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By W Patton, I Minniakhmetov, H Talebi, U Mueller

The sustainability of mining projects is linked to informed investment decisions based on public reporting of exploration and mineral resource estimation results. In Australia, public reporting guidelines are established by the Joint Ore Reserves Committee reporting code through the JORC Code (2012). Although the assessment of uncertainty in the results reported is a requirement, this is often communicated qualitatively and evaluated subjectively. This can become a liability particularly in the early stages of mining projects when spatial domains of geological interpretation and mineralisation envelopes inform resource estimations’ reliability. A recent review of JORC reports found no reports used quantitative assessments of the geological interpretation or mineral resource estimation envelopes, and 27 per cent of reports did not address the question of quality of geological interpretation. Reports that did address the quality used 19 different terms to communicate quality. This work presents methodologies for quantitative uncertainty assessment and communication and explores how they could be applied in public reporting practice. Quantitative uncertainty reporting would benefit mine planning and financial modelling as they normally assume the geology is 100 per cent right (since no error is reported or only a single deterministic model is provided). The complexity, cost, and additional work of doing a quantitative assessment could hinder a straightforward implementation. This could be overcome if mining companies budget for quantitative uncertainty assessment and associated professional development. A compulsory requirement for the inclusion of uncertainty assessments in public reporting or adopting standardised subjective language would improve industry practice.

Mar 22, 2022

By E R. Ramanaidou, M Wells

The aim of this paper is to summarise all known Phanerozoic ooidal ironstone deposits worldwide, including Australian deposits such as the well-known channel iron deposits (CID). Nearly 400 occurrences have been catalogued based on stratigraphy, geographical coordinates, facies, grade, tonnage and iron bearing ore minerals. The description also includes details on the geochemistry, genetic models and main references. Brief statistical analysis provides an overview of the variation between these deposits. This compilation offers a basis for better understanding of the ooidal ironstone deposits and a global evaluation of this important resource worldwide.

Jan 1, 2009

By M Castello, P Bouchard, M Sabsabi, A Blouin, B Nguegang Kamwa, M Constantin, K Fytas, M Laflamme, K Rifai, F Vidal

Canada’s Quebec province operates 26 metal mines, 19 of which are producing gold and generating over C$1.8 billion (US$1.3 billion) annually. In all those mines, numerous samples of rock are collected and analysed daily in laboratories in order to determine their gold content. However, laboratory results are generally available within 48 hours of sampling (depending on the number of samples received by the laboratory and the priority of the results), thus potentially slowing down mining activities. In an attempt to find a solution for delayed laboratory results, Laval University, in partnership with the National Research Council Canada (NRC), the National Institute for Scientific Research (INRS) and four mining companies (Agnico Eagle, Canadian Malartic, Hecla Québec and Iamgold) have launched the Laser-Induced Breakdown Spectroscopy (LIBS) project for in situ real-time mining sample analysis. This work aims to minimise the amount of LIBS point sampling necessary to be representative of a full scan of the analysed area. Eight sampling patterns are investigated. A statistical analysis of the data was performed by varying the pattern steps. Results show that two of the patterns, 1 and 5 (single diagonal crossing the stratification of the samples with opposite slopes) minimise the amount of point sampling while remaining representative. The most successful results are obtained from steps which are greater than 6. In terms of the type of material, pattern 5 and steps 9 are better for core sampling, while pattern 1 and steps 8 are better for rock sampling. The geological explanation for these results is the heterogeneous distribution of gold in the sample which seems to be more homogeneous in the rocks than in the core sample due to the small rock size. In terms of the mineralisation, pattern 5 is better for mixed sulfides and quartz veins, and steps 8 and 9 are better for quartz veins.CITATION:Nguegang Kamwa, B, Rifai, K, Laflamme, M, Constantin, M, Castello, M, Vidal, F, Bouchard, P, Fytas, K, Blouin, A and Sabsabi, M, 2017. Sampling strategy by statistical analyses of LIBS data in the context of a portable gold analyser, in Proceedings Tenth International Mining Geology Conference 2017, pp 221–232 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 20, 2017

