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By David Norval

The increased tendency to use hydrometallurgy as an extraction step towards final refining following a pyrometallurgical smelting process requires melts which have to be cast and or comminuted which can then be taken up into solution or leached. To generate surface area for optimal leaching, a common process is to granulate and in many cases mill, which is a general practice with friable material with properties associated with higher sulphur, carbon and silicon levels. However, in the case of metallic melts milling can be unfeasible due to the ductility of the granulated particles. Water solidification is capable of producing either fine particles by means of granulation or atomisation. Atomisation however, can produce particles as fine as 40 microns without a milling circuit.

Jan 1, 2005

By Miles T. Stephens, Felipe Calizaya, Jacob O. Kingston

Currently, the Bear Canyon Mine is facing the challenge of excessively high coal and rock temperatures in one of its headings. In Mine No.3, the air temperature at the 6th Right panel reached 36.4ºC and the coal 83.9 ºC. Due to these severe work conditions, the mining plan has been altered by changing the mine direction to avoid the high temperatures. To investigate the problem, drill holes were developed from the entries and the rock temperatures monitored using K-type thermocouples. The measurements confirmed the existence of localized “hot spots” in the mine. This paper presents a summary of ventilation surveys that were conducted in this mine. It includes the results of coal and rock temperature measurements from drill holes, interpretation of results using a heat flow simulator and the identification of hot spot areas. It also includes a summary of methods that were developed to reduce the hazard and control the problem.

Jan 1, 2005

For the last few years, a new and innovative technique has been successfully used to determine refractory and castable thickness in various metallurgical vessels. The acousto ultrasonic-echo (AU-E) technique uses stress waves to detect metal penetration and delaminations within refractory linings. In addition, it is capable of measuring the thickness of refractory layers and build-up material. The inspection and measurements can be carried out while the furnace is in full operation. The present paper discusses the principles of the AU-E technique, and its advantages and limitations. A number of case studies are presented to demonstrate various capabilities of this new Non-Destructive Testing (NDT) technique.

Jan 1, 2005

By J. J. Jonas, G. R. Stewart, N. Pokutylowicz, S. Yue, R. Varano, A. Elwazri

Differing thermal histories in and around a weld can lead to differences in grain size, phase composition and morphology of precipitates; mechanical properties will vary accordingly. Hardness testing gives limited information and the machining and testing of tensile and/or impact specimens that would reveal these variations (which may occur over very small distances) is not practical. Therefore, in this investigation, shear punch testing was applied to measure the variation in the room temperature mechanical properties of a welded pipeline steel.

Jan 1, 2005

By R. M. G. Machunter

The presence of ultra-fine particles affects the separation performance of wet gravity separation equipment. Several studies have been undertaken to establish the maximum level of these particulates that can be tolerated by spiral separators and it has been found that unless the ultra-fine material is effectively processed, relatively low proportions in the ROM material combined with high feed rates can result in degradation in plant performance and/or excessive water consumption. The maximum level of particulate material in the process water has been determined by examination of separation performance of spiral separators under varying slime loading. This work has been conducted utilizing various feed sources and a robust ‘rule-of-thumb’ has been derived.

Jan 1, 2005

By K. Nielsen, V. Bauer

"The paper presents a brief overview of the long mining history and the more recent political development in the Slovak and Czech Republics as well as in Norway and Sweden. Mining used to be very important sources of economic wealth in the four countries, but in today’s economy does exploitation of non-energy minerals usually account for less than one per cent of the GNP. The paper will discuss and compare the mining legislation, land use planning and mineral policies framework in the four countries and how this may influence sustainable management of mineral resources including planning for mineral supply, landbanks and sterilisation of resources. The paper will then identify some positive and negative elements in each country’s political and administrative framework."

