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By B Vietnieks, N Widmer, L White, E Tata, J Natukunda, D C. Ilouga, J P. Tyler

The Republic of Uganda aims to exploit its’ significant, un-developed iron ore resources to supply the required raw material for developing its’ iron and steel industry across all the stages of the supply chain. Large prospects of iron ore exists in Uganda in the eastern (Tororo) regions and southwestern (Kisoro-Kabale) regions of the country. The Kisoro-Kabale iron ore projects covers mineralisation in hematitic banded iron formation (itabirite) in the north-eastern Congo-Tanzania Craton; covering ten Iron ore prospects. The prospects include Kamena, Karukara, Nyamiringa, Kyanyamuzinda, Rugando, Katagata, Rwengongo, Kijuguta, Kihumuro and Katuna. High-grade hematite ore prospects in south-western Uganda have known grades ranging from 55 per cent to 68 per cent iron ore content with an exploration target estimated at over 500 million tonne (Mt). Small scale production of iron ore from the south-western regions provide raw material to existing steelmaking and direct reduction iron ore plants located in the Jinja and Iganga districts of eastern Uganda. Large quantities of iron ore and other steelmaking raw material, however, are required to be imported into Uganda due to the limited exploration and development of their own iron ore mining operations. A joint collaboration between the European Union (EU), the Department of the Geological Survey and Mines (DGSM), Ugandan Ministry of Mines in partnership with Australian drilling and mining consultancies, ADT Africa and Kalem Group as a EU funded project was undertaken during November 2022 and September 2023. Exploration and evaluation of the ten iron ore prospects in south-western Uganda was undertaken through geological mapping, drilling, assaying, and technical studies with the view to attract investment for the development of Uganda iron ore mining and steelmaking industry. The collaboration developed mineral exploration policy, guidelines and standards, an iron ore exploration manual, a geological data management policy, and to support the sustainable development of iron ore mining in Uganda through building the capacity of local Ugandan geology and mining personnel through the transfer of knowledge and expertise from experienced iron ore experts. The quantification of these resources is an important first step in assessing their economic potential and attracting mining investors. This paper presents an overview of the investigation program and the preliminary results as an important first step in attracting mining investors to this exciting new iron ore province.

Sep 18, 2023

By P Hodkiewicz

Recent structural interpretations based on historic stope shapes were used to develop a rapid and innovative method to domain and simulate structurally complex, high-grade gold veins at depth in the Edna May deposit. This involved ‘implicit’ modelling of drill hole data using Leapfrog software, which allows complex wireframe domains to be built and updated rapidly, compared to ‘explicit’ manual wireframing methods that are too subjective and time consuming. Conditional simulation was used for resource estimation, in order to simulate the highly variable gold grades associated with the veins. Similar modelling methods could be used to determine the mining potential of other historic gold deposits that are receiving renewed interest because of the high gold price.Gold at Edna May is hosted in the Edna May Gneiss, which is a WNW-striking tonalitic intrusion along a shear zone that dips approximately 45° towards the NNE. Gold occurs in multiple 0.5 - 5 m thick arcuate quartz veins that plunge steeply towards the west. Two phases of historic underground mining at Edna May (1911 to 1922 and 1935 to 1947) produced 360 000 ounces of gold at an average grade 19.5 g/t from seven ‘reefs’ to a depth of 240 m. This established Edna May as one of the highest grade gold mines in Western Australia at the time.Recent drilling by Catalpa Resources confirmed the potential for down-plunge continuity of high-grade veins. New structural interpretations, based on historic level maps and wireframe re-constructions of the arcuate stope shapes, were used as ‘structural trends’ in Leapfrog to model the mineralisation. The resulting wireframes capture the complex distribution of gold in the deposit and were used as domains for resource estimation.Conditional simulation using the Turning Bands method was used to simulate the expected variability of gold grades associated with this mineralisation style and the median of the 100 realisations was used to report an inferred resource. Results of this modelling method are being used to target vein extensions at depth, to consider different underground mining scenarios, and to assess the risks associated with developing and mining this high-grade and high-nugget gold deposit.

