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By Bezuidenhout M, Moolman D. W

In the minerals industry numerous problems cannot be solved by conventional mathematical models owing to their complexity or a lack of phenomenological understanding. Neural networks provide one way of mapping the ill-defined relations between process variables and functions for such ill-defined problems. Consequently, processes such as leaching and froth flotation are mostly controlled in an empirical way by using rules of thumb. In addition, these processes involve so many independent and dependent variables that the plant operator finds it difficult to visualise or even observe a change in process conditions. The structure of froths developed on the surfaces of industrial scale froth flotation cells has a significant effect on both the grade and recovery of valuable minerals in the concentrate. Although these effects are well known at the process operational level, where considerable heuristic knowledge is available, little work has been reported on a detailed characterisation of the mechanisms and the visual characteristics of the surface froth. Recent results from an on-line observation of froths in several plants have proved the relationships between image features representing froth behaviour and metallurgical results. It will be shown how supervised and unsupervised neural nets are being used on operating plants to interpret computer vision data. In froth flotation the operator is supposed to visually observe process changes from the appearance of the froth, which is an unreasonable demand under industrial conditions. The system described here determines textural parameters on-line, and tracks the changes in process conditions via a Self-Organising Map (SOM) neural net. This monitoring system warns the operator about fluctuations in reagent addition, and gives an idea of the type of froth encountered. In another example, changes in the mineralogical characteristics of gold ores are represented on an SOM map, based on the diagnostic leaching behaviour of such ores.

Jan 1, 1997

The St George orebodies are situated within the tectonically disrupted eastern limb of the Boogardie Syncline.Highly disturbed rafts of banded chert formations occur within a sequence of felsic volcanic tuffs. The chert forms the hostrock for the gold mineralization.The gold distribution within the irregular and narrow banded chert formations is erratic and patchy. The average gold content of the two orebodies is between 3 - 4 g/t Au.Economic mining of these relative small, irregular and low grade St. George orebodies can be carried out by using a highly selective mining method.The highly selective mining method uses an excavator as the principle mining tool. Blasting, breaking and loading of the rocks is done in a different way than by using a front-end loader as with the conventional mining method. Simple, and therefore cheaper, blasting breaks the rocks and lifts them up without major displacements.

Jan 1, 1984

Through the use of structural analysis programs such as Unwedge and considering the shear strength of applied fibrecrete it can be shown that fibrecrete can provide a higher factor of safety in a ætypicalÆ underground development excavation than standard rock bolts. This paper describes the progression of ground support from an æas requiredÆ component of mining to the use of bolts and surface support as a mandatory requirement. With the mandatory requirement for surface support, fibrecrete has been considered and applied as a secondary feature but simple analysis and practical observations indicate that it may be considered as primary support. The key elements to its implementation are: When is it safe to work under fresh fibrecrete and how do we practically determine this? How much ground support does fibrecrete provide? How can we reduce the cost of fibrecrete? An examination of these questions indicates fibrecrete can be much safer,less expensive and quicker to install than normal ground support elements. This paper explores practical examples from sites where significant benefits have been achieved by mine operators.

Jan 1, 2005

By OÆBrien D, Priddle D

In order to avoid costly moisture penalties on coal shipments and to minimise rail freight costs, screen bowl centrifuges were selected and installed in the Mount Thorley Coal Preparation Plant for dewatering fine coal product. The Mount Thorley fine coal circuit consists of desliming the -0.5 mm (ww) fine coal in two stages of classifying cyclones prior to recovery by froth flotation. Provision has been made to bypass the flotation circuit with the classified flotation feed reporting directly to product and the centrifuge dewatering circuit has been designed to handle either flotation feed or flotation product. Major mechanical failures of the gearboxes and the ceramic tiling occurred early in the operation life of the machines which led to design changes being made to achieve satisfactory operation. This paper discusses the operating experience at Mount Thorley with respect to both mechanical and metallurgical performance of the screen bowl centrifuges since their installation in 1985.

