Search Documents

By J. E. Pahlman

One of the goals of the Bureau of Mines is to develop metallurgical pro-cesses that conserve energy and/or that take advantage of abundant domestic energy sources. Western lignites and subbituminous coals can be used for firing pellet induration and metallization furnaces. However, the refractory linings of these furnaces must be able to withstand attack from corrosive alkali metal oxides present in the ash of many of the low-rank fossil fuels. The Bureau of Mines conducted dynamic and static slag tests on high-alumina and alumina-silica refractories to determine their resistance to lignite ash slags. The investigations showed that increased alkali content in the lignite ash caused increased corrosion and erosion of the tested refractories. The degree of corrosion decreased with increasing alumina content, with the 99-percent-alumina refractories having the highest resistance. In general, the matrix phase was attacked preferentially to the alumina grains. Also, porosity reduction and tar impregnation enhanced the corrosion and erosion resistance. The 90-to 99-percent-alumina refractories are recommended for use as furnace linings in alkali slag environments.

Jan 1, 1979

By Samuel W. McNary

In August 1984 the U.S. Bureau of Mines conducted a study of the mineral resource development potential of the Badger Canyon-Antelope Creek area, within the Boulder-Pioneer wilderness study area, about 5 miles northeast of Ketchum, 10. The purpose of this study was to investigate in greater detail an area which was designated by the U.S. Geological Survey (USGS) and the Bureau as having a moderate mineral resource potential for zinc, molybdenum, lead, and silver, and a low potential for copper. One hundred twenty-eight soil samples were taken along a 6,2S0-ft traverse on the ridge separating Badger Canyon and Antelope Creek. 5 Five rock samples were collected from old prospect pits and mineralized outcrops. All samples were analyzed for gold. Silver, copper, lead, zinc, molybdenum, arsenic, antimony, vanadium, and mercury. The metal concentrations in the soil samples along the traverse are irregularly distributed. Samples collected near old prospect pits tend to be high in lead and zinc, undoubtedly a reflection of underlying galena-and sphalerite-bearing quartz veins. All of the copper and mercury values in the soils are less than the detection limit, as are most of the lead, molybdenum, and antimony values. Except for lead and zinc values, the metal concentrations in the rock samples are low. Galena and sphalerite were observed in quartz vein samples collected at the old prospects. The results of the study indicate that the galena-sphalerite-bearing quartz veins and veinlets are too narrow, widely-spaced, and low in metal values to be economic. Low concentrations of metals in the soil and rock samples, combined with the lack of major mining activity in the past, indicate that the area has a low likelihood for economic development.

Jan 1, 1986

By J. P. Conway

The yielding-rock-bolt concept, as developed in South Africa, consists of a smooth-bore die or collar fitted to a standard rock bolt. Laboratory testing at the Bureau of Mines Spokane Mining Research Center under slow and fast strain rates showed that extrusion loads can be controlled by varying the configuration of the die bore and that theoretical analysis (using basically Sachs' theory of wire drawing) predicts extrusion loads of the different die-bore configurations. A derived equation, based on this research, can be used for designed die-thread combinations for any desired extrusion load. Dynamic loading resulted in slightly higher loads (15 percent) than static loading. The strain hardening effect, which increases yield and ultimate strength, was partly offset by adiabatic heating of the threads, which decreases strength.

Jan 1, 1975

By John P. Conway

This Bureau of Mines investigation was undertaken to determine the feasibility of lock-bolt support in Tertiary-gravel material. Pull tests were performed on five types of rock-bolt anchors to determine their optimum anchorage capacity. Four of these anchors are commercially available; the fifth, an explosive-anchor bolt, was developed by the Bureau of Mines. To increase anchorage capacity, epoxy grout was used with several of the commercial types of bolt. Tests showed that sufficient anchorage could be obtained by employing epoxy-resin grout with the commercially available wedge bolt, or by using the explosive-anchor bolt. Also estimated are bolt spacing and cost of a rock-bolt support system.

