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By D. W. Scott

Thermodynamics is a powerful tool for investigating rotational isomerism in substituted ethanes and related molecules. Accurate calorimetric data can be interpreted to give information, not only about the energy difference between conformations, but also about the shape of the potential barrier hindering rotation from one conformation to another. However, a deterrent to this use of thermodynamics is the labor required to calculate the contributions to the thermodynamic functions for assumed potential functions. Tables of thermo-dynamic contributions for appropriate potential functions can eliminate that labor and greatly facilitate the thermodynamic study of rotational isomerism. In this research, tables of contributions to the thermodynamic functions were compiled for two potential functions typical of some commonly encountered examples of rotational isomerism. TYPES OF POTENTIAL FUNCTIONS Potential function 1, illustrated in figure 1, A, has two equal minima higher than the third. It has the general shape of the barrier to internal rotation in n-butane, for example. The trans conformation of n-butane has the lowest energy, and the two skew or gauche conformations have equal but higher energy. Potential function2, illustrated in figure 1, B, has two equal minima lower than the third. It has the general shape of the barrier in 2-methylbutane, for example. The two C1 conformations of 2-methylbutane have equal energy much lower than the assumed Cs conformation, which has not been observed spectroscopically.

Jan 1, 1962

Lower the respirable dust expo-sure of longwall mine workers by reducing the amount of air-borne respirable dust generated during coal extraction. Approach Increase the moisture content of the coal seam through water infusion before the coal is mined. How Water Infusion Works Increasing the moisture content in coal tends to prevent respirable dust from becoming air-borne during mining and transport. The moisture content of the coal seam can be increased by infusing water into the seam. Water under pressure is forced into the cracks (cleats) of the coal seam through sealed bore-holes. The effectiveness of water infusion is a function of the amount of water the coal seam accepts (its infusibility), which depends on the cleat density (cleat spacing) and cleat size (crack diameter). Thus the effect of water infusion on dust control depends mainly on coal seam characteristics. Water infusion techniques are generally used to restrict the flow of methane gas to the working face; however, the technique provides an alternative dust control method in mines with severe dust problems which limit production.

Jan 1, 1987

By Ulrich Neumann

Mining coal by employing a method called longwall mining is gaining more and more popularity in the United states since it offers many advantages over the conventional deep mining methods. Those advantages are a higher productivity, an almost total extraction of the mineral since no pillars must be left behind for support, and an increase in safety since the personnel are protected by the shield supports and rarely have to work near unsupported, exposed root. However, on some longwalls, the dust levels liberated by various equipment such as belt conveyors, chain conveyors, crushers, longwall shearers, and moving shield supports can exceed the maximum permissible limits and therefore have an adverse effect on productivity. Many attempts have been made over the past years to reduce the dust liberation by changing designs, installing various types of sprays or scrubbers, treating the mine water with wetting agents, or even using foam to catch dust before it becomes airborne. In the year 1984, the Bureau of Mines awarded Eickhoff Corporation a contract to demonstrate a water-jet-assisted cutting system for the multiple purposes of reducing dust levels, improving bit consumption, and increasing material size. During the previous phases of this contract, various trials were conducted aimed to design, build, and test d shearer loader to meet the objective of the contract. In the early stages of the research program, it was expected to see a reduction in the overall power consumption of the machine due to the fact that the high-pressure water jet would pre-cut the mineral in front of the bit. This, in turn, would then reduce the bit wear. Since there is less cutting action performed by the bit, a reduction of the dust liberation and a reduction of product fines was sought.

