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By F. Hees, A. H. Bracken, L. I. Boshoff

"Biological cementation of the Mandena heavy mineral sand deposit in Madagascar was causing difficulty in dredge mining and hence in planning and control of production rates. An investigation was initiated to better evaluate the geotechnical properties of the orebody by defining the distribution and geotechnical properties of the cemented strata, in order to generate a site-specific geotechnical model for the deposit. The geotechnical characterization was developed by an integrated approach using several ground investigation techniques such as piezocone (CPTu) testing, geotechnical drilling, standard penetration testing (SPT), as well as laboratory testing. The final outcomes of the investigation included a 3D geotechnical model showing the distribution and extent of the cemented areas, as well as the typical geotechnical parameter ranges associated with each of the defined geotechnical units. The interpretations developed were incorporated into the mine and production planning to ultimately optimize operational planning and control.IntroductionQIT Madagascar Minerals (QMM) is a heavy mineral sand mining operation at Mandena, near Fort Dauphin in Madagascar. During the final planning and commissioning stages of the project, the need to fully characterize the unusual geotechnical conditions was identified and a geotechnical investigation became necessary.Nature of the problemDuring the commissioning phase it was found that mining production was being hampered by biologically cemented/indurated layers encountered within the sands. Closer inspection of the indurated horizons in the dredging face revealed that these layers contain a high loading of bacteria and fungi. It appears that the bacteria produce an extracellular (outside the cell) polysaccharide (i.e. sugar and carbon salts), which form a gelling biofilm to trap nutrients. There are a number of different bacteria. The fungi, on the other hand, produce a network of fibrous strands that bind the sand grains together. Thus both bacteria and fungi probably contribute to the ‘apparent cohesive’ strength or binding of the indurated sand (Lynn, 2008)."

Jan 1, 2017

By H. Karabulut, S. Gündüz, K. Karacif, M. A. Erden

The corrosion properties of iron-based composite materials containing graphite and silicon carbide (SiC) reinforcement were investigated. The effects of silicon carbide reinforcement were investigated by adding 0.5% graphite and 1%, 2%, and 4% SiC. A powder metallurgy method was used to produce the composite samples. Iron, graphite, and silicon carbide powders were blended for one hour with a threeaxis mixer and then unidirectionally pressed under a pressure of 750 MPa. After pressing, the composite materials were sintered at 1100°C for one hour. The corrosion properties and microstructure, density, and hardness properties of the composite materials that can affect the corrosion properties were also investigated. It was determined that the pore ratio and hardness of the composite material increased, and corrosion resistance decreased, with increasing silicon carbide content.

Jun 2, 2022

By R. V. Ramani, R. Stefanko

"The favorable mining conditions in the United States of America that resulted in the development of the highly productive room and pillar systems are largely disappearing. Increasing mechanization, poorer natural conditions, and greater concern for health, safety and environment gave impetus to the enactment of the Federal Coal Mine Health and Safety Act of 1969. These regulations prescribe more stringent requirements in face ventilation and mine air distribution, necessitating significant changes in existing ventilation systems. Stringent mandatory standards were applied to respirable dust control for the first time, and simultaneous control of both gas and dust has affected the face as well as primary distribution, most notably on haulage entries.The size and complexity of the present-day mining operations, and the need to evaluate various system changes in a limited time, call for scientific methods in mine planning. In this paper, the authors trace the previous applications of computers to mine ventilation planning and discuss the results of their work in applying a ventilation simulator developed at Penn State. The paper includes an analysis of current trends and suggestions for future research and development."

Jan 1, 2014

By R. J. Cocks

Water auditing and water efficient practices are evolving as the quantitative tools for water balance reporting in the mining and minerals processing sector. This paper was written to describe the process of water auditing in a gold mining environment. It will contribute towards building an appropriate water management framework for The Cooperative Research Centre (CRC) for sustainable resource processing (CSRP). The research assists with the assessment of water balances in mining and hydrometallurgical processes and provides, on the ground, steady-state data for ongoing probabilistic modeling underway at most of Newmont?s gold mine operations. Five Newmont case study mine sites including the Tanami Granites Goldmine are central to this PhD water project study. The function of the Tanami-Granites water audit exercise was to measure a controlled flow of various water quality types and set a framework to establish further research for water efficiencies and water conservation in mining.

