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By M. R. Peterson

The U.S. Bureau of Mines (USBM) is investigating alternative methods to strip metal-loaded solvent extractants. Hydrolytic, precipitation, and hydrogen pressure stripping all recover metal or metal salts directly from the organic solvent extractant. Pure metals, metallic oxides, or metal salts can be formed, allowing direct production of value-added products. Aspects affecting commercial application are emphasized, including metal recovery from actual ore leach solutions, particle size control, organic modifier and diluent effects on stripping and metal recovery efficiencies, metal grade, seed addition, mixing intensity, recycling efficiency, and reactor plating. Metal separations from copper ore leach solutions and complex waste leach solutions were examined.

Jan 1, 1995

By Diogo Peixoto Cordova, Italo Gomes Gonçalves, Andre Cezar Zingano

The top-down extraction sequence in the sublevel open stope method relies on rib pillars to support excavations, making pillar and stope stability crucial for controlling dilution. This study introduces an integrated methodology using a genetic algorithm to optimize the layout of open stopes and rib pillars while considering both economic and geomechanical performance. The methodology incorporates user-defined parameters such as the minimum size of stopes and pillars, maximum accepted dilution and acceptable percentage of pillar failure. A profit function that attributes economic value to the geometric configurations, including geomechanical performance, is employed. The geomechanical performance, assessed using numerical models in FLAC3D, includes the average percentage of pillar failure and potential dilution. The study was tested on a mining panel from an underground gold mine using a top-down mining sequence. The optimization achieved an 8 percent increase in net profit compared to the traditional engineer’s design when 70 percent hangingwall support efficiency was assumed, and a threefold reduction in pillar failure percentage. When no hangingwall support was considered, the net profit increase reached 22 percent. These results demonstrate that the proposed methodology enables integrated optimization, balancing mining costs with geomechanical performance and reducing the need for secondary support compared to traditional methods

Nov 1, 2024

By J. Seiter

Mining has always been among the most hazardous of occupations, and with the increasing demand for coal and minerals, safety in mines assumes even greater importance. Worldwide, underground miners are being exposed to noise and respirable dust hazards associated with roof bolt drilling. These hazards are now being understood to cause irreparable damage to the health of miners. The objective of this research was to discover if a Polycrystalline Diamond Cutter (PDC) drill bit generates less respirable dust and hazardous noise than a competing Tungsten Carbide (WC) bit, in dry vacuum drilling. In order to control the drill parameters the drilling tests have been conducted in a laboratory setting. The results were met by determining the quantities of dust and noise generated using each drill bit and analyzing those levels by using monitoring devices and software to collect the data. This paper includes information on experiment setup, equipment used, drilling parameters, and data collected. The test results suggest that there are noticeable trends that the PDC bits produce less dust than WC bits but more testing is needed to substantiate these trends.

Feb 23, 2014

By H. Shafick Hanna

The major problems are identified the high phosphorus content and the fine dissemination or encapsulation of mineral impurities, in, ,the iron bearing minerals, A process which combined extreme fine grinding techniques with magnetizing roasting or flotation separation methods, is suggested. By these methods concentrates assaying 60-61 percent Fe exceeding the widely accepted upper limit of 56 percent Fe set for these ores, were produced with 75-90 percent iron recovery. Moreover it was shown that the phosphorus content of these concentrates could be reduced from 0.25 to 0.03 percent phosphorus by acid leaching. A brief discussion on production costs based on current and future developments in iron ore processing is given.

Jan 1, 1980

By Amy McBrayer, Andrea Brickey

Limited research has been conducted related to the development of mathematical optimization models for production scheduling at large surface coal mines using the area, i.e., strip, mining method. Increased economic and technical challenges have led to a new interest in production schedule optimization models for these type of mining operations like those currently applied to model underground and open pit mines. While area mines share similar characteristics to both open pit and underground metal operations, neither an open pit nor underground production scheduling model adequately depicts an area mine mathematically. We present an integer programming model with blending constraints and discuss the challenges and opportunities related to the implementation for area mines as well as future research in area mine production scheduling.

