Search Documents

ALTHOUGH discovered as long ago as 1817, by Strohmeyer, the use of cadmium did not become in anyway general for nearly a century. Its properties, although well known, did not recommend it to users of metals generally, and it was, on the whole, regarded more in the light of a nuisance to zinc producers than anything else. Its real value was not appreciated until both the United States of America and Germany, who are entirely dependent on outside sources for their supplies of tin, were faced with the unpleasant fact that their tin stocks were being rapidly depleted, with practically no prospect of having them replenished. This resulted in serious efforts being made in the UnIted States of America to conserve what tin was available, and, as a consequence, several metals were tried in the hope that they would prove satisfactory substitutes for tin. Among these was cadmium, and it was found that cadmium could replace tin in a manner sufficiently satisfactory to permit of its use in many directions where tin had been used before.It is on this ability of cadmium to replace tin that its use became in any way general at first; but since then new avenues of development have been opened up in which its physical and chemical properties are proving their value. It is highly probable that its use will extend very considerably as time goes on. OCCURRENCE OF CADMIUM.There are several cadmium minerals known, but none of them occur in profitable quantities as ores. The cadmium of commerce is derived almost entirely from zinc minerals and ores in which it is almost invariably present in proportions which are usually very small. Cadmium behaves metallurgically almost the same as zinc, and hence constitutes a fraction of 1% of almost all spelter.

Jan 1, 1923

By K Zic, P Pickering, P Fraser

Water is a defining feature of the Pilbara. Its management was and remains vital for the pastoral industry which European settlers established when they first came to the Pilbara, and for the mining industry which now dominates economic activity in the Pilbara. Water availability in the Pilbara is, however, problematic. Severe droughts and major floods can occur at close intervals. In response to this uncertainty, the Department of Water undertook a Prefeasibility Study to determine, at a high level, the water requirements and opportunities in the Pilbara region. This paper reports on the outcomes of this study and the water integration opportunities in the region, identifying the sources of water supply and offers possible options for managing this water sustainably for the present and future demand. A range of supply opportunities is reviewed including: dewatering from mining operations, surface water, and desalination. All opportunities were subject to order of magnitude costing, including capital, whole of life and retail unit pricing with preferred options receiving further interrogation through triple bottom line (TBL) analysis to prioritise solutions. Options were also subject to intangible quantification (IQ) including benefits from the reduction of carbon emissions to ensure that the preferred option is based on factors other than just the least cost. Demand analysis was undertaken to identify current and future requirements and were assessed through review and integration of regional and sub regional master plans and consultation with mining, agriculture, industry and the community. The paper concludes that the viability of a Pilbara integrated water supply scheme depends on the development of a financial mechanism involving both government and industry participation models. The agreed scheme formed the basis of a submission to Infrastructure Australia for funding assistance.

Jan 1, 2009

We can look at the water treatment and management strategies at some recently commissioned mines and minerals processing sites to see the likely future of water in mining. The future of water in mining will be based on a holistic approach to understanding the site water balance, appropriate treatment, reuse where possible, and environmentally managed discharge where required. This paper describes advanced and innovative water treatment and reuse processes as used by mines and mineral processing operations from around the world. Underground mining can often require dewatering to prevent groundwater seeping into and flooding the mine workings. Mining and processing often accumulates wastewaters in a tailings dam. The mine water can contain contaminants such as dissolved salts, iron, arsenic, manganese, heavy metals and acidic and odorous sulfates. On-site reuse, environmental discharge requirements, as well as community needs for water, drive mine operators to consider the most appropriate water treatment process. Mining water treatment for the future is described using case studies of innovative processes. The case studies include treatment of mine dewatering water for beneficial application from Australian mines, Ballarat Goldfields and Bendigo mining, treatment of produced water from oil and gas projects, and treatment for arsenic removal of tailings water from mining and processing at Goldcorp mines in Canada. Advanced and innovative processes including membrane filtration, reverse osmosis at extreme conditions, advanced biological treatment and water management are all part of these case studies. This paper uses real case studies of advanced and innovative mine water treatment processes to explain and examine the technology and the reasons for designing specific processes. The focus is on innovative processes that may be more widely used in future mining û where the water is used for sustainable environmental discharge or treatment to a quality that can be beneficially used by the mine or the local community.