Jan 1, 1991

Crystalline silica is the scientific name for a group of minerals composed of silicon and oxygen. The term crystalline refers to the fact that the oxygen and silicon atoms are arranged in a three-dimensional repeating pattern. This group of minerals has shaped human history since the beginning of civilization. From the sand used for making glass to the piezoelectric quartz crystals used in advanced communication systems, crystalline silica has been a part of our technological development. Crystalline silica's pervasiveness in our technology is matched only by its abundance in nature. It's found in samples from every geologic era and from every location around the globe. Scientists have known for decades that prolonged and excessive exposure to crystalline silica dust in mining environments can cause silicosis, a noncancerous lung disease. During the 1980's, studies were conducted that suggested that crystalline silica also was a carcinogen. As a result of these findings, crystalline silica has been regulated under the Occupational Safety and Health Administration's (OSHA) Hazard Communication Standard (HCS). Under HCS, OSHA regulated businesses that use materials containing 0.1 or more crystalline silica must follow Federal guidelines concerning hazard communication and worker training. Although the HCS does not require that samples be analyzed for crystalline silica, mineral suppliers or OSHA-regulated businesses may choose to do so if they wish to show that they are exempt from the requirements of HCS. Because crystalline silica is an extremely common mineral and the HCS will affect many mineral commodities, it is important then, that there be as clear an understanding as possible of what is and what is not crystalline silica, and where it is found and used, and how it is qualitatively and quantitatively identified. This primer is an attempt to accomplish this in as nontechnical a manner as possible. This primer will examine crystalline silica. Part I will describe, in nonscientific terms, what crystalline silica is and how we come in contact with it. Part" will discuss the regulatory decisions that have created new interest in this ancient and widespread substance and will present a nontechnical overview of the techniques used to measure crystalline silica. Because this primer is meant to be a starting point for anyone interested in learning more about crystalline silica, a list of selected readings and other resources is included. The detailed glossary, which defines many terms that are beyond the scope of this publication, is designed to help the reader move from this presentation to a more technical one, the inevitable next step.

Jan 1, 1992

By Will H. Coghill, I. L. Feld, G. D. Coe

The object of this paper . is to make known the superior classification accomplished in a hydraulic classifier designed to make use of principles determined by recent research ... The details of the design , the results of preliminary research , and the final testing are given . The classifier of the new design shown in figure 1 and another one like it are in operation as concentration classifiers in a Birmingham iron- ore mill recovering 4 tons per hour of concentrates from table middling that ` otherwise would require regrinding and retabling . The four factors that contribute to the successful operation of these classifiers are ( 1 ) a teeter column of small diameter , ( 2 ) use of an open - bottom tooter column classifier with a periodic pincer instead of the usual type , which terminates in a vortex, ( 3 ) a sorting chamber under separate hydraulic control , and ( 4 ) a teeter column of more than the usual depth . · At the outset it must be stated positively what the authors mean by hydraulic classification : They mean the reconstruction of a multimineral ground product into fractions graded with respect to size , so that cach fraction has the heavy mineral segregated in the fine sizes and the light mineral segregated in the coarse sizes . This definition presupposes that in multiplespigot classification the low specific gravity minerals are carried beyond the first cells to the later ones . The reader must take into account that , from the standpoint of classification , " ores " may be divided into two types , represented - by the following : ( 1 ) Joplin flint - blende ores , which , because of the hardness of the flint and the softness of the blonde , yield upon comminution a product that already has the essence of classification ; and ( 2 ) Birmingham Big Seam iron oros , which contain " easily shelled - out " sca sand and , upon reduction to about 10 mesh , yield a heterogeneous mixture in which the size analyses of the respective " floats " and " sinks " arc almost identical .

Dec 1, 1945

By Nicholas Kyriazi

The Bureau of Mines has been developing breathing and metabolic simulator technology since 1970. Breathing simulation has been widely achieved throughout the world and used in the testing of open-circuit breathing apparatus, but satisfactory metabolism simulation has not been achieved. This situation required that the testing of closed-circuit breathing apparatus, which are the only type used in mines, be done using human test subjects. The goal was a machine that could accurately simulate both the breathing and the metabolic functions of a human being for testing of closed-circuit breathing apparatus. The advantages of using such a machine instead of a human being for testing respiratory protective devices lie in its ability to quantify metabolic input, its repeatability, and the lack of a need to deal with the vagaries of human subjects. This report will describe the breathing and metabolic simulators that have been developed and used by the Bureau over the past 15 yr.

