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By Mousset-Jones P, McPherson M. J

Underground airways are characterized by irregular shape and uneven surfaces including large-scale natural roughness, fractures, and a super-imposed sand roughness. Swirls in the grooves of the wall and separation because of the periodic variation of the open cross sec- tion, due to the blasting patterns, make it almost impossible to calculate average con- vective heat transfer computationally on the bases of the geometrical description of the surface. However, dimensionless friction factors can be used to characterize the surface effect of an airway and an analogy between heat and momentum transfer can be applied to calcu- late an average convective heat transfer Coefficient.

Jan 1, 1988

By U Berg, T Neumann, Y Song

Eutrophication of water bodies is one of the most severe environmental problems worldwide. It is well known that the availability of phosphate, as the limiting nutrient, is crucial for increased primary production and eutrophication. Calcite exhibits positive surface charge in most natural waters and can therefore be used for phosphate immobilisation. In this study, sorption experiments were performed in order to test different calcite materials regarding their suitability for use in restoration of eutrophic lakes. These short-term experiments were performed under different hydrochemical conditions (pH, SICC, initial dissolved P concentration) and with varying calcite properties (specific surface area and amount) in order to predict the long-term stability of the Ca-P-bonds. Peculiar shapes of isotherms that could not be explained only by adsorption processes were detected in the individual experiments. Depending on the residual P-concentration in solution, the isotherms can be divided into three sections indicating different processes responsible for the P-fixation on calcite surfaces. Adsorption prevails in equilibrium with lowest residual P-concentrations. The inflection of the isotherm at moderate residual P-concentrations suggests that precipitation and transformation of a Ca-P compound becomes dominant. This is supported by characteristic Ca/P-ratios for different Ca-P-compounds (b-tri- calcium-phosphate, octa-calcium-phosphate). On the new surface, phosphate ions again are fixed by adsorption. The observed transformation of P-bonding is crucial for sustainable phosphate immobilisation on calcite surfaces. While pure adsorption processes are reversible, the development of a thermodynamically stable Ca-P-phase, like hydroxylapatite, will lead to a lasting immobilisation of phosphate.

Jan 1, 2008

By M P. Sandy, J B. Simpson

The empirical stope design techniques developed by Mathews et al (1981) and refined by Potvin (1988) and others, have gained rapid acceptance in Australia in the 1990s as a simple, æfirst-passÆ means of designing primary stopes. However, it is recognised that these æstability graphÆ methods can only provide broad design guidelines. Recently published stability graphs (Hutchinson and Diederichs, 1996) encompass a wide range of geological environments, which are not discussed, and the influence of time and blasting practices cannot be easily reviewed. The æscatterÆ in the graphs must reflect, to some degree, different operating practices as well as subtle but important differences in the pre-mining conditions that are not adequately accounted for in the æmodified stability numberÆ. Development of a ælocalÆ, site-specific stability graph may overcome some of these problems. At NormandyÆs Golden Grove Operations, Western Australia, detailed reviews of stope stability performance, including Cavity Monitoring System (CMS) surveys, are undertaken for every stope, with the objective of developing a series of local stability graphs, customised to site conditions and calibrated in terms of æAverage Falloff ThicknessÆ (AFT). Cablebolting of stope hangingwalls is used to develop reinforced æbeamsÆ on each sublevel, effectively dividing the full span into smaller, more stable æsubspansÆ. By analysing stope stability performance in terms of fall-off, cost-benefit studies can be undertaken of the effect of cablebolting and other options for modifying stope spans. The approach used to develop the local stability graphs, and their integration into routine stope design procedures at Golden Grove, is described. The experience gained during stope extraction in the Scuddles orebodies has been successfully applied to the Gossan Hill æC-PanelÆ orebody. This methodology should be applicable to other underground mining operations.

