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By Steven E. Mischler, Jay F. Colinet

The Mine Safety and Health Administration (MSHA) promulgated a rule in 2014 that required numerous changes in compliance dust sampling requirements for coal mine operators. Two key parts of this rule were the lowering of the respirable coal mine dust standard from 2.0 mg/m3 to 1.5 mg/m3 and requiring operators of underground coal mines to use a continuous personal dust monitor (CPDM) for compliance sampling. The CPDM currently approved for compliance sampling is equipped with a display that provides miners with in-shift information on their respirable dust exposure. The goal was to provide an indication of a potential overexposure and empower the miner and mine operator to implement changes in controls and/or operating practices to prevent an overexposure from occurring.

By Alan J. Zeni

Drainage of water from abandoned underground mines has become important in recent years because of safety concerns when mining near abandoned works or reentering abandoned mines for further development. Seepage from inundated mines causes environmental damage and may threaten homes and communities. Where topography permits, horizontal drilling can provide a quick and cost effective method for solving trapped water problems. The mechanics of the horizontal drilling operation as applied to water drainage are discussed in this paper.

Jan 1, 1990

By P. B. Grote

The report provides a general description of DOM technology, sources for DOM technology, and identifies approaches and requirements for acquisition by the Enterprise of DOM technology by conventional means. The approaches identified assume the Enterprise enters into a contractual/ joint venture arrangement with an uncommitted and competent systems management firm at various stages of the DOM system acquisition process. The approaches provide for training through work/study as well as through direct participation in acquisition programs. The potential success of the alternatives are evaluated in terms of the likelihood of the acquisition of an ongoing Enterprise economic DOM operational capability. The study concludes that sources exist and that the Enterprise should under-take the development of its own technical capability through conceptual design prior to selecting its source for systems management expertise.

Jan 1, 1980

By V Poizat

In different parts of the world the term epithermal is commonly used for a variety of deposit styles. Using the redox state of the ore-forming fluid (inferred from mineralogy and alteration), the metal assemblage of deposits, and other characteristics, at least five different styles of epithermal deposit can be distinguished. Most of these different deposit styles appear to be related to magmatic fluids, with differences resulting from different compositions of source magmas. The most common style of epithermal deposit (low-sulfidation gold-silver deposits associated with calc-alkaline volcanic rocks) remains the most difficult to explain; the metals in these deposits may be derived by basement leaching without magmatic input, or they may come from magmatic volatiles, with contaminated I-type or S-type magmas as the most likely source.

Jan 1, 1995

By Christopher Mark

A coal burst is defined as the sudden, violent ejection of coal or rock into a mine opening. Coal mines in the North Fork Valley (NFV) of Colorado?s Gunnison River have a long history of coal bursts in a wide variety of settings. These have included longwall and room-and-pillar, development and retreat, and single- and multiple-seam mining. In contrast to other coalfields, where bursts are typically associated with strong, massive sandstone and extremely high stress, many bursts in the NFV have occurred beneath shale roof and some distance from the most highly stressed locations. The goal of this paper is to attempt a systematic study of the entire burst history in the NFV, in order to gain insight into their characteristics and causes. The primary sources of information are the reports of investigations conducted by the Mine Safety and Health Administration (MSHA) Roof Control Division over the past 15 years. This paper provides details on the geologic mapping conducted as part of these investigations, as well as a regional plot of burst locations using a Geographic Information System. The mapping indicates that many of the NFV bursts have been associated with structural features, including low-angled faults and well-defined zones of high-density jointing that exhibit little or no displacement. Some of these features appear to extend for several miles, impacting more than one mine.

