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By Robert F. Holub

The Bureau of Mines has made a study of the magnitude of the variations of radon daughter mixtures, with the objective of determining whether these variations reflect the existing physical conditions in uranium mine atmospheres or if they are merely random or systematic errors. To accomplish this, many data have been plotted using a triangular graphing technique which shows that plateout affects RaA more than RaB or RaC, and that it is impossible to find simple correlations between working level ratios, radon daughter mixtures, and age.

Jan 1, 1978

By Brian Kenner, Peter Swanson, Todd Krahenbuhl

NIOSH has developed an automated PC-based seismic event (induced earthquake) monitoring system for use in mine ground control studies. The distribution and coordination of data acquisition and processing functions across a local area network is a central feature of the system. Mine-wide installations utilize multiple, autonomous seismic networks located both underground and on the surface. Seismic event locations, magnitude estimates, and other processed data are distributed for display and analysis on network nodes both underground and in the offices of mine engineers and managers. This paper describes the system’s design philosophy, hardware and software components, examples of installations, and a few observational results.

By H. H. Dewing

The Bureau of Mines conducted a laboratory-scale investigation of a technique that produces zinc sulfate and elemental sulfur from sphalerite concentrates by reaction with sulfuric acid at 175° to 200° C and ambient pressure. The objective of the investigation was to develop a hydrometallurgical method of producing zinc from sulfide concentrates that does not generate sulfur dioxide pollutants. Reaction with 80-to 85-pct sulfuric acid produced 4 moles of sulfur for every 3 moles of sphalerite reacted, with minimal production of sulfur gases under optimum conditions. More than 98 pct of the zinc was recovered as zinc sulfate after 3 hours at 175° C. The reaction mixture was leached with simulated spent zinc electrolyte containing 13-pct sulfuric acid to recover zinc sulfate from the insoluble, high-sulfur residue. Neutral zinc sulfate, which is required for electrolysis, was separated from the sulfuric acid solution by crystallization as ZnS04?7H20 at -10° C. Up to 80 pct of the water in the recycled electrolysis solution was removed by the crystallization process; evaporation was used to further concentrate the sulfuric acid for reuse in leaching sphalerite. Advantages of the proposed method over conven-tional roasting and leaching include virtual elimination of sulfur dioxide, production of a solid sulfur byproduct, and higher zinc recoveries due to elimination of zinc ferrite losses.

Jan 1, 1978

By Leonard J. Prosser, Joseph Cervik, John H. Perry

The Bureau of Mines has developed several techniques for draining methane from coalbeds in advance of mining. Drilling long horizontal holes from an underground location is one such technique, which was successfully demonstrated in the Pittsburgh and Sunnyside Coalbeds. The same technique has now been applied in the Mary Lee Coalbed at Jim Walter Resources, Inc. 's No. 4 Mine, Brookwood, Ala. , where two holes were drilled horizontally--one to a depth of 1,010 feet (308 m) and the other to 540 feet (165 m). The 1,010-foot (3083) hole proved successful in degasifying a portion of the Mary Lee Coalbed. The hole drained methane for 1 year, during which time the initial gas flow of 200,000 ft3/d (5,663 m3/d) declined to 65,000 ft3/d (1,840 m3/d). Total gas production was 40 x lo6 ft3 (1.1 x lo6 m3 ). The gas was of commercial quality, with 98 pct methane and a heat rating of 990 Btu/ft (36.89 Mj/m3). The methane emissions from the faces of the mine section advancing into the degasified zone were reduced by 60 pct. The 540-foot (165-m) hole was terminated prematurely when it became impossible to maintain an open hole. Because of caving, very little gas was drained through this hole.

Jan 1, 1982

Provide the U.S. mining industry with the means to measure and control exhaust emissions of diesel engines used in underground mines. Approach Diesel research is divided into four primary areas: exhaust aerosol measurement, particulate control, gaseous emission control, and chemical and biological characterizition of particulate matter. Diesel research is frequently cosponsored by industry; collaborative research ventures between industry, academia, other government agencies, and the Bureau arc common. Diesel research at the Bureau is conducted in the diesel engine research facility at the Bureau?s Twin Cities Research Center (TCRC). This facility is a state-of-the-art laboratory capable of performing emissions testing, exhaust control evaluations, and safety tests. Background Exposure of mine workers to airborne contaminants from diesel engine exhaust is potentially harmful. The National Institute for Occupational Safety and Health has recommended that whole diesel exhaust be regarded as "a potential occupational carcinogen" and that ?reductions in exposure to diesel exhaust in the workplace would reduce the risk." The U.S. Mine Safely and Health Administration (MSHA) convened an Advisory Committee on Standards and Regulations for Diesel-Powered Equipment and is beginning to implement its recommendations, which cover health, safety, and certification and approval issues surrounding the use of diesels underground. In January 1992, MSHA published an advance notice of proposed rulemaking to regulate diesel particulate matter in underground mines.