Jan 1, 2009

By A. V. Rasskazova

Theoretical substantiation of leaching of clustered ultra-fine gold by the electro-photo activated cyanide and chloride solutions is given in the paper; and processes of activation of leach solution by electrolysis and photo-activation are described. Comparative experiments on electro-photo activated leaching of ultra-fine gold from refractory ores by cyanide and chloride solutions were carried out. The material for research is primary ore of the Pogromnoe deposit (Russian Federation, Trans-Baikal Territory). The ore is characterised by the minimum sulfide minerals and the organic carbon content. Gold in ores of this deposit is presented as mainly ultra-fine. Gold inclusions in quartz and silica-alumina minerals (metasomatic minerals) are ultra-fine. Sulfide minerals (2.5-3%) are presented in ore generally by pyrrhotine (gold content does not exceed 10 g/t). Standard cyanide technology provides 49.5% gold recovery. Photo-electro activated air saturated NaCN provides 69.9% gold recovery. Laboratory research of chloride-hypochlorite column leaching demonstrated that the electro-photo activated method provided 78.9 % gold recovery to pregnant leach solution. Chloride-hypochlorite photo-electro activated solution can provide higher level of gold recovery with shorter process duration (10 days) in comparison with cyanide (40 days). The final decision regarding the choice of leach solution has to be done on the basis of technical and economic calculations. Keywords: Ultra-fine gold, cluster chemical reactions, active clusters, leaching, electro-photo activation of leach solution

Jan 1, 2020

By G. Akdogan, S. M. Bradshaw, A. P. Van Wyk, T. Punt

Recycling has become an important part of the lithium-ion battery (LIB) life cycle due to the growing demand for energy storage in applications like electric vehicles and renewable energy. Recycling spent LIBs provides a secondary source for strategically scarce metals, like lithium and cobalt, helping to reduce the environmental impact of LIBs. Organic acids have been proven to be effective lixiviants with the benefit of reduced environmental impacts, amongst which citric acid has shown to exhibit similar extraction performance when compared to mineral acids. Leaching LCO and NMC batteries with 1.5M citric acid and 2 vol.% H2O2 at 95°C, 20 g/L for 20 minutes achieved 93% Al, 90% Co, 96% Li, 94% Mn and 94% Ni dissolution. The strong chelating property of citric acid affects the separation of the metals, providing unique extraction opportunities. The first extraction uses 12 vol.% D2EHPA at a pH of 2.5 and O/A ratio of 2 to separate 96.4% Mn and 100% Al from the PLS in two counter-current stages. Stripping the loaded organic with 1.25M citric acid at an A/O ratio of 3 allows for up to 91% stripping of the manganese in a single stage. The second extraction then separates 96.5% Li from the PLS in three counter-current stages using 20 vol.% D2EHPA at a pH 5.5 and O/A ratio of 5. The raffinate remaining after the second separation contains 48.4 wt.% Co and 50.3 wt.% Ni. Keywords: Hydrometallurgy, lithium-ion batteries, metal recycling, citric acid, solvent extraction

Jan 1, 2020

By L. W. Helle

In this investigation, which was conducted at the Metallurgical Research Plant, Lulea, Sweden, a series of experiments were carried out using a water-model to simulate the gas rinsing of a ladle containing liquid metal. The factors examined include the effect of gas flowrate, the position of a porous plug or lance, the immersion depth of the lance, and the geometry of the bath at the time of complete mixing. Mixing times were recorded by conductivity measurements. The results showed that there is a threshold level for mixing above which no advantage is to be gained from an increase in the gas flowrate. It is suggested that the results can be applied to rinsing ladles in working situations, the levels being approximately 270 dm3/min for 40 t ladles and 780 dm3/min for 150 t heats. The optimum siting of the lance or porous plug is a position that is three-quarters of the internal radius from the centre of the ladle with the lance penetrating as deeply as possible into the ladle. The best design of liquid bath is that having a diameter-to-height ratio of I. An equation was developed for the calculation, by dimensional analysis, of the time required for mixing during gas rinsing, and a comparison of the calculated mixing times with the results from production trials shows a satisfactory agreement (with a correlation factor of 0,91). Thus, an equation is available for the calculation of the stirring time needed to completely mix the bath in production situations.

