Search Documents

By E. D. Palmes

A new type of personal sampler for quantitative estimation of atmospheric concentrations of contaminant gases was first reported from this laboratory in 1972. The sampler requires no pumps or flow regulators and employs instead the motion of the gas molecules them-selves to furnish the power for sampling. Under this grant, work was completed on development of a kit for the field determination of both NO2 and NO. Detailed instructions for the preparation of the samplers and the use of the kit was supplied to the Technical Project Officer. Attempts were made to adapt the same type of sampler to the measurement of SO2 and CO. Both gas chromatographic and turbidimetric procedures for the final estimation of the S02 proved to be unsatisfactory. For CO no reagent was found which would react sufficiently rapidly with this gas to utilize the essential feature of the diffusion sampler, the maintenance of a diffusion gradient which is at least approximately numerically equal to the ambient concentration. A number of publications on use of the NO2 sampler, both at occupational and community air pollution levels, have resulted from this work.

Jan 1, 1979

By Harvey Patashnick

Current state-of-the-art microweighing technology represented by the Tapered Element Oscillating Microbalance (TEOM) is utilized as the basis for a new generation of Personal Dust Exposure Monitors (PDEM's). Two design configurations are presented. The first is an end-of-shift analysis system which uses small TEOM-PDEM cannisters that replace the filter cartridges in the current PDEM system. All other components carried by the miner (cyclone preseparator and pump) are the same. After the shift the TEOM cannister is plugged into an interface box which enables a minicomputer to automatically identify the unit, determine the dust mass increase during the shift, compute the shift average dust mass concentration, and print out and/or store the data. The second design is a real-time TEOM-PDEM system which is capable of operation over a 10-hour shift and on demand display real-time dust concentration level, time weighted average, and shift average concentration. As a result of the design study, a prototype end-of-shift analysis system was fabricated and delivered to the Bureau of Mines. A description of this system which consists of six TEOM cannisters, interface electronics and minicomputer is given. The system represents a significant advance in the dust monitoring program in terms or accuracy and automation.

Jan 1, 1983

By Randolph E. Scheffel, David C. Fitch, David K. Hogan, Mark R. Welsh

In Oct. 1981, Ranchers Exploration and Development Corp. began producing silver bullion from the Escalante mine and mill complex, located in southwestern Utah. Current in-place reserves are estimated at 2.42 Mt (2.67 million st) of ore, containing about 936 t (33 million oz) of silver at an average grade of 428.5 g/t (12.5 oz/st). The vein-type deposit is being mined underground through a decline that is currently 864 m (2,835 ft) in length, but will ultimately be at least 1.5 km (5,100 ft) long. The mine is completely mechanized with rubber-tired equipment, and is producing 680 t/d (750 stpd) of ore, five days a week, or 177 kt/a (195,000 stpy). Additional capacity is available. The cyanide leach mill and associated refinery are presently producing 4.35 t/month (140,000 oz/month) of silver bullion-an an¬nual rate of about 52.25 t (1.68 million oz). With minor modifications, the mill can produce up to about 70 t/a (2.25 million oz/year), and expansion is currently underway. History The Escalante property is located 68 km (42 miles) west of Cedar City, UT, on the west side of the Escalante Valley, where the vein forms a gentle ridge in an area of low, rolling hills. For years, the vein has been the object of considerable exploration, but never became more than a sporadic producer, primarily due to low silver prices. Heber Holt of Enterprise, UT, staked the original four claims in 1896; they were patented in 1910. During the next 48 years, limited exploration and mining activity was conducted on the property. Systematic evaluation and development did not, however, begin until March 1958, when Samuel S. Arentz, a prominent mining engineer and consultant, formed several joint ventures with mining and oil companies that conducted drilling, drifting, mining, and water drawdown tests on the property. However, it remained uneconomic, principally because of low silver prices and costs for pumping large flows of underground water. In 1975, Ranchers obtained an option on the property and in 1979 began a drilling program. As of May 1982, the company had drilled 70 core holes, bringing the number of exploratory holes drilled on the property to 138. Test mining began in 1979 as silver prices increased, and full mine development began in 1980. Mill construction began in Sept. 1980, and on Aug 29, 1981, the first ore was fed to the mill.

