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The dynamic response of holdup in a continuous ball mill has a direct influence on the rate function of grinding kinetics and is useful for predicting the variation in the size distribution of the finished product with time.A model was proposed involving three interacting, completely mixed chambers and this was used to derive analytically the transfer function of the system, from which the unit impulse response and the unit step response of the holdup with feed rate were obtained.The theory was confirmed by comparing it with previously published experimental data for the residence time distribution of particles passing through a ball mill.

Jan 1, 1975

By G Metzner, R Rodriguez, C Savage

OK Tedi Mining Ltd. (OTML) is in the process of optimising the concentrator performance. One aspect that has been recently implemented is an upgrade of the existing expert control philosophy on the grinding circuit and this will be the topic of this paper. Ore grinding in SAG mills is a multi-input multi-output (MIMO) process subject to several disturbances, most typical being quick acting disturbances such as changes in ore characteristics like hardness and particle size and slow acting disturbances such as ball charge variations and liner wear. The OTML SAG mills treat ore from diverse ore bodies and receive fresh feed subject to large changes in particle size. These circumstances make these mills particularly challenging to control. In this paper, a comparative analysis is presented between the performance of the OTML SAG mill #2 before and after the commissioning of a hybrid control strategy. The strategy uses Expert Knowledge combined with advanced disturbance rejection to reduce the variability of the main process variables, especially pressure and power. It further optimises the overall operation by driving the SAG mill #2 against process constraints (e.g. high power, high motor temperature and high scats recycle rate) and maintaining the operation at or near this point. This strategy is implemented by a combination of the manipulated variables (i.e. fresh feed tonnage and % solids) at any given time.The paper will present trends and a statistical analysis of the comparative results of the mill operation over a period of months, showing a 30% reduction in mill power / pressure variability and a 12% improvement in average power drawn. An increase in throughput was also observed, but cannot be conclusively attributed to the change in mill control due to other changes that were made to the SAG mill #2 during the period of comparison. An additional benefit includes better acceptance from the operators with improved consistency of the SAG mill #2 operation across shifts.The paper will also discuss further improvements envisaged in the continued optimisation of the grinding control circuit.CITATION:Savage, C, Rodriguez, R and Metzner, G, 2013. Hybrid process control strategy for the Ok Tedi Mining Ltd semi-autogenous grinding mill #2 - A comparative analysis, in Proceedings MetPlant 2013 , pp 202-214 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 15, 2013

Analyses of scheelite from all the known scheelite fields in the South Island of New Zealand have shown that the scheelites are essentially molybdenum-free. The scheelites are almost stoichiometric CaWO4, except for some strontium replacing the calcium, with a maximum of 0·92 per cent SrO. Variation in strontium content appears to be' related to the metamorphic grade of the enclosing rocks.

Jan 1, 1970

By Fisher N. I

Disequilibrium ratios (U3O8/eU3O8), which assess the degree to which gamma activity represents the uranium content of a sample, have been measured on a representative set of samples from the ore zone of a carnotite ranium deposit located at Yeelirrie, Western Australia. A statistical analysis has been performed to investigate the dependence of the ratios on lithology and on the location of the sample in the orebody. The analysis indicates that dependence on lithology and on position across the orebody is negligible. Samples from the western end of the orebody and those from below the water table level tend to have slightly lower ratios than samples from other positions, although these trends are small compared with a large random variation in the data. The large random variation could result from some redistribution of the daughter isotopes of uranium within the orebody. On the basis of the results from all the samples, the estimated deficiency of uranium relative to radium in the ore zone of the deposit is 11 per cent.

Jan 1, 1980

By Manca PP, Lassandro R, Caranassios A, Massacci G, Ciccu R

The paper discusses the state of the progress reached in the development of the diamond wire tool for cutting hard rocks. To the advances of this relatively new technology a substantial contribution has been provided by the research being carried out at the University of Cagliari on samples of granite rocks from different Sardinian stone quarries. On the basis of field experiments and laboratory test data, the mechanism of diamond wire cutting has been assessed. In particular the influence of the rock features and operational variables on tool performance (cutting rate and bead wear) has been Elucidated.

