Search Documents

By Q. Xu, P. Somasundaran

Adsorption of nonionic/anionic surfactant mixtures on kaolinite has been studied, with •Sodium dodecylsulfate as the anionic surfactant, and •Octaethyleneglycol mono-n-dodecylether as the nonionic surfactant. Synergistic interaction between these surfactants was found to cause adsorption of the nonionic surfactant with its hydrophilic chains protruding into the bulk, leading to substantial changes in wettability and dispersion characteristics of kaolinite. Similarly, hydrophobicity changes are observed also for silica particles upon adsorption of nonionic ethoxylated alcohols owing to possible changes in the orientation of the adsorbed surfactant molecules at the interface.

Jan 1, 1993

By K. S. Shivakumar, R. Bhima Rao, M. R. Patil

Liberation size can be estimated using various techniques such as grain counting, frequency curves, X-ray intensity and the mesh of grind. The present investigation deals with the estimation of the liberation size of graphite flake contained in a schistose ore from Shivaganga, India. It was observed that the flakes are liberated at from 75 to 150µm. The rougher flotation concentrate obtained after grinding the run-of-mine ore for 5 min contained 54% fixed carbon. This represented the first stage of liberation. After regrinding to <90 µm in the presence of sodium silicate and guar gum, a cleaner concentrate containing 82% fixed carbon was obtained.

Jan 1, 1998

By C. R. Jenkins, G. S. Taylor

Three sedimentation ponds had their performance evaluated before and after installation of modifications. Each pond had a floating baffle installed, two had siphon outlets, and one had a floating outlet device. Baffles inhibited short circuiting, and the outlet devices retarded flow following a rainfall event and drained the pond, creating a large storage volume to maximize detention time. Total suspended solids and settleable solids tests were measured on samples of influent and effluent to evaluate pond performance. Particle size analyses were conducted on samples containing measurable amounts of solids. Performance improved in each pond, with baffles providing the major improvement.

Jan 1, 1987

By Charles D. Litton

This Bureau of Mines paper describes a novel fire detector that can be used to discriminate between smoke produced by a fire and smoke produced by a diesel engine. The detector uses a pyrolysis technique whereby a sample of smoke- laden gas passes through a short, heated tube within which fire smoke particles pyrolyze and increase their number concentration and decrease their average size, while diesel smoke particles are unaffected. The detector is designed for use in mines that use diesel-powered equipment where the detection of fires is complicated because of the diesel emissions background levels of smoke and other products of combustion.

Jan 1, 1989

By W. D. Presley, T. R. Harrell

This paper will be a case history of the shaft and tunnel concrete lining techniques used at the Rocky Mountain Pumped Storage Project located in northwest Georgia. Emphasis will be placed on the shaft lining techniques with only a brief description of the tunnel concrete lining techniques. The 10.67 meter (35 foot) diameter shaft and tunnel concrete linings are 0.61 meter (2 foot) nominal thickness with a single row of reinforcing bars. The tunnel was placed in 18.29 meter (60 foot) lengths with bulkheaded end sections. The 172.72 meter (566.68 foot) vertical shaft was placed in 3.05 meter (10 foot) high sections using jump forming techniques.

Jan 1, 1985

By S. J. Jung, F. Lock

This research came about because of the recognized need for a safe, easy way to line small-diameter bored raises (less than 150 cm). Currently, an operator must go down the raise and apply the concrete lining manually, using the shotcrete method of application. With an automated system, there would be no man positioned in the bore itself. All control functions could be commanded from a central location. Shotcreting in the confined space of a small-diameter bored raise presents problems that can be overcome by the application of shotcrete using a remote system.

Jan 1, 1995

By F. M. Doyle, Jiang Tao, Xu Shi, Chen Jin, E. Peters

Tafel curve technique and leaching tests have been applied to study the kinetics of gold leaching with thiosulfate. Results show that cupric ions and ammonia play the part of catalysts in the leaching of gold with thiosulfate. The activation energy of gold dissolution is calculated as 27.99 KJ/mol in the absence of both cupric ions and ammonia. However, the energy is reduced to 15.54 KJ/mol in a solution of 0.01 mol/L Cu (NH3)2 4* and 0. 5moVL total ammonia. The reaction order of Cu (NH,) g is one in the range of 0.001~0.1mol/L. These results support the electrochemical-catalytic mechanism pro- posed by the authors and explains the behavior of cupric ion and ammonia (Jiang Tao, et al., 1993)

Jan 1, 1993

By Jozef Szymanski, Julian Partyka, Jerzy Krynicki

In order to study blast-induced dust in a hard rock metal mine experimentally and analytically, a part of a stope mined by Vertical Retreat Mining (VRM) was monitored throughout its lifetime. Dust measurements were used to describe the dust source, to study the dynamics of removal of airborne dust from the blasting area, and to examine a variation in dust production with a stope&apos;s progress. An analysis based on graphical and analytical comparisons of blasts taking place in a single stope is presented and discussed. Also, some transient phenomena of dust flow in the stope vicinity, caused by the blasts only, are examined.

Jan 1, 1997

By John M. Anderson

This paper examines the methods available to improve climatic conditions around a deep, high production longwall district of a British coal mine using results from a computer model. Such methods include the provision of increased ventilation quantities, the application of refrigeration, the reduction of heat input at source and the use of alternative ventilation systems. An approach to the solution of a climatic problem is explained with reference to other coal mine contaminants and a cooling strategy for deep high production British coal mines is described.

Jan 1, 1987

By W. H. Su, S. S. Peng

Extensive investigation has been conducted to determine the causes of a series of roof falls occurring in an underground coal mine located in southern West Virginia. Underground observation, along with laboratory testings and finite element analyses, were conducted to search for possible mechanisms for the roof falls. Results of the investigation have led to a better understanding of the mechanisms involved in the roof falls. Necessary modifications of mine layout and roof support plan are proposed for improving safety and profitability at the mine.