Jan 1, 1971

Aluminum alloys are used in two broad classifications: wrought and cast. Wrought alloy products, which are formed into final shape by rolling, forging, extruding. etc., contain low percentages of alloying elements; whereas cast aluminum products, which generally are not worked before use, may contain higher percentages and a somewhat different selection of alloying elements. For example, wrought aluminum alloys usually contain less than one percent silicon and cast alloys contain as much as 18 per-cent silicon. While there are good techniques available for separating aluminum alloys from mixed scrap, there are no efficient ways to separate wrought aluminum from cast aluminum. The high levels of silicon, iron) copper, and zinc from the cast alloys make wrought-cast mixtures unacceptable for wrought alloy production. Consequently, separated wrought aluminum scrap commands a premium price on the market. Since increasing amounts of mixed aluminum alloys are being recovered from automobile scrap, this separation is important for efficient recycling of these alloys. Approach The difference in thermo-mechanical properties between the two classes of aluminum alloys is used as the basis for the separation process. Casting alloys lose their ductility within a certain temperature range while wrought alloys remain ductile. As temperature increases, aluminum alloys gradually become weaker, and at a certain temperature, each alloy loses strength and ductility due to incipient melting in localized areas. For casting alloys that temperature generally lies between 520° to 560° C, but it is above 600° C for most wrought alloys. Mild crushing, therefore, in the proper temperature range will result in complete fragmentation of the casting alloys but only plastic deformation of the wrought alloys. A simple screening step then is used to separate the oversize wrought pieces from the fragmented cast alloys.

Jan 1, 1984

By Roy Greenfield

Estimates are given for the distance from a seismometer at which a miner can probably be detected. The procedure in making these estimates was to first establish the natural noise levels at the output of a surface seismometer for the 25 to 100 Hz frequency passband. The noise levels give the range of values which may be expected in areas with no man-made noise. For each noise level, we give the detection threshold which, when exceeded, indicates that a signal has been received. Based on the signals recorded by Westinghouse, curves are given which show the peak signal amplitude as a function of source- to-receiver distance (slant range). Curves are given for the Westinghouse seismic thumper, a 50-pound timber, and a sledge. For a given type of source, the receive signal strength depends more strongly on slant range than on any other factor. However, there is approximately a five-to-one scatter in the amplitudes. Thus, further study of factors affecting the signal amplitude might allow better estimates to be made for any particular geological setting. Combining the signal amplitude with the detection thresholds for the different noise conditions gives the distances at which a miner should be detected. These are given in Table l* below. [ ] The text also gives the increase in detection ranges which should occur if steps are taken to increase S/N by 10 dB. We feel that 10 dB is a conservative estimate of the improvement possible. During an actual rescue operation, the seismic crew and system should be capable of making on-site estimates of their detection capability, based on measurements of the site noise, and upon the best available estimates of the

Jan 1, 1974

[ ]

Jan 1, 2011

By David J. MacDonald

Stability constants, that is, equilibrium constants for complex-formation reactions, have been determined by a titrimetric method for complexes formed by the transition metal ions Ni2+, Cu2+, Zn2+, and Cd2+ with the structurally analogous bidentate ligands N-ethylethylenediamine and 2-(ethylthio)-ethylamine. The sulfur containing ligand was found to be the weaker of the two chelating agents for each of the four metals. Absorption spectra of the individual complexes have been determined in order to calculate their crystal field stabilization energies. The combined results suggest a linear relation between free energy of chelation and ionic radius of the metal ion.

Jan 1, 1972

By G. W. Jones, R. E. Kennedy

"INTRODUCTION Information relative to the ignition temperatures of acetylene and acetylene-air mixtures has become of particular interest recently due to a number of explosions that have occurred in 500-pound, double-rated, medium-pressure acetylene generators in shipyards on the West coast. Various suggestions have been made as to the causes of these explosions prominent among which has been that air finds its way into the acetylene generators during abnormal operation or that air remains in the carbide hopper of the generator following the purging and charging operations.This raises the question as to how and to what extent the presence of small percentages of air in acetylene affects the ease of ignition of such mixtures at the various operating pressures of the acetylene generators. The range of operating pressures in the 500-pound, double-rated generators involved in the explosions may vary from below atmospheric to 15 pounds gage.The present report gives the results of an investigation made to determine the effects of pressure on the ignition temperature of pure acetylene and of acetylene containing varying percentages of air:EXPERIMENTAL Apparatus A preliminary investigation showed that a heated quartz surface gave lower ignition temperatures than other material tested.A ""hot-spot"" method of ignition was found desirable in the case of the acetylene mixtures since the violence of the explosions was reduced by keeping most of the test mixtures at room temperature. Explosive violence was reduced further by using an ignition tube 17 mm. or less in diameter."

