Search Documents

By J. B. Boisvert, O. Leuangthong, T. Acorn

Optimizing final pit limits for stochastic models provides access to geologic and economic uncertainty in the pit-optimization stages of a mining project. This paper presents an approach for optimizing final pit limits concurrently over all realizations in a stochastic model and using a risk-management framework to manage the geologic and economic uncertainty. A heuristic pit optimizer is used to find multiple uncertainty-rated pit shells. These uncertainty-rated pit shells follow the mean-variance criterion to approximate the efficient frontier for final pit limits. Stochastic dominance rules are then used in a risk-management framework to further eliminate suboptimal solutions along the efficient frontier. This results in a smaller set of final pit shells that can be further analyzed for production scheduling. Additionally, the original solutions are analyzed for changes in the mining limits, and two regions are targeted as potential regions for further exploration.

By M Berry, F MacCorquodale

The ownership, management and employment structures operating in the Australian minerals industry have dynamically evolved during the last 30 years. One of the most dramatic changes, from an exploration and mining geology perspective, is the reduction of in-house geological expertise and an ever increasing reliance on contract and consulting services.For all companies - big and small - two key issues resulting from these changes are the management of core geological intellectual property (IP) and competitive advantage. This is because there are less experienced geologists at exploration and mine sites, there are fewer head-office technical service teams to support mine sites, exploration teams are smaller with less specialists employed, and there is an ever-greater dependence on contract and consulting services.This paper reviews and explores these issues with an industry-wide geological context, then provides a case study of how Newcrest Mining Limited (Newcrest) has dealt with these issues in exploration. Newcrest has grown from a one-mine company with an Australian exploration focus, to a large global company with multiple operations and an extensive international exploration portfolio. NewcrestÆs management of its geological IP and competitive advantage has evolved as the company has grown and responded to market conditions, including its internal restructuring in mid-2013.CITATION:Berry, M and MacCorquodale, F, 2013. Managing geological intellectual property and competitive advantage - Newcrest Mining LimitedÆs experience, in Proceedings World Gold 2013 , pp 37-44 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 26, 2013

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

Nov 25, 2010

By R Cox, S Pandey

The coal seam gas (CSG) industry is expanding rapidly in the Surat and Bowen basins. CSG production involves pumping water from the coal seams to release the gas adsorbed to coal particles. The reduction in water pressure in the coal seams will cause some reductions in water pressure in overlying and underlying aquifers because there will always be some interconnectivity between the formations. The Surat Basin is a sub-basin of the Great Artesian Basin, which contains aquifers of high economic, environmental and cultural value. The Condamine Alluvium is also an important water resource, which overlies parts of the eastern margin of the Surat Basin.Under the Queensland (Qld) regulatory framework, an area of intensive CSG development involving multiple CSG operators can be declared to be a cumulative management area. For such areas the Office of Groundwater Impact Assessment develops assessments of future impacts on aquifer water pressures and develops and manages arrangements. The results are published in underground water impact reports.The Surat underground water impact report (QWC, 2012) was approved in December 2012. This paper summarises the place of the report in the Queensland regulatory framework, the content of the report and progress in its implementation.CITATION:Cox, R and Pandey, S, 2013. Managing groundwater impacts in the Surat Basin, in Proceedings Water in Mining 2013 , pp 169-174 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 26, 2013

By D. R. Willmer, E. J. Haas

As national and international health and safety management system (HSMS) standards are voluntarily accepted or regulated into practice, organizations are making an effort to modify and integrate strategic elements of a connected management system into their daily risk management practices. In high-risk industries such as mining, that effort takes on added importance. The mining industry has long recognized the importance of a more integrated approach to recognizing and responding to sitespecific risks, encouraging the adoption of a risk-based management framework. Recently, the U.S. National Mining Association led the development of an industry-specific HSMS built on the strategic frameworks of ANSI: Z10, OHSAS 18001, The American Chemistry Council’s Responsible Care, and ILO-OSH 2001. All of these standards provide strategic guidance and focus on how to incorporate a plan-do-check-act cycle into the identification, management and evaluation of worksite risks. This paper details an exploratory study into whether practices associated with executing a risk-based management framework are visible through the actions of an organization’s site-level management of health and safety risks. The results of this study show ways that site-level leaders manage day-to-day risk at their operations that can be characterized according to practices associated with a risk-based management framework. Having tangible operational examples of day-to-day risk management can serve as a starting point for evaluating field-level risk assessment efforts and their alignment to overall company efforts at effective risk mitigation through a HSMS or other processes.

