen the shaft about 500 feet, to partly excavate three level stations and a crusher station, and to cut a station for the loading pocket. Figure 1, a vertical section of the lower part of the shaft, shows the details of the deepening programme.During the planning period, Giant had a rather small supervisory staff and at the same time was experiencing a heavy labour turnover. As it was obvious that production would suffer if the sinking crew were recruited at the mine, it was decided that the merits of contracting-the shaft sinking to an independent contractor should be investigated."

Jan 1, 1955

By Gerry Doeksen

The paper deals with three case studies: (a) the handling of wet concentrates (5 to 8 per cent moisture) through feed bins; (b) the handling of the same product in rail cars; and (c) the handling of dry concentrates (less than 0.5 per cent moisture) through feed bins. In each case, the paper discusses the problems of rat-holing. In each of cases (a) and (c), there is a discussion on the consequent extreme variations of feed rates coming from the feeders, making automation of process control difficult to impossible. Currently available bin-flow theory and flow property tests are used as aids in redesigning the bins. The paper concludes with illustrations of the final results after the redesigned hoppers were installed and tested. There is also a discussion on the advantages of the new mass-flow bins on adjacent feeder performance.

Jan 1, 1970

By Abdelkabir Maqsoud

Different management options and rehabilitation strategies are available for mine wastes that produce acid mine drainage (AMD). One of them consists in building a cover with capillary barrier effects (CCBE) on the tailings to limit the availability of oxygen, an essential component of the chemical reactions leading to the generation of AMD. Prior to cover construction, a monitoring strategy must be established to evaluate the response and performance of the cover system. The key parameters to monitor should include matric suction and volumetric water content in the CCBE, oxygen flux (and/or oxygen concentration) through and below the cover, and the main meteorological parameters for the impoundment. In this paper, different techniques available to measure the targeted parameters are described and their main properties are given. Recommendations (based on existing cases) on the location and the number of monitoring stations and on the measurement frequency for each monitored parameter are also proposed.

May 1, 2007

By M. A. EI Zeky, A. E. El-Nikbaily, M. A. Shahin

"Possible mechanisms of microsilica dust formation and factors affecting its quantity have been discussed. General mathematical models to predict the dust quantity based on electrical and coke consumptions, and flue gas temperature as functions of silicon recovery in the process and silicon content of the alloy have been established. It has also been shown that the flue gas temperature can be used as an additional process control parameter. Comments are made on the effect of the dust formation on the whole process economics and it is pointed out that the formed microsilica dust is a valuable by-product and not an industrial waste. INTRODUCTIONFerrosilicon is produced in electric arc furnaces with submerged electrodes. The charge mixture consist s mainly of quartzite, coke as the reducing agent and iron chips. The products are ferro silicon and carbon monoxide, various other volatile materials, water vapour and silicon monoxide gas. Carbon monoxide and silicon monoxide oxidize at the charge surface when mixed with air entering through the furnace hood openings. The off-gas contains a considerable amount of dust, which is mainly very fine particles of silica formed as a result of oxidation. The emission of dust containing gases to the atmosphere causes serious pollution problems to the environment. Therefore, the control of the formation of the dust, preventing it from escaping to the atmosphere, and dealing with this very fine dust collected from the flue gases represent important technological and economical parameters in the ferrosilicon production industry.This paper is concerned with the relations between the quantity of formed micro silica dust, as a function of both silicon recovery and silicon content in the alloy, and various other technological parameters; and their possible effects on the energy consumption and economics of the whole process."

