Development of a dynamic-physical process model for sieving

在机械加工工程和材料制备技术中，经常需要根据颗粒大小和形状对分散的固体系统进行分离。这在组合工艺中是必要的，因为块状材料通常由不同的、高度非球形的和宽尺寸分布的颗粒组成，但在后续工艺步骤中需要定义窄尺寸分布。在这种背景下，筛分是一种技术上简单但非常适合的分离过程，它可以不连续地和连续地进行。尽管筛选过程具有既定的性质，但设计、优化和缩放过程并非微不足道，因为该过程及其子过程及其动力学仍然没有得到令人满意的理解。尽管进行了良好的开发，但是仍然缺乏基于物理的过程模型。为了设计或优化筛选过程，应用了基于颗粒的模拟方法，例如离散元素法（DEM），该方法允许在适当验证后对过程步骤筛选进行详细建模。同样，现象学模型也适用于设备特定参数和操作参数的优化。其中，固定过程仿真包中使用的简单模型只考虑分离操作的整体结果。其他模型包括分层和粒子通过筛管之间的相互作用。通常，现象学模型的经验确定的、材料的、操作的和设备的特定参数是通过实验确定的，而过程步骤筛选的动态模型的参数的直接推导很少通过DEM应用进行。特别地，这适用于在湿度影响下具有复杂形状的真实粒子的系统的研究。在拟议项目的前两个资助期内，研究了干湿颗粒在现实系统中的不连续和连续筛分，湿筛分将集中在第三阶段。通过在spp1679内进行的实验研究验证的DEM模拟，并将验证新系统的性能，在不同的机械激励下，在不同的操作条件下，对具有真实颗粒形状的多分散系统进行了不连续和连续的筛选过程。采用由观测关系和预测性质扩展的动态现象学模型来表示数值结果。采用简化的DEM模拟来获得新的、运行时高效的模型所需的参数，这些模型可用于动态、组合的大块固体过程模拟。

In mechanical process engineering and materials preparation technology, it is frequently required to separate disperse solid systems according to their particle sizes and shapes. This is necessary within combined processes because bulk materials often consist of particles of different, highly non-spherical form and broad size distribution but, defined narrow particle size distributions are needed for subsequent process steps. On this background, sieving is a technically simple but well-suited, separation process which can be performed discontinuously and continuously. Despite its established nature, the design, optimization and scaling of screening processes is not trivial since the process, plus its subprocesses and its dynamics, is still not satisfactorily understood. Although, good development takes place, there is still a lack of physically based process models.In order to design or optimize screening processes, particle-based simulation methods, such as the Discrete Element Method (DEM), are applied, which allows the modelling of the process step screening in detail after an appropriate validation. Likewise, phenomenological models are suitable for the optimization of apparatus-specific and operational parameters. Therein, simple models, which are used in stationary process simulation packages, only consider the integral outcome of the separation operation. Other models include the interactions between stratification and particle passage through the screen. Usually, the empirically determined, material-, operating-, and apparatus-specific parameters for phenomenological models were determined experimentally, whereas direct derivations of parameters for dynamic models for the process step screening were rarely carried out by DEM applications. Particularly, this applies to investigations of systems with real particles of complex shape under the influence of wetness.While during the first two funding periods of the proposed project, discontinuous and continuous sieving in realistic systems with dry and moist particles was investigated, wet screening will be focussed in the third phase. By means of DEM simulations, which were validated by experimental investigations within the SPP 1679 and will be validated for the new system properties, discontinuous and continuous screening processes are performed time resolved with different mechanical excitation for polydisperse systems of real particle shapes with the effect of wetness under changing operational conditions. Dynamic phenomenological models, which are extended by the observed relationships and predictive properties, are used to represent the numerical results. Simplified DEM simulations are applied to obtain the required parameters for the new, runtime efficient models which can be used in dynamic, combined bulk solids process simulations.