Abstract
The antisolvent crystallization of sodium chloride was carried out in batches to observe crystallization phenomena using ethanol as an antisolvent. Generally, antisolvent crystallization produces fine, variously shaped agglomerated crystals, because of the high supersaturation produced by the addition of antisolvent in the local area of the inlet region. The authors have proposed a new idea to relieve high bulk supersaturation through the operational conditions of high ethanol concentration. The obtained crystals seemed to be unagglomerated and monodispersed in the optimum range of ethanol concentration. Based on the observation of crystallization phenomena, it was considered that nucleation induced by antisolvent addition would occur at the local supersaturation level produced on the interface between starting solution and feed solutions. On the other hand, crystal growth would proceed at the supersaturation level produced by sufficient mixing of feed solution and starting solutions. The number of crystals produced increased with increasing relative initial supersaturation ratio σn Average crystal size increased with increasing operational supersaturation ratio σg. The induction time was influenced by both relative initial supersaturation ratio and operational supersaturation ratio. Since the number of crystals depended on the relative initial supersaturation ratio, nucleation was believed to be influenced by local mixing.
