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By D. A. Cowen

Toll and custom treatment of base metal concentrates have been performed for decades as mines and concentrators are developed distant from capital and, energy-intensive smelting and refining facilities. Commercial treatment terms have been developed and refined for over a century, and are negotiated taking into account a complex array of quality and economic factors. Treatment of third-party concentrates in the South African platinum industry is a comparatively recent development, brought about by the opening up of mineral rights and operations being developed that are smaller than the critical size required to sustain capitalization of smelting or refining plant. Published commercial terms have not been demonstrated to reflect the complexities and subtleties of base metal concentrate markets. This paper outlines some key elements and parameter ranges of base metal concentrate treatment contracts, and applies similar principles to typical Merensky and UG2 platinum group element (PGE) concentrates to determine potential value distribution between the mining and treatment parties in tolling arrangements.

Jan 1, 2012

By G. Kleyn

"Sub-standard practices and their adverse impact on safety performance remain a challenge in the South African gold mining industry. The purpose of this study was to investigate the root causes of sub-standard practices and the effect on safety performance in South African gold mines. The focus of the study was on the underground production operations at a gold mine in the Free State. The study consisted of three parts: a personal investigation into the causes of sub-standard practices at the mine, a comparison with the results of a cultural study performed at the West Wits mines, and a behavioural survey.The studies described in this article yielded similar results in terms of the key drivers behind sub-standard practices. It was found that substandard practices had a number of causes, and the origin lies within the habits, attitude, and behaviour of employees. Current methods of addressing sub-standard practices and improving safety performance were found to discourage employees from performing work safely and according to procedure. It was concluded that the lack of critical behavioural habits for the given work environment and job title could possibly be the primary reason for the occurrence of sub-standard practices. IntroductionSince the implementation of the Mine Health and Safety Act, 1996 (Act 29 of 1996) and the Mine Health and Safety Regulations, the South African mining industry has been striving to improve health and safety performance and has placed great emphasis on adherence to mine standards.The Act requires employers in the mining industry to report accidents, incidents, and dangerous situations to the Regional Principal Inspector of Mines in their area. The data provided by employers is captured and analysed by the South African Mines Reportable Accident Statistical System (SAMRASS) and made available for public viewing (Department of Mineral Resources, 2011).A review of the national mine-related accident statistics shows clearly that the South African gold mining industry has improved its safety performance markedly over the past decade, but is still facing major challenges (Figure 1). These include meeting the Mine Health and Safety Milestones (Department of Mineral Resources, 2011)."

Jan 1, 2016

The November General Meeting of the Branch was held at the S1. Helena Club on Friday, 15th November, 1968. Mr. J. G. Kirchner (Chairman of the O.F.S. Branch) was in the chair. There were also present: President: Mr R. C. J. Goode. Eighteen Members: Mr A. E. Gilfillan (Council Member), Messrs T. Zadkin, J. N. Saunders, N. A. Honnet, D. D. Waterman, C. R. Netscher, (Committee Members), Messrs G. Thorburn, Z. Lombard, H. V. Henwood, C. J. Isaac, S. L. S. Swart, J. D. McNamara, H. H. Schellhorn, J. W. Wilson, G. C. P. Labuschagne, L. J. Thorne, R. C. Espley-Jones, J. Handley. Seventeen Associate Members: Messrs H. J. Reeders, R. Campbell, P. A. Hoffman, D. E. Couperthwaite, M. D. de Lange, G. J. C. Young, G. W. Futcher, U. Visser, F. H. De Groot, E. Schmid, K. G. Pearce, D. A. Viljoen, H. W. M. Eschenburg, R. Still, W. B. Howe, A. H. Edwards, R. H. Drake. Three Graduates: Messrs T. R. Stromsoe, J. G. Cockburn, T. A. Ward. One Affiliate: Mr O. A. Huss. Twenty-three visitors. Total present: 64. Apologies were reseived from Messrs L. O. W. Leimer, V. C. Barnes and A. Louw. WELCOME TO VISITORS The Chairman declared the meeting open and extended a special welcome to the following: Mr R. C. J. Goode, President of the S.A. Institute of Mining and Metallurgy; Mr A. E. Gilfillan, Member of Council and Mr D. A. Viljoen, all from Johannesburg. Also to Mr J. D. McNamara, the guest speaker for the evening who had made the trip from Oranjekrag. MINUTES OF PREVIOUS GENERAL MEETINGS The minutes of two meetings, viz., the General Meeting held on 26th June, 1968 together with those of the Annual General Meeting held on 14th August, 1968 were taken as read and their adoption moved by Messrs T. Zadkin and D. D. Waterman. MATTERS ARISING FROM THE MINUTES There were no matters arising from the minutes. ADDRESS BY PRESIDENT OF COUNCIL, MR R. C. J. GOODE With regard to the 75th Anniversary of the Institute, the President called upon those present to bear the following two dates in mind, viz.: 21st March, 1969-Banquet at the Wanderers' Club, to which ladies are invited. 24th March, 1969-General Meeting at Kelvin House at 9.30 a.m., the speakers being the President of the Institute, the President of the Chamber of Mines and Dr H. J. van Eck.

