Search Documents

By David A. Monaghan, Kenneth R. Maser, Adi R. Gurdar, D. Randolph Berry

3. Preliminary Evaluation of Mine Sealing Techniques As the first stage in the development of a technique for the remote sealing of mines, a state-of-the-art survey of various mine sealing techniques was conducted. This was expanded to include a review of different materials offering some potential for use as a mine sealant. Techniques for the remote placement of materials for other applications were evaluated, and system concepts for dis¬tributing remotely placed materials were developed. This preliminary review led to the development of a functional description of a general mine sealing technique to meet the specified conditions. Various potential system configurations were synthesized. These were subjected to a preliminary evaluation based on estimated confidence in system performance, development risk, cost, and sealing time. Based on this preliminary evaluation, promising mine¬sealing techniques were selected for further development. This section presents a review of the following: (a) Techniques for constructing permanent seals from within a mine. (b) State of the art in remote sealing for mine fire control. (c) Techniques for remote placement of materials for other applications. (d) Systems for distributing remotely placed material. (e) Materials for mine sealing. (f) Synthesis of remote mine sealing concepts.

Jan 1, 1973

By F. N. Kissell, R. J. Bielicki

The Bureau of Mines found sulfur hexafluoride (SF6), released from a lecture bottle, to be an ideal gaseous tracer for studying mine ventilation systems. Air samples were collected in glass syringes and analyzed by electron-capture gas chromatography. In these studies, the lower limit of detection was about 1 part per billion by volume (ppb) of SF6 per part of air. Experiments conducted in a Pennsylvania limestone mine showed this technique useful in evaluating the effectiveness of auxiliary fans, measuring low flow velocities, probing the air circulating near a working face region where ventilation appeared to be poor, and estimating volumetric flow rates in airways of large cross-sectional area and having low flow velocities. This technique was also used in a western vein-type metal mine to measure the amount of return air being recirculated into the intake air due to leakage through old stoped areas.

Jan 1, 1974

By Charles Vaught

This is the second in a series of four articles that discuss underground firefighting preparedness. As with the first article in the May-June issue, it is based on interviews with 214 miners conducted at 7 underground mines (?A? through ?G?) by researchers of the National Institute for Occupational Safety and Health?s (NIOSH) Pittsburgh Research Center [Vaught et al. 1996].In the first article, the authors presented an overview of the study conducted by NIOSH on mine fire response preparedness and provided a general perspective on underground mine fires. In this article, we will describe miners? preparedness to evacuate a fire and their experience with incipient fires

Jul 1, 1997

Impermeable geologic faults in the coal seam can cause intermittent production problems or can cause unexpected amounts of water or gas to issue from degasification boreholes. These faults also can impact methane emissions into the mine workings, especially if they hinder proper and effective degasification of the coal bed. They may also act as barriers for methane flow in the coal seam. Although this might seem beneficial for advancing mine workings, faulting may also cause gas pressure buildups and result in compartmentalization of the gassy regions from which large quantities of water and methane may rush into mine workings. This study uses reservoir simulations to illustrate the effects of impermeable faults, with and without throws, on the production performance of vertical and horizontal degasification boreholes. These boreholes were drilled from the surface to intercept the coal layer and fault and were assumed to produce methane two years prior to mining of the coal seam. Longwall advances and face position related emissions and reservoir properties were characterized using sector definitions along the path of the panel grids. This work numerically evaluates water and gas productions of each borehole and presents the effects and the impacts of impermeable faults on methane emissions due to an advancing coal face. The results can be used to understand the effects of impermeable faults on borehole productions and face emissions due to these coal seam anomalies.

