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By D. E. Pollock, J. A. Organiscak

Water sprays and water powered scrubbers have both been utilized in the mining and milling industry to suppress airborne dust. Unconfined water sprays operated at lower water pressures of ?689 kPa (?100 psig) can be very effective at wetting the mine product at the dust source and significantly reducing the amount of respirable dust that becomes airborne. However, unconfined waters sprays can be somewhat ineffective in actually removing airborne dust from the air. On the other hand, water powered scrubbers operating at higher water pressures of ?1,724 kPa (?250 psig) in physical enclosures or ducts have previously been demonstrated to be very effective in removing airborne dust from the air. These higher operating water pressures are uncommon in many mines and mills, so their use is limited. The National Institute for Occupational Safety and Health (NIOSH) recently investigated the performance of a lower-pressure, water powered inline series spray scrubber for removing localized airborne dust emitted at the source. Results showed noticeable improvements in airborne dust capture efficiency through the operation o f multiple inline series hollow cone spray nozzles within a round duct or pipe at the same water pressure as a single spray. Operating hollow cone spray(s) at higher water pressures noticeably improved airflow through the scrubber and yielded some additional scrubber efficiency improvements. Thus, in-line spray scrubber efficiency trade-offs were observed to be made by altering spray power components of water pressure and/or quantity (number of sprays). Results show that, on average, up to 0.23 and 0.32 m3/s (484 and 679 cu ft per min) of airflow at 0.81 and 0.69 dust capture efficiencies can be achieved with three 81° and 33°hollow cone inline series sprays, respectively, operating at 1,655 kPa (240 psig).

By Bowles Oliver

"Modification of Quarry Process.Limestone beds are formed by processes of nature, processes that have been in operation for thousands and perhaps millions of years. Therefore, their com- position and physical properties are long-established and unalterable features over which man has no control. He must take them as he fields them.It is undoubtedly true that the character of lime depends largely on the nature of the parent limestone. A high-calcium lime cannot be manufactured from a dolomite, nor can a pure lime result from the calcination of an impure raw material. However, in the process of turning limestone into lime man is not entirely helpless in his control of quality. Even though a deposit is variable in character a single lime product of uniform quality may be produced by judicious quarrying. A single grade of product may not always be desired, the producer may wish to supply the needs of a variety of users each demanding U different grade or quality of lime such a series of graded products may be produced in part at least by modifying the quarry method. Thus, by changes in quarry practice a single product or a variety of products may be made. The latter problem will be considered at a later time, and the present paper devoted to the first named question' that of producing a single grade of lime from a deposit of variable rock,It is realized of course that uniformity in the product is influenced greatly by manufacturing processes such as calcining' hydrating' grinding or storage, but the present discussion is confined to the influence of raw materials only. In considering the various devices that may be employed it is realized that much remains to be learned, and it is hoped that many operators will contribute to the discussion as they have already done in connection with previous papers of this series."

May 1, 1923

By Byron. O. Pickard

"An Arizona mining company recently demonstrated a new use for the geophone by successfully locating leaks in compressed-air lines which were buried under from 1-1/2 to 2-1/2 feet of fine rock fill. The following information is abstracted from data sent to the Bureau of Mines by the superintendent of the mine.The company has two parallel main compressed-air lines, about one and one-half miles long, buried under an average of two feet of fine rock fill. One of the lines is a four-inch high-pressure (1000 pounds) main, and the other line a ten-inch low pressure (90 pounds) main. The two mains are separated by a 10 to 3C foot interval, and run from the compressor plant to the No. 2 shaft, where they are taken underground. A pump line is also buried in the immediate vicinity.Several leaks, not audible enough to be located, were developed in the Alms. Various =Abode were suggested that did not seem practicable to the management. Finally, the company obtained a Bureau of Mines' geophone and experimented with it. The first test& were conducted while the pumps were running, and while there was noise on the concrete pavement, all of Which caused so much vibration in the geophone that it was impossible to detect the leaks.The second attempt was made at the close of the day shift when the compressors were not operating and when the pumps could be shut down. The valves in the far end of the surface lines were closed, and the lines were pumped to full pressure (90 and 1,000 pounds respectively).Geophone readings were then taken at 7 or 8 foot intervals directly see the lines. Several leaks some very large in the high-pressure line were audible with the geophone at distances varying from 15 to 30 feet. A con-le leak in the low-pressure line was found at a distance of 10 feet. detecting the leaks, no difficulty was found in locating them exactly. ""At this time"", laid the superintendent of the mine, are unable to large a leak must be in order to be located under two feet of loose geophone. The fill we worked over was quite loose and dry and unfavorable for the work in question. However, we have no that the instrument is a valuable adjunct to our business""."

