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By Seth C. Schaefer

The Federal Bureau of Mines studied the Gibbs free energies of formation of chromous fluoride (CrF2), chromic fluoride (CrF3), and chromium (II,III) fluorides (CrF2.40 and CrF2.45) with high-temperature galvanic cells employing calcium fluoride doped with 1 mole-pct yttrium fluoride as the electrolyte. Free-energy changes were obtained from open-circuit potential measurements for the following cells: Cr, CrF2 // CaF2 // NiF2, Ni (a) NiO, NiF2 // CaF2 // CrF3 , Cr203 (b) CrF2 , CrF2.40 // CaF2 // NiF2, Ni (c) and CrF2 ?45 , CrF3 // CaF2 // NiF2, Ni (d) with the following overall reactions Cr(s) + NiF2 (s) = Ni(s) + CrF2 (s) (1) 3NiO(s) + 2CrF3 (s) = 3NiF2 (s) + Cr203 (s) (2) 5CrF2 (s) + NiF2 (s) = 5CrF2.4O (s) + Ni(s) (3) and 3.64CrF2.45 + NiF2 (s) = 3.64CrF3 (s) + Ni (s) . (4) These results were combined with the best available literature values of ?Gf° of NiF2, NiO, and Cr203 to deduce Gibbs free energies of formation for the chromium fluorides expressed as follows: ?Gf°(CrF2) = -179.31 + 24.33 X 10-3T ± 0.43 kcal-mole. (5) (858.1 - 964.9 K) ?Gf° (CrF3) _ -226.16 + 1.82 X 10-3T ± 0.79 kcal/mole (6) (880.8 - 957.8 K) ?Gf°(CrF2.40) _ -213.65 + 32.14 X 10-3T ± 0.44 kcal/mole (7) (0053.9 - 936.8 K) and ?Gf°(CrF2.45) _ -176.17 - 12.67 X 10-3T ± 0.80 kcal/mole (8) (875.1 - 937.6 K). Free energies and equilibrium fluorine pressures for three univariant and one bivariant equilibria are illustrated.

Jan 1, 1976

By G. S. Rice, R. V. Wheeler

"In September 1923, a proposal was made through official diplomatic channels by the British Safety in Mines Research Board to the United States Bureau of Mines for ""closer cooperation between the two countries in investigations into the causes and means of prevention of mining dangers."" This proposal was cordially accepted by the Bureau of Mines and was officially approved.In the spring of 1924 cooperation was .formally begun. It contemplated, as stated officially, ""full exchanges of information, a joint program of research, and periodic exchange of personnel so as to assure concordant results. By making the resources of both organizations available it will hasten the attainment of results, will secure better: checks for, accuracy, and in the end will save money for both by avoiding duplication and repetition.""This joint work has been carried-on successfully since that time and has developed valuable results, reports on which have been issued from time to time. The progress report which follows gives the results of the studies and work carried on in 1929.During 1929 all the phases of our cooperative research, begun in previous years, have developed normally. The exchange of formal monthly reports on all programs of mutual interest has been continued and has proved an invaluable, means of maintaining contact between the investigators of both organizations. There has been no diminution in the exchange of routine progress reports on specific subjects or in direct correspondence. The interchange of personnel has been maintained, and we can say that the mutual benefits to be derived from this form of cooperation are so great as to be difficult to overestimate. It leads to an appreciation of methods of research and modes of thought in the interpretation of results obtainable in no other way, and engenders a frankness and intimacy which must continuously enhance the value of future cooperation.Dr. S. R. Katz, who was assigned for service with the Safety in Mines Research Board in April, 1928, returned to America in May, 1929. During his stay in England he completed, in cooperation with members of the board's staff, the equipment of a gas-mask laboratory and designed and tested a new form of gas-mask canister. A publication of the Safety in Mines Research Board dealing with this investigation has been prepared and approved and will .be .issued in the near future. In additions Dr. Katz imparted to those with whom he was associated much of his knowledge and technique regarding his particular subjects. He delivered two lectures to the board's staff, the subjects be ""Gas Masks"" and ""The Intensity of Odors"", and gave papers before the Midland Institute of 'lining Engineers and the Birmingham University Mining Society on the subject of ""Industrial Gas Masks""."