Jan 1, 2016

By J P. Evert

Didipio gold-copper mine operation is situated in the island of Luzon, approximately 270 km north of Manila in the Philippines, in an area of high seasonal rainfall. The hydrogeological water flow model implied that there would be high connectivity between regional structures and underground operations. This model predicted that underground mine groundwater inflows were expected to quickly rise as the decline progressed to a peak of 510 L/s. Designing a capital pump station to deal with 510 L/s has its own challenges, however developing the decline down to the required level, always dealing with 300 L/s of water and constructing the pump station is extremely challenging and required a robust water management plan and mine design. When dealing with expected high volumes of water, underground mine design and scheduling plays a key role in protecting electrical infrastructure, equipment, secondary pumps, and the decline from flooding. A good drainage system and controlled dewatering plan is essential for safety and progress. This paper details the dewatering techniques and mine designs required to accomplish decline development with high water inflows as used in the Didipio project. It will describe the learnings and outcomes that are achievable with a flexible design, as new structures are mapped, and water intersections are increased. It also highlights the potential for adaptability in mine planning to provide evolving improvements or to evade problems that are expected from the constant reconciliation of data recorded during development.

Mar 29, 2023

By Philip Weaver

The MIDAS project is funded by the European Commission (DG Research) and began on the 1st November 2013. The project will investigate the environmental impact of deep-sea mineral and energy extraction: specifically, polymetallic sulphides, manganese nodules, cobalt-rich ferromanganese crusts and the potential mining of rare earth elements. As deep-sea mining becomes ever closer, and the International Seabed Authority begins to develop its regulatory framework for exploitation of deep-sea minerals, MIDAS is well timed to provide fundamental scientific information. The MIDAS partnership represents a unique combination of scientists, industry, social scientists, legal experts, nongovernmental organisations and small and medium enterprises. MIDAS is carrying out research into the nature and scales of the potential impacts of mining including 1) physical disturbance of the seabed by mining, the creation of mine tailings; 2) the potential effects of particle-laden plumes in the water column, and 3) the possible toxic chemicals that might be released by the mining process. Key biological unknowns, such as connectivity between populations, impacts of the loss of biological diversity on ecosystem functioning, and how quickly the ecosystems will recover will all be addressed. The plan is to use this information to aid development of recommendations for best practice in the mining industry. A key component is the involvement of industry within the project and through stakeholder engagements to find feasible solutions. The project will work closely with European and international regulatory organisations to take these recommendations forward into legislation. A major element of MIDAS will be to develop methods and technologies for 1) preparing baseline assessments of biodiversity, and 2) monitoring activities remotely in the deep sea during and after exploitation, including ecosystem recovery. To carry out this work MIDAS is conducting a number of research cruises to examine the above issues at potential sites for exploitation of SMS and nodule deposits. This talk will present some of the recent findings of the project.

Sep 1, 2014

By A Golsby

Although much talked about, social licence to operate (SLTO) is a relatively new concept that has been deemed as one of the four biggest business risks to a mining project over the life-of-mine. There is no accepted single definition of SLTO and this author understands SLTO to be stakeholder perception of the legitimacy of a project, a company or an industry. At a specific site, and across different sites within the same organisation, SLTO ranges through different levels according to stakeholders’ degrees of acceptance in time and space. Management of SLTO is vital for the mining sector but is difficult as it is informal and intangible. Although there are no key performance indicators, there are certain indicators that enable relative measurement of the ‘level’ of the SLTO. Because of the importance of the SLTO, information management during the entire life-of-mine, from exploration to rehabilitation, becomes crucial for the continued operation of a project. This paper identifies ten basic principles for the management of information to support the SLTO.CITATION:Golsby, A, 2014. Managing information to support a social licence to operate, in Proceedings Life-of-Mine 2014 , pp 389–398 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 16, 2014

By B Beale

Bow-tie analysis is a commonly used tool in the Major Hazard Facility sector to identify, display and control risks that have the potential to pose serious harm to personnel. It is a simple but powerful risk management tool that displays traditional risk assessment outputs as easily interpreted ‘bow-tie diagrams’. These are an effective and versatile communication format that can be applied to any type of risk (eg safety, environmental, assets etc) and as such show great benefit in managing operational hazards in mining.

