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By Oszkar Bíró, Peter Mittag, Bernhard Aigner, Stefan Pirkeri, Philipp Glttleri

"This paper considers CFD modeling of processing and melting of small metallic particles by means of electrical heating. The particles fall continuously onto a liquid metal bath which is heated by an electric arc. After melting of the particles liquid metal is tapped.The charging behavior of the particles in the supply unit as well as in the reactor freeboard is studied by means of Euler-Euler granular simulations. The flow situation in the metal bath due to gas injection and magnetic fields is calculated by combining Navier-Stokes and Maxwell solvers. The macroscopic melting process occurring during the continuous charging of the particles is studied by kinetic laws for melting reactions. The temperature field is evaluated by balancing heat sources due to Joule's heating and heat losses due to latent heat of melting as well as convection and radiation.As a result of these simulations the fully three-dimensional flow fields of particles and gas in the atmosphere is obtained. Furthermore the flow field as well as the magnetic field in the metal bath can be studied. As a main result the three-dimensional concentration field of the still unsolved particles in the liquid metal can be evaluated.IntroductionIn this paper a metallurgical process for melting small iron particles is investigated by means of CFD-simulations. In a first process step the preheated and already mostly reduced iron particles fall continuously into the reactor through a vertical tube mounted at the lid of the furnace. In a second step the particles are melted in the liquid metal bath. Meanwhile the melt is heated by electric arcs to provide the heat needed for melting the incoming particles.In Figure I a sketch of the geometry setup considered in this paper is provided. The particles fall from a height of approximately 12 meters onto the bath surface in the center of the furnace. The melt is heated by electric arcs that are placed symmetrically around the center axis."

Jan 1, 2001

East Otago gold deposits are hosted in Otago Schist that is the metamorphosed equivalent of Permian-Triassic Torlesse terrane greywackes. Relatively undeformed Torlesse sequences in Canterbury have <l m - 50 m bedding, with c. 500 m - l km and c. three kilometre scale units, typically either: 1) thick-bedded, massive, sandstones; 2) thin-bedded sandstone-argillite flysch; or 3) siltstone- or argillite-dominated units. Such lithological layering in Otago was intensely folded, deformed, and overprinted by metamorphic fabrics during Jurassic-Cretaceous regional metamorphism. Although primary sedimentary structures can no longer be recognised, a æghostÆ lithological variation is still present in Otago represented by psammitic (sand-derived), interlayered (sandstone-siltstone derived) and pelitic (siltstone-mudstone derived) schist. Lithological æunitsÆ in the schist are typically either 20 100 m or c.1 - 2 km thick, and are oblique to faults and shears hosting gold mineralisation at Macraes, Barewood, Nenthom, and Oturehua. Lithological variations and folds in lithological units are important in the along-strike distribution of gold in these deposits, and in the development of relatively high-grade pods and shoots at l00 m - 1.5 km scales. Ramps, flats and step-overs (known to be locally important for controlling mineralisation) are commonly located at lithological boundaries, presumably by local refraction of faults or shear zones as they propagated through folded stratigraphy. The various lithologies have also responded differently to deformation, causing variations in permeability that affected the penetration of mineralising fluids. Mapping lithological variations in barren host-rocks, either directly+ by fieldwork or indirectly by aerial geophysics, is a key to understanding and predicting the distribution of gold at mine and deposit scales.

Jan 1, 2001

By D. H. McCain

Through a unique partnership between the Colorado Mine Safety and Training Program (CMSTP), the Colorado Rock Products Association (CRPA) and the Higher Education and Advanced Technology (HEAT) Center, a video packed, dazzling CD-ROM training program was developed for new miners entering the aggregate industry. Why this product was developed, and why the aggregate industry, will be discussed along with the challenges faced throughout the project. Cooperation from every one involved including MSHA made this the product of which all other training materials in the mining industry will be measured against in the 21st Century. This product's versatility and wide application makes it a tool that is as critical to a mine's success as any earth moving machine. Developed with both state and federal grant moneys allows this product to be affordable to small operators and independent contractors. The quality of this two CD-ROM set rivals any commercially made CD-ROM training.

