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By R Trueman

An improved ability to predict dilution for narrow vein deposits enables more accurate economic comparisons between mechanised longhole stoping and other narrow vein mining methods, as well as reducing uncertainty surrounding dilution estimates for deposits at the prefeasibility/ feasibility stage. This paper proposes narrow vein dilution prediction and minimisation strategies for both greenfield sites and operating mines, respectively. The narrow vein dilution method (NVD method) is a tool for more accurately predicting longhole narrow vein dilution. The method is based on a new concept called benchmark stoping width. Benchmark stoping width is based on probabilistic analysis of overbreak distributions from a typical longhole narrow vein mine. The premise for the NVD method is that dilution associated with longhole stoping can be predicted using the benchmark stoping width. In addition to dilution prediction, the NVD method also includes strategies for narrow vein dilution minimisation generally, including; filling, cablebolting, stress relaxation, extraction sequencing and blast overbreak.

Jan 1, 2008

By Yu AB, Azahari HL

Indonesia has the largest coal reserves in the south-east Asian region. According to estimates from the World Energy Confer- ence, it has reserves of 18 billion mt lignite, 4.4 billion mt sub-bituminous coal and 774 million mt bituminous coal (Wyllie,1988). In recent years, substitution of coal for oil in power plants has been the goal of the Indonesian government since proven deposits of coal are about five times as large as national hydrocarbon reserves and most of Indonesia's power stations are still oil fired. Recently a coal fired power plant has been built in Java Barat, which will have a full capacity of about 3000 MW. It is intended to supply coal for this power plant from Bukit Asam mining area (South Sumatra). Coals from Bukit Asam - which are of the lignite or brown coal type - usually contain considerable moisture . It should be noted that reference to moisture in coal pertains to the total moisture content. This is comprised of what is commonly termed as equilibrium moisture and surface moisture. Surface moisture typically affects combustion process as well as pulveriser performance since it possibly influences the relative ease with which coal may be ground. In practice, the surface moisture produces agglomeration of the fines in the pulverising zone and reduces pulveriser drying capacity because of the inability to remove the fines as quickly as they are produced. This agglomeration has also the same effect as coarse coal during the combustion process because the surface area available for the chemical reaction is reduced, hence the combustion efficiency is also reduced. The influence of the moisture of some coals on their grindability (Hardgrove Grindability Index) has been previously correlated by several authors; some of them will be mentioned later. Those correlations, however, could not be immediately applied to any coal since it is still believed that there are other factors which influence the grindability of the coal, such as type and rank of the coal. The relationship between coal moisture content and its grindability has been investigated by Ellmann and Belter (1955). It was found that, for North Dakota lignites, the grindability varied as the moisture content changed. In Britain, Fitton, Hughes and Hurley (1957) stated that, for Bilsthorpe coal, over a wide range of free moisture content (from air-dried to about 30 per cent moisture), the Hardgrove Grindability Index (HGI) remains virtually unchanged. In addition to that, it was suggested that it would be slightly advantageous to dry the coal below its air-dried moisture content (at temperature ¦ 100¦C) to increase the ease with which coal could be ground, especially for low-volatile coal and high-volatile non-caking coal. Furthermore, it was also concluded that a broad relationship appeared between coal rank and Grindability.

Jan 1, 1993

The mining, metallurgical, and petroleum industries can be viewed as financial or as social institutions or both. The differences between these two conceptions of their businesses will influence their environmental and social actions. During the next 10-20 years western industry will be subject to a drop in the growth of a more highly educated labour force and to the emergence of holistic economics, new national goals, and a new ecological perspective. The profitability of the mining industry may therefore be influenced by the human side of its business to a greater degree. The increas- ing human, social, and environmental responsibilities can be discharged by improving the miner's equip- ment; by learning to look at situations through the eyes of all those involved; by developing common `languages' which governments and the public can understand; and by mediating where feasible on the international scene.

Jan 1, 1978

Design of underground extraction layouts to protect surface improvements is an important area of subsidence research in the Coal Mining Engineering Branch of the Department of Mineral Resources, New South Wales, Australia. Some conventional partial extraction layout are important with reference to coal recovery and surface subsidence. The analysis ofsubsidence data collected from field surveys over longwall panels in the Southern Coalfield of New South Wales allows assessment of the effect of pillars left unmined between the longwall panels in reducing surface subsidence. The availability ofa wide variety of layouts with ranging degrees of surface movements affords considerable flexibility in designing layouts to suit a particular situation.Total extraction of coal should be the aim as far as possible. Partial extraction layouts should only be considered when surface subsidence movements caused by total extraction are not acceptable to the surface improvements.

