Search Documents

By J. Stachurski, N. A. Abdel-Khalek

Flotation tests were carried out on six coal samples of different rank as well as their oxidized samples. A mixture of diesel oil and alcohols was used in these tests. Surface oxidation caused a distinct decrease during flotation recovery with some improvement in the grade. The reduction in the recovery increased with increasing concentration of the oxidizing agent. The floatability of low rank coals was affected by oxidation to a higher degree than the floatability of medium and high rank coals. The recovery-size curves of oxidized samples were similar in shape to the recovery-size curves of non-oxidized coals.

Jan 1, 1991

A study was undertaken to determine the effects of five industrial frothers on the relationship between entrainment recovery and water recovery. The experiments were conducted using a Batequip rectangular 60L steel flotation cell that was run in parallel with the first cell in a copper/silver prefloat rougher circuit. The concentration of the frothers ranged from 2.5 to 8.4 g/t. The experiments were repeated at three different froth depths. A power function was found to fit this relationship with no discontinuity in the relationship caused by the changes in frother type and concentration and froth depth.

Jan 1, 2002

By Robert S. Post

A highly respected coal mining company in West Virginia updated their stacker belt by switching to a new magnetic coupling. The savings they achieved are the subject of this paper. A steep incline and heavy belt loads are powered by a dual drive arrangement. The magnetic couplings were custom designed for complete fluid coupling retrofit and easy installation in the field. Maintenance personnel updated the drives in just a few hours. Over the following several weeks, adjustments were made to the couplings for optimum performance. Cost savings are found in reduced down time, no coupling maintenance, and equipment protection.

Jan 1, 2000

By J. Litsenberger, T. E. Marshall, L. Burke, R. Melville, A. T. Iannacchione

Excessive levels of horizontal stresses cause ground fall hazards in underground mines in the Appalachian Basin. At an underground stone mine in Pennsylvania, a modified stress control mine layout is reducing the hazardous conditions associated with excessive horizontal stresses. A microseismic monitoring system is in place to measure levels of rock stability and provide information on the effectiveness of the design technique. The microseismic data is supplemented with frequent and extensive mapping of roof falls and roof rock damage. Findings to date show that the stress control layout provides more stable conditions and thus a safer environment for the mine workers.

Jan 1, 2001

By Robert C. Bates

Background is given on the various equations used to describe diffusion and convective flow of radon in porous media. Bureau-developed equations for modeling diffusion and Darcy flow through multilayered porous media are described briefly, and examples of their use are given. Analysis results discussed include: The transient effect of pressure changes in different length models, time dependent flux changes in multi-layered models, and radon flux through pinholes in sealants

Jan 1, 1980

By J. T. Gepford, K. A. Prisbrey, T. Scott, M. Spangler

Using neural networks for plant control is challenging. The objective was to show how to make a neural network effective, even with noise, lag times, and unmeasured disturbances in the plant. The procedure was to evaluate the neural network in a laboratory flotation vision system and in a plant refractory gold autoclave system. Although the resulting neural network easily conquered simple laboratory data, the noisy plant data was much more difficult, and adaptive linear models were equally effective. We concluded that the neural network needs support by combining it with other tools found in the best control packages.

Jan 1, 2000

By W. Swisterski, G. Romaniszyn, S. A. Lukasiewicz

The present paper analyzes the motion of a particle of material in a horizontaly rotating tumbling mill. The sliding of the particle under action of dynamic and friction forces and its free flight fall are analyzed. It was found that mechanism of free-fall occurs at supercritical rotations of the mill.

Jan 1, 1991

By William F. Riggs

The name of this symposium speaks for itself in the connotation normally assigned to the term 'political. "In this paper, various donors have contributed their stories of metallurgical bloopers, blunders, and scams. The paper covers areas from human error stories, through technical blunders, to outright scams. Included are some stories that involve geology as it relates to metallurgy, warehouses of precious metal concentrates, reagent selection, solutions that treat the symptoms instead of the problems, improper technological transfers, humorous design mistakes in the interest of being exacting, and many more. The stories are all true with the names and dates withheld and the cases presented in the true sense of the "John Doe Stories."

Jan 1, 2001

By S. Bhattacharjee, S. K. Singh, R. K. Galgali

A method for the preparation of zirconia- toughened mullite using dc plasma is presented. An indigenously developed 50-kW thermal plasma reactor is used for the preparation of zirconia-toughened mullite using a dissociated zircon and alumina mixture. Both XRD and SEM studies of the product confirmed the formation of mullite and zirconia. The zirconia grew as equiaxed grains of uniform size (~5 µm) in a mullite matrix.

Jan 1, 2002

Laboratory techniques have been developed at the Julius Kruttschnitt Mineral Research Centre which relate comminution energy to size reduction. These relationships have been applied in the mathematical modelling of autogenous and semi-autogenous mills. Since their development in 1987 these models have been successfully used in many wide ranging design and optimization studies. A description of the basic structure of the models is presented with particular reference to ore characterization. Two case studies are presented which illustrate their effectiveness in evaluating and predicting the effects of circuit changes.

