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By Brian W. Hester

All gold occurrences in Tanzania are of Precambrian age and in geological settings similar to gold deposits in other parts the world. The three main areas of interest are perhaps the least prospected of areas of gold mineralization in Precambrian rocks in non- aligned, or market economy nations. Historic production exceeds 77.660 kg (2.5 million oz). Current results by small scale workers go unreported, but have been estimated to be as high as 11.000 kg (350.000 oz) annually. Gold occurs in both lower and upper Precambrian rocks. In the older. gold is associated with greenstones and iron formations typical of many cratonic areas of Precambrian age. The Tanzanian Craton lies in the north west quarter of the country where it is flanked on both east and west sides by mobile belts involving upper Precambrian rocks of high metamorphic grade. Gold occurs in fractures in the western belt within two distinct areas.

Jan 1, 1989

By H. Soto, G. Barbery

The effect of particle size on the flotation of coarse particles is analyzed. It is concluded that turbulence and the presence of the froth layer are detrimental to the recovery of coarse particles during conventional flotation. A counter-current column cell is proposed to avoid these two factors. In this column, a net upwards flow of water is prevalent, such that no froth is allowed to form on the top. Also, the levitation of heavy bubble-particle aggregates is helped by the ascending water current. Preliminary work at laboratory level with kilogram-size samples indicated that under similar conditions recoveries in the column were much higher than in conventional cells. Flotation results obtained with coarsely sized phosphate and quartz samples are presented. One interesting feature of this type of column is very fast flotation kinetics. Thus, a short column (only 55-cm collection zone) yielded, full recovery of floatable values.

Jan 1, 1992

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 Hassan Madani, A. Malek Mohammadi

Dorreh barite mine located in the central part of Iran is one of the largest barite mines, in the country. The mine is subdivided into three blocks, which are called block 1,2,3 according the barite quality. In the central part of each block, a heavily concentrated grid of exploratory drill holes have been drilled and the reserves of area was calculated based on these holes, some years ago. It was decided to compute the reserve of the area by geostatistical methods, in the form of an M.Sc. project. In order to study the area, three regionalized variables including density, thickness and density-thickness (accumulation) was studied and the spherical variograms were fitted to these variables. These models were evaluated by cross-validation method. The optimized block size was chosen in order to compute the reserves by kriging method. The reserves of explored parts of each block of mine was calculated and the results were extended to the whole area of the blocks. The reserve of the explored parts and the total reserve of the area were calculated to be 96,000t and 1,670,000t respectively.

Jan 1, 1996

By Rimas Pakalnis, Lyndon Clark, Tom Brady

A major focus of ground control research presently being conducted by the Spokane Research Laboratory of the National Institute for Occupational Safety and Health (NIOSH) is to incorporate data on weak rock masses into existing design relationships, with an emphasis on updating the span design curve for manned entries and the overbreak curve for longhole entries. Both curves were originally developed at the University of British Columbia, Vancouver, BC. The original database has been augmented by information from mines throughout the United States, Canada, Australia, and Europe. The common factor in all these mines is the presence of a weak back and/or walls. In most cases, the ore zone is the weakest rock unit and must be stabilized so that the mineral-bearing rock can be extracted safety. The current NIOSH research attempts to provide rock mechanics tools to assist a mine operator in making economic decisions that will also ensure a safe working environment. This paper documents the Nevada database with a special emphasis on Nevada underground gold mines.

Jan 1, 2005

By M. C. Williams, T. P. Meloy

With the increasing power of computers to simulate and control processes in the mineral industry, predicting the potential use of computers in the minerals field is not a hazardous enterprise, but predicting the timing of their use is. Like the railroad industry, technology invades the mineral industry, rather than being an industry like electronics that creates technology. Because of this invasive nature of computer technology in the minerals field, this paper predicts what will be possible to do effectively and economically with computers in the mineral industry. Moreover, this paper explores the problems of using the emerging computer technology in the mineral industry. For example, if not now, it soon will be possible to control the output of a mineral processing circuit - high grade, high flow or a mixture of it - to meet the daily market conditions and to sell each day that daily "mill" output as "mill" futures on the commodity market. Finally, suggestions are made which may be done to prepare the industry for the computer revolution in the mineral industry.

Jan 1, 1993

By Michael Michaylov, Elena Vlasseva

On the basis of well known and widely used in mine practice retreat longwall mining system, physical and mathematical models of air leakage dynamics have been created. Flow is assumed viscous-inertial and considering natural anisotropy of porous media of a gob area. As a result of modeling pressure and leakage distribution and velocity field can be defined. Thus the model presented in this paper can be used as aerodynamical prediction of gob area characteristics.

Jan 1, 1995

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 James R. Aggson, Verne E. Hooker, Dennis R. Dolinar

The stability of underground openings and mining systems is closely related to the in situ stress field. This paper presents a short discussion of the three-component borehole deformation gage and overcoring technique which the Bureau of Mines uses to measure in situ stresses, and a summary of stress data that the Bureau has gathered in the process of evaluating ground control problems. Specific ground control problems and stress distributions are discussed as examples.