Jan 1, 2000

By R S. Suglo, G-K Er

Mineral processing is an essential component of a mine production chain and it accounts for significant proportion of the production cost. Over the past decade, significant research progress has been made in processing plant efficiency using theoretical, experimental and simulation modelling techniques. However, these studies are limited to process plant system as stand-alone units with no interactions with the mining units. In order to maximise the total mining system efficiency and more accurately simulate the system, the processing plant must be modelled as part of an integrated mining system. This becomes increasingly important in continuous surface mining systems, with limited ore processing capacity. In addition, plant efficiency is roughly estimated with known parameters or with simplistic statistical data, without regards to the stochastic processes governing these parameters, such as processing plant feed introduction. In this paper, a comprehensive model of the ore processing plant system is given and the object-oriented design (OOD) of the system is briefly introduced. The joint operation of ore processing plant system and haulage system is analysed. Numerical modelling is used to analyse the ore processing plant system under different conditions. Analysis of the results show that the optimum plant capacity is 0.7 tons/sec (2520 tons/hour). The results also show that the plant system resources cannot be fully utilised because the production rate is always less than the plant capacity. When plant capacity reaches an optimum value 0.7 tons/sec, the production rate is about 0.64 tons/sec. The underlying stochastic processes associated with plant and mine capacities cause this variability. In order to reduce this variability, there is the need to tightly set tolerances for the function variables.

Jan 1, 2003

The general principles of technical due diligence best practice that are involved in assessing a mineral property in the early stages of its development are described and a bibliography of relevant papers is attached. The issues specific to the evaluation of gold deposits are highlighted. The Australasian Institute of Mining and Metallurgy's (The AusIMM) initiatives in this area, dealing with the proper public reporting of Reserve/Resource information (JORC Code) and property assessment/valuation (VALMIN Code), will be used as a framework against which the illegal tampering with drilling samples to artificially boost their gold content (salting) from the Busang gold deposit (Kalimantan, Indonesia), owned by Bre-X Minerals Limited (Calgary, Canada), will be reviewed. While the Busang saga was based upon fraud, through salting the samples, the general lessons to learn from such a scam are worth documenting. In Australia, most of those working in the mineral industry belong to long established professional institutes and consultant associations (eg The AusIMM or Mineral Industry Consultants Association [MICA]) that require their members to work within their technical limits and to comply with best practice guidelines, or risk being judged and found wanting by their peers in the context of strong Ethics Codes. There is also a strong interface between such representative professional bodies and the corporate and financial market regulators (ASC/ASX), which closes the monitoring loop. Canada has only now seen the wisdom of having this type of early warning system in place. Fraud and deliberate deception will be always possible, but deception on the enormous scale that occurred at Busang is most unlikely with proper surveillance systems in place and the use of accredited technical professionals. There should have been more hard data available about so big and rich a deposit owned by a C$6Bn company.

Jan 1, 1997

By H Aral, L Malishev

The carbothermic chlorination of titaniferous materials such as rutile, synthetic rutile (SR), upgraded slag and ilmenite in a fluidised bed is an established commercial process. In this work, ilmenite sourced from the Murray Basin area of South Eastern Australia was chlorinated and an assessment of the chlorination characteristics of the ilmenite, in terms of pre-treatment, type of reductant and reaction time was made. Selective chlorination of Murray Basin ilmenite to remove Fe and Mn was achieved in this work. A synthetic rutile sample containing around 93 per cent TiO2, one per cent Fe2O3 and 0.5 per cent MgO was produced at a chlorination temperature of 1000¦C with around 25 per cent loss of Ti as TiCl4. Raising the reductant to ilmenite ratio in the chlorination reactions increased the amount of Ti chlorinated. However, complete chlorination of Murray Basin ilmenite to produce FeCl3 and TiCl4, was not achieved under the conditions used in this work. Pre-oxidation of Murray Basin ilmenite before chlorination had little affect on its reactivity, compared with æas receivedÆ ilmenite. In contrast weathered West Coast ilmenite chlorinated appreciably better than West Coast primary ilmenite, in terms of bed residues remaining and amounts of elements removed. The presence of large amounts of Mg and chrome spinel grains in the Murray Basin ilmenite used in this study are likely to make it difficult to chlorinate directly in a commercial chlorinator. However, this is not to say these ilmenites will be unsuitable for chlorination applications. Further work is needed in the separation of Mg and chrome spinel grains from Murray Basin ilmenites and the products resulting from these tests could then be assessed in terms of chlorination performance, so that further processing options can be explored.

