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By I. Iwasaki, K. A. Smith, X. Cheng

A cathodic decomposition model was examined for both pyrrhotite and chalcopyrite in an attempt to analyze the formation of surface coatings in deoxygenated solutions at natural, near neutral pH. Combination potentials established between the mineral-grinding media pair were simulated by applying a potential of -0.455 V (vs. a standard hydrogen electrode) either to a pyrrhotite or to a chalcopyrite electrode. Chronoamperometry was used to study the polarization behaviors and alteration of mineral surfaces through cathodic processes. The kinetic parameters of cathodic decomposition of pyrrhotite and chalcopyrite were determined and compared. It was concluded that pyrrhotite decomposed faster than chalcopyrite in near-neutral pH solutions. Both minerals were then covered by a film consist¬ing mainly of iron hydroxides, which adversely affected their flotation.

Jan 1, 1999

By C. Tsatsanifos

Following closure of an old asbestos mine in Zidani, Kozani Prefecture, Greece, the geotechnical and environmental restoration of the tailings slopes was required. The geotechnical aspects of the restoration included the formation of gentler slopes to increase stability, in combination with drainage works for the same purpose. The environmental aspects of the restoration included covering the slopes with successive layers of soil in order to minimize infiltration of rainwater, and hence the potential for further transport of asbestos fibers, and to provide a suitable layer for revegetation of the slope. The paper presents results of slope stability evaluation using both limit equilibrium and finite element analyses and raises some issues related to reducing impacts to the geoenvironment when designing such restoration projects.

Jan 1, 2006

By C. Stephan, E. Weiss, J. Trackemas, M. Sapko

The National Institute for Occupational Safety and Health (NIOSH), Pittsburgh Research Laboratory (PRL), in collaboration with the Mine Safety and Health Administration (MSHA), the mining industry, and seal manufacturers recently conducted a series of full-scale experiments within the underground experimental mine at PRL’s Lake Lynn Laboratory. The purpose of the experiments was to evaluate the explosion-resistant characteristics of several new seal designs for rapid deployment during mine emergencies. These seals can be deployed in 6 to 10 hr and are capable of withstanding explosion overpressures in excess of 140 kPa (20 psi). These novel seal designs use available mine materials, do not require conventional rib hitching, and, most importantly, can substantially reduce exposure time for coal miners during sealing and mine recovery operations.

Jan 1, 2003

By Charles C. Y. Chen, Duane R. Skidmore

Batch leaching of Ohio #1, Ohio #4A and Ohio #5 coals was conducted with the thermophilic. sulfur, oxidizing microorganism: Sulfolobus acidocaldarius. Four different size fractions of each coal, with median sizes of 508, 200, 90, and 49 microns, were subjected for 10 days to leaching in a 5% coal-water slurry at 72°C and a pH of 2. Release rates and extent of sulfate and iron I1 and I11 ions from the coals during the leaching process and distribution of sulfur forms (sulfate, pyritic and organic) in the coal samples before and after treatment were determined. Data indicated that Ohio #1 coal, with an initial sulfur content of 0.6%, showed no significant changes with leaching in total sulfur content or forms of sulfur. The Ohio #4A coal, with initial total sulfur content near 5%, yielded product, for sizes below 200 microns with 90% reduction of pyritic sulfur while the extent of organic sulfur removal varied with coal particle size. Results similar to those for Ohio #4A were observed on the Ohio #5 coal, which had an initial total sulfur content of 3% and a final sulfur content near 1%. The findings were interpreted in terms of basic biological, chemical and physical mechanisms.

Jan 1, 1989

By Dalva L. Moellenberg

Introduction Hard rock mine closure (often referred to as decommissioning), mined land reclamation and financial assurance requirements are receiving considerable attention by governments and organizations around the world. In the United States, federal agencies and the states continue to consider and make changes to laws governing mine closure and mined land reclamation, most of which were originally enacted in the mid-1970’s through the mid-1990’s. Internationally, a number of prominent groups and various countries currently are considering new laws, regulations and policies for mined land reclamation. For example, the European Union has conducted a review of existing European laws concerning mining wastes and mine water and is considering new directives concerning mine waste and mine water management and liability schemes that are likely to significantly impact mine closure and mined land reclamation. Many countries, particularly those outside of North America, Europe, and Australia, have recently adopted or are considering new mine closure and reclamation legislation and regulations. These include significant hard-rock mining countries such as Chile, Peru and South Africa. This paper identifies recent developments in hard-rock mine closure and mined land reclamation laws in the United States, focusing on several of the more significant and controversial developments. It also discusses some of the more significant international efforts to consider mine closure and mined land reclamation laws and policies and some of the notable conclusions and trends from those efforts. The focal issues discussed in this paper include requirements for the reclamation of open pit mines, including backfilling; consideration of and measures to address the mining of sulfide ores and potential for acid mine drainage; and new requirements for the estimation of closure and reclamation costs and for financial assurance for closure and reclamation.

