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By F C. D Michelin

As mines get deeper, the critical underground temperature limits will be exceeded, and an increasing number of mines will need to implement, expand or modify cooling systems. Surface cooling plants have many advantages over underground cooling such as efficient heat rejection, and lower relative capital cost; however the delivery of cooling through long underground distances can result in lost refrigeration capacity before the chilled air reaches the areas it is needed most. Refrigeration plants are therefore often overdesigned in size and capacity to compensate for underground losses.More mines are now utilising real-time monitoring and automated control of ventilation airflow and fan systems to ensure the conditions underground are safe and productive, and power consumption is efficiently managed. There may be significant opportunities to extend ventilation monitoring and control into the refrigeration delivery and control system.Energy reduction is an effective way to reduce costs and CO2 emissions, which is an increasingly important part of corporate governance. More efficient refrigeration control is a further step toward reducing energy consumption. This paper looks at an added step in how real-time monitoring can assist in controlling the output and chilled air delivery of a cooling plant. The requirements, implementation, benefits and challenges will be discussed.

Oct 12, 2022

By F P. van der Meer, E Lessing, E Matthies

High pressure grinding rolls (HPGR) technology is growing to be a common comminution tool in iron ore processing. The technology finds a wide acceptance and presents specific benefits in coarse ore grinding and closed-circuit grinding in preparation of ball mill feed, right down to the other end of the particle size spectrum for iron ore pellet feed preparation.A growing number of minerals processing plants are facing higher operating costs and difficulties due to a scarcity of process water, which in some cases is a result of more stringent environmental constraints. In addition, many new iron ore deposits are located in more arid regions of the world. These challenges have led to operators taking a new look at dry processing of iron ores.The use of dry crushing and classification technology in cement production from blast furnace slag, clinker material or limestone feed stocks indicates that the technology may be applied in minerals processing. In addition, dry processing provides the possibility of generating a final product from finely disseminated and inter-grown ores at sizes near or well below 100 µm, as may be required for beneficiation techniques such as in fine magnetic separation, flotation or magnetic flocculation.Dry grinding by HPGR has a number of specific features, challenges and opportunities, including balancing power input, moisture content requirements and classification efficiency in the process design. HPGR parameters and the latest HPGR design and sizing capabilities indicate considerable potential benefits from this dry processing technology.This paper highlights some of the specific issues that play a role in dry HPGR application, with respect to energy and materials balances. Examples of dry HPGR practices and process studies in iron ore mineral processing are discussed.CITATION:van der Meer, F P, Lessing, E and Matthies, E, 2015. Iron ore final grinding by high pressure grinding rolls and air classification, in Proceedings Iron Ore 2015, pp 197–204 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 13, 2015

By B Roache, A Vakili, R Talebi

When a highly anisotropic or weak rock mass is subjected to high-stress conditions, it can lead to large ongoing deformations or squeezing ground conditions. Squeezing ground conditions can impose increased support costs, delays associated with rehabilitation, and disruption to production schedules. Ultimately, in more severe cases, it may result in complete drive closure. Several recent case studies investigated the squeezing mechanism and measures to control squeezing ground in underground mines and also to design appropriate ground support systems. Effective management of squeezing ground conditions requires a sound understanding of the failure mechanism and the driving forces. Once the failure mechanism is understood, the appropriate ground support system should be tailored to specifically manage the critical driving forces that control the squeezing mechanism. Support type, support stiffness, reinforcement length, support density, installation times and mining sequence all have important impact on the effectiveness of the support system. This paper provides a case study at the Ballarat Gold Mine in Australia, where drive squeezing was associated with foliated ground conditions located below 700 m depth. Numerical modelling was used to better understand the failure mechanism and the driving forces that lead to squeezing conditions. The effectiveness of various support types was compared to installed ground support performance. This has provided a credible methodology for assessing and optimising the selection of reinforcement in squeezing ground conditions. CITATION:Talebi, R, Roache, B and Vakili, A, 2018. Understanding and modelling squeezing ground conditions at the Ballarat Gold Mine, in Proceedings The Fourth Australasian Ground Control in Mining Conference (AusRock), pp 107–118 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 30, 2018

