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By Roe-Hoan Yoon, lsmail Yildirim, Jinhong Zhang

Inorganic fillers and pigments such as kaolin, diatomaceous earth silica, and talc were treated with various surfactants, and the changes in their surface properties monitored. When they were treated with a cationic surfactant, they became hydrophobic and the overall surface free energies were decreased substantially. The decrease in surface free energy was mostly due to the decrease in the acid-base component (ysab) of the surface free energy, indicating that hydrophobizing an inorganic pigment entails a reduction in ysab. It was found that the surface characterization technique employed in the present work was useful for studying the effects of using various other surfactants for surface treatment.

Jan 1, 2003

By J. G. Wargo

In situ leaching of disseminate gold deposits has been studied from a theoretical perspective to outline the operating environment for the process. Rock permeability and the relationship of permeability to the site of gold particle deposition are key factors in predicting the efficiency of in situ leaching. Permeability measurements, however, have rarely been made during gold exploration, so that secondary geologic features of the deposit must be used. This paper examines some of the geologic characteristics of disseminated gold deposits and comments on the problems and possibilities of in situ leaching of gold.

Jan 1, 1987

By W. R. Dearman, N. Turk

The theoretical relations between the strain and stress Mohr circles make it possible to establish a relation between the internal friction angle [ ] and the Poisson's ratio (v) of rocks. The internal friction angle is related to the Poisson's ratio as Sin [-] = (1 - v)/(l + v). This relation gives lower friction angle values than the triaxial Mohr envelopes and higher values than those given by surface sliding friction tests.

Jan 1, 1986

By P. Sanchez-Mejorada

Quimica del Rey, SA, a subsidiary of Industrias Peñoles, SA de CV, produces sodium sulfate from brines extracted from a playa of Laguna del Rey, located in the State of Coahuila in northern Mexico. The spent brine is used as raw material for the production of magnesium oxide. The brine, which contains ions of sodium, magnesium, sulfate, and chlorine, occurs filling intercrystalline voids of a lenticular evaporite deposit whose main constituents are glauberite (sodium-calcium sulfate) and blöedite (sodium-magnesium sulfate).

Jan 1, 1987

By J. Devon, D. L. Ewart

Long-term coal mining plans are often based on attainment of an average cost of coal. This is achieved by blending low- and high-cost coal production. Coal that is beyond the economic limit of the reserve is mined in a misguided effort to improve reserve recovery. Long-term contracts should be least cost-based and generate the best net present value from the economic reserve within the context of a rational mine plan. The selected economic reserve should he mined on a low- to high-cost basis to benefit from the time value of money.

Jan 1, 1996

By Luis Dr. Sobral

In this study, the removal of zinc, cadmium and copper from an aqueous sulphate solution, derived from the biomass desorption process, was examined by using a reaction system with a three-dimensional high surface area electrode (RNiF). This reaction system was found to be extremely effective in reducing metal concentrations to the ppb range. The effect of cathode potential and flow rate were studied for three different nickel foam porosities. In addition, current- potential curves were recorded, at a rotating vitreous carbon electrode, to deter- mine the possibility of depositing the aforementioned metals separately.

Jan 1, 1998

By Scott D. Kinsala, Patrick T. Flynn, Andrew T. Rosol

During calcination of diatomaceous earth, cristobalite is formed in varying percentages. Also, during efforts to recycle products containing natural diatomaceous earth, various heat treatments are used which may or may not result in the formation of cristobalite. The ILO (International Labor Organization) Encyclopaedia of Occupational Health and Safety states that conversion begins at 450'C and in the presence of a flux, is complete at 800'C. Due to the potential adverse health effects associated with crystalline silica, a more thorough understanding of the time/ temperature relationship is needed. Tests performed under controlled conditions do not substantiate the claims made in the ILO Encyclopaedia.

Jan 1, 1991

By T. R. C. Aston

Extensive undersea coal reserves, identified in the offshore portion of the Sydney coalfield, Nova Scotia, have resulted in the implementation of a multi-year research program to develop site specific guidelines for the undersea longwall mining operations. At present, uncertainty exists regarding the applicability of the current undersea mining guidelines. Preliminary studies have revealed four potential schemes for monitoring seafloor longwall subsidence profiles: seasurface, subsea, geophysics, and direct monitoring. However, further work has indicated that the use of marine geophysical techniques may be the most effective method of identifying and evaluating seafloor subsidence profiles by comparing pre- and post-mining seafloor topographies.

