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By P. D. Bergman

The high price of pollucite ore, its limited availability, and the need to provide stack removal of S02 present formidable obstacles to the use of pure cesium as a seeding material in MHD power generation. Cost estimates indicate that mixed potassium-cesium seeding is preferable to the use of either pure cesium or pure potassium. Cheaper electricity and higher open-cycle MHD operating efficiencies result from the use of mixed seed. Savings of $3,000,000 per year in power costs for a 1,000-MWE open-cycle MHD power-plant are envisioned if the mixed seeding technique is adopted.

Jan 1, 1972

By Jeffrey Johnson, Thomas Brady, Radford Langston, Mary MacLaughlin, Hendrik Kirsten

The magnitudes and directions of in situ stresses affect the stability of mine openings, as well as the type and amount of ground support needed to maintain a safe working environment for miners. Using hollow inclusion stress cells, researchers from the Spokane Research Laboratory of the National Institute for Occupational Safety and Health obtained two in situ stress measurements from the face of two footwall lateral drifts at the Stillwater Mine near Nye, MT. The first measurement, obtained in 1997, was collected under the valley beneath the Stillwater River. The second measurement was obtained in 2002 under the main frontal massif of the Bear tooth Mountains in the western sector of the mine. Although few data are available, the major principal stress under the valley has been recorded as nearly horizontal in a north-south direction perpendicular to the ore body, while beneath the mountains, stress runs east-west parallel to the ore body. This paper documents the measurements, describes the in situ stress state, and discusses a finite-difference analysis of the biaxial test.

Provide respiratory protection for escape in a toxic or oxygen-deficient atmosphere with a device small and light enough to be belt-worn. Approach Combine a 10-minute, belt-worn respirator with a stored, larger, long-duration (60-minute) attachment that can be plugged into the 10-minute unit without removing the mouthpiece. How It Works The 10-minute device will be carried by the miner at all times, and the 60-minute canister or attachment will be stored near the miner. In the event of a disaster, the 10-minute device would be donned immediately. The miner would then proceed to the stored 60-minute unit and plug it into the 10-minute unit. For the 10-minute unit, a breathing circuit was developed in which air is passed through the KO2 bed twice per respiration. The 60-minute canister differs from the 10-minute unit in that air is drawn only once through the chemical bed per respira-

Jan 1, 1981

By L. A. Haas

The degree of reduction of various silica-graphite mixtures was studied in a batch reactor to determine optimum physical conditions for maximizing the carbothermic reduction of silica. The extent of interaction was determined for reactant mixtures in loose powder and briquet forms at pressures less than 0.01 torr and temperatures up to 1,445° C. Molar ratios were varied from 0.05 to 6.5 with maximum reaction at a ratio of about 1.5. The solid-solid reaction did not appear to involve gaseous intermediates. The extent of reaction better correlated with the number of interparticle contacts than with the true surface area of the reactants. Carbonized dextrose was a better reductant than graphite.

Jan 1, 1968

By John M. Gomes

Two methods for electrowinning tungsten from wolframite [(Fe,Mn)W04] were investigated. The first method, direct electrowinning from wolframite concentrate dissolved in molten salt mixtures composed essentially of various combinations of sodium phosphates, sodium borates, and sodium halides, yielded impure products. The second method was electrowinning from a halide-tungstate melt that was obtained from a high-temperature, two-phase extraction of tungstic oxide (W03) from wolframite. Electrolysis in electrolytes prepared from addition of sodium metaphosphate (NaPO3) and boric oxide (B2O3) to the halide-tungstate melt produced tungsten metal of 99.9 percent purity. Tungsten carbide (WC) was electrodeposited from the halide-tungstate melt when the melt was adjusted to contain 82 mole-percent NaCI and 6.0 mole-percent each of W03, sodium metaborate (Na2B204), and caustic soda (NaOH).