Jun 25, 2023

By R. Hogg

A standard procedure for determining size-specific gravity distributions of fine coal (including the -400 mesh fractions) by sieving and centrifugal sink-float separation is described. The significance of using a centrifugal sink-float technique and the effect of the magnitude of the centrifugal force on the separation of fine coal are confirmed in the present study. The relative merits of cumulative versus incremental sink-float are discussed. The procedure is evaluated quantitatively using data obtained for the products of froth flotation of -100 mesh coal.

Jan 1, 1994

By B. Goertz

Since the turn of the century the mining industry in the United States has had a number of serious mine explosions, fires and ground fall disasters that have led to a major re-evaluation of mine communication and rescue practices. One of the hindrances of current underground communication technologies is the potential of lost or cut connections when a serious accident, such as an explosion, fire, inundation or major ground fall, takes place. The Mine Improvement and New Emergency Response Act of 2006 (MINER Act)1 mandated that each underground coal mine in the U.S. must provide for two-way wireless, post-accident communications between underground and surface personnel as well as electronic tracking of underground workers One area that has gained renewed attention in the mining sector is Through-The-Earth (TTE) communication. TTE technology has a major advantage in that transceiver devices can be carried by miners and set up quickly during an emergency, since they require no wire connection to the surface. TTE technology uses ultra-low frequency (1 to 4 kHz) electromagnetic waves, requiring relatively large wire loop antennas and highly sensitive receivers. The signal bandwidth is narrow and the permissible antenna currents in coal mines are restricted, which has led to limited usability of TTE technology in the past, as evidenced in research studies conducted by the U.S. Bureau of Mines in the 1970s. Yenchek (2012)2 pointed out that recent advances in receiver and signal processing technology have enabled voice and text communication capabilities and much improved sensitivity that offers new possibilities for TTE communication in mining applications. One company that has been developing such technology is Vital Alert Communication Inc. Vital Alert has been providing TTE communications since 2003 with a growing focus on emergency response and portable systems. The company?s Canary® Go System is one such product that looks to provide reliable communication capabilities in a portable, user friendly unit that can be utilized both for normal operation and mine rescue scenarios. Researchers at the Colorado School of Mines (CSM) have tested the Canary Go TTE communications system in the CSM Edgar Experimental Mine to determine signal propagation distances, signal quality and aspects of practical application.

Feb 23, 2014

By Darrell V. B. . McClarty

In 1996, Rio Algom, Denison Mines and the Elliot Lake Research Field Station (ELRFS) formed a consortium to implement a regional environmental information management system (REIMS) for the Elliot Lake area in Ontario, Canada. ELRFS is an affiliate of Laurentian University in Sudbury, Ontario, The discovery of uranium in the Elliot Lake region in post-World War II led to the development of 12 mines and 11 associated mills between 1955 and 1958. During the late 1980s, declining world demand for uranium, combined with the discovery of high-grade uranium ore in other areas of the world, made the Elliot Lake mines uneconomical. As a result, all area mines ceased opera¬tions by the end of 1996. The eight facilities and three tailings management areas operated by Denison Mines and Rio Algom's five mining waste management areas contain 150 Mt (165 million st) of potentially acid-generating tailings. The areas cover 13.2 km2 (3,265 acres) and receive drainage from an additional 13 km2 (3,212 acres). The primary objective of the joint initiative was to implement a personal-computer-based, regional, environmental-information management system for managing historical data and ongoing environmental programs in the Elliot Lake region. The Elliot Lake consortium decided it needed an information system with an integrated, process-oriented and requirements-driven approach to collect and manage the environmental information. Following a study of environmental information management systems currently used by the mining industry, the consortium decided to base REIMS on the "Envista" product. This is a commercially available, environmental information management system marketed by Envista Technologies of Saskatoon, Canada.

