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The leaching of gold and silver by ammonium thiosulfate solutions in the presence of copper has been actively studied in recent years. Newmont Gold Company has successfully tested the ammonium thiosulfate for gold extraction following biooxidation pretreatment of low grade refractory carbonaceous/sulfidic ores. In this paper, the chemistry of the copper catalyzed leaching process is reviewed. Factors affecting both the leaching reactions and the stability of the lixiviants are reviewed and discussed from a solution chemistry perspective.

Jan 1, 1996

The strength of anchorage of various types of roof bolts in permafrost depends on the types of rock in which they are installed. Variation in the mine thermal regime results in weakening of the roof and walls, and at times total loss of ice cement bonds takes place in the surrounding rockmass. In mines with positive ventilation air temperature, the wedge or expansion types of bolts may become weakened due to the transfer of heat into the anchorage through the metal rod and subsequent thawing of rocks. Effective operation and evaluation of roof bolt systems for mine workings in permafrost require predictions of the dynamics of wall thawing by warm ventilation air. This paper presents an analysis of the temperature distribution in the frozen host ground surrounding roof bolts, the area of interest being the vicinity of the anchors for point anchored bolt and the entire length for split set bolt

Jan 1, 1994

By Jean-Marie Deschamps

In an approach to the complicated study of bauxite from Les Baux de Provence it is necessary to consider the paleogeographical context of all the bauxites in southern France. These bauxites are of Karstic type, belonging to a metallogenic area extending from the Pyrenees Mountains to the Alpine Massif. Within this area each deposit does not always correspond to the same geological period. There are differing opinions regarding the origin of Karstic-type bauxite and a discussion of these various theories is beyond the scope of this paper. Bauxite of Les Baux, in Provence, was discovered in 1821 by the chemist, Berthier, near this picturesque village located in the region of Arles. It is Les Baux from which the name of bauxite originates. For a long time this bauxite was of no interest because of high silica 'and mediocre alumina content. Besides, the calcium carbonate content is somewhat high and is one of the main characteristics of Les Baux bauxite. The problem of exploration of the Les Baux deposit has been to prospect minable zones according to traditional norms where silica and carbonate are low.

Jan 1, 1977

By Phillip J. Maddex

During the last 10 years there have been many new developments in transport and handling equipment. Important technical and economic developments that can be used to reduce costs are; new terminal and materials handling concepts large river tows - 40,000 tons and 9000 hp towboats slurry loading and unloading of ocean vessels long distance pipelining of solids development of the shuttle train (unit train) large ocean barges ? 25,000+ tons ? pushed & towed 150,000 ton self-unloading super tankers - 300,000+ tons container shipping Some of these developments have been discussed at SME meetings in papers describing the transportation of minerals from new mines. But, only a few papers described improved transportation from older operations. Since transportation is a major part of the delivered cost for minerals, the economic benefits to be gained by putting new transportation developments to work are very substantial. Frequently good transportation planning and management makes the difference between a marginal ore body and a very profitable one.

Jan 1, 1972

By M. L. Smith

The U.S. Bureau of Mines Cost Estimating System (CES) has been used for prefeasibility analysis and mine cost engineering since 1978. In the past, prefeasibility analysis with CES has involved the solution of regression equations. The new generation of CES uses an object-oriented expert system in a Windows? environment. Knowledge bases are structured around generic mine models which access shared knowledge bases for system design.

Jan 1, 1994

By T. P. Smirnoff, R. J. Redmond, K .. N. Murthy

To minimize disruption to the Hollywood District of Los Angeles, a mined station using the New Austrian Tunneling Method (NATM) was developed. This paper presents the key factors contributing to the settlements and dynamic behavior of the unique binocular station design.

Jan 1, 1993

By Otis M. Clarke

Although most bauxite mined is used to make metallic alu¬minum, more than a million tons of bauxite is used annually in the United States in the manufacture of refractories, chemicals, abrasives, and cement. Raw material requirements are becoming increasingly difficult to meet because high-grade bauxite, required for some uses, is limited. The supply of raw material for high-alumina refractories is most critical because a low-iron bauxite is needed. Although there are substantial bauxite reserves in the world, bauxite suitable for use in refractories is limited to a few districts.

