Browsing by Author "Iwasaki, Iwao"

Now showing 1 - 13 of 13
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    Control of Residual Sulfides in Flotation Tailings of Cu-Ni Duluth Complex via Grinding Media Selection
    (University of Minnesota Duluth, 2001) Iwasaki, Iwao
    The effects of grinding media chemistries on ball wear and flotation were compared by grinding a Cu-Ni bearing Duluth Complex sample using forged steel and 27% Cr cast iron balls under nitrogen, air and oxygen atmospheres. Both types of balls increased their wear in air and oxygen atmospheres, but Cr balls wore only one-third as much as forged steel balls. The wear increased roughly in proportion to the oxygen content of the mill atmosphere. Flotation recoveries of sulfide minerals were adversely affected when the sample was ground in a nitrogen atmosphere. Residual sulfur in flotation tailings ground using both types of grinding balls under an air or oxygen atmosphere was lowered to about 0.15%, with Cr balls producing somewhat lower sulfur values. Davis magnetic tube tests on flotation tailings lowered the residual sulfur to 0. 1 % or less by recovering mainly pyrrhotite. PGM recoveries paralleled the recoveries of sulfur, although Pd recoveries remained somewhat lower, implying that a part of Pd might be associated with pyrrhotite. Pd, not recovered in flotation, appeared to be recovered by magnetic separation of flotation tailings.
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    Effect of a Magnetic Field in the Filtration of Fine Magnetic Concentrates – Final Report
    (University of Minnesota Duluth, 2001-10-31) Iwasaki, Iwao
    The effect of a magnetic field on the filtration of magnetic taconite concentrates was investigated. A magnetic field was applied by using magnetic sheet strips in parallel and checker configurations. Faster filtration rates under magnetic fields appeared to be attributable to the uneven thickness of filter cakes caused by magnetic field distribution, particularly when filter cakes were thin.
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    Effect of Salt Additives on Concrete Degradation (Phase II): Executive Summary
    (Minnesota Department of Transportation, 1995-02) Jang, Ji-Won; Iwasaki, Iwao; Weiblen, Paul
    This research builds on a previous investigation, which found that corrosion-inhibitor-added deicing salts caused degradation of concrete by both anions and cations. The latest research phase looked at methods to detect the chemical reactions between concrete and corrosion-inhibitor-added deicing salts, and to determine the chemical compositions of the precipitates formed by chemical reactions between concrete and the corrosion-inhibitor-added deicing salts. The research led to the following conclusions: * a simple method was developed for the detection of chemical reactions between deicing chemicals and concrete; * the results provided clear evidence of the chemical reactions between concrete and the corrosion-inhibitoradded deicing salts; * the different amounts of precipitates (chemical reaction products) found in the test cells were dependent on the type and concentration of corrosion-inhibitor-added deicing salts; * precipitates formed by chemical reactions between deicing chemicals and concrete were identified by using chemical analysis, scanning electron microscopy, and X-ray diffraction analysis; * and precipitates were calcium and/or magnesium phosphates as a major component, and gypsum as a minor component.
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    Extraction Metallurgy of Copper from Chalcopyrite Concentrates without Sulfuric Acid Generation via Chlorination - III. Integration of Gaseous Chlorination and Selective Oxidation
    (University of Minnesota Duluth, 1999) Iwasaki, Iwao; Tamagawa, T.; Fu, N. X; Kobayashi, M
    A 3-stage fluidizing bed process of chlorination, selective oxidation and sulfur chloride conversion was tested for processing of a chalcopyrite concentrate. It was found that the use of excess oxygen was essential to a stable operation in the oxidation reactor. The oxygen-excess gas will inevitably cause the oxidation of the sulfide concentrate in the chlorination and sulfur chloride conversion reactors. A new flowsheet is proposed to separate the chlorination and the selective oxidation steps with separate flow paths of the fluidizing gases, thereby preventing the passage of oxygen-excess gas in the chlorination and sulfur chloride conversion reactors. The feasibility of the proposed flowsheet was demonstrated in a laboratory-scale fluidizing bed setup.
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    Extraction of Copper from Chalcopyrite Concentrates without Sulfuric Acid Generation via Chlorination - I. Gaseous Chlorination of Sulfide Concentrates
    (University of Minnesota Duluth, 2000) Iwasaki, Iwao; Tamagawa, T.; Tabaian, S. H; Fu, N. X; Kobayashi, M
    A gaseous chlorination process for hydrometallurgical treatment of a chalcopyrite concentrate was investigated. The overall process is visualized to consist of low temperature chlorination-selective oxidation, followed · by aqueous chloride leaching and SX-EW for producing electrolytic copper, elemental sulfur and ferric oxide. In this article, the chlorination phase of the process is described. Initially, the chlorination behavior of chalcopyrite-concentrate micro-pellets was investigated using a small batch-type fluidized bed reactor. The optimum conditions thereby established were used in continuous chlorination tests. The chlorinated products thus prepared were used in the selective oxidation phase of the investigation.