Jan 1, 2005

By F. Stober, D. Wanblad, J. Ndlovu, L. R. Nelson, L. P. S. de Villiers

The single six-in-line furnace of the Polokwane Smelter is the largest installed high-intensity furnace for platinum group metals (PGM) base metals sulphide smelting in the world. The furnace employs state-of-the art technology to deliver a planned throughput of 650 000 t/a dry concentrate at a design 68 MW power input. This furnace, at double the capacity of previously existing PGM furnaces, offers low unit operating and capital cost through the resulting economies of scale. Key features of the design include:

Jan 1, 2005

By D. J. Fourie

During the production of pure TiO2for the pigment industry, ilmenite, containing 35?60% TiO2, is reduced to high titania slag, containing 70?95% ?TiO2? and pig iron. The high titania slag produced, consists mainly of titanium in different oxidation states and FeO in equilibrium with liquid iron. To predict the phase and chemical reaction equilibria in a furnace, a suitable solution model is required with accurately determined binary interaction parameters, as slag melts tend to behave very non-ideally. This paper investigates two popular slag models, namely, modified quasi-Chemical (MQC) model and the cell model and provides the binary interaction parameters based on recently published data of the ternary system and critically assessed published unary and binary data. Very few modelling results have been published on the ternary Ti-Fe-O system pertaining to high titanium slags. The solution models, with their regressed interaction parameters, can subsequently be implemented in commercial software of the slag-metal phase equilibria to predict how much and which type of solids will precipitate for a given bulk slag chemistry and operating temperature or, alternatively, above which temperature should a furnace be operated to avoid excessive solids precipitation.

Jan 1, 2005

Although the mining industry has achieved record-low fatalities and injuries for each of the last three years, there are still too many miners injured or killed in this nation ís mining operations. Many mining injuries or deaths might have been prevented by using risk assessment to identify and control or eliminate the hazards associated with a task. To focus attention on the importance of conducting risk assessments in keeping mining workplaces safe and healthful, MSHA introduced this initiative on October 12, 2004. This initiative is called SLAM. SLAM is an acronym for Stop, Look, Analyze, and Manage. The steps involved in SLAM are: Stop ñ stop and consider the work involved Look ñ look for and identify the hazards Analyze ñ analyze what needs to be done Manage ñ manage safety by developing and implementing controls Everyone should be aware of the risks of an accident before beginning a task. It may not always be obvious that performing a seemingly routine task could result in an accident. That is why conducting a risk assessment is so important. Itís important to remember that over time a mining workplace seldom remains unchanged. Risks must be assessed whenever procedures or processes change, whenever new tasks are started, or non-routine tasks are performed.

Jan 1, 2005

By Shemek Oginski

The 5 km (16,194 lf) of 6.1m (20 ft) diameter TBM driven tunnel built by the J.F.Shea Co. will serve as sewage overflow storage. The TBM tunnel and four connecting tunnels excavated by drill and blast methods in hard granite will remain unlined. Based on the Geotechnical Baseline Report (GBR), the Contract documents provided a design with no required pattern of rock bolts, no probing, no pre-excavation or consolidation grouting, and lastly, no final lining of the tunnels was deemed necessary. This paper will provide a general overview of these topics with the emphasis on the actual ground conditions encountered versus the projected conditions provided in the GBR and how the GBR reflected the design of the project. Proposed modifications to the temporary and permanent ground support will be presented and the necessity of probing and pre-excavation grouting will be evaluated.

Jan 1, 2005

By K. J. Stanaway

Major world ilmenite and rutile accumulations reveal similar regional geology and Proterozoic age deeper crustal source rocks. During crustal collision titanium crystallizes as ilmenite and rutile at buried sites of high pressure and temperature rock metamorphism. Hydrothermal activity can convert titanium minerals to rutile, but titanium migration and enrichment seem only local. Many melts crystallize rocks with iron-titanium oxides in solid solution, but titanium enrichment at economic scale takes place in basic intrusive melts often associated with anorthosites and charnokite. Sedimentary placer enrichments have formed since the Proterozoic with water-resistant ilmenite, and rutile segregating by gravity from quartz sands deposited from flowing water. Placers have residual, alluvial, strand and shallow marine variants. Time, organic acids, and sand permeability play lead roles in the leaching of iron from ilmenite during weathering and diagenesis.