Jan 1, 2001

By J. L. Jambor, M. J. Baker, M. J. Logsdon

"Abstract - Prior to the development of the Diavik Diamonds Project, baseline studies were conducted to determine the geochemical characteristics of four kimberlite orebodies as an aid in the design of both the water-management system and the facilities for containment of processed kimberlite and ore stockpiles. Materials tested included field samples of volcaniclastic and pyroclastic kimberlite, processed kimberlite (i.e., kimberlite ore which had been screened and washed as part of the processing procedure), and sedimentary mudstone (a minor xenolithic unit which was assimilated during kimberlite emplacement). Approximately 200 samples of kimberlite materials were collected as part of the geochemistry program. Test-work included whole-rock chemical analyses, acidbase accounting, kinetic leach tests using columns, and mineralogical analyses. Diavik kimberlite has major oxide and trace-element concentrations consistent with global averages for kimberlite. The mean total-sulfur content of the kimberlite material is 0.22 wt% S, but with a significant range. The kimberlite has an excess of carbonate minerals over sulfide minerals (average CO2 = 4 wt%, present mainly as calcite), and has a mean neutralization potential of 311 kg CaCO3 equivalent/tonne. A reactive form of framboidal pyrite associated specifically with the mudstone xenoliths is the primary source of sulfide-sulfur. Long-term kinetic tests confirmed the preliminary interpretations that were made from the static-test results. Kimberlite and processed kimberlite are net acid-consuming materials that produce alkaline drainages and have low but detectable leaching rates for SO4 and specific trace metals such as Al, Co, Cu, Ni, and Zn. If segregated from the kimberlite, mudstone xenoliths are acid-generating (pH = 3) and produce an effluent with elevated concentrations of SO4, Fe, Al, Cu, Ni, and Zn. The study demonstrates that xenolithic units in Diavik kimberlites have an important effect on the environmental geochemistry of the ore rock. The mineralogy and aqueous geochemistry of the kimberlite materials are such that they may not be suitable for general earthworks or as an alkaline agent and should report to an engineered facility to protect site water quality."

Jan 1, 2001

By Lynne Chastain

The Eastern Shoshone and Northern Arapaho tribes of the Wind River Indian Reservation, Wyoming are interested in developing their industrial mineral resources. The U.S. Bureau of Indian Affairs (BIA), Division of Energy and Mineral Resources (DEMR) is assisting the tribes in evaluating the potential of their industrial mineral prospects for development. Gypsum occurs on both sides of the Owl Creek Mountains in the basal portion of the Jurassic Gypsum Springs Formation. The gypsum resources that are being evaluated crop out along the northern flank of the Owl Creek Mountains in the Sweetwater basin, a small topographic sub-basin of the Big Horn Basin. From October 1998, to April 1999, DEMR personnel mapped, sampled, and drilled the southcentral butte within the Sweetwater basin. Samples were analyzed for free and combined water, and major mineral oxides to determine gypsum purity. Gypsum purity averaged 93.6 percent for surface samples and 95.1 percent for drill core samples. The basal portion of the Gypsum Springs Formation is comprised of several beds of gypsum up to 9 feet (2.7 m) thick separated by 0.5 to 2.0 foot (0.15 to 0.61 m) thick lenses of siltstone and limestone. Overall gypsum in the formation ranges from 35 to 90 feet (11 to 27 m) in thickness. A resource of approximately 7 million short tons (st) (6.4 million metric tons [mt]) has been identified.

