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By B Firth, G OÆBrien, B Jenkins

In coal flotation, particles of different components of the coal such as maceral groups and mineral matter and their associations have different hydrophobicities and therefore different flotation responses. By using a new coal grain analysis method for characterising individual grains, more detailed flotation performance analysis and modelling approaches have been developed. The method involves the use of microscopic imaging techniques to obtain estimates of size, compositional and density information on individual grains of fine coal. The density and composition partitioning of coal processed through different flotation systems provides an avenue to pinpoint the actual cause of poor process performance so that corrective action may be initiated. The information on grain size, density and composition is being used as input data to develop more detailed flotation process models to provide better predictions of process performance for both mechanical and column flotation devices. A number of approaches may be taken to flotation modelling such as the probability approach and the kinetic model approach or a combination of the two. In the work reported here, a simple probability approach has been taken, which will be further refined in due course. The use of grain data to map the responses of different types of coal grains through various fine coal cleaning processes provided a more advanced diagnostic capability for fine coal cleaning circuits. This enabled flotation performance curves analogous to partition curves for density separators to be produced for flotation devices.

Jan 1, 2005

By Brett Zernich, Michael Krulc, Brett Robinson

This paper provides an account of the efforts undertaken to construct the Northeast Interceptor Sewer (NEIS) project, which is a portion of a much larger program in Los Angeles, California to upgrade the city’s wastewater facilities. The project consisted of a number of elements, including both soft ground and rock slurry wall shafts, drilled shafts, soft ground EPBM mining, rock TBM mining, large diameter pipe placement, and underground structure construction. The need to complete the project under strict schedule constraints, in addition to the challenges of underground construction in congested urban areas, necessitated the work be undertaken with the proper balance of state of the art equipment, and thoughtful planning. The paper will detail the means, methods, and equipment used on the project, as well as discuss several of the unforeseen conditions encountered during construction.

Jan 1, 2005

By M. Syamujulu

In 1994, Nkana smelter commissioned a multimillion US Dollar Chilean Teniente converter (CT) in its operations in order to improve its smelting technological base. The main objective was to reduce the overall smelting energy costs and increase the sulphur capture for sulphuric acid production to support the company?s leaching operations at Nchanga tailings leach plant. A decade of CT operations have since ensued following its installation and start-up. This paper provides a technical and operational audit of the performance of the CT in the first 10 years of its operations at Nkana smelter.

Jan 1, 2005

By Chaoxun Zhao, Daniel Tao, Craig Blue, Narendra B. Dahotre, Rick Honaker, Bhupendra K. Parekh, Hongyang Han

Equipment wear and corrosion have significant adverse impacts on the operating cost and efficiency of mineral processing plants. In this project advanced surface enhancement technologies are being investigated to decrease the wear and corrosion rate of metal surface. Enhanced metal surfaces are achieved through surface conversion, enrichment, and coating by use of advanced High-Density Infrared (HDI) and other technologies. Studies have been done to determine the effects of process parameters on surface properties and identify optimum conditions. The microstructure of the enhanced metal surfaces was characterized by SEM, EDS, and microindentation. Laboratory wear testing was carried out to investigate the wear performance and the viable coating candidate was determined.

