| 摘要 |
PROBLEM TO BE SOLVED: To obtain a coarse ammonium sulfate crystal having a stabilized average particle diameter and a particle size distribution without causing a cycling phenomenon in a crystallization process by making sulfamate ion and a metal ion coexist in an ammonium sulfate solution concentrated in a deposition process of ammonium sulfate crystal. SOLUTION: The amount of sulfamate ion is 0.10-5 wt.%. Monovalent to trivalent metal ion is preferable as a metal ion. For example, Ce ion, Li ion, Na ion or Ca ion may be cited as the metal ion. The amount of the metal ion added is 10 ppm to 1 wt.%. A method for making both the ions coexist is not particularly restricted. A metal sulfamate is added as a habit modifier to a solution. Otherwise, sulfamic acid or a sulfamic acid compound such as ammonium sulfamate and the metal salt are added to a concentrated ammonium sulfate solution to carry out crystallization. According to this method, a cycling phenomenon in which an average particle diameter is periodically changed and the average particle diameter is changed in a width of >=20% the maximum value in one cycle will not occur.
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