Jan 1, 2005

By J Masliyah, Z Xu

The largest oil sand deposit in the world is located in Alberta, Canada, with a total proven reserve of 2.5 trillion barrels of oil. The water based extraction process is currently being used in commercial operations to recover bitumen by flotation from oil sand ores. A recognised challenge in bitumen extraction is the reduced bitumen recovery when processing ores containing high fines content or æweatheredÆ oil sand ores, collectively known as poor processing ores. Inspired by demonstrated success of using kerosene as collectors in coal flotation, an innovative idea of using oily bubbles (air bubbles coated with a thin layer of oil or solvent) was tested to improve bitumen flotation recovery from poor processing ores. In this study, dynamic contact angle of air bubbles or oily bubbles on bitumen and induction time of bitumen-oily bubble attachment in water were measured to justify the use of oily bubbles in bitumen recovery from poor processing ores. The type of oil or solvents, including kerosene, toluene and naphtha, used in generating oily bubbles showed a marginal effect on the contact angle values, similar to the values measured with air bubbles. However, the spreading of an air bubble was found to be much slower than that of oily bubbles on a bitumen surface. The induction time for oily bubble-bitumen attachment was found to be much shorter than that for corresponding air bubble-bitumen attachment in the process water from poor processing ores. The reduced induction time for kerosene-coated air bubble-bitumen attachment correlates well with the improved bitumen recovery from poor processing ores using kerosene-coated oily bubble flotation technology.

Jan 1, 2005

By D C. Curry, M F. Young

Many flotation operations need to improve liberation to increase recovery, yet often plant operators are concerned that finer grinding will produce æslimesÆ with low flotation recovery. Yet simple circuits can be designed to give good liberation and excellent fines recovery. The economics of fine grinding has changed fundamentally with new stirred milling processes like the IsaMill. This has also transformed flotation design due to the clean surfaces produced in the inert grinding environment and the narrow size distribution produced by the IsaMill. Past poor experiences with æovergrindingÆ in flotation circuits was often due to the wide size distribution and the degradation of mineral surfaces produced by conventional devices using steel media, like ball mills and tower mills. The correct practice is to design both grinding and flotation together to suit the liberation characteristics of the ore. This may result in several stages of grinding and flotation, recovering mineral as soon as it is liberated, then applying further grinding energy only to those particles that still need liberation. Flotation then occurs in relatively narrow size bands and with minerals with similar liberation characteristics. Though the circuit may look more complex on paper, in reality it is far simpler to operate since each section performs predicably. Circuit design also needs to address materials handling. Finer particles affect froth handling and dewatering, but can still be easily handled by standard products with careful attention to design of launders, pumps and pumpboxes, and de-aeration before thickening and filtering. Excellent examples of designing circuits to include ultrafine grinding include Mt Isa and McArthur River (MRM). In the last decade these operations have produced over ten million tonnes of concentrate with an average grain size below 10 ¦m and above 80 per cent recovery. At Mt Isa, zinc recovery was increased by ten per cent by applying fine grinding to existing poorly liberated streams. In fact, grinding finer in the IsaMill actually improved the recovery of fine particles by ten per cent, and maximum particle flotation recovery occurs for 10 ¦m particles. A more recent example is the flotation of Platinum Group Metals (PGMs). The use of conventional ball or tower milling to improve liberation is severely limited by the impact of commonly associated chromite on classification, and degradation of flotation performance by the steel grinding environment. The ability of open circuit IsaMills to deliver a narrowly sized ultrafine product with clean mineral surfaces is transforming the design of platinum flotation circuits. The science and practice of fine-grained flotation is now thoroughly proven. The availability of the 2.6 MW IsaMill has made ultra fine grinding a practical tool for flotation plant design. It is expected to become a standard choice for future applications of both fine-grained ores and for minerals with difficult flotation characteristics.