By J Li, A McFarlane, J Yu, L L. Kuhar, R Meakin, N Chapman

"Column leach tests are used frequently to predict recoveries and reagent consumption for nickel laterite heap leaches. These column leaches often run for more than 100 days and therefore require long-term monitoring and data analysis to achieve the desired information. To minimise the cost and time required to obtain relevant information for nickel laterite heap leaching, we have developed a small-scale hydrogeometallurgical laboratory test to serve as a proxy to column, and by inference, heap leaching. In excess of 50 leach tests were conducted using four different small-scale proxy and column leach tests to compare predicted nickel recoveries, acid consumption and leach kinetics and to determine whether insight into potential scale-up effects can be obtained. The most promising proxy test was identified and we achieved a statistically significant recovery and acid consumption correlations between this test and the column leach tests. The accuracy of the small-scale tests was confirmed by column tests run on new laterite ores. This geometallurgical proxy could be of use for the population of block models and process selection during the mine planning phase or for optimisation and control during processing.CITATION:Li, J, Kuhar, L L, Meakin, R, Chapman, N, McFarlane, A and Yu, J, 2016. A Geometallurgical Proxy for Nickel Laterite Heap Leaching, in Proceedings The Third AusIMM International Geometallurgy Conference (GeoMet) 2016, pp 335–340 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Jun 15, 2016

By Q Yu, G Ren, Z-Y Chen, J Yang

The wedge shape theory of the rock fragmentation range in bench blasting is presented according to the dynamic characteristics of rock fragmentation by blasting in open pit under the condition of hole-by-hole initiation. The finite element software ABAQUS was used to analyse the rock fragmentation mechanism. The rock mass stress contours, crack propagation and damage evolution of different moments were obtained. The results showed that the wedge shape theory of blasting is closer to the rock fragmentation in hole-by-hole blasting and is useful to the design and calculation of charge weight.CITATION:Yang, J, Chen, Z-Y, Yu, Q and Ren, G, 2015. The wedge theory of borehole charge design for bench blasting and its numerical simulation, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 169–176 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

By G McKay, M Erskine, S Macklin

The City of Sydney is currently investing in a number of infrastructure projects that require tunnel excavations within the Triassic Hawkesbury Sandstone. It is generally accepted that this formation has high residual stresses of ‘tectonic’ origin, so much so that these stresses have been implicated in a number of well-known failures and problems for tunnelling. These include failure of ‘roof beams’ comprising discrete beds in the crown of tunnel excavations; stress-induced spalling and ‘slabbing’ of tunnel walls; shear displacement between beds causing the failure of rock bolts; strain in adjacent infrastructure and, the necessity for re-grouting of high conductivity fractures due to stress relief dilation after excavation. Whilst there is an extensive published database of in situ stress measurements comprising ‘hydrofrac’, ‘over-coring’ and ‘slotter’ stress measurements, these data indicate a considerable spread of results. The traditional approach to interpreting this data has been to attempt to fit linear correlations to stress versus depth data, based on personal experience and ‘back-analysis’ of monitoring data during construction. However, there are a number of such correlations in the literature and there is divergence of opinion regarding the assessment of ‘background’ in situ stress and appropriate upper and lower bound values for design. This paper provides a brief review of the published data; suggestions on an alternative ‘risk-based approach’ to assigning in situ stresses for design; and, proposals on how in situ stress tests may be conducted in future to improve the quality of the database available to designers.CITATION:Macklin, S, McKay, G and Erskine, M, 2014. A review of the in situ stress database for tunnel design in the Hawkesbury Sandstone, Sydney, New South Wales, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 171–178 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By R McCarthy, P Hawke