Jan 1, 2005

By M J. Kelleher

CREAM is an acronym for coal recovery, evaluation, analysis and management and is a business improvement project at BMAÆs Goonyella Riverside mine that is focussed on maximising coal recovered. In August 2003, Goonyella Riverside was set a challenge to quantify coal loss and dilution and their relationship to cost, revenue and ultimately profit. While the mine was confident in its site forecasts of recovery (and loss), it was clear that the traditional measurement and analysis systems were inadequate to firstly, identify key loss areas and mechanisms and secondly, successfully quantify the benefit of various coal recovery initiatives. The path that BMA Goonyella Riverside has travelled to maximise coal recovered can be divided into four key steps: Mapping the process û This step involved the development of a coal flow process map for Goonyella Riverside that stepped through each component of the process from the coal reserve to the customer and identified key measurement points for the purposes of reconciliation. Understanding coal loss and identifying opportunities û This step involved conducting two detailed Reserve to Customer projects at the mine site to track a block of coal from the reserve to the customer and to gain a greater understanding of the relationship of dilution, coal loss mechanisms, revenue and costs associated with recovering additional coal. Coal data systems development û Two important coal data systems have been developed and implemented at Goonyella Riverside in the past twelve months, namely SnowdenÆs Coal Reconcilor and SeamFix. These systems enable coal losses and dilution to be quantified and reconciled back to the initial coal reserve. Implementation of loss reduction initiatives û This step involved the formation of a business improvement project referred to as æCREAMÆ in August 2004, for the purposes of improving pit coal recovery and maximising business value. To date a series of coal recovery trials have been run in a number of pits at Goonyella Riverside that have yielded significant improvements in business value. The key to the success of this project has been the discipline to follow a defined process map, management commitment through resourcing and shared key performance indicators, a successful acceptance strategy resulting in holistic ownership and the implementation of sustainable reconciliation systems. Coal loss and dilution are now quantifiable and their relationship to cost, revenue and ultimately profit is well understood. This paper discusses the process that Goonyella Riverside has adopted to maximise coal recovered.

Jan 1, 2005

By Chi M. Phan, Anh V. Nguyen, Geoffrey M. Evans, Graeme J. Jameson

Surfactants are used to control the interfacial properties of the gas-liquid and liquid-solid inter- faces inflotation. This paper investigates the dynamic adsorption of surfactants at the gas-liquid intelface. The dynamic adsorption process was modeled by considering the surfactant mass transfer to the gas-liquid interface by dimion and the Langmuir and Frumkin adsorption isotherms. The numerical computation was applied to solve the non-linear governing equations. The dynamic adsorption was measured in tenns of the dynamic surface tension using the pen- dant drop method. The theoretical modek were compared against the experimental data obtained with non-ionic (Dowfroth 250) and ionic (sodium dodecylbenzene sulfate, SDBS) surfactants. The theoretical results agreed well with the erperimental data for SDBS, but not for Dowfrother 250, especially for the initial stage. Reasons for the variation in results are given in the paper.

Jan 1, 2005

By W. R. Tyson

Pipelines for the transport of gas and oil are being designed to operate at increasing pressures in increasingly harsh environments. The steel used to construct these pipelines must have adequate toughness to tolerate weld imperfections (i.e. withstand bending strains) and to arrest running cracks (i.e. to prevent propagation of axial fractures). The problems posed in specifying suitable toughness parameters and the approaches currently being used to measure them are discussed.

Jan 1, 2005

By J. Gao

We present results from our investigation of the concept and practice of using surface-charged latex nanoparticles as building blocks for conductive membranes. Nanoparticles were synthesized by free-radical co-polymerization of two hydrophobic monomers, butyl acrylate (BA) and methyl methacrylate (MMA), a crosslinker, N, N'- methylenebisacrylamide (BIS), and a charged monomer, sulfonate styrene sodium salt (NaSS), in water. The resultant nanospheres were characterized with static and dynamic laser light scattering. Thin films were cast from concentrated particle dispersions, followed by incubation at ?110 °C. Conductivity, water uptake and final charge content were measured. The membranes have higher conductivities than both amorphous films cast from sulfonated BA-MMA-Styrene copolymer chains and BA-BIS-MMA-NaSS gel films. TEM images and neutron scattering spectra confirm the particulate structure of the membranes.

Jan 1, 2005

By Y. Huang

Corrosion of GaAs in aqueous electrolytes is a major limitation in implementing GaAs-based photoelectrochemical solar energy conversion systems, In this work, the corrosion behavior was investigated by electrochemical methods and surface analysis approaches, in both H2SO4 and NH3?H2O solutions, Open-circuit measurements showed that the cleaned GaAs surface was very sensitive to water/air, Impedance measurements for n-GaAs showed that an inductive loop only appeared at a high corrosion rate because a reaction intermediate is the oxidant for a further decomposition step in combination with chemical reaction with water, The results suggest that the same corrosion/decomposition mechanism occurred on n-GaAs in the two solutions, When the surface-hole concentration was low, the hole injection or generation process was the rate-determining step, At large reverse bias on n-GaAs, with high-hole concentration, the corrosion rate was limited by a Faradaic adsorption process, involving an adsorbed intermediate, The different surface compositions after corrosion in the two solutions can be explained by the dissolution of As(0), Further oxidation of As(0) to As(III) in NH3?H2O solution is still slow, as suggested from X-ray photoelectron spectroscopy (XPS) analysis,

