Risk-Based Operation of a Continuous Mixed-Suspension-Mixed-Product-Removal Antisolvent Crystallization Process for Polymorphic Control

Innovations in the continuous crystallization field are required for the pharmaceutical industry to go through the paradigm shift from batch to continuous processing. To do so, different risks associated with the continuous crystallization have to be identified and discussed. In this work, a continuous antisolvent crystallization of the model compound indomethacin (IMC) from a ternary solvent system in a mixed-suspension-mixed-product-removal (MSMPR) to produce the desired polymorphic gamma-form is evaluated, and potential risks for process failure are identified. One of the main risks identified with the continuous crystallization is gaining a balance between the inlet and outlet flows. Two novel and different level controls are proposed in this work to overcome this risk, an ultrasonic sensor and image analysis based on a video recording of the level. These two methods demonstrate improved process robustness upon implementation. Additionally, different process parameters were investigated and showed that the seed load has a significant effect on maintaining the desired polymorph and avoiding process failure. To the best of our knowledge, this is the first study on continuous crystallization of IMC for the polymorphic control of gamma-IMC.