Jan 1, 1992

A major problem in open pit mine planning is to determine the optimum pit limit of the mine. The optimum pit limit is the one with maximum discounted net profit and satisfies technical conditions. A number of optimisation techniques have been proposed for determination of pit limits. Among these techniques, those based on graph theory are suitable to solve the three-dimensional (3D) problem. In this paper, two maximum flow methods named, Dinic's algorithm and Push-Relabel algorithm have been used to find the optimum pit limit of an iron ore mine. This method has been implemented in Gol-e-Gohar iron mine in south east of Iran in order to find the final pit limit. Issues, like properties of the mine and orebody, are studied. These properties include wall slope, sulfur and phosphor grade restrictions. The result shows that these properties have significant effect on the determined pit limit.

Dec 6, 2010

By D Craw, D Wilson, D Chappell

Gold is extracted by cyanidation of a sulphide-rich concentrate at Macraes mine, and after cyanidation, the concentrate is discharged to tailings impoundments. The concentrate tailings were discharged to a dedicated concentrate impoundment from 1989 to 1993, afterwhich they were blended with the flotation tailings. Since mid-1998, concentrate tailings have been redirected to the dedicated concentrate impoundment. The concentrate tailings contain up to 1 ppm gold, and will be reprocessed in the future. However, it is a regulatory requirement that a contingency plan be in place to rehabilitate the concentrate tailings should the mine operation cease for any reason. Initial predictions suggested that the sulphide-rich tailings would oxidise and acidify, creating a potential long term environmental problem. Investigations of the state of the tailings after 4 years show that these predictions were overly conservative. Only minor oxidation has occurred in the upper 2 metres of the tailings where the pH has locally dropped from 10 (discharge condition) to between 7 and 8. Below 2 metres, the tailings are essentially unchanged from their deposition state. The low rate of change in the tailings is due to their very low permeability which in turn is a consequence of the fine grain size (ca. 15 ¦m). Dewatering is extremely slow, and incursion of oxygenated water is negligible. Calculations suggest that water movement over 30 m will take at least 100 years and possibly 1000 years. The contingency plan is to capitalise on the very low permeability and keep the tailings from drying with a semipermeable cap. A layer of limestone will be added to the top of the tailings, beneath the cap, to enhance alkalinity of any percolating water. If acidification does occur, contrary to expectations, any acid produced will be neutralised by underlying calcite-bearing schist, schist in the concentrate impoundment wall, and the flotation tailings immediately downstream. In addition, dilution by alkaline ground and surface waters would further ameliorate any acidic discharge.

Jan 1, 1998

This paper reviews the development and operation of a small underground tin mine in NE Tasmania. Tin mineralisation was discovered in the Lottah area in the 1880s with early alluvial and eluvial workings leading to the development of large low grade open pit operations. Apart from short lived activities operations ceased in 1915. Intensive exploration in 1978 - 1981 outlined substantial tonnages of low grade tin mineralisation (0.2% Sn) of open pit material. An underground ore body was also located (800 000 tonnes 0.6 per cent Sn). Spectrum Resources Australia Pty Limited acquired a 98 per cent interest in the property in 1988. Mine and mill development began in early 1989 based on an underground mine utilising trackless mining using room and pillar with fill stoping. The milling circuit involves primary jaw crushing, Barmac secondary crushing to 1 mm, Mogensen and DSM screens with jigs and tables to make a wet concentrate. Final tin concentrates are produced by high tension and magnetic separation. Planned production rates are 500 t/day with a mine life of six to seven years.

