Browsing by Author "Benner, Blair R"

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Alternative Technology for Sediment Remediation Demonstration Plant
(University of Minnesota Duluth, 2000-11) Benner, Blair R; Wu, Chuying; Zanko, Lawrence M
Duluth-Superior Harbor is a major port on Lake Superior located between the cities of Duluth, Minnesota, and Superior, Wisconsin. The harbor and the lower Saint Louis River that discharges into the harbor area have a history of water quality problems resulting primarily from municipal and industrial discharges in and upstream of the harbor. The port is a major debarking point for grain shipments overseas and for taconite pellets for the lower Great Lakes ports. To allow navigation, the shipping channels must be dredged annually. The dredged material has been stored in a confined disposal area developed at the Erie Pier location in Duluth. This facility is nearing its capacity and other methods for handling the dredged material must be found. The Coleraine Minerals Research Laboratory, a division of the Natural Resources Research Institute of the University of Minnesota - Duluth, has been studying the application of mineral processing techniques for treating contaminated soils. The laboratory sampled the Erie Pier site and designed a demonstration plant to treat about 50 tph of material from the site. Based on the previous work and the plant design, the U.S. Army Corps of Engineers awarded the laboratory a contract to construct and operate the demonstration plant. The plant consisted of a feeder followed by a grizzly screen to remove large rocks and miscellaneous junk. The grizzly undersize was conveyed to a double deck screen equipped with water sprays. The screen undersize flowed to a sump and pump. The slurry was then pumped to an agitated tank. Material from the tank was pumped to two cyclones to make a size separation. Cyclone overflows were collected and channeled to settling ponds to allow the solids to settle and to provide water for the plant. Cyclone underflow was stockpiled as a sand product. In addition to sending the cyclone overflow to the settling ponds, a belt filter press was tested for about two weeks to treat a portion of the overflow to produce a cake that could be easily handled and a clear filtrate that could be recycled. The objective of the program was to treat different types of materials found at the Erie Pier site to produce a coarse product (cyclone underflow) that contained less than 12 percent by weight particles finer than 200 mesh (75 microns). The underflow should be free draining so that it could be moved by loaders. The distribution of solids, water, inorganic compounds and organic compounds would be monitored. The settling characteristics of the cyclone overflow would be determined. A total of four separate samples were processed in the plant. Sample 1 was a sandy feed containing between 13 and 32 percent in the passing 200 mesh fraction. Sample 2 was a finer material that was removed from the site during construction of the settling ponds. Sample 2 contained between 30 and 52 percent in the passing 200 mesh fraction. Sample 3 was a fine sample dug from the north end of the site where the finest material should have been. Sample 3 was only run for one day due to a break down of the front-end loader used to transport the feed to the plant. The fourth sample was the drained cyclone underflow from the processing of samples 2 and 3. Maintaining a consistent feed to the plant was a continual problem. Clay material in the feed was difficult to disagglomerate and the material tended to form balls, which rolled down the screen decks. Additional water sprays and belting on the top screen deck improved the break up of the clay material but did not eliminate the problem. Another feed problem was the amount of vegetation in the feed. This material tended to bridge in the feeder and to plug the two screen decks, reducing screening capacity, at times significantly. Compounding the feed problem was the loss of the variable frequency drives on the two pumps. Loss of the drives effectively eliminated the ability to make any significant changes in the flowrate to the cyclones and, hence, the ability to affect the cyclone split. Attempts were made to control the cyclone feed by installing a by-pass line to return some of the cyclone feed back to the cyclone feed sump. These attempts were unsuccessful and on numerous occasions resulted in overloading the cyclone feed pump motor causing the motor to stop. Samples of the cyclone feed, overflow and underflow, as well as belt filter press cake and filtrate, when operating, were taken hourly. These samples were saved for future analysis. In addition to the saved hourly samples, a grab sample of each stream was taken hourly and made into a daily composite. The daily composites were filtered with a portion of the filtercake being used for size analysis and the remainder being air dried for chemical analysis. Sample 1 was processed at feed rates up to about 63 tph with no loss in performance. In all tests with Sample 1, the cyclone underflow