Jan 1, 1999

By Charles A. Stone, Eric C. Wang

"Top-down wall construction was selected to excavate the tunnel portal headwall areas of the ORB East End Crossing tunnel. Benefits included an expedited construction schedule realized by staging excavation and rock support with development of temporary construction access roads. Rock mass properties, proximity to right-of-way lines, and blasting impacts were considered to design suitable lift heights, intermediate bench locations, and permanent ground support systems to provide supported permanent excavations. Carbonate rock formations contained adverse subsurface geotechnical features including solution cavities, clay seams, weathered joints, pinnacled rock, and boulders, which were addressed by flexibility in design. The resulting over-break conditions and long-term water infiltration issues required economic design solutions. This paper discusses the unique considerations required during design of top-down tunnel portal headwalls excavated in carbonate rock formations including temporary excavation and permanent ground support systems which provided flexibility for unforeseen over-break, minimized construction delays, and provided long-term stability. PROJECT BACKGROUND The East End Crossing is an approximate 8-mile highway connection of the Louisville-Southern Indiana Ohio River Bridges East End Crossing (ORBEE) project. Currently under construction, this connection will link State Road 265 in Indiana with the Gene Snyder Freeway in Kentucky to form an outer loop bypassing the Louisville-Southern Indiana metropolitan area. This highway project features a 2,510-foot long, three-span cable-stayed bridge over the Ohio River, and a 1,680-foot long tunnel. The project, being managed by the Indiana Finance Authority and Indiana Department of Transportation, is scheduled to open to traffic by the end of 2016. The new twin three-lane tunnel under the historic Drumanard Estate requires steep cut excavations for approach and tunnel portal walls on the order of 60 feet deep through overburden soil and carbonate bedrock formations. This paper focuses on the design considerations for the permanent support of the top-down wall construction of the tunnel portal headwalls and approach retaining walls."

Jan 1, 2016

By Minor S. Jameson

This paper presents considerations in support of a U. S. oil import policy more restrictive than the present Government import program. A lower level of imports and greater long-range stability in the relationship between imports and domestic production are recommended. Reference is made to increasing world-wide surpluses of oil and wide disparities in foreign vs. domestic costs. Resulting economic forces are held responsible for the increase in imports (excluding residual fuel oil) of almost 300 percent and the change in ratio to domestic crude production from 5.4 percent to 13.9 percent during the period 1946-1956 prior to import restrictions. It is pointed out that these imports continued to increase during the years of import restrictions to a ratio of 17.3 percent of domestic production in 1961. Data are presented showing that increasing oil markets outside the United States provide an outlet' for more than 80 percent of total foreign production, with 90 percent of the increase in foreign production going to foreign markets. Attention is called to the fact that, if there had been no increase in United States oil imports during the past five years, foreign production would have increased by 45 percent in contrast to a static level of domestic crude oil production. The need for a less restrictive import policy in the interest of encouraging foreign oil development, therefore, is questioned. Declines since 1956 in the range of 30 percent in domestic exploratory crews, rotary rig activity and wildcat well completions in the United States are cited, together with a decrease of 9 percent in industry employment and increases of 9 to 18 percent in elements of cost. Recognizing that factors other than imports affect the domestic industry, it is concluded that continuing declines in the vigor, capabilities and competitive structure of the domestic industry can be expected unless further import restrictions are imposed. The public interest in assuring adequate domestic supplies is considered in the light of the role of oil and gas as a source of almost three-fourths of U. S. energy requirements and the economic benefits from petroleum production with a value exceeding the combined value of all other minerals in the United States.

Jan 1, 1962

By Jose M. S. Ramos

This paper describes the slope stabilization procedure at Cauê Mine, Companhia Vale do Rio Doce - CVRD, Itabira, State of Minas Gerais, Brazil. Cauê Mine, is a large open pit, to produce about 41 million tons of iron ore during 1974, and an intensive program of investiga Lion was carried out to provide the basic data for stabilizing its slopes, The ultimate rock slope in the W area will be about 400 m high with dipping angles decreasing gradually from top to bottom of the pit. The investigations started in 1969 and since then many geologists and engineers, from both CVRD and Geotécnica S/A., assisted by international consultants, have given their contribution to the achievement of solutions. It is hoped that this paper may contribute to the slope stability of other mines in tropical climate.