Jan 1, 1989

Sampling and analysis of mineral deposits need to be executed without fear or favour of financial or personal impacts. Examples are given to illustrate the effects of departures, witting and unwitting, from correct use of appropriate techniques and/or equipment with emphasis on exploration and mining of porphyry copper deposits of the Pacific Rim. Some of the results of errors on the low and high sides of true value in exploration, resource or reserve estimations and in production caused by sampling and/or sample preparation mistakes, faulty practices, equipment and/or analysis are considered.

Jan 1, 2004

By Griffiths J. B

From its mining lease at the northern end of Cohens Reef at Walhalla in the North Gippsland Mountains, the Long Tunnel Extended Gold Mining Company produced 13,695 kg of gold, which at 1980 prices represents a value significantly in excess of $200 million. In the period 1885 to 1908 the mine was one of Australia's principal reef gold producers, being top Victorian producer in six of these twenty-four years. Prior and subsequent occupants of the lease produced an additional 160 kg of gold. The Extended and the other mines on Cohens Reef whilst contributing importantly to the financial resource of Victoria, were the sole important support for the substantial town of Walhalla that had grown up around them. When the mines closed, Walhalla gradually reduced from a bustling developed town to the present attractive mountain village so favoured by tuurriSts. To allow the visitor to obtain a better ;ri.icrstanding of Walhalla's mining past, important parts of the Long Tunnel Extended Gold Mine workings and site are being

Jan 1, 1981

By M J. Nugus

A substantial cost is invested into the data collection phase of any exploration or development program; notwithstanding, it is impractical to expect a database of information can be collated to ensure a perfect geological interpretation. The question then becomes, is there a possible alternative interpretation and what is the likely impact of the variations? Modelling in 2005, of the Cosmo lode at Sunrise Dam Gold Mine, Western Australia led to consideration of the philosophical implications associated with resource management. It was concluded that several plausible geological models could be constructed from the known geological database. To varying degrees, this predicament is common to all geological reconstructions, as several alternative geological models can be generated at almost any stage that will impact on the resultant resource estimation and mine plan. The significance of that variation and the associated risk of multiple geological models (MGMs) requires due consideration. What is being suggested is that using plausible multiple geological models advances the holistic understanding of a mineral deposit within the bounds of the data collected, providing fluidity for updating geological knowledge and building inherent variability into the design and planning departments where variations of the geological models may materially impact on the resource performance.

Jan 1, 2006

The basic purpose of blast design is to produce rock in a size range which is within the requirements of the materials handling system. Once this is achieved, one would like to find the fragmentation which minimises total production costs. The former objective requires that fragmentation be assessed by some means, possibly as simple as counting the number of oversize rocks. To determine the 'optimum' fragmentation, however, accurate knowledge of the complete fragmentation distribution is required. The use of muckpile surface images to determine blast fragmentation is the only feasible technique when one does not want to disturb the production cycle; however, a number of problems exist with the use of images amongst which are determining size from a two-dimensional particle shape, estimating the fines which are missing due to image resolution, the size of a 'representative' sample, errors due to the distortion of particle images, etc This paper briefly describes methods of determining rock size from images and expands on the various errors which exist in assessing fragmentation by photographs. Methods to minimise and account for the errors are given, when possible.

Jan 1, 1976

By Jagger N. D

Lead residue from the Zinc Leach Plant at Pasminco's Port Pirie Lead Smelter was previously filtered on a vacuum drum filter and further dried in a gas fired rotary kiln prior to stockpiling and transport to the Sinter Plant. This process involved several materials handling stages, recycled significant amounts of zinc and often resulted in poor environmental conditions. These problems have been overcome by pumping the thickened leach residue approximately 450m to the Sinter Plant where it is filtered in a Larox Automatic Pressure Filter. The filter cake is discharged onto a conveyor belt, held in a storage hopper and then fed directly to the main sinter plant feed stream. Filtrate is returned to the process for additional zinc recovery. The laboratory and pilot plant filtration results are briefly discussed and compared with the operating plant data. The filter installation and ancillaries are described in detail along with the commissioning, operating and maintenance experience over the past 4 years. This installation has overcome the environmental and materials handling problems and resulted in annual savings of approximately $1 million.

