Search Documents

Present value maximisation studies are a useful aid in enhancing the economic performance of open pit mining operations. Maximising present value helps to reduce the risk of financial failure. Maximisation of present value also means that the capital invested is being used most efficiently. A characteristic step in determining the present value of an open pit mining operation is to set out the sequence in which increments of material (ore of various grades and waste rock) are mined. Traditionally, present value maximisation has been performed by selecting a cut-off grade for each increment so as to maximise the present value of the total operation, by an iterative process using computers. Kenneth F Lane has developed a method and applied it to many mining operations. An alternative method for determining the maximum present value of an open pit mining operation is given. In this method the maximum present value is determined by working backwards from the end of the operation life, progressively asking the question of each increment `what cut-off grade maximises the the present value at the start of mining of that increment?' The method allows calculations to be performed by a `spreadsheet' package. Present value determinations are characteristically performed under constant conditions (eg prices, costs) throughout the operation life. Unfortunately real life circumstances are rarely constant, with the costs of mining inputs rising at variable rates. The prices received for mineral products have been shown to broadly trend downwards with time in real terms. Treatment of such changes in the determination of the maximum present value of an operation is discussed.

Jan 1, 1994

The city of Kalgoorlie-Boulder is located 595 kilometres east of Perth in Western Australia, and has a population of just over 30 000. Western Australia's third largest city lies on one of the richest goldfields in the world, with over 45 million ounce

Jan 1, 1998

By R Milton, D Hake, H Sprague

The North Western Sewer tunnel extends over 11.5 km in the North Western suburbs of Melbourne.The $253 million tunnel project provides a critical link in the Melbourne Sewer Network. The existing sewers fail to service the increasing demands of the growing population of the North West regions of Melbourne. This project will protect the environment and improve the standards of service of the existing system. This paper concentrates on Section three of this project, consisting of the final 4 km of the Contract, three access shafts and a cut and cover section of tunnel.Transfield Tunnelling as Head Contractor constructed the tunnel for Melbourne Water Corporation, with Enetech Streamline, formally Streamline Australia, a trading arm of Melbourne Water acting as Superintendent.Excavation of Section three of this project commenced in September 1994 and project completion is scheduled for October 1998. The tunnel passes below the residential suburb of Essendon, through some of the most challenging ground conditions ever attempted to be tunnelled in Australia.

Jan 1, 1999

It is well known that in most areas of Central Europe it is not difficult to find water - usually at shallow depths - and to recover and use this water. What is much more difficult, however, is to find water sources that offer both sufficient in quantity and qual- ity. Far too often, there are sources that offer abundant quantities but of poor quality or vice versa, i.e. high quality water but insufficient volumes. In the former case where water quality is not adequate - which is more often than not due to anthropogenic factors and only very rarely a result of geogenic effects - the application of treatment techniques can help to turn such water into potable water that is suitable for human con sumption.

Jan 1, 1988

Magneto flotation is a recently developed method aimed at simultaneous utilisation of the magnetic and flotation properties of minerals in separation processes. In this method, magnetic minerals are prevented from reporting to the froth product while non-magnetic minerals are being floated. With suitable ores, this makes it possible to reduce or entirely eliminate the cleaning and scavenging operations that are otherwise necessary in conventional flotation and magnetic separation systems. This paper describes the testing of magneto flotation on a Canadian magnetite ore. The ore sample used in the experimental work contained a total of 32.89 per cent Fe of which 87.60 per cent was magnetic in the form of magnetite. Magnetoflotation yielded, in a single step, a final concentrate assaying 69.10 per cent Fe and with an overall recovery of 84.84 per cent representing a magnetic iron recovery of 96.39 per cent. Comprehensive comparisons were made with conventional magnetic separation and flotation, and it was found that with these methods at least four processing steps were required to achieve results similar to those obtained with single-stage Magnetoflotation.

Jan 1, 1993

This paper provides a financial perspective to the valuation of Australian resource companies and projects. Valuation exercises need, however, to be seen in the broader context of a thorough business appraisal, one that incorporates all disciplines employed in the resources industry. Fine tuning a discount rate or determining a particular capital structure is likely to be less important to valuation than an adequate understanding of industry dynamics and a company's likely performance in future years.

