Search Documents

By M. S. Seehra, V. S. Babu

"INTRODUCTION The accurate determination of the free silica index in coal mine dusts is an important requirement because severe health hazards are believed to be associated with the inhalation of respirable-sized silica particles.1-6 Free silica refers to the three polymorphs of silica (Si02)viz., quartz, cristobalite, and tridymite-although quartz is usually the dominant form in most mine dusts.6 The free silica index is the concentration in micrograms of free silica in air per m3 of air sampled corrected to standard conditions of 25°C and 760 mm/Hg, the present MSHA (Mine Safety and Health Administration) limit on time-averaged basis being 100 µ.g/m 3 for coal mines. A recent review7 has concluded that quartz, cristobalite, and tridymite particles impart nearly equal long-term hemolytic damage when compared on a per unit surface area basis.At present, two experimental methods-viz., transmission infrared spectroscopy (TIRS) and x-ray diffraction (XRD)-are commonly used for the determination of silica concentrations in mine dusts. In TIRS, which has been adopted by MSHA and is commonly called the P7 method, the silica absorption band near 800 cm - 1 is used for quantification. However the mineral kaolinite, which is commonly present in mine dusts, also has absorption band, albeit weaker, at 800 cm- 1• To correct for this interference, one uses the stronger 915-cm -1 band of kaolinite to determine the concentration of kaolinite, and the kaolinite contribution to the absorbance at 800 cm-1 is then determined from a calibration curve, leading to the determination of silica by subtraction. In the XRD technique, usually an internal standard such as CaF 2 is used to determine the concentration of silica from line intensity measurements. XRD has the added advantage that concentrations of quartz, cristobalite, and tridymite can be determined.8•9 In an exhaustive study on the precision of the techniques ofTIRS and XRD for monitoring worker exposure,9 the conclusion has been reached that both methods measure silica within 253 of the ""true"" value 953 of the time in a single laboratory."

Nov 1, 1995

By R. D. Brown

This Bureau of Mines report describes a new methodology for identifying and sorting scrap metals using two modern portable instruments: a thermoelectric sorter and a hand-held emission spectroscope. The method, tested on a 27-sample stainless steel and superalloy array, makes it possible to group and/or identify a typical mixture of high-value metal scrap in two or three steps, whereas as many as seven or eight steps are needed to perform the same separations using chemical spot tests. A portable fluorescent X-ray analyzer identified 19 of the 27 alloys in the sample array by name or type; these alloys are included in the microprocessor memory. The remaining alloys were identified by using the analyzer in its elemental analysis mode and comparing the results wit.h alloy specification chemistry.

Jan 1, 1984

By J. C. Edwards

The Bureau of Mines developed a mathematical model for analysis of the impact of scrubber bed length, porosity, and gas flow rate on the absorption of C02 in a breathing apparatus. The model accounts for the decrease in available absorbent through chemical conversion. The pre-dicted efflux of C02 from a canister containing LiOR compared favorably with measured values reported elsewhere. It was determined from a com-putational study that the time for breakthrough of C02 at a prescribed level is nearly directly proportional to bed length and inversely pro-portional to gas flow and porosity.

Jan 1, 1987

By Joe Maher

Adequate mine roof support to insure the safety of men and equipment is essential to successful mining. It is also expensive, amounting to more than one-fifth of the total mining cost at the White Pine mine. Cost effectiveness is therefore a prime consideration in developing optimum roof support. Roof bolt length is an important cost factor. This Phase II work compared uniform four-foot length Resin Bolts with the hitherto standard alternating four-foot and six-foot Resin Bolts, aiming at more cost-effective roof bolting. The data generated under this Phase II show that there is no discernible difference in the roof support given by uniform four-foot, and by alternating four- and six-foot, Resin Bolts in the relatively difficult ground selected for a severe initial test comparison; subsequent data from less difficult ground led to the same conclusion, namely no discernible difference between four-foot and four-six foot bolting.

Jan 1, 1975

By U. E. Brown

This papery describing the mining methods employed by the Bunker Hill and Sullivan Mining and Concentrating Co. at Kellogg, Idaho, is one of a series being prepared by the United States Bureau of Mines on mining practices, methods, and costs in the United States. The Bunker Hill and Sullivan mines are situated in the western part of the Coeur d'Alene district at Kellogg, Shoshone County, Idaho. The mines were discovered during the summer of 1885 and except for two short periods of labor trouble, between 1890 and 1900, have been in continuous operation. About 575 men are employed at the mine. The production is about 1,400 tons of lead-silver ore per day. This is treated in the company's concentrator and smelter at Kellogg.

