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By M. A. Marticorena, R. Stratton-Crawley, C. I. Basilio

Diethylenetriamine (DETA) is a selective depressant for nickeliferous pyrrhotite during pentlandite flotation. Laboratory flotation tests conducted on ore and process samples showed that pyrrhotite rejection is greatly improved by small additions of DETA; however, the effectiveness of this depressant is most noticeable when the mineral sample is oxidized. LIMS and XPS analyses conducted on flotation products and pyrrhotite specimens showed that the difficulty in pyrrhotite rejection arises from inadvertent activation of the mineral by heavy metal ions, such as Ni2+, cu2+ and Ag+, that are present in the process water. In the presence of DETA, however, the mineral is deactivated under oxidizing conditions. The deactivation mechanism may involve oxidation of the activation products, which are likely in the form of heavy metal sulfides, followed by solubilization by DETA. FTIR spectra of pyrrhotite electrodes contacted with DETA showed no trace of the reagent on the surface, substantiating the view that its role is one of complexing agent that enhances the dissolution of activation products under oxidizing conditions. FTIR spectra of pyrrhotite contacted with amyl xanthate solutions showed that both dixanthogen and iron xanthate are formed on the surface, the latter becoming more predominant at higher potentials. In the presence of DETA, however, only a small amount of xanthate is adsorbed on the mineral at potentials (Eh) approximately 200 mV higher than the case without DETA.

Jan 1, 1995

By E. H. Cho, Q. Luo

Pittsburgh No. 8 coal, cleaned by conventional froth flotation, was oxidized in a 2-L Parr stirred bench-top autoclave. Autoclave tests were carried out for up to 5 hrs under the following conditions: 150 to 225ºC, 60 to 500 psi 02 and 15 to 60 g of coal per 600 mL of distilled water. The oxidation of coal was evaluated by measuring the total acidic group formed on the surface of the coal and by measuring the adsorption (under standard conditions) of calcium ion from a solution. The degree of oxidation of the coal increased continuously, without much leveling off, with increasing oxygen pressure. With increasing temperature, the oxidation of the coal increased sharply between 150 to 175ºC and then leveled off above 175 °C. The adsorption of calcium was >3% on coal oxidized under the most favorable conditions. The adsorption of calcium on coal increased sharply with increasing equilibrium pH. The loss in Btu was found to be sensitive to oxidation temperature. This study concluded that the optimum oxidation of coal is achieved over 3 hrs at high oxygen pressures (e.g., 500 psi) at ~170ºC. This study also concluded that, when measured in terms of calcium adsorption, Btu loss and reaction time, the oxidation achieved in an autoclave is far superior to that achieved in a fluidized bed.

Jan 1, 1996

By James S. Goff, Stephen J. Navin, Wesley W. Moulton

The White River Shale Oil Corporation (WRSOC) is developing a prototype oil shale facility on Federal Lease Tracts Ua and Ub located in northeastern Utah. This paper covers the successful driving of 1,525 m (5,000 ft) of dogleg downgrade decline with a 70-ton Paurat Roadheader mining machine and a conveyor muck-handling system. Ground support is with rock bolt and shotcrete; welded wire mesh is optional. The Upper Decline of 3.89 m by 8.69 m (12.75 ft by 28.5 ft) was mined through the Uinta Formation sandstones and shales in 210 days. The sandstones have a compressive strength in the 48 MPa (7,000 psi) range with a few bands of shale up to 137.8 MPa (20,000 psi). Green River Formation dolomitic marlstone with some sandstone lenses was mined in the Lower Decline 3.89 m by 5.64 m (12.75 ft by 18.5 ft) in 175 days. The Green River marlstones are tough massive formations ranging up to 206.8 MPa (30,000 psi). Roadheaders for use on steep slopes must be modified to accommodate the particular problems associated with mining downdip. The paper concentrates on the application of Roadheaders to steep slopes and the problems of mining tough materials such as marlstone. The paper also shows the advantage of using the method of excavation on long drives.