Jan 1, 2008

The desire for minimising impacts of mining activities on the environment, and in particular, water resources; is usually tempered by the costs and practicalities of implementing æbest practiceÆ measures. This paper briefly discusses the theoretical and practical options for water management for typical mines and quarries in a range of environments to assess if adverse impacts can be completely eliminated or at least be perceived as doing so. The regulatory requirements for water resources management are usually an essential part of mine planning and operations that can be a primary focus for all stakeholders. As such they can distract attention from implementing best practice in water management for the benefit of the environment and the community for altruistic reasons that have a long-term benefit for the mining industry as a whole. Cost-effective options for supply, demand and quality management of water that comply with basic regulatory requirements are readily available. Making a mine æinvisibleÆ in a practical sense, in terms of impacts on water resources would require eliminating potentially contaminated discharges, minimising demand, maximising reuse and recycling and putting back a healthy proportion of the clean water that is taken out of the natural environment for use in mine operations. This may sound simple enough and there are many well-known standard approaches that are usually applied. But which are the most effective, and who benefits? New approaches to water management are becoming more affordable and can benefit the bottom line as well as the environment, but can they make a mine ædisappearÆ? The perception of whether a mine is æinvisibleÆ in terms of its impacts on water resources is as important as the actions taken to try to achieve such an objective. The viewpoints and thresholds of perceptions of the different stakeholders are therefore relevant to how ævisibleÆ mining activities become.

Jan 1, 2006

By O Pasca, B Hogg

Consistent slag blow end point detection remains one of the challenges in the Peirce-Smith converters at Mount Isa MinesÆ Copper Smelter. Under blowing results in foaming on copper blow and carry forward of oxide skims to the anode furnace. Over blowing results in high copper losses to the slag. Both present safety issues and contribute to lower copper production. The end points of the slag making phases are assessed by inspection of a bar sample. A bar sample is a thin accretion layer that adheres to a steel bar when it is inserted into the tuyere while the converter is blowing. This method is biased and subjective, so there is heavy reliance on operator experience. The Semtech Optical Process Control (OPC) system was installed in early 2002 for converter slag blow end point detection. Initial plant trials did not improve all aspects of converter operations, and uptake by operators was poor, so the system was not used. In early 2005, the Semtech OPC system was re-visited and another short trial was conducted to evaluate the permanent use of the system for slag and copper blow end point detection. During this trial, the Semtech OPC method was found to be superior to bar sampling for slag blow end point detection. The implementation and refurbishment of the Semtech OPC system has resulted in plant improvements and given a better insight into converter operation during blowing. Oxide skim generation carried forward to the anode furnace has been shown to decrease with increasing compliance with Semtech OPC. Some of the expected improvements to converter operation were not found to be significant. Semtech OPC is now well received and utilised by converter operators. Individual paper available only. Not included in book or CD ROM Proceedings.

Jan 1, 2005

According to the Australian Bureau of Statistics, fatalities from road transport accidents represented an average of over 97 per cent of all transport related accidents between 1997 and 2002. With increasing traffic density, tunnels are becoming a more viable means of providing alternative travel routes to ease areas of congestion in the road transport network. However, unlike open road conditions, a fire incident in the confined space of a tunnel environment may impact upon many users that are remote from the incident location. In this context, designing for an appropriate level of safety in tunnels is therefore an important consideration for achieving consistency in the life safety measures for users of the road transport network. Unfortunately, like fire safety engineering design for buildings, there are presently no clear measures in the design processes to assess the adequacy of the design in terms of attaining the level of safety implicated in the design objectives. This is partly due to the indeterminate nature in which the design objective or the level of performance measure is stated û the intent of the objective is relatively clear but the measure of it is not. Another reason is the lack of a standardised procedure for determining the critical design variables affecting life safety. This is important to ascertain consistency in the use or adoption of the important parameters for design. This paper looks at the processes involved in the fire engineering design of road tunnels that are currently practised. A review of the design processes for fire safety in road tunnels is provided, which includes the range of fire scenarios in a tunnel environment, the traffic flow and composition, the relevant fire protection systems, the ventilation and smoke control system, the egress provisions and the benefits of incorporating fire brigade intervention. A simplified risk assessment approach is developed for a typical road tunnel to assess and evaluate the impact of a range of design parameters on life safety. Using a sensitivity technique, the important variables are then identified and means of reducing design variations associated with them are recommended. The technique may be further refined for use in the development of codes or guidelines in order to develop a suitable means of deriving more consistent design values, and hence achieve better consistency in the overall level of safety in the design.

