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By W. Robert Rose, Randall Pyper, Carlos Mirabal, Jaime Eguivar

In 1984, work was started to determine the viability of heap leaching silver-containing waste dumps from Cerro Rico near Potosi - Bolivia, at an elevation of 4300 meters (14 100 it.). The result today is an unusual heap leach utilizing fine crushing, grinding, and agglomeration to process 1000 tonnes per day of ore containing 200 g/tonne silver. The unique metallurgical, economic, and political factors will be discussed which led to the decision to build a heap leach rather than a conventional agitation leach plant. Capital and operating costs will be given along with some of the uncommon process design and equipment problems encountered while developing the operation.

Jan 1, 1990

By J. A. Nelen, R. B. Cook

Panned stream-sediment, geochemistry-based gold exploration in those parts of the southeastern Piedmont proximal to the Fall Line must take into account potential contamination from basal fluvial sediments of the Coastal Plain. Anomalies attributable to the incorporation of placer gold of Coastal Plain origin into modern Piedmont drainages have been identified in portions of Lee, Macon, and Tallapoosa Counties, AL, and Baldwin and Hancock Counties, GA. Identification and interpretation of such multicyclic anomalies must be based on knowledge of the local maximum Cretaceous transgression, paleotopography, modern and paleofluvial system dynamics, and fineness trends and Au-Ag zoning in gold grains.

Jan 1, 1990

By R. W. Bartlett

Aeration curing, over- a long duration in wet- red stockpiles, shows promise as an affordable pretreatment method for oxidizing gold encapsulating sulfide minerals, and possibly organic matter, in low grade refractory ores. Following aeration pretreatment, the ore is reclaimed, neutralized, and cyanide leached by conventional practices. Large tonnages of subeconomic material, including mine stripping waste, may he converted into ore by this new technology. The results presented show that a successful application of this technology will likely require crushing to about -2 cm (-3/4 in.), followed by aeration in a wet stockpile for long periods, up m three years. Natural convection may he inadequate, hut forced air ventilation, at modest pressures and power consumption, is affordable.

Jan 1, 1991

By Joe M. Bryan, George E. Rodger

The development of small precious metal mines in the western states has been directed at heap leach operations. Crushing plants are an essential adjunct to heap leach operations. They must meet environmental air quality regulations which generally follow a similar pattern from state to state. Prior to mine construction a permit must be obtained and an operating permit granted during or shortly after the start-up period. The typical construction permit application consists primarily of drawings, specifications and an explanation sufficient to indicate that the mass of particulate matter entering the atmosphere is below minimum standards. The operating permit may be granted following demonstrations that air emission control equipment or methods comply with information submitted in the construction permit application.

Jan 1, 1987

By D. R. Kalasky, J. M. Mutmansky, B. Kolonja

This paper considers simulation of truck dispatching systems using maximum expected production of the truck-shovel system as the measure of performance. Two analysis methods are utilized: multiple comparisons with the best (MCB) and the combination of MCB with the variance reduction technique known as common random numbers (CRN). These two techniques are compared via simulation experiments. Results show that the combined procedure of MCB with CRN is the superior tool to use to reduce the total number of replications needed to ensure the specified probability of correct selection from a number of systems. In this case study, MCB with CRN reduced the variance by 29% and the number of required replications by 48%. Also, the MCB with CRN procedure narrowed the confidence interval by 18%.

Jan 1, 1995

By Y. J. Wang

The concept of subsystem characteristic curves for multiple-fan ventilation networks is presented through the construction of characteristic curves for two-fan, series-parallel networks. By considering fans as the individual network branches, the multiple-fan network is viewed as consisting of two components: any one fan branch, which is called the reference fan branch, and its associated subsystem. Thus, F subsystems can be designated for the network with F fan branches. Each subsystem contains one or more fan branches. The subsystem characteristic curve is the pressure-vs.-quantity curve of the subsystem. As illustrated in the example networks, the subsystem characteristic curve is not a strictly increasing curve and does not pass through the origin. The intersection of the characteristic curves for the subsystem and the reference fan branch represents an operating point. Multiple intersections therefore represent multiple operating points.

