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By S Mitra, D O’Dea, N Barrett, T Honeyands, E Copland

This work describes a novel mapping technique that allows the direct overlay of calculated local phase equilibria on micrographs of the physical system. The technique demonstrated integrates FactSage™, ver 8.2 (by Thermfact Ltd. and GTT-Technologies) phase equilibria calculations with mapped compositions determined by Scanning Electron Microscope – Energy Dispersive X-ray Spectroscopy (SEM-EDS) to visually express calculated properties while preserving the spatial information of the sample. The developed methodology is used to analyse interrupted blast furnace softening and melting tests containing mixed burdens of lump and sinter. Tests are interrupted at 1300C and cooled to room temperature for analysis. Phases present at room temperature are analysed to infer the liquid fraction and phases present at high temperature. Analysis of the interface regions between the dissimilar burdens allows insights to be gained into the interaction mechanism. During the transition from solid to liquid, migration and interaction of liquid oxide across the interfaces of the dissimilar burdens has been observed and demonstrated to impact softening and melting performance. Specifically, interaction of the oxides generated by lump (primarily FeO, SiO2 and Al2O3) and sinter (primarily FeO, CaO, SiO2, Al2O3 and MgO) are analysed, and the occurrence of a range of new mineral phases such as merwinite, melilite, olivine and bredigite observed.

Jun 19, 2024

By R Jacobs

"The Jaguar project is relatively unique in that it was evaluated, financed, built and operated to completion within the last ten years, providing the opportunity to holistically review and reconcile expectations against the actual outcomes. It is a case study that allows wider conclusions to be drawn with respect to the risks and opportunities involved with project evaluation and execution.Jaguar is located in the Leonora Mining District of Western Australia and was commissioned in mid-2007 as an underground accessed, single high-grade volcanic-hosted massive sulfide (VHMS) deposit with an on-site concentrator, producing copper and zinc concentrates exported via the Port of Geraldton to South-East Asian markets.The feasibility study (FS) had several iterations (JML, 2005a); the last dated July 2005 was specifically targeted to secure project funding, and summarised the reserves-only portion of the resource and its planned exploitation. The commissioning of the mine was the transition for the owner Jabiru Metals NL from junior explorer to producer and the project was the dominant asset of the company.Jaguar operated through several significant deviations from the linear project plan set out in the FS, including the Global Financial Crisis (GFC), a corporate takeover and disruption to the mine plan from the onset of material geotechnical issues. Whilst the GFC or mining disruption were not specifically predicted in the FS or peer reviews, the generic effects of the events were assessed in the project risk assessment and they influenced subsequent management decisions. In parallel to the internal project-specific risks, the short planned life of Jaguar was a risk to the continuation of the corporate entity which was being addressed by significant investment into brownfields exploration to extend or replicate the project, and ultimately added value such that attracted a corporate takeover.Holistically, the project delivered the returns predicted in the FS, but in a much different guise than was expected. This paper will describe the reality of operations compared with the study predictions and expectations through the perspective of the project and corporate risk assessment.CITATION:Jacobs, R, 2016. Jaguar base metals project case study – has reality reflected the study?, in Proceedings Project Evaluation 2016, pp 86–97 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 8, 2016

A magnetometer survey 'was the Darkes Forest area between 1968. The instrument used was model MZ4 with sensitivity 9.4 conducted over part of 30th April and 3rd May, an ABEM torsion magnetometer gammas per scale division. The survey consisted of a closed magnetometer loop along lines cut for a previous magnetometer and seismic reflection survey by Wongela Geophysical in March, 1968. The magnetic results of the previous survey were not satisfactory in some areas and are presented as a comparison in instrumentation. Station separation in the present survey was 100 feet with tie-in readings at shot points of the previous survey (usually 1320 feet apart)

Jan 1, 1969

By D J Maconochie

The use of rock bolts as permanent support has been prohibited by client specifications in several recent large tunnel projects in Australia. The justification for this appears to lie in concerns with proper and verifiable installation procedures rather than concerns with the intrinsic durability of the corrosion protection systems. However, in civil tunnels, preventing the use of permanent rock bolts for long-term support results in the use of cast in place concrete lining which in some instances would otherwise be unnecessary.