Jan 1, 1986

By E. C. Tarpley

The Federal Bureau of Mines has studied solvent extraction as a means of concentrating the mineral components in coal. Solubilities of a number of American coals were determined using abietic acid as a solvent. The effect of rank on solubility was investigated, and maximum solubility was found with coals of intermediate rank. Vitrinite is the most soluble petrographic component; fusinite, micrinitc, and exinite are nearly insoluble. Spore exines also have a low solubility. Abietic acid is a hydrogen donor and reduces pyrite to ferrous sulfide. Mild hydrogenation of high-molecular-weight fragments of the coal structure to those of lower molecular-weight probably contributes to the solvent action. Even where solubility of the coal substance exceeds 90 percent, contamination of the mineral matter with coal makes identification of the mineral components difficult. Further separation might be possible by the application of float and sink techniques to the residue. INTRODUCTION Work n the solvent extraction of coal is conducted to recover commercially useful products and to characterize coal;. and obtain information on their structure. Some coals, particularly those of low rank, contain waxes, resins, and humic acids which can be removed by solvent extraction and find varied industrial uses. In World War II, solvent extraction of coal was conducted on a commercial scale in Germany to obtain a low-ash feed material for hydrogenation and to produce electrodes carbon for the aluminum industry.4 5/

Jan 1, 1960

The U.S. Bureau of Mines and the U.S. Mine Safety and Health Administration (MSHA) are participating jointly in a research program to evaluate the strength characteristics and air-leakage resistance of various proposed seal designs for use in underground coal mines. The full-scale seals were constructed in the USBM's experimental mine at the Lake Lynn Laboratory, air-leakage tested, then subjected to pressure pulses of 20 psig or greater. In experiments prior to this study, seven seal designs using solid-concrete blocks were tested. Only the standard-type seal passed the explosion and air-leakage criteria. Tests also were performed on four seals constructed with low-density foam blocks. All four of these seal designs withstood the pressure pulse. In more recent studies, nine cementitious foam seal designs of varying thicknesses and densities were investigated. Six of the nine designs successfully survived the explosion overpressures. Six wood-block convergence seals also have been tested. The typical 3-ft-thick, wood-block seal design currently used in many coal mines did not maintain its integrity, in the absence of convergence forces, following the explosion test. Five modified wood-block seals successfully withstood the 20-psig pressure pulse. Based on these tests, three alternative seal construction materials, cementitious foam, low-density foam block, and wood, have been approved by MSHA for use in underground coal mines.

Jan 1, 2010

By A. Wahab Khair, S. Jung

"This paper deals with the fracturing process of laterally confined blocks of coal subjected to impact indentation. During the test, blocks of coal with approximate dimensions of 10 in. x 10 in. x 6 in. were laterally confined to predetermined equivalent in-situ stresses and then subjected to an impact indentation by dropping coal cutting bits (various shapes) attached to a known weight from a known height. During the test a number of parameters, namely surface strains (using strain gages), penetration depth (using L.V.D.T.) and acoustic emission characteristics were measured. After the test, the fractured surfaces were photographed with the aid of a camera attached to a microscope. The fracture, its intensity and extended zone within the coal blocks were mapped using sonic techniques. By correlating measured parameters, fractured zones under a given set of test parameters were identified and characterized.INTRODUCTION To improve the understanding of basic failure mechanisms in coal cutting, a better knowledge of fracture and crack regions caused by the indentation in coal is needed. This study reports the detailed experimental procedure used in fracture analysis of indentation experiments on coal specimens using the Acoustic Emission (A.E. hereafter) and sonic techniques. The relationship between microcracking and the inelastic deformation of rock was confirmed by a series of experiments in which the A. E. generated by the cracking in the rock specimen were recorded and the number of events were compared to the strain measurement. (Scholz, 1967).According to fracture mechanism theory, crack initiation in brittle materials such as rocks begins from ""flaws"" either pre-existing or induced by the indentation process itself. Rocks are pervaded by natural cracks and pores, from which numerous possibilities for crack initiation arise (Lindquist, Lai and Alm, 1984)."

