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By B Vorster, T Medhurst, A Huey

Roof conditions at Oaky North Mine can be prone to stress related damage and/or time dependent degradation. The ability to identify these areas prior to mining has proved challenging using traditional methods. To help alleviate this situation, a study was initiated to investigate methods for roof characterisation using geophysical logs. This involved the use of neutron log data to provide an indirect measure of the proportion of carbonaceous/micaceous laminae present in the immediate roof strata. Detailed analysis of the shale–porosity inter-relationships arising from this analysis provided a means to estimate the proportion of laminations for a given roof interval. This paper outlines the process and how it was used to improve the current GSR modelling and hazard mapping process.

Nov 29, 2022

By T M. Campos, J Silva, L M. Tavares, J Lichter, L P. Alves, B K. N Rocha, H D. G Turrer

The depletion of the richest ore deposits and the increase in number of mining projects involving deposits with complex mineralogy, higher competence and lower grade has led to an eminent need for improving understanding on multicomponent behaviour in mineral processing. One particularly relevant case is the ball milling of itabirite iron ores fed to the processing plant of Minas-Rio operation in Brazil. Dealing with the two main mineralogical components of the ore, namely hematite and quartz, the operation faces some challenges to improve understanding on how the two components behave in the process. Mathematical models have showed potential to give support in this task, but its applications to describe this type of industrial-scale grinding is still missing. The present work demonstrates the application of a multi-component ball mill model to simulate a closed ball mill circuit with hydrocyclones using the commercial software Integrated Extraction Simulator (IES). Model was calibrated on the basis of bench-scale tests and industrial surveys. Multi-component simulation results are then compared to those considering a single component in the feed, demonstrating the value and great insights that can be achieved by using the former in optimising plant operation.

Aug 24, 2022

By M Ranjan, C R. Borra, P Palai, P P. Sahoo

Change in mould slag composition during casting of medium alloy steel is caused by the redox reaction between molten steel and mould flux. Mould flux generally contains a certain amount of SiO2, but elements such as Al, Mn and Ti in high/medium alloy steels reduce SiO2 in the mould flux, causing remarkable changes in the composition of the mould slag. As a result, the properties of the mould slag change greatly as continuous casting proceeds. This causes casting instability, process abnormality and casting defects. Effect of Ti as an alloying element in steel on mould slag is studied extensively through high temperature laboratory measurements and plant measurements. TiO2 gets picked up by the mould slag up to 3 per cent during casting a steel grade containing 0.1 per cent Ti. This changes the mould slag composition and results in decreasing the slag viscosity by up to 10 per cent and decreases slag break temperature by 30–40°C.

Aug 21, 2024

By J Jackson, E Sellers

Blasting related indices were developed to quantify variation in rock strength and structure for each stope, and for each lift of each stope, as part of a Mine to Mill study at an underground open stope mine. The indices were derived from combinations of data from underground diamond drilling because the simplifying assumptions contained in the block model prevented sufficient differentiation in rock mass characteristics to enable adjustments to the blast design.Application of combinations of blasting related indices enabled the identification of stopes with a high potential for inconsistent and oversize fragmentation, underbreak and overbreak. The indices also fragmentation outcomes to deliver increased material flow within stopes, better digability and predict indicative mill throughput. The stopes with issuesCalibration of the results enabled adjustments to the blast design based on the rock mass conditions and accordingly improved the blast outcomes. This enabled improved productivity by reducing underbreak and overbreak, having a more appropriate fragmentation, which reduces unplanned rock handling and improves bogging. The reduction in recovery drilling creates huge opportunities to improve output by reducing production delays and decreasing the overall cost per tonne. By understanding the explosive performance and blast energy distribution in relation to rock mass blastability poor, performing designs in blind upholes and convex stopes were identified.The conclusion of the work is that value improvement, regarding increased revenue and reduced costs, can be achieved across the whole underground Mine to Mill process chain by developing stope based indices from the existing geological information to correctly tailor the blast design to the rock within, and surrounding, the stope.CITATION:Jackson, J and Sellers, E, 2017. Blasting related indices as the key to underground blasting improvements in a challenging rock mass, in Proceedings 13th AusIMM Underground Operators’ Conference 2017, pp 23–32 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 16, 2017

