Search Documents

By P. Stanley Jacobsen, Hemant B. Gala, Richard E. Hucko

Coal is the nation's most abundant fossil energy resource. However, its use is limited because of the nature and amount of associated impurities, such as mineral matter, sulfur, trace elements, and moisture. The moderate-to high- sulfur content of many U.S. coals is of particular concern as current and newer, potentially more stringent, regulations require reduction in sulfur oxide emissions. Release of particulates, NOx, and other pollutants during the coal-use cycle is also of concern. The current practice of controlling sulfur oxide emissions in the major steps of the coal- use cycle is limited mainly to coal preparation by physical beneficiation and, to a smaller extent, to post-utilization cleanup (flue gas desulfurization). Approximately two-thirds of the coal from states east of the Mississippi river is physically cleaned, whereas only 15% to 20% of the operating boilers in the utility industry are equipped with scrubbers to desulfurize the flue gas (Henzel, 1988). Physical beneficiation methods can be very effective in removing mineral matter, including pyritic sulfur, from coal. These processes take advantage of the differences in physical proper- ties between coal and mineral matter to achieve the separation. In a typical physical cleaning operation, raw coal is crushed to about a 50-mm (2-inch) top size. It is then screened into coarse, intermediate, and fine sizes. Crushing the coal liberates some of the ash-forming minerals, including a portion of the sulfur that is not chemically bound to the coal. The per- centage of impurities freed from the coal matrix generally increases as the coal particle size decreases. The coarse- and intermediate-sized coals are typically subjected to a cleaning pro- cess based on differences in specific gravity between coal particles and the associated impurities. Such cleaning processes used include jigs, dense-medium baths, cyclone systems, and concentrating tables. The fine-sized (typically less than 0.5-mm) coal, if beneficiated, is typically cleaned using a froth flotation technique based on the differences in surface proper- ties between coal and its associated impurities. At fine sizes, greater cleaning potential exists because a greater portion of the impurities is released from the coal matrix. However, this potential is not fully realized owing to inefficiencies in separating fine particles using state- of-the-art flotation technology. Overall, current commercial coal preparation processes are estimated to remove up to 60% of the ash and 10% to 30% of the sulfur, depending on the coal characteristics, with product weight recoveries rang- ing from about 60% to 90% and thermal recoveries of about 85% to 98% (Versar, 1985; Science Applications International Corporation, 1987; Hoffman- Muntner Corporation, 1978). For many U.S. coals, grinding to sizes finer than those used in current coal preparation plants is required to liberate most of the physically bound impurities from the coal matrix. As noted, conventional coal-cleaning methods are not very effective at these fine sizes. Accordingly, the expanded use of domestic coal requires the development of advanced coal cleaning technologies that can provide economic performance while reducing environmental impacts. Program Goals and Objectives The overall goal of the U.S. Department of Energy (D0E)'s Coal Preparation Program is to provide the scientific and engineering knowledge base that industry can utilize to produce economically competitive and environmentally acceptable clean-coal products for introduction as market conditions warrant. The coal preparation process(es) should remove undesirable components from coal and improve its handling characteristics, thus making the product coal technically, as well as economically, viable as a competitor with petroleum-derived fuels and natural gas, and with alternative environmental control technologies. The coal preparation process must be applicable to a wide variety of bituminous and low-rank coals. The cleaning process should reduce the variability among clean-coal products from various raw coals, thus significantly increasing the range of potential end uses for each raw coal. To the extent that deeply cleaned coal products have greatly reduced levels of

Jan 1, 1988

By S. B. Patton

A comprehensive approach to the development and organization of an expert system that is designed to assist electricians in diagnosing electrical faults m mining machinery is discussed. The system includes diagnostic, reference, and tutorial programs. The diagnostic portion of the system is based on a causal-reasoning approach which is used to establish a hierarchy of symptoms and the subsequent production rules for identifying component-level failures m the motor-control circuit of a shuttle car. With this approach, conclusions are developed directly from knowledge of the circuit and its behavior (in both working and failure modes) based on first principles, rather than the heuristics of a domain expert. The symptoms and their hierarchical structure an: formulated by creating "what-if" scenarios and performing a qualitative circuit analysis for each fault Techniques for incorporating interactive graphical displays of the circuit schematic into the diagnostic portion of the system are also presented. Supportive computer programs that provide' reference material and tutorials on the circuit are also described.

