Single droplet drying for steering particle agglomeration during spray drying

Spray drying is a process which is commonly applied within the food industry to convert a liquid into a powder. Material properties of the produced powder, such as its bulk density, flowability and reconstitution behaviour, are influenced by the level of agglomeration occurring during the spray drying process. Agglomeration during spray drying can occur when a partially-dried droplet collides with another partially-dried droplet or fully-dried particle. The relationship between the drying of droplets and the agglomeration dynamics is complex. In industrial practice, the approach to obtain agglomerated powder of desired quality is trial-and-error based and needs to be continuously repeated for different spray drying systems and products. Therefore, by improving agglomeration control, process efficiency can be increased, reducing the CO2 eq emission of the process. This project is part of a consortium that aims at developing scaling-relations that include information about particle skin properties and collision conditions to steer sticky behaviour and agglomeration in spray drying. In this specific part of the project, the focus is on agglomeration behaviour at the single droplet scale. A single droplet drying platform will be developed to study the drying of single droplets at length and time scales relevant to spray drying processes. Based on the experimental results, a model will be developed to predict the surface properties of the drying droplets. This model will be used to predict the outcome of droplet collisions. Experimental binary particle collision studies will be performed to verify and optimize the predictive model.