Search Documents

By Richard A. Allwes

The Bureau of Mines conducted an in-mine case study on two consecutive three-entry gate road systems designed in accordance with the stiff-yield pillar design concept. This Bureau study was conducted in order to further develop technology that will improve the health and safety aspects of longwall mining. Support loading and strata activity were monitored to determine the effects of retreat longwall mining on the gate road ground control system. Analyses of pillar stress and roof bolt loading histories revealed that headgate roof support elements ex-perienced cumulative loading throughout the life of the longwall panel. Tailgate pillar loadings had significantly different histories from the loading histories of the headgate pillars. Stress relief occurred in the tailgate pillars following the passage of the longwall face. More-over, the stiff-yield pillar design, with the abutment pillar placed adjacent to the working panel when part of the headgate system, provided effective ground control in that no major roof falls or roof problems were experienced in the headgate or tailgate systems during longwall mining.

Jan 1, 1985

By John R. Duda

The Bureau of Mines is developing estimates of capital investment, operating cost, and selling price for underground mines producing bituminous coal by various mining methods. This study estimates the required capital investment, operating costs, and selling prices for two hypothetical mines designed to produce 1.5 and 3 million tons per year (MM tpy)3 by using a longwall system in conjunction with a continuous-mining system. The coal properties being mined are assumed capable of sustaining a 20-year product Lon period. Wages and union welfare payments used in this study are those in effect as of December 6, 1975, as set forth under the National Bituminous Coal Wage Agreement of 1974. Costs of materials and equipment are based on January 1976 Indexes. Initial capital investment is $33.8 million for the 1.5-MM-tpy mine and $61 million for the 3-MM-tpy mine. Capital requirements, including deferred investments, were estimated to be $52.5 and $94.2 million, respectively. These figures translate into total capital investments of $34.87 and $31.31 per ton of annual production. Assuming a desired 15-percent discounted cash flow rate of return, with Federal income taxes at 50 percent, the required selling prices would be $12.06 and $10.94 per ton for the 1.5- and 3-MM-tpy mines.

Jan 1, 1976

By F. F. Aplan, J. A. Gutierrez-Rodriguez

"Contact-angle and flotation techniques were used to evaluate the influence of oxygen - both that inherent in the coal and that introduced by ambient temperature, aqueous oxidation - on a wide range of coal ranks. Oxidation was found to decrease the hydrophobicity and floatability of coal; with the effect being minor for coals of high rank but becoming increasingly important as the rank of coal is reduced. As an approximation, oxidation makes a coal behave as if it were one of lower rank. Frother only flotation' of coal· correlates with the captive-bubble contact angle whereas when oil is used as a collector, the flotation appears to follow the pattern shown by the water sessile drop on a fresh, un-reagentized coal surface. Coal recovery lost through oxidation may often be recovered by use of a variety of collectors, of which No. 2 foe! oil is among the best of those reagents tested. A simple alkali-extraction test may be used to estimate the influence of oxidation on coal preparation processes and use.INTRODUCTIONThe hydrophobicity of coal is not only a function of its rank but also of the extent of oxidation of the coal during and subsequent to its formation. Weathering and oxidation processes may proceed in-situ for coal deposits that outcrop near the earth's surface, or the oxidation of the coal particles may occur during mining, stockpiling or processing. Such oxidation, whether it affects the bulk-coal sample or on1y a thin outer layer on the coal surface, can dramatically influence the wettability of the particle and hence such processes as flotation, filtration, flocculation and dispersion.Many of the studies made on the oxidation of coals ·were designed to study its effect on flotation, coking or pyrolysis. The. present study 'is directed exclusively toward the effect of oxidation on the hydrophobicity and floatability of the coal. One of the first studies of the effect of oxidation on coal flotation was that of Sun [l] who found that as oxidation proceeds, coal becomes progressively more hydrophilic. Low-temperature oxidation (100-150°C for 250 h) generally lowered the coal floatability with an oily collector only slightly, but more extensive oxidation (200- 3500 C for 250 h) reduced coal floatability seriously. Sun also found that cationic amines were effective collectors for the oxidized coal which infers that oxidation makes the coal more negative in solution. He attributed the loss of floatability to be due to the accumulation of water-insoluble oxidation products at the coal surface. Gayle et al. [2] found that oxidation adversely affected coal flotation when an aliphatic-alcohol frother was used, though a small amount of oxidation appeared to improve the floatability of some coals using a kerosene-pine oil, collector-frother mixture in pilot-plant testing. Prolonged oxidation adversely affected the flotation recovery of the coals tested, the effect being more pronounced when an alcoholic-type frother only was used. They also noted that the reduction in floatability of lower rank bituminous coals was more affected by oxidation than was that of higher rank bituminous coals."