Jan 1, 1989

By G. Ferrara

Hydrocyclones and other dynamic separators are normally fed with pulps of water and solid particles. The particles have different sizes, shapes and densities and, except in the special case of mono-characteristic particles, are segregated into size, shape and density. Segregation is magnified by the high values of centrifugal acceleration in the hydrocyclones. This paper develops the theory of the segregation, indicates the major variables involved and reports experimental data of segregation under different operating conditions for mixtures of magnetite and/or ferrosilicon and non-magnetic minerals.

Jan 1, 1995

By Welby G. Courtney

Recent field and laboratory results related to the use of water sprays and ventilation in the control of dust at the mine face are presented. Optimization of water sprays for impaction and collection of airborne dust is discussed and guidelines presented. Exhausting versus blowing primary ventilation, dust collectors, several secondary exhaust ventilation systems, and a "throw" technique he discussed.

Jan 1, 1980

By Steven J. Schatzel

A study was made of frictional ignitions in the underground coal mining industry from 1980 to 1992. The population of frictional ignitions was correlated to a variety of potential contributing factors including the mined coalbed, geographic location, mine production, methane gas emissions, and the type of mining equipment in use. The number of frictional ignitions reported in 1991 and 1992 surpassed the annual totals in all previous years included in the study. Most frictional ignitions occur during cutting operations at a coal face by a continuous miner. The average coal production of mines experiencing frictional ignitions is greater than the average of all underground coal mines throughout the survey period. Methane drainage may have produced a drop in the ratio of gas emissions to coal production (E/P) in mines experiencing frictional ignitions.

Jan 1, 1995

By R. D. Miller, D. W. Steeples

Application of shallow, seismic reflection to problems associated with mineral exploration, mine planning, abandoned-mine detection and environmental evaluation has been successful in many geologic settings. The increased dynamic range of recording equipment and the decreased cost of processing hardware and software have made shallow, seismic reflection a cost-effective means of imaging geologic targets significant to mining operations. Seismic data possess sufficient resolution in many areas to detect faulting with displacement of less than 3 m (10 ft) in coal seams as thin as 2 m (6.5 ft) at depths of 200 m (655 ft). Subsurface voids associated with abandoned mines at depths of less than 20 m (65 ft) can he detected and mapped. Seismic reflection has been successful mapping disturbed subsurface associated with dissolution mining of salt. Complex geologic features associated with deposition of various hydrothermal minerals have been mapped with high-resolution seismic reflection at depths from 80 m (260 ft) to more than 300 m (985 ft). Faults in sulfur-hearing cap rock over salt domes have been accurately located, allowing improved efficiency of the dissolution mining process. Shallow, high-resolution seismic reflection has the potential to enhance the economics and safety of mine operations.

Jan 1, 1996

By Walter Keune

Object Modeling Technique. This formal descriptive language makes it possible to formulate requirements in the real world in such a way that they can be implemented in the form of entities (cf. Entity Relationship Model[Che83]) and methods (see Figure 1). The object {Roadway} is graphically depicted by means of the Polygon method.

Jan 1, 1996

By C. T. Holland

Coal mining has been an important industry in the Appalachian area for many years. This is particularly true in the northern part of the area, namely, in Pennsylvania, West Virginia, and Ohio. Also, in the south a great deal of mining activity has been carried on in Alabama, Kentucky, and southwest Virginia. Some of the by-products of this activity has been the production of mineralized water from the mines in copious quantitites. The southern Appalachians have been somewhat more fortunate in that the water there has had a considerable amount of alkalinity in it, which has to a large extent eliminated some of the more undesirable aspects of mine drainage. Northern Appalachia, including central and western Pennsylvania, the Monongahela basin in West Virginia, and the Appalachian area in eastern Ohio have not been so fortunate in that coals in those areas and the top and bottom rock have, in many cases, shown considerable quantities of pyrite, and the water does not carry the carbonates found farther south.

Jan 1, 1969

By Qing Wang

Open pit mines require substantial capital investment at the beginning of the operation and replacement investment at later years. The objective of obtaining the highest possible return on investment in a mining project can only be achieved with an efficient long term production plan. This plan consists of optimally determining four principal elements: 1) the amount of ore and waste to be mined each year, 2) the specific blocks to be mined each year, 3) the optimum mine life, and 4) the ultimate pit limits, which delineate the total reserve to be mined. The existing methodologies only provide solutions to one or two elements, by assuming the others known. Furthermore, the cost of mining each block in the deposit is assumed to be known and independent of the production schedule. The four elements of production planning are interrelated and the cost of mining any block is a function of the production schedule. The ultimate goal of this study, ,whose first steps are' discussed in this paper, is to develop a solution methodology that can simultaneously optimize all four elements of the production planning problem in open pit mines without making a priori assumption on any of the four elements.

