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By John C. Holtz

The Bureau of Mines studied air contamination caused by diesel exhaust in a 10,000-ft ventilated tunnel. Sequential air samples were taken at the ends and middle of the tunnel during an operating cycle. Observed and calculated results for carbon dioxide, carbon monoxide, and nitrogen oxides were essentially in agreement. Nitrogen dioxide was present only in trace amounts. It was found that contamination was related to the volume of ventilating air, the number of haulage trips, train speed, and engine load.

Jan 1, 1968

By G. M. Potter, F. S. Wartman, M. D. Schmid

"In matte smelting of copper it has been established that the sulphpr present will combine with copper as long as the latter is present, and that thereafter it will combine with iron. The Cu-Fe ratio in the matte is determined by the Cu-S ratio, presumably owing to the much greater affinity of copper for sulphur or, expressed thermodynamically, the greater stability of copper sulphide in contact with silicate slag. Now, the work of Fournet and of Schütz, which is quoted in many elementary metallurgical texts, indicates that manganese ranks ahead of copper in its affinity for sulphur. Hence, we might expect that manganese could be concentrated from its admixture with iron. Compounds by matte smelting, and Rotts / has patented such a process. This greater affinity of manganese or sulphur is used to advantage in iron metallurgy, also, in which it is well-known that sulphur will combine with manganese and separate from metallic iron as manganese sulphide. Manganese sulphide,however, is quite soluble in silicate slags. 5/ The loss of manganese in slag in any attempted matte smelting is therefore great.If this solubility of manganese sulphide is slag is a physical one and the reaction MnO + FeS MnS + FeOIs substantially complete, then it might be expected that the addition of copper sulphide, which is almost entirety insoluble in slag, would serve to extract the manganese sulphide with the formation of a manganese-copper matte on the other hand, if an equilibrium exists in the above reaction, a copper sulphide layer would displace that equilibrium in one direction or the other, according to whether iron sulphide or manganese sulphide were more soluble in the matter layer."

May 1, 1937

By Keith L. Harris

The performance of the world economy improved significantly in 1984. Real world output!/ grew 4.3% (compared with 2.6% in 19831, the highest since the 4.4% increase recorded in 1978 (table 1). The output of industrial nations rose 4.9%, while that of the developing nations rose 3.7%. The United States and Japan had the largest increases in output of the major industrial nations, with respective increases of 6.8% and 5.8% (table 2). The components of real output with the most significant growth in the industrial countries were gross fixed investment (9.2%), consumer expenditure (3.1%), and public consumption (2.5%) (table 1). Industrial output, as measured by industrial production indices, has returned to about the 1980 level for most of the major industrial nations (table 2). Exceptions to this were industrial production in Japan and the United States; Japan's industrial production rose steadily throughout the 5-yr period and is now more than 16% above the 1980 level, and the industrial production index for the United States reached 11 1.2 (1980=100.0). Real total domestic demand grew at 8.7% in the United States, more than double the rate of Japan, which, at 4.0%, had the second-largest growth. Average demand for all industrial countries was up 5.1%. During 1984 the U.S. dollar showed great strength on international markets, contributing to large current-dollar negative net exports of goods and services and even larger negative net exports of the merchandise sector. While growing U.S. imports helped spread the benefits of the recovery, they also led to a widening of current account imbalances and growing trade tensions throughout the world.3/, 4/

