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By Donald C. Violetta

During 1963 more than 200 million tons of coal was consumed by the public utility industry. Ash residual, from the burning of this coal has caused disposal problems. In order to prevent air pollution, dust collection systems have been installed to suppress the fine ash emitted from boilers before it is discharged into the atmosphere. The collected ash, called fly ash, must be removed from the dust collection facilities and disposed in some manner, usually at a substantial cost to the utility. Many years ago fly ash disposal was not a serious problem because the demand for power was relatively low and coarse coal was burned on stoker type traveling grate machines. The low burning rates utilized on these grates did not produce large quantities of air-borne coal ash while the mechanics of this system of burning resulted in a clinkered residue of cinders. Both of these conditions resulted in the production of only small quantities of fly ash. As the demand for electricity increased, a method of burning pulverized coal was developed and was introduced to the public utility industry in 1918 at Milwaukee, Wisconsin.1 This method of firing was considered a significant advance in steam electric generation as it (1) permitted the use of coals that could not be economically fired by other methods and (2) has generally resulted in improved efficiency, greater generating capacity and lower costs.2 The utilization of larger generating units using pulverized coal substantially increased the quantity of fly ash which resulted in a' more severe disposal problem.

Jan 1, 1966

By Arnold P. Pipilen

In a study of the principal factors affecting the transport of coal-water mixtures through a centrifugal pump and a pipeline, the interrelation between solids concentration, velocity, and pressure drop was established for a bituminous lump coal (minus 2 inch) in concentrations up to 48 weight-percent. An optimum concentration was found to exist for maximum capacity of a given pipe-line, and for minimum energy requirements per ton of coal. Coal size degradation by particle fracture took place in the pump; abrasion and attrition to form fines took place in both pump and line. A novel system of studying flow of solid-liquid mixtures in pipelines by the determination of relative sound intensities was developed.

Jan 1, 1966

Jan 1, 1966

By H. Leitch

In laboratory experiments, the Bureau of Mines investigated melting, quenching, and sulfuric acid leaching of alumina from mixtures of albite and anorthite, and from anorthosites containing 26 to 32 percent alumina. Variations in pouring temperature, quenching and leaching conditions, were studied with respect to the extraction of alumina and impurities. Virtually all of the alumina was dissolved by leaching melted and quenched California anorthosite in boiling 16-percent sulfuric acid solutions for 15 to 30 minutes. The leach solutions were readily separable from the solid residue by conventional thickening and filtration techniques. Only 2 to 5 grams of SiO2, Fe2O3, or CaO dissolved per 100 grams of alumina. The quantity of SiOz in solution varied inversely with the duration of the leach and with the concentration of the H2SO4 solution used. Melted and quenched Wyoming and Minnesota anorthosites with SiO2:CaO weight ratios of 4.3 and 3.2, respectively, were less amenable to sulfuric acid leaching than California anorthosite with an SiO2:CaO weight ratio of 5.3. However, excellent results were obtained on the Wyoming and Minnesota anorthosites by the addition of SiO2 to these materials before melting, in quantities sufficient to adjust the SiO2:CaO weight ratios of the furnace charges to between 4 and 6.

Jan 1, 1966

By R. H. Schutz

TO ASSIST users in the selection of reliable and satisfactory respiratory protective devices, the Bureau of Mines bas established five schedules of minimum performance requirements for the approval of respirators. The current revisions of these schedules include 130 for self-contained breathing apparatus, 141F for gas masks, 19B and the amendments to 19B for supplied- air respirators, 21B for dust, fume, and .mist respirators, and 23B for chemical cartridge respirators. Copies of these schedules may be obtained from the Bureau of Mines, Publications Distribution Section, 4800 Forbes Avenue, Pitts- burgh, Pa., 15213. Approval tests on respirators are performed only at the request of the manufacturer of the respirator and at his expense. If the deice meets the approval requirements, a certificate of approval is granted on the complete respirator. This certificate states that as long as the respirator is manufactured as originally approved, or in accordance with any changes covered by an extension of the original approval, the manufacturer may advertise and sell his respirator as being approved by the Bureau of Mines. Many industries and regulatory agencies require that respirators approved by the Bureau of Mines he used where respiratory protection is needed. The Bureau of Mines, however, has no regulatory power over the use of the respirators that it approves. It acts as an impartial testing agency to insure the availability of suitable and safe respirators.