Jun 1, 1930

By M. G. Zabetakis

This publication presents a simplified graphic method for determining the explosibility of mine atmospheres under mine-fire conditions from mine- atmosphere composition data. Sometimes it is necessary to seal part of a mine during a fire to exclude air and thus extinguish the fire. Unfortunately, liberation of methane and formation of hydrogen and carbon monoxide in the sealed area may create an ex- plosive or flammable atmosphere if enough oxygen is present to support combustion. On the other hand, the oxygen concentration may be reduced through combustion processes and the concentration of inert gases (nitrogen and carbon dioxide) increased enough to render the atmosphere within the sealed area non-explosive. Before an area is unsealed, it is extremely important to know if the sealed atmosphere contains Flammable gases in proportions that might form explosive mixtures when air is introduced. If an explosive mixture forms and the fire is rekindled, a gas explosion will result. Various experimental methods may be used to determine the explosibility of a particular mine atmosphere; however, these methods usually are impracticable in the field.

Jan 1, 1959

By Alan D. Hartman

Standard metering of electric arc furnaces usually uses root mean square (RMS) or true root mean square (TRMS) measurements for determining power. Only sinusoidal signals are accurately described by RMS meters, and dc or high-frequency components normally are lost in standard TRMS metering. This can lead to inaccuracies when electrical signals are not sinusoidal, contain dc components, or include fast risetime perturbations, as is the case with the electric signals from an electric arc furnace. Electric arc furnace electrical waveforms, observed in research carried out by the U.S. Bureau of Mines, show high-frequency components and significant deviations from sinusoids. These perturbations and distortions make metering difficult for standard power meters. The inaccuracies in metering can cause further problems if those sensors are used in control systems. For control strategies requiring rapid response, any averaging scheme loses information that can be used in control decisions. In order to obtain better signals for both monitoring and control, a study of instantaneous, RMS, and TRMS power monitoring devices was conducted. From this study it was concluded that precision integrated circuits should be used to obtain instantaneous power with a bandwidth of at least 25 kHz. The information from these devices is more representative than that of standard meters and can be used in predictive control.

Jan 1, 2010

By Carlon S. Land

The Bureau of Mines investigated the influence of a free gas saturation on oil recovery by water drive. A digital computer was used to calculate the combined oil recovery from solution-gas drive to various states of depletion. Results of these calculations are compared and optimum conditions for the maximum oil recovery are found for various fluid-rock systems. For most of the fluid-rock systems, the calculations show an optimum gas saturation other than zero. Using fluid and rock properties as parameters, graphs are plotted showing the optimum gas saturation and increase in oil recovery brought about by the gas saturation. The effects of fluid properties and relative permeability on the optimum gas saturation are seen in these graphs. The graphs can be used as guides in connection with other considerations in determining the optimum time to start a waterflood. They should also be helpful in determining the MER of a water-drive reservoir. The effects of compressibility and solubility of the trapped gas saturation are investigated for select cases using a backward difference scheme to solve the partial differential equation of three-phase flow. From these calculations, it is observed that some benefit of a gas saturation remains for injection pressures up to 1.5 times the original bubble-point pressure.

Jan 1, 1974

By W. D. Walker

All pipelines used to transport liquid fuels over coal mines are potentially hazardous; however, this publication deals only with dangers in transporting gasoline. Since transporting gasoline by this method is an established practice, the hazards connected therewith should he recognized by coal-mine operators and pipeline companies so that every known precaution may be used to reduce and keep the hazards to a minimum. The purpose of this paper is to direct the attention of coal-mine operators and employees, pipeline-company officials, and other interested persons to the explosion and fire hazards that arise from seepage of gasoline into underground mines. A hazard is not only presented in an individual mine when gasoline enters underground workings; but, in cases where mines are interconnected, a hazard exists in mach such mine.

Jan 1, 1954

By R. V. Lundquist, H. Leitch

The solubility characteristics of three calcium aluminates , 12Ca0 · 7A120½ 3Ca0 A1203 , and 4Ca0 A12 03 Fe2O3 , were determined in water and in solutions of NaOH and Na₂ CO₂ to more clearly define their role in relation to the recovery of aluminum by the lime sinter and the lime - soda sinter processes . The calcium aluminates were prepared by sintering stoichiometric mixtures of CaCO3 , Al2O3 3H20, and Fe 0 at 1,375 ° C. The rates and extent of aluminum extractions were determined . The aluminum extractions from the aluminates were dependent on the presence of carbonate ions in the leach solutions , temperature , time , leach solution composition , and solid - liquid ratio of the slurry . The aluminum extracted from the calcium aluminates in water and in NaOH solutions varied from 4.6 to 22.9 percent . Virtually , complete extraction could generally be obtained for 12Ca0.7A120 and 4Ca0.A12 03 • Fe₂ 03 ; in one instance it was obtained for 3Ca0.A1203 , when an excess of carbonate ions was present over that required for the conversion of all of the calcium in the aluminates into CaCO3 . In some cases of poor aluminum recoveries , extractions could be improved by regrinding and releaching the solid residues .

