Ye Xin, Chu Dongyuan, Lou Yaoyin, Ye Zhi-Long, Wang Ming Kuang, Chen Shaohua
Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China.
Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China; College of the Environment and Ecology, Xiamen University, Xiamen 361102, China.
J Environ Sci (China). 2017 Jul;57:391-401. doi: 10.1016/j.jes.2016.11.019. Epub 2016 Dec 30.
Phosphorus recovery in the form of struvite has been aroused in recent decades for its dual advantages in eutrophication control and resource protection. The usage of the struvite products is normally determined by the size which is largely depended on the hydrodynamics. In this study, flow behavior of struvite pellets was simulated by means of Eulerian-Eulerian two-fluid model combining with kinetic theory of granular flow in a liquid-solid fluidized bed reactor (FBR). A parametric study including the mesh size, time step, discretization strategy, turbulent model and drag model was first developed, followed by the evaluations of crucial operational conditions, particle characteristics and reactor shapes. The results showed that a cold model with the mesh resolution of 16×240, default time step of 0.001sec and first order discretization scheme was accurate enough to describe the fluidization. The struvite holdup profile using Syamlal-O'Brien drag model was best fitted to the experimental data as compared with other drag models and the empirical Richardson-Zaki equation. Regarding the model evaluation, it showed that liquid velocity and particle size played important roles on both solid holdups and velocities. The reactor diameter only influenced the solid velocity while the static bed height almost took no effect. These results are direct and can be applied to guide the operation and process control of the struvite fluidization. Moreover, the model parameters can also be used as the basic settings in further crystallization simulations.
近几十年来，以鸟粪石形式回收磷因其在控制富营养化和资源保护方面的双重优势而受到关注。鸟粪石产品的用途通常由其尺寸决定，而尺寸在很大程度上取决于流体动力学。在本研究中，采用欧拉 - 欧拉双流体模型结合颗粒流动力学理论，在液 - 固流化床反应器（FBR）中模拟了鸟粪石颗粒的流动行为。首先开展了包括网格尺寸、时间步长、离散化策略、湍流模型和曳力模型的参数研究，随后评估了关键操作条件、颗粒特性和反应器形状。结果表明，网格分辨率为16×240、默认时间步长为0.001秒且采用一阶离散化方案的冷态模型足以准确描述流化过程。与其他曳力模型和经验性的理查森 - 扎基方程相比，使用Syamlal - O'Brien曳力模型得到的鸟粪石持留分布与实验数据拟合得最好。关于模型评估，结果表明液体速度和颗粒尺寸对固体持留量和速度都起着重要作用。反应器直径仅影响固体速度，而静止床层高度几乎没有影响。这些结果具有直接指导意义，可用于指导鸟粪石流化的操作和过程控制。此外，模型参数还可作为进一步结晶模拟的基本设置。