Jan 1, 1992

Develop methods to detect and repair poorly functioning dust collectors on roof bolters. Approach In conjunction with a research project to reduce silica dust in coal mines, a variety of roof bolting machines operating under different conditions were examined to find out how much these machines were contributing to the silica dust problem. Results The investigation concluded that if the bolting machines' dust collector is properly maintained, very little dust can be measured in the air, even with minimal airflow over the bolter. Poor maintenance, however, frequently results in high dust levels. Three major problem areas were found. These were: (1) filter leaks, which allowed dust to escape, (2) accumulations of dust in the collection system, and (3) low airflow at the bit due to hose, fitting, and relief valve leaks.

Jan 1, 1984

By R. F. Abernethy

A chemical method of determining microgram quantities of arsenic in coal was investigated by the Bureau of Mines to supplement a semiquantitative spectrographic method of determining arsenic in coal ash. In accordance with a method recommended by the International Organization for Standardization, 1-gram samples of coal are decomposed by wet oxidation with boiling sulfuric acid (H2S04) and nitric acid (HN03) to remove the organic matter. After heating to fumes of SO3 to remove HN03, the arsenic is separated as arsine by the action of zinc in H2S04 solution. The arsine is absorbed in dilute iodine solution in which the arsenic is determined colorimetrically by the molybdenum-blue reaction. Two modifications of the method for obtaining the arsenic in solution, in addition to the wet oxidation method, give satisfactory results. The modifications are (1) furnace ashing with MgO added to the coal, followed by treatment with H2S04, and (2) extraction of arsenic from the coal by dilute HNO3 without ashing. Float-and sink-tests show that arsenic is associated mainly with mineral matter in the three coals examined. High-temperature ashing tests show that very little arsenic is volatilized from coal ash below 1,000° C, but it is virtually all removed from the ash at 1,300° C.

Jan 1, 1968

To develop and design a bit that will rapidly drill smooth and precise instrumentation holes in soft rock. Approach Use a one-piece bit made by combining a drag bit and a diamond bit. Because a smooth-walled borehole with a precise diameter is needed for borehole pressure cells (BPC) and other borehole instruments, a diamond bit is usually used. However, diamond bit drilling is slow, and the bit will tend to bind when squeezing ground is encountered. On the other hand, the drag bit will cut faster, but the walls of the drill hole will be rough and the diameter will not be as precise. The combination will provide a bit which penetrates as rapidly as a drag bit, but retains the smooth-wall and precise borehole diameter of a diamond bit. How It Works A three-foot-length of EW-size drill rod is centered in a diamond bit by welding it to three equally-positioned spacers at each end of the bit. A drag bit is attached to the EW rod with a standard EW-to-drag bit adapter as shown in the diagram. Three equally-spaced diamond inserts are set to the desired hole size and welded to the diamond bit barrel behind the crown. These inserts increase the smoothness and precision of the hole by cut-ting away any hole closure. Three equally-spaced shims are set approximately 0.020-inch under the overall insert diameter size and welded to the rear of the diamond bit barrel. The combination bit should be used on a diamond drill with either water, mist or air as the coolant.

Jan 1, 1982

By Richard Hammer

Various alternating current (ac) methods can localize faults in mining power cables. Several methods considered by the Bureau of Mines in this report are the Murray loop for short circuits, wherein a bridge provides proportional distance to the fault; capacitance measurements for open conductors; inductance measurements for shorted conductors; phase comparison, high speed recordings of voltage and current in the faulted state are compared with normal voltage and current with the difference being a function of impedance change and impedance change being a function of fault location; and standing wave measurements, detecting the resonance of the length of cable to a fault (either short or open). Portable capacitance bridges are presently available for the second method, and the fourth method is well developed for use on large power distribution systems. Because it utilizes pulses rather than ac, the time domain reflectometer (TDR) method of fault locating was not included in this investigation. However, a comparative evaluation between this versatile method and the Murray loop might prove advantageous in locating high resistance faults.