Jan 1, 1989

By Richard L. Rains

In 1984 and 1985, at the request of the Bureau of Land Management, the U.S. Bureau of Mines studied part of the 162,887-acre Mormon Mountains Wilderness Study Area (NV-050-161) in order to evaluate its identified mineral resources. The study area is located in Lincoln County, NV, about 60 miles northeast of Las Vegas. The study area had no mines or mining claims in 1985, and no mineral resources were identified within the study area, or at the Whitmore mine or Iron Blossom prospect near the study area. The alluvial fans around the southern boundary are staked with about 450 placer claims. Chemical analyses of samples indicate that some limestone in the study area is suitable for manufacturing cement or for agricultural purposes but the limestone is distant from markets and therefore not economic in the foreseeable future. The study area is blanketed with oil and gas leases, but no known productive horizons were identified.

Jan 1, 1986

By Wiliam L. Crentz

The importance of Somerset County, Pa., as a coal producer is due in large measure to the presence reserves of low-volatile bituminous coals. Although many coal beds of minable thickness are present, the important reserves are to be found in those beds underlying the Pittsburgh bed. The Kittenning beds and Freeport beds, which are responsible for the bulk of the present coal production in Somerset County and contain the largest reserves to meet future coal requirements, are usually thin and entirely free from impurities. The Pittsburgh bed, which has been such an important coal deposit in the coal areas immediately west and south of Somerset County, is of secondary importance in this county. Although generally rather friable, Somerset County coals have enjoyed wide receptability as excellent coals and to some extent have been utilized in the metallurgical market.

Jan 1, 1951

By G. M. Potter, F. S. Wartman, M. D. Schmid

"In matte smelting of copper it has been established that the sulphpr present will combine with copper as long as the latter is present, and that thereafter it will combine with iron. The Cu-Fe ratio in the matte is determined by the Cu-S ratio, presumably owing to the much greater affinity of copper for sulphur or, expressed thermodynamically, the greater stability of copper sulphide in contact with silicate slag. Now, the work of Fournet and of Schütz, which is quoted in many elementary metallurgical texts, indicates that manganese ranks ahead of copper in its affinity for sulphur. Hence, we might expect that manganese could be concentrated from its admixture with iron. Compounds by matte smelting, and Rotts / has patented such a process. This greater affinity of manganese or sulphur is used to advantage in iron metallurgy, also, in which it is well-known that sulphur will combine with manganese and separate from metallic iron as manganese sulphide. Manganese sulphide,however, is quite soluble in silicate slags. 5/ The loss of manganese in slag in any attempted matte smelting is therefore great.If this solubility of manganese sulphide is slag is a physical one and the reaction MnO + FeS MnS + FeOIs substantially complete, then it might be expected that the addition of copper sulphide, which is almost entirety insoluble in slag, would serve to extract the manganese sulphide with the formation of a manganese-copper matte on the other hand, if an equilibrium exists in the above reaction, a copper sulphide layer would displace that equilibrium in one direction or the other, according to whether iron sulphide or manganese sulphide were more soluble in the matter layer."

May 1, 1937

By R. W. Stahl

A survey of firefighting facilities and practices in coal mines conducted by the Bureau of Mines3/ showed such variations in equipment and apparent attitude toward fire protection that a comparison with other industry seemed advisable. Although other industry is confined generally to surface operations and the hazards probably are not as great, the same general methods of extinguishment are employed, so that the cost and protection at least should be comparable. An investigation of industry other than mines revealed a generally greater emphasis placed on fire-combating equipment, fire-brigade training, fire-fighting facility inspection, and fire-hazard elimination, as well as a greater average expenditure for fire protection.

