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Several industrial-scale HydroFloat separators have recently been installed at Mosaic?s South Fort Meade beneficiation plant for the purpose of improving phosphate recovery and throughput capacity. This technology was implemented after numerous laboratory, bench-scale and on-site, pilot-scale test campaigns. The results from this detailed test work provided sufficient justification for the complete retrofit of the existing coarse and ultra-coarse flotation cells. Data indicate that the metallurgical results obtained with the full-scale separators are consistent with that obtained during both the bench- and pilot-scale evaluations. The benefits, theory of operation and commissioning of the equipment are also discussed.

Jan 1, 2007

The ability to optimise a concentrator from mill feed to final products requires a simulator which integrates comminution, classification and separation modelling. In order to model this range of processes, such a simulator must handle a variety of information about the ore. The AMIRA P9 project has developed a whole-of-concentrator simulation capability which brings together a texture-based model of mineral liberation, quantitative X-ray micro-tomography analysis to measure the inputs required by this model, and a multi-component simulator software framework. In the context of this approach, the term ?multi-component? implies the ability of the simulation to handle many particle properties simultaneously; for example size, composition, density, floatability etc. The simulation software framework provides the means to manage the flow of data around a circuit flowsheet, allowing each process model to access the information relevant to that particular model. A case study based on plant data from a gold-bearing pyrite concentrator is used to demonstrate the capabilities of the multi-component approach in simulating circuits which contain comminution and separation processes.

Feb 27, 2013

By M. K. Mohanty

One of the main objectives of this study was to evaluate a fine-coal cleaning circuit using an enhanced gravity separator specifically for a high sulfur coal application. The evaluation not only included testing of individual unit operations used for fine-coal classification, cleaning and dewatering, but also included testing of the complete circuit simultaneously. At a scale of nearly 2 t/h, two alternative circuits were evaluated to clean a minus 0.6-mm coal stream utilizing a 150-mm-diameter classifying cyclone, a linear screen having a projected surface area of 0.5 m2, an enhanced gravity separator having a bowl diameter of 250 mm and a screen-bowl centrifuge having a bowl diameter of 500 mm. The cleaning and dewatering components of both circuits were the same; however, one circuit used a classifying cyclone whereas the other used a linear screen as the classification device. An industrial size coal spiral was used to clean the 2- x 0.6-mm coal size fraction for each circuit to estimate the performance of a complete fine-coal circuit cleaning a minus 2-mm particle size coal stream. The ?linear screen + enhanced gravity separator + screen-bowl circuit? provided superior sulfur and ash-cleaning performance to the alternative circuit that used a classifying cyclone in place of the linear screen. Based on these test data, it was estimated that the use of the recommended circuit to treat 50 t/h of minus 2-mm size coal having feed ash and sulfur contents of 33.9% and 3.28%, respectively, may produce nearly 28.3 t/h of clean coal with product ash and sulfur contents of 9.15% and 1.61%, respectively.

Jan 1, 2008

By K. E. Wood, K. J. DiRocco, L. A. Becker

The Russia Wharf segment of the Silver Line Phase II Project for the MBTA incorporated ground freezing and underpinning during New Austrian Tunneling Method(NATM) tunneling through timber pile foundations, urban fill, and abandoned wharf structures beneath two historic 7-story buildings with steel frames and masonry facades. During construction, the project team implemented an extensive program to monitor, evaluate, and mitigate the ground and building movements caused by the various construction activities. Mitigation included freeze cycling and building raising/lowering to compensate for ground movements and safely maintain the serviceability and occupancy of the buildings. In this paper, we present the history of the freeze, tunnel construction, and thaw-related movements that occurred and the building response that we observed.

Jan 1, 2005

By Magno Rodrigues Ribeiro, Alexandre Cabral Stelzer, Cacio José da Silva, Leonardo Nogueira Ferri, Marcelo Ciminelli Mendes, Christophe Bouché, Marco Aurélio Soares Martins, Evenilson Soprani Lopes, José Xavier da Silva Filho, Sérgio Luiz Dalvi

Since 2001, CVRD is carrying out a modernization project in it’s pelletizing plant’s automation systems, that comprehends instrumentation, control and information systems. In addition, the project includes implementation of advanced control systems, using artificial intelligence techniques, including fuzzy logic, expert systems and dynamic physical models, to increase production, reduce fuel and energy consumption and improve quality. This paper reports CVRD’s experiences in carrying out an optimization project.