FerrAus Ltd's Robertson Range and Davidson Creek Projects are located in the Hamersley Province about 100 km east of Newman, Western Australia. Significant iron mineralisation defined by an aggressive exploration program within the Marra Mamba Iron Formation is shallowly north dipping at Davidson Creek, and mainly shallowly east dipping at Robertson Range, forming part of a regional scale anticline with the granitic and greenstone basement of the Sylvania Inlier as its core. With minor exceptions, the stratigraphy is comparable with that seen in the main Hamersley Basin. Granite and greenstone basement rocks of the Sylvania Inlier are unconformably overlain by shales and volcanic rocks of the Fortescue Group. The overlying Hamersley Group is locally represented by interbedded chert, banded iron-formation (BIF) and shales of the Marra Mamba Iron Formation (Nammuldi, MacLeod and Mount Newman Members), and dolomites, cherts, BIF and shales of the Wittenoom Formation. Iron enrichment occurs predominantly in the Mount Newman Member, and to a lesser extent in the West Angela Member of the Wittenoom Formation. Enrichment varies from 20 - 30 m in thickness in elongate bodies up to 3 km in strike length, and generally thins down dip. At Davidson Creek iron mineralisation is a haematite-goethite-ochreous goethite assemblage, while at Robertson Range this assemblage is consistently overprinted by a later, goethitic alteration related to 'hardcap' weathering. Near surface hardcap alteration in both project areas comprises more siliceous, aluminous and vitreous goethite. Initial exploration completed by Rio Tinto Exploration between 1999 and 2001 indicated the potential for about 20 Mt of iron mineralisation at Robertson Range. Since 2005 a detailed exploration program undertaken by Australian Manganese Pty Ltd (a wholly owned subsidiary of FerrAus Ltd) has defined a global indicated and inferred resource totaling 164.4 Mt at 58.6 per cent Fe (ASX: FRS 17 April 2009).

Jan 1, 2009

By T Roesch, M Neurohr, S Stratton

"Dwindling commodity prices are forcing today’s mining operations to increase output. Sometimes the solution is to upgrade the existing infrastructure; however, in most cases it has to be achieved with the same or reduced workforce and with the same equipment capacity through improved process efficiency and higher uptime.Measure, Manage and Improveis the mantra for this years’ Mill Operators’ Conference and while this in most cases relates to the above process efficiency, Siemens has set its focus on the availability and uptime aspect since unscheduled downtime is one of the biggest threats to any grinding operation. Pinion misalignments, resonance, unbalance and bearing and gear meshing faults in geared trains, as well as long-term changes in the condition of the mechanical components or structures and auxiliary systems in gearless systems are the main reasons for unscheduled downtimes in today’s mill drive trains. Our paper outlines the efforts that have gone into adapting conventional condition monitoring methods in conventional, pinion driven mill drive trains as well as gearless systems to capture the gradual deterioration of wearing parts or structural changes in the drive train not only on fixed speed application but also on variable speed applications with multiple operating points. The paper further explores the use of condition monitoring systems as a tool to assess spare thermal motor capacity to potentially push equipment beyond its nameplate rating, along with the process that was followed to correlate measured frequency spectra and envelopes to ambient and load data to understand the kinematics of the drive train.Citation:Neurohr, M, Stratton, S and Roesch, T, 2016. Advancements in Condition Monitoring on Mill Drive Trains for Proactive Maintenance and Early Fault Detection Purposes, in Proceedings 13th AusIMM Mill Operators’ Conference 2016, pp 263–272 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Oct 10, 2016

