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By T Tran, F Lucien

Supercritical fluids (SCFs) have gained recognition as solvents for the extraction of a wide range of organic materials. Their principle advantages over conventional organic solvents are that they possess much more favourable transport properties and that such properties can be easily altered by adjusting the system temperature and/or pressure. More recently, SCF solvents have been employed in the extraction of metal ions. The direct extraction of metal ions using SCFs such as CO2 is normally not possible due to the charge neutralisation requirement for solubilisation. However, extraction can be achieved with a SCF solvent containing an organic complexing agent as a cosolvent (Laintz et al, 1992; Laintz and Tachikawa, 1994; Dehghani, 1996). The role of the SCF is therefore similar to the role of a diluent in conventional liquid-liquid or solvent extraction processes. In this regard, SC-CO2 is a particularly good diluent since it exhibits good solubility for many organic complexing agents. The extraction of metals with SCF solvents has been examined mainly in the analysis of environmental samples and the treatment of metal contaminated wastes. Nonetheless, some interesting results have been reported recently on the extraction of rare earth metals, which highlight the potential of SCF solvents in mineral processing applications (Laintz and Tachikawa, 1994; Dehghani, 1996).

Jan 1, 2000

The Granites Gold Mine has far exceeded the design capacity of 300,000 tonne per annum during its first sixteen months of operation. The presence of considerable free coarse gold has made it imperative that the gravity section operate at maximum efficiency. The inadequacy of acid digest- ing facilities and trying climatic conditions prompted management to initi- ate investigations into the use of Intensive Cyanidation as an alternative method for upgrading gravity concentrates prior to smelting.

Jan 1, 1988

Transport technology has produced social changes since the invention of the wheel five millenna ago when man was freed from the need to expend large amounts of energy to move goods and people. Further impetus came with the Industrial Revolution when mechanical power producing devices were applied to land and-water transport. This leap, together with the application to air transport has caused enormous social changes in our way of life. The state of technological advancement of transport modes has dictated to a large degree the develop- ment of Australia and Papua New Guinea. It is suggested that we should not make advances for technology's sake but examine the real needs of the users of transport and ensure that the un- necessary costs are not incurred. The transporting techniques for the ore, waste and slurries used by Bougainville Copper in Papua New Guinea are, in general, quite conven- tional but the scale of operations and the location has modified some modes. in particular the soft' overburden and concentrates were slurried for trans- port and the lack of experience in humid climates restricted the choice of the mine haulage truck. The near future of the transport. industry is seen as an expansion in equipment sizes but the suggestion is made that we need to examine more than the economic and technical aspects; it is necessary for the social con- sequences of our actions to bear examination by outside opinion

Jan 1, 1973

By J K. de Wet, G Balassone, J D. Singleton, V Arseneau

The Accha-Yanque zinc belt in southernPeru is a major zinc-lead rich metallogenic province. In the belt are comprised several non-sulfide-type occurrences, extending on the periphery of the Yauri-Apurfmac batholith (Oligocene-Miocene). Zinc mineralisation at Accha (almost fully oxidised) occurs in breccias of sedimentary and tectonic origin in the limestone of the Ferrobamba Fm (Middle to Upper Cretaceous). Non-sulfide association consists mainly of smithsonite and hemimorphite replacing both primary ore minerals and carbonate host rocks. Mn(hydr)oxides and Zn-clays (sauconite), can be locally very abundant. Differences in mineralogy of the ore and gangue minerals, as well as the composition of the host rock can have a profound impact on zinc recovery and reagent consumption, and therefore on the economic value of the deposit. An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation.

Jan 1, 2008

A major problem with many items of underground equipment is that they have either been converted or adapted from surface equipment, or that they have been designed and assembled in comfortable offices and factories with adequate lighting, specialised tools, and ample space. As soon as they are in use underground in cramped spaces maintenance frequently becomes difficult, parts are awkward to change, and a whole range of accidents can happen.Similarly, ingenious operators discover a whole range of uses for which the equipment was not designed, such as using a loader bucket for a work platform, or scaling backs with it.Design modifications of equipment and removal of hazardous components that can trap limbs is expensive when the dangers are discovered in operation, sometimes posthumously, and it is not surprising that workers compensation insurance premiums are high. The cheapest place to ensure that equipment is safe is in the design office, where the operator should be considered first, rather than being added to a purpose built machine as an afterthought.

