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Air–Liquid Segmented Continuous Crystallization Process Optimization of the Flow Field, Growth Rate, and Size Distribution of Crystals

Su, Min, Gao, Yanyan
Industrial & engineering chemistry process design and development 2018 v.57 no.10 pp. 3781-3791
Reynolds number, crystallization, crystals, hydrodynamics, hydrophobicity, models, process design
The continuous crystallization behavior of an air–liquid segmented tubular crystallization process was investigated using glycine as a model compound. Process parameters such as aspect ratio of the liquid slug, Reynolds number, seed loading, tubing material, slug shape, and tube crystallizer arrangement were optimized experimentally for their effect on the growth rate, size distribution, and morphology of the produced crystals. An Eulerian liquid–solid two-phase model coupled with a realizable k−ε model in a computational fluid dynamics platform was also used to simulate the suspension state and the flow trajectory of crystals in a liquid slug. The results of our study indicated that a uniform crystal size benefiting from a heightened flow dynamics of crystals can be achieved under the following conditions: a slug aspect ratio of 1:1, 2 wt % seed loading, a Reynolds number higher than 22.87, a tubing material with highly hydrophobic properties and a resulted highly spherical slug shape. The growth rate of crystals was the highest when the slug aspect ratio of the slug was 1:1. The horizontal arrangement of the crystallizer has a more homogeneous slug velocity and crystal velocity in slug though the crystal growth rate and crystal size were not significantly affected by different arrangements. These results give an insight into the air–liquid segmented tubular continuous crystallization process.