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By Sabri Ergun

Previous studies of magnetic separation of pyrite from coals have been reviewed critically. Magnetic susceptibilities of United States coals of differing rank have been measured. The effects of crushing, magnetic mixing, drying, weathering, and heat treatment on the enhancement of the magnetism of pyrite have been analyzed. The importance of size distribution of pyrite in the coal and the necessity of crushing to liberate the pyrite has been discussed. It has been found that the inherent susceptibilities of the carbonaceous, mineral-free portions of coals (? -0.5 X 10-6 in cgs units) and of relatively pure pyrite isolated from coals (? -0.3 X 10-6) do not permit efficient separation of pyrite from coal; the average susceptibility of the magnetic fraction of coal must be raised to 3 X 10-6. Friction forces encountered in crushing sedimentary pyrite embedded in coal do not increase its susceptibility. Subsequent weathering or heat treatment below 400° C leads to the formation of iron sulfate and hence increases the effective paramagnetism of pyrite. Ferromagnetic compounds of iron are not formed in significant quantities at temperatures below 400° C. The degree of liberation and apparent susceptibility of pyrite are the most important parameters in its separation. It is concluded that effective beneficiation of coals can be achieved by magnetic separation. A sufficient increase in the susceptibility can be achieved by converting less than 0.1 percent of pyrite into ferromagnetic compounds of iron. Such conversions occur only at temperatures >500° C. An investigation of the dielectric properties of coals and pyrite in the frequency range 0.1 to 60 Mhz indicates that the imaginary dielectric constant of the pyrite is about 100 times larger than that of coal. Exploratory experiments indicate that pyrite can be selectively heated to temperatures above 500° C without appreciable rise in the temperature of coal. It appears that dielectric heating of coals in the Ghz frequency range is the most feasible method of enhancing the paramagnetism of pyrite.

Jan 1, 1968

By Oliver Bowles

Accidental explosions in coal mines are due to various causes, but many of them can be directly attributed to coal dust; others that probably in no way depend on dust as a primary cause are propagated, greatly intensified, and made more disastrous by the presence of coal dust. The fact that coal dust in a bituminous mine will explode as a result of a fire-damp explosion has been generally accepted for many years, but the belief has also been held by many that coal dust is not in itself dangerous when unmixed with an explosive gas. Therefore, in past years little attention was given to dust in mines free from fire damp, and many disastrous explosions have resulted from lack of knowledge of the danger from coal dust. In the explosives gallery and experimental mine of the Bureau of Mines experiment station, Pittsburgh, Pa., it has been proved repeatedly and conclusively that coal dust will explode violently when no inflammable gas is present. PROPAGATION OF DUST EXPLOSIONS A coal-dust explosion is an extremely rapid burning or combustion of the coal particles. Their burning consists essentially of the combination of the hydrocarbons in the coal with the oxygen of the air, a process that generates heat and flame and produces hot gases and water vapor. These gases and vapors have a volume many times that of the original coal particles; thus they exert an outward motion and pressure which constitute the explosive wave. When fine particles of coal are suspended in the air, each particle is surrounded by the oxygen of the air, and thus is well placed to oxidize or burn rapidly whenever the temperature is high enough. If some particles are ignited from any cause they will fire others, and the combustion will extend from particle to particle with extreme rapidity wherever enough coal dust of sufficient purity is present.

Jan 1, 1925

By H. H. Fields, Stephen Krickovic, M. G. Zabetakis, Albert Sainato

The Bureau of Mines is in the process of degasifying a virgin area in northern West Virginia from the base of an 839-foot -deep vertical borehole. An in situ gas pressure hole 199 feet long, and seven degasification holes ranging in depth from 500 to 850 feet (average 618 feet) were drilled in an 8-foot-thick virgin Pittsburgh coalbed from the enlarged (14-foot-diameter) bottom of this borehole. The in situ pressure at the back end of the hole and the range of gas and water flows from degasification holes as they were completed and closed off were 203 psi, 79,000 to 257,000 cfd (average 160,000 cfd), and 5 to 8 gpm per hole (average 6.8 gpm), respectively. Twenty-four hours after the seven holes were connected through individual water traps to a common collector for natural venting of the gas through pipes to the atmosphere, the total gas and water flows and the in situ pressure dropped, respectively, to 971,000 cfd, 1.3 gpm, and 18 psi. Eighty days later the corresponding values dropped to 529,000 cfd, 0.50 gpm, and 13 psi. After 180 days of degasification, 91 million cubic feet of gas had been removed from the affected virgin area. This represents 60 to 70 percent of the gas calculated to be contained in the area of coal affected by the holes.

