Particle Size Distribution and yield control in continuous Plug Flow Crystallizers with recycle

• Plug-Flow Crystallizer with recycle and adjustable extraction position is modeled and simulated.
• The modality of the Particle Size Distribution can be controlled by changing the recycle ratio and the extraction position along the axis of the PFC.
• The yield of the process can be enhanced by changing the recycle ratio and the extraction position along the axis of the PFC.

Plug Flow Crystallizers (PFCs) are one of the most widely employed forms of continuous crystallizers. PFCs are usually selected for processes with fast kinetics and short residence times. One key limitation of PFCs is that normally they do not operate at equilibrium conditions as a consequence of the short residence times. Thus, the resultant yield from PFCs is generally less than that of the equivalent batch process.Recycling the mother liquor back through the PFC is one approach, which can potentially be used in order to mitigate against this drawback, allowing for an amelioration in the continuous process yield.In the present work, the effects of introducing a recycle stream and adjusting critical recycling parameters, namely recycling ratio and axial extraction position, on an idealized PFC are examined. Particular attention is focused on the resultant volume average size of particles d4,3, and the process yield η. The influence of feed velocity along with the recycle parameters on the maximum and minimum yield and size of crystals achievable is also investigated.The proposed continuous PFC, as conceptualized and modeled with recycle, facilitates practical application in an industrial setting, allowing for augmented continuous process yields, whilst furthermore facilitating PSD control.