(610d) Polymorph Selection in Continuous Crystallizers in the Presence of Wet Milling
In this contribution, we are expanding on this previous works and consider the case where wet milling is used to tune the particle size distribution and potentially alter the polymorphic outcome. We thus present a mathematical model of continuous crystallization with wet milling for polymorphic systems. The model relies on one-dimensional population balance equations including breakage terms. Making the process model dimensionless, we identified a surprisingly small number of additional dimensionless groups that describe the process outcome in terms of polymorphic form when breakage is present. The resulting model is solved using a finite volume scheme (FVS)5. Operating regions where the metastable/stable polymorph can reliably be obtained can again be identified. In comparison to the work by Farmer et al.4, we show that the operating region where the metastable/stable polymorph is obtained can be enlarged by tuning key dimensionless numbers in the breakage kinetics. We combine this type of analysis with an investigation of the productivity of such systems and report regions of attainable particle sizes4,5
We show that introduction of a wet suspension mill therefore represents an attractive way to obtain the desired polymorph even if the underlying kinetics of nucleation and growth are disadvantageous. Apart from this finding, we show that introducing breakage increases process productivity and allows to tune particle size more extensively.
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