Jan 1, 1931

By R. V. Lundquist, H. Leitch

The solubility characteristics of three calcium aluminates , 12Ca0 · 7A120½ 3Ca0 A1203 , and 4Ca0 A12 03 Fe2O3 , were determined in water and in solutions of NaOH and Na₂ CO₂ to more clearly define their role in relation to the recovery of aluminum by the lime sinter and the lime - soda sinter processes . The calcium aluminates were prepared by sintering stoichiometric mixtures of CaCO3 , Al2O3 3H20, and Fe 0 at 1,375 ° C. The rates and extent of aluminum extractions were determined . The aluminum extractions from the aluminates were dependent on the presence of carbonate ions in the leach solutions , temperature , time , leach solution composition , and solid - liquid ratio of the slurry . The aluminum extracted from the calcium aluminates in water and in NaOH solutions varied from 4.6 to 22.9 percent . Virtually , complete extraction could generally be obtained for 12Ca0.7A120 and 4Ca0.A12 03 • Fe₂ 03 ; in one instance it was obtained for 3Ca0.A1203 , when an excess of carbonate ions was present over that required for the conversion of all of the calcium in the aluminates into CaCO3 . In some cases of poor aluminum recoveries , extractions could be improved by regrinding and releaching the solid residues .

Jan 1, 1964

By J. W. Jensen

Alloys of manganese and copper containing from 65 to 80 percent manganese possess mechanical strength and vibration-damping capacity in an unusually high degree. The success of their use in reducing vibration in structures depends, to some extent, on their fatigue properties. This report describes the results of fatigue tests on alloys of four compositions. Three metallurgical conditions were investigated for each alloy. Or the basis of the data in this report, the general rule that vibration-damping manganese-copper alloys are comparable to mild steel in hardness and strength may be extended to include fatigue strength. Methods for casting and fabricating these alloys were described in a previous report,4 which contained data on the mechanical and damping properties of the solid-solution alloys, and on alloys aged for 2 hours at 450° C. The aging heat treatment of solution-treated alloys results in optimum mechanical and damping properties throughout the range of specified composition. However, in the present work, measurements also were made on alloys aged for 2 hours at 500° C., because it was theorized that the additional precipitation of a-manganese under these conditions might have a pronounced effect on the fatigue strength of the alloy.

Jan 1, 1961

By Howard P. Hamlin, John W. Sweeney

Shales from 14 locations in Indiana were sampled , tested , and evaluated to determine feasibility of producing lightweight aggregates by rotary - kiln and sintering methods . Sampling procedures and the geology of the significant shale units are discussed . Preliminary testing was conducted in a muffle furnace , and continuous tests were made in a 16 - inch by 14 - foot rotary kiln . The aggregate weighed 37.0 to 47.2 pounds per cubic foot . Concrete cubes employing the aggregate were tested to determine the qualities of the concrete . Compressive strength of the concrete using seven bags of cement per cubic yard , after autoclave curing for 6 hours , ranged from 3,600 to 5,850 pounds per square inch . Four samples made suitable lightweight aggregate in the laboratory rotary kiln . Four samples tested by sintering methods made unsatisfactory aggregate .

Jan 1, 1965

By L. B. Pankratz

The Bureau of Mines measured heat capacities of alpha and beta spodumene (LiAlSi2O5) and of beta eucryptite (LiAlSiO4) over the temperature range 51° to 298° K. The entropies at 298° K were found to be 30.9 ± 0.2 cal/deg mole for alpha spodumene, 36.9 ± 0.3 cal/deg mole for beta spodumene, and 24.8±0.2 cal/deg mole for beta eucryptite. High-temperature heat content measurements above 298° K were conducted for the same compounds. Measurements were made to 1,150° K for alpha spodumene, 1,600° K for beta spodumene, and 1,470° K for beta eucryptite. Tables of heats and free energies of formation are given from the elements and from the constituent oxides.

Jan 1, 1967

By K. Kar, M. Gautam, J. T. Jurewicz

The 10-mm Dorr-Oliver cyclone has been widely used as a personal sampler for size selective sampling of particles within the respirable range (Dp < 10 gm). Because of their inertia, the particles are unable to follow the swirling flow (outer vortex) within the cyclone. The particles migrate to the bottom of the cyclone, depending on their size, and get trapped into the inner vortex which leads to an eventual blow-off from the top of the cyclone. By measuring the size distribution of the particles in the free stream and in the collected sample, the aspiration efficiency of the cyclone can be calculated. Velocity difference between the free stream and sampling velocity. Inlet orientation, particle impaction and deposition, particle inertia and free stream turbulence result in the departure of the aspiration efficiency from unity and this, in turn, leads to inlet bias. Although the effect of inlet bias on sampling efficiency has been investigated in past, the results lack detailed information and show only some general trend. In this effort, a systematic, in-depth experimental work on the effect of inlet bias on the sampling efficiency has been undertaken using non-intrusive Laser Doppler Anemometry (LDA), Aerodynamic Particle Sizer (APS) and impactors.

