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By Alvin Kaufman

Geothermal plants are competitive with conventional units. A geothermal plant can produce electric energy for 6.70 mills per kwhr, compared with 6.96 mills for coal, 6.74 mills for oil, and 7.04 mills for gas. These costs include fixed and variable charges. Potential for geothermal power exists in the Western United States, Alaska, and possibly Hawaii. Assuming that the current downward trend in cost per kilowatt of coal will cease and that the relative cost of gas and oil, already trending upward, may rise considerably more, geothermal energy will be utilized where available, in producing electric energy. It will be used in California first because it is directly competitive with gas-and oil-fired installations there. A long-term appraisal is difficult because little is known about the sources of geothermal power and the electric generating capacity which the steam fields will support. However, a market for geothermal steam-generated electricity exists within the Western States.

Jan 1, 1964

By W. S. Landers

This bulletin is a detailed study of low-temperature, entrained-bed carbonization of a Texas lignite. The lignite studied was from the Sandow strip mine and is representative of the Rockdale formation of the Wilcox formational group. Carbonization was conducted in a continuous entrained-bed reactor at several temperatures in the 8801 to 1,52°C F range, and at air-coal ratios it the 0 to 10.30 scf/lb range (moisture- and ash-free basis). Carbonization rates ranged from 97.1 to 410.0 lb/hr (as-received basis), At the higher air-to-coal ratios employed, all or most of the carbonization heat was provided by internal combustion with air in the reactor. At the lower air-to-coal ratios, parts of the heat for carbonization was supplied externally. It was demonstrated that the entrained-bed carbonization of lignite is a complex reaction and that several variables, of which carbonization temperature, air-to-lignite ratio, and the average size of lignite are important, act together to influence both the carbonization yields and the properties of the resultant products, Process variables established by pant tests were used to design the industrial scale carbonizer operated at Rockdale, Texas, by the Texas Power & Light Company as agents for the Aluminum Company of America. Properties of the carbonization product obtained from the industrial scale reactor were essentially the same as those obtained from the pilot plant reactor operated under the same conditions.

Jan 1, 1968

By A. B. Needham

This report describes the exploration work done in 1941 in connection with the search for strategic minerals as authorized by the Strategic Materials Act approved by the President on June 7, 1939. It deals with the various manganese deposits and showings in the Tombstone mining district of Cochise County, Ariz. The exploration project comprised a study of the geology, mapping of the areas, and exploration of various mines and deposits by sampling old drifts, crosscuts, and scopes, supplemented by diamond drilling from underground stations. The Federal Government's manganese-purchasing programs have revived interest in occurrences such as the scattered deposits near Tombstone. Because of this, the Bureau of Mines project report on the Tombstone district, prepared originally in 1941 but not published, has been revised and now is being made public.

Jan 1, 1956

By H. E. Powell

Basic data were recorded on the decompositions that take place during thermal decomposition of siderite (FeC03). Both the naturally occurring and a synthetically prepared mineral were studied by differential thermal, thermo-gravimetric, X-ray-diffraction, and chemical (including gas) analyses. Thermal decomposition was studied in the media of dry air, moist air, dry carbon dioxide, dry helium, and dry carbon monoxide and at atmospheric and at reduced pressures. Results showed the thermal decomposition of FeC03 to be an extremely complex process, dependent on environmental factors and side reactions that cannot now be completely controlled. Therefore, full understanding of the reaction involved must depend on additional research with advanced evaluation techniques.

Jan 1, 1965

By Thomas M. Nasiatka

This report briefly describes the present state of the art and the technological highlights of tunneling from its inception to the present. The discussion is concerned primarily with tunnels driven through relatively competent rock for mine development and various civil purposes. In addition to pinpointing the major technological breakthroughs in tunneling, this report indicates their general effect on the speed of tunneling. The tunneling speeds are based upon data from approximately 80 tunnels listed in the appendix. These data include length; cross section shape and dimension; type of rock; tunneling method; method of breaking, loading, and transporting the rock; average linear progress rate; and cost in values during the period of construction. Most of the tunnels described have diameters of 15 to 30 feet.

