Assessment of predictive models for characterizing the atomization process in a spray dryer's bi-fluid nozzle

Abstract

Spray drying as a commonly used process to produce amorphous solid dispersions of poorly water soluble active pharmaceutical ingredients (API) involves dissolution of the API and often a polymer, surfactant, and/or other functional excipient(s) into a volatile solvent. This feed solution is then pumped to an atomizing nozzle to produce droplets inside the drying chamber. The current paper aims to utilize non-scaled parameters to characterize the atomization process. A bi-fluid nozzle with two different designs commonly used in a lab-scale spray dryer was investigated under different operating conditions. The feed solutions were made of several excipients commonly used to produce amorphous solid dispersion composites. Atomization characterization is presented via both mean droplet size and size distribution. Various models are evaluated for predicting droplet mean diameter and span suitable for extrapolating atomization in the spray drying process. These approaches may be extended to other nozzles and across scales.