Search Documents

By C Paoletti

About 15 years ago the debate on the reliability of sampling procedures for agricultural food and feed commodities was initiated by a few brave scientists who questioned the representativeness of what, at the time, were routine sampling procedures established exclusively on the basis of tradition and practical feasibility. Over time several national and international organisations contributed to the discussion, developing standards and publishing papers either to underline the fact that sampling is always a source of error, in itself, which cannot be overlooked, or to minimise the relevance of sampling on the basis of argumentations linked to time and money limitations. The latter dominated, but is nevertheless impossible to accept from both a scientific and a responsible management perspective. Here the author presents an historical overview of these past 15 years, illustrating the most controversial issues, reporting major achievements in food/feed sampling, highlighting milestones, as well as unresolved problems that still need the attention and contribution from the sampling community. The need to incorporate Theory of Sampling (TOS) into food/feed safety assessment (pre-market), as well as into food/feed safety monitoring (post-market) has recently been highlighted, and the practical applicability of TOS to base food/feed safety decisions on representative sampling, has been explored and documented via concrete examples of risk analysis in different areas of food/feed industrial production chains. Now it is time to move forward and ensure that TOS is fully integrated into the well-established Food and Agriculture Organization (FAO) / World Health Organization (WHO) risk assessment approach, in order to guarantee a transparent and correct universal frame for risk assessment and the subsequent management decision-making process. WCSB8 offers the ideal platform to explore the best way to do so, switching from a theoretical discussion of correct sampling principles for food and feed agricultural commodities to practical recommendations in the interest of consumers, worldwide. These 15 years have also been a personal journey of interesting dimensions, indeed a veritable roller-coaster ride in-and-out of the scientific, technological, industrial and (last but not least) regulatory worlds. The start was WCSB2 in 2004, when I flew to Australia to discover if in other areas sampling had been identified as an unavoidable issue and, if so, what the solution was. There, I found a good travel companion who today is still on my side, to assemble the puzzle and explore how to shape the future, to concretely answer to the 15 years’ quest for proper sampling in the assessment and monitoring of food/feed safety.CITATION:Paoletti, C, 2017. Assessing and monitoring food and feed safety – a 15 year quest for proper sampling, in Proceedings Eighth World Conference on Sampling and Blending , pp 39–44 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2017

By T A. J Hopper, S Mukkisa, M L. Johns, K T. O’Neill

Technological advances the sensor design and performance for logging while drilling (LWD) instrumentation offer considerable opportunities in iron ore exploration. Here we focus on the development of a nuclear magnetic resonance (NMR) LWD tool. NMR is an advanced geotechnical logging technology capable of providing in situ measurements of the porosity, pore size and permeability of the formation of interest. The ability to provide real-time characterisation of iron-ore systems is beneficial to both drilling operations as well as real-time formation evaluation. The development of an NMR LWD tool for mineral exploration drilling has previously not been achieved due to the significant technical and environmental challenges associated with the design and operation of such a tool. The tool outlined in this work is designed to work in reverse-circulation (RC) drilling systems. As such, the tool needs to be compatible with the RC drill-string, as well as being highly robust to survive the shocks and vibrations experienced during RC drilling operations. The magnetic physics of the probe must be capable of measuring at the appropriate depth into formation whilst being subject to the array of motions experienced during drilling operations. Furthermore, conducting accurate NMR measurements in an iron ore formation is challenging and the measurement methodology must be tailored to characterise the magnetic environment. The tool also requires high-powered electronics capable of operating the necessary pulse sequences for excitation and acquisition. The resultant tool design must therefore optimise the inherent trade-offs which exist between the physical components (ie mechanical structure, magnetic components and electronic hardware) in order to operate appropriately whilst not hindering RC drilling operations. Current experimental analysis of the prototype indicates that the current probe design exhibits the required measurement specifications and is nearing field testing. Future work will look towards commercialisation of the instrument.