contained less than 10 percent in the passing 200 mesh fraction. Weight recovery to the underflow ranged between 73.3 and 92.6 percent. In general, the heavy metals and organic material were concentrated in the cyclone overflow, but since the total weight recovery in the cyclone underflow was high, the majority of the heavy metals and organics in the feed remained with the cyclone underflow. The processing of Samples 2 and 3 were more difficult due to the large amount of vegetation contained in the feed. Plant feed rates were generally between 7 and 14 tph. The low feed rates were caused by the vegetation problem and by the need to feed the cyclone a low percent solids to try to make the desired size split. But even at the low percent solids in the feed, the cyclone underflow contained between 18 and 29 percent in the passing 200 mesh fraction. Weight recovery to the underflow ranged from 55 to 72 percent. Despite the high minus 200 content, the cyclone underflow was easy to dewater and formed into a steep sided conical pile. As with Sample 1, the heavy metals and organics were concentrated in overflow sample, which, due to the higher weight recovery, contained the majority of the heavy metals and organics from the feed. Since the cyclone underflows from Samples 2 and 3 still contained too many fines, the cyclone underflow pile was reprocessed through the plant. Resultant cyclone underflow contained between 10.9 and 14.7 percent in the minus 200 mesh fractions and recovered over 90 percent of the feed weight. Again the heavy metals and organics concentrated in the cyclone overflow. Performance of the belt filter press was very impressive. The resultant filtercake was very easy to handle by conveyor belts and would be very easy to haul by truck. The filtercake was almost dry to the touch. Filtrate from the belt filter press was very clean, with turbidity measurements less than 5 ntu. To produce these results required about 1.5 pounds of polymer flocculant for every 3900 gallons of cyclone overflow treated. Analysis of the filtrate indicated no residual polymer in the water.
Applicability of U.S. Steel's Drop Weight Test to Autogenous Grinding
(University of Minnesota Duluth, 2009-01-14) Benner, Blair R
The purpose of this test program was to determine if this procedure could be used for predicting the energy needed to autogenously grind taconite.
Bench Scale Tests to Separate Mercury from Wet‐Scrubber Solids from Taconite Plants
(University of Minnesota Duluth, 2007) Benner, Blair R
Characterization of Residue from the Pressure Oxidation Leaching of Bulk Copper-Nickel Sulfides from the Duluth Gabbro
(University of Minnesota Duluth, 1999) Benner, Blair R; Niles, Harlan B
The copper-nickel bearing material in the Duluth Gabbro represent a potentially significant reserve of copper and nickel with lesser amounts of cobalt and platinum group elements (PGEs). To help promote the development of this resource, the Coleraine Minerals Research Laboratory (CMRL) has conducted a series of investigations into methods of processing the material. A bulk sulfide flotation process followed by oxidation pressure leaching resulted in high extractions (>98 %) of the copper and nickel in the flotation concentrate. During the leaching, the iron in the flotation concentrate leaches and precipitates as either hematite (crystalline or amorphous) or as a basic iron sulfate (jarosite). The leaching should also leave the PGEs in the residue. If the hematite was present as a crystalline material, then if may be possible to recover a high grade iron product from the residue. If any PGE minerals could be found, then it may be possible to develop a method to recover and concentrate the PGEs. The Minnesota DNA through the Minerals Coordinating Committee funded the current study. The purpose of the research was to characterize the leach residue as to the iron bearing material and to determine if any PGE minerals could be found either by X-ray diffraction (XRD) or by electron microprobe analysis.
Classification of Stockpiled Material from the Larson Quarry
(University of Minnesota Duluth, 1987) Benner, Blair R
J. L. Shiely Company has contracted the Natural Resources Research Institute to conduct laboratory tests to determine the technical feasibility and to develop preliminary flow sheets and equipment requirements to produce marketable products from minus 5/16-inch stockpiled material at the Larson Quarry. Either screening followed by a spiral classifier or a spiral classifier alone can produce a product containing about 83 percent of the weight and about 6 percent minus 200-mesh material. Flow sheets and equipment requirements are given for both options at 100 and 150 TPH. Based on the equipment requirements the classifier without screening appears to be the best option. Both options use a thickener to treat the classifier overflow. Laboratory tests indicate that it will be feasible to recycle the thickener overflow. Chemical analysis of the minus 200-mesh material, thickener underflow, indicate that the materials should be chemically suitable for agricultural lime.
