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By M. R. Shahan, C. E. Seaman, Mischler S. E., T. W. Beck

"Float dust deposits in coal mine return airways pose a risk in the event of a methane ignition. Controlling airborne dust prior to deposition in the return would make current rock dusting practices more effective and reduce the risk of coal-dust-fueled explosions. The goal of this U.S. National Institute for Occupational Safety and Health study is to determine the potential of open-air water sprays to reduce concentrations of airborne float coal dust, smaller than 75 µm in diameter, in longwall face airstreams. This study evaluated unconfined water sprays in a featureless tunnel ventilated at a typical longwall face velocity of 3.6 m/s (700 fpm). Experiments were conducted for two nozzle orientations and two water pressures for hollow cone, full cone, flat fan, air atomizing and hydraulic atomizing spray nozzles. Gravimetric samples show that airborne float dust removal efficiencies averaged 19.6 percent for all sprays under all conditions. The results indicate that the preferred spray nozzle should be operated at high fluid pressures to produce smaller droplets and move more air. These findings agree with past respirable dust control research, providing guidance on spray selection and spray array design in ongoing efforts to control airborne float dust over the entire longwall ventilated opening. IntroductionCoal mining processes produce airborne dust that naturally deposits on the floor, roof and ribs of mine airways. These fine dust particles, termed float coal dust when smaller than 75 µm in diameter, are deposited in the return entries of coal mines and can be reentrained by pressure waves induced by methane-air explosions (Rice et al., 1911; Nagy, 1981; U.S. National Institute for Occupational Safety and Health (NIOSH), 2006). These particles are also those most likely to participate in coal-dust-fueled explosions, which can potentiate and propagate explosions resulting in extensive damage. In order to meet compliance requirements of at least 80 percent incombustible content in the composition of material deposited in mine entries (U.S. Mine Safety and Health Administration (MSHA), 2016), coal mines apply an inerting agent, specifically, rock dust (Harris et al., 2009). Should methane be present in the mine atmosphere, the required fraction of incombustible content is further increased by 0.4 percent for each 0.1 percent methane. The removal of airborne float coal dust (AFCD) prior to deposition is an approach intended to make current rock dusting practices more effective by increasing the proportion of inert material to combustible material, resulting in a lower risk of coal-dust-fueled explosions."

Jan 1, 2018

By John Ward Smith

Dawsonite-bearing oil shale of Colorado's Green River formation offers a unique and vast (more than 5.9 Gt of A120 j) resource of easily extractable alumina. The processing methods required by the thermal reactions of dawsonite and its oil-shale carrier also require production of shale oil, soda ash, and nahcolite as marketable coproducts. These production methods are presented. The alumina production process is contrasted with the Bayer process to describe technical advantages of extraction of alumina from oil shale which may offset the problems associated with processing a relatively lean ore. While alumina production from oil shale requires development of new technology, the technical problems appear solvable. Only the political problems arising from the now onerous and completely unnecessary federal oil-shale withdrawal appear less solvable.

Jan 1, 1982

By L. K. Marshall

The importance of high quality underground mine ventilation is readily apparent. The principles of primary and auxiliary mine ventilation, however, are sometimes less readily apparent. The first article in this two-part series discusses some general aspects of primary and auxiliary ventilation. Next month's article will detail considerations involved with auxiliary mine ventilation.

Jan 1, 1982

By J. M. Kurtz

Ten Methane Monitoring Systems and Machine Control Circuits were examined and tested per the requirements in CFR Title 30, Parts 18 and 27, the Standard UL 913 and the document "Test Requirements For Instruments or Apparatus to be Considered for M.E.S.A. Intrinsically Safe Certification (Tentative)". The test results indicate that none of the products complied with all parts of all requirements as interpreted by Underwriters Laboratories Inc.

Jan 1, 1980

By William Escudero

El presente trabajo describe el planeamiento estratégico para el sostenimiento de la sociedad minera El Brocal a través de la gestión en el trabajo organizacional. Su principal objetivo es aumentar la productividad y la reducción de costos de minado y la planta concentradora. Para ello, se tomó el modelo de planeamiento estratégico desarrollado por Fred David y se realiza el análisis y diagnóstico interno de la empresa, a partir de los antecedentes, situación actual de la empresa, evaluación de la misión, objetivos actuales y cadena de valor de la empresa, luego se clasifica a la industria minera y se integra los resultados obtenidos, la matriz de evaluación del factor externo (EFE) y la matriz de evaluación del factor interno (EFI); para así elaborar la matriz (FODA) a partir de la cual se formula as estrategias por seguir. Finalmente, se redefine la misión de futura de SMEB y se ejecuta las estrategias y las acciones en las áreas funcionales.