May 5, 2022

The Kelian gold mine which was developed in East Kalimantan Indonesia in 1990 - 1992 is scheduled to complete mining and processing operations in 2004. This will have a major impact on the neighbouring communities who have benefited from the jobs, economic activity and infrastructure development which has been generated by the mine. Currently, there are no formal regulations or standards specifying the procedures for relinquishment of mining leases in Indonesia. Furthermore, a move towards regional autonomy, providing greater authority and responsibility to local (regional) areas, has recently been implemented in Indonesia and limited capacity exists in the new regional governments. Consequently, in October 2000, Kelian Equatorial Mining (KEM) initiated a partnership with the local community and government to explore sustainable post-closure options for the mine site and community development programs. The Kelian mine closure strategy seeks full involvement of all stakeholders through the Kelian Mine Closure Steering Committee (MCSC) in the development of sustainable solutions which will enable communities to secure long-term benefits and minimise post-closure risks from the KEM operations. This organisation, jointly chaired by the Head (Bupati) of the regional West Kutai government and the KEM President Director, with representatives from the local communities, governments and NGOs, has developed a Charter, a website and evaluation criteria to ensure accountability and transparency. There are four technical working groups, consisting of representatives from the mine, local community leaders, NGOs, Universities, Local, Provincial and Central Government Departments, which report to the Steering Committee. These working groups have researched, developed and recommended sustainable options to the Steering Committee. The MCSC has met quarterly to examine options in accordance with the criteria set out in the Charter and has endorsed sustainable solutions which have support from Government, Community and the mine. This paper describes the closure risks, sustainable outcomes derived through the Kelian mine closure steering committee process and outlines the methodologies used to develop and endorse sustainable solutions in a society with limited capacity undergoing enormous change and uncertainty.

Jan 1, 2003

By J. Rafael Otaíza, Francisco Mardones

This work has addressed the problem of creating a predictive model of the maximum particle velocities in the rock mass (PPV). The model designed specifically can model the subsequent vibrations of blasting based on geometric parameters, explosive loading, and the blasting process itself. Models based on artificial intelligence (AI) algorithms can find useful non-linear patterns to solve classification, regression, clustering, among other problems. They are flexible mathematical transformations adaptable to various objectives and types of data. With their different levels of abstraction, they can find a function that relates the input variables to the sought-after response. These models have been successfully used in similar contexts (Prashanth, (2018)) and have achieved state-of-the-art results in the field (Lawal, (2021)). The main challenge is to adapt them to the context of Chilean mines, in addition to including the geometric information of the blasting and the heuristic to obtain the set of optimal parameters, it is proposed to follow the work of (Simonyan, (2013)) and obtain "saliency maps" adapting it to tabular variables. We implemented an Artificial Neural Network (ANN) with a large number of neurons in the hidden layers. Models based on neural networks can find useful non-linear patterns to solve classification, regression, clustering, among other problems. They are flexible mathematical transformations adaptable to various objectives and types of data. With their different levels of abstraction, they can find a function that relates the input variables to the sought-after response. The literature shows that, for the problem of rock type identification, basic neural networks perform well (Simonyan, (2013)), but lack uncertainty estimates. This is a data-driven model, and in this sense, the model training was carried out using data from multiple operations in the large copper mining industry in Chile. In these databases, data consistency and the balance of the various independent variables that have the greatest impact on the model were ensured. With the above, the optimal hyperparameters of the model were determined, obtaining a predictive R-squared of 0.94.

Jan 21, 2025

By C E. Woolley, A Hosseini, J Foster

Northern Star’s Thunderbox Open Pit C-Zone cutback was designed to maximise extraction in a short life excavation; In fresh rock on the western wall this included 20 m to 30 m bench heights with 6.5 m to 10 m berm widths and a 90° pre-split angle. Rock mass quality in this area is generally fair to good, however, there are sections where the dominant foliation runs parallel with the designed pit wall, and more closely spaced, altered, foliation is present: these areas are difficult to predict and prone to failure. Stringent controls and monitoring were required in order to safely access below these areas, in particular the use of slope stability monitoring radar, Trigger Action Response Plans (TARPs), re-entry procedures, visual inspections, drone inspections and day-to-day personnel awareness of the hazard. Robust and comprehensively planned remediation was also required after two significant slope failure events where long reach equipment and rope access techniques were utilised to remediate the areas in question safely, but also in a timely manner, such that expected production targets were impacted as little as reasonably practicable. This combination of rigorous risk management and well planned remediation resulted in a successful and complete extraction of the C-Zone cutback with no impact to operational safety.

