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

ANALYTICAL PRESSURE - VOLUME COMPUTATIONS FOR THE MINE PROTOTYPE A new coal mine is projected, with entrance by slope 1,500 feet long. Nine main entries will be standard for development, five as intake and four as return. One return shaft is planned near the slope bottom, and an intake shaft and portal are planned 5,000 feet north of the slope bottom. The slope will have an area of 150 square feet and a perimeter of 55 feet. A belt and supply track will be within the slope. The return shaft will be circular with a diameter of 18 feet and will be 500 feet deep with an escapeway. Two hundred feet of the shaft and 500 feet of the slope will be concrete lined. Select the fan to operate five units per shift and drive the 5,000 feet to a proposed new portal, using the slope for an intake. Two main splits are planned with the maximum of three units on any split. The amount of air desired at each unit is 25,000 c.f.m; a shop at the slope bottom will require 10,000 c.f.m. In the solution of this or any similar problem, the first step is to determine the resistance factors. CALCULATION OF R FACTORS Slope area = 150 sq. ft.; Perimeter = 55 feet; Length = 1,500 feet. The friction factor K must be established. Five hundred feet of the slope is smooth lined, moderately obstructed by belt; K = 35. The remaining 1000 feet is in sedimentary rock and moderately obstructed; K = 85.

Jan 1, 1975

By E. G. King

In continuation of the study of thermodynamic properties of the common interoxidic compounds of ferroalloy elements, this report gives the results of low-termperature heat-capacity measurements and entropy evaluations of the monotungstates of sodium, magnesium, and calcium. Previous reports4 5/ of this laboratory dealt with low-temperature heat capacities, entropies, and heats of formation of the sodium vanadates. Heat-capacity measurements of the monotungstates of sodium, magnesium, and calcium (Na2W04, MgW04, and CaW04) were conducted throughout the temperature range 51° to 298° K. The entropies at 298° K. were evaluated and then combined with entropy data for the elements and oxides to obtain entropies of formation. This information is an essential part of the data needed for thermodynamic appraisals of chemical reactions of these substances. No similar data for any tungstate are to be found in the literature.

Jan 1, 1961

By Jürgen F. Brune, R. Karl Zipf, Michael J. Sapko

Seals are barriers constructed in underground coal mines throughout the United States to isolate abandoned mining panels or groups of panels from the active workings. Historically, mining regulations required seals to withstand a 140-kPa (20-psig) explosion pressure. However, the Mine Improvement and New Emergency Response Act (“MINER Act”) requires the Mine Safety and Health Administration (MSHA) to increase this design standard by the end of 2007. This report provides a sound scientific and engineering justification to recommend a three-tiered explosion pressure design criterion for new seals in coal mines in response to the MINER Act. Much of the information contained in this report also applies to existing seals. Engineers from the National Institute for Occupational Safety and Health (NIOSH) examined seal design criteria and practices used in the United States, Europe, and Australia and then classified seals into their various applications. Next, the engineers considered various kinds of explosive atmospheres that can accumulate within sealed areas and used thermodynamic calculations and simple gas explosion models to estimate worst-case explosion pressures that could impact seals. Three design pressure-time curves were developed for the dynamic structural analysis of new seals under the conditions in which those seals may be used: unmonitored seals where there is a possibility of methane-air detonation or high-pressure nonreactive shock waves and their reflections behind the seal; unmonitored seals with little likelihood of detonation or high-pressure nonreactive shock waves and their reflections; and monitored seals where the amount of potentially explosive methane-air is strictly limited and controlled. Figure 1 is a simple flowchart that illustrates the key decisions in choosing between the monitored or unmonitored seal design approaches and the three design pressure-time curves. For the first condition, an unmonitored seal with an explosion run-up length of more than 50 m (165 ft), the possibility of detonation or high-pressure nonreactive shock waves and their reflections exists. The recommended design pressure-time curve rises to 4.4 MPa (640 psig) and then falls to the 800-kPa (120-psig) constant volume (CV) explosion overpressure. For unmonitored seals with an explosion run-up length of less than 50 m (165 ft), the possibility of detonation or high-pressure nonreactive shock waves and their reflections is less likely. A less severe design pressure-time curve that simply rises to the 800-kPa (120-psig) CV explosion overpressure may be employed. For monitored seals, engineers can use a 345-kPa (50-psig) design pressure-time curve if monitoring can ensure that (1) the maximum length of explosive mix behind a seal does not exceed 5 m (16 ft) and (2) the volume of explosive mix does not exceed 40% of the total sealed volume. Use of this 345-kPa (50-psig) design pressure-time curve requires monitoring and active management of the sealed area atmosphere. These design pressure-time curves apply to new seal design and construction.