Jan 1, 2008

By J J. Cilliers, K Hadler

The potential of air rate profiling to significantly improve the flotation performance of a bank of cells has been shown by numerous studies. To date many profiles have been evaluated; balanced, increasing, decreasing and combinations of these. An increasing air rate profile, where the air rates are increased proportionally to each cell down the bank, has been typically found to yield improved flotation performance compared to other profiles. Air rate profiling has two distinct components; determining the correct total air rate for the bank, and determining the correct distribution of that air. This can be done simultaneously by finding the optimal air rate to each cell in the bank in turn through air recovery optimisation. Air recovery is the fraction of the inlet air which overflows the weir of a cell as unburst bubbles. The peak in air recovery (PAR) is a robust measurement of optimal performance for the operating conditions in the cell, and sets the PAR air rate. In this study, plant trials of different air rate profiles and profiling based on PAR, were evaluated. The total air rates to the bank for all profiles tested were approximately equal, allowing direct comparison. The highest cumulative mineral recovery was achieved by operating at the PAR air rates for each cell down the bank. Different distributions of the same total air rate to the bank gave the same cumulative upgrade ratio, but lower cumulative recoveries. In this work the upgrade ratio is defined as the ratio of the concentrate grade to the feed grade. The increase in cumulative mineral recovery, at the same upgrade ratio, in this study was greater than 33 per cent. Air recovery based optimisation of air rates to banks of cells significantly improves flotation performance as it simultaneously determines the optimal air rate to the bank, and the optimal distribution of that air.

Jan 1, 2009

By P K. Seccombe

Sulfur isotope data are available for 18 low-sulfide orogenic gold systems hosted by the Lachlan Orogen in eastern New South Wales including those in the northern Hill End Trough (Hargraves, Hill End, Napoleon Reefs, Sofala-Wattle Flat, Stuart Town, Windeyer) and adjacent areas (Bodangora, Lucknow, Springfield), the Gilmore Fault Zone (Adelong, Sebastopol) and those in the Parkes district (Calarie, London-Victoria, Wyoming One-Myall United). Other systems for which data are available include Mongarlowe, Murrumbateman, McMahons Reef and Yalgogrin. The d34S data for many of the larger deposits including Adelong, Bodangora, Calarie, Hargraves, Hill End London-Victoria, Lucknow, Sebastopol, Sofala-Wattle Flat, Stuart Town and Windeyer (Group 1) are all very similar and have average d34S values close to zero per mil. Near 0ë d34S signatures imply that sulfur was sourced from a magmatic reservoir. Furthermore, the large Wyoming One deposit has d34S values significantly below 0ë with the data implying that sulfur was sourced from a fractionated magmatic reservoir. Group 2 deposits include those at Mongarlowe, Murrumbateman, Napoleon Reefs, McMahons Reef and Springfield . These deposits have average d34S values significantly above 0ë. With the exception of Springfield where sulfur was probably sourced from the Hill End Trough, Group 2 deposits are an order of magnitude smaller than Group 1 deposits. The results suggest that many of the larger orogenic-related gold deposits hosted by the Lachlan Orogen in eastern New South Wales derived sulfur and gold as a result of leaching and recycling from a magmatic reservoir. Alternatively, there may have been direct mantle-derived input; however, this is considered unlikely on geological grounds. An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation.

Jan 1, 2008

By Armstrong A

Queensland is Australia's second largest mining state with world-class deposits of coal, base metals, bauxite and magnesite. The total value of Queensland's mining production is about $5 billion per annum, and coal accounts for around 55 per cent of that total. The environmental issues which arise as part of management and regulation of the industry are resolved within the EMOS process. The Environmental Management Overview Strategy is the cornerstone of the policy 'Environmental Management for Mining in Queensland' developed jointly by the Queensland Department of Minerals and Energy and the mining industry. The Gordonstone Coal Mine is the largest underground mine to gain approval under the new policy. Accordingly, Gordonstone has a well planned environmental management program which takes into account site-specific factors and provides for continuous compliance with the provisions of the Mineral Resources Act in a self-regulatory context.

