Browsing by Subject "Taconite ore"

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    Improving Taconite Processing Plant Efficiency by Computer Simulation
    (University of Minnesota Duluth, 2007-03-30) Bond, William M; Ersayin, Salih
    This project involved industrial scale testing of a mineral processing simulator to improve the efficiency of a taconite processing plant, namely the Minorca mine. The Concentrator Modeling Center at the Coleraine Minerals Research Laboratory, University of Minnesota Duluth, enhanced the capabilities of available software, U sim Pac, by developing mathematical models needed for accurate simulation of taconite plants. This project provided funding for this technology to prove itself in the industrial environment. As the first step, data representing existing plant conditions were collected by sampling and sample analysis. Data were then balanced and provided a basis for assessing the efficiency of individual devices and the plant, and also for performing simulations aimed at improving plant efficiency. Performance evaluation served as a guide in developing alternative process strategies for more efficient production. A large number of computer simulations were then performed to quantify the benefits and effects of implementing these alternative schemes. Modification of makeup ball size was selected as the most feasible option for the target performance improvement. This was combined with replacement of existing hydrocyclones with more efficient ones. After plant implementation of these modifications, plant sampling surveys were carried out to validate findings of the simulation-based study. Plant data showed very good agreement with the simulated data, confirming results of simulation. After the implementation of modifications in the plant, several upstream bottlenecks became visible. Despite these bottlenecks limiting full capacity, concentrator energy improvement of 7% was obtained. Further improvements in energy efficiency are expected in the near future. The success of this project demonstrated the feasibility of a simulationbased approach. Currently, the Center provides simulation-based service to all the iron ore mining companies operating in northern Minnesota, and future proposals are pending with non-taconite mineral processing applications.
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    Mercury Distribution around Taconite Concentrators
    (University of Minnesota Duluth, 2003-12-09) Benner, Blair R
    Sources of mercury in the environment have become an area of concern for the various regulatory agencies. Taconite production has been identified as one of the sources. Previous programs have indicated that the majority of the mercury in the ore is rejected to the tailings basins, but it appeared that some plants rejected a greater portion than other plants. The purpose of this study was to determine if the differences in mercury rejection were ore related or flowsheet related. Samples were taken around the various concentrator unit operations from !spat-Inland, National Steel Pellet Company, Evtac, Hibtac, and Minntac. The sampling program was not designed to provide definitive mercury balances around the concentrator, but rather to provide a "snapshot" of what was happening with each unit operation. Each unit operation was sampled so that the feed was taken first, followed quickly by simultaneous sampling of the concentrate and tails. This sampling should provide a good balance around each unit operation. The sampling protocol, potential error sources, and measures to minimize the various potential errors are discussed. All of the samples were analyzed for total iron, Satmagan iron, silica, alumina, calcium, magnesium, manganese and sulfur at the Coleraine Minerals Research Laboratory (CMRL). A split of each sample was sent to Frontier Geosciences for total mercury analyses and sequential extraction mercury analyses on the feed, coarse tails, fine tails and concentrate samples from each plant. The sequential extraction is supposed to give an indication of the mercury compounds present. It was anticipated that the sequential extraction method could be used to determine if different plants had different forms of mercury in their ore and if different mercury compounds behaved differently during concentration. The first stage of extraction uses DI water; the second stage uses a pH 2 solution; the third stage uses lN KOH; the fourth stage uses 12N nitric acid; and the fifth and final stage uses aqua regia. The mercury content in the plant crude ore feeds ranged from a low of 9.44 ppb to 27.90 ppb. The plant concentrates ranged from a low of 6.19 ppb to a high of 16.10 ppb. There appeared to be no relationship between the mercury in the feed and the mercury in the concentrate. The standard Excel correlation program was run to relate the various elements to the mercury analyses. For all plants the correlation coefficients for sulfur and mercury content were greater than 0.8 and were greater than 0.9 for four of the five plants. As would be expected, the mercury content correlated positively with the gangue elements and negatively with the iron and magnetic iron analyses. This indicates a selective rejection of mercury to the tails and suggests that the mercury is not associated with the magnetite. The sequential extractions indicated no significant leaching of mercury in either the water or pH 2 solution. This indicates that there is no easily solubilized mercury present in the ore and that the mercury rejected to the tailings should not leach into the water. The sequential extractions indicated no obvious differences in the feed to the five plants. There is some question as to whether the sequential extraction is reflecting different mercury forms or is just indicating the difficulty in extracting mercury from the mineral lattices. The sequential extractions indicated no differences in plant performances.
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    Physical and Image Analysis Sizing of Mine Run Taconite Ore
    (University of Minnesota Duluth, 1993-10) Niles, Harlan B
    The United States Bureau of Mines (USBM) has developed an image analysis system to determine the size distribution of mine-run taconite ore. The results can be used to evaluate fragmentation so that blasts can be designed for better productivity. ~he Coleraine Minerals Research Laboratory (CMRL) has been testing the system at Minntac with apparent success, but there was no method available for testing the accuracy of size distributions determined by image analysis. The Iron Ore Cooperative Research Committee approved and funded a project to screen mine-run ore and compare the results to sizing by image analysis. Three samples, about 2500 tons each, were sized on 6 and 12 inches in a contractor's vibrating grizzly plant at Minntac. Size analyses were extended to 65 mesh by sizing samples of minus-6 inch at the Coleraine laboratory. Between 30 and 60 plus- 12 inch pieces from each bulk sample were measured to provide thickness-width-length aspect ratios and to indicate large-fragment dimensions and weights that are encountered in mine-run ore. The average ratio of thickness to width to length was 1.00:2.20:3.21. Fragment volumes ranged from 4 to 80 cubic feet. Weights of these would be approximately 800 pounds and 16,000 pounds. After the size fractions had been weighed, they were recombined, each sample was loaded into rail cars, and they were dumped at number one primary crusher. The USBM and CMRL video-taped the ore as it was dumped and processed the tapes through a computer to produce an image analysis size distribution for each of the three samples. Because of a large discrepancy between the contractor's and the track scale weights, the size analysis of sample number one was not acceptable. The physical size analyses of samples two and three and their corresponding image analysis size distributions were nearly identical for fragment widths of at least 12 inches. Size. distributions of mine-run ore by the image analysis system have been proven reliable for evaluating the effective fragmentation of individual blasts for sizes down to 12 inches in width.