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By David J. Ellis

The mineral industry of Benin continued to be confined to the production of cement, crude oil, salt, and sand and gravel. Only crude oil and cement were exported, with the value of crude oil exports and cement exports constituting about 20% and 2% of export revenue, respectively. The value of crude oil exports was less than the cost of imports of refined petroleum products. Production of crude oil was unchanged from 1986, averaging 5,500 barrels per day (bbl/d). The Government managed the facilities at the Semé Oilfield while actively seeking a new manager to replace Pan Ocean Oil Co. of Switzerland, whose contract was canceled in 1986. Recoverable reserves of crude oil were estimated to be between 18 and 30 million barrels.

Jan 1, 1989

Improve mine refrigeration system efficiency while providing free electrical energy to mines. Approach Convert the potential energy of incoming mine water falling down long vertical shafts into electrical energy by means of a turbine-generator system located at the bottom of the mine shaft. How it Works Converting the energy of falling water into useful work is a well-developed engineering concept. Water flowing down long vertical pipelines into deep mines develops high pressure that can be used to operate a turbine-generator system at the bottom of the pipeline. A thermal energy recovery system of this type offers three advantages: 1. In systems without turbines, the potential energy of the water is converted to heat. The water temper-ture will automatically

Jan 1, 1985

Improve the dust control effectiveness of dry collection systems on surface coal mine drills. Approach Use a dust pelletizer to convert the respirable dust particles discharged by the dry collector into dust pellets that present no health hazard. Background Blasthole drills are well-known sources of respirable dust that can contain significant amounts of quartz. The drills frequently use a dry cyclone-filter type collector that can obtain dust reductions theoretically greater than 95 pct. However, surface mine drills using dry collectors typically have three major dust sources that significantly reduce the overall effectiveness of the collection system: (1) the dust collector dump cycle, (2) drill shroud leakage, and (3) leakage around the drill stem seal in the drill table.

Jan 1, 1989

By J. E. Meacham

The U.S. Bureau of Mines investigated recovery of manganese from basic oxygen furnace (BOF) steelmaking slags because the slags represent a large potential resource of a metal for which there is no domestic production. BOF slags were leached using fluosilicic acid, a byproduct of the fertilizer industry. Manganese and iron were extracted as soluble manganous and ferrous fluosilicates while the calcium and magnesium remained in the tailings as insoluble fluorides. Treating the pregnant liquor with sodium chloride, precipitated sodium fluosilicate (Na2Sif6) which was recovered as a byproduct. Manganese and iron were precipitated as hydroxide-carbonate salts with the addition of sodium carbonate to the treated liquor. Recoveries for manganese and iron were 73 to 83 and 67 to 70 pet, respectively.

Jan 1, 1991

By R. L. Montgomery

Electronegativities of the rare-earth elements were calculated from heats of formation. The values obtained from different compounds varied widely. The postulates of Pauling's electronegativity theory were interpreted for bonds that are primarily ionic; the study showed that many compounds obey rules of the form expected. Revised electronegativity values are given for the more electropositive elements, including the rare-earth metals (which are near magnesium in electronegativity). Estimates of un-known heats of formation are made from electronegativities and are compared with other estimates. INTRODUCTION Calculation of the electronegativities of the rare-earth elements is interesting to show how these metals stand relative to the other metals and to each other, and also possibly to systematize the thermochemical data on them.

Jan 1, 1960

By Mary H. Brown

The heats of formation of oxalic acid and sodium, potassium oxalates, and lithium oxalates were related by solution calorimetry to the heat of formation of (COOH)2.2H20, a value believed to be reliable as reported in the literature. The following heats of formation were determined: (COOH)2(a), -198.1±0.1; (COOH)2(ß), -197.8±0.1; UAW,, -328.7±0.4; Na2C204 -316.2±0.1; K2C204, -321.9±0.2; and K2C204-H20, -393.5±0.2 kcal/mole. The heat of the crystalline transformation (COOH)2(a) ? (COOH)2(ß) was determined to be 0.30±0.02 kcal/mole at 298.15° K.

Jan 1, 1970

Improve the accuracy of commonly-used mine air velocity measurement techniques. Approach The Bureau of Mines, through a contract with Ketron, Inc., conducted a detailed study to establish appropriate, generalized correction factors for commonly-used air velocity measurement techniques. The techniques used were centerline readings, continuous traverse and split traverse vane anemometer readings, and smoke cloud readings (see Bureau of Mines Bulletion 589 for details on the proper use of these techniques). The various measurement techniques were used at different mine test sites to measure different air velocities. The data collected from the test sites were used in a statistical analysis which determined a generalized correction factor for each measurement technique. The correction factor multiplied by the measured velocity was used to provide the true velocity.