Jan 1, 1968

By D. Harrington

The fiscal year which ended June 30, 1932, although one of acute financial de ression was, nevertheless, one of distinct encouragement to those who have long struggled against the much too prevalent occurrence of accidents in coal mines, especially of coal mine fire and explosion dis- asters, both of which are now known to be readily preventable. Table 1 summarizes some important information about explosions in the United States coalies for the fiscal year which ended June 30, 1932, insofar as such information is available to the safety division of the United States Bureau of Mines, the personnel of which are under instruction to get in touch with and report on all mine explosions in their respective districts, including not only those occurrences with loss of life but also those in which for- tunately no lives, are affected. Table 1 gives data on 33 ignitions in 10 States with a total of 87 deaths for the year; the number of ignitions (33) is considerably groater than the number (26) for the previous fiscal year, and is exactly the aver- age number for the past four fiscal years; the mumber killed in the 33 ignitions (57) is materially lower than that (217) for the preceding fiscal year or the average (150) for the past four fiscal years. The States with the greatest number of deaths from explosions in the fiscal year ending June 30, 1932, were Virginia; 54; West Virginia, 11; Pennsylvania, 7 (6 being in anthracite mines); Alabama and Colorado, 4 each; Illinois and Kentucky, 3 each; and Maryland, 1. The greatest number of ignitions listod wes that for West Virginia, 7; then came Pennsylvania with 6 (2 being in anthracite mines); Alabama with 5; Colorado, Illinois, Tennessee and Virginia, 3 each; and California, Kentucky, and Maryland, 1 each. The 1931-32 record as given in Table 1 includes several States which were not listed in the previous year: Colorado, Kentucky, Maryland, Tennessee,

Jan 1, 1933

By L. A. Morley

Volume IV of the final report examines the problem of indirect contact of overhead high-voltage power lines by mining personnel. This refers to the contact of energized lines by workers through some intermediate conductor such as a metallic tool or a piece of high-reaching mobile equipment, thus the term "indirect contact." The shock hazard presented by such contact has been a major cause of electrical fatalities associated with mining operations. The report volume is divided into three major areas. The first gives a general background of overhead lines, basic characteristics, and associated hazards, and continues to describe presently used techniques and devices which attempt to alleviate the contact problem. The second area narrows the discussion to the mining industry by presenting a detailed analysis of 39 overhead-line contact accidents in mining since 1970. The third major section uses the information from the first two areas to formulate recommendations to prevent these accidents and subsequent electrocutions at mining operations.

Jan 1, 1982

By R. E. Campbell

Uranium metal of improved purity was prepared by electrorefining commercial magnesium-reduced uranium in a molten sodium chloride-uranium trichloride electrolyte. The best operating conditions for the preparation of refined metal were established as follows: an electrolyte containing 8.7 to 13.3 weight-percent uranium; initial cathode current densities from 300 to 1,500 amp/sq ft; and a molten salt temperature of 860° C. Ingots produced from electrorefined uranium crystals prepared with these operating conditions were substantially free of metallic impurities. The only impurities in the refined and consolidated metal were present in low or undetectable amounts.

Jan 1, 1965

By John C. Edwards

Standard smoldering and flaming combustion tests using smaIl coal samples have been developed by the U.S. Bureau of Mines as a method to evaluate the response of a smoke detector. The tests are con-ducted using a standard smoke box designed and constructed according to Underwriters Laboratories. The tests provide a standard, easily reproducible smoke characteristic for smoldering and flaming coal combustion, based upon a comparison of the smoke optical density and the response of a standard ionization chamber to the smoke. With these standard tests, the range of threshold limits for the response of a smoke detector and the detector's reliability can be evaluated for nearly identical smoke visibility and smoke physical characteristics. The detector's threshold response limits and reliability need to be well defined prior to the instrument's use as part of a mine fire warning system for improved mine safety.

Jan 1, 2010

By Maria I. De Rosa

Table 19 and figure 7 show the number of fires and fire injuries for surface metal/nonmetal mines by state during 1990-2001. Table 19 also shows the injury risk rates, employees' working hours, and lost workdays. A total of 79 fires occurred in 16 states during 1990-2001 for these mines. Forty-five of the fires caused 44 injuries and 2 fatalities (including 9 fires and 7 injuries involving contractors). The yearly average was 6.6 fires and 3.7 injuries. Sixty-five fires with 31 injuries and 2 fatalities occurred at metal mines, and 14 fires with 13 injuries occurred at nonmetal mines. The Ewhr value was 546 x 106 hr (In = 0.016), and the LWD value was 13,134. Nevada and Arizona had the most fires (19 fires, 10 injuries, and 1 fatality; and 19 fires and 11 injuries, respectively). They were followed by Minnesota (11 fires, 4 injuries, and 1 fatality) and Alaska (6 fires and 4 injuries). Of these states, Alaska had the highest injury risk rate value (In = 0.079). Table 20, partly illustrated in figure 8, shows the number of fires, fire injuries, fire fatalities, risk rates, employees' working hours, and lost workdays by time period. The number of fires increased during the second period, then decreased during most of the remaining periods. The number of fire injuries decreased during most of the periods (a small increase is seen during the last period), accompanied by a decline in employees' working hours during most of the periods (a small increase is seen during the third and fourth periods). The In values follow patterns similar to those shown by the number of fire injuries. Tables 21-26 show the number of fires by ignition source, method of detection and suppression, equipment involved, location, and burning material by time period. Figure 9 shows the major variables related to fires for 1990-2001. Table 27 shows the number of fire injuries per number of fires causing injuries and total fires by year, ignition source, equipment involved, and location.