Jan 7, 2007

By J. Grumer

Nine dust and gaseous inhibitors of propagating coal dust-air flames (lean, stoichiometric, and rich) were evaluated in a newly developed 15-cm-id, 3.6-meter-long instrumented flame duct, under conditions such that wall quenching was virtually absent and the dust concentration was temporally and spacially uniform to within about t5 percent. Listed roughly in order of increasing efficiency, the inhibitors evaluated were rock dust (calcium carbonate), powdered oyster shells (calcium carbonate), Halon 1301 (trifluorobromomethane), Halon 1211 (difluorochlorobromomethane), sodium chloride, Super-K (potassium chloride), regular-grade fire extinguishant powder (sodium bicarbonate), Purple-K (potassium bicarbonate), and Monnex (potassium bicarbonate combined with urea). Experiments were extended to clouds containing 1 and 2 volume-percent of methane. The inhibition of lean, stoichiometric, and rich methane-air flames without coal dust was also examined in a few instances; results agreed with those obtained for coal dust-air flames.

Jan 1, 1971

By Peter Swanson, Collin Stewart, Wendell Koontz

A seismic monitoring network has recently been installed in the North Fork Valley coal mining region of western Colorado as part of a NIOSH mine safety technology transfer project with two longwall coal mine operators. Data recorded with this network will be used to characterize mining related and natural seismic activity in the vicinity of the mines and examine potential hazards due to ground shaking near critical structures such as impoundment dams, reservoirs, and steep slopes. Ten triaxial strong-motion accelerometers have been installed on the surface to form the core of a network that covers approximately 250 square kilometers (100 sq. miles) of rugged canyon-mesa terrain. Spread-spectrum radio networks are used to telemeter continuous streams of seismic waveform data to a central location where they are converted to IP data streams and ported to the Internet for processing, archiving, and analysis.

By C. R. McCann

The Bureau of Mines conducted an experimental study of conditions needed to produce flames of pulverized coal when the heat needed for ignition is sup-plied only from the flame and hot furnace refractory. An electrically heated furnace which burned about 1 pound of coal per hour was designed and fabricated. A sheath of air, surrounding the primary coal and air stream, was used to prevent entry of hot gases from recirculating combustion products. Furnace temperatures needed for ignition ranged from about 1,8300 F for an Illinois coal to 2,250° F for a Beckley seam coal. Apparent flame velocities were about 2 to 5 feet per second, increasing with volatile content of the coal and with distance from the burner mouth to the flame. The time required for ignition, approximately 0.02 to 0.07 sec, was a better measure of flame behavior than was velocity.

Jan 1, 1969

By W. W. Staley

This paper discusses the design of small head frames that will fill the needs of prospectors and small operators whose operations are conducted through shafts. The head frames considered were designed to handle relatively small tonnages. It was assumed that the shafts in which buckets are used would not exceed 300 feet in depth and that not over 60 tons of rock would be hoisted, in, 14 hours. In the design of the larger head frames, a hoisting capacity of about 250 tons per 6 hours from a depth of 300 to 500 feet was assumed. Under these conditions, hoisting speed, rate of acceleration, and weight of rope have a negligible effect on the head frame design and, therefore, have been ignored in the following, discussion. Because timber is relatively cheap and easily obtained in most mining areas, the discussion has been confined to timber construction.

Jan 1, 1937

By Bernard Porter

The solubility of UO2 was determined at 1,250° C. in ternary melts of UF4 and BaF2 with CaF2, LiF, and SrF2. The solubility of Ce02 was measured at 800° and 850° C. in a solution of CeF3, BaF2, and LiF. The amount of La203 which dissolves at 950° C. in a binary mixture of LiF and LaF3 and a ternary of LiF, LaF3, and BaF2 was also measured. In each case, the amount of soluble oxide was mound to be less than 5 weight-percent. A procedure was developed for filtering fused, oxide-saturated fluoride melts in order to obtain a representative sample for chemical analysis. The oxide content of the samples was determined by an inert-gas fusion procedure.

Jan 1, 1961

By Larry J. Nicks

The Bureau of Mines is investigating the catalytic activity of rare-earth compounds to develop a catalyst for the cathode reaction of a hydrogen-oxygen fuel cell. This report presents the results of studies of the catalytic activities of lanthanide oxides for the oxidation of hydrogen at 150° to 250° C. Preliminary activity tests were made with approximately stoichiometric mixtures of hydrogen and oxygen diluted with helium. A series of tests was also run under oxygen-rich conditions in which specific rate constants and activation energies were determined. Variations in rate constants up to 2,000 times were observed for the various lanthanide oxides. The three most active catalysts were oxides of Ce, Pr, and Eu, having specific activities of 6.93 X 10-7, 4.88 X 10-7, and 4.06 X 10-7 moles H2.sec-1.m-2, respectively, at 200° C.