Mar 8, 2011

By R Bertuzzi

"This paper presents preliminary results of ongoing research being carried out at the University of New South Wales Australia (UNSW) into improved methods for estimating rock mass strength. In this paper the rock mass strength of Hawkesbury Sandstone is assessed. An estimate is first made based on an extensive database of intact rock strength data being collated by the author and the assumption that rock mass strength can be determined following the geological strength-index (GSI) approach. The resulting strength envelope is then compared with nine documented case studies where stress induced failure has occurred in tunnels excavated within Hawkesbury Sandstone. The case studies cover a range of conditions: construction dates from 1880s to 2006 spans from 3.2 to 12.5 m depths from 17 to 124 m excavation methods of drill and blast, roadheader and tunnel boring machine (TBM).Finite element modelling is used to assess the likely magnitudes of the principal stresses that were present at the time of the failures. The finite element models are interrogated to provide the values of major and minor principal stresses in and around the mapped failure zones. Failure and stable points are then compared to the proposed strength envelope(s) of Hawkesbury Sandstone derived using the Hoek-Brown and the spalling criteria. The ability of the Hoek-Brown rock mass strength criterion to differentiate between the ‘failed’ and ‘stable’ zones is considered to be remarkable.CITATION:Bertuzzi, R, 2014. Estimating the rock mass strength of Hawkesbury Sandstone, in Proceedings AusRock 2014: Third Australasian Ground Control in Mining Conference, pp 417–424 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Nov 5, 2014

By C Lutherborrow

The Sangdong Tungsten/Molybdenum Deposit is located in the Republic of Korea and was discovered in 1916. At this time Korea was a colony of Japan. It was mined for two years after discovery closing in 1918. Full production recommenced in 1933, and from that point until 1945, it was the major source of tungsten for armour plate for the Japanese military. After World War 2 the US government ran the mine until late 1946. The mine operation then passed to Korean ownership but production ceased during the Korean War and did not recommence until late 1953. The mine ceased operation in 1992 due to low metal prices. From the late 1960s to the time of closure, Sangdong was the largest tungsten mine in the world (Kim, 2002). An understanding of changing mining methods over time has been critical in assessing the potential of redeveloping the Sangdong Deposit.

Aug 22, 2011

Two characteristics of the modern mining industry are that there is a skill shortage and that young professional people rise rapidly into highly responsible supervisory positions. With this responsibility comes the burden of identifying and managing health and safety risks. Without the benefit of a comprehensive health and safety training program, these young professionals may be putting both themselves and those under their supervision at risk. The Moura Mine explosions and the asbestos health disaster should not be just artifacts of history, but highly valued lessons that impress the need for comprehensive health and safety risk management strategies on young professionals. From the perspective of the former secretary of the Committee to implement the findings of the Moura (Disaster) Inquiry and as the former coordinator of the Coal Workers Health Scheme, key issues in occupational health and safety management systems are explored.

Jan 1, 2005

By J Light

Since 2019, the mine planning team at Olympic Dam has been establishing and maturing a shift from deterministic to probabilistic scheduling techniques. This paper outlines this journey undertaken by the mine planning team, key learnings from implementation and further work required to increase the level of planning maturity. Olympic Dam (OD) is a highly variable, polymetallic orebody with a vertically integrated value chain from operations to final product. The processing plant has a tight set of quality constraints which are managed through timing of stopes from varying parts of the orebody. Value is eroded for the operation when forecasted quality of the mine feed encounters disruptions from unplanned changes to the timing of stope starts. As production has moved from the historic Northern Mining Area into the more geologically complex Southern Mining Area, average stope size has reduced, resulting in increased mining fronts required to meet production targets. This has created a problem of increased schedule complexity and difficulties in identifying and communicating resource priorities within a large set of individual stope critical paths. The problem was approached by considering each stope as an individual project constructed by teams working across multiple projects at any one time. The operation could then be considered a multi-project environment with shared resources and enables the application of Critical Chain Project Management (CCPM) to the mine plan. Key to CCPM is the addition of time buffers to protect the critical path of a project form upstream or downstream processes. Implementation of time buffers protects the stope start date against compliance to plan variance. The monitoring of each time buffer consumption, as a proportion of total construction activities completed enables proactive prioritisation of resources. This resulted in an increase in the number of stopes starting in accordance with the mine plan, simplified communication of priorities to all levels of the operation, increased compliance to plan and a clear measure of schedule risk during planning routines.

