(333e) Predicting Drying Performance of Pharmaceutical Spray Dryers By Means of Multiphysics Simulations

Spray drying is a process of forming a dry powder out of liquid solution by drying with a hot gas flow. It is often applied in the pharmaceutical industry in the manufacturing of thermally sensitive materials including pure active pharmaceutical ingredients (APIs), amorphous solid dispersion (ASDs) of purely soluble APIs or of formulations of pharmaceutical proteins. Despite of many years of industrial experience, the development of successful spray drying processes is not straightforward and often requires time- and material consuming experiments. Therefore, predictive modeling approaches are highly relevant for a fast-track and low-risk development of successful spray drying processes. This motivates the present work, in which we evaluate the applicability of multiphysics simulation technique to predict the drying performance of industrial scale pharmaceutical spray dryers. The proposed multiphysics simulation approach consists of a Lagrangian particle tracking (LPT) within a wall-modeled large eddy simulation (LES) framework. Accurate inflow droplet statistics for the spray are obtained from an embedded volume of fluid direct numerical simulation (VOF-DNS) of the pneumatic nozzle atomizer. For comparison purpose, experiments on an industrial scale spray dryer, namely the GEA PHARMA-SD Type PSD-1, were carried out for pure acetone and excipients/acetone solutions. It is shown that the proposed holistic numerical approach allows accurate predictions of spray drying process conditions such as outlet temperature, residence time distribution, particle size distribution. Finally, the effects of turbulent heat transfer, fluid dynamics, mixing and drying conditions on the performance of the GEA PHARMA-SD type PSD-1 spray dryer are discussed.