Jan 1, 1994

By L. Xu, R. Bhaskar

While a NIOSH accepted procedure exists for determination of quartz in the respirable dust samples from coal mines, no specific procedure has been defined for quartz determination in bulk samples. In this study, the effect of particle size on the estimation of quartz using the infrared technique was evaluated. Several laboratory tests were performed to determine the dependence of the infrared absorbance peak height on the different sizes of quartz particles. The significant dependence observed between quartz particle size and the measured peak height indicates the potential for erroneous interpretation of the quartz in bulk samples depending on how the samples are prepared. A procedure to reduce the effect of size in the determination of the quartz content is suggested.

Jan 1, 1994

By Joe W. Cotton, Thomas A. Wheeler

This paper briefly covers theories behind caking of crystalline salt particles, and methods of its prevention. The main factors that influence the extent of caking are humidity, storage pressure, temperature variations, and length of storage time. Careful adherence to control- ling these variables are more critical than the addition of even the most efficient anticaking reagent. The principle characteristics that a successful anticaking reagent must possess are: high retention at the temperature of application, good coating of reagent on the particle surface, capability of in- creasing the hydrophobicity of the particle, reducing the surface tension of liquids, and/or creating of a barrier between particles that prevent contact between particles, and modifying the crystal structure of the salt between the particles. Methods to evaluate the reduction of caking tenacity with the application of various anticaking reagents, reagent volatility and reagent degradation in plant and laboratory scales are discussed. Various types of anticake reagents used today in industry are organic active and inactive reagents, inorganic inert and inorganic salt crystal modifying re- agents.

Jan 1, 1986

By S. L. Huang, J. D. Rockaway, N. B. Aughenbaugh

Shale has long been recognized for its tendency to swell when exposed to the atmosphere. Interaction of moisture with exposed shale strata can cause serious ground stabi1ity problems, since the initial strength of a shale is reduced if the material is sensitive to moisture variations. In this paper, the authors present a classification system to estimate the response of swelling generated within shales. This characterization of the swelling potential is based upon plasticity, susceptibility to moisture, mineralogical constituents of clay size particles, and fabric. Use of this classification system in conjunction with other existing rock properties tests will provide data for more rational engineering design.

Jan 1, 1986

By J. M. Mutmansky, Y. J. Wang

The method usually used to predict the direction of flow in a connecting airway is to conduct a survey of the two existing nodes to be connected by the new pressure airway. It is then assumed that the air will flow from the node with the measured higher pressure to the node with measured lower pressure. This paper examines this direction-of-flow problem using properties of the system characteristic curve for a two-terminal network and specifies some conditions that will ensure that the air will flow in the direction anticipated. It was concluded that the only requirement is that all characteristic curves of the fans in the network should be strictly decreasing. Five numerical examples illustrate some important proper- ties of the direction-of-flow problem.

Jan 1, 2000

By R. F. Al-Fariss

The phosphoric acid industry is expected to develop in Saudi Arabia in the near future. There are three main reasons for expecting this: the discovery of phosphate deposits in the Sirhan-Turayf region, the construction of phosphate fertilizer facilities of the TSP, DAP and NPK plants on the east coast of the country, and the availability of an ample amount of sulfur As a by-product from the petrochemical industries. This study is a part of the research work performed in the chemical engineering department At King Saud University to evaluate the Saudi phosphate rocks for the wet process phosphoric Acid production and to test different flotation methods for the carbonate rich phosphate rock In a laboratory scale flotation cell. Experimental results for the above tests, as well as Beneficiation by calcination, are presented.

Jan 1, 1993

By R. A. Metz, James W. Clark, William C. Dixon, Kevin L. Wiley, Thomas R. Couzens

This paper is a description of certain geologic aspects of the Inspiration mining operation. It is not a geologic description of the Inspiration deposit nor an exposition of all the geologic work involved in the development and exploitation of the deposit. A few specific examples of the application of geology and geostatistics to the mining process are given to illustrate the progress that has been made in making the Inspiration Mine more efficient and cost effective, and a statement of the philosophy of geologic applications is offered.

Jan 1, 1992

By J. G. Groppo, J. G. Justice, B. K. Parekh

Removal of particulates and/or metal ions from mineral/coal processing waste water is a necessity from the environmental point of view. This paper describes application of a novel AC- electrocoagulation technique to remove the particulates as well as metal ions using AC power. A series of laboratory tests conducted on a stable black water sample obtained from a sub-bitminous coal operation provided a clear supernatant (-10 NTU) from the suspension. The process also shows promise in removal of up to 90 percent of phosphate ions and other metal ions (copper and nickel) from solution. A preliminary economic evaluation of the process will also be included.

