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By R. L. Pozzo

A previous investigation showed that corrosion currents estimated from polarization curves for the pyrrhotite-grinding media system under abrasion correlated well with corrosion currents estimated from marked ball wear test data by applying the Faraday's Law. Freshly abraded metal debris were magnetically attracted to pyrrhotite and lowered the rest potentials of the mineral particles, thereby affecting the corrosive wear. The investigation was extended to explore the interactions between a nonmagnetic sulfide mineral, pyrite, and abraded metal debris and their effects on the corrosive wear mechanism. The electrochemical behavior of a three-electrode system involving pyrrhotite, pyrite and grinding media was also investigated as a first step towards elucidating the nature of interactions that occur in the grinding of complex sulfide ores.

Jan 1, 1987

By Hans Hamrin, Bruce Kennedy

Once an ore body has been probed and outlined, and sufficient information has been collected to warrant further analysis, the important process of selecting the most appropriate method or methods for mining can begin. At this stage, the selection is preliminary only, serving as the basis for a project layout and feasibility study. Later, it may be found necessary to revise the details, but the basic principles for the ore extraction should remain a part of the final layout. With respect to the basic principles employed, relatively few mining methods are used today. For the purposes of this presentation, the principles are classified as follows: 1) For naturally supported stopes, the available methods are room-and-pillar mining and sublevel stoping. 2) For artificially supported stopes, the available methods are shrinkage stoping, cut-and-fill mining, square-set mining, and longwall mining. 3) For caving methods, the available techniques are sublevel caving and block caving. Due to the uniqueness of each ore deposit, the variations on each of these methods are nearly limitless. It is impossible to include even the major variations in this chapter; the goal of this chapter is to present the principles as a guide to the mining engineer in adapting the general methods to specific needs. The selection process described herein is intended to supply the techniques by which the candidate methods available for a given ore body can be reduced to one or two feasible approaches. The feasible approaches then can be evaluated in detail, and the particular modifications can be investigated. In describing costs and economic factors, all values herein are expressed in terms of 1978 US dollars.

Jan 1, 1982

By J. H. Rowland, A. C. Smith, K. A. Teacoach

Current regulations for fire suppression systems in underground coal mines to protect conveyor belt installations have been in place since the Coal Mine Health and Safety Act of 1969 was enacted. Over time, the coal conveyer equipment being used and ventilation conditions underground have changed significantly, particularly the width of the conveyor belts and the use of belt air at the face. The effect of these new conditions on the effectiveness of suppression systems during a fire is not known. The National Institute of Occupational Safety and Health (NIOSH) conducted a study to evaluate the effect of air velocity, water sprinkler activation temperature and a limited water application time on the effectiveness of water sprinkler fire suppression systems to extinguish large-scale conveyor belt fires. The fire tests were conducted using both new and used 1.8-m-wide, fire-resistant rubber belt that met the Mine Safety and Health Administration (MSHA) flame-resistant requirement specified in Title 30, Code of Federal Regulations, part 18, section 18.65 (also known as the 2G test). Tests were conducted using standard response sprinklers with activation temperatures of 68° C and 141° C at air velocities of 0.5 and 5.1 m/s. Two tests were conducted at both air velocities for each sprinkler activation temperature, one using a new belt and one with a used belt. The results showed that the suppression system was able to suppress the fires in ten minutes to the point that a miner could extinguish it with a fire hose. However, in several of the tests, the fire reestablished itself a few minutes after the sprinkler water supply was cut off and quickly grew out of control. This report discusses the large-scale experimental configuration, the installation specifications of the fire suppression system and the results and conclusions regarding the effect of air velocity, sprinkler activation temperature and limited water application on the suppression system performance.

Jan 1, 2010

By P. C. Miller

The paper reports laboratory results from the bioleaching of chalcopyrite ores and concentrates using a mixed moderate thermophile culture. Copper dissolution in excess of 95% was achieved in all cases with the majority of tests indicating copper dissolution in excess of 98%. Aspects of downstream processing are discussed in relation to iron rejection by precipitation. The laboratory results indicate the need for careful control of the pH value to prevent co-precipitation of the copper with iron. A comparison of capital and operating costs is given indicating potential differences between the use of toll smelting and bacterial leaching on site. A discussion is given highlighting the sensitive cost areas of these two process routes.