Jan 9, 1982

By L Yang, L Chen, E Hu, D Tang

Online monitoring of particles cumulative percent passing (PCPP) for a target size at hydrocyclone overflow, compared with traditional offline methods, provides PCPP feedback in real time, and is advantageous in enabling energy-efficient comminution, increasing downstream flotation efficiency, and improving upstream resource knowledge. However, existing online approaches are generally costly and bespoke, and some are sensitive to operational changes. Therefore, this study proposes a new low-cost alternative based on accelerometer measurement for online PCPP monitoring in the overflow of hydrocyclones and provides a preliminary experimental investigation under dry condition. The proposed method uses a sensing probe inserted into the overflow pipe of a hydrocyclone to receive particle impact from the incoming slurry, with accelerometers attached to the probe and mounting frame outside the pipe for particle-probe impact detection. As a preliminary investigation before studying particle-probe impact events in slurry, tests under dry condition without fluids were conducted using dry sand particles in free fall from a fixed height. Accelerometer measurements are analysed in both time and frequency domains through root-mean-square (RMS) and fast Fourier transform (FFT). Results show that accelerometer measurements are useful in estimating mass flow rates, which are correlated to the accelerometer output amplitude RMS values in time domain, in a non-linear mapping. Different particle size classes can be identified by examining the accelerometer output amplitude at a known mass flow rate. Different particle size classes feature their distinct signature frequencies (SFs) that can be examined via FFT and the SF is found to be independent of the mass flow rate. The results imply that any PCPP changes can be detected by the change in the accelerometer output amplitude as well as a shift in SF, which demonstrates the effectiveness of using accelerometers to gauge changes in PCPP. Based on the current findings in dry condition, future work will investigate particle-probe impact events in slurry.

Aug 24, 2022

By S. Al-Thyabat

In this work, the floatability of Jordanian phosphate slime (-38 µm) was evaluated in a batch column flotation cell, 100 cm high and 5 cm inner diameter. Flotation was conducted using sodium oleate as a collector and methyl isobutyl carbinol (MIBC) as frother. Rougher flotation yielded concentrate assaying 29.19% P2O5 with 90.29% recovery at the following flotation parameters: 2.6 cm/s superficial gas velocity, 20 ppm frother dosage, 0.205 mM collector concentration and 40% weight solids. It was also found that conditioning with the same collector dosage but with a different solids weight percent gave different flotation results. However, pulp collector concentration was the key operating parameter; increasing collector dosage at the same solids weight percent decreased flotation recovery by 3%, while increasing solids weight percent at the same collector dosage increased phosphate recovery by 18%.

Jan 1, 2011

By L. P. James, W. W. Atkinson

Utah has produced about one billion troy oz. (31.7M tonnes) of silver, more than any U.S. state except Idaho. Several very high grade ore systems, now closed, occur within large polymetallic limestone-hosted districts related to plutonic complexes. These Utah mines fed several major lead smelters for nearly a century. Interaction of magmatic chloride-rich fluids with carbonate rocks localized significant bonanzas within these districts. A low sulfidation state was produced in the fluids by their passage through limestones. The Bingham porphyry mine has also yielded more byproduct silver than other porphyry copper-gold systems. Away from exposed intrusive rocks, some large silver-only systems occur in Mesozoic sandstone and in caldera-related veins in volcano sedimentary rocks. Thick permeable latest-Proterozoic basement meta quartzite sequences present beneath western Utah may have been important, as perhaps they were in the Coeur d’Alene district of Idaho, in providing chloride and silver-rich ore fluids. However, it is clear that specific Tertiary magmatic events played an essential role in the evolution of the Utah silver-rich metallogenic province. The largest silver districts in the state are genetically related to porphyritic plutonic rocks.

