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By P Scholtz

Sustainability is one of those fuzzy words like innovation: everybody has an idea what it means, but if one starts asking for concise definitions then it becomes clear that everybody puts their own nuance on the meaning of these words. It’s not because these are difficult words per se, but rather because our understanding of them is highly dependent on the environment we work, live and play in. To remove any ambiguity and aligned with the risks that are faced by the human population today, the definition for sustainability that will apply for this paper is: generating value in the short term without destroying value in the long term.CITATION:Scholtz, P, 2018. Sustainable post-closure development – is it achievable?, in Proceedings Life-of-Mine 2018, pp 58–59 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 25, 2018

By D Kent, R Paine

"Automated mining systems are increasingly being seen as a key requirement for a productive mining operation in the future. The importance of an integrated communication network infrastructure to support such systems is growing.This paper outlines the introduction of automated mining systems in large conventional mines as well as their growing role in block cave mines currently operating or being developed. The paper will then focus on a case study of how the communication infrastructure is fundamental to the operation of such systems and explain why the resultant communication networks require much more than just increased bandwidth (data capacity) to properly support the automation system within the overall mine operation.Mining operations already embarking down this road are discovering that the required network must be based on a true enterprise level architecture to not only enable the mine’s current plans for remote and automated mining, but also provide a scalable and integrated platform for future developments and requirements. The emerging issues for the communication network to truly support automation systems include: increased complexities of operating and maintaining multiple networks integration issues with disparate systems problems with reporting particularly as demands for corporate reporting and compatibility with enterprise systems become the norm ongoing management challenges, which will only increase with the proliferation of new technologies.The paper will explore how certain mining operations are addressing this by adopting a long-term strategy for automation deployment, which includes laying the necessary foundation architecture to meet their current requirements, while supporting their future visions for the fully automated mine.CITATION:Paine, R and Kent, D, 2014. Developing the foundation communication infrastructure to support remote and automated mining initiatives in underground mines, in Proceedings 12th AusIMM Underground Operators’ Conference 2014, pp 151–158 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 24, 2014

By G Love, S Maher

In Victoria’s onshore Gippsland Basin, geology is driving brown coal developments, and geologists are key decision-makers. Prompted by volatile energy prices and the likelihood of a carbon constrained future, significant work has been carried out on the next generation of technologies to be applied to this giant resource. These include new-generation gasification technologies, coal conversion processes yielding products as diverse as diesel and fertiliser, drying technologies producing thermal and metallurgical coals and in situ conversion processes. However, coals aren’t coals, and brown coal available for new projects will have different quality parameters and mining economics from that currently mined.New projects are likely to be developed on coals with moisture contents averaging 60 per cent and corresponding low energy values. Whilst ash values will be low, averaging just 5 per cent (dry basis), this will at times approach 10 per cent, which is a level that would challenge the installed-generation technologies. Sulfur values will average 0.4 per cent (dry basis), but at times exceed 0.6 per cent, requiring technologies that address the potential for sulfur dioxide emissions. Whilst localised high levels of the fluxes iron (>1 per cent dry basis) and sodium (>0.3 per cent dry basis) would increase fouling of installed technologies, they may be suitable for selected next-generation technologies.Project viability for this next generation of technologies will be strongly influenced by mining cost, and geologists are playing a role in identifying higher-value coal. At its simplest, this is being achieved for open cut mines through regional, vertical strip ratio assessments, which are considered a first-order proxy for mining cost. Follow up assessments are incorporating mining and processing cost, coal quality penalties and product revenues. At a regional scale, it is informing the likely location and relative timing of future mine developments, as well as thinking around rehabilitation strategies, infrastructure and land-use planning.For deeper coal, factors like macro permeability, the ability to isolate seams from aquifers, groundwater chemistry, pressure temperature conditions, connection with groundwater recharge and in situ biota are being used as vectors to in situ coal conversion opportunities.Matching coal to the next generation of technologies has benefited from regional-scale geological studies of coal quality and mining economics, and has benefited from early engagement between geologists, technology developers and project proponents.CITATION:Maher, S and Love, G, 2014. Matching brown coal to the next generation of Latrobe Valley projects, in Proceedings Ninth International Mining Geology Conference 2014 , pp 77–84 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 18, 2014