Jan 1, 2005

Solid Energy New Zealand (SENZ) uses a 20+ year period for integrated planning of all its business activities. It has an ongoing program of coal resource assessment to optimise future mines within this 20 year period, using a six step resource and mine planning process. Desktop review and conceptual study at preliminary Levels 1 and 2 are based on general coal resource information. Further coal resource investigations are carried out for the more detailed evaluations in secondary assessment, prefeasibility study, feasibility study and detailed engineering from Levels 3 to 6. At Levels 1 and 2, completing conceptual planning, including preliminary resource evaluation and economic appraisal to the target cost uncertainty level of ¦33 per cent, is challenging in New ZealandÆs highly variable geological and geographical conditions. Where coal deposit geometries are relatively simple, approximate methods for determining pit limits using overburden strip ratios, seam thickness, physical boundaries, and quality cut-offs may be sufficient. Many New Zealand coalfields are however complicated structurally, with multiple seams and extensive folding and faulting. Coal seams are characterised by variable dip, thickness, and quality over relatively short distances. In the North IslandÆs Waikato coalfields, coal is typically overlain by weak sediments and clay rich strata that necessitate very flat cut and fill slope angles. The proximity of these deposits to major infrastructure (including towns, highways and rail lines), significant environmental features such as the Waikato river and lakes, and valuable dairy farmland, add further complexity. Traditional preliminary mine planning techniques applied in these conditions are insufficient. Pit optimisation software, widely used in the metalliferous mining industry since the 1980s, offers the ability to analyse many more specific factors affecting pit limits, mine layouts, and economics, with more rigour and for a much larger number of scenarios, than traditional methods allow. SENZ therefore decided to adapt and use æWhittleÆ pit optimisation software for Level 2 analysis of several Waikato opencast prospects. This paper describes this work.

Jan 1, 2005

Inco Limited has been evaluating options for streamlining the overall flowsheet at its Sudbury, Ontario operations to improve productivity and to minimize the cost of at¬mospheric emissions reduction. Some of the flowsheets being considered include vari¬ous levels of copper/nickel separation at the Clarabelle Mill where all Inco's Sudbury Basin ores are processed. This paper reports on the laboratory and miniplant studies car¬ried out during the flowsheet development for a commercial Cu/Ni separation plant. There are two potential feed streams for Cu/Ni separation. It was determined that Cu/Ni separation from the rougher concentrate requires no regrind, and a very clean copper concentrate is produced, but the recovery of copper is limited to about 70% from ore. Cu/Ni separation is more difficult from the bulk concentrate because of the presence of excess flotation reagents in the slurry and due to locked particles. By replacing the slurry water with clean process water, and by addition of some hydrogen peroxide, entrainment is minimized and excess reagents are removed from the surface, providing a satisfactory separation of copper from nickel. Fine regrinding is required to increase liberation of the locked particles and to obtain 85% copper recovery with minimal nickel contamination of the concentrate.

Jan 1, 2005

By A. Eftimie, M. Stanley

The World Bank Group (WBG) believes that extractive industries can make significant contribution to sustainable development and poverty reduction, providing that environmental, social, and corporate governance issues are properly managed. The WBG recognizes that stakeholders have legitimate concerns about the impact of extractive industries, and management proposals are built around the central theme that investments and policy advice in the extractive industries should lead to poverty reduction. To help governments create appropriate policy and regulatory frameworks, this paper focuses on the linkages between overarching policies and laws and the management / governance of extractive industries at the local communities. It encourages the use of new instruments designed to help ensure that local communities benefit from extractive industries.

Jan 1, 2005

By Chris Roper

The Gavia Autonomous Underwater Vehicle is a two-man portable AUV that is capable of performing seafloor surveys in water depths to 2000 meters. The standard survey sensor suite includes a dual frequency side scan sonar and high resolution digital camera. Additional survey sensors are currently being incorporated into the Gavia AUV, include Sub Bottom sonar, Swath Bathymetry sonar and Multi Beam sonar. The modular design of the Gavia AUV allows the end user to quickly incorporate new sensors including client developed propriety sensors.