Jan 1, 2012

By D. Grgic, A. Giraud, F. Homand

RESUME : Le comportement mécanique partiellement saturé du minerai de fer a été étudié à partir d’essais de compression simple sur des éprouvettes à pression capillaire imposée par les solutions salines. Les échantillons restent peu saturés (32 %) même pour une humidité relative de 94 %, du fait de la présence de mésopores. Jusqu’à 90 % d’humidité relative la résistance diminue régulièrement. De 90 % à 94 % une forte chute est observée et pourrait être liée à la fois aux effets capillaires et à l’hydratation de certains minéraux. Le cycle hydrique subit par la roche dans la mine a été modélisé en 1D à l’aide d’un code de calcul entièrement couplé pour les milieux poreux partiellement saturés. Les calculs ont montré notamment une diminution importante en paroi des contraintes totales au cours de la phase de désaturation et une augmentation importante au cours de la phase de resaturation. Ces variations pourraient induire un endommagement du massif et être à l’origine d’instabilités, et soulignent l’intérêt d’une modélisation avec une géométrie plus adaptée. MOTS-CLEFS : mines de fer, partiellement saturé, pression capillaire, résistance, modélisation. ABSTRACT : The partially saturated mechanical behavior of iron ore has been studied from uniaxial compression tests on samples in which the suction is imposed with aqueous solutions. Samples are little saturated (32 %) even for a 94 % relative humidity because pores are too large. Up to 90 % relative humidity the strength decreases regularly. From 90 % to 94 % a great decrease is observed ; it could be explained by the capillary effects and the moisturizing of some minerals. The hydrous cycle imposed to the rocks in the mine has been modeled with an 1D fully coupled code for partially saturated porous media. The computations have shown an important decrease in the total stresses at the wall during the desaturation stage and an important increase during the re-saturation stage. These variations could induce a rock mass damage and instabilities, and highlight the necessity of a modeling with a well-adapted geometry. KEY-WORDS : iron mines, partially saturated, suction, strength, modeling. ZUSAMMENFASSUNG : Das mechanische Verhalten von teilweise gesättigten Eisenerz wird durch einachsige Druckversuche untergesucht. Die Prüfkörper haben einen durch Salzlösungen gestimmten kapillarischen Druck. Sie bleiben kaum gesättigt (32 %), sogar bei einer relativen Feuchtigkeit von 94 %, aufgrund der Anwesenheit von Mesoporen. Bis eine relative Feuchtigkeit von 90 % verringert sich gleichmässig die Druckfestigkeit und zwischen 90 % und 94 % merkt man eine starke Abnahme in Verbindung, möglicherweise, mit kapillarischen Effekten und Hydratation von bestimmten Mineralen. Die nümerische 1D Modellisierung des gezwungenen Wasserzyklus im Stein der Mine ist mit einem für porösen Medien ganz vernetzten Rechnungcode geführt. Sie zeigt besonders ein bedeutendes Sinken der Gesamtspannung während der Entwässerung und eine bedeutende Steigerung während der Sättigung. Diese Veränderungen könnten die Beschädigung des Gesteines herbeiführen und die Grundlage von Unstabilität sein. Sie unterstreichen die Wichtigkeit eine Modellisierung mit einer gut geeigneten Geometrie. STICHWÖRTER : Eisenminen, teilweise gesättigt, kapillarischer Druck, Druckfestigkeit, Modellisierung.

Jan 1, 2003

Mining activity during 1977 was limited to the production of limestone, marl, and sand and gravel, all of which were used domestically. Public works projects consumed the major portion of the construction material produced. The consortium of oil companies operating as Esso Ventures Inc., drilled one exploratory well off the coast of southern Belize. For drilling the well, Exxon Corp. received a 57% working interest in the consortium's concession located 40 kilometers east of Puta Gorda. No other offshore drilling was attempted in 1977. Esso also drilled a well on the Anschutz Overseas Inc. concession in the Toledo District of south- eastern Belize. The attempt wee abandoned, but seismic activities continued.

Jan 1, 1981

By Y. X. Zhao

This paper briefly describes the characteristics and induced factors of coal mining bumps based on the investigation of recent bumps accidents occurred in China. According to the theory of non-equilibrium thermodynamic and dissipate structure, the process of strain energy accumulation and dissipation in the ?Coal-Surrounding Rock? system (CSRS) is discussed during the preparation of coal bumps. In addition, a series of experiments are conducted to analyze the relationship between bump-prone property and micro-structural characteristics of coal. The process of coal bumps induced by propagation of fractures and deterioration of coal mass properties are also analyzed systematically.

