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By C. W. Owings, J. J. Forbes

"INTRODUCTION The recent coal-dust explosions in Illinois and Indiana have again brought forcibly to the attention of mining men the fact that mines which liberate little or no methane can have widespread explosions, if dry and dusty conditions exist and if adequate measures are not taken to control the dust hazard by rock dust¬ing or use of water.Even though rock dust has been used more or less extensively for more than 20 years as a means of limiting or preventing coal-mine explosions, many mine operators have requested information on rock dusting and means of allaying coal dust at its source. The purpose of this circular is to summarize available information on these two methods.COAL MINES TO BE ROCK-DUSTEDAll nonanthracite coal mines must be rock-dusted, except those mines or locations in a mine that are too wet or too high in incombustible content to propagate an explosion.Coal dust that contains 20 percent or more moisture may prevent ignition or propagation of an explosion. Such dust can be molded in the hands, and under such condition the roadway would be considered muddy. Mine dust that is only damp is not wet enough to prevent propagation of an explosion. Beads of water standing on accumulations of dust are not indications that the dust is wet. Only those mines or locations in a mine in which the coal dust can be molded in the hand need not be rock-dusted."

Jun 1, 1947

By W. L. Staker

The Bureau of Mines investigated methods for selectively eluting mercury, silver, and gold from strong-base anion-exchange resins, including Rohm and Haas resins lRA-430 and 900 and Dow Chemical resins 2lK, SMA-I, and SBR. Resins were typically loaded to 145 oz/st of each metal. Loaded resins were eluted with H2S04, NaCl-H Cl, NaOCl, and NaCl04 solutions. The resins tested had similar elution characteristics for mercury and precious metals. The best selective elution scheme was achieved by eluting in a column with 2N H2S04 to recover 99 to 100 pct Hg, with 200 giL NaCl in IN HCI to rec;ver 99 to 100 pct Ag, and with 2M NaCl04 to recover 79 to 89 pct Au.

Jan 1, 1987

By C. P. Lazzara, R. A. Franks, G. F. Friel, J. C. Edwards, J. J. Opferman

It was determined that a selection of different types of fire sensors could be used to discriminate mine fires from nuisance emissions produced by diesel equipment. A neural network (NN) was developed for application to coal, wood, and conveyor belt fires in the presence of diesel emissions and evaluated with the successful prediction of twenty-two out of twenty-three mine fires based upon a fire probability determination. The optimum sensor selection for the NN was comprised of a carbon monoxide (CO) sensor, two different types of metal oxide semiconductor (MOS) sensors, and an optical path smoke sensor.

Design and test a high-production coal mining machine that generates less respirable dust. Background Current coal cutting systems generate excessive amounts of airborne respirable dust and fines during the mining process. Dust control technologies, including dust dilution by ventilation and suppression by water sprays, are not always able to reduce dust levels sufficiently. The U.S. Bureau of Mines (USBM) has designed a cutting system that reduces respirable dust generated by the cutting action of the drum. This cutting system, based on geometric principles developed in the 1500's, makes use of a constant depth, linear cut to remove coal at deeper cut depths and at lower rotary speeds than a conventional rotary drum. A comparison of the linear and rotary cut paths is shown in figure 1. Approach A full-scale prototype of the linear cutting concept was valuated under laboratory conditions to determine its performance relative to standard rotary drums. Results of these evaluations show production of fewer fines, or more uniform product size, a significant reduction in the amount of airborne dust, and reduced torque and power requirements (figure 2). On the basis of these results, a contract effort was undertaken by McCracken and Associates of Bristol, TN, to design a linear cutting head for underground testing.

Jan 1, 1995

By Steve Iverson, Jeffrey C. Johnson, Henry Rodriguez, Rene Rodriguez, Michael Lhamond

To reduce fatalities resulting from personnel falling into voids formed above feeders in coal piles, the National Institute for Occupational Safety and Health at the Spokane Research Laboratory established a project to monitor coal surge piles to detect the formation of voids. A resistivity imaging method has been developed by GECOH Exploration, of Lexington, KY, in which a geophysical technique known as vertical electrical sounding (VES) is used to scan for these voids. VES operates by measuring the electrical field produced by a current in the ground at the bottom of the coal pile. This paper summarizes the results obtained from a field-scale test and shows that mapping voids within a coal pile is possible.