Jan 1, 1985

By S. A. K. Forson, Newton A. Amegbey

In order to investigate production decline in Tarkwa Goldfields Ltd., located in a tropical rain forest, amongst other areas, a health survey was conducted with the aim to see 1. The health status of the workers. 2. Which parameters carry the most information about the health situation and which of them can be applied easily during screening programmes. 3. What steps could be taken to improve the situation. In all 249 workers were investigated. A non-invasive method involving taking of body weight and arterial blood pressure was used. All subjects were required to answer a questionaire. Emphasis was placed on the history of malaria and diarrhoea within the last six months. Both management and workers co-operated fully. Another set of 110 workers from a neighbouring tyre factory were also investigated for control. Among the underground workers, the percentage body weight loss during a shift increased with decreasing body weight. Dehydration levels could be as much as 4 to 5% of body weight. This could be attributed to the fact that workers took insufficient or no water during the shift. The health status of the mine workers was generally poor and in our opinion malnutrition combined with malaria severely threatens the health and well-being of the workers. Hypertension is also a problem. An improvement in production is intimately linked with the well-being of the workers.

Jan 1, 1989

By Nick Barton, Harald Hansteen

The deformations resulting from excavation of very large openings are compared using two-dimensional F.E. continuum analyses and discontinuous physical models (20,000 discrete blocks). Both the joint orientations and the model horizontal stress levels were varied. Some models were dynamically loaded to simulate earthquakes (0.2-0.7 g). Model deformations were recorded using photogrammetry. The changes in deformation when increasing the simulated spans from 20 m to 50 m were of particular interest. High horizontal stress caused surface heave when joint orientations were favourable for arch stability. Joint orientations also determined whether the pillars between parallel openings were in a state of compression or tension. INTRODUCTION The engineering performance of large rock caverns has traditionally been learned from mining and hydro power projects, where the depth below surface is often many times greater than the span of the openings. Deformations measured in the walls and roofs of hydro power caverns generally range from about 5-50 mm, though there is a documented case where a wall moved in 126 mm (1), and another where the arch moved down 147 mm (2). The chief objectives of the present studies of large near-surface openings were threefold: (i) to provide deformation data to compare with monitored data from planned engineering projects involving large span near-surface excavations, e.g. underground sports complexes, civil defense shelters, nuclear power stations,

Jan 1, 1979

By T. Yalcin

It is well recognized that machine type and machine characteristics play vital roles in the successful application of froth flotation in mineral processing. Since the early 1900s, a multitude of machine designs have been and are still being introduced in an attempt to improve flotation efficiency. Machines based on mechanical agitation have been the most dominant in industrial practice. However, in recent years there has been a growing interest in pneumatic flotation units because of their claimed simplicity, low cost, high throughput and good metallurgical performance. This work was carried out to assess the effectiveness of pneumatic flotation on a magnetite ore. The method was applied using a prototype pneumatic flotation device that utilized a suitable nozzle for bubble generation. Important variables of the process were examined and optimized, including the nozzle size, air flow rate and froth thickness. Further tests were conducted to determine the influence of frother dosage and to explore the improvements that could be made on concentrate grade and recovery by cleaning and scavenging. Under the best test conditions, an iron concentrate was obtained with a grade of 66.4% Fe and a recovery of 97.7%. Particularly, the recovery was superior in comparison to that of mechanical flotation. This was attributed to the ability of pneumatic flotation to create and maintain a relatively thick froth layer.