Jan 1, 1992

By Frfas C, Parrilla F, Regife J. M

A project to develop the Zinclor electrowinning cell to industrial size is being conducted at Tecnicas Reunidas' Research and Development Centre with Spanish Ministry of Industry support. This project is the final development phase in zinc electrowinning from a chloride medium, the highest ZINCLOR technology development level prior to the industrial scale having already been reached. This paper covers the outcomes and conclusions corresponding to project Phases 1 and 2: Process Selection and Industrial Electrodes (1 m2) design and testing. The most important achievement reached is that there are presently available industrial cathodes and anodes for the Zinclor diaphragm cell giving an optimum response for zinc chloride electrowinning with unit power consumptions between 2.65 and 2.80 kWh/kg Zn, depending on the diaphragm type. Standard electrolysis conditions were: 65 g/L ZnC12, 3 g/L HCl, 160 g/L NaCl, 350 g/t Zn arabig gum as the addition agent, 36¦C, and 400 A/m2 current density. The selection of electrodes, diaphragms and organic additives for the industrial scale tests have been optimised. The complete electrowinning cell development, with electrodes having an active area of I m2, enables the evaluation of Zinclor Technology application for industrial processes.

Jan 1, 1993

In planning its production and investment activities the mining industry has generally paid too little attention to perceptive analysis of its market environment. The nature of world economic difficulties over the past decade is not a mystery. Essent- ially prolonged affluence has engendered a false sense of security and fostered entrenched vest- ed interests hostile to economic change. The overall outlook remains poor. For mining projects mineral demand affects both product prices and the availability of specific sales outlets. Long-term projection of demand is complex and a key to success is concentrating on analysis of fundamental deter- minants and avoiding mindless extrapolation.

Jan 1, 1983

The new generation Hlsmelt« Direct Iron Ore Smelting Process is a CRA Limited technology initiative. The process development is now focussed on commercialisation. The goal is to have the first commercial vessel operating around the year 2000. The HIsmelt« Process, based on the abundantly available iron ore fines and the more readily available non-coking coals, has the potential to fundamentally change iron ore processing through the application of high intensity techniques to replace the current sinter/coke ovens/blast furnace .technologies. The process will have great potential in the rapidly growing economies of Asia where steelmaking aspirations are based around local market focussed plants. This potential can be. realised as a supplier of premium grade iron units to electric arc furnace (EAF) steelmaking plants or as the front end to an ore based steel mill.

Jan 1, 1996

Solid Energy New Zealand Limited (æSolid EnergyÆ) is a state-owned coal mining company, producing 4.0 Mtpa from a number of opencast and underground mines in the Huntly, West Coast and Southland regions in New Zealand. The company currently exports 2.1 Mtpa of coking coal. Exports are expected to grow strongly over the next five year as the company expands production into new semi-soft and thermal coal reserves. Domestic coal demand is also expected to grow strongly, particularly in the North Island, as the Maui gas field reserves diminish, and thermal coal becomes more important for electricity generation and meeting the energy needs of forest processing and other industries. Solid Energy is expanding and developing its risk management practices across all areas of the business: strategic planning û extensive use of scenario analysis and probabilistic modelling over a 20 year period; investment decisions û development and application of a rigorous six stage æProject Assessment GuidelineÆ process for all new mine developments; geological and geotechnical risk assessment techniques û use of best practice techniques including seismic surveys; financial risk management û a dynamic approach to hedging based on effects based analysis of Cash Flow at Risk analysis against preset risk tolerances; risk financing û the use of a captive insurance subsidiary, and the experiences of a small coal company seeking to obtain insurance cover on a æhardÆ international insurance market; and integrated risk management û the challenges of trying to implement a broad integrated risk management approach across the company, that supports implementation of strategic objectives as well as meeting æcompliance or legislative basedÆ risk management requirements.

Jan 1, 2003

By Kershaw MG

At the Risdon plant of the Electrolytic Zinc Company of Australasia Limited, impurities toxic to the electrolytic production of zinc metal, notably arsenic and antimony, have traditionally been coprecipitated when precipitating iron as ferric hydroxide. With the development of a new lead/zinc mine at Elura, New South Wales, it was anticipated that the concentration of impurities, particularly arsenic, in the zinc sulphide concentrates treated at Risdon would increase. This suggested that an increase in the capacity of the iron purification step in the Risdon plant would be required to cope with the higher input of these impurities.Laboratory investigations showed that the additional capacity would be achieved, either by a massive increase in the amount of iron used as the "collector" in the process, or by a two-stage process. The latter approach was preferred as an increase in the amount of iron precipitated would lead to much higher operating costs and overloading of the existing equipment.

Jan 1, 1985

Project Hobson involves the replacement of an existing 90-year-old above-ground sewer that crosses Hobson Bay in Auckland, New Zealand, and which is nearing the end of its economic life, with a 3 km long, 3.7 m internal diameter segmentally-lined bored tunnel. The $118 M project will offer several benefits to the owner, Watercare Services Ltd, and the local community:provide capacity to meet projected growth in the region,virtually eliminate wastewater overflows into Hobson Bay and the Waitemata Harbour, andremove an obtrusive visual feature and open up the bay for recreational purposes. The geology in the region is a sedimentary formation, which has been significantly influenced by volcanic activity; 49 volcanoes are present within 20 km of the nearby city centre. The geology along the alignment is dominated by two palaeovalleys which have been infilled with a combination of marine alluvium and volcanic deposits. Watercare Services Limited has elected to manage and share tunnelling risk through, among other key measures, the implementation of a geotechnical baseline report (GBR); one of the first uses of this type of document in Australasia. This paper describes the general principles behind the use of a GBR, the development of the GBR used in Project Hobson and some lessons learnt.