Jan 1, 2005

By Nick Hasenack

In the pelletizing plant of Hoogovens, Estel BV, a varying mixture of hematites and magnetites is used for the production of acid and (occasionally) fluxed pellets. Optimum results regarding productivity, quality and process control are obtained with mixtures containing 30-40 % magnetites. A decrease of the magnetite ratio or an increase of the basicity has a great influence on both productivity and heat and power consumption. Tests have been carried out to find the extent to which magnetite can be replaced by b.f. dust, mill-scale and coke breeze. Pilot plant tests show that about 80-100 % of the production loss due to a decrease in magnetite content or to the increase in basicity can be regained without damage to the quality by adding coke breeze. The amount of coke breeze should be limited tot 1,5 %; if this percen¬tage is chosen higher, the quality of the pellets deteriorates rapidly. The amount of coke breeze to be added should be about 30 % above the theoretical value, based on heat balance considerations. The results achieved by incorporating b.f. dust and mill-scale into the pelletmix were also encouraging, but as some types of mill-scale are very difficult to grind and the supply of b.f. dust is limited, the research has not been carried out extensively in this field. The pilot plant tests on replacement of magnetite by coke breeze have been followed by industrial tests, during which the breeze was added to the ore feed before the dry-grinding system.

Jan 1, 1977

By Rudolph H. Jacobson

The leaching of heaps or sub-marginal waste ore dumps as it is practiced throughout the Southwest as well as other parts of the world, is the major method of secondary recovery of copper. In 1970, twenty percent of all domestic copper was produced by dump leaching operations (l). In recent years, this method has been successfully extended on a limited scale, for the recovery of uranium from low-grade ores (2). It is inevitable that this technique will be increasingly employed in metal production to satisfy the insatiable demand of our mineral based society. Although dump and heap leaching has been used effectively for some time (3) , its application has been more of an art than a science. Therefore, it is essential that we learn about the important factors and parameters affecting this versatile process so that we may make increasing use of this technique in the future. The dump or heap leaching process encompasses the preparation of ore for-subsequent inplace leaching, the flow of solutions and ionic species through porous rock masses, the leaching of minerals with inexpensive and, if possible, regenerable lixiviants under prevailing conditions of the inplace environment, and the recovery of metals from the pregnant liquors. It is evident that this comprehensive scope of dump or heap leaching falls under the realm of interdisciplinary science and engineering requiring the application of the principles of physics, mineral engineering, hydrology, computer modeling, operations research, economics, and allied disciplines. An exhaustive study of the phenomenology of a leach dump or heap requires detailed knowledge of the simultaneous interaction of'

Jan 1, 1972

By G. Atesok, M. Hancer, M. S. Celik, O. F. Emrullahoglu

Multivalent ions are shown to activate the flotation of colemanite in the presence of sodium dodecylsulfate (NaDDS). Floatation recoveries versus barium ion concentrations exhibit three distinct regions of floatability. Adsorption, zeta potential and solubility mesurements under comparable conditions reveal that Region I is characterized by the uptake of Me2+ ions followed by electrostatic attraction of sulfate ions onto the oppositely charged surface. The improvement observed in flotation recoveries in Regions II and III is ascribed to surface and bulk precipitation of metal dodecyl sulfate onto colemanite, respectively. While the most soluble BaDDS ions yield the highest activation, the least soluble MgDDS achieve the lowest activation. It is postulated that metal ions depending on their solubility products with DDS are capable of activating the boron minerals.

Jan 1, 1993

By Kotaro Ohga, Kiyoshi Higuchi

In our laboratory, a new detection system using smell detectors was developed to detect the spontaneous combustion of coal and the combustion of other materials used underground. Laboratory experiments were carried out on several kinds of coals, including South African coals, and machine oil, wood and rubber used in belt conveyers. The following results were obtained: 1) Spontaneous combustion of coal can be detected earlier by smell detectors than by conventional CO detection methods. 2) There were no differences in the results using different kinds of coal. 3) Combustion of other materials can also be detected earlier by this system than by conventional detectors for gas and smoke. 4) Use of this detection system enables one to discern the source of the combustion gases, whether it be coal, wood, oil or rubber.