Jan 1, 2005

By M. Santillan

Minerales Monclova S.A. de C.V. (MIMOSA) has applied different methane gas drainage technologies, according to the top industry requirements in order to keep the methane gas at the lowest possible concentration in our operations, both in the development sections and longwall sections. Our staff has used the horizontal rotary technique. In 2004 MIMOSA bought a re-built drill machine and signed a contract with Resource Enterprises Inc. (REI), which included a training program in Horizontal Directional Drilling using the reflex system. The training system was developed for a period of three months in Mine VII, with very good performance by the MIMOSA staff. After the training the equipment was moved to Esmeralda Mine, where we had already drilled holes at the development section, 2,500 ft. It was the longest distance that could be reached with our original equipment, obviously; the directional drilling program is another challenge for us and our staff, but we are very confident that our result will be better every time. We will be evaluating each borehole and expect to improve our results in each progressive borehole, until we can drill up to the capacity of the equipment. We are in the process of buying another drill with an electronic monitoring device (DD DMecca) in the following months.

Jan 1, 2009

By Henning E. Soderberg, Robert Brien, O&apos

Coal may be the answer to US energy problems, but it also has its drawbacks. If it is crushed, screened, dumped, or moved, the environmental engineer is faced with a dust problem. To control coal dust, at both minimum initial cost and reasonable operating cost, demands a working knowledge of dust control equipment design, as well as the coal handling operation. Here are some guidelines to reduce air volume requirements and cut overall system costs.

Jan 10, 1981

By E. M. Spokes

Starting in 1980, a committee of the National Research Council studied the question of why some underground coal mines are safer than others and what could be done to improve the ones with poorer performance. The results indicated that safety is improved by management commitment to safety, by cooperation between labor and management on safety matters, and by quality training of employees and managers. Younger miners have higher accident frequencies, but are less likely to be killed or permanently disabled by a lost-time accident. Methods for improving safety performance are proposed.

Jan 1, 1987

By B. Samoski

In late 1994, EPA and OSM acknowledged that efforts by any one agency or by the many different agencies to remedy the water quality impacts of decades of contamination from abandoned coal mine lands in Appalachia would not be successful if their disjointed efforts were not unified and if the local watershed organizations were not included. The result of the collaboration between EPA and OSM was the creation of a statement of mutual intent which was a pledge by government agencies, watershed organizations, and the industry to restore watersheds degraded by acid mine drainage from abandoned coal. The presenter will describe the evolution of this pledge from a paper promise to on-the-ground remediation projects.

Jan 1, 2002

By F. Freme

Coal production in the United States reached a record level in 2005, ending the year at 1.03 Gt (1,133.3 million st) according to preliminary data from the U.S. Energy Information Administration (Table 1). Production in 2005 was 19.2 Mt (21.2 million st) higher than the 2004 level of 1 Gt (1,112.1 million st) and surpassed the prior record set in 2001 by 5.1 Mt (5.6 million st). Although total U.S. coal consumption rose in 2005, not all coal-consuming sectors had increased consumption for the year. Coal consumption increased in the electric power sector by 2.2 percent and declined in the other industrial sector, while coking coal consumption decreased slightly.

Jan 1, 2006

By E. R. Spencer

An assessment of U.S. western hard-rock miners? noise exposures was conducted as part of a multi-year National Institute for Occupational Safety and Health (NIOSH) survey of noise exposures in each sector of the mining industry. Noise from selected mining equipment and operator noise exposures were measured, analyzed, and tabulated for dissemination to the participating sites and are being used to direct NIOSH research and interventions to address the greatest noise hazards. Eighty-two noise dosimeter measurements were obtained, along with time-motion studies as the miners operated hard-rock mining machines. Ninety-six percent of the operators had daily noise doses that exceeded the Mine Safety and Health Administration?s permissible exposure level. The average gold miner dosages while operating the following equipment were: haul trucks - 261%, load-haul-dumps (LHDs) - 235%, single boom drills - 221%, bolters - 214%, and dual boom drills - 163%. The worst exposure level was a silver miner with a daily dose of 873%. Time-motion data showed that this miner?s exposure accumulated most rapidly while operating a jack-leg drill. These results will be used to help prioritize noise control development by NIOSH and other partners. Disclaimer: The findings and conclusions in this report have not been formally disseminated by the National Institute for Occupational Safety and Health and should not be construed to represent any agency determination or policy.