Jan 1, 1973

By David P. Lindroth

The heat content above 25.0° C up to 1,000° C was measured for six rock types: St. Cloud Gray Granodiorite, Holston Limestone, Sioux Quartzite, Rockville Quartz Monzonite, Salem Limestone, and the basalt at Dresser, Wis. The calorimetric data were obtained with an isothermal jacket-copper block calorimeter. The experimental heat content data for each rock type are presented, along with specific heat data obtained from the temperature derivative of the heat content. For the six rock types the maximum deviations of the specific heats at a given temperature were within 10 percent below 575° C and within 34 percent above 5750°C. The increase in the values of specific heat range from a minimum of 13 percent for the basalt at Dresser, Wis. (temperature range, 100° to 1,000° C) to a maximum of 46 percent for Holston Limestone (temperature range, 100° to 870° C).

Jan 1, 1971

By Stephen A. Hare, O&apos

The melting, casting, and welding of the Raney nickel alloy (42 pct Ni-58 pct A1), a methanation catalyst useful in coal gasification, were investigated. Melting was done in graphite crucibles by heating aluminum and adding nickel using a cryolite slag cover. Casting conditions were found to be optimum when the melt temperature ranged from 1,125° to 1,200° C and the mold temperature ranged from ambient to 250° C. Suitable mold materials were found to be quartz, heat-resistant glassware, olivine, and zircon. Welding of the alloy can be accomplished using tungsten inert gas process. Tensile strength of the alloy, in the as-cast condition, was found to be 2,000 1b/sq in with an impact strength of less than 1 ft-1b. The coefficient of thermal expansion was determined to be 18.4 x 10-6/° C after heat treatment.

Jan 1, 1977

By Liming Yuan, John C. Edwards, Gene F. Friel, Robert A. Franks

Diesel fuel fire experiments were conducted in NIOSH’s Pittsburgh Research Laboratory’s (PRL) Safety Research Coal Mine (SRCM) to determine the critical air velocity for preventing smoke rollback. Such information is necessary for the preplanning and implementation of ventilation changes during mine fire fighting and rescue operations. The fire intensity varied from 50 kW to 300 kW depending upon the fuel tray area. Airflow in the 2 m high and 2.9 m wide coal mine entry was regulated during the course of each experiment; measured upwind from the fire as an average over the entry cross-section with an ultrasonic airflow sensor; and recorded dynamically with a mine monitoring system. The extent of smoke reversal was monitored with light obscuration monitors, ionization smoke sensors, and visual observations. Experimental results for the critical air velocity for smoke reversal as a function of fire intensity compared very well with model predictions based upon a computational fluid dynamics (CFD) fire dynamics simulator.

By Thomas C. Atchison

The experimental work described in this report is part of a continuing study by the Federal Bureau of Mines of the fundamental physical processes involved in breaking rock with explosives. Six explosives were tested for their strain-producing abilities in a dolomitic marble. The explosives selected for testing had a tenfold variation in detonation pressure and a fivefold variation in characteristic impedance (product of loading density and rate of detonation). Strain pulses produced by the detonation of small charges of the explosives were recorded at distances of 5 to 130 feet. Peak strain, ?, was found to decrease with distance, R, in accordance with an exponential propagation law previously determined for other rock types, namely ? = (K/R)e ?aR The absorption constant, a, did not vary significantly with the explosive and was of the same order of magnitude as that for other rock types. The different explosives produced a fivefold variation in the value of the intercept constant, K.

Jan 1, 1961

By G. Ahnell

Throughout portions of four (4) heavily mined Appalachian states subdivided by the Mine Safety and Health Administration (MSHA) as: District 3 -Northern West Virginia and Maryland; District'" -Southern West Virginia; District 5 -Virginia; and District 6 -Eastern Kentucky, active coal mine waste embankments associated with mechanical and/or chemical coal processing facilities of various levels of coal preparation were inventoried. For each site plant specifications, disposal techniques, embankments' characteristics, and coal source data were accumulated. Mapping at 1: 24, 000 and 1: 250,000 scale and Disposal Site Characterization forms were developed to present the findings. Associated abandoned surface and underground openings near each site were also indicated as well as locational data for each site and the areas environmental conditions - temperature, precipitation and vegetation types. A state-of-the-art review of coal preparation, waste disposal, and alternative uses of coal waste is also included.

Jan 1, 1982

By Alla D. Mah

The need for more and better basic thermodynamic data for the oxides of many of the rare metals is evident to anyone who attempts thermodynamic calculations involving these substances. In continuation of a Bureau of Mines program to meet this need, this paper reports new experimental values of the heats of formation at 298.15° K. of the hexagonal crystalline variety of germanium dioxide and germanium dioxide glass. The values were obtained by means of combustion calorimetry and sodium hydroxide-solution calorimetry. The calorimetric results also made possible the derivation of values for the heat and entropy of fusion of hexagonal germanium dioxide at its melting point. The newly measured data were combined with previously known entropy and high-temperature heat content values to obtain heats and free energies of formation of germanium dioxide (in the hexagonal crystalline, glassy, and liquid states) over the temperature range from 298.15° to 2,000° K.