Jan 1, 1989

By Eugene F. Mehr, Dennis C. Martin

"Development of the final slope for the 340 m (1200 ft) high hanging wall at Cassiar Mine precipitated an area of deep seated instability involving an estimated 17.6 million tonnes. The deformation mechanisms involved squeezing of soft deformable serpentinite rocks in the toe which caused planar sliding and graben toppling of the stronger sedimentary rocks in the middle and upper sections of the slope. Although movement rates up to 150mm/day were recorded, by understanding the controls on failure, the mine was able to install a suitable monitoring system and complete the open pit with only minor loss of the mineable ore. Accelerated mining was required in the last full year of operation. This paper describes the deformation behaviour, failure mechanisms and back analysis results for the failure. The monitoring systems and operational aspects related to the failure are also presented.IntroductionCassiar Mine is located in steep mountainous terrain in northern British Columbia approximately 1200 km north of Vancouver (Fig. I). During the final mining phase of the open pit, instability developed in the approximately 340 m high hanging wall (east wall) slope. A unique graben toppling mechanism was identified based on detailed assessment of slope monitoring data and visual observations. Comprehensive slope monitoring enabled mining to continue even though movement rates as high as 150 mm/day were being recorded. Three-dimensional limit equilibrium back analyses and numerical modelling have been used to assess the various controls on the slope movements and to understand the failure mechanism."

Jan 1, 1993

By J. K. Armstrong, C. Feyerabend

"As mines are constantly growing and expanding, so do the challenges for emergency response teams. They have to keep up with the pace set by current and future production techniques. Although mines have now reached depths of several kilometres and their dimensions and complexity are that of an entire city, mines rescue still must be able to reach the most remote areas within the mine in a swift and safe manner. The duration of breathing apparatus and physical human capabilities are limitations. Therefore, alternative methods have to be explored to extend the time under oxygen for mine rescue teams without putting additional stress on the team members. To address this global trend, Dräger, Goldcorp and PAUS have partnered to develop a mine rescue vehicle that allows mine rescue teams to travel for an extended period of time through a contaminated atmosphere without the use of breathing apparatus, thus extending the range of their mission. By applying currently available techniques, the safe expansion of mine production can be ensured, giving mine rescue teams the ability to respond to accidents in a safer and faster way. INTRODUCTION With the reduction of easily accessible natural resources, there is a global trend toward searching for higher ore grades underground and/or continually expanding mines underground to extend their lifetime. While in some areas this trend has just begun, in other countries mines are reaching depths or horizontal dimensions that pose extreme challenges (Codelco, 2016). These challenges include safety relevant topics, such as rock stability, heat and seismicity, but also more basic issues such as distances to the working face, which can become crucial considering the cost to develop a new shaft or decline. To overcome this, there is a growing interest in collaboration among various stakeholders to drive the development and support of deeper mines and tackle the complexity of underground mining. This is evidenced by the fact that several industry and research groups and networks have formed, e.g. the I2mine project in Europe and the Ultra-Deep Mining Network by the Centre for Excellence in Mining Innovation in Canada. Due to commodity pricing and the trend toward renewable energy, metal/non-metal mining will be the driving force behind this development."

Jan 1, 2019

By Jaime Meléndez Martínez

Recent interest in unconventional reservoirs motivates our work in laboratory measurements of seismic anisotropy. Seismic anisotropy is the variation in speed of a wave as a function of its direction of propagation. Analyzing anisotropy in unconventional reservoirs is important since anisotropy leads, for example, to differential stresses upon loading and could affect hydraulic stimulation (Reinicke et al., 2010, Zimmermann and Reinicke, 2009); in this sense, laboratory measurements are an important tool to study seismic anisotropy at small scales which can aid in the characterization of larger formations. The purpose of this work is to describe the laboratory methodology used to simultaneously measure ultrasonic P and S-waves in three different directions from a single core sample. Elastic anisotropy of a Proterozoic sedimentary rock from south-west Alberta is investigated. In metamorphic rocks seismic anisotropy is caused by preferred mineralogical alignment or foliation. Assuming a transversally isotropic medium, arrays of compressional and shear piezoelectric ceramic transducers were mounted on a sample trimmed from a core to measure travel times of ultrasonic P-waves and S-waves as a function of confining pressure at directions perpendicular, parallel, and oblique to the plane of foliation (bedding). Results show strong anisotropy agreeing with the assumption of a transversely isotropic medium. Dependence of travel times and hysteresis effects can be observed when pressurizing and depressurizing.