By T Y. Dube

In this paper current net present value (NPV) based mine valuation techniques that take into account market and private risk are discussed and analysed. Potential pitfalls that arise from the application of a portfolio, market or commodity based risk metric to a mining project are identified. An alternative non-simulative framework for quantifying and factoring market and private risk in NPV calculations is proposed and then applied to a hypothetical case study in an attempt to overcome identified pitfalls. Mathematical proof that a static discounted cash flow (DCF) calculation can underestimate or overestimate mine NPV is presented, the conditions for each are outlined and the degree of underestimation defined.CITATION:Dube, T Y, 2012. How the use of market-based risk metrics can undervalue good mining projects and overvalue poor ones, in Proceedings Project Evaluation 2012 , pp 29-34 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 24, 2012

By P Bartsch

Uranium solvent extraction, USX has been applied commercially for recovery and concentration for over 50 years. Uranium in acidic liquor, which is prepared following ore leaching, solid/liquid separation and clarification, can be treated through a sequence of operations; extraction-scrubbing-stripping, to obtain purified liquor. USX has dominated the primary uranium industry as the preferred technological route to converter grade yellowcake. The practices of design and operation of USX facilities has found renewed interest as new mines are developed following decades of industry dormancy. This article seeks to outline principles of design and operation from the practitioner’s perspective. The discussion also reviews historical developments of USX applications and highlights recent innovations. This review is hoped to provide guidance for technical personnel who wish to learn more about good practices that leads to reliable USX performance.

Aug 8, 2011

By J E. Everett, F Grobler

This study considers realistic data for a planned open pit iron ore mine, but is applicable to any open pit situation. By interpolating drill hole data, grades are generated for a rectangular block model. Each blockÆs grade designation vector has components for each analyte (chemical element or compound) influencing ore value. Interpolation by means of geostatistical kriging leads to each block being assigned its expected value, and thus underestimates the overall grade variability. Alternatively, interpolation by means of conditional simulation is a method that implements random sampling from an infinite population of solutions. Each conditional simulation has appropriate overall grade variability, but estimating any blockÆs mean and variance requires sampling from multiple conditional simulations. For a block model, an ore/waste selection criterion maximises the expected tonnage at a target grade. This criterion is a linear composite of the grade components, with positive coefficients for the beneficial analyte (iron) and negative coefficients for the deleterious analytes (such as silica, alumina and phosphorus).Although conditional simulation gives the same expected grade as kriging for each block, the expected maximum tonnage of ore selectable at a target grade may differ from that obtainable from the kriged solution. We apply the linear composite selection criterion to each of 25 conditional simulations, as well as to the kriged block model. The resulting distribution of product tonnage is confirmed to have an expected tonnage that is over 20 per cent greater than that of the kriged model. The method also enables a selection probability to be computed for each block, and thus a probabilistic pit boundary distribution to be identified and used in mine planning. Proposed extensions will consider risk-based scheduling of the multiple selection solutions through minimisation of a derived æstress factorÆ and treating the mining process as an iterative system with actual or artificial ædepletionsÆ modelled in line with the mine plan, using the updated state (with new information) to re-evaluate the mine plan for subsequent periods.CITATION:Everett, J E and Grobler, F, 2013. Risk-based ore selection from conditionally simulated block models, in Proceedings Iron Ore 2013 , pp 149-156 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 12, 2013