Jan 1, 2001

By G. A. Irons, D. Guo

"The average spout height and width produced by bottom gas injection in a water model of a steel ladle were measured with an image processing technique. It was revealed that the spout height could be described by a Gaussian curve. A combined SIMPLE -VOF model was developed to simulate the liquid surface and flow. The results showed that, though the model produced reasonable velocity distributions and free surface positions, the spout height due to the dynamic head of the rising liquid was substantially lower than observed, indicating that the bubble dynamics at the bath surface play an important role in spout height.IntroductionDue to the enormous importance of gas injection and stirring in metallurgical processes, there have been numerous publications on water and numerical modeling of such vessels. The free surface of the bath has received considerably less attention, despite its importance. At the free surface there are often important chemical phenomena occurring that require a good understanding of the fluid flow; these would include reoxidation of steel, metal splash and fume formation. Furthermore, to understand the details of slag-metal interactions such as slag entrainment, metal losses to slag and the transport phenomena associated with refining reactions, it is necessary to understand the plume and spout interactions first.There have been few experimental studies of the free surface of liquid in gas-injected ladles [1- 3], and even fewer on numerical modeling. Brimacombe and co-workers [1] studied the gas void fraction in the spout region, using a double-tip electrical resistance probe. This sensor cannot distinguish between gas in bubbles about to break and gas in the freeboard. Thus, it is a matter of judgement as to the position of the free surface. Schwerdtfeger and co-workers [2] used a single probe configuration with a wire and a counter electrode in the liquid, so that the height of the continuous liquid phase was unambiguously determined. Irons and co-workers [3] measured the spout height by ultrasonic and electrical capacitance techniques. These techniques were as reliable as the resistance techniques, but were restricted to low flow rates."

Jan 1, 2001

By S. C. Langvik

The presentation named 'Dewatering of fines by Rotary Vacuum Disc Filters' has an opening why the filtration process is important to the Iron Ore Industry. It goes on to describe the various types of dewatering machines which have been used in this industry in the last 30-40 years, and where the vacuum disc filters now dominates. It presents also the most important design changes which have been made during this period to enhance performance. Further are discussed the principles of filtration and the factors and parameters which influence performance and operating costs. As a closing is presented today's ideas and thoughts about what can be foreseen of design modifications and improvements in disc filter design in the coming ten years.

Jan 1, 2001

By D. Craig Camp

conditions. The soils included 65 m of rock not exceeding an unconfined compressive strength (UCS) of 200 kgf/cm2, 130 meters of soft clay, silt, and sand not exceeding 30standard penetration test SPT blows per 300 mm, and 220 m of rock ranging between an UCS of 400-600 kgf/cm2. The river crossing, utilizing 1778 mm OD x 19 mm wall x600 mm steel casing pipe without intermediate jacking stations, was part of a seven kilometer liquefied natural gas (LNG) transmission line in South Korea. This 440-m, 1,442-ft, river crossing was microtunneled through three different ground conditions and completed in just over three months. The crossing was achieved with an average of 25 m of ground cover and 15 m of water cover. The Kwang Yang River Crossing was part of a 7 km liquefied natural gas pipeline project for POSCO, a Korean steel producer. The microtunneling machine was custom built for this project. The microtunneling machine selected for this project was tooled with 7 button bits and 2 roller bits. None of the cutter bits were replaced during the drive. Inside the machine, before the spoils laden slurry was pump back to the surface, it would pass through an independent cone crusher. The crusher is placed in the slurry flow to make sure that none of the spoils are so large as to stop the return flow of the slurry. An additional requirement was for the inclusion of a compressed air lock. The air lock was required in the event that the cutter tools required replacement. The cutters were back loaded so that the workers would have access to change the cutters in the event of cutter failure or wear out. No intermediate jacking stations were installed for the drive. The soils included 65 meters of rock not exceeding an unconfined compressive strength (UCS) of 200 kgf/cm2 with production averaging between 7 and 20 mm/minute. The second zone contained 130 meters of soft clay, silt, and sand not exceeding 30 standard penetration test (SPT) blows per 300 mm with production averaging between 80 and 180 mm/minute. The third zone contained 220 m of rock ranging between an UCS of 400-600 kgf/cm2 with production averaging between 7 and20 mm/minute. The steel casing pipe was 1778 mm OD x 19 mm wall x 6000 mm long. The project profile, see Figure 1, shows the soil conditions. The hand written numbers locate just above the pipeline are the production dates. The circled numbers are the 10 pipe joint increments. The project required 74 pieces of pipe to span the440 m drive. Figure 2 and Figure 3 are the jacking information. Figure 3 is a continuation of the information from Figure 2. The top section of the graph is the jacking force. The jacking