Aug 1, 1922

By Thomas Fraser

The Convertol process, recently developed in western Germany, is a new method of cleaning and dewatering coal-washery slurries. It is a modified bulk-oil process, in which a very small quantity of heavy oil is dispersed over the surfaces of the coal particles, followed by a screen centrifuge operation in which the water and dirt (clay, shale, and pyrite particles) are thrown out through the screen perforations and the clean coal particles are retained on the screen and discharged as a dewatered, clean coal product of 8- to l0-percent surface moisture. It is reported, also, that the process oil, all of which is retained in the clean-coal product, adds to the coking power of the coal and facilitates the production of briquets, reducing the proportions of binding material required.

Jan 1, 1953

By Michael D. Fenton

Detailed comprehensive assessment of the performance of Afghanistan's mineral industry during 1987 is virtually impossible, owing to the paucity of reliable published information. It was evident, however, that the level of civil disorder, now in its eighth year since the arrival of significant numbers of Soviet troops, was in actuality little removed from open civil war. Insurgents controlled substantial areas of the country and imperiled any industrial activity in many places. Assistance programs by the U.S.S.R. and other Eastern European nations were directed at developing the country's meager mineral industry, but the economy was generally viewed as chaotic. The inflation rate was somewhere between 20% and 30%; major food shortages contributed to the discontent of the population, and numerous villages were devastated by Soviet and Afghan Government campaigns to destroy the insurgents and cut their supply routes. Moreover, proposals by the Soviets and the Kabul Government aimed at reducing tensions with the rebels and scaling down the warfare seemingly were taken by the opposition as signs of weakening by the Soviet-backed Government, and rather than reducing aggressions, seemed to heighten insurrectionist activities. Efforts to entice the substantial number of Afghans who have fled to nearby areas of Pakistan and Iran to return to their country seemingly were failures, and indications near yearend that the Soviet Union might soon begin withdrawal of its occupation force of nearly 120,000 did little if any to reduce disorder.

Jan 1, 1989

By G. S. Rice, H. P. Greenwald

"Experience and experiment have goth shown that a cloud of coal-dust in air can be inflamed and an explosion developed only when a certain minimum concentration of the dust in air has been equaled or exceeded. Those who have had experience in the handling of coal know that dust is frequently present in the air and may be of sufficient density to obscure an ordinary electric light at a distance of 40 or 50 feet; yet flames may be, and times without number have been, introduced into such clouds, when no additional coal-dust has been stirred up, with no effect other than the burning of the dust particles which actually enter flame. Evidently the density of the dust cloud is insufficient to give self-supporting combustion.The minimum amount of dust in air required to give a spreading flame will vary with a number of factors such as the composition of the dust and its size. This amount in a unit space may be considered analogous to the lower limit of inflammability of fire damp (methane) in air, although the variation in limit of explosibility of gas is small even when conditions of the experiment are altered. In large-scale determinations of the lower limit of inflammability of coal-dust there is no certain method by which a sample of the dust cloud can be snatched and its density determined. It is necessary to produce the best possible dust cloud from a known weight of dust, in a known volume and assume - probably with considerable error - that the dust cloud is reasonably uniform. The dust cloud must be formed and the source of ignition applied to it simultaneously; this is generally accomplished by the use of blow-out shots of black blasting powder, dynamite, or similar explosive so prepared as to blow out like a cannon shot, or by a gas explosion. The more violence attending the source of ignition, the greater is the probability that all the dust is raised in a uniform cloud; and the greater the length or intensity of the flame, the greater are the chances of ignition. As a result one may obtain a variation in apparent minimum density with different sources of ignition. This difference is more apparent than real and must remain until devices for instantaneous sampling of dust clouds during explosions are perfected."

Aug 1, 1931

By E. H. Denny

The coal and metal mines of the United States furnish this country with a large part of the fuel and material necessary to support our industries and thus make possible the welfare and prosperity of our people and even the continuance of our present-day scale of civilization. Mining companies furnish material to industry with one general purpose in mind -- the making of a profit on their work. Efforts are being made successfully and continually to reduce operating costs, to increase production per man, and to perform work as far as possible mechanically and with more efficiency. These efforts are made primarily to reduce costs, to increase production, or to do both - in other words to make more profits or more certain profits. In the endeavor to reduce expense companies are considering more and more the factors which enter into costs of production, among them the factor of accidents and their cost. This paper endeavors to estimate the approximate cost of accidents to the mining industry in order to present the saving possible through accident reduction or elimination.