Jan 1, 1966

Major activities of the Bureau of Mines Explosives Research Center during fiscal year 1965 (July 1, 1964, to June 30, 1965) are reviewed briefly. Part 1 summarizes significant accomplishments of the projects that were active during the report period. Part 2 presents short abstracts of the publications that appeared in the Bureau series and in other media during fiscal year 1965. Publications issued after June 30, 1965 are noted where pertinent in footnotes but are not abstracted.

Jan 1, 1966

By William J. Shampine

The Floridan aquifer, which underlies all of Florida, yields water with a hardness of less than 180 pmts per million (ppm) in the northwestern part and throughout much of the center of the Slate. In most of the rest of the Stale, the aquifer yields water having a hardness greater than 180 ppm and as much is 1,900 ppm. Hardness of ground water is caused by dissolved salts from the geologic formations through which the water passes or by direct pollution. Sometimes pollution may indirectly increase the hardness of ground water by increasing the acid content and thus increasing the solution of calcium and magnesium salts. Water from deep zones of the aquifer lend to he harder than water from more shallow zones. Only the hardness of water from the upper part of the aquifer is shown.

Jan 1, 1966

By Geoffrey Purcell

The flotation response to amine collector of quartz and the feldspars microcline and albite, of the pyroxenes augite and spodumene, and of olivine can be, explained by a physical adsorption model. Flotation decreases in the order given above, and the different behavior of the three groups is attributed to structural variations of the silicates, With sulfonate collector both chemical action and physical adsorption play their part in producing hydrophobic surfaces, and flotation increases in the order given.

Jan 1, 1966

By R. Gutray, J. E. Grainger

This paper deals with the use of a cement-deslimed mill tailings mixture for a scraping floor in cut-and-fill stopes at Madsen Red Lake Gold Mines Limited. It describes the mixing and placing procedures and the precautions used with respect to the floor while mining in the stopes. Details of the mix are presented, and advantages and disadvantages discussed. The paper concludes with a brief outline of the costs.

Jan 1, 1966

By J. V. Batty

The Bureau of Mines devised techniques involving the use of beta-and gamma-ray-emitting radioisotopes and successfully adapted these techniques to the density of mineralized flotation froths) the rate of flow of finely ground ore pulps) and the residence time of pulps in processing circuits. Specifically, the water and mineral loads of flotation froths were continuously measured by determining the proportion of a constant-strength beam of beta rays that was absorbed by the froth column. Continuous measurement of the rate of flow of an ore pulp was accomplished by measuring the changing width of a free-falling stream of the pulp with a collimated beam of beta rays. The residence time of solids in conditioning and resin-in-pulp circuits was accurately measured by following the progress through these circuits of a portion of the pulp that had been tagged with the gamma-emitting Ag110 radioisotope.

Jan 1, 1966

By R. W. Dalzell

The performance characteristics, efficiency, and operating pressure of jute line-brattice systems were studied under varying underground conditions; various fabric grades and installation methods were used. The test results indicate that line-brattice system efficiency is dependent upon the method of ventilation the method of installation, porosity of fabric, and size of tight rib area.

Jan 1, 1966

By A. W. Deurbrouck

The Bureau of Mines reviewed available data on the effect of crushing high-sulfur coals for the liberation of impurities in the light of increasingly stringent air pollution regulations. The survey, which provided information on Appalachian region coals only, indicated that such important coal-beds as the Upper and Lower Freeport and the Upper Kittanning show significant sulfur reductions when crushed to 14-mesh top size. For many other coalbeds amenability to sulfur liberation by crushing was indicated, although too few samples were available to draw firm conclusions,

Jan 1, 1966

By F. E. Walker

The Bureau of Mines determined total sulfur and sulfur forms for coal in 283 counties in 29 States and 2 fields of the State of Alaska. Specifically, organic, pyritic, and sulfate sulfur were measured of approximately 2,900 samples, and they include most of the coalbeds in the United States.