Nov 8, 2021

By Swayn G. P, Floyd J. M

BHAS, together with the G.K. Williams Laboratory, and Ausmelt Pty. Ltd., has examined a number of possible alternatives to conventional silver cupellation in gas fired reverberatory furnaces. Of these alternatives, a Sirosmelt furnace was preferred for both technical and economic reasons. Small scale work on Sirosmelt processes was carried out at the G.K. Williams Laboratory at Melbourne University in 1985/86. Pilot scale work was carried out at the Ausmelt plant in Melbourne in July 1987. Board approval for construction of a full size plant was received in October, 1988, and construction of the plant is currently underway. The plant is expected to provide significant savings in operating costs and silver inventory. Hygiene around the furnace should also be greatly improved. An increase in cupellation rate of at least ten times is expected, compared with the conventional reverberatory furnace.

Jan 1, 1989

By M G. Aylmore, L W. de Klerk

Roasting of refractory gold ores has been a commercial process for many years. Improvements in design of fluidised bed roasting technologies and low capital and operating costs compared with other refractory treatment processes can potentially make roasting a viable option.However, gold extraction from roasted ores carried out on laboratory scale equipment often invariably yields lower recoveries than other processes such as bio-oxidation or pressure oxidation. Non-optimal laboratory roasting conditions can incorrectly write roasting off as a process option.Low gold recoveries from the cyanidation of calcine products from roasting can often be attributed to roasting conditions not favouring gold liberation and agglomeration processes, particularly if lockups of elements such as arsenic are being pursued for environmental reasons.This paper reviews the conditions favoured for gold agglomeration and accessibility of gold to cyanide, test conditions to achieve gold liberation and agglomeration on laboratory scale and designs that incorporate staged decomposition and roasting to make roasting a more commercial option.CITATION:Aylmore, M G and de Klerk, L W, 2013. Conditions and design considerations for maximising recoverable gold in roasting of refractory gold ores, in Proceedings World Gold 2013 , pp 375-388 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 26, 2013

By A Fyans, B Ghahreman-Nejad

This paper discusses the method and results of an options study into selection of the optimal form for a 130 m high tailings/water retaining dam, located in a region of high seismicity in central Iran. The proposed dam is part of a planned expansion project for Sarcheshmeh Copper Mine (SCM), which after construction will provide 550 million tonnes of additional tailings storage over the next 27 years. Geotechnical investigation at the proposed site indicated that adequate suitable low permeability materials (i.e. clay) were not available in the immediate vicinity of the dam site and would need to be imported from a distance of well over 10 km (direct). Given the magnitude of the estimated quantity of material and construction cost it was considered prudent to compare the cost of alternative dam design options for the proposed storage. A total of five dam design options are considered including a conventional rockfill embankment dam with an upstream sloping earth core (ECRD), a geomembrane face rockfill embankment dam (GFRD), a sloping asphalt core rockfill embankment dam (ACRD), a roller compacted concrete dam (RCCD), and a filter rockfill embankment dam for tailings storage together with a separate smaller earthfill core rockfill dam (ECRD) located downstream for storage of decant water. The risks, costing and design of all options are discussed in detail and the outcome of the study is presented.CITATION:Ghahreman-Nejad, B and Fyans, A, 2018. Optimum embankment design for a tailings dam, in Proceedings Mine Waste and Tailings Stewardship Conference 2018, pp 427–438 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 23, 2018

By R Castedo, P Segarra, L M. López, J A. Sanchidrián, A P. Santos

The cylinder test allows us to determine the expansion of a copper cylinder by the detonation of an explosive charge inside. This test, originally designed for military explosives, has been adapted for industrial explosives with non-ideal behaviour. From data obtained with this test and known physical relationships, an analytical procedure has been developed to calculate the Jones-Wilkins-Lee (JWL) equation of state parameters for five ammonium nitrate/fuel oil (ANFO) and six emulsion-type explosives. A new radial wall expansion function is proposed considering a non-zero initial velocity with the consequent positive Gurney energy at unit relative volume. A set of equations is established to determine the JWL parameters, three of them obtained at the Chapman-Jouguet (CJ) point and the other three at different relative volumes. These equations, along with some constraints to ensure a physically sound solution, are solved for the JWL parameters by a non-linear least squares scheme. A 2D Lagrangian axisymmetric finite elements (FE) numerical model is developed for each tested explosive to validate the analytical results, in terms of expansion histories, with good agreement. This confirms that the set of conditions, constraints on the parameters and least squares calculation used constitute a robust methodology that fully captures the physics of the detonation products expansion involved in the cylinder test.CITATION:Castedo, R, Sanchidrián, J A, López, L M, Segarra, P and Santos, A P, 2015. Jones-Wilkins-Lee parameters for civil explosives, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 57–64 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