Jan 1, 1992

By Robert A. Jankowski, Charles Babbit, Natesa I. Jayaraman

The Bureau of Mines, together with Foster Miller Inc., has developed a compact, high pressure scrubber system for continuous miners. Powered by water energy alone, it can move up to 1.4 m3/s (3,000 cfm) of air and scrub a significant amount of the dust in the air. Full- scale model and underground trials showed excellent performance. Operated at 8.3 x 10[3] kPa (1,200 psi) and 38 L/m (10 gpm), the scrubber has reduced operator and return dust concentrations by more than 50 pct. This paper describes the full-scale model development, system fabrication and underground evaluations of this novel and inexpensive scrubber.

Jan 1, 1989

By Stuart W. Maher

A major problem in future discoveries of base metals is their "explorability". By this I mean an exploration program must be designed that assures accurate assessment of the potential for ore, but is within reasonable budgetary constraints. As we are compelled to depend more and more on non-outcropping prospects, "blind" deposits, and as drilling costs multiply, the costs of exploration increase significantly. Solutions to the problem of defining exploration targets are influenced by our conceptions of the origin and recognition o f conditions that localize ore. The maxim that "elephants should be sought in elephant country" presumes we can recognize elephant country. This paper presents a suggested origin for some mineral deposits, and their controls; particularly those termed ?Mississippi Valley type". Tennessee is used as an example of the ideas offered. Mining districts designated "Mississippi Valley type" are, and have long been, the principal sources of barite, fluorite, lead and zinc ores in the United States and elsewhere throughout the world. A large volume of literature is available describing this class of ore deposits, explaining their habitat, and invoking genetic models for them. The quality of this literature is notably uneven, some of it demonstrably erroneous, and much of it is restricted to detailed descriptions of one aspect of the problem, or to detailed descriptions of one aspect of the problem, or to a single mine, or even a single stope. If an ore deposit is thought

Jan 1, 1977

By W. G. Pariseau

Regression analysis of calculated on measured displacements were used to assess the influence of fill and fold plunge on shaft pillar mining at the Homestake Mine. These effects were neglected in the original three-dimensional finite element analysis undertaken in 1991. An average fold plunge of 15? and a 24K fill (Young’ modulus of 24,000 psi or 165 Mpa) were used in the reanalysis. Measured displacements were obtained from an array of 36 m (120 ft) multiple-position borehole extensometers installed in June 1994 and read to March 2003. Results indicate the effects of both on calculated displacements and thus on regression parameters are noticeable. However, these neglected effects would not have changed the original inference of Ross Shaft stability during pillar mining.

Jan 1, 2004

By James H. Harmon

As the trend to deeper mines, producing from marginal ore bodies, continues, mine hoists and their associated equipment will become more sophisticated, complex, large and expensive. Over the past two decades, mine hoisting equipment and systems have moved from steam engines to static rectification of ac to dc, and electronic controls are the standard. It is the intent of this section to present what is currently available in the field of mine hoisting equipment and systems. Because the present engineer has been exposed longer and more intensively to such things as computers, electronic devices, and machine design, no attempt has been made to make this a layman's article. Contributions from the electrical design and application engineer, gearing and hearing design engineers and other specialists have been incorporated. Some material will be devoted to electrical drive systems, rectifiers and gearing design among others. These items are inherent in the design of a mine hoisting system and the subsequent selection of the correct, most reliable and most economic system. The mine hoist can be a bottleneck between the underground mine and the surface mill. Correct selection of the right type of hoist is imperative. In this vital link between mine and mill, crude estimates of hoist capacity are not good enough, and the mining engineer must design and select the right hoisting system to meet the design specifications. 15.1-MINE HOIST TYPES There are two basic types of mine hoists available anywhere in the world today: the drum hoist on which the hoist rope is actually stored during the hoisting cycle, and the friction (Koepe), which merely passes the rope over the wheel during the hoisting process. Drum and friction hoists are "generic" terms which describe the two basic categories. Within each category are variations, as below. 15.1.1-DRUM HOISTS Drum hoists, as noted, actually store the hoist rope on the drum much the same as line on a fishing reel. To accomplish this task, the drums are so designed to store, in one or more layers, the footage of wire rope equal to the total maximum hoisting distance plus sufficient rope for cutting and inspection at regular intervals and for holding to the drum (see Fig. 15-1). Usual practice in hoist drum design is to allow three turns of hoist rope for holding on the drum and three turns for inspection cuttings. 1. Single-Drum Hoists-Fig. 15-2 shows a typical single-drum hoist as manufactured by most U.S. heavy-mining-equipment companies. With the exception of some very minor features, this design configuration is standard throughout the U.S.A. Fig. 15-3 is a plan view of a typical single-drum mine hoist. This particular hoist has a single-motor drive and a double-reduction set of gearing.