By N Dube, K L. Sandvik, C Mutevhe

Trojan Nickel Mine is the largest producer of Ni, Cu and Co in Zimbabwe. The mine has operated a nickel flotation concentrator and base metal refinery continuously since 1969, creating 28 million tonnes of sulfide bearing tailings, five million tonnes of permanent waste rock and about seven million tonnes of smelter slag. Exposure of the sulfide bearing minerals renders them susceptible to oxidation in the presence of water and oxygen, resulting in acidic solutions with elevated concentrations of total dissolved solids, sulfate, metals and residual flotation chemicals in various waters draining from the mine site. These pollutants pose a direct threat to the environment and human health, and understanding their deportment and behaviour in the various waste streams is essential in the mineÆs environmental objectives to prevent or minimise adverse impacts arising from its operations. A geochemical assessment of the pollutants was carried out to compute a mass balance between the major sources of pollution and the distribution and fate of pollutants in waste streams from the mine site. Waste rock, tailings, surface water, ground water and sediments were sampled, tested and analysed. Mineral composition and water chemistry data show that geochemical reactions are responsible for the release of pollutants from waste rock, tailings and plant spills. Drainage from the mine area is near neutral due to buffering by magnesium carbonates in the fine fraction of the tailings. The natural wetlands that exist downstream of the waste rock and tailings dams are effective in reducing metal loadings to water courses. However, solutes and heavy metals are occasionally released to surface and ground water, when their concentrations peak during the dry season. The results demonstrate the necessity to understand the natural chemical processes that characterise the distribution of pollutants in nature and how such knowledge can be used to develop cost effective methods to remediate pollution in the natural environment.

Jan 1, 2006

By R G. Moreby

The purpose of this paper is to provide the rationale for decision making when considering the use of three heading gate roads in Australian underground coal mines.There are currently 30 underground longwall mines in Australia with all but two employing two heading gate road longwall layouts. The volumetric capacity of these two heading ventilation circuits is evidently viable in typical block lengths and in low to moderate gas regimes. However, in gassier regimes, potential longwall production rates of 10 Mt/a, and or where block lengths are being extended to well beyond historical norms, a conventional two heading U circuit may not be adequate. Other than seam gas emission, block length and production dependent heat loads together sealed area management requirements also have to be considered.The two mines currently employing three heading gate roads have the opportunity to revert to two headings at any time but, based on operational experience to date, have not done so due to the consequential reduction in gas management capacity and lower production rates associated with gas delays and limitations on tailgate access.Although there are a number of alternative two heading longwall circuits available and employed worldwide, the custom and practice of promoting inert goaf atmospheres in most Australian coal mines to mitigate the risk of catastrophic gas explosions and spontaneous combustion often prevents the use of gas loaded bleeder systems. In this respect, Australian underground coal mines may be considered the safest in the world.The current situation is that three heading gate roads have been proven successful in Australian conditions, albeit at additional cost, where two heading ventilation circuits cannot manage net seam gas emission to the ventilation system at the production rates required. In this respect, a further important driver for decision making is the short to medium term value of CO2-e emission taxation in Australia.CITATION:Moreby, R G, 2013. The rationale for use of three heading gate roads in Australian underground coal mines, in Proceedings The Australian Mine Ventilation Conference , pp 13-26 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 1, 2013

By L Snyman, S Webster and J Samosir

Northparkes is located 27 km north of the township of Parkes in central New South Wales, Australia. The operations consist of underground block cave mines and an ore processing plant, which produces high-grade copper and gold concentrate. Production is currently sourced from the E48 Lift 1 block cave mine and open cut stockpiles. Mining commenced at Northparkes in 1994 as an open cut operation. Underground block cave mining began in 1997. Northparkes was the first mine in Australia to use the highly efficient block cave mining method, which relies on gravity and natural rock stresses to fragment and recover the ore.The E48 extraction level is located approximately 581 m below surface and consists of ten extraction drives and 214 drawpoints. Several stress measurements carried out at various levels in both E26 and E48 indicated a low underground regional stress environment and a low to moderate stress state in the E48 orebody. The E48 block used a post undercut strategy that was initiated in 2009, with production commencing in September 2010 and cave-through to the surface occurring approximately four months later in January 2011. Changes to the cut-off grade and fixed prices meant that Northparkes was able to develop an additional two drives to the north of the existing cave and one additional drive to the south. Modelling of the cavability of the additional drives indicated that the cave would not readily propagate to sufficient height of draw to mobilise the ore and tended to arch over to the existing cave shape. Based on modelling and a desire to reduce the risk of the project, preconditioning was adopted. Along with the requirement of safely hydrofracturing an active cave, a measure of the success of the preconditioning was desired. Few block cave operations have developed extension drives adjacent to existing caves.This paper summarises the lessons learnt from the development of this extension project, with a specific focus on ground control and monitoring.CITATION:Snyman, L, Webster, S and Samosir, J, 2016. E48 cave extension at Northparkes, in Proceedings Seventh International Conference and Exhibition on Mass Mining (MassMin 2016), pp 111–118 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2016

