A key enabler for
the future success of continuous manufacturing
in pharmaceutical and fine chemical production processes is the control
of product quality. Since approx. 90% of all small molecular active
pharmaceutical ingredients produced involve a crystallization step,
a holistic view on its process chain is crucial in order to ensure
a defined particle size distribution, high purity, and specific polymorphic
form. Different concepts for small-scale continuous crystallization
are available, improving the product qualities in comparison to batch.
Continuous solid–liquid separations, on the other hand, are
rather scarce. Therefore, we designed and characterized an innovative
continuous vacuum screw filter (CVSF) for solid–liquid separation,
washing, and drying of suspensions in a small scale (up to 10 g of
solid per minute). This contribution shows the general working principle
of the CVSF as well as a systematic investigation of varying operating
parameters on the particle size distribution (PSD), residual moisture,
and residence time distribution of the solid phase. As a model system, l-alanine/water is used. The results show that the PSD can be
entirely maintained while ensuring a narrow residence time distribution
of the solid phase with axial dispersion numbers between 18.7 and
76.2. The residual moisture is for all experiments in a good range
of 20–25%. Furthermore, it could be shown that the operability
is possible over 8 h. Summarizing, the modular setup of the CVSF offers
a maximized flexibility and thus rapid adaptability to changing market
demands and product requirements.