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By Edward D. Thimons

The Bureau of Mines has developed a damage-resistant brattice, intended for use as a stopping in locations where blast damage to stoppings is a problem, the roof is relatively flat, and the differential pressure across the stopping is not high. Damage-resistant brattices consist of a series of vertically hung brattice panels joined to each other by Velcro connections that improve the airtightness of the brattice. When the brattice is subjected to strong blast forces, the Velcro connections peel apart, allowing the panels to open without incurring damage. The Velcro connections can then be resealed in a matter of minutes. A preliminary test in the Bureau's Safety Research Mine and subsequent long-term testing at the White Pine copper mine in Michigan and the Retsof salt mine in New York show that damage-resistant brattices withstand blasting better than conventional stoppings, while still performing as efficient air barriers when the Velcro connections are sealed.

Jan 1, 1978

By R. V. Lundquist

The work described in this report, part of the Bureau of Mines long-range program to develop methods of utilizing submarginal domestic sources of aluminum, was undertaken to investigate the effects of iron in the lime soda sinter process, The approximate Fe2O3 content in a sinter for maximum alumina and soda recovery was 8 to 9 percent. Fe2O3 appears to inhibit gelation, and 15.5 percent Fe2O3 produces effects similar to those produced by 1 percent sucrose. In the lime soda sinter process, aluminum silicates are sintered with limestone and soda ash to yield dicalcium silicate and sodium aluminate. The sodium aluminate is extracted by leaching in caustic solution. The solution is purified by heating in an autoclave with lime to remove silica, and alumina trihydrate is precipitated with carbon dioxide. The reactions involved in sintering and leaching are complex. A number of studies by the Bureau of Mines4-9 and others1 indicate that the iron content of sinters influenced the recovery of alumina and soda and the gelation characteristics.

Jan 1, 1962

By Thomas Varley

Data on the consumption of reagents used in flotation during the years 1923 and 1924, in metallurgical plants in the Unites States, are presented in this paper. Two previous reports Lave been issued by the Bureau of Mines on consumption of oils and other reagents used to flotation - namely, "Statement of Flotation Oils," by O. C. Ralston, issued in 1913, and Serial No. 2203, "Consumption of Reagents Used in Flotation," by Thomas Varley, for the year 1919, issued in January, 1921.

Jan 1, 1925

By J. M. Kuchta

The chemical and thermal criteria used for predicting the spontaneous combustion hazard are briefly reviewed and data are presented to characterize the gas desorptions and self-heating tendencies of 29 U.S. coals. Closed vessel desorption experiments showed that CO, CO2, and CH4 are the main gases evolved and that the CO, CO/?O2 index, and 02 absorption rate increase with decreasing rank and increasing oxygen content of the coal. In this Bureau of Mines report, the effects of temperature, moisture, and other variables are discussed together with the application of the data to the complex conditions encountered in a mining environment. An important finding is that the presence of CO alone in a mine is not necessarily an indication of a self-heating reaction of the coal. Based upon experiments conducted in an adiabatic-type calorimeter, the self-heating temperatures of lignite and subbituminous coals can be as low as 30° C, whereas the bituminous coals require a temperature of about 60° C or more. The self-heating hazard is greatest when the coals are dried and exposed to a high humidity condition, apparently as a result of the "heat-of-wetting." Generally, the hazard is greatest with the western coals of the United States.

Jan 1, 1980

This part of the final report treats some problems related to coal mine carrier frequency communication systems using the trolley wire/track transmission line. This work was undertaken for a brief period of time during the summer of 1972 to help understand, quantify, and improve some of the trolley wire carrier system behavior observed and/or predicted. Calculations and estimates of transmission line characteristic impedance, inductance and capacitance per unit length, mine motor loading effects, parallel line effects, and connection impedances are presented in Chapter I. Chapter II treats the design of r-f isolators for reducing the undesired and troublesome r-f loading that mine motors present to the trolley transmission line. Chapter III treats a diversity method for combatting standing wave nulls. I. CALCULATIONS RELATED TO TROLLEY WIRE COMMUNICATIONS A. ESTIMATION OF INDUCTANCE AND CAPACITANCE PER UNIT LENGTH OF TROLLEY LINES To estimate the L and C per unit length of trolley lines, we use the eccentric line model of Section G of this Chapter, "Characteristic Imped¬ance Estimates for Mine Trolley Lines." The capacitance per unit length for an eccentric line is given by (1)