Jan 1, 2000

By Bruce I. Thomas

Reconnaissance studies of beach sands along the eastern part of the Gulf of Alaska were conducted by the Bureau of Mines to determine if any of these coastal areas warranted investigations as possible sources of valuable minerals. Because of difficult access and limited transportation facilities only a minimum of sampling, surveying, and camping equipment is utilized to obtain spot samples from key areas as well as information indicating the location, size, and character of the deposits. Such data were obtained from beaches located along approximately 247 miles of the Gulf of Alaska coastline during parts of the 1957 and 1958 field seasons. A total of 201 3-inch-diameter auger holes, spaced roughly at 1 mile intervals, were bored by hand methods to depths ranging from 3 feet to 27 feet; also 33 shovel samples were collected from selected localities. Samples were reduced to a rough concentrate in the field by panning; the rough concentrates were shipped to the Bureau of Mines laboratory at Juneau for further concentration and for petrographic and chemical analyses. Particular attention was given to the heavy-mineral content of the concentrates, although the types and relative amounts of rock-forming minerals were also determined. The reconnaissance indicated that, generally, the valuable mineral content of the beach deposits was too low to be of further interest except in the vicinity of Yakutat and Lituya Bays where erratic but possibly significant concentrations of magnetite and/or ilmenite were found. At Yakutat, about 20 miles of beachline extending southeasterly from Ocean Cape, yielded samplas containing from 1 pound to over 300 pounds of iron and from a trace to over 100 pounds of titanium dioxide (TiO2) per cubic yard of beach material. However, the higher grade samples represented local concentrations of minor importance. The general tenor of the Yakutat beach, as indicated by the airthmetical average of 27 auger-hole samples, is about 35 pounds of iron and 20.5 pounds of titanium dioxide per cubic yard of beach material. Ilmenite is the predominant heavy mineral of the beach deposits in the vicinity of Lituya Bay, but it was found in concentrations only in limited areas near the

Jan 1, 1962

1.0 Control House (DWG. NO. 56-401-G) - 1.1 Physical Description The Control House is a single story, 2728 square foot building with an adjacent transformer yard. A four foot overhang provides shade protection for the walls. The building is heated and air conditioned. The HVAC System has an elevated outside air intake and provides a positive pressure environment within the structure in order to prevent the infiltration of heavier-than-air, noxious gases. The materials of construction are as follows: Structure : Light-Gage Metal Framing Exterior Walls :Outside - Preformed, Metal Siding :Inside - Insulated Metal Liner Panels Interior Partitions :Gypsum Board over Light-Gage Metal Framing Roof :Insulated, Preformed Metal Panels Ceilings :Mechanical & Electrical Rooms - Exposed underside of Roof Panels Control Room, Lunch Room, Toilets, Entry - Suspended Acoustical Lay-In Tile Floors :Mechanical & Electrical Rooms - Concrete Slab on Grade Control Room, Lunch Room, Toilets, Entry - Resilient Tile Exterior Doorsand Windows :Preformed Metal Panel Manufacturer's Standard Units

Jan 1, 1979

By Gary Choate

The work presented in this report represents the background activity which led to the fabrication and testing of a greenhorn and crowd limit switch system for electric shovels. The program began With a literature search and manufacturers product review to gather material as a basis for concept generation. Visits to three open pit mines provided information from operation and maintenance managers which was useful in preparing design concepts. These concepts were evaluated through laboratory tests and engineering analysis to select a final design concept. The resultant greenhorn is four separate shock absorbing pads each enclosed in a housing which bolts to the end of a dipper handle adaptor. The plungers impact against stops mounted to the saddle block. The crowd limit control is a nonmechanical device which senses the location of the dipper and makes appropriate commands to the crowd motor to insure against impacting the greenhorns. The electronic crowd limit control is redundant and indicates malfunction modes. The greenhorn prevents shovel damage in the unlikely event of impact.