Jan 1, 2008

To test the feasibility of hydraulic borehole mining for the recovery of phosphate ore from the deep, water-saturated deposits of northeastern Florida. Approach Phosphate ore is remotely extracted through a Bureau of Mines-developed hydraulic borehole mining system. Hydraulic borehole mining can remove underground ore deposits that cannot be economically mined by the usual open pit or underground methods. It is environmentally compatible, causing none of the surface disruption or ground water pollution usually associated with other methods of mining. Selectivity of the borehole mining system also allows economical recovery of small or discontinuous ore deposits while minimizing the removal of host rock. The hydraulic borehole mining system has been used successfully in the past to mine uranium ore and oil sands. (For examples of these and other applications of borehole mining see T Technology News Nos. 97, 95, 63, 56, and 48) How it Works A 16-inch-diameter borehole is drilled from the surface down into the buried mineral deposit, and the mining tool is installed. The borehole mining tool consists of a 12-inch-diameter pipe string and accessories capped with a three-passage swivel, and ending with a mining section. The mining section has four slurry inlets and an eductor located near the bottom of the section and a single cutting nozzle located near the top. The tool generates a high velocity water jet that erodes and slurrifies the ore. The slurry is drawn through the inlet into the eductor which lifts it to the surface where it is deposited into a slurry discharge sump. All the support equipment is located and operated on the surface; only the mining tool portion of the system is underground during the recovery operation.

Jan 1, 1983

By Daniel C. Boteler

Data from 68 entrained-bed carbonization tests were treated statistically by the Bureau of Mines, and several useful relationships were developed among the major variables. Nine coals, ranging in rank from lignite A to high-volatile A bituminous, were carbonized in two entrained-bed carbonization pilot plants. The carbonizing reactors employed were vertically mounted cylinders, internally heated, refractory-lined, and 10 inches ID. The range of carbonization temperatures was from 825° to 1,600° F. Using a regression-analysis computer program, empirical equations were developed by which carbonization temperature, air-to-coal ratio, devolatilization of coal, char yield, and volatile matter content of product char may be predicted.

Jan 1, 1973

Decrease the dust concentrations at the shearer and reduce downtime associated with spray system maintenance. Approach Increase the quantity and quality of the water supply on longwall faces by decreasing pressure losses, Increasing pump capacity, and installing a "non-clogging" filtration system. How It Works Water sprays and ventilation are two of the primary methods of dust control on longwall operations. Increasing the quantity and quality of the water supply to spray systems is one of the more effective and least costly dust control methods that operators have at their disposal, yet this method is largely ignored. Poorly positioned spray nozzles operating at low pressures (and flows) which plug frequently cannot be effective. Water supply system Improvements should be a fundamental part of all longwall dust control plans. Upgrading a water supply system may require one or more of the following improvements depending upon where a particular system may be deficient: Increasing pump capacity for additional flow and pressure; increasing line sizes to decrease pressure losses: and, decreasing maintenance downtime and Improving water quality by installing a "non-clogging" filtration system.

Jan 1, 1981

By F. J. Smith, W. A. Gallagher, C. A. Herbert

"INTRODUCTION A fire started about 10 a.m., November 10, 1947, at the Kings mine, Princeton Mining Co., Princeton, Ind., about 1,800 feet inby the main shaft bottom on the main west haulage road at a point estimated to be 2 miles from the faces of the main west entries. No lives were lost, as 27 men escaped from the mine after a series of explosions, which necessitated sealing the mine on the surface. This information circular shows"" how adverse conditions might be overcome, when reopening a sealed mine, by expert planning and close cooperation on the part of various organizations. Conditions found in the mine after it was reopened were comparable to the worst that had been anticipated, yet the mine was recovered with comparatively little difficulty and a minimum of risk. The open workings in the mine covered a vast area, but most of the mine resumed production of coal after being sealed for only 37 days.The information contained herein also points to the desirability of adhering as closely as possible to a predetermined schedule of operations."

Feb 1, 1949

By William P. Diamond

A 3-inch pilot hole was directionally drilled to intercept the Freeport coalbed horizon horizontally at Mather, Pa., as part of a Bureau of Mines degasification project. The original concept was to continue the horizontal drilling into the coalbed, after the initial intercept, with a total of three horizontal holes eventually being completed. However, the erratic thickness (0.0 to 4.3 feet) of the Freeport coalbed at Mather was not sufficient to support the horizontal drilling degasification technique, and the site was abandoned after six attempts to locate adequate continuous coal thicknesses. The drilling of coreholes in the immediate vicinity of proposed well paths to evaluate coal thickness is essential prior to future slant hole operations. Although mechanical failures of the new directional drilling equipment, mud pump and rig breakdowns, directional control problems, and exploratory horizontal drilling in the Freeport horizon more than doubled the anticipated cost of the pilot hole, continuing improvements in directional drilling equipment and techniques should significantly reduce the time and costs of future drilling operations.