By A Bagis

Road tunnels are an accepted and effective transportation solution in urban areas to mitigate increasing traffic congestion and facilitate improved urban connectivity in a cost effective manner while meeting societal goals to reduce the impact of construction. In designing a tunnel system, there is a requirement to achieve an acceptable level of in-tunnel air quality, as well as meeting ambient air quality goals. In Australia, there is also a requirement for zero portal emissions which means that all pollutants must be emitted to the atmosphere via a ventilation stack.Traditionally, effective pollutant dispersion has been achieved by constructing tall ventilation stacks which disperse pollutants into the atmosphere at a high level. The dominant variable parameters in the effectiveness of the dispersion under the ventilation engineers control are the efflux velocity, the height of the ventilation outlet and the concentration of pollutants at the point of discharge. During off-peak operations the required ventilation exhaust rate can be reduced due to the decrease in traffic. This can lead to a drop in the efflux velocity from the stack and therefore the effectiveness of the dispersion. This potentially drives the need for a higher outlet, or an increased exhaust rate to achieve a higher efflux velocity with consequent effects on energy consumption.The paper proposes a method of varying the cross-sectional area of the ventilation stack with the use of motorised control dampers, thereby maintaining a sufficiently high efflux velocity throughout the 24 hour period independent of traffic conditions. This allows the use of a potentially shorter ventilation stack.

Mar 8, 2011

By M Haest, O Dominguez, D Mittrup

With the current focus in the mining industry on reducing costs, while simultaneously improving ore quality, infrared spectroscopy is a tool that can potentially assist companies to meet both challenges. Changes in the nature of infrared spectra are strongly influenced by changes in mineralogy, which is a key input variable for exploration (geology and orebody modelling and ore characterisation) and mining (pit design, mine scheduling and processing plant design/management).Infrared spectroscopic logging of drill holes has been embedded as a standard tool in BHP Billiton Iron Ore exploration, with a process set up to automatically deliver mineralogy and associated imagery to the end users (typically exploration geologists). The availability of consistent and automated mineralogy drill hole logs across a project is improving the output quality and reducing re-work.BHP Billiton Iron Ore is now looking into using the same infrared spectroscopic data for other applications, including improving predictions of geometallurgical and geotechnical parameters. Trials show that addition of infrared spectroscopic data to conventional data sets (element analysis and depth information) is significantly improving the accuracy of regression models to predict the lump-fine ratio.Further initiatives around infrared spectroscopic data in BHP Billiton Iron Ore include the installation of infrared spectroscopic sensors over conveyor belts, infrared spectroscopic mine face scanning and infrared spectroscopic blasthole logging. The ultimate vision is to have consistent, seamless mineralogical data from infrared spectroscopic sensing available throughout the mineral value chain (exploration/mining/processing). This seamless infrared spectroscopic data ‘bridge’ will allow the transfer of knowledge between the different sections of the value chain (exploration, mining and processing). For example, ore handle-ability could be predicted on exploration samples using regression models built from processing plant observations. In the opposite direction, information gathered about the buried stratigraphy by infrared spectroscopy utilised during exploration, could be used to predict the stratigraphy encountered during mining. This collaboration across BHP Billiton Iron Ore is expected to deliver significant savings, while improving the quality of the final product, thus helping to drive efficiency over the next decade.CITATION:Haest, M, Mittrup, D and Dominguez, O, 2015. Reaping the first fruits – infrared spectroscopy: the new standard tool in BHP Billiton Iron Ore Exploration, in Proceedings Iron Ore 2015, pp 277–284 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 13, 2015