Jan 1, 2001

By James Warner, Peggy Ganse, Glen Smoak, Raymond Henn, Sam Bandimere

Over the past several decades, cement-based grouts using ultrafine cement as are placement for portland cement have begun to gain acceptance as an alternative to chemical solution grouts, however the amount of information currently available on these grouts is limited. For this reason, the authors developed a field testing program to evaluate the penetration capabilities of various ultrafine cement grout mixes. The tests were conducted by injecting sand columns using different portland and ultrafine based grouts, the measuring penetration distances after applying equal injection pressure for the same time period. Results of tests performed in 1999 and 2000 are discussed herein.

Jan 1, 2001

By D. G. Millette, A. J. S. (Sam) Spearing

The design of a cost effective backfill system involves many aspects and various inputs from different engineering disciplines. Backfilling is a very significant mining cost and efforts need to be made in the design stage to maximise efficiency and flexibility whilst minimising costs. The aspects that need to be considered include the following: Required fill performance underground Peak and average fill tonnage requirements Backfill scheduling in the mining cycle Material selection, testing and preliminary costing Plant design and storage needs Infrastructure requirements Implications on surface waste/tailings disposal and costs Total backfill costs In order to produce a cost effective and efficient backfill operation, a multi-disciplinary project team is required that should include the following skills and functions: Mine Planning Rock Engineering Metallurgy Mechanical Engineering Environmental Health and Safety Tailings Disposal/Waste Management This paper discusses the above and indicates important aspects that should be considered.

Jan 1, 2001

By M. Grodner

Ground Penetrating Radar (GPR) is an electromagnetic geophysical reflection technique that maps reflections associated with a change in electric properties of the target medium. It can thus be used to map the geometry of geological features and fractures as these can have different electromagnetic properties to intact rock. GPR was used successfully to determine the position and nature of the fractures in the tunnel sidewall, in the area of the simulated rockburst experiment. By comparing the radar scans acquired before with those acquired after the blast, it was possible to determine which fractures were reactivated by the blast and where new fractures were developed. It was found that the mining-induced fractures that formed during the development of the tunnel were re-activated by the simulated rockburst, as indicated by their increased reflectance on the radar scans. In addition, several new tunnel sidewall parallel fractures developed in the area of the blastholes. GPR thus clearly shows how and where the fracture pattern changed as a result of the blast and contributed to the understanding of the mechanisms of damage associated with the blast, and perhaps rockbursts in general.

Jan 1, 2001

By E. D. Attanasi

Geologic resource assessments describe the location, general characteristics, and estimated volumes of resources, whether in-situ or technically recoverable. Such compilations are only an initial step in economic resource evaluation. Forecasts that assume that resources that exist in nature can be commercially produced as needed ignore economic constraints. This paper identifies, by example, the salient features of a geologic assessment that will assure its usefulness for economic analysis. These features are demonstrated with examples of coal resource assessments and coal bed gas assessments.