By J Loeb, J Dampney, P Cameron

Optimisation of Blast Design and Execution must be done right the first time. It is too late after the ore is broken. Consequences of poor design and execution negatively affect productivity from load and haul through the primary crusher to processing and hence reduce mine site profits. Harnessing and utilising ‘big data’ from geology, geometallurgy, drill hole location, powder loading, blast timing, blast movement and fragmentation to close the loop in blast design and optimise the blast increases productivity across the entire value chain from Mine to Mill. As the internet of things and artificial intelligence increases the quantity of data available, being able to capture and utilise this data to advantage is a challenge. Recent advances in software and hardware together with the increased power of cloud computing allows engineers to close the blasting loop to increase mine site productivity. Numerous case studies over the years detail significant gains from implementing the innovative technologies available to Mine to Mill projects. The opportunity is available for all members of the multi-discipline teams at each mine site to actively ensure productivity improvements are realised and maintained not only in their area, or silo of responsibility but across the entire mine site. This paper refers to recent case studies which outline how significant improvements in productivity are available to all mining operations to increase mine site profitability and dividends to shareholders.

Jun 22, 2022

By P Vass, C Butler, J Condon, B Hooper

DeGrussa Copper Mine, resource status 10.2 Mt at 5.7 per cent Cu, 2.1 g/t Au (Sandfire Resources, 2013), commenced concentrate production through its 1.5 Mt/a conventional copper flotation processing plant in September 2012. Geometallurgical assessment during the feasibility study identified potential process-critical ore factors that required further investigation to determine potential impact on processing. Ore characterisation and metallurgical processing performance test work of ore types ensued and subsequently, the first quantitative DeGrussa geometallurgy model was born. Now one year into steady state production, the geometallurgical program has evolved significantly from its infancy and provides valuable insight into ore characterisation and behaviour in the processing plant. This paper details geometallurgical investigations undertaken at DeGrussa to date; from feasibility metallurgical test work through to geometallurgical modelling and management practices, as well as reconciliation between observations at feasibility study level and subsequent observations in production.CITATION:Condon, J, Butler, C, Hooper, B and Vass, P, 2013. DeGrussa Copper Mine, Western Australia - feasibility to first production: a case study in developing a working geometallurgy model from first principles, in Proceedings The Second AusIMM International Geometallurgy Conference (GeoMet) 2013 , pp 59-66 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 29, 2013

By A Karrech, G M. Hassan, A Varghese, E Lessing, S Martins

Pumps play a critical role in mining operations, and their energy consumption and environmental impact are significant. This paper addresses the need for a holistic approach to sustainable pump deployment by expanding on previous work presented at IMPC Asia Pacific 2022 and World Mining Congress 2023. The research takes a significant step forward by outlining a structured approach to estimate and demonstrate sustainability tailored for operational slurry pumps. It details the calculation methodologies used to quantify the carbon dioxide emissions from electricity, wear materials and transport, as well as sealing water usage. To enhance practicality and usability, a simplified visual representation—called sustainability metrics—has been developed to monitor overall efficiency. The sustainability metrics consist of the availability, pump efficiency, and water utilisation efficiency. The proposed methodology is integrated with Pumps Condition Monitoring Service to maximise benefits. Three case studies, from iron ore, copper, and nickel operations globally, were employed to evaluate the proposed methodology. The findings demonstrate the critical role of sustainability calculations in understanding pumps operation. These calculations improve awareness of the pump’s role in the sustainability journey and enable effective monitoring. The studies highlight that continuous monitoring paired with effective prescriptive maintenance strategy can significantly reduce power and water consumption while maximising pump availability. The case studies also reveal significant shortcomings in current operational practices and non-optimal maintenance regimes, emphasising the need for practical recommendations to maximise savings and optimise pump performance. In the context of increasing climate change awareness and the imperative for global decarbonisation, this research highlights the necessity of critically assessing methods and operations to drive sustainability in the mining industry. By adopting a holistic approach to sustainable pump deployment, mining operations can effectively reduce their environmental impact while enhancing operational efficiency and economic viability. The proposed methodology and case studies provide valuable insights and practical recommendations for mining companies seeking to achieve sustainable practices and contribute to a decarbonised future.