Jan 1, 2000

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

By G MacSporran, I Sheppard

The practical application of LaneÆs theory on optimum cut-off grade policy has to date proved difficult for selective stoping in large-scale underground mining. The key to determining an optimum cut-off grade is the ability to rapidly perform complex mine layout designs combined with rapid output of multiple potential schedules. This paper describes aspects of the detailed investigation into estimating a practical static cut-off grade for the two main orebodies in Mount Isa MineÆs Enterprise Mine. Rule based automated scheduling software was used to evaluate thirteen different stoping layouts (including design infrastructure and capital development) of the Enterprise MineÆs two main orebodies, with over 200 schedules generated. The investigation illustrates the application of commercially available software to solve the problems of generating multiple cut-off grade stope designs and achieving the otherwise insurmountable task of rapidly generating and valuing multiple scenarios for each stoping layout. Each scenario was evaluated using modelled net cash flows of the mining, concentrating and smelting operations of the company and calculating NPV. The cut-off grade for each orebody was selected based on the cut-off grade that achieved maximum NPV û with an appropriate production rate. Underground mine scheduling is a complex task involving the adherence to a number of simple scheduling rules and the balancing of several competing drivers. The study also found that: while each scheduling rule itself is simple, the compounding complexities of their interaction preclude manual scheduling from being a realistic option. there is a maximum sustainable rate of production possible for any given stoping layout, and that the actual maximum production rate is also a function of the required number of years of sustainable production. the optimal cut-off grade was different for each orebody û a recognition of the impact of the different characteristics of each orebody.

Jan 1, 2003

By M Matheson

Increasingly, owners and operators of underground mines that have a long history are realising the economic and practical advantages of capturing historic mining records and converting hand drafted plans of underground mine workings into an electronic collection of attributed 3D wireframes that can be used for mine planning and exploration purposes. This case study looks at the conversion of historic data to 3D models, with examples from three historic mining operations where this task has been undertaken: West Wits gold projects in South Africa, Northern MiningÆs Radzimowice gold mine in Poland and Avalon ResourcesÆ Viscaria copper mine in Sweden. West Wits Mining Limited holds leases in the West Rand Goldfield of the Witwatersrand Basin, which has significant gold and uranium resources that have been mined since the 1890s. The Radzimowice Gold mine, Poland, hosts Au-Cu-As-Ag mineralisation that has been exploited since the 15th to 16th centuries. The Viscaria Copper mine is located in northern Sweden and was operational during a 15 year mining period to 1997. The process of data collection, management and modelling is inherently challenging for these mines; specifically, collation of historical information, organising this data into logical arrangements that could be validated and sequentially creating 3D models using geo-spatial computer software. Despite the challenges and costs involved in creating a digital 3D model, the conversion has added significant value to each project through identifying areas of potential new resources, aiding planning and presentation to stakeholders. This paper outlines the processes involved in conversion from paper records to a 3D model, the challenges encountered and how these can be overcome, and importantly, the practical and economic advantages of undertaking such a task for explorers, miners and investors.

Jan 1, 2009

By M A. Gontalves, A F. D C Varajpo, S A. Stachissini

Clays from the Santa Elena Peninsula, south-east of the Ecuador coast, were investigated with a view to identifying their main mineralogical, physical, chemical and textural characteristics as well as their potential for industrial use as adsorbents. Identified as calcic bentonites, two representative samples from the Tosagua Formation (Oligocene to Lower Miocene) were selected for acid activation trials. The selection criterion was based on the greatest amount of clay fraction (<2 ¦m fraction) associated with the greatest content of montmorillonite. For the activation treatments, HCl and H2SO4 solutions of 4, 6 and 8 N were used in a stirred glass reaction vessel with the clay sample under reflux during four hours at temperatures of 70¦C for HCl and 85¦C for H2SO4. Mineralogical analysis by X-ray diffraction (XRD), chemical analysis by X-ray fluorescence (XRF), differential and gravimetric thermal analysis and measures of density, surface area and porosity indicated the changes occurred in the crystal structure of the montmorillonite. The acid treated clays were utilised in trials of purification and decolourisation of soybean vegetable oil in a ratio of 2:100 (clay/oil) at 90¦C for 30 min, under constant stirring. After centrifugation of the suspension, the wavelength of the bleached oil was measured by UV-visible spectrophotometer and the bleaching capacity of the clays was determined. The best bleaching capacity of the samples was obtained with 6 N H2SO4 acid-activated clays. The bleaching capacity was compared to Tonsil, a commercial acid-activated clay and similar results between them evidenced the potential industrial application of the Ecuadorian clays to bleaching of vegetable oil.

