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By Peter W. Harben, Edward M. Dickson

The distribution of metallurgical grade bauxite deposits will be discussed with the aid of a comprehensive table and a reference map. Information will include operating companies, mine locations, ore grade, and chemical analysis, geological environment, and production capacities. General comments will be made on the distribution of production and its relationship with major consuming regions. The pattern for the future will be assessed, including potential new producers, changing specifications and industry structure.

Jan 1, 1984

By John W. Tieman

Coal is a term applied to vegetable matter (trees, grasses, etc.) which was subjected to heat and pressure through geologic ages. This resulted in a change in both the physical and chemical properties. Because its chemical composition is variable, geologists classify coal as a heterogeneous mineral rather than a homogeneous mineral. Peat represents the initial, unconsolidated stage in the development of coal. This coalification continues with time and the application of temperature and pressure to lignite, subbituminous, bituminous, and anthracite toward the theoretical graphite end member.

Jan 1, 1981

By M. S. Janssen

The development of a design equation for, and the testing of, a constant- flow airlift pump IS described. The predictions of the new airlift model agree with the results of experiments carried out using riser diameters between 0.025 and 0.300 m, submergence depths between 5 and 10 m, suspension densities between 1000 and 1650 kg/m3, and a solids dg of 70 to 100µm. The predictions o the model also agree with data from the literature for submergence depths that reached 130 m. This airlift model was employed to simulate the pulp flow through a series of tanks, each of which was fitted with an airlift pump to transfer the suspension to the next tank. Particular attention was paid to the riser diameter, submergence of the airlift pump, and control of the air supply to the airlift pump during the simulated operation of a series of tanks. The results of the simulation highlight some design parameters that could affect the efficiency and operation of a plant that employs airlift pumps to transfer suspensions.

Jan 1, 1989

By James R. Fahy, Lawrence A. Hansen, J. David Deatherage

A laboratory testing program was con- ducted to investigate the shear strength along specific soil-liner interfaces for five types of liners of varying thicknesses. Results indicated a bilinear relationship between shear stress and applied normal stresses ranging from 276 to 1000 pKa (40 to 145 psi). Friction angles along the soil- liner interface below the break point normal stress (7.5 to 19 degrees) were lower than those recorded above the break point normal stress (14.5 to 39 degrees ).

Jan 1, 1987

By Y. Topkaya, R. E. Johnson, B. R. Palmer, R. B. Bhappu, J. Brent Hiskey, Gürses Öner

Currently there is considerable interest in applying in situ leaching technology to recover copper from oxide ores. In many instances, the distribution of copper mineralization in these deposits is fracture controlled. Laboratory core-leaching experiments have demonstrated that leaching response is sensitive to the dissolution of copper from and the formation of channels along main fractures. Solution short- circuiting can be a major limitation of this technology. This paper describes the application of macromolecular polymers to achieve flow-profile control during leaching. Pre- and post-leached fractures were characterized by computerized tomography (CT) analysis.

Jan 1, 1993

By C. B. Alcock

The control of high temperature processes requires the ability to measure significant variables during operations. With increasing automatic computerized control there is need for sensors which can provide on-line chemical analyses of all phases present in a reactor without the necessity to withdraw samples from the high temperature reaction zone. Probes using electrochemical cells and conductivity measuring devices have provided the answers to some of these problems, notably the measurement of oxygen in liquid metals, and similar potential systems based on the same fundamental principles for the analysis of non-metallic and metallic elements appear feasible. In this discussion, the state-of-the-art in chemical sensors will be discussed in terms of the potential materials of construction, and, in some cases, the limitations of upper temperature at which some promising systems can, at present, be applied. It is concluded that a new phase of basic research could improve the outlook substantially by providing solutions for some problems in chemical sensors which are now well-defined.

Jan 1, 1990

The issues involved in mine closure are usually complex, and the risks are significant. Although environmental risks are paramount, other issues such as safety, community, legal, fiscal and technical factors need to he taken into account. This paper describes a simple empirical model based on the concept of the closure risk factor, which will enable decision-makers to analyze the mine closure risks at any site, regardless of the complexity of the issues and the scale, scope and location of the operation. The model enables all the issues to be captured and their individual and collective risk quantified. A number of case studies in Australia and the Pacific that illustrate the usefillness of the model are presented.