Jan 1, 1994

By P Cameron

The Julius Kruttschnitt Mineral Research Centre (JKMRC) has recently commercialised a variety of new products for the mining industry through its commercial division (JKTech). Although the products cover a wide variety of niche applications, a common thread runs through the Research, Development and Commercialisation (RD and C) process: they have emerged from industry sponsored projects. The development history of JigScan (a control system for the mineral-processing jig) is a good example of how this RD and C process works in practice. It involves building mutually beneficial partnerships between the JKMRC and the mining industry through several incremental projects with one or more industry sponsors. All research projects have objectives to demonstrate but these projects also feature a degree of product development to actively encourage and support the longer-term vision for the mature commercial technology. The process to develop JigScan as a commercial product worked because each incremental project recovered costs, provided an immediate benefit for the sponsor and contributed to the longer-term development objectives of the JKMRC. Integrating development with research need not greatly increase the cost of research objectives generally provides a more robust research outcome for the sponsor and greatly reduces the overall development risk. Successful projects often feature industry mentors actively participating in the RD and C process. Additional funding from government appears to be easier to obtain when such close partnerships with industry are apparent. Finally, the business structure of the JKMRC within the University of Queensland ensures that commercial outcomes, developed within the contractual arrangements of the underlying RD and C projects, are used to benefit and support further RD and C with the mining industry. This paper tells the story of the development and commercialisation of JigScan, and draws conclusions about this kind of RD and C model.

Jan 1, 2000

The current talk of risk management as a separate discipline and management function is like earlier imposition of Quality Control (QC) as an overlay on shoddy production management. Risk management is vital, but is integral in the way we marshal our staff, make decisions, then monitor and review and make crucial secondary decisions. New leaders must not assume that hiring experts ensures good decisions. It is only the essential step one. The worst company I worked for had more expertise than the best. The difference was in culture and decision-making processes. Failed feasibility studies, persistent technical factions in a company that cancel each other, heaps of expert consultant reports piled up like a dump of bricks, even great but half-managers in large and small companies cancelling expertise at their disposal, are the worst manifestations. Just daily foul-ups are common even amongst smart people. We miners have made a great industry but are content to drift far below excellence, even where that word is bandied around. All the management literature and management courses will not right the situation û we have been sending budding managers to this good stuff for two generations and the effects are worthwhile but marginal. A few key ideals, ideas and slogans are not the way. These make inspiring books that work about as long as the Christmas spirit does in the real world. What we need is a coachesÆ manual and a standard of the essential package of culture and work processes that make excellence possible and show how to maintain it long term. It has not been written until now because most managers want to remain dilettante amateur managers without the discipline that creates excellence. First, believe excellence is possible and worth any effort; then commit to it.

Jan 1, 2007

The paper deals with the taking of soundings in connection with coal mining operations under part of the Pacific Ocean adjoining John Darling Colliery.INTRODUCTIONIn the early days of mining in the Newcastle District there did not appear to be any definite law specifying the limits to which mine workings, other than certain borings, could extend under tidal waters.As time went on, a figure of 120 ft. was fixed as the minimum thickness of strata between the roof of the seam and the sea bottom; beyond this mining operations are disallowed. The laws relating to working coal under tidal waters are as follow:-The minimum width of pillars to be left shall be eight (8) yards and the maximum width of bords or other excavations shall be six (6) yards, but the lessee may at his discretion increase the minimum width of the pillars or decrease the maximum width of the bordsor other excavations so as to increase the general safety.The eight (8) yard pillars shall be left unwrought.In on-road of every pair of Winning-off or leading headings, a bore shall be kept going ten (10) feet in advance for the purpose of foretelling the presence of any fissure, wash-out, open joint, fault, dyke, or otherwise, and all winning-off headings shall be driven atleast one hundred (100) yards in advance of the working bords.The most accurate and trustworthy information shall be obtained by the lessee not only' of the depth and character of the ocean bed, river, lake, or estuary deposit, but also of the strata overlying the coal seam.When working under the ocean, strata shall be bored through and proved a minimum thickness of thirty (30) feet at the face of the leading headings or levels immediately such headings or levels are under the ocean, and...