By M Z. Abzalov

Drilling mineral sand deposits has specific challenges, which are different from drilling hard rock deposits: Drilled sequences are represented by non-consolidated free-flowing sands to semi-consolidated clayey sands and indurated layers. Valuable heavy minerals (ilmenite, rutile, zircon, leucoxene) have an average density of 4.6 g/cm3, which is significantly heavier than the hosting sand matrix; mainly represented by quartz (density = 2.6 g/cm3). The large difference in the mineral densities can result in sample segregation in the drilling rods and capturing devices causing biased composition of the recovered samples. The drilled strata can contain beds of consolidated sediments, hard pan lenses and concretions. Therefore, chosen drilling equipment should be flexible and permit a switch from drilling the free-flowing sands to hard rock drilling. Thickness of the sand hosted mineralisation varies from several metres to more than 170 m. Mineralisation is distributed above and below the water table. Evaluation of the mineral sands deposits is based on hundreds of drill holes and many thousands of samples, therefore drilling methods should be fast and cost effective. The drilling methods commonly used for mineral sand deposit evaluation, include aircore, triple tube diamond and sonic; including its variants, such as vibrocore drilling technique. The ability of the studied drilling techniques to properly address the above listed challenges in mineral sand deposits, whilst maximising the quality of the obtained samples has been compared in three deposits: Corridor Sands (Mozambique), Richards Bay (Republic of South Africa) and Fort-Dauphin (Madagascar).This study has shown that aircore samples tend to be negatively grade biased, underestimating the heavy minerals content, in particular when drilled intervals are located below the water table. Triple tube diamond core method can produce non-biased samples. However, results can be marred by incorrectly chosen drilling mud. Sonic drilling is a relatively new technique based on a high frequency vibratory technology. It is the only production drilling technique that allows a continuous relatively undisturbed sample of unlithified sands to be obtained. The main limitations of this technology preventing its wider use for developing mineral sand resources are the relatively high drilling costs, in particular when the depth of drilling exceeds 100 m, and speed of drilling advance.

Oct 5, 2011

By V Matousek, A Sellgren, R Visintainer, G McCall

A 4-component model for settling slurry pipe flow has been previously described by Wilson et al (2006) and Sellgren et al (2014) to predict pipeline friction loss (hydraulic pressure gradient) over a range of slurry compositions: from fine to coarse particle size, narrow to broad particle size distribution, and low to high solids concentration. The method applies a weighted average of established pipeline models for various settling slurry flow regimes, according to the volume fraction of solids falling within the applicable size range for each model. Further development of the model was undertaken by Visintainer et al (2017a, 2017b), based on a comprehensive set of laboratory tests in 203 mm (8 inch) and 103 mm (4 inch) pipelines, and it was also adapted to the modelling of slurry pump performance derates. However, this work was all performed with solids having a specific gravity near 2.65, as is typical for many mineral processing and dredging applications. The goal of the present work is to test the applicability of these models for settling slurries having a higher solids specific gravity, as may often be seen in the mineral processing of iron ore deposits. To that end, a test program was carried out in a 103 mm (4 inch) pipe loop using various compositions of an iron ore product having a solids specific gravity of 4.75 and containing both coarse and fine solids. By screening and flushing operations, a range of particle size distributions were created having different proportions of the coarse and fine elements. In all, 19 tests were performed with d50 particle sizes ranging from 50 μm to 3.2 mm and delivered solids concentrations from 10 per cent to 43 per cent by volume. Particle size distributions varied from very narrow to very broad, with d85/d50 ratios ranging from 1.75 to 26. Pipeline pressure gradient and pump performance data were collected and used to test the applicability of the previously developed 4- component models and to propose improvements to the models for the handling of high-density solids.

