Institut für Verfahrenstechnik

Lehrstuhl für thermische Verfahrenstechnik

Agglomeration and coating are key particle technology processes in, among others, the fine chemical, pharmaceutical and food industries. They can efficiently be conducted by spraying binder or coating material on fluidized particles (of, typically, some tens to hundreds µm in size), with simultaneous evaporation of the liquid from the sprayed solution or suspension. With coating taking place when droplets deposited on the fluidized particles cannot promote agglomeration, the two processes are complementary and competing. Their products differ fundamentally in structure and application properties, since agglomeration of primary particles by binder usually aims at the fast reconstitution and solution in water (instant behaviour), whereas controlled release of active ingredients is usually desired when coating core particles. So, it is important, and a goal of this project, to track the transition from agglomeration to coating. Since coating can be simply seen as the absence of agglomeration, this is intimately related to the further goal of better understanding the kinetics of agglomeration. If, additionally to operating in the vicinity to coating, only the very first stage of formation of dimers from primary particles is considered, uniquely favourable conditions for process understanding and modelling are obtained. Therefore, incipient spray fluidized bed (SFB) agglomeration at the border to coating is in the focus of this project.