The Newcrest Mining Limited Telfer Gold Mine consists of an underground sublevel cave (SLC) operation located 734 m directly below active open pit operations. Open pit and underground current production rates are 50 million and 5.7 million tonnes per anum (Mt/a) respectively. The SLC was initiated in late 2006 with breakthrough planned to occur on the 5484 bench of the west wall in late 2009. Risk to the south ramp was identified during this time, resulting in the construction of the north ramp. The SLC was continually tracked from initiation with a suite of monitoring systems and managed with a Major Hazard Management Plan (MHMP) and associated Trigger Action and Response Plans (TARP). At breakthrough the eastern limb of the cave was located within a 70 m horizontal distance from the south ramp. The south ramp was closed in October 2009 due to significant slope deformation, extensive cracking in the berms and batters between the ramp and breakthrough bench and a major failure 250 m to the north of the cave breakthrough. Wall response was first identified from slope deformation measurements taken by the wall monitoring radar in May 2009, at which point the SLC was 160 m from breakthrough. The impact of the SLC on the slope is a unique case with the monitoring systems in place able to provide data on the slope reaction to the SLC progression. This paper will discuss the management of the south ramp such as the early interpretation of risk associated with cave breakthrough, monitoring systems implemented to track the cave progression and wall deformation, data integration and interpretation and risk management. Following the closure of the south ramp further instrumentation programs and risk assessments were conducted to determine the risk of re-opening this haulage route. The outcomes of this program will also be presented.

Nov 25, 2010

By C B. Smith, G L. Boxer, S W. Moss, A L. Jaques, V Lorenz, M J. Rayner

The Ernest Henry Iron Oxide Copper Gold deposit is hosted in a large dilation between two moderately dipping shear zones found in the footwall and hanging wall of the deposit. These shears are controlled by a large diorite intrusion to the north-east and south-west of the deposit, formed ~1660 Ma. A shear zone dubbed the ‘Interlens’ uncovered through underground workings truncates the main orebody into two lenses, and is hypothesized to have formed in conjunction with the Hanging Wall Shear Zone and Footwall Shear Zone. All three shears dip moderately to the SSE (50–140) from open cut exposures through to the current mining horizon approximately 800 m below the surface. Routine geological work and a capital drilling campaign has identified a significant flexure in these sub parallel ore bounding shears with increasing depth. A shift in shear orientation in the Interlens over approximately 100 m vertically from ~50° to the SSE to a steep, easterly trend (~85° to the east) is observed in both drill core and exposures in the underground workings. It is hypothesized the diorite intrusive to the south-west of the deposit controls the shear zone geometries at depth. The geometry of the Interlens mirrors the surface expression of the Proterozoic package of the orebounding shears to the south-west of the deposit, suggesting the surface geometries of the shear zones are consistent with depth. Additional drilling to explore the validity of this hypothesis is planned for the near future to better understand the structural controls on the Ernest Henry mineralisation with increasing depth.

Mar 22, 2022

By D Johansson, A Nordqvist, D Mihaylov, N Petropoulos, M Wimmer

The flowability of the caved rock masses in the sublevel caving (SLC) mining method is of great importance. During the blasting process of a SLC-ring, the caved rock mass in front of the ring is compacted. As a result of this compaction, the mechanical properties of the fractured rock masses change, for example void ratio, angle of internal friction and structure of the compacted material. The changed mechanical properties of caved rock mass and recent blasted material can influence the mobility of the material, which could result in blockage of the flow path of the material. The identification of the involved mechanisms in this process can be done after a series of tests in different scales. However, there is no available equipment for dynamic measurements during blasting, ie velocity and displacement of the burden and in the caved masses. This study focuses on the development and laboratory evaluation of a measuring system that can be installed in a borehole. The first trial was carried out in a pillar, where two blastholes had been drilled (9.5 m) parallel with the drift and two measuring holes (16.5 m) were perpendicular to the drift. Two measuring systems were installed in the measuring holes. Some preliminary tests were carried out to find suitable initiation procedures for the emulsion explosive. Applicability and robustness of the developed measuring system were also evaluated. In addition to these tests, an expandable cement mixture was developed to firmly anchor the measuring systems in the boreholes. The measuring system consists of an anchor, armoured cable in a pulling tube and a protective case. The anchor is equipped with uniaxial and triaxial accelerometers. A potentiometric measuring system for displacement up to 2 m is installed at the end of the pulling tube and connected to an extendable spiral cable. All sensors are connected to a data acquisition system (DAS). Both measuring systems have their own DAS to acquire data in case of failure of one of the systems. The measuring system was tested in laboratory conditions with impact velocity up to 10 m/s. It was proven to be functional and gave reliable results.CITATION:Petropoulos, N, Mihaylov, D, Johansson, D, Wimmer, M and Nordqvist, A, 2015. Design of equipment for dynamic burden measurements, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 493–500 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