Jan 1, 1977

By Clayton Vernon Deutsch, Marcel Antônio Arcari Bassani, João Felipe Coimbra Leite Costa, Vanessa Cerqueira Koppe, Pedro Henrique Alves Campos

Traditional linear approaches oversimplify the complexities of ore blending. Adopting nonlinear blending models in mining and mineral processing is critical to enhancing prediction accuracy and allowing optimization regarding nonadditive variables, such as metallurgical recovery. This study implements a simulated annealing algorithm in short-term mine planning that seeks to optimize the metal recovery by considering how to blend the ore in the mine better. Two nonlinear metallurgical recovery models are used as inputs to the algorithm to represent synergistic and antagonistic blending. The results of the case study demonstrate that the optimized schedule exhibits improvements in both blending behaviors when contrasted with conventional linear-based scheduling plans.

Jan 1, 2025

By Lynn B. Hales, Randy Ynchausti

Expert systems are now being used effectively to streamline and improve the performance of supervisory computer control strategies. Their advantages have led to use in both batch and continuous applications. Expert systems in the context of real-time process control, will be defined and examples of their successful implementation in autogenous, semi-autogenous and ball mill grinding circuits will be discussed.

Jan 1, 1990

By R. C. Beers, R. J. McKinley, R. D. Stewart

Preliminary test results at Occidental Research Corp.’s Irvine, CA, research facility indicate the viability of a new induced fluorescent sorting technique for preconcentration of limestone, coal, and oil shale. The patented “Oxylore”* process is a preconcentration stage that takes advantage of selective surface chemistry to label either ore or gangue particles with a fluorescent coating that can be detected by activation with ultraviolet light. The technology was originally developed by Ted Matthews (SME-AIME Fall Meeting, 1974, Preprint 74-B-328) and was acquired by Occidental in 1977. The firm has continued development of the process since its acquisition.

Jan 6, 1980

By C. O. Hamilton

Poor plant start-up performance is usually blamed on poor design and unsatisfactory equipment. But, in most cases, the real cause of poor performance is inadequate preparation for operations and maintenance. Inadequate maintenance preparation, unlike inadequate operations preparation, will not immediately manifest itself in a new plant. However, not taking advantage of the window of opportunity afforded a new plant to organize the maintenance operation ensures that the new equipment honeymoon is unexpectedly short. Also, once a plant has entered a “breakdown mode,” it is extremely difficult to turn around.

Jan 1, 1991

By J. Frostiak

The Campbell gold operation of Placer Dome Inc. produces an arsenopyrite-sulphide concentrate which must be treated either by roasting, biooxidation or by pressure oxidation to obtain high gold recoveries. Pressure oxidation is a proven process and has the inherent advantage of meeting the stringent environmental regulations in the province of Ontario. A comparison of biooxidation and pressure oxidation was completed early in 1990 and the latter was selected by Placer Dome as the preferred process for replacement of the roasters. The commercial plant design was based on technology supplied by Sherritt Gordon and in July of 1991, the existing roaster operation was shut down and a new pressure oxidation plant was commissioned. The following summary describes the start up of the new facility and presents typical operating data.

Jan 1, 1992

By R. Krishna, L. A. Kumar

The paper suggests a new empirical model for predicting mining subsidence. The parameters considered are Lithological Factor, which in this context meant percentage of sandstone, Rock Mass Factor (depending upon the RQD value of drill-hole cores), width: depth ratio and percentage extraction of coal. More than 250 drill-hole cores from seven longwall panels and 11 bord-and pillar (room-and-pillar) workings were analyzed from an extensive data bank of Singareni Collieries Company Ltd. (S.C.Co.), Andhra Pradesh, India. Excellent subsidence agreement was found with the suggested model.

Jan 1, 1993

By J. M. Keane, C. K. Chase

Critical to successful dump and heap leaching of copper is an adequate evaluation of applicable parameters. This paper deals with methods to establish optimum conditions for dump and heap leaching copper so that commercial operations can proceed. Discussion is also offered of ore occurrences and preparations for dump or heap leaching.