Jan 1, 1974

By Oliver Bowles

This report covers the character, properties, origin, occurrence, and uses of the traprocks and describes briefly the methods and equipment employed in quarrying and preparing them for market. Production of traprock occupies an important place in industry. In 1960 the output in the form of crushed stone reached nearly 58 million tons valued at $87 million. Traprocks are also shaped into blocks of dimension stone for monuments, building construction and decoration, and specialized products such as surface plates.

Jan 1, 1963

By F. H. Gibson

In recent years physico-chemical techniques have been applied for rapid analysis of coal and coke ash as replacements for classical wet-chemical methods. Although the classical methods are accurate, they are time consuming because many chemical separations are necessary to complete an analysis, and they require skilled analysts for accurate work (12).4 For the past several years the Bureau of Mines has applied some of the newer physico-chemical techniques in its continued search for new and improved methods at analysis. The methods of analyzing coal and coke ash evolved from this work include spectrophotometric methods far SiO2, A120, , Fe203 , TiO2, and P2O5; chelatometric titration for CaO and MgO; and flame photometry for Na20 and K2O. The methods are rapid and direct, are suitable for analyzing a group of samples at the same time in production work, and dire results with almost the same accuracy as classical procedures. With the new methods, complete analyses in duplicate can be obtained at a rate of 2 to 3 times that of conventional methods.

Jan 1, 1962

By Walter R. Storms

The Iron Mountain tungsten deposits first were visited by a field party of the Federal Geological Survey in May 1942 while beryllium deposits in that district' were being examined . Later they were examined by F. A. Rutledge , an engineer of the Bureau of Mines , and an exploration project was recommended , work upon which began in March 1943 and was terminated in April 1943 after intensive trenching and sampling had been completed .

Mar 1, 1947

To improve operational effectiveness of enclosed cab filtration systems. Background Enclosed operator cabs are widely used on mobile excavation equipment in the mining and construction industries. They protect the operator from bad weather, noise, and airborne dusts. The inside cab environment usually must be kept at very low dust concentrations because of quartz dust generated from the excavation of silica-bearing rock. Most cab designs achieve heating and air conditioning effectiveness by recirculating most of the interior cabin airflow, with a smaller portion of the outside air added to the cab as makeup air. Both the recirculated cab airflow and exterior makeup air added to the cabin should be efficiently filtered, with the makeup air positively pressurizing the cab interior. Ideally, operator cab air filters should provide at least 99% capture efficiency for dust particles as small as 0.3-pm aerodynamic diameters. These higher efficiency air filters provide good dust control for the equipment operator, but tend to accumulate dust more quickly than lower efficiency air filters.

Jan 1, 2001

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 H. E. Perlee

Mathematical expressions are derived for the histories of the pressure, flame radius, mass fraction burned, and burned and unburned gas temperatures associated with a spherical flame propagating concentrically in a spherical vessel. The equations are solved numerically for a 9.5 pct CH4/air mixture using the best available information for the burning velocity, expansion ratio, and specific heat ratio. Calculated histories are in complete accord with experimental measurements. The accuracy of calculated histories is determined relative to errors in the system parameters, and it is found that 10 pct errors in either the burning velocity or the expansion ratio results in a 40-pct error in the pressure history. A 10-pct error in either burned or unburned specific heat ratio results in a 22-pct error &apos;in the pressure history. It was further established that the usual assumption of constant specific heat ratio is unacceptable, but equating the burned and unburned specific heat ratios result in no apparent error in the histories. The cubic law (P = Kt3 + Po) is derived and discussed, and it is found that the law is valid only during the early period (P<2 atm) of flame growth.