Jan 1, 1981

By E. S. van Druten, M. C. Bekker

"The complete and successful closure of a mine in the South African environment remains problematic. Closure remains an elusive mining phase due to unclear roles and responsibilities, inaccurate closure management data, and the inability of stakeholders to conceptualize and integrate closure information into business processes. Currently there are no proven methods available to address the complexities encountered during a closure application, and to date no mine has been granted full closure. Many mines are left abandoned and unrehabilitated, resulting in risk to investors, surrounding communities, and regulators. This investigation aimed to determine, categorize, and rank reasons for unsuccessful mine closures. Focus groups consisting of public and private stakeholders were identified and surveyed through a structured, rank-order questionnaire to determine the relative importance of reasons why achieving formal and final mine closure remains elusive. Various requirements and aspects were identified and listed according to four categories: namely, primary, secondary, process drivers, and information sources. These aspects should be considered in the development of an integrated mine closure model.Background and rationalePrior to 1956, mine closures were not subject to legislative requirements, being merely governed by insufficient environmental regulations under the Mines and Works Act 27 (MWA) (Swart, 2003). In 1981 the Chamber of Mines (COM) published a document titled ‘The rehabilitation of land disturbed by surface coal mining’, which constituted the first notable contribution to environmental protection. This guideline was later referenced in the Minerals Act of 1991, which for the first time laid definite environmental burdens on the Mining Right Holder (MRH). The Minerals Act of 1991 was superseded by the current Mineral and Petroleum Resources Development Act (MPRDA) and the Mineral and Petroleum Resources Development Act Regulations (MPRDAR), which specify a regulatory process for mine closure applications and financial provisions."

Jan 1, 2017

By D. Govender

Theoretical flotation models suggest that there is a positive relationship between bubble-particle collision rates and turbulent kinetic energy dissipation. Fine particle flotation performance is generally enhanced by increased collision frequency and hence higher energy dissipation. Contrarily, increased turbulence in the rotor-stator region is related to higher detachment frequency of the coarser size range. Therefore, the optimal modes of recovery for the ?fine? and ?coarse? size classes appear to be diametrically opposed. Industrial applications have previously confirmed that applying greater power to flotation slurries yields significant improvements in fine particle recovery. However, recovery of the coarser size class favours a different flotation environment. An improvement in the flotation kinetics of the fine and coarse size classes, provided there is no adverse metallurgical influence on the intermediate size ranges, is obviously beneficial to the overall recovery response. Managing the local turbulent kinetic energy dissipation, and hence the power imparted to the slurry, offers the benefit of targeting the particle size ranges exhibiting slower kinetics. FLSmidth recently introduced the practical implementation of this concept. In principle, it decouples flotation regimes where fine and coarse particles exhibit preferentially recovery. In the case of naturally aspirated machines (Wemco®), it is referred to as Hybrid Energy Flotation? and incorporates at least three phases: ? Standard flotation machines (standard energy input, rotor speed (r/min), rotor size/type) at the beginning of the row, where flotation is typically froth-phase limited and operational and set-up parameters have a limited influence on the recovery ? Higher-powered flotation machines (high rotor speed, high-power rotor size/type) at the end of the row to improve fine particle recovery ? Lower-powered flotation machines (low rotor speed, low power rotor size/type) to enhance coarse particle recovery. A CFD-based flotation model is used to highlight the effect of turbulent dissipation energy on attachment and detachment rates. Preferential collection zones for ?fine? and ?coarse? particles are predicted for both forced-air and naturally aspirated machines. The greater predominance of UG2 ore types, coupled with the skewed feed distribution of platinum group metals (PGMs) to the finer size fractions, suggests that PGM flotation circuits are not designed for optimal recovery across the size distribution. The application of the hybrid energy concept to PGM flotation offers a possible shift towards a more efficient flotation circuit solution through a managed distribution of energy.