By C. H. Elder, M. C. Irani

Two degasification test boreholes were drilled to depths of 1,238 and 1,212 feet on Bureau of Mines property at Bruceton, Pa., as part of the Bureau's long-range coal degasification program. The holes provided detailed geologic information and geologic sections, which were correlated with regional stratigraphic cross sections prepared by the Pennsylvania Geological Survey. Gas content determinations and coal analyses were made on the Upper Freeport, Middle Kittanning, Clarion, Brookville, and Mercer coalbeds; gas content of the coalbeds ranged from 53 to 165 cubic feet per ton. Formation pressure and gas flow tests were conducted on selected coalbed intervals in borehole 1; formation pressures ranged from 292 to 473 psig. The middle Kittanning coalbed was hydraulically stimulated using very heavy gelled water, but gas production remained low because gel residue and formation water inhibited the flow of gas. Gas contents in the Clarion, Upper Brookville, and Mercer coalbeds were anomalously low owing to the proximity of porous sand- stones which act as reservoirs for gas migrating from coalbeds.

Jan 1, 1977

By Charles L. Kimbell

The series summarizing the prices of the major nonferrous metals on the stock exchanges of the United States and the United Kingdom has been continued this year in tables 23 and 24. Time constraints have prohibited preparation of other price information that has appeared in this study in previous years. Users are urged to consult the 1993 USBM publication Metal Prices in the United States through 1991, which gives an analysis of historical price series and trends, or the 1993 edition of Mineral Commodity Summaries for current U.S. prices on non fuel commodities, and to utilize U.S. Department of Energy sources for information on fuel material costs.

Jan 1, 1993

Eliminate the occurrence of false fire detection alarms caused by the operation of diesel-powered vehicles in underground coal mines. Approach Fire detection systems used in underground mines are based on measurements of airborne combustion products such as carbon monoxide or smoke particles. The effectiveness and credibility of these systems can be reduced by the occurrence of false alarms that result from the operation of diesel-powered equipment, which produces the same combustion products. False alarms end up being very costly to the mine operation in terms of downtime and labor needed for verification. To improve upon current fire detection systems used in the presence of internal combustion engine products, the U.S. Bureau of Mines developed a fire detector that can discriminate between the occurrence of real mine fires and the presence of engine smoke.

Jan 1, 1989

By Charlie Wyche

Principal mineral products in the Dominion of Fiji were gold, silver, pit and quarry construction materials, and cement. In 1981, the combined value of these commodities accounted for about $11.6 million,2 over 85% of the total value of mineral output. Production of cement, sand and gravel, and quarry products increased substantially above the 1980 level. Mining bated on gold production was decreasing, and employment in the industry was declining. The better grade deposits in the one active mine were worked out, and only another 10 years' production at current rates was estimated to remain. While the high world gold price of 1979-80 led to intensive exploration, there has been little sum.

Jan 1, 1983

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Jan 1, 2011

By W. E. Lamont

The Federal Bureau of Mines conducted research to develop methods of removing phosphorus from the earthy, calcareous hematite ores of the Birmingham, Ala., iron district while simultaneously improving the grade and recovery of the iron values prior to furnacing. An attempt was also made to identify the phosphorus minerals present in the ores. The ores contained about 36 percent iron, 12 to 16 percent CaO, 15 to 20 percent hydrochloric acid insolubles, and 0.30 to 0.36 percent phosphorus. Fractions containing 5 to 15 percent phosphorus were isolated from the ores. Collophanite, Ca3P2O3?nH2O, a member of the apatite group, was the only phosphate mineral identified. Beneficiation methods using flotation and reduction roasting with magnetic separation yielded good grade iron concentrates, but were not as effective for reducing the phosphorus content of concentrates. Reduction roasting followed by fine grinding, magnetic separation, and acid leaching gave iron concentrates containing 62.5 percent iron and 0.04 percent phosphorus with an iron recovery of 82.9 percent and a phosphorus rejection of 93.7 percent. Reoxidation of reduced magnetic concentrates followed by acid treatment gave iron concentrates containing 58.1 percent iron and 0.02 percent phosphorus with 89.6 percent recovery of the iron and 96.5 percent rejection of the phosphorus.

Jan 1, 1973

By E. E. Remmenga

Often a collection of analytical data, which should reasonably be expected to follow the normal distribution, contains too many extreme values, which the experimenter is inclined to eliminate according to some arbitrary procedure. The stepwise computer procedure described for this purpose is similar to many other truncation procedures; however, because truncation of a basically normal distribution causes a downward bias in the estimated variance, this procedure provides a graphical method to compensate for the bias.

Jan 1, 1971

By Fred N. Kissell

Methane-flow and pressure data taken from a mine in the Pocahontas No. 3 coalbed are compared with flow rates from lump coal obtained in laboratory experiments. From this, it is concluded that the main source of gas is the intact coalbed rather than a "crushed zone" near the working face. The permeability and sorption capacity of the intact coalbed are calculated and gas emission rates are theoretically accounted for.

