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By Robert F. Kehrman

As with many new technologies, the rapid growth in solution mining for uranium has created uncertainties regarding the environmental impact of mining operations. In solution mining, the largest area of concern is the impact of the process on the quality of ground water supplies. As a result, a rapid and reliable technique of detecting lixiviant excursions is desirable. Such a method would replace the periodic sampling technique and should provide a more or less continuous monitoring method. To this end, resistivity techniques were evaluated as an alternate means of tracking lixiviant movement. A program was devised which had five specific tasks. These were: (1) evaluation of the techniques, (2) development of the most promising technique or techniques, (3) field testing of the techniques, (4) testing of the BuMines probe, and (5) reporting. The result of the analytical and field work is that various resistivity/ resistance techniques do provide a means of detecting lixiviant movement in Northern Wyoming. Surface and downhole galvanic surveys and controlled source audio magnetotellurics (AMT) were evaluated. All three techniques showed some degree of success.

Jan 1, 1979

By C. Özgen Karacan

Degasification and methane control in underground coal mining is an important area augmenting conventional ventilation in order to prevent possible fires and explosions due to excessive methane emissions. Coal bed reservoir engineering has been applied for many years to coalbed methane production. In recent years, modeling the flow and draining methane, not only from coal bed itself but also from the overlying strata, have been recognized as important areas of expertise for supplementing underground ventilation. This paper demonstrates the applications of coal bed reservoir engineering and modeling techniques for optimizing and controlling methane emissions in longwall and continuous miner sections. Practical applications and some considerations are presented for reservoir modeling, borehole performances, and face emission predictions for various coal bed and borehole configurations. A section on field reservoir studies and well bore log analyses for methane control are also presented as a complementary way of controlling methane and optimizing ventilation.

Jan 1, 2009

By Vernon C. Allison

The explosibility of coal dust has long been recognized by competent investigators as constituting one of the dangers of mining coal and in the use of pulverized coal as a fuel in industrial plants. The Bureau of Mines has carried on extensive series of experiments dealing with this subject, and has not only developed methods for the practical prevention of this danger, but in the, course of these experiments has developed a standard method of determining the relative explosibility of coal dusts and other organic dusts.3 Oil shale contains compounds 'of carbon and hydrogen that are either of a petroleum nature and are strongly ,adsorbed upon the incombustible part of the shale, or else are present in the shale as a compound ("kerogen") which has the property of changing into petroleum-like products when acted upon by heat. The oil shales may contain varying amounts of the organic matter, ranging from a trace to more than 66 per cent, depending upon their richness; therefore, it is important to know whether the dusts formed in mining and handling these oil shales are explosive when mixed with air and if so, to indicate remedial measures. This paper gives the results of explosibility tests of several pulverized oil shale's, selected as being typical of those which in the future may be used in commercial shale-oil production test on a sample of typical Colorado oil shale has been., published in an earlier paper.4

Jan 1, 1926

By Miles B. Royer

The experimental blast furnace has attracted increasing interest during the past decade as a practical means for investigating a broad range of blast-furnace smelting problems. Under experimental-furnace conditions, information can be obtained with less expenditure of time and raw materials and, therefore, at lower cost than comparable information could be obtained under industrial operating conditions. Furthermore, the experimental furnace may be operated beyond the range of smooth operation, even to failure, to delineate the limits of operability. Such deviation from normal operating practice would be economically intolerable in industrial operations where production and operating stability might be disrupted. The Federal Bureau of Mines experimental blast furnace at Bruceton, Pa., near Pittsburgh, has been operated and under development since 1951. However, the usefulness of this experimental data to industrial practice was somewhat nebulous in early experiments, and the correlation of the experimental blast furnace with the industrial blast furnace was not known.

