Scale-up of high shear mixer-granulator based on discrete element analysis
Scale-up of high shear mixer-granulator based on discrete element analysis
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DOI：
10.1016/j.powtec.2012.03.009
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发表时间：
2013-02
影响因子：
5.2
通讯作者：
Hideya Nakamura;H. Fujii;S. Watano
中科院分区：
文献类型：
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作者：
Hideya Nakamura;H. Fujii;S. Watano
为了开发一种基于颗粒行为的运动学和动力学相似性的放大方法，采用三维离散元法（DEM）模拟了不同容器尺寸（2 - 112 L）的商业高剪切混合器中颗粒的运动。分析了容器尺寸对颗粒内部流动和碰撞能量的影响。结果表明，在桨尖速度不变的情况下，不同的容器尺寸下，内部颗粒剪切流的大小基本保持不变。这意味着，在放大高剪切混合器时，应采用恒定的桨尖速度来实现运动相似。然而，在恒定的桨尖速度下，单位时间内的累积颗粒碰撞能量显着降低与容器尺寸的增加。这表明，为了实现动力学相似性，应调整制粒时间，以便在不同的容器尺寸下保持制粒时间内的累积颗粒碰撞能量。基于模拟结果，我们提出了一种放大的方法，其中可以确定最佳造粒时间，以实现相同的累积颗粒碰撞能量在不同的容器尺寸，同时保持相同的叶轮尖端速度。该方法可以提供不同血管尺寸之间的运动学和动力学相似性。通过使用具有不同容器尺寸（2至216 L）的商业高剪切混合器的湿法制粒实验证实了所提出的放大方法的有效性。
For developing a scale-up method based on the kinematic and dynamic similarities of particle behavior, motion of particles in a commercial high shear mixer-granulator with different vessel sizes (2 to 112L) were simulated using a three-dimensional discrete element method (DEM). Effects of the vessel size on the internal particle flow and the particle collision energy were analyzed. It was found that under the constant impeller tip speed magnitude of the internal particle shear flow can be nearly maintained at different vessel sizes. This implies that the constant impeller tip speed should be employed to achieve the kinematic similarity when scaling-up the high shear mixer-granulator. However, under the constant impeller tip speed the cumulative particle collision energy per unit time significantly decreased with an increase in the vessel size. This suggests that in order to achieve the dynamic similarity the granulation time should be adjusted so that the cumulative particle collision energy over the granulation time can be maintained at different vessel sizes. Based on the simulation results, we proposed a scale-up method in which the optimal granulation time can be determined to achieve the same cumulative particle collision energy at different vessel sizes while maintaining the same impeller tip speed. This method can provide both the kinematic and dynamic similarities between different vessel sizes. Validity of the proposed scale-up method was confirmed by an experiment of wet-granulation using a commercial high shear mixer-granulator with different vessel sizes (2 to 216L).