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By Kihong Park

A hygroscopicity tandem differential mobility analyzer (HTDMA) technique is used to determine size-effect of nanoparticles (NaCl, (NH4)2 SO4, KCl, NH4NO3, MgCl2,CaCl2) on their hygro­scopic properties (deliquescence relative humidity (DRH) and hygroscopic growth factor (GF)). The HTDMA system uses a combination of two nano DMAs and two regular DMAs to measure particle size change in a wide dynamic particle size range. Particles are subsequently analyzed with a transmission electron microscopy to investigate the potential effect of particle structure or morphology on the hygroscopic properties. We found that structural properties of NaCl and (NH4)2SO4 particles also play an important role in determination of the DRH and GF and are more pronounced at smaller diameters. Data show that the DRH of NaCl nanoparticles increased from *75% up to *83% RH at 8 nm and that their GF decreased with decreasing size. The extent to which the GF of NaCl nanoparticles decreased with decreasing size was greater than theoretically predicted with the Kelvin correction. The GF of furnace-generated NaCl nano­particles that have pores and aggregate shape was found to be smaller than that of atomizer-generated particles that are close to perfectly cubic. For the case of atomizer-generated (NH4)2SO4 nanoparticles, we observed no signi?cant size-effect on their DRH, and the measured GF agreed well with predicted values using the Kelvin correction. For furnace-generated (NH4)2SO4 nanoparticles, a gradual growth at moder­ate RH without noticeable deliquescence behavior occurred. Their TEM images showed that contrary to atomizer-generated (NH4)2SO4 nanoparticles the fur­nace-generated (NH4)2SO4 nanoparticles are not perfectly spherical and are often aggregates having pores and holes, which may favor holding residual water even in the dried condition. For atomizer-generated KCl, MgCl2, and CaCl2 nanoparticles, we observed no signi?cant size-effects on their DRH and GF for the mobility size as small as 20 nm.

Jan 1, 2008

By C. M. Mason

A series of gelatinous permissible explosives was prepared with increasing sodium nitrate content and subjected to an improved technique for evaluating incendivity in coal dust-air and coal dust-gas-air mixtures. Those explosives containing an appreciable amount of sodium nitrate were found to be very hazardous in coal dust-air and coal dust-gas-air mixtures.

Jan 1, 1969

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

1 11 THIS IS A DIGITAL COMPUTER SIMULATION OF THE VENTILATION SYSTEM OF A MINE LOCATED IN WASHINGTON COUNTY, PENNSYLVANIA. THE VENTILATION SURVEY ON WHICH THIS SIMULATION IS BASED WAS RUN FROM OCT. 27-30 AND ON NOV. 2, 1976 IN THE ACTIVE PORTION OF THE MINE INBY COMBS SHAFT AND THE INACTIVE PORTION AFCUND AND INBY DONAHOO SHAFT. FOLLOW-UP SURVEYS WERE THEN RUN ON FEB. 18 AND FROM MARCH 7-11, 1977 TO INCLUDE THE MAIN HAULAGE SYSTEM OUTBY THE ACTIVE AREAS OF THE MINE. ALL SURVEY DATA WAS NORMALIZED TO A STANDARD DENSITY OF 0.075 POUNDS/CU.FT. PRIOR TO THE CALCULATION OF INPUT PARAMETERS FOR THIS SIMULATION. IN THIS RUN, THE ORIGINAL VENTILATION NETWORK HAS BEEN MODIFIED TO INCLUDE NEW INTAKE AND RETURN AIRSHAFTS AT THE WEST MAINS.

Jan 1, 1977

By W. L. Staker

Alternatives were developed to the conventional ammoniacal carbonate leaching-steam stripping procedure for recovering copper as an oxide from contaminated scrap metal. By entraining air bubbles in the leach solution, the copper dissolution rate was increased to 1.5 g/in2 of copper surface per hour, compared to 0.5 g/in2/hr produced by conventional agitation in stirred tanks. Using entrained nitrogen gas bubbles for agitation in conjunction with powdered sulfur not only resulted in rapid dissolution but also simultaneous precipitation of the copper from solution as a high-grade cuprous sulfide.

Jan 1, 1971

By R. Pakalnis, C. A. Dreesbach, L. A. Martin

Instrumented cable bolts developed at the Spokane Research Laboratory of the National Institute for Occupational Safety and Health were used in conjunction with existing ground control systems to monitor rock mass loads at Tg Soda Ash’s trona mine, Granger, WY. Axial and shear loads were determined to levels of strain gauge accuracy of ±5 N or ±5 microstrain. These gauges were embedded in a remanufactured king wire that replaced the conventional king wire. Cable bolt performance, quality of grout, and installation techniques were also assessed. By using instrumented cables, a mine operator can determine axial load along the cable at predefined gauge locations. These data provide necessary input for an operator to design a safer working environment for miners.