May 1, 2009

By B. S. Xakalashe

Keywords: Pyrometallurgy, silicon, solar cells Silicon has been the dominant material in the photovoltaic (PV) industry since its application in the space industry in 1958. This review focuses on crystalline silicon solar cells, primarily due to their dominance in the photovoltaic industry, omitting other photovoltaic cell technologies such as second generation (e.g. thin films) and third generation (e.g. nano-structured solar cells). The value chain for the production of crystalline silicon solar cells has been reviewed. The primary processing steps for the production of silicon solar cells from quartz are as follows: bulk production of metallurgical-grade silicon via carbothermic reduction in a submerged furnace, refining of metallurgical-grade silicon via the chemical means to polycrystalline silicon, or through the metallurgical route to solar-grade silicon, wafer manufacturing, and, lastly, silicon solar cell manufacturing. During downstream processing, solar cells are interconnected and encapsulated into solar modules (panels), which can be used individually or incorporated into a photovoltaic system for electricity generation and supply. The cost for crystalline silicon based solar cells is approaching one US dollar per watt peak ($1/Wp), while the most cost-effective solar modules in industry have reported costs below $1/Wp, and are based on CdTe thin films. Solar cell energy conversion efficiencies as high as 22% have been reported in industry for crystalline silicon solar cells.

Jan 1, 2011

By P. L. Ngwenyama, I. Maubane

Soundless chemical demolition agents (SCDAs) are proving to be the future of sustainable and environmental-friendly mining. These expansive chemicals become critical when there is a need to break rock close to communities, environmentally sensitive areas, and critical structures and infrastructure. Unlike explosives, the SCDAs do not generate air-blast, ground vibrations, flyrock, noise, dust, and noxious fumes, which can negatively affect the environment, surrounding communities, sensitive areas, and critical structures and infrastructure. Over the years, several types of SCDA products have been used successfully in the civil and construction industries for the demolition of old and dilapidated buildings near vibrations and environmentally sensitive areas. They have also been used to fragment boulders in the mining and construction industries. However, to date, no study has investigated the applications of soundless chemical demolition on a large-scale in opencast mines. Therefore, this study evaluated whether soundless chemical demolition can break large volumes of in situ rock. This was done by conducting five trials using Nex-Pand soundless chemical demolition agents in four different surface mining sites. Trial 1 was unsuccessful as it was unable to break the rock due to the large confinement between the drilled holes and the use of a hole diameter that was 182% larger than recommended. Trial 2 was a success as it was able to fracture the rock with a crack width that reached 110 mm after 72 hours. Trial 3 generated cracks at the biggest hole diameter of 102 mm. The cracks developed and ceased to increase after 96 hours at a crack width of 100 mm. Trial 4 achieved the smallest crack width due to a very competent rock compared to the other sites. Trial 5 generated cracks at a slower rate than other trials because of the use of Nex-Pand powder at lower ambient temperatures than recommended. These trials proved that soundless chemical demolition agents can replace explosives in areas closer to sensitive infrastructure and communities. This will ultimately enable mines to unlock value and access deposits in these areas.

Jul 23, 2025

By Cz. Mora, A. Pawelczyk, D. Hreniak, P. Nowak, A. Dyonizy, S. Strek, W. Strek, K. Grabas, A. Ostrowski

Globalization and a growing demand for limited raw material resources have forced changes in the approach to the supply chain. This is particularly true in the case of rare earths, which are regarded as one of the most important development indicators of modern technologies. To ensure a secure supply of commodities, the European economies have been prompted to investigate REE recovery from sources which until recently, for technical or economic reasons, were considered not sufficiently attractive. An interesting example is apatite phosphogypsum waste dumps. The REE content in these waste dumps averages around 0.5-1 %. One of the most important phosphogypsum locations in Poland is the Lower Silesia region where a phosphoric acid Chemical Plant "Wizów" operated for several dozen years. In this work, rare earths are leached from the phosphogypsum crystalline structure by a chemical treatment and can then be separated into individual chemical compounds. The technology used in these recovery tests, matches up to a coherent European raw materials policy supporting effective management of resources and promoting waste materials recycling.