Mar 29, 2023

By B N. Noller, J C. Ng, S L. Bruce

Mining activities can result in the transfer of harmful elements, including arsenic and lead, into the environment. In Australia, one of the potential future uses of rehabilitated mine land is to stock grazing animals. Elemental uptake is dependent on bioavailable fraction for adsorption upon exposure. Bioavailability data are generally lacking in order to provide realistic health risk assessments relating to harmful elements from mine tailings in Australian conditions. Another key component of risk assessment is the ability to estimate a realistic exposure, or dose rate, of the tailings to the grazing cattle over a set period of time. Hence, we aimed to conduct grazing trials directly on rehabilitated tailings facilities in order to provide valuable in situ information on heavy metal dose rates and associated accumulation. For the laboratory-based evaluation of comparative bioavailability, groups of cattle were fed five days a week on a normal diet spiked with mine tailings or soluble pure salts of target elements (eg sodium arsenate, sodium arsenite and lead acetate) for about eight months. For the field validation, cattle were allowed to graze directly on rehabilitated tailings facilities over a similar length of time. Blood and a biopsy of the muscle and liver were periodically collected to monitor arsenic accumulation. At necropsy, blood, muscle, liver, kidney and other saleable tissues were measured for arsenic concentrations. Although this study was focused on arsenic, lead and other metals were also measured. Predictive models for arsenic and other metals have been established to calculate the maximum grazing duration without the risk of exceeding specific food safety guidelines. The outcome of this study is a predictive model for maximum beneficial use of certain rehabilitated tailings for cattle grazing where grazing activities do not impact on the integrity of the tailings dams.CITATION:Ng, J C, Noller, B N and Bruce, S L, 2014. A predictive model for beneficial use of rehabilitated mine tailings for grazing cattle after mine closure, in Proceedings Life-of-Mine 2014 , pp 563–572 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 16, 2014

By H Ishikawa, S Palaniandy

The gravity-induced stirred mill such as the TowerMill is an energy-efficient grinding solution used in secondary, tertiary, and regrinding duties in the mineral processing concentrator. The interest in this technology is emerging, with more than 300 mills installed globally in various grinding duties and commodities for the last 30 years. Although the technology is matured, there are still opportunities for improvement and the development of new knowledge to improve its circuit energy efficiency and reduce water consumption. Recent studies show that a combination of stress intensity, ore hardness, slurry density, and mill feed configuration can be used to evaluate the performance of the grinding circuit. A recent pilot-scale TowerMill test work at various stress intensities shows that a lower operating work index and size-specific energy were achieved at higher agitator tip speed and using medium size grinding media. These outcomes were confirmed through several site trials. A smaller 17 mm grinding media has reduced the operating work index and size-specific energy by 18 per cent and 11 per cent, respectively, compared to the 20 mm in a magnetite concentrator. Moreover, the conversion from top feed to bottom feed configuration has reduced the operating work index and size-specific energy by 13 per cent and 37 per cent, respectively. The circulating load was reduced by 34–38 per cent, leading to a reduction in the dilution water consumption in the hydrocyclone feed sump by 20 per cent. A variable frequency drive offers flexibility to change the stress intensities on the TowerMill, where a 35 per cent reduction in specific energy was achieved when the ore became soft. This paper explores the potential design and operating strategies that can be implemented to enhance the energy efficiency, reduce water consumption and reduce CO2 emissions in the circuit and finally evaluate its impact on the total cost of ownership.

Aug 24, 2022

By L Nagy, K P. Juhasz

The authors were engaged to optimise a traditional rebar cage reinforced concrete segmental lining by means of finite element analysis (FEA) using macro synthetic fibres for the Shanghai metro extension. The aim of this study was to reduce or entirely replace the original steel reinforcement of the segmental lining, in order to make the precast production process faster and more economic. The outer diameter of the tunnel was 6200 mm, the thickness of the segments was 350 mm.The numerical calculations were performed by Atena Finite Element software, which is based on the combination of Menétrey-William and Rankine failure surfaces on the compression and tension sides respectively. The effect of the macro synthetic fibres was modelled as tension stiffening on the tension surface.A one-to-one full scale model of an assembled tunnel ring using the original reinforcement cages was tested at Tongji University in Shanghai, July 2013. The ring was tested to differing load levels where load and displacement were measured until failure. The author’s first step was to calculate the real displacement characteristics of the original reinforced concrete (RC) ring, then calculate the numerically modelled version, so as to compare them. The material parameters of the concrete and rebar used had been determined through basic material tests conducted at the Tongji University. (Bi, Liu and Wang, in press).The numerical modelling undertaken has shown good correlation with the full-scale physical test results. Optimisation of the lining reinforcement was achieved through the addition of fibres, resulting in a substantial reduction of the steel rebar cages. Several results have been computed with the numerical model using different dosages of macro synthetic fibres, showing that the mass of steel reinforcement could be reduced by 50 and 75 per cent respectively.CITATION:Juhasz, K P, Nagy, L and Winterberg, R, 2014. Full-round numerical modelling of a macro synthetic fibre reinforced tunnel boring machine tunnel in the Shanghai Metro extension, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 477–484 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By A Grace, C Sennersten, T Taylor, A Davie, R Lyu, D Pentecost, C A. Lindley, J Craig, L De Macedo Camargo