Jan 1, 2001

By Alan E. Isaacson

Extensive gravel deposits exist within a six-county area in the mountains surrounding the Salt Lake Valley, and in the mountain ranges to the west. The six-county area includes Davis, Salt Lake, Summit, Tooele, Utah, and Wasatch Counties. The majority of these are beach deposits from prehistoric Lake Bonneville. However, real estate development associated with a projected population increase of 54 percent over the next 20 years is expected to remove most gravel deposits in Salt Lake County from consideration for mining, forcing gravel operations to relocate from eastern Salt Lake Valley to the Oquirrh and Stansbury Mountains farther west. The gravels in these ranges are of lower quality and require additional processing to manufacture asphalt and concrete. Replacing gravel resources along the Wasatch Front with resources in the Oquirrh and Stansbury Mountains over the next 20 years has the potential to increase construction costs by nearly $1 billion. The majority of this cost (82 percent) is the result of increased transportation costs due to longer distances to market. The remainder of the cost is attributable to lower quality gravels that will require additional processing in the manufacture of asphalt and concrete. The following analysis and discussion does not take into consideration the amount of crushed stone that is currently being used in the construction industry in northern Utah, its use as a substitute for lower quality gravels, or as a factor in the base case projection.

Jan 1, 2001

By Joram M. Amir

Even when they are cased! [ ] In bored piles, as well as in drilled shafts, and in caissons too, defects will occur! [ ]

Jan 1, 2001

By G. Abramov

The 20th Century saw the modern mining industry enriched by one outstanding method of extracting of mineral resources called Borehole Mining (BHM). Mean while, despite its successful track record in wide ranging locales, few specialists are yet aware of this technology. The intent of this article is to introduce borehole mining to a wider spectrum of drilling and mining professionals. The BHM method is based on in-situ water jet cutting of rock mass. On Fig. 1 the schematic of the method is presented. The borehole mining tool 1 is lowered into the borehole 2 and high pressure water 3 is pumped down. At the bottom part of the tool, one portion of that water comes out through the hydromonitor nozzle 4 in a shape of water jet 5 and cuts the material 6 creating slurry 7. The other portion of high pressure water then comes to the hydroelevator 8 (jet pump, eductor) which produces a vacuum. When the slurry reaches this vacuum zone, the eductor sucks the slurry and pumps it up to the surface, where rock parts are separated from water in a tank 9 or a pond and clarified water is pumped down again closing the re-circulating BHM water supply system. The borehole mining tool is suspended on a drill rig tower 10 which allows the tool to rotate and move vertically along the borehole axis. While extracting rock mass, underground caverns (stopes) 11 are created. If necessary, compressed air 12 can be injected to the raising slurry flow to create an airlift effect. Also, a secondary agent 13 (such as oil, foam, etc.) can be added to the stope through the gap between the tool and the casing. As seen from the illustration, BHM is the remote mining method of extracting of mineral resources through boreholes by high pressure water jets.

Jan 1, 2001

By R. J. Matetic

Researchers associated with the National Institute for Occupational Safety and Health (NIOSH), Pittsburgh Research Laboratory (PRL), are investigating injuries (fatal and nonfatal) attributed to water well drillers during well drilling activities. Injury data, obtained from various sources, suggest that many water well drillers are experiencing unnecessarily high insurance premiums and very avoidable citations or violations from the direct result of accidents, injuries, and fatalities occurring throughout the water well drilling industry. Expensive insurance premiums and unnecessary citations are the direct result of poor health and safety practices. Visits to numerous water well drilling sites were conducted by NIOSH personnel to characterize and identify the injury data collected and to provide inexpensive strategies to prevent, minimize, and eliminate safety and health issues associated with water well drilling activities.

Jan 1, 2001

By C Li

Removal of gangue minerals from ilmenite concentrates can beaccomplished by relatively low temperature roasting in controlled gasatmospheres to selectively enhance the magnetic separationcharacteristics of the ilmenite. At roasting temperatures below 800¦C the magnetising reactions are often not consistent with phase equilibria considerations. Metastable phases can nucleate and control the roasting products. In weathered ilmenites the phase assemblages and microstructures in the altered ilmenite grains can influence the roasting reactions. In this paper we give an overview of the phase chemistry of chemically weathered ilmenites and of metastable phases formed by low temperature roasting. We also report the results of roast experiments conducted in a neutral gas atmosphere. Major increases in magnetic properties after short roasting times at low temperatures were obtained for a range of ilmenite concentrates. For example heating a secondary ilmenite concentrate from Western Australia for 15 minutes in nitrogen at 600¦C gave an increase in the three kilogauss magnetic fraction from three to 92 wt per cent. The solid state phase changes accompanying the inert atmosphereroasts were characterised by combining elemental analyses withquantitative phase analyses of the ilmenite concentrates and their roast products. It was found that the phase reaction that is principally responsible for the increase in the magnetic properties of weathered ilmenites involves a transformation of disordered ferrous-containing pseudorutile to an ordered ilmenite-hematite solid solution containing typically ten to 35 mole per cent of the hematite component. Examples are given of the application of the inert atmosphere roast to effect separations of ilmenite from gangue minerals.