Jan 1, 1973

By Michael Li

Unsaturated flow and solute transport were studied in three large columns measuring 1.5 m diameter x 2 m height, loaded with up to 3.7 t of oxidised waste rock, which was excavated from the Stratmat pile at Heath Steele Division, Noranda Inc. and contained elevated concentrations of zinc in the pore water. The bottom of each column was partitioned into 37 squares, each of which was drained independently. Following rain simulations at the top of the rock bed, the drainage in each drain port was monitored for volume and physicochemical parameters at pre-determined intervals. This paper describes some of the observations resulting from the experiments. The main conclusion of the study is that unsaturated flows in waste rock are heterogeneous, and flow channelling is ubiquitous. The results imply that the transport of solutes from oxidised waste rock to its toe drainage is subject to various controlling mechanisms, including geochemical equilibrium control and successive pore water dilution control.

Jan 1, 2000

By J. D. Morgan

Introduction In 1987, the US economy continued to grow steadily, reaching an annual rate of $4.6 trillion in the last quarter. The value of domestically processed mineralbased materials rose slightly to $250 billion. The value of US metals rose sharply to more than $7 billion. Industrial minerals rose slightly to $18 billion recycled scrap was valued at $4 billion. Metal prices rose sharply toward year-end. A number of mining and metal companies experienced increased profitability, fostering more optimism about the future. Consumer demand strongly affects mining because the US economy is relatively saturated with long-lived products. Consumer, mortgage, and federal debt continue to rise. 244 million citizens already possess 170 million licensed motor vehicles and 100 million dwelling units. New car production fell 9% to 7.1 million units, but truck and bus production rose 9% to 3.8 million units. New housing starts fell 10% to 1.6 million units. Excess productive capacity exists not only in the US, but also in many other countries. Consequently, the US mineral industry is encountering stiff competition from others, as well as increasing competition from newer engi¬neered materials. Domestic production of plastics rose 9% to 25 Mt (27 million st) - on a volume basis, double all metals. Some 7% of petroleum goes to make petrochemicals including plastics. Imports of nonfuel mineral-based materials in 1987 were valued at $37 billion and exports at $24 billion. Imports supplied a significant proportion of total US consumption of several important mineral materials, including many classified as strategic and critical. In December, the Congress mandated that any major changes in stockpile goals be made only by law, and that the Department of Defense submit annually detailed stockpile supply/demand analyses. Concern about apartheid in South Africa continued, resulting in increasing interest about chromium, manganese, platinum-group metals, cobalt, vanadium, and gold. The National Critical Materials Council continued to monitor the US materials position. The Defense Production Act, authorizing priorities and allocations, supply expansions, voluntary agreements, and the National Defense Executive Reserve continues in effect through Sept. 30, 1989. Under the DPA, the US Bureau of Mines maintains the Emergency Minerals Administration. Further consultations were held with Canada to strengthen the North American defense industrial base. Coal production, 60% from open pits, rose 2% to 825 Mt (910 million st) valued at $21 billion. Nearly four-fifths was burned to generate 56% of US electricity. Exports included 42 Mt (51 million st) of metallurgical coal and 24 Mt (27 million st) of steam coal, with a total value of $3.3 billion. Domestic petroleum production fell 5% to 480 Mm' (3 billion bbl). Uranium mining, including recovery from phosphates, fell 4% to 5.9 kt (6500 st). Nonfuel minerals Major metals: Raw steel production - a major consumer of many minerals - rose 7% to 79 Mt (87 million st). Domestic iron ore production rose 11% to 44 Mt (48 million st), about 96% pelletized. Net imports, though, fell 8% to 11 Mt (10 million st). Raw steelmaking capacity fell 6% to 102 Mt (112 mil-

Jan 5, 1988

By Shosei Serata

Salt cavities have been proven to be a suitable structure for underground storage of various matters in gas, liquid or solid form. Since the technique of underground storage was developed mainly through field experiences in solution mining, a wider use of solution cavities for storage of gaseous and solid matters requires evaluation of three basic rock mechanics problems; cavity instability, boundary rock failure and surface subsidence. Cavity instability is due to the non-linear long-term creep properties of the surrounding ground media which are sensitive to cavity pressure changes associated with the storage. The cavity boundary rock failure is caused by the loss of effective confining pressure to the boundary rock media in the process of storage of gaseous and solid matters. Surface subsidence is the final outcome of the stress envelope originated around a cavity, eventually reaching the ground surface. The rock mechanics processes of instability, failure and surface subsidence are explained by using various field examples in salt domes and bedded formations. Methods of solving the problems are discussed including stress relief, stress control and computer optimization of design.

