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By Douglas W. Fuerstenau

A detailed experimental study of breakage kinetics in a batch rod mill indicates that while the system is inherently nonlinear, the feed disappearance kinetics for the finer sizes and the coarser sizes at high holdups is well represented by first-order behavior. The set of breakage distribution functions was found to be normalizable and independent of particle holdup in the mill. The size discretized initial breakage rate functions were found to be inversely proportional to particle holdup and almost directly proportional to particle size. A linearized grinding model that results from the first-order Taylor's series expansion of the breakage rate expression was found to give good simulations of the mill product size distributions without recourse to any parameter improvement routines. Material transport through rod mills was evaluated by investigating the effect of operating variables on the holdup and residence time distribution of particulate solids flowing through the mill. Identical experiments performed in a continuous ball mill helped delineate the fundamental differences in particulate transport through these two types of mills. Mechanistic interpretations of the observed transport phenomena are presented, and their implications in the context of tumbling mill analysis and design pointed out.

Jan 1, 1980

By Kenneth L. Cashdollar

The Mine Safety and Health Administration (MSHA) and the West Virginia Office of Miners? Health, Safety, and Training (WVOMHS&T) investigated the explosion at the Sago Mine in West Virginia, which occurred on January 2, 2006, and resulted in 12 fatalities. As part of the investigation, the agencies requested that the National Institute for Occupational Safety and Health?s (NIOSH) Pittsburgh Research Laboratory evaluate the effects of explosions on specific mine ventilation seals and other structures and objects at its Lake Lynn Experimental Mine (LLEM). The results of the LLEM study would assist MSHA and WVOMHS&T in a more thorough understanding of the various questions that arose during their investigations of the explosion. Six large-scale explosion tests were conducted in the LLEM from April to October 2006. The protocols for these tests, and in particular the procedures for constructing various Omega block seals, were developed mainly by MSHA and WVOMHS&T. NIOSH developed the experimental procedures at the LLEM that would provide the required range of explosion pressures against the seals. Three 40-in-thick seal designs using Omega 384 low-density block were constructed in the LLEM and exposed to various explosion pressures. These seal designs are referred to in this report as the ?2001 design,? the ?hybrid design,? and the ?Sago design.? The 2001-design Omega block seal (80 in high) located in crosscut 2 of the LLEM survived all six explosions, with pressure loadings up to 51 psi. The 2001-design Omega block seal (88 in high) in C-drift was destroyed during Test 2, which subjected the seal to a head-on explosion that resulted in a pressure loading of 51 psi. The height difference between the two seals and the orientation of each seal to the explosion were contributing factors. The higher seal would be weaker for the same seal thickness. The hybrid Omega block seal in crosscut 3 survived an explosion at a pressure loading of 25 psi and failed during another explosion at a pressure loading of 39 psi at the seal. Based on these tests, it seems that the hybrid seal design is weaker than the 2001 seal design. The Sago Omega block seals were constructed in crosscut 3 and C-drift before Test 3. The crosscut 3 seal survived a pressure loading of 18 psi and was destroyed during an explosion at a pressure loading of 35 psi at the seal. The C-drift seal survived a head-on explosion that resulted in a pressure loading of 21 psi and was destroyed during an explosion with a pressure loading of 57 psi at the seal. Based on these LLEM tests, it seems that the Sago seal design is weaker than the 2001 seal design, yet it still complied with the requirements of 30 CFR 75.335(a)(2) that were in effect at the time of the mine disaster. During these LLEM explosion tests, the distance of seal debris travel was also measured. In Test 5, the C-drift seal was destroyed during a head-on explosion that resulted in a pressure loading of 57 psi, and the seal debris was thrown over 500 ft. In Test 6, the C-drift seal was destroyed during a head-on explosion that resulted in a pressure loading of 93 psi, and the Omega block debris was thrown over 900 ft. During these tests, the explosion pressure effects on other structures and objects were also documented. Unless otherwise specified, all of the pressure data listed in this report represent the highest recorded smoothed (averaged over 10 ms) explosion pressure loadings. The information in this report was used by MSHA and WVOMHS&T as supporting data in their analyses and investigative reports of the Sago Mine explosion.