Jan 1, 1995

By S. D. Thompson, L. Adler

Several researchers in the last 20 years have developed computer simulation models for designing coal mine belt systems. A careful review of these reveals that each omitted or oversimplified important factors, especially in belt loading. To remedy this, the coal mine belt capacity simulator (CMBCS) was developed to include various types of probability distributions, delays, and longwall and continuous haulage. CMBCS is computer coded in FORTRAN and employs the Monte Carlo simulation technique. Basically, the model simulates the loading and corresponding flow of coal through a belt system. By recording spillage and belt stoppage statistics for the simulated flow, belt and surge bin capacities can be evaluated. A complete user's guide is available. The modeling and verification of CMBCS are briefly described, and its major advantages and disadvantages are explored.

Jan 1, 1987

By Paul M. Godlewski, Gerry Millar, Harvey W. Parker

Recently, over 70 railroad tunnels in the western USA have been enlarged and rehabilitated "live track," utilizing modern excavation and lining methods, in most cases to clear the larger double-stack container cars. This paper presents the general conditions of the tunnels and the technical aspects and costs of the rehabilitation of approximately 40 kilometers of tunnels, which range in length from a few hundred meters to 13 kilometers. Concrete-lined tunnels were rehabilitated by grouting and rock bolting, while unlined or timber-supported tunnels were relined with shotcrete and rock bolts. High output lining methods were required because of limited track time. Enlargement has been accomplished primarily by carving notches out of the concrete linings with a roadheader, or occasionally with saws. Unlined tunnels were enlarged by drill-and-blast or roadheader excavation.

Jan 1, 1991

By S. Mathur, Pradip

Polyacrylic acid (PAA) was evaluated as a selective flocculant for the dolomite-apatite system. PAA with a molecular weight (MW) of 4 million was found to flocculate both dolomite and apatite. However, the flocculation behaviors of dolomite and apatite were significantly different with 450,000 MW PAA, which was found to be the lowest molecular weight fraction capable of flocculation. In single-mineral tests with a dosage of 2 kg/t PAA, 90% of the dolomite and 35% of the apatite flocculated. Selectivity was achieved in mixed mineral tests. From a feed consisting of an 80:20 mixture of apatite and dolomite, respectively, a concentrate containing 90% apatite was obtained with a 70% recovery. The dolomite rejection was about 75%, which corresponds to a 2% MgO content in the concentrate.

Jan 1, 1997

By L. F. Nicolai, W. J. Schlitt

Lateral migration of leach solution in heaps and dumps is attributed to two phenomena. One is site-specific anisotropic conditions that exist on a macroscopic scale on the surface or within the rock piles. The second is associated with a random walk phenomenon that causes dispersion of solution, especially at gradients in flow or hydrostatic pressure. The latter phenomenon is a general condition that will occur in any leaching operation. Its effects are modeled by computer analysis and are compared with available field data on heap leaching. Under appropriate assumptions, the observed 58° angle of solution dispersion can be reproduced by the model. The combined effects of both anisotropy and random walk are also discussed. Finally, the impact of lateral solution flow on actual leaching operations is considered.

Jan 1, 1988

By Denis McDermott

This paper describes the process used at three mines to devel­op safety and training programs. The mines are located in Australia, New Zealand and the United States of America. The aims of the programs were to promote and reinforce safe and healthy behaviour, increase productivity and efficiency and to provide a fair and objective basis for the payment of wages. There were common aspects to each of the projects: • mandatory legislation required employers to provide employ­ee training in work performance • employees had little previous involvement in the design and development of the training provided • training had been unstructured with employees relying on the "buddy system" to acquire new skills; the degree of skill acquired by an employee depended on the knowledge and teach­ing capacity of the worker to whom the novice was assigned • appointments and promotions had been based on judgements by supervisors and these were not generally understood by employees • employment conditions for employees were covered by an industrial agreement between management, unions and employ­ees. The degree of sophistication of the industrial agreements varied however none provided a description of work performed in each classification, nor the career or promotional path for an individual • supervisors with the responsibility to train, develop, motivate and reward employees expressed concern that there were no structured processes ( eg work standards or wage progression cri­teria) to support their role.