By R Jones

OneSteel Whyalla’s grate-kiln-cooler pelletising plant was commissioned in 1968 processing haematite feed from the local South Middleback Ranges mining area. The existence of a magnetite resource beneath the haematite ore at Iron Duke had been known for some time. In 2004, a decision was made to covert the primary iron source for the Whyalla steelworks from haematite to magnetite – known as project magnet. The intent of the project was to convert the feed to the steelworks from haematite to magnetite and to free up the remaining haematite resource for export. The pelletising plant was cut over to a magnetite feed in 2007.The thermochemical differences of magnetite compared to haematite are threefold:1. the introduction of an exothermic reaction during conversion of magnetite to haematite,2. the absence of bound water which existed within the haematite, and3. lower gangue content requiring lower fluxing levels and therefore lower calcination energy demand.The combination of these differences results in a significantly different induration requirement for magnetite as compared to haematite. The change therefore required extensive research and test work to design modifications to the furnace and to ensure appropriate risk mitigation for the Whyalla steelworks.Preliminary pot-grate test work was performed to define the pellet chemistry and confirm the suitability of the magnetite to produce pellets suitable for the OneSteel blast furnace. A heating curve was developed by use of computer-based heat and mass balance modelling. Extensive pilot scale grate-kiln-cooler test work was then performed to confirm the heating curve and to verify and fine-tune the pellet properties. Computation fluid dynamics was used to design the physical changes to the furnace required to achieve the proposed heating curve.Following installation of an additional preheat zone, including a wall and dilution air fans, into the preheating furnace, and installation of an additional wall into the cooler, the modified furnace was commissioning in December 2007. The plant performed as expected during commissioning with the actual heating curve matching the proposed curve and the produced pellets within blast furnace specifications.

Jul 11, 2011

By R A. Pax, B Cornish

"Although it is well known and easily experienced that the feed size distribution influences the throughput and stability of operation of a semi-autogenous grinding (SAG) mill, the details are poorly understood since it is often only the input and output measurements that are used to identify unfavourable in-mill conditions. Load cells and power monitoring are sometimes used but are generally poor indicators of the mechanisms that lead to such unwanted conditions.At the MMG Century operation a 12-microphone array around the SAG mill using non-contact acoustic measurement methodology has been used to diagnose the in-mill conditions to facilitate improved throughput and stability of operation. Use of acoustic measurement and control has provided a demonstrated increased throughput of at least 20 per cent as well as improved stabilisation of the mill. Since the information derived from the acoustic noise from a mill allows discrimination of the behaviour of the steel balls and the rock, a number of in-mill conditions can be identified with signals that include toe and shoulder angles, water holdup and the ball to rock ratio.Feed size variations, measured online with an imaging system, have been used to determine their effect on the internal charge behaviour. It has been found that circumferential segregation of steel balls and rock occurs as well as poor mixing of large rocks. Both of these effects are not conducive to optimal breakage rates of different size fractions. Longitudinal segregation effects also occur. This paper presents and discusses these results and illustrates how the new acoustic knowledge can be used to manage and improve mill operation and stability.Citation:Pax, R and Cornish, B, 2016. Understanding Size Effects of Semi-autogenous Grinding (SAG) Mill Operation as a Pathway to Solving Feed Disturbances - Case Study using the MMG Century SAG Mill, in Proceedings 13th AusIMM Mill Operators’ Conference 2016, pp 321–330 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Oct 10, 2016

