Search Documents

Application of the Anaconda Simplified Work Index for Multiple Test Sizes Vale uses Bond Work Index measurements extensively in a number of applications. The Bond Work Index is usually a good parameter for checking scale up procedures when sizing ball mills, as well as the basis for variability analysis whenever drill core data is available. It is typical to measure between 100 and 150 Bond Work Indexes, depending on the deposit characteristics. The Bond procedure is relatively complex and time costly. It also requires relatively large amounts of sample, which are very expensive to be obtained. The benefits of the Anaconda simplified procedure are: considerably smaller sample requirements and laboratory time. This makes it very much attractive at Vale's development centre, including geometallurgical mapping, operation efficiency control, mine to mill, etc. The Anaconda simplified procedure was implemented and evaluated at Vale's Development Centre using a number of ores and several samples of each ore totalling more than 190 measurements. The Anaconda simplified method was calibrated for several test sieves and a correlation for any test size was determined for Vale's test mill. The calibration was also extended for two sample top sizes. The relative error of the simplified procedure was found to be in the range of nine per cent which is within the expected error Bond standard procedure. The implementation of the Anaconda method at Vale's development center has been used with great success over the past years in several green field, brown field projects and operating plants.

Sep 13, 2010

By R Wolff

One critical factor in open pit mining projects is the estimation of the recoverable reserves. The reason for this is that at the valuation stage there is a lack of information about future metal prices and production costs. Consequently, the estimation of the recoverable reserves needs to be done based on a fixed break-even cut-off grade (BECG), in which fixed expected metal prices and production costs are assumed throughout the operating life of the mine (OLM). In this paper, an alternative technique for estimating the recoverable reserves of an open pit mining project is presented and explained in detail. The main characteristic of this technique is that it estimates the recoverable reserves of the project using mining costs as reference: this is done due to the fact that mining costs are easier to model than metal prices. Another important characteristic of this technique is that it uses the uncertainty of the geology of the orebody, given by simulations of the deposit, to make final strategic decisions, such as the selection of the operating life of the mine and the optimal production rate, which minimise the risk of not achieving future production targets while maximising the upside potential of future rewards. As it will be shown, the final outcome of the proposed technique is the generation of a robust open pit design, that include cutbacks and ultimate pit limits, called the marginal open pit mine design (MOPMD). One characteristic of the MOPMD is that, at each production period, it will be characterised by their respective geological uncertainty, given as probability distributions of ore, waste and metal quantities, and by marginal economical project indicators, such as cut-off grades and metal prices, among others. The details follow in the paper.

Jan 1, 2006

By R Garzon

For resources projects with healthy net present value (NPV) and low cash flow volatility, conventional discounted cash flow (DCF) analysis will continue to provide the dominant investment decision-making criteria. However, DCF analysis can be biased because it often applies a single risk-adjusted discount rate (RADR) to compare the value of projects with different risk characteristics. Many of the difficulties with DCF modelling arise from analystsÆ inability to determine appropriate risk discounts and to estimate expected spot prices inputs for the commodities produced over the life of the project. Modern asset pricing (MAP) is a very valuable complement to DCF analysis in addressing some of these issues. Most papers dealing with MAP, however, while academically rigorous, tend not to be explicit in terms of practical application of this methodology in routine project evaluation. This paper has the objective of reviewing the MAP methodology and of demystifying its complexity, by providing a simple but realistic step-by-step evaluation of a mining project, comparing its DCF and MAP NPV values. The paper concludes that MAP provides a minimum, risk-adjusted æfloorÆ value, thus representing a valuable complement to any DCF valuation.

Jan 1, 2007

By D J. Williams, S Islam

Worldwide production of black coal amounts to about 8 billion tonnes. Perhaps 20% of this annual production is washed to improve its quality, generating perhaps 250 million tonnes of coal tailings annually, generally in the form of a slurry. The coal tailings slurry is typically thickened to about 25% solids by mass prior to disposal to a tailings storage facility (TSF), and hence comprise mostly water (about 85% by volume), plus sand, silt and clay-sized mineral particles and carbonaceous material. While the tailings settle and consolidate on deposition in the storage facility, their high moisture content makes them prone to run-out should the tailings dam fail, and makes rehabilitation of the tailings difficult. Hence, it is important to understand the consolidation and shear strength of coal tailings. Laboratory consolidation testing of coal tailings from a slurry to a soil-like state has been carried out in a purpose-built, large-scale, slurry consolidometer, instrumented with load cells and pore water pressure (PWP) transducers. Laboratory vane shear testing of coal tailings produced at different gravimetric moisture contents has also been carried out. The test results have allowed a regression model to be developed relating the peak vane shear strength of the coal tailings to their gravimetric moisture content.CITATION:Islam, S and Williams, D J, 2018. Consolidation and shear strength of coal tailings slurries, in Proceedings Mine Waste and Tailings Stewardship Conference 2018, pp 62–71 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 23, 2018