Jan 1, 1985

By Howard D. Jacobs

A bulk sample of oxidized taconite taken from the western Mesabi Range was evaluated by the Bureau of Mines using the Bureau-developed selective flocculation-desliming-cationic (or anionic) flotation process. The raw ore sample containing 32.3 pct Fe was treated by both cationic and anionic flotation. Using the cationic system the concentrates averaged. 37.2 wt-pct of the feed and contained 62.8 pct Fe and 4.7 pet Si02 with an iron recovery of 72.3 pet. With the anionic system, concentrates averaged 37.7 wt-pet of the feed and contained 63.0 pct Fe and 5.3 pct 8i02 with an iron recovery of 73.5 pct. A comparison of reagent costs showed that the cationic process cost 144.1 cents per long ton of crude ore and the anionic process 178.7 cents per long ton of crude ore. Reclaimed water comprised 86 pct of the total water requirement for anionic flotation and 88 pct for cationic flotation. The ore used in this study was one of three samples representing about 3.25 billion tons of oxidized taconite containing from 32 to 36 pct feed iron. Previous study had indicated that selective flocculation-desliming-cationic flotation would produce concentrates from the other two samples of 61.7 pct Fe and 5.1 pct Si02 at 67-pct Fe recovery, and 63.5 pct Fe and 4.3 pet Si02 at 8S-pct Fe recovery. By developing a successful treatment for these ores, the Bureau has insured the availability of technology for processing an amount of raw iron ore which, by itself, would supply U.S iron needs for 50 to 75 years at expected consumption rates.

Jan 1, 1981

By L. A. Neumeier

A refinement of the tungsten-cobalt phase diagram is presented for compositions to 85 at. pct cobalt and for temperatures to the solidus. Preparation of alloys by powder metallurgy methods is described, and the results of studies made by a combination of techniques involving microscopy, X-ray diffraction, thermal analysis, and dilatometry are discussed. The existence of u-W6Co7 is confirmed (rhombohedral D85 structure). The W6Co7 phase forms periectically at 1,685'115° C by reaction of liquid with primary W; the peritectic melt is at 71 at. pct cobalt. The homogeneity range of u-W6Co7 extends to both sides of the ideal stoichiometric ratio, through a compositional range of about 5 at. pct. The compositional limits for u-W6Co7 vary slightly below 1,471°±5° C, the temperature of the eutectic reaction forming u-W6Co7 plus a. The eutectic composition is at 79 at, pct cobalt. The existence of WCo3 is confirmed (hexagonal D019 structure). WCo3 forms peritectoidally at 1,093°±5° C by reaction between a and u-W6Co7 and exists over a narrow homogeneity range of 0.5 to 0.6 at. pct. The solid solubility of cobalt in tungsten is low (maximum 0,9 at, pct cobalt) and results in contraction of the tungsten lattice. Tungsten is extensively soluble in a-Co at higher temperatures; the a-Co lattice is expanded by the presence of tungsten in solid solution. There was no indication of the formation of a o-phase nor of any intermediate phases other than WeCo7 and WCo3. The WeCo7 and WCo3 phases are compared with similar phases in other systems.

Jan 1, 1967

By J. T. McCartney

Thin sections of coal have been prepared for many years either by cutting on a microtome (1,2)5 or by grinding and polishing (2,1). Specimens of most coals had to be demineralized in hydrofluoric acid and softened in caustic solutions before they could be successfully cut with a conventional microtome. Some lignites could be cut without pretreatment. Jeffrey (1) obtained sections from coals of all ranks, although long and tedious pretreatment was required for anthracite. His sections were less than 1 cm.2 in area (probably much less for high rank coals) and about 5 microns thick. Thiessen (2) also cut sections of softened coals, mostly of low rank. His sections were a few square millimeters in area and about 3 microns thick. However, Thiessen preferred ground and polished sections for detailed studies because they were larger and had not been chemically attacked by softening media. He prepared ground sections as large as 4 cm.2 in area and usually 5 to 10 microns thick. Thousands of such sections, covering complete column samples of many coal beds, were studied for a number of years (4). With the development of the electron microscope and increased interest in quantitative optical studies of coals, a need for much thinner sections arose. However, no suitable technique for preparing such sections was known until Fernández-Morán developed a diamond knife for cutting ultrathin sections of hard materials (5). Workers at the Centre d'Etudes et Recherches de Charbonnages de France applied this new tool to the cutting of coal sections and have recently described their technique to the Burg, of Mines. Using their methods, with some modifications, researchers of the Bureau of Mines have succeeded in cutting ultrathin sections of coals ranging in rank from lignite to

