Search Documents

By BO HYUN KIM, MARK K. LARSON

The floor-heave and no-floor-heave phenomena at a western U.S. coal mine could not be properly simulated in numerical models using conventional shear-dominant failure criteria. Although the previous numerical study using FLAC3D very reasonably demonstrated these phenomena, 3DEC modeling in conjunction with the discrete fracture network (DFN) technique was performed to better understand the true behavior of floor heave associated with underground mining in an anisotropic stress field. As a result, the latter models predicted floor heave that agreed with relative amounts of observed heave from each gateroad system, but the cause of heave was mainly related to the degree of anisotropy instead of the size of the pillar.

Sep 1, 2022

By K. Kavouridis

Coal is broadly recognized as sure, competitive, diversified, not vulnerable and predictable in price energy resource. In power generation coal is playing a dominant role in the EU-27 with 25% of installed capacity and almost one third of the power generation. The role played by the domestic resources and especially by coal are increasingly becoming the focus of the EU energy strategy. There is a strong pressure for the decarbonization of the energy mix. The Emission Trading system (ETs) can have an impact on the shift to lower carbon-intensity fuels. The impact of ETs on coal can be important, because it is very short sighted and only defines the period up to 2008-2012. The ETs CO2 regime must ensure that investment in coal-fired plants in the long term are supported. EU Research Institutes and Coal Industry identified an important CO2 reduction potential by improving the efficiency of the conversion of solid fuels into electricity. Highly efficient clean coal technologies can contribute to reasonable costs and challenge the issue of climate change. It must be pointed out that the EU Energy policy should now concentrate on the necessity to effectively support demonstration projects and to create the legal framework for the integrated approach of efficiency enhancement and CCS. It is not a right approach to implement CCS before the technology is demonstrated and before it is clear that it will be commercially viable.

Jan 1, 2007

By Russell B. Dix

Laboratory column leach tests are used routinely to evaluate gold and silver ores for heap leaching. The tests are fairly straightforward. The ore to be tested is placed into an appropriately sized leach column. Then an alkaline cyanide solution is applied to the ore and the effluent solutions are collected. The effluent solutions are then put through a column of activated carbon to recover the gold and silver in solution. Zinc precipitation may also be used for silver ores or if the ore contains a significant amount of soluble silver in addition to gold. The length of the leach time in the tests is mainly a function of how quickly the precious metals are recovered from the ore. At the completion of the tests, the tailings are assayed and the recoveries determined from the calculated head grades. The amount of ore to be used for a test is partly a function of its crushed size. The coarser the size, the larger the sample size for the column. A typical small-scale laboratory column test on ore crushed to -12 mm (-0.5 in.) would usually be conducted in a 100- to 150-mm-diam (4- to 6-in.-diam) column 2 m (6.6 ft) in height, containing about 20 to 45 kg (44 to 99 lb) of ore. A comparable test on the same ore crushed to 50 mm (2 in.) would be conducted in a 200- to 300-mm-diam (8- to 12-in.-diam) col¬umn 2 m (6.6 ft) in height, containing about 80 to 200 kg (176 to 441 lb) of ore. Larger-scale tests can be run by increasing the column heights and diameters. Conducting larger-scale tests results in increased costs for sample procurement, preparation, and running of the tests. The additional data obtained from

Jan 1, 1989

By T. E. Breaux

Repair of large rotating apparatus such as ball mills is uncommon but under certain circumstances is achievable. This paper describes the successful repair of trunion on a 14 foot diameter by 20 foot long ball mill. Diagrams of the repair are included for visual perspective and non-destructive test procedures are outlined.

Jan 1, 1988

By A. K. Gangopadhyay

This paper discusses the effect of grinding media composition, mineral type and slurry environment on the wear rate of various grinding media (balls). Sufficient wear data have been obtained and correlated with the modes of wear determined from examination of the ball surfaces using scanning electron microscopy. Five modes of wear have been identified to be operative under certain slurry conditions for the various ball compositions studied.