By K. Duffy, W. Valery, L. Pyle, P. Holtham

A conceptual scoping study was conducted to investigate pre-concentration options for upgrading ore from an Ag-Pb-Zn deposit. The low grade of the ore would result in only modest economic returns, given current market conditions. Several pre-concentration options were considered. These included: selective mining, crushing and pre-screening (following either standard or high intensity selective blasting), bulk ore sorting, particle sorting, jigging, dense medium separation, or combinations of these approaches. Flowsheets were developed for each option, and the upgrade performance was modelled using Limn to determine mass balances and stream tables. Due to the limited availability of test work data, the models were based not only on what test data was available but also on case study data found in the literature. The Bazin technique was used to derive assay by size data for different streams following crushing. Equipment lists and preliminary layouts were established based on the stream tables, and capital and operating costs were estimated for each flowsheet. This information was used to carry out a preliminary economic evaluation using net present value and sensitivity analysis. In this case, the most economically attractive process was found to be particle sorting; although further benefits may be realised by combining with bulk sorting. This paper describes the methodology used and the key findings of the study. Keywords: Pre-concentration, pre-screening, ore sorting, jigging, Ag-Pb-Zn, particle sorting, bulk ore sorting

Jan 1, 2020

By Y. Zhou, G. Chisakuta, P. Bwando, G. Mitshabu

A newly started copper hydrometallurgical plant was confronted with a manganese oxidation issue in electrowinning. This oxidation, in the absence of the amount of iron required to stabilise the electrolyte oxidation-reduction potential, is known to produce oxidants (MnO2, MnO4) that can cause accelerated degradation of the organic phase components in solvent extraction and corrosion of lead anodes in electrowinning. The overpotential required to build up the protection layer on new anodes causes an increased electrolyte potential that creates oxidized species in the electrowinning tankhouse, and these species come back to solventextraction plant with the recycled spent electrolyte. This paper discusses the impacts of manganese oxidants on the health of a plant organic phase. It also outlines the actions taken using iron scraps and sulfur dioxide to mitigate the problem that happened due to the lack of ferrous iron sulfate available on site, as recommended for better control.