Sep 1, 2024

Since early-2001, Kalgoorlie Consolidated Gold Mines (KCGM) has successfully operated an ultra fine grinding (UFG) circuit to supplement its roaster capacity for the treatment of the refractory gold flotation concentrate. A second UFG mill was installed in 2002 taking the total UFG capacity to over 20 tph while grinding to 11 to 12 microns and achieving over 90 per cent gold recovery. A development program in 2002/3 involving plant trials, pilot plants and laboratory testwork resulted in process improvements and a better understanding of the milling and gold leach processes that assisted in narrowing the gap between UFG and roasting. This paper details the operation of the ultra fine grinding process at KCGM as a non oxidative treatment for the extraction of gold from a refractory ores.

Jan 1, 2003

By H Tran

Local communities are undertaking an increased role in mine project decision making processes, associated with growing pressure and expectations from regulators, financiers and the general public. This is particularly evident in international projects within developing economies. Environmental and social issues are often complex. Solutions demand difficult choices and trade-offs between sustainable development dimensions: economic growth, social equity and environmental integrity. Proactive stakeholder engagement can play a critical role in assisting decision-makers in determining the operational reality of sustainable development by jointly exploring project trade-offs between proponents and affected stakeholders. Good stakeholder engagement has other potential benefits, ranging from reduced financial risk due to regulator delays, legal disputes or negative publicity to increasing market share through good public image. Approaches to consultation and disclosure have changed from short-term regulatory based focuses, to longer-term, strategic tools for relationship building, proactive risk management and new business identification. Approaches to consultation form a significant opportunity to contribute to overall social sustainability. This paper discusses, based on authorsÆ experience, the broader concept of stakeholder engagement and its contribution to social sustainability of the mining industry. The focus is on key considerations for an effective stakeholder engagement. Three case studies outline how broad based, proactive stakeholder engagement can contribute to improved operation and overall sustainability. The case studies include: a greenfields project in Ghana; a long-term mine in Australia; and an open-pit mine in Vietnam.

Jan 1, 2009

By M E. Watson

Minimising dilution and ore loss is an important part of ensuring profitability of a gold mining operation. White Foil open pit gold deposit is a low-grade deposit and therefore managing ore quality is a high priority. Ground movement through blasting can displace ore and waste boundaries up to 10 m from their in situ location and therefore requires stringent ore movement monitoring and adjustment. There are currently only two options for monitoring blast movement – utilising visual targets (commonly lengths of polypipe) but this has widely been replaced by electronic blast movement monitors (or BMM). Regardless of the technology used, the basic principle is to compare the pre- and post-blast locations of the targets to determine the movement of the rock mass during blasting, which is then used to determine the final location of ore and waste boundaries.The Blast Movement Technologies (BMT) BMM system has been used at White Foil since June 2014. The system has been effective and reliable during that time; however, the annual cost of using the BMM system is greater than other monitoring alternatives. As such, the open pit geology team conducted a study comparing the BMM system against the conventional polypipe technique. The objective was to quantify the profit and loss that would occur based on the ore block transformations from both methods. Eight blasts were selected where polypipes were installed in additional holes adjacent to the BMM monitoring holes. The resulting movement vectors from the respective methods were used to create post-blast ore blocks by transforming the in situ ore blocks. While polypipe is a cheaper alternative, the BMM system tracks ore and waste boundaries more effectively resulting in better quality control, enhanced ability to minimise dilution and ore loss thus maximising profit. For these eight blasts, it is calculated that the BMM system resulted in A$664 978 extra profit through a reduction of ore loss. The total cost of a yearly BMM package was recovered in the first two blasts of this study. The primary reason for the difference is that polypipe had a poor recovery rate of 32 per cent compared with 92 per cent for BMM at White Foil. Therefore, the data used to transform the ore blocks was less representative, resulting in inaccurate post-blast ore block boundaries when using polypipe.CITATION:Watson, M E, 2017. Blast movement monitors or polypipe? A study into cost-effective blast movement monitoring at White Foil gold mine, Western Australia, in Proceedings Tenth International Mining Geology Conference 2017, pp 433–440 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 20, 2017