Jan 1, 1973

By C. K. Rose

A hydraulic scaling rig was placed in operation at the Bureau of Mines oil-shale mine near Rifle, Colo., in 1953. The rig consists of a self-leveling platform mounted on a hydraulic-powered boom. The boom is mounted on the bed of a diesel truck. The equipment provides a movable work platform from which two men can work in safety and comfort while barring loose rock from the backs and walls of the rooms, pillars, and haulageways. INTRODUCTION As a part of its synthetic liquid fuels program the Bureau of Mines has developed a mine in the richer oil-shale beds of the Green River formation near Rifle, Colo. An important part of the work of the Oil-Shale Mining Branch is investigation of techniques for low-cost mining of oil shale on a commercial basis. It is evident that scaling loose rock from the high backs and walls of the mine represents a portion of the direct mining cost. This paper describes the development of a scaling rig for operation in the upper heading of the mine, which is 39 feet high.

Jan 1, 1954

By Phyllip Worley, Frank E. Chase, Christopher Mark

The Harris No. 1 Mine, located in Boone County, WV, has been longwalling the Eagle Coalbed for over 30 years. Harris has experienced numerous interactions associated with the extensive room-and-pillar and longwall mining operations which have been conducted in the overlying No. 2 Gas Coalbed. The problems have included roof falls, excessive rib sloughage, and gateroad and bleeder entry closure. A detailed evaluation of the multiple seam experiences at Harris No. 1 Mine was conducted as part of the National Institute for Occupational Safety and Health (NIOSH) nation-wide multiple seam mining case history data base. One observation from the Harris gateroad case histories was that smaller, critically loaded, upper seam pillars seemed to cause more severe ground conditions than did wider pillars. The LaModel program was used to investigate this supposition, and the results confirmed that “critical” sized pillars do transmit the highest amounts of stress to adjacent seams. In addition, the data suggest that the probability of a major multiple seam mining interaction increases when the depth of cover is 1,000 ft or greater and when the Eagle seam pillars have a Analysis of Longwall Pillar stability factor less than 1.50.

By F. P. Miknis

Previous studies at the Bureau of Mines have shown that broad-line nuclear magnetic resonance (NMR) techniques have potential applications for rapid evaluation of oil-shale deposits. In a continuation of this study the techniques of pulsed NMR have been applied in a similar manner. The basis for the pulsed NMR oil-shale assay method lies in the assumption that the free induction decay (FID) amplitude following a 90° pulse is proportional to the potential oil yield. This assumption was tested on two groups of oil-shale samples, numbering 141 and 263 samples, from two different oil-shale cores. For both groups of samples a small number were selected as calibration samples. Free induction decay amplitude measurements were made on the 141 and 263 samples. The best least-squares regression line was obtained for the calibration samples, and the oil yields of the remaining samples were calculated using the slopes and intercepts obtained in the regression analyses. The agreement between measured and calculated oil yields was good, the indexes of determination being 0.93 and 0.89 for the groups of 141 and 263 samples, respectively.

Jan 1, 1974

By M. K. Larson, J. P. Dunford, E. G. Zahl, T. M. Brady

Researchers at the Spokane Research Laboratory of the National Institute for Occupational Safety and Health, Spokane, WA, have collaborated with three Western longwall coal mines in an on going effort to develop technologies that will aid in providing safe and stable working areas. The goal of the research described here is to develop a stress monitoring system that will provide immediate information to mine managers for making daily safety decisions as areas of poor ground are mined through. Initial work has focused on answering preliminary questions regarding the reliability and use of stress change patterns. Research is concentrated on monitoring horizontal stress because horizontal stress is transmitted over long distances through stiff strata, thus allowing an extended length of entry to be monitored. This paper presents an explanation of the concept, key results from field tests at two mine sites, and a proposed process for implementing a monitoring system. System design layouts, instrument use, data collection and interpretation methods, and processes to present findings to mine staff are described. Additional validation and correlation with actual failure mechanisms are required before this approach can be recommended at ongoing operations. However, initial results indicate that this approach shows promise in mines prone to bumps and roof falls associated with large stress changes. In particular, analyses of measured changes in horizontal stresses appear useful.