Jan 1, 1988

By Keh-Jian Shou

"This study adopts and analyzed a shield tunneling case in Taiwan, with a diameter from 5.25m to 6.70m and the smallest radius of curvature 100m, which was constructed in gravel formations as well as a vibration sensitive area. In this case study, a vibration monitoring plan, comprising the sensors inside the shield machine and on the surface, was proposed and performed to provide the vibration data during the construction. In this project, the major vibration reduction considerations were increasing the open ratio of the cutter head (to reduce the cutting function) and reducing the rotational speed of the cutter head. The results of the construction suggest the appropriateness of the above considerations. The findings could provide suggestions to the other similar shield tunneling cases. INTRODUCTION Underground vibrations during shield tunneling are typically isolated and absorbed by the soil. However, a portion of these vibrations may disseminate to the surface. These vibrations are considered micro-vibrations, which generally do not pose a threat to surface structures, and are thus seldom the focus of research. The present project was located in the Hsinchu Science Park where shield excavation bypassed numerous high technology manufacturing plants (e.g., wafer manufacturing plants). The vibrations generated by shield tunneling may affect the vibration-sensitive manufacturing equipment and instruments in these plants, and induce problems in manufacturing processes. Therefore, research to comprehensively understand the characteristics and potential influence of such vibrations is essential. To clarify the characteristics and potential influences of vibrations generated during shield tunneling, the vibration level in the excavation of the Taoyuan International Airport Access (TIAA) Metropolitan Rapid Transit (MRT) Project was examined, as it possesses similar excavation conditions to the present project. The parameters collected from relevant tests were provided as a reference to the firms along the excavation route of the present project to explain the effects of vibrations, and to relevant units for shield machine selection and project execution. No yield problems resulting from shield machine induced vibrations were reported by the firms, and the vibration levels measured in the present project were comparatively lower than those in the TIAA MRT Project. Because the related literature is scarce, this study aims to analyze the collected measurement data and provide suggestions on shield machine selection or designs. Such that we can more properly evaluate and control the impact of shield tunneling induced vibrations in similar projects."

Jan 1, 2016

By D. J. Brunner, S. Mathur, D. McKinney

With the advent of faster micro-processors, the use of numerical methods to simulate complex fluid dynamic phenomena in three dimensions for use in design has become prevalent in the automotive, and turbo-machinery industries. The Computational Fluid Dynamics (CFD) method divides the region of interest into small control volumes which form the mesh representing the physical characteristics of the problem, and uses the finite volume method to intergrate the equations for the conservation of mass, momentum, energy and species over each control volume. Recent developments in CFD software expedite mesh generation, and enable the use of unstructured grids, comprised of tetrahedral volumes in three dimensions and triangular areas in two. CFD more accurately represents complex geometries and allows for relative movement of meshes enabling simulation of multiple moving bodies. 'ibis paper presents two examples of how CFD simulation can be used to assess mine and tunnel ventilation problems formerly addressed by application of analytical solutions which were developed assuming ideal incompressible conditions. CFD simulation is used to evaluate the impact of varying the airflow in a descentionally ventilated airway on the layering along the roof of smoke and hot gases resulting from a vehicle fire. Control of the smoke layer is required to enable safe egress from the vehicle, particularly if the vehicle is for personnel transport, and to ensure control of the fire contaminants throughout the ventilation system. The airflow required to prevent layering against the ventilation direction, calculated from the Bakke and Leach relations (Bakke and Leach, 1962), is compared with the CFD simulation results. An evaluation of the pressures, generated as a vehicle enters a tunnel portal, using CFD simulation, is also presented for unflared and flared portal configurations. These simulation results are compared with predictions derived using an analytical method which assumes one-dimensional and incompressible flow. Results of the CFD simulation are presented in an animated video format. SIMULATION OF BACKLAYERING In designing a ventilation system for a transit tunnel, the ability of the ventilating air to control and prevent backlayering of smoke and hot gases resulting from a vehicle fire is of prime concern. The buoyant nature of hot smoke causes it to rise relative to the colder, fresh air provided by the ventilation system. If the vehicle fire occurs in a descentionally ventilated tunnel, the smoke may tend to move upgrade in a layer above the incoming ventilation airflow. The layer may become thick enough to engulf a substatntial part of the tunnel cross-section upgrade of the incident that comprises the evacuation route. This effect is termed "backlayering' and it is similar to the development of methane layers in mines for which most studies related to backlayering have been done. Prediction Techniques Analytical A number of studies have been conducted (Bakke and Leach, 1962) to define the characteristics of this phenomena and as a result have produced relations which are used both in the mine and transit ventilation fields to define the air velocities required to control layering. In the transit industry the air velocity required to prevent the backlayering phenomena from occuring during a vehicle fire is called the "critical velocity" (Associated Engineers, 1975) and is dependent upon a number of factors: tunnel height, cross-sectional area and grade; ambient air temperature and density; and the heat release rate of the fire. Common practice in transit ventilation design is to provide an airflow which meets or exceeds the critical velocity. In order to determine whether or not the critical velocity can be achieved with a particular ventilation system, a one-dimensional simulation of the tunnel network is typically performed using programs such as the Subway Environment Simulation program (SES) originally developed in the late 1970's (Associated Engineers, 1980). The results obtained from SES are compared to the critical velocity to determine the adequacy of the ventilation system. Computational Fluid Dynamics For the backlayering simulations, a commercial CFD code which has been used successfully in a wide variety of engineering applications, was used. It provides numerous options for modeling laminar and turbulent flows, multiple turbulence models, definition of multiple species and chemical reactions between them, a variety of boundary conditions (including constant pressure and constant velocity inlets) and the ability to apply user-defined FORTRAN subroutines. It includes the ability to model conductive, convective, and radiative heat transfer. FLUENT also permits the use of "body-fitted coordinates" to match the computational mesh or grid to complex real-world geometries. Computational Fluid Dynamics Model The model developed to simulate the backlayering phenomena is comprised of an airway of rectangular cross-section, 4 meters wide, 4.5 meters high, and 200 meters long. A laterally

