Continuous crystallization is a widely viewed topic as it has many advantages in industrial production. However, it is very resource intensive and time-consuming to determine operation conditions through trial and error. Computer simulation appears to an effective method in continuous crystallization design. The continuous cooling crystallization of paracetamol in a 5 L crystallizer was modeled to investigate the effect of mixing on the particle size distribution (PSD). A novel coupled computational fluid dynamics–population balance equation (CFD–PBE) simulation was developed in which the PBE was discretized using a high-resolution central scheme and solved simultaneously with CFD equations in ANSYS FLUENT 15.0 utilizing user-defined scalars. The influences of both internal grid and external (spatial) grid on the final PSD were studied, and an appropriate grid was chosen. The spatial distribution of velocity, temperature, slurry density, and nucleation rate were simulated. The continuous cooling crystallization under different stirrer speeds, bath temperatures, and residence times was investigated. It was found that (a) higher stirrer speeds lead to uniform distribution but smaller PSD, and (b) as the average temperature gets higher, or the residence time gets longer, the influence of mixing on final PSD gets smaller.

中文翻译：

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混合对对乙酰氨基酚连续冷却结晶产物粒度分布的影响（使用计算流体力学-人口平衡方程模拟）

连续结晶是一个广受关注的话题，因为它在工业生产中具有许多优势。但是，通过反复试验来确定操作条件是非常耗费资源和时间的。计算机仿真似乎是连续结晶设计中的一种有效方法。对乙酰氨基酚在5 L结晶器中的连续冷却结晶进行建模，以研究混合对粒度分布（PSD）的影响。开发了一种新颖的耦合计算流体动力学-人口平衡方程（CFD-PBE）仿真，其中使用高分辨率中心方案离散化了PBE，并使用用户定义的标量在ANSYS FLUENT 15.0中与CFD方程同时求解。研究了内部网格和外部（空间）网格对最终PSD的影响，并选择了合适的网格。模拟了速度，温度，浆液密度和成核速率的空间分布。研究了不同搅拌速度，浴温和停留时间下的连续冷却结晶。结果发现：（a）较高的搅拌速度可导致均匀分布，但PSD较小；（b）随着平均温度升高或停留时间变长，混合对最终PSD的影响会变小。