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By Lars Lövgren, Jörgen Jönsson

Heavy metals may be retained within deposits of sulfide minerals under oxidation and in the nearest recipients of drainage water by sorption to secondary iron precipitates. The extent of sorption is strongly influenced by solution pH and presence of complexing ligands, such as sulfate and natural organic acids. Desorption of metals and organidinorganic anions to recent secondary Fe precipitates, collected at the Kristineberg mine, Sweden, has been investigated under different geochemical conditions. Elemental composition and structural characterization (X-ray powder diffraction) indicate presence of schwertmannite. While metals such as Ni and Pb were fractionally desorbed from the precipitates under acidic conditions, oxyanions, e.g. arsenatdarsenite and sulfate were desorbed preferably under alkaline conditions. In a separate study the adsorption of NOM onto synthetic goethite was investigated. NOM adsorption showed a strong pH dependence, 95% was adsorbed at pH 3 and 40 % was adsorbed at pH 9. Addition of 2 mM of sulfate desorbed about 10 % of the adsorbed NOM.

Jan 1, 2000

By Jack S. McPartland, Gene E. McClelland

It is advisable, for any heap leach project, to develop an historical metallurgical data base to predict production heap performance before ore is mined and placed onto the heap. A data base would include results from: interval assays, cyanide solubility tests, and bottle roll tests on exploration drill cuttings samples; and those results plus column leach test data on diamond drill core or bulk ore composites. Subsequent larger scale heap leach test data can then be compared to the historical data base, to blast hole composite data during mining, and eventually to production data. This paper does not discuss metallurgical comparisons between assays, cyanide solubility tests, and bottle roll tests on exploration drill cuttings samples, but does discuss metallurgical comparisons from bottle roll tests, laboratory scale column leach tests, and pilot scale heap leach tests on core and bulk ore samples with operating data for three U.S. commercially producing heap leach operations. Provided that representative core or bulk samples are used for evaluation, heap leach test results accurately predict or understate the success of the commercial operation and remove most of the uncertainty from the investment decision.

Jan 1, 1990

By W. E. L. Minter

Discussion by E.S. Cheney Minter (1990) has provided an excellent summary of the sedimentology and theories of origin of the Witwatersrand paleoplacer Au/U deposits. However, recent stratigraphic, metamorphic and structural -tectonic research is radically changing the concepts about the Witwatersrand that now occur in most textbooks, review articles and North American minds. Presently, these concepts are biased by the past sedimentological research so well described by Minter. Specifically, the Witwatersrand Supergroup is Archean, does not occupy a depositional basin and is significantly metamorphosed and deformed. Thus, many of its sedimentary features, including the mineralogy of its ores, have been modified. The importance of the Witwatersrand ores cannot be overestimated. Since their discovery in 1886, they have produced 52% of the gold mined in all of human history (Pretorius, 1989). Setting Only one depositional item needs to be added to the excellent

Jan 1, 1992

By Fernando Concha, Arturo Barrientos

The flow in a hydrocyclone is divided into a boundary layer around the walls, an exterior inviscid flow and an air core in the center of the equipment. The boundary layer flow over the lateral walls is associated with the short circuit of particles to the underflow, while the boundary layer over the top of the hydrocyclone and the outer part of the vortex finder tube is related to the short circuit of particles to the overflow. Classification takes place in the exterior flow. The model can be validated with pilot or industrial data and simulates the performance of hydrocyclones in a wide range of design and operating variables.

Jan 1, 1992

By Hans Skretting, Abraham A. Dor

This paper briefly reviews the historical development of the Rotary Kiln-Electric Furnace Process, which was first applied commercially to the treatment of qarnieritic ores in New Caledonia in the mid-fifties. It describes various technological improvements introduced, since, in industrial plants or developed in pilot facilities where a wide variety of nickel oxide ores has been treated success- fully over the years. Major categories of ores are characterized. The effect of their physical and chemical properties on their performance in the electric furnace is discussed. The relationships between ore composition, ferronickel grade and slag composition are analyzed and their effect on slag and metal tapping temperatures, nickel recovery, and electrode voltage are discussed.