Jan 1, 1977

Control dust generated during overburden drilling at surface coal mines using either wet suppression or dry collection systems. Approach For the wet suppression systems, a range of water flow rates was tested over a number of holes. Each hole was drilled at a specific and constant flow rate. A recording flow meter was mounted in the water line near the control system pump. For the dry collection systems, each drill was tested with the front of the shroud set at different heights above the ground. Because of the irregularity of the ground surface, all height measurements were taken at the front of the shroud. Background Wet drilling systems consist of a water tank mounted on the drill from which water is pumped into the downhole air line. The water droplets in the bail air conglomerate dust particles as they travel up the the annular space of the drilled hole, thus controlling dust as the air bails the cuttings from the hole.

Jan 1, 1987

By O. C. Baptist

The gravitational pressure gradient (GPG) in porous sandstone containing free gas was determined to define the proper GPG to use when calculating the rate of downdip flow of oil in the Sub-Scalez No, 1 sand, Elk Hills field, Naval Petroleum Reserve 1. The GPG was determined at several gas saturations using long, artificially consolidated sandstone models that were mounted vertically in some tests and horizontally, with rotation, in others. Also determined by laboratory and field tests were relative permeabilities, capillary pressure relations; critical gas saturation, water sensitivity, and depletion drive performance. The critical gas saturation in the models having an absolute permeability of 1 to 2 darcys was about 2 percent of pore volume. The GPG with the critcal gas saturation was that due to the weight of the gas-saturated oil. The GPG in the upper part of the models was reduced as gas saturation increased to a value considerably larger than the critical. The exact gas saturation at which the GPG became less than that due to the weight of the oil could not be determined but was estimated to be of the order of 10 percent of pore volume. Tests indicate that the rate of oil production is not permanently reduced by exposure of the sand to fresh water but that the rate of injection of fresh water will be considerably less than that to brine, Methods for determining the factors mentioned above are discussed.

Jan 1, 1967

By C. H. Elder, Fred N. Kissell, S. D. Maksimovic

The Bureau of Mines evaluated the hydraulic stimulation of a gob-degasification borehole to determine if this procedure would aid in degasifying a longwall panel. The stimulated borehole did not degasify the longwall panel as expected either before or after mining of the panel started. It reduced the underground methane emission only 11 pct, considerably less than the reductions effected by two unstimulated boreholes in the same panel. Some probable reasons for the reduced methane flow from the hydraulically stimulated borehole are very low reservoir gas pressure, location of hydraulically stimulated zones within the grouted casing, a casing break caused by lateral shifting, possible vertical movement of rock strata during caving, grouting of a 4-inch pipe blocking three stimulated zones, plasticity of shales, and possible hole damage by swelling of water-sensitive minerals. The borehole was also located between two second-mined areas, which may have allowed partial degasification of the overburden and the coalbed in advance of mining. Finally, a period of 3 months is probably not long enough for the borehole to degasify the overburden before mining.

Jan 1, 1977

By Roy F. Abernethy

This report describes a method developed by the Bureau of Mines for the determination of beryllium in coal ash. Samples are put into solution by standard wet chemical procedures. Interfering elements are complexed with Na2EDTA, and the beryllium is separated by extraction of its acetyl acetone complex with chloroform or carbon tetrachloride. Final determination is made with Beryllon II.

Jan 1, 1970

By David E. Emerson

The Bureau of Mines has developed a mass spectrometer method for deter-mining the helium-3 content of high-purity helium. The work was performed to evaluate experimental methods for removing helium-3 from high-purity helium and to better determine the composition of pure helium used in research. This was accomplished by increasing the inlet sample pressure, ionizing current, and amplification of the current produced by the ions collected on a conventional mass spectrometer that had been modified. With these modifications, the helium-3 content was determined in the parts-per-million and parts-per-billion range in helium-4.

Jan 1, 1976

Reliably detect fires by sensing sub-micrometer-sized particles released into the air by smoldering or burning materials. Approach An extremely sensitive, ionization-type fire detector has been built that continuously draws air samples through its ionizing field and collects the ionized smoke particles downstream, thereby generating a proportional electrical output signal. (An offshoot instrument measures the size distribution and number of sub-micrometer particles in air.) How It Works Mine air to be monitored is drawn through the instrument assembly by a small pump. A pre-filter and cyclone remove dust particles and other particles larger than 0.6 micrometer diameter. The air and remaining aerosol-sized particles flow through a gastight tube which contains the detector. See diagram. Smoke and other sub-micrometer-size particles moving Into the detector, pass through an Ionizing field, and are struck by alpha particles released from radioactive source located on the axis of the tube, The alpha particles move radially outward until they strike smoke particles or molecules of air or water. When struck, a smoke particle or molecule loses an electron and becomes positively ionized.