Jun 1, 2012

By C. I. Godwin

"The relative-value (R-value), discrimination-factor (D-factor), and vector-ratio (V-ratio) method (RDVM) provides a geological knowledge-based statistical and geological-genetic interpretation scheme for geochemical data that enhances discovery in geochemical exploration. The practical advantage of RDVM is that it synthesizes geochemical features geologically related to ore-deposit discovery in three steps: reclassifying element concentrations using log-probability plots into R-values; calculating geologically defined D-factors from R-values; and determining V-ratios. D-factors are the sum of R-values, divided by the number of R-values summed. Based on the analyses selected, D-factors mimic rock or mineral deposit signatures. V-ratios refine interpretations of rock type and vector to orebody locations.RÉSUMÉ La méthode de la valeur relative (valeur R), du facteur de discrimination (facteur D) et du rapport de vecteurs (rapport V) (RDVM), fournit un schéma d’interprétation des données géochimiques basé sur les statistiques et les connaissances géologiques et la génétique géologique; ce schéma contribue aux découvertes en exploration géochimique. L’avantage pratique de la RDVM est qu’elle fait la synthèse des caractéristiques géochimiques reliées géologiquement à des découvertes de gisements de minerais en trois étapes : une reclassification des concentrations des éléments au moyen de courbes de probabilité logarithmique en valeurs R; un calcul des facteurs D définis géologiquement à partir des valeurs R et la détermination des rapports V. Les facteurs D sont la somme des valeurs R divisés par le nombre de valeurs R additionnées. Selon les analyses choisies, les facteurs D imitent les signatures de la roche ou des gisements minéraux. Les rapports V peaufinent les interprétations des types de roches et dirigent vers des emplacements de gisements."

Jan 1, 2016

By J. M. Simard, S. Morissette, P. Coursol, P. Mackey

A new, powerful model is presented that focuses on plant logistics and scheduling aspects of the smelting, converting, fire refining and casting operations at the Horne smelter. This plant complex is the largest custom copper smelter in North America. It handles a wide range of feeds and utilizes a number of proprietary continuous and batch technologies that require good scheduling in order to maximize plant capacity and efficiency. The present model was developed by Xstrata Process Support, in collaboration with the Horne smelter, and uses the Arena® software to evaluate the impact of a number of plant variables on the annual copper capacity of the plant. Model development was carried out by Xstrata Process Support, in collaboration with the Horne smelter, through the effective combination of process chemistry knowledge and detailed knowledge of the plant operation (including all material flows and transfers, as well as information such as operating on-line times, plant stoppages and also scheduled and unscheduled maintenance activities). A number of case studies were then examined, including the impact of anode furnace and casting cycle times on annual copper capacity and the impact of a one-crane mode of operation in the converter aisle, which normally operates with two cranes in service. The model predictions were found to match actual plant results very well. The present modelling of plant logistics and the scheduling aspects were found to add important dimensions at the plant with regard to projections of the real-life plant capacity. As demonstrated in the present case, this type of model and application can have a significant impact on optimizing operations at a given plant. This impact is particularly important in the current market environment, where emphasis is on maximizing plant output and lowering costs. These models can help yield the easily obtained gains that are clearly desirable in these times. Xstrata Process Support has developed Arena models for other operations and is available to explore new applications for a win-win situation at other plants, including mines and concentrator operations.