Cleanup of Lead Contaminated Soil from Battery Reprocessing Sites
(University of Minnesota Duluth, 1990-04) Benner, Blair R; Bleifuss, Rodney L
The hazards of lead in the environment have been a matter of increasing concern over the past several years. The most common sources of lead contaminated soils are those related to abandoned lead battery reclamation sites. There are over 200 such sites in the United States and several real and potential sites in Minnesota. Under present regulations such contaminated soil must be removed and placed in an approved and licensed landfill. The purpose of this study was to demonstrate that by applying conventional mineral dressing techniques it is possible to detoxify a significant percentage of the soil and thereby reduce the cost of landfill disposition. Prior test work at the Natural Resources Research lnstitute's Coleraine Minerals Research Laboratory (CRL) on a sample from a battery reprocessing site in Wisconsin demonstrated that partial detoxification of the soil was practical. The object of this study was to apply similar techniques to material from a Minnesota site. The Shafer Metal site on north Plymouth avenue in Minneapolis was selected for this study after consultation with personnel from the Minnesota Pollution Control Agency and the Minnesota Department of Transportation who own the property. The lead contamination at the Shafer Metal battery reprocessing site occurs in three principal modes: lead metal fragments, surficial coatings of precipitated lead sulphate and lead dioxide, and lead incorporated into fused plastic material. The lead metal consists primarily of fragments of battery plates and connectors. The precipitated lead compounds occur as coatings on the rock and sand particles in the soil. The fused plastic material could have resulted from melting and casting of the lead, or operation of an incinerator. After preliminary sampling to confirm the distribution of lead contaminated soil at the site, three bulk samples of about 800 pounds each were collected for testing. These three samples were subjected to a series conventional mineral processing techniques involving attrition scrubbing, screening, and gravity separation. The tests demonstrated that over 60% of the material can be separated as a clean rock and sand product that can be disposed of on site. About 5% to 10% of the material can be recovered as a lead-rich product that would be acceptable feedstock to a lead smelter. About 25% of the weight would contain so much lead that it would have to be treated as hazardous material. Some 5% to 10% of the material would be rejected as a coarse trash product eligible for disposal in conventional landfills. The EPA Synthetic Precipitation Leach Test for Soils (Method 1312) was run on the rock and clean sand portion which represents over 60% of the material. The tests demonstrated that this material had been effectively detoxified and could be disposed of on site. Based on these test data a treatment flow sheet to detoxify the material represented by the bulk samples taken at the Shafer Metal site was developed. The flow sheet includes the following process steps: I) Coarse screening to remove tramp trash; 2) attrition scrubbing to remove the lead compounds from the coarser rock and sand particles; and 3) gravity concentration to separate a high lead product, a clean rock and sand reject, and a lead-bearing fused plastic product. A minus 165 mesh fines fraction is also produced containing the natural fines from the soil and the lead released by the attrition scrubbing. The recommended treatment flow sheet is based on using conventional mineral processing equipment. The equipment could be sized small enough to be truck mounted, or set up as semi-portable units for on-site treatment. Engineering such a portable treatment plant was included in the extended project, but is beyond the scope of this abbreviated study. Whether treatment of the Shafer Metal site is practical depends upon the cost of building and operating such a treatment plant on site as opposed to direct disposal. It is recommended that this study be extended to include the design and engineering of a portable or semi-mobile treatment plant and that further continuous pilot plant operations be supported to confirm some of the coarse gravity separation steps. There are other similar sites in Minnesota that are contaminated by lead that would be amenable to similar treatment. Costing out the plant required and demonstration of the viability of the treatment flow sheet would make it possible to offer alternatives to the expensive disposal of such hazardous material in a licensed disposal site.