By T Muzondo, C Prins, D De Vaux, R Schouwstra

The Mogalakwena Platinum Mine in the northern limb of the Bushveld Complex is Anglo American PlatinumÆs only open cast operation exploiting the Platreef. The Platreef, which extends along the basal contact of the Bushveld Complex, is geologically and mineralogically a much more complex orebody than the Merensky and UG-2 reefs. Changes in the footwall and the genesis of the Platreef translate into a number of rock types being present. These rock types vary in hardness and recovery potential and present challenges to metallurgical staff trying to optimise the concentrator. A true understanding of the implications of treating these rock types is required if the maximum value from this orebody is to be obtained.In order to more accurately forecast production and incorporate ore variation in the mine plan and comminution and flotation circuits, a geometallurgical approach to managing the operation has been used and is being further developed.CITATION:Schouwstra, R, De Vaux, D, Muzondo, T and Prins, C, 2013. A geometallurgical approach at Anglo American PlatinumÆs Mogalakwena Operation, in Proceedings The Second AusIMM International Geometallurgy Conference (GeoMet) 2013 , pp 85-92 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 29, 2013

Corrosion affects the performance of rock support and reinforcement at various underground mines, including the George Fisher Mine, where recent studies showed that this risk to mining operations is generally not well understood. Corrosion reduces the capacity and life expectancy of ground support and generally is undetected unless the traditional destructive pull out test is employed to detect defect bolts. Where it is still acknowledged that the pull out test has still an important role to play in determining critical bond lengths for static and quasi static ground support designs, it does not provide an underground operation with any reassurance regarding its bolt's integrity, which has been compromised by in situ aggressive conditions. Non-destructive rock reinforcement calibration testing on single and twin strand cable bolts, rebar bolts and friction bolts at the George Fisher Mine enabled the testing team to detect bolts with compromised integrity in one area of the mine. The non-destructive rock reinforcement integrity testing conducted uses a complex 'Stress Wave Analysis' package based on the processing of clear seismic signals imparted into the rock reinforcement element that is being tested. The seismic signals are processed by 'Fourier Transform' into various criteria which can be used to produce models of the element such as mechanical admittance, frequency spectra and velocity which are all being used in the final modelling of the rock reinforcement element under analysis. This paper highlights the enormous potential to effectively manage the geotechnical risk that corrosion presents for an underground mining operation.

Nov 25, 2010

By M Thompson

"The Jaguar concentrator, 60 km north of Leonora, Western Australia (WA), consists of a standard closed circuit semi-autogenous grinding (SAG) and ball mill producing a float feed of approximately 60 micron at 70 t/h. Following comminution, separate copper and zinc concentrates are produced by differential flotation. These concentrates are subsequently dewatered by thickening and then filtration.Separate audits of the Jaguar Operation’s copper and zinc concentrate thickeners were conducted to evaluate their performance, following occasions where site personnel had identified unnecessary loss of copper and zinc concentrate to the thickener overflow. The feedwells were identified as the source of the observed problems due to the following issues with their design/duty:lack of retention time in the feedwell as current design is completely opennot conducive to effective mixing required for efficient flocculationdiameter of the zinc concentrate thickener feedwell was undersize for its duty.To improve the performance of the thickeners, it is planned to replace both concentrate thickener feedwells with a high rate design for their respective duties in February 2016. The audits also identified that the feed system requires modifications with particular importance placed on minimising air entrainment of slurry into the thickener feedwell. Minimisation of air entrainment is hoped to be achieved by providing constant head pressure through installation of weir arrangements in the feedboxes and redirecting each feed pipe so that it feeds tangentially into the feedwell. In addition, improvements to the control philosophy of both thickeners will be made with the installation of an ultrasonic bed level probe and bed mass sensor, in order to make real-time adjustments to the underflow pump speed to maintain steady state operation.Following the feedwell replacement and modifications to both thickeners it is expected that losses of recovered copper and zinc will decrease to undetectable levels. Subsequently it is anticipated that a more consistent, homogenous underflow can be produced for downstream filtration.Citation:Thompson, M, 2016. Concentrate Thickeners Feedwell Replacement, in Proceedings 13th AusIMM Mill Operators’ Conference 2016, pp 273–278 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Oct 10, 2016