By J. P. Morris

This paper describes a gas-transport method for measuring vapor pressures of liquid metals. Vapor pressures of iron and nickel were determined at temperatures between 1,540° and 1,620° C. The results can be represented by the following equations: log Pmm (iron) -19,460/T + 9.147, log Pmm (nickel) -2l,030/T + 9.689. The study was undertaken as part of a program to determine thermodynamic activities in liquid iron alloys.

Jan 1, 1957

Provide a means through which members of the mining community can easily and readily access information on human factors/ergonomics as it relates to mining. Approach As part of a research study aimed at reducing human error accidents in mining the Bureau of Mines developed a computerized information retrieval system which provides relevant human factors or ergonomics information on 19 mining-related special interest categories.

Jan 1, 1988

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

1 14 THIS IS A DIGITAL COMPUTER SIMULATION OF THE VENTILATION SYSTEM OF A MINE LOCATED IN WASHINGTON COUNTY, PENNSYLVANIA. THE VENTILATION SURVEY ON WHICH THIS SIMULATION IS BASED WAS RUN FROM OCT. 27-30 AND ON NOV. 2, 1976 IN THE ACTIVE PORTION OF THE MINE INBY COMBS SHAFT AND THE INACTIVE PORTION AFOUND AND INBY DONAHOO SHAFT. FOLLOW-UP SURVEYS WERE THEN RUN ON FEB. 18 AND FROM MARCH 7-11, 1977 TO INCLUDE THE MAIN HAULAGE SYSTEM OUTBY THE ACTIVE AREAS OF THE MINE. ALL SURVEY DATA WAS NORMALIZED TO A STANDARD DENSITY OF 0.075 POUNDS/CU.FT. PRIOR TO THE CALCULATION OF INPUT PARAMETERS FOR THIS SIMULATION. IN THIS RUN, THE ORIGINAL VENTILATION NETWORK HAS BEEN MODIFIED TO INCLUDE NEW INTAKE AND RETURN AIRSHAFTS AT THE WEST MAINS. IN ADDITION A CONNECTION HAS BEEN MADE BETWEEN THE MINE UNDER STUDY AND A SHAFT IN A WORKED OUT MINE IN THE 1 FACE AREA. THIS SHAFT IS CONSIDERED AN INTAKE SHAFT FOR THIS RUN.

Jan 1, 1977

Reduce the dust levels to which jacksetters and helpers on auger mining sections are exposed by identifying viable, effective methods for control-ling respirable dust on these sections. Approach The Bureau of Mines con-ducted laboratory tests and respirable dust surveys to identify the factors that distinguish clean auger mining operations from dusty ones. Study Results Results of the Bureau's study revealed that ventilation is the most important element of auger mining dust control. The four must important venitilation parameters are airflow, curtain configuration, curtain setback, and curtain installation.

Jan 1, 1988

By R. L. Wise

Heat content studies were conducted on burned shale, spent shale, and three grades of raw oil shale from the Green River Formation. Corrections were made for product enthalpies. The results were compared with previous work, indicating good agreement below retorting temperatures, but some differences at retorting temperatures. A general equation was developed relating heat content to oil-shale grade and temperature.

Jan 1, 1971

Provide exhaust face ventilation to remotely-controlled continuous mining machines making extended advances without exposing workers to unsupported roof. Approach Modify the sprayfan to move additional air to and from the coal mine face. Unmodified, sprayfans are capable of ventilating the face with 20-foot brattice setbacks. Additional sprays on the rear of the mining machine allow setbacks to be extended up to 40 feet.

Jan 1, 1988

By Pablo Velasco

Ecuador had limited mineral output, al-though the Government attempted to stimulate metallic mineral exploration and also evaluated a gypsum and a phosphate deposit. A pilot plant to exploit gold deposits was established, and there was extensive gold exploration activity in southern Ecuador. Domestic output of iron and steel declined sharply. Among all minerals, petroleum output was the dominant factor with both exports and production increasing significantly over that of 1988. Crude oil exports contributed 63% of total export earnings and about 70% of the central Government's revenue.

Jan 1, 1986

Improve mine refrigeration system efficiency while providing free electrical energy to mines. Approach Convert the potential energy of incoming mine water falling down long vertical shafts into electrical energy by means of a turbine-generator system located at the bottom of the mine shaft. How it Works Converting the energy of falling water into useful work is a well-developed engineering concept. Water flowing down long vertical pipelines into deep mines develops high pressure that can be used to operate a turbine-generator system at the bottom of the pipeline. A thermal energy recovery system of this type offers three advantages: 1. In systems without turbines, the potential energy of the water is converted to heat. The water temper-ture will automatically

Jan 1, 1985

By H. H. Fukubayashi

This Bureau of Mines report describes the development of a pyrometallurgical process for the recovery of the zinc and lead contained in brass smelter flue dusts, which constitute a recycling or disposal problem. Tests on brass flue dust from several sources were made in a quartz tube, heated by an electric furnace to temperatures as high as 1,050° C. The dusts were mixed with carbon and heated in an oxygen-free atmosphere. It was demonstrated that 98 pct of the zinc and 12 to 25 pct of the lead, both in the metallic state, could readily be removed from the dusts. It was also found that 75 pct of the zinc could be recovered, with less than 0.1 pct of the lead, in the absence of chlorides. Pelletization techniques were investigated and 0.6 inch pellets were found to be optimal. Pelletizing results in a tenfold reduction in volume.