Aug 22, 2011

By J Edman, RáBeamish, G Cambourn, B Beamish

Moist Adiabatic Benchmark (MAB) and R70 testing have been applied to core samples of a multiple seam sequence from a borehole at the Doyles Creek Project. The coal samples range in rank from high volatile B bituminous to high volatile A bituminous, with a general increase in coal rank as depth increases in the borehole. The intrinsic coal reactivity to oxygen decreases with coal rank as indicated by the R70 values. The time taken to reach thermal runaway shown by the MAB testing however is strongly modified by the interaction between the intrinsic coal reactivity, the moisture content of the coal and the retained gas content of the coal. This is clearly demonstrated by the lowermost seam of the sequence. The MAB test for coal from the Whynot Seam took 20 days to go to thermal runaway, which projects to heating issues taking between eight to 12 months to occur for loosely piled coal found in coal roof falls or a longwall goaf and uncompacted stockpiles, assuming sufficient air is available for coal oxidation. The results from this project illustrate leading practice for the operational planning and development of an appropriate spontaneous combustion management plan (SCMP).CITATION:Beamish, B, Cambourn, G, Lewis, G, Edman, J and Beamish, R, 2013. Application of leading practice spontaneous combustion assessment to exploration at the Doyles Creek Project, in Proceedings The Australian Mine Ventilation Conference , pp 293-298 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 1, 2013

By H Wright

Black Rock Cave (BRC) is a sublevel cave which was developed in 2018–2020 and has been in production since November 2020. BRC is part of the Mount Isa Mines complex and extracts a leached orebody comprising of high-grade chalcocite ore, situated below the historic Black Rock Open Cut workings. The mine is owned by Mount Isa Mines and operated under contract with PYBAR Mining Services. In 2021 a number of rockfalls occurred throughout the mine and were increasing in frequency. This culminated in a major rockfall on the decline in June 2021, after which the decision was made to withdraw all persons from the mine, initiate rehabilitation and conduct further investigations to deduce a safe method to provide long-term support. The rockfall investigations have shown that the corrosive nature of the highly leached rock mass can consume a split set in less than 18 months. A review of potential corrosion resistant ground support methods concluded that steel split sets have a safe lifespan of six months at BRC, and that all workings must have corrosion resistant support installed prior to exceeding the safe life of the friction bolts. The review recommended the use of 4 m cable bolts as the most suitable method of corrosion resistant support. This new support system, and the requirement to rehabilitate all mine workings within the leached orebody, had an impact to the schedule and an effect on both equipment and manning levels at BRC. Accelerated jumbo rehab allowed access to the production levels within two months of the rockfall. Cable bolting then followed the jumbo bolting in all leached areas. The direct impact has been ten months of reduced production, due to night shift closures of the decline to enable cable bolting. The impact to the mine has been minimised by the small flexible team that enabled the mine plan to change rapidly and often to accommodate the challenging conditions. In less than two months from the rockfall event, production had resumed. Within ten months of concluding that the mine required; full rehabilitation, a new support system and a full re-schedule, normal mining operations had restarted, with pre-event productions rates being achieved.

Mar 29, 2023

By T O&apos, Sullivan

Reconciliation of metal production from a sublevel cave (SLC) mining operation is a complicated process. SLC reconciliation is unlike reconciliation for open stope operations, where a tonnage of extracted ore can be assigned to an exact volume of in situ ore, and a direct comparison made between the estimation of contained metal and actual metal production. In SLC operations the ore extracted from a particular SLC drawpoint will be composed in part from the parcel of freshly blasted in situ material, in part from varying components of ore material (from cave stocks) flowing down from other previously mined areas vertically above the current draw position and in part from external dilution. This leads to difficulties in reconciling production grades against estimated grades. The problem is that we know how much metal we have produced but we can not precisely say where it has come from. Metal production reconciliation is fundamental in assessing ore reserve estimation accuracy and performance and in determining a draw management strategy for SLC mining. In terms of contained metal, differences in extracted metal compared to in situ metal represent changes to cave stocks. To generate local estimates of the cave stocks, differences in metal for each ring are treated as additions to or subtractions from a series of vertical columns of stocks extending throughout the height of the cave. The sum of metal differences (extracted versus in situ) for each vertical column results in a residual metal map at any particular mining level. The metal maps show areas where the metal production has been greater than or less than expected. The maps also highlight areas in the cave where residual metal is located, areas where targeted overdraw can reduce cave stocks.

