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By B. J. Sauer

Misapplication of ac induction motors for mine crusher and mill applications has long been a frustration for the driven equipment supplier and the mine operator. Proper selection of ac induction motors is critical to providing efficient production. This paper focuses on the selection of ac induction motors for gyratory crusher, conecrusher and grinding mill applications. The criteria for motor selection includes: proper enclosure, driven equipment torque requirements, bearing life, temperature rise, starting requirements, ambient temperature, altitude and accessory requirements.

Jan 1, 2002

By Charles E. Scott

The molybdenum industry has been in a depression since the beginning of the decade. Real molybdenum prices are significantly reduced from 1979-1980 levels when there was a perceived capacity shortage and continued expectations of burgeoning demand. Primary capacity brought on stream since then has been unable to operate profitably and indeed, in light of high inventories and reduced demand, has been largely unnecessary. Structural changes in the molybdenum industry will be needed in the future to weed out superfluous capacity and to expand demand through new product applications.

Jan 1, 1986

By Rick Sarkisian, Greg Girardey, David Keech

The Conveyor Equipment Manufacturers Association (CEMA) specification B105.1 "Welded Steel Conveyor Pulleys" adequately defines pulley assembly standards for light material handling applications. However, most mining applications demand pulleys of higher reliability and load capacity than that offered by CEMA standard pulleys. Various sources have published specifications for "Engineered" conveyor pulleys. Typically, these specifications require T-section type pulleys applicable to operating belt tensions exceeding 439 N/mm (2,500 lb./in.). This paper examines the application of CEMA standard pulleys, T-section pulleys and also a mining duty pulley design. The mining duty pulley fills the void between CEMA standard pulleys and T-section pulleys and can eliminate the high cost and long lead times associated with T-section type pulleys.

Jan 1, 1998

By Paul Chamberlin

Management has assorted roles to play, many of which are listed, that may call for consultant input. Consultants also play various roles, and some of these are discussed as well. The relationship between management and the consultant depends mainly on management's preparation for the assignment and on their monitoring during the assignment. Consultant costs are discussed briefly and suggestions for keeping consultant costs under control are given. In addition, some qualities of a good consultant are covered.

Jan 1, 2001

By Milton E. Wadsworth

The evolution of engineering education and research has been profoundly influenced by computer technology and has concomitantly followed changes in this technology. Today, virtually all faculty have access to at least two hierarchies of computers: desk personal computers and at least one echelon higher (workstations or a variety of mid-sized computers). Most faculty have access to three or even four hierarchies: the two listed, plus super-mini and super computers. The ready availability of computers at a low cost has increased dedicated and site-specific computer technology. This has permitted universities to move into the field of macro-engineering, to address increasingly complex problems in resource recovery, manufacturing and many other areas, including important societal problems, like the environment. The creation of university research centers indicates the growing importance of macro-engineering involving large systems of interactive components. Funding agencies have increasingly favored such centers since they cross disciplines, generate inter-university consortia and foster university-industry programs.

Jan 1, 1992

By D. P. Harding

Quick, inexpensive and accurate mineral-phase identification is of utmost importance to applied mineralogists. The precise relationship between the intensity of measured backscattered electrons in a scanning electron microscope and the average atomic number of the specimen is still argued. Nevertheless, much can be gained by using backscattered electron images to identify mineral phases in a specimen. An application was developed to facilitate this method and makes it a practical, inexpensive and valuable option in many mineralogical investigations. Keywords: Mineral identification, Scanning electron microscope, Backscattered electron detectors

Jan 1, 2003

By Peter D. Warwick

Recent investigations conducted by Federal, State, and industry organizations suggest that significant coalbed gas resources may exist in the Cretaceous and Paleocene-Eocene coal beds of the Gulf of Mexico Coastal Plain. Exploration efforts have focused on three areas which are in south Texas, north-central Louisiana, and south-central Mississippi (Figure 1). Coal-bed gas production is currently underway in south Texas and in north-central Louisiana. In Mississippi, several test wells have been drilled but no data are available on their production potential.