Jan 1, 2009

By Edward D. Graf

Once the heavy work of mining, supporting and completing an underground structure is finished, there is frequently the problem of handling unwanted water infiltration into the opening. Methods of controlling the infiltration vary from collecting and channelling the inflow to shutting off the water at the surface of the opening or within the ground formation. Discussed are various methods of controlling ground water inflow from within the structure including collector pipe systems, shotcrete, cement grout, bentonite, and various chemical grouts. Case histories illustrating some of the methods and materials will be presented.

Jan 1, 1987

By C. K. Kocsis

A study was undertaken to evaluate the thermal environment and determine the contributing heat sources within the existing 153 Orebody of Coleman/McCreedy East Mine which would then enable the prediction of the climatic conditions in the mine?s future 170 Orebody. The study entailed continuously monitoring, for a 2-week period, the dry-bulb temperature, humidity and barometric pressure along the existing intake airways from surface down to the 4810 Level and throughout an active mining area on that level. Furthermore, the mining activities and associated equipment that could be responsible for any changes in the temperature and humidity conditions within this mining area were also monitored. These data were then used to develop and validate a climatic simulation of the mine?s mechanized cut and fill mining method. This climatic model was then transposed to the future 5700 Level in the deeper 170 Orebody, to determine the environmental conditions within its production workings and along the main haulage route ascending from that area. Based upon the simulations performed it was shown that the level of ventilation planned for the new orebody should be able to maintain adequate environmental conditions. However, this study did emphasize the importance of the appropriate distribution of airflow in workplaces that used auxiliary ventilation in order to sustain a suitable thermal environment.

Jan 1, 2009

By M. Alley, P. Schroeder, L. Zelazny, S. Nagle

The Old Hickory mineral sands ore body in Virginia (>2000 ha) currently supports a productive rowcrop agriculture. Reclamation experiments were implemented on pilot-scale mining pits from 1995 to 1998. Half of each mining pit was topsoiled (25 cm) while the remaining half was left as either (1) mixed tails/slimes or (2) re-graded subsoil over tails/slimes treated with 112 Mg/ha yardwaste compost. Post-mining productivity was estimated to be reduced by 23%, 3%, 27%, and 20% for each crop (wheat/soybeans/corn/ cotton) in sequence when compared to undisturbed soils. Variability in surface texture and compaction limit restoration of soil productivity.

Jan 1, 2002

By Wern-ping Chen

To mitigate and control the combined sewer over-flows from 17 outfalls in Detroit, MI, three outfalls in Dearborn Heights, MI and eight outfalls in Redford Township MI, the Detroit Water and Sewerage Department (DWSD) completed the preliminary design of a storage tunnel in 2005. In 2006, a final design revised the alignments and the inside diameter (ID) of the tunnel. The revised tunnel system includes an 11.28-km (7-mile) 9.14-m (30-ft) ID tunnel, a 24.4-m (80-ft) ID pump station, two work shafts about 15.2-m (50-ft) ID each and 14 drop shafts with various IDs. A small portion of combined sanitary and storm sewers serve the majority of the Rouge Valley water-shed. This includes Detroit, MI and most of the western suburbs. The Northwest Interceptor (NWI), that extends between Eight Mile Road and Ford Road and roughly parallel to the Rouge River, intercepts sanitary sewage and some wet weather flows from trunk sewers in the tributary areas for transport to the wastewater treatment plant (WWTP) for treatment. During extreme storm events, when the capacity of the NWI is exceeded, the excess combined sewer and overflow (CSO) over-flows into the Rouge River through 17 outfalls to local rivers. The purpose of the Upper Rouge Tunnel system (URT) is to capture and significantly reduce the uncontrolled CSO from these 17 outfalls in Detroit, three outfalls in Dearborn Heights and eight outfalls in Redford Township. When implemented, the

Jan 1, 2007

By Joseph L. Young, Richard A. Bohling

To keep Homestake's Bulldog Mountain silver and lead mining and milling operation in southwestern Colorado workable, natural ground water and decant water from the mine's sand backfilling operation must be continually pumped from the workings. Left untreated, this water exceeds maximum allowable levels for various contaminants that may be discharged to the environment. To comply with regulations, a National Pollutant Discharge Elimination System (NPDES) permit was obtained and a mine water treatment plant for heavy metals removal was constructed in 1977. Due to equipment capacity and operational problems, and the lack of on-site technical personnel and analytic equipment, the first water treatment plant could not consistently meet permit limits. In 1979, Homestake entered into a consent decree with EPA and the Colorado Department of Health, calling for the construction of a water treatment facility to meet NPDES permit limits. Initial construction began in the spring of 1980 and the plant now produces effluent acceptable for discharge.

