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By D. W. Fuerstenau

Experiments using an optically polished Pyrex disk and aqueous dodecylammonium acetate (DAA) films showed that the velocity with which the films recede increases markedly if the runs are repeated at short time intervals, where equilibrium cannot be reattained. This results from DAA molecules being desorbed from the disappearing liquid-air interface and being deposited on the solid-air interface being formed. Controlled experiments with Pyrex particles in a modified Hallimond tube showed a similar increase in flotation rate, again due to excess adsorption of DAA molecules that were transferred to the solid-air interface from the bubble on contact.

Jan 1, 2002

By J. L. Yordan, T. Hilderbrand, R-H Yoon

High brightness clays are produced from Georgia kaolin by flotation. Fatty acids are used commonly as collectors for anatase, which represents the major colored impurity in the crude. This process requires activation of the minerals with divalent cations such as Ca2+, in which case proper control of the activation step is crucial to the success of the flotation process. In the present work, laboratory tests have been conducted using alkyl hydroxamates as the collector for anatase. A major advantage of using hydroxamate is that this new collector requires no activator. The laboratory tests show also that the hydroxamate collectors produce consistently better products with higher yields from a variety of kaolin clays.

Jan 1, 1994

By José Salim, T. V. Subrahmanyan

The occurence of primary stratiform and vein gold deposits in the Precambrian rocks of Northeastern Brazil is discussed. The stratiform deposits are related to clastic sediments (quartzites and conglomerates). The veins are associated with quartz and sulfides and are structurally controlled by shear zones. The gold was recovered for a long time by small miners. Developmental programmes for large scale mining are now envisaged. The recovery problems and gold economics are also discussed.

Jan 1, 1988

By A. Wright, R. L. Kastelic, W. C. Feyerabend

Gold Fields Mining Corp. is evaluating gold mineralization beneath thick, wet alluvium at the Chimney Creek project, Humboldt County, Nevada. Contamination of reverse-circulation samples has been visually apparent since drilling began in the area. Tests have shown that, while contamination can affect assays, reverse-circulation holes appear to define mineralized zones almost as well as diamond-drill holes. To improve reverse-circulation sample integrity, several techniques were tried (including a stiff-mud injection system) but with limited success. Diamond-core drilling continues to be used in conjunction with reverse-circulation drilling to further delineate the mineralization.

Jan 1, 1993

By Jan K. Wolski

This paper presents a simple method for determining air temperature gradients along a tunnel with time-dependent intake air properties. The variable intake air properties may be the flow direction and rate, air temperature and humidity, and the carbon dioxide content. The transient intake air properties are simulated by a series of steady intake air conditions, using a superposition method. The mathematical model was verified by reduced-scale experiments in the Waldo mine. The method may be usefull in conditions where the computation speed is more important than the precision of the results.

Jan 1, 1995

A number of factors affecting the properties of cemented aggregate fill (CAF), particularly its strength development have been studied through a series of laboratory investigations carried out at the Western Australian School of Mines in the Western Australia in recent years. The outcomes of these investigations indicate that apart from cement dosage, aggregate particle size distribution, aggregate quality, additional fine materials, water salinity, admixture dosage and sample scaling all contribute significantly to the development of cemented aggregate fill strength.

Jan 1, 2001

By B. Towson, R. F. Dalton, G. W. Seward

This paper reviews the successful application of oxime reagents for the solvent extraction of copper and considers the role that well focussed research initiatives can play in bringing further radical change to the metallurgical industry. Particular reference is made to the Cuprex Metal Extraction Process (CMEP), for the treatment of low grade or difficult to treat sulfide concentrates, using the reagent Acorga CLX- 50 to recover the copper and the reagent Acorga ZNX-50 for the recovery of zinc from chloride solutions. Other new extractants, currently in development, are also referenced.

Jan 1, 1994

By A. F. Symonds

The effects of harmonic resonance between the supply impedance and power factor correction capacitors on systems with large harmonic sources, such as mine winders, are well known. The similar effects of resonance with cable capacitance are not commonly encountered and, hence, are not always considered in the design of medium-voltage networks. This article considers some of the aspects of resonance between the supply impedance and the cable capacitance and presents one successful approach to solving the problem.

Jan 1, 1998

By Janice M. Zinck, W. F. Griffith

Four different high density sludge-type processes, Cominco HDS, Geco HDS, Tetra HDS Process and the Staged- neutralization process were studied for their effectiveness in treating a low strength Zn-Fe rich acidic drainage solution. Each proms was run continuously for at least two weeks after obtaining steady state conditions. The final effluent quality, lime consumption, sludge density, settleability, filterability, viscosity, neutralization potential, metal leachability, operating and capital costs were measured and evaluated for each process.