Sep 1, 2009

By C. E. Brechtel

A testing program was conducted to design a cemented backfill fur hydraulic placement in underhand cut and fill mining of a steeply dipping coal seam. The testing evaluated the use of three different backfill aggregates, locally available at the coal mine, with Portland cement and five different pozzolans, including a Class F fly ash, a Class C fly ash, a cement kiln dust and ground smelter slag. Both viscosity and uniaxial compressive strength of backfill mixtures with different pozzolan and Portland cement contents were used to evaluate their suitability. Based upon the results of preliminary testing, an optimum mixture of alluvial sand with six percent Portland cement and ten percent Class F pozzolan was chosen for further compression testing.

Jan 1, 1985

By Thomas J. Peters

The Snowbank study area, which had been proposed as Wilderness, lies about 5 air mi southwest of Cascade, Idaho, and about 60 air mi north of Boise. The eastern boundary of the north-south-elongate study area lies 1-to 2-mi east of Cascade Reservoir; the western boundary is contiguous, in part, with the western boundary of Valley county. The 8,200-acre study area is underlain by Cretaceous granitoid rocks of the Idaho batholith. Three prospects were found in or near the study area during a library and field search. Gold occurs at one 30-ft adit, but the gold-bearing structure appeared too narrow to contain resources. Two other prospects appeared essentially unmineralized. No evidence of geothermal activity was observed. Rock in the area is not potentially useful as dimension stone because it does not split into flat slabs. To be used as aggregate, the rock would require crushing and hauling to distant markets. One of 18 alluvium concentrate (placer) samples contained free gold, worth $1.07 per cubic yard of gravel (at a $350 per oz gold price). No alluvial bars were seen; deposits were too small to contain gold resources or be considered gravel resources.

Jan 1, 1993

By John A. Organiscak

The Bureau of Mines conducted a survey of eight shearer longwall operations to identify factors that affect respirable dust generation from longwall roof supports. The longwalls surveyed were in coal seams located in different geographic regions of the United States. Data were collected on mining (geologic) conditions, support design, operational characteristics, and amount of respirable dust generated from roof supports. Analysis indicated that mining conditions are the main factors that affect the generation of dust during roof support movement. Both roof strength and depth of cover above the coal seam showed relationships with the amount of support dust generated. Several practices are currently employed to effectively control roof support dust; however, some of these controls are limited. More research and development is needed to improve dust control technology for longwall roof supports.

Jan 1, 1985

By R. J. Traube

The purpose of the Inherently Safe Mining System (ISMS) project is to develop continuous and conventional coal mining equipment and systems which will reduce the incidence of fatal and nonfatal accidents in the working sections of underground bituminous coal mines by application of existing technology. This 3-year program, initiated on 18 June 1971, is being conducted in three phases: ? PHASE I (8 months) Systems Analysis Concept Design Planning ? PHASE 11 (16 months) Design Procurement Manufacture Preliminary Testing ? PHASE III (12 months) Underground Coal Production Demonstration.

Jan 1, 1972

By I. L. Nichols

The inplace cyanidation leaching of gold from placer deposits is a potential method for treating gravels too deeply buried and too low in gold content to be processed economically by conventional dredging methods. Laboratory experiments were made to evaluate those placer cyanidation factors adaptable to small-scale studies. The variables investigated included gold particle size and location in sand beds, cyanide solution flow rate, and cyanide solution strength as factors affecting gold solubility rates. The solution flow rate, in turn, was influenced by variables such as bed slope, solution head pressure, and sand size, and the effects of these factors were studied. Free gold, minus 150-mesh and finer in size, is rapidly dissolved by dilute cyanide solutions from mixtures of gold and silica sand prepared to simulate placer deposits. About 94 percent of minus 325-mesh free gold was extracted in 5 hours from silica sand mixtures, and 94 percent extraction of minus 150-mesh gold was obtained in 21 hours with 0.1 percent NaCN solutions. Moving solutions were almost twice as effective in leaching free gold from silica sand mixtures than stagnant solutions.

