Development of an Archimedes Tube Crystallizer for Small-Scale Continuous Cooling Crystallization
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Beschreibung
In the pharmaceutical and fine chemical industry with production rates smaller than 1 t/a, continuous processing offers benefits regarding product consistency due to the achievement of a steady state. Especially in this field, high requirements on product quality need to be fulfilled. In particular, current researchers focus on achieving a narrow particle size distribution (PSD) with a pre-defined median particle size d50.
A promising concept regarding the stated aims is the Archimedes Tube Crystallizer (ATC). Based on the Archimedes screw principle, individual fluid batches are moved through the apparatus by rotation. For continuous cooling crystallization, the ATC consists of two rotating elements: an inlet tank designed to feed the apparatus with segmented liquid-gas flow and tempered coiled tubing for the characteristic Archimedes part. The development consists of four steps: First, an operable ATC design is realized. Second, ideal plug flow behavior of liquid and solid phase is proven in characterization experiments. Third, a flow map is set up based on experiments and CFD simulations, with which the qualitative suspension state in the ATC can be predicted. Finally, sensitivity analysis and optimization based on a first-principle model are used to set up tube-in-tube cooling. Validation experiments regarding temperature profile prove the high accuracy of the simulations. Seeded cooling crystallizations conducted are highly reproducible and suggest a close link between product particle size distribution and qualitative crystal suspension state.
Overall, the ATC’s proven ideal plug flow leads to precise crystal growth times that are flexibly adjustable due to elimination of tube length limitation by pressure loss. Thus, together with the prediction of qualitative suspension state by flow map, it is demonstrated that the ATC developed is applicable for successful PSD control in continuous cooling crystallization.
Autor*in
Jana Maria Sonnenschein
Themen in »Development of an Archimedes Tube Crystallizer for Small-Scale Continuous Cooling Crystallization«
Continuous crystallization Cooling crystallization Model-based design