Jan 1, 2000

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 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'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 M. K. Pathak, A. K. Mukhopadhyay, D. C. Panigrahi

Changes in machinery operating and design parameters often result in unexpected vibrations or changes in the vibration patterns. Vibration in a system is an undesirable element that can cause machinery distress. Potential damage can be prevented by identifying the vibration level that is due to the changed operational parameters. This is necessary for the safe and reliable operation of plant equipment. This paper presents a documented study on vibration events that resulted from alterations in operating and design parameters in a mine ventilation fan and analyzes the causes by defining the sequence of events that led to its performance deficiency. This paper is based on experimental effort to study the vibration behavior of a ventilation fan under varying operating conditions.

Jan 1, 1999

By Sheldon Shepherd

Fifty years ago, belt scales were mechanical devices based on a complex weight balancing design. Today's systems use load cells to assess material weight, belt speed sensors and microprocessor-based integrators to continuously compute the rate of material transferred along a conveyor. Belt scales have become important assets to a plant. They help maximize the use of raw materials, control inventories and aid in the manufacture of a consistent product. Choosing and installing a belt scale system may seem complicated but it can be simplified by following a few guidelines.

Jan 1, 1999

By A. M. Taweel, M. T. Ityokumbul, A. I. A. Salama, M. W. Mikhail

The liquid-phase mixing within CANMET's Western Research Centre's (WRC) 0.76-m-diem pilot-plant flotation column was characterized using a salt tracer. The process variables studied were frother addition and, gas and liquid flow rates. The response of the column to a tracer pulse was monitored at three axial and two radial locations. The results showed that the 2-tph flotation column was well mixed. Discussed are the implications of this observation to column design and scale-up.

Jan 1, 1996

By G. V. Basham

"Environmental audit" is a phrase that can raise the blood pressure of otherwise cool and calm corporate personnel. There is widespread concern that any organized effort to find environmental problems will do so and may result in the imposition of substantial liability against the business that engages in such activities. However, such audits can reduce rather than enhance possible liability. Relevant issues include: the role of the attorney in the process, liability risks associated with environmental audits, steps to maximize confidentiality of audit results, reporting requirements and use of audit results in a proactive manner.

Jan 1, 1995

By Y. Akin, M. S. Celik, T. Batar, F. Arslan

Despite its importance in various diverse industries, research on beneficiation strategies of boron minerals has not received enough attention. Boron minerals are primarily upgraded by wet processing methods. However, severe environmental constrains have accelerated the development of dry processing techniques such as calcination. Interestingly, the boron minerals colemanite, ulexite and borax undergo decrepitation, shrinkage and expansion, respectively, upon heat treatment. Each mineral then requires a different beneficiation scheme. In this study, laboratory and pilot-plant studies conducted in our laboratories on the calcination of boron minerals are briefly reviewed and their implications to commercial operations are discussed.

Jan 1, 1999

By Stephen Pogorski, Colin R. Phillips, Atika Khan

An optimized counting scheme for a mixture of radon daughters and thoron daughters typical of Ontario mines, developed in a previous study, was experimentally examined under mine conditions. The counting scheme requires a 10 minute sample and 5 1/2 hours counting instead of a 60 minute sample and more than 40 hours counting as required by a previous method. Taking into account the uncertainties associated with concentrations, flowrate and radioactive decay, the precision of the counting scheme was analyzed and found to be on average better than the 40 hour method.

Jan 1, 1981

By J. L. Fuller, N. A. Abdel-Khalek

This paper contains a brief summary of design descriptions and generally accepted designations for longwall ventilation systems. Various ventilation systems for longwalls developed using single-entry and multiple- entry systems are discussed. Design considerations specific to longwall mining are included.

Jan 1, 1991

By W. A. Rickelton, A. J. Robertson

The ability of triisobutylphosphine sulfides to selectively recover silver from acidic sulfate solutions containing zinc and copper is described. Selectivity is explained in terms of the concept of hard and son Lewis acids and bases. Silver is stripped from the solvent using a novel strip feed (thiosulfate salt), and the recovery of metallic silver from the strip liquor by electrolysis or cementation is suggested. The high selectivity of extraction for silver and the utility of the stripping reagent are demonstrated in continuous, countercurrent, mini-plant tests. Important reagent properties, such as hydrolytic stability and low aqueous solubility, are discussed.

Jan 1, 1988