Jan 1, 2002

By C. W. Matthews

Introduction Screening is defined as a mechanical process which separates particles on the basis of their size and their acceptance or rejection by a screening surface. The key element in this method of particle sizing is obviously the screening surface, the medium that contains the apertures for the passage of the undersize material. This surface must be strong enough to support the weight of the material being screened, flexible enough to yield to the vibrating force applied to it, yet light enough to provide a reasonable ratio of open area to attain a practical through- put. To balance all of these factors is difficult enough. The problem is compounded, however, because screening media are made in a great variety of types, shapes, sizes, and materials of

Jan 1, 1985

By Slobodan Vujic, Goran Cirovic, Dragan Radojevic

Mine production systems (MPS) are characterized, more or less, by the following properties: uncertainty, subjectivity, impreciseness, polysemy, instability, indefiniteness and lack of data. From modern study aspect these MPS mathematically belong to the class of fuzzy systems. With this in mind, the usage of fuzzy sets is recommended as a methodology that treats impreciseness, indefiniteness and complexity of mine production systems in a satisfactory manner. Fuzzy modelling, discussed in this pa- per, is applied as a mathematical implement. The objective of the paper was to show production optimization in practice on the ex- ample of bauxite open pits where fuzzy linear programming (FLP) was used following the criterion per income. The variables in criterion function are linguistic variables while both variables and variable restrictions are presented by triangular fuzzy numbers (TFN). The term "satisfactory income" presented through triangle fuzzy numbers was introduced instead of "maximizing the income". sensitivity of the obtained solutions has been analysed

Jan 1, 1996

By L. W. Ashton

Geochemical exploration guidelines were developed from a study of 460 rock chip samples collected at nine disseminated gold deposits in Nevada. Obtaining high grade Au samples is difficult because gold content is extremely variable, even over 8 m (25 ft) distances. For reconnaissance sampling, pathfinder elements are reliable indicators with threshold values of 100 ppm As, 1 ppm Hg, and 50 ppm Sb. Arsenic is the most reliable of the three elements, being significantly enriched in all deposits. If the pathfinder threshold levels are reached with low Au content, more samples should be collected. Successful disseminated gold exploration requires large numbers of samples.

Jan 1, 1990

By K. A. Natarajan, Namita Deo

The interaction of Bacillus polymyxa and minerals such as hematite, corundum and quartz resulted in significant surface chemical changes, both on the cell surfaces and on the interacted oxide minerals. After such treatment, quartz was rendered relatively more hydrophobic, while hematite and corundum were rendered more hydrophilic. Biopretreatment was observed to be beneficial in the separation of silica from hematite and alumina by both selective flocculation and flotation. The possible role of bacterial adhesion and metabilites in the biobeneficiation process is illustrated.

Jan 1, 1998

By R. B. Krog

Airflow patterns in longwall bleeder systems are affected by gob permeability and porosity and the condition of the gateroad entries after mining. As longwall panels are mined, areas of the caved zone and portions of the remaining gateroad entries become inaccessible, making direct ventilation measurement impossible. Mine operators are left to estimate direction and amount of airflow in the gob and the surrounding gateroads. The most readily available locations are where air enters the worked-out area, approved measurement point locations (MPLs) and/or evaluation points such as bleeder evaluation points, intake evaluation points, and the outer bleeder entry. Ventilation models (network or Computational Fluid Dynamics, CFD) can model the gob and the surrounding bleeder system but calibrating these models is difficult without field data. NIOSH installed a tube sampling system ahead of a longwall face and, as the face retreated, released a slug of tracer gas (SF6) to determine transportation times and flow rates in the inaccessible gateroads. The data was used to calibrate both network and CFD ventilation models for a longwall panel. Both model types were used to predict the airflow patterns in the gob and to determine the airflow rate from the longwall tailgate corner back to the bleeders.