Jan 1, 1966

By Oren C. Baptist, Carlon S. Land

Laboratory research has been conducted to evaluute the effect of clay hydration on the permeability to gas of water-sensitive reservoir sands. Samples of a .sandstone containing trace amounts of montmorillonite and a sample of montmorillonite were .studied in the laboratory to detertnine whether swelling or dispersion was the cause of permeability reduction in these samples. Heliuin, containing various amounts of water vapor, was used to hydrate the clay minerals and to determine the gas permeability at various stages of clay hydration. The amount of water adsorbed by the samples using this method is small. The nonwetting-phase permeability at higher water saturations war investigated by saturating the with water and measuring the permeability to humid helium while decreasing the water saturation, Relative-permeability curves obtained from results of these procedures were used to estimate the effect of the swelling of trace amounts of mont/tlorillonite on the permeability of the .samples. Most of the damage to the permeability when reservoir sands containing trace amounts of montmorillonite are exposed to fresh water is due to dispersion and movement of clays. Blockage of pores by the increased volume of expanded montmorillonite is believed to result in permeability damage that is small in comparison to the observed damage to the samples tested. INTRODUCTION Studies have shown that permeability is severely damaged when sands containing only small amounts of montmorillonite are contacted by fresh water.15 When samples of sands containing large amounts of montmorillonite are placed in fresh water in the laboratory, these samples may completely disintegrate, forming an unconsolidated mass of larger volume than that occupied by the dry sample." In this case, it is apparent that the swelling of montmoril-lonite has destroyed the pore structure of the sand. If only a trace of montmorillonite is present in a sand. samples may remain intact when saturated with water, although the permeability to water is a small fraction of the gas permeability of the dry sample. Many workers in the field of water sensitivity have attributed this reduction in permeability to the blocking of pores and reduction of pore size by the increased volume occupied by expanded mont- niorillonite. if the sand contains a detectable amount of montmorill'onite or mixed-layer clay containing rnontmorillonite. Logically3 the smaller amount of montmorillonite present in a sand, the smaller should he the effect of montnlorillonite swelling on permeability; however, the quantity of montmorillonite sufficient to cause severe damage by swelling is not known. Although hundreds of samples have been tested in our laboratory, no correlation has been established between the amount of montmorillonite in samples and the permeability reduction caused by fresh water. To many petroleum engineers, the phrase "clay swelling" is synonymous with "water sensitivity", or "permeability reduction" implying that any formation damage due to the hydration of clays is caused by swelling. Although all clays adsorb water on their surfaces, montmorillonite is the only clay mineral commonly found in reservoir rocks which adsorbs water between intercrystalline layers, resulting in expansion of the clay particle. As montmoril-lonite swells, the first few layers of water adsorbed between platelets are strongly held and well oriented, and the montmorillonite retains its crystalline structure, although expanded. As swelling of sodium montmorillonite continues, the platelets become farther apart and the forces orienting the platelets in the crystalline structure become weaker, resulting in a less orderly orientation of platelets. In an abundance of water, small groups of platelets may become detached from the original monl-rnorillonite particle and may be dispersed throughout the water phase. Because of its swelling properties, sodium montmorillonite is very easily dispersed in water. Particles of other clay minerals. such as illite and kaolinite may also be dispersed in water. causing water sensitivity of sands not containing montmorillonite. The presence of an immobile layer of water adsorbed on the surface of clays has been considered a possible cause of the low permeability to water of dirty sands. Grim states that the thickness of the layer of immobile water held by sodium montrnorillonite is three nlolecular layers or 7.5 A (angstroms), with some orientation of water extending to 100 A. Assuming a very thick, immobile water layer adsorbed on the surface of a pore represented by a capillary tube, the maximum effect of the water layer on permeability can be calculated. Using a pore radius of 10 ' cm and an immobile water layer of 50 A. the calculation shows the permeability to be reduced only 2 per cent. Similar calculations can be used to show that the effect of electro-osmotic counterflow is of the same order of magnitude as that of bound water. The reduction of the permeability to water by either an immobile water layer