Jan 1, 2002

By A. M. Elmherig, M. R. Sunu, R. N. Singh

The presence and orientations of fractures and discontinuities in rock masses exposed in a surface mining excavation are likely to have a great influence on both slope stability and blasting efficiencies. The classification of rock materials requires detailed investigations which are of interest to the design engineer. In designing a safe mining excavation, an engineer must take a number of decisions regarding face support and orientation based on the evalu¬ation of local strength and structural conditions encountered. The description of rock masses requires information additional to the properties of the rock material, discontinuities and other characteristics of engineering importance. Such information involves the acquisition of the following data: The description of the rock mass with reference to major geological structures. The orientation, nature, spacing and persistence of discontinuities. Degree of weathering. A critical review of rock mass classification systems and their application to surface mine excavation design and stability analysis is presented. The field investigation techniques for collecting rock mass data are described together with the techniques of analysis and presentation of data. Laboratory tests are carried out to determine intact rock strengths and deformation parameters of rock. The paper presents two case studies from the British hard rock surface mining industry to illustrate the application of the rock mass classification systems to stability analysis and excavation design.

Jan 1, 1986

By Shallesh K. Patel, Richard M. Powers, Patrick Zhang

Perceived environmental impacts from flotation reagents used in the phosphate industry have been of concern for nearly a decade. A research program was initiated to determine the distribution, fate, and consequences of flotation reagents (fatty acids, fuel oils, and amines) within the environment. Therefore, laboratory investigations of biodegradation and soil attenuation of the reagents were conducted along with field flotation mass balances and groundwater investigations in clay settling, sand tailings, and undisturbed areas. Sample analysis and a reagent mass-balance model indicated that most reagents are distributed in clay settling and sand tailings areas. Groundwater analyses showed no fatty acids or amines in any of 19 surficial or intermediate aquifer water samples. In contrast, fuel oils were detected in the surficial aquifer at all sand tailings areas in concentrations ranging between 8.5 and 0.5 mg/L. Fuel oil was also detected in trace amounts (0.6 mg/L) in one intermediate aquifer well located in an active sand tailings area. All fuel oil concentrations detected were very low and, coupled with a biodegradation rate of approximately 10% per month, all concentrations should be within reference levels in six months. Based upon the results of this study, use of flotation reagents in the beneficiation process of the Florida phosphate industry present no long-term threat to the environment.

Jan 1, 1999

By J. R. B. Lima

The present work emphasizes the selection in the separation of the apatite/calcite by the direct anionic flotation versus the double flotation, with a reverse second stage of the Jacupiranga phosphate ore. The double flotation would allow the obtaining of two concentrated solutions: one of them mainly constituted by a calcium carbonate material (CaCO3) and the other one, phosphatic (apatite). The calcium carbonate concentrated solution is used for the production of cement. The presence of phosphatic material in the calcium solution is not desirable, phosphor being a harmful element to cement. On the other hand, smaller quantities of calcite in the phosphate concentrate would represent a substantial economy in the processes of production of phosphated fertilizers. These processes make use of sulfuric acid to the solubilization of the apatite and the presence of calcium material consumes acid. Also that, when carbonates are solubilized, unwanted products are formed resulting in losses in the process and diminishing the quality of the fertilizer produced. These characteristics are discussed in the paper and are compared to another Brazilian phosphate ore, the reverse route of which can be considered more adequate. The results are discussed according to recent discoveries, and special emphasis is given to the use of corn starch and its crucial role in promoting the selection in the direct flotation process.

Jan 1, 1993

By Robert H. Marshall

The application of simulation to production planning at a large, complex open-pit mining operation proved to be challenging and enlightening. The mine is divided into two separate pits and several dump areas which are served by the same truck fleet. The operating system consisted of shovels of two different sizes, wheel loaders, and a fleet of three different truck types moving material from seven source locations to ten dumping sites. The interconnecting haulroad network included many common segments. There were operating constraints unique to the system, such as: traffic rules; manpower limitations; shovel, material-type, and destination priorities and production limitations; and a unique, non-centralized dispatching method for truck distribution. The truck distribution was further constrained by the matching of trucks to shovels, loaders, and destinations by truck type. The gathering and transformation of input data as well as the evaluation of results and validation of the model were also challenging. Despite a high level of sophistication in production reporting, some input data were neither readily available nor backed by field observation. As a result, many innovative techniques had to be used to develop realistic input data and to validate the simulation results. Nevertheless, this case study definitely proved the feasibility of applying computer simulation techniques to short and long range mine planning and budgeting at a large, complex mining operation.