By R Durchholz, A-J Heiertz, R Schmitz

Mining of lignite is the largest bulk materials handling activity in Europe. In order to mine this lignite, with an average calorific value of only a third of bituminous coal in an economical way, highly efficient opencast mining technology is mandatory. The total continuous mining of overburden and lignite was introduced more than 60 years ago and was subsequently developed stepwise into the largest mass transport system of the world. In 2011, the Inden Mine, one of three RWE Power mines, stripped 90 Mbcm of overburden to produce 22 Mt of lignite. In total, nearly 100 Mt of Lignite was produced from the three mines of RWE Power in Germany. Beside bucket wheel excavators (BWE), several high-performance in-pit crushing and conveying (IPCC) systems, which allow the adoption of continuous mining systems, even for typical shovel and truck (S&T) operations, are available today. RWE Power assists operators considering a change from the S&T to IPCC technology, both in the planning process involving large-scale belt conveyor systems and later with operational know how transfer. In a number of cases, the challenges associated with this system change have been addressed and solved successfully. One key challenge is managing the development of skills for operating the belt conveyor systems efficiently. This paper compares the effectiveness of S&T to different configurations of continuous mining operation for an up to 170 m deep mine with a total annual output of 117 Mbcm. From the mine operatorÆs point-of-view, the quantity and skill level of staffing required for operation and maintenance are discussed in detail. The main conclusion of this paper is the larger the operation becomes and the longer the mine life is, the earlier fully continuous mining systems should be planned and implemented.CITATION:Schmitz, R, Durchholz, R and Heiertz, A-J, 2012. Change challenges for large open pit mines, in Proceedings Eighth Open Pit OperatorsÆ Conference , pp 103-110 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 18, 2012

By E Jak, P Hayes, J Chen, M Shevchenko, E Nekhoroshev, D Shishin

Recent decades have seen significant advancements in analytical and experimental techniques, thermodynamic theory, and computational capabilities in high temperature research which are particularly timely to address the challenges of increasingly complex and variable feedstocks in both primary and secondary pyrometallurgical processes, the need to optimise and improve them. Currently a research program is in progress on the development of the 20-component multi-phase thermodynamic database for pyrometallurgical smelting, refining and recycling systems describing thermodynamics and phase equilibria of molten slag, matte, speiss, salts, alloys and associated solids. The integrated experimental and modelling program has been supported for nearly two decades by several consortia of 14 major international companies with over 30 operations around the world, integrates many components, incorporates many in-house developments, and brings together many different groups of professionals of different levels from junior and mid-career to senior from both industry and university sectors. The aims of the paper are:  to outline the many components and issues of the overall program including analytical, experimental and thermodynamic modelling research as well as implementation of the results in industrial practice, professional education, planning and organisation issues.  to highlight the opportunities, challenges, and possible solutions.  to present these to all different groups of professionals involved in the current program.  and thus, importantly, to facilitate possible future further developments and collaborations in the field of phase equilibria and thermodynamics of complex high-temperature systems.