Jan 1, 2012

By J. P. Hoffman

In 1988 the Japan Iron and Steel Federation started a research-and-development programme known as DIOS (direct iron-ore smelting). Eight Japanese integrated steel producers and the Coal Mining Research Centre, subsidized by the Ministry of International Trade and Industry, are involved in the project. The aim of the programme is to have a 500 v/d pilot plant for the production of iron via an oxygen-coal in-bath smelting converter in operation by mid 1993. The three main components of the DIOS process are as follows: ?a fluidized bed for the pre-reduction of iron-ore fumes ?in-bath smelting reduction in a converter ?off-gas reforming by the addition of coal fines. The main drive is to provide a smelting process that is more energy-effective, using coal instead of coke and/or electricity. The advantages claimed include inter alia ?direct use of fine iron ore ?direct use of non-coking coals-low coal consumption ?low capital expenditure-replaces costly coke ovens, agglomeration plants, and the blast furnace ?economical production on mini-plant scale ?less of an impact on the environment. This concept of 'direct steel has been carried over to the production of stainless steel direct from the ores, again bypassing such energy-intensive units as the submerged-arc furnace for the production of ferrochromium. A number of Japanese companies have indicated a certain amount of success. Several interacting elements are recognized that could have a productivity-limiting aspect. The possibility of the direct production of stainless steel from chromite is discussed briefly with reference to the Highveld of the eastern Transvaal as a possible site for such a plant

Jan 1, 1992

"Coal seam gas problems can adversely affect the safety and productivity of underground coal mines, leading to fatalities and financial losses. Conventional gas management technologies using ventilation and gas drainage are unable to deal with the high and irregular gas emissions associated with high-production longwall mining. New technologies need to be developed to supplement the traditional gas management techniques to minimize the hazard of coal seam gas. Thin spray-on liners (TSLs) have gained some success for rock surface support since their introduction to the mining industry. Due to their relatively low permeability and appropriate mechanical properties, TSLs also show potential to be used as a gas management tool in underground coal mines.In this paper we review the current gas management challenges and discuss the potential use of TSLs as a gas management tool in underground coal mines. This may involve reducing gas migration into the excavations/roadways, enhancing in-seam gas drainage, and preventing spontaneous combustion. Some potential areas for future research work are identified. IntroductionWhen a coal seam is influenced by mining activities, gas stored inside is liberated into the underground ventilation system. Gas emissions have created serious difficulties for the coal mining industry around the world. Therefore, coal mines have to develop effective strategies to control the gas concentration below the threshold value to meet statutory requirements. Ventilation has been the first solution in gas management for underground coal mining. When the emitted gas cannot be effectively diluted by ventilated air, gas drainage using pre- and/or post-drainage has to be introduced. However, even with ventilation and gas drainage, irregular gas emissions usually increase the gas concentration in roadways and slow down the development rate, thus causing significant economic loss to the coal mining industry (Thakur, 2006). Therefore, new technologies need to be developed to address this issue and mitigate the explosion risk."

