Digital Design of Batch Cooling Crystallization Processes: Computational Fluid Dynamics Methodology for Modeling Free-Surface Hydrodynamics in Agitated Crystallizers
Digital Design of Batch Cooling Crystallization Processes: Computational Fluid Dynamics Methodology for Modeling Free-Surface Hydrodynamics in Agitated Crystallizers
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DOI：
10.1021/acs.oprd.0c00240
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发表时间：
2020-11-20
影响因子：
3.4
通讯作者：
Roberts, Kevin J.
中科院分区：
文献类型：
--
作者：
Corzo, Diana M. Camacho;Ma, Cai Y.;Roberts, Kevin J.
间歇冷却结晶过程的数字化设计的框架，提出了包括三个阶段，这是基于不同程度的过程复杂性，结晶器流体动力学与结晶动力学，从而与预期的晶体尺寸分布相结合。在第一阶段的框架，计算流体动力学方法的开发，以准确地评估流体动力学在一个典型的分批结晶器配置，包括一个20 L规模的碟底容器与一个单一的beavertail挡板搅拌的后退曲线叶轮，用于制药以及在精细化工行业。具有这种配置的结晶器的流体力学特征是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非常重要。预测的平均速度分量与使用激光多普勒风速仪的实验测量结果的比较表明，改进的预测，获得使用差分的湍流应力输运模型与VoF的建模的气-液界面相比，使用剪切应力输运模型，并与平坦的液体表面。这项研究表明，一个准确的处理液体的自由表面捕获涡流的形成是必不可少的可靠预测的结晶器的流场。虽然涡流深度预计将随着叶轮雷诺数的增加而增加，但流体动力学宏观参数（包括功率数、叶轮流量数和二次循环流量数）对雷诺数的依赖性表明，它们在湍流状态下基本上是恒定的，但当流体粘度增加时，流动处于过渡和层流状态时会发生波动。
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.