Modeling of particle distribution and dispersion in spray and spray drying processes

喷雾干燥工艺旨在生产具有规定性质的颗粒，包括颗粒结构、几何性质、堆积密度和化学结构。首先，产生喷雾，喷雾在过程中蒸发和干燥--该过程受到液滴相互作用、阻力、重力和颗粒形成等因素的影响。本项目的范围是喷雾和喷雾干燥过程的建模和模拟，特别关注喷雾和喷雾干燥的特性，以及它们对所得粉末特性的影响。特别是，与雾化过程及其在对流介质中的传输相关的喷雾不均匀性还没有得到很好的理解。此外，有关颗粒的形成及其对所得粉末的性能的影响的详细信息是必需的。在本项目中，从雾化喷雾到粉末的完整过程进行了研究，通过数值模拟，其中喷雾的分布建模使用直接求积矩法（DQmoments），这是一个强大的方法，包括所有感兴趣的物理过程。第一阶段涉及一维数学模型的建立和验证，使用BASF的实验数据，在室温下将水喷雾注入氮气中。在第二阶段，研究了二维轴对称水和聚乙烯吡咯烷酮（PVP）/水溶液喷雾到静止空气中的系统。对于PVP/水喷雾，为了处理液滴的双组分蒸发和干燥，开发了一种新的蒸发和干燥模型，并在DQESTO中进行了分析和实现。还对甘露醇/水滴的双组分液滴蒸发和干燥模型进行了评价。最后阶段涉及PVP/水喷雾干燥成粉末，其中将研究PVP和Mandarin的干燥条件（如气体温度和速度以及液滴尺寸）对颗粒形成和特性的影响。

Spray drying processes aim to produce particles with prescribed properties including the particle structure, geometric properties, bulk density and chemical structure. First, a spray is generated, which in the course of the process evaporates and dries – the process is influenced, for instance, by droplet interaction as well as drag and gravity force and particle formation.The scope of the present project is the modeling and simulation of spray and spray drying processes where special attention is given to the characteristics of both the spray and spray drying, and their effect on the characteristics of the resulting powder. In particular, spray inhomogeneity associated with the atomization process and its transport in the convective medium is not well understood. Moreover, detailed information about the particle formation and its influence on the properties of the resulting powder is required.In the present project, the complete process ranging from atomized spray to powder is studied by means of numerical simulation where the distribution of the spray is modeled using direct quadrature method of moments (DQMOM), which is a powerful method to include all physical processes of interest. DQMOM must be coupled to the evaporating and drying environment.The first period concerned the setup and verification of the one-dimensional mathematical model using experimental data from BASF, where a water spray was injected into nitrogen at room temperature. In the second period, two-dimensional axi-symmetric systems of water and Polyvinylpyrrolidone (PVP)/water solutions sprayed in to still air are studied. For PVP/water sprays, in order to treat the bi-component evaporation and drying of droplets, a new evaporation and drying model is developed, analyzed and implemented in DQMOM. The bi-component droplet evaporation and drying model was also evaluated for Mannitol/water droplets. The final period concerns the drying of PVP/water sprays into powder where the effect of drying conditions such as gas temperature and velocity as well as droplet size on particle formation and characteristics will be investigated for both PVP and Mannitol.