Jan 1, 1973

By Myles E. Altimus

One responsibility of a manager is to improve his human organization. Some executives believe a manager should be measured and compensated accordingly on the basis of his ability to improve the quality of his human organization. Officials in the coal mining industry have had a tough road to travel in this regard due to fluctuating coal production demands, contractual obligations, and improved mining equipment and methods. The time may have finally arrived when we are able to recruit, select, and develop men from the labor market to fill vacancies, This is particularly true of our maintenance organizations. Because of the importance of this responsible function and the types of skills required, we must develop an extensive improvement pro- gram. Anyone in the industry who fails to undertake a manpower audit and who accepts a philosophy which will not permit collective planning, organizing and con- trolling the improvement of the human element throughout his maintenance organization may certainly cause deterioration within his company.

Jan 1, 1966

By M. J. Lowe

National Institute for Occupational Safety and Health (NIOSH) studies show that 43.5% of surveyed coal preparation plant workers had noise exposures exceeding the Mine Safety and Health Administration Permissible Exposure Level. Sound levels around vibrating screens in these plants often exceed 90 dB(A). NIOSH is currently developing noise controls for horizontal vibrating screens. To characterize noise sources, NIOSH researchers performed sound pressure level (SPL) measurements on a vibrating screen at their Pittsburgh Research Laboratory. The results show that the entire screen contributes to noise below 1 kHz and the vibration mechanism housings are most significant above 1 kHz. Constrained layer damping (CLD) treatments and an enclosure were used to reduce mechanism housing noise. These were evaluated using sound power level measurements according to ISO 3744. The CLD treatments reduced the A-weighted sound power level by 3.1 dB in the 1 to 10 kHz one-third-octave bands. A panel-on-frame vibration mechanism enclosure using various types of panels further reduced the A-weighted sound power level from the CLD configuration in the 1 to 10 kHz one-third-octave bands by 3.7, 4.0, and 3.9 dB for aluminum, steel, and Dynalam panels, respectively. The combination yielded a 7 dB reduction from baseline in A-weighted sound power for the same frequency range.

Jan 1, 2010

By J. G. Groppo

Froth flotation technique is an effective and efficient process for recovering of ultra-fine (minus 74 pm) clean coal. Economical dewatering of an ultra-fine clean coal product to a 20 percent level moisture will be an important step in successful implementation of the advanced cleaning processes. This study is a step in the Department of Energy's program to show that ultra-clean coal could be effectively dewatered to 20 percent or lower moisture using either conventional or advanced dewatering techniques. The main focus of the pilot plant study was on proof-of-concept testing of a dewatering technique for a fine clean coal product. The coal industry is reluctant to use the advanced fine coal recovery technology due to the non-availability of an economical dewatering process.

Jan 1, 1997

By John M. Smith

Kaolin is an important industrial mineral because of its unique properties and low cost. Strictly defined, kaolin is the name given to a group of hydrous aluminum silicates of which kaolinite is the most common mineral (1). Through common usage the mineral, kaolinite, is called "kaolin" or "china clay". In 1972 over 4, 000, 000 tons of kaolin will be beneficiated and shipped by domestic producers. By far the largest user of kaolin is the paper industry which utilizes approximately 65 to 70 per cent of the total production. Kaolin is used in paper as a filler in the interstices of the sheet and as a coating to impart smoothness, gloss, brightness, and printability to the paper. The rubber industry is also a large user of kaolin where it is used as a filler because it adds strength, abrasion resistance, and rigidity to both natural and synthetic rubber goods. Kaolin is used as an extender in paints because it is chemically inert, has a high covering power, gives desirable flow properties, and is low in cost. In ceramics, kaolin is used in whitewares, tile, insulators, refractories, and in some face brick where a white color is desired. Kaolin is also used extensively in plastics as a filler in thermosetting and thermoplastic mixes to give smoother surfaces, a more attractive finish, good dimensional stability, and resistance to chemical attack. Many other process industries use kaolin as a filler, suspending medium, or for color improvement.

Jan 1, 1972