Sep 13, 2001

By K L. Brown

In the Waiotapu geothermal area only Champagne Pool, 109 ng/L, and Waiotapu Geyser, 7.6 ng/L, have dissolved Au concentrations greater than 5 ng/L and most springs have concentrations less than 2 ng/L. When Au concentration data are combined with other physico-chemical data from each spring including; pH, reduced sulphur concentration and temperature, the degree of Au saturation can be calculated. All samples sites except Champagne Pool, Waiotapu Geyser and the Artists Palette are under-saturated with respect to Au(s) by 1 to 3 orders of magnitude. This indicates that adsorption or co-precipitation or both are important processes depositing Au beneath hot springs. Deposition of Au by adsorption or co-precipitation beneath hot springs implies that dissolved Au may not have to reach saturation concentrations for ore to deposit. This interpretation is supported by the presence of substantial Au as sub-microscopic components within sulphide minerals in ore deposits and indicates depositional efficiency beyond that possible through precipitation of Au(s).

Jan 1, 2004

By Victor V. Verbinski

This report presents the development of a raw coal concentration sensor for hydro-transport of coal and refuse (rock) from underground mines, and the results of an international test series carried out at the Colorado School of Mines Research Institute in Golden, Colorado, the U.S. Bureau of Mines, Hydraulic Transport Research Facility in Pittsburgh, Pennsylvania, Saskatchewan Research Facility in Saskatoon, Saskatchewan, Canada, and the Steinkohlenbergbauverein Test Facility in Essen, West Germany. Test results are presented for a three-component sensor and also for the more rugged two-component (all nuclear) sensor.

Jan 1, 1988

This publication summarizes, for potential contractors and all other interested parties, the research and development of in-house and contract projects programmed by the Bureau of Mines for fiscal year 1983 (October 1, 1982-September 30, 1983) under its Health and Safety Technology program. The objective of these projects is to provide an ordered and sequenced series of advance toward the Bureau's overall goal of providing the systems technology required to create a more healthful and safer working environment for the Nation's mining and minerals processing workers.

Jan 1, 1982

By Michael L. Boninger, Erik J. Wolf, Rory A. Cooper

Although wheelchair users are regularly subjected to whole-body vibrations little research has been conducted to assess these vibrations or attempt to reduce them [2,3,5]. Most of the wheelchair and whole-body vibration research done to this point has been conducted on manual wheelchairs. Van Sickle et al showed that manual wheelchair propulsion over a simulated road course produces vibration loads that exceed the ISO 2631-1 standards for the fatigue-decreased proficiency boundary at the seat of the wheelchair as well as the head of the user [6]. In a study by Boninger et al [1], 66% of wheelchair users reported neck pain since acquiring their wheelchair. One of the key reasons believed to be the cause of pain, was the exposure to whole-body vibration. Kwarciak et al [4] and Wolf et al [7] performed similar studies using two methods of analysis to evaluate vibrations on suspension and non-suspension wheelchairs while descending curbs of varying heights. Both studies revealed no significant difference in the abilities of the wheelchairs to reduce the amounts of vibrations transferred to the wheelchair user. Although the efforts of wheelchair companies to reduce the amounts of whole-body vibration transmitted to wheelchair users through the addition of suspension systems is encouraging, the technology is not yet ideal. Additionally, the research to date has focused on manual wheelchairs exclusively, while little attention has been shown to powered wheelchairs. Methods This study includes the use of two suspension electric powered wheelchairs: The Quickie S-626 and the Invacare 3G Torque SP Storm Series. Each subject tested all of the configurations of the suspension wheelchairs. These included the Invacare with suspension, the Quickie with suspension set to three settings (most stiff, least stiff, and 50% stiffness), and both wheelchairs with solid inserts to act as non-suspension wheelchairs. Sixteen able bodied subjects have been recruited for this study so far. In each of the configurations of the wheelchairs, the subjects traversed an Activities of Daily Living (ADL) course. Vibrations were collected from a tri-axial accelerometer attached to a seat plate beneath the cushion during driving over the activities course. A mixed model ANOVA was used to determine if there were differences between suspensions based on Vibration Dose Value (VDV). Results Statistical analyses of the VDV data revealed significant differences between the six different suspensions over each of the obstacles in the activities of daily living course. Post-hoc analyses revealed that for each of the obstacles, significant differences existed between the Invacare suspension and the Invacare solid insert. For the Quickie power wheelchair the solid insert setting was not significantly different from the most-stiff setting for each of the obstacles