Jan 1, 2008

By S N. Nyoni, K C. Corin, C T. O’Connor

Considering future water scenarios, as influenced by the increasing scarcity of water and the move towards sustainable process engineering etc, the closed water circuit becomes an important point of study in metallurgical operations, such as in milling and flotation. However, a deterrent in the use of recycled process water is often a lack of understanding of the effects of the accumulation of dissolved ions and other process chemicals. Recovery of the valuable minerals may be impacted by the concomitant complex mineral-pulp chemistry interactions. Literature indicates that these interactions are not necessarily antagonistic to process outcomes. Wet milling using steel media results in the dissolution of Fe from the media, the rate of which is dependent, inter alia, on the type of media and the chemical conditions of the aqueous environment in the mill. The pulp-phase interactions of dissolved ions with sulfide minerals may result in significant changes to the chemical conditions in the mill, which may subsequently impact negatively on the flotation recoveries. To understand the effect of these interactions in the context of the processing of sulfide minerals, this study seeks to consider the effect of three factors, viz mineral type – pyrite (Py) and galena (Gn) -, milling media of different compositions – forged steel (FS), 21 per cent high chrome and ceramic media -, and water chemistry, viz, deionised water (DI) and synthetic plant water (SPW). Ceramic media and galena are used for the respective control cases where the milling media and sulfide mineral contribute no Fe species. Using DI as a control case, a high ionic strength case is used to mimic the changes in water chemistry for a closed water circuit. Batch flotation tests are used as a diagnostic tool to determine the effects of these media-water-mineral interactions to investigate correlations between the chemical reactions occurring and chemical species present during the milling process and the ultimate flotation performance.

Aug 24, 2022

By K Kuganathan

This paper describes a new methodology that can be applied to compare several bench extraction strategies requiring backfill. The method is applicable at the planning or operational stages and can be used to maintain dilution within design parameters and improve the overall economics of bench stoping operations. The parameters influencing bench performance have been empirically rated based on economical, geomechanical, operational and backfill properties. Four different extraction strategies have been considered and rated from most preferred to less preferred using an integrated approach to bench extraction.

Jan 1, 1998

By Szpindler G

The results of pot-furnace tests with 35 bituminous coals from 20 seams in New South Wales and Queensland were used to establish the relationship between coal properties, as determined by standard laboratory tests, and the combustion process. The rate of combustion is influenced chiefly by the expansion of the fuel bed, but this cannot be accurately predicted from the crucible swelling number of the coal.The effects of various other factors, such as calorific value and ash yield, were investigated and statistical analysis of the results shows that the coals could be classified satisfactorily according to two experimentally derived parameters, namely heat-release rate at an air flow rate of 260 lb/sq.ft/hr and air flow rate giving stoichiometric combustion. The grouping obtained is shown to be related to ash yield and swelling number.INTRODUCTIQNThe rate of heat release from the fuel bed of a travelling grate stoker and the efficiency with which the heat is used depend upon the design and method of operation of the furnace as well as upon the properties of the fuel. It is difficult to draw general conclusions concerning the influence of fuel properties from tests on a single stoker installation. In the pot-furnace test, on the other hand, a part of the same combustion process as occurs on a travelling grate is carried out in isolation, uninfluenced by furnace design variables, and consequently the effects of coal properties and of the method of pretreatment can readily be demonstrated.While the combustion pot provides a rapid method of assessing the combustion characteristics of a fuel during the ignition and burn-out stages under standard conditions, and of predicting changes in performance with changes in fuel or in air flow rate, it is unable to simulate certain features of furnace design and operation. Data from combustion pot...

Jan 1, 1962

Open pit planning and scheduling play a significant role in establishing, maintaining and improving the economics of open pit mining ventures.The development of an open pit plan and schedule involves consideration of the following elements:ò the market for the mineral, ò the mineral deposit,ò the treatment process, ò the external factors,ò the mining method,ò the scale of operations, ò the open pit design,ò the open pit schedule,ò the calculation of economic performance, andò the implementation of the open pit plan and schedule.The above factors are described and discussed. Open pit planning and scheduling is the linkage which enables a mineral deposit amenable to open pit mining to meet a market requirement for the particular mineral. To effect this linkage the open pit planner should have a good detailed appreciation of both the mineral deposit and the market.