Jan 1, 2011

By Malcolm J. McPherson

Observations of environmental parameters in mines have traditionally been made by means of hand-held instruments, these being employed as a basis to ensure that atmospheric conditions in the mine remain within limits commensurate with safety, to safeguard the health of personnel, and to ensure that statutory requirements are met. Thus, starting from the first flame safety lamps of the early nineteenth century, numerous portable instruments have been devised over the years to indicate levels of dust, temperature, humidity, and concentrations of gases including oxygen, methane, and carbon monoxide. Similarly, portable instruments have been used to measure air velocity and pressure. For routine monitoring purposes, hand-held equipment suffers from many disadvantages. Readings are intermittent, often with long delays between successive observations, making short-term trend analysis impossible. Portable instruments are more liable to damage; they are labor intensive and provide a very limited amount of information either for control or planning purposes. The 1960's and 1970's have seen an accelerated development of mine environmental monitoring equipment. Alarm methanometers to give localized audiovisual signals became more common. These were followed by a variety of instruments which gave local, then local/remote continuous records, particularly of methane concentration and airflow. More sophisticated transducers and transmission systems were developed allowing further parameters to be monitored. This led to a proliferation of paper strip and chart recorders which had to be maintained and inspected regularly for trends and abnormalities.

Jan 1, 1979

By William H. Mount

INTRODUCTION The requirements of mine ventilation demand the constant attention of the mine operator. Just as the physical mine structure changes with time, the ventilation requirements of a particular mine change considerably from season to season and even from day to day. No ventilation system can remain adequate indefinitely; and all systems require monitoring and adjustments to achieve proper ventilation. Instead of being given fore- thought and planning, mine-ventilation systems too of- ten are erected hastily, merely to correct an already un- healthy situation. The usual result is an inefficient and costly system that, in some instances, may prove in- effective in providing fresh air to the point of need. The ventilation of mines is a combination of both art and science. The fluid that must be moved is in- visible; its properties change drastically with temperature, barometric pressure, and humidity; and the methods of measurement are not precise. In part, ventilation engineering must rely upon the art of good industrial ventilation experience and sometimes even the trial-and- error method. However, the properties of air can be determined with relatively inexpensive equipment; with some care, measurement accuracies within 5% of the actual values can be obtained. Thus the art of ventilation gradually is being supplanted by improved engineering practices. Although the direction of flow and the volume may not be predicted correctly by airflow equations in every situation, it is better to try to predict the behavior of a given ventilation before installation than to proceed blindly with a system design. When used with the discretion that comes from education and experience, the basic laws of ventilation can provide sub-stantial insight into the design of an air-handling system; and they can prevent wasteful or even dangerous designs from being installed. Since the mine operators who read this text will have varying amounts of exposure to ventilation theory, the basic laws of airflow and of mechanical ventilation are presented in the first section. The emphasis has been placed on the interpretation and use of fan characteristic curves that are supplied by fan manufacturers. Considerable information can be obtained from these fan curves, particularly when they are used with a graphic model of the mine, drift, or duct in which the fan or fans are to be installed. A few minutes spent comparing the various characteristic curves can help the designer obtain the correct fan for the job. However, the under- standing of a few fundamentals is necessary; and this text has been prepared to provide ample and understandable information in a "how-to" style. In subsequent sections of this text, more down-to- earth subjects will be covered, including the problems of air recirculation, relative merits of installing fans in series or in parallel, expected maintenance requirements (vibration, lubrication intervals, etc.), fan noise and some remedies, effect of an inlet bell on the fan per- formance, basic air-measurement techniques and equipment, and similar miscellaneous items. Although this text is not intended to be a comprehensive bible of mine ventilation, it has been prepared as a guide that provides some useful information to individuals responsible for the quality of the underground environment. Every person working underground is en- titled to the safest environment that can be provided within the limitations of existing technology and at a reasonable cost. Adequate ventilation is well within both limits, provided that the system is designed intelligently, in conjunction with the mining plan, and not as an after-

Jan 1, 1982

By Dhananjay Kumar

In past, no serious attempts have been made to study the effects of operating environments on performance characteristics of a mining system. In this paper, proportional hazards model (PHM) analysis technique is introduced which can be used to analyze the effects of operating environments on the performance of a mining system. It can be used to select suitable materials, manufacturers or designs of items for a particular working environment. In this paper some applications of the PHM are discussed with examples from a Swedish mine. Its application for decision making in maintenance is also discussed.

