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By T. Plikas, L. H. Gunnewiek, L. Oshinowo

Electric furnace smelting is one of the principal unit operations for ferroalloy production, and increased process intensity, improved availability, minimal maintenance and a longer campaign life are common objectives for electric furnace operation in order to obtain favourable economics of production. Furnace designers have continued to develop innovative solutions that have allowed these objectives to be realised, e.g., furnace cooling systems, and numerical modelling plays a key role in the design process. Enhanced understanding of the energy transfer process in the furnace and the ability to develop, evaluate and optimise components of the crucible design to match process requirements are the key motivators for modelling. This paper provides an overview of recent applications of numerical modelling to the design of electric furnaces. The aim is to illustrate what can be done, and identify areas where further work is needed in this field. Examples include furnace bath modelling, crucible cooling system design, taphole design, baking of Soderberg electrodes, off-gas systems, and fume control and building ventilation. It is argued that the trend is for numerical models to become more encompassing while at the same time more accessible, and therefore further improvements in furnace design will be realised with continued and well validated modelling efforts.

Jan 1, 2004

By Jeremy P. Doolan, Leigh B. Neindorf, Geoff W. Capes

The development and use of rock mass classification tools have been a key component for improving stope design over the past 4 years at the Xstrata Zinc George Fisher Mine in northern Queensland, Australia. In 2003, stope extraction data from 3 years of open-stope mining provided an excellent situation to review the assumptions in the feasibility study. Extracted stope profile information, drillhole geotechnical data, underground observations, and oral and written communication were used to develop a thorough stope reconciliation performance database. With-out collecting the back analysis data and presenting the data in a usable format, engineers are left to debate opinion instead of engineered judgment. This can lead to biased and uninformed design parameter choices with the potential to repeat poor design. This paper demonstrates some effective, practical examples of empirical data collection where rock mass classifications tools were developed and used to create improved confidence in predicting stope stability and failure profiles. The work contributed to design changes that resulted in a reduction in stope hangingwall dilution and an increase in head grade while continuing to ramp up production from 2003–2005.

Jan 5, 2007

By C. Hellar

A new dual-boom remotely controlled roof bolter was designed, fabricated, and then tested in an underground coal mine. Remote-control functions allowed complete bolting cycles to be performed on two booms with both operators located within protective cabs. Capabilities included 3-to 6-foot-long bolts in 5-to 8-foot seams, limited to bolts 20 inches shorter than seam height. Machine was in compliance with all regulations including dust collection, machine lighting, and permissibility.

Jan 1, 1979

By P. H. Mutschler

The Bureau of Mines studied the costs of transporting fossil fuels, coal, and residual fuel oil from areas of production to consumer regions. Transportation data were stratified by type of carrier, size of shipment, and distance to determine what general effects these variables have upon transportation costs. Economics of haul for coal exist for longer versus shorter distances, and for larger versus smaller trainload sizes. Tanker and barge transportation of residual fuel oil does not show economies of haul for longer distances. It is shown that tanker size and seasonal variation are primary factors influencing the cost of shipping. Railroad transportation data show that coal from western coalfields could be competitive with foreign residual fuel oil in selected midwestern fossil fuel markets. However, the western coal would not be competitive in the New England and the eastern seaboard energy markets.

Jan 1, 1973

By C. E. Lapple

To improve mine health and safety conditions, there is need for a portable instrument that mine inspectors can use routinely for rapidly checking concentrations of dust in mine atmospheres. On October 23, 1969, Stanford Research Institute was authorized by the U.S. Bureau of Mines to conduct a study aimed at developing such an instrument under Contract No. H0100186. The results of that study are reported in Technical Report No. 1, "Development of Portable Instrument For Measuring Coal Mine Dust Concentration," August 1970. In that study it was demonstrated on bench-scale that a near-forward optical scattering device gives a linear correlation between mass concentration and optical readout over a range of 2 to 200 mg/m3 with excellent reproducibility. The same correlation was obtained for the Respirable* dust fraction of three different coal dusts within ± 10% and an extreme spread of ± 30%. Based on these results a prototype instrument was designed which was expected to meet all the necessary requirements of a portable instrument for mine use. Because of the excellent results obtained, a further study was authorized by the Bureau of Mines on May 10, 1971 under Contract No. H0111688. The prime objective of this study was to build, calibrate, and deliver to the Bureau of Mines two prototype instruments based on the design previously developed. The emphasis was to be on providing instruments which would meet certain minimum standards of size, weight, response time, sensitivity, ruggedness, reproducibility, permissibility, and cost (ultimate); optimization of the design was to be considered only insofar as it would not significantly delay the development. One instrument was to be delivered after initial calibration of both instruments with Coal Dust PGH. The second instrument was to be used for further calibration with a number of other coal and rock dusts and for assessing other relevant performance characteristics. This report summarizes all the results of this second study.

