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By S Natsui, Y Goto, S Kawanishi, J Takahashi, H Nogami

The demand for copper increases yearly, and further improvements in copper smelting efficiency using flash furnaces are required. This study was conducted to understand and promote the interfacial reaction associated with the collision of silica flux and iron oxide particles, ie the formation reaction of fayalite slag, in the reaction shaft of the flash furnace. High-temperature microscopy was used to observe the reaction behaviour of a 2 mm granular SiO2 reagent in contact with micrometreorder- sized FeO reagents in situ. When the amount of FeO was lower than the stoichiometric amount with SiO2, the molten slag formed at the interface between FeO and SiO2 diffused into the SiO2 particle before dissolving the remaining FeO particles. It did not contribute to the subsequent reaction, and despite having the lowest amount of FeO among the samples in this study, many unreacted FeO particles remained on the surface of the samples after testing. On the other hand, under conditions with high FeO content and close to the eutectic composition of the FeO-SiO2 system, a liquid phase formed from low temperatures, gradually increasing in volume and eventually completely dissolving the 2 mm SiO2 grain. These results indicate that the early-stage slag is essential in increasing the interfacial area between FeO and SiO2 and facilitating the supply of FeO to SiO2. In other words, the FeO/SiO2 determines the amount of liquid phase and significantly influences the subsequent interfacial reaction rate between FeO and SiO2. Therefore, the local FeO/SiO2 of the particles falling down the reaction shaft should also be optimised to ensure early slag formation. Meanwhile, the time required for 2 mm SiO2 to complete the reaction for the temperature history employed in this study was significantly longer than the particle residence time in the reaction shaft. Further detailed investigation of the effects of silica flux particle size, composition, and reaction temperature on the reaction time will help find the conditions under which the reaction of silica flux can be completed in the reaction shaft. These kinetic approaches could contribute to future innovations in the copper smelting process using flash furnaces.

Jun 19, 2024

By E K. Chiw, S-M Jung, S M. Masuka, ika

The world reserves of high-grade iron ore have depleted necessitating the need to utilise any existing natural iron ore deposits to meet the demands of the world’s expanding economy using hydrogen in the reduction process to curb CO2 emission. These low-grade ores include iron ores with high phosphorus content. The thermodynamic conditions in the blast furnace allow for the reduction of phosphorus that readily dissolves into the molten iron. Phosphorus in the gaseous state readily dissolves into the molten iron and therefore must be removed due to its negative influence on the mechanical properties of steel. The removal of phosphorus from molten iron is difficult causing the phosphorus to concentrate in metallic iron. The aim of this study is to provide basic knowledge on the phosphorus distribution after reduction using the CO-H2 and possibly provide the optimum conditions for phosphorus partitioning into slag, increasing the probability of its removal by magnetic separation. Total porosity, pore size distribution and surface area of the pellets used were measured using a mercury pressure porosimeter. The reduction was carried out using thermogravimetric analyses (TGA). The reduction rate increased with increasing H2 and was highest when 100 per cent H2 was used. Metal elements distribution in the reduced pellet was clarified using electron probe microanalysis (EPMA) and showed that phosphorus was distributed in the same areas as Ca. More phosphorus was concentrated in slag when 50 per cent CO–50 per cent H2 was used, increasing the probability of dephosphorization using magnetic separation. The concentration of phosphorus into slag was related to the rate of reduction. Further investigations into the reduction kinetics of this ore by CO-H2 is suggested to validate these findings. Nevertheless, a comprehensive thermodynamic analysis of the reduction of phosphorus containing phases found in iron ore with carbon, CO and H2 was provided to assist in selecting the optimal reduction experimental conditions.

