Search Documents

By John Nagy

The Bureau of Mines adapted thermal theories explaining combustion of gases to correlate parameters affecting ignition of dust dispersions. The dust dispersions were ignited in a Godbert-Greenwald furnace at atmospheric pressure. Ignition temperature and the concentrations of fuel, admixed inert powder, and atmospheric oxygen were related mathematically. Values for these parameters obtained in laboratory experiments for cornstarch agreed with theory. The developed equation permits extrapolation; the predicted upper igni-tion limits correspond with limited experimental data from laboratory and large-scale tests. Explanation of the effect of fineness of dust on ignition parameters is attempted by introducing a surface-area constant to modify the activation energy. Arguments are presented to show that the ignition process is a solid-gas phase reaction rather than an ignition of prevolatilized gases.

Jan 1, 1966

By T. E. Gray

This report describes the preparation characteristics of the more significant coalbeds in Butler County, Pa. It is one of a series planned to determine which coals are suitable for producing metallurgical coke, either as mined or after beneficiation. More than 2 million tons of coal was produced in Butler County in 1958, of which about 25 percent was cleaned mechanically in four cleaning plants. Updating the 1942 coal-reserve estimates made by Ashley to December 31, 1958, more than 1,266 million tons of recoverable coal reserves remain in the county in beds that arc 24 inches or more thick. The Upper and Lower Freeport, Upper, Middle, and Lower Kittanning, Clarion, and Brookville beds were selected on the basis of production and estimated minable reserves. Sample locations were chosen after a study of the literature, conferences with mining engineers and mining company officials in the field, and examination of the available sites. Four samples each were collected from the Upper Freeport and Middle Kittanning beds, three samples from the Brookville bed, two, samples from the Upper Kittanning bed, and one sample each from the Lower Freeport, Lower Kittanning, and Clarion beds.

Jan 1, 1960

By G. W. Reimers

Conditions in the underground mine environment can cause self-heating of sulfide ores as a result of exothermic oxidation reactions, which may result in mine fires. This Bureau of Mines report describes thermal analyses of finely ground chalcopyrite, chalcocite, galena, pyrrhotite, marcasite, and arsenopyrite, to characterize their responses under oxidizing conditions. Thermal gravimetric analysis (TGA) and differential thermal analysis (DTA) were used, in the temperature range 1000 to 5000 C. Chalcopyrite showed an initial weight gain, due to formation of sul-fates, a weight loss, caused by ignition of iron sulfide to iron oxide, and a final weight gain, indicating the conversion of copper sulfide to sulfate. Chalcocite did not ignite in the temperature range studied but exhibited a rapid weight gain, because of the rapid conversion of copper sulfide to sulfate. Likewise, galena failed to ignite but underwent a steady weight gain when oxidized in a moist atmosphere, showing conver-sion of lead sulfide to sulfate below the ignition point. Marcasite underwent a rapid weight loss, indicating ignition, at 2000 C. Moisture in the oxidizing atmosphere lowered the ignition point of marcasite and arsenopyrite but not that of pyrrhotite. All the sulfides exhibited exothermic behavior at temperatures below the ignition point.

Jan 1, 1987

By D. Harrington

"In at least three out of every four working faces in metal mines there is no attempt made to cause air circulation other than by use of compressed air, and in at least nine cases out of ten the compressed air is released merely by opening, or partly opening, the valve and allowing the compressed air to escape through open air hose used to convey the compressed air to the drilling machines. Usually no blowers are in use during periods of drilling, as the exhaust from the drill provides cool, comparatively fresh air for the driller; however, in some instances, the compressed-air line is provided with a tea connection, which permits taking air for the drill from one side of the tee, and air for ventilation through a separate hose used as a blower, simultaneously with drilling.Table 1 contains temperature and humidity data as to compressed-air blowers from open end of air hose at 36 working places in eleven metal mines of four States, embracing the mining of gold, silver, copper, lead and zinc ores, and at horizons ranging from 500 feet below the surface to as low as 4900 feet.It is noticed that the ordinary air surrounding the worker at the face gives an average wet bulb temperature of 81.7° F. for the 36 working faces, with 84.7° F. dry bulb and 87.2 per cent relative humidity. The average wet bulb tem¬perature of 36 readings at these working faces of compressed air at the end of the,hose as the air issues from the hose was 67.4° F., or 14.3 degrees lower than the average wet bulb readings of the air of the working places; however, the average dry bulb temperature of the 36 readings of compressed air as it issued from the end of the hose was 79.7° F., or only 5 degrees less than that of the general air (84.7°); the relative humidity was 51.1 per cent as against 87.2 per cent for the surrounding air. Readings were taken in five raises, seven crosscuts, ten drifts and 14 stopes.It will be noted that the velocity or movement of the general atmosphere at each of the entire 36 working faces, was found to be practically imperceptible; this might readily be inferred since compressed air is rarely used on blowers if there is adequate circulation of the general air of the place. Where rook temperatures could be obtained readily, they are shown; it is noticeable that the dry bulb temperature of the air of the working place varies little from the rock temperature, and that the dry bulb temperature of the compressed air as it issues from end of air hose varies only a few degrees from the temperature of the surrounding rock; in some instances the dry bulb temperature of the compressed air as it issued from the end of the air hose was higher than the rock temperature or the dry bulb temperature of the surrounding air."