Jan 1, 1989

Copper entering a lead ,smelter in concentrate or from other sources is recoVered as matte and speiss which contain appreciable quantities of lead. The matte and speiss are usually sold to copper smelters to recover the copper content and also any gold and silver in these products, but the value of the lead is largely lost. Some copper plants pay for portion of the lead content, but regarded as a means of recovering lead it is more costly and less efficient than if the lead were recovered at the lead smelter.Because of the value of this lead loss, the metallurgy of copper recovery has assumed greater importance in recent years owing to the rise on the price of lead.Two processes are in use today to produce matte and speiss, namely the iron matte process and the soda matte process developed by the American Smelting and Refining Co. 1 in D.S.A. The latter process is characterised by a higher copper to lead ratio than the older iron matting process.The following analyses are typical of matte and speiss produced at Broken Hill Associated Smelters, by both processes, although the soda matte process is still in a developmental stage and experience indicates that matte and speiss of lower lead tenor can be produced under favourable conditions.

Jan 1, 1951

By M Roper, M Lovitt

WMC Resources Olympic Dam Operation located in South Australia, is a poly metallic underground sublevel open stoping (SLOS) mining operation with a current annual production rate in excess of 9.0 Mt. Stope size, geometries, geotechnical considerations, drilling and blasting are critical components in stope performance. These factors are further influenced by stringent ventilation requirements due to the presence of airborne radioactive contaminants from uranium mineralisation. Stope planning is complex and mass blasting methodologies have been trialled at Olympic Dam with the view to reducing the frequency of stope blasts, improving stope stability, productivity and ultimately improving overall stope performance. A key aspect in the ability to undertake underground mass blasts of this scale is the application of i-konTM electronic initiation technology by Orica. In the past two years in excess of three million tonnes has been initiated utilising this electronic technology, with an average blast of 250 000 t ranging to the largest to date being 580 000 t. By providing flexibility in blast designs, the use of electronic detonators has allowed mass firings over multiple sublevels. This has resulted in a significant reduction in stope extraction steps compared to conventional pyrotechnic firings. The benefits of this reduction in the number of stope blasts are wide ranging from improved stability of interim stope voids between blasts, reduced blasthole damage, improved blast vibration management and reduction of complex changes to ventilation systems for blasting.

Jan 1, 2004

By Watson DF

Calculation of the amount of metal in an ore deposit or mining block should be approached by multiplication and integration of appropriate numerical manifolds describing the spatial distribution of the relevant variables, viz. grade, specific gravity and also thickness for bivariate data. Construction of a numerical manifold necessarily involves some form of interpolation but detailed characteristics of this are often not specified in various automatic methods, some of which even provide manifolds with discontinuities. A manifold used in calculations should describe in a geologically plausible way the spatial distribution of the variable of interest. Different approaches to the problem are discussed and compared. Particular computational inconsistencies emerge when "accumulation" is used as a variable in calculations of average grade. If an ore deposit is variable in relation to its sampling and especially if selection of mining blocks according to grade cut-off is a necessary operational decision, the biases introduced by accumulation methods can bring about serious problems of over-evaluation. Modern computational techniques make unnecessary the use of accumulations; because of potential inconsistencies it would seem unwise to use them in any ore reserve computation.

Jan 1, 1987

AND INTRODUCTION The Lochiel coal deposit, a large Tertiary soft brown coal deposit in the mid north of South Australia, is currently being investigated by the Electricity Trust of South Australia (ETSA) as a potential source of fuel for a base load power station. Feasibility studies indicated that the proposed dragline method of overburden removal was viable but economically sensitive to both highwail and dump batter angles. The unusual properties of the unconsolidated overburden sediments and the groundwater regime posed a number of intimately related hydrogeological and geotechnical questions which were addressed before and during the excavation of a trial pit. All strata at Lochiel are of soil strength, and artesian aquifers occur above and below the coal. From the initial evaluation of the deposit a number of hydrogeological questions were defined. These related to the rate at which the pore pressure in the silts is reduced by dewatering, the extent of the reduction in pore pressure due to prestripping, and the feasibility of dewatering and depressurising carbonaceous silty sand sequences. The site of the trial pit was selected to answer these and other questions from the basis of a detailed geological, hydrogeological and geotechnical understanding. The trial pit dewatering system simulated a full scale mine dewatering system and included ten pumped wells, twenty drainage wells, and nearly 400 monitoring instruments. It operated from September 1986 to June 1987. The excavation was carried out between February and May 1987.