Jan 1, 2005

By S. Esmaeili

The yield strength model developed by Esmaeili, Lloyd and Poole [1] has been adapted to model isothermal aging in Cu-containing AA6xxx alloys, with (a) a moderate and (b) a very low Cu content in the solution-treated, as-quenched, condition, Isothermal calorimetry has been used to analyze the kinetics of precipitation in these alloys, While the kinetic parameters for the low Cu alloy has been derived from the present experiments, the previously determined kinetic parameters for the high Cu alloy AA6111 has been used to model the precipitation kinetics in the moderate Cu alloy. The age hardening responses of both alloys have been well predicted by the model.

Jan 1, 2005

By Helen Joyce, Larry Twidwell, Jay McCloskey, Eric Dahlgren, Andy Hadden

The reduction of dissolved selenium oxyanions from mine wastewater utilizing an elemental iron cementation technology on been studied on a laboratory scale at Montana Tech of The University of Montana and on a pilot scale at MSE-Technology Applications as a water treatment process potentially capable of removing dissolved selenium to GO WL. Laboratory and pilot scale studies using elemental iron have demonstrated effective removal of dissolved selenium. Enhanced selenium reduction rates have been demonstrated when galvanically coupled iron/copper and iron/ nickel are utilized. The laboratory and pilot scale results are presented and discussed.

Jan 1, 2005

Anglo Coal Australia (ACA) takes a proactive position with regards to attracting and retaining employees at a graduate level. Currently, ACA has graduates in its program across all disciplines: Mining Engineering, Mechanical Engineering, Electrical Engineering, Commercial, Occupational Health and Safety, Environmental Engineering, Human Resources, Safety Engineering and Processing Engineering. The current program is three years in duration and involves two (generally) equal periods at different ACA mine sites or Brisbane Corporate Office. ACA takes an active role in promoting its status at the university level by maintaining a scholarship program. Six undergraduate scholarships are offered each year across all disciplines. Associated Vacation Employment is offered to each scholarship holder during the period of his or her university study. This commitment to education is regarded highly by future graduates. ACAÆs active role in sponsoring student bodies is also known and appreciated amongst the university population. ACAÆs graduate program has been a successful training program for future leaders of the coal mining industry. The company is committed to making the program more suited to the needs of the graduates across all disciplines and as a result the program is not stagnant but is constantly changing and evolving. Recently the æGraduate PassportÆ has been drafted with an aim to keep each graduateÆs needs in relation to experience and training firmly in focus for the duration of the three-year program. Appropriate training for each graduateÆs position is supported by the company; for instance, support through funding and time for a commercial graduateÆs CPA qualifications is provided.

Jan 1, 2005

By J. N. Van der Merwe

In the process of pillar extraction, pillars are seldom if ever extracted completely. The pillar remnants, or snooks, play an important role in the extraction process. At the working face, they need to be stable to provide a measure of support in the immediate area. Further back, they have to fail in a controlled manner to prevent undue load build-up on the pillars that have not yet been extracted. The stability condition at the working area is the result of interaction between the stability of the pillar and that of the roof rock. It is shown that the primary mode of roof layer failure is by bending induced tension. Direct tension can be excluded in most practical conditions, and only in exceptional cases will the first failure be in shear mode. Panel spans required to cause the first goaf to be formed, predicted using analytical considerations, are of the same order as has been observed in practice. Once the first goaf has formed, the horizontal stress is reduced and failure will occur at more frequent intervals. It is shown that bending induced tension is the most likely mode of failure in an unjointed roof layer. In roof layers with a high frequency of weak or uncemented jointing, failure can be expected to occur at spans equal to the joint spacing. In this context, failure will occur at the smallest of the spans required to induce tensile roof failure and the joint spacing. A fundamental procedure to evaluate the likely roof layer failure in a stacked beam system is developed. This can to be used to estimate the loading condition on snooks. It is shown that snooks assist in stabilizing the immediate roof beam. The sizes and positions of the snooks relative to the position of the next pillar to be stooped, control the magnitude of the contribution to stability. The further the snook is from the next pillar, and the larger it is, the greater the contribution to the stability of the immediate roof. Under the condition of loading by the immediate, continuous roof beam, the position and size of a single snook controls the load acting on it. The closer it is to the nearest solid, provided that the roof overhang extends beyond the snook, the greater the load on it. However, once the immediate roof beam fails, the loading conditions change. The snook is then loaded by the tributary area load. A procedure is developed to assess the condition of snooks for different situations. Using the fundamental considerations developed in this paper, snooks can be designed to be stable during the active mining phase in their immediate vicinity, but to fail once the next line of pillars has been extracted.

