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By Waldo Valderrama, Luis Magne, Paola Grandela

The effect of liner shape on power consumption was studied in a small laboratory mill under various operating conditions. It was found that the angle subtended between the lifter front face and the face in contact with the mill case has the most significant influence. The increasing height of lifter reduced power consumption, whereas the lifter spacing did not show any influence. The effect of height is less relevant at lower front angles. Highest power consumption is achieved with a 45" front angle. A comparison of cylinders and balls under identical conditions gives higher power consumption for ball charges. The data does suggest that, for maximum power draw, slip in the outer layers of the charge and the early recirculation of energy to the mill case should be avoided. Both factors prevent an efficient energy transfer to the mill charge.

Jan 1, 1995

By Brian Kenner, Peter Swanson, Todd Krahenbuhl

NIOSH has developed an automated PC-based seismic event (induced earthquake) monitoring, system for use in mine ground control studies. The distribution and coordination of data acquisition and processing functions across a local area network is a central feature of the system. Mine-wide installations utilize multiple, autonomous seismic networks located both underground and on the surface. Seismic event locations, magnitude estimates, and other processed data are distributed for display and analysis on network nodes both underground and in the offices of mine engineers and managers. This paper describes the system's design philosophy, hardware and software components, examples of installations, and a few observational results.

Jan 1, 2002

By Vitaly T. Borisovich

Mining economics courses have been taught in Europe for more than two centuries and in the United States for most of this century. They are the mineral industry's version of engineering economics offered by industrial engineering departments. In the 1930s, mineral economics first appeared in American mining schools. This subject goes beyond the deposit and the mine. It examines the economic aspects of mineral resources in general and the individual mineral industries in particular. In 1947, the first degrees in mineral economics were granted in the United States. There are mining and geological engineers who specialize in mining economics. But it has rarely become a separate degree program. Rather, in this country and several others, a graduate student in a mining department or school will include economics in his course work. Then the person writes a thesis or dissertation on a mining economics topic. One exception is found in Moscow at the Department of Geoeconomics of the Moscow Geological and Prospecting Institute (MGPI). To place this program in perspective, some background is needed on education in the Soviet Union.

Jan 1, 1991

By Gary J. Goldberg

Through the early 1980s, surveying at Bingham Canyon required a great deal of repetitive and manual work. The advent of total station surveying equipment provided an opportunity to improve the speed and accuracy of surveying work while reducing manpower needs. An evaluation was made of total station systems and their ability to meet the surveying requirements of Bingham Canyon. This culminated in the purchase of a total station system as the mine reopened in 1986. The surveying department at Bingham Canyon during the early 1980s consisted of three, four-man crews using theodolites and self-leveling levels to perform the majority of the field work. Office work involved data reduction and hand plotting. Although hand-held programmable calculators were used, a great deal of time was spent manually transferring field notes to final calculations. After shutting down in early 1985, plans for start-up of mining operations in 1986 included a review of all aspects of the operation for cost and productivity improvement. Applying total station survey capabilities offered the potential to improve surveying accuracy and speed while reducing manpower needs.

Jan 1, 1990

By D. B. Dreisinger, H. J. Sohn, J. S. Sohn, G. A. Kordosky

The transport of lithium through a supported liquid membrane was studied with a mixture of D2EHPA and TBP in kerosene as a mobile carrier. In the flat- sheet supported liquid membrane(SLM) system, experiments were carried out to investigate the effects of concentration of mobile carriers in the membrane solution, hydrogen ion in the feed solution, and temperature on the transport of lithium. Experimental results agreed well with a transport model for permeating lithium across the liquid membrane. The permeation rates of lithium can be explained in terms of diffusion of a Li-complex through the membrane phase. For a practical application of an SLM method, a hollow fiber module has been used and lithium can be concentrated more than three times in 24 hours.