Jan 1, 1989

Silica-Kaolin Sand Wet Sizing The Bulgarian deposits of silica-kaolin sand are localised in the eastern part of the Danube plain. After wet separation the raw material yields two products - washed kaolin (different grades) and silica sand (different grades). The water washing technology includes: disintegration; spiral classification; hydrocyclone classification and dewatering of kaolin grades; hydroclassification; sizing using drum screens and dewatering of silica sand grades. Research and development program has started to improve the silica-kaolin sand separation in processing plants. Based on the raw material and tails characterisation data and the preliminary experiments using Derrick Stacksizer screening machines a silica-kaolin sand wet sizing technology was developed. The full-scale pilot flowsheet includes the following units: Derrick Stacksizer equipped with 0.43 mm opening Derrick Urethane Panel; 500 mm Flat bottom Hydrocyclone; Derrick Stacksizer equipped with 0.150 mm opening Derrick Urethane Panel; 100 mm Hydrocyclone and Derrick Dual Motor Linear Motion Machine equipped with 0.064 mm opening Derrick Pyramid Panel. The pilot-test data clearly demonstrate that the new silica-kaolin sand wet sizing technology is suitable for Bulgarian silica-kaolin raw material. There are possibilities to increase the silica sand recovery increasing the production of silica sand grade PK 0.16 and starting the production a new grade PK 0.10.

Sep 13, 2010

By Gutsche O, Kapur PC

Experimental data on the production of fines as a function of specific grinding energy consumption show that in general the energy utilisation in a choke fed high-pressure roll mill is higher than in a ball mill, but lower than in the single-particle mode of comminution under slow compressive loading. There is some evidence to suggest that the presence of water in feeds improves the energy efficiency of pressurised roll milling somewhat. Within a wide range of energy input, the size distributions of the ground product are self-similar, the logarithmic median size decreases linearly with the amount of fines produced and the inverse of the median size increases linearly with the energy spent. The production of fines as a function of energy expended follows essentially the same pattern as the one frequently encountered in media mills. The kinetics of grinding in the high-pressure roll mill can be simulated satisfactorily by modifying the standard particle population balance equation in order to account for energy dissipation in the tightly compressed bed. Common characteristics and important differences in grinding by the media mill and the high-pressure roll mill are highlighted.

Jan 1, 1993

Spatial data processing using geographic information systems produces qualitative results which are superior to those from other existing software tools. However, the answers to various quantitative questions in mining operations is often limited by the capacity of the GIS to process appropriate spatial data. The efficient operation of a large underground mine demands that an adequate GIS be put in place.

Jan 1, 1995

By M Simpson, K Brodie, J L. Mauk

Subaqueous water-rock reactions that occur at the pit wall/lake water interface can affect the pH of pit lakes. Many pit lake water chemistry models neglect subaqueous reactions, which may create inaccurate predictions over time. A mineral quantification method is presented that defines the wall rock mineralogy of active open pit mines, using samples collected from the Martha Mine, a low-sulfidation epithermal Au-Ag deposit in Waihi, New Zealand. The mineral quantification method has five components: field observations and sampling, X-ray diffraction analyses, selection of representative samples, geochemical analyses, and mineral accounting. Predicted mineral concentrations closely match observed mineral concentrations visually estimated using petrographic techniques. Results of the method can be incorporated into a geochemical model of long-range pit lake water quality resulting from subaqueous water-rock reactions.

Jan 1, 2003

Sampling systems are never perfect. They all have some bias and give variable sampling errors. The ways of thinking about bias and precision should be different before and after construction (or reconstruction) of a sampling system. Before a sampling system is constructed, the fundamental error variance can be estimated using GyÆs formula or by doing test work on the material to be sampled. The component of sampling variance which varies with the number of sample increments can be computed for the expected patterns of grade variation. The smallness of the bias can be checked using discrete element modelling, by checking that the proposed design complies with clauses in standards, or by copying an existing sampling system that performs well for similar material. After a system has been constructed, sampling precision can and should be monitored directly. Anyone claiming to take responsibility for a sampling system should know its precision. Bias could be checked by comparison to a more accurate sampling system, such as stopped-belt sampling, under conditions where bias seems most likely. However, it is more practical to conduct regular checks that the system is still operating as designed, that the design is still appropriate despite any changes to material flows, and that sample masses are consistent with the correct operation of the sampling system. If precision is not regularly assessed then it should be assumed to be very poor. If a sampling system is not regularly inspected then it should be assumed to be biased.