May 1, 1921

By Graham W. Marks

In broadening the utility of spectrochemical methods 9f analysis of ore samples 3,4/ a procedure employ in the total energy method, has been adapted to determination of silver in ores. Silver is the first element in group I of the periodic table to be studied in the Bureau of Mines program. Two silver lines in the spectrum, Ag X\ 3280.683 and 3382.89lR were used in the study, and the problems that had to be overcome were: (1) Influence of extraneous elements on line intensities, (2) preparation of standard curves, and (3) improvement in equipment and technique to increase accuracy. Sodium, potassium, sulfur, selenium, iron, cobalt, and nickel yielded low intensities and hence low results, particularly on the samples high in silver, but addition of 60 percent or more of lime counteracted these effects. One calibration curve must be used for samples low in silver and other for those high in silver. The chocks with fire assaying were close enough for preliminary or exploratory investigations, and the method is much more rapid.

Jan 1, 1948

By Aldo L. Furno

Sufficient quantities of combustible vapors are released by some sulfurs to produce flammable atmospheres under prolonged storage. Hydrogen sulfide and carbon disulfide appear to be the principal flammable constituents in the vapor space above molten sulfur. If sufficient carbon disulfide is present, ignition of the vapor-air mixtures can occur spontaneously on contact with the heated surfaces found within storage tanks.

Jan 1, 1963

By Harold E. Heide

Although the United States has been the largest consumer of tin, only a small quantity of tin was produced or. the North American Continent during peace times, and thy deficiency was made UP by foreign imports. Because the most important sources of tin wore cut off by the war with Japan, it became necessary to increase imports from South America and Africa and, if possible, develop domestic tin reserves. Most of the tin produced in North America has come from the Seward Peninsula, Alaska, and a substantial portion of this was produced from the Potato Mountain area. Tin was first identified as occurring in the Seward Peninsula by A. H. Brooks in 1900, when a part of heavy concentrates from Anikovik River and Buhna Creek, one of its tributaries, proved to be stream tin. 4/ His report was given considerable publicity by the daily press, and the first steamers north in 1901 carried a number of prospectors bound for the Seward Peninsula to search for tin. The deposits of stream tin on Buck Creek in the Potato Mountain area were discovered in the fall of 1901. 2/

Jan 1, 1949

By William H. King

The Mercur Dome mine is in the Camp Floyd mining district, Tooele County, Utah (fig. 1). The property lies between 6,000 and 8,000 feet altitude on the southwesterly slope of the Oquirrh Mountains, a short distance west of Mercur, the district settlement. Mining began in the Mercur area in 1870. Operations at the Mercur Dame mine were started in 1937 after several claims had been consolidated into one group. Preliminary examination of the ground by F. H. Gunnell, a Bureau of Mines engineer, disclosed the presence of vanadium in a carbonaceous shale horizon. Rocks near the Mercur Lame property are chiefly sediments of Carboniferous age, including the Madison and Deseret limestones. The main shaft penetrates the Deseret formation to a point a few feet above the 1,000-foot level where it enters the Madison limestone. The flat-lying vanadiferous shale horizon is exposed on the 1,000-foot level near the top of the Madison limestone. The Bureau of Mines development program, consisting of diamond drilling, auger hole drilling, and sampling, was planned to determine the extent and assay value of the vanadiferous bed. Seven diamond-drill holes totaling 300 feet were drilled from the 1,000-foot level of the mine. Eight hand auger holes were drilled in the back of the drift on this level (fig. 2). Assay determinations were made on 74 samples from the drill holes and supplemental channel samples and are tabulated in this report. The concluding section embodies results of metallurgical tests.

Jan 1, 1949

By T. A. Henrie, E. K. Kleespies

Carbon reduction of rutile and ilmenite in nitrogen and ammonia atmospheres was studied as a method of preparing titanium nitride . Ammonia was a better nitriding agent than nitrogen . The contact between the solid reactants , carbon and rutile , was a prime factor in nitrogen atmospheres and was of lesser import in dissociated ammonia . The reduction process for conversion of rutile to the nitride required carbon . The nitriding of ilmenite- carbon mixtures produced titanium nitride and elemental iron .