Jan 1, 2014

By F. Seitz

STAFF: Editor, Gerhard Derge Carnegie Institute of Technology Schenley Park Pittsburgh 13, Pa. Editorial Assistant, M. A. Redmerski Managing Editor, James J. Burke THE METALLURGICAL SOCIETY: John Chipman, President; W. R. Hibbard, Jr., Post-President; C. C. Long, Vice-President; T. D. Jones, Treasurer; R. W. Shearman, Secretary. PUBLICATIONS COMMITTEE OF THE METALLURGICAL SOCIETY: R. Maddin, Chairman; Dennis Carney, J. C. Fulton, J. H. Hollomon, T. B. King, C. C. Long, W. 0. Philbrook, J. D. Sullivan, David Swan, and F.L. Vogel. Review and selection of manuscripts is under the supervisian of the following Publications Committees: Extractive Metallurgy D ivis ion: T. 0. King, Chairman; S. J. Dick inson, R. P. Hermsdorf, R. Schuhmann, Jr., and H. H. Kel logg. Institute of Metals Division: F. L. Vogel, Choirmon; R. L. Smith, Vice Chairman; R.W. Balluffi, J. H. Bachtold, A Servi, C.D.Graham, Jr., C. G. Goetzel, F. E. Joumot, Jr., G. E. Pellissier, Paul Gordon, Jock Washburn, Harold Margol in, A. U. Seybolt, I. R. Kromer, R. A. Meussner, R. W. Guard, M. Harmon, J. N. Hobstetter, Dean Starr, P. Shewmon, R. Gordon, J. 0. Betterton, and E. Morgan. Iron and Steel Division: W. 0. Philbrook, Chairman; F. C. Langenberg, C. W. Sherman, J. Wagstaff, and E. J. Whittenberger. Published bimonthly by the American lnstitute of Mining, Metallurgical, and Petroleum Engineers, Inc., 29 West 39th Street, New York 18, N. Y. Telephone: PEnnsylvania 6-9220. Subscription $20 per year for non-AIME members in United States and North, South, and Central America; $25, foreign; $5 for AlME members. Single copies, $4.00, single copies foreign, $5.00. The AlME is not responsible for any statement made or opinion expressed in its publications . . . Copyright 1959 by the Americon Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. . . . Registered cable address, AlME New York ... Indexed in Engineering Index, Industrial Arts Index, and Chemical Abstracts . . .Second class postage paid at New York, N. Y. , ond Ann Arbor, Mich. Volume 215, Number 3

Jan 1, 1960

By J. Moore Samuel

THE prospective change in ore receipts at the Copper Queen reduction works necessitated a careful study of conditions to determine the most economical method of smelting. The first step, calculating the known, probable, and possible results, showed the economy of a unimetallurgical flow sheet f which the three pyrometallurgical stages would be roasting, reverberatory smelting, and converting. The past and future ore receipts (not including converter flux) are as follows: AVERAGE MONTHLY FUTURE MONTHLY RECEIPTS, 1918 RECEIPTS TONS PER PER CENT. OF TONS PER PER CENT. OF MONTH TOTAL RECEIPTS MONTH TOTAL RECEIPTS Ore 84,553 82.3 43,000 44.0 Gravity concentrates 16,375 15.9 25,500 26.0 Flotation concentrates 1,883 1.8 29,400 30.0 Total 102,811 100.0 97,900 100.0 Of the 102,811 tons per month received in 1918, only 28,945, or 28 per cent., was treated in the roasters and an average f 14.1 roasters out of 20 were in operation; the remaining ore was treated in the blast furnaces. The change to "all reverb." practice, therefore, called for considerable additional roaster capacity, which could be obtained either by building additional units, or by remodelling the present units so as to give increased unit capacity. In view of the progress in roasting practice since the construction of the Copper Queen roaster plant and the heavy investment in that roaster plant, the second plan seemed to be the more desirable. The Copper Queen roaster plant consisted of twenty six-hearth, McDougall roasters, 18 ft. in diameter, equipped with cast-iron arms that originally were water cooled but now are air cooled. They have no top dry hearth and the feed is discharged through the top arch, near its periphery, by plunger feeders from two bins at opposite sides of the roaster.