Jan 1, 2008

Following GyÆs earlier proposals for the use of StudentÆs t-test, a simplified, effective method and philosophy are proposed to test for maximum tolerable bias in data sets as well as in sampling devices. The philosophy of testing is particularly emphasised to derive important practical implications in terms of decision-making and risk control. Conclusions are offered which should equally matter to manufacturers and users of sampling equipment.

Jan 1, 2005

The accuracy with which block estimates are perceived is obtained by calculation of the kriging variance. This is dependent upon the model chosen for the semi-variogram of the deposit. For an extensive series of spherical semi-variograms the changes in the kriging variance resulting from various degrees of misassignment of the relative nugget effect are investigated. The results are reported as contour maps of percentage change in kriging variance as a function of the range and relative nugget effect of the true model.

Jan 1, 1985

By K Dudley, D Readett

The design of entrainment control processes in copper SX plants has been studied by use of models based on achievable plant performance. A number of alternatives have been assessed for their suitability in minimising the transfer of deleterious species from PLS into the electrolyte. The position of the wash (scrub) stage in the circuit, either before or after the loaded organic tank, has been the subject of considerable debate. The modelling shows that at ænormalÆ entrainment levels, the performance of the circuits are very similar. However at high entrainment levels the selection of the wash after the loaded organic storage has significantly lower transfer of contaminants. When considering the inclusion of a loaded organic coalescer the results of the modelling again show that the best circuit has the loaded organic storage/coalescer before the wash stage. The overall control of EW contaminants includes both a wash stage and an EW bleed flow. The total water use for these two flows is shown to go through an absolute minimum. The minimum flow rate is not greatly dependant on the total entrainment from the SX settlers. This can be a useful operating strategy if the quantity of high quality water for make up is limited by the capacity of the water treatment plant (eg RO). However the minimum cost option is to maximise the flow of water to the wash stage and minimise the EW bleed stream. The main driver for this is the cost of the cobalt sulphate contained in the electrolyte. Some results from the latest circuit modifications at the Nifty and Girilambone Copper Projects are presented to confirm the benefits of using both coalescing systems and a wash stage. The EW bleed has been reduced to a level that is less than the loss internally in the SX stage to stage entrainment. There has been an occasional need to add chloride to the EW to maintain sufficient concentration to act as a growth modifier.

Jan 1, 2002

By W Whiten

The determination of mineral composition is necessary in the mineral sands industry. Tiwest has developed a procedure for safe and convenient determination of the mineral composition using a magnetic separation followed by chemical analysis using X-ray fluorescence spectroscopy. This then requires the conversion of the elemental assays to mineral compositions. A project at the Julius Kruttschnitt Mineral Research Centre has developed a convenient analysis method for this conversion. This analysis is based on a reconciliation of the of the assays of the sample with the standard mineral assays by making minimal adjustments based on the assay accuracies to both sets of assays. As well as providing the mineral composition it to be tested for other applications and variations of the procedure to be evaluated. Given a range of samples, testing for the accuracy of the assays of the standard minerals, has been demonstrated.

Jan 1, 2001

Mere recognition of the need for technic- ally strong human resources in the'extractive metallurgical industries has not prevented the decline in the education base for broad spec- trum metallurgists. The ability of chemical engineers to perform very effectively in many extractive metallurgical positions does not remove from the need for a general metallurgic- al education system. The intrusion of chemical engineers into extractive metallurgy is only symptomatic of the problems facing the minerals industry and its educators. The prospect of a career in the minerals base industries is unattractive to potential students by virtue of perceived inadequacies in the professional basis of the industry and ignorance of its sig- nificance to Australia's future, as assisted by excessive secrecy and a low profile public Image.

Jan 1, 1987

Thermo Fisher Scientific is a supplier of samplers, instruments, analysers and consumables to the mining industry under the Thermo Scientific brand. The critical need to provide a representative sample to the analyser has played a pivotal role in product development. Products discussed are the Analysis and Sampling Station (AnStat) for mineral slurries, the Coal Quality Manager (CQM) and the prototype Bore Hole Analyser (BHX) with optional drill chip recovery system. Analytical techniques used in the above products are XRF, PGNAA and LIBS respectively. The company also designs and supplies conventional mechanical sampling equipment and complete sampling systems for bulk material applications (historical Ramsey brand). These products and application of them are presented.

