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By Paul D. Chamberlin

The evolution of heap and dump leaching has followed the development of agglomeration, materials of construction for leach pads and ponds, solution distribution systems, testing techniques, and state regulations. They are now mature processes. Possible future directions and developments are discussed. In situ leaching of precious metals is waiting to be commercialized. Regulators are reluctant to allow the use of cyanide because of the potential for excursions and operators are reluctant because of the potential for lawsuits. Developments in alternative lixiviants are needed before in situ leaching is accepted.

Jan 1, 1989

By E. Topuz, C. Patrick

Longwall face-to-face equipment transfers or moves are the largest source of nonproductive time in a long wall-mining system. Detailed planning and resourceful thinking are paramount for economical, safe and timely longwall moves. New equipment and innovative techniques are frequently tested to reduce overall more time. Determining the cost-effectiveness of these ideas is difficult since the decision is influenced by many subjective factors. A project scheduling simulation model of the longwall move process was developed to analyze and assess the economic viability of innovative transfer methods and equipment. The model provides a project-duration frequency distribution and lists of critically indexed activities and paths. It compares the monetary savings from reduced transfer time and capital costs for several ideas.

Jan 1, 1996

By Todd R. Taubert, Kenneth L. Bickel

The U.S. Bureau of Mines (USBM) pioneered the development of disposable filters for reducing diesel particulate emissions from permissible mining machines. The USBM is now evaluating filter media that can withstand the high exhaust temperatures on nonpermissible machines. The goal of the evaluation is to find an inexpensive medium that can be cleaned or disposed of after use, and will reduce particulate emissions by 50 % or more. This report summarizes the results from screening tests of a lava rock and woven fiberglass filter media. The lava rock media exhibited low collection efficiencies, but with very low increases in exhaust back pressure. Preliminary results indicate a collection efficiency exceeding 80 % for the woven fiber media. Testing of both media is continuing.

Jan 1, 1995

By D. M. Richards, A. D. MacPhail

Highland Valley Copper currently mines two low-grade ore bodies, Lornex and Valley. The partnership was formed in 1986. As a cost reduction measure, it was decided to use an in-pit crushing and conveying system to deliver the ore from the Valley Pit to the Lornex mill 3 km (1.8 miles) away and 175 m (575 ft) above the pit rim. The system uses two gyratory crushers that feed a series of conveyors to transport up to 130 kt/d (143,000 stpd) to the main stockpiles. This paper describes the performance of the in-pit crushing system as it is currently configured, as well as its evolution to date and future planned moves.

Jan 1, 1995

By Guerry H. McCullen, Bruno Despujol

Quartz and phosphate grains from concentrates and ores from Atlantic Coastal Plain sediments often are wholly or partially coated by humates. Coatings were studied in situ using infrared microscopy, by transmission Fourier transform infrared of extracts, and scanning electron microscopy. The 14C age of the coatings is about 20,000 years, much younger than the mineral substrates. Coatings on double flotation concentrates indicate that the conditioning pH may be too low, allowing coated quartz grains to follow phosphate grains through beneficiation. Organic matter from coatings may contribute to processing problems as well as affect final product quality.

Jan 1, 1999

By A. E. Stewart

Slope design in an open pit mine includes determining bench height, bench face angle and berm width. Case histories are presented of two highwall slopes (160 and 220 m or 525 and 720 ft high) excavated in dipping strata in an op¬erating coal mine. These examples illustrate the influence that bench face angle can have on the stability of an entire slope. The two highwall slopes, the lower of which experienced significant instability, were excavated in approximately the same lithologic and structural environment. The main differences between the slopes were the angle at which the bench faces were excavated and the excavating methods that were used. Relevent aspects are also described of the engineering geology, slope design and excavation procedures.