Jan 1, 1971

By B. J. Moore

This publication contains analyses and related source data for 675 natural gas samples from wells and pipelines in 24 States and 5 foreign countries. The samples obtained and analyzed during calendar year 1980 are included in tables 1-4. Those samples included in tables 5-7 were collected during the years 1960 through 1979. However, permission to publish the analyses of those samples was not given until the past year when the operators were again contacted to seek release of the information. All of these samples were collected as a part of Bureau of Mines investigations of the occurrences of helium in natural gases of countries with free market economies. This survey has been conducted in the United States by the Bureau of Mines since 1917. In late 1965, the survey was expanded to include foreign gasfields. The analyses published herein were made by mass spectrometer and a special helium analysis apparatus, which are described in Bureau of Mines Bulletins 4862 and 576. The results of the investigation of the occurrences of helium are published annually to make the information available as soon as possible to the gas industry and the general public. Twenty-two previous publications have presented the results of 12,152 gas analyses made prior to 1980. The first three, Bulletins 486,' 576,5 and 617,6 contain analyses and related source data on 5,218 gas samples collected from 1917 through 1980. The other

Jan 1, 1981

By R. B. Stotelmeyer

Mineral resources, or a potential for their discovery, occur at 34 localities in the Glacier Peak Wilderness and adjacent areas of the north Cascade Range of Washington (see plate). Eighteen of the mineral deposits are in the established Wilderness, four are in or partly in contiguous RARE II (Roadless Area Review and Evaluation) lands recommended by the Forest Service for addition to the Wilderness (A, D and G6031.), three are in adjacent RARE II lands excluded from wilderness consideration, and nine are in nearby roaded areas excluded from the RARE II inventory. Mineral commodities that might be produced from the Wilderness and recommended additions are gold, silver, copper, lead, zinc, molybdenum, arsenic, cadmium, tungsten, cobalt, limestone (marble), pumice, and volcanic cinders. Mineral production from adjacent lands might include most of these commodities, plus antimony, decorative stone, pyrite, silica, and garnet.

Jan 1, 1982

By L. R. Burdick, J. F. Barkley

"The agglomerating index of coal is an index based upon the nature of the coke residue left when the standard volatile-matter determination of the well-known proximate analysis is made. In this determination a small amount of coal is heated in a container to about 950° C. (1,742° F.), at which temperature the volatile matter is driven off, leaving a coke formation. The coke residues for various coals are quite different in physical structure: and, for some time past, work has been done on studies of the nature of these residues in connection with the coking of coal. In 1934 Gilmore, Connell, and Nicolls proposed use of the agglomerating index for indicating the dividing line between noncaking coals and those having weakly caking properties. 4/ Its use was adopted in the standard classification of coals by rank as a requisite physical property index to differentiate semianthracite from low-volatile bituminous coal and also high-volatile ""C"" bituminous from subbituminous ""A"" coal, as shown in table 1, the standard coal classification adopted by the American Society for Testing Materials and the American Standards Association. 5./In studying the agglomerating properties of coals based on the coke residue the Bureau of Mines has adopted the notation given in table 2. Coals that in the volatile-matter determination give a coke residue either in the form of an agglomerate button that will support a 500-gram weight without pulverizing or a button that shows swelling or cell structure are considered to be agglomerating."

Nov 1, 1938

By R. E. Zane

The Northwest Experiment Station of the Bureau of :,!in-s, in cooperation with the College of Mines, University of Washington, has completed a detailed investigation-of the physical and chemical properties of western cokes made or used in the Pacific Northwest, as evaluated by standard methods./ One of the properties determined, to which more or less importance has been attached, was reactivity5/ or combustibility. As no standardized procedure is available, it was necessary to develop a workable method for evaluating this property. The combustibility of coke is usually measured by the formation of carbon dioxide with time at a particular temperature or by the reduction of carbon dioxide to carbon monoxide. Analysis of the resulting gases commonly is required to evaluate the result. The method described in this paper is simple and direct in that the sample of coke or other carbonaceous material is weighed as it burns; the loss in weight and time is indicated by a balance and clock arrangement. Gas analyses are not required. Methods similar in principle have been used by Tu, Davis, and Hottel6/ and by Oshima and Fukuda7/ for determining the combustion rate of carbon and for studying the effect of ash on combustion characteristics. Both methods are more elaborate in procedure and apparatus required than that described here. Briefly, the method comprises burning a sample of coarsely grained coke or

Jan 1, 1940

By John Nagy

Dust explosion data obtained in laboratory studies by the Bureau of Mines are presented for activated carbon, asphalt, charcoal, carbon black, coal, coke, gilsonite, graphite, lignite, miscellaneous carbons, pitch, tunnel dust, and mixtures of these materials with other ingredients. The explosion hazard is shown to increase as the volatile content of the dusts increases.