Nov 8, 2021

By F van de Venter, J Monama, T Kale

For a multitude of years fine iron ore, -1 mm, across the world has been deposited as discard material in tailings facilities. This contributes to environmental problems, decreases plant yield and increases the cost of processing. Fine iron ore recovery processes are often deemed unfeasible or uneconomical, due to the complexity of the reclamation thereof in comparison with high-grade ores. However, recent advances in the recovery of fine iron ore using the Optima Classifier® has shown great promise. The Optima Classifier® is a new hindered settling separator that makes use of an upward current of water for density separation. It’s unique design combines three different separating zones for increased efficiency and recovery. In this study the potential of the Optima Classifier® to produce a +63 per cent Fe concentrate from -1 mm feed material was evaluated from a standalone and process perspective. It was found that a +63 per cent Fe product can be produced from a single stage, using the Optima Classifier®. Fine iron ore feed with an average head grade of 50 per cent Fe was upgraded to average concentrate grades of 63.2 per cent Fe. Displaying upgrade ratios of up to 1.26 in a single stage. A three-stage, rougher, cleaner and scavenger system did however show the best performance with recoveries of up to 70 per cent, yielding 56 per cent of a 63 per cent Fe product. Furthermore, the dewatering of the product and tailings was evaluated using the UltraG ultra-fine dewatering screen ensuring dry, stackable material. The tailings could be used in codisposal, while loads on thickeners and filter presses are significantly reduced. The high throughput of the Optima Classifier® ensures a small plant footprint, minimal civil and structural requirements and low operating utility consumption such as electricity, minimising the carbon footprint of a fines beneficiation plant. The Optima Classifier® in combination with the UltraG dewatering technology has provided a platform for economical recovery of fine iron ore, both current arising and historical. Providing opportunity to lower plant operating costs, reduce environmental liability of tailings facilities and increasing immediate process water recovery

Sep 18, 2023

By M Olsson, U Nyberg, K Widenberg, P Svedensten, F Ouchterlony

During 2007 and 2008, the project Optimal Fragmentation in Blasting II was conducted at the Långåsen quarry of NCC Roads AB near Arlanda. The main goals were:an evaluation of the effect of using electronic delay detonators (EDDs) in quarry blastinga validation of the design curve concept introduced at the Vändle quarry.Five production blasts were monitored. After a first trial round, the remaining four rounds each had about 100 Ø89 mm holes in a 14–19 m high bench charged with site mixed emulsions. In rounds 1 and 2, a tighter pattern than normal was used in one half of the rounds, raising the specific charge there from 0.7 to 1.0 kg/m3. Non-electric initiation was used with two holes per 25 ms delay in-row and 67 ms between rows. In rounds 3 and 4, electronic delay detonators were used instead, with 10 and 5 ms in-row delays respectively.The monitoring encompassed drill hole collaring and alignment, in-hole deviations, the rock structure in the bench faces from 3D imaging, first row burdens, etc. Eleven 400 t samples were taken from the muck piles and sorted in the quarry and sieved in the laboratory (lab). The lab data made up a fines tail that was grafted onto the in-pit sorting data to form sieving curves for the test piles. These curves were then compensated for the absence of boulders to construct the sieving curves for the blasted muck pile.These have been used to derive fragmentation model formulas for the non-electric rounds, also called design formulas. They are based on blast geometry, charging data and the properties of the rock mass. The formulas may be used to estimate the effect of changing blasthole pattern, borehole diameter and stemming length for example.The use of EDDs gave several unexpected results. In comparison with non-electric initiated rounds with a somewhat lower specific charge the fragmentation was much coarser; x50 increased from 160 to 200 mm. The effect of raising the specific charge in the non-electric initiated rounds from 0.72 to 0.99 kg/m3 was a much finer fragmentation; x50 decreased from 160 to 120 mm.CITATION:Ouchterlony, F, Nyberg, U, Olsson, M, Widenberg, K and Svedensten, P, 2015. Effects of specific charge and electronic delay detonators on fragmentation in an aggregate quarry – building fragmentation model design curves, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 727–740 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