Jun 19, 2024

Ventilation challenges are often encountered when an underground mine expands to new zones and it often is the case to make a thorough review of the existing system and assess immediate and future airflow needs at the desired quantity and quality. An unexpected mine plan change that calls for increased development and production from new areas can impose a strain on the existing ventilation system. Budgetary constraints can also demand creativity in design on the mine ventilation engineerÆs part. Since the addition of several mining horizons it had become obvious at the Meikle mine that something had to be done to increase airflow quantity and quality in the old main zones because most of the ventilation resources had been channelled for development in the new mining horizons. An airflow assessment of the existing system had to be performed and it was determined that the airflow quantity had to be increased by at least 30 per cent and the quality of the air had to be improved by reducing nuisance and respirable dust and at the same time reducing the airflow temperature before it was used in a few mining zones. At the conclusion of the airflow assessment it was determined that a third centrifugal fan would be installed on a new 3.05 m diameter borehole from surface to underground. By a careful study of temperature conditions over time it was determined that an evaporative cooling spray chamber would be sufficient to cool the airflow down from the high dry bulb temperatures observed down to saturation at the wet bulb temperature. At the same time excessive nuisance dust generated as a result of the airflow travelling a long way in a haulage drift will be knocked down in the spray chamber resulting in cool, clean air in the mining districts. Expansion of the existing surface ammonia refrigeration plant was out of the question for several reasons. The fact that the airflow was hot and dry meant that evaporative cooling spray chambers could achieve lower working temperatures at a very low cost compared to the expansion of the chilled water plant. The expansion of the ventilation system at Meikle mine and the use of evaporative cooling spray chambers were demonstrated to be very successful and the information presented in this paper can be of benefit to other mines experiencing the same ventilation problems as was the case at the Meikle mine.

Jan 1, 2005

By P Marlow

Raiseboring is an attractive method of constructing shafts, being safe, fast and comparatively cheap. But this means back-reaming through weathered ground. However in the gravels and weathered near-surface rocks typical of the Western Australian goldfields, back reaming large diameter shafts through to the surface is risky and conventional sinking from surface has normally been required.An alternative construction approach has recently been used to stabilise the weak surficial materials and allow raiseboring through to the surface. The method is based on first installing rings of non-contiguous reinforced bored piles around the shaft perimeter, for temporary support, then back reaming shafts at full diameter through to the surface. Immediately after the reaming head is removed, the weak exposed materials are supported using remotely sprayed fibrecrete.The method has been successfully applied to four shafts since July 2007; 3 m and 4 m diameter shafts at Trident Mine, a 3 m diameter shaft at Wattle Dam and a 4.5 m diameter shaft at Athena Mine.Bored pile layout designs have varied from eight to 24 piles, of diameters 120 to 270 mm, in one or two rings. In one case, the top 10 m of the proposed shaft was pregrouted. Subsequent surveys have confirmed that fallout occurred in some shafts, out to the ring of piles, implying that the piles inhibited collapse.The practical implementation of the method was not always easy and many valuable lessons have been learnt. This paper documents key aspects of the method and the critical elements for its application.

Mar 21, 2011

By C D. Rose

"The primary objective of this paper is to demonstrate a different approach to predicting and verifying mechanical sampling system precision. Early in the year 2011 an experiment was conducted to evaluate the sampling precision being obtained by a three-stage falling-stream mechanical sampling system for coal owned and operated by Peabody Energy. This system collects samples from lots averaging approximately 14000 t being loaded onto rail cars at a flow rate averaging about 9000 t/h. In phase 1 of the experiment, a total of 60 increments were collected in a two day period at preassigned intervals using a cross-belt sampler located on a conveyor belt feeding a silo upstream of the sampling system under evaluation. Coal variability parameters were calculated from the resulting laboratory analysis data using the gauge-invariant fractal model developed by the author.Estimates of precision of the three-stage system as a function of the number of increments were calculated using the variability parameters determined in phase 1. In phase 2 of the experiment, duplicate samples of 30 lots of coal were taken by the three-stage sampling system, enabling calculations of the precision being achieved by the system. Phase 2 precision estimates are in reasonable agreement with those of phase 1. Conclusions drawn from the experiment include the following: Experimental variograms or the equivalent correlograms are essential in understanding sampling issues and for designing a sampling system to meet specific precision requirements. Consensus coal sampling standards provided by ISO and ASTM may be improved by treating all stages of a mechanical sampling system as æsamplingÆ rather than considering downstream sampling stages as æsample preparationÆ, to be treated in a separate part of the document. The coal industry would profit from use of methodology for routinely monitoring the overall measurement precision and the precision of the individual components of measurement: sampling, sample preparation and laboratory testing. This would not only give necessary credence to the measurement results but would also no doubt, lead to more efficient sampling system designs.CITATION:Rose, C D, 2012. Evaluation of precision being obtained by a three-stage sampling system for coal, in Proceedings Sampling 2012, pp 115-124 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Aug 21, 2012