Jan 7, 1921

By J. H. Nixon

A three phase program evaluated commercial proximity warning devices, developed and designed a microprocessor-based electrostatic field measurement instrument, and utilized this instrument to investigate the electro-static fields about power lines. The Phase I program consisted of test and evaluation of these commercially available proximity devices. The evaluation results were reported in the Phase I report entitled ?Evaluation of Proximity Warning Devices? dated 22 February 1980. The Phase II program resulted in the design and development of a microprocessor-based Distributed Sensor A.C. Electrometer which measures the electrostatic field present at 17 discrete locations along a crane boom. Operator control of the measurement system allows simultaneous electric field measurements from 17 probes, print out of the electric fields measured, and data archiving on magnetic tape for post measurement analysis. Under the Phase III program, electrostatic fields around a crane boom were measured by the instrument at 17 high voltage power lines of various voltages and geometries. The electric field data was processed and plotted versus boom distance from the power line. Analysis of the electric field data indicate that the distances at which a single sensor alarm will activate, vary by a factor of 3 to 1. This is due primarily to variations in boom orientation. The results also indicate that in the case of multiple power lines, a single electrostatic field sensor cannot reliably be used to determine the distance from a power line.

Jan 1, 1982

By Robert L. de Beauchamp

The Bureau of Mines designed a chlorination apparatus to prepare CrCl2 free of CrCl3 by the direct reaction of chlorine and chromium. Equipment and procedures were developed for routine preparation of 25-pound batch quantities of anhydrous CrCl2. Calcium, iron, nickel, and silicon impurities were in the 0.01 to 0.05 percent range, and all other impurities were below 0.01 percent.

Jan 1, 1968

By R. B. Schluter

Magnetite pellets were simultaneously reduced and indurated on a laboratory scale in order to determine the effects of temperature, induration time, degree of metallization, and sulfur content upon the physical and chemical properties of prereduced pellets. The reductants were commercially-pure tank gases. Among the findings were these: 1,100° C is the minimum temperature that will produce acceptably hard pellets using carbon monoxide as the reduc-ing gas. Prolonged treatment time improves the pellets' crushing strength, but the rate of improvement falls off sharply after 2 hours' induration. At 1,120° C, 75-percent metallization produces the maximum crushing strength; there was no corresponding peak at 900° or 1,050° C. Sulfur in the furnace atmosphere lowers the required induration temperature. A few tenths of 1 percent sulfur in the pellet increases the sintering rate of metallic iron in pellets by forming a liquid FeS phase that facilitates iron transfer.

Jan 1, 1968

By J. P. W. Bennie, A. de Jong, G. M. Denton

Mintek together with Middelburg Steel & Alloys, developed the DC arc furnace process for the production of ferroalloys with the expressed objective of smelting ore fines (<1mm) without the need for agglomeration. In the case of ferrochrome production, the DC arc furnace, being a semi-open bath operation, loses radiant energy directly from the bath to the furnace roof and sidewalls above the melt. This energy loss is reflected in a higher electrical energy usage per ton of alloy than for a submerged-arc operation smelting lumpy ores or sintered pellets. The difference increases still further when pre-heated sintered pellet feed is used in a submerged-arc operation. This shortcoming of the DC arc furnace can however be overcome by preheating the feed to the furnace in a fluidized bed or flash reactor fuelled by cold furnace off-gas. In addition to fluidization and preheating testwork, various preheating flowsheets with associated mass and energy balances have been developed and compared from a techno-economic viewpoint. The three major advantages identified were: a) fluidized beds can preheat ores and fluxes up to 950°C without sticking and defluidizing, b) the open bath DC arc furnace does not require expensive coke or char to maintain the burden porosity and, c) the capital cost associated with the milling, pelletising and sintering plant falls away since ore fines are used directly.