Jan 1, 1947

The recent trend of installing flotation cells with volumes as large as 200 m3 in concentrators is driven mainly by economic considerations such as lower capital, operating and maintenance costs. Despite the economic advantages, the metallurgical benefits from these large cells have not yet been fully realised by the industry. This is mainly due to the lack of understanding of cell operation, viz cell mixing and hydrodynamics, gas dispersion and froth transportation behaviour in large cells. There is still no rational basis for selecting optimum cell operating conditions and down-the-bank operating profiles. The relationship between cell operating conditions and metallurgy is not well established. This has resulted in poor utilisation of cell capacity in many operations. The present trend of installation of fewer cells in a bank requires each cell to be operated very efficiently. Optimisation of cell operation provides an opportunity for significant metallurgical improvements in a flotation circuit with minimal capital expenditure. Extensive work on optimising of cell performance has been carried out at various Teck Cominco operations in Canada, Peru and USA. Three different levels were involved in this work. The first level was aimed at identification of cell operating conditions for optimum mixing and hydrodynamics, gas dispersion, entrainment and froth flow behaviour in individual cells. The objective of the second level was to identify the optimum bank operating profile for cells down the bank in a circuit. The third level then focused on controlling these cell operating conditions and bank operating profiles for tighter control of concentrate grade and recovery for optimum bank metallurgy. This paper presents some of the major findings at all three levels and demonstrates the importance of each level in optimising the performance of flotation banks installed with large cells.

Jan 1, 2005

By W Ilahi

Underground metalliferous mining methods often result in the formation of vertical openings to facilitate the extraction of orebodies. These development and production techniques can result in the creation of vertical open voids, which include stopes, orepasses, ventilation raises and other excavations. There are risks associated with the use of mobile plant in the vicinity of these voids, especially during backfilling and when bunds are constructed at the edge of a stope or void. These voids can present unacceptable risks if not adequately managed.

May 5, 2022

By B Goebel, G Baker

The Australian Magnesium Corporation Limited (AMC) is constructing the worldÆs largest magnesium metal plant at Stanwell, 24 km west of Rockhampton in Central Queensland. The $1.3 billion, 97 000 tonne per year plant is scheduled to commence production in mid-2004. It will produce magnesium from magnesite using the innovative, locally developed AM Process Technology which enables magnesium to be produced at internationally competitive costs. The technology will enable the plant to have the lowest environmental impact of all the available magnesium production processes. The project will meet current world-best-practice environmental and emission standards while on a life cycle analysis, magnesium produced by the Stanwell plant will result in net reduction in global greenhouse gas emissions. Magnesium is the lightest of the structural metals. Its high strength to weight ratio and ease of casting and machinability makes it particularly suitable for the manufacture of light weight automotive components. Reducing the weight of motor vehicles through the use of light weight materials such as magnesium is the current primary means adopted by the automobile manufacturing industry to improve motor vehicle fuel efficiency and the lowering of emissions of greenhouse gases. The Australian Magnesium or AM process has been developed over the past decade by AMC in conjunction with the CSIRO to produce magnesium from magnesite mined at AMCÆs Kunwarara deposit. Over $200 million has been spent developing the AM process, designing, building and operating a demonstration plant at Gladstone and to complete an environmental impact statement and receive environmental approvals as well as funding for the commercial Stanwell Project. The paper outlines the development of the AM process technology, the operations of the Gladstone demonstration plant confirming the process technology, its operating costs and environmental performance. The paper covers the particular attention that was given to minimising the production of CHCÆs, the development of new cover gases for molten magnesium, the minimising of emissions of greenhouse gases and the life cycle analysis of magnesium as a replacement for steel and heavier metals in motor vehicles which confirmed its use resulted in a net reduction in global greenhouse gas emissions. The project received both Commonwealth and Queensland Government environmental approvals by August 2000.