Jan 1, 1972

By G. X. Wang, R. E. Siemens, M. C. Fuerstenau, D. Chandra

Soda roasting of concentrates from Mouat, Montana, was performed in a temperature range of 450 to 650 degrees C and chromium was solubilised by water leaching at room temperature. It was found that high extraction yields of chromium were primarily dependent on the conversion of Cr3+ to Cr6+ during the roasting step, and this was enhanced significantly by simple attrition of chromite particles during this step. Gangue impurities (mainly Si) were more detrimental to Cr extraction than lattice impurities such as Al or Mg. It appears that oxidation proceeds into grains along a preferred crystallographic plane in the cubic lattice of the chromite. The effects of roasting time, temperature, soda to chromite ratio and particle size on the extraction of chromium are presented

Jun 18, 1905

By Michael Mann, Kenneth K. Eltschlager

The International Society of Explosives Engineers (ISEE) Standards Committee has recently updated both the Field Practice Guidelines for Blasting Seismographs and the Performance Specifications for Blasting Seismographs. The revisions are the result of public and industry input along with recommendations of the ISEE Blast Vibration and Seismograph Section. The committee is comprised of blasting seismograph manufacturers, users and general interest personnel. On an as needed basis, subject matter experts are enlisted to advise the committee. Three phases of activities are necessary for each revision cycle: request for comment on the existing standard, first draft revision of the standard based on public input, and final draft approval by the ISEE Board of Directors. The ISEE standards revision process will be explained and each standard will be discussed along with the significant revisions from the latest revision cycle.

Jan 1, 2018

By Martin Kesting

The world wide growth dynamics and the continuously growing demand for energy, results in increasing energy prices. Looking from this point, the efficient exploitation of fossil fuel deposits has become a more important factor to the production of energy raw materials than ever before. This shall be reached by an increase of the automation degree of the bucket wheel excavator in the open pit mining as well as a quality increase of the entire mining process chain. A further optimization of this operation can only be achieved by gathering additional information about the input parameters. The earlier and more exact the description of the input parameter, the greater the effectiveness of the entire process chain. To address this major issue, the RWE Power AG assigned the Institute for Transportation and Automation Technology with the research project "SIMT, Sensory Identification of Material Type and Detection of the Interfaces" [Kes07]. Presently, the control of the bucket wheel excavator is carried out manually by the operator, as well as the visual identification of the different geological layers and the energy raw materials. In this paper, a sensor-system is introduced, which was developed in order to transfer the manual material identification and detection of interfaces into an automatic online procedure. A special challenge and the main focus of this contribution is the integration of this sensor system into a bucket of the bucket wheel excavator. For measuring procedures where direct contact with the in situ material is necessary, the sensor has to be integrated into the bucket. Since direct contact with the material is not necessary, it can be integrated next to the bucket wheel. The results of a preliminary study show that although there is a broad spectrum of sensor technologies for material and interface identification, only a few are suitable for an application in on-line measuring at the bucket wheel excavator. Taking into consideration the demands on the sensor technology, the studies carried out and comparable applications of individual sensor technologies which have already taken place in practice, the integration of the following measuring systems have been realized: ground penetrating radar / reflection measurements, geo electric, resistance geo electric technology. The solution developed in the research project offers for the first time the direct integration of sensor systems into the bucket of a bucket wheel excavator. It will now be possible to test other measurement methods and sensors, not only for the ones already mentioned. As an example the integration of a triaxial accelerometer to measure the solid borne sound and vibrations concerning the cutting of different materials will be shown.