Jan 1, 1998

By Jeff W. Butwell

Mill flotation tailings impounded at the Gooseberry Mine site between 1976 and 1984 were determined to be an economic source of gold and silver recoverable by standard heap leach technology in conjunction with feed agglomeration. Metal recovery at 85 percent Au, 75 percent Ag is attained on properly agglomerated (pelletized) tailings which average 85 percent -75 micron. Because the impounded tailings averaged over 18 percent moisture (32 percent moisture maximum at depth) in place behind the storage dam, the mining method, mixing and agglomeration technique, and materials handling practice were major considerations in making this operation a financial success.

Jan 1, 1990

By J. Partyka, J. S. Stachulak

Dust produced during blasting in a copper/nickel based mine was studied and characterized. A stope utilizing the crater blasting technique, or the vertical retreat mining (VRM method), was examined. Two dust monitors were used to measure an airborne dust produced during blasting operations. The data collected in situ was primarily used to formulate the boundary value problem for a generalized equation that describes the transportation process of airborne dust from all places where dust is produced by the VRM mining method. The field data was also used to define the analytical forms for the initial and boundary conditions, to provide a simple and reliable equation for flow of dust in a stope vicinity, and to identify the non-measurable constants. The effects of the amount of blasting material and of the ventilation system in use on dust concentration are also discussed.

Jan 1, 1995

By Martin L. Smith

Sampling and subsequent geostatistical structural analysis is being carried out on the Bunker Hill Superfund site in northern Idaho's Silver Valley. This paper reports on the findings and methodology used in the initial sampling campaign which had the goal of determining an appropriate sampling grid design, spacing and protocol. Emphasis is placed on those characteristics, of mine wastes which are unique and require special consideration when applying geostatistical analysis. This study represents one of the first applications of geostatistical techniques to the problem of hazardous mining waste site characterization. Remediation of Superfund projects similar to the one described herein represents opportunity as well as liability for the mining industry.

Jan 1, 1992

By F. G. Boehm, T. S. Golosinski

This paper identifies the components of belt conveyor shifting force as a vertical force, Pv, a lateral force, Ph, and a longitudinal force, Pl. A method for estimating these forces is proposed that relates each of their values to the properties of the conveyor structure and rails, the shifting operation parameters, and other site-specific conditions. The effect of this force on the shifter behavior is analyzed, and guidelines are developed for selecting a suitable shifter. As well, other equipment requirements for the shifting operation are discussed.

Jan 1, 1988

By J. R. Diehl, R. W. Lai, R. W. Hammack, S. U. M. Khan

Cyclic voltammetry (CV), flotation response, evolved-gas analysis (EGA), and X-ray photoelectron spectroscopy (XPS) were employed to evaluate the major differences in the surface property and surface reactivity of a selected coal pyrite and a mineral pyrite. Surface properties of pyrite were evaluated in terms of flotation response in the presence of both an anionic fluorosurfactant and sodium hydrosulfide. The charge transfer adsorption and oxidation potential of sodium hydrosulfide were evaluated using cyclic voltammetry. Drastic differences in the flotation response have been observed between the coal pyrite and the mineral pyrite. Significant differences in the cyclic voltammograms at pyrite surfaces of these two sources were also observed. Measurements by XPS and EGA were used to determine the oxidation products and the rate of oxidation of the coal-pyrite and the mineral-pyrite surfaces.

Jan 1, 1991

By R. A. Wharton, Z. Yang, R. W. Smith

The electrokinetic and flotation behavior of the green alga Chlorella vulgaris was studied in the absence and presence of Pb(II), Al(III) and flotation collectors. It was found that the presence of Al(III) is necessary for good flotation of the organism, whether or not Pb(II) is present, when dodecylammonium chloride or sodium dodecylsulfate is used as collector. Best flotation using dodecylamine is at about pH 8, and best flotation when using sodium dodecylsulfate is at about pH 4. It appears because of the small size of the organisms that the Al(III) is necessary for flocculation to enhance bubble-cell contact and C. vulgaris removal from water. When N-dodecyl-2-aminopropionic acid is used as collector, good flotation occurs at about pH 4 without the addition of Al(III).

