Search Documents

By D. Montagna

The Kroll-Betterton process for debismuthizing lead is based on adding calcium and magnesium to impure molten bullion to form solid Ca-Mg-Bi inter-metallic compounds that float on the surface as drosses. Present practice in industry is to hand-skim off these drosses, often followed by hydraulic pressing to squeeze out some of the entrapped liquid lead. In an effort to develop an improved technique, the use of an argon-shrouded dipping centrifuge to perform the required phase separation was investigated. Centrifugation experiments demonstrated that the bismuth content of an impure bullion could be lowered from an initial 0.5 percent down to 0.03 percent with a lead recovery of 90 percent, which is comparable to lead recovery after hand skimming of drosses in commercial lead-debismuthizing operations. Centrifugation provides better control in removing drosses, faster operation with less oxidation and relatively little fuming, and recovery of a lead bullion that approaches commercial specifications.

Jan 1, 1972

By Dean E. Bluman

The Bureau of Mines investigated the convective heat transfer coefficients for recirculated suspensions of 30-micron glass beads in inert gas. Coefficients for the suspensions were not significantly higher than coefficients for the pure gas. Reynolds numbers of the suspensions were 20,000 to 35,000; solids loadings ranged from 0.0 to 0.7 pound per pound of gas. Comparison of the results with published data showed the direction of heat flow to have no effect at the test conditions.

Jan 1, 1967

By Stephen D. Cramer

The solubility of methane, carbon dioxide, and oxygen was measured in brines at temperatures from 0° to 300° as part of Federal Bureau of Mines research on the corrosion of metals in high-temperature geothermal and mineral processing environments. Solubilities were measured by the technique of extracting pure gas, dissolved at pressures where Henry's law was applicable, from known volumes of brine. The results were smoothed with respect to temperature. The solubility, expressed in terms of the Henry's law constant, reaches a maximum at temperatures ranging from 60° to 100° C for methane and oxygen, and from 160° to 170° C for carbon dioxide. The Henry's law constant increases, that is, gases are salted out of the brines, in the presence of dissolved salts. Salting-out coefficients are strongly dependent upon temperature. The temperature dependence of the Henry's law constant for geothermal brines is different from that for sodium chloride brines owing to the more complex chemistry of the geothermal brines. The solubility of oxygen and carbon dioxide in brines exposed to air saturated with water vapor and at a total pressure of 760 mm Hg is reported for temperatures from 0° C to the normal boiling point.

Jan 1, 1982

By Robert K. Koch

Laboratory-scale studies on defluorination of natural and synthetic fluorspars by pyrohydrolysis at 1,500° C. were made to determine the feasibility of developing a process for producing hydrogen fluoride from siliceous fluorspars. It was found that the reaction (at 1,500° C.) is not promising for process development, even though a silica-free offgas can be generated. The primary difficulty is the low hydrogen fluoride content of the offgases; an HF content of 6 percent was the best achieved. Previous research by the Bureau of Mines has demonstrated that offgases averaging 27 percent hydrogen fluoride can be produced under carefully controlled conditions at 1,280° C. The lower temperature process is a better method for production of HF. However, charges in which the CaF to Si02 mole ratio varied from 0.4 to 2 could be processed with similar results. Also, combined alumina and ferric oxide contents up to 25 mole-percent did not noticeably alter the rate of defluorination. Therefore, virtually any natural siliceous fluorspar would respond in essentially the same manner when exposed to water vapor at 1,500° C.

Jan 1, 1962

By Frank E. Federspiel

In 1986 and 1987, at the request of the U.S. Forest Service, the U.S. Bureau of Mines examined the 47,000-acre Electric Peak study area (part of the formerly-designated RARE II Non-wilderness Recommended Area no. 1609) to evaluate its' identified mineral resources. The study area is in Powell and Jefferson Counties, YT, about 30 mi southwest of Helena and 30 mi north of Butte. Three lode localities within the study area contain an estimated 159,000 tons of identified subeconomic resources containing gold, silver, and accessory lead, copper, and zinc. Resources at those localities range from 10,000 to 134,000 tons with grades ranging from 0.04 to 0.32 oz/ton gold, 0.92 to 16.42 oz/ton silver, 0.14 to 79.65 percent lead, and as much as 0.41 percent copper and 0.68 percent zinc. One property also contains 0.15 percent antimony. Gold, silver, and base-metal content in samples of poorly exposed mineralized structures indicate that further exploration may identify resources on seven additional study area localities.