Jan 1, 1984

By Charles H. Tiernon

Separation of particles on a table deck* results from differences in specific gravity, plus a number of other interrelated phenomena: size of particles; shape of particles; stratification (consolidation trickling); and hindered settling. The effective use of these factors may be controlled and aided by the following table adjustments: differential action of the drive or head motion; speed of motion; length of stroke; side tilt; end elevation; size of deck area; shape of deck; character of deck surface; riffle design; amount and distribution of wash water; feed water-to-solids ratio; feed rate; and feed uniformity. The typical concentrating table used in the US coal industry is essentially a rhombohedral-shaped deck supported by a suitable subframe. It generally slopes in the direction of the short axis, tilts upward at the refuse end of the long axis, and is differentially reciprocated in the direction of the long axis. This head motion tends to move the particles longitudinally toward the end of the table. At right angles to this movement, wash water (distributed along the high side of the table) tends to move particles down the slope parallel to the short axis of the table. Hence, the natural path of a particle on a concentrating table is from the feed box corner to the diagonally opposite corner of the deck (Fig. 1). There is a natural tendency for heavier particles to sink to the deck of the table and for lighter particles to stay nearer the surface. As a consequence, the heavier particles are carried further along the longitudinal axis since, being on or near the surface of the deck, they are more affected by the table's reciprocating action. The lighter particles, being at or near the top of the moving bed, travel slower in a longitudinal direction and thus separate from the heavy particles. Wash water and the diluting water in the feed cause lighter gravity particles to move down the short axis of the table. The feed material then fans out from the feed box, where it enters onto the table with heavy gravity particles moving in one direction and lighter particles moving in another. By properly adjusting all of the previously mentioned factors, a clear-cut separation is possible between high- and low-gravity particles, or between refuse and coal. Riffles are of great importance to tabling. They create considerably more capacity than is possible with smooth decks, and they are responsible for better separation accuracy. Particles in their downward movement along the deck's slope are delayed behind the riffles. Hindered settling, consolidation trickling, and other phenomena occur as the particles tumble over the riffles and stratification ensues. The heavier particles settle to the deck of the table and are trapped behind the riffles, thus insuring their positive movement toward the end of the table. Since stratification and separation of particles are not complete as a result of any one riffle, a series of riffles are used. The cycle of stratification and hindered settling is repeated from riffle to riffle. The result is purer products as particles fan out and progress forward and downward over the table. The smallest, heaviest particles stratify downward to the surface of the deck more quickly and are carried out by table movement toward the refuse end at a faster rate than coarse, heavy particles. Light gravity, larger pieces ride on the top layer of particles and flow down the deck's slope as a result of the cross flow of wash water at right

Jan 8, 1980

By William A. Griffith

The recent recession has severely impacted the performance and results of virtually all of our natural resource companies. The depressing climate continues to linger and recovery maybe sometime away. Problems remain for resource companies in the steel and petroleum industries as well as the mining business. In February, at the AIME Annual Meeting in New York, an All-Institute session presented a variety of views on the situation. A. T. Yu, chairman of ORBA Corp., Mountain Lakes, NJ, organized presentations by top management personnel of four natural resource companies. This well attended session heard management strategems for the present and views for the future. A compilation and synthesis of these presentations, gathered by Dr. Yu, are presented here for ME readers. Leading off will be William A. Griffith, president and chief executive officer of Hecla Mining Co., Wallace, ID. Other speakers presented here include Wilfred P. Schmoe, executive vice president of Du Pont Co., Wilmington, DE; Frank W. Luerssen, chairman and chief executive officer of Inland Steel Co., Chicago, IL; and Adam H. Zimmerman, president and chief operating officer of Noranda Mines Ltd., Toronto, Ontario. First, then Griffith's remarks. Introduction The key to successfully managing a natural resource company in austere times is good management in good times. In other words, position the company during prosperous times to survive the times when the well dries up. Although we know how to manage properly, for various reasons we sometimes do not do it. We forget the lessons of history. We allow ourselves to be carried away by our egos. We fail to position our companies properly in good times. As a result, in bad times we find ourselves in deep trouble. We need constant reeducation in the things we already know. In the natural resource industries, proper positioning in good times involves becoming a low-cost producer, retaining the flexibility to pull in our horns, developing a lean and effective organization, and maintaining a healthy balance sheet. Nothing improves the chance of survival during austere times as much as being able to produce at a lower cost than your competitors. In our business, that means having low-cost mines - low cost because the ore bodies are high grade or favorably located, and because they are efficiently operated. It also means recognizing the competition. The key numbers are the cost to produce an ounce of silver or gold. Nothing else really counts. And our competition is every other precious metal mine in the world. Flexibility is important when one gets stuck with a high-cost operation, often because things do not work out as we expect. It is important to be able to shut down an operation quickly and easily, without high holding costs, and without disrupting the corporate organization. A lean and mean, effective organization of competent people is vital during bad times. A company will not have that if it is not developed and maintained during good times. Finally, a natural resource company has to develop a healthy balance sheet during good times if it is to survive the bad. Money in the

