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By Manuel Gomez

The mean and the standard deviation were used to describe general sulfur and ash populations as well as specific populations of these variables from one coal seam. Both the mean and the standard deviation were incorporated in the exploration process to determine the number of drill cores necessary for seam evaluation and to guide the sequential drilling plan. Probability regions were computed to establish a basis for predicting probable ranges of average sulfur and ash concentrations that may be expected upon continued or future drilling. A computerized plot program was utilized to interpolate sulfur and ash concentrations between grid points. The plot program, which is essentially a moving average technique, permits a rapid evaluation of sulfur, sulfur forms, and ash spatial distributions as a drilling program progresses sequentially. This information, in the form of contour plots, can be made available to both the mining engineer and the fuel technologist in advance of mining to outline reserves, to improve selective mining, and to anticipate preparation facilities.

Jan 1, 1972

By Mark I. Copeland

A study was conducted to determine if commonly used alloying additions or coating materials can prevent the formation of a liquid-copper phase during the reheating of copper-containing steels. If so, the tendency of such steels to surface-crack during hot-working might be eliminated. Steel specimens were scaled by heating them either isothermally or in a programed manner that simulated industrial furnace practice. Metallographic examination of the heated specimens showed that molten fayalite (Fe2Si04) completely prevented the formation of liquid copper at the surface. Fayalite, which melts at 2,200° F (1,205° C), was formed by internal oxidation of the silicon contained in the steel. By forming complex molten oxides, coatings of borax glass were also effective in preventing the occurrence of liquid copper at the steel surface.

Jan 1, 1972

By R. O. Dannenberg

The Bureau of Mines investigations described in this report were undertaken to devise a process to economically recover precious metals and copper from low-grade, complex electronic scrap generated in large quantities by military and civilian electronic operations. Leaching with various media is applicable to certain selected items of electronic scrap but cannot be practically applied to complex mixtures of scrap. A process comprising incineration, caustic leaching to remove aluminum, smelting with a siliceous slag, and electrolysis recovered 99.9-percent-pure copper metal and anode slimes assaying more than 7,000 ounces per ton of combined precious metals. Silver, gold, and copper recoveries were 93, 95, and 87 percent, respectively. Cost analysis indicated that an alternative process using direct smelting of the scrap to make assayable products for sale to a custom smelter would provide better overall financial returns.

Jan 1, 1972

By Mark I. Copeland

The formation of A1203 dispersoids 0,14 and less in size in dilute iron-aluminum alloys by internal oxidation in wet hydrogen and dispersion strengthening of iron by application of the technique to iron powder were found to be feasible by the Bureau of Mines. In flowing H2-1.5 H20 gas, A1203 dispersoids 0.1w and less in size formed (at 650° to 750° C) in Fe-l and 2 Al sheet material but not in Fe-3 or 4 Al alloys. With higher temperatures and/or higher H2O/H2 volume-ratio gases, A1203 and FeA1204 dispersoids >0.14 in size formed in all the sheet materials- Minus 100-mesh Fe 2 Al powders were internally oxidized under conditions that promoted formation of fine A1203 particles in sheet material, and then the oxidized powders were hydrogen reduced, sintered, extruded, and evaluated. During internal oxidation, fine A1203 dispersoids formed within the powder grains, and coarse FeA1204 particles formed on the powder surfaces and grain boundaries. The FeA1204 content was essentially eliminated during sintering by reacting with the unoxidized aluminum that remained in the center of the larger internally oxidized powders. The tensile strength at 800° C depended upon the aluminum-oxygen weight ratio of these elements in the extrusions and reached a maximum of 17,000 psi. The stress-rupture strengths at 800° C of the better alloys were comparable with those of type 310 stainless steel.

Jan 1, 1972

By R. L. Schmidt

The Methane Control and the Respirable Dust Groups at the Twin Cities Mining Research Center (TCMRC) cooperated recently in obtaining production samples of approximately 1 ton each, from the loading conveyors of a ripper, a borer, and a loading machine in conventional development headings. These samples were sized, in four stages, from plus 4 in to minus 10 µm. The conventional product had the least fines of the three production methods. The borer product had more fines than did the ripper product, but it also had a greater amount of large pieces. All three products, as sampled, had essentially the same amount of minus 10-µm particles. Photomicrographs and surface?-area comparisons were made. Gas -adsorption, surface-area determinations on particles under 37 µm give essentially the same value. Surface-area calculations, assuming spherical particles and no porosity, give a smaller area to the conventional product.