Jan 1, 1982

By Li Honggui, Liu Maosheng, Zhao Zhongwei, Sun Peimci, Li Yunjiao

Leaching of Shizhuyuan low-grade refractory tungsten ore was carried out in a mechanically activating reactor. The effect of experimental parameters-temperature, amount of Na2C03, addition of NaOH, ratio of liquid to solid and leaching time - on the recovery of WO3 was studied. The WO3 recovery up to 96.99% have been achieved when the tungsten ore was digested by soda not more than three times the stoichiometric amount at 185-195°C for 1 .O-2.0 hours. Iso-extraction countour diagrams were drawn to illustrate the effect of various parameters on leaching. The WO3 recovery could be expected to increase 10-15% compared to that of conventional soda autoclave process.

Jan 1, 1995

By C. M. Brown

Common operating philosophies and objectives of mining and mineral process operations are discussed. Key information required to effectively monitor operations is reviewed in conjunction with the impact of external variables such as commodity price changes on strategies adopted.

Jan 1, 1991

By D. J. Murdock, Wyslouzil, I. M. Flint

The highly competitive nature of the international iron ore market has forced producers to improve the quality of their pellets. The demand for low-acid pellets suitable for direct reduction has resulted in an increase in the number of plants utilizing reverse froth flotation for silica reduction. Column flotation is being favored for this service because of low capital and operating costs and improved metallurgical performance compared to conventional flotation cells. This paper describes the benefits of column flotation and discusses some important aspects of circuit design.

Jan 1, 1995

By Brij M. Moudgil, Ivan U. Vakarelski, Yakov I. Rabinovich

Polymer and surfactant dispersant are widely used to disperse filler particles within a medium. Sur- faces active dispersants form self-assemble structures at the solid-liquid interface. The mechanical properties of the surfactant structures have been determined to strongly influence the dispersion behavior. In this study the atomic force microscope (AFM) is used to determine the elastic modulus and yield strength of a steric dispersant layer adsorbed to a rigid non-deformable surface. To interpret these values a model for elastic body contact based on a modified Hertz theory is applied. The results from this method may aid in the design of application-based dispersant systems.

Jan 1, 2003

By Fernando Concha, Arturo Barrientos, María Cristina Bustos

Manufacturers referred to high capacity thickening as a filtration operation rather than thickening in spite of the fact that it is performed in thickeners and that conventional thickeners can be operated as high capacity thickeners by changing the feeding level and operate it in a different manner. In this work we derive a phenomenological model for high capacity thickening based on mass and momentum balances. The difference with a conventional thickening is the presence of a surface source within the variable domain. The model can be used to design, simulate and to develop control strategies.

Jan 1, 1995

By R. Sripriya, Ch. V. G. K. Murty, N. D. Rao, P. V. T. Rao, A. Ramu

Studies were carried out to improve the performance of hydrocyclones at Tata Steel's chrome ore beneficiation plant in Sukinda, India. The optimal cut point of the hydrocyclones was determined in the laboratory using a stub cyclone. In the tests, the operating and design variables, including spigot diameter, density of feed slurry and inlet pressure, were varied. Subsequently, plant trials were carried out, and attempts were made to develop a model of the hydrocyclone using the Rao, Lynch and Plitt model. The cyclone efficiency was represented by the parti¬tion curve, and the performance was evaluated mathematically from a reduced efficiency curve, represented by the equation:

Jan 1, 2000

By Muhammad O. Rahim

The importance of planning ventilation systems in modern coal mines cannot be overemphasized. Interconnected entries, airflows around and through mined-out areas, leakages through stoppings and other control devices, and the use of multiple fans all contribute to the complexity of ventilation network analysis. Fortunately, the availability of computer programs (e. g., Didyk et al., 1978; McPherson, 1966; Wang and Saperstein, 1970) has greatly reduced the difficulty in net- work analysis. However, to obtain a suitable solution to the practical problem, a ventilation engineer has to simulate various conditions based on the proposed ventilation layouts and the capacities of available fans. It is often a trial-and-error process, although engineering knowledge and judgement are required.

Jan 1, 1982

By Yongqin Zhang

A single bubble released into surfactant solution first accelerates, reaching a maximum velocity then decelerates to reach a terminal velocity. Modeling this "velocity profile" is fundamental to understanding the motion of bubbles in flotation systems. This contribution considers the terminal velocity. Modeling is by a combination of the Navier-Stokes equation for flow around the bubble and the Marangoni effect induced by surfactant on the bubble surface. Numerical simulation is shown to agree with experiment for bubbles in pure water and surfactant solutions.

Jan 1, 1999

By Patricia T. Foley

An analysis of the demand for copper shows a widely varying pattern of end use. For example, copper tube is the most popular material for hot water supply in the US and northern Europe, but galvanized steel is used in Japan and plastics are used in developing countries. In addition to such peculiarities of end use, the demand for copper varies among countries depending on the stage of industrialization and the extent that the copper processing industries are developed. Brazil, with its abundant supplies of bauxite and hydroelectric power, uses aluminun in place of copper wherever possible. South Korea, with its export oriented economy and its advanced custom smelting and fabricating industries, favors copper. Understanding the details of demand in different countries enhances statistical derived forecasts and illustrates potential new markets.

Jan 1, 1986

By H. J. Chen, Y. Luo, S. S. Peng

Surface subsidence resulting from underground coal mining can cause problems for buried pipelines. In this paper, a technique for assessing the level of stress on a subsidence-affected pipeline is introduced. The main contributors to the stress are identified, and mitigation techniques for reducing the stress are proposed. The proposed mitigation techniques were then successfully tested.

Jan 1, 1998