Jan 1, 1989

By Robert T. Mann

This paper is one of a series being prepared for and published by the United States Bureau of Mines on the quarrying, crushing, and grinding of limestone for cement manufacture. These papers are designed to disseminate technical information regarding the methods used. The cost tabulations represent operating expenditures only and not total coats. It is recognized that publication of total costs might in many instances cause embarrassment to individual producers, as well as to the industry as a whole. On the other hand, operating costs are essential to the technical discussion and study of the methods employed. The attention of the reader is specifically called to this differentiation in order that no misunderstanding of the scope of the cost tabulations shall ensue. ACKNOWLEDGMENTS The author wishes to acknowledge the assistance of J. B. Thoenen, mining engineer of the Bureau of Mines, in the preparation of this paper.

Jan 1, 1933

By Leo J. Neill, O&apos

Abrasives are essential to the manufacture of munitions - airplanes, gas, shells, tanks, and in fact every product that involves metal forming or finishing. An indication of the importance of abrasives in the national defense and aid-to-Britain programs is the close peace-time correlation between demand for abrasives and automobile production, which in recent years has consumed more than 35 percent of the total output of abrasives. Unprecedented demands on the abrasives industry are forecast by the rapid expansion in airplane output, tie increased mechanization of all armed forces, and the consequent speeding up not only of the factories where finished munitions are made but also of the steel mills and other factories were additional large quantities of abrasives are needed for snagging or rough-grinding semifinished products before they can be used by the fabricators. A recent survey by the artificial abrasives manufacturers indicates that they can readily increase their output 75 percent compared with the previous peak of 1937 without building new plants. By overhauling production schedules, their maximum production possible could be increased to 182 percent of the 1937 output, and the nature of the industry is such that plant capacity could be increased rapidly if need therefor should arise. No figures on the estimated requirements for abrasives in 1941 or 1942 have as yet been compiled, but the industry feels that it can meet demands as they develop.

Jan 1, 1941

By H. W. Sheffer

Technical and economic aspects of community refuse disposal systems and their effects on the environment are identified and described. Seven landfills and two incineration systems, located throughout the United States, are reviewed.

Jan 1, 1971

By D. E. Andrus

This paper, which describes the milling practice at the Montana mine concentrator of the Eagle-Picher Lead Co., is one of a series being prepared by the United Slates Bureau of Mines. LOCATION The Montana mine is situated on the eastern edge of the Oro Blanco mountains at an elevation of 4,300 feet. It is in the Oro Blanco mining district, Santa Cruz County, in the southern part of Arizona, about 4 miles north of the Mexican border, 30 miles northwest of Nogales and 80 miles southwest of Tucson. Amado, a station on the Southern Pacific Railroad, midway between Tucson and Nogales, and about 40 miles northeast of the mine, is the shipping point and is reached over an excellent highway.

Jan 1, 1931

By William J. Wuest

This U.S. Bureau of Mines report presents an overview of ground control considerations associated with floor heave. Factors affecting heave, such as in situ stress, floor characteristics, and mine geometry, are described. Floor-displacement monitoring and data analysis methods are outlined. Finally, floor heave remediation is discussed. The remedial techniques are divided into four categories: mine maintenance, supplemental support, mine structure, and techniques for multiple-seam operations. Other subjects covered in the report include laboratory and in-place testing of floor rocks, U.S. and international case studies, effects of mine layout, determination of excess horizontal pressure, and types of heave failure. The emphasis of this report is on practical considerations; theoretical discussions are kept to a minimum.