Jan 1, 1961

By Charles C. Myers, Robert M. Doerr

The apparatus described was developed for determining the kinetics of gas - solid reactions at high temperatures by measuring the volume of gas consumed with respect to time . This apparatus consists essentially of a horizontal precision- bore glass tube connecting a small reaction chamber in a furnace to a large constant - temperature reservoir . A drop of mercury in the tube separates the two sides of the system and serves as an indicator that moves at a speed proportional to the rate of gas consumption . The sensitivity of the apparatus depends inversely on both the density of the gas in the system and the cross - sectional area of the tube ; with a tube having an area of 0.079 cm² , the sensitivity for oxygen at 308 ° K and 0.5 atm is 20 cm/mg . The reproducibility of data with the volumetric apparatus is good .

Jan 1, 1964

By E. J. Gleim

Many people consider the mining of coal to be an extremely hazardous occupation; but it should be remembered that most large industries have to meet special conditions which, if not dealt with properly, might become hazards to life and property. Mining men may not always be fully aware that some practices and certain equipment that is incorrectly designed or maintained can lead to dangerous conditions. In endeavoring to help the coal-mining industry to prevent accidents and disasters, the Bureau of Mines has engaged in a program of education on conditions and practices that must be avoided. An effective way to teach safety is by visual demonstration. For example, it is generally known that certain kinds of electrical flashes have ignited explosive atmospheres in mines, but actually to see and hear explosions caused by electrical sparks of different size and character under laboratory control is likely to teach a much more emphatic and lasting lesson than would be learned by merely reading about them. The interest manifested by those who witness the demonstrations seems to prove that this is true. The purpose of the demonstrations is not to discourage the use of electricity in mines, but rather to indicate what types of equipment (including some generally regarded as harmless) can ignite gas and what safeguards have been developed to prevent such ignitions. It is hoped that this information will improve the ability of mining men to cope with underground hazards.

Jan 1, 1937

By L. C. IlsLey

The first thing to consider in prevention of electric shock is the voltage of the circuit. No person can be sure that he will not be killed, even from a 110-volt circuit, if he makes proper contact with the circuit so as to cause the maximum current to pass through his body. As the voltage is increased to 250 volts, 500 volts, or 2,300 volts the danger from contact with the electric circuit is increased, Alternating current of the same nominal voltage is possibly more dangerous than direct current. Experience has taught us that both will cause death, and that if the fatalities from this source are to be kept low, certain precautions in the guarding of circuits must be observed.

Feb 1, 1929

By Donald O. Capstick

In 1481, U.S. Bureau of Mines personnel conducted a survey of mines, prospects, and mineral resources in the Table Mountain RARE II area. There are no mines or active prospects in the study area. One prospect in the study area, the Waterfall Prospect, is estimated to contain 480 tons (440 t) of indicated subeconomic tungsten resources averaging about 0.18 percent tungsten trioxide (W03). Other tungsten occurrences are at the Stevens Prospect, just northwest of the area. Stone and sand and gravel deposits in the area are not considered to be resources because equal or better quality material is available closer to major markets. INTRODUCTION The 4,400-acre Table Mountain study area is 13 mi (21 km) southwest of Bishop, California, on the eastern flank of the Sierra Nevada range. The John Muir wilderness adjoins the study area on the southwest (fig. 1).

Jan 1, 1982

By H. D. Baylor

This paper, describing the operations of the Louisville Cement Co. in quarrying limestone for the manufacture of quicklime, is one of a series being prepared for and published by the United States Bureau of Mines on stone quarries throughout the United States. Those papers are designed to disseminate technical information regarding the methods used. The cost tabulations represent operating only and not total costs. It is recognized that publication of total costs might in many instances cause embarrassment to individual operators as well as to the industry as a whole. On the other hand, operating costs are essential to the technical discussion and study of the methods employed. The attention of the reader is specifically called to this differentiation in order that no misunderstanding of the scope of the cost tabulations shall ensue. ACKNOWLEDGMENTS The author acknowledges the assistance of J. H. Lemmon, plant superintendent, Charles Taylor, plant engineer, and F. H. Compton, chief engineer, of the Louisville Cement Co. in the compilation and preparation of this paper.