Jan 1, 1984

Minimize airborne respirable quartz dust produced by continous mining machines. Approach Install a shovel-mounted underboom water spray system on the off-curtain side of the mining machine. Dusty air containing quartz is momentarily trapped under the boom, where it is captured by fine spray mist. The remaining dust cloud is directed immediately behind the curtain before it can migrate back to the machine operator's location. How It Works Previous studies have shown that most of the dust generated by continous mining machines occurs under the boon as the cutter head shears down. The primary source of respirable quartz dust on many continous mining operations is cutting or trimming roof rock immediately prior to shearing. This results in very high concentration , of

Jan 1, 1989

By Richard J. Bielicki

Poor mixing of methane and air at coal mine working faces causes fluctuating methane concentrations. If these fluctuations are large enough, methane levels can periodically exceed safe limits, even though the time average methane concentration may be satisfactory. Concentration fluctuations measured underground can result both from variations in methane emission rate and poor mixing. The present paper reports on a statistical analysis of fluctuations at a constant methane emission rate, that is, on fluctuations due only to poor mixing. A full-scale model of a working face was used. Both peak heights and elapsed times between peaks were evaluated. Good mixing was indicated by normal, Poisson, and exponential distributions while poor or incomplete mixing was indicated by log-normal or gamma distributions.

Jan 1, 1974

By Scott W. Hazen

This report describes the design, analysis, and results of a special experimental mine-sampling project conducted as part of the Bureau of Mines continuing program on sample-methods research. The experimental project was conducted at the Bureau?s Denver Mining Research Center and at the Climax molybdenum mine within the framework of a cooperative research agreement between the Bureau and Climax Molybdenum Co., Division of American Metals-Climax, Inc. The primary objective of the project was to investigate the interrelation-ship between sample volume, number of samples, the standard deviation of an assay distribution, and the precision required for an estimate of grade of ore, and to develop this interrelationship into a relatively simple method of application for use in mine sampling.

Jan 1, 1962

By J. H. Field

Synthesis of hydrocarbons by the Fischer-Tropsch reaction in a hot-gas- recycle system was demonstrated to be technically feasible. This project was undertaken, by the Bureau of Mines, to determine if the system was operable and to ascertain the optimum conditions for the production of gasoline. Carbon steel turnings packed with a void volume from 88 to 90 pct. were satisfactory catalysts, but steel catalysts with greater void volume, either turnings or steel wool, were not as active. Good temperature control with a pressure drop of less than 0.5 pounds per square inch (p.s,i,) per foot of catalyst bed of turnings was obtained by operating with a recycle to fresh feed ratio of 20 and by splitting the total gas flaw and injecting portions into the reactor at different entry ports.

Jan 1, 1961

By A. Gene Collins, Cynthia A. Pearson, Cathy J. Waters

The chemistry of selenium and tellurium is discussed , along with a method of preparing a synthetic oilfield brine , an oilfield brine sampling method , and methods for determining selenium and tellurium in complex oilfield brines . Selenium either can be reduced to the elemental form with sulfur dioxide and determined semiquantitatively by color comparison of the red amorphous form or can be converted to selenite and determined quantitatively by reacting it with 3,3 ' - diaminobenzidine and obtaining its spectral absorbance at 420 mu . Tellurium can be reduced to the elemental form with hypophosphorous acid , and the spectral absorbance of its red hydrosol can be measured at 400 mu . Less than 0.05 mg / 1 of selenium and 0.1 mg / 1 of tellurium can be determined by the described methods .

Jan 1, 1964

By O. T. Barrett, R. F. Aberethy, H. N. Cooper, Thomas Fraer, William L. Crentz

"INTRODUCTION The object of the techniques described in this report is to determine the possibilities of separating the components of a raw coal into such grades as may be necessary to recover some exceptionally clean functions for special purposes.To do this commercial gravity methods would require separation at very low specific gravities, entirely outside the range of conventional practice. Hence, a technique has been developed for breaking down cool ample, into very close fractions within the gravity range of the (-lean coal matter as well as for separating it from the refuse and particles.Such data on the fundamental specific-gravity consist of the clean-coal matter will serve to appraise the difficulty of the problem and to chow be accomplished if and when effective methods of making such separations commercially are developed."

May 1, 1945

By James R. McVey

Tests during pillar robbing, longwall operations, and other mining activities indicate that roof-floor convergence rates can be used as an indicator of imminent roof failure. A large number of electrical-mechanical devices have been built to measure convergence as well as convergence rates, but most obstruct mine traffic and are costly and time consuming to install. The Bureau of Mines has designed and is evaluating three types of small ultrasonic units to make these measurements. The new instruments provide nonobstructing measurements up to 35 ft away. The ultrasonic transducers can be attached to a roof bolt, placed in an unsupported area (by means of a toss basket), or handheld. Total distance to the target and rate of closure are displayed digitally to 0.001 ft and 0.01 ft/min, respectively.