Jan 1, 2008

By R-H Yoon

Increasing the upper particle size limit of flotation would allow operators to increase mill throughput, save operating costs, simplify flow sheets, and increase rate of return. However, coarse particle flotation is difficult for various reasons, of which bubble-particle detachment has been identified as the major limiting factor. In the present work, the process of bubble-particle detachment has been studied by directly measuring the forces required to detach air bubbles from hydrophobic solids. The measurements were conducted using a hanging balance apparatus. The measured forces were converted to detachment energies that can be compared with the work of adhesion, which in turn is a function of hydrophobicity, surface tension and contact area. The results were converted to detachment energies using the Young-Laplace equation for capillarity. In the present work, the solid surfaces were hydrophobised by coating them with octadecyltrichlorosilane and cetyltrimethylammonium bromide. The results show that bubble-particle detachment occurs in two steps. In the first step, air bubbles are deformed, while the three-phase contact (TPC) line is pinned, until contact angle reaches advancing angle. In the second step, the TPC line moves along the surface until solid/air interface is replaced by solid-liquid interface. In general, the energies of detachment measured in the second step are in good agreement with calculated work of adhesion. Thus, the energy required during the first step effectively represents an energy barrier for bubble-particle detachment. It has been found that the energy barrier varies with surface roughness and surface tension. The results of the present investigation suggest, therefore, that coarse particle flotation can be improved by control of particle hydrophobicity, surface roughness, and surface tension.

Jan 1, 2005

By S Grano, J Ralston

Selective oxidation of minerals was used in this study to separate by flotation the copper sulphide minerals of chalcocite, covellite and chalcopyrite from the arsenic copper sulphide minerals of enargite and tennantite. It was found that a satisfactory separation of these minerals was only possible after selective oxidation of their surfaces in slightly acidic pH conditions, or after oxidation and selective dissolution of the surface oxidation products with a complexant in basic pH conditions.

Jan 1, 2000

By Pattinaja MA

Mathematical modelling was carried out to determine the probable convergence and vertical stress patterns around a retreating longwall panel in an underground coal mine in New South Wales. An 'Electrical Resistance Analogue' and a program called 'THREED' based on the displacement discontinuity method were used for the modelling. Parts of the obtained results are presented here and compared with some measurements of convergence at the site. The modelled and measured data agree better qualitatively, than quantitatively.

Jan 1, 1986

By Stevens P

The Isa Mine of Mount Isa Mines Limited currently produces 5.4 million tonnes of copper ore and 3.3 million tonnes of silver, lead and zinc ore annually. Of this, 5.1 million tonnes of copper ore and 2.2 million tonnes of silver-lead-zinc ore is produced by sublevel open stoping. This paper summarises the capabilities, operating practices and problems encountered with current production drilling practices used to drill sublevel open stopes at Mount Isa.

Jan 1, 1982

By Wencai X

The conversion relationship between the Bond Work Index W1, specific output of mill and the energy efficiency of grinding were developed using dimensional analysis. These relationships were validated and the value of the conversion coefficient ~ was also obtained using a new installed device for measuring grindability of ores. With the new simulating algorithm the mill specifications, output and size distribution of grinding products of industrial mills can be calculated based on laboratory measured results. This algorithm is more accurate and simpler than any of the other empirical relationships. KEYWORDS: Conversion coefficient method, grindability, grinding Constant.