Jan 1, 1982

By D. W. Fohlen, B. A. Filas

The International Finance Corporation (IFC), the private investment arm of the World Bank Group (WBG), requires all IFC-financed projects to comply with its environmental and social policies and guidelines. IFC's review process involves an environmental and social assessment and the implementation of an Environmental Action Plan (EAP) that will set forth the necessary actions to bring the operation into compliance. This paper provides an overview of the environmental and social policies and guidelines that apply to mining projects and examines how WBG/IFC policies and guidelines are applied to mining projects in developing countries. In addition, it includes a review of the increased emphasis IFC is giving to social issues over the past several years based on the existing WBG policies. IFC’s process for the environmental and social review of proposed investments is briefly discussed. The paper focuses on how IFC emphasis has shifted from the traditional environmental and impact mitigation analyses of a few years ago to the integrated social and environmental awareness, action (EAP), and implementation programs (social plans) required today. Today, IFC's focus is to promote sustainable development by investing in projects that directly benefit local communities and the environment. Examples of these changes will be highlighted by a review of recent investments located in West Africa. The goalposts have not moved, but the rules of the game have become tougher.

Jan 1, 2001

By Michael DiMatteo, Michael D. Gardner, Eric F. Perry, John K. Felbinger, Robert S. Evans

A hydrologically isolated surface coal mine was reclaimed using acid material handling, alkaline addition and ground-water management techniques. Eight pit floor drains were installed during reclamation to intercept ground-water flow in the mine backfill and minimize water table buildup. All drains began flowing within six months of installation. Water quality and ground-water discharge have been monitored for four years after mine closure. A thin water table aquifer about five to seven feet thick has developed in minespoil about 20 to 40 feet thick. Ground-water flow direction is largely controlled by geologic structure and the drains. Median ground- water discharge is about 0.43 gallons per acre per minute, and varies an order of magnitude between wet and dry seasons. About 19 % of precipitation enters the aquifer as recharge. Seven of the eight drains typically discharge net alkaline water. Alkalinity is produced continuously and concentrations are highest during dry periods. Conversely, sulfate and acidity concentrations increase during wet periods as slugs of accumulated acid products are leached. Overall water quality is controlled principally by minespoil geochemistry and added alkaline material. The drains have successfully directed ground-water to a planned discharge area. Without the drains, a ground-water mound was expected to form against a buried highwall and discharge over a large area.

Jan 1, 2000

By G. Lodewijks

Today most belt conveyors used for the transportation of bulk solid materials are driven in a centralized way with all drives in one location. The dynamics of these systems has been studied since the early seventies of the previous century and are well understood. Compared to the more conventional belt conveyor system with a centralized drive station positioned at the head and/or tail of the system, a decentralized driven layout with drive stations distributed along the whole length of the belt offers a number of advantages. However, to make a decentralized driven configuration a good alternative to a centralized driven, the system designer will have to balance these benefits with the increased complexity. The full potential of a decentralized driven system can only be realized if the right balance is found between the locally applied drive force and the motion resistances occurring along the system. From previous research it was found that in a multiple driven belt conveyor system the most dominant belt behavior occurs in the belt section between the tensioning device and the first drive station. In this paper different possibilities are analyzed to improve this dominant belt response and optimize the starting behavior. This can be accomplished by changing the predescribed start up profile, starting the drive stations in sequence rather then all at the same time and altering the locations of the drive stations.