Oct 1, 2009

By Robert F. Stewart

The oxidation of structural materials at high temperatures in gas-cooled systems can be greatly retarded by the addition of small amounts of hydrogen to the inert coolant. In experimental equipment for gasifying coal with heat transferred by helium, the oxidation of graphite and metals (molybdenum, tungsten, and certain stainless steels) by trace impurities in the coolant helium was virtually eliminated by adding 0.1 to 1.0 percent hydrogen. The reaction of hydrogen with praphite does not preclude its use to retard oxidation; at 2,400° F. only 0.2 pound of graphite per square foot per year is lost for each percent of hydrogen in the helium. The addition of hydrogen appeared to prevent the mass transfer of carbon often associated with oxidation of graphite, without causing noticeable embrittlement of stainless steels and molybdenum or other damaging effects. This method has been tested in precision gas-recycle systems and applied successfully for more than a year in a pilot-scale unit operating at 250 pounds per square inch gage and 2,400° F. It is now used routinely and can be applied to many gas-cooled systems operating at high temperatures.

Jan 1, 1962

By Fabien Miller

Automation technologies are increasingly envisaged to improve underground mining productivity. However, the technologies need to be used and adopted gradually in order to get the best benefits. This paper presents the technical and operational aspects of autoguided production vehicles at Brunswick Mine. During 2001 Noranda?s Brunswick Mine has successfully commissioned an automated haulage zone where two optically guided trucks transport ore from a remotely operated chute to two orepasses. Operational advantages include increased system capacity and enhanced safety and comfort for the operator. The data obtained up to now indicate that the system can operate reliably in mine production

May 1, 2002

By Yoneji Kanoh, Masahiko Ohtsuka

In Japanese tunneling history, it has commonly been accepted that the long-round driving is difficult due to the complicated geological condition. Therefore, the maximum past record has been less than 3 m per round. A new record of advance was established in the 99 m2 headrace tunnel of Imaichi Water Power Station Project with an advance of 239.5 m in a month by drilling 3.9 m deep blast holes. The geology of the headrace tunnel composed of pyroxine andesite (ie. 960-1770 kg/cm2, VP3.1-4.3 km/s) which had several clay seams and open cracks and was moderately weathered. Automatic shotcrete machine was used for shotcreting. Rock support was specified according to the N.A.T.M. with each different rock type. The contractor achieved a remarkable tunneling advance not earlier experienced in Japan.

Jan 1, 1983

By H. O. McLeod, J. M. Campbell

Data analysis of pentane and hexane adsorption from natural gas in a fixed bed of silica gel shows that constant length mass transfer zones form, the curvature of the adsorption isotherm controls the growth of the mass transfer zone and surface diffusion of molecules inside the silica gel particle controls the mass transfer rate. Curvature of the hexane isothem is more than the curvature of the pentane isotherm. Because of this curvature the hexane adsorption zones reached a constant length. In contrast, the pentane adsorption zones were always increasing in length during each run. A procedure was developed to obtain correct mass transfer coefficients using effluent curve slopes. These transfer roefficients increase with the amount of hydrocarbon adsorbed on the silica gel particle. The characteristic shape of the hexane effluent curves also show that molecular diffusion inside the silica gel particle controls the adsorption rate of pentane and hexane. INTRODUCTION The purpose of this study was to determine the mechanisms that control the dynamic adsorption of hydrocarbons from a natural gas onto silica gel. Before one can deal effectively with multicomponent adsorption, the transfer mechanisms by which a single hydrocarbon component is adsorbed from the gas stream must be defined. Two principal investigations of this system have been published ' and indicate that diffusion through the gas around the particle controls the adsorption rate. Some of the experimental observations in each study either do not support this transfer mechanism or are inconsistent with the mathematical model used in analysis. In this study surface diffusion of molecules inside the particle controls the mass transfer rate of pentane and hexane. This mechanism is indicated by the effluent curve shape for a constant length transfer zone and by the variation of the mass transfer coefficient with concentration of the adsorbed hydrocarbon. THEORY AND DEFINITIONS — MATHEMATICAL MODELS Mathematical solutions for the isothermal adsorption of a trace component from a carrier gas are derived from three relationships: the mass balance or continuity equation, the equilibrium relationship between the gas and solid phases, and a mass transfer rate equation. The transfer rate is proportional to the adsorbate concentration gradient within either the gas or solid phase. Mathematical solutions of these equations usually give the adsorbate concentration as a function of time and distance from the bed inlet. That part of the bed in which the adsorbate concentration changes from a maximum to a minimum value is called the transfer zone. This transfer zone is directly related to a plot of the effluent concentration vs time which has a characteristic S-shape. This general shape is determined by the continuity equation and occurs in many processes of diffusional transfer.