Jan 1, 1964

By Worthen Bradley

This paper describing the metallurgical practice and costs at the reduction plant of the. Sulphur Bank Syndicate, Clearlake, Calif., is one of a series of papers on the treatment of ores being prepared by the Bureau f Mines. The reduction plant and mine of the Sulphur Bank Syndicate are on the eastern shore of Clear Lake, in Lake County, Calif., 4 miles from the town of Clearlake and 125 miles north of San Francisco.

Jan 1, 1931

By K. B. Higbie

The quantitative separation of tantalum from columbium has been obtained through several liquid-liquid extraction processes. The valuable metals are separated by selective extraction from organic feed solution using a mineral acid or by selective extraction from aqueous feed solutions employing an organic solvent. The greatest degree of separation was obtained when organic ketones, particularly methyl isobutyl ketone, were used. Approximately 200 combinations of various organic solvents and mineral acids were tested as possible separation systems in which the tantalum or columbium content was extracted from organic solutions of the anhydrous pentachlorides.

Jan 1, 1956

By Raymond B. Ladoo

"The name bentonite has been applied to a group or series of clay-like materials characterized by an alkaline oxide and alkaline earth content of 5 to 10 per cent, fine grain Giza, high absorptive powers, and usually very strong colloidal properties.Bentonite probably represents no mineral of fixed composition, and its physical properties vary considerably. The type material from Wyoming is light yellow or greenish yellow in color, but from other localities it may be cream colored, white, gray, pink, dark brown or even black. It is exceedingly fine grained, very plastic and highly absorbent. The appearance may be dull or powdeay, but a freshly cut surface usually has a waxy luster. Some varieties have the appearance of wax and may be cut into very thin, translucent shavings. The fracture of the type material is roughly conchoidal, that of other varieties is platey and shale-like, while still others have no typical fracture. Bentonite is highly absorbent; .hen wetted it will absorb more than three times its weight or seven times its volume of water. Some varieties when wetted with water expand to more than six times (some experimenters report eight times) their original volume. The wetted material is exceedingly smooth and soft and feels like soft soap. Unlike most clays, bentonite is easily fusible at a comparatively low temperature.Under a high-power microscope bentonite seems to consist of extremely small, more or less rounded, grains of uniform size, but the texture of most varieties is so fine that individual grains can not be distinguished.Some varieties when finely ground and thoroughly agitated with water will stay in suspension indefinitely, forming a translucent gelatinous mass. The addition of small amounts of acids or sodium chloride seems to have little or no tendency to raid coagulation or settling. Other varieties of similar analysis and appearance go into suspension more easily, but settle out again in a comparatively short time. It has been suggested that the material which stays in suspension indefinitely is a true colloid of the emulsion or lyophilic type."

Oct 1, 1921

By A. B. Hooker

A list of permissible mine equipment approved by the Bureau of Mines prior to January 1, 1940, was published as Information Circular 7207.3 Three supplements published as I. C. 7240,4 I. c. 7283,2/ and I. C. 73166/ completed the list of equipment available to January 1, 1945. The present list is a revision of the previous lists, together with the additional equip- ment approved from January 1, 1945, to January 1, 1947. In preparing this list, certain items have been omitted, either because the manufacturer is no longer in business or manufacture was discontinued several years ago. However, some discontinued equipments that are still in service and for which repair parts are available are marked with an asterisk to indicate their limited status. The remaining obsolete equipments are listed in tabular form in Appendix 1. Appendix 2 lists seven satisfactory fuels available for use in permissi- ble flame safety lamps and shows where the fuels are available. The equipments listed were approved only when inspection and tests showed that they met the minimum standards of safety as outlined in "schedules" based upon laboratory tests as well as on performance underground. This circular is published so that users and potential users may be in- formed of the many types of permissible equipment available for reducing hazards incidental to coal mining and as an aid in identifying the equipments.

Dec 1, 1947

By H. Kenworthy

The objective of this investigation was to evaluate the technical feasibility of smelting certain low-grade domestic iron ores in an electric furnace. Laboratory-scale experiments showed that a high recovery of iron in the form of pig iron can be obtained from east Texas ores containing less than 25 percent iron. The pig iron was amenable to standard-or electric-furnace-refining methods for producing steel. Car-bon, silicon, and phosphorus were the primary impurities removed in refining. Overall recoveries of iron as pig iron exceeded 95 percent, in contrast with commercial mineral-dressing recoveries on these particular ores of 50 percent of the iron as a 45-to 50-percent iron concentrate.

Jan 1, 1958

By Manuel Gomez

Primary, low-temperature tars are generally known to alter with time. The effect is believed to occur, in some instances, without the external influence of air, light, or heat. Since one of the processes occurring during extended storage is oxidation, the action of mild oxidation induced by air and heat, in addition to the effect of storage, was studied. The principal effect in aging and oxidation is formation of pitch at the expense of the distillate fraction. The fraction boiling above 270° C. is mainly involved in pitch formation due to storage, whereas all fractions are affected to some degree when tar is heated at 125° C. in the presence of air. If the effects of air are considered, the aromatic and tar-acid fractions seem to be important in pitch formation.