Many underground mine void spaces are not suitable for human entry due to unprotected roofs, instability or having an unknown safety state (eg if they are many decades old). Investigations of these voids may nevertheless be important for general mine safety, for example to detect propagating collapses or water accumulation, prevent accidental intrusion by new developments or drilling to reassess old spaces for re-mining. Robots are an ideal technology for investigating these spaces, especially flying, rotary-wing robots that can access and map vertical structures and spaces while avoiding rocks, water and mud that have accumulated on void floors. To operate in underground mines, we are developing customised unmanned aerial vehicles (UAVs) as well as interactive 3D virtual models of the vehicles and their underground environments for controlling vehicle operation and visualising incrementally gathered survey data. Using a game/simulation engine to provide an interactive interface for UAV operation makes it possible to orchestrate external spatial information and video feeds with in-game cameras for optimal visualisation that is not limited to the position, orientation or field of view of cameras mounted on the UAV. First and third-person points of view with respect to the UAV are provided, together with 2D and 3D gaze tracking to provide effective interfaces for geology and mine engineering experts without the need for specialist UAV piloting skills. Ongoing work is addressing the provision of greater levels of autonomy for these vehicles to support mapping well beyond the line of sight of operators and geological characterisation of rock surfaces using sensors mounted on them, including miniature X-ray fluorescence and Raman spectrometers. Gathered data is fed into more general 3D models of the mine, block models and orebody so that the UAVs function as elements of a mobile perceptual system for intelligent mining.CITATION:Sennersten, C, Lindley, C A, Davie, A, Lyu, R, Grace, A, Evans, B, Pentecost, D, Taylor, T, De Macedo Camargo, L, Craig, J, Salomao, G N, Hellicar, A, Biggins, D, Timms, G, Coombe, M, Shahriar, M S, Smith, G and Rahman, A, 2015. Unmanned aerial robots for remotely operated and autonomous surveying in inaccessible underground mine voids, in Proceedings Third International Future Mining Conference, pp 101–108 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 4, 2015

By D McCoy

Titanium feedstocks are the building blocks of the titanium value chain. They can be mined directly, as is the case for ilmenite, leucoxene and rutile, or manufactured from ilmenite by extracting various quantities of non-TiO2 components from the ore by chemical and/or thermal processes.While feedstocks can be grouped into categories of materials with similar characteristics, they are essentially unique products from very different mining locations around the world. In fact, no two feedstocks are exactly the same. As such, the variations between the available feedstocks, in combination with the permutations in processing technologies to turn the feedstocks into titanium pigment or metal, mean that choices between feedstocks are specific to the location in which they are utilised.In this paper, the authors examine the key requirements of titanium feedstocks to the TiO2 pigment and metal sectors. Apart from the well known differences between feedstock choices for the sulfate and chloride process, the more opaque considerations in feedstock sourcing are examined.

Oct 5, 2011

By M Goers, M Almond

"The use of reverse circulation (RC) drilling for grade control sample collection was selected by the Pueblo Viejo Mine Geology department at the recommencement of the operation in 2010. This method was selected because it allows: for multi-bench drilling (60 m hole depth, four benches of mining) to aid mine planning and provide a detailed close spaced drill data comparison with the reserve model angled drill holes to optimise the drill hole interception of the vertically controlled mineralisation dry sample collection in areas of excessive surface and groundwater mining operations to commence with the long assay return period (due to the need for the samples to be shipped overseas for analysis) until the on-site laboratory is operational.To date, 118 302 m of drilling has been completed throughout the operations of two open pits: Monte Negro and Moore. Two drill rigs (contractor and site-owned and operated) with three generations of sampling systems have been used to date. Throughout the drilling a 20 per cent quality assurance, quality control (QAQC) sample check (blanks, field duplicates and standards) have been used to check the drilling and laboratories performance. In addition, a total of 1104 fines samples were collected to compare the drill chip samples collected and the fines lost with two of the sample systems used.The drilling to date has highlighted the need for a complete and coordinated system to be used before sufficient confidence in the quality of the samples collected is achieved.The complete system must be set-up and coordinated to obtain the best quality sample possible. This complete package includes: drill bit size and shape for the rock being drilled and mineralisation targeted face sampling hammers with the correctly sized hammer shrouds sample hose routing to reduce sample flow turbulence and choking blow-down valves to eliminate drill hole water that has entered the drill string during rod changes correct drilling techniques targeting sample quality a sample system that captures the fines for inclusion into the sample.These improvements can be obtained without reducing the drilling rates.The measurements required to demonstrate the improvement in the sample quality will be the focus of future work within the department.CITATION:Goers, M and Almond, M, 2012. Bit to bag - The importance of a total coordinated system in reverse circulation drilling, in Proceedings Sampling 2012, pp 65-72 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Aug 21, 2012