Jan 1, 1985

By Tullemans FJ

This paper describes the general approach to ore reserve estimation and mine planning used at the Kidston Gold Mine. The geological setting and exploration is briefly summarized for background information.A geostatistical study of the deposit was carried out to determine the geological ore reserve. This was confirmed using a manual polygonal technique. Optimum pits outlined by a Lerchs-Grossman open pit design algorithm were manually smoothed allowing mineable reserves to be calculated. Mine production schedules based on kriged block grades and tonnages are continuously updated using production blasthole assays. An arithmetic mean technique of block grade estimation has proved successful to date. After milling approximately 4.9Mt of ore, the mill grade of 2.13g Au/t is only 0.5% above the mine estimate of 2.12g Au/t. The difference in contained gold between "As staked" blasthole reserves and kriged mineable reserves is 3.8%. The application of blasthole kriging as a basis for ore/waste classification in erratically mineralized areas is being evaluated. Planned future developments are briefly mentioned.

Jan 1, 1986

By M Grigorescu, J H. Hodgkinson

The expansive, open cut iron-ore mines in Western Australia typically experience few days of rain per annum, often amounting to less than 250 mm. Unlike mines where rainfall is frequent, they may be less prepared for extreme rainfall events. Such events can cause erosion, flooding and sedimentation, drainage alteration, spoil and stock heaps wetting and effect slope stability. Such impacts may threaten personnel safety, infrastructure, and production. The CRATER (‘Climate Related Adaptation from Terrain Evaluation Results’) framework collates and interprets a mine’s pre-existing data and semi-quantitative information to assess vulnerability to, and ultimately plan to avoid or minimise, flood-related hazard to infrastructure, people, downtime, environment and revenue. Outputs assist decision makers to design investment strategies for minimising mining operations’ vulnerability to climate. Previously developed for smaller, wetter mines in Queensland’s coal region, the outputs provide a hot-spot map, fault tree analysis and an assessment of the mine’s capacity to adapt. The multicriteria evaluation (MCE) within a geographic information system (GIS), equally suits iron-ore mines’ siteconditions (elevation, slope, drainage, soil and vegetation) to identify critical inundation areas. Hotspot results provide target zones for in-depth fault-tree analysis that, in turn, present a range of sitespecific adaptation options. Rainfall-intensity and the number of rain days since the 1970s have increased over central and eastern parts of the Pilbara Region. While tropical cyclones may become less frequent, they are projected to increase in intensity. Although some parts of the Hamersley Ranges receive more than 500 mm per annum, rainfall in the Pilbara is generally very low. Therefore, experience of the impacts of extreme rainfall events in the constantly changing topography of Western Australia’s iron ore region may be sparse. Minimising potential effects can be proactively assisted using CRATER.

Nov 8, 2021

By A E. C Peres, P R. M Viana

The role of flotation columns in comparison with conventional mechanical flotation cells is discussed under the scenario of Brazilian flotation technology. All iron ore concentrator circuits commissioned since 1990 incorporated column only flotation technology in rougher, cleaner, scavenger configuration. Columns were also added to existing circuits, especially at the cleaner stage. Columns were also incorporated to phosphate ore flotation circuits operating mechanical cells. In two phosphate concentrators, columns substituted for all mechanical cells. Columns perform the cleaning stage in a large sulfide copper concentrator, following rougher flotation in tank cells. Scavenger of the cleaner tailings is performed in tank cells at this plant. Other ores that are concentrated in flotation columns include graphite, talc, lead-zinc sulfide, and a zinc hydrometallurgical residue for silver recovery.

Jan 1, 2005

By K Nakashima, K Aya, T Sumita, N Saito

Electro slag remelting (ESR) is one of the methods used to produce high-cleanliness steel. In the ESR method, the product steel electrode is immersed in flux, and the electrode is melted by the Joule heat of the flux generated by high current. CaF2-based melts are mainly used as fluxes, but the electrical conductivity of CaF2-based melts varies widely among researchers and measurement methods. Therefore, this experiment aims to measure the electrical conductivity of CaF2-based melts based on the van der Pauw-Ohta method, which does not require the cell constant that is a fundamental error factor in electrical conductivity measurement at high temperatures. The measurement temperature was set at 1450–1600°C, and dehydrated Ar flowed through the furnace at 200 mL/min. Electrodes were fabricated by Pt-30mass per cent Rh alloy, and the electrodes were connected to an impedance analyser using a four-terminal probe. The electrodes were immersed in the melt, and the impedance and phase angle were measured by AC frequency sweep (50 Hz to 200 kHz). The electrical conductivity was then calculated by utilising the impedance’s real part values when the impedance’s imaginary component was zero. The electrical conductivity showed a positive temperature dependence. The electrical conductivity of 60(CaO⋅Al2O3)-40CaF2 melt increased with increasing temperature but was found to be roughly one-third of those of the previous studies. In the conductivity measurement of 60(CaO⋅Al2O3)-40CaF2 melt, the AC frequency with a phase angle of 0° was found to be different depending on the temperature and immersion depth. By sweeping the frequency, the impedance at the phase angle of 0° can be obtained, which enables us to measure the electrical conductivity more accurately.

