Abstract
In order to clarify the relationship between the conditions of crystallization and the characteristics of solid-liquid separation in a batch crystallization process, the anti-solvent crystallization was conducted for various conditions, and subsequently dead-end filtration of the produced crystal suspensions was carried out under constant pressure. Glycine, a type of amino acid, was used as a target material, and methanol and ethanol were used as the anti-solvents. In addition to determining the size distributions of produced crystals by a laser granulometer, the photomicrographs of them were observed directly using a digital microscope. The experimental data clearly demonstrated that the filtration properties of glycine crystal suspensions were strongly affected by the crystallization conditions. Ethanol produced the large crystals compared to methanol, and consequently led to the high filterability. The glycine crystals became smaller and the specific filtration resistance of the filter cake consisting of glycine crystals became larger with an increase of the anti-solvent concentration in either case of methanol or ethanol. Moreover, the glycine crystal suspensions with higher filterability were produced by adding the anti-solvent to the glycine solution than by adding the glycine solution to the anti-solvent. And also, the slow addition of the anti-solvent achieved a higher filterability than the instantaneous addition. It was also found that the filter cake of the glycine crystal was moderately compressible and the filtration rate increased with an increase of the applied pressure.