Jan 1, 1988

By P. R. Tisot

The structural response of propped oil shale fractures was determined for each of two different grades of Green River oil shales (38.0 and 29.0 gpt) as they were heated in an inert atmosphere from ambient to subretorting temperatures (below those required for rapid pyrolysis of the organic matter). Small oil shale cores were propped apart by 3-mm glass beads to simulate a small cross section of a propped oil shale fracture between an injection and a producing well. These specimens were then heated at a uniform bate up to 800° F in a specially designed test cell under stress levels from 100 to 1,000 psi in biaxial and in triaxial confinement. Under the conditions of heat and compressive stress utilized in this study, all of the propped fractures in the two oil shales underwent structural deformation ranging from partial to complete collapse, as evidenced by proppant embedment. Structural collapse of induced fractures would in turn result in serious impairment or complete loss of the fracture flow capacities of the specimens. Results from this Bureau of Mines study indicate that underground retorting of Green River oil shale may be seriously impaired by loss of permeability when utilizing propped fractures in oil shales assaying more than 28 gpt.

Jan 1, 1975

By A. B. Hooker, R. A. Kearns

Material used for flame safety lamp gauzes should possess the following qualities: (1) mechanical strength, (2) resistance to corrosion under service con- ditions, (3) a relatively high thermal conductivity, (4) a melting point above the ignition temperature of mine gas. Heretofore, three metals have been used for flame lamp gauzes, namely: steel, brass and copper. While each of these has the requisite qualities to some extent, none of them is an ideal gauze material. Copper gauzes lack mechanical strength, especiall, after they have been heated; brass and copper both have comparatively low melting points so that before the gas ignition is reached the gauze metal is attacked and oxidized under the action of the heat. Steel corrodes readily in damp atmos- pheres and if the lamp stands unused under these conditions for some time, the gauzes become unfit for service. Tests of these three materials have shown that steel offers the highest degree of safety. Manel metal, the natural alloy of nickel and copper, is practically noncor- rodible. Its relting point is approximately the same as that of steel. From time to time it has been suggested that this alloy might be a better gauze material than steel, since gauzes made of Monel metal should have all of the good qualities that steel gauzes possess and, in addition, would not corrode appreciably in ordinary mine atmospheres. One advocate of this use for Monel metal, the International Nickel Co., through their development engineer, Mr. Robert J. McKay, cooperated with the Interior Department, Bureau of ines, to the extent of supplying twelve sets of 30 mesh, Monel-metal gauzes for tests. Those gauzes were made up by the same lamp manufactur- er ho rade the steel gauzes used in the previous investigation. Being made by the same processes as the steel gauzes, these Manel-metal gauzes were needlessly given the same anti-rust coating that is always applied to steel gauzes to prevent any corrosion before the gauzes are used. In previous tests the Bureau of Mines had collected data as to the behavior of steel gauzes. In determining the value of Monel metal as a gauze material, it was planned to obtain similar data with Monel-metal gauzes, and thus make a direct comparison with the steel gauzes. In addition, steel and Monel-metal gauzes

Apr 1, 1923

Spectrochemical methods were developed to determine beryllium in the concentration range 0.0015 to 4.0 percent in siliceous mineral beneficiation products. Two methods are described. They are (1) a fusion-pellet-spark procedure (spark method) and (2) a sustaining alternating-current arc procedure (arc method). In the spark method the sample is fused with lithium tetra-borate and vanadium pentoxide. The resulting bead is crushed, mixed with powdered graphite, and briquetted. This is analyzed spectrographically using controlled high-voltage spark excitation. In the arc method the sample is diluted with germanium metal, graphite, and vanadium pentoxide. Weighed charges are packed into cupped graphite electrodes and subjected to excitation with a sustaining alternating-current arc. Vanadium serves as internal standard for both methods. Effects due to matrix variations in samples and standards are eliminated either by fusion with lithium tetraborate in the spark method or by dilution with germanium and graphite in the arc method. Beryllium determinations show deviations from accepted chemical values of approximately 5 and 8 percent for the spark and arc methods, respectively. Analyses can be made more rapidly by the arc procedure with a sacrifice in precision and accuracy. Either method can be applied to the determination of beryllium in silicate rocks.

Jan 1, 1962

By John K. Alley

Fibrous silicon carbide was produced by thermal decomposition of certain silicates contained in graphite crucibles. Induction heating was used to produce the necessary temperature and thermal gradients. Both green and white fibers were mainly the beta modification even though each color grew within a different temperature zone. Alpha silicon carbide, present in insufficient amounts for X-ray detection, was identified by electron diffraction. The white fibers formed in a zone between 1,365° and 1,634° C (±50° C). The green fibers (less contaminated) formed in a much more narrow zone between 1,650° and 1,672° C (±50° C). The average lengths and widths of microscopic fibers grown by this method were 1.5 mm/0.002 mm (white) and 1.2 mm/0.0035 mm (green); however, same fibers observed by electron microscope had cross-sectional measurements of 150 to 300 A. Both differential thermal analysis and thermogravimetric analysis showed that silicon carbide fibers oxidized in air at temperatures above 500° C. Fibrous silicon carbide was indexed as a cubic cell with the dimensions a = 4.358 A. The density calculated from X-ray data was 3.217 g/cm3.