Jan 1, 2008

By Ronny J. Sadri

Under contract to the Department of Energy, Fluor Mining & Metals, Inc. and Bonner & Moore Associates developed a group of computer models that can be used to simulate single seam dragline operations. These models have been subsequently modified by Fluor for use in multi-seam dragline mining situations. The single seam model analyzes the digging, spoiling, and walking patterns of draglines to identify possible parameter changes to increase productivity. Parameters such as key-cutting, panel width, digout length, and bench height, etc., are analyzed in this process. The models were tested using data from four operating mines. Field demonstrations were performed to correlate computer optimization results with field data. Productivity was greatly enhanced at one mine site by a change in some of the operating parameters. The multi-seam study has as its objective the development of a broad- based mine planning tool which would be used to identify and quantify the different procedures employed in multi-seam dragline mines to increase their productivity. The major problem identified in multi-seam mining is the sequencing of the different stripping and mining operations. The multi-seam model has the same capabilities as the single seam model. In addition, it models up to four seams with three partings per seam. It allows the operation of several draglines at different levels, and analyzes the effect of ramps, rehandling, and ancillary mining equipment.

Jan 1, 1982

By G. M. Wilemon, B. J. Scheiner

The Bureau of Mines conducted investigations on extracting phosphate values from fine-particle wastes generated during the mining and beneficiation of phosphate ore by leaching dried wastes using a H2SO4-methanol mixture. Although phosphatic clay waste contains up to a third of the phosphate originally present in the ore, recovery of these values represents a significant challenge due to the fine grain size of the material, the particles averaging less than one micrometer in diameter. Waste samples obtained from two Florida producers yielded phosphate extractions of 71 and 84 pct, respectively, when leached under ambient conditions and at a stoichiometric acid ratio of 1.4:l. Elevated temperatures did not improve the amount of phosphate extracted. Undesirable A12O3, Fe2O3, and PlgO impurities were largely rejected; higher grade wastes gave acids that meet established industry impurity standards and lower grade samples yielded acids that marginally fell short of the standard. Separation of the crude acids from the insoluble residues was accomplished via vacuum filtration through either filter paper or commercial filter cloths. Both filtration rates and solids retention were improved by the addition of 0.5 lb/ton of poly(viny1 acetate) (PVAc) or poly(ethy1ene oxide) (PEO) to the methanol-acid slurries. These results show potential for substantially increasing the reserves of an important domestic resource.

Jan 1, 1989

By Judith A. Marks, Deane K. Smith, Jan M. Mutmansky, Maria Klimkiewicz

The mechanical mining of coal seams where roof, partings, and floor rock are extracted along with the coal often introduces large numbers of quartz particles into the mine atmosphere. This study concentrates on the quartz properties in situ and in the airborne dust to determine how they are released from the source rock and whether they are fractured by the mining machinery. Three mines using drum-type continuous miners from different geographic areas were sampled to provide a data base. The roof and floor rocks were primarily siltstones containing 5% to 25% quartz measured by the X-ray powder diffraction (XRPD) method. Much of the work presented here is based on the morphologies of the mineral grains determined by the scanning electron microscope (SEM). The study concentrated on particles of 0.2 to 10.0 µm and on particles containing > 75% Si. Mechanically-crushed quartz particles were also examined for comparison purposes. Particle shapes from the airborne samples suggested that fractured quartz particles were rare. Particle statistics also show that the average size of quartz particles in the airborne samples were similar to the average size of all particles. The conclusion is that very few quartz particles from the source rocks are fractured during mining due to their small initial size and the protection of the associated clays.

Jan 1, 1991

By J. Herbst, A. J. Lynch, E. V. Manlapig, G. C. Throne, J. S. Hall, G. Poling

Modelling of industrial sulphide flotation based on data collected in several flotation plants is discussed. A mechanistic approach is used in which it is recognised that flotation is a two stage process with concentration occurring both in the pulp and in the froth. The important features of the model, which is a kinetic model, are – 1. for each particle species there is a range of flotation rates which corresponds to the range of particle sizes, 2. the flotation rates of the liberated gangue particles which have no hydrophobic properties are dependent on the flotation rate of water and are controlled by variables such as the air and frother addition rates, and the pulp level, 3. as an approximation the valuable sulphide particles may be regarded as being present in two groups with high and low flotation rate constants, 4. increase in the addition rate of collector tends to increase the proportion of sulphide particles which are in the high flotation rate constant group. The actual flotation rate of each group of particles is a combination of an "inherent" flotation rate and a flotation rate which is dependent on the flotation rate of water, at particular air and frother addition rates and pulp levels there is a physical limit to the rate at which particles can be transported into the concentrate and this is recognised in the