Jan 1, 1974

By Aurel Goodwin, Diann Kraft, V. S. Znamensky

This chapter deals with the Mine Safety and Health Administrations's (MSHA] concern and obligations with regard to asbestiform minerals. Asbestiform minerals are defined as the magical group of hydrated, silicate minerals that possess a fiberlike structure capable of being woven into cloth. Their unique combination of properties, such as resistance to heat and chemical attack, high tensile strength, and flexibility was recognized centuries before Christ. Pausanias, the early Greek geographer, speaks of golden lamps, made about 430 BC, with in- combustible wicks of Carpathian flax. The Ro- mans used asbestos as cremation clothes to con- serve the ashes of deceased persons of rank. Charlemagne had an asbestos table cloth that he used to pass through fire to clean (Lanza, 19381. Early recognition of the health hazards associated with exposure to asbestos was documented in the first century by Pliny the Elder, a Roman naturalist, and Strabo, a Greek geographer. Both wrote of slaves with sickness of the lungs, whose occupation was that of weaving asbestos into cloth. This concern for the health of asbestos workers disappeared over the ages. Today, with the use of modern technology, asbestos products have been greatly exploited. The asbestos output has increased over a hundredfold in the past 70 years. World production has jumped from 454 t/y (500 stpy) in 1900 to 4.5 Mt/y (5 million stpy) in 1978. An increase in health problems for asbestos workers accompanied this increased usage. However, it was not until the modern era that the association of asbestos with chronic respiratory disease was rediscovered. Reports were published at the turn of the century documenting the effects of asbestos exposure on textile workers. One such report in 1907 by H.M. Montague Murray described the post mortem findings on a 34-year- old carding machine operator. Murray de- scribed the lungs as showing extensive diffuse pulmonary fibrosis spicules of asbestos. Subsequently, more reports of pulmonary fibrosis following inhalation of asbestos were published, including an epidemiological study of asbestos miners in 1930 (Merewether and Price, 1930), at Thetford, Que., Canada. This study took place at the mine 52 years after large-scale mining of asbestos had begun. But, the cancer- producing potential of asbestos was not established until 1949 when a report by Merewether in England described an excess of cancer of the lung and pleura [the lining of the lungs) among individuals dying from asbestosis (Merewether, 1949). In the past decade much attention has been focused on asbestosis, mesothelioma, and bronchogenic carcinoma, as the three major biological effects associated with asbestos ex- posure. Parenchymal and pleural asbestosis is a fibrosis in the substance of the lung with thickening and often calcification of the membranes lining the thoracic cavity. Mesothelioma is a malignant tumor of the membranes lining the thoracic or abdominal cavities, and bronchogenic carcinoma is a cancer of the lung tissue itself. These diseases occur in various degrees and combinations. The severity and occurrence of these biological effects are directly influenced by conditions such as dose response relationships, intensity of exposure, duration of exposure, lapse of time since initial exposure, and cigarette smoking. Numerous studies indicate that the relationship between these conditions and the incidence of disease is proportional. Congress has recently concluded (Congressional Record, 1979) that, "exposure to asbestos fibers has been identified as significantly in- creasing the incidence of cancer and other severe or fatal diseases such as abestosis." Congress conveys its concerns for the safety and health of the nation's miners through the Federal Mine Safety and Health Act of 1977 in which it gave MSHA the authority to set safe

Jan 1, 1986

By B. W. Cavender

Capital investments are made for a variety of reasons, ranging from providing incremental capacity at existing operations to developing and implementing new technologies intended to radically improve a company's capabilities. These projects generate very different business opportunities and create value in distinctive ways. For incremental improvements, the capital budgeting process assures at least a loose fit between short-term goals and readily available resources. However, the criteria used to evaluate capital projects often prevent a company from committing to more aggressive goals, which lie beyond the firm's current abilities or resources. Such projects may not have clearly identifiable future cash flows, and the degree of interaction with other projects and the nature of the risk incurred may be difficult to estimate. Additionally, by focusing only on quantifiable benefits, the budgeting process often fails to recognize "soft" improvements such as increased operating flexibility or new knowledge generated by such projects. By rejecting these projects, the capital budgeting process may actually harm the company's future competitive position.