Jan 1, 1932

By F. D. DeVaney

An examination of the physical properties of manganese ores is being made at the Mississippi. Valley Station of the United States Bureau of Mines in cooperation with the Missouri School of Mines and Metallurgy, Rolla, Missouri. The object of the study is to find out how much these ores can be beneficiated by such processes as jigging, tabling, magnetic separation, and flotation. Some. of the results were given in an earlier report.4 Eighty samples obtained from various prospects and mines throughout the country have been examined; this is a very small part of those that should be examined before the work can be a definite factor in-the appraisal of manganese ores or the guide in beneficiation which the operators seek. The ore deposits are not expected to reach to great depths vertically, after the manner of copper and gold, but in lateral distribution their greater extent is notable. This applies particularly to the residual and replacement deposits of manganese.

Jan 1, 1929

By K. O. Bennington

Enthalpies of formation of three sodium titanates were determined by hydrofluoric acid solution calorimetry, The values obtained for formation from the elements at 298.15° K are -370.9±0.5 kcal/mole for Na2TiO3, -832.1±0.9 kcal/mole for Na2Ti307, and -1,510.9±1.7 kcal/mole for Na2Ti6013. Tables of enthalpies of formation and Gibbs energies of formation are given as a function of temperature both from the elements and from the component oxides for Na2Ti03 and Na2Ti307.

Jan 1, 1973

By M. S. Seehra, V. S. Babu

"INTRODUCTION The accurate determination of the free silica index in coal mine dusts is an important requirement because severe health hazards are believed to be associated with the inhalation of respirable-sized silica particles.1-6 Free silica refers to the three polymorphs of silica (Si02)viz., quartz, cristobalite, and tridymite-although quartz is usually the dominant form in most mine dusts.6 The free silica index is the concentration in micrograms of free silica in air per m3 of air sampled corrected to standard conditions of 25°C and 760 mm/Hg, the present MSHA (Mine Safety and Health Administration) limit on time-averaged basis being 100 µ.g/m 3 for coal mines. A recent review7 has concluded that quartz, cristobalite, and tridymite particles impart nearly equal long-term hemolytic damage when compared on a per unit surface area basis.At present, two experimental methods-viz., transmission infrared spectroscopy (TIRS) and x-ray diffraction (XRD)-are commonly used for the determination of silica concentrations in mine dusts. In TIRS, which has been adopted by MSHA and is commonly called the P7 method, the silica absorption band near 800 cm - 1 is used for quantification. However the mineral kaolinite, which is commonly present in mine dusts, also has absorption band, albeit weaker, at 800 cm- 1• To correct for this interference, one uses the stronger 915-cm -1 band of kaolinite to determine the concentration of kaolinite, and the kaolinite contribution to the absorbance at 800 cm-1 is then determined from a calibration curve, leading to the determination of silica by subtraction. In the XRD technique, usually an internal standard such as CaF 2 is used to determine the concentration of silica from line intensity measurements. XRD has the added advantage that concentrations of quartz, cristobalite, and tridymite can be determined.8•9 In an exhaustive study on the precision of the techniques ofTIRS and XRD for monitoring worker exposure,9 the conclusion has been reached that both methods measure silica within 253 of the ""true"" value 953 of the time in a single laboratory."

Nov 1, 1995

By H. J. Heinen

The Bureau of Mines, investigated a cyanidation-carbon adsorption technique for extracting gold from arsenopyrite concentrates. Agitation leach experiments were conducted on 85-pct-minus-35-mesh gravity concentrates containing 21.8 oz gold and 6.4 oz silver per ton. Results obtained in leaching the concentrates showed that 96.9 pct gold and 90.7 pct silver extraction could be achieved in 96 hours of agitation. Gold and silver were recovered from the resulting pregnant solution by exposure to granular activated carbon in a countercurrent system. Carbon loadings of 2,556 oz of gold and 502 oz of silver per ton were achieved. These loadings are significantly higher than heretofore thought practical.