Jan 1, 1964

By J. E. Hamak

This publication contains analyses and related source data for 151 natural gas samples from 19 States. Of the total samples, 138 were collected calendar year 1989. The remainder were collected earlier, but releases to were not received until 1989. All samples were obtained and analyzed as part of U.S. Bureau of Mines investigations of the occurrences of helium in natural gases of countries with free market economies. This survey has been conducted since 1917. The analyses published herein were made by mass spectrometer and chromatograph.

Jan 1, 1990

By John W. Thatcher

A demountable X-ray tube vacuum spectrograph was designed by the Bureau of Mines for the determination of long-wavelength X-ray spectra from the light elements. This instrument was operated for both secondary and combined primary-secondary excitation of the aluminum K-series. There was an increased analytical sensitivity for elements in period 3, and an indication that with improved X-ray tubes or direct election excitation of the sample, X-ray determination of elements in period 2 is also possible.

Jan 1, 1965

By C. S. Compton, T. E. Marshall, D. R. Dolinar, R. Grau, L. J. Prosser, A. T. Iannacchione, D. C. Oyler

Unrecognized roof beam failures resulted in 69% of the falls of ground injuries occurring in underground U.S. stone mines from 1990 to 1996. Field investigations at 45 underground stone mines suggest that excessive beam sag or deflection is the principal unstable roof behavior characteristics associated with miner injuries. Laminated roof structures, common in most underground stone mines, allow the immediate roof to separate into distinct beams. The timely determination of roof beam deflection could provide stone miners with advanced knowledge of potentially hazardous roof. Existing methods to assess roof conditions consist of observational and monitoring techniques. Observational techniques include open drillholes, sounding, wedging, and borescopes. Monitoring techniques include scratch tools, extensometers, telltales, Miners Helpers, and Guardian Angels'. Miners have difficulty utilizing these techniques because roof beams are located an average of 8 m (26.5 ft) above the miner's head in environments that are dark, dusty and noisy and these deflections are measured in millimeters of movement. To help mitigate the potential for falls of ground injuries to underground stone miners, the National Institute for Occupational Safety and Health (NIOSH) has developed the Roof Monitoring Safety System (RMSS) to aid in monitoring dangerous levels of roof beam deflection. If enough site-specific information is collected and placed on highly visible maps, individual mining operations could establish general guidelines for responding to specific roof beam deflection occurrences. This would help in implementing a pro-active, comprehensive roof control plan for reducing falls of ground injuries.

By Ivan L. Nichols

Tailings dumps at Mercur, Utah, contain about $7 million worth of gold in 3.5 million tons of mill tailings assaying about 0.07 ounce of gold per ton. Commercial mining and milling at Mercur ceased in 1942. To determine whether improved technology was now available that might permit economic reprocessing of the Mercur dumps, the Bureau of Mines probed for a low-cost method that would be applicable to these tailings. A composite sample prepared for laboratory studies assayed 0.062 ounce gold per ton. About 10 percent of the gold occurred as a water-soluble cyanide. Conventional cyanide leaching dissolved 32 percent of the gold, and hot, strong cyanide solution dissolved 42 percent. Results were not improved by pretreatment with acids, bases, or oxidants. After expensive preroasting, gold recovery by cyanidation was increased to 65 percent. The simple procedures were ineffective, and more effective procedures were too costly for economical processing of Mercur tailings.

Jan 1, 1970

By Daryl E. Radcliffe

The Bureau of Mines studied the displacement of the roof in a portion of the Bear coal mine near Somerset, Colo, Horizontal-and vertical-displacement gages were installed in a five-entry section during normal room-and-pillar mining procedures. Monitoring of the roof continued until this section was mined out. Displacement measurements in combination with known time lapses between mining and bolting operations indicate that once support is achieved, the length of unsupported time does not appear to affect long-term roof stability in the mine under investigation.