By R Wynn, R A. Pax, S Mann, B Cornish

The semi-autogenous grinding (SAG) mill at the MMG Century operation has failing load cells that are essential to the control strategy used to stabilise the mill. Currently, mill-bearing pressure is used as a proxy for the load cells, but it has been found to be a noisy signal and lacking in useful sensitivity. It is also prone to variations and drift due to temperature. After consideration of a number of options, a non-contact acoustic array has been installed around the SAG mill to provide a more stable proxy load signal as well as other information about the internal operation of the?mill.The installation consists of 12 microphones to provide some detail into the operational differences that occur during normal operations at the MMG Century SAG mill. This acoustic approach acknowledges that operational grinding mills emit significant acoustic emissions that are a consequence of the dynamic environment prevailing inside them.Previous studies have attributed the acoustic noise to a range of events that occur inside these mills (Pax, 2011; 2012). Consequently, non-contact acoustic determinations of in-mill behaviour can provide powerful insights into the operation of the primary comminution tumbling mills. By measuring key microphone signal attributes at different positions around a mill, a holistic picture of mill internal operation can be developed.This paper will describe the installation of the 12 microphones and discuss the use of the acoustic load signals as a proxy for failing load cells. It will also present data from new observations of internal mill dynamics and the results of implementation of control using these acoustic signals. Key to the control approach has been the development of a logically coherent picture of the processes inside the mill.CITATION:Pax, R A, Wynn, R, Mann, S and Cornish, B, 2014. Implementation of acoustic arrays for semi-autogenous grinding mill?operation, in Proceedings 12th AusIMM Mill Operators’ Conference 2014 , pp 273–282 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 1, 2014

By P Woodward, T Ly, N Muhamad

OZ Minerals' Prominent Hill copper-gold concentrator is located 650 km north-west of Adelaide in the Gawler Craton of South Australia. The concentrator was built in 2008 and commenced commercial production in early 2009. The Prominent Hill concentrator is comprised of a conventional grinding and flotation processing plant with a design capacity of 8 Mtpa. The flotation circuit includes six rougher cells, an IsaMill for regrinding the rougher concentrate and a Jameson cell preceding the three stage conventional cell cleaner circuit.Since its commissioning, the Prominent Hill flotation circuit has been the focus of a series of projects aimed at continual performance improvement. This has been achieved by a systematic approach of project identification, evaluation and implementation which has led to a progressive improvement in flotation performance. Innovations that have been successfully implemented include aspects of cell design and operation, and reagent suite optimisation.Improvements to the mechanical cells initially focused on the installation of a modified rotor-stator design in the rougher circuit, as recommended by Outotec. Isolated cells were fitted with this technology and proven to provide a benefit for copper recovery before the design was trialled in subsequent cells along the bank. Based on this success, further modifications were made to other aspects of the rougher and cleaner cells.Laboratory trials conducted at Prominent Hill involve a screening process identifying potential reagents from a list of products, which are then rigorously tested in the laboratory before one is selected for trial in the concentrator. Where these reagents have demonstrated a statistical improvement in performance they have typically been incorporated permanently into the flotation circuit. This paper discusses the process of continual improvement at the Prominent Hill flotation circuit and the optimisation achieved by the implementation of key initiatives.CITATION:Woodward, P, Muhamad, N and Ly, T, 2013. Optimisation of the Prominent Hill flotation circuit, in Proceedings MetPlant 2013 , pp 431-444 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 15, 2013