Jan 1, 2001

By David Chapman, Glen Frank

Due to the transport mechanics of the depositional environment, glacial soils display a very wide range of grain sizes and behavior. Several nonstandard drilling, sampling, and analytical techniques are therefore required to characterize the subsurface. The paper summarizes the geotechnical investigation for the design of a large project in glacial geology, which will include both large and small diameter pressure balance tunneling. The paper focuses on the challenges presented by the glacial environment and the techniques required to identify and characterize it for design and contract document preparation.

Jan 1, 2001

By John ?gren, Martin Schwind, Henrik Larsson

"A new model for internal oxidation, as well as similar processes, has been implemented on computer. It is based upon a combination of random walk and cellular automata and is capable of treating 3-dimensional cases. To model diffusion, it utilises quantised units of matter. All steps of the process are included: nucleation, growth and coarsening. The effect of grain boundaries on diffusion as well as nucleation is taken into account. Further possible development is briefly discussed; especially the treatment of nucleation needs further consideration. IntroductionComplex diffusion-controlled processes may now be simulated on a routine basis when concentration varies along one co-ordinate only. One-dimensional simulations capture much of the information of interest but not all. For the case at hand, especially the spatial and the size distribution of precipitates, as well as the impact of grain boundaries, would be interesting information not accessible from 1-D simulationsSolving the full Fick-Onsager law in three dimensions does not seem feasible with the computers of today. In the model described in this article, random walk by quantised units of matter are considered. The model should be useful for a number of cases involving dispersed systems. With further development, it would indeed seem possible to simulate most types of phase transformations.Previous workWe have previously published two articles [1,2] on the new approach discussed in this work. In those articles we described the basic idea and showed, among other things, that very good agreement with an experimental concentration profile can be obtained, in a single-phase system, using independently assessed thermodynamic and kinetic data. Also, Schwind used the same random walk based concept to model coarsening [3]."

Jan 1, 2001

By Andre Vien, Jean-François Dupont

"Over the past several years, Svedala has developed a continuous charge monitor (CCM) for tumbling mills. It consists of a strain gauge embedded into a rubber lifter and associated electronics. This paper describes the installation and use of such a device on a SAG mill at the Holt-McDermott Mine. Comparison to measured static volumetric load and bearing pressure and inclusion of the measurement into a control strategy and its potential for condition monitoring is discussed. INTRODUCTIONWhile the measurement of load is very important in all kinds of grinding applications, the biggest benefits are expected from AG and SAG milling. This is what motivated Holt-McDermott to take a closer look at this problem, with a view to optimizing SAG mill performance.In many cases, the SAG mill control problem can be stated as maximizing throughput while avoiding a volumetric overload, with the other constraints (e.g. power, grind size, upstream/downstream equipment constraints, etc.) playing a less important role. This is certainly true at Holt-McDermott where the SAG mill is the production bottleneck about 90% of the time, and anything that can be done to increase SAG mill throughput will have a significant impact on operating profit.Although the goal of maximizing throughput while avoiding volumetric overload is simple to state, it has proven to be much more difficult to achieve. The mineral processing industry has expended a great deal of time and effort to devise control strategies in the pursuit of this objective. While much progress has been made, there is still room for considerable improvement. Across the industry it is probably fair to say that overloads occur relatively infrequently, but the real losses accrue as a result of the tendency to run rather conservatively."

Jan 1, 2001