Jan 1, 2005

By A Kamkar-Rouhani

The paper describes a mineral potential mapping of gold and other base metals in Mahneshan area, Iran, using geographical information system (GIS), in which, the method of weights of evidence is used to combine spatial data obtained from different sources to make prediction for mineral potential. This is a quantitative tool for mineral resource mapping that can be used to delineate and predict favorable areas for further exploration by using the characteristics of known and similar mineral deposits. In accord with the descriptive model for gold and other base metal deposits, the spatial distribution of 20 known mineral occurrences was used. In addition, digital evidential maps were used in this study. The maps include maps of lithological units, faults and first derivative of total aeromagnetic data, remotely-sensing data of alteration and also geochemical evidential maps produced on the basis of the results of chemical analyses of samples taken from the stream sediments in the area, and analysed for Cu, Pb, Zn, Sb, As, Ag, Au, Ba and Hg elements. The binary maps were produced and then combined with the model of weights of evidence using 20 known mineral occurrences to obtain a final map of the favourable areas for further exploration of gold and other base metals in the study area. The final map is a predictive GIS model of the mineral deposits in the area. An interesting matter about the final predictive GIS model is that the faults are mainly located in favorable areas which possesses the most probability of mineralisation. Therefore, the faults in these areas have priority for further exploration of gold and others base metals.

Jan 1, 2005

By Pengfu Tan

A thermodynamic model has been developed to predict the distribution behaviors of Cu, Fe, S, O, Pb, Zn, As, and heat balance in a lead blast furnace. The modeling results have been validated by the plant data of a lead smelter in Asia. The model can be used to predict for any set of controllable process parameters such as feed composition, smelting temperature, degree of oxygen enrichment and volume of oxygen-enriched air. The effects of the blast air, industrial oxygen, and coke charge on the distributions of Cu, Fe, S, O, Pb, Zn, As, and heat balance, and on the lead loss in slag have been presented and discussed.

Jan 1, 2005

By Michael S. Kucker, Stuart Warren, Robert A. Robinson, Michael J. Lehnen, David McAllister

Geotechnical conditions exposed by the phased exploration programs have had a major impact on the selection of excavation and support methods, dewatering requirements, size of openings, vertical alignment, and estimated cost of construction for the Beacon Hill Tunnel and Station section of the “Link” Light Rail. Beacon Hill is comprised of a very complex glacial geology, including numerous slickensided fractures, injected sand dikes, and multiple perched groundwater levels as revealed by a phased boring program and exposed in a test shaft. The Geotechnical Baseline Report (GBR) presents this complex geology along with a “tool box” of alternative additional support systems to accommodate the varying ground conditions during construction of the station excavation. Additional explorations will also be accomplished during construction to further refine the geotechnical interpretations and provide an opportunity to use pro-active ground improvement techniques to optimize the station excavation and support requirements.

Jan 1, 2005

By K. N. Santini, J. M. Barker

The perlite industry in the United States continued to undergo rapid change and increased competition last year as it did in 2002. U.S. production in 2004 was 510 kt (562,000 st),an increase following five consecutive years of decline (Table 1). Perlite is exported to Canada and to the Pacific Rim. These partially offset imports. Perlite imports from Greece to the eastern and Gulf Coasts of the United States declined by about 22 percent after reaching a record 240 kt (264,000 st) in 2003.But their market remains protected by high rail rates from western U.S. plants. Minor imports of perlite persist by Termolita from Mexico.

Jan 1, 2005

By Jim Nickerson, James McCleish, Tom Abkemeier, Nicholas Willig

The purpose of this project is to convey sanitary sewage from an existing pump station to a new waste water treatment plant. This paper will discuss the design and construction aspects of the project. The scope includes construction of three main shafts ranging from 34 to 100 feet in diameter at depths of 200 to 230 feet and 21,000feet of tunnel. Shaft construction consisted of slurry wall excavations keyed into claystone and limestone at depths ranging from 114 to 130 feet, followed by rock excavation utilizing drill and blast methods. The tunnel is being excavated in the Warsaw and Salem shale and limestone formations utilizing a 12'-6" diameter Wirth hard rock TBM.

Jan 1, 2005

By Terra Dinamica, Frank Lucca

This paper discusses blast design for vibration control in tight construction blasting. Topics include blast pattern geometry, blast design formulas, loading, explosives & initiation selection, and utilizing borehole deviation equipment and lasers, and rules of thumb. The paper will also explore vibration prediction, neighbor relations, and related topics, such as blast plan submittal. Various projects from metropolitan construction blasting operations will be used as examples. Examples include blasting in the inner city, next to pipelines, and in housing developments.