By N Kado, T Iwama, R Inoue, S Ueda

Steelmaking slags are usually used as roadbed and civil engineering materials. However, the expansion phenomenon, which is caused by the volume expansion during hydration of free CaO and free MgO contained in steelmaking slag, is indispensable. Since the hydration of free MgO in steelmaking slag is much slower than that of free CaO, it is qualitatively considered that free MgO contributes to the hydration expansion of steelmaking slag over a long period of time. Similar to free CaO, free MgO consists of undissolved MgO and crystallised MgO in steelmaking slag. The latter precipitates during slag cooling. When divalent metal oxides (FeO, MnO, CaO) are dissolved in the crystallised MgO to form a MgO-based solid solution, it is expected to inhibit the hydration reaction similar to precipitated CaO. From the previous hydration test of Magnesioferrite, which was calcined after mixing MgO and Fe2O3 reagents, it was found that the higher the Fe2O3 concentration, the slower the hydration reaction progressed. In this study, by clarifying the influence of calcination conditions of MgO-FeO and MgO-FeO-MnO solid solutions, which were prepared by the calcination of mixture of MgO, FeO and MnO reagents, on their hydration reactivity, the effect of composition and thermal treatment on the formation of free MgO that is not hydrated (or easily hydrated) were discussed. To investigate the influence of MgO grain size, coarse MgO particles, which were obtained by crushing MgO crucible, were also used for heat treatment. With increasing the amount of FeO and MnO in the MgO-FeO-MnO solid solution, the hydration reaction became more suppressed. The expansion suppression effect was higher with solid-solved FeO than with solidsolved MnO. When the calcination temperature of the MgO-FeO solid solution was increased, the Fe3+/Fe2+ concentration ratio increased, resulting in a higher hydration rate.

Jun 19, 2024

By G M. Jeffress, D C. Arne

There are two discrete aspects to collecting portable X-ray fluorescence (pXRF) data to obtain reliable results and to comply with reporting requirements under the 2012 edition of the JORC Code (JORC, 2012) – sampling method and quality assurance. A robust sampling program is required to obtain representative material for analysis. The appropriate method should be established for a particular project using a small orientation study. A variety of approaches to sampling soils, drill cuttings, rock faces and diamond drill core are discussed. These include using multiple spot analyses, scanning using a single operating beam and the collection of cutting saw pulps. The operator must also be aware of the attenuating effects of analysing through sample bags of different material types for various elements as well as the limitations of current pXRF instruments in reporting reliable data for certain elements. The analysis of the samples must also be accompanied by a quality assurance program in order to generate data that are ‘fit for purpose’. This includes recording X-ray tube resolution on a routine basis, using matrix-appropriate standards for which total elemental concentrations are available, using silica blanks, capturing sufficient duplicate analyses to constrain data precision and obtaining check assays to calibrate pXRF data against laboratory data. Examples of quality control approaches and data are presented. Table 1 of the 2012 JORC Code also recommends that information on instrument make and model, reading times and calibration be provided in any reporting of pXRF data. To this should be added information on operating mode and temperature, software version and moisture content of the samples. A robust sampling methodology with a suitable quality assurance/quality control program should produce pXRF data of sufficient quality for public reporting purposes, provided that the data are presented using appropriate cautionary language and adequate supporting information.CITATION:Arne, D C and Jeffress, G M, 2014. Sampling and analysis for public reporting of portable x-ray fluorescence data under the 2012 edition of the JORC Code, in Proceedings Sampling 2014 , pp 57–64 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 29, 2014