Jan 1, 1965

By F. A. Rutledge

The Batesville district in north central Arkansas is one of the important sources of manganese ore and ferruginous manganese ore in the United States, with a history of production dating back to 1849. From studies by the Federal Geological Survey, it was recognized that the district probably still contains substantial reserves of low-grade ore. It was natural, therefore, that the deposits in this area should be among the first investigated by the Bureau of Mines under the Strategic Materials Act of June 1939, by which the Bureau was authorized to explore domestic deposits of strategic minerals, at that time designated as those of antimony, chromium, manganese, mercury, nickel, tin, and tungsten. The field work of the Bureau of Mines in the Batesville district was done in two distinct phases. Under project 308, active from August 1940 to June 1941, carbonate-oxide ores were investigated at five separate areas in which 100 trenches, test pits, shafts, and edits aggregating 4,364 linear feet were excavated and 839 samples were taken and assayed. Under project 323, in progress from February 1941 to January 1942, wad deposits were explored at 10 separate areas by 408 prospect shafts, churn-drill holes, and bucket-drill holes aggregating 23,680 linear feet from which 285 samples were taken and assayed. Processes for beneficiating the wad ores were investigated at ore-testing laboratories of the Bureau of Mines.

Jan 1, 1952

By F. D. Stevenson

Thermodynamic properties of metal halides and, in particular, vapor pressures have become of great importance in recent years owing to increased application of chemical processing to extraction of metals from their ores. Vapor pressure data serve not only as a valuable source of latent heat of vaporization and fusion values but also differences in metal-halide vapor pressures often provide the basis for their separation by conventional mass transfer operations. This literature search was made to provide a ready reference to experimental vapor-pressure data of metal halides and oxyhalides. Results are reported in two main sections: (1) A tabulation of vapor- pressure references for each of the metal halides (listed by metal) for which actual experimental data are reported (table 1), and (2) a bibliography of the citations. Metal halides and oxyhalides are listed by chemical formula and chemical name, based on the stock4 system. To facilitate location of the references, a listing of the journal titles and their abbreviations follows the bibliography.

Jan 1, 1963

By A. E. Harak

To determine the retorting characteristics of a column of mine-run, ungraded oil shale ranging in size from fines to 5-ton pieces, a 150-ton batch-type retort was designed and constructed at the Bureau of Mines Laramie Energy Research Center, Laramie, Wyo. The retort vessel is 45 feet high by 11 ½ feet inside diameter, and is supported in a 95-foot-high steel superstructure. Mine-run shale from the Bureau of Mines facility near Rifle, Colo., assaying about 25 gallons of oil per ton, was used as the test shale. To date, 11 runs have been completed, and the results of the last 10 of these are reported. The effects of oxygen content of the retorting gas and the superficial gas velocity of the retorting gas on oil recovery from a column of mine-run oil shale were studied. In one run, the average particle size of the shale was substantially increased to determine its effect on oil yield. Oil recoveries ranged from a low of 39.3 to a high of 65.8 volume-percent of Fischer assay.

Jan 1, 1974

By Launa G. Mallett, Charles Vaught, Dana C. Reinke, Lisa J. Steiner, Lynn L. Rethi, Kathleen M. Kowalski-Trakofler, Jr. Brnich, William J. Wiehagen

Safety and health professionals recognize that training is a critical element of any effective safety and health program. An extensive literature survey has led the authors to conclude that we are at the beginning of a revolution in training due to changes in the demographics of the workforce, the rapid growth of technology, and the universal ascendance of the information age. Of present major concern in the mining industry is how to provide appropriate training for an aging workforce and concurrently develop training for the expected influx of new and less experienced miners as older workers retire. This report explores the key issues in the changing safety and health training area as identified by the multidisciplinary team of NIOSH researchers who conducted the literature survey. Issues include generational differences between newer mine workers and the present workforce with respect to their physical, psychological, social, and cultural characteristics; their learning styles and work expectations; and the impact of technology. Some preliminary conclusions are offered for future training needs.