Comparison of One and Two Stage High Pressure Rolls Grinding followed by Ball Milling with Conventional Rod and Ball Milling
(University of Minnesota Duluth, 1999) Benner, Blair R
With the development of the autogenous wear surface, the high pressure roller press (HPR) is receiving interest from the mineral industry. Previous work by the Coleraine Laboratory had indicated energy saving using a single stage of HPR compared to rod milling and an energy saving using 2 stage HPR compared to single stage HPR. The purpose of this study was to compare three flowsheets using the same feed and producing a final size of about 85 percent passing 270 mesh. The flowsheets were as follows: (1) Rod mill followed by wet magnetic separation with ball mill grinding of the magnetic concentrate; (2) HPR closed with a 3 mesh screen followed by wet magnetic separation of the screen undersize and ball milling of the magnetic concentrate; (3) HPR closed with a 3 mesh screen with the screen undersize being upgraded by dry magnetic separation followed by open circuit HPR on the magnetic concentrate with wet magnetic separation of the HPR product and ball milling of the wet magnetic concentrate. The test work indicated that the single stage HPR required 27.25 kWh/It of new feed compared to 34.0 kWh/It for the rod mill to produce an 85 percent passing 270 mesh ball mill discharge. The two stage HPR flowsheet was even more energy efficient, requiring only 23.29 kWh/It of new feed. With the single stage HPR, the energy savings appears to be only in the coarse grinding. The ball mill grindability, as measured by the operating work index, was essentially the same for the rod mill and HPR magnetic concentrates. The two stage HPR resulted in energy savings in both the coarse grinding and in the ball milling. The operating work index for the ball mill portion only was 23.5 kWh/It of ball mill feed for the two stage flowsheet compared to about 29 kWh/It for the other two flow sheets. Davis tube tests on the ball mill discharges suggest that there is a liberation benefit associated with the two stage HPR flowsheet, but not with the single stage HPR flowsheet.
Comparison of One and Two Stage High Pressure Rolls Grinding followed by Ball Milling with Conventional Rod and Ball Milling
(University of Minnesota Duluth, 1999-07-20) Benner, Blair R
With the development of the autogenous wear surface, the high pressure roller press (HPR) is receiving interest from the mineral industry. Previous work by the Coleraine Laboratory had indicated energy saving using a single stage of HPR compared to rod milling and an energy saving using 2 stage HPR compared to single stage HPR. The purpose of this study was to compare three flowsheets using the same feed and producing a final size of about 85 percent passing 270 mesh. The flowsheets were as follows: (1) Rod mill followed by wet magnetic separation with ball mill grinding of the magnetic concentrate; (2) HPR closed with a 3 mesh screen followed by wet magnetic separation of the screen undersize and ball milling of the magnetic concentrate; (3) HPR closed with a 3 mesh screen with the screen undersize being upgraded by dry magnetic separation followed by open circuit HPR on the magnetic concentrate with wet magnetic separation of the HPR product and ball milling of the wet magnetic concentrate. The test work indicated that the single stage HPR required 27.25 kWh/It of new feed compared to 34.0 kWh/It for the rod mill to produce an 85 percent passing 270 mesh ball mill discharge. The two stage HPR flowsheet was even more energy efficient, requiring only 23.29 kWh/It of new feed. With the single stage HPR, the energy savings appears to be only in the coarse grinding. The ball mill grindability, as measured by the operating work index, was essentially the same for the rod mill and HPR magnetic concentrates. The two stage HPR resulted in energy savings in both the coarse grinding and in the ball milling. The operating work index for the ball mill portion only was 23.5 kWh/It of ball mill feed for the two stage flowsheet compared to about 29 kWh/It for the other two flow sheets. Davis tube tests on the ball mill discharges suggest that there is a liberation benefit associated with the two stage HPR flowsheet, but not with the single stage HPR flowsheet.