Jan 1, 2023

By A. F. Spinks, S. P. Nicholls

"The Lower Orebody at Chingola Division of Nchanga Consolidated Copper Mines, Limited, is a stratified orebody that is mined by a continuous caving system. The accurate determination of the developed and semi-developed ore reserves has always been difficult. The new system proposed in 1971 is designed to update and, as new informa¬tion becomes available, to account for the depletion of, the reserves.There are three main inputs to the system. These are borehole data, survey data and extractions data. The borehole data are input to a geological borehole master file system, which holds every recorded detail of a borehole in an easily extractable form. These data can be extracted for ore reserve calculations or for contour mapping of orebodies and rock types. The grades for use in the ore reserve calculations are extracted from the relevant boreholes.The survey data are information on the position of the blocks and drifts, taken from plans, and information on the scraper drift and trough drive positions taken from sections. The information is extracted from the plans and sections using a D Mac pencil follower. The ore reserve is calculated from the survey data and the borehole data.Data on extractions are taken from scraper operators' logs, tramming records, skips hoisted records and accepted mill tonnages and grades. Using these data, the mill tonnages are reconciled back to the drifts, to deplete the current ore reserves.As new workings are brought into operation and further evaluation holes are drilled, the relevant data are input and the new developed ore reserve is calculated."

Jan 1, 2014

By S. Heukelman

Zincor uses O2 enrichment (up to 26% O2 in the fluidizing air) to increase the processing rate of zinc concentrates in the fluidized bed roasters. The aim of this study is to determine whether O2 enrichment can be reduced by introducing micro-pelletized concentrate into the feed blend, while maintaining current roaster feed rates and calcine quality. It was found that, with a load of 20% micro-pellets introduced into the feed blend, that O2 enrichment could be reduced by 60%. It was determined that entrained particles spend on average between 0.46 hour and 2.44 hour in the roaster, compared to particles remaining between 3.93 hour and 4.00 hour in the bed overflow. This compares well with a radioactive tracer test performed by Spira. The required reaction time for micro-pellets was found to be less than the residence time inside a Zincor roaster. The result achieved indicated that the average particle residence time inside the roaster was increased successfully in order to compensate for the longer reaction time required to roast micro-pellets at lower levels of O2 in the fluidizing air.

Jan 1, 2011

By M. Rhodes

The Sukari project, which is owned by Centamin Egypt Ltd, is located in southern Egypt, 770 km south of Cairo but close to the Red Sea. The project is the first new gold development in Egypt and was commissioned in the middle of 2009. In 2007, Centamin purchased the CIL plant from the Kori Kollo mine in Bolivia. This plant was originally designed to treat 6.5 Mtpa of oxide ore. The Sukari deposit contains an oxide zone close to surface with a thick zone of mixed oxide and sulphides below this. The sulphides contain relatively coarse pyrite and arsenopyrite with fine <10 µm gold inclusions. Eventually, the sulphide ore will be mined from underground. Metplant Engineering Pty Ltd, a subsidiary of Bateman Engineering Pty Ltd was contracted to design modifications and additions to the Kori Kollo plant to enable it to treat the Sukari ores. The plant was designed to treat the three ore types in stages. Throughput was set to 4 Mtpa, dueto Sukari ore being harder, at a head grade of 1.7 g/t to produce 200 000 oz of gold. The oxide circuit was based on the use of the Kori Kollo plant and the difference with mixed ore was that the oxide circuit would treat flotation tailings rather than ore. This circuit has a leach capacity of 26 000 m3 and residence time of 24 hrs The main feature of the upgraded mixed ore plant was the addition of a flotation circuit to produce a concentrate which would be reground and treated in a separate leach and elution circuit. Ore is crushed in a gyratory crusher and the comminution circuit uses a conventional SABC producing a product with a P80 of 150 microns. The throughput of 580 tph of oxide ore and 500tph of mixed ore was set to match the mills from Kori Kollo, with the addition of the pebble crusher to accommodate the more competent Sukari ore. The flotation circuit comprises a single rougher circuit to maximize recovery. The concentrate is thickened prior to regrinding which is carried out in a tower mill and two SMD mills operating in series. The final product, with a P80 of 12 microns, from the regrind circuit is leached in a CIL circuit with a total capacity of 2 550 m3. Gold is recovered through a conventional pressure Zadra circuit. Tailings from both circuits report to separate tailings thickeners and are pumped to a tailings storage facility. The circuit is designed to maximize the recovery of water. The project lies in one of the driest deserts in the world and a feature of the operation is the use of sea water from the Red Sea. This water is pumped 25 km from the coast.