Jan 1, 1979

By Charles L. Kimbell

For 1991, the aggregate value of world international export trade in mineral commodities was roughly estimated at $685 billion in current 1991 dollars. The estimated level was about 6 % higher than that for 1990, but still more than 3 % below the record high set in 1980, and the year was the fifth in a row in which the value of exported minerals advanced. Table 8 provides a data series for the estimated value of world export trade in all mineral commodities from 1979 through 1991, as well as a breakdown of this total into fuel and non fuel commodities. The data shown are based on the historically more traditional and realistic (from the viewpoint of data availability) practice of reporting trade values for the year before the year of review. Despite the considerable increase in the dollar value of mineral commodity exports, their share of total export merchandise trade declined to 19.1 % in 1990 from 19.7% in 1989. At 19.1 %, this share was very near the recent year record low of 19.0% reached in 1988. Comparable 1991 figures were not available in time for inclusion here, but it is expected that the mineral commodity share of the total will be little altered from that of 1990.

Jan 1, 1993

By Richard A. Winters

In 1987, at the request of the U.S. Bureau of Land Management, the U.S. Bureau of Mines studied the 334-acre Mountain Lakes Wilderness Study Area (OR-011-001) in order to evaluate its identified mineral resources. The study area is located in Klamath County about 15 miles northwest of Klamath Falls, Oregon, and is adjacent to the Mountain Lakes Wilderness. The area is underlain by Pliocene-age basaltic andesite. No mining districts are in the study area nor were any claims recorded or found. There are no oil and gas lease applications. There are no identified mineral resources in the study area. INTRODUCTION This report describes the USBM (U.S. Bureau of Mines) portion of a cooperative study with the USGS (U.S. Geological Survey) to evaluate mineral resources and potential of the Mountain Lakes WSA (Wilderness Study Area), at the request of the BLM (U.S. Bureau of Land Management). The USBM examines individual mines, prospects, claims, and mineralized zones, and evaluates identified mineral and energy resources. The USGS evaluates potential for undiscovered resources based on areal geological, geochemical, and geophysical surveys. Results of the investigations will be used to help determine the suitability of the WSA for inclusion into the National Wilderness Preservation System. Although the immediate goal of this and other USBM mineral surveys is to provide data for the President, Congress, government agencies, and the public for land-use decisions, the long-term objective is to ensure the Nation has an adequate and dependable supply of minerals at reasonable cost.

Jan 1, 1988

By T. D. Ralston

This Bureau of Mines report presents a mathematical model for heterogeneously catalyzed chemical reactors operating under turbulent conditions. The model includes reaction kinetics on the catalyst surface as well as diffusion of the reacting components within the reactor. Three applications of the model to tube-wall methanation reactors are discussed. The first application is a computation of catalyst activity from measured reactor data. This result is then used in a reactor sizing problem and a problem of reactor simulation with recycle. In addition to the reactor model, a novel approach to solving the recycled reactor problem is given.

Jan 1, 1974

By Robert A. Bruce

A motion transducer based on coherent mixing of laser light backscattered from rough surfaces is evaluated in terms of sensitivity, bandwidth and range. Tests made with a prototype composed of a 4-mw HeNe laser, a silicon avalanche photodiode, and a 15-cm aperture telescope demonstrate that remote measurements with reasonable bandwidth and accuracy are feasible at distances up to 100 meters.

Jan 1, 1977

Determine safe practices for surface mine blasting near pressurized gas, oil, and water transmission pipelines. Background Surface mine blasters regularly have to address the issue of how blasting affects transmission pipelines that run near and sometimes through their permit areas. Regulatory approaches to blasting have ranged from no regulation at all to strict limits intended to prevent cosmetic cracks in plaster interior walls of homes, but they have not directly addressed the impact of blasting on nearby pipelines. Concerned with both productivity and safety, the mining industry and its regulators have requested guidance on safe practices for mining near pipelines. The Pipeline Research Group of the American Gas Association has sponsored studies of the effects of small close-in blasts because of vibration concerns related to the installation of new pipes into existing pipeline right-of-ways. By contrast, the recent study in which the U.S. Bureau of Mines (USBM) took part is the first addressing large-scale mining blasts.

Jan 1, 1995