Sep 18, 2023

By M Sandy, P Bamford

The Challenger Gold deposit was discovered in 1995 by Dominion Mining Ltd in a remote western area of the Gawler Craton in South Australia. Mine development commenced in 2002 with initial production from an open pit supplemented by ore from a very small adjacent auxiliary pit. Development of the underground mine commenced in 2004. The orebody plunge of just less than 30 degrees requires careful attention to mine design. Production from the M1 orebody, with less than 800 ounces per vertical metre (ovm) and very limited æsurgeÆ capacity, requires careful scheduling and implementation to ensure continuity of ore feed for milling. Initial production results from underground stopes included more dilution than anticipated. The narrow, high-grade zones proved to have much more complex geometry than early interpretations had indicated. Greatly improved understanding of the mineralisation controls resulted in important changes being made to the underground mine design and method. Coupled with careful control of development and drilling and blasting practices, this resulted in an immediate reduction in dilution and high recoveries of the resource. The benefits of these changes flowed through in the 2005/06 financial year, resulting in a 150 per cent increase in gold production to 108 080 oz and a sharp reduction in cash operating costs to A$280/oz. This was followed in 2006/07 with production of 108 91 oz of gold at an operating cost of $309/oz and in 2007/08 with 109 326 oz of gold at $367/oz. Production to June 2008 has been mainly from the M1 orebody, with the lowest stoping to date on the 580 m Level (615 m below surface) above development mining on the 520 Level. The rate of vertical advance of mining this orebody has averaged 150 vertical metres per year. The increased current combined JORC compliant resource and reserve position of over one million ounces, now includes the M2 and M3 orebodies with a current total average gold inventory up to 1400 - 1500 ovm. Exploration has intersected other shoots and all shoots are open at depth. The adjacent M2 and M3 orebodies are being developed for stoping. The narrow width of these zones from 1 m up to 4 m will require continued focus on ore zone definition, accurate development and careful drill and blast practice. In addition, to minimise cost increases in the current period of rapidly escalating labour, equipment, consumables and energy costs, high productivities will need to be maintained to allow the established rapid mining advance to continue at low unit costs.

Jan 1, 2008

By M Rea, E O’Connell

Decarbonising explosives manufacturing and catalysing low-carbon mining supply is a significant global challenge. Low-carbon manufacturing precincts – clusters of geographically close businesses across multiple industries that share a goal of adopting firmed renewable energy and decarbonising process emissions – offer one potential solution. In an Australian first, Orica commissioned tertiary catalyst abatement technology in 2023 to mitigate greenhouse gas (GHG) emissions at its Kooragang Island (KI) facility in New South Wales (NSW), Australia. The EnviNOx® technology (ThyssenKrupp Industrial Solutions AG, Dortmund, Germany) used reduces nitrous oxide (N2O), a potent greenhouse gas arising as a by-product of nitric acid manufacture. As a result, mining customers in NSW are now benefitting from ammonium nitrate (AN) products that are almost 50 per cent less emissions-intensive than those Orica previously offered. The $37 million project is a private-public partnership that has involved partners across Federal and State government, global engineering and technology vendors, local community groups and local carbon advisors to overcome financial barriers.

Sep 1, 2024

By J Foster

The Lanfranchi Nickel mine is located approximately 48 km south of Kambalda in Western Australia. Mining first commenced in the mid-1970s under the previous owner, Western Mining Corporation Ltd. After two years on care and maintenance, Panoramic Resources (previously known as Sally Malay Mining Ltd) purchased the operation in November 2004. The site currently produces approximately 10?000 tonnes of nickel metal annually from approximately 430?000 tonnes of ore. The Ore is mined from four main orebodies; Deacon, Helmut South, Lanfranchi and Schmitz. The Helmut South orebody is situated approximately 790 m below surface and extends to a resource depth of 940 m. Horizontal thickness of the orebody ranges from 10 m to 45 m in width, with the average being 30 m. Previous mining at the Lanfranchi operations specifically the Helmut orebody, had a history of seismic activity. When Panoramic Resources acquired the operation it was decided that seismicity was going to be an issue and therefore a mining method needed to be selected that could effectively manage this potential risk. The dip of the orebody is quite shallow at 45º, with a 30º plunge to the south . The hanging-wall comprises of very weak ultramafics. Due to these factors the orebody posed several mining challenges. To safely and effectively mine the Helmut South orebody in the Lanfranchi Nickel mine, underhand cut and fill mining was selected as the most appropriate mining method. Paste fill comprising of cemented gold tailings was the backfill of choice. This paper is intended to convey some of the key learnings from the use of a mining method that has not been commonly practiced in Australia.