Jan 1, 1929

By H. C. Loesche

The problem of signaling to the hoisting engineer from the cage in a shaft mine has been given considerable thought and attention by engineers and mine operators seeking to Increase the safety and efficiency of hoisting. HISTORY R. L. Rutherford,3/ an employee of the Magma Copper Co., Superior Ariz., realizing the need for a simple and practical moving-cage signaling system, began a serious of experiments early in 1937, Available electrical moving-cage signal in operation at this date required that signal wires be installed in the shaft to make a simple, positive signal without wires, the first experiments used the pipe lines in the shaft for carrying the signal current, but these experiments were not successful.

Jan 1, 1945

Continuously separate mixture of non-magnetic materials (such as scrap, precious metals, or certain ores) at a reasonable cost. Approach Nonmagnetic materials of different densities are rapidly float/sink separated by an augmented lifting force produced In a magnetic fluid (liquid) by the effect of an external magnetic field. The magnetic fluid is a colloidal suspension of magnetite In kerosene, prepared by a low-cost process. How It Works Separation is accomplished in an open trough filled with magnetic fluid. A magnetic field is established in the fluid, by energizing an electromagnet having poles on each side of the trough. Due to the design of the magnet poles and air gaps, the magnetic field is strongest at the bottom, about 10,000 oersteds, and uniformly decreases in strength to about 2,000 oersteds at the top of the fluid. Therefore, the magnetic field gradient increases with depth. The magnetic force attracts the entire separation medium (magnetic fluid) creating a reaction force of equal magnitude and acting in the opposite direction. This reaction created within a magnetic fluid/magnetic field combination is called a magnetic levitation force. It increases with the field strength. In this case because the magnetic field is strongest at the bottom of the trough, the magnetic levitation force will quickly float lighter material while heavier material sinks.

Jan 1, 1980

By Raymond M. Kacmar

This report presents the Bureau of Mines research on the hardware reliability prediction for two Bureau monitoring projects. The basic concepts of reliability predictions are introduced along with the reliability models and assumptions used for this particular evaluation. The results of the reliability predictions are for ground-fixed and naval-sheltered environments.

Jan 1, 1986

By R. R. Wells

This report summarizes the results of laboratory investigations by the Alaska Mining Experiment Station, Juneau, to determine the practicability of treating cinnabar-stibnite ore by bulk flotation and controlled-atmosphere roasting of the concentrate. Ore from the Red Devil mine near Sleetmute, Alaska, was selected for testing; it is typical of ores widely distributed throughout the Kuskokwim River Basin. The material, consisting of stibnite and cinnabar in ankerite, dolomite, and quartz, assayed 1.55 percent Hg and 2.87 percent Sb. Continuous treatment of the ore in a laboratory flotation circuit recovered 95.7 percent of the mercury and 82.6 percent of the antimony in a concentrate that assayed 20.4 percent Hg and 34.6 percent Sb.

Jan 1, 1958

By H. H. Schrenk

[A calorimetric method3/ for the determination of benzene in amounts as low as 0.001 m has been developed recently at the U.S. Bureau of Mines Pittsburgh Experiment Station by the authors, with the assistance of chemical personnel from the Allegheny County (Pa.) Relief Works Division. The method is based on the direct nitration of either liquid or gas - phase benzene, followed by neutralization, extraction with butanone, and final treatment with sodium hydroxide which produces a violet color. The color is matched with color standards of known values. Although the method is adaptable to many conditions the primary objective was a procedure that would be suitable for hygienic investigations.]