Jan 1, 1963

By John O. Atkins

[Experiments were conducted by the Bureau of Mines on five types of simuated lunar rock (dacite, tholeiitic basalt, vesicular basalt, pumice, and uluth Gabbro) to study the effects of various simulated lunar environments n their strength and deformational properties. Specimens were tested in an ltrahigh vacuum (UHV) system at pressures ranging from atmospheric down to 0-11 torr and at temperatures of -130°, 20°, and 135° C. All tests were onducted with a servocontrolled testing machine. Rock specimens tested at 0° C in UHV exhibited significantly higher compressive strength and Young's odulus than those tested at 20° C in atmospheric pressure. The magnitudes f increase are related to the porosities and permeabilities of the rock pecimens; high porosity and permeability allow better outgassing and thus nprove surface cleanliness in UHV. The compressive strength generally ncreases but Young's modulus decreases as test environments change from 20° C i UHV to 135° C in UHV. No significant difference was observed in the iysical properties measured at 20° C in LTV and -130° C in UHV. Anisotropy i strength and Young's modulus exist both in UHV and at atmospheric condi¬'.ons with the same symmetry pattern. The orientations of the principal axes iy, however, change from the atmospheric to UHV condition. The results idicate that rock fragmentation in lunar environment will require more ergy than that at 20° C in atomospheric pressure.]

Jan 1, 1974

By Everett A. Sondreal

Data are presented on the characteristics of lignites with emphasis on the composition and fusion properties of the ash. Differences in the analyses of commercial-grade lignites are related primarily to variations in moisture and ash contents. Lignite ash is generally characterized by high concentra¬tions of alkaline earth oxides and a greater tendency for retention of sulfur in the ash than higher-rank coals. Composition of ash varies significantly within and between mines. The differences within mines are significant for short distances and may be eliminated under certain circumstances by normal mixing occurring during mining. The sulfur in lignite averages 0.6 percent and is found primarily in the organic or pyritic forms with only a trace of the sulfate. During the stan¬dard laboratory asking procedures, from 60 to 100 percent of the original sul¬fur is retained in the lignite ash. Trace elements, such as uranium and germanium, in the ash from commercial¬-grade lignites are present in low concentrations, but others, primarily copper and silver, are present in specific samples in concentrations approaching those found in some commercial ores.

Jan 1, 1968

By R. V. Subramanian

This project financed by the Bureau of Mines investigated the use of polymers to achieve rock bonding and reinforce coal mine structures for better or permanent ground support. Support was achieved by pumping the polymers into the rock interstices to bond the mass together for increased structural competence. Holes were drilled in the mine roof, after which the polymers were injected at about 100 psi to permeate the cracks. Initial laboratory work indicated that of all the resin systems tested, the epoxy resins could most likely be modified to be suitable for rock injection. This was confirmed when several potentially suitable resin systems underwent intensive evaluation. In a series of three field tests, two conducted in a copper mine with coal mine-type shale and the third in a coal mine, it was shown that the polymers penetrated cracks less than 0.005 inch wide. The fast-setting epoxy systems, cured out in thin films under mine conditions, produced a bond exceeding the strength of the uncracked virgin rock.

Jan 1, 1974

By J. Dean Warner

In 1984, as part of a project to evaluate Alaskan occurrences of certain critical and strategic minerals, the Bureau of Mines investigated a columbium-bearing regolith on upper Idaho Gulch, near Tofty, AK. The regolith is derived from weathering of a dolomitic marble and consists mostly of iron oxide minerals with accessory apatite, zircon, xenotime, rutile, monazite, and the columbium minerals aeschynite, columbite, and ilmenorutile. Two regolith lenses contain 340,000 lb of columbium resources at an average grade of 0.07 pct. Calculated composite concentrates from two regolith samples (approximately 200 lb each) contained 53 and 57 pct of the columbium at grades of 0.97 and 0.86 pct, respectively. In each case the grade could be improved to 1.1 pct Cb with a sacrifice of 9-pct recovery. The regolith's mineralogy, trace-element geochemistry, and similarity to descriptions of other columbium-enriched regoliths suggest that the underlying marble may be a carbonatite. The lack of associated alkalic igneous rocks and the stratiform nature of the regolith, however, may be interpreted as evidence for sedimentary origin of the marble. The marble and regolith are a lode source for some of the minerals in the Idaho Gulch placer deposit.