Jan 1, 1988

By Barnett LJ

The Kellogg slag fuming model is extended to apply to the Port Pirie plant which uses recuperative heating of secondary air. Exten- sive investigations of plant operations pro- vide parameters for use with the model, and verification that the resulting model provides simulation which is very close to actual plant performance. The model is used to_deter- mine optimum slag fuming operating conditions, and the results of several other investigations with the model are briefly described.

Jan 1, 1975

The introduction ofa submerged entry tundish nozzle incorporating a cylindrical internal space for argon distribution to its inner bore slab is described. In co-operation with the refractory supplier, four major phases of nozzle development have been undertaken. Problems as well as successes are outlined.Significant reduction in alumina clogging ofnozzles has been achieved along with a decrease in nozzle consumption, using resin bonded alumina graphite with up to 4 different materials "zoned" to give resistance to thermal shock, gas leakage, and erosion.

Jan 1, 1985

By D A. Kepert, D Clark

During early 2004, Fortescue Metals Group (FMG) began an aggressive exploration and drilling program in the Chichester Range, targeting iron enrichment developed in the Nammuldi Member at the base of the Marra Mamba Iron Formation. The timely recognition by FMG of distinct zones of (hypogene) microplaty hematite (mplH) enrichment overprinted by extensive supergene mineralisation led to an early reappraisal of the geological history of the area and characterisation of the possible structural and stratigraphic controls on mineralisation. Regionally, the Chichester Range dips gently at less than 5¦ to the south, however, detailed mapping shows that this regional limb is overprinted by low amplitude, long wavelength, north/south to northeast/southwest trending folds. The locations of major structures in the Marra Mamba Iron Formation, combined with spectral analysis of known mineralisation, allowed extrapolation and prioritisation of exploration target areas. The delineation under cover and understanding of these structures was enhanced by detailed airborne magnetic data. Recognition that supergene mineralisation was associated with a palaeotopography that continued significantly under cover to the south under sediments of the Fortescue River valley led to the discovery of extensive supergene mineralisation together with additional mplH mineralisation. A model for the landscape evolution and preservation of enriched Nammuldi Member was generated in order to help communicate both the complexities involved with targeting drill holes beneath cover and the potential limits to the lateral extents of mineralisation.

Jan 1, 2005

By Slattery T. E

Recent develognents in zinc flotation at the North Broken Hill Limited concentrator are discussed. An outline of the history of zinc flotation and a description of current practice is presented. Installation of on-stream X-ray analysis probes has resulted in inproved metallurgical performance and focussed attention on automatic control. Results are presented of investigations made over the past six years which have led to the formulation of experimental schemes for the automatic control of zinc flotation.

Jan 1, 1983

Instantaneous outbursts have occurred at Metropolitan Colliery from the pick and shovel work of early days to the modern mining techniques of today. Developments have been the introduction of an emission index to measure the proneness of the coal to outbursts, drainage and destressing by large diameter holes, attempts at higher productivity by the introduction of pulsed infusion shotfiring and improvements in ventilation. The future plans and aims for the Colliery include prediction of outbursts, seam gas pre- drainage and longwall mining.

Jan 1, 1980

For the purpose of this paper the Otago Region is that covered by the Otago Regional Council. This area, like other South Island Regions, has a river system starting in the Mountains and are all gravel bed rivers. The gravel from these rivers has been the major source of aggregate in the region since the development of the province began. The majority of the aggregate is a mix of greywacke, schist and quartz, which will be referred to later with its production problems. The region has been broken down into various areas.

Jan 1, 1992

By Houchin MR, Jenkins DH

This paper examines the importance of processing to the properties and performance of high purity zirconia ceramics. Many of the principles discussed, however, apply to ceramic processing in general. For fabricated ceramic articles to display their wide range of high performance properties, they must be made fully dense. The precursor powder and postpowder processing requirements necessary to achieve full density in the fabricated body are discussed. Brittleness, the anathema of ceramics, can be overcome in zirconia by incorporation of toughening mechanisms. Transformation toughening and microcrack toughening and their origins in partially stabilized zirconia are reviewed.

Jan 1, 1989