Reducing energy use and material loss by better control of agglomeration during spray drying

Spray drying is a process which is commonly applied within the food industry to produce powders. 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 occurs when a partially-dried (sticky) 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. During large scale production, this lack of control of agglomeration negatively impacts operation efficiency of spray dryers (e.g. due to fouling and lower production capacities) and leads to significant material losses (in the form of off-spec product). By increasing efficiency and reducing losses, the CO2 eq emission of the process can be reduced by improved agglomeration control. Besides, improved agglomeration control will contribute to a reduction of fine dust emission from dryers, for which increasingly strict regulations are reinforced by the government. This project therefore aims at developing scaling-relations to steer sticky behaviour and agglomeration in spray drying.

Agglomeration studies will be performed at two scales. At the single droplet scale, drying kinetics, the evolution of (sticky) surface properties and binary particle collisions will be studied under well-defined, realistic drying conditions (Nienke Eijkelboom). At the pilot scale, sticky zones will be identified and systematic spray drying trials with various nozzle positions and drying conditions will be performed. Critical parameters from the single droplet drying studies will be translated to formulate recommendations for process conditions in spray drying. (Anneloes van Boven). The results of both scales will be combined to develop scaling-relations to steer sticky behaviour and agglomeration in spray drying.

Partners involved in this project are University of Hohenheim, ISPT, Corbion, Danone, DSM and FrieslandCampina. The project is financially support by TKI Energie.

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