Jan 1, 1992

By C. H. Riggs

This petroleum-engineering report of the Atlanta oil field in BO them Arkansas reviews reservoir conditions and pressure-production history of one of the important Smackover limestone fields in southern Arkansas. The study of the field was made and the report prepared to aid operators in this and similar fields to increase the efficiency of recovery through the application of better engineering practices. A similar study of the Magnolia field in Arkansas by Carpenter and Schroeder was the first of these reports prepared under a joint agreement between the Arkansas Oil and Can Commission and the Bureau of Mines. The increasing demands for petroleum and its products and the steadily increasing cost of discovering and developing oil field; emphasize the importance of conserving known reserves of oil and gas. In recent years vast improvements have been made in the technique of oil recovery, both by better utilization of the natural energy stored in the reservoir and by improved methods of applying external energy to the reservoir system. This report may aid in oil conservation by careful evaluation of the several factors that did or did not contribute the greater recovery in the Atlanta field and by suggesting improvements in production methods and applications.

Jan 1, 1949

By Henry C. Meeve

This report describes work done in the Creede Mining district, Mineral County, Colo., in 1965-66 as a part of a Bureau of Mines study of the silver production potential of the United States. The ruining history of the district is briefly covered, and representative former and current mining operations are described. Mining and milling costs of the Emperius Mining Company's operation are given in some detail as being representative of the cost of mining typical Creede ore bodies under current technology. An estimate of the silver reserves and resources of the district is presented, subject to many uncertainties stemming from inaccessibility of old workings, lack of mining records, and low level exploration activity, all of which limit the opportunity to accurately evaluate ore potential. The report concludes with an analysis of future silver production trends in the Creede district. An increase of silver production to as much as I million ounces yearly is projected, possibly starting in 1969. As long as ore bodies in the zone of enrichment, in which silver is a major constituent, contribute a substantial part of Creede production, silver price will affect overall production rates appreciably. As the richer are bodies become depleted, an increasing portion of production again will be coming from primary sulfide ores in which silver is a byproduct of lead and zinc. When this occurs, the level of silver production will be governed chiefly by lead and zinc production and prices and can be expected to decline to the 1960-66 level, which amounts to an average of 240,000 ounces per year.

Jan 1, 1968

By Robert F. Chaiken

More than 500 fires are now burning in abandoned coal waste banks and coal deposits in the United States. Once established, such fires can burn for decades, and extinguishing them by conventional methods such as surface sealing to exclude air, excavation to remove fuel, or flushing to cool the fire zone is usually difficult and always expensive. Burnout Control, a technique developed by the Bureau of Mines for the control of abandoned fires, involves the accelerated combustion of coal in place with total management of the heat and fumes produced. A burning waste bank or mine is placed under negative pressure relative to the atmosphere, and heat and combustion products are drawn from the combustion zone through an exhaust ventilation system. Heat produced appears as sensible heat in the exhaust, at temperatures as high as 1,000° C (1,832° F), and can be recovered for the production of steam, hot water, process heat, or electricity. The Bureau's first field demonstration of Burnout Control was at Calamity Hollow in Allegheny County, PA (near Pittsburgh). Calamity Hollow was the site of an underground mine in the 1900's and was surface mined in the 1940's. In the winter of 1961-62, a fire of undetermined origin was discovered in the exposed coal. In 1963, the Bureau constructed a trench barrier around the fire and a surface seal over the affected area. The fire was isolated, but not completely extinguished. In 1979, when the Bureau began work on the Calamity Hollow Mine Fire Project, to demonstrate controlled burnout, the fire was still smoldering on the hot side of the trench barrier. The project, which was begun in December 1979 and ended in July 1982, consisted of the design, construction, operation, and subsequent dismantling of a Burnout Control ventilation system. This report is the fourth in a five-part series that describes the Calamity Hollow Mine Fire Project. The first report, part 1, describes the design and construction of the field installation. Part 2 will present the results of a continuous 4-month burnout operation. (Because part 2 involves the analysis of a substantial body of data, it will not be published until after publication of parts 3, 4, and 5). Part 3 describes the instrumentation used to control and monitor the progress of the burnout operation. This part (part 4) and part 5 both deal with the closeout phase of the field demonstration. The quenching of the fire is described in this report, and part 5 will describe the final excavation and backfilling of the heated zones. The reports in this series document the Calamity Hollow controlled burnout demonstration, which showed that (1) controlled in situ combustion is a feasible method for controlling underground fires in abandoned mines, (2) the resultant thermal exhaust output is sufficient for energy utilization, and (3) water injection with fume exhaustion is a potentially effective method for cooling large underground fire zones. Further trials of both Burnout Control and water injection with fume exhaustion are planned.