Jan 1, 1972

By M. J. Ferrante

Low-temperature heat capacities and high-temperature enthalpies were determined calorimetrically for Na2Cr04, A reversible transition was found at 700° K with an isothermal heat of transition of 2,263 cal/mole. High-temperature X-ray diffraction analysis showed that the transition was a crystal change from the low-temperature orthorhombic form to the high-temperature hexagonal form. At 795° K the hexagonal form had the parameters a, = 5.691 and co = 7.478 A. Powder diffraction data for the high-temperature form are given and possible structures discussed. The melting point was determined to be 1,065° K with a heat of fusion of 5,810 cal/mole. Enthalpy and entropy increments from this investigation were combined with other data from the literature to calculate enthalpies of formation, free energies of formation, and equilibrium constants of formation from 298° to 1,400° K. Equations that represent enthalpies above 298° K are given.

Jan 1, 1972

By Helen W. Lang

The Bureau of Mines has developed a very rapid gas chromatographic method for routine determination of oxygen, nitrogen, methane, and carbon dioxide in mine atmosphere samples. Analysis is accomplished in 3 min; readout appears on a single strip chart. The gas sample is split between two columns contained in separate chromatographs. A 5 A molecular sieve column separates oxygen, nitrogen, and methane; a porous polymer column separates carbon dioxide from an air peak. Direct selective analysis of methane from this unresolved air peak is accomplished using a hydrogen flame ionization detector (FID). Carbon dioxide is catalytically converted to methane and detected by FID.

Jan 1, 1972

By F. N. Kissell, R. J. Bielicki, J. H. Perkins

A sorption apparatus for measuring the equilibrium sorption isotherm and the rate of diffusion of methane from fine-sized coal was designed and constructed. Preliminary work that used Pittsburgh and Pocahontas No. 3 coal shows that the diffusion coefficient varies with pressure and that the fracture spacing in these two coals is substantially different.

Jan 1, 1972

By R. J. Bielicki

A sorption apparatus for measuring the equilibrium sorption isotherm and the rate of diffusion of methane from fine-sized coal was designed and constructed. Preliminary work that used Pittsburgh and Pocahontas No. 3 coal shows that the diffusion coefficient varies with pressure and that the fracture spacing in these two coals is substantially different.

Jan 1, 1972

By G. W. Reimers

Metastable pyrophoric wüstite (FexO, with x between 0.89 and 0.95) was found to be much easier to grind to colloidal state than were its stable disproportion products magnetite or iron. The grinding of polycrystalline magnetite appears to be complicated by the magnetic flocculation arising from interparticle attraction. This is superimposed on the attraction of a fluctuating electric dipole for a neighboring induced dipole. More than 85 pct of the tumbling time was saved by grinding antiferromagnetic wüstite instead of the ferrimagnetic oxide of iron (Fe304). Disproportionation of colloidal wüstite to the stable ferromagnetic and ferrimagnetic colloidal particles of alpha-iron and magnetite, respectively, was accomplished rapidly at temperatures above 250° C but below 570° C, the eutectoidal stability point of the wüstite phase.

Jan 1, 1972

By Richard A. Dick

Eight blasts were fired in a 2-1/2-ft bench in the Stewartville member of the Galena Limestone formation in an aggregate quarry near Stewartville, Minn. The shots were dimensionally proportional to production-size bench blasts and were about 5 to 10 percent of full scale. The effects of site, timing of initiation, and burden-to-spacing ratio were studied in a 2 x 2 x 2 factorial experiment, using three boreholes, caw;, containing a 1/2-in charge diameter of high-density ammonia dynamite, in each blast. Detonation velocity measurements indicated that the dynamite detonated satisfactorily in the 1/2-in charge diameter. The effects of the three experimental variables were analyzed by weight for the percentage of oversized material produced and for size distributions determined by screening the entire muckpiles. The bench faces were painted before each shot in an effort to determine the origin of the oversized material. The square pattern (burden and spacing = 15 in) produced finer overall fragmentation and less oversized material than the rectangular pattern (burden = 15 in; spacing = 22-1/2 in). Sites 1 and 2 were about ft apart. Although site 2 produced slightly better overall fragmentation than site 1, the amounts of oversized material produced showed no significant difference. The timing of initiation (instantaneous or delayed) did not significantly influence the overall fragmentation or the amount of oversized material produced.