Jan 1, 2004

By Clyde L. Holmberg, Paul Zinner

"INTRODUCTION In view of the large tonnage of low-grade iron ore and iron-bearing material known to exist at the western limits of the Gogebic range, the Bureau of Mines undertook an investigation of the area for the purpose of evaluating the iron-bearing formations as sources of iron for possible future utilization.After 6o years of exploration an, development on the Gogebic range, the area investigated by the Bureau represents the known western limit of direct-shipping ore mined from operations on the Gogebic range.An area about 2 miles in length between the villages of Pence and Iron Bolt in Iron County, Vic., was selected for investigation, and trenches wore excavated through the overburden and fully across the iron-bearing formation to obtain 108 bulk samples for beneficiation tests. Exhaustive tests involving gravity and flotation methods, magnetic separation, and magnetizing roasts followed by magnetic separation were conducted on the samples to determine the ammability of the individual formations and the entire iron-bearing zone to beneficiation.Empirical data on the character and mineral content of the formations arc tabulated herein, as well as the results of the beneficiation tests."

Dec 1, 1947

Brief descriptions of several types of unit pulverizeI&apos; are given and the functioning of the components that crush, carry, dry and classify the coal is considered. A distinction is drawn between pulverizers which crush particle beds and those .operating by free-crushing. The overall performance of pulverijlers is considered in terms of correlations between mill variables, coal grindability, abrasiveness, moisture and particle size. Brief discussioiJ. of the influence of pulverized fuel quality on boiler operation and of pulverizing costs concludes the paper.INTRODUCTIONModern coal pulverizers function as carriers of materials and as crushers, as dryers and as size classification machines and, thus, the unit pulverizer comprises. several components that normally function as separate apparatus. The controls of the unit pulverizer must have sufficient flexibility to accommodate rapid variations of boiler load or coal quality. Further, the machine must be robust, yet easy to maintain preferably at annual intervals-so that maintenance costs are small (for coal is a relatively cheap material). Usually, the full load of a modern pulverized-fuel fired boiler can be raised with one pulverizer off-line. All coals, from anthracites to brown coal, may be prepared as pulverized fuel (hereafter P.F.) .Each pulverizer of a direct-fired boiler has, broadly, to supply the burners with coal powdered so that about 80 per cent passes a 200 B.S. sieve and only a small proportion, less than about 10 per cent, remains on the 100 B.S. sieve. The classification processes must prevent any appreciable proportion of coarse particles in the P.F. and yet not return excessive proportions of &quot;finished&quot; fines. The quality of the P.F. should not vary greatly with output rates which may be anywhere between the maximum rate and one quarter ofthe maximum. The suspension of P.F. in the primary air...

Jan 1, 1957

By Gerald T. Homce

A system capable of monitoring mine electrical power systems and detecting impending component .failure could significantly improve power system safety and reduce unscheduled equipment downtime. Such monitoring would require a method of evaluating electrical parameters, calculated from terminal values, for indications of component deterioration. The U.S. Bureau of Mines has targeted electrical failure of squirrel cage induction motors and examined the use of mathematical models to aid in this evaluation. The initial stage of this work is complete, and has produced polynomial networks called adaptive learning networks (ALN&apos;s) that can detect and quantify winding insulation leakage simulated on laboratory motors. In this modeling process, empirical data from laboratory motors were used to select the electrical parameters most significant for assessing? motor conditions, and mathematical expressions relating these parameters to simulated deterioration were formed. ALN&apos;s developed thus far can process readily measured motor terminal information and quantify power and current levels of laboratory-simulated leakage to within 1% and 3% of full load values, respectively, for motors in the 10-to 150-hp size range. The next stage of this research is validation of these ALN&apos;s for actual motor failures; this stage is currently underway, using accelerated life testing of laboratory motors.

Jan 1, 2010