Study on Mechanism in Crystal Growth with Adhesion Phenomena of Suspended Fine Crystals in Mother Liquid

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  • MASAOKA Koji
    Research Institute of Salt and Sea Water Science, The Salt Industry Center of Japan Depasrtment of Materials Science and Engineering, Graduate School of Engineering, Yokohama National University
  • MISUMI Ryuta
    Division of Materials Science and Chemical Engineering, Faculty of Engineering, Yokohama National University
  • NISHI Kazuhiko
    Division of Materials Science and Chemical Engineering, Faculty of Engineering, Yokohama National University
  • KAMINOYAMA Meguru
    Division of Materials Science and Chemical Engineering, Faculty of Engineering, Yokohama National University

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  • 微結晶の付着現象を伴う結晶成長機構に関する検討
  • ビケッショウ ノ フチャク ゲンショウ オ トモナウ ケッショウ セイチョウ キコウ ニ カンスル ケントウ

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We investigated effects of the particle size of fine crystals on the apparent crystal growth rate by adhesion phenomena of fine crystals suspended in mother solution on a seed crystal surface. The mother solution was sampled from a crystallizer operated under conditions of supersaturation ΔT＝1－5 K and amount of suspended fine crystals Nfine＝0.2－7×105 number/kg-solution. And the particle size distribution of fine crystals on the filter after filtration of mother solution was measured by image analysis using a microscope. As the result, the median diameter and distribution constant of Rosin- Rammler distribution, were 3-6 μm and 1.1-2.3, respectively. Median diameter of fine crystals increased with supersaturation degree of mother solution. Crystal growth rate and nucleation rate of fine crystals were thought that they are low. We presupposed three effects of fine crystals on the apparent crystal growth of a seed crystal adhered. 　Effect 1; Increase of crystal growth unit 　Effect 2; Making starting point of crystal growth accelrated 　Effect 3; Decrease of supersaturation by nucreation and growth of fine crystal　 We estimated the rate of Effect 1 and 3 on the apparent crystal growth rate by apply of measured particle size of fine crystals to an apparent crystal growth rate equation of a previous paper. As the result, the distribution ratio of Effect 1 and 3 were low. A temporary enhancement of crystal growth with steps formed by adhesion of a fine crystal was estimated from a previous report and it was an appropriate value compared with Effect 2. We, therefore, concluded that the main factor of enhancement of the apparent crystal growth rate by adhesion of fine crystals is Effect 2.

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