Jul 1, 2004

By S. H. Lorain

This paper is one of a series on mining methods and costs being published by the U. S. Bureau of Mines. The operations of the Quartz Hill Mining Co., near Dewey, Mont., afford an interesting example of the cost of mining small bodies of direct shipping ore; they also illustrate the effect of the unavoidable periods of unusually high exploration and development costs in this type of mining upon the cost per ton of producing ore. The importance of skilled geological guidance and the necessity of avoiding unnecessary overhead and capital expense at small mines are shown. Operating conditions at Quartz Hill are typical of those in many other mining districts of southwestern Montana. It is believed that the costs presented here may be of value in the preliminary estimation of costs to be expected by conservative operators under similar conditions elsewhere. The information contained in this paper was obtained during a visit to the Quartz Hill mine in August 1936.

Jan 1, 1937

This work presents: 1.) the results obtained from measurements of temperature profiles in pillars and at working faces of three coal mines located in Colorado and New Mexico, 2) a comparison of the experimental results with theoretical predictors based on linear heat flow models, and 3) temperature profile predictions based on a two dimensional coal mine model with an inclined crack located in the roof or wall of the opening. The thermal properties of the coal and shale samples taken from the mines were used as input data for the computer model. Good agreement was found between the measured profiles and the theoretical values obtained with the one dimensional model. The two dimensional model results show that a visible crack (0.01-0.07-ft thick) in a coal roof causes a surface temperature difference from 0.2 to 1°F at the edge of the crack for rock exposed to air from 1 hr to 288 hrs and with the air to rock temperature differences from 2°-6°F. A temperature difference of 0.3 °F was found between solid and broken rock in a shale roof with a 0.03-ft thick crack inclined 45° to the horizontal after a ventilating time of 48 hrs and the air to rock temperature difference of 2.1°F.

Jan 1, 1972

By David A. Summers

The use of high pressure fluid cavitation is investigated as a means of breaking an ore into its constituent grains. This Cavitational Rock Dissagregation (CRD) is found to be possible and effective in breaking down galena ore, both in sandstone and dolomite host material. The technique did not work as well in comminuting and cleaning oil shale, because the cavitation drove the oil into emulsion with the water. The presence of dominant bedding in the rock also caused preferential breakage to these lines, rather than to the individual grain boundaries. This problem was also encountered in tests on igneous ore where weakness plants of the overall ore proved weaker than the boundaries of the individual grains. It was found that the prevailing expression of cavitation erosion dependence on pressure was not absolutely valid. In contrast it was found that CRD is much more sensitive to jet flow diameter, and when this was recognized it was found possible to erode rock with compressive strength of up to 350 MPa with operating jet pressures of 10 MPa.

Jan 1, 1982

By Laurance L. Oden, Jack C. White, Alan D. Hartman

The U.S. Bureau of Mines, under a Memorandum of Agreement with the American Society of Mechanical Engineers (ASME), established design criteria for a facility to field residues from municipal waste combustion. This facility, which is available to potential users on a cost-sharing basis, is also applicable to a variety of inorganic waste materials from smelting or melting operations. The design consists of a mechanical feed handling system, electric arc melting furnace, fume-off gas handling system, and thermal oxidizer for final off gas treatment. Screw conveyors and a bucket elevator deliver up to 2,000 Ib/h of minus I-in material to a three-phase electric arc melting furnace. This unique 800-kVe A furnace has a water-cooled shell and roof to minimize interaction of the melt with the refractory lining. The volume of the hearth below the slag taphole is approximately 1.2 st of steel. The furnace is sealed, allowing atmosphere control within the furnace and fume duct by nitrogen or inert gas injection. A jet-pulsed baghouse removes particulate from the off gas and serves as an acid gas scrubber. The clean off gas is heated to 1,800' F for 1 s in a propane-fired thermal oxidizer before being vented to the atmosphere.

Jan 1, 1993