Jan 1, 1993

By R. J. Sweigard, T. Beckman, C. T. Justice, E. D. Thompson, T. C. Hopkins

As a means of permanent disposal, fine coal refuse is often pumped as a slurry into surface impoundments. As the available volume is filled, the embankment heights are frequently increased. The additional embankment material is often placed upon consolidated fine coal refuse. There has been concern about the long-term effect of consolidation of this material at or above the liquid limit on its shear strength. A laboratory investigation was performed using three different types of fine coal slurry taken from central Appalachian coal-preparation plants. The refuse was consolidated in 3-m (10 ft) Plexiglas columns under incremental amounts of surcharge loading. The incremental loads were designed to simulate the effect of increasing the height of a refuse embankment on top of the consolidating coal slurry. After the refuse in the columns had consolidated for several months, the columns were cut apart, and triaxial tests were performed on both the consolidated and unconsolidated material for comparison of their shear-strength parameters.

Jan 1, 1998

By R. Venugopal, T. C. Rao, J. P. Barnwal, K. Udaya Bhaskar

The performance characteristics of a multigravity separator for the recovery of heavy minerals of lead, zinc, copper and silver from a lead rougher-flotation concentrate were studied. Factorially designed experiments were carried out on three operating variables, i.e., the amount of wash water, the drum inclination and the drum rpm, of a multigravity separator. The experiments were carried out at two levels of each variable. With the experimental data, regression equations were developed for different metal grades and recoveries. The analysis revealed that drum speed has a major influence in determining the heavy-metal grade and recovery. Drum inclination is the next most important variable, with the amount of wash water being the least important. A concentrate containing 40% lead, 9.4% zinc, 1.5% copper and 1,400ppm silver was obtained with recoveries of 74.8%, 65.9%, 64.1% and 53.2%, respectively. Finally, the predicted values of grades and recoveries at intermediate levels are compared to actual experimental data to test the validity of the equations developed.

Jan 1, 2000

By J. A. Pagliero, R. T. Quiroz, S. H. Castro

Selected voltammograms in tetraborate buffer solutions in the presence of ethyl xanthate or isopropyl xanthate at pH 9.3, for chalcocite, covellite, chalcopyrite, and enargite mineral electrodes, are presented. The concept of critical Eh of dixanthogen condensation (Ehc) is introduced, and the line of Ehc is thermodynamically defined in plots of log [X i] vs Eh, for methyl, ethyl, propyl, and butyl xanthates. A reaction scheme of xanthate oxidation in four steps, involving the dixanthogen condensation step, is proposed. A first attempt to interpret mineral flotation from a more general point of view is made. The electrochemical mechanism of dixanthogen formation and condensation is considered as a particular case of a more general and relevant phenomenon, which is the decomposition of the collector giving hydrophobic colloidal forms, whose associative behavior in bulk solution and at the mineral/solution interface is governed by colloid chemistry.

Jan 1, 1989

By J. H. White

It is hypothesized that the Hotelling valuation principle (HVP) can determine the value of developed gold reserves using simple methods and easily obtainable data. This paper reports the results of an empirical test of this hypothesis. The model for the HVP is given by [V R=Cp-0(1) or V - CP-0' R(2)] where p = current spot price of gold per oz, [c] = average extraction cost of gold per oz, V = current market value of the gold in the ground (dollars) and R = gold reserves (oz). Using publicly available data from North American gold companies, we obtained data for V, R, p and c, and we ran a simple linear regression using Eq. (1) as the definition of the dependent and explanatory variables. By examining the value of the coefficients of the resulting regression equation, we can draw conclusions as to whether or not the HVP can be confidently used as an estimator of the value of developed gold reserves.

Jan 1, 1997

By K. Gum, W. C. Hirt, D. A. Rice

Selective flocculation was used to produce a superclean zinc concentrate by minimizing silica contamination. Research was carried out on a flotation concentrate from the Jersey Miniere Zinc Company (JMZ) in Gordonsville, TN. The material was first dispersed with sodium silicate and then causticized tapioca starch was used to selectively flocculate the sphalerite, leaving the silica in suspension. This technique has been applied commercially to iron ore beneficiation but never to zinc processing. The feed material assayed 0.45% SiO2. The use of 0.56 kg/ t (1.13 lb/st) sodium silicate and 0.070 kg/t (0.141 lb/st) causticized tapioca starch resulted in a 98.2% zinc recovery and produced a purified zinc concentrate assaying 66.0% Zn and 0.24% silica. The target level for silica contamination in JMZ zinc concentrates is currently 0.30% Si02. This work demonstrated that selective flocculation is a potential method for cleaning flotation concentrates, particularly where low silica products are required.

