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By A. B. Cecala

A cooperative research effort was established between the Tilden Mining Company LC, the United Steelworkers of America, and the National Institute for Occupational Safety and Health to lower respirable dust levels in an iron ore grinding and concentrator plant. This cooperative effort involved three field studies to evaluate different techniques to lower respirable dust levels. The greatest impact on lowering respirable dust concentrations throughout this facility was achieved through ventilation changes. The most significant improvement was realized by changing the ventilation profile throughout the entire facility. The ventilation to this grinding and concentrator facility was provided by approximately 40 roof fans operating in either the intake or exhaust mode. The operation of these fans was significantly changed in an attempt to pro-vide more of a directional flow pattern throughout the facility, as well as to more closely balance the intake and exhaust air volume. This change accounted for a 31 pct reduction in respirable dust levels in the primary grinding area of the mill. Another successful modification was to improve the sealing of a reclaim tunnel to the outside and by barricading the access point from the reclaim tunnel to the concentrator plant. This minimized the dust liberated in the conveyor tunnels from traveling through the reclaim tunnel and into the plant. These two modifications illustrate the impact that improvements in ventilation can have on lowering respirable dust concentrations in iron ore processing facilities.

By M. J. Ferrante

High-temperature enthalpy and X-ray powder diffraction studies were con-ducted on aluminum sulfide (Al2S3) as part of the Bureau of Mines effort to provide new data for the advancement of mineral technology consistent with environmental preservation and energy conservation. Relative enthalpies were measured with a copper-block calorimeter from 298.15 to 879 K. Tabulated values are listed for heat capacity, entropy, Gibbs energy functions, and relative enthalpies between 298.15 and 900 K. Enthalpies were also given in the form of an equation and combined with published data to calculate standard enthalpies of formation and Gibbs energies of formation for reactions of crystalline aluminum with crystalline, liquid, and gaseous diatomic sulfur. The hexagonal, rhombohedral, and cubic phases of Al2S3 were identified by X-ray powder diffraction studies, and the indexed powder diffraction patterns of these phases are given. The hexagonal phase was stable to about 852 K and was partially converted to the rhombohedral form at 879 K.

Jan 1, 1981

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 Neil B. Young

Analytical results for nahcolite, dawsonite, total extractable alumina, and oil yield are presented for samples representing Green River Formation oil shales in the saline section of two cores from Colorado's Piceance Creek basin. Analyses are also reported for samples extending the analyzed section of Colorado corehole No. 3 beyond that reported previously. These data permit evaluation of the deposit for possible production of three coproducts--shale oil, alumina, and sodium carbonates--from the saline section of the formation at these sampled points.

Jan 1, 1970

By J. Brad Seymour, Mark K. Larson, Richard L. Rains, Douglas R. Tesarik

For several years, researchers from the Spokane Research Laboratory of the National Institute for Occupational Safety and Health (NIOSH) have been using geotechnical instruments in underground mines to study ground control problems and develop means of reducing accidents and fatalities caused by ground falls. This paper describes many of the different types of instruments, sensors, and data acquisition equipment that have been used for these studies; briefly explains the advantages and disadvantages of various sensor technologies; provides practical recommendations regarding the use of specific instruments and data acquisition systems; and outlines a general approach to the design and implementation of a successful instrumentation plan. A wide variety of instruments are commercially available for measuring deformation, strain, stress, and/or load. If used correctly, these instruments can provide important quantitative information regarding the mining-induced behavior of the host rock, the performance of ground support systems, and the safety and stability of underground workings. Data collected from these instruments can warn mine staff of impending ground control failures or hazardous working conditions, as well as provide valuable information for the design of ground support systems and the configuration and sequencing of mining excavations. We hope that the practical information presented in this paper will encourage a more widespread use of geotechnical instruments in underground mines and lead to reliable measurements that aid the engineering decisions affecting the safety of miners.

Jan 10, 2000

By Charles Findlay, Stephen Krickovic

A methane emission rate study was conducted in 1969 on a longwall section of a Lower Kittanning coalbed mine in central Pennsylvania. The longwall face was mined with a drum shearer between developed headings on the head end and headings on the tail end that were driven with a ripper-type continuous miner as needed. The study was conducted over 22 consecutive shifts (7-1/3 days). The average methane emission rate from the Lower Kittanning coalbed during mining at the face and developing the headings at the tail end of the face was 34 cfm. Caving of the gassy overlying strata as the result of mining at the face increased the methane emission to rates ranging from 702 to 1,049 cfm.