By F Carrick, W A. Ellis, D R. Mulligan, S I. FitzGibbon

"One of the major environmental impacts of mining is the destruction of habitat. The koala (Phascolarctos cinereus) is an iconic Australian marsupial that has been severely affected by land clearing and its decline is continuing. This has placed pressure upon mining companies and government agencies to ensure koalas are managed throughout the life-of-mines - from land clearing through to rehabilitation of post-mining landscapes. This paper reports on the æKoala VentureÆ research partnership between The University of Queensland and Rio Tinto. As part of the Koala Venture program we examined koala use of two types of restored environments: rehabilitated mined land (20 sites) natural regrowth forests (six sites), at Blair Athol Coal Mine in Central Queensland, Australia. Searches for koala scats revealed evidence of koalas in ten per cent of rehabilitated sites (2/20) and 33 per cent of natural regrowth sites (2/6). Two factors were identified as being of greatest importance in facilitating koala recolonisation of restored habitats. Firstly, all recolonised sites were located close to native forest occupied by koalas (mean 135 m ¦ 52). Proximity to source animals is considered crucial to recolonisation of suitably restored habitats. Secondly, three of the four recolonised sites were dominated by koala food trees, most of which were large enough to be utilised by koalas. Availability of suitably abundant food resources is, therefore, also considered crucial. The requirement for these two factors, in combination, is highlighted by the absence of koalas at several sites that contained abundant food trees, but that were distal to areas with source animals, and vice-versa.Our research demonstrates the enormous potential for restoration of wildlife habitat on post-mining lands, even for species with specific requirements such as the koala. Consideration of the ecological requirements of wildlife during rehabilitation planning is critical to enhancing the likelihood of recolonisation.CITATION:FitzGibbon, S I, Ellis, W A, Mulligan, D R and Carrick, F, 2012. Rehabilitating post-mining landscapes for wildlife - A case study from the Koala Venture research program in Central Queensland, in Proceedings Life-of-Mine 2012, pp 319-324 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Jul 10, 2012

By F R. M Pires, R M. Carvalho

Supergene processes in banded iron formation (BIF) result in important dissolution, material transport and simultaneous disorder of the residual bands. The rock physical properties such as density, porosity and rheology change during the weathering attack. The itabirite, Paleoproterozoic metamorphic BIF from Quadrilßtero Ferrffero (QF) û Brazil, shows several weathered facies. Strong linking between topographic surface, rock density and iron grade occurs within the weathered zones. This linking is due to partial dissolution of silica and carbonate from itabirite and gravitational rotation and break of the remaining blades, generating kink-like slump structures. The original itabirite density, 3.7 t/m3, decrease at the first leaching steps, until 2.7 t/m3, and increase at the end of the leaching process until 3.6 t/m3. Iron grade increases from 38 per cent to 68 per cent and depressions (sinkhole), subsequently filled by Cenozoic basinal sediments, are developed over the enrichment zones. The formation of important supergene iron ore deposits of QF is intimately related to such a process. Several iron deposits at QF, such as Pico do Itabirito, Fßbrica Nova, Casa de Pedra, Tamanduß, -gua Claras, Cappo Xavier, etc., reveal the aspects related to the proposed evolution, implying that the formational process of the soft iron ores had a regional character. Granular medium model helped in the understanding of the development of the structure and the formation of the deposits. A numerical model has been developed in order to simulate a leaching system in a two-dimensional matrix, composed of two types of materials: leachable and unleachable. Equal volume proportion and vertical banding were considered. Drilling data was used as multipoint attractors to remove leachable matrix nodes.

