Application of shear stress-based scale-down approaches for crystallizer design and optimization

초록

The crystallization process is a key purification technology where the final product's Particle Size Distribution (PSD) directly impacts quality and efficiency. While 60 L pilot-scale optimization is actively pursued to reduce costs, reliably applying these results to the plant scale remains limited due to hydrodynamic mismatches. Specifically, crystal breakage is highly sensitive to shear stress induced by agitation and circulation, challenging the reproducibility of the final PSD. This study aimed to establish hydrodynamic equivalence between a plant-scale forced-circulation crystallizer and a 60 L pilot-scale stirred crystallizer using CFD simulations. A 3D CFD analysis of the plant system was performed to quantify the volume-averaged shear stress and flow characteristics, serving as key scale-down indicators. Subsequently, the structural design (e.g., baffles, dual impellers, HSM) and agitation conditions of the lab-scale crystallizer were systematically adjusted to replicate the plant's shear stress environment. CFD simulation results confirmed that the proposed design reproduced the volume-weighted shear stress distribution of the plant-scale system in both mean value and overall distributional shape, providing a quantitative basis for addressing scale-induced hydrodynamic mismatches. In conclusion, a scale-down approach utilizing quantitative CFD-derived hydrodynamic indicators provides a practical framework for establishing hydrodynamic equivalence across scales. This methodology contributes to bridging laboratory and plant data, facilitating efficient process optimization across various hydrodynamically sensitive processes.

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