Mar 1, 1992

By Charles S. Allbright, Frank G. Schwartz, Marvin L. Whisman

Radioactive tracer techniques were used to gain a better knowledge of the types of compounds that cause gum formation in gasoline during storage . A selected organic compound was labeled with tritium and purified . An unstable gasoline was tagged by adding a small amount of the labeled compound . After storage of the gasoline at 110 ° F for 16 weeks , the gum that had formed was recovered . The amount of the test compound converted to gum was determined by liquid scintillation counting . About 70 compounds , including several classes and types , were studied . The compounds , listed in order of descending reactivity in the test fuel , were sulfur compounds , nitrogen compounds , polycyclic hydrocarbons , olefins , alkylbenzenes , and saturates . In the order of decreasing percentage of each in the gum , the compounds were monoolefins , alkylbenzenes , sulfur compounds , polycyclic hydrocarbons , nitrogen compounds , and diolefins . This type of information should be helpful in developing a method for predicting the storage stability of gasoline .

Jan 1, 1964

By A. E. Isaacson

Bureau of Mines researchers developed and tested equipment to measure corrosion rates on a commercial scale mill. Bench-scale experiments were designed for duplicating ore grinding conditions closely enough so that realistic rate determinations could be made in laboratory tests. Rates measured in a laboratory system compared favorably with those measured in the field. Cast steel was found to have corrosion rates in a copper mill and laboratory test cell of 22 and 21 mpy, respectively. Corrosion was found to account for less than 5 pct of the total grinding media wear in the operations studied.

Jan 1, 1988

By T. Estelle Gardner

Heat-capacity measurements were made over the range 8° to 350° K on beryllium sulfate dihydrate and beryllium sulfate tetrahydrate using an adiabatic calorimeter. No anomalies were noted in the curve for either compound. Smooth values of heat capacity, entropy, enthalpy function, and free-energy function were calculated from the heat-capacity data at 10° K intervals and at 273.15° and 298.15° K. The entropy values calculated at 298.15° K were 39.01 ± 0.12 entropy units (eu) for the dihydrate and 55.68 ± 0.17 eu for the tetrahydrate.

Jan 1, 1967

By Thomas P. Mucho, David C. Oyler, Jim Pablic, Dennis R. Dolinar

A room and pillar coal operation in central Pennsylvania was experiencing roof cutters and long running roof falls caused by high horizontal stresses. The roof conditions created hazards for the miners, and caused several production panels to be abandoned prematurely. The mine requested assistance from the National Institute for Occupational Safety and Health (NIOSH) in applying the "advance and relieve" mining to reduce the affects of the horizontal stress during panel development. The "advance and relieve" plan that was developed called for removing a pillar on one side of the panel as it was being advanced, thus creating a cave. The caving then relieved a portion of the horizontal stress across the panel. Because the horizontal stress direction is key to the success of this method, stress mapping as well as mining experience was used to establish the direction of the horizontal stress. Subsequent field measurements provided an estimate of the stress magnitude. Three panels were mined using this technique, and good roof conditions were achieved in all these panels. Instrumentation was used to monitor the stress changes in the roof created by the cave. Stress relief of over 1,000 psi was measured 120 ft from the cave and to depths of 20 ft into the roof. The lateral extent of the stress relief zone across the panels appears to be about 400 to 500 ft. This case history has provided much insight into the practical application of the "advance and relieve" method discussed in this paper.

By R. L. Thorne

The Snettisham Peninsula, 30 miles southeast of Juneau, Alaska, was studied by the Bureau of Hines to obtain basic information about the size, grade, and metallurgical characteristics of a large basic intrusive containing titaniferous magnetite. The investigation, which was part of a continuing program to determine the potential reserves of iron and titanium ores in Alaska, included transit and magnetometer surveys, followed by diamond core drilling and metallurgical testing. The magnetic attraction of a part of the Snettisharn Peninsula is noted on early navigational charts prepared by the Coast and Geodetic Survey. Reconnaissance examinations by the Geological Survey and a preliminary dip needle survey by the Territorial Department of Mines indicated the general nature of the basic intrusive, but little was known as to the grade and extent of the magnetite mineralization. The detailed survey by the Bureau of Mines proved an area of approximately 390 acres in which generally high magnetic anomalies with exceptionally high localized anomalies occur. Subsequent drilling across B representative section of the deposit yielded core samples, which assayed from 11 percent to over 45 percent total iron. A large sample of core composited to represent the drilled portion of the de-posit assayed 18.9 percent Fe, 2.6 percent Ti02, and 0.29 percent S, 0.32 percent P, and 0.05 percent v.