Jan 1, 1978

By M. S. Oudenhoven

The Bureau of Mines conducted an investigation to determine the theoretical stress distribution in the vicinity of explosively expanded rock bolt anchors independent of their bolts. Plane-strain solutions applicable to this problem were obtained by combining the field pressure with the uniform pressure that would be produced by vertically placed anchors having 2-, 3-, and 4-foot spacings. High rock stress which would be produced by an anchor was localized, as would be expected from St. Venant's effect, and increased as the field pressure decreased.

Jan 1, 1967

By C. J. Johnson, C. J. Bise

"As the US coal industry moves into the next century, it is becoming more apparent that the effective application of new technology is the only way it can remain competitive in the energy marketplace. Examples of this emphasis are with us today in such diverse areas as face-ventilation and excavation-equipment applications. The focus of this new technology is directed toward improvements in health and safety, cost control, and productivity.Room-and-pillar mining accounts for approximately 68% of the nations underground coal production; this percentage is not expected to decrease markedly in the near future. As such, this paper analyzes the impacts of the changing technological climate on future room-mid-pillar operations by comparing a base-case section (current) to three scenarios incorporating new or emerging technology. A microcomputer-based comparative analysis will reflect the changes in section production and costs.IntroductionThe ultimate goal for any coal mining company is to effectively use its human and financial resources to maximize its profits through the extraction of its reserves. Although recent workforce reductions in the industry have resulted in a more efficient use of labor and increased productivity, there comes a point in time when further reductions in the numbers of workers in each operating section are impossible with existing equipment. For example, Farinelli and Bise (1987) found that labor cost constituted 62% - 73% of the cost per ton of coal at the mining section, with a minimum crew size. Thereafter, efforts to increase productivity must focus on more efficient mine plans and technology.The fact that an increase in productivity can be realized by reducing non-productive time (change-out and tram time) and converting it to productive time has been known and demonstrated for quite some time. What has not been demonstrated frequently is the quantification of the potential productivity increase of currently emerging technology or ""add-on"" equipment. It is one thing to be able to say that a piece of equipment will make an operation more productive, but it is another thing to be able to quantify the productivity increase that will justify the purchase of the new equipment. Not only is a financial benefit possible in room-and-pillar mining with an increase in productivity, but a decrease in the time necessary to develop a longwall panel can also occur.The purpose of this paper is an analyze the impacts of a changing technological climate on future room-and-pillar operations by comparing a base-case section (current) to several scenarios incorporating emerging technology. To do this, four cases will be developed. A base case, consisting of the typical manner in which continuous-miner sections are currently operating, is compared to three layouts incorporating: (1) flooded-bed scrubbers on radio remote-controlled continuous miners, (2)a continuous miner with side-mounted roofbolters, and (3) a continuous miner with side-mounted roofbolters used in conjunction with a continuous-haulage system."

Jan 1, 1989

By Donald F. Reed

In the latter half of 1948 the Bureau of Mines investigated the Magnet Cove Rutile Co.'s prerty in northern Hot Spring County, Ark. This work was supplemental to the work done by the Bureau on the same property in 1945.2/ It was undertaken for the purpose of investigating the extent of the ore body toward the south and west and at depth and to obtain representative samples of the ore for metallurgical tests. For the latter purpose, the samples were so taken as to minimize alteration of the physical characteristics of the ore, these characteristics being determining factors in working out processes of bencficiation. During the investigation, 27 holes were drilled, 10 with a diamond-coro drill end 17 with churn-drill rigs using a Baker standard cable-tool core barrel. Drilling developed an extension of the ore deposit westward from the previously mined area but did not disclose the full depth of mineralization. Metallurgical tests to determine methods of beneficiating the ore and utilizing the resultant products are now in progress.

Dec 1, 1949

By Holmes, George H. Jr.