Jan 1, 1999

By A. W. Dickerson

Following on from many years of research aimed at improving the effectiveness of truck haulage operations in mines operated by BHP Minerals, BHP Research developed a concept for an Innovative Large Mining Truck, (ILMT) which has the potential to significantly improve the cost effectiveness of rear dump mining trucks. The ILMT concept reduces the empty vehicle weight dramatically, greatly reduces unequal rear tyre loading and improves ride and handling characteristics. The concept has been taken to the "proof of concept" prototype truck stage with the cooperative efforts of BHP Coal, BHP Research, Liebherr Mining Truck, Inc., Liebherr-Australia and Birrana Engineering. Testing of the prototype truck commenced at a coal mine in Queensland, Australia during May 1996. Preliminary results from the testing program are very encouraging. Expectations are being met and in some cases exceeded.

Jan 1, 1997

By K. Nagata, T. Kawashima, S. Tejima

The expanding volume of maritime coal transportation is intensifying the problems concerning large vessel service, port construction, trans-shipment, and environmental control. The major problem is the shipment of coal. Customary methods for bulk transfer must be improved and new systems developed. Slurry unloading has a key role in the new systems. This report reviews progress in slurry transportation research that has been done in Japan since the 1960s, when large-scale experiments for domestic transportation were done. Experiments on the effects of vibration on the slurry cargo and on reslurrying are focused on.

Jan 1, 1987

By G. W. Riley, D. E. Pickett

HINDERED SETTLING CONCENTRATION In the free settling of mineral particles in a liquid, the falling particles are at a distance from each other so that no particle is affected by its neighbor. In hindered settling, the concentration of particles is sufficiently high so that each particle is affected by its proximity to other particles in the suspension. Richards and Locke86 have described the hindered settling phenomenon as the condition “.. where particles of mixed sizes, shapes and densities in a crowded mass, yet free to move along themselves, are sorted in a rising current of water, the velocity of which is much less than the free-falling velocity of the particles but yet fast enough so the particles are in motion." This is the condition normally encountered in mineral con¬centration processes. The well known Newton equation for free settling of coarse (ap proximately +10-mesh, 1/16-in. or -- 2000-µm) spherical particles is:87 where v," is free settling velocity, cm/sec; p' is density of the fluid; p is density of the particle, g/cm3; d is particle diameter, cm; g is acceleration due to gravity, cm/sec2; and Q is coefficient of resistance, dimensionless, ~0.4. For the settling of fine spheres in water (approximately 150 mesh or 100 µm) the equation of Stokes pertains:87 where µ is viscosity of the fluid in poises and the other symbols have the same meaning as those in Eq. 1. For particles whose size lies between about 10 mesh (--2000 µm) and 150 mesh (100 µm), their settling velocity can be determined from experimental data. These data are available in convenient form in the text by Taggart88 based on the original work of Richards. Alternatively, a Reynolds number-coefficient of resistance plot may be used to determine the settling rate of such particles.87 The settling rate of spherical particles under hindered settling conditions can also be calculated from Eqs. I and 2 by replacing p', the density of the fluid, by p" the apparent density of the suspen¬sion. The concentration of particles in the fluid thus imparts an appar¬ent density to the composite fluid or suspension greater than that of the liquid alone, resulting in a buoyant effect on the larger particles. Particle shape affects the settling rate of both coarse and fine particles. The general effect is to reduce their settling velocities and the effect is greater for coarse particles and for those settling under hindered settling conditions than for fine particles or free settling ones. For two particles of differing densities but settling at the same velocity under Newtonian conditions, the ratio of their diameters from Eq. 1, called the free settling ratio is: where L signifies the lighter particle and H, the heavier particle. Under Stokesian conditions the exponent would be 0.5. For hindered settling conditions the fluid density p' is replaced by the apparent density of the suspension, p", to obtain a generalized equation for the hindered settling ratio: assuming both particles settle in approximately the same regime. The free settling ratio as given by Eq. 3 has been called by Taggart88 the "concentration criterion" and is used to predict the effectiveness of any gravity concentration process (see Introduction to this section). Based on Eqs. 3 and 4, if two particles of densities pH and p,, settle at the same velocity, the diameter of the lighter particle will be larger than that of the heavier particle. For example, in the case of galena (pH = 7.5) and quartz (pL = 2.65) settling in water (p =1.0) under free settling, Newtonian conditions 3.9. Thus, a quartz particle nearly four times as large as a galena particle will settle at the same velocity. Any quartz particle just slightly less than four times the diameter of the largest galena particle may be separated from it. Under hindered settling, Newtonian condi¬tions in a suspension where p" = 1.65, dL/dH = 5.85 or any quartz particle just slightly less than about six times the largest galena particle may be separated from it. Reference to Eq. 4 indicates that a superior separation between two minerals of differing densities is favored by: (1) coarse particles settling under Newtonian conditions, (2) a large difference in (pa - PL), and (3) separation under hindered settling conditions where p" is high. Of course, there are practical limits to increasing p" excessively because at very high percent solids suspen¬sion fluidity would be lost and the hindered settling separation process defeated. Examples of hindered settling separators are the Dorrco-Fahren¬wald sizer,89 the Rheolaveur box 90 the Spitzkasten,89 and the Willoughby washer.91 These devices make a mineral separation on the basis of both specific gravity and size and all of them are essentially obsolete except for the Dorrco-Fahrenwald sizer and similar devices which still find application for the removal of coarse particles from a much finer particle assemblage and for preconcentration ahead of shaking tables. However, nearly all gravity concentration processes (jigs, tables, flowing film concentrators, heavy media separators) and many sizing devices (sizing classifiers, clarifiers, thickeners, hydrosepa¬rators) make use of the hindered settling phenomenon during the separation of particles. JIGGING Introduction In jigging, a mixture of ore particles, supported on a perforated plate or screen in a layer or "bed" with a depth many times the thickness of the largest particle, is subjected to an alternating rising and falling (pulsating) flow of fluid with the objective of causing all