Jan 1, 1961

By Donald P. Tuchman, Robert P. Vinson, Steven J. Page

Researchers at the National Institute for Occupational Safety and Health (NIOSH) have long used stationary tapered element oscillating microbalances (TEOMs®) in laboratory settings. They have served to assess the mass concentration of laboratory-generated particulates in experimental , dust chambers and they provide a reference method for comparison with other particulate- measuring instruments. Current NIOSH research is focused on further adapting TEOM technology as a wearable personal dust monitor (PDM) for coal mining occupations. This investigation's goal is to help identify, quantify, and provide means for resolving certain TEOM- related error. The present research investigated bias caused by thermal effects on filter assemblies. New filters used in the PDM for 8 h tests show an average positive bias of 25.5 pg, while similar tests of equivalent filters used in two 1400A model TEOMs show an average positive bias of 34.3 µg. The derived bias values allow correction of previously collected biased data. Also, pre- heating the filters for 24 h at 46° C shows significant bias reduction, with PDM pre-heated filters subsequently averaging -3.3 µg and 1400A TEOM filters averaging 5.9 µg. On a single-point comparison to gravimetric sampling, a 25.5 µg bias is only significant at low mass loadings. At 2.5 mg, this bias represents a negligible 1 % of the mass measurement. If ordinary linear regression is used, the bias is still insignificant. However, if the more valid weighted linear regression is used, it gives more weight to the smaller dependent variable values, which are more impacted by the bias. Consequently, what is 1% bias on a single high-mass value can translate into a larger bias percentage at high-mass values when performing a weighted regression on data that include a large number of low-mass values.

By J. H. Perry, Joseph Cervik, G. N. Aul

The Bureau of Mines is conducting research to determine the effectiveness of long holes in degasifying an area of the Upper Split of the Lower Sunnyside coalbed at Kaiser Steel CO.'s Sunnyside No. 1 mine. These holes were drilled from the two outside entries of a section that was closed to mining because of excessive methane emissions. Two holes drilled to 430 and 450 feet produced initial gas flows of 160,000 and 127,000 cfd, respectively. Sixteen days after the completion of the second hole, the total gas production declined to just over 144,000 cfd. In 9 months of degasification, over 35 MMcf of commercial-quality gas has been removed from the coalbed. The combined gas flows declined to 106,000 cfd in the 9-month period. The two holes have reduced face emissions by about 40 pct.

Jan 1, 1978

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

The initial results from the magnetic sludge factorial experiment are summarized in Table 2. For ease in interpretation, the four separate variables are identified with the high and low level of each variable being represented by + and - signs, respectively. Several important relationships are evident from an inspection of the data in Table 2. For example, magnetic sludges were obtained only during the high temperature tests. Secondly, with the exception of the last three tests, there is an apparent correlation between settled sludge volume (or sludge settling rate) and pH. Data on residual dissolved Fee+ indicate that precipitation of iron is not complete at pH 8 and room temperature (Tests l, 3, 5, and 7). Although this should not have any confounding effect on the interpretation of the results, it is an important observation and an aspect of the overall conceptual process that should be considered carefully during any future developmental work. The data in Table 2 were employed more fully in the calculation of main effects and variable interactions for each of the three responses. For this purpose, a codified design and calculation matrix, shown in Table 3, was used. The derivation of this matrix is described by Davies.(9) The positive or negative signs for variable interactions are obtained simply by algebraic multiplication of the signs for each single variable involved in the interaction. Main effects and interactions are calculated by multiplying the response values (Table 2) by the corresponding effect elements (Table 3), summing the results, and dividing by 8. The resulting value for single variables is also sometimes designated as an average effect, since (for tyro levels of the variable only) it is simply the difference between the average response of all trials carried out at the first level of the variable (factor) and that of all trials at the second level. If the effect of one variable changes at different levels of another variable, the two variables are said to interact. The relative importance of the variable or variables in question is reflected by the absolute magnitude of the calculated main effect or interaction. First-order (two variable) interactions are usually easy to interpret in terms of the physical behavior of the system. Second- and higher-order interactions are often less readily understood, and are often of minor significance in any case. The main effects and interactions derived from the present study in the manner described above are listed in Table 4. It should be noted that