Jan 1, 1980

By Edward D. Thimons

Because of the high number of accidental methane gas ignitions in metal and nonmetal mines, the Bureau of Mines searched for a simple guideline that would allow mine personnel to evaluate the methane hazard in a given mine. Air samples were collected by the Bureau in 53 metal and nonmetal mines and analyzed for trace evidence of methane gas. Samples were collected in the returns and at the working faces. Those mines classified as gassy by the Mine Safety and Health Administration had a significantly higher average methane concentration than those classified as nongassy. Of the 9 gassy mines sampled, 7 had methane concentrations above 100 ppm, whereas only 1 of the 44 nongassy mines had a concentration above 100 ppm. The 100-ppm concentration may be used as a simple and convenient guideline for forecasting the methane hazard in a mine, whether or not the mine is classified as gassy. There was no consistent correlation between commodity mined and methane concentration, nor was there a correlation between mine depth and methane concentration. Neither of these factors can be considered a guideline for predicting methane hazards.

Jan 1, 1979

By Edward D. Thimons

The Bureau of Mines conducted in-mine tests to determine correction factors applicable to low-velocity airflows (below 150 fpm) measured by the smoke cloud, vane anemometer, and oil of wintergreen tracer gas techniques 0 The average correction factors found for these methods of measurement were lower than those reported in the literature for use with higher velocity measurements. All tests measured airflows with controlled average velocities ranging from 50 to 100 fpm. Correction factors averaged about 0.75 for readings taken by the centerline smoke cloud method, remotely controlled and stickheld center" line anemometer, and split traverse stick-held anemometer. For hand-held centerline anemometer and oil of wintergreen tracer gas readings, correction factors averaged about 0.67. Since special anemometers are needed to measure airflows in this low-velocity range, and since proper calibration of these anemometers is difficult and expensive, the use of anemometers for low-velocity measurement is imprac-tical. On the other hand, smoke and oil of wintergreen give results as con-sistent as those obtained with specially calibrated, low-velocity anemometers. Furthermore, they are easy to use and inexpensive.

Jan 1, 1979

By Maria I. De Rosa

The U.S. Bureau of Mines conducted experiments for predicting materials' ease of combustion (smoldering onset, smoldering, flaming, and decomposition rates) by means of submicrometer smoke particle characteristics for the development of a simple test method. The experiments were carried out in an approximately 20-L furnace, with a 10-L/min airflow through the furnace for a 14-min duration, at set furnace temperatures of 150°, 250°, and 1,000° C. The variables studied as a function of time were the onset time of smoke particles, time and duration of maximum smoke particle generation, average concentration of smoke particles, and particles' average diameter, mass weight loss, and furnace temperatures. Results show that the onset time of smoke particles is predictive of materials' ease of smoldering, and the time of maximum smoke particle generation and its duration, coupled with mass weight loss, are predictive of materials' ease of smoldering and flaming (depending on the experimental temperatures), and decomposition rates.

Jan 1, 2010

By Martin Hertzberg

The concept of limit burning velocities, formulated in an earlier Bureau of Mines report (RI 8127), is applied to the problem of flame propagation through tubes of finite size. The limit burning velocity for conductive-convective wall-loss quenching (process b) is (Su)b = [aPe,] where the proper choice of critical Peclet constant, Pe, is determined mainly by the ratio of contact-perimeter loss area to flame-zone cross sectional area. This ratio of loss area to propagation area relates to the shape of the flame front and its control by buoyancy and by boundary conditions. The comparison of (Su)b with previously defined limit velocities for systems mixed by natural convection allows one to assess the influence of tube dimensions and boundary constraints on the "true" or earthly limits for the three directions of propagation. The flame quenching caused by inert powders is shown to be similarly described in terms of a limit burning velocity, (Su)?b. The tube's surface-to-volume ratio (~1/ro) is simply replaced by the powder's surface area per unit volume of the flammable mixture. Thermal loss quenching by these "internal walls" occurs at a critical Peclet constant somewhat higher than that observed for tubes, and the problem is complicated by the finite heat capacities of the powders and particle lag effects in the flame front.

