Abstract Summary (Max 250 words)
Crystallisation is widely used in the fine chemical industries to produce solid products with desired properties. Crystalline products exhibit a particle size and shape distribution, which affects downstream processing (e.g., filtration) and product quality. Designing reproducible crystallisation processes that deliver a target PSSD is therefore critical. In practice, non-uniform mixing and spatial heterogeneities in hydrodynamic properties, such as energy dissipation rate, can influence crystallisation. While coupled CFD–population balance models have been developed to explore these effects computationally, systematically derived experimental datasets for quantifying the effect in reality and model validation remain limited. This study examines mixing effects in seeded batch cooling crystallisation through experimental investigation. Unlike conventional studies that focus primarily on particle size distributions (PSD), this work quantifies the evolution of particle size and shape distributions (PSSD) under varying hydrodynamic conditions. Experiments are performed in stirred tank crystallisers of different scale and geometry, with impeller speed and suspension density systematically varied. PSSDs are measured using imaging-based characterization devices and population dynamics are probed at different locations through focused beam reflectance measurement (FBRM). Spatial variations in solute concentration are quantified through local sampling, using ATR-FTIR spectroscopy, and gravimetry. Additionally, local suspension density, impeller-shaft torque (for power input), and slurry viscosity are measured. Reproducibility and scalability are assessed by comparing crystallisation behaviour and product properties across scales using defined scale-up criteria. The experimental insights provide a quantitative basis for understanding how hydrodynamics govern crystallisation outcomes and aid the digital design of reproducible and scalable crystallisation processes.