By M I. Pownceby, S P. Suthers, V Nunna, G J. Sparrow

Global demand for iron and steel has increased substantially over the past 20 years and there has been a greater focus on developing suitable processing options to treat low-grade hematite-goethite ores containing higher levels of silica and alumina impurities. The processing applicable to reduce the impurity levels in these lower-grade iron ores depends on their mineralogy and a thorough understanding of the process dynamics associated with the separation technology. Different separation technologies used to remove silica and alumina from low-grade iron ores were reviewed. The major concentration methods that may be applied to upgrade lower-grade lump iron ores include magnetic separation, wet and dry heavy media separation, and air-pulsed jigging. The technologies applicable to beneficiating iron ore fines include wet and dry gravity and magnetic separation, flotation, and roasting followed by magnetic separation. It is necessary to investigate the application of separation technologies on a case-by-case basis to select economically viable beneficiation strategies suitable for the particular low-grade iron ore. A commercial flow sheet is expected to involve the implementation of several separation technologies.

Nov 8, 2021

The role of government and the community has changed significantly over the last two decades in relation to environment protection, particularly in the mining sector. Increased community expectations have moved well ahead of regulatory requirements, and there is now a much greater appreciation generally of the concepts of ecologically sustainable development and intergenerational equity, and the gap between current practice and practices which would be in harmony with these concepts. Besides providing a `safety net' through regulations to ensure that basic environmental performance standards are met, government is now working proactively with the mining industry to encourage higher levels of environmental performance. This paper describes some initiatives between the Commonwealth government and the industry designed to achieve these higher levels of environmental performance, through programs aimed at the paradigms of best practice environmental management and continual improvement.

Jan 1, 1997

The mining industry is the largest source of foreign income for South Africa. It is also the main source of employment in the country and, as an industry; it is also one of the largest. Due to the labour-intensive nature of the industry, labour costs in South African mines make up nearly 50 per cent of the total mine cost. It is thus imperative to have optimum labour planning and labour management systems in place.The focus of this study was to investigate current underground labour-planning models. It is shown that there are serious limitations. The range between an oversupply and undersupply of labour can be as high as ten per cent. A new system was therefore developed to ensure a constant labour demand and supply on a daily basis. One of the main objectives was to determine the existing labour supply range and thus the requirements to fill the undersupply. For this purpose, a specific methodology was designed to capture and process all the relevant information. Mine personnel was involved throughout the entire process to ensure ownership of the new model. This buy-in was achieved through planning workshops, interactive presentations and discussions. The improved frequency of daily blasts validated the new system by providing the correct amount and mix of the labour force. The new labour-planning model was then extended to optimise revenue. Implementation on a mine resulted in increased income of R95 million.

Dec 6, 2010

By P J. Cullen, B P. Banerjee, S Raval

Continuous monitoring of mining impacts on the surrounding environment is a necessary sustainability criterion. Traditional monitoring approaches such as in situ sampling and airborne and satellite-based remote sensing have several limitations. Over the past few decades, unmanned aerial vehicles (UAVs) have evolved into popular platforms for remote sensing. UAV-based remote sensing has been successfully applied in different sectors, including agriculture, forestry, urban environments and disaster management. However, the potential of UAVs for mine environmental monitoring has not yet been fully established. This paper envisages the use of UAVs and sensor systems to monitor the environment of future mines.CITATION:Banerjee, B P, Raval, S and Cullen, P J, 2015. Unmanned aerial vehicles for mine environment monitoring, in Proceedings Third International Future Mining Conference, pp 137–144 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 4, 2015

