In a classical continuous crystallization, following successful initiation via seed addition, the next major operational challenge is to manage the secondary nucleation rate such that the available surface area for crystal growth is commensurate with achieving almost complete desupersaturation within the target residence time whilst also producing crystals with the required size distribution. Typical strategies for commodity materials manufacture revolve around making large particles which are easy to isolate by filtration and washing. This is usually achieved by actively suppressing nucleation and operating at modest supersaturations with extended residence times.

1.2.1.3.1 Ultrasound-induced Nucleation Sonocrystallization is the application of ultrasound to influence crystallization processes. The most common approach may be more accurately termed “sononucleation” where ultrasound is used to trigger controlled primary nucleation. Insonation can also make a distinctive contribution by generating new particles through breakage of existing crystals (see next section on secondary nucleation) allowing operation at low supersaturation levels whilst maintaining a large population of crystals which are appropriately small for direct formulation.