Mar 1, 1945

By Maust. E. J., W. R. Crane

"IntroductionIn the study of mine drainage in the red iron ore mines of the Birmingham district of Alabama, an extensive series of measurements were made in order to determine the drainage from the area overlying and adjacent to the mines. Gaging rods were generally used in measuring streams, and weirs in ditches and sometimes as a check on rod work. These tests in turn were checked by current meter tests. In all, 725 separate stream gagings and 97 weir measurements were made. Certain relationships were worked out, particularly between rod and weir tests, which permitted obtaining results that are much more accurate 'under the existing conditions, than any available formula would give. The large number of weir measurements and the period covered by the tests made it impracticable to construct a weir for each observation so portable, adjustable weirs were built. The methods used are described here for the benefit of those interested in measurement of streams in connection with a study of mine drainage or otherwise. The Drainage AreaThe area draining the mining district lies between the crest of Red Mountain and Little Shades Creek, and for convenience was divided into sub-districts adjacent to certain groups of mines. Gaging stations were established on Little Shades Creek at the upper and lower boundaries of each sub-district, also at points on the tributaries near their junction with the creek. The difference between the volumes of water flowing in Little Shades Creek as it entered and left the sub-districts represents the flow from the tributaries on both sides of the creek. Since the flow coming from the sub-districts was measured direct, the inflow from the tributaries on the opposite side of the creek can be computed from the three volumes determined."

Oct 1, 1926

The Federal Mine Safety and Health Act of 1977* defines respirable dust as dust measured with a device approved by the Secretary of Labor and the Secretary of Health and Human Services [30 USC 842(e)]. The approved sampler for respirable coal mine dust is the coal mine dust personal sampler unit (CPSU) [30 CFR 74; Jacobson 1971; Jacobson and Lamonica 1969]. The CPSU is generally called the 10-mm nylon cyclone, although the 10-mm nylon cyclone is actually just one component of the CPSU. The CPSU may either be mounted on a worker (with the sampling head positioned in the breathing zone for personal exposure monitoring) or in a fixed location for area sampling [Tomb 1990]. The CPSU consists of a pump unit, a sampling head assembly, and a battery charger if rechargeable batteries are used in the pump unit [30 CFR 74.2]. The sampling head assembly contains two stages. The first stage is a 10-mm nylon cyclone, which has collection characteristics similar to an elutriator. The amount of dust penetration depends on the flow rate [Jacobson and Lamonica 1969]. The second stage is a membrane filter (vinyl, pore size 5 pm) that collects the dust passing through the cyclone. The dust collected on the membrane filter is weighed to a precision (standard deviation) of 81 pg [Parobeck et al. 1981], and the respirable dust concentration in the mine atmosphere is then determined from the mass of dust collected and the volume of air sampled [Tomb 1990].

Jan 1, 1997

By J. B. Newson

This is one of a series of circulars dealing with mining methods, practices, and costs. It describes the method of sinking a shaft 60 inches in diameter with a shot drill, as employed at the Idaho Maryland mine, Grass Valley, Calif. The operation involved a great deal of experimentation in applying the shot-drill method to large bore drilling, overcoming mechanical and other difficulties which developed during sinking, and developing operating technique. Under such circumstances, costs are obviously higher than they would be after the pioneer work has been done, but even so, these actually obtained compare favorably with costs of sinking by more conventional methods. ACKNOWLEDGMENTS The authors are indebted to Mr. Errol McBoyle, president of the Idaho Maryland Mining Co., not only for his cooperation and advice during the sinking of this experimental shaft, but for permission to prepare this article for publication with the inclusion of cost data.