In high stress mining environments, production drill rigs are often employed for rapid drilling of boreholes for systematic cable bolting. One outcome of this drilling method is the need for larger boreholes than would normally be drilled using customised bolting machines, such as the Tamrock Cabolter. Past laboratory studies indicate that, under ideal grouting conditions, borehole diameter has little effect on the pull-out strength of cable bolts with high bulb densities. However, the sensitivity of pull-out strength to large boreholes and less ideal variations of grout strength have not been investigated. To explore these sensitivities, industry standard single embedment tests were conducted on large boreholes simulated using steel pipes. Four borehole diameters were tested, namely: 42 mm, 52 mm, 81 mm and 106 mm. In each case the grout water to cement ratio was varied from 0.35 to 0.45 and two cable bolt bulb spacings were considered, namely: one and three bulbs per metre. The results indicate that, across the range of parameters tested, variations in peak axial load at failure corresponding to changes in hole diameter were statistically insignificant.

Nov 25, 2010

By B Hayes

The Ambuklao and Binga Rehabilitation Project is a 175 MW hydro power project currently under construction across dual sites in the north region of Luzon Island, Philippines. When it was built in 1956, the Ambuklao Dam harnessed the second largest hydro-electric reservoir in Asia. However, due to landslide erosion and prolonged silt infiltration caused by an earthquake in 1990, the power plant has been rendered inoperable since 1999.To bring the power generating facility back to life, the project scope entails the rehabilitation and construction of civil structures, shafts and tunnels. A major component of these works is the decommissioning of a section of the seven metre diameter headrace tunnel by installing a concrete plug. The headrace tunnel is part of a closed waterway system that connects the dam via a shaft, exhibiting a hydrostatic pressure of 13 bar (1300 kPa) at the location of the new tunnel plug. In addition, the power station ball valves have seized ajar and the damaged intake riser is unsafe toaccess thereby requiring the plugging operation to be carried out under live flowing conditions.Working under hydrostatic pressure and live conditions, the headrace plug will be an underwater tremie pour operation that includes drilling and concrete injection through blow out preventer caissons installed in the floor of an underground chamber above the tunnel. The purpose of this paper is to describe the key engineering and planning components involved in this operation including pre- and post-grouting, chamber crane, sonar, local water compensation, jet flushing, drilling, caisson installation, and concrete design, production, delivery and placement. The success of this task rests on the strategic preparation and operational management of risk and safety in a challenging rural environment.

Mar 8, 2011

By A L. Wills

Cliffs Natural Resources Pty Ltd (Cliffs) operates iron ore mines in the Koolyanobbing region of Western Australia. Ore is mined from three separate hubs and trucked to Koolyanobbing. There it is crushed and screened to lump and fines finished products and railed to Esperance port for export to Asian customers. Cliffs is renowned in the marketplace for its consistent product quality. In 2010, 9 Mt of ore was exported to Asia.Over the last three years, Cliffs has systematically refurbished its product quality system (PQS), to improve efficiency of production while maintaining its high standard of product quality. Particular attention has been given to reducing inventory, which has required significant modifications to the production process design.In redesigning the production process, emphasis was placed on maximising the application of the inherent blending in each of the production process steps and dedicated blending was only introduced where essential. Simulation modelling and statistical analysis of process capabilities were utilised to develop a system that optimises inventory, minimises rehandle, eliminates several decision-making steps and maintains a pull focus throughout the value chain.The new planning functions are now fully integrated and effectively control long-term grade variability rather than relying on long-term stockpiling. The production process design and the daily crusher blend plan are used to control short-term grade variability. With the upgrading of the planning processes the accuracy and consistency of algorithms for lump per cent and lump and fi nes grades became more important and an increased geometallurgical function has been added to the company.The continuous stockpile management system was upgraded to increase the effectiveness of the daily crusher blend planning process and is now the sole intervention point in the production process for grade-based decisions. Grade control systems were modified to utilise advances in software and geostatistics to deliver accurate short range planning models. The reconciliation and sampling systems have also been refurbished with an emphasis on practical application and feedback loops.Accountability and transparency are provided by management reports that are generated from a centralised data warehouse and the introduction of a corrective action system. Standardised reports are available to all stakeholders and a quarterly KPI scorecard assists the management review process.The successful rejuvenation of the PQS has culminated in operational efficiency through the implementation of an integrated end-to-end process flow. Shareholder value is maximised through maximising recovery of the resource and minimising costs. Customer focus is maintained by reliably delivering product with acceptable and low grade variability.