Extraction and Characterisation of Extracellular Polymeric Substances from the Mineral Surface During Bioleaching of Chalcopyrite Concentrate A mixed culture of moderately thermophilic microorganisms was used to bioleach chalcopyrite concentrate in a stirred tank reactor. The results show that up to 84.7 per cent of copper extraction could be achieved in 24 days at a pulp density of 6 per cent. The leaching rate of chalcopyrite concentrate tended to increase with an increase of dissolved total iron concentration. Furthermore, the extracellular polymeric substance (EPS) on the surface of the chalcopyrite concentrate was extracted and analysed. EPS was extracted at the first, third, eighth, 16th and 24th day during bioleaching, which mainly consisted of proteins, lipids, sugars and ferric irons. After the eighth day the total amount of EPS remained relatively constant. However, the amount of ferric iron in the EPS decreased in a large scale. The ore residue analysis indicates that the decrease of ferric iron was mainly due to the formation of jarosite on the mineral surface.

Sep 13, 2010

By T Baumgartl, B Richards

The association of specific plants and plant communities with soils developed over underlying superficial orebodies and mineralisation has been long recognised. It has given rise to the use of plant indicators for geobotanical exploration as a regular component of primary minerals reconnaissance where there is an undisturbed vegetation cover. That the chemical composition of indicator plants is a measure of their soil environment has further led to biogeochemical prospecting methods for minerals and its use in the mapping of underlying ore deposits. Where there is a strong surface expression of metal and metalloid anomalies, concentrations of potentially phytotoxic elements may reach a level at which they have strong selective impacts on plant populations. In such circumstances, natural selection has operated in the development of a unique flora composed of plant species and individuals with genetically-based tolerances to the stressed environment in which they continue to survive. These plants are called metallophytes. Metallophytes occur globally on all metalliferous sites, both in pristine undisturbed environments and in areas of mineral workings, ancient and modern. However, the best-developed primary metallophyte vegetation is found in the most ancient areas where there has been a long-term evolutionary impact of the underlying geology through ore weathering and dispersion of metals into the rhizosphere zone. Natural selection of metal-tolerant races of plants in these largely undisturbed areas can eventually lead to speciation and the development of an endemic regional metallophyte flora (Baker et al , 2010). Mineral wastes resulting from mining activities also allow colonisation by metal-tolerant individuals leading to the establishment of metallophyte communities. The distribution and extent of such communities is determined by regional and local factors relating to climate and substrate conditions and the availability of suitable plant resources on which natural selection can operate (Baker, 2009).The ability of metallophytes to tolerate extreme metal concentrations commends them as the optimal choice for ecological restoration of mineral wastes and metal-contaminated sites. Metallophytes have recently also spawned several novel phytotechnologies, including phytoremediation and phytomining (Chaney et al, 2000, 2005; Baker and Whiting, 2008). Action towards conserving the global metallophyte resource base is imperative because many species are under threat of extinction from new and extensive mining activities (Whiting et al, 2004). This has been identified as a priority in the Mining, Minerals and Sustainable Development (MMSD) Project of the Global Mining Initiative in 2002 but positive responses from the minerals industry have been slow. The last decade has, however, seen an ever-increasing interest in metal-tolerant and metal-accumulating plants, both from an academic standpoint and their use in revegetation and phytostabilisation (Tordoff et al, 2000; Baker and Whiting, 2008; Baker, 2009). Few studies have highlighted the need to conserve and develop these unique plants (Whiting et al , 2004). This presentation identifies future research needs for the conservation and exploitation of the global metallophyte biodiversity and its potential in sustainable mine closure. CITATION:Baumgartl, T and Richards, B, 2012. Evaporation and salt transport under variable climatic conditions, in Proceedings Life-of-Mine 2012 , pp 179-186 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 10, 2012

The relationship between comminution testwork results and the milling circuit that is subsequently selected is not a direct one and frequently involves recourse to databases of past test results. This in itself reflects the lack of a systematic engineering approach in the design process. This paper reviews comminution tests for SAG mill design in an attempt to identify where the essential information comes from that will be used in mill selection. The conclusion is that results from traditional test methods, including obscure and little used procedures like the Mokken test, are more valuable from an engineering perspective than parameters for breakage rate based modelling. Suggestions are made on ways in which existing test procedures can be enhanced in order to generate parameters that can be directly related to characteristics of the milling circuit being designed.