Jan 1, 1970

To provide a means for mechanically separating and recovering nonferrous metals continuously from non-magnetic reject material produced at scrap automobile shredding facilities. Approach The Bureau of Mines developed a water elutriator system that separates metals from shredded scrap auto-mobiles based on differences in specific gravities. A premium-quality product, containing aluminum, magnesium, lead, zinc die cast, copper, copper alloys, and stainless steels, is obtained. How It Works Mixed nonmagnetic reject material currently being separated at automobile shred-ding facilities is introduced onto the top of an upwardly flowing vertical column of water. The water, overflowing a weir in the top of the vertical column, carries with it the floating, lightweight waste materials, mostly combustibles, while the heavier pieces sink through the rising water. Medium-density substances such as glass, rubber, and heavy plastics are carried off through a side port, located in the upper third of the column. The cleaned, mixed metal product sinks to the bottom and is continuously removed from the base of the column with a bucket elevator having perforated buckets. All three categories of material are removed from the system on separate wire mesh belt conveyors. Most of the water drains through the belts into a holding tank and, after settling, is recirculated back through the elutriator column. The purity and recovery of the metal product are influenced by two elutriator operating variables: the flow rate of water through the vertical column, and the height of the overflow weir at the top of the column.

Jan 1, 1983

By A. N. Styler

As part of its water-jet assisted rock cutting research, the Bureau of Mines has initiated a study into the mechanism of rock fragmentation by water-jet-assisted mechanical tools. The objective of this research is to increase coal extraction efficiency by seeking an improved understanding of the synergistic relationship between mechanical cutters and water jets, enabling the design of more effective cutterheads. Rock chips collected during laboratory traverse speed jet-assisted cutting tests were analyzed with respect to the size distribution of the chips and the forces measured during cutting. As the water-jet pressure was increased, the size distribution of the product became coarser with V-face type cutting tools producing less fine material than conical cutting tools. Fracture mechanics theory accounted for less than 10 pet of the energy consumed during fragmentation of the rock. The energy consumed by processes other than rock breakage decreased with the use of water jets and increasing advance rate.

Jan 1, 1987

By R. C. Ellman

Significant effects of in-the-mill drying on the pulverization of lignite have been demonstrated in an experimental impact-type pulverizer by tests in which the primary variable was temperature of the sweeping gas. Reduced power requirements and increased product fineness were observed as the extent of drying was increased. Pulverization with in-the-mill drying was studied in comparative tests made on lignites from five mine sources. All of the lignites responded in a similar manner; however, differences in the pulverizing characteristics of the individual lignites were significant. For one lignite, the electrical input to the pulverizer driving motor with minimum sweeping-gas temperature was 33.9 kw.-hr. per ton, decreasing to 14.0 kw.-hr. per ton with a sweeping-gas temperature of 658° F.; for another lignite, at comparable operating conditions, the electrical input decreased from 59.1 to 19.0 kw.-hr. per ton. In the first case, the product fineness increased with increasing temperature of sweeping gas from 65.2 to 79.2 percent through a 200-mesh sieve, and in the second case, from b2.7 to 86.9 percent through a 200-mesh sieve.

Jan 1, 1962

This section contains a summary of our investigation of the soil conditions (type, porosity, moisture content, etc.) at the two sites (Lanse and Kato, Pennsylvania) selected for field testing of latex as a soil sealant. Other natural conditions such as rainfall, frostline, depth of the water table, etc., were also measured and recorded for possible later use in assessing the effect of the latex seal on the total environment. The numbered sites referred to throughout this report are shown on the maps of the Lanse and Kato sites (Figures 1 and 2). KA, RB and KC are positions at the Kato site - all other numbered positions refer to the Lanse site. Two other terms used throughout the report which should be explained are “horizon” and "profile". These are synonymous terms for soil layer, A horizon (or A profile) referring to topsoil and B horizon (or B profile) referring to subsoil. The properties that control the flow of water through the soil are of special interest because these will also govern the passage of a sealant into and through the soil. Normally the particle size distribution is a good measure of soil permeability, which is directly proportional to sand content and inversely proportional to silt and/or clay content. Tables I1 and I11 show the percentages of gravel or stones, sand, silt and clay of Lanse and Kato soil samples. According to the United States Department of Agriculture classification, the gravel is ,ignored and the residue separated into sand, silt, and clay fractions. Figures 4 and 5 indicate by means of the USDk soil texture triangle that the variability of composition of Lanse soil ranges from sandy loam in the creekbed to clay loam. The variation is even greater among soil samples from Kato. Porosity of soil, also known as percent voids, is another indication of how readily water will travel through soils. Soil density usually increases and porosity decreases with depth, and as expected, the porosity of the top soil at Kato, a forest, is exceptionally porous and open (see Table IV) The pore diameter and length of soil capillaries is extremely variable, and its distribution in the field is impossible to determine. In addition to the capillaries, soil also contains many macro cracks, crevices, and passages around stones and roots. All these affect the flow rate of water through soil. Poiseuille's law states that the rate of flow of a liquid through a narrow tube is proportional to the 4th power of the radius of the tube. Pore size normally decreases with depth and in soil containing appreciable amounts of silt and clay this is especially true. Thus, deeper soils should be less permeable and such was the case at Lanse and Kato.