Jan 1, 1993

By J Kleynhans, D Vermeulen, V Cogho

A number of rehabilitated open cast coalmines in SA are already decanting. The paper focuses on the situation at one of these mines where the following information exist: monthly decant rates and rainfall; sulfate concentrations of the decanting water; water level measurements inside the mine prior to decanting; ABA analyses; information about the rehabilitation (drainage slope, vegetation, soil used). A 2D-model was constructed for the mine and calibrated against six years of flow data. About 85 per cent of the decant outflow rate comes from direct recharge on top of the rehabilitated mine while the other 15 per cent is derived from lateral groundwater inflows. The estimated recharge value was 17 per cent of the rainfall. Measured sulfate values showed that the sulfate generation rate for the mine was in the order of 7 kg/ha/d. Conclusions from the study are:most of the water decanting from rehabilitated open cast coal mines is derived from recharge via rainfall; given a specific sulfate generation rate, then: the lower the recharge the less the decant rate but the higher the sulfate concentration of the decanting water and vice versa; future prediction of the decant rate must be stochastic according to expected percentile monthly rainfall values; and as a first assessment of the predicted sulfate concentration of decant water from rehabilitated open case mines, the 7 kg/ha/d sulfate generation rate can be used.

Jan 1, 2003

In response to requests from the iron ore mining industry, the Commonwealth Scientific and Industrial Research Organisation (CSIRO) Division of Mineral Physics has developed a number of bulk analysis techniques in which analyses are obtained directly from ore samples weighing many kilograms or from ore located on conveyor belts.Because penetrating neutron and gamma radiation is used, measurements are obtained from a large volume of ore, which ensures thal the analyses are represelllative of the bulk.Two different gamma-ray techniques have been developed to measure iron ore grade. The first is based on backscallering of 60CO gamma rays, while the second involves measurement of the annihilation radiation which arises when the ore is irradiated wilh 226Ra gamma rays. Both techniques measure the iron concentration with an accuracy (1 s) of better than 0.4% Fe.A thermal-neutron irradiation technique using a 252Cf neutron source has been developed for the simultaneous determination of iron and the aluminium impurity (expressed as AI2O3) in iron ore fines on a conveyor bell. Because the conveyor speed must not exceed about 0.05 m/s, if good accuracy for AI2O3 is required, an auxiliary analysis bell is required Lo avoid inLerference with normal ore processing. Dynamic trials have demonstrated that accuracies of 0.6% Fe and 0.1% AI2O3 can be obtained.

Jan 1, 1985

By M Brooks, M Nelson

A fundamental study was carried out on super pit sulphidic gold ore to establish the most influential flotation characteristics which were subsequently used in the development of an optimum flowsheet to achieve best economical recovery of gold. In developing the flowsheet, consideration was given to existing operational constraints in the treatment of the Super Pit ore. The fundamental study also included an innovative diagnostic investigation to establish the location and value of gold in the major mineral assembly of the super pit ore from a metallurgical rather than a mineralogical perspective. This study mapped a metallurgical fingerprint of the major types of super pit ore in relation to the location and association of gold.

Jan 1, 2000

By Meakins R. L, Talaska A, Kenny D, Haycraft J. A, Dickson B. L

A vehicle-mounted radiation detector interfaced to a microprocessor called PRAM (programmable radioactive analyser mobile) has been developed to provide grade control for selective mining of a soft rock uranium ore. The grade of ore over which the vehicle passes is determined and indicated by several coloured lights to a pegman who walks behind the vehicle. Coloured pegs are then laid out to mark the uranium grade ranges on the floor of the mine pit. Comparison between grade ranges determined by the PRAM and by prior drilling and downhole logging at the Yeelirrie deposit, Western Australia indicate good agreement. Use of the PRAM decreases the cost, manpower and time required to grade extensive areas of a mine pit floor.

Jan 1, 1982

By Y Wu, F-J Ping

Today, coal production accounts for about 65 per cent of the nationÆs gross energy in China. By the year 2010, the output of coal is planned to increase to 1.65 billion tonnes and by the year 2020 to 1.9 - 2.0 billion tonnes. To meet these energy needs the Chinese coal industry is developing underground coal production on a massive scale. The new drive introduced by using direct torque control (DTC) is now proven technology for mine shaft hoisting. The drive offers unequalled speed and torque control performance as well as a low impact on the supply network by controlling the power factor to unity with a minimum of harmonics distortion.

Jan 1, 2005