Modelling of hierarchical structure formation during spray drying via CFD-DEM coupling and continuous species transport

微米和纳米范围内的颗粒和聚集体结构是分析技术以及化学、生物技术和制药行业中无数产品的基础。例如，由颗粒组成的限定多孔系统用于层析纯化、催化应用(例如，用于能量存储或催化活化反应)以及用作限定释放活性药物成分的载体系统。相应应用的多孔系统的产品性质不仅取决于物质性质本身，而且在很大程度上还取决于下面的颗粒或集合体结构。除了纳米和微粒积木的材料和表面特性外，后续的工艺步骤，如配方、加工和干燥，对结构的形成和相关的技术应用特性具有决定性影响。这就产生了这样一个问题，即如何而且必须为各种应用构造这样的集合体系统，以便例如确保最佳的质量传输，同时表现出定义的机械稳定性。在以前的项目中，已经通过喷雾干燥纳米颗粒悬浮液来生产和研究各种聚集体系统。在本项目中，将建立CFD-DEM模拟，以揭示颗粒尺度的结构形成机理，并全面描述由此产生的骨料微观结构，特别是WG SChilde在第一个干燥阶段形成的分级结构。同时，WG Levy将进一步开发一种基于连续物种传输模型的建模方法。为此，计划在第一和第二干燥阶段考虑多种颗粒大小和颗粒相互作用。来自CFD-DEM模拟的知识将支持模型的开发，以在保持低计算成本的同时受益于它们在颗粒尺度上的信息。这将允许有效地研究不同工艺和配方条件对产品的影响。最终，这些模型应该能够对喷雾干燥过程中的结构形成进行工艺优化和预测。

Particle and aggregate structures in the micro- and nanometer range are the basis of countless products in analytical technology as well as in the chemical, biotechnological and pharmaceutical industries. Defined porous systems composed of particles are used, for example, in chromatographic purification, in catalytic applications (e.g. for energy storage or catalytically activated reactions) and as carrier systems for the defined release of active pharmaceutical ingredients. The product properties of porous systems for the respective application depend not only on the substance properties themselves, but also to a large extent on the underlying particle or aggregate structure. In addition to the material and surface properties of the nano- and microparticle building blocks, the subsequent process steps such as formulation, processing and drying have a decisive influence on the structure formation and the associated technical application properties. The question arises as to how such aggregate systems can and must be structured for the various applications in order, for example, to ensure optimum mass transport and at the same time exhibit defined mechanical stability. In previous projects, various aggregate systems have been produced and investigated by spray drying from nanoparticulate suspensions. In this project, CFD-DEM simulations will be established to reveal the structure forming mechanisms at the particle scale and to fully describe the resulting aggregate microstructure, in particular the formation of hierarchical structures in the first drying stage by WG Schilde. In parallel, a modelling approach based on a continuous species transport model will be further developed by WG Levy. For that, the consideration of multiple particle sizes and particle interactions in both the first and second drying stages is planned. Knowledge from the CFD-DEM simulations will support the model development to benefit both from their information on particle scale while keeping the computational cost low. This will allow the influence of different process and formulation conditions on the product to be investigated efficiently. Ultimately, the models should enable process optimization and prediction of structure formation during spray drying.