Jan 1, 1935

By Donald H. Mullen, Walter R. Storms

"INTRODUCTION The Copper Flat area of the Central mining district, Grant County, N. Mex., has been visited by numerous engineers 4/ of the Bureau of Mines and geologists 5/ of the Federal Geological Survey. In December 1944 the Bureau. 6/ proposed that geophysical work be done in that area in order to locate favorable sites for future company exploratory and development work. This geo-physical work was begun early in 1945 but never fully completed because of insufficient funds. The engineers who made the survey recommended that more work be done, especially to locate the bottom of the Copper Flat laccolith by resistivity-depth surveys. All known minable zinc-lead ore bodies had been found above this laccolith in the Copper Flat mine, but it was thought that other minable ore deposits should occur in favorable limestones beneath it. The geophysicists also recommended core drilling beneath the laccolith.In the summer of 1946, following some mapping by S. G. Lasky of the Federal Geological Survey, funds were appropriated for a Bureau of Mines project in the Copper Flat area. The project was completed in June 1947. 8/"

Apr 1, 1948

By W. C. Hudson

"Sillimanite, kyanite, and andalusite are aluminum silicates having the same chemical composition (Al2Si05) and are used in the ceramic industry for the manufacture of high-grade refractories. ""Natural sillimanite with added corundum or other alumina to just short of mullite 2SiO2) proportions is unequalled for jobs where strength at high temperatures, resistance to spalling, and resistance to slagging by acid slags is desired. High-grade porcelain ware also requires these minerals.""At the same cost, sillimanite would be preferred for most uses, but the lack of any large source of sillimanite has given economic preference to kyanite or andalusite for special refractories and high-grade porcelain ware.""3/The possible economic value of the sillimanite schist in the piedmont Plateau was first recognized by Dr. L. L. Smith, of the University of South Carolina, who published an article in the Engineering and Mining Journal, August 1943, on an occurrence of sillimanite schist in South Carolina.The Bureau of Mines was interested in developing a large source of sillimanite to relieve the shortage of high-grade refractories, and initiated a project to locate the ore-bearing areas in Georgia and South Carolina and to develop the most favorable ones.Two hundred and seventy-eight outcrops of sillimanite-bearing schists were found by a Bureau of Mines engineer.4/ The schist occurs irregularly throughout a belt extending from Talbot County, Georgia; to Spartanburg County, South Carolina, about 220•miIes long and approximately 15 miles in maximum width. The Bureau drilled four areas of the more coarsely crystallized schist in Georgia and South Carolina:In its program of exploration of mineral deposits, the Bureau of Mines has as its primary objective the more effective utilization of our mineral resources to the end that they make the greatest possible contribution to national security and economy. It is the policy of the Bureau to publish the facts developed by each exploratory project as soon as practicable after its conclusion. The Mining Branch, Lowell B. Moon; chief; conducts preliminary examinations, performs the actual exploratory work; and prepares the final report. The Metallurgical Branch;.R. G. Knickerbocker; chief, analyzes samples and performs beneficiation tests. Both these branches are under the supervision of Dr. R. S. Dean, assistant director."

Sep 1, 1946

By Zsuzsanna Zborovszky

Investigation of the discharge duration power and current relation required for ignition. The current and power amplitude-discharge time curve was found to flatten out over 3 ms. It is concluded that discharges having at least 3 ms power maximum are required for reliable testing of the ignition limit for resistive circuits. Investigation of the effect of molten cathode on the discharge duration and igniting ability of the discharge. The surface tension of the liquid metal causes a very fast separation and consequently a much shorter discharge duration than the solid electrode would have. The minimum discharge voltage effect overrides the effects of the temperature of electrode, material, or atmosphere. Investigation of the effect of different surface layers on the discharge duration. Oxides and sulfates were found to give significantly longer duration than the "clean" metal itself in most cases. The lowest ignition current was obtained with CdS04 coatings. Ignition was obtained with 0.7A at 30V, which is below the corresponding minimum igniting current obtained from the BASEEFA curve for circuits containing Cd, Zn or Mg.

Jan 1, 1977

By W. M. Dressel

In producing feed for a lead blast furnace, concentrates analyzing 70 to 80 pct Pb are sintered to produce a physically acceptable low-sulfur product which contains only about 50 pct Pb. Mixtures of PbS with varying amounts of SiO2, CaO, Fe 20., and ZnS were heated in an oxidizing atmosphere at 1,000° C; the products were cooled and examined to determine the problems involved in producing sinter with substantially higher lead levels. Microscopic and electron microprobe studies of the above products as well as experimental and commercial sinters indicate that sinters consist essentially of lead silicates, lead-zinc silicate, calcium zinc silicate, and spinel (ferrite). Lead oxide and lead sulfate areas appear to result from insufficient mixing of the materials prior to sintering. The data give an insight into the process and show that sintering results from a complex interaction of all constituents and that sintering is not simply a matter of diluting the mixture to control the oxidation of lead sulfide.