By V. Castranova, K. Van Dyke

"I. INTRODUCTIONA mechanism which is present in leukocytes and capable of releasing histamine from rabbit platelets was first described by Barbaro and Zvaitler in I966. A soluble mediator between rabbit leukocytes and platelets was also detected by Siraganian and Osier in 1971. This factor was isolated and characterized in 1971 by Benveniste et al. and named platelet activating factor i PAF). It was shown to be released from rabbit basophils through an antigen - IgE-dependent mechanism. The presence of PAF in human leukocytes' and its aggregation and releasing effects on human platelets were also demonstrated. Chemical analysis has shown that PAF is a glycerophospholipid with a choline polar head group. an ester-linked acyl chain at the second carbon and a nonester link at the first carbon.' The structure of the mediator was found to be 1-O-alky1-2-acetyl-sn-glyceryl-3-phosphoryl choline and it has been chemically synthesized.""' A variable portion exists in the alkyl group attached to the first carbon which can have a variety of molecular sizes such as C and C (where Cu is more abundant). Recent work by Pinckard et al."" has shown that there are at least five variations of the alkyl group.PAF has been shown to have a broad range of biological effects. Release of PAF from alveolar macrophages may be important in asthma, allergy, and shock states. In a rabbit model of antigen IgE anaphylaxsis. PAF can induce all of the effects of antigen challenge and. therefore is presumed to be a key mediator in production of anaphylaxsis. In addition to aggregating and degranulating platelets it is a potent chemoattractant."" and causes contraction of guinea pig ileum contraction of lung tissue and enhanced capillary permeability PAF has important effects in the kidney and is also known as the renal hypotensive factor proposed by Blank et al. who found the structure of PAF independently of Benveniste et al.' In producing these responses. PAF acts by a receptor-like mechanism. In platelets. PAF selectively desensitizes itself but not thrombin or collagen. In smooth muscle tissues a similar phenomenon occurs with anaphylatoxin or other stimuli.In vivo. PAF probably acts in concert with other agents in producing its various biological effects. It causes platelets to release histamine serotonin and RCS (rabbit-contractile substance formed from prostaglandins PPG2, PGH2 and TXA2) which contracts rabbit aorta. PAF can cause cells to release SRS-A and leukotriene B."

Jan 1, 1989

By F. A. Rutledge

The Bureau of Mines Investigated the Copper Bullion claims at Rua Cove on the east coast of knight Island in Prince William Sound, Alaska, during November-December 1948 and March-April 1949. This project was part of the Bureau of Mines program for developing critical and strategic minerals in Alaska, Mineralization at the copper deposit on the Copper Bullion group of claims is mainly pyrrhotate and chalcopyrite, confined to a northeast-trending shear zone in the greenstone 2,000 feet northwest of Rua Cove. The property has been partly developed by two adits, by a number of crosscuts from the upper adit, and by several diamond-drill holes.

Jan 1, 1953

By Byron A. Baker

The Bureau of Mines used a windowed cell to measure the phase-boundary pressures of two related series of gas-condensate fluid mixtures. Normal butane was added to the mixtures incrementally to determine its effectiveness for lowering phase-boundary pressure. All the experimental data were correlated, so that the pressure required to maintain light oils mixed with natural gas in the single phase may be computed for secondary recovery applications. The heavy hydrocarbon parts of the mixtures were distillation fractions of a Gulf Coast condensate. Intermediate normal hydrocarbons in the butane-heptane range and natural gas were added to the fractions in selected proportions, so that phase-diagram pressures of 26 fluids were actually studied. The experimental range of temperatures was 50° to 280° F. Two correlations were developed to represent phase-boundary pressures by means of a polynomial. Independent variables represent natural gas content, disparity of properties of components comprising the mixtures, and temperature. A fourth variable, for one correlation only, was the quantity of normal butane added to the original mixtures. The latter correlation with four independent variables contains 15 coefficients and is estimated to be accurate to 135 psi.

Jan 1, 1973

By T. J. Driscoll

In this Bureau of Mines investigation, the electrochemical polarization behavior of Fe and Fe-1BCr has been characterized in rigorously controlled 1[N] H2S04 solutions stirred with oxygen or an inert gas. Samples that under-went various levels of corrosion or passivation were examined using Auger electron spectroscopy (AES) and ion sputtering. Passivation of iron occurred at a potential of approximately 0.6 volt (1) in poorly stirred, oxygen-saturated solutions for forward polarization (scanning from cathodic to anodic potentials); (2) in pH-adjusted (increased), well-stirred, oxygen-saturated solutions for forward polarization; and (3) in well~ and poorly stirred, oxygen-and helium-saturated solutions for reverse polarization. Passivation of Fe-18Cr occurred at a potential of approximately -0.1 volt in helium-, nitrogen-, and oxygen-saturated solutions for all cases of forward polarization and most cases of reverse polarization. Elemental depth profiles obtained from AES sputtering measurements indicated that films or adsorbed species were present on iron samples in solution subjected to open-circuit, active, and transpassive corrosion, cathodic reduction, and passivation. This conclusion was reached by considering the distribution of the solution species, primarily sulfur, in the films, which were composed primarily of iron and oxygen. Sulfur was present throughout the films on actively corroding samples, in the outer regions of films of passive and transpassive samples, and on the film surfaces of open-circuit and cathodically reduced samples. For Fe-18Cr, sulfur was found on the surfaces of films on passive samples only, indicating that only the passive samples had films on their surfaces in solution. The films on electropolished and passive Fe-1BCr samples had the largest chromium concentrations, estimated to be approximately 45 at. pct, with less chromium in films of cathodically reduced, active, and open-circuit samples, in that order.