Jul 11, 2011

The transition from low stress to high stress conditions is a challenge eventually faced by most mines in Australia that extend to depths greater than (generally) about 1000 m. In areas with strongly adverse 'stress versus depth' gradients, such as some parts of Western Australia, significant stress-related problems have occurred at depths as shallow as 300 m below surface. The actual depth at which the 'transition' occurs is a function of the local pre-mining stress field, the strengths of the various rock types hosting the deposit and the layout and sequencing adopted in the mine. Stress-related damage can result in increased support costs, and delays associated with rehabilitation and disruption to production. In the worst case, where strong seismicity and associated damage occurs in active mining areas, 'exclusion' zones and 're-entry' protocols may be required. These can severely disrupt production. A key aspect of managing the transition is the recognition of the onset of stress-related ground behaviour. Damage mapping can be used to develop understanding of the relationships between mining activities and the local and regional response to them. Carefully documented case histories provide a basis for calibrating numerical models. This paper discusses some of the typical styles of ground behaviour observed in higher stress conditions in underground mines. A simple damage classification scheme is described to assist in 'damage mapping' of mine tunnels. An example of damage mapping is presented to illustrate an approach commonly used for recording stress-related damage.

Nov 25, 2010

By G P. S Resende, D E. G Oliveira, E A. S Baeta, T F. Bravin

There is currently in the mining industry, as well as in other industries, a movement seeking to increase investments in decarbonisation processes to help combat global warming. Among some initiatives taken is replacing diesel-powered mobile equipment in the mines with electricity-powered equipment, such as electric off-highway trucks or even belt conveyors in the mining operation. Samarco is a Brazilian mining company that since its conception has used a conveyor belt mining system in its mining operation, using only a small number of trucks to complement the mining process. This mining process that combines conveyor belts and trucks has brought environmental gains for the company since the environmental impact of conventional truck-only mining is greater than that of the combined system. To measure these gains, a medium-term mining plan was developed in which two fleet scenarios were detailed. One scenario contemplated a high level of detail of belt mining seeking its maximisation, while the other considered the operation performed 100 per cent by trucks, eliminating the use of conveyor belts. Through the comparison of these two scenarios, it was possible to make an inventory of atmospheric emissions and greenhouse gases for each one of them considering data such as types of equipment, diesel consumption, total distance travelled and energy consumption. The results showed that the fleet scenario with conveyor belts results in periods with up to 15 per cent less greenhouse gas emissions and 37 per cent less total particulates compared with the truck-only scenario. Therefore, the results confirm the environmental benefits of the method and the need to look for ways to even expand it in future operations through a study to identify the potential areas in the long-term mining plan.