Jan 1, 1971

By John C. Edwards

Chapman-Jouguet detonation calculations were carried out for pentaerythri-tol tetranitrate (PETN), TNT, and ammonium nitrate-fuel oil (AN-FO) explosives using the compressibility form of an equation of state of hard spheres based upon Percus-Yevick (PY) theory, and a chemical equilibrium detonation code called TIGER. Similar calculations were also carried out with the Becker-Kistiakowsky-Wilson (BKW) equation of state. For PETN, the BKW equation gives somewhat better agreement with experimental values of detonation velocity and pressure. However, in terms of experimental temperatures and concentrations of the minor product species (NO), the predictions of the PY equation are shown to be more satisfactory. Similar comparisons of experimental and theoretical results for TNT and AN-FO indicate that the PY equation has general utility in predicting the detonation properties of condensed explosives at moderate loading densities (Po < 1.3 g/cm3).

Jan 1, 1974

By Sarah P. Guerrino

This chapter summarizes data on crude nonfuel mineral production for the United States, its island possessions, and the Commonwealth of Puerto Rico. Included also are the tables that show the principal nonfuel 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, 1987

By D. E. Seizinger

Analytical methods for oxygenates in exhaust gases were studied, and emissions of these compounds from automotive engines were measured with and without an oxidation catalyst in the exhaust system. Hydrocarbons, simple mixtures of hydrocarbons, and a single gasoline were used as fuels. With the more complex gasoline, successful analysis was possible only with exhaust from the catalytic system which preferentially converted and thus removed interfering hydrocarbon species. However, it was shown that an estimate of the oxygenate yield from gasoline used in a noncatalytic system can be synthesized from data obtained with simple fuels. Such synthesized data were used for comparison of noncatalytic with catalytic systems. Compared with those of previous studies, results of this work indicate that the action of the catalyst introduced no new oxygenates and reduced both the carbonyl and the total of oxygenates. It is concluded that the compositional character and class distribution of oxygenates in exhaust from catalytic systems may differ significantly from the composition and distribution for oxygenates not subjected to catalytic conversion. The findings also support previous estimates that noncarbonyls may constitute a significant fraction of exhaust oxygenates and may warrant attention in procedures for measurement of the oxygenates.

Jan 1, 1973

By B. G. White

NIOSH researchers have identified a pattern of fracture zone development that suggests an explanation for fracture formation around rectangular openings in underground mines. This pattern is characterized by shearing and dilation that result in either faults or in the repeated formation and propagation of en echelon fractures from sites of tension. Two computer modeling codes, Fast Lagrangian Analysis of Continua (FLAC) and Particle Flow Code (PFC), were used to model different aspects of this pattern. Use of very small elements with FLAC enabled the identification of sites of initial tension near the skin of square-cornered rectangular openings, while PFC allowed the initiation and progressive development of fractures from these sites to be followed as the fractures evolved. Such studies can lead to a greater understanding of how roof support can be better selected and installed for specific conditions in underground mines prone to roof falls and rock bursts. These studies may also lead to modifications of corner and opening shapes that could be incorporated into mine designs to produce more stable mine openings and reduce the risks of rock falls and rock bursts.

By McHenry Mosier

Although local conditions at each mining property affect the percentage of increase in drilling speed for a given reduction in gage of bit, the results of drilling tests conducted at the Mount Weather testing adit show such a large advantage in favor of the smaller gages that they should be indicative of the possibilities at most mines. GENERAL DISCUSSION Although it is common knowledge among miners that drilling speed ill- creases with reduction in gage of bit, the large amount o this increase is not so universally realized, A recent Bureau of Mines4/ survey of drilling practices in 28 metal mines showed that the maximum gage of starters is 3 inches and that at 50 percent of the mines starters are 2-1/4 inches or larger, Because this size appears too large for conditions at most&apos; mines where abrasion is moderate and where powder distribution permits, the use of smaller bits presents a favorable opportunity for reducing drilling costs.