Jan 1, 2016

By R. G. Votteler, A. C. Brent

"The first in this series of two papers, on the potential of renewable electricity sources for mining operations in South Africa, investigated the internal structure of mining corporations to evaluate feasible alternative electricity sources that were identified as through earlier research. The purpose of this paper is to combine current knowledge about the external macroeconomic and the internal environments to produce a clear picture of how renewable sources of electricity could perform from the perspective of mining corporations in South Africa. The multi-attribute value theory (MAVT) approach was adapted to structure the research and results. The model was fed with real-time data provided from five different energy companies and four mining corporations operating in South Africa. The results show that the performance of hybrid versions of the currently used electricity sources (diesel generators and Eskom grid connection) with solar PV and onshore wind is favourable compared with the current sources alone. The advantage of diesel generators is significantly greater than that of the Eskom grid connection. By combining the macroeconomic influences with the MAVT results, hybrid solar PV versions are identified as having the greatest potential. In second place are hybrid wind solutions, which have the shortcoming that good wind conditions occur only in coastal regions where there are fewer mining activities. Geothermal hybrid versions are the least favourable owing to the lack of service infrastructure and high initial investment costs.IntroductionRecent developments in the macroeconomic environment necessitate an investigation of the internal structure of mining corporations to evaluate possible alternative electricitygenerating sources (Roehrl and Riahi, 2000). To be able to combine current knowledge of macroeconomic factors and the internal structure of mining corporations, the research process is presented in two papers. The first paper (Votteler and Brent, 2016) investigated the internal structure and argued that a strategic tool should be used to evaluate electricity sources from the perspective of mining corporations. The multi-criteria decision analysis (MCDA) approach was selected as the most appropriate strategic tool. Based on a literature review of previous similar MCDA approaches in energy planning, it was concluded that no adaptation of MCDA methods could be found from a corporate, mining, or South African perspective. Finally, the paper investigated the internal evaluation structure in collaboration with mining corporations, by identifying the criteria they use to evaluate electricity sources."

Jan 1, 2017

By K. Grossauer, W. Schubert

For tunnelling in poor and heterogeneous ground a reliable on-site short-term prediction is required to allow a safe and economical construction. With the use of absolute displacement monitoring data and advanced software for evaluation of the data in combination with a routine update of the geological model a considerable increase in the reliability of the short-term prediction could be achieved. The paper deals with theoretical considerations, numerical studies and case histories from alpine tunnels in heterogeneous rock. Tunnelbau in schlechtem und heterogenem Gebirge erfordert auf der Baustelle eine verlaessliche Kurzzeitprognose, um ein sicheres und wirtschaftliches Bauwerk gewaehrleisten zu können. Die Verwendung von absoluten Verschiebungsmessdaten und deren Auswertung mit Hilfe von hoch entwickelten Softwareprogrammen in Kombination mit einer laufenden Aktualisierung des Gebirgsmodells ermöglicht eine erhebliche Erhöhung der Verlässlichkeit von Kurzzeitprognosen. Dieser Beitrag beschäftigt sich mit theoretischen Ansätzen, numerischen Modellen und Fallstudien von Tunnelvortrieben in heterogenem Gebirge. La construction de tunnels dans la montagne hétérogène de faible résistance exige un pronostic fiable à court terme sur le chantier, afin de pouvoir garantir un ouvrage sûr et économique. L'utilisation des données de mesure de décalage absolues et de leur évaluation à l'aide de logiciels sophistiqués en combinaison avec une mise à jour courante du modèle de la montagne permet une augmentation considérable de la fiabilité des pronostics à court terme. Cette contribution présente des approches théoriques, des modèles numériques et de cas pratiques de progressions de tunnels dans des montagnes hétérogènes.

Jan 1, 2003

By More-O&apos, R. C. Ferrall, J. W. Wilson

SYNOPSIS The theory of elasticity has been shown to provide a means of determining the stresses and displacements induced by mining in deep level hard rock mines. This theory has been incorporated into an electrical resistance analogue on which the plane of a reef or ore-body can be modelled to enable the rapid determination of stresses and displacements at points in the plane of the reef. This electrical analogue has been used to determine energy release rates caused by scattered mining, which, to some extent, is a measure of the degree of hangingwall fracture. A correlation between predicted energy release rates and actual underground conditions in stopes in the O.F.S. goldfields has been encouraging enough to define parameters on which future stoping layouts can be based. The use of the elastic theory through the analogue has been extended to the assessment of the influence of stoping operations on off-reef excavations. Underground conditions at damaged and undamaged areas have been compared with predicted elastic stresses at the positions under review, resulting in the derivation of design parameters for use in siting off-reef excavations in the prevailing geological conditions in the O.F.S. and Klerksdorp goldfields. The analogue has also been used to assess the vulnerability of certain un mined dykes to bursting. Correlations between stresses induced on dykes by stoping and dyke behaviour underground has enabled critical stress levels to be determined for several persistent dykes occurring in the O.F.S. and Klerksdorp goldfields. A number of long and short term planning projects at mines operating in the Anglo American Corporation and General Mining and Finance Groups are described, where the data derived from the electrical resistance analogue is processed by computer programmes and assessed on the strength of the design factors derived from the correlation of field work and the elastic theory.