Jan 1, 1995

By S. Subbarayan, S. Chander, M. S. Klima

A laboratory study was conducted to investigate the potential for recovering anthracite from coal preparation-plant tailings. The study included washability analyses, cyclone simulations and froth flotation testing Samples were collected from either the tailings streams or the slurry ponds of five anthracite-cleaning plants. From each sample, a washability analysis was conducted on the 28x100 and 100x200-mesh fractions. Using the above data, along with published partition data, simulations were performed with various cyclone-staging arrangements for both water-only and dense-medium cyclones treating the 28x200-mesh fractions. Separate froth -flotation tests were conducted on the 28x100- and 100x200-mesh fractions from three of the plant samples. The washability, simulation and flotation results are presented as grade-yield curves.

Jan 1, 1996

By B. Ainsworth

The 1972 discovery of the Howards Pass lead-zinc deposit was the product of systematic regional geochemical surveys used to evaluate conceptual geological models for the metal-rich black shales of the Selwyn Basin. Motivation of personnel involved in all aspects of work was as critical a factor to the success as the existing corporate attitudes and infrastructure. Exploration programs were flexible but maintained a focus only on targets of sufficient economic potential to support operations in remote locations. Direct costs for the programs that lead to the discovery were in the order of $500,000 (Canadian 1972). Geological reserves today stand at over 500 Mt (511 million st) of 7% combined lead-zinc, containing a higher grade zone of nearly 10 Mt (11 million st) of 16% combined lead-zinc.

Jan 1, 1991

By S. Moutsatsos

The impact that societal issues can have on mineral resource projects has proven to be a critical component of feasibility studies around the world during the past ten years. The recently signed Impact Benefits Agreement (?IBA?) for the Victor Project in Northern Ontario between De Beers Canada Inc. (?De Beers?) and the Attawapiskat First Nation provides an opportunity to capture the interactive process followed, the controlling parameters and the implications for the future. The uncertainty about the time required to complete an IBA makes it one of the key intangibles in risk assessment of a feasibility study. This paper considers items related to the significance of engaging communities at the early stages of exploration in a project and the catalytic effect that alignment of interests and interaction in a pre-IBA period can have. Furthermore, the de facto link between permitting and the successful conclusion of the IBA and the role of external advisors in the project are discussed. The paradox of empowering and supporting communities through the negotiation process, and the implications of the IBA to maintaining good relations throughout the life cycle of a project are also explored.

Jan 1, 2007

By Nico Bezuidenhout, André M. van Niekerk, Jan J. G. Vermaak

This paper documents empirical evaluations of geochemical data that was recorded during a seven year pilot scale experiment. The experiment was aimed at assessing the effectiveness of natural soil covers for rehabilitation of coal discard facilities. Ten test cells were constructed using different natural soil cover materials and configurations. Results of the evaluation indicate that, although a pH breakthrough was not recorded for the single layer soil cover cells as was the case with the uncovered cells, single soil covers were not effective in preventing ARD oxidation processes. Multi layered soil covers were found to be able to create anaerobic conditions leading to a reduction in ARD oxidation processes and an improvement in leachate quality.

Jan 1, 2000

By Robert Sutton, Milan Sjaus

Conveyor pulleys are an important and integral component of a conveyor. Conveyors work in sequence to make up conveyor systems. Each conveyor system is only as reliable as its crudest component. If the pulley fails, then the whole material handling system stops. So what is the effect of this downtime? What are the costs of repair? How much are we willing to pay to solve the problem? What should we spend to prevent an unscheduled shutdown? Do we use the technological improvements at our disposal or do we ignore them to satisfy immediate cost savings? This study will focus on the cost of pulleys relative to the total conveyor cost, the cost of downtime, the maintenance costs and the costs for resolution of the problem. Some philosophic and design concepts are injected for illustration and discussion.