By D Teyhan, J Kirsch

Traditionally, most Australian iron ore mining operations have been surface-based. Processing plants were designed to handle dry ores. In recent years mining operations in the Pilbara have progressively moved below the water table exposing wet, sticky ores which have caused lost efficiency in screening operations as particles tend to agglomerate and adhere, blinding screening media. Miners and vibrating screen manufacturers have experimented with a shift from linear motion to elliptical motion screens. Elliptical motion conveys and lifts particles. Effective on flat deck (horizontal and inclined) or sloping decks it can be configured to provide a controlled transport rate, applying pressure in all directions to maximise screening efficiency. In practice, elliptical motion screens have proven to be effective in dislodging sticky particles from screening media, reducing blinding rates and improving screen efficiency. Moisture and clay content change during the life of a mine. These changes are sometimes the effect of seasonal rainfall, in other cases due to increased groundwater and clay content as mining operations go deeper. To compensate for such changes and optimise screen efficiency, changing the ‘shape’ of elliptical screen motion is required. This has traditionally required shutting down processing plants and making mechanical screen adjustments. Plant downtime is costly and machine adjustment has been a ‘trial and error’ practice. This paper will explore the results of a field trial that is currently underway in Brazil of a next generation elliptical motion screen design that allows operators to make changes to exciter rotational direction, speed and screen stroke angle, through electronic drive phase control. The machine’s electronic drive system synchronisation is enhanced for stability with a unique mechanical timing system. Operating at up to 6 g, screen adjustments can be made on the fly without stopping production. Early trial results are showing up to 50 per cent improvement in screen efficiency compared with traditional elliptical motion machines under certain feed conditions.

Aug 24, 2022

By D Teyhan, J Kirsch

Traditionally, most Australian iron ore mining operations have been surface-based. Processing plants were designed to handle dry ores. In recent years mining operations in the Pilbara have progressively moved below the water table exposing wet, sticky ores which have caused lost efficiency in screening operations as particles tend to agglomerate and adhere, blinding screening media. Miners and vibrating screen manufacturers have experimented with a shift from linear motion to elliptical motion screens. Elliptical motion conveys and lifts particles. Effective on flat deck (horizontal and inclined) or sloping decks it can be configured to provide a controlled transport rate, applying pressure in all directions to maximise screening efficiency. In practice, elliptical motion screens have proven to be effective in dislodging sticky particles from screening media, reducing blinding rates and improving screen efficiency. Moisture and clay content change during the life of a mine. These changes are sometimes the effect of seasonal rainfall, in other cases due to increased groundwater and clay content as mining operations go deeper. To compensate for such changes and optimise screen efficiency, changing the ‘shape’ of elliptical screen motion is required. This has traditionally required shutting down processing plants and making mechanical screen adjustments. Plant downtime is costly and machine adjustment has been a ‘trial and error’ practice. This paper will explore the results of a field trial that is currently underway in Brazil of a next generation elliptical motion screen design that allows operators to make changes to exciter rotational direction, speed and screen stroke angle, through electronic drive phase control. The machine’s electronic drive system synchronisation is enhanced for stability with a unique mechanical timing system. Operating at up to 6 g, screen adjustments can be made on the fly without stopping production. Early trial results are showing up to 50 per cent improvement in screen efficiency compared with traditional elliptical motion machines under certain feed conditions.