Jan 1, 2006

By M Lynch, B White

The historic city of Charters Towers in North Queensland is underlain by an extensive labyrinth of old mine workings in a large number of flat lying, subparallel, main and cross-cutting cross reefs extending of the order of 5 km along strike and down to a depth of 700 m in parts. These old workings produced over 6.6 million ounces of gold at a grade of over one ounce to the tonne prior to closure in 1920.Citigold is progressing the development of a modern, high productivity, low cost new mine to extract extensions of these reefs as well as other as yet un-mined reefs. To do this it is changing the paradigm for operating in such circumstances. This paper first briefly reviews the setting for the development and then discusses the philosophies and concepts that Citigold is proposing to use, harnessing technology to create a mine that exemplifies more productive and safer mining based on operating in the digital age.The paper addresses how a modern approach is being applied to the planning of a mechanised, deep, narrow vein, hard rock gold mine under a city. It also describes briefly the successful æexperimentationÆ with longhole open stoping methods developed at the companyÆs small underground operation (the Imperial Mine) to the south of the city, which will also be expanded substantially as part of the Charters Towers Gold Project.The paper also addresses the development of new and/or modified technologies in the venture, with the objective of pursuing continuous and autonomous mining methods. The company is adopting a holistic systems approach, addressing people, process and technology in order to efficiently identify and locate the high-grade ore zones and then extract them effectively at a high grade by minimising waste development and haulage, dilution and energy consumption, and with minimal environmental impact.CITATION:Lynch, M and White, B, 2013. Brave new world autonomous mining systems, in Proceedings World Gold 2013 , pp 157-166 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 26, 2013

By L Manca, P B. Hills, D Tyler, N Pollington

This paper describes a collaborative project undertaken by Newcrest Mining Limited (Newcrest) and pitt&sherry to identify, develop and then implement global best practices to manage the exposure to inrush (dry and mud) hazards in underground mining operations. An extensive literature review was undertaken to identify past experience globally and the current state of knowledge and practice in managing inrush hazard. A key requirement of the literature review was the development of a list of guiding questions which would form a framework for approaching operators to discuss the topic, capture recent learnings and understand current operating practices to allow the development of a best practice solution. An initial cohort of 14 mines across four continents chose to contribute and detailed interviews were carried out by the project team. The outcome from the literature review, interviews with participating mines and various internal discussions was a comprehensive summary document detailing Basic versus Best Practice management of the inrush hazard. This document is being used as a gap analysis tool by Newcrest to assess and guide the management of inrush hazard at their existing and future operations. The summary document has also been provided to the participating mines for their consideration. The project is iterative and will continue to evolve as new experiences, knowledge and practices come to light.

Mar 15, 2021

By G Cavanough, A Olsson, J Rock, A C. Torrance

There are various methods currently in use to determine detonation performance of bulk explosive products including velocity of detonation (VOD), high speed photographic analysis, fragmentation analysis and unconfined detonation of samples. For assessment prior to detonation the current practice is limited to a measurement of cup density. This paper presents additional techniques that have been developed to provide measurement and assessment of bulk explosive products. Techniques applicable prior to detonation include a mobile laboratory to allow on-site chemical and physical analysis of sensitised products and ‘in-hole density’ measurement to monitor the in-hole density during sleep time. Assessment of detonation performance is achieved using detonation pressure sensors. These sensors allow measurement of detonation pressure, average VOD, propagation time and magnitude of the pressure induced in the explosive column by detonation of adjacent blastholes.CITATION:Cavanough, G, Torrance, A C, Rock, J and Olsson, A, 2015. Measurement and assessment of bulk explosive products, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 477–484 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

By A G. L Pratt

Change and its relationship with the introduction of new technology is a constant of human history. The mining industry has many examples of this relationship. This record contrasts with its present day struggles to move beyond a public perception of being just ‘dirty, dumb and dangerous’. The drivers for the introduction of new technology are frequently listed as the occupational health and safety of people working in the mines, reductions in direct operating costs, and increases in productivity.This paper discusses the issues that a mining business needs to deal with to implement new technology with the best possible conditions for success. It comments on how the strategic and tactical components of technology planning relate to and interact with change management. The central discussion is directed at the role that people play in the successful implementation of new technology. The introduction of autonomous underground haulage equipment provides a background for the discussion of this topic.The paper uses case study references, equipment supplier information and research findings. The aim is to offer a high-level view of the issues a mine operator needs to consider when approaching the introduction of new technologies for underground mining.CITATION:Pratt, A G L, 2017. Technology change in underground mining – things to consider, in Proceedings 13th AusIMM Underground Operators’ Conference 2017, pp 103–114 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 16, 2017