Jan 1, 2004

By P. G. Barnard

The Bureau of Mines investigated the effects of various additions of rare-earth metals or rare-earth oxides on the mechanical properties of cast and wrought plain-carbon steels. Rare-earth metals, as misch metal, were added to medium-carbon steel in amounts to 0.70 weight-percent; rare-earth oxides, as a commercial mixture, were added in amounts to 1.50 weight-percent. The melting and casting of conditioned steels were done in a vacuum-induction furnace, to avoid formation of oxides from the melting atmosphere and to pro-vide better control over chemical composition. At room temperature, data for tensile strength, yield strength, elongation, and hardness of cast and wrought steels were obtained by standard testing equipment and procedures. Impact tests were conducted on as-cast steel specimens. The greatest amount of tensile ductility and impact strength was obtained in as-cast steel with 0.50 to 0.70 weight-percent misch metal additions. No significant improvement on mechanical properties was indicated in wrought steels containing rare-earth metal additions in the range from 0.10 to 0.70 weight-percent. In general, the rare-earth oxide additions up to 1.50 weight-percent had little effect on the tensile properties of steel in the cast, wrought and annealed, or wrought and normalized condition.

Jan 1, 1967

By R. V. Ramani, R. Stefanko, G. W. Luxbacher

C THRM 1 C CALCULATION OF MINE HEAD LOSSES FROM ALTIMETER SURVEY DATA TURN 2 C PENNSYLVANIA STATE UNIVERSITY - MINERAL ENGINEERING DEPARTMENT THRM 3 C THRM 4 C THRM 5 C THIS PROGRAM CALCULATES PRESSURE LOSSES USING THERMODYNAMIC RELATION- THRM 6 C SHIPS BASED ON POLYTROPIC FLOW BETWEEN STATIONS. FOR REFERENCE SEE THRM 7 C "A NEW TREATMENT OF MINE BAROMETER SURVEYS" BY M. J. MCPHERSON IN THRM 8 C 'THE MINING ENGINEER' NO. 109, VOL. 129, P 23. THRM 9 C THRM 10 C THRM 11 C THRM 12 C IDENTIFICATION OF ARRAYS THRM 13 C NOTE THE PROGRAM HAS BEEN DIMENTIONED FOR FOURTY (40) DATA POINTS THRM 14 C BASEC(6;2) BASE INSTRUMENT TEMPERATURE CORRECTIONS THRM 15 C TRAVC(6,2) TRAVERSE INSTRUMENT TEMPERATURE CORRECTIONS THRM 16 C BASER(I) BASE INSTRUMENT READING THRM 17 C TRAVR(I) TRAVERSE INSTRUMENT READING THRM 18 C TDRY(I) DRY BULB TEMPERATURE AT TRAVERSE STATION THRM 19 C TWET(I) WET BULB TEMPERATURE AT TRAVERSE STATION THRM 20 C ELEV(I) ELEVATION AT TRAVERSE STATION THRM 21 C VEL(I) AIR VELOCITY AT TRAVERSE STATION THRM 22 C TBDRY(I) DRY BULD TEMPERATURE AT BASE STATION THRM 23 C BASC(I) BASE READING CORRECTED FOR INSTRUMENT TEMPERATURE THRM 24 C TRAV(I) TRAVERSE READING CORRECTED FOR INSTRUMENT TEMPERATURE THRM 25 C BBASE(I) TEMPERATURE CORRECTED BASE READING IN BAROMETRIC THRM 26 C PRESSURE THRM 27 C BTRAV(I) TEMPERATURE CORRECTED TRAVERSE READING IN BAROMETRIC THRM 28 C PRESSURE THRM 29 C BTRAVS(I) BAROMETRIC TRAVERSE READING CORRECTED FOR ATMOSPHERIC THRM 30 C CHANGES THRM 31 C RELHUM(I) RELATIVE HUMIDITY THRM 32 C ASW(I) AIR SPECIFIC WEIGHT TURN 33 C R(I) GAS CONSTANT FOR MOIST AIR THRM 34 C STPRES(I) STATIC PRESSURE CHANCE BETWEEN STATIONS (I) AND (1-1) THRM 35 C TOPRES(I) TOTAL PRESSURE CHANCE BETWEEN STATIONS (I) AND (I-1) TURN 36