Jan 1, 1977

By Charles D. Martens

Raw non fuel minerals produced in the United States during 1981 had an estimated value of $25 billion, about the same as that of 1980. In terms of 1980 dollars. the value of minerals produced during 1981 was $23 billion.2 This chapter includes tables for 1980 that were not available for publication in the 1980 Minerals Yearbook, but does not include the corresponding tables for 1981. The underlying causes of the overall decline in U.S. nonfuel mine production during 1981 were varied, but the common factor was the worldwide recession. In some cases the decline was traced to foreign competition. For example, iron ore production was lower in part because of increased imports of steel products such as coiled steel sheet. Another problem experienced by the domestic mining industry was the continuing difficulty in attracting capital. This was due in part to the attractiveness of investments outside the mining industry, such as short-term, high-interest securities. Another reason was the importation of commodities from countries where overall costs were lower because of such factors as high ore grade, lower taxes, lower wages, government subsidies, and less stringent safety and environmental regulations.

Jan 1, 1982

By Frank E. Cash

"INTRODUCTION The producing iron-ore ranges in the Lake Superior district are the Marquette and Menominee in Michigan, the Gogebic in Michigan and Wisconsin, and the Cuyuna, Mesabi, and Vermilion in Minnesota. These ranges produce about 85 percent of the iron ore mined in the United States. The accident experience in connection with this production is better than that of the regions producing the remaining 15 percent. Production and shipments vary slightly from year to year owing to stockpiling underground ore during the winter, or nonshipping, season but closely approximate each other over a period of years. This information circular supplements, combines, and continues the data contained in Information Circulars 7321 3/ and 7410 4/, including statistics for 1946 and 1947.Whereas the title ""Accident Experience"" is used for uniformity and logical indexing throughout this report, ""injury"" will be used as a general term to apply to disabilities of all degrees.During the 8-year period 1940 to 1947, inclusive, 619,054,023 long tons of iron ore was shipped from the Lake Superior district. 5/ Michigan and Wisconsin shipped 117,828,939 tons, or 19.03 percent of the total, and employed approximately 9,260 men. Minnesota shipped 501,225,084 tons, or 80.97 percent of the total, and employed an approximate annual average of 12,260 men. The tons produced and shipped per man employed in Minnesota is much greater than in Michigan and Wisconsin, owing to the large open-cut production in Minnesota."

Jun 1, 1949

By T. A. Kubala

Electric discharge ignition has been reinvestigated in a modified Hartmann apparatus for lycopodium powder with air. Minimum stored energy to ignite air dispersions of lycopodium was 25 to 30 mj; ignition occurred with 1 gram of lycopodium dispersed into the 2.7-liter vessel. Ignition energy was measured as a function of the weight of powder used, although some reservations are expressed concerning the uniformity of the lycopodium-air mixtures. In particular, wall layers of lycopodium, remaining after dispersal of 1 gram of lycopodium, were as easily ignitable as the most easily ignited air dispersion. Thus, an unanswered question has arisen concerning the role of surface coatings in the flammability of all marginally ignitable mixtures.