Jan 1, 1997

By M. Misra

The dissolution of mercury during gold cyanidation is the cause of many environmental, health and processing problems. A study was undertaken to find a suitable reagent for the removal of mercury bearing complexes from the leach liquor. Removal of mercury from synthetic solutions and process water from a gold mine was investigated using sodium sulfide, sodium and potassium dimethyl dithiocarbamates as precipitating reagents. The results have shown that efficient mercury removal could be achieved by addition of potassium dimethyl dithiocarbamate (KDTC), by formation of stable mercury compounds. The resultant mercury-potassium dimethyl dithiocarbamate precipitates are stable under present plant operating conditions and do not have any deleterious effect on gold adsorption by activated carbon. Furthermore, it is also possible to stabilize the mercury in the heap during cyanidation by adding dimethyl dithiocarbomate.

Jan 1, 1998

By F. T. Paleari

Radial gas holdup profiles have been measured in a 50x400 cm flotation column using a multi-cell conductivity probe. Three different bubble generation systems were examined: up to eight vertical filter cloth spargers, three horizontal filter cloth spargers, and three (horizontal) Cominco-type spargers. The variables tested were: number of spargers, symmetry of their arrangement, and height above spargers. Batch water with up to 20ppm frother concentration was used. The general observation is that the profiles tend to be uniform (i.e. flat) with some exhibiting a slight wavy shape. The vertical sparger arrangement proved the most difficult to achieve profile symmetry. The horizontal spargers gave uniform profiles at right angle to their length but a decreasing gas holdup along their length; the Cominco-type spargers gave slightly less scatter in the data. Switching off selected spargers (to simulate malfunction) did not produce strong asymmetry in the profiles.

Jan 1, 1993

By Thomas E. Newman

This paper is a case study using new laser-terrain-mapping technology by EagleScan, Inc., for creating topographic maps. Holnam, Inc., has used this technology to create maps and volumetric calculations of several mines in the United States. The information is superior to conventional methods through accuracy, manpower, time, and cost. Holnam, Inc., was the first cement manufacturer to use the Digital Airborne Topographic Imaging System (DATIS?). The technology uses the DATIS? to produce high-resolution terrain maps and volumetric assessments of any area. DATIS? is a mapping instrument that integrates (1) a Light Detection and Ranging (LIDAR) instrument to measure terrain elevation using laser light, (2) a large-format digital camera, (3) a relative position Global Positioning System (GPS) to measure aircraft position, and (4) an Inertial Measurement Unit (IMU) to measure aircraft attitude. The DATIS? can measure up to 220,000 elevation samples per mil. The system continually collects data on the aircraft's position and measures the time for each laser pulse transmission to return from the ground, giving each sample a GPS reference. The system can operate at night, in overcast sky, and during high-wind conditions and can measure terrain below vegetation cover, unlike standard aerial photography used for traditional surveying and mapping. Surveyed ground-control panels are no longer necessary with this new technology, and only one ground GPS base station located within 60 mi from the aircraft position is required. A computer elevation-point data file is created with the x, y, z coordinates of each laser elevation sample. With this file, CAD engineering programs can create topographic maps that rival products using conventional aerial mapping techniques. Volumetric measurements of stockpiles and pits are also available due to the high density of points collected from an area. This new technology radically changes the turnaround time for map users, giving a product in the format used by today's cartographers. The time line from flight to maps is measured in days instead of weeks.

Jan 1, 1999

By R. C. Timberlake

In the past three years there has been a great amount of attention given to phosphates world wide, and in particular to the Florida Phosphate Industry. I would like to relate some of the most recent history of the industry and give you a personal outlook for the future. Phosphate rock has been produced in Florida since its discovery on the Peace River in the 1880's. Through 1976, approximately 720 million ST of rock had been mined from Florida reserves, and it is my opinion that there are at least 1.2 billion tons remaining which are consolidated, accessible and can reasonably be expected to be permitted for mining. Over half the 1.2 billion tons will be deeper, more scattered, leaner and will produce lower grade rock than the Bone Valley of Central Florida has tradition-ally produced. In 1973, '74, '75 and '76 the Florida Phosphate Industry produced 32.6, 34.0, 38.2 and (38.0) (P) million ST of phosphate rock respectively. This rock was produced by ten mining companies, Agrico, Borden, Brewster Phosphates, Gardinier, Grace, IMC, Mobil, Occidental, Swift, and USS Agri-Chem; mines are located -17 in Polk County, one in Hillsborough County and two in Hamilton County, Florida. Phosphate rock is used by local companies in Florida primarily to produce phosphoric acid from which DAP and TSP is manufactured. Florida acid producers use about 15 million STPY in acid plants in Florida, and another 7.5 million STPY is consumed by acid producers in plants on and near the Mississippi River. Somewhat