Jan 1, 2005

By S G. Hagemann, M E. Barley

The Mt Tom Price deposit is a world-class high-grade hematite deposit in the Hamersley Province of Western Australia with an original resource of 900 Mt of almost pure hematite, averaging 63.9 wt per cent Fe. Petrological and geochemical studies at both the Southern Ridge and the North deposit at Mt Tom Price have identified three hypogene alteration zones between unmineralised BIF and high-grade iron ore: distal magnetite-siderite-stilpnomelane; intermediate hematite-magnetite-ankerite-talc-chlorite; and proximal martite-microplaty hematite-magnetite-apatite alteration zones.Fluid inclusions trapped in siderite within the distal magnetite-siderite- stilpnomelane alteration zone at the North deposit revealed primary high salinity (25.5 eq wt per cent NaCl-CaCl2) inclusions that homogenised between 107¦ and 142¦C into liquid. Fluid inclusions trapped in ankerite within ankerite-microplaty hematite veins in the intermediate hematite-ankerite-magnetite-talc-chlorite alteration zone at the North deposit revealed mostly H2O-CaCl2 pseudosecondary and secondary inclusions with salinities of 22.4 - 25.4 eq wt per cent and 22.9 - 25.9 eq wt per cent CaCl2, respectively. Pseudosecondary inclusions homogenised between 153¦ and 449¦C and secondary inclusions homogenised between 103¦ and 157¦C. Fluid inclusions trapped in apatite within talc-microplaty hematite veins in the intermediate hematite-magnetite-talc-chlorite-apatite alteration zone at Southern Ridge revealed that primary, medium salinity (7.0 - 9.0 eq wt per cent NaCl) inclusions homogenised between 181¦ and 257¦C and primary high salinity (22.8 - 25.9 eq wt per cent CaCl2) fluid inclusions homogenised between 118¦ and 257¦C into liquid. Microthermometric analysis of quartz from quartz-hematite veins from the Southern Batter Fault, Southern Ridge show a complex fluid inclusion history. Primary fluid inclusions consist of: low- and high-salinity H2O-NaCI inclusions trapped at temperatures of approximately 140¦ to 230¦C; vapour-rich inclusions of unknown compositions; and æcomplexÆ salt-rich (Ca, Mg, K and Na inclusions).Secondary inclusions consist of medium-salinity fluid inclusions trapped at temperatures of about 140¦ to 280¦C.A two-stage hydrothermal model is proposed for the formation of both the Southern Ridge and North deposits. Early 1a hypogene alteration involved the release of hydrothermal NaCl-CaCl2-rich (25.5 eq wt per cent) basinal brines (110¦ - 150¦C) from the underlying Wittenoom Formation and directed upward along normal faults and focused within the silica-rich rocks of the Dales Gorge Member, by the shales of the underlying Mt McRae Shale Member and overlying Whaleback Formation. Within the Dales Gorge Member hydrothermal basinal brines migrated laterally within large-scale folds with permeability controlled by shale bands and the NW trending dolerite dyke sets. Fluid rock reactions transformed unmineralised BIF to magnetite-siderite-iron silicate BIF, with subsequent desilification of the chert bands. Stage 1b hypogene involved an increase in temperature of the hydrothermal, CaCl2-rich saline (24 eq wt per cent) basinal brines (250¦ - 300¦C) resulting in formation of hematite-ankerite-magnetite-talc-chlorite alteration and the crystallisation of microplaty hematite. Late stage 1c hypogene alteration involved the interaction of low-temperature (~120¦C) basinal brines with the hematite-ankerite-magnetite mineral assemblage. At the Southern Ridge deposit this process was very intense (ie high fluid flux), therefore resulting in the almost total removal of ankerite and resulting in the increased porosity of the ore. Stage 2 supergene enrichment in the Tertiary resulted in the removal of residual ankerite and apatite and the weathering of the shale bands to clay.

Jan 1, 2005