By A G. L Pratt

The record for autonomous haulage systems in underground mining over the past 15 years is patchy, marked by many trials and attempts, with few examples of sustained operation until relatively recently. The drivers for the introduction of this technology are variously listed as the occupational health and safety of people working in underground mines, reductions in direct operating costs and increases in productivity.This paper reviews the trends for operation of semi-autonomous and autonomous haulage achieved by underground mines and the defining features of the technology currently available. The inclusion of autonomous haulage as part of mining studies and the fundamental conditions for its successful application is discussed in the paper. The components required for an autonomous underground haulage system are outlined and the key aspects that need to support its effective implementation are examined together with their associated opportunities and risks. Special note is made of the critical role people, including executive leadership, have in ensuring the successful introduction of this technology.The paper draws on published case study material, equipment supplier information and research findings. The aim is to offer a high-level insight into what is required for the application of autonomous haulage technology and its successful implementation in underground mines.CITATION:Pratt, A G L, 2016. Autonomous haulage systems in underground mining – what is required for success? In Proceedings International Mine Management Conferenc, pp 35-52 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jun 22, 2016

By P de Caritat, A Davidson, A Mann

Top outlet sediments from the National Geochemical Survey of Australia have been extracted by a partial extraction method for over 50 elements including gold. The partial extraction results from this low-density survey show discrete coherent anomalies for Au in the vicinity of many of AustraliaÆs known goldfields, and in the vicinity of some minor gold occurrences. In several instances catchment outlet anomalies for Au have been recorded from areas not known to contain significant economic gold. Several large economic goldfields are shown to not produce anomalies in catchment outlet samples. A survey of overbank samples in the Swan Avon catchment of Western Australia at double the sampling density shows that low level anomalies (>1 ppb) can be traced back to source using overbank sediments. Follow-up of one of the Au anomalies at Kent River in previously regarded non-auriferous terrain (western Albany-Fraser Belt) indicates a non-economic, but perhaps geochemically significant, Au anomaly with associated pathfinders including palladium. This may indicate that further exploration of the western part of Albany Fraser Belt for Au is warranted. The combination of catchment overbank samples and partial analysis technique has been shown to be effective at locating the source of gold anomalies from initial low-density continental and regional surveys.CITATION:Mann, A, Davidson, A and de Caritat, P, 2013. High resolution soil geochemistry for gold exploration at the continental, regional and prospect scale, in Proceedings World Gold 2013 , pp 167-174 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 26, 2013

By D Symonds, S S. Kanchibotla, L Kennelly, G McNamara, J Gaunt, B Adiyansyah

Ban Houayxai is a gold-silver mine operated by Phu Bia Mining Limited in Laos since 2012. The first two years of operation processed predominately soft oxidised ore but subsequent years were expected to process more fresh hard ore. Fragmentation of the fresh primary ores was also expected to be much coarser than for the soft oxide ores. This coarser and harder ore is expected to significantly reduce mill throughput and mining productivity. The Ban Houayxai management realised the potential downside risk when processing fresh harder ores and implemented a blast optimisation project to deliver finer fresh ore to the mill without unduly increasing blast induced dilution and damage.JKTech and the Ban Houayxai drill and blast team began a joint blast optimisation project in April 2013 to achieve finer fragmentation from fresh ores. This was achieved by modifying the bench geometry, blast patterns and applying exceptionally high levels of quality control during implementation. Blast induced ore loss and dilution was controlled by adjusting the ore blocks for blast movement. Finer fragmentation from these modified designs improved mill throughput for the hard fresh ore by 46 per cent above design on average. These new practices have been embedded in site operating procedures and have provided a quick reference ‘cookbook’ document for the engineers.CITATION:Gaunt, J, Symonds, D, McNamara, G, Adiyansyah, B, Kennelly, L, Sellers, E J and Kanchibotla, S S, 2015. Optimisation of drill and blast for mill throughput improvement at Ban Houayxai Mine, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 307–314 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