Jan 1, 1977

By J. H. Dietz

The electric assist option for diesel-electric trucks can improve truck productivity while maintaining the inherent flexibility of a truck and shovel operation. In addition, the resulting cost reductions offer a rapid investment payback for many mine situations. A review of the present technology and performance experiences verify the projected benefits in productivity and operating cost. New technologies can further improve the productivity/cost scenario.

Jan 1, 1984

By L. G. Austin

A simple finite difference algorithm has been used to compute a simulation model for unsteady-state ball milling. The model considers the mill to act as if it were three fully-mixed reactors in series (one-large/two- small), it incorporates the-Rogers-Austin mass transfer law relating mill hold-up to flow rate through the mill, and it allows for the reduction in breakage rates caused by over-filling of the mill at high flow rates. The computation is rapid and requires only small storage space. Examples are given of use of the model.

Jan 1, 1984

By Y. J. Wang

The Hardy Cross iterative method is the most popular technique for solving a ventilation network problem with natural air splitting. This method tradition-ally solves each mesh equation by an approximation during each iteration. It is thus interesting from both theoretical and computational viewpoints to be able to solve for an exact solution to the mesh equation. Presented in this paper is an algorithm for computing the exact solution to the mesh equation with a variable fan pressure. The algorithm uses signum functions for air quantities to generate an alternative mesh equation in the form of a quadratic equation, which has two solutions defined by the well-known quadratic formula. The condition that the derivatives of the alternative and the original equations must be the same provides a basis for the correct choice between the two solutions.

Jan 1, 1997

By P. R. Taylor

This investigation (Bowles, 1990) involves consideration of technology utilized by three separate fields of metallurgy and materials science: 1) The recovery of metals employing the use of solvent extraction, 2) The fabrication of materials using powder metallurgy, and 3) The use of composite materials in fabrication of engineering materials. The research considers each of the processes in order to realize the benefits of each. In light of the fact that materials have an intended use -it does seem plausible to simplify the process required between "mother earth" and final use. For instance, a primary copper producer that already employs a solvent extraction and electrowinning process could produce value added products directly. Part of the existing extractant flow could be diverted into a pressurized hydrogen stripping process in order to produce specialty composite powders. Innumerable methods have been employed for the recovery of metals; solvent extraction, the one considered in this study, was used due to the possibility of it providing a pure powdered metal. The use of solvent extraction in the recovery of metals has gained wide acceptance and its use proves beneficial in many applications (Ritchey and Ashbrook, 1984). Pressure hydrogen stripping of solvent extractants may provide the benefit of flowsheet simplification compared to conventional solvent extraction followed by electrowinning. It may also provide the benefit of direct production of high purity metal powder (Demopoulos and Distin, 1985).

Jan 1, 1992

By T. W. Meikle

Three nutrient amendments and a biological seed inoculant were evaluated for use in establishing vegetative cover on waste rock substrates. Randomized blocks were placed on three substrates. Treatments included two types of organic fertilizer, mineral fertilizer, Azospirillum bacterial inoculant, plus controls. The seed mix consisted of native grass species adapted to low nutrient conditions. Canopy cover has been monitored for three growing seasons. Results indicate: 1) two of three substrates support plant growth following amendment with organic fertilizers; 2) organic fertilizers increase cover substantially over mineral fertilizer; and 3) Azospirillum had no effect on canopy cover.

Jan 1, 1999

By Roberto Pimentel de Souza

CURD started producing pellets in 1969, with one two-million ton straight grate plant. In the beginning of April '73, the second unit came on stream with an additional capacity of 3 million TPY of pellets. In January '77, the third unit started, bringing the annual capacity to 8 million TPY. For the present year 3 more units, 3 million each, are expected to begin production. CVRD's experience is given about the use of different binders and additives. Over the years several kinds of pellets have been produced to satisfy the market requirements. General quality information is given regarding each.

Jan 1, 1978

By D. N. Madge

A description will be given of an approach to plant process automation based on the strategy of first developing an information system followed by later development of process models. The advantages of this approach over the unit process control will be outlined. Some insight will be given into the risks associated with this method. These risks can be shown to be primarily economic.' Some reference will be made to two Cominco installations in the interests of illustrating the generality of the information systems approach.

