Browsing by Subject "Green ball quality"

Now showing 1 - 3 of 3
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    Green Ball Characterization
    (University of Minnesota Duluth, 2005-09-13) Kiesel, Richard F
    The objective of this research project was to correlate the physical quality of green balls with their behavior in the elastic region of the deformation curve under load. An understanding of the parameters that are key to the production of these quality standards will help to improve the quality of their products. Green ball quality is accepted by the industry as one of these key parameters. A procedure to further characterize green balls and develop a relationship to current quality assessment procedures will provide insight to the physical attributes and integrity of the green balls. A digital force gauge and compression test stand interlocked with PC based software was used to collect data and develop the relationship with the deformation of the green ball. Data on both wet and dried green balls were collected on varied bentonite additions and green ball moisture concentrations. The slope of the deformation curve, in the elastic region, was studied with regards to the green ball drop number, moisture content, wet strength and dry strength. The deformation behavior of the green balls is indirectly proportional to the slope of the deformation curve. As the elasticity of the green ball increases, the dry drop number, wet drop number and dry compressive strength is reduced. Although no significantly strong relationships are present, it is believed that the relationships to green ball quality, by collecting sufficient data over a period of time, can be significant.
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    Investigation of Papermill Sludge as a Taconite Binder
    (University of Minnesota Duluth, 1989-03-16) Goetzman, Harold E;
    Bentonite has been used by the taconite industry since commercialization of the process in the early 1950's. Although many alternate binders have been tested, including organic materials, bentonite still remains the preferred binder. Bentonite has the unique qualities that promote stable green balling conditions and provides acceptable strengths during drying, preheating, and contributes to the fired pellet strength at an acceptable cost. The incentive to consider other binders is based on such factors as improving the metallurgical properties of the pellets, decreasing their silica content, and lower overall costs. The USBM conducted a number of small scale tests using papermill sludge and other additives in place of bentonite as a binder for taconite pellets. Their balling tests indicated that acceptable green-ball strength could be achieved with papermill sludge. The fired pellet evaluations, however, were based on muffle furnace tests which do not accurately predict the fired pellet quality. Although the fired pellet data were also encouraging it was recognized that pot-grate tests were needed to obtain more definitive test data that could be directly related to commercial practice. Subsequently, the USBM recommended that the IRRRB fund an extension of the program to include pot-grate tests to verify the fired pellet quality obtained in the muffle furnace work. A test program was prepared by the Coleraine Research Laboratory of the Natural Resources Research Institute (NRRI) in cooperation with Dr. J. Nigro and Dr. L. Haas, USBM, and Mr. S. Dickinson, IRRRB. The contract proposal was submitted to the IRRRB January 27, 1988. The contract included evaluation of concentrate and sludge filtering and blending aspects, green-ball quality, and fired pellet quality based on pot-grate tests. This report presents data on all three aspects as stated in the contract and conclusions regarding future efforts in this area.
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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.