By C D. McCullough, M Gerner

Rarely do opportunities arise allowing closure of a mine site to be planned as a key beneficial land use asset within a new urban growth area; particularly so well prior to cessation of mining.Pit lakes are common mine closure legacies for many open cut mines and may form in open cut mine voids extending below the water table upon closure. Mine closure guidelines increasingly require post-mining land uses of equivalent capacity to premining conditions and that minimise long-term post-mining liabilities and maximise benefits to stakeholders and the environment. However, risks presented by pit lakes are regularly neglected in closure planning or are not able to be addressed to allow beneficial end use of the lake or surrounding land.This paper describes strategic planning initiated by quarry owners ten years before mining ceases. In liaison with the planning agencies, the planned closure of a large 100-year-old limestone quarry pit will form a lake on mine completion, with a well-considered beneficial end use in an urban setting in mind. The quarry pit and adjoining land at Batesford South about the edge of the City of Greater Geelong, Victoria, Australia. Geelong is experiencing growth pressures that necessitate development of a new growth area from about 2025.A multidisciplinary expert team assessed the constraints, opportunities and feasibility of rehabilitating the quarry and pit lake and developing the surrounding land as Geelong’s next urban growth area.The concept is exciting and demonstrates that a former mine site could become a valued home to about 40 000–45 000 people. About 30 per cent of the land will also be developed as an ecological riverine corridor including the pit lake that will become a regionally iconic lake as the centrepiece of an urban development.Our paper outlines technical challenges and how these can be met to achieve closure and beneficial use that meets the social, economic and environmental expectations of contemporary urban planning.CITATION:Gerner, M and McCullough, C?D, 2014. Planning for the future – development of beneficial end use from a quarry pit lake, Victoria, Australia, in Proceedings Life-of-Mine 2014 , pp 99–112 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 16, 2014

By C Zhang, G Si, J Oh, X Zhu

The presence of rock joints has a huge impact on the strength, deformability, and permeability of fractured rock masses by providing surfaces of weakness on which further deformation are more prone to occur, and by serving as the major channels of water flow due to low matrix permeability. In earlier studies, water flow-through rock joints is often assumed as laminar flow between two ideal smooth parallel plates, and the well-known cubic law was derived and widely used to characterise the hydraulic behaviour of rock joints. However, natural rock fractures are irregular and of spatially varied aperture. Thus, the concept of equivalent hydraulic aperture was introduced to modify the cubic law. Numerous works have been conducted on the relation between hydraulic aperture and mechanical aperture incorporating various geometrical parameters. The surface roughness is one of the most sensitive factors for water flow-through rock joints. The aperture distributions are irregular in natural roughed fractures relative to the parallel plates. Barton et al (1985) and Olsson and Barton (2001) incorporated the joint roughness coefficient JRC in evaluating hydraulic aperture and proposed an empirical equation based on fluid flow tests. However, their equations do not conform to the dimensional consistency. Many other researchers (Zimmerman and Bodvarsson, 1996; Xiong et al, 2011; Li et al, 2019) considered aperture distributions in their equations. But the aperture distributions change during shear was always neglected. The contact of rock joints also has a significant impact on the hydro-mechanical behaviour of rock joint, since fluid tends to flow-through a rough joint along connected channels while bypassing the contact obstacles with tortuosity. Nonetheless, previous research mostly considered joint roughness or aperture changes based on 2D joint profiles, while the contact and tortuosity based on 3D surfaces were often overlooked. Only a few works have been made on quantifying the effect of contact area on flow behaviour (Walsh, 1981; Zimmerman et al, 1992; Zimmerman and Bodvarsson, 1996; Yeo, 2001), and mostly ignored contact area change induced by shearing and the associated impact on flow behaviour. Summarily, the quantification of fracture geometry effects on water flow in single rock joints still needs further investigation, especially when considering coupled shear-flow processes. This paper, therefore, aims to study the impacts of contact area and aperture distributions of the single rock joint on the flow behaviour. The evolutions of contact area and aperture distributions induced by shear are considered. Then, an improved model for estimating the hydraulic aperture with the mechanical aperture incorporating the above factors is developed. Finally, a series of shear and shear-flow tests are conducted on artificial joint samples and the model performance is verified by comparing against the results of experimental tests.

