Numerical simulation of film coating process in a novel rotating fluidized bed
Numerical simulation of film coating process in a novel rotating fluidized bed
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DOI：
10.1248/cpb.54.839
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发表时间：
2006-06-01
影响因子：
1.7
通讯作者：
Watano, Satoru
中科院分区：
文献类型：
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作者：
Nakamura, Hideya;Iwasaki, Tomohiro;Watano, Satoru
本文采用离散元法(DEM)-计算流体动力学（CFD）耦合模型对新型旋转流化床（RFB）膜层覆膜过程进行了数值模拟。在三维柱面坐标系下对离心力场中的粒子运动和流体运动进行了模拟，并将该模型应用于薄膜涂覆过程。采用简化的假设，即只有在喷射区域内存在粒子时才会有粒子被涂覆，对RFB中的薄膜涂覆过程进行了数值分析。并进行了实验，通过观察涂层颗粒的色差来评价喷涂材料的均匀性。数值模拟结果可以很好地模拟三维气泡运动和颗粒循环。此外，利用本文提出的模型，还可以直观地显示PFB中单个颗粒上喷射物质的质量。分析了喷涂材料的分布与喷涂时间的关系。计算得到的喷淋材料的质量分布可以用正态分布函数表示，与前人的研究结果在定性上一致。采用数值和实验两种方法研究了气体速度和离心加速度等操作参数对喷射材料均匀性的影响。通过数值模拟对RFB与常规流化床的包覆过程进行了比较。结果表明，由于循环时间大大缩短，在RFB内喷涂材料的均匀性大大提高。
In this study, numerical simulation of film coating process in a novel rotating fluidized bed (RFB) was conducted by using a Discrete Element Method (DEM)-Computational Fluid Dynamics (CFD) coupling model. Particle movements and fluid motions in a centrifugal force field were simulated at three-dimensional cylindrical coordinate, and this model was applied to film coating process. Film coating process in a RFB was numerically analyzed by using a simplified assumption that a particle was coated only when a particle existed within a spray zone. The experiments were also conducted and uniformity of sprayed material was evaluated by investigating color difference of the coated particles. As a result of the numerical simulation, three-dimensional bubble movements and particle circulation could be well simulated. In addition, mass of the sprayed material on a single particle in a PFB could be visualized by using our proposed model. The relationship between distribution of the sprayed material and the coating time was also analyzed. Calculated mass distributions of the sprayed material could be expressed by a normal distribution function, showing qualitative good agreement with the previous studies. Effect of the operating parameters, such as gas velocity and centrifugal acceleration, on the uniformity of the sprayed material was also investigated by both numerical and experimental approaches. Comparison of the coating process in a RFB with that in a conventional fluidized bed was also conducted by the numerical simulation. The result showed that uniformity of the sprayed material was greatly improved in a RFB due to the much smaller circulation time.