By M Bloss, B Roberts

BHP Billiton Olympic Dam required a well-tested software product suitable for strategic optimisation and scheduling of options for a potential underground mining project. The company has a standard software package called Blasor® that is used for open pit optimisation of complex deposits such as iron ore, copper-gold-uranium and silver-lead-zinc. It applies a mixed integer programming formulation (MIP) to produce conceptual pushback designs and an optimised pushback sequence. Schedules can then be run on the resulting mine designs. Existing pushback designs can also be imported into the model and an optimum schedule generated. One of the key advantages of Blasor is that multiple strategic mine schedules can be quickly generated according to the various scenarios, options and constraints that are being investigated.It was realised that Blasor, if carefully configured, could be adapted for use in underground planning. The concept of using Blasor as an optimiser for underground strategic scenarios is to represent the underground stope and development data in the form and structure of an open pit mine. In simple terms, underground stoping areas are modelled in the form of pushbacks (phases) with vertical walls. The phase dependency tools in Blasor are used to link mine blocks and their access development drives. These underground phases are imported into the optimiser. Artificial block models are constructed using stope design tonnage and grade data at various fixed cut-offs. A variable cut-off grade model has also been developed using a method of parcels to represent each cut-off grade increment.So far, this approach has been successfully used to investigate the optimum stope design cut-off for various strategic options, the economic potential of a series of mining and processing configurations and to provide guidance on the optimum sequence for developing and mining the various stoping blocks in the resource. Examination of the results has highlighted the most suitable development paths for more detailed study.CITATION:Roberts, B and Bloss, M, 2014. Adaptation of an open pit optimiser for underground strategic planning, in Proceedings Orebody Modelling and Strategic Mine Planning Symposium 2014 , pp 249–256 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 24, 2014

By F Weir, B Estrada

The impact of seismic loading on open pit slope stability in Australia is often only considered where the slopes are located adjacent to tailings facilities or other major infrastructure. The debate regarding application of seismic loading in open pit design in Australia is usually founded on limited reporting on significant damage of open pit operations during earthquakes, the common perception that earthquakes do not occur in Australia or that they are unlikely to occur during the mine life of the mine. It is frequently overlooked that pit slopes that have withstood strong earthquakes in highly active seismic regions are often designed under strict seismic guidelines. This paper discusses the factors that impact earthquake performance of open mine slopes. These factors include topography, slope geometry, rock material and mass properties, water management and intrinsic pit design. Further, the paper presents insights into the characteristics of earthquake activity in Australia such as magnitude distribution, earthquake depths, areas prone of earthquake activity and general seismic hazard that are relevant to pit design. Guidelines are provided on the conditions and circumstances under which earthquake design in open pit mining should be considered. In addition, this paper provides recommendation on the applicable methods for assessment of the impacts of earthquake loading on pit slope stability.

Jun 22, 2022

By B Armstrong

The Proterozoic poly-metallic Trilogy deposit was discovered in 1997, and until recently, mining evaluation was stalled due to poor metallurgical performance. Unlocking the substantial economic value of the deposit required a coming together of geologists, mineralogists, metallurgists and mining engineers, who by working collaboratively, uncovered the detail necessary to allow the required metallurgical breakthroughs to occur. The deposit itself is described as a sedimentary exhalative (SEDEX), with an enriched lead-zinc-silver core surrounded by a broader envelope of copper-gold mineralisation. The geological domains were defined in broad terms based on the style of mineralisation, assay values and lithology. These domains, while adequate for the resource estimation process, failed to translate into representative metallurgical domains. Additional work with new techniques defined regions in the deposit with altered processing properties which could not be recognised by conventional geological logging. Such additional complexities could not be appreciated at the outset of the metallurgical test work program.These regions were defined by applying the EDTA analysis method for recognition of where the valuable sulfides, particularly galena, had been partially modified by oxidising conditions. Hence, the flotation response of the valuable sulfide minerals was diminished and the increased amount of heavy metal cations available in the system significantly reduced selectivity in the flotation process.Understanding the detail of this complexity was essential in determining representative metallurgical domains, which was the first step in the long road of development.