Jan 1, 2009

By M. Ataei, F. Sereshki, R. N. Masir

Given the inherent risks and disruptions in underground coal mining operations, strengthening the resilience of critical infrastructure has become a vital priority. This paper aims to evaluate the resilience of the underground coal mining environment using historical data and expert judgment. The study serves as a framework for optimising the utilisation of critical infrastructure to minimise operational disturbances. To achieve this, a practical methodology has been developed, incorporating nearly two and a half years of collected operational data, a hierarchical structure, and a systematic approach. Furthermore, a case study is conducted to demonstrate the real-world applicability of the proposed method. Finally, the resilience index isintroduced as a straightforward summation of ranked impact factors, providing a clear metric for resilience assessment.

Dec 15, 2025

By B. P. Watson, A. Carpede, W. O. Kekana, N. Fernandes, W. Theron, M. P. Mahlangu, G. Betz

The research described in this paper was done to confirm the Upper Group 2 (UG2) PlatMine peak pillar strength formula (Watson et al., 2007), which was determined from a back-analysis of failed and unfailed pillars. Underground measurements were made on a stable pillar that was loaded by firstly reducing it’s length and then by mining the surrounding pillars until pillar failure took place. The pillar was instrumented with suitably positioned strain cells and closure meters, which allowed both the average pillar stress and strain to be determined. The paper describes the methodology applied to identify a suitable position for the instrumentation, as well as the results. A stress/strain curve is presented for a UG2 pillar with a w/h ratio of 2.0, at Booysendal Platinum Mine. The measured pillar strength was similar to the predicted strength using the PlatMine pillar strength formula for UG2 pillars. The PlatMine formula has been successfully implemented on Booysendal Platinum Mine, and about 3 670 pillars have been cut without a single failure. An additional revenue of US$1.3 billion was calculated for the 25-year life of the mine as a direct result of the improved pillar design, given the January 2020 platinum group metals basket price. An extended life of mine and better mining efficiencies will also be realized.

Aug 1, 2021

By A. E. Lewis, J. Du Plessis, J. Chivavava

Current metallurgical processes lack selective and efficient REE recovery from aqueous leach liquors. Antisolvent crystallisation is used to selectively recover pure inorganic salts from aqueous solutions without excessive chemical use in ambient conditions. Yttrium sulfate octahydrate (Y2(SO4)3.8H2O) was used as a representative rare earth salt to investigate the effect of antisolvent selection on the crystal morphology and size distribution of the final crystalline product produced through antisolvent crystallisation. The antisolvents of choice were short length alcohols that are water miscible i.e. methanol, ethanol, 2-propanol and t-butanol. All experimental parameters except the type of antisolvent were kept constant under isothermal conditions. The large reduction in solubility of the salt by the antisolvent creates high supersaturations. This leads to high product yields as observed in this study at > 91%. In general, a variety of morphologies were successfully formed in each individual alcohol including; rods, plates, prismatic cubes and starburst clusters. The powder X-ray diffraction (XRD) analysis indicated that Y2(SO4)3.8H2O was the only species present for all final products. There was a change observed from the starburst and rod structures for the shorter alcohols towards prismatic cubes for the longer alcohols due to different strengths in the solute-antisolvent interaction at the crystal growth faces. The crystal sizes increased with an increase in the alcohol chain length because of the lower supersaturation conditions due to a limit in the mass transfer induced by the bulkier alcohol structure. In conclusion, it has been shown that the particle morphology and size can be greatly affected by the selection of antisolvent even under high supersaturation conditions, contributing to understanding the effect of different antisolvents on the final particle characteristics. The engineering of favoured product characteristics can therefore be achieved by antisolvent crystallisation, presenting a viable alternative process for the recovery of REE. Keywords: Antisolvent crystallisation, rare earth elements, morphology, particle size