Mar 21, 2011

By D Will

RedrossThe Redross orebody averages 1 m wide, has a strike of 50 - 350 m, dips at 55° and has a basalt footwall and an ultramafic hanging wall. The most successful and innovative aspects of mining Redross were:•ore development innovations, 90 per cent of development was split fired with a shanty back profile to enable larger and more productive equipment to be used and resulted in higher development grades, improved project payback time and improved ore recovery;•hand held stoping using a multiple level, bottom up ‘V’ shaped hand held stoping method that allowed mining on multiple levels with hand held productivities between 50 and 90 tonnes per shift;•the use of 1 m cement pillars and 7 m high crown pillars were used to create multiple mining areas that enabled high overall production rates from hand held mining this orebody; and•the use of vertical cement pillars to enable hand held mining of adjacent stopes without leaving ore pillars.MarinersThe Mariners orebody averages 3 m wide, has a strike length of 50 - 250 m and dips at 50° with a basalt footwall and poor ultramafic hanging wall. The most successful innovative ideas of re-opening Mariners were:•Dewatering the existing mine workings utilising ‘oilfield’ technology by installing a long submersible pump in on existing pump rising main. This enabled the mine to be dewatered at rates up to 100l/ sec and helped overcome the 45 to 55 L/s inflows.•Overcoming the technical problems associated with Mining N07 ore blocks which had severely deteriorated from being underwater for five years by using reverse firing techniques to improve extraction rates and reduce dilution.•Mass firing a large mining block in the N08 with minimal void space because of deteriorating ground conditions.•Use of a longhole version of the Redross hand held mining method to achieve 100 per cent extraction of the N09 higher grade lenses.

Mar 21, 2011

By J Ta’ala, M Handyside

Mechanical sampling from conveyors has historically been a staple in the iron ore industry when information related to chemistry, sizing and moisture is required. In order to comply with ISO 3082:2009, samples can be taken either on a mass or time basis provided no bias is introduced by periodical variation in quality or quantity. With the introduction of mechanical sample carousels, you also have the opportunity to collect samples on a mass or time basis. In order to optimise automatic sample stations in a changing production environment, BHP Billiton Iron Ore (BHPBIO) has developed a simulation model that enables the various combinations of mass–mass, mass–time, time–time and time–mass to be investigated.The sample station model can utilise actual (variable) feed rates to achieve high resolution and enables the simulation of sample size variation. Cutter speeds and other settings can then be adjusted to better optimise the performance of the sample station with regards to optimal sample size as well as ensuring the sample station is in compliance with ISO 3082. The model can also assist process engineers in adjusting settings to better optimise the sample station and reduce unwanted events such as blockages. The model can be easily modified to conform to various sample station designs. This paper demonstrates the use of the model and the benefits that can be achieved.CITATION:Handyside, M and Ta’ala, J, 2014. Simulating time versus mass basis?sampling, in Proceedings Sampling 2014 , pp 155–164 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 29, 2014

By D J. Kilkenny

Work practices involved in shaft construction can be aligned with current industry standard operating practices. However, the working environment during conventional shaft construction introduces unique conditions which can not always be overcome by hard engineering controls. To provide an improved working environment, future shaft diameters will generally be greater than has historically been the case for the Australian hard rock mining industry. This paper aims to explore both what can be constructed from the contractors perspective, and how does an owner extract maximum business efficiency from an asset that in many ways is likely to be larger, more complex and more expensive than initially envisaged.Newcrest Mining Limited, or an associated company, has constructed two major shafts over the last seven years. In both cases, Byrnecut Mining, or an associated company, was the contractor engaged for the shaft sinking activity. The first is the 1127 m deep, 7.0 m diameter production and intake airway at the Telfer Gold Mine, the second is a 295 m deep, 5.5 m diameter split shaft at the Gosowong Gold Project in Indonesia that was primarily designed as both an intake and exhaust airway. Importantly both shafts are designed to provide emergency egress from the respective underground operations.From an Australian shaft sinking perspective, the construction of these two shafts resulted in the following learnings: •constructability is of equal importance to desired functionality;•allow six months of interactive design between the owner/engineer/contractor/regulator to get it right;•shaft sinking and equipping are intimately entwined, therefore engineering of both needs to be complete prior to any activity commencing; and•the mobilisation of both equipment and experienced personnel to a new shaft sink takes up to eight months.Shaft sinking is not extinct in the Australian hard rock mining industry. But, if you are considering constructing a shaft, approach it as a long life asset, front end planning to a high level of detail is required to unlock its full value. Think – plan – think and remember it’s going to take 12 months to get from the whiteboard to firing the first cut.