Jan 1, 1992

By Y. M. Jiang, D. W. Park

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, 1998

By Normand Tassé

Reactive barriers, which consume oxygen, are prospective though unconventional alternatives to physical barriers for Acid Mine Drainage prevention. However, a reactive barrier implies a problem of duration. Pore gases were analysed in several wood waste piles in order to understand the factors which control wood degradation and help to determine the effective life span of such a cover. Long term efficiency seems to strongly depend on the degree of water saturation at the bottom of the pile, likely because the development of a microbial biomass in such an environment helps to keep the amounts of nutriments and readily metabolizable organic substrates at a high level, which in turn promotes oxygen consumption.

Jan 1, 2000

By Jorgen Elbrond

Before and in the early stages of industrialization, mining was the undisputed leader in technology. It represented the high-tech of the time. Early mechanization bears witness to that. Hoisting and rock breaking driven by waterpower are such examples. The mines' use of the steam engine was a major incentive to its development. By these means new mines could be opened and more metal supplied. Understanding of systems was essential for miners when shaping the infrastructure of the mines for the transportation of ore, material and men and for the evacuation of water and for ventilation. The irrigation systems of ancient mines are such examples. However, with the industrial revolution other more specialized branches of industry advanced further, and the mines became users of other industrial branches technologies. The mining industry had, however, always been quick to recognize a good thing and use it, when time was right. But, compared with other branches of industry, the mining industry has the disadvantage of working in a rugged environment with (and actually inside) a raw material which is abrasive and highly variable with respect to mechanical properties. This determines the rather high unpredictability of mining machines' performances and their low availabilities and explains a part of the delays in introducing technological advances.

Jan 1, 1989

By G. Raspa

This article describes a procedure for calculating the recoverable reserves of stratified orebodies characterised by a thin and irregular layers. An application on the phosphate deposits in the N'Zeto region of the Popular Republic of Angola is also described. The procedure consists in building a block model of the deposit through the conditioned multivarial geostatistical simulation of small areal units. The recoverable reserves are then calculated and defined by applying to the model a selection processes based on measured geological/economic parameters taken from the drillholes: thickness of overburden and mineralised layers, economic grain-size fraction, grade. The procedure also takes account both of the geometrical constraints of the mining method and dilution. For reasons of confidentiality, a multiplier has been applied to the values adopted for the sampling data.

Jan 1, 1992

By I. E. Lewis, W. R. Hopkins

Flowsheet improvements, such as series/parallel SX plant configurations, discontinuation of plant sumps and improved filter pumping concepts, the use of in-settler baffle systems, and the Krebs and combined mixer-settler designs offer opportunities to reduce SX plant cost. Today's plants employ permanent cathodes and mechanical stripping, and the increased capital cost can be offset by labor savings and higher current densities. The wider use of HDPE and new cell construction materials also reduce capital cost. The "Portelex" type of relocatable design embodies such new, cost-saving measures in a simple basic plant. Organic inventory and losses are reduced by new, fast-settling, hybrid organic reagents with improved kinetics and selectivity.

Jan 1, 1991

By Jed H. (Original by) Mosgrove

Good mine ventilation starts at the drawing board. A coal mine will either be adequately ventilated or not, depending upon how good a job was done in the planning. Poor planning will not only result in inadequate ventilation, but may also lead to low productivity. A mine foreman cannot achieve high productivity while trying to maintain 4.2 ma/s (9000 cfm) of air at his last open crosscut.

Jan 1, 1981

By Gary Schaffer, Anthony Stentz

Surveying of mines is a necessary step in coal mining to assemble maps which are used for tracking progress in the development of the mine and to plan future coal removal. A first approach for automatically building high-resolution two-dimensioml maps of underground coal mines is presented. The technique assembles laser rangefinder scans obtained from several locations within the mine into a consistent global map of the mine. Each range scan comprises thousands of data points collected in one second, thereby achieving higher resolution and much faster measurement compared to a human using a transit. The raw data (range scans) are processed to fuse them into a consistent representation. This paper describes a first approach to automated surveying and presents initial results of merging range scans. Improvements to the scan-merging algorithm are proposed.

Jan 1, 1993