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By Keith G. Wallace

Coal mine ventilation systems are often subject to high leakage rates. As a result, changes in airflow resistance will strongly affect the efficiency with which air is delivered to the working place. One major source of airflow resistance is the line brattice used to direct air from the last open crosscut to the working face. Because it is a great distance from the fan, the resistance of the line brattice can result in more overall leakage than an equivalent resistance closer to the fan. Substituting auxiliary fans for brattice eliminates this source of resistance, with improvements in system efficiency and cost. Also, in some mines, the leakage that leads to spontaneous combustion can be reduced. The benefits obtained by several different brattice and fan substitutions have been studied by Mine Ventilation Services, Inc., Lafayette, CA, under contract to the U.S. Bureau of Mines. Changes in main fan duty were compared with additional costs associated with auxiliary fans. Results indicate that in some circumstances, considerable leakage reductions and cost savings are possible.

Jan 1, 1990

By Kenneth L. Cashdollar

The Pittsburgh Research Laboratory (PRL) of the National Institute for Occupational Safety and Health (NIOSH) and the Mine Safety and Health Administration (MSHA) conducted joint research on dust explosions by studying post-explosion dust samples. The samples were collected after full-scale explosions at the PRL Lake Lynn Experimental Mine and after laboratory explosions in the PRL 20-L chamber and the Fike 1-m3 chamber. The dusts studied included both high and low volatile bituminous coals. Low temperature ashing for 24 hr at 515°C was used to measure the incombustible content of the dust before and after the explosions. The data showed that the post-explosion incombustible content was always as high as or higher than the initial incombustible content. The MSHA alcohol coking test-was used to determine the amount of coked dust in the post-explosion samples. The results showed that almost all coal dust that was suspended within the explosion flame produced significant amounts of coke. Measurements of floor dust concentrations after LLEM explosions were compared to the initial dust loadings to determine the transport distance of dust during an explosion. All of these data will be useful in future forensic investigations of accidental dust explosions in coal mines or elsewhere. Disclaimer: The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the National Institute for Occupational Safety and Health or the Mine Safety and Health Administration.

Jan 1, 2006

By J. Baicker

A two-inch diameter probe containing an intrinsic germanium detector, a canister-type solid cryogen cooling system, cooled FET preamplifier, linear amplifier, high voltage supply, analog-digital converter, microprocessor, buffer memory, bidirectional cable link, and all power supplies has been designed, assembled and tested. A surface support vehicle was designed, built and outfitted. A mini-computer system was constructed and preliminary software developed and tested. A special handling system for a Cf-252 neutron source was designed and has been ordered. The entire system (less the neutron source) is ready for its first field tests. Lab description of the system is presented.

Jan 1, 1978

By Martin H. Stanczyk

The Bureau of Mines studied continuous closed-circuit attrition grinding of a coarse commercial filler-grade kaolin to produce paper-coating-grade clay having a particle size analysis of at least 70 percent minus 2-micron equivalent spherical diameter (esd). The coarse clay, containing about 12 percent minus 2-micron-esd material, was ground in a Bureau-developed 10-inch-diameter attrition grinder in closed circuit with a 5-foot-diameter bowl classifier. In the best test, a finished product containing 82.7 percent minus 2-micron-esd material was obtained when grinding 20 pounds of raw clay per hour at percent solids with a 100-percent circulating load. Energy consumption was about 341 kilowatt-hours per ton of clay feed, or 487 kilowatt-hours per ton of minus 2-micron-esd material produced. Closed-circuit grinding gave some-what greater particle size reduction and lower energy consumption than either batch or continuous open-circuit grinding.