Jun 19, 2024

By Parker C. J, Mikula P. A

The excavation for the Sydney Opera House Parking Station comprises a large donut shaped underground cavern with a central sandstone pillar. The maximum effective roof span is about 19 m and the rock cover is between 7 m and 8 m. Permanent support for the roof and the various services tunnels consists of a combination of tensioned anchors, and untensioned dowels, and mesh with shortcrete and fibrecrete as the final lining. Steel sets were installed at main intersections.Fundamental to the design philosophy for excavation of these spans at such shallow rock cover was the use of monitoring to check on the adequacy of the installed support. Prior to excavation, extensometers, inclinometers, piezometers and surface settlement survey stations were installed. Underground survey stations, anchor load cells and shotcrete pressure cells were installed as excavation proceeded. Excavation commenced at the crown using an initial heading and three widening stages. Geological mapping during excavation confirmed borehole expectations, namely sandstone beds 1 to 4 m thick interbedded with thin shale units. Bedding plane contacts varied over short distances from tight partings to thick brecciated seams. Jointing was subvertical and joints tended to be bed-limited.

Jan 1, 1993

By Grady B. V O, Cavell K. J, Ault A. R, Newman O. M G, Malcolm J. McPhersqn

Cyclic voltammetry (CV) has been evaluated as a technique for monitoring the quality of an industrial zinc sulphate electrolyte. The basis of the method involves measuring a change in the polarisation of the zinc nucleation reaction at an aluminium surface and relating this to the impurity content and/or the overall quality of the electrolyte. Specifically, the technique aims to be able to indicate and quantify detrimental synergism between impurity elements, something which traditional analytical techniques are incapable of providing. The technique has found some success with regard to monitoring glue additions in a range of metal electrolytes. It has been found that investigations by a number of workers over the past 15 years have produced variable and often misleading results due to the inadvertent use of commercial purity aluminium working electrodes. It has been shown that impurity elements in the working electrode can give rise to a range of responses that are not obtained when pure aluminium is used and that the response is variable due to the lack of surface homogeneity of commercial purity aluminium electrodes. Furthermore, it was demonstrated that previous detection limits reported in the literature were based on the presence of additional peaks in the cathodic scan and not polarisation effects. The results of this study have shown that when a pure aluminium working electrode was used, the method was incapable of detecting any change in polarisation for an electrolyte containing three common impurities (Co, Ni and Ge), at concentrations that would significantly reduce optimum electrolytic performance. A range of methods was tried to sensitise the technique, including raising the temperature and acidity, and adding antimony in order to induce some synergism. In all cases the polarisation response was unchanged. Consequently, apart from the commercialised application for monitoring additions of antimony and levelling agents such as glue, CV has very limited application as an electrolyte screening technique.

Jan 1, 1993

By Kitzinger F

The economic climate of the Canadian mining industry forced an increased interest in rapid, continuous excavation techniques for hard rock formations. The potential applications and advantages of continuous mining over the present drill- blast-muck labour intensive cyclical methods are considerable. Noranda investigated an electrical technique, Plasma Blasting showing considerable promise for mining hard rock. The background of the technology and the theory of blasting rock with electricity is described. The Plasma Blasting process is based on the fast discharge of stored electrical energy into a small amount of electrolyte, suitably located in the rock. The electrical energy converts the electrolyte into high pressure plasma, which expands very quickly, thereby, generating a shock wave. This shock wave produces a stress field inside the rock, resulting in a blast similar to that made by chemical explosives, but without the deleterious fumes. Noranda is currently blasting boulders of 4-5 tonnes and is at present constructing a mobile, autonomous secondary rock breaker for underground and open pit applications. Tests on in situ hard rock formations will lead to the development of a continuous mining machine. Production rates of 500 tonnes per man-shift could be obtained with such a machine.