Jan 1, 1970

By K. Böde

Hochtief AG Germany has developed a comprehensive management and information system for the construction industry named Aristoteles. This system is an efficient supporting tool to manage a variety of construction sites as well as operating business units with required economic targets. As such, Aristoteles offers wide-ranging control of complex economic processes in construction in a consistent manner. In this paper the process oriented functions of the system will be described with special emphasis on finance accounting and cost control. The basic elements in this respect are tender estimation, creation of initial project budgets and running budgets, regular determination of work done and result forecast to the end of the project. Further, cost accounting, monthly reporting, and all balance-related postings are included. On the basis of the extensive reporting (targeted/actual cost comparison, cost manager, project report, actual/targeted hours worked comparison, overhead cost report, amendment report or project (result) lists of all projects realized by one business unit), the responsible managers can make justified project evaluations, project controls and variance analyses during the project period and derive appropriate management measures. Thus, Aristoteles includes all substantial elements for the risk management of the operational business. In big construction joint-stock companies it is of crucial importance to satisfy the information requirements of the investors. In this respect the system provides a transparent presentation of the financial, investment and profitability situation of the company. In the international construction industry the balancing rules according to IAS (International Accounting Standards) have already been used to a larger extent. In accordance with these rules the partial profits of the work during execution can be shown as realized even before completion of a long-term contract. The validity of Aristoteles will be outlined briefly. Major advantages using the system are highly enhanced accuracy of project controlling, systematic overhead allocation to projects, change of attitude of the project personnel due to increased cost consciousness and improved flow of information within the company.

Jan 1, 2003

The Iscor Board has given its Mining Division the authority to proceed with detail engineering and design for a Heavy Minerals Project which comprises a mine in Northern Province near Gravelote, a mine in KwaZulu/Natal near Richards Bay and a central processing complex with a beneficiation plant and smelter which will be located near Richards Bay and Empangeni.

Jan 1, 1996

By P. A. Botha

The production of iron and steel generates various types of waste materials containing oxides, carbon, and flux material. Usually, these materials are land-filled at the plant site or are hauled away for disposal. Some of these waste materials are hazardous, and they must therefore be recycled or disposed of properly. The influence of different waste materials in iron-ore sinter blends on the quality and operational parameters in sinter production is described. The recycling of waste materials such as dolochar, scrap fines, mill scale, electric-arc furnace slag, basic-oxygen-furnace mud via the sintering process can achieve a saving in the cost of the raw materials (for example, fuels and flux) and a reduction in pollution. A comparison of a typical sinter with a sinter produced through the utilization of waste materials shows a distinct correlation between certain types of waste material and some metallurgical properties and operational parameters. Dolochar (and arc-furnace slag) in a sinter blend acts as part of the fuel and flux that are normally added to a sinter mix. In general, dolochar improves the quality of the sinter and decreases the consumption of coke. Other waste materials adversely influence the quality of the sinter, but not necessarily the operational parameters such as the production rate. At Vanderbijlpark, approximately 15 kt of various waste materials per month are successfully recycled in the sinter plant. Investigations into the handling and recycling of other waste materials may indicate that even more waste materials can be utilized.