Jan 1, 1981

By Maria I. De Rosa

Table 1 and figure 1 show the number of fires and fire in¬juries that occurred in underground coal mines by state during 1990-1999. Table 1 also shows by state the risk rates, employ¬ees' working hours, lost workdays, and coal production. Over¬all, 87 fires occurred in 12 states. Twenty-seven of those fires caused 34 injuries (the yearly average was 8.7 fires and 3.4 injuries). One fire and one injury involved a contractor. The underground mine fires required 25 mine rescue team interventions and 30 mine/section evacuations followed by 13 mine/section sealing/flooding/CO2/N2, gas injections. The Ewhr value was 1,003 x 106 hr (In = 0.007), the CP value was 4,008 x 106 st (Frr = 0.022), and the LWD value was 208. Virginia had the most fires (15 fires and 7 injuries). Pennsyl¬vania had the most fire injuries (12 fires and 9 injuries), fol¬lowed by Kentucky (12 fires and 6 injuries), and Alabama (12 fires and 4 injuries). Among these states, Alabama had the highest fire risk rate value (Frr = 0.073), whereas Pennsylvania had the highest injury risk rate value (In = 0.016). Table 2, partly illustrated in figure 2, shows by time period the number of fires, fire injuries, risk rates, employees' working hours, lost workdays, and coal production. The number of fires and fire injuries show a decrease followed by an increase during the five time periods (see table 2 and figure 2). This was ac¬companied by a decline in employees' working hours throughout the periods and an overall small decrease in coal production. The In and Frr values follow patterns similar to those shown by the fire and injury values. By comparison, data from Pomroy and Carigiet [1995] show that during 1978-1992 a total of 11 states were involved in 164 underground coal mine fires (yearly average, 10.8) with 43 injuries (yearly average, 2.9) and 27 fatalities (yearly average, 2; however, the 27 deaths occurred during a single fire caused by an overheated air compressor [MSHA 1984]). The CP value was 5,340 x 106 st (yearly average, 356 x 106 st) (Fn = 0.031). Data on employees' working hours and injury risk rates were not available. Tables 3-8 show the number of fires by ignition source, method of detection and suppression, equipment involved, location, and burning material by time period. Figure 3 shows the major variables during 1990-1999. Table 9 shows the number of fire injuries per number of fires causing injuries and total fires by year, ignition source, equipment involved, and location.

Jan 1, 2004

By I. A. Jacobson

In a closely controlled laboratory retorting system for oil shale, a relationship was developed by the Bureau of Mines between the temperature in the retort and the weight ratio of ethylene to ethane in the gases produced. Reciprocal temperature was shown to be directly proportional to the log ([ethylene]/[ethane]). From this relationship a number, called retorting index, was developed. The retorting index has the dimension of temperature, but its magnitude depends on both temperature and residence time for the reactants in the heated zone in the oil-shale retort. The slopes of the lines relating reciprocal temperature and the logarithm of the ethylene-ethane ratios are nearly constant for each of the retorting processes for which data have been presented. The retorting index should be a valuable tool to control the operation of oil-shale retorts, either aboveground or in situ. If an optimum operating condition can be established, the maintenance of the optimum or the departure from it should be easily monitored by use of the index.

Jan 1, 1974

By J. Hudy

The performance of six dense-medium washers was evaluated in five preparation plants. Three of the plants were making a two-product separation that produced a clean coal and a refuse; one plant employed dense-medium vessels in series to effect a primary and a secondary separation; and one plant was equipped with a two-compartment washer effecting two separations in one vessel. The separate secondary drum-type washer produced a low-ash metallurgical coal and an intermediate-ash product suitable for plant fuel or steam generation. The two-compartment washer produced a premium anthracite product and a middlings product. The sharpness-of-separation values ranged from good to excellent for the five primary separations and for the secondary separation.

Jan 1, 1968

By Phyllis Lyday

Mining did not contribute significantly to the economy of Benin, a small country on the coast of West Africa, during 1978-79. During these years, Benin continued to be rated by the United Nations as one of the 25 least developed countries in the world; its gross domestic product was under $200 3 per person per year. Salt from seawater, sand and gravel, bricks, and imported clinker for cement were the only minerals which contributed to the economy. Minerals were not expected to play an important role in the commercial sector of Benin's economy during the next decade. Joint projects included infrastructure development to create a coordinated road and rail system between Niger and Benin that was begun in 1960 as ?Operation Hirondelle." In 1976, an agreement for the construction of a rail link from Niamey, Niger, to Parakou was signed. At Parakou, the rail line would join the existing line to the port at Cotonou. Construction of the rail line was expected to take 6 years, and the cost was estimated at $287 million in 1979. During late 1979, the Federal Republic of Germany granted Benin a loan of $12 million for reconstruction of the port at Porto Novo. Benin and Nigeria were discussing a joint adventure in crude salt exploitation.