Jan 1, 1990

By N. N. Manu

In the Central African Copper Belt, sulfidization flotation is the standard practice for dolomitic copper oxide ores. It is a delicate process, and its plant application requires close control of the reagent addition. This paper presents the results of a thorough laboratory investigation. It features the monitoring, during sulfidization, of the pulp pH, the residual sulfide ion concentration and redox potential. Variables examined during the process were: retention times, sulfidizer additions, pH, collector type, dispersant dosage and reducing agent addition. Implications of the findings for plant application and process control are also briefly examined.

Jan 1, 1994

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 R. N. Tempel, M. Lengke

Arsenic sulfide (orpiment, realgar, amorphous AsS and As2S3) oxidation rates were measured in mixed flow reactors at pH-2 and at temperatures of 25 ° to 30 °C. The measured oxidation rates for arsenic sulfide solids by dissolved oxygen are in the range of 10-11 to 10-10 mole m-2s-1 after being normalized to final surface area. The order of arsenic sulfide oxidation rates decreases at pH-2 from amorphous AsS > realgar > orpiment > amorphous As2S3. Compared to pyrite, arsenic sulfide oxidation rates are approximately 1.5 to 15 times slower than pyrite oxidation rates at pH-2.

Jan 1, 2003

By Richard R. Klimpel

This paper summarizes the author's laboratory and industrial experiences in designing and evaluating frothers for optimal coal flotation circuit performance. The key variables discussed are particle size distribution hydrocarbon addition rate, frother chemical structure, and frother dosage. A number of detailed examples will be used to illustrate the important rare/recovery/selectivity interactions that can occur.

Jan 1, 1995

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 J. Kelleher, R. Saulters, K. H. McDaniel, L. Griswold

To improve underground safety and visibility during mining applications, the Waste Isolation Pilot Plant designed and built a dry-dust filtration unit. The unit works in conjunction with a Spendrup 1120-70 fan with ventilation tubing to filter the face exhaust air during mining operations. The closed- loop system is designed to filter 17 m3/s (36,000 cfm) and is intended to screen 10- µm (1,250 mesh) and larger particles at 90% efficiency. To accomplish this, the unit uses a combination of Dollinger Staynew Inertial Spin filters, cyclones and traditional mesh filter media.

Jan 1, 2002

By B. Govindarajan, T. C. Rao

A simulation of batch-flotation experiments was carried out using a simple empirical model to identify the process parameters that would give maximum yield at any given ash level. The relationship between the maximum yield values and the percentage ash-reduction ratio (ARR) has shown two regions where the collector and the frother dosages have individual influences on the flotation performance. Based on this observation, a simple "selection-criterion diagram" is proposed. This diagram can he used to select the process parameters to achieve maximum yield, for a given ash content of the concentrate and at any given flotation period.

Jan 1, 1997

By S. R. Clifford

Organic contaminants can be removed from river sediment using conventional flotation methods. Organic contamination in sediments is one of the most significant pollution problems facing the Great Lakes region. Using conventional flotation, the majority of the organic contamination can be collected in a concentrate, leaving a "clean" tailings. This provides a cost savings by reducing the amount of material requiring further treatment. The concentrate can then undergo additional flotation stages, or other contamination removal procedures, to further remove the organic contaminants.

Jan 1, 1994

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 L. W. Saperstein, MJ. Carlson

With the goal of improving the strength characteristics of pneumatically emplaced material used for localized subsidence control, the binding additives fly ash, bentonite, and portland cement were examined for their effect on the support capabilities of coal refuse. It was found that, within certain concentration ranges, all three offered some increase in the ultimate strength of the backfilling mixture. However, portland cement gave the greatest percentage increases. Selection of the appropriate backfilling mixture will allow for the most economical and efficient subsidence control when pneumatic stowing is employed.

Jan 1, 1990

By A. K. Bakshi

In cold regions, rinsing of spent cyanide from leach heaps is stopped during winter and is resumed again after the snow melts. The effect of this idle time on the overall removal process was studied in this experiment. Samples were collected for rinsing tests from one heap at a gold mine near Fairbanks, Alaska. Continuous and interrupted rinsing of this sample were carried out in test columns. The rinse solution was analyzed at regular intervals to determine the rate of cyanide removal from the solids. It was found that total cyanide concentration per rinse cycle for interrupted rinsing test was higher than for the corresponding continuous rinsing test. As a result, interrupted rinsing required less rinsing cycles than continuous rinsing.

Jan 1, 1995

By Joe Maloney, Steve Shadow

Mining conditions at Cyprus Amax's Twentymile Coal Company (TCC) require the use of regenerative conveyors. Regenerative conveyors were first used in the Southwest Mine District and then in the challenging East Mine District. This paper will discuss the development and refinement of the equipment used to brake the regenerative conveyors.

Jan 1, 1998