The Cherry Creek tungsten district was explored by the Bureau of Mines from April 16 to August 13, 1942. This district is in north-central White Pine County, Nev., 50 miles north of Ely. Principal work was done on the property of the Cherry Creek Tungsten Mining Co. and at the adjacent Chance mine, although the entire district was examined and mapped. The exploratory work was done in cooperation with the Federal Geological Survey and comprised surveying, trenching, sampling, long-hole and core drilling, rehabilitation of mine workings, road building, drifting, and shaft sinking. The more important tungsten occurrences were explored by trenching and diamond drilling. Sixteen holes, having a total length of 2,515 feet, were drilled. The project resulted in partial development of three new tungsten deposits and small increases in the reserve tonnage of two scheelite-bearing lenses that were being mined by the company. The following pages summarize the history of the district, outline the ownership of the properties explored, and describe the physical features and mineral deposits. Mining and milling practices at the Cherry Creek tungsten mine are outlined, and the plan and results of project work are presented in detail together with surface maps, assay maps, and drill-hole logs.

Jan 1, 1950

By H. C. Carpenter

Lignite tar made by low-temperature Lurgi-Spülgas carbonization of North Dakota lignite was hydrocracked in single-pass, fixed-bed operation at 3,000 pounds per square inch over cobalt molybdate catalyst to produce gasoline, and at the same pressure, over zinc chromite catalyst to crack the high-boiling phenolic compounds to low-boiling phenolics. Hydrocracking the raw tar or the creosote-oil fraction from the tar over cobalt molybdate removed most of the oxygen, sulfur, and nitrogen in the forms of water, hydrogen sulfide, and ammonia, and produced gasoline yields from 31 to 59 volume-percent. The gasoline fractions contained from 0.1 to 7.7 volume-percent tar acids, but tar-base percentages were too low for reliable measurement; removal of these materials with dilute caustic and acid solutions also reduced the sulfur and nitrogen to 0.01 weight-percent or less.

Jan 1, 1963

By David N. Montgomery

The characteristics of a closed cavity acoustic coupler were measured. Various configurations were investigated to determine their feasibility for use in a portable audio dosimeter calibrator.

Jan 1, 1976

By K. Kar, A. Sreeoath, M. Gautam

"This paper presents results of an experimental investigation of the sampling efficiency of a blunt cylindrical sampler oriented with respect to the oncoming flow. The number of particles sampled by the cylindrical blunt sampler and an isokinetic sampler is measured using the TSI Aerodynamic Particle Sizer. A technique is described to conven the ratio of the particles sampled into the sampling efficiency. The experimental data thus obtained is then compared with the impaction model of Vincent and Mark (1982) with the empirical constant determined from our experiment.. The comparison shows excellent agreement for 0° and 90° orientation.1.0 IntroductionCylindrical dust samplers are widely used in practice to determine the concentration of the airborne particulate matter. The sampler is simply a means to collect particles from the ambient, whose concentration is subsequently measured by some size selective techniques. Gravimetric and optical techniques are the two most commonly used methods to measure the particle sizes. While impactors are used in gravimetric analysis, Aerodynamic Particle Sizer, Aerosizer. Electron microscope, Coulter Counter etc. use the optical method to measure the particle sizes. The Aerodynamic Particle Sizer (APS) and the Aerosizer are the new generation devices which employ the time of flight of particles within intersecting laser beams to determine the particle size.The introduction of the sampler in the free stream disturbs the flow pattern due to two distinct actions of the sampler on the fluid stream: one of them results due to the conformity of the flow to the geometry of the circular cylinder and the second one is caused by the flow into the suction orifice. If the sampler performance is determined by the number of particles entering into the sampler inlet relative to the number of particles present in the free stream, then the particle trajectory outside the sampler and into the inlet is the deterministic factor for the sampling efficiency. The particle trajectory inside the sampler is not important in this case."

Nov 1, 1995

By N. Greninger

The Bureau of Mines examined the possibility of a seasonal variation of respirable dust concentration in U.S. coal mines. The first step was to review company and MSHA-inspector dust samples that had been collected during the past several years in 14 selected mines for compliance purposes. Results indicated severe scatter in data; most standard deviations of the dust concentrations measured in winter and summer months were comparable in magnitude with the mean values of dust concentrations for the seasons. Therefore, a detailed statistical analysis was conducted. At the 90% confidence level, the company samples of three mines had winter means 0.15 to 0.54 mg/m3 higher than the summer means; six mines had negligible seasonal variations; and five mines had winter means that ranged from higher to lower than the summer means. Inspector data, however, were too sparse for analysis. In view of both the low frequency of occurrence of a seasonal effect and its wide scatter in several of the mines, the study was ended with the conclusion that seasonal varia-tion in respirable dust levels, in general, is an insignificant factor.

Jan 1, 1986