Sep 18, 2023

By C Ausa, Nyunt Htay, A, L Deiparine

The main tectonic elements in Myanmar are a late Mesozoic and Cenozoic magmatic arc system in the west, repeated in northern Myanmar by more than 300 km of dextral movement on the Sagaing Fault, and the back-arc continental region affected by early and late Mesozoic orogenies, in the east. Historically most lode gold production has been from latest Cretaceous high-grade mesothermal veins and derived placers in the Wuntho and Tagaung-Myitkyina segments of the magmatic arc. Placer deposits in the Ayerwaddy River north of Myitkyina are currently worked by more than 100-bucket dredges. South of Wuntho, the magmatic arc and Pegu Yoma fold belt host epithermal gold with associated As, Sb and Zn in mid-Tertiary marine sediments. MyanmarÆs most productive lode gold deposit, the Kyaukpahto mine, lies within a north-trending district east of the magmatic arc and north of Mandalay. Here mineralisation and associated jasperoidal silica occur in Eocene sandstones and Permian and Triassic carbonates. Possibly this district continues southeastwards, across the Sagaing Fault, as sediment-hosted Sb Au and locally skarn Au mineralisation within a 1100 km long fold-thrust belt. Also present in the back-arc region are sandstone-hosted Au Cu in a Palaeozoic slate belt, and gold and stratabound gold-base metal mineralisation in the medial metamorphic belt. While untested targets remain in the magmatic arc, particularly for high sulphidation Au, the best potential is clearly within the back-arc slate and fold-thrust belts in the western part of the Shan Plateau and in northeastern-most Myanmar.

Jan 1, 1999

By J A. Rumball

Measuring cyanide in the leach liquors associated with high copper and/or sulfide ores is a non-trivial exercise. It is well known that copper complexes with cyanide and reduces the amount of cyanide available for gold leaching. What is not so well known is that the rhodanine end point overestimates the amount of cyanide available for leaching in the presence of copper. Sulfide ions also interfere with a rhodanine end point titration, although this is less of a problem as the black silver sulfide precipitate formed clearly indicates to the operator that something is wrong. Thiosulfate, which forms readily from the alkaline oxidation of sulfides, causes an overestimation of the cyanide available for leaching due to the formation of Ag(S2O3)-. The net result of these observations is that rhodanine is rarely of value as an end point indicator in complex solutions. It generally overestimates the amount of cyanide available, providing plant metallurgists with a false sense of security. Potentiometric titrations are generally much more capable of accurately measuring cyanide in complex solutions. The interfering effect of copper can be resolved and it is even possible to estimate the copper concentration using the inflexions associated with the titration of CN- + Cu(CN)43- versus Cu(CN)32-. Using the potentiometric method sulfide ions can be determined before the cyanide measurement is made due to the formation of AgS2, although the electrode will foul with repeated measurements. Thiosulfate can also be distinguished from cyanide with a potentiometric titration. Rhodanine and potentiometric titrations are both affected by the pH of the liquor. At pH 9.2 half the cyanide will be present as CN- and half as HCN(aq) with only the CN- being titratable. This does not hold in the presence of a buffer active around pH 9. In the presence of sufficient buffer, both the CN- and HCN(aq) are titrated. Ca(OH)+ may buffer the pH when large amounts of lime have been added.

Jan 1, 2007

By A N. Parry, G van Wyk

"Sensor based automatic ore sorting technologies are used in the minerals industries to efficiently remove waste and submarginal grade material from crushed and screened run-of-mine (ROM) ore, producing a coarse (typically >10 mm) upgraded preconcentrate at an early stage in the mineral processing circuit. This avoids additional energy intensive downstream processing of this rejected component of the ROM feed, leading to lower unit operating costs and reduced tailings disposal volumes.Test work on bulk low-grade gold ore stockpile samples from Central Norseman Gold Proprietary Limited has been conducted, indicating high gold recoveries as well as high material rejection rates. A financial model, based on these results, evaluates grade sensitivity and identifies a minimum stockpile grade for adequate financial returns. The base case modelling estimates that the ex-stockpile grade (including the fines bypassed fraction) can be more than doubled through ore sorting and that the project will be highly viable with strong cash flow generation at stockpile grades as low as 0.7 g/t gold. The modelling will enable the company to benchmark ore sorting options against stockpile reclaim and screening operations currently employed. Citation:Parry, A N and van Wyk, G, 2016. Upgrading Low-grade Gold Ore Stockpiles by Preconcentration Using Ore Sorting - an Assessment of the Economic Impact and Viability, in Proceedings 13th AusIMM Mill Operators’ Conference 2016, pp 179–190 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Oct 10, 2016