Investigation on the usage of effervescent atomization for spraying and spray drying of complex rheological food liquids and on the resulting particle and product properties

喷雾干燥是粉状食品生产中的关键工艺步骤。为了降低成本和提高产量，应减少用水，提高饲料中固体含量。这可能是单相或多相进料，通常表现出复杂的流变行为。如果进料的粘度增加，由于较高的固体含量，雾化更难以实现与传统的压力雾化器。在较高的粘度，使用气动雾化器将是有益的，但他们往往是由于高气体消耗下降。因此，本研究项目重点采用一种特殊的内混式气动雾化器——泡腾雾化器进行喷雾和喷雾干燥，其耗气量特别低。本文的主要目的是研究气泡雾化的科学基础。这将使其用于复杂的复合食品，并控制喷雾干燥过程后产生的粉末特性。将建立基本的工艺和性能功能，以便允许特定的产品开发和颗粒特性控制（递归工艺设计）。这需要对液滴的雾化和干燥进行定义和示例性描述。还需要颗粒结构及其对产品性能的影响，以建立所需的工艺和性能函数。从以前的结果开始，一个重点将放在窄液滴尺寸分布和稳定喷雾所需的工艺参数上。除工艺参数外，雾化器内部流态对喷雾性能的影响研究将是优先考虑的问题。因此，这将是不同实验工作和2D/ 3d模拟的主题（由合作伙伴进行）。对此，将采用子项目B10 （Weigand）发明并使用的数学模型。这将有助于确定雾化器的相关几何参数，以调整其设计，以达到预期的喷雾效果。第二个重点将是与传统雾化工艺相比，气泡雾化的分类和评级。为此，将研究喷雾性能、雾化效率及其对多相进料（乳液）内部结构的影响。此外，将研究生产者和消费者感兴趣的选定产品特性。

Spray drying is the key process step in the production of powdery food. For cost reduction and improved yield, it is favorable to use less water and a higher solid content in the feed. This may be single-phase or multiphase feeds, which often show a complex rheological behavior. If the viscosity of the feed increases due to a higher solid content, atomization is more difficult to achieve with conventional pressure atomizers. At higher viscosities, the use of pneumatic atomizers would be beneficial, however they are often declined due to a high gas consumption. Therefore, this research project focuses on the use of a special internal mixing pneumatic atomizer called effervescent atomizer for spraying and spray drying, which has a particularly low gas consumption. The main goal of this proposal is to investigate the scientific fundamentals of the effervescent atomization. This will enable its usage for complex compounded foods and control of the resulting powder characteristics after the spray drying process. Essential process and property functions will be established in order to allow specific product development and control of the particle characteristics (recursive process design). This requires the definition and exemplary description of the atomization and the drying of the drops. The particle structure and its influence on product properties is also needed to establish the desired process and property functions. Starting from previous results, one focus will be on the process parameters required for narrow drop size distributions and stable sprays. Investigations on the influence of the flow pattern inside the atomizer in addition to ALR (process parameter) on the spray performance will have priority. Therefore, this will be the subject of different experimental work and 2D/3D-simulations (to be conducted by cooperation partners). Concerning this, a mathematical model invented and used by subproject B10 (Weigand) will be applied. It will help to identify relevant geometrical parameters of the atomizer for aligning its design to achieve the desired spraying results.Second focus will be the categorization and rating of the effervescent atomization compared to conventional atomization process. For this purpose, the spray performance, the efficiency of atomization as well as its influence on the inner structure of multiphase feeds (emulsion) will be examined. Furthermore, selected product properties which are of interest for producer and consumer will be studied.