Jan 1, 1962

By Robert M. Doerr

The research objective was to determine the effect of aluminum alloy additions on the oxidation behavior of cobalt-nickel alloys. Thirty high-purity alloys were reacted with 02 at 0.5 atm at 1,351°, 1,389°, and 1,429° K in a volumetric apparatus for about 300 min. The alloy compositions consisted of Co-Ni master alloys (0, 22, 50, 70, 91, and 100 wt pct Ni) with aluminum additions of about 0, 1, 2, 4, and 8 wt pet. Large early deviations from, or changes in, the parabolic rate constant were encountered, but in most cases, the reaction rate declined approximately in accordance with the parabolic rate law. A sharp peak in the parabolic oxidation rate constant was observed for specimens containing a to 22 percent nickel and 1 to 2 percent aluminum at 1,351° K, and the rate constants for these compositions were lower at the higher temperatures. Specimens containing 8 percent aluminum reacted far more slowly than did any of the others.

Jan 1, 1971

By J. R. Welty

High-temperature thermodynamic data have, in recent years, become increasingly important for the extractive metallurgist. The extraction of metals from their ores previously was based on trial and error methods, involving hours of testing and often costly equipment fabrication. Using thermodynamic data it is frequently possible to predict the feasibility of a proposed metallurgical process as well as the optimum operating conditions for the process with reasonable accuracy. Such predictions can save consider-able tim~ and expense. Widespread use of thermodynamic analyses has been handicapped by lack of dependable experimental data. Investigators, notably K. K. Kelley (4)4. have devoted many years to determining and compiling such data. These investigators, although prolific in their production of thermodynamic values, have been unable to meet all the needs of industry and other branches of science. This becomes obvious when one considers the aeronautical and nuclear fields, in which previously unimportant, therefore uninvestigated, substances have become of prime importance.

Jan 1, 1962

By Wilbur I. Duvall

This report presents experimental data on the propagation of explosion- generated strain pulses in rock. Tests were performed in 5 different rock types, employing 10 different types of explosives. Charge sizes ranged from 0.5 to 50 pounds, and travel distances ranged from 2.5 to 70 feet. Analysis of the data shows that the experimental peak strain data satisfy an exponential decay propagation law of the form: ?R/W1/3 = Ke ?aR/W1/3. For a particular rock, parameter K is a linear function of the calculated detonation pressure or the calculated energy density of the explosive. For a particular explosive, K is a linear function of the elastic parameter of the rock, p2, a result, which is at variance with elastic theory. The absorption constant, a, is independent of type of explosive but dependent upon rock type. However, no definite relation between a and the physical properties of the rock could be established.

Jan 1, 1959

By R. V. Ramani, P. M. T. White, D. Sutton

4.1 Introduction Using methods outlined in previous sections of this report, programs were written and/or obtained to: i) select best combinations of "a" and "k" for up to 8 different value parameters, ii) calculate available and unavailable ore tonnages and other statistics, and iii) produce contour maps of various parameter characteristics and available tonnages on a line printer. All the above programs are written in Fortran IV for execu¬tion on IBM 360/370 computers. 4.2 Calculation of Coal Reserves The Ore Reserve program suite consists of the following sections: (a) UNIT 1: This unit is a subroutine called by Unit 2 to determine values for "a" and "k" from the given data. (b) UNIT 2: These programs calculate ore reserves and are composed of a main program and several sub¬routines. In the following, their functions are abbreviated: i) MAIN - calls subroutines, reads run parameter variables, reads borehole data and interpolates grid node values for the area of investigation

Jan 1, 1974

By James R. Means, George Bowser

A new phone system was developed that provides eight full duplex communications channels over a single twisted shielded phone line, with no central switching station or line amplifiers. This system greatly simplifies installation and maintenance over that required with conventional switching systems. The system is based on microprocessor technology and digital frequency synthesis. Frequency division multiplexing is used over a bandwidth of approximately 300 kHz, and a baseband voice channel (compatible with conventional pager phones) is provided as a backup to assure communication if the multiplex features fail. Multiplex operations are controlled over a 30-kHz digital channel. The system is designed to operate with up to 16 km (10 miles) of cable plant and a maximum phone separation of 8 km (5 miles). The digital techniques permit a limited amount of monitoring and control capability to each phone. This consists of two pair of contact inputs or outputs, to be used as desired. These "flags" may be read or controlled by a dispatcher's phone.