Sep 5, 2011

By M Ind, B Usher

Environmental regulators are increasingly adopting risk-based approaches to protect aquatic ecosystems. The Australian and New Zealand Environment and Conservation Council (ANZECC) and the Agriculture and Resource Management Council of Australia and New Zealand (ARMCANZ) (2000) introduced a risk-based approach to water quality guidelines that use decision frameworks to adapt water quality guidelines to local environmental conditions. Environmental quality objectives are no longer a simple ‘pass or fail’ number such as restricting total suspended solids (TSS) concentration to a specified limit for a particular rainfall event. This approach ignores spatial and temporal variability and the complexity of aquatic ecosystems. The risk-based approach establishes levels where adverse effects may occur. If these objectives are not met, further risk-based investigation is undertaken to assess the potential impact to the ecosystem. Klohn Crippen Berger (KCB) developed a dynamic simulation to predict the variability of sediment discharges, which is applicable for risk-based impact assessment of aquatic ecosystems. The application of the methodology over the life of a mine site is illustrated using a proposed South Pacific mine.The site location is in extremely rugged terrain with a high annual rainfall of approximately 4.7 m. There were two major sediment ponds proposed to reduce sediment discharges. A sediment and hydrology model was developed in Goldsim to provide daily estimates of run-off flows and sediment concentrations. A modified algorithm based on the Australian water balance model was created and incorporated into the Goldsim model and calibrated using recorded field data.The sediment module was developed based on a Revised Universal Soil Loss Equation (RUSLE) assessment, an annual prediction of soil loss over a catchment. A land-use type erosion vector was developed for different land-use types and for each of the subcatchments, a subcatchment erodibility vector was calculated. This vector and the daily rainfall erosivity factor were used to estimate the daily soil loss. The estimated soil loss and the modelled run-off yielded predictions of daily sediment concentrations. Finally, a sediment settling module was used to predict the daily efficiency of the sediment ponds and hence discharged sediment concentrations.The results of this modelling form the first part of a quantitative risk-based assessment into suspended solids impacts. The second part is the assessment of the effects of these predicted TSS concentrations on aquatic ecology. As part of the feedback-loop required in a risk management framework, if the environmental quality objectives are not met then further management decisions and actions may be required to reduce the risks presented by suspended solids. This may include modifications to: the mine-development plan; construction techniques and scheduling; processing techniques; rehabilitation strategies; or hard-engineering solutions such as sediment basins or flocculation.The Goldsim water-balance model provides a quick and efficient method of testing potential remedial actions on predicted sediment loads and concentrations. In combination with a cost-benefit assessment, options for reducing sediment releases from the mine site can be effectively and quantitatively compared thereby providing mine operators with a basis for decision-making. Regulators can also be satisfied that potential impacts to aquatic ecology have been comprehensively assessed and the necessary management decisions have been initiated to limit risk to the environment.CITATION:Ind, M and Usher, B, ?2014. A dynamic sediment simulation to predict the variability of suspended solids concentrations over life-of-mine for application to a risk-based environmental assessment, in Proceedings Life-of-Mine 2014 , pp 191–204 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 16, 2014

By M Saghaeian, V Sheikhzadeh, R Hejazi

Mining dilution is one of the most important factors affecting the economy of mining projects. Instead of quantifying dilution in mining studies, it is common to assume a general dilution such as 5 per cent for massive deposits. Dilution increases the operating costs in the plant by increasing the tonnage of material to be milled. It prolongs the mine life by reducing plant’s effective capacity. It also reduces the feed grade. In most cases, lower feed grade means lower plant recovery. Dilution also increases the cut-off grade, which in turn reduces the overall ore utilisation of a mine. In this study has been investigated applying pre-concentration by dry magnetic separation for decreasing of dilution impact on reserve estimation and open pit design in low-grade iron ore mine. Based on the preliminary open pit design and assumption 3 per cent as dilution factor, the mineable ore in life-of-mine (measured + indicated) has been estimated with Fe = 25 per cent, SiO2 = 49.7 per cent. Based on the experimental test work on the ore, by dry low intensity magnetic separation of dry HPGR product grinding circuit, it is possible to remove diluted waste material and liberated gangue before concentrate plant, so that around 34 per cent rejected and Fe grade increase from 25 per cent to 33 per cent and by weight recovery 66 per cent. The results of the test work showed that this methodology could decrease largely the impact of dilution in the feed to the plant. It also slightly effect on the reducing of dilution factor impact for open pit design and optimisation and leads to increase the mineable tonnage in the low-grade magnetite iron ore mine.