Jan 1, 1983

Under contract from U. S. Bureau of Mines, Harza Engineering Company in cooperation with Eastern Associated Coal Corporation, conducted a ground control study of two mechanized longwall panels at the Federal Number 2 Mine. The mine is located in Northern West Virginia, and the coal is mined from the Pittsburgh Coal Seam. The prime objective of the study was to collect data which will aid in the proper selection of the longwall supports system and to control the entry caving problem. Instruments installed in the mine were borehole pressure cells, convergence recorders, roof sag recorders, horizontal roof strain indicators, differential floor movement systems, and lateral roof and floor movement systems. Instruments installed on the surface, above the instrumented longwall panels, consisted of slope indicator system, vertical bed settlement probe system and shear displacement detecting system. A comprehensive surface subsidence study was conducted in conjunction with the instrumentation. In addition to the instrumentation and monitoring, special tests were conducted to determine the bearing capacity of the roof and floor rocks, in situ modulus of coal, roof and floor rocks, and response of borehole pressure cells to ground stress. Cores of coal measure rocks were collected for the physical property tests. Face observations were made to detect various roof behavior parameters under the different jack setting pressures. This report essentially describes the instrumentation work, special tests and presents the data collected.

Jan 1, 1976

By Kenneth P. V. Lei

The Bureau of Mines investigated a silver-catalyzed oxidative procedure for leaching an arsenical copper sulfide concentrate containing 10 pct As and 32 pct Cu_ Currently, there are no environmentally safe means to treat arsenical copper concentrates in the United States. Leaching was conducted in a 2-L autoclave reactor. The effects of catalyst concentration, O2 pressure, temperature, and H2S04, Cu, As, and Fe concentrations in the leaching solution on extractions of metals from the concentrate were determined. The best leaching conditions for extracting 95 pet eu and As and less than 21 pct Fe were 260 g/L concentrate, 0.007 mol/L (1.0 g/L) AgCI, 3.0 mol/L (294 gIL) H2S04, 1000 C, 60 psig 02, and 6 h. Copper as CuS04-5H20 was recovered by crystallization from the pregnant solution. Arsenic, as AS203, was recovered from the copper mother liquor by solvent extraction, with tributyl phosphate, S02 reduction of As5+ to As3+ in the strip solution, and crystallization of the As3+. The silver catalyst was recovered by contacting the leached residue with a brine solution. A conceptual scheme is proposed for treating arsenical copper sulfide concentrates.

Jan 1, 1987

By R. A. Vik

The influence of thermal treatments on the grindability of low-grade hematitic iron ores from Michigan and Minnesota was examined in bench-scale tests. Treatment factors were roasting temperature, roasting atmosphere, and ore cooling conditions. Bond ball mill grindability and work indices were used as response indicators in evaluating the condition of the ore. Of the three treatment factors evaluated, roasting atmosphere, which brought about the con version of iron oxides to magnetite, had the most significant effect; roasting temperature had the next most important effect; and cooling condition had the least effect. Optimum grindability was obtained with reduced-quenched products of both ores at 650° C, near the alpha-beta phase transformation of quartz.