Jan 1, 2000

By R. Bruce Tippin

The silicates represent the largest and most common group of minerals on earth. Yet in spite of the chemical similarities, numerous mineral processing plants worldwide are operating successfully to yield varied commercial products for numerous uses. The silicates that are commercially produced in the United States by flotation include quartz, feldspar, mica, spodumene, talc, kaolin, and wollastonite. The operation of several plants and the conditions affecting mineral separation by flotation are described. Because the process is usually dictated by the desired market, specifications for the most common products are provided. Potash is a basic fertilizer component, along with phosphate and nitrogen. Potash is typically produced from underground evaporite beds or recovered from natural brine solutions. Flotation of potash is unique in that it is processed in a saturated salt solution. The potash flotation process is outlined and several commercial operations are described.

Jan 1, 1999

By R. Hogg, R. H. Weiland, P. Bunnaul

The dewatering of flocculated clay suspensions by compression in a centrifugal field was investigated. The results were analyzed with respect to the direct applicability of centrifugal dewatering (as in solid-bowl centrifuges) and indirect applications to gravity sedimentation systems. An important objective of the study was to evaluate the self-weight effect using centrifugal forces to simulate consolidation of deep sediments. Experiments were conducted in which the sediment mass and initial structure were maintained constant while the effective sediment weight was varied by centrifuging at different speeds. The relationship between the limiting sediment density and the applied consolidation stress was found to be the same for both gravity and centrifugal consolidation, indicating that small-scale laboratory tests can be used to predict consolidation in deep beds. The effects of the initial structure were also studied using controlled variations in flocculation conditions. The results imply that, for the flocculated suspensions studied, the longterm consolidation behavior is relatively insensitive to the actual extent of flocculation.

Jan 1, 1995

By Y. K. Yen, J. D. Miller, C. L. Lin

Particle size segregation is a common phenomenon in many particulate processes and has many undesirable effects. The size segregation which occurs on a belt conveyor causes a serious problem for on-line particle size measurement using image-based techniques. Whether particle size distributions measured from the top layer of the belt are representative of the total particle population is largely dependent on the degree of size segregation. Therefore, it is important to understand the nature of such size segregation in order to make appropriate corrections for on-line particle size analysis. Monte Carlo simulation has been used to provide segregation information on particles with simple geometry and the results can help to determine important factors in experiments with irregularly shaped particles. It is expected that the relationship between the particle size distribution of the top layer and that of the entire particle population on a belt conveyor can be formulated as a model based function.

Jan 1, 1997

By Staff

GENERAL DESCRIPTION The Lucky Friday mine is located in Mullan, Sho-¬shone County, Idaho. The mining method is horizontal slice cut-and-fill (with timbering for support or un¬timbered) using hydraulic sand. Cemented sand fill at a 1:17 ratio is used in sill pours and at a 1:7 ratio for the final 152 mm (6 in.) capping in successive stope floor pours. Annual production with 100% cut-and-fill mining is 167 829 t (185,000 st). The average depth of mining is 1296 m (4250 ft) and the average travel time to the stope is 45 min. GENERAL ORE BODY REQUIREMENTS AND LIMITATIONS Size The ore body is 396 to 488 m (1300 to 1600 ft) long on strike, 1421 m (4660 ft) on dip, with an average width of 2.3 m (7.5 ft). Dip varies from vertical to1.2 rad (70°) Ground Conditions, Ore Value, and Production Requirements The ore body contains quite strong argentiferous galena and quartz. The hanging wall and footwall are strongly sheared and fractured. Ore value is $211/t ($192/st).

Jan 1, 1982

By Thomas H. Koenning, James R. Boulton

The coal mined by Cyprus at the Shoshone mine near Hanna, WY is highly susceptible to spontaneous combustion. Spontaneous heatings have occurred in the gob of several of the longwall panels and, in some cases, following roof falls. Prevention and detection methods have evolved over the years as more has been learned about the occurrences. Seal design and construction have progressed to reduce air leakage into the gob. Pressure balancing has been successful as a supplement to good workmanship in reducing leakage. Early heating detection has improved as knowledge has been gained. Prior methods of detection relied upon thermocouples detecting a temperature change. Later a gas chromatograph was used to analyze gob gas samples. Initially the products of combustion (POC) were relied upon for detection. Most recently, lack of oxygen depletion in the gob has been used as an early warning of problems. Examples are presented to illustrate the evolution of spontaneous combustion control at the Cyprus Shoshone coal mine. Methods have been developed which minimize the oxygen concentration in the gob and reduce the potential for spontaneous combustion.

Jan 1, 1997