Jan 1, 1990

By M I. Pownceby, S Bhargava, F Charalambous, S McMaster, R Ram, J Tardio

"A key component of any geometallurgical investigation involves being able to predict element or mineral recoveries from simplified input data such as bulk chemistry and/or mineralogy. This relies on the metallurgist having access to accurate information regarding the chemistry of the ore and gangue minerals as well as the likely impact on processing/extraction caused by the impurities (present either as gangue or as substitutional impurities). In this study the chemical properties of two commercially important uranium minerals, brannerite (U4+Ti2O6), and uraninite (U4+O2), were characterised using X-ray diffraction (XRD), scanning electron microscopy (SEM), and electron probe microanalysis (EPMA). Significant levels of impurities were present in both samples with the uranium minerals deviating significantly from their ideal chemical formulae. Differences in chemistry were due to: cationic substitution decay of the uranium isotopes into radiogenic lead and other daughter products mixed uranium oxidation states post-depositional alteration.As well, the brannerite sample showed evidence of significant radiation-induced metamictisation. Leach tests to measure the ease of extraction of uranium from both samples were conducted over a wide range of conditions (temperature, acid concentration and oxidant concentration). For uraninite, the lower U dissolution rates observed in the natural sample compared to a synthetic UO2 sample were directly attributed to the presence of impurities. For brannerite, significant metamictisation of the natural sample led to enhanced U extraction rates compared to a heat treated fully crystalline sample. This study highlights the importance of detailed mineralogical characterisation studies in any uranium process mineralogy investigation as the compositional, textural and microstructural aspects of the main uranium phases present will likely play an important role in any process to extract uranium.CITATION:Ram, R, Charalambous, F, McMaster, S, Pownceby, M I, Tardio, J and Bhargava, S, 2013. Chemical and microstructural characterisation studies on naturally occurring uranium minerals - implications for processing, in Proceedings The Second AusIMM International Geometallurgy Conference (GeoMet) 2013, pp 325-334 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Sep 29, 2013

By S F. Simmons

The Ohaaki Rhyolite and the Rautiwiri Breccia are two volcanic units occurring in the shallow and deep parts of the Broadlands-Ohaaki geothermal system. Alteration of these units by chloride waters results in distinct mineral assemblages that also have distinct whole rock compositions. The Ohaaki rhyolite is altered to an assemblage dominated by quartz, adularia, illite and pyrite as a consequence of silica, potassium and sulfur metasomatism. Locally, these rocks contain up to 0.5 ppm Au. The Rautiwiri Breccia by contrast is altered to an assemblage dominated by albite, adularia, quartz, illite, chlorite and pyrite in association with modest sodium metasomatism. Whole rock oxygen isotope compositions of altered rocks range between 3.3 and 7.5 ë, and are generally lower compared to their fresh rock equivalents having values of 9.5 to 10.6 ë; the result is broad pattern of lower values with increasing alteration intensity.

Jan 1, 2002

By D Craw, J Youngson

Recent exploration for mesothermal gold deposits in the Otago Schist has focussed largely on extensions of, or analogies to, the reverse fault-hosted Hyde-Macraes Shear Zone deposit. Abundant normal fault-hosted mesothermal and epithermal vein deposits in the Otago Schist have attracted less attention, largely because they have limited lateral extent and steeper dips. Northwest-striking normal fault-hosted vein sets near Barewood and Hindon in east Otago crosscut schist foliation on the Barewood-Hindon plateau at a high angle along a combined strike length in excess of 20 kilometres. The trend of the vein sets is not linear, but rather contains several right lateral steps. Almost all veins dip steeply to the northeast. Angular discordance between schist foliation and the plateau surface along the trend increases from near zero at the northwest end of the veins to about 30¦ at the southeast end. Crude formation depth estimates decrease from about 7.5 km at the Barewood end of the zone to

Jan 1, 2002

May I first of all say that I am fully conscious of the great compliment paid to me when I was invited to accept the Presidential Chair for this current year. I realise that it is an onerous task by reason of the fact that the Chair has been occupied in the past by so many able and distinguished men, and I realise also that I have been set a standard which is hard to emulate. "It is my desire however, in accepting the post that I may be able to contribute in some small measure to the further advancement Of the aims and objectives of the Institute and I thank you all for the confidence you have shown in me.Secondly, on behalf of the Company and in my Presidential capacity, I want to extend to each and everyone of you a hearty welcome to Whyalla and I hope that you will all return to your respective fields of endeavour feeling that you have had a most interesting, enjoyabIe and instructive time with us here in Whyalla.In this year of 1951 marking as it does the culmination of the first 50 years of Federation in Australia and yet another half century of human endeavour and progress, we are brought to a point where it is perhaps natural that we should pause, to review what has been achieved, in that span of time, and to look at the tasks ahead.It is no exaggeration to say that the story of Australian development since the inauguration of the Commonwealth 50 years ago has no more remarkable chapter than that of the-growth of its manufacturing industries.Each decade has borne witness to steady and substantial growth of our secondary industries and whilst it is true that our financial well-being still rests heavily on our primary production, we have, as a nation, moved surely in the direction of a more balanced economy. More and...