Jan 1, 2020

By T. R. Marshall

SAMREC (The South African Code for the Reporting of Exploration Results, Mineral Resources and Mineral Reserves) Clause 7 notes that ‘Documentation detailing Exploration Results, Mineral Resources and Mineral Reserves from which a Public Report is prepared must be prepared by, or under the direction of, and signed by a Competent Person.’ Similar statements with respect to Competent Valuators (CVs) and Qualified Reserves Evaluators (QREs) are contained in the SAMVAL (South African Code for the Reporting of Mineral Asset Valuations) and SAMOG (South African Code for the Reporting of Oil & Gas Resources) codes respectively. What does it mean to be a Competent Person (CP) in the context of compiling/signing-off on SAMCODE (South African Mineral Code) compliant documents? What do the registration and experience requirements mean? Who is ultimately responsible for the report and what does such responsibility prescribe?

Sep 1, 2021

By O. Koatlhai

Mine closures have traditionally prioritised environmental rehabilitation, often overlooking the deep socio-economic disruptions that follow, particularly in mining-dependent communities. This paper argues that mine closure should not mark the end of prosperity but rather the beginning of a sustainable transition. The coproduction model, which integrates community participation, governance, and economic planning, offers a transformative approach to closure planning. Drawing on case studies from Ghana, Zambia, and Indonesia, this research examines the successes and failures of past closures, highlighting the critical role of stakeholder engagement, skills development, and economic diversification. By incorporating emerging technologies such as AI-driven economic forecasting, blockchain for governance transparency, and decentralised finance (DeFi) models, mining companies can ensure a just and sustainable post-mining future. This study challenges outdated closure models and presents a forward-looking strategy that sees mine closure not as an endpoint, but as a catalyst for social resilience and economic transformation. It underscores the need for policy reforms, stronger governance, and investment in alternative industries to prevent mining towns from becoming economic wastelands. By shifting the paradigm from remediation to regeneration, this research calls for a new era of mine closure planning that puts people and prosperity at its core.

Apr 25, 2025

By M. Handley

The Witwatersrand Basin contains by far the most gold ever found, and has hosted mining from its discovery in 1886 to the present. For many years, South Africa was the world’s largest producerof gold, nearly all of which came from the Witwatersrand. Since 2000, South Africa has fallen back several positions because of declining gold output. There are many complex and varied reasons for this; however, declining gold resources in the Witwatersrand Basin are not one of them. As far as the author knows, there are no qualified estimates in the literature of gold remaining in the Witwatersrand Basin. This paper collects mining data from several sources and then, using elementary gold accounting and error analysis, attempts to estimate the amount of gold remaining in the Witwatersrand Basin. It includes gold underground in existing and defunct mines, in evaluated ore resources, and dumps. Compiled data from 1887 to 2019 shows that 50 200 t of gold were produced by Witwatersrand mines, while it is estimated that a further 48 100 t remainunderground, both within and outside of mine leases, a further 1 600 t on the surface in tailings,and an unknown amount in rock dumps. Nearly all of this gold will remain inaccessible with current mining methods, and major technical developments in mining will be necessary before any of the gold can be categorized as a code-compliant resource or reserve. To win this prize, the mining industry will have to rethink its approach to mining, both in old mining leases and in the unexploited ground. It will also have to find effective means of preventing gold theft and informal mining, which are on the rise.

Apr 5, 2023

By K. J. Craig, M. A. Swart, Q. G. Reynolds, L. Hockaday

A solar reflector soiling study was carried out at a ferromanganese smelter in South Africa to assess the soiling rates at different locations around the plant. Several meteorological parameters were monitored to give insight into the conditions that lead to increased soiling. Mineralogical characterization of dust samples collected from the reflectors and the atmosphere revealed that only a certain size fraction is of importance with regard to soiling, and that the dust can be attributed to both raw materials and smelter products. Proximity to the dust source was the primary driver for increased soiling. The site that experienced the most soiling was very close to raw material heaps; this was deemed an outlier and was excluded from the summary statistics. The secondary driver for increased soiling was location relative to the smelter dust sources and the wind’s direction and speed. The reflector set at the best location experienced 13.1% less soiling than the set at the ‘worst’ (but still feasible) location, represented by an averaged mean daily reflectance loss of 0.0186. The study revealed that while there are periods of intense soiling at this particular site, proper planning of reflector location in relation to the smelter dust sources can significantly mitigate the soiling rate.

