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

在本项目中，稠密剪切颗粒流中的颗粒动力学应以转子式造粒机为例来描述。为此，气固两相流动将采用离散元方法(DEM)和计算流体动力学(CFD)相结合的方法来描述，其中将使用磁粒子跟踪(MPT)来验证模拟的有效性。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。描述工艺和材料参数对制粒和包衣过程中单颗粒动力学影响的数学模型应在DEM中开发和实施。这个项目的核心内容是通过实验验证的模拟来表征液体的存在对粒子动力学的影响。应开发和实施一个液桥模型，该模型包含正常碰撞和倾斜碰撞时湿颗粒之间的毛细作用力和粘性作用力。MPT方法用于捕捉颗粒的三维运动，是表征和监测致密颗粒流(球形和非球形颗粒)的一种高度创新的方法。到目前为止，稠密颗粒流中的颗粒运动可以用非常昂贵的实验装置来很好地描述，例如正电子发射粒子跟踪(PEPT)。利用本项目中使用的MPT方法，首次不仅可以测量粒子的速度和加速度，还可以测量粒子的旋转，这是其他现有方法无法捕获或充分解决的问题。MPT的测量范围必须扩大到更小的颗粒尺寸。这将通过重新设计测量设置和改进对外部磁场(包括地球磁场)的屏蔽来实现。应通过流态化涂层的方式制造具有与床颗粒的物理性质相适应的特性的标记颗粒，并用于测量。在喷雾造粒和涂层实验的基础上，将从颗粒生长速度和涂层质量两个方面对模拟和实验研究的结果进行评估。

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.