Jan 1, 1971

By Dhaval Patel, Kim Witte, Charles Vaught, Michael T. Stephenson, Steve Booth-Butterfield, Cynthia Zuckerman, Brian L. Quick

This longitudinal field study was designed to encourage Appalachian coal miners in West Virginia and Pennsylvania to engage in hearing-protection behaviors. Method: Participants were mailed postcards that featured either a positive, negative, or neutral message on the outside of the postcard and a message encouraging hearing protection behaviors on the inside. The first posttest measurement of the effectiveness of the persuasive messages was conducted about a week after the postcards were mailed. The delayed posttest measurement was conducted six weeks later. Results: Responses from 307 coal miners revealed that the positive or neutral messages generated significantly more self-reported hearing protection behaviors than the negative message. Identical results were obtained in a delayed posttest assessment of miners' self-reported hearing protection behaviors. The positive message was also more effective than either the neutral or negative message in preventing defensive mechanisms from emerging over time. Impact on Industry: Positive and neutral messages were convincingly more than negative messages in facilitating self-reported hearing protection behaviors among coal miners. Similarly, the positive messages kept defensive processes at bay. Keywords: Hearing protection; Hearing loss; Coal miners; Campaign; Messages

By Fred Leighton

The Bureau of Mines monitored a rock-burst-prone pillar in a metallic ore vein, up to and through failure, to measure its reactions to increasing loads, as it was mined. Three parameters were monitored: the stress changes at chosen points within the pillar, the displacement characteristics of the drift above the pillar, and the micro-seismic activity in and around the pillar. In descending order of effectiveness, the microseismic technique, vibrating wire stress measurements, and displacement measurements reflected the pillar reactions, and all showed good correlation to one another. A major rock burst in the pillar, which destroyed about 100 feet of drift above the pillar, occurred at the end of this study. This burst was preceded by a large anomaly in the microseismic activity in the failure area.

Jan 1, 1982

By W. S. Sanner

A High Splint coal was carbonized in a low-temperature, fluidized-bed sys-tem to study the effects of thermal cracking on the products of decomposition. The coal was fluidized in recycle gas at 485° to 600° C, and the products were cracked at 600°, 700°, and 800° C in a bed of fluidized coke. Yields of tar, pitch, paraffins, and olefins decreased as carbonization temperature increased. Thermal cracking of the tar vapors produced the highest tar yields at 600° C, and light oil yield increased at cracking temperatures up to 700° C. At an 800° C cracking temperature, the yield of light oil decreased.

Jan 1, 1969

By Maria I. De Rosa

The major fire and fire injury findings for all coal mining categories for 1990-1999 are reported in tables 37-38. Table 39 and figure 13 show the number of fires. fire injuries, risk rates, employees' working hours, and coal production (under- ground and surface coal mines only) by time period for all coal mining categories. Table 40 shows major findings (for under- ground coal mines only) for 1978-1992. For all coal mining categories, 458 fires occurred during 1990- 1999; 157 of those fires caused 164 injuries and 2 fatalities (Ewhr = 2,070 x l0%r, Irr = 0.016: C'P (for underground and surface coal mimes only) - 10,363 x l0\t, Frr = 0.044, LWD = 14,753). Twenty-nine fires and 17 injuries involved contractors. Sixty-six fires required firefighting interventions by mine rescue teams (25 times in underground mines) and fire brigades and fire departments (at least 41 times at surface coal operations). In all, 51 fires destroyed or heavily damaged equipment (including 16 pieces of mobile equipment) because of failure of other firefighting methods, late fire detection, undetected fires, or fire size. A total of 114 fires were detected late, and 42 fires were undetected. The greatest number of fires and fire injuries occurred at surface coal mines; the highest risk rate values were also calculated for this category. For all coal operations, the ignition sources that caused the greatest number of fires were flame cutting/welding spark/slag/flames (1 03 fires or 23% with 69 injuries), hydraulic fluid/fuel sprayed onto equipment hot surfaces (98 fires or 2 1 % with 29 injuries), spontaneous combustion/hot coal (62 fires or 14%), electrical short/arcing (49 fires or 11% with 18 injuries), and conveyor belt friction (3 1 fires or 7% with 6 injuries).

Jan 1, 2004

By M. J. Ferrante

Relative enthalpies of cuprous iodide (CuI) were measured at the Bureau of Mines to provide thermodynamic data for the advancement of min-eral technology. Enthalpy measurements between 298.15 and 1,396.3 K were made with a copper-block drop calorimeter. The temperatures of transition were measured by differential scanning calorimetry (DSC). Reversible transitions were determined at 643 K with a standard enthalpy of transition [(6Htr)] = 0.74 kca1/mol, at 679 K with a [6Htr = 0.65 kca1/mo1, and at 868 K] with a standard enthalpy of fusion [(6H~) = 1.895 kca1/mol.] Tabulated values are listed at selected temperature increments from 298.15 to 1,600 K for the standard relative enthalpy (HO -H298), heat capacity (CpO), entropy (SO), and Gibbs energy function [-(Go -H298)!T]. The enthalpy data are also given in the form of equations and combined with thermodynamic data from other investigations to derive values of standard entha1pies of formation [(~HfO)], Gibbs energies of formation [(6GfO)], and logarithms of the equilibrium constants of formation (log Kf).