Jan 1, 1951

By J Ferreira

To speed up multivariate geostatistical simulation it is common to transform the set of attributes into spatially uncorrelated factors that can be simulated independently. One decorrelation method is the method of minimum/maximum autocorrelation factors (MAF), where a two structure linear model of coregionalisation is assumed. The transformation decorrelates the theoretical model exactly, but the actual data are only approximately decorrelated. The MAF transformation can therefore be seen as a special case of a non-orthogonal approximate diagonaliser of a set of symmetric matrices. A more general approach for approximate joint diagonalisation (AJD) has been developed in the context of blind source separation. For these AJD algorithms no assumptions are made beyond symmetry of the individual matrices and so they can be applied to a family of experimental semivariogram matrices. In their application there are no restrictions on the number of structures in the linear model of coregionalisation (LMC) thus removing one of the conditions placed on the subsequent modelling of the spatial structure of the factors. In this paper the general background for the U-WEDGE AJD method is presented. It is shown that the U-WEDGE method achieves better spatial decorrelation than the MAF method. The factors derived from U-WEDGE are simulated using conditional turning bands simulation and then backtransformed to attribute space.

Sep 26, 2011

The need for the hydraulic transportation of coal in the New South Wales coal industry, both from the coal face to the surface and from the coal mine to the consumer or the port for export, is explained. Details of research projects currently in'progress and involving the hydraulic transportation of New South Wales coals are given together with information on the hydraulic transportation of coal in the United States of America.The potential of hydraulic transportation as a viable alternative to the proposed expansion and upgrading of the New South Wales railway system to meet the projected New South Wales coal production to the year 2000 is described.

Jan 1, 1980

The area between Merrygoen and Digilah is located on a structural high that separates the Sydney Basin from the Great Artesian Basin, and hence the stratigraphic succession of younger rocks overlying the basement is relatively thin. The stratigraphy is briefly described and it is shown that fluvial sedimentation prevailed from Upper Permian through to Middle Jurassic times. Flint clays occur in the Permian, Triassic and Jurassic but only those in the Jurassic appear to have commercial value at present. The chemical, mineralogical, and physical properties of the flint clays are discussed.

Jan 1, 1973

A pilot plant has been constructed for the low temperature carboni-zation of Wallarah (N,S,W6) coal at the rate of 300 pounds per hour. The plant was built and tested at Australian Mineral Development Laboratories for Broken Hill Pty, Ltd. Char product was required within the specifi-cation 15.5 `S' 1 per cent volatile matter. The design was based c atz an entrained state carbonizer developed by Parry and U.S. Bureau of Mines co-workers at Denver, U.S.A. The method involved the carbonizatioan of fine coal by entrainment with air in an externally heated reactor.. The heat required for carbonization of tits coal was supplied to the be, both through the reactor walls and also by internal cambustion of products .