Jan 1, 1975

By M. H. Kline

The Great Gossan Lead in Carroll County, Va., is one of the largest undeveloped sulfide ore bodies known in the eastern United States. It extends for 16.7 miles along the western slope of the Blue Ridge Mountains (fig. 1). The various known segments of the deposit, extending from the southwest end to the northeast, are: The Great Outburst or Iron Ridge segment, Chestnut Creek, Copperas Hill, Sarah Ellen, Wild Cat, Cranberry, Dalton Hill and offset segment to the south of the Cranberry, Little Reed Island, Little Vine, and the Betty Baker at the northeast end. All of these segments have been explored or mined to various extents in the past for the iron gossan and secondary copper ore. The Great Outburst or Iron Ridge segment is now being mined by the General Chemical Division of the Allied Chemical & Dye Corp. for the sulfur and iron content of the primary ore. These deposits are becoming increasingly of Interest as a. large potential source of iron and sulfur owing to their proximity to Birmingham, where the burned cinder sells at a premium, and to the acid markets of the region.

Jan 1, 1949

By A. W. Fahrenwald

The logic leading to the development of the experiments in this paper already has been stated in Part I,3 but is briefly as follows: The results of the batch-grind experiments in which time of "grind" and fineness of finished product were the variables, strongly indicated (1) that batch grinding involving a single grind could not be operated under any condition to give maximum mill efficiency, (2) that the, sieve analysis of the feed charge in the mill materially affected the efficiency of the mill, and (3) that the percentage of finished product in the mill is a vital factor in ball-mill efficiency. A laboratory closed-circuit grind technic designed to simulate present closed-circuit grinding suggested itself, in which: a ball mill and a classifier constitute the grinding unit. The features of the closed-circuit grinding system are: (1) Short large diameter mills, (3) rapid flow of pulp through the mill, (3) continuous automatic removal of finished product from the system, and (4) high circulating loads. The high circulating load is a result if the short length of the Mill - that is, of the time the charge remains in the mill - and the small percentage of finished material produced during each circuit of the feed through the mill.

Jan 1, 1930

By W. E. Wallace, V. Robinson, M. F. Keane, V. Vallyathan

"An in vitro study of the biologic responses of surface-modified and native silica and kaolin was made to provide comparative information on the supression of cytotoxicity by pulmonary surfactant. The release of alveolar macrophage cytoplasmic enzyme, lactate dehydrogenase (IDH), and lysosomal enzymes B-N-acetylglocosaminidase (B-NAG) and B-ghucuronidase (B-GLUC) and sheep blood-cell hemolysis were moni¬tored as indicators of cell membrane damage and cytutoxicity. Surface modification of silica and kaolin with dipalmitoyl lecithin (UPI) resulted in complete abrogation of cytotoxicity of both minerals. These findings indicate that surface modification of minerals with different adsorption properties by pulmonary surfactant generally lessens their prompt adverse effects.INTRODUCTIONAcute and chronic silicosis are well-characterized clinical and pathologic entities resulting from the inhalation of crystalline silica (Morgan and Seaton, 1984). Kaolin, a layered aluminosilicate clay frequently mined and used in manufacturing, contains tetrahedral silica alternately layered with alumina octahedra. Kaolin is relatively .inert biologically, and distinctly greater pulmonary burdens are seen in patients with kaolinosis than are seen in patients with silicosis. Crystalline siliea (quartz) induces a significantly greater degree of fibrosis in exposed animals in vivo than does kaolin (Hamilton and Hardy, 1974; Parkes, 1982; Hunter, 1976; Sheers, 1964; Warraki and t-lerant, 1963; Lynch and Mciver, 1954; Lapenas et al., 1984).This difference in pulmonary disease associated with the two types of dust is not reflected by in vitro cytotoxicity as Jetermined by pulmonary macrophage bioassays or erythrocyte hemolysis. Cytotoxicity studies using crystalline silica and kaolin of similar size fractions show comparable bioassay response on a mass basis. These cellular bioassays, therefore, do not correlate with the relative in vivo pathogenicity of silicates."

Jun 1, 1988

By D. B. McGilvra

This paper, describing the mining practices and methods at the Black Rock mine, is one of a series of similar papers on mining methods in the various mines of the United States being prepared by the Bureau of Mines. The Black Rock mine is located in the northeast corner of the Butte district, about 3 miles from the center of the town of Butte, and is owned and operated by the Butte & Superior Mining Co.

Jan 1, 1930