(550b) Crystallization Technology Using Taylor Vortex Fluid Motion

The crystallization is a phenomenon that a crystalline solid of solute is formed out of the solute-dissolved solution or gas via nucleation and growth under a supersaturated condition. Thus, the crystallization technology is frequently used for the separation/purification and particle/powder processes in wide areas of industries. In my lab for the last two decades, the principles of the crystallization have been intensively investigated for their applications to the separation of chiral isomers, purification of the bio-products, polymorphs and phase transformation of the active pharmaceutical ingredients, synthesis of nano-particles etc. Among those, new crystallization technology using the Taylor vortex fluid motion has been the hottest subject for the last two decades.

The Taylor vortex fluid motion is induced in the gap between two co-axial cylinders when rotating the inner cylinder. Even though this fluid motion was found over 100 years ago, its application to the crystallization was first attempted in my lab to the gas(CO₂)-liquid(Ca(OH)₂) reaction crystallization of calcium carbonate twenty year ago. In this study, it was found that the mass transfer rate at the gas-liquid interface in the Taylor vortex fluid motion was 3-4 times faster than that in the random eddy fluid motion, producing the nano-size spindle calcite particles in the Taylor vortex crystallizer. In the anti-solvent crystallization of guanosine mono-phosphate, the Taylor vortex crystallizer in continuous mode demonstrated the 100 times in crystal productivity over conventional crystallizer in the batch mode. In addition, the periodic Taylor vortex aligned the solute molecules in the solution, resulting in the polymorphic nucleation of stable form of the sulfamerazine, which was not possible in the random eddy flow. Further, the high flexibility in operation of the Taylor vortex crystallizer such as distributive feeding strategy and temperature gradient technique was developed for the high crystal productivity and the narrow crystal size distribution. By the study for two decades, the high applicability of the Taylor vortex to the crystallization technology in variety of the material processing was demonstrated in my lab.