Jan 1, 1987

By T. G. Carnahan

The Bureau of Mines conducted laboratory-scale weathering research on a leach residue containing elemental sulfur and mixed metal sulfides. Experiments were performed to determine pH and impurity element concentrations in the effluents as functions of time and to determine the effects on effluent concentrations of mixing the residue with dolomite tailing material. Four 800-day tests were conducted simultaneously. Soluble metal concentrations, especially zinc and copper, were excessive in the effluents from washed and unwashed samples of the residue. Concentrations of up to 20 g/l of Zn and 12 g/l of Cu were obtained. The pH values of the unwashed and washed residue effluents at the completion of the experiments were 2.8 and 1.9, respectively. Sulfuric acid from oxidation of pyrite caused the pH decrease. Mixing unwashed residue with dolomite tailing to maintain a near-neutral pH minimized the heavy metals content in the effluents. The pH in the dolomite tests increased slowly after the first 360 days and attained values of 7.8 and 8.2, respectively, for tailing containing 1 pct leach residue and for tailing devoid of leach residue. Dissolved zinc and copper did not exceed 0.10 g/l of Zn and 0.001 g/l of Cu.

Jan 1, 1982

By J. E. Emmerling

The Federal Bureau of Mines investigated dust suppression obtained with three different water-spray nozzle systems during underground continuous coal mining at the face. The nozzles were the "regular" nozzle normally used by the mine, and high-efficiency and low-efficiency nozzles selected on the basis of an airborne capture theory of respirable dust by spray drops. The high-efficiency nozzle used one-third less water than the others throughout the testing. Results depended on the type of cutting operation at the face. The sump-downshear operation appeared to involve a significant amount of capture of airborne respirable dust. The same amount of dust was measured when using the high-efficiency and regular nozzles. The dust levels when using the high-efficiency nozzle were about 20 pct less than those measured when using the low-efficiency nozzle. The sump-upshear operation seemed to involve a predominance of other aspects of dust suppression, such as impaction of spray drops onto the face. Compared with the downshear operation, there was a significant reduction in dust levels for a total face operation when using the regular nozzle; dust levels when using the regular nozzle were about 15 pct lower than those measured when using the high-efficiency nozzle.

Jan 1, 1975

By G. B. Atkinson

The Bureau of Mines, in cooperation with McDermitt Mine, investigated a method for recovering mercury metal from mercury sulfide flotation concentrate by a hydrometallurgical technique. This preliminary report shows the feasibility of leaching mercury with a cupric chloride solution and electrowinning mercury from the solution. Proposed chemical reactions are shown in equations 1 through 3: 2CuC12 + HgS + 2CuCl + HgC12 + S°; (1) electrolysis HgC12 ?Hg + C12; (2) 2CuC1 + C12 ? 2CuC12. (3) A bench-scale leaching-electrowinning apparatus capable of treating 2.36 kg of sulfide concentrate in 11 days was operated continuously. An acid chloride solution containing, in grams per liter, 70 Ca, 60 Cu, 30 Fe, and 80 Hg was used as both leachant and electrolyte; 99.5 pct of the mercury was solubilized from the sulfide concentrate. Electrolysis of the leaching solution recovered mercury metal at an average current efficiency of 32 pct and an average energy consumption of 1.2 kwhr/lb Hg. Results from a preliminary economic evaluation indicated that a plant producing 31,500 flasks of mercury per year would have a capital cost of $3.7 million and an operating cost of $62 per flask of mercury.

Jan 1, 1983

By Travis Q. Lyday

The Other South Pacific Island states extend from Palau, also called Belau, near the Philippines in the west, to French Polynesia in the east. However, a number of countries and territories have been omitted, from this chapter because their mineral production was insignificant to the local economy. These include the French over-seas territories of French Polynesia and Wallis and Futuna Islands; independent states, including Kiribati, Marshall Islands, Micronesia, Palau, Tonga, Tuvalu, and Vanuatu; the New Zealand freely associated state of the Cook Islands, and the New Zealand dependency of Niue. What mineral production existed in these islands was limited to construction materials such as coral reef limestone, crushed stone, and sand and gravel in minor quantities solely for domestic consumption. FIJI The mineral industry of Fiji continued to be dominated by gold, although this sector contributed less than 1 % to the gross domestic product (GDP) of the country. Gold and silver together ranked second in value among the country's exports. Fiji's economy contracted 11% during the 8-month period following the first, on May 14, of two military coups. Although the island nation had been a member of the British Commonwealth of Nations since its independence on October 10, 1970, Fiji's membership terminated with the emergence of the Republic or Fiji on October 15.