Jan 1, 1959

By F. E. Brantley, D. A. Martin

Synthetic zeolites were tried as selective adsorbents for recovering sulfur dioxide from synthetic gases and gases produced from gypsum decomposition . Initial adsorption tests , using the synthetic gases , indicated that three of these compounds , having sulfur dioxide capacities of up to 29 grams per 100 grams of adsorbent , were satisfactory . Regeneration studies showed that over 90 pct of the sulfur dioxide desorbed from the loaded beds was of sufficient purity for direct liquefaction . However , all zeolites tested lost adsorptive capacity with repeated use . The zeolite determined to be the most promising in the preliminary synthetic gas tests was also evaluated for capability in adsorbing sulfur dioxide from gases produced by the thermal decomposition of gypsum . Despite small amounts of hydrogen sulfide in the gypsum decomposition offgas , good adsorption of sulfur dioxide was attained . The economic practicality of utilizing zeolites for sulfur dioxide removal from industrial gases was not evaluated , but the technical feasibility was demonstrated .

Jan 1, 1963

By W. P. Diamond

The Bureau of Mines has been involved in the drilling of vertical, horizontal, and directional coalbed gas drainage boreholes for mine safety since 1964. In that time, boreholes have been drilled in most of the major coal regions of the United States under a wide variety of geologic conditions. Many of the geologic conditions that occur in the coal measures are detrimental to gas drainage; others may be beneficial. Analytical techniques to determine the gas content of coal samples and evaluate regional trends of gas distribution have been developed. Drilling techniques that maximize the acquisition of coalbed gas data and geologic information have been determined. Although some of the geologic factors influencing the placement and potential success of coalbed gas drainage boreholes have been reported in papers on individual projects, a complete, systematic compilation has not previously been available. The objective of this paper is to pro- vide information on specific geologic factors that should be considered prior to, during, and after the drilling of coalbed gas drainage bore-holes. Many of the commonsense considerations that have been learned through many years of Bureau of Mines experience, but have generally not been reported formally, are included for those who may be considering coalbed gas drainage drilling for the first time, or who have not had the opportunity to encounter a substantial number of geologic situations.

Jan 1, 1982

By D. D. Fischer

Recovery and separation of molybdenum and rhenium from a process solution was accomplished by a technique developed by the Federal Bureau of Mines involving a combined solvent extraction and activated carbon adsorption procedure. The processing sequence required treatment of the solution with S02 to reduce the chlorate ion and adjust the pR prior to solvent extraction of molybdenum and rhenium with a tertiary amine. Molybdenum and rhenium were stripped from the organic phase with an NH40H solution, and the strip solution was then passed through activated carbon to preferentially adsorb the rhenium. After washing entrained molybdenum from the column with a brine solution, rhenium was eluted with an MeOH-H20 mixture. The activated carbon was regenerated with water. Molybdenum was recovered as (NH4)6Mo7024 by evaporating the column effluent. Rhenium in the column eluate was reextracted with a tertiary amine, stripped from the organic phase with dilute NH40H, and recovered as NH4Re04 by evaporating the strip solution. The final (NR4)Re04 product contained < 80 ppm impurities. Sodium sulfate was crystallized from the first solvent-extraction raffinate by lowering the solution temperature to 0° C. Precious metals contained in the original process solution were adsorbed onto the activated carbon.

Jan 1, 1975

By J. P. Hansen

Wustite beds were reduced with carbon monoxide and mixtures of hydrogen and nitrogen in the temperature range 900° to 1,300° C to determine the effect of temperature, gas flow, and surface area on the rate of reduction to iron. The composition of the gas stream as it passed through the wustite bed was continuously measured with infrared absorption cells and heated-wire methods. The change in composition was used to calculate the reaction rates. Arrhenius plots of the data give heats of activation of 34 kcal for particles using CO, 27 kcal for particles using H2, 24 kcal for pellets using C8, and 6 kcal for pellets using H2. The velocity of reduction is dependent on the area of reacting interface and the driving potential of the gas (reducing gas concentration minus equilibrium concentration) as well as the exponential temperature effect. The reaction rate was independent of the gas velocity over the range of conditions studied.