Jan 1, 2009

By E. P. Wiechmann, J. A. Henríquez, P. E. Aqueveque, L. G. Muñoz, G. A. Vidal

"The original segmented intercell Optibar succeeded in reducing the magnitude and occurrence of short circuits. It also improved the specific energy consumption of the process. This paper expands the load current source concept introducing a triple segmented bar. This new bar adds immunity to dirt contacts and open circuits. Moreover, it further improves the standard deviation of current densities. As compared with industrial practices this development should accomplish an 8% specific energy reduction. Also, a plant implemented with BBS should be able to work with 12.5% higher process currents than Walker without compromising the operation.INTRODUCTIONIn 2011 the technology based on current mode was implemented at industrial scale. The success of this technology moved CIM Magazine (Lanktree, 2011) to write in the Jan 2012 issue an upfront story of this technological innovation. To cover the story, the technical reporter Graham Langtree was appointed by Peter Braul Editor of the upfront section. The article tells that “More than 40,000 tonnes of copper have been refined in a year-long test run of Optibar Inc.’s new technology at Barrick Gold’s Zaldívar copper plant in northern Chile. The new segmented intercell bars being used in the Compañía Minera Zaldívar refinery have slashed energy costs, reduced short circuits during refining and allowed the production of heftier, purer sheets of copper – gains that all promise to boost the plant’s margins. A copper refining tank house containing the cell circuits typically consumes 2,000 kWh of electricity to produce a single tonne of grade-A copper. Yet, monitoring the energy efficiency of the Optibar technology after increasing the weight of harvested copper sheets, the project’s engineers recorded a 92 kWh-per-tonne cut in energy consumption, a savings of 4.6 per cent. “Today, with the power prices we have, Optibar technology represents a potential savings for the whole plant of US$1.5 million per year,” says Robert Mayne- Nicholls, executive general manager of Barrick Gold’s Chilean operations.”"

Jan 1, 2012

By Antoine Fournier, Karen St. Seymour

"Responding to market developments, interest in locating deposits of wollastonite has grown significantly. The many occurrences in the Grenville marbles of Quebec can be grouped into disseminated type and discordant vein-type deposits. Disseminated-type wollastonite occurrences have the disadvantages of lower grade, the need for more elaborate mineral separation, and failure to meet ""long grain"" technical specifications. Vein-type deposits have better grades and technical characteristics; exploration should be focussed on these and in the contact-metamorphic aureoles of fluid-rich intrusions. SOMMAIREEn réactions aux nouveaux de bouches, l'interet pour les gîtes de wollastonite a crû de façon marquée. Les nombreux indices sis dans la province de Grenville au Québec peuvent être regroupes en deux catégories soit: les indices dissémines et les indices en veines discordantes. Les indices dissémines ont le désavantage d'être moins enrichis, de requérir une séparation minéralogique plus complexe, et leur wollastonite ne possède pas le degré d'acicularité voulu. Les indices en veines sont plus enrichis en plus de rencontrer les critêres techniques; les efforts d'exploration devraient se porter vers ce type de gites et aussi, sur les auréoles métamorphiques de contact d’intrusions riches en fluides."

Jan 1, 1992

By P. J. Urso

"This paper discusses the mining problems encountered at the Fording River coal mine to date, and how they have been solved. All of the production now comes from surface mining, but underground hydraulic mining is planned and briefly described. Other facets of the operation, including markets, equipment and personnel, are covered. IntroductionFording Coal Limited was formed in 1968 to mine and market metallurgical coal resources held by the company in the East Kootenay region of southeastern British Columbia. The company, at its Fording River operations, holds approximately 48,000 acres of coal lands, having an estimated 2.0 to 3.0 billion long tons of metallurgical coal in place. (Although not a point for further discuss ion in this paper, the company also holds approximately 1.0 million acres of mineral rights. These consist primarily of coal in Alberta, potash and coal in Saskatchewan, and minor industrial mineral holdings of limestone, salt and bentonite in the three western provinces.)Fording Coal is owned 60% by Canadian Pacific Investments Ltd. and 40% by Cominco Ltd. Inasmuch as Cominco itself is owned approximately 54% by CPI, it is seen that the effective CPI ownership of Fording is about 82%. The company, originally staffed and managed by Cominco, has been independent since January, 1978, with its own board of directors, management, staff and employees.The company's head office is in Calgary, Alberta. The Fording River operations are located approximately 45 miles north of the Crowsnest Pass, near the Alberta/British Columbia boundary, only 95 air miles and 200 road miles from Calgary.A contract was signed in 1969 with the Japanese steel mills to provide 45 million long tons of metallurgical coal over IS years, commencing in 1972 at an annual rate of 3 million long tons per year. Despite some start- up difficulties, the mine and plant facilities achieved their rated capacities in 1975, producing and shipping at the 3-million-Iong-ton level. The coal specifications are shown in Table I."