Jan 1, 1992

By L. L. Oriard

The author describes three case histories of fracture-control blasting demonstrations. This is a technique in which the walls of blast holes are scribed or notched in order to enhance the development of blast_induced fractures, and to control their direction. One demonstration was that of a tunneling application in a rock that was generally competent but strongly foliated, hence strongly anisotropic. P second test was conducted for perimeter blasting of a structural excavation in a massively jointed limestone. A third field test was conducted for tunneling through an old concrete structure. Increased applications are envisioned with new tool modifications being developed at the University of Maryland.

Jan 1, 1981

By K. N. (Mani) Subramanian

A 2.5 meter diameter column has been successfully used in a 100 tph flotation plant at the Harbour Lights Mine in Leonora, Western Australia, to produce a final gold bearing sulfide concentrate from the ore in a single stage. This pioneering application of column flotation cells to rougher stage was pilot tested using a 11 cm column, which demonstrated column's capability in rougher, scavenger and cleaner flotation stages. A hybrid circuit involving columns and mechanically agitated flotation cell s was adopted for the commercial installation. This paper describes pilot plant results, design of the plant flotation circuit, and early results of commercial operation.

Jan 1, 1988

By C. A. Wiggins

The new Niagara Falls Intake Tunnel, mined in the highly fractured Lockport Dolomite, encountered prolific inflows of water contained in rock seams directly linked to the Niagara River. These inflows were pressurized and, more significantly, contained high concentrations of dissolved H2S gas. The contractors attempts to control the water/gas inflows included cement and chemical grouting from inside the tunnel. Ultimately, improving the rate of air exchange in the tunnel by increasing the fan capacity, in conjunction with a pattern down-hole pre-grouting program along the tunnel alignment allowed the contractor to control the concentration of H2S gas and complete the tunnel.

Jan 1, 1997

By Klaus Schönert

Theories are proposed to explain consistently a class of phenomena and are established with experiences, hypotheses, and laws. Not all concepts need to be presented in a mathematical format. A comminution theory must incorporate fracture physics, particle breakage, stressing events in crushers and mills, material transport, comminution kinetics and models, etc. In this paper the state of knowledge of some of these aspects is discussed. An attempt has been made to show the benefit of theory in comminution practice.

Jan 1, 1995

By Michael G. Nelson, Brandon J. Peterson

Currently, decisions made by mine management are usually based on economic analysis and predetermined rating systems and tables. As financial and other constraints on mining operations become more severe, more accurate methods are required. Discrete-event simulation programs have been used successfully in many mining applications, including the simulation of open-pit, truck-and-shovel operations. However, these simulations could not model complex systems well enough to provide the detailed modeling of the haulage roads and other mining operations that is needed today. The recent advances in computing technology combined with the recent abilities of simulation to realistically simulate complex systems and visually present results in 3D have made simulation a more detailed and valuable aid in the evaluation of mining projects.

Jan 1, 2002

By D. Malhotra

This paper discusses the need for periodic auditing of mineral processing flowsheets and the potential benefits a company can gain from a study of this nature. A carefully designed flowsheet audit can have a significant impact on the metallurgical performance in the plant. Several case studies illustrating the potential benefits that can be attained from flowsheet auditing of mineral processing plants are discussed.

Jan 1, 1988

By Priscilla P. Nelson, Steven D. Glaser, Thomas D. Rourke, O&apos

Construction records from six projects which employed full-face TBMs to drive 18 km of tunnel in sedimentary rock have been analyzed. More than twenty individual causes of delay could be identified. Delay causes are characterized on the basis of frequency and duration of incidents. Average utilization and downtime distributions are presented for each project, and frequency distributions of downtime per shift are discussed.

Jan 1, 1985

By R. W. Smith, R. K. Mehta, X. P. Zheng, A. M. Raichur, M. Misra

Experimentation was per formed on the flotation of apatite and dolomite separately using anionic collectors in the presence of Mycobacterium phlei. Also, the flotation of mixtures of dolomite and apatite in the presence of anionic collectors and in the absence and presence of the bacterium were studied. It was found that M.phlei functions as a depressant for both minerals. However, it functions as a better depressant for dolomite than for apatite. Experimentation was extended to two different Florida dolomitic phosphate rocks. In this investigation a concentrate grade of less than 1.0% MgO was achieved with a 75% P2O5 recovery.

Jan 1, 1999

By T. Gouri Charan, G. V. Rao

A spherical agglomeration process for the separation of scheelite fines of less than 30 µm in very low concentration of 0.04% WO3 in a binary mixture with quartz fines of less than 30 pm has been described. A concentrate containing 14% WO, with more than 90% recoveries could be achieved by means of anionic sodium sulfo succinate collector at pH 3.5 and also with commonly used anionic sodium oleate at pH 10.5 as per the conceptual flowsheet suggested. Such a process is envisaged as commercial potential for the recovery of fine-grained scheelite present in the tailings of gold plants as found in India.

Jan 1, 1991

By R. A. Metz, Ted H. Eyde, Dan T. Eyde

Industrial minerals deposits present sampling and grade control problems not normally encountered in metal mining operations. No longer are industrial minerals simply crude ground mineral products but are in fact high purity chemical raw materials. Operators of industrial minerals mines and processing plants now must meet increasingly stringent specifications established by the consumer of the final products. Meeting these stringent specifications requires not only sophisticated processing techniques but equally important careful sampling and grade or quality control at the mine. A well-trained geological staff can assure an adequate supply of uniformily high quality feed to the processing plant. In the final analysis this results in significantly higher operating profits.

Jan 1, 1992