Jan 1, 1990

Quite apart from economic considerations, the following performance parameters must be considered when selecting an explosive for a particular blasting operation. 1. total energy yield/kg, and more particularly, strain energy/kg and bubble energy/kg of charge 2. charge weight/m of blasthole 3. sensitivity of the charge 4. water resistance of the charge The effective division of an explosive's total energy into strain energy (SE) and bubble energy (BE) is explained as is the influence of each energy component on blast results. Because some rocks require a high strain energy for effective breakage, while others are most satisfactorily fragmented by bubble energy, values of SE and BE are more meaningful than those of total energy. Unfortunately, our extensive knowledge of the effects of certain variables on total energy has not yet been completely supplanted by the influence of these variables on SE and BE values. Relative SE/kg and BE/kg values are presented for a range of explosives. The 'charge density of ammonium nitrate/ fuel oil (ANFO)-type explosives is essentially constant throughout the length of the charge; because of their compressibility, slurry

Jan 1, 1974

By Jankola W. A, Delong O. J

Historically, the silica content of zinc concentrates treated at Cominco's Trail Operations has been low. Silica in the roaster calcine seldom exceeded 1.5 per cent because of the low silica content of concentrate from Cominco's Pine Point mine. With the shutdown of Pine Point, alternate sources of concentrate were required and it was anticipated that calcines containing greater than two per cent silica (with excursions above three per cent) would have to be treated. Previous experience indicated that the existing leaching circuit could not tolerate such high levels. Therefore, a research program was undertaken to identify the key factors affecting silica precipitation; to compare different process alternatives; and to make recommendations for modifications to the existing plant. A project to modify and upgrade the leaching circuit has now been completed. Calcines with higher silica contents are successfully treated, but the upper limit of the circuit is unknown. The results of the research work will be discussed and the new leaching plant will be described. Recent operating results will also be presented.

Jan 1, 1993

By M Wilkes, C-Q Liu

Microbial oxidation of refractory sulphide ores (particularly gold and copper ores) are well-established techniques that are increasingly employed because of their low capital and operating costs and environmental benefits. CSIRO has established a multidivisional project, the æBioMineral Processing InitiativeÆ, with the goal of generating new and improved high temperature micro-organisms for biological oxidation of these refractory ores. The project is currently focused on the discovery/generation of novel hyperthermophiles for the bioleaching of copper from chalcopyrite. As part of this project we are investigating the practicalities of genetic modification of iron/sulphur oxidising micro-organisms. The molecular biology of iron/sulphur oxidising acidophiles is still in its infancy. This work is aimed at improving our knowledge of vectors, promoters, selectable markers, gene transfer and expression in these organisms. The Acidithiobacillus ferrooxidans genome is currently available and genomics is proceeding at a rate where in the next few years we can expect at least one or two relevant microbial genomes to be sequenced each year. New genes that impart useful characteristics to iron/sulphur oxidising acidophiles will be available from published genomes and the study of newly isolated hyperthermophiles. We need to be in a position to clone and express those genes. This paper will describe the isolation, transfer and expression of thiocyanate hydrolase genes in Escherichia coli and At. ferrooxidans. Most common antibiotics are not effective against iron/sulphur oxidising acidophiles. Also, the use of antibiotics or their resistance markers outside of a laboratory setting would not be appropriate. Resistance to thiocyanate should be a useful selectable marker, without implications for human or animal health. Additionally, thiocyanate resistant iron/sulphur oxidising acidophiles might have application in gold bio-oxidation plants in arid areas where reuse of contaminated tailings water is desirable. The cloning of thiocyanate genes in broad host range plasmids under the control of E. coli and At. ferrooxidans promoters and the expression and phenotypic effects in both species will be described.

Jan 1, 2002

By Bearman R. A, Parkin R. M

Traditional quality control procedures for aggregates production within the quarry industry rely on off-line laboratory analysis, resulting in poor performance and inconsistent product quality. A high speed on-line aggregate classification system is described here. A product sampling system directs aggregate through an inspection chamber where a novel imaging system digitises the particle geometry. Data processing algorithms extract dimensional data and image features, while a neural network classifier assigns a qualitative shape descriptor to each rock particle. This system provides each sampled batch with a complete analysis of size and shape distributions, complementing a new generation of cone crusher technology to maximise product quality and plant efficiency.