Jan 1, 1980

By R. A. Horn, S. M. Telfer

"Canada has a per capita GDP second only to Japan among the G7 countries and a positive trade balance which ranks third among the world's major economies. International trade represents a very large part of the national economy and as a proportion of GDP is larger than that of all the other G7 countries with the exception of Germany. On the negative side the Canadian current account deficit relative to the size of the economy is significantly worse than that of all major industrial countries, due mainly to the cost of servicing an immense foreign debt and to a large and worsening negative trade balance in manufacturing.The outflow of money may be reduced by increasing the productivity and competitiveness of those sectors of the economy in which Canada already has a leading competitive position and which have the potential for further growth. The mining industry is uniquely qualified in this respect in that Canada is the western world's largest producer of metals and mineral products and has the geology and the exploration skill to replenish reserves assuming that an adequate level of investment is maintained. In 1989 the minerals industry contributed $8 billion to the country's balance of payments and with the exception of forestry is the only sector of the economy which has shown consistently increasing foreign earnings over the long term.In recent years there has been a decline in exploration in Canada and a significant increase in countries such as Chile. The demand for hard currency to finance the development of the newly emerging capitalist economies of the CIS and Eastern Europe is also driving these countries to seek foreign investment to allow them to exploit their natural wealth more efficiently. Canada is therefore facing growing international competition for risk capital and in the future its trade surplus will probably decline in the face of lower cost foreign production.Canada rightly exercises a high level of environmental control on its mining operations; however a significant deterrent to investment is the fundamentally unjust application of the many provincial and federal environmental laws, under which a mining company, even if it takes every measure to protect the environment, runs the risk of eternal and unlimited future liability. If this situation is not rectified the effect will be an increase in global pollution as mines in countries with more lax application of law and regulations controlling environmental damage replace those of Canada. Tax benefits and incentives are a more efficient means than arbitrary regulations in minimizing environmental damage."

Jan 1, 1994

By Xiaoguang Zhao

The coal mining area in Northern Shaanxi, China, has been taken as the study area, and the damage mechanism of the ecological environment is discussed on the basis of analyzing the characteristics of natural eco-environment and resource development in this area. Mining subsidence is taken as an example, and by using the Gray Correlation Analysis method, the key impact factors have been selected. An assessment model with fuzzy comprehensive evaluation has been constructed, and 12 coal mines have been quantitatively assessed. This paper also constructs an ecosystem health assessment method and index system in the coal mine area on the basis of ecosystem health theory, and assesses the ecosystem health status in the Shenfu coal mining area from 2000?2006. The research results are expected to help the eco-environment protection process in the designated coal mining area.

Aug 1, 2013

By A. W. F. Smith, P. B. Prangnell, D. N. Crowther, P. J. Apps

It is well known that the refinement of grain size in metals leads to a significant improvement in important mechanical properties. As part of a European collaborative project, processing schedules have been investigated aimed at producing a homogeneous ultra-fine ferrite and spheroidised carbide aggregate microstructure structure in high carbon (CMn) steels (0.6-1.2wt%C), via conventional 'warm' rolling and innovative Equal Channel Angular Extrusion (ECAE). Suitable deformation schedules were determined from dilatometry and thermo-mechanical Gleeble simulations. Evidence of an ultra-fine ferrite and carbide aggregate microstructure following 'warm' rolling is given. A significant improvement in tensile strength, particularly proof stress (0.2%) was also noted in comparison to material deformed at higher temperatures. Concurrent Equal Channel Angular Extrusion (ECAE) experiments investigated microstructural evolution with incremental strain. Extensive analysis was carried out using various techniques, including high resolution Electron Back Scattered Diffraction (EBSD). Evidence of ferrite grain refinement was noted in a eutectoid composition steel. A sub-micron ferrite structure was observed following high strains (E-3.33) and the mechanical properties exhibit a marked increase in tensile strength.