Jan 1, 1972

By Charles L. Kimbell

The series summarizing the prices of the major nonferrous metals on the stock exchanges of the United States and the United Kingdom has been continued this year in tables 23 and 24. As a result of the lack of availability of comprehensive data on the prices of metals in Canada, the table that had presented that information in past years in this chapter has been discontinued and the price series for nickel that had been in that table now appears in the table presenting metal prices in the United States.

Jan 1, 1993

By R. L. Montgomery

Electronegativities of the rare-earth elements were calculated from heats of formation. The values obtained from different compounds varied widely. The postulates of Pauling's electronegativity theory were interpreted for bonds that are primarily ionic; the study showed that many compounds obey rules of the form expected. Revised electronegativity values are given for the more electropositive elements, including the rare-earth metals (which are near magnesium in electronegativity). Estimates of un-known heats of formation are made from electronegativities and are compared with other estimates. INTRODUCTION Calculation of the electronegativities of the rare-earth elements is interesting to show how these metals stand relative to the other metals and to each other, and also possibly to systematize the thermochemical data on them.

Jan 1, 1960

Improve underground long-hole drilling efficiency and safety by developing a lightweight, easily transportable drilling pust that can be adjusted to fit a range of mine opening heights. Background Standard one-piece commercially available steel posts weigh approximately 10 pounds per foot. Transporting these posts underground and carrying them over obstacles and through small mine doors is very difficult. Because the length of a one-piece post cannot be adjusted, variations in mine opening height at the drilling site must be accommodated. This is accomplished by stacking several wooden blocks to form a base for the post, resulting in a dangerously unstable drilling setup. The only alternative to this unstable setup is to obtain a longer post. There problems can be reduced by the use of a two-piece telescoping aluminum post having a 3-foot adjustment range in 6-inch increments. The two-piece extendable post will be easy to transport and carry underground. It will fit any opening height within its adjustment range. One large wooden block is used as a base and one cap block is used at the top to bear against the mine roof. This arrangement results in a stable, rigid setup.

Jan 1, 1990

By A. E. Raddatz

The Bureau of Mines has determined the electrochemical rate of anodic dissolution of vanadium metal in a VC12-VC13-NaC1 electrolyte at 860' C for the purpose of elucidating the reaction mechanism. Rate measurements were carried out with the help of specially designed equipment capable of continuously recording the weight loss experienced by a cylindrical vanadium anode immersed in the molten salt electrolyte while a constant current is maintained through it. The rate is expressed as a function of current density and VC13 concentration, and the reaction is interpreted in terms of an adsorption mechanism. Multiple regression analysis of the data gave the following rate equation: Rate x 104 (g.cm-2.sec-1) = -0.38 + 2.64 current density (amp-cm-2) + 0.69 log, (mole-percent VC13).