Mar 21, 2011

By C Parihar, R Garg, A Bhandari, S Bhandari

Blasting can impact the efficiency of entire downstream mining operation. Individual technology solutions for blasting have been available in the industry for many years but all of them only cater for certain aspects of blasting. Many of them are based on individual research and/or experiences. Some of the available software solutions are not suitable to be used in the field as that they need advanced skills or tools. Also, most do not take technology advancements like mobility, advanced data analytics, web solutions and integration into consideration. Hence, no technology platform is currently present in the industry that addresses all potential needs a blaster may need in an integrated manner.This paper presents an integrated solution that takes care of all aspects of blasting – design blasts according to mine plan; collect data after drilling has been carried out (as there is often difference in designed and actual drilled hole locations in the field); predict blast results in terms of fragmentation, flyrock, ground and air vibrations, wave front reinforcement and flyrock distance; and after assessment, allows changes in charging, delay timing and sequence. The technology solution is a secure, cloud-hosted, web-based software-as-a-service solution that can be accessed from anywhere. Also it has a mobile app, which is available for both Android and iPhone/iPad. The mobile app is also integrated with the web-based solution using application programming interface calls to the central data repository.Case studies for two limestone mines are presented where this solution is being used in its initial format. This software platform enabled analysis of the outcome from a previous blast pattern and then subsequently allowed optimisation of blasting operations based on historical data. Uses of this platform have resulted in improved key performance indicators in these two limestone mines. The mobile app as part of this platform enables extensive field blast data capture and analysis and also various predictions before a blast. Data collected include blast parameters, individual hole charging, initiation pattern, videos, photographs and vibration records for analysis/reporting. The key features of the solution are a blast designer, a detailed blast data collection/analysis and a series of environmental predictors. These predictors give blast results in terms of fragmentation, flyrock, ground and air vibrations and wave front reinforcement and take remedial steps before blasting to optimise and control adverse environmental impact. Many features, such as fragmentation predictor and mobility solution, are completely unique features that are not available elsewhere in such a field personnel-friendly manner.CITATION:Bhandari, S, Parihar, C, Garg, R and Bhandari, A, 2015. An integrated technology solution for optimised and environmentally-controlled blasts, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 393–400 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

As the title indicates the central themes discussed in this contribution are sustainable development, information systems, and extractive industry. More specifically, the objective is to present a prototype for the systematic generation of extractive industry (henceforth: EI) û specific sustainability information. The paper begins with the authorÆs viewpoints on the core notions of sustainability, and development, as well as their relationship to information. These set the stage for the introduction of the information system (IS), as well as the follow-up sustainability information system (SIS) extractive industry sustainability information system (EISIS) concepts and related discussions. The paper continues with a second part, in which, efforts to research and develop an EISIS prototype are described. First, the team is presented. Second, the systemÆs aim and target groups are briefly discussed. After, an articulated overarching EISIS conceptual model emphasising capital accumulation, and service flow concepts û is presented. This is followed by a detailed description of the assembled prototype with a focus on data and information generation. The formulation of data generation, storage and transmission processes, as well as its use in sustainability interpretation rules and their embedment in the conceptual model is made with respect to monetised stock and flow parameters, measured in the appropriate dimensions. In the third part, the author presents and discusses the results of a first round of prototype experimental development in three major EI firms. First, the system observation, and data analysis protocols are described. Second, a review of protocol implementation, and respective results, is made. Finally, the overall performance of the proposed prototype, and development process issues are discussed, before suggesting areas for improvement and future research. The paper ends with a conclusion in which the author provides a retrospective balance of the æknowledge creation projectÆ, as well as a prospective outlook for research in this field; before acknowledgements are made and references provided.

Jan 1, 2009

By J Zhou, L Crompton, K P. Galvin, J L. Sutherland, C P. Lowes, C Bezuidenhout, J Bijzet