Jan 1, 2002

By B Upton, J Mitchell

The use of hydro scaling and in-cycle shotcrete to replace conventional jumbo scaling, mesh and bolting as the primary method of ground control for run of mine development has been investigated through extensive trials at the Waroonga mine, Agnew Gold Mining Company.These trials have progressed from investigating the productivity aspects of the method through to a three month mine-wide trial, which may yet lead to the adoption of this potentially best practice ground control technique at Agnew.Ov erseas trials and research have shown that hydro scaling results in a significant improvement in the shotcrete-rock bond strength. Good adhesive bond strength ensures that the shear strength of the shotcrete layer rather than itÆs flexural or tensile strength is fully mobilised as rock mass reinforcement.This maximises shotcretes ground reinforcement capability and it is suggested that a bolt-less fibrecrete support design is feasible using the hydro scaling technique.

Jan 1, 2005

Project approvals are the key mechanism to balance the environmental, social and economic aspects of a project. The assessment approaches vary significantly between states, with some having a strong emphasis on social, economic and environment, while others focus primarily on the environmental issues. There are a number of approaches which proponents and governments should consider which not only deliver better project outcomes, but can save proponents time and resources in delivering the project.   These approaches are not new but are often poorly implemented. This paper considers a number of these approaches and outlines the benefits they bring.

Jun 1, 2010

By K B. Quast

Changes in feed size distribution can have significant effects in rod mill grinding. The product sizing resulting from wet batch milling of a tin ore showed little influence on fines production after truncating the feed at either the coarse or fine end. The addition of fine material caused a less amount of fines to be produced and a possible increase in grinding at coarse sizes, although this is complicated by the changing feed size distribution. The changes in feed size distribution caused no tendency for preferential grinding of the cassiterite.

Jan 1, 1998

By R Wilson, S Luke, R Williams, B Freeburn

"In 2010, two McLanahan RSS14×50 scrubber screens were installed at Fortescue Metals Group’s (Fortescue) Christmas Creek site. By 2015, the trommel (screen) section had effectively reached the end of their serviceable life. This was determined by regular measurement of structural components over the previous 18 months that tracked wear life. At the same time, numerous trials and optimisations had taken place on screen panel design and material composition. During 2015, a new set of trommels were designed, manufactured and installed that incorporated many new features: increased open area to facilitate high throughput, improved wear protection for structural members, simplified trommel panels and realigned discharge ports to reduce wear on exit. Numerous other upgrades have taken place on the drive system, feed chutes, liner and weir configurations and park brake, to name a few. This paper will highlight how regular measurement drove design changes and how the site and the original equipment manufacturer (OEM) managed a replacement program that has delivered improved performance.Citation:Wilson, R, Luke, S, Freeburn, B and Williams, R, 2016. Regular Measurement Defines Upgrades on Scrubber Screens, in Proceedings 13th AusIMM Mill Operators’ Conference 2016, pp 285–290 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Oct 10, 2016

By Green A. D M

The establishment of the Imperial Smelting Furnace at Sulphide Coporation Pty. Limited for the smelting of zinc and lead made it necessary to design and install sintering capacity to produce approximately 500 t.p.d. of zinc-lead sinter. The updraught sintering process installed is a recent development and the plant was designed with adequate flexibility and equipment to enable operating staff to investigate the process and achieve maximum production under optimum operating conditions.Sulphur dioxide gases from the sinter machine are passed to a contact acid plant for the manufacture of sulphuric acid.