Jan 1, 1974

Reduce the number of conveyor-related accidents in the mining industry by providing recommendations for effective operation of conveyor belt cleaning systems. The Problem Troughed belt conveyors provide effective, and efficient materials transport and their use has increased throughout the mining industry. Carryback, the spillage that accumulates under the belt, is a problem even with belt cleaning systems installed. Mining personnel are exposed to safety and health hazard; as they attempt to clean up this spillage. Approach To investigate the influence of metal-segmented-blade belt cleaners on the amount of carryback spillage, the. Bureau identified and tested the following parameters: (1) amount of pressure applied to the cleaner blades, (2) friction between the blades and conveyor belt, and (3) wear rates of different metal blades. The test parameters were quantified by recording the amount of carryback material passing the metal cleaner blade, and the weight loss of the blades. The data collected were used to identify the following critic d operational parameters of a segmented-blade conveyor cleaner system: (1) the existence of an optimal operating pressure for the conveyor and cleaning systems and (2) elimination of recessed patterns on the working side of the conveyor belt.

Jan 1, 1989

By M. J. Ferrante

Relative enthalpies of cuprous iodide (CuI) were measured at the Bureau of Mines to provide thermodynamic data for the advancement of min-eral technology. Enthalpy measurements between 298.15 and 1,396.3 K were made with a copper-block drop calorimeter. The temperatures of transition were measured by differential scanning calorimetry (DSC). Reversible transitions were determined at 643 K with a standard enthalpy of transition [(6Htr)] = 0.74 kca1/mol, at 679 K with a [6Htr = 0.65 kca1/mo1, and at 868 K] with a standard enthalpy of fusion [(6H~) = 1.895 kca1/mol.] Tabulated values are listed at selected temperature increments from 298.15 to 1,600 K for the standard relative enthalpy (HO -H298), heat capacity (CpO), entropy (SO), and Gibbs energy function [-(Go -H298)!T]. The enthalpy data are also given in the form of equations and combined with thermodynamic data from other investigations to derive values of standard entha1pies of formation [(~HfO)], Gibbs energies of formation [(6GfO)], and logarithms of the equilibrium constants of formation (log Kf).

Jan 1, 1987

Table B-1. Summary of respirable coal mine dust samples collected under 30 CFR 90 by MSHA inspectors for underground occupations, 1988-92* [ ]

Jan 1, 1997

By Richard G. Geyer

One aspect of a program to improve the chances of survival following coal mine disasters is the development of a communications system which will allow surviving miners to make their circumstances known to rescue teams. Various communications techniques can be considered, including electromagnetic systems, acoustic systems, and hybrid systems. The electromagnetic and acoustic systems would be independent of existing mine communications systems and set up specifically for use in emergencies. Hybrid systems might use a short emergency link to existing telephone systems in the mine. Many variations are technically possible, and the primary task is in evaluating the relative merits of each, so that the most workable system can be selected.

Jan 1, 1973

By L. C. IlsLey

Figure 1 is a reproduction of a chart recently prepared by the Bureau of Mines at its Pittsburgh Laboratory to show the Bureau's approval work in connection with electrically operated mining equipment. Nearly 27 years of approval work, covering 346 approved units, are shown on this chart. These approvals are arranged according to year of approval and the manufacturer to whom approval was granted. Forty-five manufacturers are represented, and a scheme of using various colored tabs permits the following subdivision of the equipment: Cutting machines, loading machines, conveyors, battery-operated locomotives, battery-operated power trucks, drills and drilling machines, rock-lusting machines, pumps, room hoists, air compressors,, and miscellaneous, The greatest number of approvals granted to a single manufacturer is 80; the next highest is 65, and the third is 49. Several manufacturers have been granted only a single approval. The chart shows all approvals granted for, motored equipment. Some of these units have since become obsolete, and a few are used to a very limited, extent if at all.

Jan 1, 1941

By Kenneth J. Miller

The Bureau of Mines conducted an investigation to improve the flotation response of coals that are difficult to wash by froth flotation. A literature survey and experimentation showed that, for the most part, refractory coals can be floated with oily collectors and frothers. Collector reagent consumption can be minimized and the selectivity of the flotation enhanced by assuring adequate, but not prolonged, reagent conditioning. Where flotation selectivity is especially poor, two-stage rougher-cleaner flotation is recommended. It was concluded that a major problem with refractory coals is predicting when they will appear in a flotation circuit so that supplementary flotation collectors can be added. Coal losses due to variation in the floatability of the feed might be reduced if a nonpolar collector such as kerosine or fuel oil is used along with a frother as general coal flotation practice.

Jan 1, 1977

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