Contact Secondary Nucleation as a Means of Creating Seeds for Continuous Tubular Crystallizers

Abstract

The control of crystal size of any crystallization process is especially important in the pharmaceutical industry where small sizes are often desired. Seeding is often used as a method of controlling crystal size and suppressing primary nucleation in batch processes. The continuous mixed suspension mixed product removal crystallizers are self-seeded; however, crystal attrition and contact secondary nucleation due to crystal interaction with the impeller influence the crystal size. In this study, a nuclei generation device (nucleator) employing contact secondary nucleation is described. The nucleator consists of a “crossed” flow tube with four openings. Two of the openings are the inlet of supersaturated solution and the outlet of crystal slurry, respectively. The other two openings are for contact nucleation, where the parent crystal comes into contact with a platform under an applied stress. The rate of nucleation and the size of the crystals generated can be controlled by supersaturation (S = c/cs) and ...