Jan 1, 1964

By E S. Bernard

Toughness testing of fibre reinforced concrete (FRC) at 28 days age is typically undertaken as part of quality control for the many applications where fibres are used in concrete, including shotcrete, tunnel segments, and cast-in-place tunnel linings. The performance achieved at 28 days is usually assumed to be retained with increasing age. However, as the average strength grade of concrete used in most tunnelling applications, including tunnel segments, has steadily increased over the last 20 years, this assumption is becoming increasingly unviable. This is because for some types of fibre the mode of post-crack fibre behaviour depends on the strength of the concrete and can change from a desirable high-energy pull-out mode to a low-energy rupture mode as the strength and age of concrete increases. This paper describes a series of trials performed over two years in which the American Society for Testing and Materials (ASTM) C1609/C1609M beam tests were used to assess the performance of FRC reinforced with two widely used brands of steel and macro-synthetic fibre. The hooked-end steel fibres used for half the beams exhibited a dramatic fall in performance beyond 56 days age as the mode of failure changed from pull-out to rupture. The other fibre did not exhibit a fall in performance with age. This phenomenon highlights the need to quantify performance of FRC at much later ages when long-term performance is required, for example, to resist seismic events or changes in ground stress due to nearby excavations. As an alternative, a reduction factor may be applied to the performance of FRC mixes for which evidence of satisfactory long-term performance is not?available.CITATION:Bernard, E S, 2014. Age-dependent changes in post-cracking performance of fibre-reinforced concrete for tunnel?segments, in Proceedings 15th Australasian Tunnelling Conference 2014, pp 229–236 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By C Taylor, E Retz

Sequential Gaussian conditional simulation of wide-spaced exploration data has been completed in order to optimise a drilling grid at Fortescue’s Eliwana deposit. The aim of this drill grid is to improve the confidence in the Inferred Mineral Resource. A mineralised domain within the Joffre Member of the Brockman Iron Formation was selected to be tested as it makes up a large proportion of the Inferred Mineral Resource and is drilled at a reasonable spacing.One hundred realisations of Fe, SiO2 and Al2O3 grades were completed in the domain. Three realisations were selected for each analyte to represent the range of equiprobable values and a further realisation was selected to represent the truth data set. These realisations were used to flag theoretical drill holes on varying spacings and patterns. The theoretical drill holes were used to estimate into block models using ordinary kriging.These estimates were analysed and the accuracy and precision of each drill spacing was assessed. It was concluded that the greatest improvement in estimation results was noted at either a 100 m × 50 m or 50 m × 50 m spacing.CITATION:Taylor, C and Retz, E, 2015. How much do we need to drill?, in Proceedings Iron Ore 2015, pp 491–500 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 13, 2015

By D Craw, C Smith, C Rufaut

Oceana Gold (NZ) LtdÆs, Macraes Gold Operation currently has two tailings impoundments, the larger of which covers approximately 75 ha. When an impoundment is temporarily out of use, the surface dries and dust can be blown from the surface to the surrounding area. At present water spraying is used to stabilise the surface, but this is not ideal as Macraes mine can experience water shortages during the summer. This paper examines an alternative method of surface stabilisation using vegetation as a ground cover. The tailings have a low natural fertility, so it is important to determine what will actually grow in the tailings, and whether amendments are necessary. Also important is the effect of the amendments on arsenic mobility in the tailings as the schist rock at Macraes has naturally elevated levels of arsenic. Three plants species, rye corn, barley, and lupin, were grown in metre-deep lysimeters at Macraes mine site. The plants were grown in unaltered tailings, and tailings with one of two amendments added: Bioboost (an organic fertiliser containing biosolids), and superphosphate fertiliser. The leachate from each lysimeter was collected and analysed monthly to determine the extent of arsenic mobility. In addition, laboratory experiments were set up to determine arsenic mobility in tailings with amendments at the centimetre scale.   All plants grew best with the fertiliser amendment, with rye corn growing the best overall. Plants growing in unaltered tailings either barely survived (rye corn, barley) or died (lupin). Plants in the Bioboost amended tailings grew only slightly better than in the unamended tailings. Laboratory experiments indicate that the addition of phosphate fertiliser greatly increases arsenic leaching at the centimetre scale when compared to unamended tailings. The addition of Bioboost only marginally increases arsenic leaching, compared to unamended tailings. This trend has not been repeated in the lysimeter trials on the metre scale over four months. Current results suggest that of the plant types trialed and amendments used, rye corn with superphosphate is the most practical short-term tailings stabilisation method at Macraes.

Jan 1, 2004

The New Zealand Minerals Industry is small but growing. Over the next 10 years it will be facing stiff international competition for skills to support this growth, particularly from Australia who are forecasting that a further 70 000 people will be employed by 2015.   The value of commodities mined and quarried in NZ continues to increase; and the value of coal, metals and industrial minerals production reached $1.505 billion in 2006, an increase of 15 per cent on 2005. Production increases will continue à. Latest Crown Minerals statistics show that national prospecting and exploration expenditure rose to $29.9 million in the year ended March 31 2006 û an increase of 46 per cent from the $20.4 million spent in the March 2005 year. The equivalent 2001 year expenditure was only $2.48 million.   The industry already experiences difficulty in recruiting the people it needs with ongoing demand for skilled underground miners, trades people, and mining professionals. This discussion paper will outline the national context with regard to labour, skills and training. It will suggest options and provide an opportunity for conference participants to discuss the way forward.