Jan 1, 1987

By B. Howerton, M. M. Matlock, D. A. Atwood

In the Gold-Cyanide Process (GCP) the cyanide anions act to solubilize the gold and silver present in the ore, and mercury as well. The resulting mercury and cyanide rich effluent are serious health and environmental problems. Currently, there is no mercury treatment from the ore leach solution since there are no precipitating agents or other technologies which can be used effectively in the pH ~ 10solutions. Recently, however, we have developed a new chelate ligand that is impervious to this level of pH and it can be used to precipitate Hg from NaCN solutions. On an actual sample taken from an active gold mine the chelate selectively reduced the mercury level from 34.5 ppm to 0.008 ppm within 15 minutes. Importantly, the gold and silver levels remained unchanged throughout this process. Thus, the environmental impact of Hg released in the GCP can be drastically reduced. Moreover, with a mercury treatment technology now available it may be possible to change, or reinvent, the entire GCP process.

Jan 1, 2003

By S. G. Haycocks, M. Karmis, C. Haycocks

Risk assessment is a primary factor in the decision to mine some near surface orebodies, such as limestone, by either surface or underground methods. Identification and quantification of risks demonstrate that environmental concerns are greater for surface operations than underground, and may include such factors as runoff, spoil piles, aesthetics, dust, and large site reclamation. Risk assessment also includes local public feeling towards surface and underground operations while considering the balance between environmental impacts and the economic effects of mining on the local community. A complete understanding of the risks involved permits a comprehensive and accurate comparison between the two mining alternatives.

Jan 1, 1992

By Leonard Harris

The 1980s marked a boom in gold mining and exploration in the United States particularly in the state of Nevada which lifted this country to second place in the world, after South Africa, in gold production. With this boom came many positive aspects such as increased employment, increased investment, increased payment of federal and local taxes, higher purchases of goods and services and higher expenditures on social and economic uplift programs. With the arrival of Minera Yanacocha in Peru in 1992, the gold mining boom shifted to this country which has lifted Peru to first place in Latin America in 1996 and ninth place in the world in gold production. As in the case of the United States in the 1980s, similar positive impacts are being felt throughout Peru in the 1990s.

Jan 1, 1998

By T. C. Eisele

Previous work by the authors has shown that the performance of a flotation column can be improved by the use of horizontal baffles. These baffles prevent axial mixing and also reduce "churning" of the froth by breaking up or preventing the formation of large air bubbles. In this paper, results from tracer experiments are presented that show the effects of horizontal baffles on the reproducibility and stability of the column operation. The baffles prevent random disturbances, such as unusually large air bubbles and turbulence, from rapidly propagating along the height of the column. Because these factors are responsible for much of the variations in column performance between tests, the result is that the horizontal baffles make the column performance more reproducible, with fewer short-term variations.

Jan 1, 1999

By K. R. Wood, P. M. Blythe, J. A. Finch, M. L. Lavallee

A new analytical approach for characterizing and improving the performance of ball milling is presented. Individual ball mill circuit design and operating variables can be related to overall circuit performance through two distinct parameters for classification and breakage. The ball mill circuit functional performance equation is presented. Applications in the industrial plant and in the research field are discussed.

Jan 1, 1991

By G. Jeffrey Taylor

The environment at the lunar surface is drastically different from the one we are used to on Earth. The Moon has one-sixth of Earth&apos;s gravity, virtually no atmosphere, a surface bathed in radiation and micrometeorites, large temperature gradients, low seismicity, and a dusty, rubbly surface. To successfully mine and process materials on the Moon and to mitigate degradation effects in the hostile lunar environment, these factors require new designs for equipment and development of new techniques and technologies.

Jan 1, 1990

By Ron Allum, Ed VanDerPas

The application of high speed tunneling in a deep underground copper mine is essential for an ambitious expansion project at Magma Copper Company&apos;s San Manuel Mine. At stake is the future of over 1,300 employees at the largest producing full gravity block caving copper mine in the world. A joint venture of Frontier-Kemper Constructor&apos;s Inc. and Deilmann Haniel GmbH is helping create that future through the successful application of tunnel boring technology. This paper examines the details required to assemble, deploy and operate a 4.62 m open main beam tunnel boring machine (TBM) in a 1048 m deep operating mine accessible only by shaft.

Jan 1, 1995

By A. Arik

The accurate estimation of mining-block grades continues to be a challenging task for ore reserve practitioners. The estimation method used and the variability of the mineralization in the deposit are two factors that affect the accuracy of the estimates. The objectives of this study are to determine how different estimation methods perform on a given deposit and to determine the impact that the nature of the mineralization has on the results. A comparison of several estimation methods for prediction accuracy is performed based on conditional simulation results.

Jan 1, 2002

By Mengxiong Guo, Xuxin Shao, Yong Bao

In the paper, the adsorption properties of dissolved ions on the surface of collophane and dolomite are studied using zeta potential measurement, ESCA and UV adsorption spectrum both in distilled water and in the supernatant of each other. The effect of dissolved ions on the flotation separation of collophane and dolomite under SCO depressant and oleate is discussed on the basis of above analyses.

Jan 1, 1993

By John E. Urosek, Timonthy R. Watkins

Room and pillar mining accounts for approximately 73 percent of the active gobs used in the United States in 1993. The Mine Safety and Health Administration conducted field investigations on six different types of bleeder systems used to ventilate areas mined by room and pillar methods. This paper discusses investigations that were conducted at mines using four of these systems.

Jan 1, 1995