Control of Crystal Size Distribution Using a mL-Scale Continuous Crystallizer Equipped with a High Speed Agitator

概要

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A mL-scale continuous crystallizer was newly developed to produce small crystals with a narrow size distribution. The crystallizer was used for the poor solvent crystallization of glycine and L-alanine. The crystallizer was composed of a stainless-steel mixing vessel with an inner volume of 0.9 mL and a high-speed agitator that can agitate the crystallization solution up to 24,000 rpm. Glycine or L-alanine aqueous solution and poor solvent (methanol) were supplied into the vessel at a constant flow rate and intensely mixed by the agitator. The average residence time was set at 0.33, 3.3 and 33 sec by changing the flow rate of amino acid solution and poor solvent. The crystals obtained by the crystallizer were small and uniform in size, comparing with those obtained by a conventional beaker-scale semi-batch and continuous MSMPR type crystallizers. For example, glycine crystals having the size of one 38th times were obtained, comparing with crystals obtained by a semi batch crystallizer. The short residence time that can be attained by the present mL-scale crystallizer was advantageous for production of small crystals with a narrow size distribution. The size distribution could be further controlled by changing the mixing ratio of poor solvent.