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By V. A. Marple, K. L. Rubow

"IntroductionA particle dispersion system has been developed to aerosolize bulk powders or material deposited on surfaces such as filters. The size distribution of the aerosolized particles can then be obtained by sampling the particles with an aerosol sizing instrument such as a TSI aerodynamic particle sizer (APS) or a cascade impactor.Of particular interest is the applicability of using this technique to obtain the size distribution of particles collected on filters. This system has been used to determine the size distribution of coal dust particle collected on membrane filters. The use of this device in this application is quite intriguing in that, if this technique can be shown to accurately determine the size distribution of airborne particles, one can easily collect particle samples using either personal or area particle samplers, determine the mass concentration of the collected material through gravimetric techniques and then use the particle dispersion system coupled with the APS to determine the particle size distribution. With this technique one can determine the particle size of dust in environments, such as underground mines, where it would be inconvenient or impossible to use a particle sizing instrument.Particle Dispersion SystemA prototype particle dispersion system has been developed for aerosolizing particles. A schematic diagram of the system is shown in Figure 1. The system consists of mechanism for advancing the particle sample beneath a dust pickup tube, a venturi for deagglomerating the particles, and a instrument for analyzing the aerosolized particulate matter.The procedure to analyze a particle sample is as follows. The particles to be aerosolized are placed on a sample plate from where the particles are picked up by an air stream flowing upward in a small capillary tube (dust pickup tube). This tube operates as a small vacuum cleaner passing over the sample plate. The air is drawn up the capillary tube at a rate of 2 L/m by a venturi aspirator. This is accomplished by placing the outlet of the capillary tube near the throat of the venturi. The accelerated velocity of the air creates a low pressure in this region which draws flow up the capillary tube. From the outlet of the capillary tube particles are transported to the inlet of the APS where a small fraction are sampled and the aerodynamic diameter of the particles determined. The particles which are not measured by the APS are passed into a HEPA filter."

Mar 1, 1989

In the interest of safety ii: coal mining, the Bureau of Mines recommends: That all active underground coal mines, whether working or idle, have one or more fans in continuous operation. The capacity and installation shall be such that the entire mine workings are adequately ventilated at all times. Main fairs shall be located on the surface in fireproof housing offset from the line of any mine opening. The housing shall be provided with ample pressure-relief doors or other devices easily opened by the force of an explosion. The installation shall permit prompt reversal of air flow. For mines that liberate gas, the fan shall have at least two independent sources of rower immediately applicable. Ventilation of underground workings in coal mines is needed whether or not explosive gas is present. Natural ventilation is unreliable and often uncontrollable. Main fans should be on the surface; if they are in the mine, fire or explosion may make access difficult or dangerous and render the installation inoperative.

Jan 1, 1939

By C. D. McMaster, John C. Hartley

Three systems that monitor ventilating fans are described . These electronic monitoring systems automatically perform most of the operations required to conform with the provisions of the Federal Mine Safety Code in the event of fan failure or slowdown .

Jan 1, 1964

By G. R. Hopkins

One of the largest items in the expense of operating a refinery is the cost of the fuel used in distillation and for miscellaneous purposes such as in the heating of buildings and in the generation of electricity. On a B. t. u. basis, the average refinery consumes approximately one-tenth as much fuel as it produces. Theoretically, the fuel consumption at refineries should be much smaller than this, but furnaces can not be designed to be 100 per cent efficient and, in addition, a large part of the waste heat is low-temperature heat which would not pay for the expense of recovering it. Annual surveys of fuel consumption at refineries have been made by the United States Bureau of Mines, beginning with 1925. During the 5-year period, 1925-1929, the refineries made steady progress in fuel economy. This is evidenced by the computed figures of heat requirement per carrel of crude oil refined, which show a decline from 829,000 B. t. u. in 1925 to 639,000 B. t. u. in 1929 (see fig. 1). In 1930, however, 'the trend in fuel economy was reversed and the quantity of heat utilized in refining the average barrel of crude oil rose to 672,000 B. t. u. There were undoubtedly a number of reasons for the apparent decrease in fuel economy at refineries in 1930, chief of which were the tendency to carry the distillation farther instead of merely topping the crude and a gain in the consumption of waste oils, such as acid sludge, which in actual practice yield less heat per unit consumed than has been theoretically assigned to oil.