Jan 1, 2005

By Varadajan Seshadri

Keywords: torpedo car, kinetics, physical modeling A 1:6 torpedo car physical model was built to assess the optimum refining conditions for pig iron desulfurization in the torpedo car considering the industrial parameters used in the steel plant CSBM (Companhia Siderurgica Belgo-Mineira, João Monlevade, MG, Brazil). The refining practice in this plant is through injection of a CaO-CaF2-Mg powder in the pig iron melt. Similarity between the model and prototype were established through Froude and turbulent Reynolds criteria. Mixing times were evaluated by pulse tracer addition and the kinetics of metal/slag interactions were assessed from experiments investigating iodine transfer from kerosene to water. The influence of parameters such as level of metal, gas flow rate, lance penetration, lance orientation were also evaluated.

Jan 1, 2005

By G. P. L. van der Linde

EVERY OREBODY IS UNIQUE [ ] GEOLOGY AND MINERALIZATION DIFFERENT [ ]

Jan 1, 2005

By Jonguk Kim

Hydrothermal sulfides were recovered from the16°50?S triple junction area in the North Fiji Basin, at a water depth of ca. 1900 m. The chimney samples can be divided into three groups according to their major metal contents: 1) type 1 (Fe-Cu-rich), 2) type 2 (Fe-Cu-rich with minor Zn), and 3) type 3 (Zn-rich) chimneys. Type 1 chimneys are mainly composed of chalcopyrite and pyrite, and are enriched in elements commonly precipitated under high temperature conditions (> 300°C), such as Cu, Co, Mo, and Se. Type 3 chimneys consist dominantly of sphalerite and marcasite with traces of pyrite and chalcopyrite, and are enriched in elements commonly associated with low temperature (150 to 250°C), such as Zn, Cd, Pb, As, and Ga. Type 2 chimneys show mineralogy similar to that of type 1 chimneys but their metal contents range between type 1 and type 3 samples. Trace element compositions of basaltic rocks indicate that magma generation in the triple junction area was influenced by two different sources: N-MORB and E-MORB. Sulfur and lead isotope patterns of the hydrothermal chimneys show distinct differences between the type 1 and type 3 chimneys. For example, type 1 sulfides are depleted in 34S and have lower Pb isotope ratios compared to type 2 and 3 chimneys. The d34S values (0.4 to 5.6?) of chimney sulfides are typical range of sulfur isotope composition of sediment free mid-ocean ridge hydrothermal system. Type 2 and 3 sulfides show slightly higher d34S values than type 1 sulfides, which can be explained by subsurface boiling of hydrothermal fluids followed by mixing of saline solutions with ambient seawater. Lead isotope compositions of the chimneys indicate that the Pb in type 1 and type 3 chimneys originates from hydrothermal leaching of N-MORB and E-MORB volcanic rocks, respectively. Considering that both these chimneys are located in the same area, our model suggests that type 1 chimneys formed by hydrothermal circulation controlled by an intrusion of N-MORB magma; the fluids were not influenced by boiling during the formation of type 1 chimneys. In contrast, type 3 chimneys are younger and were formed by hydrothermal circulation closely related to E-MORB magma intrusion at shallower depth. The necessary conditions for phase separation of the hydrothermal fluids that formed the type 3 chimneys might result from changed P-T conditions in a shallower high-temperature reaction zone beneath the hydrothermal venting site. Under these conditions the fluid may cross the two-phase boundary for seawater, ensuring subcritical phase separation. The mineralogical and geochemical properties of these chimneys suggest that type 1 and type 3 chimneys were probably black smoker and white smoker, respectively. Type 2 chimneys might be product of low-temperature replacement of type 1 chimneys, which is related to formation of type 3 chimneys.

Jan 1, 2005