Jan 1, 2002

By F H. Henrfquez, A G. Oroz

Design and operating conditions of large size mechanical flotation cells were evaluated by comparing them with actual operating conditions in a plant. The objective was to determine the time scale-up factor, typically based on empirical rules. Experiments were conducted on the rougher flotation circuit at Minera Escondida Ltd. The circuit consisted of self-aerated mechanical cells of 160 m3, arranged in six parallel banks with nine cells each. The rougher circuit flotation kinetics were evaluated from direct sampling and local mass balances around each cell of the bank. Adjusted overall mass balances were also developed. This information was used to fit different kinetic flotation models, and it was found that the rectangular distribution function was the most appropriate to describe the distributed rate constant for industrial operation. Then, a rougher flotation simulator was developed to describe the actual operation in terms of the operating variables (mass flowrate, solid percentage, feed grade) and the actual volumetric flowrate entering to each cell. In this study feed pulp samples were taken in parallel from the rougher circuit and were simultaneously floated in the laboratory. The kinetic behaviour was then modelled at a laboratory batch scale in order to determine the time scale-up factor between laboratory batch flotation data and industrial size flotation. The time scale-up factor observed for large sized cells, 160 m3, was found to be reasonably similar to those previously determined for self-aerated mechanical cells, but of lower size, operating at similar recoveries. In addition, the relative effect of mixing, between laboratory batch and an industrial flotation bank, was quantified by the parameter, separating the impact that kinetic and mixing changes have on the time scale-up factor. In general, the rougher flotation operation was found to reach the predicted metallurgical target, and the optimal separability criterion was also respected. The diagnostic generates information about the internal state of the process and helps to identify potential improvements for design, operation and control of the circuit.

Jan 1, 2005

By A G. Tomkins

"Approximately 32 per cent of the worldÆs total gold production has come from greenstone belts (Frimmel, 2008). In these regions numerous small to large, quartz vein-associated gold deposits are hosted in metamorphic rocks ranging from lower greenschist to granulite facies. Historical exploration has focused its efforts on rocks of greenschist to lower amphibolite facies because these seem to contain the most deposits. Consequently, these regions are now reaching mature brownfield status, particularly in developed nations, and finding new deposits is becoming progressively more difficult. In comparison, regions of similar tectonic setting, but instead containing high-grade metamorphic rocks of mid-amphibolite to granulite facies, have received little attention because the first explorers found fewer deposits there.However, these regions certainly do contain some very significant gold deposits such as Hemlo in Canada (~684 t Au), Renco in Zimbabwe (~31 t Au mined since 1980), the very profitable Challenger deposit in South Australia (~36 t Au; recovered + reserve + resource), and the most recently discovered Tropicana deposit in Western Australia (~182 t Au; reserve + resource). High-grade metamorphic terrains therefore offer explorationists an excellent opportunity to move onto relatively green fields within developed nations, which carry less risk associated with development. However, explorationists have comparatively little knowledge of the geological controls on gold distribution in high-grade terranes because: industry experience lies in traditional lode-style gold deposits these gold deposits are geologically more complex there has simply been minimal research conducted on these deposits as a holistic group.Furthermore, research conducted in the last five years has shown us that the previous widely accepted model for gold genesis in these terranes, the crustal continuum model, is incorrect. Here, I discuss features from several gold deposits hosted in high-grade metamorphic rocks and use these to define two categories for explorationists to consider: deposits that formed prior to peak metamorphism (metamorphosed gold deposits) deposits that formed well after peak metamorphism (post-metamorphic gold deposits). There are none that have been convincingly shown to have formed during peak metamorphism.CITATION:Tomkins, A G, 2013. Gold deposits in highly metamorphosed terranes, in Proceedings World Gold 2013, pp 23-26 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Sep 26, 2013

By M S. Henderson, R D. Alorro, L G. Dyer

An alternative leaching system for rare earth element recovery from monazite is under development. The initial stage utilises oxalic acid to convert the rare earth phosphate into an oxalate salt through dissolution and reprecipitation and it is the efficiency of this stage that governs the overall recovery achieved. It has previously been proposed that lixiviant consumption is the primary limitation in this process. This work further investigates a range of conditions in an attempt to further elucidate the factors influencing the achievable conversion in this stage. It has been shown that the pH may be governed by multiple reactions both consuming and producing acid (thus the mild change over time). The importance of proper mixing and potential to operate at lower temperature with only moderate impact on kinetics has also been demonstrated. Staged/sequential leaching is more effective in fresh solution as opposed to restoring the lixiviant concentration with subsequent reagent addition, suggesting some impact of solution composition. However, contrary to previous findings, subjecting the leach residue to fresh solution resulted in significant decline in leach rate and overall dissolution. This may be because a greater proportion of conversion was achieved in stage 1 in this work than in previous investigation. This may indicate that eventual passivation or the presence of some more refractory REE minerals limits dissolution. Iron dissolution was relatively consistent upon exposure to fresh solution, displaying the ability of the solution to continue to leach the goethite component of the concentrate.

