| 摘要 |
PROBLEM TO BE SOLVED: To provide a crystallization method which allows crystal of a raw material to be obtained with high productivity from a liquid containing the raw material.SOLUTION: In a crystallization method: a liquid (A) containing a raw material is indirectly cooled by a heating medium (X) 16 via a cooling surface 10a of a crystallizer to serve as a suspension (B) 14 containing crystal of the raw material in a crystallization operation; the heating medium (X) 16 is switched to a heating medium (Y) having higher temperature than the heating medium (X) in the middle of the crystallization operation, and then the crystallization operation is interrupted; a melting operation for removing scale 12 attached to the cooling surface 10a is carried out by melting at least a boundary surface of the cooling surface 10a and the scale 12 out of the scale 12 attached to the cooling surface 10a by the heating medium (Y), without increasing temperature of the suspension (B) 14 containing the crystal of the raw material by 2°C or more compared to the temperature immediately before the interruption of the crystallization operation; and thereafter, the heating medium (Y) is switched to a heating medium (Z) (the heating medium (X) 16) having lower temperature than the heating medium (Y) and then the crystallization operation is re-started. |