Jan 1, 1972

By George M. Meisel

This paper is devoted to a discussion of the factors governing design of concentrators for large grinding circuits. Emphasis is placed on the manner in which use of ever larger grinding mills has affected the size of grinding bays, service cranes, gear reducers and electric motors, and the selection of ancillary equipment for cushioning of the starting load of large mills. Information is presented on the effect of using large grinding mills on the capital and operating costs of concentrators, e. g. : (Fig. 1) ? Benefits in lower cost of mills, drives and materials handling equipment, plant space, power, grinding media, operating labor and maintenance, and in ease of instrumentation and automation. ? Penalties in distribution of materials from the grinding mills to multiple lines of equipment which have not been developed to commensurately large sizes, and higher cost of ancillary equipment.

Jan 1, 1968

By M. M. Foss

Geophysical methods are gaining acceptance in the evaluation of coal mine ground control condition. The use of in-seam seismic investigations has contributed significantly to the body of information concerning ground control feature identification and analysis. Seismic methods have been used successfully in locating voids, faults, fracture zones, roof and floor rock interfaces, and more recently in characterizing in-seam stress distribution. Seismic tomography is an effective tool in data interpretation for several of these applications, but as is the case with other engineering application of geophysical techniques, there are limits as to how much substantive information can be interpreted from a given data set. This paper discusses some of the applications of in-seam seismic geophysical tomography, and the limits to which the transformation from raw data to information should be taken.

Jan 1, 1995

By Drummond Earley III

The U.S. Bureau of Mines is currently conducting laboratory experiments to study the reactions occurring during in situ leaching of oxide copper ores hosted by biotite-poor granite and biotite-rich granite porphyry. Detailed pre-leach and post-leach petrographic examinations of the rock samples are combined with the leach solution chemistry resulting from core leaching experiments to enable an evaluation of the various reactions which are responsible for the observed fluid chemistry. The information resulting from these laboratory studies is being utilized to support the design of the Bureau's ongoing field research project at the Santa Cruz deposit near Casa Grande, AZ. Atacamite and chrysocolla are the primary copper minerals present in this deposit, and both are readily soluble in the dilute 5% sulfuric acid solutions used in these experiments. In addition to the dissolution of copper minerals, biotite dissolution also occurs during the experiments, contributing K, Mg, Fe, and Al to the leach solution. The biotite dissolution appears to be non-stoichiometric, as it is progressively altered to vermiculite and finally, amorphous silica. While K, Mg, and Fe concentrations in solution steadily increase with time, Al quickly reaches a maximum, and then remains relatively constant for the remainder of the experiment. This suggests that Al saturation is achieved, and this Is supported by the presence of precipitated Al sulfate and aluminosillcate clay mineralization in the post-leach rock samples.

Jan 1, 1990

By Allen D. Graham

The coal industry in South Africa is briefly outlined. Test- work carried out on bulk samples of coal in the laboratory and used in the design of the Van Dyks Drift washery are described. Factors affecting the selection of equipment and the designed capacity of the plant are discussed. A description of the crushing plant, washery and load out section is given together with performance data obtained in the final acceptance tests. New features incorporated in the Van Dyks Drift plant and in more recent plants of the Group are outlined.

Jan 1, 1982

By B. F. Westfall

Throughout the 1960's and 1970's world trade grew rapidly, reaching a peak of USS1.8 trillion in 1980. Since then the world recession of the early 1980's shrunk trade to about US$1.6 trillion. The reduced cash flow to developing economies made it difficult to service their huge international debts, Nowadays lenders are reluctant to grant Third World countries additional credit. The shortage of export financing, plus trade barriers set up by developed countries, is further inhibiting international trade. Therefore, countries are turning to new and creative alternatives to financing imports of consumer as well as of investment goods. Non-cash transactions, including different forms of countertrade, are rapidly growing alternatives to traditional trade financing patterns. In 1983 about 30% of international trade, or close to US$600 bill ion, were presumably done by non-cash transactions, up from barely 2% in 1976. By year 2000, half the world trade is likely to be conducted on basis of barter. As of mid-1984 some 88 nations used countertrade regularly and Governments of at least 15 Latin American countries had arranged or mandated commercial countertrade.

Jan 1, 1986