Jan 6, 2006

Develop a mobile manipulator that one person can use to lift and maneuver 50- to 600-pound loads. It can be used in maintenance shops and mines to reduce lifting accidents (Figure 1 and 2). Background Lifting heavy items is one of the leading causes of injury in the workplace. Mine Safety and Health Administration statistics showed that, in 2004, back injuries accounted for over 20% of all injuries (1,699 cases) and resulted in 110,000 lost days of work. Forty-one percent of those injuries resulted from materials-handling or maintenance activities.1 In addition to back injuries, lifting injuries include hernias, ruptures, sprains, and strains resulting from losing control of the item being lifted. Factors associated with accidents are weight of the item being lifted, awkward postures, inadequate handholds, and the working environment itself. High accident rates were noted when lifting items that ranged from 50 to 600 pounds, particularly in tight working quarters where maneuverability was critical. Research indicated that a mobile lifting arm would eliminate many lifting accidents in environments where other lifting devices (fork lifts, overhead cranes, mobile A-frames) would not be practical. NIOSH has built a first-generation mobile manipulator unit designed to be used on hard, level floors such as in a shop. The complexity of motion, number of moving parts, compact design, and design constraints of the manipulator required advanced computer-aided design work (Figure 3). As a result of the design work, thirty-eight claims are included in the patent applications. NIOSH will be conducting field trails and working with manufacturers to put the manipulator into industrial use.

Dec 1, 2006

By M. Kuchta, A. Newman

LKAB’s Kiruna Mine, located above the Arctic Circle in northern Sweden, is the second-largest underground mine in the world today. The orebody is a world-class high-grade magnetite deposit, from which three raw ore products are extracted. We use mixed integer programming to determine a production schedule, i.e., which production blocks to mine, and when to start mining them, so as to minimize deviation from planned production quantities while adhering to the operational constraints of the mine. The resulting model contains thousands of binary variables and a commensurate number of constraints, precluding us from obtaining a schedule in a reasonable amount of time. We describe a method that builds on prior, related work, to expedite solution time. Keywords: underground mining, production planning, optimization, integer programming

Jan 1, 2003

By W. F. Riggs

1 Flotation Analogy To explain flotation in simpler terms the following analogy will be used. A factory (the flotation cell) manufactures a product (collector coated mineral). The product (collector coated mineral) is transported to market (the launder). A truck (the frother) is used to transport the product (collector coated mineral) to the market (the launder). The truck (the frother) transports the product over a road (the froth bed). The truck (the frother) and product (collector coated mineral) are supported by tires (the air). 2 Assumptions This operating philosophy assumes that the correct collector dosage is present along with the correct particle size distribution, pH conditions, etc. and that the minimum required frother dosage is correct. 3 Collector Addition The collector addition as used at a flotation plant is based on dosage rate as determined by the amount of mineral value entering the concentrator. Collector is normally added at two points in the concentrator: The primary flotation circuit and staged addition in the rougher scavenger circuit. Surveys have shown that the staged collector addition provides an increase in the kinetics and increases the recovery of the valued mineral in the rougher scavenger circuit. 4 Frother 4.1 Frother Dosage As explained in the above analogy, frother can be likened to the truck that transports the product (collector coated mineral) to market (the launder). Just as you would not use a truck rated at 15 tonnes to transport a 20 tonne load, you cannot expect to transport coarse minerals to the launder when there is insufficient frother present. Frother dosage must always be at, or above the minimum target. If less frother than the required minimum is used, then coarse mineral particles will not be supported and transported to launder where the mineral is recovered. To the naked eye the froth characteristics, even when insufficient frother is used, will appear to be correct. You cannot see the coarse particles that are not being recovered in the froth. (See Section 4.2 below for an explanation of why this occurs.)

Jan 1, 2006

By McHenry Mosier

Mechanical loading, adopted long ago in open-pit, coal, and non-metal mines, was not used extensively in underground metal mines until the World War. In less than a decade it became standard practice in underground work in many mining districts. In 1924 the Missouri School of Mines and Metallurgy, in cooperation with the Federal Bureau of Mines, published a bulletin entitled "Mechanical Underground Loading in Metal Mines," which was prepared by Charles E. van Barneveld, mining engineer, Bureau of Mines.

Jan 1, 1940

By Rodney D. Lamond

The need for blast vibration monitoring can be attributed to a combination of three factors: Structural damage, Blast design and Human annoyance. Traditionally, vibration damage criteria are prescribed in terms of peak particle velocity (PPV), as measured or predicted in the ground surrounding a blast. The PPV in the vicinity of a blasthole is strongly influenced by the quantity of the explosive per delay. In general, the existing prediction models give reliable results but fall short of addressing the change in PPV when the charge is decoupled and/or distributed.