Jan 1, 1977

By Sean Gallagher

This report describes research by the Bureau of Mines on alternative materials-handling strategies for reducing the costs and incidence of back injuries in low-seam coal mines. Strategies recommended for redesigning materials-handling tasks include elimination of tasks, mechanization of tasks, and matching lifting tasks to the physical capabilities of underground miners. The report also discusses other methods that can be used by management to reduce the costs associated with back injuries.

Jan 1, 1989

By Bertha R. Klahold

"In response to numerous inquiries regarding tests and analyses of minerals and related inorganic materials; Bureau of Mines Information Circular 6999, ""Laboratories That Make Fire Assays, Analyses, and Tests on Ores, Minerals, Metals and Other Inorganic Substances,"" by C. W. Davis and M. W. von Bernewitz, was published .in 1938 and revised in 1939 (I. C. 6999R). In this paper on analytical and testing laboratories, the original text has been rewritten and expanded, and a table has been added, in which are listed laboratories prepared to offer a number of special testing services in addition to ordinary assays and chemical analyses. The arrangement of laboratories on, a geographical basis has been maintained.This circular is compiled as a public service, and none of the laboratories listed herein is recommended over any other,These lists were compiled from questionnaires sent to organizations whose work is connected with mineral and metallurgical testing. The response in general was very satisfactory, and the author takes this opportunity to express her appreciation to the officers of the listed laboratories for their cooperation.Acknowledgment is also made of the valuable assistance of the members of the technical staff particularly Morris Slaving/ of the Eastern Experiment Station of the Bureau of Mines at College Park, Md., in the preparation of the questionnaire and technical descriptions.Many mineral samples are sent to government agencies in the National Capital with the request that they be assayed or chemically analyzed. It should be emphasized that there is no place in Washington D. C. where assays and quantitative analyses are made for the public b the Federal Government.Virtually all of the States maintain a bureau of mines, a geological survey, or some similar organization, frequently at the State University, where minerals found by residents of the State will be identified free of charge. Usually, a charge is made for assays. Specific tests, as on clays, are made by some of these offices.The Federal Bureau of Mines, although it attempts to avoid duplication of services rendered by State Bureaus, is always glad to give advice as to prospective markets. It does not compete with private assayers and chemists, but with respect to samples sent to its field laboratories, it does offer to identify them as far as this can be done by inspection and simple optical and chemical tests. This examination is usually sufficient to indicate whether the material has commercial value, or at least if the expense of an assay would be warranted. Except in connection with its own technical investigations, no assays or other special tests are made by the Bureau of Mines.The Federal Geological Survey and the National Museum also make simple tests of specimens as a public service. Neither of these bureaus nor the Bureau of Mines, however, can afford to render such services on long suites of specimens submitted by mineral dealers, well drillers, or others, when such work can be done regularly by commercial concerns."

Oct 1, 1949

By D. E. Redmon

Exploration of hidden mineral deposits becomes increasingly important as known ore reserves are depleted. The primary objective in any exploratory program is to obtain enough reliable information to evaluate accurately the potential of the mineral deposit. Constant improvement in equipment and technique has established drilling as one of the most valuable methods of exploration. This paper presents the results of studies of several drilling methods currently used in the search for uranium deposits in sedimentary formations from surface drill sites. Also presented is a description of drilling with wire-line equipment from an underground location in metamorphic rocks. The studies were conducted in the Colorado Plateau area and in northwestern New Mexico and Wyoming. Statements of a general nature pertain to conditions or situations existent in those areas.