Jan 1, 2002

By R Knight

"In project evaluation there are two matters of keen interest to non-executive directors: the process by which an investment recommendation is reached, as well as the investment itself, as presented. It is sometimes mistakenly believed that Boards of directors are interested only in the result. That is not so. The process by which project evaluations are derived and socialised with the Board is as important as the result, sometimes more so.Setting aside the gloomy predictions of the doomsayers and looking through short-term volatility in supply and demand, the overall availability of mineral resources more often than not exceeds demand. There are in reality more development projects in prospect at any one time than are needed to meet the market. Only the fittest will prosper, although some others may survive.Optimism springs eternal in the mining industry and every project promoter, executive or entrepreneur has a convincing project development case. Some will create value for shareholders, but the historical evidence suggests that many will fail to meet the expectations set in their evaluation.Boards of directors make the final decision to invest, or not, in a new mine. Knowledge is power, and on that basis the balance of power favours management. Management has the facts (or in some cases, what passes for fact) and the passion to invest. The non-executives have the power of approval – yes or no – but before making a decision directors must demonstrate due diligence, the essential precursor to project approval.Management has a vital part to play in facilitating that due diligence process and in encouraging the independent thought processes of the Board. A closed approach by management fosters a negative, risk-averse attitude on the part of the Board. One that encourages an understanding of the rigour of the project evaluation process and the robustness of the result will allow directors to understand better the implications of their decision.CITATION:Knight, R, 2016. Project evaluation – a non-executive director’s perspective, in Proceedings Project Evaluation 2016, pp 11–19 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 8, 2016

S. A. Tomich (Consulting Geologist, Perth) : I would like to commend Mr. Haycraft on his presentation on the economic geology of the North End of Kalgoorlie. This is an intriguing area which is in the Kalgoorlie field but not of it, inasmuch as it is separated spatially from the main Golden Mile by the Golden Pike Fault. Mr. Haycraft has stressed the differences-the mineralogical and structural differences of economic significance between the two areas.I would like to ask whether he is satisfied that the lithological sequence in the North End is the duplicate of that in the main Golden Mile area irrespective of the postulated effects of erosion, and more specifically whether there is any chance that the quartz-dolerite-greenstone of the North End may be in any way dissimilar from the quartz-dolerite-greenstoneof the Golden Mile which is tellurude bearing.J. A. Haycraft: In relating the quartz-dolerite in the Hannan's North-Mount Charlotte area back to the Golden Mile, we find some quite close similarities. Although the rocks are similar they are not necessarily one and the same.At Mount Charlotte we have three varieties of dolerite- a coarse-grained gabbroic dolerite on the eastern side of the orebody, the host rock medium grained and on the western side, a fine grained dolerite. Further west we have an amphibolitic variety of quartz dolerite.Recent drilling south of the Golden Pike fault on the Enterprise No. 20 level had indicated a remarkably similar sequence of rocks. We drilled west through a wide section of medium grained rocks into a fine grained rock and then into amphibolitic quartz dolerite before intersecting the Golden Pike fault. Williamstown dolerite was located west...

Jan 1, 1965

Solid Energy New Zealand (SENZ) uses a 20+ year period for integrated planning of all its business activities. It has an ongoing program of coal resource assessment to optimise future mines within this 20 year period, using a six step resource and mine planning process. Desktop review and conceptual study at preliminary Levels 1 and 2 are based on general coal resource information. Further coal resource investigations are carried out for the more detailed evaluations in secondary assessment, prefeasibility study, feasibility study and detailed engineering from Levels 3 to 6. At Levels 1 and 2, completing conceptual planning, including preliminary resource evaluation and economic appraisal to the target cost uncertainty level of ¦33 per cent, is challenging in New ZealandÆs highly variable geological and geographical conditions. Where coal deposit geometries are relatively simple, approximate methods for determining pit limits using overburden strip ratios, seam thickness, physical boundaries, and quality cut-offs may be sufficient. Many New Zealand coalfields are however complicated structurally, with multiple seams and extensive folding and faulting. Coal seams are characterised by variable dip, thickness, and quality over relatively short distances. In the North IslandÆs Waikato coalfields, coal is typically overlain by weak sediments and clay rich strata that necessitate very flat cut and fill slope angles. The proximity of these deposits to major infrastructure (including towns, highways and rail lines), significant environmental features such as the Waikato river and lakes, and valuable dairy farmland, add further complexity. Traditional preliminary mine planning techniques applied in these conditions are insufficient. Pit optimisation software, widely used in the metalliferous mining industry since the 1980s, offers the ability to analyse many more specific factors affecting pit limits, mine layouts, and economics, with more rigour and for a much larger number of scenarios, than traditional methods allow. SENZ therefore decided to adapt and use æWhittleÆ pit optimisation software for Level 2 analysis of several Waikato opencast prospects. This paper describes this work.