Jan 1, 1966

By S. J. Aresco

The Bureau of Mines has been active in promoting the purchase of coal for Government use under specifications that define the requirements in terms of heating value of the coal, expressed in British thermal units, and the composition as shown by proximate analyses. To these, when required, are added the ash-softening temperature, the free-swelling index, and the Hardgrove grindability index. Under most of these specification contracts the bidders guarantee the quality of the coal, and that guaranteed by the successful bidder becomes the standard of his contract. The deliveries are sampled in accordance with instructions4 issued by the Bureau of Mines; the samples are analyzed in the Bureau laboratory to determine whether the coal is of the quality guaranteed by the contractor; if it is not, a price adjustment is made. Analyses of the delivered coal and tipple samples (samples collected at mine tipples as coal is being loaded into railroad cars or trucks) provide valuable data for use in evaluating future bids. In addition, the continuous sampling of coal as delivered is a check on the practical results obtained in burning the coal.

Jan 1, 1966

By Willis Beckering

The Bureau of Mines designed a cell having four variable compartments in series to facilitate analysis of multicomponent mixtures. Use of the cell considerably decreases the time required for differential absorption analyses. A solution of a major component is placed in each compartment, and the light absorbed by each of these components is varied by increasing or decreasing the path length of the appropriate cell. Simple calculations then establish the amount of the component present. In analyzing unknown mixtures, compensation is made for compounds known to be present, and the differential spectrum representing components not accounted for is recorded and analyzed.

Jan 1, 1966

By L. H. Robinson

A proposed method of drilling utilizes sequential detonation of two types of explosive charges delivered to the hole by a conventional drilling fluid through pipe. A shaped charge first produces a long thin hole. A second charge, called a gauging charge, is pumped into the thin hole, explodes, and enlarges it to full gauge. In one suggested configuration, the explosives are contained in cylindrical capsules 4- to 5-ft long. A drilling head is positioned 2- to 3-ft off bottom. When a capsule is pumped to the bottom of the hole and stops, pressure inside the drill pipe increases and differential pressure detonates the explosive. Primacord along the length of the capsule disintegrates the capsule. The debris circulates out of the hole with the drilling fluid. The gauging-charge action was examined using 2-ft cubes of Berea sandstone. The sandstone (18 per cent porosity) was vacuum-saturated with water and surrounded by concrete. To prevent reflected tensile pulses, the acoustical impedance of the concrete matched that of the sandstone. A 750-psig pressure was applied to a drilling fluid within a shaped-charge-formed hole before detonating the gauging charge. In these tests, 190 gm of rock were removed for each gram of explosive detonated. A similar series of experiments on low-porosity (0.40 per cent) metamorphic limestone provided a more rigorous test. Extensive fracturing from the gauging-charge action prevented an estimate of the volume of the expanded hole. The diameter of the hole was irregular, ranging from about 2 to 4 in, or about fivefold larger than the hole created by the shaped charge. INTRODUCTION In the past, explosives have found a varied but somewhat limited use in the oil field. An early well stimulation technique, still in use today, in vo lves shooting ni troglycerin to en large the borehole and to increase matrix permeability near the wellbore. Bullets and jets are now the conventional method of perforating casing and tubing. Detonations are frequently used to "back off" or "shoot off" stuck pipe and, of course, seismo-graphic work has long depended on explosive-generated pulses to find attractive earth structures. Efforts to use explosives in drilling operations have received limited examinations1-3 which, in one respect, is surprising because explosives offer one way to transmit large amounts of energy directly to the bottom of the hole. Recently, Ostrovskii l described a Russian method of drilling with explosives that utilizes small capsules containing explosives which are pumped into the mud stream to the bottom of a borehole. As the capsules leave the end of the drill pipe, a detonation mechanism is armed. Impact detonates the explosive. In another configuration, two liquids (an oxidizing agent and fuel) in the capsule are separated by a frangible membrane. Separately, the liquids are nonexplosive. Near the bottom of the drill pipe, the capsule passes through a narrow constriction which ruptures the membrane. The mixing of the liquids produces an explosive. Impact is again used to detonate the explosive. About the time Ostrovskii was developing his method, Humble Oil & Refining Co. was independently doing research on another explosive drilling concept based on the sequential detonation of two types -of explosive charges. The proposed technique consisted of alternately pumping a shaped charge and then a "gauging charge" down a well. The shaped charge should drill a long, tapered hole, and the gauging charge should expand it to full gauge. This paper presents the visualized drilling concept and gives results of laboratory work which showed that sequential firing of charges can form hole at an attractive charge-to-rock removal ratio. An important finding was that increased environmental pressure, which is to be expected in wells, increases rock removal efficiency of the gauging charge.