Jan 1, 1980

By C. W. Owings

When explosions have occurred in mines where rock dust has been used to some extent, generally to a very limited extent, the press has immediately characterized those mines as "rock-dusted." To persons familiar with the method of rock-dusting, it is apparent that if rock-dusting is done properly, if all mine surfaces are rock-dusted to within at least 40 feet of the faces of rooms and entries, and if the incombustible content of the dust is more than 65 per cent, there is little likelihood that an explosion of coal-dust will occur. The report that an explosion has occurred in a "rock-dusted" mine immediately conveys to the mind of the alert safety advocate the information that the mine is inadequately rock-dusted or that either dust sampling of the rock-dusted surfaces has not been done or, if done, the mine has not been redusted with sufficient promptness. Rules for Collection of Samples Collection of dust samples is by no means intricate, but a few simple rules must be kept in mind if the results are to be dependable. A sample must represent the true average conditions of the dust in the section or zone in which it is taken, and therefore 'the point at which the sample is to be collected must be selected with care. During an explosion much if not all of the dust on the ribs, roof, timber, and road in the affected region is blown into the air; the sample, therefore, should contain all loose dust and material on: the surfaces to a depth of about 1 inch, if that amount is present. If there is considerable sand locally along the track, care must be taken not to include enough of this material to vitiate the sale and distort the results; however, if the sand is distributed throughout the region being sampled it should be included. Dust should not be collected from recesses in the ribs, such as hitches cut for timber, as the character of the dust in such places is often different from that on the ribs proper. Samples should not be collected at points where the dusting machine has been loaded or at a point where the machine has stopped and discharged for a longer period than at other points on the entry or in the rooms. In short, the sample must represent AVERAGE CONDITIONS, and if there is any doubt as to the character of the dust it is far better to have too much combustible matter than too much incombustible matter in the sample, as it is best to err on the side of safety if it is necessary to err.

Jan 1, 1929

By R. E. Lindstrom

Electrooxidation techniques were investigated on a bench scale by the Bureau of Mines to determine the applicability of the process for extracting molybdenum and rhenium from low-grade molybdenite concentrates. Parameters affecting the extraction, such as pulp density, power consumption, reagent requirements for pH control, and electrolytic cell configuration, were studied. Molybdenum and rhenium extractions of 98 to 99 percent were achieved from several concentrates containing 4.76 to 28.6 percent molybdenum and 180 ppm to 1,000 ppm rhenium. Optimum results were obtained by maintaining pH values between 5.5 and 7.0 during electrolysis and allowing the final pH to rise to about 8.2. Reagent consumption was 4 to 6 pounds of sodium carbonate per pound of molybdenum extracted. The power consumption declined from a range of 12 to 25 kilowatt hours per pound of molybdenum extracted with immersion electrodes to 9.7 kilowatt hours with a bipolar flow-through cell; however, molybdenum extraction was independent of cell configuration.

Jan 1, 1973

By B. J. Scheiner

The Federal Bureau of Mines investigated an electrolytic oxidation procedure for extracting lead, zinc, copper, and silver from lead-zinc concentrates. Concentrates slurried in brine were pumped through the anode compartment of electrolytic cells equipped with selective ion diaphragms. Hydrochloric and hypochlorous acids generated in the anode compartment converted the metal sulfides in the concentrates to soluble metal chlorides, sulfate ion, and elemental sulfur. Metal extractions of 92 to 100 pct were obtained from lead-zinc concentrates at an energy consumption ranging from 1.5 to 5.0 kW-hr/lb metal extracted. Sodium hydroxide was formed in the cathode compartment at a current efficiency of >99 pet. Silver and copper were extracted from refractory tetrahedrite minerals, but the process entailed a relatively high energy consumption. Sealing the top of the diaphragm cell utilized the chlorine more effectively, thereby reducing energy consumption 10 to 50 pct.

Jan 1, 1975