Jan 1, 1979

By Donald P. Blasko

The Bureau of Mines investigated two areas of the Alaska Peninsula (Iniskin Peninsula and Becharof Lake) where oil and gas seeps were known to occur in an attempt to determine (1) whether the seeps are still active and (2) the amount of bitumen contained in the drainage leaving the seeps. The oil, water, oil-water, and gas were sampled and analyzed. Five oil samples were taken at four separate oil seeps. The API gravity of the oil ranged from 8.90 to 21.4° and the sulfur content was from 0.12 percent to 0.59 percent. Four of the seven gas samples obtained revealed fair high caloric values, ranging from 746 to 924 Btu/cu ft, and averaging 844 Btu/cu ft. A total of 44 water samples were obtained. Bitumen content of the water was as high as 9,773 mg/l at one seep, but averaged less than I mg/l where the seep-drainage water entered the Gulf of Alaska.

Jan 1, 1976

By W. A. Cole

This report covers the preliminary phase of an investigation of clays, shales, and certain rocks in Wisconsin to determine the feasibility of processing lightweight aggregate in the State. The study was extended to include rotary-kiln testing of a limited number of shale samples, and to an appraisal of the Maquoketa shale resources in eastern Wisconsin. A total of 45 samples of clays, shales, and other argillaceous rocks of Wisconsin were tested. The lower Maquoketa shale is the only material found to date that offers possibilities as a source of material that can be processed in a rotary kiln for lightweight aggregate. Bedrock occurrences of the Maquoketa shale are found in the eastern and southwestern parts of the State. The populous southeastern region of Wisconsin presents a large potential marketing area for lightweight aggregate. For this reason special study was directed to the Maquoketa shale in the eastern district.

Jan 1, 1961

By J. J. Demeter

Anthracite from the four producing regions in Pennsylvania was both ashed in the laboratory and burned on a chain-grate stoker to determine the sulfur-retention properties of its ash. The retention of sulfur in laboratory-prepared anthracite ash was shown to be related to ashing temperature and to the amounts of sulfur and calcium present in the coal. At the usual laboratory ashing temperature of 750° C sulfur retention ranged from 0.8 to 13.2 percent of the total coal sulfur. Sulfur retention in the ash was negligible, o to 0.3 percent, at 1,200° C, which is the thermal decomposition temperature of calcium sulfate; thus calcium sulfate does not form and cannot serve as a sulfur-retaining agent. In several tests the anthracite was mixed with 6 or 10 percent dolomite prior to firing in the chain-grate stoker. The dolomite did not improve sulfur retention owing to the high temperature in the fuel bed. Sulfur retention was, however, related to the unburned carbon in the ash. The relationship of the percentage of original coal sulfur retained in the ash (Y) to the percentage of the original carbon in the coal remaining in the ash (X) is expressed by Y = -0.579 + 0.914X. The percentage of sulfur retained is almost directly proportionate to the percentage of original coal carbon in the ash.

Jan 1, 1968

By Deborah A. Kramer

As part of the Nation's growing concern with the competitiveness of U.S. firms in the world economy, especially with respect to advanced materials, the Bureau of Mines assessed the actual and potential recovery and manufacturing capabilities for gallium and gallium arsenide (Gacis). GaAs has advanced from a laboratory curiosity to a material with important "high-tech applications within only the last few years, and although protected North American gallium supplies are currently considered adequate, consumption could grow to the point that this assessment would need reevaluation.