Platinum Group Metal (PGM) bearing ores from the Upper Group 2 (UG2) reef often contain significant concentrations of chromite which can potentially be upgraded to produce a saleable product. A common approach is to implement gravity separation on the PGM flotation circuit tailings. However, where the particle size range of interest is broad and the lower size limit ultra-fine, the challenge is how to maximise the recovery at a saleable product grade without compromising throughput. This study was concerned with the performance of a REFLUX™ Classifier for beneficiation of a PGM bearing chromite ore and the benefits of size classification. The sample had a nominal top size of 0.5 mm and was processed over the complete size range and in two discrete size classes following classification at 106 µm. The primary goal was to produce a concentrate exceeding 40 wt. per cent Cr2O3, ideally approaching 42 wt. per cent Cr2O3, with minimal PGM losses above 106 µm. A major challenge was to process at the required solids throughput in a single stage with the feed pulp density constrained to a nominal upper limit of 30 wt. per cent solids. It was found that varying the controller density set point of the REFLUX™ Classifier produced strong control of the product grade. Products as high as 41.1 wt. per cent Cr2O3 were produced at 78.6 per cent recovery for the +106 µm material, while in the −106 µm portion the product grade was as high as 41.4 wt. per cent Cr2O3 at 83.2 per cent recovery. Processing the feed in discrete size classes enabled the volumetric feed and fluidisation rates to be optimised for a given application; hence, superior performance was achieved at the finer sizes. This work has demonstrated the value in considering feed preparation as well as technology selection in developing a robust process solution.

Aug 24, 2022

By S J. Tear, L D. Queen

"An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation. The Frieda River Project is located in the north-west of Papua New Guinea. The target commodities for a bulk mining operation are copper and gold associated with a large felsic porphyry system. The project comprises a series of deposits, with the Horse-Ivaal-Trukai (HIT) being the largest. It also includes the adjacent smaller Koki and Ekwai deposits.Previous resource estimates for the HIT were made using 14 separate mineralised domains based on structure, copper grades, lithology and alteration. H&S Consultants (H&SC) has revisited the deposit and concluded that a simpler methodology could be used for resource estimation without using wireframes as hard domain boundaries. This conclusion is based on reviewing all the available geological data combined with geological and resource experience of porphyry deposits.It is generally acknowledged that porphyry deposits form by diffusion of mineralising fluids through the host lithologies, meaning that sharp boundaries are unlikely unless these fluids encounter specific physical or chemical boundaries. It is important to prepare a comprehensive geological model prior to attempting resource estimation as it forms the framework for the estimates; however, not all geological features may be relevant to the distribution of mineralisation and there can be a tendency to overcomplicate the estimation process by using too many domains. Unless a hard boundary can be identified consistently and unequivocally, it is generally better not to use a boundary in that location.H&SC completed unconstrained models with no top-cutting using both a simple flat search ellipse and a steep search ellipse to generate global resource estimates reported within a predetermined pit shell at a 0.2 per cent copper cut-off. Both outcomes are within 10 per cent for the tonnes, contained copper tonnes and gold ounces compared to the constrained resource estimate. The slight differences are most likely due to the different search strategies, but also indicate the robustness of the unconstrained modelling approach.CITATION:Queen, L D and Tear, S J, 2015. The Frieda kiss – keeping it simple , in Proceedings PACRIM 2015 Congress, pp 361–368 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 18, 2015

By M Rayner, C Tsouris, A Komelkov

X-ray fluorescence (XRF) is a widely accepted technique for the elemental analysis of iron ores and their concentrates. Wavelength-dispersive, or WDXRF, and energy-dispersive, or EDXRF, spectrometers offer distinct advantages for particular applications, elements and concentration ranges and are, therefore, more complimentary than people might realise. A key example is the ability of EDXRF to identify, and often quantify, unexpected elements in production samples that would typically be missed by routine WDXRF. In this paper we discuss recent technological advances in XRF and present a novel application example that demonstrates the additional technical and practical benefits of using both EDXRF and WDXRF to characterise iron ores and concentrates.CITATION:Tsouris, C, Komelkov, A and Rayner, M, 2015. A novel approach to the characterisation of iron ores and concentrates using recent advancements in wavelength- and energy-dispersive x-ray fluorescence spectrometers, in Proceedings Iron Ore 2015, pp 591–594 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 13, 2015

By C Bartle

In many operations the use of less electrochemically reactive grinding media in the first grinding stage (for example, rod milling and high aspect ratio SAG milling) is rarely considered. Therefore, in reality a plant may inadvertently be using a 'mixed' media charge. That is, whilst employing inert grinding media during secondary grinding, electrochemically active forged steel grinding media may be used in the primary grinding stage. This paper discusses the impact of such a circuit on the pulp chemistry and flotation response of a refractory gold ore. The Wiluna concentrator has two grinding circuits operating in parallel. Line 1 operates a single ball mill in closed circuit with cyclones, and utilises high chrome grinding media, while the second circuit (Line 2) consists of a rod mill (with forged steel rods) in series with a ball mill, which also utilises high chrome grinding media. The cyclone overflows from both circuits are combined to feed a sulfide flotation circuit. Pulp chemistry surveys were completed around both grinding circuits, and laboratory flotation tests were conducted on the cyclone overflows. The results demonstrate clearly that the rod mill/ball mill circuit operated at significantly lower Eh and dissolved oxygen values, while the percentage EDTA extractable iron was considerably higher, when compared to the single stage ball milling circuit. These variations in pulp chemistry had a marked negative impact on the laboratory rougher flotation response, and suggests that plant performance may be affected.