Jan 1, 1992

The philosophy of computer control of grinding and flotation at ZC/NBHC is presented. The performance and reliability of the in- stalled systems are discussed.

Jan 1, 1978

The control of industrial grinding circuits in Australian concentrators has been practised for many years in one form or another. Some have established simple feedback loops in areas such as fine ore bin feeders (tonnage control), mill pump sump levels (flow control) and water additions (density control). There are also some sophisticated systems which infer circuit product size using complex measurements of mass flaws and water additions in the circuit and attempts are made to control those flaws to produce a constant circuit product size. The inferred size method in Australian concentrators has become firmly entrenched in the last ten years and control techniques involving the use of direct size measurements with reliable on-stream sizers have been Ignored.

Jan 1, 1983

By D R. Swinbourne

In the recent past a number of smelting plants were commissioned in India to supply the rising demand by domestic steelworks for manganese-based ferroalloys, and they enjoyed cheap electric power and readily available high-grade manganese ore. Presently, the cost of electric power is much higher than in some neighbouring countries, there continues to be poor transport infrastructure and the prices of high-grade manganese ore have increased. Additionally, the Indian Government has opened its economy to the outside world, resulting in the import duties on ferroalloys being drastically reduced. In this paper the current situation in India will be detailed, the electric arc furnace and blast furnace smelting methods for ferroalloys compared and proposals for the construction of a new ferromanganese blast furnace in India outlined. The future of ferroalloy smelters in India will be assessed and actions which could be taken to improve their position discussed.

Jan 1, 2000

By James D

Fletcher Challenge Limited through its subsidiary Grampian Mining Co Ltd has carried out an ore evaluation of one of New Zealand's largest known deposits of ilmenite located at Barrytown on the west coast of the -South Island, New Zealand.The ilmenite is located in a beach sand environment which has previously been mined for gold. Two analytical techniques were developed to quantify the resource. Considerable difficulty was experienced in this phase of the evaluation due to the presence of major inclusions within the ilmenite grains. Wet and dry concentration circuits, utilizing spiral, wet magnet, high tension and plate electrostatic separators have been G47designed to produce ilmenite from the ore. Studies to utilize the titanium content of the Barrytown ilmenite have been made. Recent work has been directed towards a titanium dioxide pigment process.

Jan 1, 1986

By C Zhang, G Si, J Oh, X Zhu

The presence of rock joints has a huge impact on the strength, deformability, and permeability of fractured rock masses by providing surfaces of weakness on which further deformation are more prone to occur, and by serving as the major channels of water flow due to low matrix permeability. In earlier studies, water flow-through rock joints is often assumed as laminar flow between two ideal smooth parallel plates, and the well-known cubic law was derived and widely used to characterise the hydraulic behaviour of rock joints. However, natural rock fractures are irregular and of spatially varied aperture. Thus, the concept of equivalent hydraulic aperture was introduced to modify the cubic law. Numerous works have been conducted on the relation between hydraulic aperture and mechanical aperture incorporating various geometrical parameters. The surface roughness is one of the most sensitive factors for water flow-through rock joints. The aperture distributions are irregular in natural roughed fractures relative to the parallel plates. Barton et al (1985) and Olsson and Barton (2001) incorporated the joint roughness coefficient JRC in evaluating hydraulic aperture and proposed an empirical equation based on fluid flow tests. However, their equations do not conform to the dimensional consistency. Many other researchers (Zimmerman and Bodvarsson, 1996; Xiong et al, 2011; Li et al, 2019) considered aperture distributions in their equations. But the aperture distributions change during shear was always neglected. The contact of rock joints also has a significant impact on the hydro-mechanical behaviour of rock joint, since fluid tends to flow-through a rough joint along connected channels while bypassing the contact obstacles with tortuosity. Nonetheless, previous research mostly considered joint roughness or aperture changes based on 2D joint profiles, while the contact and tortuosity based on 3D surfaces were often overlooked. Only a few works have been made on quantifying the effect of contact area on flow behaviour (Walsh, 1981; Zimmerman et al, 1992; Zimmerman and Bodvarsson, 1996; Yeo, 2001), and mostly ignored contact area change induced by shearing and the associated impact on flow behaviour. Summarily, the quantification of fracture geometry effects on water flow in single rock joints still needs further investigation, especially when considering coupled shear-flow processes. This paper, therefore, aims to study the impacts of contact area and aperture distributions of the single rock joint on the flow behaviour. The evolutions of contact area and aperture distributions induced by shear are considered. Then, an improved model for estimating the hydraulic aperture with the mechanical aperture incorporating the above factors is developed. Finally, a series of shear and shear-flow tests are conducted on artificial joint samples and the model performance is verified by comparing against the results of experimental tests.

Nov 29, 2022