Jan 1, 1992

By J. A. Herbst, Z. Rogovin

In order to develop more accurate procedures for scale-up and design of semi-autogenous grinding mills through detailed mathematical models, a better understanding of the charge motion and rocklball segregation is needed. To achieve this a 0.61 m (2.0 ft) diam by 0.305m (1 .0ft) length plexiglas mill was constructed as a scale model of a commercial SAG mill. Rock motion in the rotating mill was simulated using various sizes of ceramic balls. Quantitative measurements of dynamic angle of repose, water and slurry motion, holdup and size segregation of the charge were taken. In addition, a video presentation (available to the public) was prepared to elucidate charge and water motion at various mill speeds, charge volumes, rocksize distribution, and flow rates.

Jan 1, 1990

By H. Braun, T. Kind, K. Gloe, D. B. Dreisinger, H. Stephan, O. Heitzsch, G. A. Kordosky

Municipal garbage incineration processes with coupled wet flue gas cleaning systems generate effluents containing toxic heavy metals such as mercury, zinc, cadmium and copper. The separation of these metal ions from the obtained scrubbing solutions is possible using liquid-liquid extraction. Extraction studies has been performed both with commercial extractants Aliquat 336, di(2-ethylhexyl) phosphoric acid and novel chelating agents as acyl thiourea and lipophilic oxathiaaza alkanes. Advantages and disadvantages of the investigated extraction systems are discussed. The paper reports on the basic research as well as on the testing in a laboratory scale.

Jan 1, 1993

Little faith can be placed in a coal resource estimate without a clear understanding of the estimate's accuracy. Different types of coal resource estimates require different levels of accuracy. Prospecting surveys typically are done with widely spaced boreholes, while a much higher level of accuracy is required for mine design. Either way, a measure of the accuracy clearly indicates the level of confidence that can be placed in the results of the estimate. Geographic information systems (GIs) are becoming a commonly used tool for resource estimation because they not only provide a database management platform but also the graphical capabilities to visualize resource characteristics. interpolation methods used commonly in these resource studies do not typically provide a quantitative answer to the question: "How accurate is the estimate?" By comparing localized measurements at multiple locations to the interpolated thickness distribution used in a resource estimate, a quantitative analysis of accuracy can be obtained. The technique is demonstrated with a case study from Central Appalachia.

Jan 1, 2000

By G. T. Adel, J. D. Miller, C. L. Lin

In view of the success of recent laboratory studies using X-ray computed tomography (CT) to determine coal washability and with the availability of high-speed CT systems, it now seems possible to design an on-stream washability system for the control of coarse coal-cleaning circuits. Design features for such a system are examined and possible control strategies are discussed for different applications.

Jan 1, 1995

By Mustafa Yalçin, Ali Ihsan Arol

Coconut shells are the most widely used raw material for the production of activated carbon used in the gold production by cynanide leaching. There have been efforts to find alternatives to coconut shells. Shells and stones of certain fruits, have been tested. Although promising results to some extent were obtained, coconut shells remain the main source of activated carbon. Türkiye has become a country of interest in terms of gold deposits of epithermal origin. Four deposits have already been discovered and, mining and milling operations are expected to start in the near future. Explorations are underway in many other areas of high expectations. Türkiye is also rich in fruits which can be a valuable source of raw material for activated carbon production. In this study, hazelnut shells, peach and apricot stones, abundantly available locally, have been tested to determine whether they are suitable for the gold metalurgy. Parameters of carbonization and activation have been optimized. Gold loading capacity and adsorption kinetics have been studied.

Jan 1, 1995