Jan 1, 2005

By Haydn H. Murray

Common clay includes a wide variety of clay and other fine- grained rocks that are used in many ways. These clays are some- times classified as miscellaneous clay and shale. Most products made from them are fired and include such things as structural and face brick, drain tile, vitrified pipe, quarry tile, flue tile, conduit, pottery, stoneware, and roofing tile. Very large tonnages of these materials are bloated by firing to form lightweight aggregate, and large quantities are used in making portland cement (see the specific chapters in this volume). Uses not requiring firing of a finished product include filler for paint and other products and shale and clay used for packing dynamite in blastholes and for plugging oil and gas wells that are no longer in use.

Jan 1, 1994

By R. Reifsnyder, J. LaRosa Thompson

Slurry or slimes dispersion is a critical factor controlling the efficiency of sulfide mineral comminution and concentration operations. The PQ Corporation has conducted innovative sodium silicate-based studies to determine the effects of enhanced dispersion on whole ore grinding and flotation behaviors and on downstream separation and cleaning steps. The work has advanced the understanding of the role of pulp rheology on the optimization of commercial grinding, agitation leaching, and flotation operations. This paper reviews the role of sodium silicate as a selective wetting agent and surface charge modifier in sulfide mineral systems, and discusses the results of silicate experiments conducted on various ores of copper and molybdenum, gold, platinum-palladium, and copper zinc, all of which contain clay minerals or highly floatable gangue constituents.

Jan 1, 2002

By J. Vaino Huhta

An exploration program which covered an area of about 17 000 km2(6564 sq miles), was carried out between 1966 and 1969 by the United Nations project named "Mineral Survey of the Azuero Area." The target became Cerro Petaquilla, Province of Colon, Panama. See Fig. 1. Regional exploration led to discoveries of many geochemical anomalies and minor mineralization, but it was only toward the end of the project that a promising target was indicated by a large zone of comer and molybdenum anomalies in stream sediments in a remote 1, area between the Cordillera and the Caribbean coast. Follow-up surveys established the presence of porphyry-type copper mineralization in the area now known as Cerro Petaquilla.

Jan 1, 1991

By Z. T. Bieniawski

After many significant advances in mining, including development of sophisticated methods for strata characterization and numerical modeling analyses, the engineering design process in mining strata control is as primitive as it was two decades ago. Yet, major advances in design methodologies have occurred in other branches of engineering. Is creative design in mining a myth only? Are we deluding ourselves when we talk about innovative mining design of today? Did you know that most design experts are often unaware of their own decision-making processes? This paper explores the methodology of creative engineering design as a new recognized discipline.

Jan 1, 1987

By E. S. Cheney

Minter (1990) has provided an excellent summary of the sedimentology and theories of origin of the Witwatersrand paleoplacer Au/U deposits. However, recent stratigraphic, metamorphic and structural-tectonic research is radically changing the concepts about the Witwatersrand that now occur in most textbooks, review articles and North American minds. Presently, these concepts are biased by the past sedimentological research so well described by Minter. Specifically, the Witwatersrand Supergroup is Archean, does not occupy a depositional basin and is significantly metamorphosed and deformed. Thus, many of its sedimentary features, including the mineralogy of its ores, have been modified. The importance of the Witwatersrand ores cannot be overestimated. Since their discovery in 1886, they have produced 52% of the gold mined in all of human history (Pretorius, 1989).

Jan 1, 1991

By K. E. Lasaridi

Increasing soil organic matter was considered to be an important factor for the establishment of vegetative cover in abandoned quarries of perlite and bentonite in the island of Milos. For this reason, the feasibility of composting local organic wastes and by-products for use as a soil amendment was examined in this study. A mixture of organic wastes of vegetative origin and seaweed, in proportions that correspond to local material availability, was composted in laboratory scale reactors and the composting progress and compost quality were evaluated. Temperature, airflow and respiration rate were continuously monitored and various compost quality parameters, such as C/N ratio, nitrate nitrogen and seed germination were analysed. Addition of inorganic nitrogen was necessary for the biodegradation of the substrate, while the main problem for the compost utilisation was related to its high electrical conductivity, characteristic of seaweed containing mixtures, which further increased with nitrogen addition.