Jan 1, 1979

By V. Kontogianni

The underground extraction of coal is associated with ground movements extending from the mining area to the ground surface, which result in bowls of ground subsidence, with amplitude exceeding the amount of several meters and occasionally with important tilt and curvature of ground surface. Such changes at both the underground environment and surface topography lead to destruction of buildings, failure of utilities and transportation networks, and occasionally formation of areas vulnerable to flooding, or even small pools. Based on geodetic surface measurements of ground elevation changes, various theories and empirical models relating surface subsidence with the geometry of underground voids formed have been proposed, and predictions of expected subsidence in the form of contours have been estimated. In this study a case study of planning of a new highway network through areas in which coal extraction was also planned is discussed. This work is partly funded by EU. The optimum solution selected was a modification of the initial highway planning, so that the road is increased in length and by-passes the richest coal-field, where maximum post-exploitation subsidence was predicted, and only crosses either minor coalfields, which are not to be exploited, or even margins of main coalfields, in which minor post-exploitation subsidence is expected.

Jan 1, 2006

By C. J. Johnson

As the U.S. coal industry moves into the next century, it is becoming more apparent that the effective application of new technology is the only way it can remain competitive in the energy marketplace. Examples of this emphasis are with us today in such diverse areas as face-ventilation and excavation-equipment applications. The focus of this new technology is directed toward improvements in health and safety, cost control, and productivity. Room-and-pillar mining accounts for approximately 80% of the nation's underground coal production; this percentage is not expected to decrease markedly in the near future. As such, this paper analyzes the impacts of the changing technological climate on future room-and-pillar operations by comparing a base-case section (current) to three scenarios incorporating new or emerging technology. A microcomputer-based comparative analysis will reflect the changes in section production and costs.

Jan 1, 1988

By T. A. P. Sankar, S. Gundiah, Pradip, R. A. Kulkarni

Two modified polyacrylamide flocculants, namely polyacrylamide with glycolic acid functionality (PAMG), and a copolymer of acrylamide with N-acryloyl-[T]- aminobutyric acid (HPVP), were synthesized, characterised and evaluated for selective separation in apatite/quartz and apatite/dolomite/calcite systems, respectively. PAMG flocculant was found selective in the separation of tricalcium phosphate (TCP) from its mixtures with quartz at acidic to neutral pH range. The selectivity deteriorated at alkaline pH. In contrast, polyacrylic acid (PAA) flocculant was found most effective only in the alkaline pH range. HPVP flocculant (even though flocculating all three minerals namely apatite, dolomite and calcite) was observed to be quite selective for the separation of calcite from apatite-dolomite minerals in single mineral tests in the presence of sodium hexametaphosphate dispersant at neutral pH. There was, however, no selectivity observed during tests on synthetic mixtures. This loss in selectivity is attributed to the phenomenon of hetero-flocculation, as reported earlier, for separation in an apatite-dolomite system with polyethylene oxide.

Jan 1, 1993

By Donald L. Bott

A computer model called the Quality Compliance Model was developed to optimize the mine planning and sequencing in area coal mining with respect to the limit on pounds of sulfur dioxide per million BTU imposed by regulations. The objective of the model is to maximize the amount of high sulfur coal mined from various benches while meeting the specified compl'ance standards. Given multiple seams and multiple benching operations, the mining sequence from each pit is simulated. The rate of mining is controlled such that the in-pit blending will maximize the usage of high sulfur coal and meet compliance standards. The compliant coal can be stockpiled for usage at a later date, or it can be disassociated. This calculation can be based on any given rate of production, i.e., from as small a unit as a unit train to as large as monthly or yearly production.

Jan 1, 1982

By Stephen J. Reynolds

Arizona's geologic history is complex, resulting in a diversity of rock types and earth materials, including those of commercial interest. Regional variations in geologic history gave rise to three geologic provinces and an inequitable distribution of both metallic and nonmetallic mineral wealth. The Colorado Plateau is largely composed of flat-lying Paleozoic and Mesozoic sedimentary rocks and late Cenozoic volcanic fields and sedimentary deposits. Associated resources include gypsum, halite, sylvite, clays, specialty sand, flagstone, volcanic products, and aggregate. The adjacent Transition Zone features a large expanse of Proterozoic rocks, economically important Devonian and Mississippian carbonate rocks, and Tertiary volcanic and sedimentary materials. Nonmetallic resources in this province include facing and dimension stone, aggregate, decomposed granite, chrysotile asbestos, gypsum, clay, barite, fluorspar, zeolites, and limestone used for lime, cement, and railroad ballast. The Basin and Range Province has the most complex geologic history and, therefore, the most diverse assemblage of industrial mineral occurrences. These include halite, gypsum, clay, aggregate, decomposed granite, diatomite, zeolites, perlite, pumice, kyanite, limestone, marble, stone, and others. In addition, young stream deposits yield vast quantities of sand and gravel, Arizona's most economically important nonmetallic mineral commodity.

