CFD-PBE-PBE simulation of an airlift loop crystallizer
CFD-PBE-PBE simulation of an airlift loop crystallizer
复制标题
气升式环路结晶器的 CFD-PBE-PBE 模拟
DOI：
10.1002/cjce.23086
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发表时间：
2018
期刊：
影响因子：
--
通讯作者：
Mao Zai-Sha
中科院分区：
文献类型：
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作者：
Li Qian;Cheng Jingcai;Yang Chao;Mao Zai-Sha
在这项工作中，我们在 OpenFOAM（开源现场操作和操作）中开发了一个用于气升环路结晶器中结晶过程的完整求解器（CFD-PBE-PBE）。它将计算流体动力学 (CFD) 与气泡和晶体的总体平衡方程 (PBE) 相结合。求解器中还包含气液传质和化学反应模型。描述气泡合并和破裂的 PBE 通过单元平均法求解。在描述结晶过程的 PBE 中考虑了一次成核、二次成核和颗粒生长。该求解器通过 CO2 与 Ca(OH)2 溶液在气升式反应器中反应形成碳酸钙进行了验证。系统地研究了化学增强因子和结晶动力学对预测的影响。当使用适当的结晶动力学时，预测的 pH 值、Ca2+ 浓度、平均粒径和晶体尺寸分布 (CSD) 随时间的变化与已发表的实验数据定性和半定量一致。进一步对初始浓度和表观气速等操作参数的影响进行了数值检验。空塔气速的增加导致 OH- 和 Ca2+ 的消耗率增加，而在当前的模拟中颗粒直径似乎没有变化。反应物初始浓度越高，颗粒直径越小，CSD 越窄。预测结果表明所开发的求解器是可行的，可用于气升环路结晶器的设计和放大。
A complete solver (CFD‐PBE‐PBE) for crystallization processes in an airlift loop crystallizer is developed in OpenFOAM (open‐source field operation and manipulation) in this work. It combines computational fluid dynamics (CFD) with population balance equations (PBE) for both gas bubbles and crystals. Models for gas‐liquid mass transfer and chemical reaction are included as well in the solver. PBE describing bubble coalescence and breakage is solved by the cell average method. Primary nucleation, secondary nucleation, and particle growth are considered in the PBE describing the crystallization process. The solver is validated with the formation of calcium carbonate via the reaction of CO2with Ca(OH)2solution in an airlift reactor. Effects of the chemical enhancement factor and crystallization kinetics on predictions are systematically investigated. Variation of predicted pH value, concentration of Ca2+, mean particle size, and crystal size distribution (CSD) with time is in qualitative and semi‐quantitative agreement with the published experimental data, when the appropriate crystallization kinetics are used. Effects of operation parameters such as initial concentration and superficial gas velocity are further numerically examined. The increase in superficial gas velocity results in the increasing consumption rates of OH‐and Ca2+, while the particle diameter seems unchanged in the present simulation. A higher initial concentration of reactants will lead to a smaller particle diameter and a narrower CSD. The predicted results indicate that the developed solver is feasible, and can be used for the design and scale‐up of airlift loop crystallizers.