Jan 1, 1965

By Allen D. Look, Alan A. Sharp

"INTRODUCTION The bottoming of the United Verde sulfide pipe has shortened the expected life of the United Verde mine to a matter of a few years. First located in 1876, this Arizona mine has had a long period of activity, having reached a peak production in 1929 of over 71,000 trans of copper. Through these many years of successful operation, a safety program has evolved in keeping with the proficiency developed in mining the ore body. It is the purpose of this paper to record the safety practices in effect at this mine so that others may have the benefit of lessons ,learned through experience 'and years of work toward an improved accident record.ACKNOWLEDGEMENTSAcknowledgment 'is 'made to ,the Phelps Dodge Corp. for its cooperation in making available data contained in this paper, and to C. E. Mills, general superintendent; W. W. Little, mine superintendent; John Riordan, employment agent; and G. S. Leisk, safety engineer, for their helpful suggestions and information furnished.GENERAL INFORMATIONThe United Verde copper mine is situated just west of Jerome, Ariz., at an altitude of approximately 5,500 feet. Purchased by the Phelps Dodge Corp. in 1935, the mine employs approximately 500 men - 385 underground and 115 on the surface."

May 1, 1949

By G. R. Fitterer, C. H. Herty

"INTRODUCTION Manufacturers and consumers of steel have come to realize during the past few years that cleanliness is of great importance in steels which must meet rigid specifications for various physical properties. Of equal importance is the consistent production of steel which is uniform in these properties. For maximum utility steels should be uniform not only from heat to heat, but also from ingot to ingot and within each ingot. In the manufacture of killed steels such as the higher carbon forging grades, uniformity as indicated by the usual chemical analysis in easy to obtain, provided that a normal top discard is taken, as is always the case in steels poured with hot—top practice. No such uniformity, however, holds true for the nonmetallic matter, which consists for the most part of the products of deoxidation of the steel.For a large tonnage of steels which go into articles manufactured by deep—drawing processes, killed steel has never been successfully applied because with the present deoxidation practice, low—carbon killed steel is almost invariably extremely dirty. To obtain the desired qualities for deep drawing, the steel is rimmed, — that is to say, deoxidized with manganese and perhaps a small amount of aluminum, — the resultant product being of high purity in the skin of the ingot, but very badly segregated at the center of the ingot, particularly in the upper—central section. This segregation necessitates a very heavy top discard, and one of the major segregates is carbon which renders the steel too hard to draw properly. If clean, low—carbon killed steel could be made successfully, much better ingot yields would be obtained than by the present rimming steel practice. Furthermore, banded structures and outside and inside seams, which are undoubtedly due in a large measure to blowholes in the ingot, are defects which are very difficult to control in rimmed steel. These defects would be minimized by clean killed steel."

Feb 1, 1931

By A. C. Fieldner, G. W. Jones

Tests were made at the Government Fuel Yard , operated at Washington , D. C. by the Bureau of Mines , Department of the Interior , in order to determine and improve the adjustment of the carburetors on the trucks used for transporting coal from the Fuel Yard to the different Government buildings in Washington . The tests were made possible through the hearty cooperation of G , S. Pope , engineer in charge of the Fuel Yard . Joseph Burrows and A. E. Foote of the garage department assisted during all the tests and supplied information on the mileage obtained by the trucks for the months preceding and succeding the time the tests were made . The Mack trucks used range in capacity from 2-1/2 to 7-1/2 ttoonnss .. The majority of the carburetors were Stromberg G- 3 type , as shown in Table 2. During the winter months , when the demand for coal is heavy , from 30 to 35 trucks are used . At the time the tests were made , only about ten of the trucks were in daily use , owing to the small demand for coal during the summer months , and scarcity due to labor conditions . Samples of the exhaust gas were taken on the trucks kept in service for summer hauling in order to determine the carburetor adjustment as used . Changes were then made to a more economical adjustment wherever possible , without sacrificing flexibility of operation and power . In every case the adjustments were maintained for maximum power , but were adjusted to the leanest position to give that power . In all but one case the carburetors were found to be adjusted too rich for maximum power and economy . These results are considered in detail in a later part of this report .

Jun 1, 1923