Jan 1, 1931

By T. D. Ralston

This Bureau of Mines report presents a mathematical model for heterogeneously catalyzed chemical reactors operating under turbulent conditions. The model includes reaction kinetics on the catalyst surface as well as diffusion of the reacting components within the reactor. Three applications of the model to tube-wall methanation reactors are discussed. The first application is a computation of catalyst activity from measured reactor data. This result is then used in a reactor sizing problem and a problem of reactor simulation with recycle. In addition to the reactor model, a novel approach to solving the recycled reactor problem is given.

Jan 1, 1974

By Helen W. Lang

The Bureau of Mines has developed a very rapid gas chromatographic method for routine determination of oxygen, nitrogen, methane, and carbon dioxide in mine atmosphere samples. Analysis is accomplished in 3 min; readout appears on a single strip chart. The gas sample is split between two columns contained in separate chromatographs. A 5 A molecular sieve column separates oxygen, nitrogen, and methane; a porous polymer column separates carbon dioxide from an air peak. Direct selective analysis of methane from this unresolved air peak is accomplished using a hydrogen flame ionization detector (FID). Carbon dioxide is catalytically converted to methane and detected by FID.

Jan 1, 1972

By T. E. Purcell

(a) Moisture. - Moisture, "as fired," is specifically significant in pulverized-coal firing because of its effect upon the continuity of raw-coal feed to the pulverizer, pulverizer capacity, flame stability, and speed of ignition. The extraneous moisture content is a rough index of potential difficulties in unloading and maintaining the flow of raw coal to the pulverizer and of pulverized coal to the furnace, with the troubles increasing geometrically as the percentage increases. Sticking or other stoppage of coal flow at any point between the bunker and the furnace is especially serious with pulverized-coal firing because there is danger of immediate loss of output. Where moisture is a problem, the designer must exercise great care in the design of coal-handling and preparation apparatus.

Jan 1, 1951

By Jack E. Fraley

Magnesium oxysulfate cement has been specially formulated as a sealant in underground coal mines for reducing sloughing of shale roofs and coal ribs, for reducing air losses through block stoppings, for constructing sprayed stop-pings over approved jute cloth or metal lath, and for reducing combustibility of polyurethane foam. A standard spray machine (Mining Enforcement and Safety Administration (MESA) approved) was used for the underground testing. Our research shows that a 1/2-inch coating reduces shale and coal sloughing, reduces air losses through block stoppings, and prevents fire propagation through a metal tunnel lined with polyurethane foam. During the underground tests, excess mixing water was used to improve pumping the slurry to the spray nozzle. This was later found to increase shrinkage cracks in the cured coatings. Controlling excess water is important to an acceptable coating.

Jan 1, 1976

By Charles L. Kimbell

The series summarizing the prices of the major nonferrous metals on the stock exchanges of the United States and the United Kingdom has been continued this year in tables 23 and 24. As a result of the lack of availability of comprehensive data on the prices of metals in Canada, the table that had presented that information in past years in this chapter has been discontinued and the price series for nickel that had been in that table now appears in the table presenting metal prices in the United States.

Jan 1, 1993

By W. H. Eddy

The Bureau of Mines conducted laboratory batch and continuous flotation processing tests on waste granite fines from South Carolina to determine the possibility of recovering high-quality feldspar and glass sand. Three flotation systems were used for removal of the iron-bearing biotite: Two employed an alkaline anionic-cationic circuit and the third employed an acid cationic circuit. Commercial-grade products were obtained when the remaining biotite was magnetically removed from the feldspar and quartz concentrates. Continuous flotation processing yielded a feldspar concentrate containing, in percent, 3.60 Na20, 5.60 K20, and 2.25 Ca0, with recoveries of 75.3, 66.6, and 72.6 percent, respectively. The feldspar tailing was high quality glass sand containing 98.0 percent Si02 and 0.025 percent Fe203; about 60 percent of the quartz was recovered.