Jan 1, 1965

By C. Özgen Karacan

This study presents the results of core-log analyses from the exploration boreholes, the analyses of face advance rates, and the results of downhole monitoring studies performed in gob gas ventholes for calculation of changes in hydraulic properties in the longwall overburden at a mine site in southwestern (SW) Pennsylvania section of Northern Appalachian Basin. In the ?rst part of the study, coal measure rocks in overburden strata were analyzed and the locations where possible fractures and bedding plane separations would occur were evaluated. In the second part, the hydraulic conductivities were computed by two different slug test analyses methods using the water level changes measured in gob gas ventholes as longwall face approached. Hydraulic conductivities were analyzed with respect to the changes in overburden depth, the locations of the borehole, and mine face advance rates. These data were used to interpret the potential productivities of the gob gas ventholes as a result of fracturing and changes in hydraulic conductivities. The general results showed that the probability of fracturing and bedding plane separations in the overburden increase between strong and weak rock interfaces. Also, the probability of bedding plane separations increases as the interface is close to the extracted coal seam. Evaluation of slug tests showed that the hydraulic conductivity developments in the boreholes and their potential production performances are affected by the underground strata and the roof materials. In situations where the roof material is stiff and thick, the development of high permeability fractures around the borehole will be less. Results also indicated that borehole location with respect to face position affects the fracturing time and permeability evolution as well. Greater overburden depths generally cause earlier fracturing as longwall face approaches, but eventually result in lower hydraulic conductivities and potentially less effective boreholes. Increasing mining rates also resulted in generally lower hydraulic conductivities in the overburden. The results of this study were intended to improve the interpretation of gob gas venthole performance and to provide better siting of these boreholes.

Jan 1, 2009

By C. A. Herbert

In summer, when hot, moisture-laden air enters a coal mine in the region east of the Mississippi River, the moisture is likely to condense on the roof and ribs because the incoming air is cooled below its dew point upon contact with the roof, ribs, and floor of the mine passageways. When the roof and ribs become wet owing to this condensation they are said to "sweat." In many mines, as soon as this sweating begins, shale or slate roof that appears solid and strong in winter begins to cut and fall. For a long time most mining men believed (many still believe) that the roof trouble was due to this sweating. However, from observation of conditions in one mine the operators concluded that the trouble was caused by expansion and contraction of the roof due to changes of temperature. This opinion was confirmed by experiments at several mines in cooling the air as it entered the mines. Methods used in these mines for cooling the air are described in this circular. MINE A At mine A the roof gave considerable trouble in the summer, and it was observed that where a spray of water from a leaking dam kept the roof wet and at a uniform temperature no difficulty was experienced with the roof, although it had cut and fallen on either side of that point. From this fact the company officials concluded that changes of temperature in the air rather than moisture caused the trouble and that if the incoming air were cooled to approximately normal strata temperature much of the additional roof trouble experienced during the summer would be overcome.

Jan 1, 1940

By G. E. Walden

The Bureau of Mines is currently engaged in a continuing investigation of the thermodynamic properties of certain inorganic compounds. As a part of this investigation, the heat contents of bismuth and cerous chlorides were measured throughout the temperature ranges of 370° to 630° K. and 370° to 1,200° K., respectively. Equations representing heat contents as a function of temperature were derived from the data by the method of least squares. These equations were used to calculate heat contents at selected temperature intervals ranging from the ice point to 650° K. for bismuth chloride and to 1,200° K. for cerous chloride; also, the heats of fusion of both compounds were calculated at their respective melting points. EXPERIMENTAL Materials The cerous chloride used in this investigation was supplied by the National Carbon Company of Cleveland, Ohio. A chemical analysis indicated Ce 56.57 percent and Cl 43.39 percent. No attempt was made to purify the compound or identify impurities since the analysis showed only about 0.04 percent total impurities. Reagent grade bismuth chloride was used without additional purification.

Jan 1, 1961

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 W. A. Calhoun

This investigation of low-grade bauxites as potential sources of aluminum by caustic desilication and alumina extraction was undertaken by the Bureau of Mines to develop extractive methods for winning alumina from domestic deposits of low-grade bauxites. This report is the second of a series covering the work by the Bureau of Mines' Rolla, Mo., and Bauxite, Ark., laboratories. The first report published in the Journal of Metals, December 1951,3/ and dealt with kaolin and halloysite. The present investigation is concerned with low-grade bauxites only. The purpose of these investigations is to increase the domestic supply of aluminum ores. With eventual depletion of high-grade deposits, aluminous materials, such as low-grade bauxite, clays, shales, and high-iron laterites, will become our principal domestic sources of aluminum. The development of extractive processes for winning alumina from these low-grade materials is one of the many national security measures undertaken by the Bureau of Mines. A method has-been developed in the laboratory for successfully treating high-silica bauxites from domestic deposits. In this process the bauxite was calcined at 980° C. to form amorphous silica and alumina. The calcine was then leached by percolation with 15-percent sodium hydroxide solution at 940 to 96° C., removing 67 to 77 percent of the silica with a loss of 4.1 to 5.0 percent of the alumina. The sodium hydroxide in the spent liquor used in desilication was 95 percent recoverable, and comparable desilication results were obtained with 100-percent reclaimed liquor, The indicated cost of reagents, for sodium hydroxide and lime used in the desilication and regenera¬tion of spent liquor, was about $4.00 per ton of calcine treated.