Jan 1, 1974

By R. Barany

The heats of the glass-crystal transformation of nepheline (Na0.7794K0.2206AlSiO4) and wollastonite (CaSiO3) and the heat of formation of nepheline at 298.15° K were determined by solution calorimetry. For the glass-crystal transformations, the heat values were -9.0 ± 0.3 kcal/mole for nepheline and -8.1 ± 0.2 kcal/mole for wollastonite. The heat of formation of nepheline was -34.8 ± 0.6 kcal/mole from the oxides and -501.0 ± 0.5 kcal/mole from the elements.

Jan 1, 1966

By M. L. Whisman

Radiotracer techniques were developed for stoichiometric studies of photochemical reactions associated with atmospheric smog formation. Stock blends of separate hydrocarbon and oxygenated compounds were prepared and calibrated. 14C-labeled reactants and products in reaction systems involving hydrocarbons and nitrogen oxides at the ppm level were analyzed for qualitative and quantitative data. Precision and accuracy of these methods developed by the Bureau were determined by replication and statistical treatment of data, and these methods are described.

Jan 1, 1969

By D. N. Nilsen

The Bureau of Mines is investigating a method to recover Ni, Cu, and Co from low-grade domestic laterites through reduction roasting, leaching, sol-vent extraction, and electrowinning unit operations. The objective of this research is to develop processing technology that can convert low-grade domestic deposits containing critical metals into national reserves. As a part of this research, a solvent extraction system was investigated for the extraction of nickel and copper, followed by the separation and production of suitable electrolytes. Nickel and copper were coextracted from ammoniacal ammonium sulfate leach liquors (pH~9.5) with LIX 64N extractant in a laboratory-size mixer-settler continuous circuit. Three extraction stages resulted in >99-pct extraction of nickel, substantial copper extraction, and essentially no cobalt extraction from leach liquors. A crowd stage reduced the ammonia loading on the solvent by maximizing nickel loading. Residual ammonia was removed from the loaded solvent with a pH-controlled scrub. Nickel and copper loaded on the solvent were separated by selective stripping. Typical nickel strip circuit operation using electrolyte containing 90 grams per liter (g/l) Ni and 11.9 g/l H2S04 yielded >99.9 pct Ni stripped from the solvent in five stages. The copper loading on the recycled solvent was controlled in a copper strip stage using electrolyte containing 25 g/l Cu and 160 g/l H2S04,

Jan 1, 1981

By A. W. Henderson

The growing importance of halide metallurgy for preparing high-purity metals has stimulated research to extend halogenation reactions to the direct extraction of metals from low-grade sources. This Bureau of Mines investigation involves a pioneering study of chlorination reactions in the presence of a fluorine donor. Tin slags containing tantalum and columbium and a zircon concentrate containing a relatively high ratio of hafnium to zirconium were studied. Direct chlorination of these materials at 500° C. yields only a 5-percent conversion of tantalum and columbium or zirconium and hafnium to anhydrous chlorides. This investigation showed that small additions of calcium fluoride to the reaction increased the recovery of tantalum and columbium to 95 percent and the recovery of zirconium and hafnium to 27 percent. These results were achieved with ratios of calcium fluoride to mineral or slag of only 0.2. Silica, the major impurity in the materials studied, was found to be converted to silicon tetrafluoride during chlorination in direct proportion to the quantity calcium fluoride added to the charge. However, large additions of calcium fluoride decreased the volatility of the resulting halides of tantalum, zirconium, and hafnium. Smaller amounts of calcium fluoride also favored recovering minor metal constituents in the zircon concentrate (uranium, thorium, and rare earths).

Jan 1, 1962

By Robert K. Koch

Laboratory-scale studies on defluorination of natural and synthetic fluorspars by pyrohydrolysis at 1,500° C. were made to determine the feasibility of developing a process for producing hydrogen fluoride from siliceous fluorspars. It was found that the reaction (at 1,500° C.) is not promising for process development, even though a silica-free offgas can be generated. The primary difficulty is the low hydrogen fluoride content of the offgases; an HF content of 6 percent was the best achieved. Previous research by the Bureau of Mines has demonstrated that offgases averaging 27 percent hydrogen fluoride can be produced under carefully controlled conditions at 1,280° C. The lower temperature process is a better method for production of HF. However, charges in which the CaF to Si02 mole ratio varied from 0.4 to 2 could be processed with similar results. Also, combined alumina and ferric oxide contents up to 25 mole-percent did not noticeably alter the rate of defluorination. Therefore, virtually any natural siliceous fluorspar would respond in essentially the same manner when exposed to water vapor at 1,500° C.