Nov 29, 2022

By O Rojas

The Telégrafo copper – gold deposit is located in the Centinela district of the Antofagasta region in northern Chile. Telégrafo is a porphyry copper deposit of Eocene – Oligocene age which has a total mineral resource in measured, indicated and inferred categories equal to 2.6 billion tonnes with an average grade of 0.38 per cent copper.Currently the project is in the prefeasibility study phase, including an infill drilling campaign to improve the knowledge of the deposit that should result in an improvement of the mineral resource classification. In this context was decided to review the classification criteria in order to optimise the drill hole density necessary to support the project.This paper presents an application of conditional simulation to evaluate the risk related to drill hole spacing, using a geostatistical approach that mimics the process of evaluation of resources from the perspective of geological modelling and grade estimation. The first step of the approach is the generation of conditional simulations using the available samples to generate several plausible scenarios of the deposit in terms of copper grades and geological units. These scenarios are considered as the unknown reality of the deposit and sampled by synthetic drill holes in order to replicate the geological model process and copper resource estimation. In this way it is possible to establish differences between the possible scenarios and the generated resource estimation models for several simulated drill hole spacing alternatives. These differences or errors can then be quantified in terms of estimated mean, metal content and tonnage over different production volumes.The resulting errors were useful in assisting the decision making process related to the design of drill hole spacing for each category of mineral resource in the Telégrafo project, and to redistribute the budget associated to the drill campaigns for the next stage of the project.

Aug 22, 2011

By A Rantala, J Timperi and J Kaartinen, T Maksimainen, O Haavisto

"X-ray fluorescence (XRF) is the most common technique used for online slurry assaying in base metal flotation applications. Typically, assays from feed, concentrate and tailings slurries are used to monitor and control the flotation circuit, with possible additional sampling locations in other main slurry flows inside the circuit. The elemental content detection from the XRF spectrum is relatively straightforward as the spectrum contains element-specific peaks whose height corresponds to the element concentration in the sample. However, centralised XRF analysers measure the elemental concentrations line-by-line, which may increase the sampling interval for an individual line and cause unnecessary response delays, especially in large flotation plants. Reflectance spectroscopy is an emerging technique that can be used to obtain more frequent measurements from slurries. The measurement is based on the mineral-specific absorbance of light in the visible and near-infrared (VNIR) wavelength range. Due to this relatively inexpensive and simple measurement system, it is possible to conduct the measurement simultaneously in several slurry lines. However, the information contained in the VNIR spectra is more difficult to interpret as concentrations of all the minerals in the sample contribute to the measured spectrum and changes in solids content, particle size and mineralogy disturb the elemental content estimation. Therefore, frequent calibration of the measurement is required. This study presents the application of combined reflectance spectrum and XRF measurements for rapid online slurry assaying in a copper-nickel flotation plant. The XRF assays are utilised as calibration samples for the reflectance spectrum measurement, keeping the calibration model up-to-date. The rapid reflectance spectrum analysis is then used to provide an almost continuous estimate of the slurry contents, enabling further improved process monitoring and control.Citation:Haavisto, O, Maksimainen, T, Rantala, A, Timperi, J and Kaartinen, J, 2016. Reflectance Spectroscopy with X-ray Fluorescence for Rapid Online Assaying in a Copper-nickel Flotation Plant, in Proceedings 13th AusIMM Mill Operators’ Conference 2016, pp 85–92 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Oct 10, 2016

In dense medium processes for the beneficiation of minerals the consumption of medium (generally ferrosilicon) represents a major component of the operating cost. This provides a strong incentive for improvements in heavy medium recovery circuit design and operation. A major thrust in heavy medium plant design over the past decade has therefore been towards circuits which reduce medium losses. In this paper recent trends in plant design are examined in relation to the factors infl uencing circuit performance and medium losses. Operational details ' which have a significant effect on losses are discussed and illustrated by means of plant and pilot plant test data, with particular emphasis on the performance of wet drum magnetic separators. While the emphasis is on reducing the consumption of the high-cost ferrosilicon medium used in minerals beneficiation, most of the principles described in this paper are equally relevant to the design and operation of magnetite recovery circuits for coal preparation plants.

Jan 1, 1987