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Title:
CRYSTALLIZING METHOD FOR CONTROLLING GRAIN DISTRIBUTION
Document Type and Number:
Japanese Patent JP3807086
Kind Code:
B2
Abstract:

PROBLEM TO BE SOLVED: To efficiently obtain crystal grains having a uniform grain size with good reproducibility by periodically increasing and decreasing the temp. of slurry during concentrating a crystallization mother liquid.
SOLUTION: Dissolution and crystallization are repeated in a vacuum concentrating vessel by a temp. swing method. When the increase in the solubility during raising the temp. exceeds the increase in the concn. due to the introduction of a crystallization mother liquid, the liquid is in an unsatd. state in which the slurry crystal is partly dissolved and fine crystals are fast dissolved to disappear. When the slurry liquid concn. exceeds the solubility by cooling, the growth of the crystal begins according to the supersaturation degree. As the supersaturation degree increases as the cooling proceeds, the crystal growth rate also increases. In this case state, since the slurry liquid concn. is in a metastable supersaturation region, the natural production of a secondary nuclei hardly occurs. By further cooling and concentrating to increase the supersaturation degree, the production of the secondary nuclei occurs. By repeating this cycle, the dissolution of fine crystals and the crystal growth in the metastable supersaturation region occurs to decrease the fine crystals. Thus, the crystallization of the controlled grain size distribution can be carried out without requiring another facility or without changing the operational conditions such as an extended concentration time.


Inventors:
上田 洋
福士 博司
小澤 宗之
Application Number:
JP7394898A
Publication Date:
August 09, 2006
Filing Date:
March 23, 1998
Export Citation:
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Assignee:
味の素株式会社
International Classes:
B01D9/02; C13B30/02; C13B25/00; (IPC1-7): B01D9/02; B01D9/02; B01D9/02; B01D9/02; B01D9/02
Domestic Patent References:
JP6226003A
JP62247802A
JP49029821B1
Attorney, Agent or Firm:
霜越 正夫