Jan 1, 1998

By Hasan Kolayli

Zeolites are common secondary components of a variety of igneous rocks. However it is extremely rare to reach such abundances to form a rock. An unusual rock composed almost entirely of natrolite, a zeolite mineral, has been discovered ; in a mountainous terrain called the Kop mountain range in the eastern Turkey. In the region, country rocks are essentially metamorphic rocks. These unique rocks are resulted through metasomatic changes acted on microdioritic and andesitic parent rocks occurring generally as dikes and stocks in the country rocks consisting chiefly of serpentinized harzburgites. These metasomatic rocks are investigated with respect to their mineralogical, petrographical, and geochemical characteristics. These products consisting dominantly of natrolite are termed "natrolitite" and those containing additional pargasite, an amphibol mineral, are termed "pargasite-bearing natrolitite or pargasitic natrolitite ". The dikes and stocks show concentric zoning, each of which has distinct chemical and mineralogical compositions: Na2O and H2O contents show enrichment outward from the core to chill zones whereas, SiO2 and CaO show depletion. Mineralogically, plagioclase variety, abundance and chemistry change outwards from the center due to partial to complete replacement of natrolite: anorthite contents of plagioclases decrease outward, which is indicated by A1203 and CaO decrease and SiO2 and Na2O increase, showing inverse relationship with increasing natrolite content.

Jan 1, 2005

By B. K. Mishra, R. K. Rajamani, P. Songfack

Primary grinding in SAG mills is gaining more importance with respect to the conventional crushing, rod and ball milling operations. This is due to the reduced operating costs generated by lower steel consumption. However. SAG milling is inherently susceptible to more severe risks and problems since it attempts to combine several stages of the conventional crushing and grinding into a single stage. This paper analyzes the SAG milling operation by predicting the motion of rocks and steel balls. The well-known discrete element method (DEM) is used to calculate the trajectories of individual entities, and their collision with one another. A computer code previously used for studying the motion of grinding media in ball mills is enhanced to handle the interaction between heavy spherical steel balls and light chunks of rocks, usually ellipsoidal in shape. The DEM based software called MILLSOFT can animate the charge motion for different design of liners. A case study of a 9.75-m diameter SAG mill is presented and the effects of lifter bar height and configuration on the overall dynamics of the charge are discussed. Also the effect of spacing between liners on lifting the charge is presented. This new approach has a large potential because it shows in detail the effect of each design or operating parameter on the performance of SAG mills.

Jan 1, 1998

By A. Exikis

Simulating a ventilation network of an underground mine can help in solving complex ventilation systems with many features, selecting proper fan specifications, location and settings. Early computer systems running simple network simulations were able to provide solutions to the most common and immediate problems regarding underground mine airflow. The more advanced systems available today can perform more sophisticated modeling and simulation of a mine?s ventilation network and present their results in a more understandable and easy to communicate form. This paper presents a ventilation network case study from an underground mine. All aspects of mine ventilation network modeling and simulation are discussed as well as the results from the simulation process. The algorithms and techniques used are thoroughly explained. Some useful guidelines for the application of ventilation network software are also provided in the text.

Jan 1, 2006

By K. T. Stafford, N. A. Iverson, V. T. McLemore

Laramide porphyry copper deposits are large, low grade (<0.8% Cu) deposits that contain disseminated copper minerals, breccias, and stockwork veinlets of copper and molybdenum sulfides associated with porphyritic intrusions in Southwestern New Mexico. Critical minerals, such as PGEs, tellurium, indium, germanium, and gallium are recovered from the anode slimes remaining after copper is refined. Detailed age dating, mineralogy, geochemistry, along with geologic mapping could refine the location of critical minerals within specific systems and could identify porphyry systems with elevated critical minerals that could become economic, in addition to the already produced copper, gold and molybdenum.

Feb 1, 2023

By G. W. Cutting

Interlocking material balances on complex mineral dressing plants greatly assist in metallurgical investigations: indeed, without such a balance, there is no firm basis upon which to base process performance evaluations. To achieve balances both qualitative and quantitative data must be rationalised in conjunction with the process flowsheet. WSL has developed a range of programs to evaluate interlocking material balances. However, to obtain maximum benefit from the balances, answers of direct value at the process level must be provided: WSL has developed also a range of programs for this purpose. Practical examples are given, which illustrate the benefits obtained from process balances.

Jan 1, 1979

By R. D. Stewart

Abstract. Induced fluorescent sorting is a means of beneficiating an ore by selective labeling with a reagent combination which fluoresces when activated by ultraviolet light The reagent combination normally consists of a surface active compound and a fluorescent dye. The surfactant adheres selectively to a specific surface and carries the dye with it. Upon activation with ultraviolet light, the labeled pieces, in the size range 1.27 cm to 20 cm (0.5 to 8 in.), are detected during free fall by photosensitive cells and ejected by water jets. Either ore or gangue may be labeled.

Jan 1, 1980