Jan 1, 1972

By John H. Soulé

"INTRODUCTION The property of the Silver Spot Mines Co. is in the Boston Hill area within and adjacent to the southwest corner of Silver City, N. Mex. The area was visited by Bureau of Mines engineers 3/ in 1941 and 1942 during the investigation of possible sources of manganese. The area was visited again in November 1944 4/ to study the possibilities of geophysical exploration of the manganiferous-iron deposits. This geophysical work was performed in 1945 5/, confirmed the existence of known deposits of manganiferous-iron ores, and indicated the probable extent and situation of others.The Silver Spot property was churn-drilled from 1926 to 1929 during exploration for manganiferous-iron ores. The sludges from a number of the holes indicated low-grade lead-zinc mineralization. Lead and zinc minerals also were found on the dumps of some of the old shafts when the property was visited by D. H. Mullen, an engineer of the Bureau of Mines late in 1946. A diamond-drilling project was proposed. It was started in April 1947 with the intention of investigating the best of the known ore indications as shown by the old churn-drill holes and thus gathering new data upon which to base future work. Only one hole was drilled before the project was terminated because of lack of funds and time."

Mar 1, 1948

By Walter C. Lorenz

Samples of materials containing pyrite from various coal mines and coalbeds were studied to compare their compositions and oxidizing characteristics. Pyrite was the only form of iron sulfide identified, but X-ray diffraction, emission spectrography, and microscopic analyses revealed similar suites of minerals and trace elements. The pyrite occurred usually in spherical clusters of very small crystals. The oxidation of pyrite in solutions of PeSO4 and Fe2(SO4)3 and in the presence of an iron oxidizing bacterium Ferrobacillus ferrooxidans, was studied through a manometric technique. FeS04 or Fe2(SO4)3 solutions had no appreciable influence on pyrite oxidation under the test conditions, The bacterium acted as a catalyst, greatly increasing the oxidation rates; however, in three samples that also contained calcites, bacterial oxidation was greatly reduced. The oxidation rates also increased approximately as the percentage of pyrite in the samples increased. For the series of samples studied, there was no definite correlation of the results with the location of the various mines nor with the acidity of alkalinity of the mine drainage.

Jan 1, 1963

By D. Z. Hobbs

Because an economic method for preparing pure boron has not been developed, a program was started by the Bureau of Mines to evaluate existing techniques or to develop new methods for preparing the pure element. This report describes investigations directed toward the development of techniques for the preparation of pure boron by fused-salt electrolysis. Only two of the several fused-salt baths tested were satisfactory for the preparation of boron. These baths contained (1) potassium fluoride, lithium fluoride, potassium fluoborate and boron trioxide; and (2) potassium fluoride, potassium chloride, and boron trioxide. Of these two mixtures, the latter was more satisfactory. Elemental boron of from 90- to 95-percent purity and, in isolated cases, as high as 98-percent purity, was prepared from these two types of fused-salt baths. There appeared to be no distinct differences either in the yields or the purity of boron prepared at current densities ranging from 795 to 1,000 amperes per square foot. Current efficiencies were as high as 85 percent.

Jan 1, 1961

By Parviz F. Rad

The Bureau of Mines conducted groove cutting experiments in marble, lime-stone, granite, and quartzite with a 7-inch disk cutter under a normal thrust of 7,000 lb. The values of muck weight per unit length, specific energy, cutting coefficient, and groove depth for each of these rocks were determined for groove spacings ranging from 0.1 to 4 inches, and from these results the values of optimum and critical spacing were computed" The results indicate that compressive strength may be used to predict some of the cutting characteristics of the independent grooves. Considering all the cutting characteristics, particularly those for the interacting grooves, Shore hardness, coefficient of rock strength, and torsional velocity correlate with cutting characteristics better than do other physical properties. Some of the field applications of the principles established in this report are identified.