Jan 1, 1993

By P. Lloyd

Perceptions of disaster caused by burning fossil fuels have reached such a pitch that they seriously threaten the very future of the industry. Coal is a dirty word. A leader in Business Day(January 192009) claimed ?There is no disputing that renewable and non-polluting energy sources are preferable to the country?the true cost of so-called cheap coal-fired power stations is neither reflected nor accounted for by Eskom?the true and immediate but unacknowledged cost of continued coal mining is apparent in the catastrophic level of acidification from mining runoff of all significant natural water resources in the country?and their waters have been rendered unfit for human consumption. Air quality is in a similar state with?increases in pulmonary disease causing workforce absenteeism and compromised childhood development, among many other health problems recorded in areas polluted by coal mining.? The upshot is that our latest coal-fired power station, Kusile, is being required to use flue gas desulphurization. The costs are considerable, and the benefits minimal. Meanwhile, exports are being threatened by EU directives and an assumption that South African coal gives off excessive quantities of SOx and NOx when burned. The industry needs to arm itself with clear responses to these and similar misconceptions, and to communicate those responses loudly and clearly, if it is to survive.

Jan 1, 2011

This paper describes DRA?s involvement with the expansions at Tati Nickel, Phoenix Mine, that have taken an initial plant design of 3.6 Mtpa (originally built by Murray & Roberts), up to 5 Mtpa, and eventually 12 Mtpa capacity. Initially, the plant could not achieve the design name plate capacity for the first few years of operation, as a consequence of the notoriously hard and abrasive nickel ore affecting primarily the operation of the crusher circuit. In order to extend the life of mine, Tati? assessed and then redefined the mining plan, choosing to increase the Phoenix mine reserves to a lower cut-off grade. In order to increase nickel units produced, the concentrator had to therefore treat additional tonnage at lower head grades. Site investigations and field tests around the comminution circuits are outlined, indicated that the milling circuit could be increased to 650 tph, from the initial design of 470 tph, for a similar feed grade and recovery. A project was initiated to debottleneck the crusher circuit and achieve the new target throughput. (Project 5M). This was followed by a feasibility study of the impact of pre-concentration by DMS, which after promising laboratory tests, was followed up with the installation of a 200 tph ?demonstration? plant. The success of this demonstration plant provided the impetus to expand the supply to the 5 Mtpa mill from a large preconcentration stage. A gyratory crusher (one of the largest and most powerful) will receive ore directly from the open pit operation, feeding into a secondary-tertiary crushing plant followed by a modular DMS preparation circuit. Four large DMS processing modules have been installed to treat the tonnage, with high expected rejection levels. Finally a review of the DMS process capability on an ostensibly disseminated micro-gabbro nickel ore is given, which shows the remarkable impact that preconcentration can have on an operation, both in terms of profitability and a successful process ?expansion?. The performance of the DMS plant has significantly extended the life of mine, allowing the mine to significantly reduce mine cut-off grades and curb its previously selective mining practice.

Jan 1, 2009

Geologists in some underground gold mines collect grab samples from broken ore piles or trucks as a method of grade control. It is often known as muck sampling. Generally, the goal of grab sampling is to try and reconcile the mined grade at the ore source to the predicted grade and/or predict the mill feed grade. The mass of the sample collected is limited by health and safety issues, as well as the capacity of the laboratory to process the samples within a given timeframe. In general terms, grab sampling is known to be problematic because samplers tend to over sample the fines, and/or pick out high-grade fragments; surface sampling of piles does not test material within the pile; muck piles in development drives/faces are likely to be zoned due to the blasting sequence; high or low-grade material may preferentially segregate in the pile during mucking; the five percent mass reject size of the material in muck piles is very large from underground blasting; some correlation usually exists whereby the larger fragments are enriched or depleted in the critical component of value; and the average error made in estimating the true stockpile grade is likely to be high. The method is prone to chronic fundamental sampling, grouping and segregation, delimitation, and extraction errors. Substantial warnings must be given with respect to the use of grab sampling for grade control in gold mines. The method may appear to work sometimes, which can be attributed to a fine gold particle sizing and more disseminated distribution. As with all sampling methods, its appropriateness must be determined by ore characterization and heterogeneity testing to ensure the method suits the ore type.

Jan 1, 2009