Spray drying from yesterday to tomorrow: An industrial perspective

This article presents an overview over various spray drying methods and their applications. Additionally, some design methods are described, beginning with the initial calculations based on heat and mass balances, over 1D methods applied when the first computer became available up to modern 3D CFD design tools. The limitations of the methods are demonstrated. The overview of spray drying methods and tools is given from an industrial perspective. Thus, the mentioned simulation and experimental methods are focused on those which are usually applied in development processes for new or existing products. On the other hand, available equipment in lab and pilot scale are reviewed for both proof of principle and for scale-up. Especially for spray drying processes targeting on dust free powders, fairly large-scale experiments have to be carried out even for proof of principle. The scale-down of these processes is still an unsolved problem. Finally, some suggestions for further development and process modifications are given in order to show that there is still development work to do, even for such an old technology. These suggestions are derived from a personal point of view. Included are an improved down-scaling, an optimization of the residence time distribution with larger drying time for the big droplets and a more monodisperse atomization process. According to the opinion of the author, it should be possible to find technologies to improve and to enlarge the application of spray drying processes.