Jun 22, 2022

By Kristen R. Bingham

"Today, more than ever, drilling and blasting contractors are challenged to manage the ever-changing risks associated with blasting operations. New neighborhoods are encroaching upon mine sites and blasting projects are confronted with increasing scrutiny by permit issuing authorities and nearby residents disgruntled by new construction. The act of transporting explosives material to and from thejobsite is far from easy and trouble-free. At the same time, the pressure to stay in compliance with the growing number of government regulations continues to mount. While new tools and technology are appearing in the workplace to address some of these challenges, losses still occur. Can the datagenerated by this technology help drilling and blasting contractors make better decisions? While basic risk management principles are still applicable, do new tools and technology assist in the effort to prevent losses? What are the downsides? In this age of new technology, is face-to-face interaction still necessary? While technology is certainly a useful component in the drilling and blasting world, can it be helpful in defending claims?"

Jan 1, 2017

By F. Nelson

RJB Mining is the largest coal producer in the UK. In January 1995 the Company acquired the Central North and Central South Regions of British Coal consisting of: ? 15 operating collieries -including capital equipment ? 2 care and maintenance mines ? 16 operating Opencast sites ? Interest in 26 prospective and 46 potential Opencast sites ? Approximately 417 million tonnes of proven and probable reserves and considerable mineral resource ? 9 million tonnes of coal stocks ? Long term contracts to supply approximately 90 million tonnes of coal to National Power and PowerGen to the period of 3 March 1998 ?Approximately 7,600 employees and 4,500 mining contractual labour. Up to the acquisition RJB Mining had the capacity to produce 14 million tonnes of saleable output with an approximate 1,500 strong workforce.

Jan 1, 1998

By Rob Jameson

"The demand for commercial and residential construction has continued to evolve across the United States over the last decade. Our markets demand larger, deeper and inherently more complex structures, located within increasingly constrained urban locations and with challenging geotechnical conditions. As project demands incrementally escalate, specialty contractors are continuously challenged to extend their state of practice. Development in the size and capabilities of construction equipment, tooling, techniques, monitoring and verification systems over the last decade has consistently allowed contractors to build larger and deeper. For support of excavation (SOE), in addition to scale, selection of the most appropriate system has been a key to success in the most challenging ground conditions. This selection process is based on sound engineering and construction practice, and also prior experience, both positive and negative. Ultimately many Owners have chosen to manage their risk of SOE construction through design-build contracts, which allows specialty constructors to optimize the balance of cost, schedule, scope and associated risk based on their local expertise. Successful implementation of a design-build methodology begins long before a contractor is selected, with identification of key project requirements and risk factors during the feasibility studies and design development phases. In these early stages of the project development, advice and budgets are frequently solicited from Specialty Contractors. The Owner, Construction Manager and Consulting Team will filter this input from multiple sources to provide their specific recommendations, develop construction documents and select the appropriate form of contracting. Only in the final stages, after award of a Design-Build Subcontract, can the successful specialty contractor directly influence risk management approach on the project. A case study is presented from Block 9 in San Francisco’s Transbay District. This project demonstrates the incremental identification, assignment and mitigation of construction risk through the planning and design build process for SOE on the deepest planned excavation in San Francisco.INTRODUCTIONThe mature urban development market in United States results in high demand for complex Support of Excavation (SOE) schemes on constrained sites. The Design-Build approach can be applied to increasingly difficult SOE challenges, combining regional specialty subcontractor knowledge and experience in order to optimize solutions for cost and schedule. The most successful applications will involve early engagement of shoring subcontractors within the project teams, during feasibility and design development stages, in order to identify key scope and risk issues, and their potential solutions. Throughout the project development, it is important to reasonably assign responsibility for construction risks amongst the project stakeholders who are best able to control them.This paper presents a case history for San Francisco’s Block 9, a well-planned and successfully executed design-build SOE project in San Francisco’s Transbay Redevelopment area. Throughout the 4 year period from the Developers initial proposal to the Redevelopment agency, through completion of excavation down to subgrade, the project team developed a series of increasingly refined SOE schemes, with corresponding scope definition and cost and schedule estimates. This program relied on early identification of key challenges and risks for the project, and evolved through multiple phases of proposals as first the General Contractor (GC) and then Specialty Shoring Subcontractor were engaged for the project. The scheme, cost and schedule refinements continued throughout construction in order to accommodate unanticipated conditions and events as they unfolded."

