Strategies for managing clogging and encrustation in compact continuous crystallizers: Anti-solvent crystallization of paracetamol with fluidic oscillator and helical coil

The operation and effectiveness of continuous crystallizers are often hindered by clogging and encrustation. This becomes particularly important for crystallizers without any moving parts – such as fluidic oscillators (FO), helical coils (HC). In this work, we have investigated the occurrence of clogging and encrustation phenomena during the anti-solvent crystallization of paracetamol with a FO and HC as continuous crystallizers. The onset of clogging was identified via visual observation as well as via pressure sensor and PAT tools like the FBRM probe. Different ways for eliminating or at least delaying onset of clogging and encrustation such as the use of additives, loop configuration, external vibratory motors, and gas injection were experimentally investigated. Computational fluid dynamics (CFD) models of FO were used to simulate solid–liquid flow with and without gas injection. The simulated results were used to identify potential locations of particle clogging and to develop mitigation strategies. The experimental and simulated results were analyzed to develop strategies to mitigate clogging and thereby demonstrate the operation of the continuous crystallizer without clogging for 20 to 120 times of the residence time for different operating supersaturation levels. The presented results and analysis will be useful for several applications based on compact fluidic devices and narrow channels handling solid particles.