Jan 1, 2007

Attempts to rationalise the geological environment of nickel sulphide deposits associated with Archaean ultrabasic rocks has produced much speculation as to the origin of the sulphides and the relative importance of geochemical, mineralogical, textural and structural characteristics of the host rocks. From an economic viewpoint the object of such work is to establish geological criteria which can be used as an exploration guide. Exploration procedure for nickel sulphide mineralisation of the 'Kambalda type' (Hudson, 1972), which occurs at or near the basal contact of Archaean ultramafic flow units and lenses consisted of geological mapping, surface prospecting with soil sampling and rock geochemistry.

Jan 1, 1987

ThePike River coal field is located between 700 and 1000 m above sea level on the West Coast of the South Island. The area contains a resource of some 60 million tonnes of coal in a single coal seam and is part of the Paparoa mountain range that receives between 6.0 and 6.5 m of rainfall per annum. The area has been isolated and has received no on the coal plateau but has been extensively logged in the lower 3.5 km of Pike Stream. The PRCC development proposal recognises this and calls for an environmentally benign development that includes underground development of this resource. The coalfield abuts and is partly overlain by the Paparoa National Park. The underground development will enable a number of environmental goals to be readily achieved: it will be out of sight of the public,it will not impact the national park,noise will be mostly absent,there will be absolute minimal disturbance to the land surface,coal will be transported from the mine to a dewatering complex on PRCC land in a slurry pipeline thus obviating the need for trucks and noise in Pike Stream valley,all water draining from the mine will be collected, treated if required to consent standards and discharged from a single point,the road into the area will allow for an effective predator control programme to be undertaken enhancing native bird life,an environment suitable for the reintroduction of Whio (Blue Duck) will be created, andthe net effect of the mine development on the environment will be positive.

Jan 1, 2003

The demand for gallium has increased significantly over the last few decades due to the expanding use of Ga compounds in the electronics industry. Because it is widely dispersed and rarely found naturally in concentrations greater than 0.1%, Ga is expensive (approximately US$500/kg) and difficult to produce in large quantities.   A previous study of metals in geothermal systems reported significant quantities of Ga present in the muds on the northeast margin of Lake Rotokawa, an acidic lake associated with a high-temperature geothermal field situated in the Taupo Volcanic Zone of New Zealand. Similar muds are present in many other geothermal fields in the zone, suggesting that geothermal muds could be a commercial source ofGa.

Jan 1, 1994

By P Corbett, P Sheffield

Springvale Mine is an underground coal mine in the western coalfield of New South Wales which utilises retreat longwall mining technique. The mine encountered significant gateroad floor heave issues during retreat of LW415. Floor heave has subsequently impeded longwall advance as well as longwall bolt up and recovery to some extent during the extraction of the next five longwalls. Floor heave at Springvale Mine develops throughout the lifecycle of the mine roadways, and is most prevalent in longwall gateroads. Floor heave has been measured as early as 2 weeks after roadway development and continues to develop through the post-development phase, with a rapid increase in close proximity to the longwall face. This paper presents a case study of the evolution of understanding of floor heave behaviour at Springvale Mine based on geotechnical characterisation, an intensive convergence monitoring program (roof and floor movement) and spatial correlation of monitored locations with longwall face position. The analysis considers previously known factors contributing to floor heave including mining depth, geological and physical properties of the rock mass and mine design geometry. Investigation results indicate a strong correlation between floor heave magnitude and roof dilation magnitude, geophysically inferred faulting in underlying strata, areas of localised stress concentration and mine roadway dimensions. This paper also discusses the predictive model which was developed as a result of the study, which is now the basis of the floor heave removal program used to manage roadway convergence at the mine. Floor heave monitoring, prediction and management strategies (including floor reinforcement and removal) are also discussed. CITATION:Sheffield, P and Corbett, P, 2018. Managing floor heave in an underground longwall coal mine, in Proceedings The Fourth Australasian Ground Control in Mining Conference (AusRock), pp 78–94 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 30, 2018