Jan 1, 2017

By J Li, J Regan, D Payne

The Caval Ridge Mine is an open cut coalmine and located within the Bowen Basin region in Central Queensland, and commenced mining and processing operations in 2014. A number of geotechnical challenges for managing dragline bench and lowwall stabilities have been encountered in both southern and northern pits over the years. Southern Pits contain steep seam dips of up to 15° (27 per cent) whilst the northern pits also have shears below pit floors. Geotechnical guidelines to manage the risk of dragline bench failure and lowwall instability have been developed and improved since these geotechnical challenges were identified. The dragline guidelines include dragline tub offset distances from the 60° Line (SDL) or buttressing thickness for different seam dips greater than or equal to 8°. The low wall stabilisation guideline established floor disruption widths and depths depending on seam dips and presence of floor shears to known depths of up to 3 m. As mining operations advance, lowwalls have remained stable until floor disruptions were fired, then returned to stable soon after the shot. The maximum distance of lowwall cracking with blasting has been as far back as the second spoil peak (the prestrip truck dumps construction limit). These failures need to be eliminated to allow the operational flexibility and haulage benefit of constructing the prestrip truck dumps behind the first spoil peak, while maintaining no risk to personnel or equipment. The floor shear depth was verified by collaborating with the exploration teams and taking advantage of the already planned 8-inch coal quality core holes, drilling them an extra 5–10 m past the coal seam floor and locating the shear presence. With this continuous improvement effort, no lowwall failures have occurred during floor disruption firing from the second strip after the new floor disruption depth guidance have been applied. This paper documents the processes for developing these geotechnical guidelines, operational implementation, and outcomes. Operational applications over the years confirmed that these guidelines have effectively managed the dragline bench and lowwall failure risks related with the steep seam dips and floor shears in this open cut coalmine.

Nov 29, 2022

By R. D. Williams

"In a very real sense, Butte, MT is where the copper came from that won two world wars. The price for that unrestricted mining and smelting of copper came due in 1983 when Butte was declared a Superfund site.One of the most complex remnants of this mining history is the Parrot Tailings site. The Parrot smelter operated from 1881 to 1910, moving Upper Silver Bow Creek to the south and depositing approximately 283,000 m3 (370,000 cu yd) of waste material adjacent to Upper Silver Bow Creek. Additional mixed waste from other processing sites deposited below the Parrot tailings at the Northside Tailings, Diggings East and Blacktail Creek Berm total approximately 171,000 m3 (224,000 cu yd) of contaminated material. As part of the Superfund remedy, the U.S. Environmental Protection Agency (EPA) proposed leaving all these wastes in place. This proposal prompted a detailed criticism by several geoscientists familiar with the site. The EPA’s 2006 Record of Decision (ROD) did in fact leave these wastes in place, which set the stage for a series of studies that continue to refine how best to protect extensive completed Superfund Remediation downstream of Upper Silver Bow Creek. History of the Parrott Mine and tailingsPlacer gold was discovered in Silver Bow Creek, the headwaters of the Clark Fork River only a few miles from the Continental Divide in 1864. This discovery led to a stampede of placer and lode claims. One of the first lode claims located was the Parrot lode, located in the fall of 1864. Progress for developing a mine at the Parrott was slow, and it was not until 1876 that one of the original locators encountered a rich vein of chalcocite. Butte had its first copper mine.The Parrott Mine was patented in 1879 and by 1881 the Parrot, having lost a “t”, concentrator and smelter were built. The smelter and concentrator were an immediate success with a considerable market for processing the district’s rich copper ore. In 1885, the employees of the Parrot smelter bought the Butte Reduction Works, another smelter. In 1885, dams were built on Silver Bow Creek to contain various tailings and related processing byproducts (Fig. 1).By 1890, the various smelters in Butte rendered Butte’s air quality as suffocating (Fig. 2). An 1889 funeral procession was rumored to have gotten lost in the thick smelter smoke and somehow ended up at the Centennial Brewery. A city ordinance was passed late in 1890 in an attempt to control smoke. The Parrot smelter employed approximately 500 men by 1890. Through the 1890s, the tailings produced grew from approximately 91 t/d (100 stpd) to more than 181 t/d (200 stpd). Copper values in the tailings were initially as high as 4 percent, but as the processing improved that was reduced to 1.5 percent."