Jan 1, 1967

There is an alternative theory of the high grade orebodies of the Middleback Group, based on the primary nature of the high grade ores in an area of carbonate deposition, with lesser amounts of siliceous and aluminous sediments. The environment is thought to have been unstable, possibly volcanic, and to have been a subsiding basin, substantially isolated from the open sea.Jaspilites, iron bearing talc rocks and iron bearing carbonate rocks were derived from the primary sediments by metasomatic alteration after metamorphism.The metasomatic agents were carbon dioxide and water vapour which were mobilized from the primary dolomite and reacted with a metamorphically produced group of iron bearing and iron free amphiboles, forming talc and progressively releasing silica and iron oxides from the iron amphiboles.The talc rocks in turn released silica which reconstituted jaspilites into their present 200 ft thick crust or zone.The theory accounts for the present disposition of a jaspilite zone over a talc zone which in turn overlies a carbonate zone, and accounts for the down dip changes found in bores which penetrate these zones.INTRODUCTIONIron Duke (Fig. 1) lies some 34 miles south west of WhyalIa in South Australia, and is the most southerly ore body in the Middleback Ranges.The Middleback Ranges are divided into a northern range and a southern range meridionally disposed and separated by an erosion gap called Kimba Gap.The South Middleback Range contains four orebodies;Iron Duke at the southern extremity, Iron Duchess north of Iron Duke and on the same ridge, Iron Knight also on the same ridge, which has been breached by erosion between theDuchess and Knight orebodies, and north east of Iron Knight, the Iron Chieftain.Cook's Range is the eastern range of the South Middleback Range and no large orebodies are known to occur there.

Jan 1, 1963

By C. R. Stephan

Explosion-resistant seals in underground coal mines isolate the environment within the sealed area from the active workings of the mine. The current United States Title 30 Code of Federal Regulations (CFR) requires these seals to be constructed of solid concrete blocks. The CFR also allows for alternative methods or materials to be used to create a seal if they can withstand a static horizontal pressure of 138 kpa (20 psi), provided the method of installation and the material used is approved in the ventilation plan. The purpose of this report is to identify those explosion- resistant seals that have been tested and meet or exceed all the requirements of the CFR.

Feb 24, 1997

By M. Q. W. Jones

This paper summarizes important features of a compilation of thermal properties of stratified rocks from Witwatersrand gold mining areas. The database consists of more than 1000 thermal conductivity measurements, more than 700 density measurements, and nearly 100 heat capacity measurements. Most important rock types and stratigraphic units are well represented. Heat capacity does not differ significantly from one rock type to another, and density is relatively uniform although particular rock types are characterized by distinct average values. Different rock types also have distinct thermal conductivities, but this parameter varies by a factor of four to five. Primary factors controlling the thermal properties are mineral composition, degree of metamorphism, and porosity. In addition, the temperature dependence of thermal conductivity and heat capacity of quartzite may significantly decrease the thermal diffusivity of this rock at deep mining levels.

Jan 1, 2003

By P Allen, E Gleeson, D Boakye, R Chesher, S Konopa

"An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation. Not only do epithermal gold deposits provide many challenges in estimating mineral resources, the complexities of these deposits also provide technical challenges in assessing appropriate mining and processing strategies, as well as social and environmental planning and management. The characteristics of epithermal gold deposits include being highly variable with respect to geometry and gold grade distribution, the presence of other economic contributors, mineralogy, texture, rock strength, weathering and alteration overprint. These characteristics influence the economic value of mining projects in an interlinked manner. Consequently, successful exploitation of epithermal deposits requires a holistic approach, coupled with the effective integration of geological data to meet all aspects of mine development decision-making. This paper presents examples of the key technical challenges encountered in estimating and mining epithermal deposits. It also highlights why these issues need to be addressed from the viewpoint of geology, sampling, resource estimation, mine planning, mineral processing and social and environmental planning for the true value of the mining project to be realised.CITATION:Konopa, S, Chesher, R, Gleeson, E, Allen, P and Boakye, D, 2015. Challenges in maximising the value from epithermal gold deposits, in Proceedings PACRIM 2015 Congress, pp 127–132 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 18, 2015