Jan 1, 1960

By Donald W. Ross

Petroleum oils of widely different grades have long been clarified or decolorized by contact with fuller's earths. More recently, so-called activated clays have also been used for this purpose. Still more recently ouch clays have been used in the form of nodules termed "catalytic pellets." Clays of varied appearance and from different localities possess the desired bleaching qualities, but evaluation of such clays, so useful to the oil industry, has not been simple. Previous methods of identification and evaluation have largely followed procedures of production methods and were not primarily based upon the fundamental properties of the clays. Thus) a false assumption has grown up that) bleaching clays probably have no common properties on which a-method of comparison can be based. Fuller's earths and activated clays have a large absorptive capacity for the color constituents of petroleum and its products decolorizing is accomplished by bringing the oil into intimate contact with the clay and later separating the decolorized oil from the clay with its load of absorbed coloring matter. Former practice in absorbing "color" was to use the clay as granules or In' powdered form. More recent practice is to use clay pellets that are more abrasion-resistant than the granules. The oil is either filtered through a bed of clay, percolation method, or agitated on contact with the clay, contact method. Viscous oils are decolorized at an elevated temperature, so that their viscosity is lowered to the point at which thorough contact with the clay is insured. Nonhumidifying, nonoxidizing gas, such as dry steam or dry nitrogen, is used to seal such hot oil masses from the atmosphere.

Jan 1, 1948

By Ronald S. Conti

The Bureau of Mines conducted a comprehensive laboratory study of the thermal ignitability of various carbonaceous dust clouds with particular emphasis on various ranks of coal dust. The tests were conducted using a new 1.2-L furnace. Autoignition temperatures of dust clouds were obtained as a function of coal volatility and particle size. Dust particles and gas samples were collected by a rapid-sampling system in order to study the reactions involved in preignition and postignition processes. The autoignition temperatures measured in the new 1.2-L furnace were significantly lower and therefore more conservative than those measured previously in the Godbert-Greenwald furnace. The combined effects of thermal and electrical ignition of dust clouds were also studied in the 1.2-L furnace using electrical discharges of varying energies at ambient and elevated temperatures. The minimum spark energy necessary to ignite a dust cloud decreased significantly as the temperature of the dust cloud increased.

Jan 1, 1983

By Chas. F. Jackson

This paper is published as a progress report for the first half of 1929 on the study of wining methods and costs in the Eastern and Central States. Data obtained from 25 mines using open-stope methods are correlated and summarized. Some of these mines have been described in considerable detail in reports already published as Information Circulars. In addition to the published reports on individual mines, considerable data have been obtained from other mines which were visited and studied during the course of the investigation. Many of these mines will later be described in detail in separate papers, and when the field has been covered in this manner it is planned to issue a bulletin on open-stops methods of mining which will amplify the subject matter of the present paper. Definition of ?Open-Stops?. - The term "open-stopes" as employed by the Bureau of Mines is applied to all naturally supported stopes; that is, stopes in which the excavated ore is not replaced by support of an artificial nature other than preps or stulls and in which the ore or (and) capping are not caved during the active life of the stopes.

Jan 1, 1931

By H. C. Carpenter

This literature study of methods for desulfurizing residual fuel oil was conducted by the Bureau of Mines at the request of the Department of Health, Education, and Welfare. The sulfur compounds in residual fuels are believed to consist chiefly of condensed thiophenes and other polycyclic sulfur compounds. Hydrodesulfurization appears to be the most promising method for desulfurizing these oils and is the only method applicable to all types of sulfur compounds. There are indications in the literature that hydrodesulfurization without hydrocracking of residual oils may require higher pressures than used in present desulfurization processes, but no cost data and little experimental data are available on the higher pressure operation. Literature proposals for hydrogenating residual oils and heavy crude oils are exclusively for hydrocracking the oils to lower boiling products with accompanying partial desulfurization of the residual fuel fraction. Costs of the hydrocracking operations appear the closest available to probable costs of hydrodesulfurizing the oils, and have been reported (in 1955 to 1957) as $500 to $840 investment cost per daily barrel of capacity, with total operating costs of 70 cents to $1.10 per barrel.

Jan 1, 1963

By H. C. Carpenter

This literature study of methods for desulfurizing residual fuel oil was conducted by the Bureau of Mines at the request of the Department of Health, Education, and Welfare. The sulfur compounds in residual fuels are believed to consist chiefly of condensed thiophenes and other polycyclic sulfur compounds. Hydrodesulfurization appears to be the most promising method for desulfurizing these oils and is the only method applicable to all types of sulfur compounds. There are indications in the literature that hydrodesulfurization without hydrocracking of residual oils may require higher pressures than used in present desulfurization processes, but no cost data and little experimental data are available on the higher pressure operation. Literature proposals for hydrogenating residual oils and heavy crude oils are exclusively for hydrocracking the oils to lower boiling products with accompanying partial desulfurization of the residual fuel fraction. Costs of the hydrocracking operations appear the closest available to probable costs of hydrodesulfurizing the oils, and have been reported (in 1955 to 1957) as $500 to $840 investment cost per daily barrel of capacity, with total operating costs of 70 cents to $1.10 per barrel.

Jan 1, 1963