Jan 1, 1992

By H. Sevim

The logic and capabilities of a long-term production planning method for open pit mining are presented. This is a new method that can be used to obtain simultaneous solutions to the four interrelated parameters of open pit mining: mine life, specific blocks to be mined each year, the amount of ore and waste to be mined each year, and the ultimate pit limits. An efficient milling cutoff grade can also be obtained through a systematic analysis. A production plan for a real-life gold deposit is given to illustrate the logic and the capabilities of the method.

Jan 1, 1994

By Y. M. Jiang

Longwall faces can move at high advancing rates, but many geological variations can cause unexpected instabilities and production losses. The rapid movement makes it necessary to evaluate different geologic conditions in the rock mass as fast as possible to assess their effects on the longwall face and shields. It is believed that prompt awareness of geologic conditions is the key to preventing instability at a longwall face. This paper introduces the application of fuzzy set theory for characterizing and evaluating roof conditions. Real-time monitored data coupled with fuzzy set analysis provides valuable information, such as shield leg pressure, developing load on shields, intervals of periodic weighting and the ratio of developing loads during periodic to normal times.

Jan 1, 1997

By J. C. Yingling, R. Kumar, J. Sottile

The capability for on-line measurement of the quality characteristics of conveyed coal now enables mine operators to take advantage of the inherent heterogeneity of those streams and split them into wash and no-wash stocks. Relative to processing the entire stream, this reduces the amount of coal that must be washed at the mine and, thereby reducing processing costs, recovery losses and refuse-genera¬tion levels. In this paper, new ap¬proaches for optimal control of the segregation process using time-se¬ries models and empirical distribu¬tions are presented and demon¬strated using field data.

Jan 1, 2000

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. Rajamani, I. Shah

The development of liquid-level control algorithms, based on sets of linguistic rules expressing human operator's "intuitive" control strategies, have been reported. The main objective of the present paper is to illustrate the implementation methodology. The experimental work was done with a 28.3Lflotation cell. The control variable (height of pulp in the cell) was controlled by manipulating the outflow rate. The controller algorithms were programmed and implemented using an Applelle computer and a Keithley das Series 500 measurement and control interface. It is pointed out that the scheme of fuzzy controllers is simple to use and powerful enough to handle complex and nonlinear systems.

Jan 1, 1987

By Fathi Habashi

Precipitation of a metal from an aqueous solution of its salts by another metal is known as cementation, because the precipitated metal is usually cemented on the added metal. This phenomena was once described by the alchemists as "transmutation," when they dipped a piece of iron in a solution of copper sulfate and the iron was coated with a layer of metallic copper. The process can be predicted in terms of electrode potentials. The metal with the more positive (oxidation) potential, as given in Table 13-1 of the electromotive series, will pass into solution and displace a metal with a less positive potential.

Jan 1, 1970

By D. T. Hristopulos, A. Pavlides, C. Roumpos

In many of the lignite mines in Greece that supply the nearby power plants, the lignite deposits are multilayered and faults destroy the spatial continuity. This fact complicates lignite exploitation and the profitability evaluation of each layer. The location of a lignite layer could be so deep compared to other layers, that its exploitation would not be profitable. The purpose of this paper is the development of a suitable profitability index to help with the evaluation of the profitability of separate lignite layers. The definition of the profitability index is given and an algorithm is formulated that calculates the profitability index and evaluates whether each layer should be mined by comparison with a critical threshold value. The profitability index algorithm is applied to the multilayered lignite deposit of Amyndeo mine. It should be noted that the proposed index could be used in any kind of multilayered deposit, not just lignite.

Jan 1, 2011

By Mark E. White, John H. McCowan, Michael C. Costello

Minproc Engineers has carried out the design construction and commissioning of thirty two process plants in the period 1978-87. Twenty eight are gold silver recovery plants, and of these twenty two were gold alone and six were gold and silver. In most plants carbon was used for gold adsorption. Desorption has been carried out using the USBM Homestake method, the Anglo American Research Laboratories method, and the Micron Methanol method. Electrowinning has utilised steel wool, stainless steel wool, and aluminium cathodes. Electrorefining using polished stainless steel cathodes is practised. This paper summarises the experience gained in these operations

Jan 1, 1987