By Daryl E. Radcliffe, Raymond M. Stateham

The Bureau of Mines, under a Cooperative Agreement with the Bear Coal Company, Somerset, Colorado, conducted a large scale evaluation of the effect of time lapse on roof stability. Time lapse in this study is the interval between exposure and permanent support of the mine roof. The study indicates that time lapse is not a critical factor in roof stability provided permanent support is installed before catastrophic failure begins. Concurrently with the time lapse study, investigations were made of stress distribution around resin-grouted bolts, the regional stress field, and anomalous geologic conditions. The behavior of the resin-grouted bolts, at least in the Bear mine, appears to fit the Coulomb-Navier Theory. Geologic conditions are primary factors in trends of roof stability that extend across the mine.

Jan 1, 1982

By David E. Nicholson

The Bureau of Mines has constructed a special compression chamber for developing stress-strain relationships of mine backfill and simulating the high compressive ground pressures encountered in underground mines. A one-dimensional, or Earth-Pressure-at-Rest model is proposed for backfills subjected to these pressures. Results of the compression tests performed in the chamber indicate that reliable stress-strain relationships can be developed from these tests. The primary objective of the test series was to evaluate the effectiveness of compaction of common backfills in retarding ground closure. Analysis of the stress-strain data shows an eightfold reduction in relative strain in optimum well-graded, compacted backfills over poorly graded, loose backfill material. Analysis of the one-dimensional compression test data also indicates a significant retardation of transmitted stress in dense compacted samples of backfill and natural sands. Although not fully understood, a deformation mechanism is thought to occur at the intergranular contacts in cyclic fashion causing frictional heat loss and a reduction in transmitted stresses in the densely packed materials. The experimental values of transmitted stress are compared with theoretical values of effective stress calculated from the one-dimensional compression relationships developed by Hendron (4).3 These experimental values of transmitted stress compare very closely with the theoretical values of effective stress.

Jan 1, 1968

By Charles C. Boley

High-volatile A bituminous coal from the Allen mine, Las Animas County, Colo., blended with char produced from the same coal yielded accept-able metallurgical coke in a 500-lb movable-wall test oven. Nineteen experimental runs were carried out using several concentration levels of two different chars, 5.6 and 19.6 percent volatile matter, produced by entrainment carbonization of the base coal. With the higher-volatile char, an acceptable coke was produced at a 22.5-percent concentration; the lower-volatile char did not produce an acceptable coke at the concentrations investigated.

Jan 1, 1972

By F. D. Everett

This report summarizes the results of a nationwide investigation completed in 1964 to determine the nonferrous base metal ore reserves and potential sources of ore and to evaluate criteria for their ultimate exploitation. Engineers of the Bureau of Mines contacted mining company officials, reviewed reports and Government records, and where necessary made personal appraisals in arriving at the results. The estimates are presented by metals in ores in geographic regions and include some of the problems affecting the reserves and potential sources. The recoverable metal in the measured ore category and in the total ore reserves was estimated as follows: [ ] At the 1963 rate of domestic mine production these total reserves would be adequate to provide copper for 62 years, lead for 121 years, and zinc for 42 years. Data also are given for gold, silver, and other coproducts. Reserve estimates greatly exceed those of previous investigations; some prior estimates of copper reserves are included for comparison (table 23). Projections of requirements for base metals indicated the United States will need approximately 45 percent more copper in 1970 and 110 percent more by 1980 than was consumed in 1960; similar projections for lead indicate increases of 20 percent by 1970 and 45 percent by 1980; zinc projections are 40 percent more by 1970 and 90 percent by 1980. Much of the production of gold and silver is a coproduct of base metals recovery and the projected need for the precious metals exceeds all the United States can produce. Some problems of the industry are mentioned. A graphic evaluation of the economic availability of the reserve and potential sources is shown.

Jan 1, 1967