Jan 6, 1985

By Yuusaku Tominaga

A flexible expert system for a personal computer has been developed to take countermeasures for prevention of emergency in underground coal mines. The system makes a diagram to estimate maximum airflow rate of a specified branch such as coal face or advancing face, etc. under the conditions of opening regulators set in any two different branches, by computer simulation. The system approximates the ventilating condition underground by using both measured values and safety factor derived from the rules in the system. The probability of happening gas explosion, spontaneous combustion and mine fire underground is shown on a display and countermeasures in a data base in the system are selected according to a confidence factor. When it is recognized in the system that either safety factor or confidence factor of countermeasure has a small value, the system sends information relating to reasoning in the system to registered human experts by computer communi¬cation and facsimile. The replies in file transfer from the experts are stored in the system and reconsultations for estimation of underground condition are started automatically. As the replies in facsimile are shown on the display, user inputs new rules and, values for reconsultation. It is shown that the system is available to take better countermeasures as the condition' of a network in coal mine is changed by mining day by day.

Jan 1, 1992

By Chris Chmura, Ketut Karmawan, Ian J. Duckworth

P.T. Freeport Indonesia operates a mining complex located in the highlands of West Papua, Indonesia. Present production from PTFI’s DOZ Underground Block Cave Mine is approximately 40 thousand tonnes per day (ktpd). This paper describes the design process and recommended ventilation infrastructure necessary to expand the DOZ Mine reserves and to increase sustained daily production above 50 ktpd. The enlarged footprint will feature longer production panels of up to 650 m in length, more active draw points, a second large gyratory crusher, and additional men and mobile equipment. The increased ventilation capacity will be achieved through the development of new, dedicated ventilation drifts, and primary Underground exhaust fans.

Jan 1, 2005

By Georgene Renner, William R. Yernberg, William Gleason

American Commercial (ACI) offers a selection of ground control solutions. Beginning with steel liner plates installed in the Gratiot Avenue sewer system in Detroit, MI 1920, ACI is one of the leading designers and manufacturers of underground steel supports in North America. ACI is also a leader in fire-proofing underground structures with its Promat Fire Protection Boards. The sandwich panels have been used in many new and retrofit tunnel and underground construction projects worldwide. Ease of installation and replacement, cost effectiveness and superior performance have made this product line the premier choice of owners and designers for structural protection, fire-life safety requirements and architectural finish needs.

Jan 1, 2007

By D. Leppert

Large deposits of natural zeolites may provide cost-effective alternatives for treatment of soil and water contaminated ) with heavy metals and radionuclides. Research on the Bikini atoll demonstrated that addition of clinoptilolite to the soil significantly reduces cesium uptake by plants. Re- search on the potential use of zeolites in soils at Bunker Hill, ID indicated only minor benefits at very high contamination levels vs. US Bureau of Mines (USBM) work on the use of zeolites for treatment of mine waste waters emphasized problems with natural waters that previous studies have not addressed. High levels of competing calcium in natural waters significantly decrease the effectiveness of zeolites for heavy metal sorption and may limit the usefulness in these applications.

Jan 1, 1991

By Richard M. Crowell, Laurie M. Tahija, Keith D. Dagel

Echo Bay Mines Ltd. operates a gold heap leach in Round Mountain, Nevada, U.S.A. In the past two years, the mine has expanded operations from 13.5 kt/d (15 kst/d) to 41.0 kt/d (45 kst/d), making it the world's largest gold heap leach operation. The expansion is a separate system from the previous 12 year old plant, yet very similar. The flowsheet contains open circuit primary, secondary, and tertiary crushing with interstage screening. A leach pad stacker loads reusable asphalt leach pads. The process plant features carbon adsorption, pressure strip, electrowinning, and electrorefining.

Jan 1, 1990

By Dipl. -Ing. H. -J. Sager

The ‘Westerschelde Tunnel’ underpasses the estuary of the Schelde in the Netherlands. The tunnel will consist of two tubes which are driven by two hydroshields (slurry shields). The tunnels will each have a length of approx. 6.6km and a bore-diameter of 11.33 m. Demanding ground conditions had to be considered during the design of the shield machines. Loose sands, extensive clay formations and high ground water pressures of up to 6.5 bar will be encountered during the tunnel drive. The tunnelling activities will start in the middle of 1999 and are scheduled to end by the end of 2001.

Jan 1, 1999

By J. Alvarez, S. Helle, U. Kelm, M. Pincheira

The principal geological and mineralogical characteristics of Chilean porphyry copper deposits are described. Elevated contents of fine grained ore and gangue material may cause copper losses and pose problems or render useless the flotation process. Examples of chalcopyrite and bornite size distributions are given. The state of the art of mineralogical and mineral chemical characterization in Chile is evaluated permitting analyses to lm and nm level by lacking the regular use of direct surface analysis.