Nov 8, 2021

By D R. Anstey

The mining of magnetite iron ore in Western Australia will generate large volumes of waste rock and tailings over many decades. The need to dispose of these materials will result in massive waste landforms that will require significant planning and management. The formation of comparable man-made landforms is relatively common, as exemplified through past practice in gold and iron ore (haematite) mining. Unfortunately, the performance of these landforms, with respect to long-term stability (erosion resistance), the release of low pH seepage water and aesthetic impact, has commonly been disappointing and environmental legacies have been created as a result. Lessons that have been learnt from past, large mining operations indicate that there is a need to rethink the methods of waste disposal and landform development applied to magnetite mining. The environmental compliance criteria applied to magnetite mines for the storage of tailings and waste typically include minimising dust generation (particularly as the tailings and mine waste may contain asbestiform minerals), control of silt, minimising visual intrusion and management of potentially acid forming materials. In addition, the climate of Western Australia and the paucity of both surface and groundwater in the vicinity of the magnetite mines frequently necessitate water consumption to be minimised. This paper discusses the potential to co-mingle magnetite mining waste streams in a variety of ways to concomitantly satisfy the environmental compliance criteria and the operational requirements of the mine. These methods include co-mingling of coarse tailings and waste through dry-stacking, deposition of tailings as a paste, co-disposing of all wastes to form an integrated landform and the co-mingling of all waste streams to produce PasteRockTM (a blend of tailings paste and crushed waste rock). The paper demonstrates how these techniques can be applied to the magnetite mining industry to provide better outcomes than might be achieved using more conventional techniques, currently employed in large-scale mining operations.

Jan 1, 2009

By Wright JK, Turner RE, Batterham RJ, Morrison AL

Simulation can play an important role in the design, optimization and control of complete industrial processes, the most appropriate method depending on the particular application. Most commonly, process models or simulators are means of representing the process which are either purely mathematical or physical. Mathematical models, however, almost invariably need to be based to some extent on experimental data or require experimental verification before they can be used with confidence. Ways in which experimental and mathematical modelling techniques can be combined to best effect are discussed, with reference to the simulation of iron ore induration and direct reduction processes. A novel method is presented for the simulation of direct reduction shaft furnaces. Small scale apparatus has been developed in which ore or pellet samples are subjected to the changing environment of the industrial process. The time dependent conditions (solid temperature and gas compositions) are provided by a mathematical representation of heat transfer and the conservation of mass and energy in the process Simulated.

Jan 1, 1986

By J E. Everett, F Grobler

This study considers realistic data for a planned open pit iron ore mine, but is applicable to any open pit situation. By interpolating drill hole data, grades are generated for a rectangular block model. Each blockÆs grade designation vector has components for each analyte (chemical element or compound) influencing ore value. Interpolation by means of geostatistical kriging leads to each block being assigned its expected value, and thus underestimates the overall grade variability. Alternatively, interpolation by means of conditional simulation is a method that implements random sampling from an infinite population of solutions. Each conditional simulation has appropriate overall grade variability, but estimating any blockÆs mean and variance requires sampling from multiple conditional simulations. For a block model, an ore/waste selection criterion maximises the expected tonnage at a target grade. This criterion is a linear composite of the grade components, with positive coefficients for the beneficial analyte (iron) and negative coefficients for the deleterious analytes (such as silica, alumina and phosphorus).Although conditional simulation gives the same expected grade as kriging for each block, the expected maximum tonnage of ore selectable at a target grade may differ from that obtainable from the kriged solution. We apply the linear composite selection criterion to each of 25 conditional simulations, as well as to the kriged block model. The resulting distribution of product tonnage is confirmed to have an expected tonnage that is over 20 per cent greater than that of the kriged model. The method also enables a selection probability to be computed for each block, and thus a probabilistic pit boundary distribution to be identified and used in mine planning. Proposed extensions will consider risk-based scheduling of the multiple selection solutions through minimisation of a derived æstress factorÆ and treating the mining process as an iterative system with actual or artificial ædepletionsÆ modelled in line with the mine plan, using the updated state (with new information) to re-evaluate the mine plan for subsequent periods.CITATION:Everett, J E and Grobler, F, 2013. Risk-based ore selection from conditionally simulated block models, in Proceedings Iron Ore 2013 , pp 149-156 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 12, 2013

By J Elder

Magnetic separation equipment has long been used to upgrade and beneficiate a wide variety of minerals and materials. Over the years, significant advances in both wet and dry magnetic separators have improved their operability and separation performances, broadening their use.But no one answer exists to the question: what is the right type of magnetic separator? For many minerals, including ilmenite, both process routes may be viable. There are technical, production, as well as economic reasons for choosing wet versus dry. However, recent developments illustrate that a new generation of wet magnetic separators is approaching performance once seen only in dry magnetic separation. With quality and production performance becoming similar, the choice between wet and dry magnetic separation is not as cut and dry as it once was.

Oct 5, 2011