By S Maritsa, E K. Chiw, S M. Masuka, ika, T Chisahwira

The challenges facing the iron and steel industry on a global scale include depletion of resources, excessive energy consumption and CO2 emissions. The demand for iron products in Zimbabwe is increasing due to massive infrastructural development like the expansion and improvement of mines, transportation systems and water reticulation systems. In Zimbabwe, cast iron is mainly produced from recycling scrap metals. However, there is currently a shortage of scrap, which has resulted in the vandalism of state-owned properties such as bus terminals and railway wagons and lines. Nevertheless, Zimbabwe is rich in limonite ores, which are idle, and it is the aim of this research that this ore be effectively used to produce feed for the blast furnace. The Blast furnace is still the dominant route for producing cast iron where sintering and coking processes are the main routes for preparing the Blast furnace feed. Sintering limonite ore fines produce a product of poor grade because of the high value of loss on ignition that has a negative impact on Blast furnace efficiency. Furthermore, the sinter plant and the coke making plant are a source of huge environmental pollutants. Since low-grade Zimbabwean coal fines are also available in abundance, they were used in the preparation of the composite materials ensuring maximum utilisation of this resource. Results showed that the limonite ore-carbon composite pellets sample with the binary basicity ratio (CaO/SiO2) of about 0.27 and coal addition of 2.5 wt per cent achieved above the minimum physical quality requirements for pellet of drop number of at least 4, a dry compression strength greater than 2.2 kg/pellet and an indurated compression strength greater than 250 kg/pellet. Limestone was used as the binder avoiding the addition of more impurities from bentonite since the limonite ore has a high SiO2 content of about 8.78 wt per cent.

Sep 18, 2023

By G Collecutt, T O’Beirne, D Humphreys, J Greenwood

Much of our knowledge of the behaviour of underground coal dust explosions has been derived from less than full-scale experimental explosions in facilities as small as 0.25 m diameter pipes. Although a substantial body of research has been undertaken in larger galleries approaching the size of full-scale modern mine roadways, there are still questions regarding the scaling of results to full-sized roadways in modern coalmines. Questions also surround the issue of comparing or scaling results between smooth and rough walled galleries, round and rectangular galleries and galleries with differing wall thermal properties due to different materials of construction.This paper will examine the influence of gallery size, cross-section area and wall roughness and thermal properties upon the characteristics of a coal dust explosion. Data from past explosion research will be examined and assessed for its application to the problem along with theoretical considerations for these factors.Recommendations on the design and minimum appropriate size of explosion galleries for assessing the performance of explosion inerting strategies, passive and active explosion barrier performance and determination of appropriate pressure ratings for ventilation structures will be made.CITATION:Humphreys, D, Collecutt, G, Greenwood, J and O’Beirne, T, 2015. The impact of facility construction and scale on the characteristics of experimental coal dust explosions, in Proceedings The Australian Mine Ventilation Conference, pp 301–308 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 31, 2015

By Windsor C

A review of the current pit design procedures and their performance has been undertaken recently by Mining Research Associates (MRA) and the CSIRO Division of Geomechanics. Visits were made to mines covering a wide range of operations. A questionnaire was completed by each mine in order to collate the relevant information. Interviews were also made with representatives of the Mines Departments to ascertain their role in regulating mine designs. Design expectations were compared with field performance, and reasons for variations noted. Problems associated with designs were identified and suggested methods of alleviating the problems have been made.