Jan 1, 2004

By Y. Héroux, A. Chagnon, M. M. Savard

"Résumé - Le gite de Pb-Zn de Gays River s'accompagne d'anomalies des propriétés de la matière organique (MO) et des assemblages de minéraux d'argile (AMA). L'association entre la minéralisation, la distribution de la réflectance de la MO et des AMA suggère que ces traceurs peuvent servir à I ‘exploration des sulfures de métaux de base dans cette région.A I ‘emplacement du gîte, la réflectance varie considérablement (0,8% à 1,88%), pouvant même afficher une baisse avec I ‘enfouissement, ce qui est interprète comme une altération chimique de la MO. Les valeurs les plus élevées s'accompagnent localement de quelques textures en mosaïque et délimitent une anomalie thermique au centre sud de la région. Parmi les minéraux des argiles identifies, I ‘illite et la chlorite sont terrigènes alors que la smectite, la kaolinite et la corrensite sont authigènes et, à l' instar de I ‘altération de la MO, résultent des nouveaux équilibres chimiques créés suite à la précipitation des sulfures.Abstract - The Gays River Pb-Zn ore deposit is associated with anomalies defmed from the characters of the organic matter (OM) and from the clay minerals assemblages. The relationships between these anomalies and the mineralization at the mine suggest that these parameters can be used as new guides for the exploration for base-metal sulfides in this area.The vitrinite reflectance (RJ shows a wide range of values (0.8% to 1.88%) and exhibits an anomalous suppressive effect with depth of burial at the mine site, suggesting a chemical alteration of the OM. The highest R"" values are associated with mosaic textures and outline a therrnal anomaly at the south-center of the studied area. Among the identified clay minerals, illite and chlorite are terrigenous, whereas smectite, kaolinite and corrensite are authigenous and, like the alteration of the OM, are due to the new chemical equilibria resulting from the precipitation of the sulfides."

Jan 1, 1994

By G. V. Fernandez

Sociedad Minera Cerro Verde S.A.A leaches secondary copper sulfides. In recent years, the mine has introduced innovations that have improved the management of mineral crushing, agglomeration, curing, and leaching. The crushing plant, for example, uses the concepts of degree of balance and percentage of time in an operationally balanced state which, displayed in real time, facilitate more intensive and uniform utilization of the crushers. High agglomerate quality is ensured with the correct dose of moisture, which is adjusted to the changing characteristics of the mineral through the use of electrical conductivity measurements. The amount of acid used for curing the agglomerate is also adjusted by using quality control information. Finally, the stockpile irrigation regime is managed using the criteria established by the "Lixiviant Request Rate", which optimizes the addition of leaching solution, creating such benefits as faster recovery, and reduced acid and energy consumption.

Jan 1, 2007

By E. A. Roux

As the first mine-to-metal zinc operation utilising atmospheric leaching, solvent extraction and electrowinning, Skorpion Zinc faces unique challenges and opportunities. One of these challenges is found in the solvent extraction circuit, in which di-ethylhexyl phosphoric acid (D2EHPA) is used as the organic extractant. Although D2EHPA is an excellent extractant for zinc, it suffers from the co-extraction of ferric iron, which is produced during leaching and by the corrosion of the grinding media. This situation is partially mitigated by iron precipitation in the neutralisation step prior to solvent extraction. Unfortunately, some ferric iron still reports to the solvent extraction process. This leads to a slow build up of iron in the organic phase. Chemical stripping is used to maintain the Fe concentration at an acceptable level. In this paper, the efficiency of the iron removal process is discussed.

Jan 1, 2006