Jan 1, 2008

By J Player, R de Vries, E Villaescusa, H Saw, R Hassell

The use of cemented rock fill (CRF) for support of open stope walls has increased in the Australian underground mines operations over the last five years due in part to its low capital cost. In open stoping the exposed CRF masses require adequate strength and stiffness, in order to resist the forces and to limit the displacement associated with movements in the rock mass surrounding the excavations. The CRF material preparation often involves the use of large particles, either from crushed rock or from development mining waste sometimes up to 1 m in diameter. However, the use of waste rock, which has a poorly graded particle size distribution may not achieve the required minimum target strength due to segregation and large air voids within the fill mass. This paper describes the optimisation of CRF strength by either crushing the waste rock or the addition of sand to the mix. Both methods increase the level of fines in the mix design. Cylindrical samples having 400 mm diameter and 800 mm heights were prepared for uniaxial compressive strength (UCS) testing. The UCS test was determined using the Western Australian School of Mines (WASM) large-scale static test frame. The laboratory results were compared with a database of large-scale CRF strength mixed without sand from a number of mine sites around Australia. The comparison shows a significant strength development in the CRF mixing with addition of sand for a given cement percentage. Due to the higher strengths achieved by the addition of sand and the crushing of the waste material these CRF types require less cement to achieve the same strength. This has the potential to improve the overall economics of open stope mining due to less dilution of the exposed fill mass.CITATION:Saw, H, de Vries, R, Player, J, Hassell, R and Villaescusa, E, 2017. Optimisation of cemented rock fill strength for open stope support, in Proceedings 13th AusIMM Underground Operators’ Conference 2017, pp 85–90 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 16, 2017

By S Hille, J Karageorgos

With the increased variability of todayÆs large-scale mining operations, consistent flotation performance is important to improving and sustaining overall recovery through the circuit. The Newcrest Telfer Mine has implemented advanced process control technology to obtain stable level operation and consistent mass pull in the copper rougher and scavenger flotation circuits. The final result has been an overall reduction in variability, which impacts on both copper and gold recovery. This paper describes the methodology and implementation of the improvements in control at the Newcrest Telfer Mine as being an essential part of the business for minerals processing.

Jan 1, 2007

By T BoBo, D La Rosa, P Cameron

Efficient pre-concentration using natural and induced deportment starts with effective blast design. Leveraging these characteristics using Size-Based Grade Engineering® techniques requires detailed understanding and measurement of the particle size distribution (PSD) of the Run of Mine (ROM) ore. In turn, blasts must be designed to optimise fragmentation for the pre-concentration method. To be successful, fragmentation outcomes must be predicted and measured as part of the blast design process to account for the response ranking of the rock mass. The upgrade achieved using Size-Based Grade Engineering® methodologies will rely on the proportion of feed that reports to the screen undersize, so particle size distribution of the feed stock is of paramount importance if the potential benefits are to be achieved and maintained. Measuring actual fragmentation in the ROM ore and comparing with predictions allows the modification of subsequent blast designs to optimise fragmentation for pre-concentration scenarios. Automating this process can deliver significant increases in productivity and mine site profits. This paper discusses the importance fragmentation plays in Size-Based Grade Engineering® and explores technologies and methodologies used to measure it, consistently ensuring the best outcomes.