Aug 24, 2022

By J D. Grobler

In the heavy minerals industry wet high intensity magnetic separators (WHIMS) are widely applied for primary magnetic separation of magnetic minerals and non-magnetic minerals. This piece of equipment is well known for its robustness to handle a wide range of feed conditions and still produce stable product qualities and yields. A heavy mineral production plant aimed to increase production through their WHIMS plant containing 11 duties and 26 units. Instead of adding new units an alternative approach was followed to firstly maximise the efficiency of the current circuit and secondly to consider possible reconfiguration of the circuit to produce additional product tons for minimal capital investment. In order to characterise the current circuit’s efficiency, identify pockets of excellence and determine the areas for improvement the whole circuit was surveyed several times and mineral mass balances were drawn up.This paper aims to: discuss the modelling process of the WHIMS circuit,explain the calibration and validation process followed to ensure the accuracy, anddemonstrate the sensitivity analysis performed on the different options. From this analysis an efficiency criteria was developed to compare different circuit configurations that enabled the production plant personnel to make an informed decision on the way forward.

Oct 5, 2011

By A Giyose, V Malysiak, K Davey

Batch flotation tests were conducted on a haematite-bearing Sishen iron ore slimes sample from South Africa using reverse cationic flotation. The effect of grinding on flotation performance, the flotation response of various key impurities in the sample, and the feasibility of increasing metal recovery by refloating tailings in a scavenger flotation step were investigated. The test results indicate that reverse cationic flotation is effective in rejecting impurities from the iron ore sample tested. From a head grade assaying 6.4 per cent SiO2, 2.14 per cent Al2O3, 0.402 per cent K2O, 0.082 per cent P and 0.194 per cent TiO2, the levels of impurities were reduced to 1.83 per cent SiO2, 0.88 per cent Al2O3, 0.095 per cent K2O, 0.066 per cent P and 0.174 per cent TiO2 in the final concentrate at a Fe recovery of 74 per cent. The flotation response of SiO2, Al2O3 and K2O were found to be better than that of P and TiO2. The testwork demonstrated that grinding to 80 per cent passing about 49 microns is essential for upgrading the Sishen iron ore to produce >67 per cent Fe concentrate grade. This grind size corresponds to about 80 per cent liberation of haematite from the gangue minerals. Fe recoveries up to 76 per cent were obtained by refloating the rougher tailings in a scavenger stage, with little effect on the final concentrate grade. Size-by-size Fe recovery data obtained indicated that particles below ten microns were mostly lost in the desliming stage conducted prior to flotation whilst some reported to the froth by entrainment. Some of the coarser haematite-gangue composite particles reported to the froth product by genuine flotation.

Jan 1, 2009

By K Higuchi, K Saito, O Ishiyama

Iron ore in Australia is predicted to increase in its phosphorus content in the near future, which is detrimental to properties of steel product. Steelmakers are concerned by the content of phosphorus in iron ore will exceed limits for steelmaking and increase the converter slag ratio to molten steel, which will finally lead to a decline in competitiveness in high-grade steel production. In this paper, fundamental development of a dephosphorisation technique by reduction gasification is considered. Basic reduction examination was carried out using Australian and a synthetic model iron ore sample with phosphorus compound reagent, varying reaction time and composition of substances to find out suitable process condition for dephosphorisation. With successful lowering of phosphorus concentrations by gasification reduction of the iron ores, dephosphorisation was assumed and further elucidation works were carried out. More than 10 mass per cent of dephosphorisation ratio is obtained from Australian iron ore through batch-type 25 g furnace experiment using hydrogen as a part of reducible mixed gas. Lowering of phosphorus content occurred preferentially either in wustite or in another reducing zones, suggesting a relationship between reducing conditions to efficient dephosphorisation of iron ores. Another result of the fundamental experiment using a model sample with reagent is different dephosphorisation occurred with different reagents contributing to with unified reduction model for phosphorus, providing positive possibility for comparative evaluation, even if new morphologies of phosphorus in iron ore are clarified in future. According to these approaches, it is important to reduce iron ore efficiently and to avoid gasified phosphorus retaining and reattaching to adjacent iron ore particle at the same time. A kiln-type furnace is suggested to overcome previous technical issue, and additional experiments using larger rotating furnace were carried out for verification.

Sep 18, 2023