Jan 1, 1954

By M. E. Tyrrell

The Bureau of Mines produced building brick of good quality in an investigation designed to explore the possible utilization of high-glass fractions of municipal incinerator residues in the manufacture of building products. Common clays, lime, and sodium silicate were used as binders for the nonplastic residues Test bricks were formed by dry-pressing, soft-mud molding, and stiff-mud extrusion. A run of standard-size face brick dry-pressed and fired in the West Virginia University Coal Research Bureau pilot plant demonstrated that SW-grade glass-clay face brick can be produced on a commercial scale without difficulty. A cost evaluation made for production of the brick showed an estimated cost of $42.13 per thousand bricks for a shuttle kiln plant and $28.70 per thousand for a tunnel kiln plant.

Jan 1, 1972

By D. B. Eccleston

Natural gas and mixtures of natural gas and hydrogen were used as fuels in a laboratory engine to determine the relationship of emissions to air-fuel ratio and to establish practical lean limits for air-fuel ratio. Synthetic gas manufactured from coal (Synthane) and natural gas were used as fuels in a vehicle to obtain comparative data on emissions and performance. Results showed that lean limits for air-fuel ratio when using hydrogen-enriched natural gas were extended significantly beyond Chat of natural gas. Synthane pro¬duced exhaust that was significantly less reactive than exhaust from natural gas. With lean air-fuel ratios, the acceleration performance of a vehicle fueled with Synthane was improved over its performance when fueled with natural gas.

Jan 1, 1972

By Davis E. Traut

TiC14, AIC13, and VC14 were coreduced simultaneously via a Kroll-type magnesium reduction to form an alloy sponge as part of a research effort by the Bureau of Mines to produce titanium alloy powder. Reduction tem-peratures of 750°, 850°, and 950° C, a range of chloride feed rates from 34 to 152 Ib/(ft2·h), and crucible diameters of 7-3/4 and 10-1/4 in were tested. Microprobe analyses using a 40-um-diam spot showed no effect on alloy microhomogeneity (distribution of Al and V in the Ti, considered critical as a powder property), due to changes in process variables within these ranges. Statistical analysis of these data for alloy sponge indicated greater variation in the chemical composition (AI and V) than that found in commercial Ti-6Al-4V plate or Plasma Rotating Electrode Process (PREP) powder. Therefore, a one-step approach to pow-der, such as grinding the Ti alloy sponge, would not produce a powder product of acceptable chemical homogeneity. An approach that homoge-nized the sponge, such as with a melting step, would produce an accept-able powder product with respect to chemical homogeneity.

Jan 1, 1987

By Dean H. Ambrose

Computer programs are presented that provide mine electrical systems based on computer modeling for design and safety analysis suitable for large or small computer systems and handheld calculators. Bureau of Mines research has resulted in load-flow, fault, grounding, reliability, short-circuit, transient, and cable ampacity computer models that enable mine power system engineers to analyze their system or to design a system. This report describes the capabilities of the program.

Jan 1, 1984

By W. H. Young

THE DOMEST[C bituminous coal and lignite industry remained fairly steady in 1959 compared with 1958. Although mechanization continued to expand and production increased slightly, consumption, average value, exports, and employment decreased. The percentage of underground production mechanically loaded, the percentage of total production mined by stripping, and tonnage per man per day were at their highest levels. Production.-The output of bituminous coal and lignite in 1959-412 million tons-was 0.4 percent greater than the 410.4 million tons produced in 1958. Production was retarded in 1959, largely owing to the steel strike and reduced exports.