Jan 1, 1986

By T Suwa, S Ishida, J Xue, S Fuchida, H Shimada, Y Aoki, C Tokoro

Pyrite depression with prolonged pre-conditioning treatment in high salinity water has attracted much of researchers’ interest in recent years considering the increased utilisation of multiple stage flotation, closed water circuits, clay minerals, and sea water in flotation plants. In this study, the role of calcium (Ca)/magnesium (Mg) precipitates in stabilising the dissociative ferric hydroxy-xanthate (FHX), and its effect on modifying the balance of hydrophobic/hydrophilic species on the pyrite surface were primarily investigated. The total amount of extractable Fe-bearing species on pyrite concentrates and tailings after floatability test was quantitively determined using ethylenediaminetetraacetic acid (EDTA) extraction tests combined with inductively coupled plasma optical emission spectroscopy (ICP-OES). A more evident accumulation of extracted-Fe in pyrite concentrates rather than it in pyrite tailings was observed at both pH 9 and 10.5 when pyrite was pre-conditioned in Ca/Mg-bearing solutions for 360 min. Fourier transform infrared (FTIR) spectroscopy showed the main xanthate derivatives changed from di-xanthogen (1155 cm-1 ) to FHX (1167 cm-1 ) on the oxidised pyrite samples that were preconditioned in Ca/Mg-bearing solutions. Scanning electron microscopy-energy dispersive spectrometry (SEM-EDS) suggested the preferential accumulation of FHX upon secondary Ca/Mg-bearing precipitates as reflected by the higher Fe/S ratio together with the decrease of O element herein after xanthate conditioning. Although the hydrophilic secondary Ca/Mg/Fe-bearing minerals on the pyrite surface generally deteriorate pyrite’s floatability, the upper section of these secondary hydrophilic aggregates is partially covered by FHX alongside with further multilayer-adsorbed di-xanthogen. The precipitated Ca/Mg-bearing precipitates promotes the immobilisation of dissociated FHX derived from the reaction among iron oxyhydroxides and xanthate anions upon the localised secondary Ca/Mg/Fe-bearing minerals via acid–base complexation. Therefore, this phenomenon alleviates the hydrophilic modification of secondary Ca/Mg/Fe-bearing minerals to pyrite considering the immobilised FHX upon localised precipitates shows a slight hydrophobicity, and meanwhile, the upper FHX benefits the multilayer adsorption of di-xanthogen via the interaction among their inner hydrophobic alkyl chains.

Aug 24, 2022

Australian continental crust has accreted and consolidated by thirds: 1/3 during Archean time, 1/3 during Early to mid-Proterozoic time, and 1/3 during latest Precambrian to mostly Paleozoic time. The progression of orogenic systems and the crustal consolidations they represent seem not fundamentally different in basic orogenic processes from better known Mesozoic-Cenozoic examples in that accretionary, continental margin, collisional, and intraplate intracratonic inverted and/or reactivated systems are all recognizable in the tectonic evolution ofAustralia.

Jan 1, 1995

There are many compelling reasons why correct sampling schemes should be standard practice in the mining industry, yet there are numerous examples where poor sampling practices are known to exist in the business yet permitted to continue. It is not just technical issues that can be ascribed to the reasons for the continued use of incorrect methods. This paper proposes non-technical reasons why incorrect sampling practices continue, and identifies potential ways to overcome them.

Mar 1, 2010

By Dunn J, Nguyen G, Graham J

A pyritic gold concentrate from the Golden Mile, Kalgoorlie, was roasted over a range of temperatures in a pilot scale fluid bed reactor. The calcines were subsequently cyanide leached. Mineralogical studies of the con- centrate, calcines and leached residues were also undertaken. Calcines produced at 500'C gave the poorest gold extractions and high cyanide consumptions. Gold recoveries of approximately 90 per cent were obtained from calcines produced at 550-600'C but higher roasting tempera- tures resulted in an increase in the residual gold content of the leached calcine. There is some evidence of flash smelting of the pyrite at the higher roasting temperatures and encapsulation of gold particles. Mineralogical examination of the calcines shows that the mechanism of oxidation is temperature dependent. At 500'C pyrite is directly oxidized to hematite with a concentric layered texture which appears to inhibit lixiviant access to enclosed gold particles. At higher temperatures the conversion sequence pyrite-pyrrhotite-hematite produces a spongy calcine which al- lows easier penetration by the leaching medium.