Jan 1, 1986

By Richard J. Mahany, Terry S. Cory

This report describes the results of a measurement and analysis program to characterize wireless radio transmission in metal/non-metal mines over a wide frequency range from 0.2 - 1000 MHz and over a variety of mine environments. Six mines were chosen based on the relative economic significance of their product to the U.S. economy. Mine types include oil shale, uranium, potash, lead/zinc, copper, and silver. Particular mines were chosen so that the group would embody the most important mining techniques. The results show that transmission at medium frequencies are optimum for wireless mine communications, in agreement with extensive testing previously performed by the authors in coal mines, and that mine-wide wireless systems are feasible with a minimum requirement for new dedicated wiring. At least one need for such a wireless system was identified in each mine visited.

Jan 8, 1981

By R. V. Ramani, R. Stefanko, G. W. Luxbacher

MINE VENTILATION NETWORK ANALYSIS

Jan 1, 1977

By A. D. Mah

To assist Bureau of Mines research in extractive metallurgy and to add to the thermodynamic data base useful to others, energy calculations were made for 63 reactions relating to investigations on the production of anhydrous aluminum chloride from chlorination of clay.

Jan 1, 1982

By A. J. Leighton

An improved mathematical model with the attendant computer program to calculate multiphase fluid flow in petroleum reservoirs is presented. The model is used to simulate the behavior when a fluid is used to displace hydro-carbon fluids in a reservoir. The method is an expansion of a previously published method, in Bureau of Mines RI 7011, but handles constant injection rate as an alternative to constant pressure. Program documentation is provided along with thorough explanations of the added program features. Using the program, the petroleum engineer can calculate oil recoveries for different flood patterns and operating conditions and select the conditions most likely to optimize recovery. Experience with the previous model demonstrated the need for the improvements in order to simulate reservoir behavior more accurately. The improved method will result in improved oil recovery. In this paper, the significant improvements are described in detail so that anyone interested can put the program to use.

Jan 1, 1975

By R. V. Higgins

A numerical method is presented to calculate the isopressure (isobar) lines and streamlines for an oilfield from the pressure distribution. A knowledge of these lines is useful in the study of the flow of fluids in underground reservoirs, especially for those containing gaseous and/or liquid hydrocarbons. This work was done primarily to enable determination of the shape factors needed in the calculation of petroleum reservoir performance. However, it has application for the flow of water in aquifers, or electricity or heat in odd-shaped geometry. Techniques previously developed were used to calculate the pressure distribution. From this pressure distribution, the isopressure lines were calculated accurately by the method presented in this paper. Then by successively projecting orthogonal lines from one isopressure line to another, the streamlines are determined. From the coordinates of the isopressures and the streamlines, the shape factors can then be determined by a published method. Computer methods are presented to calculate the streamlines and isopressures for any well-spacing pattern existing within a field with multiple wells. The method reproduces the flow net for several well configurations having extensive geometrical variations. Such information provides the petroleum engineer with data from which he can compute oil recoveries for different patterns and thereby maximize the recovery of hydrocarbons from the reservoir.

Jan 1, 1972

By A. J. Kraemer

[The Bureau of Minas for a number of years has been studying the properties of crude petroleum from producing fields in the United States and Western Hemisphere and has published a series of reports on these fields, including oil fields of Texas.5]

Jan 1, 1927

By Geo S. Rice

"The most authoritative compilations on the coal resources of the British Isles are given in ""The Coal Resources of the World"" issued by the 12th International Geological Congress, 1913. The reserve, calculated to a depth of 6,000 feet, in seams containing not less than two feet of merchantable coal are as follows: Mining at present is conducted at depths from about 800 to 3500 feet. The shallower coals have largely been exhausted. The present average hoisting depth probably is about 1500 feet.The thickness of individual beds at present mined varies from about 2-1/2 feet up to 40 feet in thickness, the latter thickness being found in North Staffordshire. The coal is rarely found level, but is approximately level in some parts of Yorkshire. Anthracite is mined in limited quantities in Wales, and Wales also produces a very high grade semi-anthracite or smokeless coal, which is fa famous the world round, and is equaled only by the Pocahontas and New River coals in the United States:As concerns the methods of mining, these vary widely according to the pitch of the bed, the thickness of coal, and natural conditions, but the prevailing method is some form of longwall or semi-longwall, by which all the coal is extracted. The other principal method is a so-called pillar and, stall method, by which the coal is mined out, leaving square or rectangular pillars which are extracted on the retreat, making it virtually, a retreating longwall system. This method is applied where the roof is strong, and particularly in the thicker beds, as the longwall method is not so well adapted for mining where the thickness exceeds five or six feet, unless it is what is called a multiple seam, one in which there are partings of rock that provide material for building walls, which the roof in subsiding gradually squeezes down."

Jul 1, 1920