Jan 1, 2005

By P Louden, C Rothnie, G Showers

Tiwest employs several methods to assess the quality of heavy mineral concentrates in ore and process samples. Mineralogy is determined using a method called MA98, developed in conjunction with JKMRC over the last three years (Zhang and Whiten, 2001). A range of other techniques are also used to characterise ore, heavy mineral concentrates and mineral products. MA98 is the culmination of efforts since 1989 to determine mineralogy from chemical analysis without recourse to heavy liquid fractionation, which has traditionally been used to discriminate between light-heavy , zircon, rutile and leucoxene. The major advance with MA98 is the use of statistical mass balancing for all chemical species, as opposed to reliance on key chemical species for each mineral. Three magnetic fractions are analysed by X-ray fluorescence spectrometry, with a minerals balance performed for each. Heavy mineral concentrates processed by this method include drill samples, process samples from the wet concentrators and Dry Mill, and mineral products. TBE can be avoided for higher heavy mineral grade samples since quartz is determined from SiO2 balance. In this sense the method is sufficiently universal and robust to cope with a wide range of sample types and compositions. The MA98 algorithm provides abundant information in addition to mineralogy, including TiO2 and Fe2O3 grades of ilmenite and leucoxene, and concentrations of weakly magnetic zircon and kyanite. Information such as this is invaluable in tracking different minerals through the processing plants. Other ore assessment procedures used by Tiwest provide for modelling of orebodies by mineral sizings, Fe in zircon, and FeO and U+Th in ilmenite. Microscopy is used to provide important qualitative information such as grain shape, surface staining and degree of cementing. These quality measurements are included with mineralogy in geological ore models and are available for mine scheduling. In using the above methods to characterise heavy mineral concentrates, Tiwest is better placed to predict and monitor plant performance and product quality from any ore zone.

Jan 1, 2001

Agitation leaching data has generally not been analysed to extract the maximum amount of information that is available. Analysis of heap leaching systems has been developing over the last five years to include the underlying rate determining process. This has been found to be diffusion control for all copper leaching; irrespective of whether they are oxide or sulfide minerals. Extension of the diffusion model has enabled better scale-up protocols to be developed. Acid consumption in copper heap leaching operations has been found to be a first-order chemical controlled system. The analysis of the data is relatively straightforward. However the interpretation and scale-up is not as direct as for agitation leaching. The differences in the residence time distributions (RTDs) are required to properly account for the scale-up between test columns and field. The leaching of oxide copper in agitated systems has also been found to be diffusion controlled. However, there are significant differences in the control mechanisms. Initially the leaching control is the supply of acid to the mineral surface. This is limited by the diffusion through the surface boundary layer and is thus subject to the level of agitation. Higher agitation provides thinner boundary layers and faster diffusion rates. Similarly, higher grade material creates a thicker concentration boundary layer and relatively slower leaching. Acid consumption in agitated leach systems is also a first-order system. However, the interpretation of the RTD is easier from batch testing to continuous multiple CSTR series plant operations. Altering the method of acid delivery can significantly reduce acid consumption rates. Predilution of the acid minimises the local acid concentration near the addition point and can reduce the consumption by up to 50 per cent. Modelling of the combined leach rate(s) and acid consumption rates in agitated systems allows comparison of various leaching strategies and selection of the most appropriate. Similarly, the model allows the identification of economic limits to leach recovery; where the cost of acid consumption is greater than the value of the copper recovered. From this analysis selection of residence times for agitation leaching can be determined. The modelling tools are useful in identifying optimum conditions for the leaching process.

Jan 1, 2005