Jan 1, 1966

By G. B. Walker

The success of Heavy Media Separation, the static sink-float process, is evidenced by the operation of an estimated 300 installations treating many millions of tons per year of a wide variety of mineral products ranging in value from gravel to diamonds. The static heavy media process is usually limited to the treatment of plus 1/4 inch material. Mr. Victor Rakowsky, who was largely instrumental in the development and application of heavy media separation, recognized the need for a new apparatus and process which would extend the application of heavy media into the finer size range without placing a restrictive limit on the top size of the feed. He recognized the requirement for the application of centrifugal force to augment the force of gravity in separating fines by sink-float techniques.

Jan 1, 1966

By Wallace W. Key

This report concerns types, quantities, specifications, and uses of non-metallic minerals as a basis for improving their supply, conservation, and utilization. Supply-demand details concerning mineral fillers, roofing granules, and roofing rock used in asphalt are incorporated in this report, along with highlights on production and sales of roofing, floor tile, and other related asphalt products of California. Comparable data for the United States are included. Although large quantities of commercially prepared mineral fillers are used in asphalt for paving and related applications in other States, addition of commercial fillers for these uses rarely is required in California because of the natural fines available. On the other hand, California manufacturers of asphalt products other than paving utilize about 300,000 tons of asbestos, diatomite, limestone, mica, soapstone, slate, and other nonmetallic minerals as filler, mainly for roofing and flooring. Also, about 500,000 tons of roofing granules is produced in California, most of which goes into roofing manufacture in California. In addition, a significantly large and growing tonnage of relatively coarse mineral aggregates are used on low-angle, built-up, asphalt roofs to produce an attractive surface and offer protection against the elements. Nearly all minerals used in asphalt products manufactured in California come from local sources, except asbestos and mica--and there are indications that local deposits of these commodities could be utilized in some use categories.

Jan 1, 1966

By William A. Kneller

A considerable range of composition exists in rocks that have been described as chert, jasper, or flint. Their composition may be opaline, chalcedonic, quartzose, or mixed. Certain cherts, when incorporated in concrete, are known to possess nondesirable thermal and chemical properties. The inability of chert to withstand thermal shock above the freezing temperature of water is an example of such a property. Cryothermal reactions may cause disintegration of concrete, due to repeated cycles of freeze and thaw. Thermal properties are significant because small temperature changes may cause inordinate expansion and resultant fissuring of concrete. Freezing of entrained water in chert may cause excessive physical failure in concrete. Some cherts react chemically with alkalies liberated during the hydration of the cement, with resultant cracking and deterioration. Sources of concrete aggregate in Ohio have been viewed with suspicion because they contain considerable chert derived from Middle Devonian and Pennsylvanian carbonate rocks. Light-colored porous cherts from the Middle-Devonian Colum- bus Limestone exhibit the least freeze-thaw durability of the samples studied. Denser cherts may also yield to freeze-thaw stresses, but tend to be more susceptible to thermal shock. Cherts rich in opaline and chalcedonic silica usually exhibit alkali-aggregate reactivity.

Jan 1, 1966