Jan 1, 1971

By H. Becke, D. Stolnitz, D. Flatley, W. Kern

Extensive solid solubilities of CdTe (zincblende-type struckre) and InTe (B37 type) in each of the rock salt-type compounds, PbTe and SnTe, have been observed. Partial phase diagrams have been determined by thermal analysis and X-ray metallography. The limiting mol fraction. X,, of the solute in the rock salt-type a phase and the corresponding eutectic temperatures, T,, are: (PbTe)l-x(CdTe)x: X,- 0.2, T, =866°C; (PbTe),-,(lnTe),: X, - 0.35, T, = 646"C; (SnTe),-,(CdTe),:X,- 0.11, T, = 784 "C; (SnTe),-,(lnTe),: X,-0.53, T, = 630°C. The lattice parameters of the a phase decrease linearly with X, even in (PbTe),-,(CdTe),, where a, (CdTe) = 6.481A > %(PbTe) = 6.459A. This is taken as proof that the cadmium atom enters an octahedral interstice of the tellurium atom sublattice; i.e., the formation of the a phase entails the direct replacement of lead by cadmium. The a, us X curve extrapolates to 6.16A at X = 1, in agreement with the value predicted for an ionic crystal of CdTe; it is also consistent with the reported lattice parameter It is well-established that the compositions of intrinsic semiconducting and semimetallic compounds conform to normal valence rules.1"5 The apparent exceptions can be explained by taking account of anion-anion covalences, as in CdSb, or of multiple cation valences, as in In Te.'This empirical generalization is the basis of the chemical approach to semiconductors2 by which the properties of an intrinsic semiconductor are rationalized in terms of the ionic-covalent bonds necessary to saturate the valence-electron complement of the anion sublattice. A fundamental shortcoming of this approach is its disregard of long-range crystal interactions. It cannot, accordingly, deal with the phenomenon of charge conduction except through the use of ad hoc postulates. As an example, a crystal of CdTe would, in the valence-bond picture: be described in terms of electron pairs, each with the same discrete energy, localized between every cadmium and tellurium atom. This is, of course, contrary to the Pauli of the high-pressure rock-salt form of CdTe, corrected for decompression from 36 kbar. The free energy of formation of the a phase of pure CdTe at room temperature is calculated from the phase diagram to be +10 kcal per g-atom, in accmd with the value calculated from the transformation pressure. The standard enthalpy is +13 kcal per g-atom, and the standard entropy is +9 eu. The latter value implies the formation of extra classical particles, such as vacancies, interstitials, or nondegenerate charge carriers, but these alternatives are not consistent with the semiconducting properties and the densities of the a phase. The extrapolated values of the lattice parameters of (PbTe),-,(lnTe), and Spectively, for the rock salt-type modification of InTe. The corresponding interatomic separation is intermediate between monovalent and trivalent indium. The qualitative implications of the results are considered from the viewpoints of both valence-band theory and energy-band theory. principle, and is corrected by methods of molecular-orbital theory in which bonds are replaced by bands of molecular orbitals whose energies, E, depend upon a crystal-momentum vector, k.7 Each band is derived from a linear combination of atomic orbitals with two electrons required to saturate each molecular orbital in the band. In a crystal of N atoms containing z atoms in its primitive unit cell, there are 2 N/z states per band which lie in a region of k space bound by the Brillouin zone. In an intrinsic semiconductor, the bands can be grouped into valence bands which are normally filled and conduction bands which are normally empty. If the highest valence band and the lowest conduction band overlap anywhere within the Brillouin zone, the material is rendered semimetallic. The quantity defines the effective mass, m*, of an electron in a conduction band (or of a hole, i.e., an electron deficiency, in the valence band) and leads directly to the concept of charge mobility through the relation \x = et/m*, where e is the electron charge and t is the lattice relaxation time.

Jan 1, 1964

By W. D. Bensema

Two different techniques were used to make measurements of the absolute value of electromagnetic noise in an operating coal mine, Itmann No. 3 Mine, located near Mullens, West Virginia. The electromagnetic environment created by 250-volt-dc and 550-and 950-volt-ac machinery in two longwall panels was measured and is reported. One technique measures noise over the entire electromagnetic spectrum of interest for brief time periods. It is recorded using broadband analog magnetic tape, and the noise data is later transformed to give spectral plots. The other technique records noise amplitudes at several discrete frequencies for a sufficient amount of time to provide amplitude probability distributions. The specific, measured results are given in a number of spectral plots and amplitude probability distribution plots.

Jan 1, 1974

By Randall M. Wheeler

It is important to be able to quantify the effects of blast delay designs on vibration characteristics. White was the first company to develop commercially available software, called Alpha-Blast, for this purpose. The program can indicate relative amplitude and frequency results to be expected from the use of particular delay intervals. If enhanced vibration effects from delays are a problem, a technique to evaluate this situation will be invaluable.