Jun 5, 2023

By R. B. Khumalo, T. Chauke, T. Mtshali, F. K. Mulenga, B. Makgate, N. M. Chiloane, T. Moyane, V. C. Madanda

While high production rates are important for the profitability of a mine, the influence of geotechnical engineering cannot be ignored. In block caving, a high-stress level is required for cave propagation; this is one of the core elements for ore recovery. Therefore, stress distribution and geological structures play a major role in the planning and layout design of the mine. This paper explores the influence of stress and geological features on the design of the mine from the feasibility study phase. The geology and stress measurement of the mine were determined through logging and overcoring, respectively. This study found that while production rate is the primary operational consideration, the long-term layout design of the undercut face advance, face angle, drawpoint spacing, and undercutting sequence is mainly governed by the stress orientation and major geological structures. Moreover, widely spaced drawpoints result in isolated draw zones, consequently, resulting in ore loss and early dilution whereas closely spaced drawpoints affect the stability of the major apex pillar. This paper also provides insight into how operations can leverage stress distribution to optimise mine layout and safety in massive mining methods.

Nov 24, 2025

By S. Schutte, J. Pelders, F. Magweregwede, S. Ngobese, W. Botha

A people-centric, systematic approach that involves different stakeholders is considered necessary to successfully address changes associated with modernizing the South African mining industry. In this paper we discuss the inclusion of various South African mining industry stakeholders, particularly the employees, in equipment design and development processes. Data was acquired through a literature review and inputs from South African mining industry stakeholders through focus group discussions, interviews, and an online survey. It was suggested that some of the areas that could be improved by the inclusion of employees in the process are design quality, ergonomics, equipment acceptance by the workforce, safety, efficiency, skills, insight into context of use, and early design iterations and identification of problems. Among the issues considered to be barriers to inclusion were lack of buy-in, lack of resources, difficulty in manufacturers accessing the mines, difficulties in involving too many people, intellectual property concerns, and unavailability of mine employees due to their key responsibilities. Identified critical factors in the equipment design and development process include iterative design, stakeholder participation throughout the process, needs analysis through consultation, and change management. A guideline was developed for worker inclusion in equipment design and development that could be used by the South African mining industry. The study identified several economic and social benefits of including stakeholders in the early stages of design and development. It is recommended that the South African mining industry considers using the developed guideline.

Apr 5, 2023

By A. Doroudgar, H. Noferesti

Unstable rock failure or rock bursting is one of the most dangerous problems in deep hard rock mines. This type of failure, that occurs uncontrollably, is associated with a significant release of strain energy from the surrounding rock. In this study, the numerical simulation of unstable rock failure was carried out using the three-dimensional explicit Lagranian finite-volume finite difference method to identify the onset and location of unstable failure events in the model. On this basis, a numerical simulation of mine pillars with width-to-height ratios of 0.5, 2 and 3 was performed. A criterion was developed, based on the calculation of the elastic strain energy, to determine the prone areas for the initiation of rockburst in the models. The results of this study showed that, in softer loading systems, due to large amounts of stored elastic strain energy, an unstable equilibrium is established, which leads to the rapid transfer of strain energy to the rock in the form of violent failure. It was also found that the unstable failure starts at the corners and free surface of the model. The new criterion developed in this study may help predict the occurrence of rockbursts in slender pillars and the design of pillars to control human and financial losses caused by this phenomenon.