Nov 10, 2020

By D Cooke

In 2010, Kalgoorlie Consolidated Gold Mines (KCGM) was Australia’s largest gold producer, with total annual production of 788 000 ounces. Of the gold produced by KCGM in 2010, 95 per cent was extracted from the Fimiston open pit, also known as the Superpit. The Fimiston operation encompasses the historic Golden Mile, from which more than 55 million ounces of gold have been extracted from the world-class Fimiston lode style mineralisation.The operational performance of the KCGM Fimiston open pit was reviewed for the period between 2005 and 2010. Key performance metrics reviewed included mined tonnes and grade, cost per ounce of gold produced and the mine to mill reconciliation trends. The years 2007 and 2008 were characterised by a decline in performance against key performance metrics. The ore zones were diluted, with the excess tonnes mined resulting in lower grade and an increase in the cost per ounce. Poor reconciliation between ore mined, the ore reserve model and the grade control polygons was also observed.A series of improvement initiatives were implemented in late 2008. As a result of changes made to the grade control and mining practices, the site performance recovered. Unplanned dilution was reduced, which had a positive impact on mined grade. The lower tonnes combined with higher grade reduced the cost per ounce to below budgeted levels in 2009 and 2010, enhancing the profitability of the operation. The operational performance between 2005 and 2010 was compared to the turnover statistics for the KCGM geology department over the same period. Turnover accelerated between 2005 and 2007, peaking at an annualised rate of 43 per cent. With the onset of the Global Financial Crisis and the implementation of retention initiatives, turnover reduced significantly between 2008 and 2010. A strong consistent correlation was observed between the turnover trends in geology and the performance of the grade control function and resultant site metrics.The cost of turnover is known intuitively, however, rarely quantified. To evaluate the benefit of the improved performance, a detailed financial model was used to quantify the impact of the grade control function. In 2010, the headgrade exceeding budget by just four per cent contributed an additional A$24 M of value to KCGM. In contrast, if the 2008 performance had been replicated in 2010 (-9 per cent on headgrade), the result would have removed A$61 M in value from the business. The KCGM experience between 2005 and 2010 demonstrates the value of human capital in a mining operation and the importance of a high performing geology grade control team to the profitability of a mining operation.

Aug 22, 2011

By C M. Standen

The SAG mill at Rasp Mine has undergone a number of liner design modifications since commissioning in 2012, making liner wear and failure difficult to predict from historical data. During 2017, several instances of liner failure or near failure were experienced resulting in unplanned downtime for emergency relines or to patch liners in the lead up to a planned shutdown. The strategy for relining mills is often to minimise the frequency of relines (and subsequent shutdown costs) by extending liner life, achieved through design modifications. However, it was observed that as the Rasp SAG mill liners wear, mill performance declined with power draw increasing and throughput declining. Opportunity and inefficiency costs start to erode the revenue per additional tonne milled for a given set of liners, and in turn the benefit of delaying relines. As such, optimising the frequency of relines becomes a trade-off between reline costs and opportunity/inefficiency costs in delaying relines. The aim of this paper is to demonstrate a frame work for analysing costs using a marginal economic analysis with the assumption that the Law of Diminishing Returns can be applied to the life of mill liners. The SAG mill operating variables can be modelled to determine their impact on costs and an optimal reline point can be defined where the total costs are minimised. This prevents unexpected failures due to accelerated wear by providing justification to reline earlier and thereby allowing efforts to be focused on sustaining milling performance.CITATION:Standen, C M, 2018. An economic approach to optimising mill reline frequency – a case study of SAG mill relines at Rasp mine, in Proceedings 14th AusIMM Mill Operators' Conference 2018, pp 197–206 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 29, 2018

By C E. Gawith

The Waihi underground mining operation currently mines epithermal veins ranging from two metres up to ten metres in width using a ‘Modified Avoca’ stoping method. This method consists of longhole bench stope mining at 15m to 18m sublevel spacing. The bulk of production drilling and blasting is top down with the extraction length of a typical stope panel nominally being 18m to 20m along strike. A stope panel is usually taken in two blasting cycles followed by the remote bogging of the stope ore. The panel is backfilled in-cycle using unconsolidated waste rock material which is tipped into the void from the upper level using a Caterpillar R2900 or R1700 sized underground loader. The underground mine first commenced production in 2008 and up until 2016, as was typical of many open stope mining operations at the time, an underground loader was used to place a waste rock bund at the top brow of the open stope. This rock bund was the principal means of protecting people and equipment from this hazard. In 2016 there was a fatality at the mine when a loader that had been tasked with building this rock bund fell into the stope void. Immediately post incident all mining and processing operations were suspended for a week to allow colleagues to grieve, to observe cultural protocols and to begin the investigation into this event. During this period senior operators, supervisory and technical staff developed an innovative system which used steel bollards to protect this open edge. With development over the following months this bollard system has eliminated this hazard from the Waihi underground mine.

Mar 15, 2021