Jan 1, 1956

By J. M. Stuve

Provisional values for the heat of formation of europium trichloride and europium sesquioxide were determined by solution calorimetry utilizing europium metal of more than 99-percent purity. The resulting values for the heats of formation of Eu203 (cubic) and EuCls (hexagonal) were -386,970 ±l,200 cal/mole and -218,740 ±650 cal/mole, respectively, measured at 298.15° K.

Jan 1, 1965

By Ray J. Holmquist

"INTRODUCTION The Elk Mountain mica deposit was examined in June 1943 by the Bureau of Mines. An exploratory project and an access road for the property were recommended, provided the zinc was put in operation under competent management. K. Garard obtained a lease on the properly and started operations in June 1944; this was followed immediately by the Bureau's exploratory work. Road construction was begun by the Forest Service in July the same year.The lessee mined mica from the richest exposure with a crew of three men for 2-1/2 months. His operation terminated late in September, but the Bureau of Mines project and the Forest Service road construction continued until snow forced suspension of activity during the first week of November.The Bureau of Mines work consisted of trenching with a bulldozer, hand excavating on undeveloped outcrops, extending an existing adit, and starting a new adit below the older workings."

Jul 1, 1946

By Raja V. Ramani, Sachin Shankar

"Re-entrainment refers to dislodgement of particles deposited by both atmospheric and nonatmospheric processes and their subsequent insertion into a flowing field. Formation of sand dunes, snow drifts, soil erosion and fugitive dust emissions are a few examples of the natural occurrence of re-entrainment. Re-entrainment studies have been done for the estimation of potential hazards from nuclear fallouts. The phenomenon of re-entrainment has been utilized for the cleaning of wafers and filters. Re-entrainment is associated with both surface and underground mining activities. However, studies on dust re-entrainment in mine atmospheres are limited. Understanding the re-entrainment phenomenon is important because dust particles lying seemingly harmless on the ground and adhering to numerous surfaces can get re-entrained and become a health and safety hazard.There are significant differences in the kind of re-entrainment encountered in underground mines and those in other fields of interest. These major differences are air velocity, direction of air flow, particle size, amount of particles, and time of exposure. While numerous studies have been done in other fields to identify the role of interacting variables and their contribution to the mechanisms of re-entrainment, no similar reported work is available for dust in mine atmospheres.In this paper, recent research efforts on re-entrainment are reviewed. The most suitable form of representing re-entrainment in underground coal mine atmosphere is presented. Various approaches to studying re-entrainment phenomenon in mines are also outlined.In the mineral industries, formation of dust particles of widely varying sizes is a natural outcome of the fragmentation required in mining the solid resources. Fine particles in mine atmospheres, particularly in the respirable size range, are a threat to the health and safety of the miners when present in high concentrations. In 1980 the National Academy of Sciences (NAS) Committee on the Measurement and Control of Respirable Dust in Mines recommended that the spatial and temporal characteristics (of fragments produced in coal mining) need to be understood so that the exposure of workers to the dust can be controlled. Recently several studies have been performed to understand the fundamental behavior of the airborne respirable dust in mine airways (Bhaskar, 1987; Qin, 1988; Polat, 1989; Bode, 1990)."

Mar 1, 1992

By V. H. Gottschalk, John Grodd, R. S. Dean

"Elemantary ConsiderationsAlthough magnetiem was first discovered in and derives its name from an oxide of iron found in magnesia and called lodestone its pracical uses date from the discoveries of Faraday concerning its relation to the electric current. We may therefore start our discussion of magnetic properties with Faraday's law for relation between induced electromotive force and the change in a magnetic where e is the electromotive force induced in an electric circuit by a unit rate of change of magnetic flux N, H is the intensity of the magnetic field, S is the area enclosed by the circuit, and i an angle between H and the normal to dS. In the simplest case we could use this law to measure the strength of a magnetic field by passing it at a measured rate through a coil of copper wire and determining the,electromotive force. As a matter of practical convenience, it will be simpler to nee the total quantity of electricity produced by a change of magnetic field. For this purpose we may let i denote the strength of the electric current induced by the change of magnetic field in time in a circuit of area a and resistance R. Then the total electric quantity. Q is given. by"

Mar 1, 1934

By J. A. Eisele

The Bureau of Mines has reviewed the literature related to the recovery of A1203 (alumina) from coal ash. A small amount of unpublished data is also reported. Of the processes studied, the alkaline-sinter process is the most promising from a technical standpoint. However, owing to the high cost of processing coal ash, the dispersed location of powerplants, and the domestic availability of higher grade alternate materials, coal ash does not rank as a primary source material for replacing imported bauxite.

Jan 1, 1979