Correlation of Metallurgical Testing of Mine Samples to Plant Feed and Concentrate
(University of Minnesota Duluth, 2007) Benner, Blair R
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 of the High Pressure Rolls for Magnetic Taconite Comminution
(University of Minnesota Duluth, 2006-04) Benner, Blair R
Dry Magnetic Separation of Rod-Mill Feed at Minntac: Progress Report No. 1
(University of Minnesota Duluth, 1986-08-14) Benner, Blair R
Pilot-plant testing at the Coleraine Research Laboratory has indicated the potential benefits of dry magnetic separation (cobbing) of Minntac rod-mill feed. Therefore, a prototype commercial unit was installed on line 18 to establish the benefits of dry cobbing. Line 18 was operated with and without dry cobbing on alternate days. The initial test period indicated, that for a short period and one splitter position, dry cobbing produced about a 5 percent increase in the magnetic iron tons in the wet cobber concentrate with a concurrent 2 percent loss in magnetic iron recovery. About 25 percent of that iron loss was associated with fine material being carried along with the dry cobber tailings. In the second test period, a flow meter and density guage were installed in the final concentrate line so that the actual long tons per hour of concentrate produced could be measured. The second test period ran for.about 2 weeks and showed a production increase of about 3 percent with essentially no loss in magnetic iron recovery. While the tests are not totally conclusive they do indicate potential benefits with dry cobbing. It is anticipated that with the recommended optimization of the splitter position and with the potential for increased iron recovery by screening the dry cobbing tailings that production increases of greater than the observed 3 percent will be realized.
The Effect of Demagnetizing Cyclone Feed on a Plant Cyclone Performance
(University of Minnesota Duluth, 2009) Benner, Blair R
The effect of demagnetizing the cyclone feed was tested at the Minorca plant under the Iron Ore Cooperative Program. The plant tests were conducted by Minorca personnel. Tests were run at cyclone feed pressures of 12, 14, and 16 psi with and without the demagnetizing coil being energized. Two test series were run at each pressure on different days. Samples were taken of the rougher concentrate (cyclone feed could not be accurately sampled), cyclone underflow and cyclone overflow. The samples were filtered and dried at Minorca and the dried samples were sent to Coleraine. They were screened through 500 mesh and the individual screen fractions were analyzed for magnetic iron (Satmagan) and silica. Results from the chemistry by size fractions were balanced using the USIMPAC program. There was good agreement between the measured and balanced data. These results indicated that the main effect of the demagnetizing coil was in the minus 500 mesh fractions. The amount of minus 500 mesh material reporting to the underflow was significantly lower when the coil was energized. Also, the silica content of the minus 500 mesh fraction in the underflow has higher, and the amount of minus 500 mesh material in the cyclone overflow was higher when the coil was on. The USIMPAC program was used with the balance data to calculate the cyclone split size, d50, and apparent by-pass for the magnetic iron and silica portion of the cyclone feed. Having the coil on or off had little effect on the d50 values for either the magnetic iron or the silica, but having the coil off increased the magnetic iron apparent by-pass by about 100 percent. Computer simulations using USIMPAC were run using previous plant data and the cyclone parameters determined above. However, this produced unrealistic results, since the previous data had a significantly coarser cyclone split. Since the cyclone splits were essentially unaffected by the coil, simulations were run with the previous data splits and the current apparent by-passes. This simulation showed an increased circulating load, but little overall effect on the line performance. Test work conclusively showed that the use of a demagnetizing coil on the cyclone feed at Minorca will significantly reduce the amount of fine iron reporting to the cyclone underflow, which should improve line performance.
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.
The Effects of Temperature on Cyclone Performance
(University of Minnesota Duluth, 2006-03) Benner, Blair R
The cyclone is widely used in the taconite industry to close grinding circuits. For a given cyclone geometry, the main operating variables are flowrate, feed size distribution, and slurry rheology. Generally the slurry density (percent solids) is used to approximate the slurry rheology. However, it is known that slurry temperature can also affect the rheology. The purpose of this test program was to determine the effect of temperature on cyclone performance as measured by cyclone weight split and cut size, D50• Two samples of cyclone feed were obtained from Evtac (now Utac). The samples were taken about 6 months apart.