Jan 1, 1998

By Donn A. Calder, Wayne C. Henderson

The Calmet Process for extraction and recovery of gold and silver from concentrates and high:grade ores has been a commercial reality for over two years. During that time period, almost seventy-five different concentrate (or ore) types have been processed in approximately 200 separate lots (a total of almost 2000 short tons). During commercial operation of the process at the plant in Fountain, Colorado, recovery of gold and silver into <lore' has averaged almost 93% for gold (range 81-98%) and over 90% for silver (range 76-97%) based on a fire assay target and calculated head values.

Jan 1, 1998

By M. Springett

Organization of teams for rapid and effective evaluation of international mining properties requires special considerations beyond those needed for domestic activities. Experience, technical ability, a sense of perspective, humor and self-discipline are vital characteristics to look for in the selection of individuals for forming an efficient and productive team.

Jan 1, 1994

By Robert W. Row

The run-of-mine coals in the U.S. being fed to coal cleaning plants have become increasingly finer due to the adoption of modern, mechanized mining methods, and economics are dictating that finer fractions, as well as the coarser fractions, be cleaned. Traditional dewatering methods (vacuum disc filters and centrifuges) are proving inadequate for preparing fine refuse for disposal or fine coal product for downstream handling. The Electric Power Research Institute has been supporting research into the nature and limitations of mechanical dewatering, and novel ways of improving it. The efficiency of various silicone-based chemicals at aiding dewatering was investigated, and it was shown that the final moisture content of hydrophilic coals after vacuum Filtration could be reduced by 1 to 5% with up to 40% increase in filtration rate by addition of one of several of these silicones. EPRI also has an on-going program at its Coal Cleaning Test Facility to investigate the performance of the Larox pressure filter in comparison with that of the disc filter and solid bowl centrifuge. While improvements to the dewatering performance currently being obtained in existing operating plants by such means are achieveable, a fundamental study has shown that, regardless of changes in operating conditions, there may be a limit to the lowest cake moisture content attainable by mechanical dewatering of a given sample of coal fines. Determination of this limit for a specific coal would be useful in designing facilities to dry and handle it.

Jan 1, 1984

By V. C. Kelessidis

Demand for multifunctional drilling fluids continuously increases. In the quest for more hydrocarbons, drilling has extended to deep water areas (now in excess of 2.000 m) and to very deep wells (now in excess of 6.000 m). In these extreme conditions, low temperatures, as low as 1-5°C on the sea bed, high temperatures, in excess of 200°C, and high pressures, more than 1.000 bars, in the bottom of the well, are frequently encountered. In these harsh environments, synthetic oil and oil based drilling fluids are used, but the former are expensive while strict environmental requirements have limited the use of the latter. Thus, drilling industry has turned back to water based drilling fluids which use bentonite as primary viscosifier and as a fluid loss control additive. However, in conditions of high temperatures, bentonite suspensions gel and loose their exceptional low temperatures properties, thus, additives are needed to overcome such problems. In this article we review these challenging drilling environments and establish the requirements for the multifunctional drilling fluids. Our research indicates that demand for continuing use of bentonite by drilling fluid industry is strong. Furthermore, we bring forward the opportunities for new additive development which can expand the operational ranges of bentonite suspensions.

Jan 1, 2007

By M. Maier

Geographic Information Systems (GIS) has evolved into a powerful tool for analyzing spatial and attribute data in many industries including mining. Modern field data collection techniques add another dimension to the use of data in the field and enhance the utilization of GIS for mining applications. This discussion will review how field data is collected and how office data and maps can be taken into the field to be analyzed and verified using pen-based computers and differentially corrected GPS.

Jan 1, 2001

By M. G. Ayat

Engineers in the field of coal preparation are continually striving to increase the efficiency of various circuits used in preparation plants. Undoubtedly, one of the important factors concerning the processing efficiency of a coal preparation plant is improved analyses and control of the processing equipment. The necessary link between the performance criteria of a circuit may be provided through on-line determination of various parameters. Currently, there are a certain number of on-line instruments developed for measurement of ash content of coal (Watt and Sowerby, 1983; Kawatra, 1976; Fauth et al., 1984; Lyman and Chester, 1980), moisture content (Hall et al., 1969), and sulfur content (Stewart et al., 1974). In the case of coal separatory units, these parameters are often directly related to the quality of the product. In other words, the extent of misplacement of refuse in the product, or vice versa, would indicate the performance characteristics of any particular coal washing equipment. Partition curves are therefore established to predict the performance of coal cleaning operations. Conventional sampling and testing is currently the major tool with which partition curves are produced and the performance efficiency of the operation is assessed. While conventional analysis techniques are accurate, they are slow and time-consuming.

Jan 1, 1987