Jan 1, 1994

By J. R. Nettle

The development of a process for upgrading offgrade titanium metal by electrorefining in molten salt led to an investigation of the electrotransfer characteristics of selected metals when alloyed with the titanium to be refined. Previous tests on seven binary titanium alloys showed that the degree of transfer of the alloying constituent depends on the constituent and on the operating procedurese.5 This report describes tests on electrorefining ternary mixtures of titanium with selected metallic elements. Ten alloys were prepared from high purity titanium and 2-1/2 percent of each of the metal pairs selected from the same elements used in the binary study; manganese, vanadium, chromium, zirconium, tin, molybdenum, aluminum. Operating variables were similar to those investigated in the binary alloy study that gave minimum alloy metal transfer. The data presented indicate the transfer characteristics of the various metals and combinations tested relative to each other.

Jan 1, 1962

By I. Marklund, W. Hustrulid

Sublevel caving is likely to remain the dominant system at both Malmberget and Kiruna for the foreseeable future. The sub-level interval has increased from 12 m in 1983 to 30 m, requiring more effective drifting and the development of a contour blasting technique to reduce requirements for rock reinforcement. Production drilling is mainly by hydraulic hammers or water-powered in-the-hole machines drilling 115 m diameter holes. Loading operations are undertaken 7 days/week with 15-25 tonne capacity electric shovels. Production has increased by nearly 70% since 1983 and productivity has risen threefold

Dec 1, 1995

By R. Patterson

Tracer gas sampling methods are useful for monitoring ventilation systems, especially in remote or inaccessible areas, and can be utilized for analysis of the ventilation system immediately following a mine emergency. However, the success of this technique is largely dependent on the accuracy of release and sampling methods. Analysis of sampling methods is crucial for rapid response and dependable results during emergencies. For the purpose of this study, four well-accepted sampling techniques currently used in the mining industry were compared using solid-phase microextraction (SPMe) fibers with sulfur hexafluoride (SF6), an industry standard, as the tracer gas. Current sample collection techniques include plastic syringes, glass syringes, Tedlar bags and vacutainers. SPMe fibers are used in a variety of industries, from forensics to environmental sampling, and are a solventless method of sampling analytes. To analyze these sampling methods, samples were taken from a 0.01 % standard mixture of SF6 and nitrogen and analyzed using electron capture gas chromatography. A relative standard error of less than 10% validated results to compare the accuracy of various methods. The technical and practical issues surrounding each sampling method were also observed and discussed.

Jan 1, 2011

By Jerome Apt

This manual has been prepared fur the help and guidance of underground coal mine operators. It details both common and unique engineering methods by which the respirable dust, which is generated in coal mines, can be controlled. This document was compiled by Apt, Bramer, Conrad and Associates, Inc. under contract number H0111464, issued by the U. S. Bureau of Mines and forms Volume II of the final report. This contract was authorized by and executed pursuant to the Federal Coal Mine Health and Safety. Act of 1969 (P. I. 91-173; 83 Stat. 742).

Jan 1, 1972

By Ross W. Smith

Microflotation and surface chemical studies were conducted on a chromite from the Stillwater Complex in Montana and on some of the minerals usually found to be associated with such chromites. Considering the chromite it was found that aging the ground mineral in air or heating it markedly affected its flotation behavior. Much of the observed effects could be attributed to oxidation reactions involving surface chromium and iron species. Strongly acid pretreating the mineral appeared to reverse such effects. Thus, it can be concluded that the manner in which the mineral (or the ore) is pretreated is of utmost importance in its flotation. Work carried out on associated gangue minerals determined how they are likely to behave in a flotation environment and how certain foreign ions derived from a chromite ore itself can affect their surface characteristics and, thus, presumably also their behavior in a flotation circuit.

Jan 1, 1981