Jan 1, 1995

By Shugen T

Due to the increase of passenger traffic, a new station is proposed which is about 6.8km from south station. An underground connection line is under feasibility study for connecting these two stations in order to avoid the in- terference with surface traffic. In this paper the traffic condi- tion and the geological formation along the planned route will be described and analysed. Different methods of con struction have been proposed and dis- cussed such as shield method, slurry wall method etc. In this paper compari- sons are made among these methods and advantages and disadvantages given. The authors proposal to construct this connection line by NATM raise wide

Jan 1, 1987

The unique chemical and physical properties that can be displayed by polypropylene and its copolymer derivatives are enabling its development as a truly versatile material for water filtration. Well known applications include spiral wound cartridge filters commonly used for household water or the office drinking fountain, to pressure membranes that provide micro, ultra or nano size filtration barriers, whilst needle-felt or woven cloth filter belts or inline pressure bag cloths are well known to the hydro metallurgist and process engineer. A relatively new filtration concept that is generating interest and applications across all industries including the mining sector involves use of a unique fabric type filtering media made from polypropylene fibres. This technology not only has a vastly wider window for potential applications, it delivers an attractive cost saving alternative to the traditional sand media or diatomaceous earth type filters, along with potential benefits for integrated filtration units. This paper discusses the proven potential of the fabric media technology with examples of performance comparisons and confidence gained from full scale operating installations at mine sites and other locations.

Jan 1, 2004

By Miskelly N

In Australia and New Zealand, the 'Australasian Code for Reporting of Identified Mineral Resources and Ore Reserves', which was released by industry in 1989, is operating successfully in a co-operative approach between industry and regulatory authorities. Similar codes or guidelines exist or are under development in the United States of America, Canada, the United Kingdom and South Africa, although the regulatory backing given to the Australasian Code is unique. International standard definitions for Mineral Resources and Reserves, and for categories of Resources and Reserves, have been under development by the Council of Mining and Metallurgical Institutions since 1994 and have already stimulated considerable convergence of definitions and reporting standards in participating countries. It is hoped that agreement on this international standard for public reporting by mining companies will be reached within the next two years, and it is expected that adoption of the standard will result in a higher and more uniform quality of reporting worldwide, with a consequently greater interest on the part of the general public and financiers in investing in the mining industry.

Jan 1, 1997

In the future to excavate sufficient coal for power generation, two dredgers would be required to dig overburden or interseam 70010 of the time and three dredgers 40010 of the time. One overburden system was not adequate for this requirement, making coal production reliability vulnerable. TS5 spreader is the new machine element of this system. The selection of the best type of machine configuration to suit the application was then subject to an internal SECV VE Study, a registration of interest and a tender for two machine alternatives. This paper outlines the reasons why SECV planned the Secondary Overburden System and how the Krupp machine met these requirements. It also identifies the main design features of the machine and its constructability which will allow the machine to be operational by the end of May, 1990.

Jan 1, 1989

By Quan P. M

The great advances made in the application of solvent extraction to the recovery of copper from low grade ore sources over the past 15 to 20 years are well known. Solvent extraction is an essential step in the recovery and purification of copper from dilute sulphate leach solutions by which some one million tonnes of copper are now electrowon annually. A reagent is also available for the selective recovery of copper from chloride leach solutions and this may hold the key to the processing of complex sulphide ore concentrates. By comparison, the use of solvent extraction in the recovery and processing of zinc has as yet found little favour and is confined to only a few specific and comparatively small applications. This is despite the ready availability of a large number of low grade zinc sources and zinc-bearing wastes and residues. It is suggested that this difference is due in large part to the absence of suitable reagents having the particular features required to enable them to fit into a solvent extraction - electrowinning based process for zinc. Ideally, for the recovery of zinc from dilute sulphate solution, an extractant should operate on a proton exchange principle and be strong for zinc in the same way that o-hydroxyaryloxime reagents are strong towards copper. It should load efficiently with zinc at the pH of typical sulphate feed streams without the need for neutralisation and yet be stripped efficiently by spent zinc electrolyte. Another factor of major importance for many applications, however, is that it should be highly selective for zinc over ferric iron. These features have now been realised in a development extractant DS5846, which is a formulation of a novel class of reagent currently under investigation by Zeneca Specialties. The properties of this reagent are described with respect to selectivity, isotherms and how they compare with phosphoric and thiophosphoric acids that have been previously proposed for the extraction of zinc. For the recovery of zinc from concentrated chloride solutions a solvating or neutral donor type of extractant is required which again should ideally have high selectivity for zinc over a number of other metals, particularly iron. The new reagent Acorga ZNX50 is based on a formulation of a novel class of compound developed specifically for this purpose. It gives efficient extraction of zinc from feed solutions that are four to six molar in chloride ion but is readily stripped at 60 - 65¦C using either water, dilute brine, or spent zinc chloride electrolyte. The reagent is highly selective for zinc over iron and a range of other metals including cadmium, arsenic, lead and magnesium.

Jan 1, 1993