Digital Design of Batch Cooling Crystallization Processes: Computational Fluid Dynamics Methodology for Modeling Free-Surface Hydrodynamics in Agitated Crystallizers,Organic Process Research & Development

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Digital Design of Batch Cooling Crystallization Processes: Computational Fluid Dynamics Methodology for Modeling Free-Surface Hydrodynamics in Agitated Crystallizers
Organic Process Research & Development ( IF 3.1 ) Pub Date : 2020-08-06 , DOI: 10.1021/acs.oprd.0c00240
Diana M. Camacho Corzo ₁ , Cai Y. Ma ₁ , Tariq Mahmud ₁ , Kevin J. Roberts ₁

Affiliation

A framework for the digital design of batch cooling crystallization processes is presented comprising three stages, which are based on different levels of process complexity, integrating crystallizer hydrodynamics with crystallization kinetics and consequently with expected crystal size distribution. In the first stage of the framework, a computational fluid dynamics methodology is developed to accurately assess hydrodynamics in a typical batch crystallizer configuration, comprising a 20 L scale dish-bottom vessel with a single beavertail baffle agitated by a retreat curve impeller, used in the pharmaceutical as well as in the fine chemical industries. The hydrodynamics of crystallizers with such configurations is characterized by vortex formation on the free liquid surface. It is therefore important to model the free surface using the Volume-of-Fluid (VoF) method. Comparison of the predicted mean velocity components with experimental measurements using laser Doppler anemometry reveals that improved predictions are obtained using a differential Reynolds-stress transport model for turbulence coupled with the VoF for modeling the gas-liquid interface compared with those using the Shear-stress transport model and with a flat liquid surface. This study demonstrates that an accurate treatment of the liquid free surface for capturing vortex formation is essential for reliable predictions of the crystallizer’s flow field. While the vortex depth is predicted to increase with increasing impeller Reynolds number, the dependence of hydrodynamic macroparameters, including power number, impeller flow number, and secondary circulation flow number, on Reynolds number reveals that they are essentially constant within the turbulent regime but fluctuate when the flow is in the transitional and laminar regimes as fluid viscosity increases.

中文翻译：

间歇冷却结晶过程的数字化设计：用于模拟结晶器中自由表面流体动力学的计算流体动力学方法

提出了分批冷却结晶过程数字设计的框架，该框架包括三个阶段，这三个阶段基于不同级别的过程复杂性，将结晶器的流体动力学与结晶动力学相结合，从而具有预期的晶体尺寸分布。在框架的第一阶段，开发了一种计算流体动力学方法，以准确评估典型批量结晶器配置中的流体动力学，该结构包括一个20 L规模的皿底容器，该容器具有一个由后倾曲线叶轮搅动的单个海狸尾挡板，制药以及精细化工行业。具有这种构造的结晶器的流体动力学特征在于在自由液体表面上形成涡流。因此，使用流体体积（VoF）方法对自由表面进行建模很重要。将预测的平均速度分量与使用激光多普勒风速计的实验测量结果进行比较表明，与使用剪切应力传输的那些相比，使用湍流的差分雷诺应力传输模型和用于对气液界面建模的VoF可以得到改进的预测型号，液体表面平坦。这项研究表明，对无液表面进行精确处理以捕获涡流对可靠预测结晶器的流场至关重要。虽然预计涡旋深度会随着叶轮雷诺数的增加而增加，但流体力学宏参数的依赖性包括功率数，叶轮流量，

更新日期：2020-08-06

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