Jan 1, 1976

By A. E. Halim, J. F. Brune

The 2006 Sago, Darby, and Aracoma mine disasters in the United States (US) forced the US government to implement the 2006 MINER Act and additional regulations that require all US underground coal mines to install and maintain refuge chambers to manage entrapment emergencies, in particular, fires and explosions. However, there is a debate on whether barricading in refuge chambers is a good strategy to survive such emergencies. Australian coal mines are not required to use refuge chambers and, instead, have adopted a strategy that focuses on instructing and training miners to self-escape to the surface. This paper analyzes merits and problems of using refuge chambers and self-escape to the surface to manage emergencies in fires or explosions in an underground coal mine. The authors found that the use of refuge chambers may not be the best strategy during extensive fires or when multiple explosions happen. In these situations, mine rescuers are unlikely able to extract miners who are sheltered in chambers and conversely, self-escape may save more lives than sheltering. Chances for successful self-escape are further improved by regular, externally assessed training such as Level 1 Emergency Exercises required in the Australian State of Queensland. These exercises put pressure on mine operators to ensure and maintain the effectiveness of their emergency management system.

By Gian-P. Lozej, Ross Y. Black, Sami S. Maddah

The Zabirah bauxite is a Cretaceous paleolaterite exposed by postTertiary uplift and erosion of the Phanerozoic sequence. The laterite profile, which is preserved in situ, occupies a prominent angular unconformity over a sequence of sandstones, siltstones and mudstones ranging from Late Triassic to Early Cretaceous in age, and is overlain by a Late Cretaceous terrigenous and carbonate package. The profile is known to be preserved over an area of 250 sq km and at depths below the present surface of up to 80 m. The bauxite layer is hard, compact and predominantly pisolitic, with a variety of subordinate, superimposed textures resulting from post-formation alteration. The bauxite minerals are boehmite and gibbsite. Boehmite generally predominates, and the boehmite:gibbsite ratio averages 2:1, with a marked tendency for the proportion of boehmite to increase down the profile. Kaolinite, a major constituent of the profile, is concentrated in two zones, one above and one below the pisolitic bauxite layer. Iron content is variable and bears a direct relationship to parent-rock lithology. Genesis and preservation of the bauxite are due to the favourable coincidence of a number of geological controls of which the most significant are the local structural and sedimentary regimes, the lithology and chemistry of the parent rocks, and the Cretaceous paleogeography of the region.

Jan 1, 1984

The response of 174 domestic water supplies to longwall mining of the Pittsburgh coal seam was compared to various physical parameters. Sixty-four percent of domestic water supplies returned to service without the need for intervention, while thirty six percent required intervention to reestablish a suitable water supply. Domestic well response is strongly correlated with the topographic setting. Valley wells showed the least effect while hilltop wells showed the greatest effect. Well response was also found to be correlated to the location of the well above the mining with greater effects observed in zones of surface tension and compression, and fewer effects in zones which are stress neutral. Ground water supplies remained unaffected or were re¬established at 149 of 150 sites, indicating that ground water resources remain available to domestic wells after mining. Results of this study support the stress-relief model of ground water flow in the Northern Appalachian Basin. Longwall mining's effect on this system is to locally increase fracture connectivity in the near surface zone. This may shift the zones of saturated fractures to greater depths beneath hilltops and hillsides, and increase recharge and storage in valleys. General trends in well response are predict¬able utilizing the stress relief conceptual model, the topographic setting of the water sources, and their location over the mine.

Jan 1, 1986