Jan 1, 1984

By S. M. Runke

The pegmatite investigations at the Rapid City, S. Dak., Experiment Station during; the pact 3 years have been primarily a study of recovering beryl from nonlithium-bearing pegmatite rock by continuous-testing methods. Beryl concentrates containing 25 to 88 percent beryl were produced from rock that ranged in beryl content from 0.1 to 2.5 percent. The beryl recovery ranged upward from 70 percent but averaged better than 80 percent. Although promising results have been obtained with flotation methods for upgrading these concentrates to standard specifications, additional work is needed to improve and simplify the procedure. In addition, it was demonstrated that several potentially useful coproducts could also be recovered from pegmatite rock. The principal coproducts were mica, feldspar, and quartz. A heavy-mineral product also was made from pegmatites containing tin, tantalum, and columbium. The recovery if these minerals in products meeting the specifications of the commercial users has been reserved for future study. The investigations also included studies on extraction of beryllium from both high-grade beryl and flotation concentrates of medium beryllium content. The procedure investigated consisted of sintering beryl or beryl flotation concentrates with limestone, acid curing the resulting sinter with sulfuric acid to dissolve the beryllium, and water leaching to extract the beryllium. Over 90 percent of the beryllium was extracted by this procedure. Most of the optimum conditions and quantities of reagents were determined for dissolving the beryllium. As aluminum and iron also were taken into solution by the acid, further research is needed on methods of recovering high-grade beryllium salts from the solutions containing these elements.

Jan 1, 1957

By Ted A. Lewtas

The effectiveness of induction fans in ventilating dead headings was studied in the laboratory and underground. The following fan attachments were evaluated: a. Aerodynamic nozzle b. Various lengths of vent tube c. Honeycomb airflow straightener. Various fan locations were also tested. The following conclusions were reached: a. A nozzle on a fan located against the drift wall gives the greatest jet penetration distance. b. Air straighteners are ineffective in increasing jet penetration. c. Induction fans are ineffective in removing contaminants from dead headings without sufficient main ventilation flow.

Jan 1, 1980

By Manuel Gomez

Primary, low-temperature tars are generally known to alter with time. The effect is believed to occur, in some instances, without the external influence of air, light, or heat. Since one of the processes occurring during extended storage is oxidation, the action of mild oxidation induced by air and heat, in addition to the effect of storage, was studied. The principal effect in aging and oxidation is formation of pitch at the expense of the distillate fraction. The fraction boiling above 270° C. is mainly involved in pitch formation due to storage, whereas all fractions are affected to some degree when tar is heated at 125° C. in the presence of air. If the effects of air are considered, the aromatic and tar-acid fractions seem to be important in pitch formation.

Jan 1, 1956

By H. D. Jacobs

A process for recovering both iron and manganese from four manganiferous ores of the Cuyuna Range was evaluated. It comprised: (1) Low-temperature gaseous reduction to convert nonmagnetic iron minerals to magnetite and manganic minerals to manganous oxide, (2) acid leaching to extract manganese, and (3) magnetic separation to reclaim iron from the leach residue. Iron recoveries from the magnetic products ranged from 70 percent to 90 percent; manganese recoveries from leach filtrates ranged from 75 percent to 95 percent. Two ores, from the Hillcrest and South Alstead properties, yielded magnetic products considered adequate for use as blast furnace feed. Although good yields of manganese were attained on all ores, appreciable iron accompanied the manganese into solution. Previous work, however, has shown that this iron can be precipitated almost quantitatively under autoclave oxygen pressure with very little loss of manganese.