Jan 1, 1989

By Stephen W. Lambert, Michael A. Trevits

The Bureau of Mines examined the wellbore of a vertical gas drainage well in the Mary Lee coalbed to determine the results of specific completion procedures in coal. A jet-slotting tool was used to cut four vertical slots through the casing about 1 ft below the coalbed. Even though stimulation treatment pressure was excessive, hydraulically induced channels were contained entirely within the target coal zone. Sand-filled, induced channels were horizontal, inclined, and vertical, and were propagated in directions similar to bedding planes, rock joint, and coal cleat directions measured in the mine. Variable gas flow rates, recorded during the productive life of the well, were attributed to chronic downhole pump malfunction and the slotted casing below the production zone.

Jan 1, 1978

By Benjamin W. Haynes

The Bureau of Mines conducted research to devise technology for increasing the Nation's mineral supply by recovering valuable constituents from currently discarded waste materials. Municipal solid waste (MSW), presently a major disposal problem, represents a significant source of metals, glass, and a combustible fraction that can be used to supplement coal in generating heat and electricity. As part of the total metallurgical system to treat MSW, this study evaluates the combustible fraction of MSW to characterize the various combustible components and to identify the principal sources of elements that eventually may be objectionable from corrosive or environmental considerations. Several possible sources for cadmium, chromium, cobalt, copper, lead, nickel, and zinc have been tentatively identified. These sources are pigments, inks, paper stock, and additives to plastics. A correlation between industry consumption values and measured concentrations in MSW was found for several elements.

Jan 1, 1978

By C. C. Shale

A semicommercia1, high-temperature electrostatic precipitator and adjunct equipment are described, and operating characteristics at 1,470° F and 80 psig are presented for both positive and negative polarity. Removal efficiency for negative corona waS about 91 to 96 percent while that for positive corona was only about 75 to 77 percent. Results are compared with those from bench-scale investigations, and equipment limitations are discussed. Theoretical aspects of the precipitation process are related to the operating characteristics.

Jan 1, 1969

By W. Blake, J. K. Whyatt, T. J. Williams

Researchers at the U.S. Bureau of Mines collected and analyzed over core measurements and other indicators of in situ stress characteristics at the Lucky Friday Mine, Mullan, ID. An analysis of these data revealed that significant local variations in in situ stress are present in this mine and that these variations existed prior to mining. High stresses were found to be associated with the most competent strata and a locked section of a fault. An estimate of the predominant stress field was developed for mine-wide modeling. The estimate shows that the greatest principal stress was oriented north of northwest. This information should provide a basis for mine-wide structural modeling of the Lucky Friday Mine and should generate important insights into localized stress conditions, which may significantly affect both local and mine-to-mine variations in seismicity induced by excavation.

Jan 1, 1995

By M. A. Elliott, H. H. Schrenk, L. B. Berger, John C. Holtz

"INTRODUCTION Among the hazards that may attend the use of Diesel engines in mines, tunnels, or other underground operations the presence of harmful or objectionable constituents in the exhaust gas must receive due consideration to prevent the formation of unsafe or unhealthful working environments in these places. Previous reports of this series have presented discussions of the composition of exhaust gas from engines in proper mechanical condition, 6/ the effect of adding some of the exhaust gas to the intake air of the engine, 7/ the effect of operation in atmospheres containing natural gas, 8/ and the effect on exhaust-gas composition of conditions that influence the characteristics of fuel injection in Diesel engines. In all these studies the properties of the fuels used were in general conformity with specifications usually recommended by the manufacturers of Diesel engines. In evaluating the physiological significance of the various components of the exhaust in these experiments, the toxic or objectionable gases determined were carbon monoxide, carbon dioxide, oxides of nitrogen, and aldehydes. Because of the low sulfur content of' these fuels, compounds such as sulfur dioxide and sulfur trioxide were not determined, although in discussion of the test results attention was directed to the fact that if fuels of higher sulfur content were used, the concentration of such compounds in the exhaust would become a significant factor in establishing the quantity of ventilating air required to furnish satisfactory dilut1on of the exhaust gas in underground working places."

Jun 1, 1943