Jan 1, 1974

By E. G. King

Cerium and thorium sulfides have found use as crucible materials for melting certain radioactive metals. However, thermodynamic treatment of these sulfides has been hampered by lack of experimentally derived entropy values. This Bureau of Mines report describes heat-capacity measurements between 51° and 298° K, and entropy evaluations at 298.15° K, for cerium monosulfide (CeS), cerium sesquisulfide (Ce2S3), and thorium disulfide (THS2). The entropy values, with Literature results for the heats of formation, are used to obtain free energies of formation at 298.15°K. MATERIALS The samples used in this work were supplied by Prof, Leo Brewer of the Department of Chemistry, University of California. The methods of preparation and some of the physical and chemical properties of these sulfides were given by Eastman and coworkers.3 4/ Chemical analyses, conducted in our laboratory, gave the following results:

Jan 1, 1959

By H. J. Sloman

"INTRODUCTION Industry, including coal mining, has come to realize that to prevent accidents the human element must be given more consideration than was customary in the past. In formulating safety rules and regulations and in the enactment of laws governing mining, too often enforcement is emphasized rather than the means of gaining willing compliance.' The purpose of this paper is to call attention to the human side of accident prevention, and the approach to this important and much-discussed subject will deviate somewhat from the usual discussions.The human being is a complex mechanism, both physically and mentally. It is difficult to establish a common denominator for the actions of humans, except in general. In establishing mining laws, rules, regulations, and standards, the ultimate objective should be to gain the best possible response of workmen, so that optimum results in accident prevention may be obtained. The complexity of human beings is apparent when the many ways 1n which they differ are considered. Some of these differences are manifested in emotional and phlegmatic types, degrees of intellect or native intelligence; and in hopes, desires, aspirations, and philosophies of life. How much simpler ac¬cident prevention would be if the response to laws, rules, regulations, or standards were equivalent to the definite movements of puppets responding to pulls on strings. Each time, the strings are pulled in exactly the same way, the puppets will respond in exactly the same manner. Human beings, although having many similar characteristics, do not respond uniformly to identical ""string-pulling""; therefore, much study is necessary before the desired re¬sponses can be obtained. To achieve the ultimate in accident prevention, it must be ""worked at"" constantly. Regardless of the adequacy of safety laws, rules, regulations, or standards, good accident records will not ""roll in"" if dude consideration is not given to the personal traits of those most likely to be involved in accidents."

May 1, 1948

By Edward L. McHugh

Digital camera and computer technologies can be used to monitor mine slopes and provide real-time warning of rock falls. NIOSH researchers assembled a surveillance system using low-cost video cameras and computer software from the security industry to test its effectiveness. The system is designed to signal an alarm when motion is detected and to record images of the scene. Masking can restrict motion detection to specific areas within the camera view; sensitivity is adjustable. The time-stamped images provide a record that can help reconstruct and quantify an event. Video motion detection can augment standard monitoring methods to increase safety in surface mines.

By T. J. Ballard

The Track Rock corundum mine was among the numerous corundum deposits investigated during the war by the Bureau of Mines in an effort to develop domestic reserves of that critical mineral. In the investigation of this property 562 feet of trenches were excavated and a l25-foot adit was reopened for the purpose of locating veins to of corundum which had been previously reported to occur in that locality. Only very minor amounts of corundum were disclosed in both the surface workings and the adit. The project was begun in May 1943 and completed in November 1943.

Jan 1, 1948

By Lippe D. Sadwin

This report describes a high-speed streak camera technique for measuring the lateral shock pressure generated by a cylindrical explosive charge detonated from one end. Experimental data show that the magnitude of the lateral pressure is approximately 50 percent that of the pressure generated from the terminal end of the charge for three explosives studied.

Jan 1, 1965

By Henry W. Busch

Determination of the aldehyde content of Diesel-engine exhaust gas has proved rather cumbersome and unsatisfactory when carried out in its entirety in field investigations; therefore, studies were conducted with a view to developing methods by which samples might be collected in the field and trans-ported to the laboratory for analysis. Experience also indicated that aldehyde samples collected in water solution and then transported to the laboratory sometimes underwent serious changes in composition if several days elapsed between sampling and analysis. Polymerization of the aldehydes, which takes place readily in dilute aqueous solutions, may have been the cause of such changes. Because of these difficulties, experiments were conducted to find a suitable stabilizer or preservative for dilute aqueous solutions of the aldehydes that occur in Diesel-engine exhaust gas, so that in field studies a known volume of gaseous sample might be collected and brought into contact with water, and the resulting solution of aldehydes analyzed in the laboratory at some later time with reasonable certainty that the results would represent the composition of the original sample,

Jan 1, 1949