Jan 1, 2008

There is growing acknowledgement that successful organisations, including mining companies, achieve their competitive advantage by better managing their employees, customers and other stakeholders. The fact that I have been asked to address this conference is perhaps evidence of the recognition of the importance of ensuring the improved management capabilities of the personnel within Australian mining companies. As many of you will be aware, prior to my appointment to the role of President of Minera Alumbrera Limited (MAA), the operator of the Bajo de la Alumbrera project, my career had been more generally focussed on industrial relations and human resources management. My appointment was met by surprise in some quarters, as it is unusual for a person without the technical background of a mining discipline to manage a world-class mining operation. However, it was recognised early in the life of the Alumbrera project that the operation did not lack technical expertise or a committed workforce; rather what was required was innovative management of the project and its operational resources, particularly given that we were operating with totally ægreenÆ workforce in a country without a large-scale mining culture. It is my experience that a particular shortcoming of mining companies is that they have tended to ægrowÆ managers based on their technical expertise rather than people management skills. Historically, many companies have assumed, or at least hoped, that their better technical people would develop the requisite skills to take on the challenges of management. Such philosophy has not always met with success. Whilst the topic for my presentation was originally published as People in the Mining Industry, within the context of the overall theme for this plenary session, People: Education for the Future, it is a subject with an extraordinary breadth of possibilities for discussion. Therefore, I have chosen to redefine my presentation to People Management Issues in Offshore Mining Projects,an issue which I consider to be an important area within the overall topic and one which has particular currency given the increased tendency by Australian miners towards offshore exploration. It is also relevant from the perspective of continued rationalisation of our industry, the recognition that there will be more large-scale, global corporate mining entities and that significantly more mining professionals will become æcitizens of the worldÆ. We therefore need to prepare our future leaders for these challenges. The topic also allows me to highlight the importance of an holistic management approach as the establishment of a new project in a foreign environment puts into stark relief the need for the application of the full range of competencies, rather than the narrow ætechnicalÆ approach to doing business. I hasten to add, however, that the mining industry is not alone in this regard and I was interested to read an article in the Weekend Australian of 22/23 January 2000, which reported on the first key speech of former Westpac CEO, Bob Joss, as Dean of the Stanford University Graduate School of Business. He said: à We know that when our students go out into the world, if they have to struggle, it will not be because theyÆre not smart enough, or they donÆt have enough good ideas. It will be because they struggle over managing themselves and their relationships to other people. The article then went on to say that Bob Joss foreshadowed an initiative to build alliances between the Business School and other Humanities departments within Stanford University to draw on their learning. Other business schools have also recognised this need, albeit somewhat late in the day, as have the most enlightened of modern corporations; in summary, successful businesses have recognised that in an age where competitive advantage through, for example, technological breakthroughs is very short-lived, it is the quality of management that will provide the leading edge. By using the Alumbrera project as a case study, I will identify certain of the challenges with which companies and individuals may be confronted in the establishment of a greenfields project outside Australia. However, many of the issues raised will have direct application in the context of the development of an Australian operation. My objective is to provide an indication of areas which should be considered at the formative stages of a projectÆs development, with particular focus on the issues of people management. I would expect that such a study would be of benefit to companies, education institutions and individuals in preparing themselves for similar experiences.

Jan 1, 2000

By Zhao JC, Chen JJJ

A water/air model was developed to simulate the refining of molten aluminium by the sparging of gas through an impeller. The optimal gas dispersion depends upon selecting the correct gas rate for a given impeller rotational velocity to prevent flooding or channelling. Correlations illustrating this flooding behaviour exist for standard impellers within standard tank geometries. However the validity of these correlations has not been substantiated for gas dispersion in high temperature molten metals with non-standard tank and impeller dimensions.

Jan 1, 1995

This paper outlines the thermodynamic and mass balance principles which affect the distribution of cobalt between matte and slag during the pyrometallurgical treatment of nickel-copper sulphides and considers the implications with regard to maximising the recovery of cobalt from the smelting and converting circuit.

Jan 1, 1994