Jan 1, 1970

By Graham W. Marks

In broadening the utility of spectrochemical methods 9f analysis of ore samples 3,4/ a procedure employ in the total energy method, has been adapted to determination of silver in ores. Silver is the first element in group I of the periodic table to be studied in the Bureau of Mines program. Two silver lines in the spectrum, Ag X\ 3280.683 and 3382.89lR were used in the study, and the problems that had to be overcome were: (1) Influence of extraneous elements on line intensities, (2) preparation of standard curves, and (3) improvement in equipment and technique to increase accuracy. Sodium, potassium, sulfur, selenium, iron, cobalt, and nickel yielded low intensities and hence low results, particularly on the samples high in silver, but addition of 60 percent or more of lime counteracted these effects. One calibration curve must be used for samples low in silver and other for those high in silver. The chocks with fire assaying were close enough for preliminary or exploratory investigations, and the method is much more rapid.

Jan 1, 1948

By M. L. Glenn

The Bureau of Mines is conducting research on substitutes for chromium-containing alloys in order to conserve imported critical and strategic materials. Part of this research concentrates on finding low-chromium substitutes for heat-resisting stainless steels for the temperature range 600° to 800° C. Ferritic alloys are emphasized that have oxidation resistance provided by chromium contents as low as 10 pct and stress rupture strength provided by the precipitation of the chi(X)-phase intermetallic compound, (Fe36Cr12 (Mo, Ti)10). Initially, research was concentrated on selecting an alloy composition having a minimum chromium content with strengthening provided by the X-phase. An Fe-(10-12 pct)Cr-6 pct Mo-(1.5-2.0 pct)Ti alloy was selected. After the alloy selection, the tensile, stress rupture, and oxidation properties were determined. Stress rupture properties were found to be similar to those of 304 stainless steel. However, the alloys possessed brittleness during both stress rupture and tensile testing, possibly as a result of too high a content of molybdenum and titanium. Higher than expected oxidation rates were found that may be caused by the high molybdenum content.

Jan 1, 1984

By E. J. Lintner

This paper is one of a series being prepared by the United States Bureau of Mines describing clay mining, crushing and grinding methods, and costs, at various operations throughout the United States. These papers are designed to disseminate technical information regarding methods used. The, cost tabulations represent local operating expenditures only and not total production costs. It is recognized that publication of total production costs may in many instances cause embarrassment to the individual operator as well as to the industry as a whole. On the other hand, operating costs are essential to the technical discussion and study of the methods employed. The attention of the reader is specifically called to this differentiation in order that no misunderstanding of the scope of the cost tabulation shall ensue. The following report deals specifically with the methods employed by the Evans Pipe Co., Uhrichsville, Tuscarawas County, Ohio. The author wishes to acknowledge the assistance of the following company officials: T. J. Evans, II, president; T. J. Evans III, vice president and general manager; and L. P. Young, general superintendent.

Jan 1, 1936

By H. A. Watson

The introduction and use of synthetic materials in various applications may lead to potential hazards from toxic, gaseous, decomposition products if these materials are subjected to conditions abnormal to their intended use, such as high temperatures or burning from accidental causes. This report covers an investigation of such possible hazards from toxic gases produced by the burning or thermal decomposition of some low-density, expanded, synthetic materials, three of which consisted of polyvinylchloride and one of acrylonitrile. In the production of certain expanded plastic materials, Chemical blowing agents frequently are used to produce a cellular structure. One of these blowing or foaming agents contains azo-bis-isobutyronitrile, which is designated in this report as PN. Information indicates that a product of decomposition of this blowing agent, formed in the blowing operation, is tetra-methyl-succino-nitrile, designated as TSN, Which is significantly toxic. Decomposition of the blowing agent, with release of its azo nitrogen, is represented by the following reaction:

Jan 1, 1951

By A. T. Harris

Ground quartzite, known in the industry as amorphous silica, is produced from a quartzite deposit near Honey Brook, Pa., by George F. Pettinos, Inc., of Bala-Cynwyd, Pa. The quartzite is mined by the open pit method and processed in a mill at the mine. The operation regularly produces five standard grades of sand and one grade of crushed stone; however, the company accepts special orders and will produce material to meet the customer's specifications. Beneficiation (chiefly crushing and screening) is controlled by laboratory screen tests on samples taken during preparation of the sand. The chief uses of the sand are for foundry operations, furnace lining, concrete aggregate, and other specialized uses. The quartzite in this deposit is of uniform composition and does not require control by chemical analysis. However, for special purposes, analysis will be furnished.

Jan 1, 1965