Jan 1, 1963

By S M. Loewen, J J. Fuykschot

Located in the north-west of Kazakhstan is a world-class podiform chromite deposit. Donskoy mining and beneficiation complex (DGOK), a branch of Kazchrome TNC, which is a subsidiary of the Eurasian Resources Group (ERG) operates two underground mines in this area, one of which is the ‘10th Anniversary of Kazakhstan Independence’ (DNK) mine.The mine currently applies the gravity caving mining method, producing 1.8 Mt/a of ore utilising a slusher layout and rail transport to the hoisting shafts. The deeper zones form the largest mineral resources at the DNK mine and are planned to be developed in the next several years. At this depth, the generally poor ground conditions, combined with the high in situ stress state will potentially lead to extremely challenging mining conditions.This paper describes a technical study undertaken by SRK to determine the possibility of increasing the maximum production rate from the currently envisaged 6.0 Mt/a to 7.2 Mt/a, and to reduce the time taken to steady state production.Based on a newly created 3D model, the inclined caving method was proposed for the largest orebodies. This method, presently not implemented at any operating mine, although planned for two other projects, was deemed very suitable to deal with the weak rock mass characteristics and the plunging morphology of the mineralisation.Dassault Systèmes’ GEOVIA’s Footprint Finder software (a module of GEOVIA’s PCBC™) was used to determine the caving zones and production schedules. The total mine design was completed in Deswik software, and resulting schedules combined in Excel.In addition to the use of an inclined caving method, several other suggestions were made to increase the productivity of the mine, such as the application of a conveyor belt system transporting multiple material types, teleremote technologies and the application of thin sprayed liners to reduce the swelling of the rock mass.CITATION:Fuykschot, J J and Loewen, S M, 2016. Inclined caving option for the DNK mine, Kazakhstan, in Proceedings Seventh International Conference and Exhibition on Mass Mining (MassMin 2016), pp 669–682 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2016

Biologically-mediated phenomena are involved in many of the natural processes by which mineral deposits are formed and ore bodies transformed and degraded. They may facilitate the environmentally-damaging effects of mining and mineral-processing operat- ions. Under contrived and controlled conditions, however, these phenomena can form the basis for economically- attractive processes for the recovery of metals from low-grade deposits by dump, heap or in situ leaching. They have application also in processes for the regeneration of leaching reagents and some potential for'-the recovery of metals from dilute solution. The micro- organisms concerned are potential sources for the production of novel flotation and solvent-extraction reag- ents. Perhaps the greatest opportunity for biotechnological processes in min- ing and metallurgy lies in the possib- ility of the evolving of novel proced- ures for the substantially complete recovery of metals from process tail- ings by the unlocking of recalcitrant and complex mineral assemblages, and for the beneficiation of some mineral materi,hls.

Jan 1, 1982

By A A. Ndiaye, A Galli

In a companion paper on current hedging practices in the mining industry (Armstrong et al, 2009) we showed that contrary to popular belief, mining groups are still using financial derivatives to hedge against foreign exchange risk and interest rate risk, and more recently against adverse changes in energy prices, notably the oil price. This paper presents a case study on a hypothetical gold mine to illustrate the impact that hedging policies could have on its profitability by reducing the downside risk due to adverse changes in the exchange rate and increases in fuel prices. The characteristics of the hypothetical mine have been set to reproduce those of a real gold deposit, the Kisladag mine that is currently being exploited by open pit methods in Turkey. This mine was selected because its feasibility study was available to the public. Geostatistical simulations are used to reproduce the inherent uncertainty on the recoverable reserves û stochastic simulations are used to generate the variability of the other three key sources of uncertainty: the gold price, the cost of energy and the exchange rate. A simple strategy based on straightforward vanilla options (puts and calls) was developed for hedging the last two risks, on the assumption that the company sells its production at the prevailing spot price.

Jan 1, 2009

When the mining and milling of 1100 copper orebody commenced at Mount Isa a satisfactory grade of copper concentrate was difficult to produce. The major concentrate contaminants were fine pyrite and silica, particularly in the minus 10 microns fraction. Studies of the 1100 orebody showed that much of the fine grained pyrite and a proportion of the silica present in the ore contained carbonaceous matter in the form of complete or partial rims and as internal carbon films disseminated throughout grains. The hydrophobic surface property of the carbonaceous material resulted in inherently flotable fine pyrite and siliceous particles.The addition of a 60:40 mixture of nigrosine and dextrine, initially to a prefloat concentrate of the inherently flotable carbonaceous material and finally to the total copper flotation feed, successfully controlled the flotation rates of the carbonaceous pyrite and silica. The objective of a 25 per cent Cu concentrate grade was then achieved without decreasing copper recovery.

Jan 1, 1971