Jan 1, 1936

Enable prospective in situ leach mine operators to evaluate the economic potential of an ore body by using a user-friendly, computerized in situ copper oxide leach mining cost model. Background As part of its research on in situ leach mining technology, the Bureau of Mines produced a 5-volume contract report that mining companies can use to design an in situ mining operation for copper oxide deposits. Written for the Bureau by the Science Applications International Corporation (SAIC) in 1988, the generic design manual also contains a computerized cost model for evaluating the economic feasibility of in situ leach mining for any specific copper oxide deposit. The cost model is to be used with Volume II of the contract report. But because of certain complexities associated with running it, the Bureau found that the model could be improved by making it more user friendly. Approach The approach taken by Bureau researchers to make the original model more user friendly was to incorporate a HELP function to define input parameters, and to enable the display of output on the monitor. An accompanying handbook, U.S. Bureau of Mines Information Circular (IC) 9284, contains further details on running, the 1990 model.

Jan 1, 1991

By D. J. Bauer

Liquid-liquid extraction techniques were investigated by the Federal Bureau of Mines for the fractionation of rare-earth solutions. Separatory funnel work using tri-n-butyl phosphate (TBP) for extracting ceric nitrate from solutions containing sulfate ion resulted in almost complete extraction. Similar tests using primary amines for splitting trivalent rare-earth pairs and fractions gave promising results. The ceric nitrate extraction procedure was scaled-up by use of pressure-bubbler equipment, a series of spray towers for extraction, washing, and stripping. In this case only 84 percent ceric nitrate extraction efficiency was achieved. This work was done using dilute sulfuric acid for stripping.

Jan 1, 1960

By C. I. Pierce

Knowledge of the water content of oil-bearing formations is important in petroleum-reservoir evaluation work. Electric logging provides a means for making reliable estimates of water content if resistivity-saturation relationships representative of the formations are available. Relationships can be determined in the laboratory by a number of methods. This report describes and presents results of a laboratory investigation conducted at the Bureau of Mines Appalachian Experiment Station, Morgantown, W. Va. (1) to evaluate an evaporation method of attaining water saturations in sandstone samples when determining resistivity-saturation relationships and (2) to compare saturation exponents derived from data obtained, using different methods of achieving water saturations. A series of tests was conducted to determine the effect of evaporation on salinity distribution within the core specimen. Results of these tests show that a zone of high salinity was set up at the surface of a sample during evaporation and that long periods were required for the sample to reach resistance equilibrium after evaporation had ceased. Equilibrium time ranged from several minutes to several days, depending on the sample size and the technique used. The high-salinity zone was removed from the sample by using auxiliary porous material in capillary contact with the sample surface during evaporation. Salinity determinations and resistance measurements indicate that, at saturations greater than the minimum interstitial values, the mechanism of flow during evaporation was one of moisture migration mainly as a liquid from the interior of the test specimens to their exterior surfaces. The concentration of the contained brine remained essentially unchanged, except for a narrow zone near the evaporating surfaces.

Jan 1, 1958

By R. Hogg, E. Kaya

"The presence of agglomerated particles in airborne dust in coal mines has been confirmed by SEM examination of static samples collected on substrates. In addition, the effect of agglomerated particles on the performance of cascade impactors and cyclone-type personal samplers has been studied. Simple procedures have been developed for evaluating the extent of agglomeration in air-borne dust by comparing the observed size-selectivity of the sampling devices with that expected under idealized conditions. Applications of these techniques in the laboratory and in underground mines are discussed.INTRODUCTIONAirborne dust is invariably present in mine atmospheres. Particle size is a primary factor in determining the behavior of the dust, its effects on miners' health and the effectiveness of dust control measures. Obviously, agglomeration of the dust particles can have important effects on: ""natural"" dust removal processes such as settling• the use of water sprays etc., for dust control• pulmonary deposition characteristicsIn addition, the presence of agglomerates could influence the effective toxicity of the dust. For example, ultrafine particles are often thought to be relatively unimportant in the development of respiratory ailments because of their low deposition efficiency. However, the latter could be substantially increased if such particles were present in larger agglomerates. It is by no means obvious that there should be significant agglomeration of the airborne dust in a mine atmosphere. In fact, calculations based on the classical coagulation theories indicate that, at the kinds of dust concentrations that exist even in what would be regarded as “very dusty"" atmospheres, the coagulation half-time* .should be of the order of weeks or even months. On this basis, agglomeration would be expected to be essentially negligible. On the other hand, laboratory experiments (Polat et al., 1991) have revealed very extensive agglomeration in the airborne dust released during the crushing of individual coal and mineral particles. It is postulated that such agglomeration occurs immediately at the point of dust generation. In other words, many of the fine fragments produced on fracture are never completely separated from their neighbors."