Jan 1, 1973

By Robert B. Worthington

This investigation was undertaken to develop a more efficient copper smelting practice that would help meet the increasingly stringent antipollution standards. Continuous smelting to copper and a 0.8-to 5-percent copper slag using pure oxygen has been demonstrated for several hours at a time in a unique double furnace, which was devised to overcome the heat losses inherent in a laboratory furnace. The use of pure oxygen to effect the smelting and conversion of copper sulfide concentrate in a single unit to produce blister copper and a very high S02 concentration provides a much reduced gas volume for more economical and thorough sulfur recovery. Although the process was successfully demonstrated for several hours at a time, extended test work using longer runs will be required to balance the system and to obtain test data for adequately demonstrating its technical feasibility.

Jan 1, 1973

By Robert C. Steckley

A study of joints in Marathon County, Wis., was made to determine the orientation of regional paleotectonic stresses and to develop a method of using optical diffraction analysis (ODA) in studying joint orientations and spacings. Standard geologic and petrofabric techniques employing the use of a geologic compass and a Schmidt net were used in gathering, describing, and reducing joint orientation data. Analysis of selected outcrops with ODA indicates that ODA can be applied to study both joint orientations and spacings. ODA is shown to be a rapid method that can be used to complement standard petrofabric techniques, especially in the study of joint spacings.

Jan 1, 1972

By J. B. Janus

This report, the 22d in a series, gives analytical data showing composition and quality of tipple and delivered samples of coal collected during fiscal year 1972. This coverage lists mines located in 20 States. Ultimate analyses are given for most of the coalbeds listed. Tipple samples were collected by Bureau of Mines engineers at tipples as coal was being loaded into railroad cars or trucks. The deliveries were sampled in accordance with instructions issued by the Bureau of Mines, and the samples were analyzed in the Bureau laboratory at Pittsburgh.

Jan 1, 1973

By T. Kessler

As part of a respirable mine-dust research program at the U.S. Bureau of Mines, spark-source mass spectrometry has been used for the semiquantitative determination of trace elements (200 ppm weight or less) in raw coals. In addition, several minor and major elements have been determined using this technique. Sixty-four elements ranging in concentration from 0.01 to 41,000 ppm weight were determined in one anthracite, two mvb, four lvb, and six hvab raw coal samples. The samples represented 10 coal seams located in Pennsylvania, West Virginia, Virginia, Utah, and Colorado.

Jan 1, 1973

By M. A. Mahtab

This report presents the geometric parameters (attitude, spacing, extent, and aperture) of fracture patterns in a selected portion (study area) of San Manuel copper mine, Arizona. The geometric parameters are quantified for input to structural analyses for studies of the influence of fractures on cavability of ores. Using an orientation analysis procedure developed earlier by the Bureau, three prominent and nearly orthogonal sets of fracture orientations were delineated in the study area. Sets 1 and 2 dip nearly vertically, and generally strike east-west and north-south, respectively, whereas set 3 is nearly horizontal. Both a horizontal rotation (of 14° to 26° for sets 1 and 2, respectively) and a tilt (of 20° for set 3) is shown to occur between the 1415 and 2015 levels of the mine. Gomparison of the three major rock types present in the study area (quartz monzonite, monzonite porphyry, and rhyolite) show that the rhyolite is characterized by short extent, small spacing, and tightness of fractures as well as the general absence of fracture set 3, which may account for its generally observed strong resistance to caving.

