Abstract: Based on computational fluid dynamics (CFD) simulation technology, this paper conducts an optimization study on the agitated crystallizer in the lactide flash crystallization process. By establishing a gas-liquid-solid three-phase Eulerian model, the effects of key parameters including inlet vapor fraction (10%~30%), impeller diameter (600~900 mm), rotational speed (80~110 r/min) and the addition of bottom-sweeping impellers on crystallizer flow field distribution were investigated systematically. Research findings indicate that maintaining the inlet vapor fraction at 20% not only prevents excessive liquid phase entrainment by the gas phase, but also ensures effective flash separation efficiency; increasing the impeller diameter to 800 mm and adding a bottom-scraping impeller can effectively reduce solid-phase deposition at the bottom; an impeller rotational speed of 90 r/min achieves uniform suspension of the solid phase. Comparative analysis between CFD simulation results and calculated value based on the empirical formula for power number shows a small deviation, confirming the reliability of the model. This research provides critical design guidance and support for the industrial scale-up of lactide crystallizers.

Key words: lactide, computational fluid dynamics (CFD), crystallizer