Jan 1, 1987

By S. K. Kawatra

With the increasing importance being placed upon modernizing the coal industry as a result of recent developments in the international energy balance, computer control has been and is being instituted in many coal cleaning plants. Control techniques that are well established in many base metal industries have been adapted to coal washing. Essential to any control scheme is an accurate measure of the parameter which is to be controlled. A sensor is required that will provide information both quickly and precisely. In fine coal circuits, the critical parameter that must be measured and controlled is the per- cent ash contained in the clean coal product and tailings. Measuring the ash content of these slurry lines on a continuous basis enables the operating conditions in the circuit to be adjusted so as to obtain optimum separation efficiencies at all times. An on-line ash monitor has been developed and tested at Michigan Technological University which is capable of making percent ash and percent solids determinations instantaneously. Two radioisotopes are employed in this system to generate signals that can be related to the density and the ash content of the slurry. Such data provide a means to execute a short term control strategy.

Jan 1, 1982

By Justus B. Deen

Given that the majority of mine ventilation operating costs are imposed by shafts, the need to predict the resistance of a planned shaft with reasonable accuracy is important. During conceptual design, shaft resistances are usually predicted by use of published friction factors, k, based upon lining and fitting configurations. More often than not, published friction factors do not directly coincide with "real" shafts, so their use is somewhat limited. For more accurate shaft resistance determination, equations both theoretical and empirical may be employed if there is detailed knowledge of the shaft. These equations treat the shaft resistance as discrete components, with their sum being the overall shaft resistance. This paper describes the basic shaft resistance equations and verifies these equations by comparison to field measured shaft resistances. Several shafts were examined which varied in depth, shape and fitting arrangements. Results are presented and conclusions drawn to show that the shaft resistance equations are accurate.

Jan 1, 1991

By M. Shen, T. D. Wheelock

The important characteristics of a gas-promoted oil agglomeration process for cleaning coal particles in an aqueous suspension were determined. Numerous agglomeration tests with scale-model mixing systems of different sizes with controlled amounts of air were conducted. The tests were conducted on high- and mediumvolatile bituminous coals using either i-octane or hexadecane as an oily agglomerant. The performance of the system was characterized by employing the minimum time required to produce spherical agglomerates (tE), the mean agglomerate diameter (dp), coal recovery and product ash content. Among these parameters, tE was found the most useful. It is a key parameter in the scale-up of an agglomeration mixing system. This parameter was found to depend on a number of system and operating variables. By controlling these variables and conducting further agglomeration tests with mixing systems that varied in size, an appropriate size scale-up rule was established.

Jan 1, 2002

By Jerry M. Whiting, Samuel Frimpong

Superior ventures selection and the subsequent management of their development and production are crucial in the competitive environment of the upstream minerals and energy industry. An important element of this chain is the management of uncertainty and risk dynamics. In the world of faster and more complicated technological and environmental changes, international competition and commodity market dynamics, thorough and sophisticated valuation must be carried out to establish a venture's value and return on investment. Thus, managers and investors must use methods that respond to market dynamics, investment and feasibility study options and provide relevant information for strategic investment decisions. Conventional methods have no built-in procedures to help investors analyse these options. Modern financial methods based on the dynamic arbitrage theory overcome these and other limitations of conventional methods. In this study, dynamic arbitrage theory has been used to formulate 3D parabolic differential equations that govern the stochastic processes of a copper mining venture with ongoing feasibility studies. The alternate direction implicit algorithm is used to solve the numerical approximations of the differential equations and their boundary conditions. Phase dynamics of the venture have been analysed to provide investors the appropriate timing for strategic investment decisions. The study also shows the amount and value of appropriate feasibility studies required to maximize the value of the mining venture.

Jan 1, 1996

By Jr. Smith

Industrial minerals are just other rocks, except for the unique characteristics that make them useful in an industrial process. There is not a ready market for this type mineral and one or more uses must be developed to sustain production. The name "olivine" is a generic term used to indicate a group of orthosilicate minerals in a solid solution series, with forsterite (Mg2SiO4) and fayalite (Fe2SiO4) as endpoints. Since neither is found alone in nature, the mineral is always a combination of the two. The commercial deposits are high in magnesium and on the high end of the melting scale in the series. The name comes from the olive-green color.