Aug 24, 2022

By Roberts T, Firth B. A

A series of flotation experiments was carried out to study the interaction between the parameters of pulp density (mass per cent of solids in feed slurry) and frother addition (on the basis of solid mass feed rate). It was found that certain combinations of pulp density and frother additions caused large losses in yield. The interactive effect of these parameters can be primarily attributed to the total amount of frother added per unit of water. Consequently it is suggested that frother additions be made on the basis of water flow rate. As frother addition increased, in terms of the amount of frother per unit of water, yield increased rapidly but above an addition rate of about 10 g/tone it reached a plateau. Such results correlated well with qualitative visual observations of changes in bubble size and dispersion, with increasing levels of frother addition.

Jan 1, 1984

By Upfold RW, Velzeboer MD

An underground mine fire will influence the ventilation equilibrium in several ways which results in a redistribution of the ventilating quantities and pressures throughout the whole mine. The ventilation carries the combustion products which constitute the greatest danger of mine fires through the mine and provides the oxygen on which the intensity of the fire depends. However, as a result of the ventilat- ion disturbances created by the fire, changes in airflow patterns can take place which are not always obvious, especially when the mine is being served by several fans. The use of com- puter simulation techniques allow for the likely effects to be tested and the different ventilation options to be evaluated as an integral part of the overall emergency/rescue planning and control procedures.

Jan 1, 1981

Underground mine ventilation is now com monly simulated on a digital computer. Such a programme, incorporating natural ventilation has been modified by others to account for methane emission and elevated local tempera- tures. At Wollongong University, the pro- gramme was further developed and extensive interactive graphics incorporated such that any view of the three dimensional mine could be viewed, and superimposed upon that view are areas where a nominated parameter has exceeded a particular value - generally at a nominated time after a particular event and usually a fire/explosion of one type or another. A further programme was developed such that up to 20 'times' could be examined at a particu- lar location after say, a fuel rich fire at some other place in the mine. The output from this programme includes a plot of methane 1, smoke 1, temperature, pressure and air flow versus time - a most useful graphic to observe the limits of safe attendance in a particular Airway.

Jan 1, 1983

By T C. Westerfield, G, M J. Mankosa

An innovative separator known as the HydroFloat cell has been developed specifically for the upgrading of coarse particles that are difficult to recover using conventional flotation cells. The novel characteristic of this separator is the formation of a hindered teeter-bed of fluidised solids into which small air bubbles are injected. The air bubbles selectively attach to hydrophobic particles and form particle/bubble agglomerates that segregate atop the teeter-bed due to their lower apparent specific gravity. The low-density agglomerates are eventually carried into the product overflow launder by the rising current of teeter water. Hydrophilic particles remain in the teeter-bed and are discharged to underflow as a high solids content tailing. Benefits of this hybrid flotation-density separator include enhanced bubble-particle contacting, increased particle residence time, and very low air demand. Test data indicate that significant improvements in the recovery of coarse particles can be achieved using this innovative technology. This article describes the theoretical basis for the development of the HydroFloat cell and provides an overview of recent pilot-scale tests conducted for the phosphate industry.

Jan 1, 2005

By Laxaminarayan Holla

Significant coal reserves in New South Wales lie underneath major bodies of natural and stored surface waters. In order that mining can occur safely and without any adverse effect on the surface, various statutory provisions and administrative guidelines have been framed for regulating the surface and sub-surface strata disturbance. There are particular bases for the existing guidelines and the assumptions which were made in their choice. Evaluation of the guidelines in the light of the knowledge gained during the last ten years indicates that they are conservative in some cases and can be made less restrictive without lowering the safety standards. The suggested changes include reduced width for pillars in both bord and pillar first workings and panel and pillar workings, and increased level of extraction for a given degree of subsidence. Changes, if implemented, would lead to increased coal recovery.

Jan 1, 1987