Jan 1, 1974

By P. G. Pigott

This investigation by the Bureau of Mines demonstrated that building bricks can be produced by the steam-curing process from various types of industrial mineral wastes. Wastes, utilized to produce bricks, consisted of copper mill tailings, roofing granule fines, asbestos fines, and zinc mill tailings. Bonding of the wastes with either Ca(OH)2 or portland cement resulted in building bricks that met ASTM specification C73-67 for grade SW and MW bricks when evaluated in accordance with ASTM designation C67-66 on sampling and testing of brick. An economic evaluation of the process indicates the total operating cost per 1,000 bricks is about $36.

Jan 1, 1974

By A. W. Hall

A neutron meter was developed for monitoring the sulfur content of coal streams. Neutrons from 80 micrograms of californium-252 penetrate the coal, producing thermal neutrons that are captured by atoms of elements present in the coal. The excited atoms emit prompt gamma rays with energies characteristic of the capturing element. These gamma rays are detected with a 6-by 7-inch sodium iodide detector and processed by electronic equipment to produce a gamma ray energy spectrum of the elements. Tests of the meter at a commercial coal preparation plant showed that sulfur in moving coal can be determined to a precision of 0.05 percent sulfur within 2 minutes. Based on this report by the Bureau of Mines, reliability of the coal-handling system proved inadequate for long-term operation, however, and improvements are planned.

Jan 1, 1975

By Ann G. Kim

Gas samples containing 02, N2, H2, He, CO2, CO, CH4, and trace amounts of C 2 to C6 hydrocarbons are analyzed by a gas chromatographic method that utilizes both thermal conductivity and flame ionization detectors. A porous polymer support and molecular sieve columns are used with argon as the carrier gas. A column selector valve makes it possible to perform a complete analysis either on one 1-ml sample in 40 minutes or on two samples in 20 minutes, one sample for each detector. Samples are introduced either by on-column injection or through a gas sampling valve. By varying operational parameters, the speed, sensitivity, and accuracy of analysis may be modified to suit a particular situation.

Jan 1, 1974

By R. F. Abernethy

The work discussed in this report was done by the Bureau of Mines to develop a method for determining trace amounts of fluorine in coal. Samples of coal mixed with calcium oxide as a fixative agent for fluorine were ashed at 600° C and the residue was fused with sodium carbonate. The melt was dissolved in phosphoric and sulfuric acids and distilled to separate the fluorine) which was determined in the distillate by a SPADNS-zirconium spectrophotometric method. Fluorine determinations of 83 commercial coals ranged from 0,001 to 0.019 percent.

Jan 1, 1967

Aid mine workers in detecting hazardous roof conditions in underground mines by developing a method of roof sounding which supplements or replaces the traditional roof sounding technique where the miner relies on experience to determine whether or not the rock is sound. Approach The Bureau of Mines developed an electronic roof sounding de-vice that acoustically determines the integrity of mine roof rock by "listening" to the variation in frequency vibrations within the rock. How It Works n previous research, the Bureau of Mines found that loose rock in a mine, when impacted, vibrates at a much lower frequency and for a lower time period than does a solid slab. By quantifying the enhancement of low frequency vibrations in loose rock over solid rock, a repeatable, objective measure of the rock's soundness can be obtained. This approach was used in developing the rock stability tester.

Jan 1, 1986

Provide sound battery safety guidelines for mine workers who maintain mobile surface mining equipment. Approach Battery-related accidents account for about 5 percent of all nonfatal disabling injuries in coal and metal nonmetal surface mines. These accidents occur despite the fact that appropriate battery safety technology (maintenance-free batteries, cable removers, fault detectors, hot-jumping systems, etc.) exists. Mine operators are not always aware of the safety measures that could be taken because this safety information is widely scattered in numerous unrelated technical reports, vendor brochures, and journal articles. A literature search of these reports and a review of relevant industry standards, handbooks, and references on battery safety, followed by discussions with mining company and MSHA personnel, provided the Bureau of Mines with the background necessary to develop procedures for proper and safe battery usage. These procedures were condensed and written in nontechnical language to serve as guidelines in assuring battery safety during maintenance of mining equipment.

Jan 1, 1986