Analysis of fluidization and shear conditions in rotary-fluidized beds under dry and wet conditions

在本计画中，密集剪切颗粒流中的颗粒动力学，应以转子为例来描述。为此，将通过离散元法（DEM）与计算流体动力学（CFD）相结合来表征气体-颗粒流，从而将使用磁粉跟踪（MPT）来验证模拟。基于DEM的模拟的应用将提供对粒子动力学、相互作用和机械应力（例如粒子旋转、碰撞速度、力和频率）的详细了解。数学模型描述的过程和材料参数的影响，在造粒和涂层的单颗粒的动态应开发和实施的DEM。该项目的核心要素是表征的液体的存在对颗粒动力学的影响，通过实验验证的模拟。应建立和实施一个液桥模型，其中包括在垂直和斜向碰撞期间作用在润湿颗粒之间的毛细力和粘性力。MPT方法用于捕获颗粒的三维运动，是一种用于表征和监测致密颗粒流（球形和非球形颗粒）的高度创新的方法。到目前为止，稠密颗粒流中的颗粒运动可以很好地表征非常昂贵的实验装置，如正电子发射粒子跟踪（PEPT）。在这个项目中使用的MPT方法，第一次不仅可以测量粒子的速度和加速度，而且可以测量粒子的旋转，这是其他可用方法无法捕获或充分解决的。MPT的测量范围必须扩展到更小的颗粒尺寸。这将通过重新设计测量装置和改进对包括地球磁场在内的外部磁场的屏蔽来实现。应通过流化床涂层制造具有适合床颗粒物理特性的特性的标记颗粒，并用于测量。在喷雾造粒和包衣实验的基础上，从颗粒生长速率和包衣质量方面对模拟和实验研究的结果进行评价。

In this project, the particle dynamics in dense sheared granular flows should be described by taking the example of a rotor granulator. For this aim the gas-particle flow will be characterized by means of the Discrete Element Method (DEM) coupled with the Computational Fluid Dynamics (CFD), whereby the Magnetic Particle Tracking (MPT) will be used for the validation of the simulations. The application of DEM based simulations will provide a detailed insight in the particle dynamics, interactions and mechanical stresses (e.g. particle rotation, collision velocities, forces and frequencies). Mathematical models describing the influence of process and material parameters on the dynamics of single particles in the granulation and coating should be developed and implemented in the DEM. The central element of this project is the characterization of the influence of the presence of a liquid on the particle dynamics by experimentally validated simulations. A liquid bridge model, which contains the capillary and viscous forces acting between wetted particles during normal and oblique impacts, should be developed and implemented. The MPT method, used for the capturing of the three-dimensional movement of the particles, is a highly innovative method for characterization and monitoring of dense granular flows (for spherical and non-spherical particles). So far, the particle movement in dense granular flows could be well characterized with very expensive experimental setups, such as Positron Emission Particle Tracking (PEPT). With the MPT method, used in this project, for the first time not only particle velocities and accelerations, but also the particle rotation can be measured, which cannot be captured or sufficiently resolved with other available methods. The measuring range of the MPT has to be extended to smaller particle sizes. This will be achieved by redesign of the measurement set-up and improved shielding against external magnetic fields, including the earth's magnetic field. Marker particles with properties tailored to physical properties of bed particles should be manufactured by means of fluidized bed coating and used in the measurements. On the basis of spray granulation and coating experiments the results from the simulations and experimental studies will be evaluated with respect to the granule growth rate and the coating quality.