Apr 1, 2019

By Chris Twigge-Molecey, John Peacey

To meet the business objectives of a metallurgical project, there is often a need for new and untried technology or equipment, whose very novelty can present serious risks to meeting those objectives. The key risk management approach is a rigorous stepwise progression from theoretical evaluations and laboratory tests to pilot plant trials. These must be followed by demonstration-scale trials before final construction of a commercial scale plant, paying particular attention to the magnitude of the scale-up between phases. Success depends on following a well-defined program, not eliminating any steps, and ensuring adequate resources are available to the development team. Chapter 6 discusses the nature of technology risks to metallurgical plant projects, and the rigorous management practices needed to identify, analyze, evaluate, and avoid or mitigate them.

Jan 1, 2015

By L Sandery, S Light

Within 22 months of commencing decline development, the Prominent Hill Ankata Underground Project achieved its full production rate of 1.2 Mt/a.In 2010 construction of the Ankata Underground Project was approved. Decline development commenced in November 2010 and the turnout for the first sublevel was reached by August 2011. The first stoping ore was produced in the first quarter of 2012 and production was successfully ramped up to full production during the third quarter of 2012.Diamond drilling commenced in October 2011 and was conducted concurrently with the underground development. This presented challenges as mining and production targets had to be balanced with underground exploration activities. To achieve production on schedule, without adversely affecting the diamond drilling program and future development, meticulous and adaptive planning techniques were required. This included involvement from engineers, geologists, underground operators and underground diamond drillers.The granularity of these planning techniques allowed the management and prioritisation of development and diamond drilling down to an almost hourly basis. A constant flow of information from drill assay results was fed back into the planning systems. This resulted in a constantly evolving mine plan as the orebody was further refined. High priority areas were identified and targeted to allow continued development and a successful rapid ramp up to full production.CITATION:Sandery, L and Light, S, 2014. Managing the diamond drilling interactions in commissioning the Ankata underground mine, in Proceedings 12th AusIMM Underground Operators’ Conference 2014 , pp 75–80 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Mar 24, 2014

By M S. Manono, K C. Corin

The optimisation and process developments surrounding the beneficiation of Cu-Ni-PGM ores is of fundamental importance when considering the continued rise in global demand for these precious metals. The selective sequential flotation of these ores is accompanied with various processing challenges such as the successful separation of the Cu-Ni-PGMs from non-sulfide naturally floatable gangue and pyrrhotite. Reagents such as sodium iso-butyl xanthate (SIBX) and sodium carboxymethyl cellulose (CMC) have proven to significantly improve the selectivity of the flotation process in their respective roles. The use of recycled water with abnormal inorganic electrolyte concentrations can modify the selectivity of these reagents, as ions may adsorb onto minerals such as pyrrhotite, thereby hindering or promoting the hydrophocity and floatability of pyrrhotite. Process water quality effects on the behaviour of pyrrhotite may have negative or positive influence on the recovery and grades of the wanted Cu-Ni-PGMs as valuable minerals associated with pyrrhotite such as pentlandite may be affected in like manner. Thus, the impact of concentrator process water quality on the behaviour of pyrrhotite needs to be determined. In this study synthetic process water at various ionic strengths was investigated against various CMC dosages to understand the behaviour of pyrrhotite during the flotation of a Cu-Ni-PGM Merensky ore in a batch flotation cell. This study showed that pyrrhotite grades increased with an increase in CMC dosage for fixed ionic strengths whereas the recoveries of pyrrhotite increased with an increase in ionic strength until 3SPW, then a trend of a decrease in recoveries was seen with 5SPW resulting in the lowest pyrrhotite recoveries. Furthermore, this study showed that moderate CMC dosages of 100 g/t resulted in the highest pyrrhotite recovery for all four ionic strengths of synthetic process water tested. It can be said that to maximise value recovery from Cu-Ni-PGM ores, understanding the behaviour of pyrrhotite against degrading water quality and reagent suites could be of paramount importance given the sensitivity of pyrrhotite to oxidising chemical conditions.

Aug 24, 2022