Jan 1, 1991

By H Jones

Closure cost estimates may be generated at any stage of a mining operationÆs life; commencing with the initial prefeasibility studies and continuing through to the final decommissioning cost estimates. However, not all mine closure cost estimates are necessarily the same. Cost estimates will vary depending on the purpose for which they are prepared, the organisations requiring or undertaking the estimate and the stage of the mining operation. Different organisations can legitimately arrive at disparate cost estimates for closing the same mine because the organisations have different reasons for requiring the estimates. Another, equally valid, reason for potentially wide variations in cost estimates by different organisations on the same mine site is the different definitions of æclosure costsÆ used by different estimators. This paper considers the different approaches by different organisations including operating companies, government authorities and financial organisations and uses a hypothetical example based on practical experience to illustrate some of these differences in estimation methods.The paper suggest that a more consistent approach to closure cost estimating in the Australian mining industry would assist mining companies, governments, the accounting industry and the broader community to better understand this complex component of mine planning. One possible approach to closure cost estimating is briefly outlined.CITATION:Jones, H, 2012. Closure cost estimation - All things to all men?, in Proceedings International Mine Management 2012, pp 115-124 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 20, 2012

By E de Necker, F D. I Hodg, L-M Cruywagen

The acid mine drainage (AMD) situation at three opencast collieries in the Witbank Coalfield, South Africa, was evaluated from different perspectives. Twenty-seven test pits were dug into the spoils of these collieries to characterise the in situ conditions of spoils of varying age. Detailed static testing was done on surrounding drill holes and additional samples were taken from the test pits. Selected samples were tested using different techniques, namely ABA, mineralogy and kinetic tests. Groundwater monitoring boreholes from the areas surrounding these spoils were also used for characterisation. The ABA results compared favourably with the in situ determinations; acidic test pits proved to be potentially acid-generating from ABA, even when the samples had neutral paste pH. Kinetic test results showed these samples to yield low pH leachate over the test period. In several of these results, the theoretical depletion of neutralising potential and the onset of acidity were well matched. NAG pH-values and final observed water chemistry corresponded for the cells predicted by ABA to acidify, but compared poorly in cells that did not acidify. Results from the non-acidic spoils were consistent with the in situ observations. Alternative kinetic test methodologies were also employed. Duplicate samples were tested in humidity cells and in aerated trays that were manually wetted on a regular basis. Results from these tests showed an excellent correlation. Detailed mineralogical determinations using XRD and XRF were used for comparison to the ABA and, in some cases, humidity cell results. These comparisons show that the ABA results are consistent with the results expected from the mineralogy. The conclusion from these assessments is that ABA, in most cases, provides information that can be correlated to the field, mineralogy and to humidity cells. The use of multiple techniques leads to a higher degree of confidence in the use of the data.

Jan 1, 2003

By G Tsatouhas, R Newell, K Y. Wong

A sulfide ion selective electrode was used to control sulfidiser addition in the flotation testing of a synthetic and a naturally occurring ore containing malachite in order to compare the behaviour of sodium sulfide and calcium polysulfide. Both slug and controlled potential sulfidisation methods of addition were used. Under defined optimum CPS conditions, calcium polysulfide was a more effective sulfidising agent than sodium sulfide on the basis of both capital and operating costs. Surface and solution studies were used to compare the mechanism of each sulfidiser. For calcium polysulfide, XPS showed that polysulfide ions are adsorbed, whereas for sodium sulfide it is the hydrosulfide ions that are adsorbed on the mineral surface. For calcium polysulfide, the CuSx layer was believed to form on the malachite surface, which promoted the flotation of the malachite, by xanthate. Studies of surface morphology of the sulfidised malachite showed that a fairly uniform sulfidised layer is formed with both reagents. The use of sodium sulfide resulted in a thinner initial sulfidised layer compared to polysulfide at equivalent initial sulfur concentration.

Jan 1, 2005

The Marvel Loch Operations (MLO) plant was treating ores from up to six MLO sources and in addition needed to blend externally sourced ores with its own ores. This presented a metallurgical accounting dilemma, which was subsequently addressed by the design, implementation and testing of an automatic sampling system. The MLO automatic sampler was well designed and has been the subject of previous internal and external reviews. The sampling action is fully automated and the unit is essentially self cleaning particularly when sampling primary ores. The purpose of this paper is to document the rationale behind the design, the specific details of the sampling station, its use for ore purchase purposes and an assessment of the sampling system to meet the needs of the operator.

Mar 1, 2010