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    Extraction of Copper from Chalcopyrite Concentrates without Sulfuric Acid Generation via Chlorination - II. Selective Oxidation of Chlorinated Products
    (University of Minnesota Duluth, 1999) Iwasaki, Iwao; Tamagawa, T.; Fu, N. X; Kobayashi, M
    A low temperature chlorination-selective oxidation, followed by aqueous chloride leaching and SX-EW for producing electrolytic copper, elemental sulfur and ferric oxide was investigated for hydrometallurgical processing of a chalcopyrite concentrate. In this article, the selective oxidation phase of the process is described. The selective oxidation requires a temperature well above the CuCl-FeCl3 eutectic points. The test procedure was developed with a batch reactor and then tested with a continuous reactor. The process was initiated by adding small amounts of chlorinated samples to a fluidizing bed of dead-roasted sulfide concentrate micro-pellets. The selectively oxidized samples thus prepared were shown to fully dissolve copper, while virtually all the iron remained undissolved.
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    Iron Ore Beneficiation in the U.S.A.: Past and Future
    (University of Minnesota Duluth, 2000-05-02) Iwasaki, Iwao
    The iron ore mining industry in the U.S. is facing strong competition from high-grade overseas sources. In order for the American iron ore industry to remain competitive, research on low-cost beneficiation methods that ensure high-quality and uniform-quality products must be maintained in order to prepare for evertightening specifications on ironmaking raw materials for blast furnaces and for direct reduction processes. In this article, some of the past developments are reviewed and future prospects are discussed with a special emphasis on flotation technology.
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    Low Temperature Gaseous Chlorination for Sulfur Oxide Free Extraction of Copper from Chalcopyrite Concentrates
    (University of Minnesota Duluth, 2002) Iwasaki, Iwao; Fu, N. X; Tabaian, S. H; Tamagawa, T.; Kobayashi, M
    Laboratory investigations of gaseous chlorination-selective oxidation process on primary copper sulfide concentrates are described for producing copper chlorides, elemental sulfur and ferric oxide. The copper chlorides can then be leached, purified and electrolyzed to produce metallic copper and chlorine regenerated for recycle. When a process, originally proposed on a pyrite concentrate analyzing 2.5%Cu using a two-stage reactor, was applied to a Cu, Ni sulfide concentrate analyzing 9%Cu, the process had to be modified to a three-stage reactor by adding a sulfur chloride conversion unit. In this manner, operational problems associated with the formation of Cu-Fe chloride eutectics and sulfur chlorides could be circumvented. When the process was extended to a 29%Cu chalcopyrite concentrate, the use of excess oxygen was found to be necessary to stabilize the operation of the oxidation reactor. A flowsheet was further modified to separate the chlorination and selective oxidation units with separate flow paths of fluidizing gases, thereby preventing the oxidation of sulfide feed in the chlorination reactor. Leaching of selectively-oxidized samples produced solutions analyzing Cu concentrations in excess of 100 g/L with Fe/Cu ratios of less than 0.03 and with Cu extractions of over 99%. Leach residues were readily filterable with cake moisture contents of 20 to 25%.
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    Next Generation Metallic Iron Nodule Technology in Electric Arc Steelmaking – Phase II
    (University of Minnesota Duluth, 2010) Fosnacht, Donald R; Iwasaki, Iwao; Kiesel, Richard F; Englund, David J; Hendrickson, David W; Bleifuss, Rodney L
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    Partial Metallization of Coal-Added Pellets for Smelting Reduction
    (University of Minnesota Duluth, 2000-11-14) Iwasaki, Iwao
    In NKK's Duplex-DIOS process, maximum annual productivity is obtained when a DIOS reactor is operated with 30% metallized feed . Laboratory tests were performed to ascertain if 30% metallization could be achieved consistently and with sufficient strength by adding coal less than the stoichiometric requirements. Partially metallized pellets were prepared using an LTV Steel Mining filter cake sample by adding coal in the amount of 35% of the stoichiometric requirements to both unfluxed and fluxed pellets. The optimum temperature of induration was in the range of 1200° to 1300°C. The product analyzed 25 to 30% metallization with compression strengths of 150 to over 300 lb, and apparent densities of 3.4 to 3.5.
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    Role of Water Chemistry on Balling
    (University of Minnesota Duluth, 2000-06) 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. Several approaches were considered and some of the approaches were tested for remedying the adverse effects, namely, displacing moisture water by softened water by washing in filtration, increased use of bentonite, and such additives as Na2C03, NaHC03, NaOH, (NH4)2C03, EDTA, modified starch, and molasses. The use of NaOH and Na2C03 were quite effective in restoring the ball quality, particularly, when a combination of a modified starch and Na OH was used. It becomes of interest to investigate the mechanism that leads to the beneficial effects of these additives, so that some other additives, besides Na+containing salts, may be suggested.
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    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.