By J D. Lubben

Hibbing Taconite is a Lake Superior-type granular magnetite taconite deposit occurring within the Biwabik Iron Formation along Minnesota’s central Mesabi Iron Range. The deposit is situated on the northern margin of the Proterozoic Animikie Basin. The deposit strikes northeast, dips gently southeast, and occupies 10 km of strike length. Mining focuses on 50 m of granular cherty and laminated slaty taconite within the Lower Cherty member.Ores generally consist of a quartz, magnetite, siderite, ankerite, minnesotaite, stilpnomelane, and haematite mineral assemblage. Processing is optimised by exploiting the physical and chemical variations that exist between three major ore types. Taconite ore averages 20 per cent magnetic iron (MagFe), 27 per cent weight recovery (WtRec) and produces a final concentrate with 4.5 per cent silica (SiO2). Since 1976, production has totalled approximately 237 million long tons (Mlt) of pellets (8 Mlt per year rated capacity).Ore processing uses a simple fl ow sheet of autogenous grinding (<0.044 mm) followed by two phases of wet magnetic separation, fi ltering, limestone/bentonite addition, balling, and firing to create pellets averaging 66 per cent total iron. A Liberation Index (LIS) is used as a primary guide for ore grading and metallurgical control. Grind requirements, magnetite liberation and silica grade are closely monitored to ensure plant optimisation and product quality.A recent program of benefi ciation of low-grade ores by in-pit crushing and dry magnetic cobbing has demonstrated that low-grade ores (<17 per cent MagFe, <25 per cent WtRec) can achieve a signifi cant metallurgical upgrade (up to 25 per cent MagFe and 40 per cent WtRec). This operation recovers 60 per cent of the total crushed volume, and has a calculated effi ciency factor (magnetic iron recovery) of 79 per cent. This paper discusses the benefi ts of this upgrading and its effects on ore blending and processing.

Jul 11, 2011

By L Scheunis, A Van den Bulck, E Jak, K Verbeken, M Shevchenko, R Starykh, I Bellemans, P-J Boeykens

As a result of the globally increasing consumer use of electronic devices, it is expected that pressure will increase on the supply chain of precious metals. Hence, recycling of these electronics becomes increasingly important, as well as optimising the current processes. One major issue in metallurgical processes is the amount of metal that is lost into the slag. This metal loss is inherent to the production process and therefore, additional processing steps such as slag cleaning may be required. Slag cleaning can be done in electrical resistance furnaces where heat is produced using the Joule effect, making the slag’s electrical conductivity an important operating parameter. Since slags are ionic liquids, the electrical conduction happens via the movement of ions which is called ionic conductivity. However, within the presence of transition metal oxides, a second mechanism of conductivity occurs as electrons are able to hop from one transition state to another, which is known as electronic conductivity. As ‘FeO’ is a common slag component in the non-ferrous pyrometallurgical industry, both mechanisms are present, but their proportions vary with the respective amounts of the two forms of the multi-valent ions and hence, with the oxygen partial pressure. The goal of the present study is to develop an experimental set-up and methodology for measuring the electrical conductivity of synthetic SiO2 – CaO – AlO1.5 – ‘FeO’ slags at various oxygen partial pressures.

Jun 19, 2024

By R Fletcher

Pacific Hydro, a leading renewable energy company from Australia, is developing a series of cascading run-of-river hydro electricity projects in the Cachapoal Valley at the base of the Andes Mountains some 100 km south of Santiago in Chile.These projects involve extensive tunnelling and underground works. The first of these projects is called Chacayes (110 MW installed capacity) and is now under construction with Astaldi SpA of Italy and Fe Grande of Chile as the EPC contractor. Astaldi SpA also has an equity stake in the project. It involves 6 km of tunnels between 5 m and 7 m diameter, of which 2.3 km is by tunnel boring machine (TBM) (5 m diameter).This paper outlines the local and regional geology, the scope of the Chacayes project, actual tunnel excavation rates and support, and compares the decision making on Chacayes between a choice of traditional drill and blast excavation versus TBM.The paper also outlines the next project planned to be developed by Pacifi c Hydro in the valley – the 140+MW Nido de Aguila project involving a main tunnel drive of 11 km with two intermediate adits, plus a 388 m shaft and underground powerhouse. The main tunnel drives are likely to be excavated by two hard rock TBMs (5 m diameter) but will need to be able to withstand high overburden pressures of up to 1300 m.Subsequent projects in the planning stages include the downstream Coya II project with two tunnels totalling approximately 10 km, one of which may be by TBM.

Mar 8, 2011