Jan 1, 2002

By Dae S. Young, Eleonora Widzyk-Capehart

A quantitative estimation of the size distribution of rock fragments is extremely important in mining, metallurgy and other geotechnical fields. This paper presents a new approach to the analysis of fragmentation. The method combines the practicality of digital image processing of the rock surface with the theoretical volume calculations based on the principles and laws of fractal geometry. The final volumetric distribution curve is compared with the results from traditional sieving indicating close agreement.

Jan 1, 1996

By T. Yegulalp, K. S. Lackner

Zero emission coal plants capture their own CO2 emissions. Since they have no smoke stack, they emit no pollutants to the air. Zero emission plants circulate a gas stream, to which fresh fuel is added and from which spent fuel and impurities are removed as solids or liquids. Coal is gasified via hydrogenation, steam reforming or CO2 gasification (Boudouard reaction). The gas is oxidized in a fuel cell and the resultant water and CO2 are partially removed before returning the remaining gas to the gasifier. The high conversion efficiency of zero emission power plants, which exceeds 70% even in realistic designs, stems from combining fuel cells with careful heat management. The paper generalizes the concepts and outlines the thermodynamic basis of zero emission power plants.

Jan 1, 2004

By Christopher J. Bise

During the past two decades, the emphasis on technological advances in US underground coal mining has focused on longwall mining. But there also has been a steady, although less spectacular, advance in the state-of-the-art in room-and-pillar mining. This has been stimulated by the successes of longwall mining in mine cost reduction, increased availability and improvements in haulage infrastructure, such as conveyor belt haulage. In addition, changes in management practices, such as nine- or 10-hour shifts, and marketing pressures have resulted in changes in the use of equipment. The net result of these changes has been the creation of modern room-and-pillar operations where average production levels currently exceed those considered very good 20 years ago. In fact, current production levels considered outstanding were considered unattainable two decades ago.

Jan 1, 1995

By Charles A. Edwards, Kenneth D. Merrill

The Construction of the Northeast Extension of the Baltimore Metro involved soft ground, compressed air tunneling. During the tunneling, gasoline and dry cleaning fluid contamination were encountered. Innovative approaches and solutions were developed to address these problems. Special emphasis was on the problem of compressed air pushing gasoline vapors into surrounding communities, resulting in an extremely dangerous situation and a public relations nightmare. Guidelines and standards were established for working in this contaminated environment. Also, through a proactive approach by all parties, all claims and disputes have been resolved.

Jan 1, 1995

By J. B. Yianatos, G. S. Dobby, J. A. Finch, A. R. Laplante, R. Espinosa-Gomez

The question is posed as to why columns typically have a collection zone 10 m high (H) by 1 m in diameter (D). Three geometry dependent factors are considered: degree of mixing, Np; volumetric bias rate, B; and volumetric gas rate, G. Increasing H:D decreased Np and B, which improves performance but decreases G, which causes the column to approach overloading. Taking typical column operating conditions, it is concluded that a collection zone H:D of 10:l is a reasonable compromise.

Jan 1, 1987

By Leopoldo Cortez, Fernando Durão

The dynamic control of a froth flotation section is simulated through a neural network feedback controller, trained in order to stabilize the concentrate metal grade and recovery by applying random step changes to the feed metal grade. The results of the application example show that this controller seems to be sufficiently robust and a good alternative to handle a non-linear process.

Jan 1, 1995

By R. Brough, T. K. Moller

There are differences in design aspects between steel and rubber linings in grinding mills. This paper describes the basic design rules for rubber liners for different grinding applications. When converting a mill from steel to rubber liners, the design must be changed from such familiar steel liner shapes as wedge bars and plates, wave liners, and ship-lap, to take advantage of the characteristics of rubber. Very little of the knowledge of the wear properties of steel can be used for the design of rubber mill liners.

Jan 1, 1990