Growth kinetics of CaF2 in a pH-stat fluidized-bed crystallizer |
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Authors: | Clifford Y. Tai P.C. Chen T.M. Tsao |
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Affiliation: | aDepartment of Chemical Engineering, National Taiwan University, Taiwan bDepartment of Chemical and Materials Engineering, Lunghwa University of Science and Technology, Taiwan |
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Abstract: | In this study, experiments were first conducted in a stirred vessel to establish the metastable region of calcium fluoride, using a pH-stat apparatus for controlling the pH value of solution. The effects of pH value on the solubility and metastable region were observed. Then, operating variables, including supersaturation, superficial velocity, pH value, seed size, and types of seed and solution, that influenced the crystal growth of the same system were investigated in a fluidized-bed crystallizer. The crystal growth rates were determined from the consumption rates of fluoride ions. The growth kinetics was explored by using the two-step growth model. The effectiveness factor was used to judge whether a controlling step was existing. The kinetics of crystal growth in a lean bed and a dense bed was also discussed. |
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Keywords: | A1. Effectiveness factor A1. Fluidized bed A1. Metastable region A1. Two-step growth model B1. Calcium fluoride |
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