Jan 1, 1962

By D. E. Anders

Saturated hydrocarbons from 60 selected samples of a 2,300-foot Green River Formation oil-shale core (Piceance Creek Basin, Colo.) were analyzed by gas-liquid chromatography techniques. Emphasis was placed upon the distribution of normal alkanes and 15 key-branched and cyclic alkanes. The latter compounds consisted of the C15, C16, C18, C19, and C20 chain isoprenoids, the 5-a and 5-ß C27, C28, and C29 steranes, three C30 pentacyclic triterpanes, and perhydro-ß-carotene. The results showed definite evidence of maturation of both the n-alkanes and the branched and cyclic alkanes; however, most if not all of the changes were limited to the indigenous soluble extract and were not the result of additional soluble extract generation from the insoluble kerogen. Source material and environmental variations were important factors in some of the observed differences in the branched plus cyclic alkane compositions.

Jan 1, 1973

By D. N. Nilsen

The U.S. Bureau of Mines investigated the use of unsupported liquid emulsion membranes (LEM&apos;s) for the extraction of copper from relatively dilute aqueous solutions (=0.3 and 2.5 g/L Cu), The performance characteristics of the three main unit operations of an LEM circuit (emulsion generation, metal extraction, and emulsion breaking) were assessed in laboratory-scale batch tests. In single-stage extraction tests using 2.5-g/L Cu feed solution, emulsion membranes extracted up to 94 pct of the copper from solutions without pH adjustment and 99.7 pct when the pH was maintained at about 2.5. Simulated two-stage crosscurrent and countercurrent circuits extracted all but 3 and 4 ppm of the original copper content, respectively. Extraction data from solutions containing mixtures of metals indicated a strong preference for Cu2+ extraction when oxime-type extractants were used in the LEM; however, some coextraction of Fe 3+ and Zn2+ was experienced. An electrostatic coalescer was used to break the copper-loaded emulsions for separation of the component phases. Up to 96 pct of the contained stripping solution (internal solution) containing the extracted copper was separated from the organic phase of the emulsion membrane. The recovered organic phase was recycled without apparent problems.

Jan 1, 2010

By S. H. Ash

As part of the work done at the Washington coal mines during the year 1929 , a study was made of the safety practices in and about the mines . Inasmuch as electrical blasting has made considerable headway it is interesting to note the manner in which it is done and the reasons why it was discarded at some of the mines . Blasting is done at the mines in the State by means of capped fuse , electric blasting " caps , " and in some instances by electric delay detonators . Black blasting powder with fuse is used at most of the open- light mines . The use of squibs was discontinued several years ago because the coal operators , without exception , recognized the dangers incidental to their use . Permissible explosive and dynamite are also used at some of the open- light mines . With the exception of some rock work and the driving of level work in gangways and air courses the explosive is detonated by means of capped fuse .

Apr 1, 1930

By W. H. Ode

Low-temperature distillation tests at 200°, 350°, and 500° C. were made on a subbituminous coal from Boulder County, Colo., and a subbituminous coal from Weld County, Colo., in connection with a survey of carbonizing properties of American coals and investigations of their chemical and physical properties. The coal represented by the sample from Weld County was reported to give off combustible volatile matter at unusually low temperatures When placed on a fuel bed. The yields of tar and oil and the composition of the gas from this coal, as obtained in the distillation tests, did not confirm this report. These yields and the gas composition of the Weld. County coal differed but little from those obtained from the coal from Boulder County. Both coals yielded tar and gas in amounts considered to be normal for coals of their rank.

Jan 1, 1937