Jan 1, 1985

By P. R. ZETTWOOG

HISTORICAL BACKGROUND A program in France to develop personal [a] dosimeters has been initiated 1974. The patent on which is based the present device was obtained in 1972 * . From 1972 to 1974, the possibilities of applying certain ionograph track detectors to the spectrodosimetry of radon daughters was explored. The first prototype were produced in 1974. It took four years (from 1974 to 1978) to produce an autonomous dosimeter whose components has a sufficient life span, especially for the turbine motor unit. Qualification in the laboratory was obtained in 1977. In 1978 it was obtained in the mine for technology (autonomy of 12 hours and a life span of more than one year) and in 1980 for monitoring. 300 dosimeters have been tested in underground mines all together. Indispensable peripheral equipment were also developed from 1976 to 1980 : calibration devices, equipment to prepare and develop the films, read out systems. The concept of an "Integrated System of Individual Dosimetry" (ISID) based on a personal [a] dosimeter measuring exposure to radon daughters, thoron daughters, ore dust and external irradiation doses was proposed at the end of 1980. Since January 1st 1981, ISID is used on a routine basis in some french mines, situated in remote area, and appears to be very competitive with the ambiant dosimetry. The latest version of the dosimeter is produced in mass series since June 1981 and should equip all french mines in 1982. DESCRIPTION OF THE INSTRUMENTATION DEVELOPMENT OF THE DOSIMETER MEASURING HEAD The measuring head is based on the use of ionographic film to detect a tracks. In fact, the measuring head is a spectrodosimeter which measures separately over the period of exposure: - the potential [a] energy inhaled due to the decay of Po 218, Po 214, and Po 212 ; - the number of Rn 222 atoms inhaled ; - the inhaled total [a] activity of the five long-lived emitters present in the ore dust. The contribution to the total inhalable potential [a] energy of these various radionuclidesin a typical underground mine is studied in Appendix I. The measuring head described in detail in Appendix II, is able to satisfy all the implications made in the ICRP recommendations. Appendix III deals with the use of this measuring head in the cases where the equilibrium factor is lower than 0.1. This situation occur in open-pit mines where account must be taken of the Rn 222 contribution, which is no longer negligible in relation to that of its daughters. CURRENT DOSIMETER PERFORMANCES Table I shows the characteristics of the latest dosimeter. Appendix IV should be consulted concerning qualification of the dosimeter in the laboratory and in mines, technological development which finally produced the [a] dosimeter and its peripheral equipment, and technical presentation of the ISID (Integrated System of Individual Dosimetry) based on the concept of a multirisk personal dosimeter. Data on the installation and operating costs of such a dosimeter, which would seem to be competitive, are also given in this Appendix. ADVANTAGES OF PERSONAL DOSIMETRY AS COMPARED TO AREA MONITORING The results of the first eight months of experiments carried out under real conditions in an underground mine site are given in detail in reference 8. Area monitoring : The monthly exposure per worker to inhaled Rn 222 was determined from the knowledge of time spent in various areas of the mine and for the different mining operations, as well as from numerous and systematic sampling of the Rn 222 concentration in all work places. Personal dosimetry : The exposure to potential energy from radon daughters was measured by an [a] dosimeter developed by the CEA and worn by each of the 160 miners during eight months. In this way 160 x 8 pairs of monthly individual exposure values have been obtained which can be statistically studied. This test was decisive for us because it proved that the [a] dosimeter was technically sound (very few defects over one year for 160 dosimeters) and especially that personal monitoring devices were superior to area monitoring devices. The following conclusions can be drawn 1. The exposure distribution obtained by personal dosimetry is log-normal. This is true for the results on the whole as well as for groups of results relating to certain explanatory variables. See fig. la, 1b, 1c. 2. The exposure distribution obtained by area monitoring does not correspond to any type of distribution. If the results of personal monitoring are taken as a reference, area monitoring tends to underestimate the high exposures and overestimate the low exposures.See fig. 2. 3. [a]-energy exposures are underestimated when calculated from radon exposures and the equilibrium factor found in the considered mines. This is due to episodes or to zones of high radon concentrations not registered