Jan 1, 1972

By L. E. Schultze

The Bureau of Mines operated a mineral recovery unit to recover metal values from post-flash geothermal brines from the Salton Sea known geothermal resource area as part of its research into the use of plentiful resources. The brine was available for metals recovery after its heat content had been used to generate electricity. The brine source was treated with lime to precipitate the contained iron, manganese, lead, and zinc before injection of the heat-depleted brine into the underground reservoir. Data are presented on the effects of process variables, such as rate and method of lime addition and air oxidation versus air exclusion. Variations in precipitation of metal values, composition of precipitates, effectiveness of slurry thickeners, and methods of treating the precipitates to recover metal values are discussed.

Jan 1, 1982

By R. Pakalnis, Richard P. Curtin, Lewis A. Martin

Instrumented cable bolts developed at the Spokane Research Laboratory of the National Institute for Occupational Safety and Health were used in conjunction with existing ground control to monitor rock mass loads at various field sites (T.G. Soda Ash, Getchell, Meikle, SSX, K-2, and Stillwater). Axial and shear loads were determined by strain gages to levels of instrument accuracy of ±5 N or ±5 microstrain as these loads were transferred to the instrumented cable bolts. These gages were 12.5 mm long and embedded into a remanufactured king wire that replaced the conventional king wire. Cable bolt performance, quality of grout, and installation techniques were also assessed. By using instrumented cables, a mine operator can determine axial load along the cable at predefined gage locations. By monitoring load on and displacement of the rock mass, more effective ground support can be selected and installed, which will lead to safer working conditions for miners.

Provide mine personnel with a convenient means of determining the optimum installation geometry of roof trusses in bedded roof. Background Mine operators frequently ask the following questions concerning roof truss installations: 1. Where should the bearing plates or brackets be placed or where should the inclined holes be started? 2. At what angle should the holes for the inclined chords or angle holts be drilled? 3. What tension should be put into the inclined chords so as to achieve the most effective results for the effort and expense? Truss hardware manufacturers have responded to these questions with answers based on what seems to work best. While designs based on past experience are frequently reliable, there was a need for a rational approach that could accommodate a variety of conditions. The Bureau has developed a procedure that enables mine operators to optimize roof truss installations in bedded roof.

Jan 1, 1989

By J. Roger Loebenstein

Demand for arsenic exceeded supply in 1980, and the major domestic and foreign producers allocated available supplies to customers. Major demand was about evenly divided between industrial chemicals and agricultural chemicals. Legislation and Government Programs.-In June 1980, the Environmental Protection Agency (EPA) listed inorganic arsenic as a hazardous air pollutant.2 Proposed regulations on arsenic emissions were to be announced on an industry-by-industry basis at a future date, and public comment on the listing and on specific regulations was to be heard.

Jan 1, 1981

By Wilbur I. Duvall

In this report, the Bureau of Mines presents a theoretical solution for the stresses and displacements in an infinite elastic plate containing a circular hole the boundary of which is loaded by applied radial stresses over four separated arcs. The problem solved is a two-dimensional approximation of the stresses and displacements developed by a large tunnel-boring machine anchored in a circular tunnel. Analysis of the solution shows that the tangential tensile stresses induced on the boundary of the circular opening can be minimized in the roof and maximized in the floor of the opening by proper spacing and loading of the four arcs.

Jan 1, 1967

By R. V. Ramani, C. B. Manula, A. Owili-Eger

This report was prepared by The Pennsylvania State University under USBM Contract No. G0111808. The contract was initiated under the Coal Mine Health and Safety Program. It was administered under the technical direction of DMRC, with Mr. G. R. Schottler acting as the technical project officer. Mr. J. A. Herickes was the contract administrator for the Bureau of Mines. These applications were developed initially as a part of the instructional material for the course Mng 422, "Mine Ventilation and Air Conditioning" at the Department of Mineral Engineering, The Pennsylvania State University. This ventilation simulator was developed under contract from the Department of Environmental Resources, formerly the Department of Mines and Mineral Industries, Commonwealth of Pennsylvania.

Jan 1, 1975

By Ronald D. Hill, Elmore C. Grim

The goal of blasting is to get maximum fragmentation of the consolidated material in the overburden with optimum drilling and blasting cost. The amount of fragmentation required is determined by the stripping unit to be used In overburden removal. Many coal seams must also be broken by blasting; this is conducted before coal removal. There are environmental factors as well as due regard for public safety, health, and welfare that must be considered in choosing the blasting plan. The blasting plan should be made during preplanning and is based on data from the overburden cores. Analysis of the data will help In determining the kind of drilling equipment and bit types that will be needed for overburden preparation.

Jan 1, 1974