Jan 12, 1981

By Y. Wang, K. S. E. Forssberg, A. Johansson, X. Lu

This paper presents the desulphurisation of a fine graphite powder below 80 µm by high gradient magnetic separation. The removal of pyrite (FeS2) and pyrrhotite (Fe1-xS) from the fine graphite powder was carried out with a modified version of the Sala dry HGMS with vibration assistance. In addition, a comparative study with dry and wet HGMS systems has also been performed. In order to establish the performance of the desulphurisation, a test series of varying parameters such as magnetic induction, matrix type/configuration and vibration were performed. As an equipment/process for removing sulphurous impurities from the fine graphite powder, the dry HGMS is deemed useful and comparative with the wet HGMS.

Jan 1, 2002

By S. A. Abdel Sabour

Conventional methods for selecting a production plan for an open pit mine is based on the assumption that ore grades throughout mine life as well as market variables are known with certainty. Another important issue that is also being ignored in the conventional procedure is the value of management flexibility to revise operating policy with time according to the arrival of new information. Based on this oversimplification of reality, an optimum mine plan that is thought to be maximizing net present value (NPV) of the project is selected. Given the multiple sources of risk affecting the estimated NPV, there is a high probability that the actual value will be different from that estimated. This could mislead decision making process regarding selecting an optimum mine plan. This paper proposes a multi-criteria ranking system for selection between alternative mine designs under both geological and market uncertainties. The system is based on integrating multiple market and geological uncertainties as well as the operating flexibility to revise the ultimate pit limits using a Monte Carlo-based real options valuation (ROV) model. To compare the methods, the article applies the proposed system, along with the conventional NPV-based method, to rank possible mine designs for a copper and a gold mine. It has been found that, considering multiple risk analysis measures while integrating uncertainty and operating flexibility results in selecting a mine design that is different from that selected by the conventional method.

Jan 1, 2009

By John D. Morton, J. H. LaVerne Palmer, Douglas J. Belshaw

An extensive programme of ground instrumentation and observation was carried out for the West Duff in Outfall Sewer tunnel project prior to and during construction, to establish the performance characteristics of the rock through which the tunnel and appurtenant openings were dug and to examine the nature of the lining-to-ground interaction. The existence of high horizontal residual ground stresses was confirmed, and values established by overcoring. Rock deformations and stress changes were monitored during tunnelling. Permanent stress and strain monitoring devices were set into the final lining and these are continuing to operate. INTRODUCTION The site is located on the north shore of Lake Ontario at Pickering, some 20 miles (32 kilometres) east of Toronto, Canada where a variable thickness of glacial or interglacial sediments overlies bituminous shale bedrock of. the Collingwood Formation which is lower Ordovician age. Approximately 50 feet (15 metres) of glacial cover exists at the shaft, though this thins abruptly at the regressing cliffed shoreline such that several small areas of exposed bedrock exist in the lakebed. The general location, overall geological section and detailed site plan and profile are illustrated in Figs.1,2 and 3 respectively. General properties of the rock as established during an extensive test drilling and site investigation programme are listed in Table 1, while stress determination by USER overcoring stress meter device are given in Table ll. These data formed the basis of analyses which were done to examine the intended outfall design, and to detail the construction procedure and the observational instrumentation programme.

Jan 1, 1979

By S. Ersayin, I. Iwasaki

Application of a magnetic field was shown to be effective in controlling iron losses in pilot-scale cationic silica flotation in the processing of magnetic taconite concentrates. The design of a magnetic field distribution device and batch flotation test results using a 1.42m3 (50 cu. ft.) WEMCO cell are reported. Major losses of iron units in froth products were in the -25µm (500 mesh) fraction, and the application of a magnetic field decreased the flotation of fine magnetite, thereby improving the selectivity of separation. The “as received” sample was sufficiently magnetized and no further benefit was gained by magnetizing treatment. Selectivity was somewhat adversely affected by demagnetizing the sample, though its effect was minimal due to the magnetic field. The device is simple in construction, low cost and may be installed readily in existing equipment.

Jan 1, 2002