Jan 1, 1981

By YOUNIS S. MUSTAFA, GHORASHI ZAIN, ABDEL-ZAHER M. ABOUZEID, AHMED A. S. SEIFELNASSR

The present paper attempts to characterize the breakage properties of a brittle rock, quartz, at different size fractions when compressed at various loads in a confined piston die.  This is to understand the interaction between the various parameters affecting the breakage behavior of a brittle solid in a confined zone. Application of the results may lead to improving the energy efficiency in the size-reduction units, which use compression as the main stressing force. 

By G. R. Hart

The expected 1990 Clean Air legislation is providing electric utilities with a series of challenges and decisions as the utilities prepare strategies to comply with the resulting regulations. This paper addresses the strategy development of a coal-based utility --the legislation, the process used, the fuel issues, the options available, and the decisions to be made.

Jan 1, 1991

By Osvaldo A. Bascur, J. Pat Kennedy

Large metallurgical complexes have more data than a small city and much of it is "real time," changing rapidly as internal and external conditions evolve. As corporations buy and sell assets and reengineer their staff, the structures and tools that were used to understand these data are lost. The lack of an integrated approach makes the profitability of metallurgical plants lag behind that of other industries despite technical advances that have occurred in recent years. This results in significant deterioration in the ability to maintain a "smart” operation. The solution is to use the sophisticated new tools built for the Internet so as to leverage information in a familiar browser format that people can use and understand. Combining real-time infrastructure with portal technology is becoming an accepted methodology. This paper introduces real-time portals and team sites to support decision making by work- groups which require both real-time and documentary information from manufacturing assets, vendors, head office and the Internet. Workers get insight from the overall process effectiveness index based on key variables such as losses due to plant availability, performance efficiency and rate of quality. Real-time portals and smart clients are part of any real-time performance management (RtPM) solution. Three case studies in large metallurgical complexes are presented. PLANTS ARE YOUR STRATEGIC HANDICAP Information technology is arguably one of the fastest moving technologies used by the mining/metallurgical industry. However, the business model for managing that

Jan 1, 2004