Particle structure development during spray drying from a single droplet to pilot-scale perspective

Crucial for achieving premium agglomerated powder products through spray drying is that the primary particle morphology and the degree of agglomeration can be controlled. However, the costs of trial runs and the wide range of products properties complicate achieving this control of particle structure during spray drying. Single droplet drying approaches are employed to study the development of the primary particle morphology and the collision behavior of droplets under well-defined conditions. These studies shed light on the underlying mechanisms but have been related less often to realistic drying and especially agglomeration. This review focuses on the potential and limitations of single droplet drying approaches to unravel the evolution of primary particle morphology and nozzle-zone agglomeration phenomena during spray drying. We discuss advances in single droplet drying approaches and how to combine these with pilot-scale spray drying to obtain the desired particle structures. • A wide range of SDD techniques exist, each providing their own benefit. • Collision behavior of droplets can be studied by modified SDD approaches. • Particle morphology development can only be studied for individual particles. • Pilot scale equipment is required to study full nozzle zone agglomeration.