Mar 1, 1992

By Gerrit V. R. Goodman, Charles D. Taylor, Edward D. Thimons

Future coal mining systems will be able to cut from crosscut to crosscut where advances could exceed 100 ft. However, limitations arise when ventilating such mining systems. In deep advance mining, there would be no workers at the face to advance ventilation tubing or curtain manually. Traditional methods also provide no means for maintaining face ventilation after the miner backs away from the face. U.S. Bureau of Mines research is studying means to provide effective ventilation at cut depths beyond the current limit of 40 ft. Several innovative ventilation schemes are currently being considered. One such method is the use of a jet fan to ventilate a deep cut. A jet fan is simply a freestanding fan using little or no ducting to direct the ventilation flow. Jet fan testing in a 90-ft entry revealed that higher exit velocities and greater penetration depth occurred when various configurations were used to confine and direct the air flow. Additional testing also indicated that 2,200 cfm of fresh air was delivered to the face 90 ft distant when a check curtain was used to limit entrainment around the fan. Without this curtain, this quantity dropped to only 1,000 cfm This testing indicated that a jet fan was capable of providing ventilation to a distant face area. It also highlighted potential problems, such as recirculation at the fan and reentrainment in the jet flow. Despite these potential problems, jet fans may be adequate for ventilating cuts exceeding 40 ft.

Jan 1, 1992

By C. C. Shale

A semicommercia1, high-temperature electrostatic precipitator and adjunct equipment are described, and operating characteristics at 1,470° F and 80 psig are presented for both positive and negative polarity. Removal efficiency for negative corona waS about 91 to 96 percent while that for positive corona was only about 75 to 77 percent. Results are compared with those from bench-scale investigations, and equipment limitations are discussed. Theoretical aspects of the precipitation process are related to the operating characteristics.

Jan 1, 1969

Minimize the effects of underground mine conveyor belt fires by developing methods to prevent automatic fire suppression system failures. The Problem Fire protection is achieved by prevention, early detection, and planned fire-fighting response. Automatic fire suppression systems are one form of planned fire-fighting response. When these systems are properly designed, installed, and maintained they can effectively control fires. Conveyor belt fires account for about 20% of underground coal mine fires. Fire protection requirements have been established for underground locations because of potential for start and spread of fire and the restricted personnel egress in a fire situation. Belt conveyor systems arc potentially dangerous because of the high fire incidence rate, high temperatures, dense smoke, toxic gases, and rapid flame-spread rate. While investigating the conveyor fire suppression problem, the Bureau identified automatic fire suppression system reliability as a potentially serious deficiency within the mining industry. Table 1 lists common failure modes fur three Fire suppression system types. This table summarizes findings of Mine Safety and Health Administration electrical inspectors responsible for inspection of belt protection automatic fire suppression systems. Batteries, contact points, control wires, and electric servocontrols are all prone to failure. Figure 1 shows rock-dust-contaminated relay contact points. This condition is dangerous because of the chance of intermittent failures, which might allow systems to pass annual functional testing, yet fail during actual fire emergencies.

Jan 1, 1989

By F. H. Gibson

An investigation was made by the Federal Bureau of Mines of methods for determining phosphorus in coal, coal ash, and coke ash. Several of these methods are being considered for international standardization. As might be expected, methods and proposals from other countries for determining phosphorus differ considerably from those accepted an standard in the United States. Some of the methods differ fundamentally in principle from the American Society for Testing Materials (ASTM) standard used in the United States; others differ only in details of procedure. Because the Bureau considered that certain of the proposed methods might offer advantages in obtaining increased accuracy and precision or in decreasing the time required for making analyses, these methods were investigated, and the results compared with those obtained by the ASTM method. The methods investigated may be grouped into three types--volumetric, colorimetric, and gravimetric. All were about equally accurate and may be used alternatively. From a practical viewpoint, when only a limited number of analyses are made intermittently, the gravimetric procedure probably is the most suitable because no special apparatus or standard solutions are required. The volumetric methods are more rapid when more analyses are made. For mass production, the colorimetric methods, although requiring a suitable photometer or spectrophotometer, are more suitable because a large throughput should be feasible.

Jan 1, 1961