Encrustation in Continuous Pharmaceutical Crystallization Processes-A Review

Encrustation is a risk factor that can cause product and process failure in continuous crystallization processes. Mitigation, prevention, and control of encrustation have been extensively researched. Various risk mitigation strategies proposed in the literature, such as coating of crystallizer walls, use of additives to control encrustation kinetics, and periodic steady-state operation show promising results in delaying or preventing encrustation. Because of the increased interest in the use of continuous crystallization in industrial applications, it is important to understand this risk factor further. This review presents recent developments on dynamic models, mechanisms, and risk factors for encrustation in continuous crystallization processes. Various design and control strategies to mitigate the encrustation risk are also summarized. Appropriate control strategies should be implemented during continuous crystallization to avoid the impact of encrustation on drug substance quality.