Jan 1, 1956

By Robert J. Evans

Reclamation costs were estimated for 20 coal surface mining operations in the Appalachian and Midwestern Coal Supply Districts (these two districts were divided into three multi-State regions). The cost data were obtained through onsite observations, interviews with mining company personnel, and the authors&apos; cost estimating procedures. The cost data are presented in terms of dollars per acre, dollars per ton of coal produced, and dollars per cubic yard of overburden moved during backfilling. The reclamation process is divided-into three cost categories: Premining planning, backfilling, and revegetation. The average total reclamation costs for the three regions are $2.77 per ton of coal produced and $8,168 per acre. As the result of comparisons of reclamation costs by region, by mining method, by slope, and by size of operation, the most important reclamation cost difference is between area mining methods ($1.73 per ton) and contour mining methods ($3.81 per ton). The Federal Bureau of Mines conducted this study to determine as accurately as possible the actual costs involved with the reclamation of coal surface mined land done in conjunction with active mining operations.

Jan 1, 1975

By Gopala N. Krishnan

The most promising candidate for the recovery of alumina from non-bauxitic sources is the leaching of clay by HCL acid followed by crystallization of aluminum chloride hexahydrate (ACH) by hydrogen chloride sparging. Hydrothermal precipitation of boehmite ( ?-A100H) from aluminum chloride solution will simplify the process, will reduce energy consumption and will eliminate corrosion problems involved in calcination of ACH to obtain alumina. This report summarizes the results of Phase I of a program to study the precipitation of boehmite from AlC13 solutions. The amount of boehmite precipitation from dilute A1C13 solutions (5 wt%) is . negligible below 200°C. Above 200°C the precipitation increases with increasing temperature approaching 40% at 300°C. Addition of HCl acid to the dilute A1C13 solution even in small quantities drastically reduces boehmite precipitation. Solution impurities such as Fe, Ca, Mg, or Na substantially promote the precipitation of boehmite. No precipitation is observed from concentrated A1C13 solution (30wt%) representing the leach liquor.

Jan 1, 1980

By Grace N. Broderick

U.S. supply and demand data for coal, by States and regions, were tabulated for the years 1960 and 1965. Estimates are provided of State-by-State quantitative data for the coal industry that can be integrated into State and regional energy balances by source, form, and consumer sectors, and used for estimates of interstate and interregional energy flows. The tables give an estimated total supply of coal available for consumption, and also report the distribution of the supply among the major consuming sectors (household and, commercial, industrial, transportation, and electricity generation). To enable comparison of coal data with those for other energy forms, tonnages were converted to British thermal units (Btu). Future energy analysis studies could be facilitated by changes in the categorization of information collected on the coal industry. The data shown are based primarily on Bureau of Mines source material.

Jan 1, 1969

By Don Belsher

Work on contract H0272007 is summarized for the period of 1 February 977 to 1 February 1978. The initial evaluation of two potential systems for the location of well casings, voids, and tunnels in coal are described. The pulse measurement equipment used for the evaluation of the antennas selected possible use with a pulse time domain system and an FM-CW system is described. A TEM horn antenna design potentially suitable for use with these systems is given. An operational comparative analysis between various antenna types is presented.

Jan 1, 1978

By John E. Pahlman

The U.S. Bureau of Mines has continued its investigation of chemical additive drilling fluids that produce a zero surface charge (ZSC) on a rock to better define the boundary conditions of the phenomenon. Laboratory drilling tests were performed on Minnesota taconite, Tennessee marble, and Sioux Quartzite using diamond-impregnated coring bits or tungsten carbide spade bits. Drilling fluids were made from chemical additives such as inorganic salts, cationic surfactants, cationic polymers, acids, or nonionic polymers in either distilled, deionized water (DDIW), mine pond water, mine well water, or tap water. These additives were tested below, at, and above their respective ZSC concentrations. Penetration and bit life improvements obtained with ZSC concentration solutions ranged from 88 and 56 pct, respectively, to over 650 pct and over 400 pct, respectively, for the additives tested. Polyethylene oxide (PEO) was found to be the best additive for ZSC-controlled drilling because a continuous range of PEO solution concentrations produced the enhanced ZSC-controlled drilling performance.

Jan 1, 1989