抄録
The WWDJ-batch crystallizer is a newly developed batch crystallizer and equipped with a double-deck jacket and a slurry sprinkler, known as Wall WetterTM, that is specially designed for agitating the solution or slurry and sprinkling it on the wall of the crystallizer headspace which is covered by the upper heating jacket. When the slurry is sprinkled to the upper heating wall, fine crystals are dissolved, and consequently, the large crystals with a narrow CSD can be produced. Cooling rate can be precisely controlled based on the three operational parameters, namely the upper and lower jacket temperatures and the rotation speed of the Wall Wetter (the circulation speed of slurry). In this work, we crystallized glycine using the WWDJ crystallizer to show its advantage on the production of large crystals with a high purity and a desired polymorphism.
The 50 % value of the cumulative crystal size distribution of the obtained glycine crystals was 950 µm by WWDJ crystallizer, compared with 480 µm in a crystallization experiment not using the Wall Wetter. Glycine has three crystal polymorphs, namely α-, β and γ-form. When the conventional crystallizer was used, the unstable α-form crystals were always obtained. However, when the WWDJ batch crystallizer was used, the stable γ-form crystals were obtained, and the appearance of polymorphs depended on the cooling rate during the crystallization. Furthermore, glycine was crystallized from the aqueous solution including L-leucine as an impurity. In the WWDJ crystallizer, only 0.52 µg of L-leucine was contaminated in the glycine crystals of 1 mg, while it was 0.75 µg in conventional crystallizer. Therefore, the contamination was reduced about 45% using WWDJ crystallizer. These results shows that the WWDJ batch crystallizer has advantage to control the CSD, purity and crystal polymorphism.