Jan 1, 1939

By J. D. Corrick

Research was conducted to develop operating techniques and define some of the limiting parameters for microbially converting hydrous calcium sulfate to hydrogen sulfide. The work was carried out in either glass stoppered flasks or anaerobic fermentors. Using the criteria of pH, temperature, number of bacteria per milliliter of test solution, and hydrogen sulfide produced, it was shown that hydrous calcium sulfate could be microbially converted to hydrogen sulfide at a rate of 7.3 g H2S/1 of fermentor volume per 24 hours. The various parameters defined were pH, temperature, and medium exchange rate. These were shown to be a pH range of 7.2 to 8.8, a temperature range of 30° to 35° C, and a medium exchange rate of 70 percent of the ferment or volume per 24 hours. It was also shown that a daily waste was between 50 and 77 percent as effective as sodium lactate in supporting the production of hydrogen sulfide and that by utilizing a gas to purge the fermentation system, a 1.7-fold increase in hydrogen sulfide was obtained.

Jan 1, 1970

By J. K. Whyatt, B. G. White

Various methods of monitoring slip movements on bedding planes, as well as examination of rock burst damage in stopes, suggest that many rock bursts in the Lucky Friday Mine are closely associated with these movements. Slip displacements along bedding simultaneously reduce the physical dimensions of stopes and increase compressive stress along stope margins. Such changes, in turn, contribute directly to sudden failures of rock and cemented sandfill surrounding stopes. We believe that the reduction of rock burst hazards must be based on a clear understanding of the basic mechanisms involved. The current work emphasizes the mechanical role of wall rock movement and seismicity in generating conditions that promote rock burst damage. Based on our interpretations of these mechanisms, we briefly address several hypothetical practices that could influence rock burst hazards in similar mining situations. The overall goal of this research is to advance the NIOSH mission of improving the health and safety of the nation’s workers.

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

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

Jan 7, 2007

By Theodore Christos

The Bureau of Mines sponsored an investigation of the thermal oxidative degradation characteristics of selected ingredients employed in the formulation and manufacture of conveyor belts. This work was done to supplement similar studies of samples from finished conveyor belts and thus provide basic data for correlation of the potential toxic behavior of a finished belt with that of the individual ingredients. This report covers the study of (1) basic polymers (styrene-butadiene, neoprene), (2) reinforcing fibers (Nylon 6,6, Dacron, viscose rayon), (3) flame-retardant plasticizers (tritolyl phosphate-isomeric mixture, tri-p-tolyl phosphate, tributyl phosphate, tris (dichloropropyl) phosphate), (4) plasticizers (diphenylphtha1ate, di-(2-ethylhexyl) sebacate), and (5) a vulcanization accelerator (2-mercaptobenzothiazole).

Jan 1, 1977

By Gregory J. Chekan

In This Chapter [Drilling, blasting, and crushers Diesel particulate Enclosed cabs Ventilation with jet fans Stopping construction methods Propeller fans as main fans] This chapter explains how to control dust in large-entry stone mines, including both silica dust and diesel particulate. Most stone mines are limestone mines, but a substantial minority are marble, sandstone, and granite mines. These mines differ from most others in that entry widths are 30 ft or more and entry heights are 25 ft or more. Such mines, developed with room-and-pillar methods, have large open areas that can make ventilation and dust control more difficult. Because of the difficulty of ventilating stone mines, improved ventilation is a major focal point of this chapter. However, the chapter also covers the control of dust from drills, blasting, and crushers. Another part of the chapter covers enclosed cabs, an effective dust control technique for some workers. BACKGROUND The major dust compliance problem in stone mines is caused by silica (quartz) in the rock. Mines in high-silica rock, 8% or more, are far more likely to have a dust problem than those where there is less silica. Geographically, the limestone in the Northeastern and South Central United States has higher silica than the rest of the country. Chekan and Colinet [2002] have analyzed Mine Safety and Health Administration (MSHA) dust sampling results [MSHA 2001] from the stone industry. They have concluded that, on average across the United States, the workers exposed to the highest dust concentrations are rotary drill operators, front-end loader operators, truck drivers, and crusher operators. However, there are many regional differences. Also, occupations that work outside of cabs, such as blasters, roof bolters, and laborers, can be exposed to high dust levels.

Jan 6, 2003