Jan 1, 1992

By Kent G. Homewood

The well-being of any company is directly related to the well-being of its employees and to the effectiveness with which the personnel resource is managed. In an era when personnel management has steadily become more complex, there is an increased awareness of employee information systems at all levels of management due to: (1) regulations enacted by federal, state, and local government agencies; (2) technological advances within the mining industry which have resulted in the requirement for highly skilled personnel; (3) increasing concern for the confidentiality of employee information; and (4) management's need for information for planning purposes to control costs and for early recognition of trends and potential problems. In the past it was sufficient to maintain records manually. Today computers are necessary to provide information on short notice and effectively manipulate large volumes of' data. This discussion will describe the following aspects of employee information systems: (1) collection and maintenance of information, and (2) applications which include employee health, salary administration, management re- sources, and labor negotiations.

Jan 1, 1979

By R. Hogg, R. C. Klimpel, D. T. Ray

The sedimentation and dewatering characteristics of flocculated slurries are determined by the size and density of the flocs. Studies of the formation and growth of flocs reveal that floc size is limited by breakage of the agglomerates due to shear in the suspension. Floc density measurements indicate that there is an inverse relationship between size and density. This relationship appears to be determined primarily by the nature of the solid particles, especially the size distribution, but it appears that agitation of the suspension can lead to some densification of the flocs, in addition to breakage. It follows that both size and density can be controlled to a significant extent by regulating the physical conditions (agitation, method of flocculant addition, etc.) during flocculation. The use of physical floc conditioning to control the sedimentation and dewatering (filtration) behavior of flocculated, fine-particle suspensions is evaluated in terms of its effects on floc size and density.

Jan 1, 1988

By I. L. Jennings

In most industrialized countries, the largest element of the mining industry in physical volume is that devoted to the extraction and processing of materials for use as construction aggregates. Required for all developments in industry and commerce, power and transportation, and housing and public services, their use is so widespread that possible sources are exploited throughout all geographic regions, as close as possible to the point of use. Thus, it is also the most frequently encountered form of mining throughout the world. These materials come from four main sources:- (a) Excavation of unconsolidated deposits of sand and gravel (b) Stone quarrying. (c) Processing of slags and other mineral wastes. (d) Manufacturing from clays and shales by heat fusion. The major uses are in: (a) Portland cement concrete, that most versatile of construction materials, including the many concrete products in current use. (b) Asphalt cement concrete; widely employed for paving roads, parking lots, airfields, etc. (c) Foundation materials, such as road base, granular backfills, railway ballast, etc.

Jan 1, 1968

By S. Ostap

INTRODUCTION Paradoxically, it has been found that the people who are the most aware of the origin, mineralogy and composition of bauxite are also the people who are the least aware of how bauxite composition affects its treatment by the Bayer process. These people are the exploration and mining geologists normally associated with aluminum producing companies. The purpose of this paper is to give some idea of how the concentration and physical nature of the different minerals found in bauxites affect the operation of the Bayer process used to extract their alumina content. The bauxites we will consider here will be only the tropical bauxites such as occurring in Jamaica, various countries in South America i.e. Guyana, Surinam, Brazil, African bauxites, Malaysia and in Australia. When we speak of the Bayer process, it will be the North American version of the Bayer process using low caustic concentrations and bauxite digestion temperatures varying between 130° to 250°C. TABLE 1 shows the minerals and elements of interest occurring in tropical bauxites. The minerals and elements listed in the table do not by any means represent all of those identified in bauxites. Using mass spectrographic analysis on six bauxites from different geographic locations, we managed to identify between 50-60 different elements. Fortunately, only about 13-14 of these elements possess the necessary chemical properties to be able to accumulate in caustic Bayer solutions. The remainder are either not attacked, or form insoluble reaction products with some main liquor component, i.e., hydroxide, aluminate or carbonate, or reprecipitate with alumina trihydrate during the precipitation stage.

Jan 1, 1984

By V. G. Papangelakis, G. P. Demopoulos

The high temperature (180-200 OC ) pressure oxidation (02 - HzSO4) process for the recovery of gold from refractory concentrates (FeS2/FeA8S) is simulated with the aid of a computer model. The model centers on the continuous operation of a multi-stage horizontal autoclave. In particular the effects of key process parameters controlling the autogenous operation of the autoclave are critically examined. The building elements of the model are (i) the continuous particle size distribution function of the concentrate, (ii) the residence time distribution function of the slurry and (iii) the shrinking core kinetics. Conversion is calculated on the basis of the segregated flow model. For the calculation of the particle size distribution at the exit of each compartment the population balance model is employed. The effects of feed rate, feed preheating, cooling, autoclave configuration and rate limiting regime (chemical reaction vs. gas-liquid mass transfer) on the autogenous steady state operation are discussed. Finally optimum reactor design and operation criteria are indicated.

Jan 1, 1990