Jan 1, 1960

By J. B. Gayle

Coke-pushing difficulties have been the subject of much controversy but relatively little scientific investigation. Nevertheless, continuing pushing difficulties can greatly decrease the life of a coke oven and should therefore be considered in the selection of the blend and operating conditions used for coke production. The present Federal Bureau of Mines investigation was undertaken to correlate results of previous investigators and to supplement these results to the limited extent practical by us of an experimental slot-type oven. To this end, pushing pressures have been determined routinely for Tuscaloosa oven tests conducted during the past 10 years. Nevertheless, the accumulated information remains incomplete in many respects, and in view of the recognized inadequacies of the data, publication is now undertaken only because of the scarcity of published information on this important problem and the discontinuation of carbonization studies with this oven.

Jan 1, 1961

By Foster Fraas

A separator for minerals of low magnetic susceptibility and fine particle size in a water suspension is described. A ring-shaped matrix of ferromagnetic fragments rotating so as to pass successively through magnetic-field and field-free regions provides for the separation. Application is illustrated in the separation of hematite and ilmenite from quartz.

Jan 1, 1966

By D. J. Parker

Ability to signal the hoisting engineer in shaft mines is of utmost importance from the standpoint of safety and economy. The problem of signalling from the cages and especially from the moving cages has received too little attention from mine operators; however, this problem has been given considerable thought and attention by at least one large metal-mining company in Utah which has devised successful, economical, and safe systems of signalling from the cage whether it is moving or at rest. A Report of Investigations on "Methods used in Utah for signalling mine hoists from moving cages," by C. A. Allen, then a metal-mining engineer in the Bureau of Mines, was issued in June, 1920. As this report contains interesting history of systems of signalling from moving mine hoists, and describes several systems then in use, it is here quoted in full.

Jan 1, 1929

By John E. Pahlman

The Bureau of Mines investigated the feasibility of removing heavy metals from mineral-process waste streams by precipitation with lignochemicals and humic acids. Lignochemicals are by products from the paper industry, while humic acids are obtained by caustic treatment of peat, subbituminous coal, and lignite. These high-molecular-weight organic materials have many functional groups, which can coordinate and form innercomplex salts with heavy metals that are crystalline precipitates. Filtering of a humic-acid-or lignochemical-treated solution or waste stream containing these precipitates removes the heavy metal sequstrates. Tests were conducted with two lignochemical samples, three humic acid samples, lime (CaO), and sodium hydroxide (NaOH) in which increasing amounts of these additives were reacted with 50 mL of solution containing Fe3+ , Al3+, Cr3+, Pb2+, Cu2+, Cd2+, Zn2+, Co2+, Ni2+, Mn2+, and Hg1+. At the appropriate pH, greater than 90-and 99-pct removal was achieved for these 11 heavy metal ions from the 10-and lOO-ppm solutions, respectively, using lignochemicals and humic acids. Removal efficienC)' with these organic materials is better than that with CaO, especially for the more toxic ions, Hg1+, Cd2+, and Pb2+. Unlike the precipitates formed with NaOH or CaO, those with lignochemicals and humic acids are compact and noncolloidal. The volume of their sludge is sharply lower than that of the finely dispersed lime or soda precipitates; thus, their removal in settling tanks or by simple filtration is enhanced.

Jan 1, 1988

By Harold Bailie

The purpose of this Bureau of Mines report is to furnish information on mining practices applied to flat-bedded fluorspar deposits in southern Illinois. It presents new and improved operating procedures and specialized techniques applicable to deposits of this type. All of the operating mines of the Ozark-Mahoning Co. in this area have been opened by vertical shafts which connect with levels consisting of haul-age ways, stopes, and loading stations. The stoping practice used locally called room and pillar, is open stoping with pillars left at different distances and diameters. To facilitate haulage and drainage, the mines are worked from openings turned off the main haulage drift on a grade to conform with the dip of the ore beds. The ore is predominantly fluorspar with smaller amounts of galena and sphalerite that contain traces of cadmium and germanium. The principal gangue minerals are limestone, calcite, shale, barite, and sandstone. The rock hardness ranges from relatively soft shale to hard, abrasive sandstone.

Jan 1, 1960

By Hillary W. Clair

An equation is derived for the rate of reaction of a sphere of metal oxide in a restricted enclosure through which a reducing gas is flowing . The equation takes into consideration the reaction rate coefficient , transport through the gas and through the porous shell of reduced oxide , the rate of gas flow , and the volume of the enclosure . The equation serves as a model for predicting the course of reduction of a particle of metal oxide in a shaft furnace .

Jan 1, 1964