Jan 1, 1973

By M. J. Kovalik

Illinois No.6, a high-volatile B coal of low fluidity, was blended with fluidized-bed char and coke breeze to improve the strength of the coke obtained from carbonizing this coal. Twenty-one tests, selected from those made in the small-scale Hanson carbonizer, were carbonized in the BM-AGA 13-inch-diameter, cylindrical retort, with a coal charge of about 90 pounds; the strength of the cokes was determined by the standard ASTM tumbler test. Using the same procedure, 10 tests were made with High Splint, a high-volatile A coal from Harlan County, Ky. Carbonization of the blends produced larger and stronger cokes than did the Illinois No.6 coal singly. The optimum blend contained 6 percent each of char and coke breeze. Further improvement in coke strength was realized by either preheating this blend prior to carbonization or by adding a small pro-portion of a premium blending coal. The former method could possibly eliminate the use of premium coking coals in blends with Illinois No. 6 coal to make an acceptable metallurgical coke. Except for no improvement in coke strength by preheating, results for High Splint coal showed behavior similar to that of the Illinois No.6 coal.

Jan 1, 1973

By Joan C. Biordi

A molecular beam-mass spectrometer-low pressure flat flame apparatus has been constructed for the purpose of examining the chemical microstructure of normal methane-oxygen-argon flames and those inhibited with Halon extinguishants. Details of construction and performance of this apparatus and of related flame temperature measurements are given. Particular attention is paid to the empirical characterization of the perturbation to the flame caused by the sampling probes. The composition profiles obtained for normal flames are compared to those of flames inhibited by CF3Br. In addition to the usual stable species (CH4, O2, CO, CO2, H2O, H2, and H2CO), the inhibitor, its products and intermediates associated with its reactions could be followed. In particular, hydrogen bromide, bromine atoms, hydrogen fluoride, and carbonyl fluoride were observed. The relatively rapid disappearance of inhibitor and early appearance of fluorinated reaction products suggest a short lifetime for the CF3 radical in this system. Observation of COF2 suggests that CF3Br is effective as an inhibitor, at least in part, by virtue of its interference with the oxygen containing species of the normal chain reaction. Profiles of the 17+ peak at low electron energy suggests that the hydroxyl radical may also be sampled, but the profiles obtained are not yet sufficiently accurate to determine the effect of inhibitor on this important flame radical.

Jan 1, 1973

By John Ward Smith

Aragonite, co-occurring with calcite and dolomite as matrix minerals, has been discovered in Mahogany zone oil shales of Colorado's Eocene Green River Formation, posing puzzles on the geochemical patterns of their separate origins, reasons for their simultaneous existence, and their interrelation. The presence of aragonite is demonstrated by X-ray diffraction. Amounts of aragonite and dolomite are significantly and inversely related, but the calcite quantity is essentially independent of either aragonite or dolomite quantity. A geochemical pattern outlining the deposition conditions that created the Green River Formation oil shale is postulated from characteristics of the oil shale. The development of the three separate carbonates--aragonite, calcite, and dolomite--the inverse relationship between aragonite and dolomite, and the independence of amounts of calcite and the other two carbonates are shown to be natural consequences of this oil-shale genesis pattern.

Jan 1, 1973

By J. S. Miller

The Bureau of Mines developed methods for fragmenting oil shale formations with chemical explosives to prepare oil shale for in situ retorting and to evaluate the extent of fragmentation by various methods. A combination of three methods of explosive fracturing was used: (1) The displacement and detonation of a liquid chemical explosive in a natural fracture system; (2) the use of 60-pct dynamite to relieve stress conditions of the rock around the wellbore; and (3) the use of pelletized TNT in a series of wellbore shots to fragment the oil shale. An attempt was made to seal or grout around the fragmented oil shale by drilling 67 holes and displacing approximately 200 bbl of neat cement in the fracture system to aid in evaluating the fragmented zone, Seven methods were used to evaluate the fragmented zone. The primary evaluation method was the recording of seismic waves to delineate the fragmented zone with results based on arrival time, amplitude, and record quality. The data from the seismic measurements indicated the extensively fragmented zone was approximately 95 ft in diameter and 70 ft thick. Results of the remaining methods of evaluating fractures--including air-flow tests, coring of the expected fragmented zone, elevation measurements to indicate overburden crowning, and surveys with high-speed camera, impression packer, and down-hole camera--agreed with and supported the data from seismic measurements. Further field application of explosive fracturing and evaluation methods is needed to determine when a zone of oil shale is effectively fragmented for efficient in situ retorting.

Jan 1, 1973