Jan 1, 1984

By Agnes Y. Lee

The Bureau of Mines has developed an effective hydrometallurgical method to recover high-purity Pb metal and elemental S from concentrates. This low-temperature process eliminates S gases and Pb emissions, in contrast to the current high-temperature smelting technology. The method consists of (1) oxidative leaching with H202, Pb02, and waste fluosilicic acid at 95° C to produce a solution of PbSiF6 and a residue containing elemental S, (2) electrowinning the PbSiF6 solution at 35° C to produce 99.99 pct Pb metal and H2SiF6, and (3) solvent extraction to recover S, leaving a residue containing Cu, Ag, and other metal values. Spent electrolyte was recycled repeatedly, with impurity buildup controlled by controlling the leach parameters.

Jan 1, 1986

By J. W. Walkiewicz

Studies were conducted by the Bureau of Mines to develop a method for fabricating Sm-Co permanent magnets. This method consisted of arc-melting, crushing and grinding the alloy, alining and pressing the powder, and sintering the green compacts. Results indicated that the optimum composition was 36.7±0.3 weight-percent Sm and 63.3±0.3 weight-percent Co. This composition was obtained by blending together Sm2C07 and SmCo5. The maximum values exper¬imentally obtained were MHC = 27.4 kOe, BHc = 7,510 Oe, Br = 7,810 G, and (BH)max = 15.1 MGOe. The optimum sintering temperatures and grinding times for maximum MHc and (BH)max were determined. Lowering the grinding temperature from 0° C to -60° C resulted in a significant increase of magnetic properties.

Jan 1, 1973

Flexible hoses with rated working pressures up to 40,000 psi are used when high-pressure water jets are employed to cut rock or improve the performance of mining machines. Hose failures at such high pressures can result in serious injuries to workers. The Bureau of Mines used fatigue and burst tests to investigate the failure modes of high-pressure hoses at their rated working and burst pressures. Fatigue failure, at rated working pressures, occurred when the inner liner of the high-pressure hose broke, allowing water to seep through the wire wrapping, although the reinforcement wires did not break. At the burst pressure, all hoses failed catastrophically when the reinforcement wires broke. Low-pressure hoses placed over the high- pressure hoses for safety failed to contain water released by catastrophic failure.

Jan 1, 1987

By M. B. Shirts

Numerous alternative processes have been proposed as being potentially more economical or less polluting than the traditional smelting of copper sulfide concentrates. One such process as recently developed in the laboratory by the Bureau of Mines is composed of a two-stage fluid-bed, oxidation-reduction roasting followed by ammoniacal leaching, solvent extraction, and electrowinning. A copper-leaching recovery of 97.4 percent was obtained, and electrolysis of the acid strip solution deposited metal assaying 99.99 percent copper. The roaster gases contain over 95 percent of the sulfur at a concentration of 12 percent which is better suited for acid making or elemental sulfur production than conventional smelter gas. When considering byproduct recovery, a preliminary estimate indicates copper production costs are com-parable to the conventional smelters.

Jan 1, 1975

By R. P. Vinson

The Bureau of Mines evaluated two real-time light-scattering dust monitors by measuring their response to Pittsburgh Seam coal dust and Arizona road dust (ARD). Both monitors, the model PDS-l, a personal dust sensor, and the model PCD-l, a digital dust indicator, are made in Japan by Sibata Scientific Ltd. Tests were conducted inside a laboratory aerosol chamber designed to maintain a uniform spatial distribution of the test dust. PDS-l and PCD-l measurements of concentrations for each test dust were averaged over 4-h test periods and compared with simultaneous gravimetric measurements. Both dust monitors responded linearly with mass concentration with both coal dust and ARD. However, the linear response of the PDS-l differed from that of the PCD-l for both dusts.

Jan 1, 1987

By Herbert R. Babitzke

As part of a project to develop refractory metal alloys suitable for high-temperature structural applications, the Bureau of Mines applied solid solution and precipitation-hardening techniques to columbium and tantalum alloys. Thirty-three alloys were evaluated to determine their formability, strength, and oxidation resistance. Three alloys had tensile strengths near 40,000 psi at 1,200° C: Cb-1N-5W-5V-10Hf (No.4), Cb-15Hf-5W-0.5B (No. 31), and Cb-15Hf-SW-IB (No. 32). Oxidation resistance of the high-strength alloys was good. Alloy4 gained only 34 mg/cm2 at 1,200° C, and 21 mg/cm2 at 1,000° C in 2 hours. Hot forming was done without any protection from oxidation.

Jan 1, 1968