Jan 1, 1981

By Doris M. Hyde

The economy of Belize continued to be relatively unaffected by activity in the minerals sector. Mining production consisted of limestone, marl, and sand and gravel. All production was used for domestic construction projects. By the end of 1979 the major oil companies had, temporarily at least, ceased active exploration efforts. Esso Ventures, Inc., after drilling three dry holes in southern Belize, planned to reappraise its activities. The Reef Exploration, Ltd., concession was acquired by Anschutz Oil Co. (81.25%). with minority interests held by Anglo Oil Co. and Carolina Oil Co. The Anschutz group drilled offshore in the Gulf of Honduras and in Belize Harbor. Echo Exploration has a con-cession along the Mexican border and Spar-tan Petroleum Corp. obtained seven exploration licenses covering 768,000 acres in northern Belize. Spartan's concessions included about 130,000 acres offshore, with the remainder along the southeastern rim of the Yucatan Peninsula. Placid Oil Co. took an interest in the Spartan acreage and became operator. Seismic exploration was underway in 1979. A Mexican company, Pan American Oil and Gas, S.A., was awarded two exploration concessions, one in southern Belize and one near the Mexican border.

Jan 1, 1981

By Robert F. Chaiken

A novel approach to eliminating environmental and public safety hazards that are associated with fires in abandoned coal mines and waste banks involves the use of in situ combustion technology developed by the Federal Bureau of Mines to accelerate the burning of the wasted coals in place. This technology would be used under exhaust ventilation control conditions that would allow for total management of the hot gases produced. Combustion stoichiometries would be optimized to minimize unburnt combustibles and to maximize the heat content of the gas products, which will be exhausted at one or more fan locations. When necessary, scrubber systems would be employed to remove air pollutants, such as sulfur dioxide; heat utilization systems (process heat, steam, and electricity) would also be employed to offset operational costs. Ultimately, complete burnout would solve the fire and acid water formation problems of the abandoned coal mine or waste bank. Pertinent technical data for burnout control are derived and discussed in terms of the important material and operational parameters. In general, it is believed feasible to operate a burnout system in an existing abandoned mine or waste bank fire at thermal power levels in the range of 10 to 100 Mw, and at exhaust gas temperatures of 1,000° C (1,830° F).

Jan 1, 1980

In This Chapter [Ventilation: dilution and displacement Water sprays: wetting and airborne capture Water additives: foam and wetting agents Dust collectors: filtration efficiency and inlet capture efficiency Reducing the generation of dust for cutting, drilling, blasting, crushing, and conveying] [This chapter will give you a general perspective on what works or doesn’t work. The chapter will also help if your dust control problem doesn’t fit any of the circumstances described in later chapters. ] This chapter describes the three major control methods used to reduce airborne dust in tunnels and underground mines: ventilation, water, and dust collectors. It also describes methods to reduce the generation of dust, so less has to be removed from the mine air. The ventilation methods provide the best use of air in the vicinity of workers and in the vicinity of dust sources. In this sense, the methods described are local ventilation methods. Most of the emphasis is on so-called displacement ventilation because it is the most effective dust control technique available. The section on water sprays outlines the dual role of sprays—wetting and airborne capture—and describes why wetting is more important. It also corrects some of the misconceptions about spray effectiveness and describes circumstances where sprays can actually increase the dust exposure of workers. The section on dust collectors outlines the circumstances under which dust collectors can be expected to function effectively. It also describes some common design and maintenance problems. The final section describes how to reduce the amount of dust that gets into the air in the first place, since once the dust is airborne it is always harder to control.

Jan 6, 2003

By Rose L. Ballard

This chapter summarizes data on crude non fuel mineral production for the United States, its island possessions, and the Commonwealth of Puerto Rico. Included also are the tables that show the principal non fuel mineral commodities exported from and imported into the United States and that compare world and U.S. mineral production, The detailed data from which these tables were derived are contained in the individual commodity chapters of Volume I and in the State chapters of Volume II of this edition of the Minerals Yearbook. Although crude mineral production may be measured at any of several stages of extraction and processing the stage of measurement used in this chapter is what is normally termed "mine output." It usually refers to minerals or ores in the form in which they are first extracted from the ground, but customarily includes the output from auxiliary processing at or near the mines.

Jan 1, 1986