Investigation in Production of Iron Ore Concentrates with Less Than 3 Percent Silica from Minnesota Taconites – Report One – Minntac Concentrate: A Final Report
(University of Minnesota Duluth, 1991) Benner, Blair R; Bleifuss, Rodney L
Investigation in Production of Iron Ore Concentrates with Less Than 3 Percent Silica from Minnesota Taconites – Report Three – Hibtac Concentrate: A Final Report
(University of Minnesota Duluth, 1991) Benner, Blair R; Bleifuss, Rodney L
Investigation into Production of Iron Ore Concentrates with less than 3 percent Silica from Minnesota Taconites Report Two · Erie Concentrate
(University of Minnesota Duluth, 1991-06) Benner, Blair R; Bleifuss, Rodney L
The pellets produced by Minnesota taconite companies generally contain between 4.0 and 7.0 percent silica. These silica levels were established initially by the concentratability of the ore, that is, its response to closed circuit ball mill grinding and magnetic concentration. Those operations that had taconite that was easy to concentrate generally produced lower silica pellets. As processing technology improved and it became possible to achieve lower silica levels constraints imposed by the blast-furnace operation became limiting. These constraints related primarily to sulphur and alkali levels in the furnace which control both the volume and chemistry of the furnace slag. Because the trend in blast-furnace practice has been to move toward lower slag volumes, pellets with lower silica levels have become more desirable. Recent extensive installation of external hot metal desulphurization facilities at many steel works allows even lower slag volumes. The basic driving force to go to lower slag volumes is the cost and availability of high quality metallurgical grade coke and related environmental problems. The recent move to produce fluxed pellets has made lower pellet silica levels more attractive because of the lower palletizing costs related to both the lower flux addition and higher production rates with a lower silica content. A common target silica level in fluxed pellets is now about 4.0 percent. A 4.0 percent silica pellet requires a concentrate containing between 3.7 and 3.9 percent silica depending upon bentonite addition levels. This lower silica level has been accomplished in some plants by the use of fine screens, while other plants require the use of silica flotation. The lower silica level has been accomplished at a relatively small incremental cost, generally less than $0.50 per ton. With increasing pressure from the blast furnaces for lower-silica pellets to reduce coke consumption, concentrate silica levels on the order of 3.0 percent may be common in the future. In addition to the need to produce a lower silica blast-furnace feed, there is a potential need to produce even lower silica concentrates, below 3.0 percent, as feed stock for direct steelmaking. Worldwide the current research emphasis is on the development of a coal-based direct-steelmaking process to replace the conventional two step, blast furnace-basic oxygen furnace, process. Most of the current prototype direct steel making processes would benefit from a lower silica feed. These low silica levels will require increasingly complex and expensive secondary treatment of normal magnetic concentrates which exceed the capability of current taconite processing flowsheets. The purpose of this test program is to establish the lower silica limits that can be achieved by current technology for various Minnesota taconites and gain a preliminary indication of the cost.Because the magnetite concentrates produced by different taconite plants range significantly in terms of their size-silica relationships the program included three different concentrate sources for evaluation. Major differences will exist between concentrates produced in a fully autogenous grinding system and those produced in a conventional rod mill-ball mill circuit in which the ball mills are closed with hydrocyclones and/or a combination of hydrocyclones and fine screens. There are also differences in the nature of the siliceous gangue minerals in the various operations. The concentrates from the western Mesabi range contain quartz and low- grade metamorphic iron silicates such as minnesotaite, stilpnomelane, and talc and iron carbonates. The concentrates from the east Mesabi metamorphosed iron formation contain high grade metamorphic iron silicates such as cummingtonite, grunerite, and fayalite as well as quartz. The type of gangue mineral greatly affects the ability to upgrade the concentrates by silica flotation. The purpose of this test program is to determine the lowest silica content that it is technically possible to produce from three different concentrate sources representing the east Mesabi metamorphosed iron formation (Erie), the unmetamorphosed central range produced in a rod mill and ball mill circuit (Minntac), and the unmetamorphosed western Mesabi produced in an autogenous milling circuit (Hibtac). Sufficient data were collected to allow preliminary cost estimates to be made at several silica levels. The cost estimates will be based on reagent consumption, regrind power and metal requirements, and iron recovery. This report contains all of the information obtained on the Erie samples. This includes the results of the initial characterization studies, basic bench scale beneficiation test results, pilot plant flotation data, and the results of the secondary and tertiary treatment of bulk flotation froth to improve overall iron recovery.
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.

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