Nov 27, 2024

By M. Steyn

This article captures the intrinsic differences of thermal coal products, their utilization and their substitution characteristics. South Africa produces approximately 245 million tonnes of coal annually. Eskom consumes 46% (approximately 112 million tonnes), 26% (approximately 65 million tonnes) is exported, and SASOL Synthetic Fuels consumes 18% (approximately 44 million tonnes) and a further 9% (approximately 22 million tonnes) is consumed by domestic users in various different industries. Marketing theory contributes significantly to understanding the importance of technical product and quality appreciation and comprehension, encompassing elements of price, distribution, and promotion. Coal product specification is determined by the inherent geology of a resource and the number of complex actions to market the product to a specific consuming market. Sampling, analyses, beneficiation application, and an array of parameters contribute to matching thermal coal products to the value-in-use it provides to the different markets and its consuming industries. Coal producer shave come under increased scrutiny since South Africa has been experiencing electricity shortages since early 2008. General misunderstandings were declared on public forums and in the media by both legislators and the South African public since a perception developed that South African coal producers are exporting coal that could be utilized by Eskom.

Jan 1, 2010

By H. Von Michaelis

The world is rapidly becoming more ?green? i.e. energy conscious. Since mining and mineral processing are massive energy users, the mining industry is seeking ways to reduce its energy footprint. In mining and mineral processing operations, energy is often the most expensive cost item. Comminution, i.e. grinding, is frequently the most energy-intensive step between mine and metal. High pressure grinding rolls (HPGR) are being installed in a rapidly growing number of ?hard rock? mineral processing operations. In the energy conscious cement industry, HPGR grinding has been standard practice for decades. HPGR is known to be energy-efficient; the question is how energy efficient? How can the energy efficiency of HPGR be enhanced? This paper reviews recent HPGR applications for the processing particularly of copper, gold, platinum, PGM-Ni-Cu and iron ores. HPGR technology is discussed with respect to energy efficiency. The harder the ore the greater the energy savings are likely to be. Typical energy savings of 10?20% can be expected when installing HPGR vs. a SAG mill. Wipf(2005) showed why conventional Bond Work index tests on HPGR product is likely to under-estimate the energy savings that can be achieved by installing HPGR. Energy efficiency of HPGR is, however, ore-specific. The biggest energy savings of HPGR tested thus far is 9.5 kWh/tonne claimed for Vista Gold?s Mt. Todd gold ore from Western Australia, a savings of over one-third of conventional SABC comminution energy. Several commercial scale iron-ore pellet feed plants install HPGR for fine-grinding of concentrate to increase the surface area of pellet feed in a manner that reduces overall energy consumption. Energy-consumption in comminution is, however, only part of the energy savings benefit story. HPGR typically also reduces the amount of steel lost through wear of mill liners and media. Marsden(2008) showed that when the energy that would have been consumed to produce the steel that is saved by applying HPGR is factored in, then the overall energy savings of HPGR is considerably greater. Johnson et al.(1988, 2005) tested HPGR in a flowsheet in which energy savings of around 50% can be expected if HPGR product screen oversize is recirculated to the HPGR. Innovative flowsheets have been proposed by Rule et al.(2008) and by Morley (2008) which are expected to result in significantly increased energy savings. HPGR applied in flowsheets in conjunction with coarse ore separation devices, e.g. ore sorting or DMS to remove barren waste from HPGR feed promises significantly greater energy efficiencies. Fine-grinding and ultra-fine grinding of ore or concentrates in conventional ball mills results in energy consumptions that increase exponentially with product fineness. Wipf (2009) presented a flowsheet in which he proposed the installation of HPGR ahead of the Aerosion ?Disintegrator? for ultra-fine grinding of ores and/or concentrates. This dry grinding arrangement is expected to achieve ap80 = 7 µm using up to 100 kWh/t less energy than could be achieved by wet ball milling. Using conventional comminution, an ore might require grinding to p80 = 45µm (? 325 mesh), for example, to liberate the valuable components, e.g. magnetite, from gangue, e.g. silica. Inter-particle comminution in HPGR may break some ores along grain boundaries thereby liberating valuable minerals from gangue at a much coarser particle sizes. Early magnetic separation rejection of silica gangue liberated from magnetite by HPGR at coarser grain sizes could further reduce downstream comminution energy consumption.

Jan 1, 2009