Browsing by Subject "Taconite plants"

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Comparison of the Primary Grinding of Taconite in a Pilot-Plant Rod Mill and Ball Mill
(University of Minnesota Duluth, 1989-04-24) University of Minnesota Duluth. Coleraine Minerals Research Laboratory
Progressive improvements in crusher design, screening efficiency, and operating experience along with the down sizing of many taconite operations has resulted in the ability of some crushing plants to produce a substantially finer product. This finer product opens the possibility of replacing the rods in the rod mill with balls. If this replacement could be accomplished substantial savings associated with metal wear and the elimination of rod charging may be realized. The purpose of this study was to compare the performance of a mill charged with rods with the performance of the same mill charged with balls at the pilot scale. The first objective was to establish whether we could achieve the same throughput rate at the same mesh-of-grind in a mill in which the rod media has been replaced by balls. The second point was to determine whether the ball media would create a significant tramp oversize problem.
Concentrator Modeling Database Development and Simulation of Ispat Inland Plant
(University of Minnesota Duluth, 2003-09-05) Ersayin, Salih
The Ispat Inland plant processes two blends of ore during different time periods throughout the year. Although these two blends have mineralogical differences, they go through the same process. The major difference in the process becomes fineness of grind required to achieve desired level of liberation, which is in tum controlled by the rod mill feed rate. This created a unique opportunity for modeling the effect of mineralogy on separation equipment and measuring reliability of the simulator in predicting perfonnance of non-concentration equipment, such as hydrocyclones and fine screens, under different operating and feed conditions. While performance of concentration devices including magnetic separator, hydroseparator and flotation banks was expected to show dependence on variation in mineralogy, particularly on liberation size, performance of classification and screening devices would be largely independent of the liberation characteristics. Therefore, the models were expected to reasonably simulate the performance of these devices for a given blend when plant data from the other blend was available. On the other hand, performance of grinding mills is mostly governed by the grindability characteristics of a given ore type. Differences in mineralogy may or may not have significant effect on their performance, depending on whether or not change in mineralogy create significant variations in grindability. If such variation occurs, then the question is: how can it be simulated? This study could also provide a guideline for refining grinding models to account for such variations.
Demagnetization of Magnetite Between the Drums of a Magnetic Separator
(University of Minnesota Duluth, 2001-04-30) Benner, Blair R
It is well known that commercial magnetic separators do not totally remove liberated silica slimes. In general, a taconite plant's final magtietic product could be reduced in silica grade by I to 2 percentage points if all of the liberated silica slimes were removed. The actual amount of reduction can be determined by running a standard Davis tube test on the material. It was thought that part of the reason for the slimes being present in the product is that they become trapped in the magnetic floes that form in the first drum of a magnetic separator and that these floes are not broken up between the drums of a commercial separator, which can have up to four drums in sen es.
Development of a Mathematical Model for Fine Screening
(University of Minnesota Duluth, 2004-04-16) Pletka, Jeremy
Usim Pac mineral processing plant simulation software is used by the University of Minnesota's Coleraine Minerals Research Laboratory Concentrator Modeling Center to simulate taconite plant operations. Its ability to simulate fine screening is limited, since the present suitable models assume a constant partition curve for a given set of screens and do not account for changes in operating conditions. As it is well known that the fine screen unit operation is sensitive to operating conditions such as feed density, loading, and size, it becomes clear that for accurate simulations, the model will require modifications. Consequently, a series of tests was performed on a pilot scale unit where several of the operating conditions were varied. Partition curve parameters were then related to operating conditions for relevant mineral components.
Effect of Magnetized and Demagnetized Feed on Cyclone Performance
(University of Minnesota Duluth, 1999-11-23) Benner, Blair R
The hydrocyclone is the primary device used to close the grinding circuits in the taconite industry. The cyclone's major advantages are high capacity, low maintenance, and relatively small size. The main drawback to the cyclone is the fact that it makes a split based on specific gravity as well as size. This has the effect of returning liberated or nearly liberated magnetite back to the ball mills for overgrinding. It is well known that fine magnetite particles will flocculate in the presence of a magnetic field and that these floes settle as pseudo large particles. Therefore, it is reasonable to assume that fine magnetite in cyclone feed would also behave as pseudo large particles and report to the underflow. A number of the early taconite plants included demagnetizing coil on the cyclone feed line. However, plant data on the effect of the demagnetizing of cyclone feed is not readily available, and since there is not a general agreement among plants as to the benefits of demagnetizing the cyclone feed, this project was undertaken to determine the effect of magnetizing and demagnetizing cyclone feed.
Iron Ore Processing Improvements through Process Modeling and Computer Simulation - 2003
(University of Minnesota Duluth, 2003-09-05) Ersayin, Salih
When the Concentrator Modeling Center was established in 1998, its first task was to define the prevailing conditions in terms of taconite plant simulation. Capabilities of existing software and unit operations needing improved models were defined. Preliminary simulations were carried out to determine how accurately the existing models could simulate taconite plant operations. Plant data was analyzed to determine how taconite plant operation could be simulated and to define the common problems and bottlenecks. It also provided some insight in terms of model development. This work indicated that there was a need for improved model development for the unit operations commonly used in taconite processing. Therefore, the Center's task was defined as "to develop advanced models, while providing simulation based assistance to the taconite plant operators using available simulation capabilities. n On the model development side, the specific objective was to develop improved models for magnetic separators, hydroseparators, fine screens and mineral liberation. Despite unsuccessful attempts to obtain federal funding for this type of work due to unwillingness of federal sources to fund projects that would benefit only a smaller section of the mining industry, the Center managed to improve the very simple models available for these unit operations using its plant database and limited funding for specific projects, Now it has the capability of simulating taconite processing more realistically. This was achieved . by analyzing available plant data and developing theoretical understanding of how these unit operations function, and along with pilot scale testing in the case of fine screen modeling. The Center's task was not only to develop these models, but also to incorporate them into the existing software, Usim Pac. Models for magnetic separators and hydroseparators were converted to the programming language of the software. The liberation model is expected to be incorporated soon. The Center's simulation efforts were concentrated on case studies involving the Evtac and lspat Inland plants. While replacing hydrocyclones in a ball mill grinding circuit with fine screens was the focus of study in the former plant, improving overall plant performance was the aim in the latter, which is still an on-going project funded by the DOE. Another simulation study was carried out to determine benefits of ore segregation in one of the taconite plants.
Magnetically Enhanced Hydroseparator Study
(University of Minnesota Duluth, 2005-03) Benner, Blair R
The purpose of this test program was to run semi-continuous tests in the plant to confirm the previous results and to determine if the buildup of magnetite on the magnet grid reached equilibrium. The tests showed that the magnetite build-up did reach equilibrium and, although the field strength did decrease with the magnetite build-up, there was no indication of diminished performance.
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.
Role of Water Chemistry on Balling
(University of Minnesota Duluth, 2003-06-20) Iwasaki, Iwao; ;
Green ball qualities are adversely affected by increased concentrations of Ca++ and Mg++ in process waters because of the replacement of Na+ in bentonite by the divalent cations through cation exchange reaction. Preliminary laboratory tests indicated that displacement of interstitial plant water in filter cakes with RO. water restored ball quality. A few preliminary pilot plant tests were performed to study the effect of removing ca++ and Mg++ ions from filter cakes during filtration by spray washing with softened water, and its effect on balling characteristics.

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