Jan 1, 1995

By E. L. Singleton

The Bureau of Mines investigated extraction of aluminum from aluminum-silicon alloys as a means of utilizing domestic aluminum silicate ores for aluminum production. Aluminum was extracted from aluminum-silicon alloys by electrolysis in molten electrolytes of NaCl-KCI-AIC13 and NaCl-KCI-AIF3 in a laboratory-scale cell. Six alloys with aluminum contents ranging from 20 to 87 percent aluminum were tested, and aluminum products of primary grade or better were obtained. More than 80 percent of the aluminum was recovered with current efficiencies as high as 91 percent. Recovery of a metallurgical-grade silicon product from the anode residue by an acid leaching procedure was possible with the 50-50 and 65-35 Al-Si alloys.

Jan 1, 1972

By L. G. Marshall

This report is one of a series published by the Federal Bureau of Mines, describing mining methods and performance at individual mining operations throughout the United States. The objective of these papers is to promote development and conservation of our mineral resources by disseminating reliable technological information on mining methods, practices, and performance. Limestone deposits in Iowa are extensive and reserves are large. Most of the past production came from the eastern third of the state, although over half of the counties in the state have produced, or are now producing limestone. The stone is used as aggregate, road metal, agricultural lime, riprap, fluxing stone, railroad ballast, and in the manufacture of cement and lime.

Jan 1, 1962

By Karl Zipf

In highwall mining, once a sufficient number of web pillars are developed, they can fail catastrophically in a domino-type failure, posing a safety hazard to highwall miners and sterilizing mineable reserves. Three recent case histories of catastrophic web pillar failure in U.S. and Australian mines are documented and analyzed with two design approaches. The conventional design approach uses only a strength criterion, while the postfailure design approach uses both strength and stability criteria to insure an acceptable failure mode should strength failure occur. Catastrophic highwall web pillar failures can cost money through equipment losses, production losses, coal reserve sterilization and lost opportunity costs. Coal recovery may be higher. but the benefits of higher recovery must balance the potential costs of failure. Application of the conventional or postfailure design approach will decrease coal recovery and revenues, but the risk of potentially costly failure is much less.

Jan 1, 1999

By L. C. IlsLey

The increasing use of Diesel engines for operating equipment on trunk-line railroads and for power-plant units has stimulated interest in the use of Diesel engines for other lines of work, among which is the possibility of substituting Diesel locomotives for trolley locomotives for mines. The possibility of developing Diesel locomotives for duty in American mines is not as remote as it might seem, particularly in view of the fact that locomotives of this type are already used in considerable numbers in European mines. A study of Diesel locomotives in Europe is contained in Report of Investigations 3320, Diesel Mine Locomotives - Development and Use in European Coal Mines, by George S. Rice and F. E. Harris.

Jan 1, 1938

By Paul E. Rosten

This paper describes some of the latest improvements that have been incorporated or planned by the Cleveland-Cliffs Iron Company to reduce operating costs and improve pellet quality. The Cleveland-Cliffs Iron Company operates and manages mining, beneficiation, and pelletizing operations in Michigan, Canada, and Western Australia. This paper deals with the grate-kiln pelletizing operations at Republic, Humboldt, Tilden, Empire, and Pioneer in Michigan, and the Adams and Sherman in Ontario, Canada. Table I characterizes .each operation in regard to location, ore type, pellet capacity and date that pellets were first produced. All of the operations with the exception of Pioneer and Tilden, utilize downdraft-two-pass grate cycles of drying followed by preheating. Pioneer utilizes an all-downdraft, three-pass grate cycle which consists of three drying zones followed by the preheat zone. The Pioneer and Tilden cycles have been described previously. (1) (2)(3) Tilden utilizes a three-pass grate cycle with a stage of updraft drying, followed by two downdraft drying stages. Recuperation systems which supply hot gases to a drying zone from second stage cooling were designed and furnished for Tilden I. Tilden II will be identical. Empire IV will also be furnished with a recuperation system. The Adams grate-kiln system was retrofitted with a recuperation system. This paper will summarize some of the efforts that are in effect or planned for grate-kiln pelletizing systems to (1) reduce operating and maintenance costs, (2) reduce energy requirements, (3) improve product quality, and (4) meet environmental standards.

Jan 1, 1977

By René Fernández

Newmont Mining Corporation has been processing refractory gold ore by roasting since January 1995. The ore is refractory due to the association of the gold with iron sulfides, namely pyrite and marcasite, and the presence of carbonaceous components and is oxidized in an oxygen-enriched gaseous atmosphere. The structural characteristics of the calcine have a strong influence on the eventual recovery of gold by cyanidation. These characteristics are strongly dependent upon the roasting conditions, mainly the roasting temperature.

Aug 25, 2002