Jan 1, 1988

By Kung-Lee Wang

The 1963 performance of the United States economy was impressive. The year was one of continued growth unmarred by a recession. By the end of 1963 the economy's expansion had already lasted almost as long as the 1954-57 upswing, and the net gain in output since the trough in activity in early 1961 compared favorably with most earlier postwar cyclical advances. There was no indication of any slow- down at yearend. Both gross national product (GNP) and national income in 1963 were 5 percent higher than in the previous year. GNP totaled $584 billion, a gain of $28 billion over 1962. Real output of goods and services rose 3.4 percent over the year. Price increases continued to be moderate. Production, employment, personal income, and corporate profits all registered new but unemployment continued high at 5.5 percent and the prospects for improvement remained poor. The economy again failed to use its full potential. Current value of mineral production kept pace with the economy. The constant dollar value of mineral production gained more than real GNP because of the relatively stable price of minerals. Mining production achieved a new high in 1963. Steel production totaled 110 million tons, 12 million tons above 1962, making 1963 the first 100- million-ton year since 1957 and lifting the steel-associated minerals group upward. The gain in ferrous metals mining was insufficient to compensate for the decline of nonferrous metals mining resulting in an insignificant decline in the metal mining total as a whole. The upsurge of construction material minerals output, with an assist from chemical and fertilizer minerals, accounted for peak production of

Jan 1, 1964

By Steven J. Page

The increasing concern for dust control in metal and nonmetal mining prompted the Bureau of Mines to investigate the dust suppression technique of applying foam to face drilling and crushing operations in a gypsum mine. Previous attempts to achieve effective dust control on face drills using other techniques, such as dry collection and boom-mounted external water sprays, have not been successful. The largest problem encountered when using these techniques has been the lack of sustained effective dust capture at the face. Results for two faces studied show that injection of the foam through the drill steel provided an average dust reduction of 95 pct. However, the use of foam on the crusher provided no dust reduction at the operator's position (because of good local ventilation) and a 27-pct average dust reduction for two feeders at a location midway between the operator's position and the crusher. The conclusions obtained from this study are that (1) foam can be an extremely effective dust control technique when used on localized dust sources such as dust generated within a blasthole during drilling, and (2) foam is only marginally effective as a dust control technique when used on nonlocalized dust sources such as dust generated during the feeder-and-crusher operation.

Jan 1, 1981

By M. J. Mechling, H. J. Sloman

"INTRODUCTION The practicability of providing safer methods of underground transportation for mine workmen and officials has been given much thought in recent years by advocates of safety, health, and efficiency. Numerous fatalities and disabling injuries have resulted from falls of roof, personal contact with both electrical conductors and timbers, and improper position or conduct of passengers while they were in man-trips. Unfavorable atmospheric exposure due to high-velocity air currents and sudden changes in temperature may adversely affect the health of mine workmen if they are transported in unprotected Cars.Recent installations of protected, man-trip cars, wherein such cars have been utilized to haul men to and from their stations in the mine, have resulted in a large reduction in exposure to haulage hazards. Where special-built cars have been used the probability of injuries to men during transportation in man-trips has been decreased, and the morale of the employees has been improved. A number of man-trip cars are in service in the coal-mining regions; those described in this circular are typical examples of a few installations."

Feb 1, 1948

By J. D. Davis

From the chemist's point of view it would be ideal if specifications for coke for any stated purpose could be written on the basis of chemical composition and burning characteristics. Unfortunately this is not possible. In fact, the physical properties of a coke are often of such major importance as to render any specified chemical requirements totally inadequate to show the quality of coke desired. For example, a furnace coke may admirably fill all chemical requirements, such as for low phosphorus, sulphur, moisture, and high fixed carbon, and still be too soft to support the burden of the furnace without excessive crushing. Again, a domestic coke though a good fuel as judged from Chemical analysis, may be of unmarketable size. Thus one can not define the quality of a coke for a specified purpose without taking into account both its chemical and physical characteristics even when this has been done the specification may fail because neither coke user nor producer can accurately define by quantitative tests the qualities most desired. In other words, there is need of accurate test methods for measuring the properties of coke and, what is equally important, for correlating the results with the behavior of the coke in use. Coke quality is determined by the kind of coal used, the coking process, and the type of equipment used in the coking process. Chemical analysis of the coals, together with small-scale coking tests, will give a good indication of their suitability; but, in general, coke must be produced on an industrial scale and tested in the equipment for which it is intended before conclusive information as to its quality is obtained.

Jan 1, 1928

By J. P. Conway

The yielding-rock-bolt concept, as developed in South Africa, consists of a smooth-bore die or collar fitted to a standard rock bolt. Laboratory testing at the Bureau of Mines Spokane Mining Research Center under slow and fast strain rates showed that extrusion loads can be controlled by varying the configuration of the die bore and that theoretical analysis (using basically Sachs' theory of wire drawing) predicts extrusion loads of the different die-bore configurations. A derived equation, based on this research, can be used for designed die-thread combinations for any desired extrusion load. Dynamic loading resulted in slightly higher loads (15 percent) than static loading. The strain hardening effect, which increases yield and ultimate strength, was partly offset by adiabatic heating of the threads, which decreases strength.

Jan 1, 1975