Jan 1, 1995

By Stavros A. Argyropoulos

The strides that have been made in recent years in applying Artificial Intelligence to pyrometallurgy, are reviewed. The computer reproduction of the way in which a human being reasons and calls on past experience and stored knowledge when faced with problem will be extremely helpful in pyrometallurgy. It is expected that Artificial Intelligence will be applied in all areas of human endeavor. Areas of pyrometallurgy that are most promising for expansion into A1 in the near future are presented.

Jan 1, 1990

By Howard R. Postovit, Bonnie C. Postovit

Raptors are birds of prey. In recent years, these birds have become highly regarded and have been given protection under various state and federal statutes. Surface coal mining can have both negative and positive impacts on raptors. Mitigation strategies and enhancement techniques can be implemented to alleviate negative impacts. The success of habitat reclamation will determine the long-range impact of mining on raptors.

Jan 1, 1989

By Louis A. Sandbak

Drift excavation by boom-type roadheaders in the San Manuel and Kalamazoo sulfide copper ore bodies has been successfully demonstrated. Geomechanical rock classification in conjunction with detailed geologic mapping has been necessary to assess roadheader performance, and to predict advance rates in the varied rock classes in the San Manuel block caving mine. Rapid excavation and less fractured ground are obvious advantages of roadheader drift excavation over conventional drill and blast techniques. The geomechanical system of Engineers International (1984) can be an effective roadheader performance and ground support tool.

Jan 1, 1985

By P. Riveros, A. Pratt, G. Deschênes

The effect of pyrite, pyrrhotite, chalcopyrite, realgar and arsenopyrite on gold dissolution in cyanide media was investigated. The cyanidation of synthetic gold ores, in the presence of various concentrations of sulphides, was studied under constant experimental conditions. A mineralogical analysis of the minerals was performed. The leaching kinetics were determined. The negative effect of sulphides on the gold dissolution rate varies with the sulphide mineral, and decreases according to the following order: realgar > pyrrhotite > chalcopyrite > pyrite > arsenopyrite. The chemical characterization of gold and sulphide minerals surfaces using X-ray photoelectron spectroscopy (XPS) was undertaken to identify the mechanisms involved. XPS analysis showed that a passivation layer of sulphides, arsenic or iron compounds may form on the gold surface as a result of the dissolution of the sulphide minerals.

Jan 1, 2002