PRELIMINARY ANALYSIS OF IN-SITU CRYSTALLIZATION IN SPRAY DRYERS

摘要

Analysis of in-situ crystallization in spray drying using the T-Tg approach is typically limited to the final particle condition at the outlet. This work explored the significance of the history dependent effect of such T-Tg computation.Analysis was based on actual single droplet drying kinetics at different drying air temperatures. To the best of our knowledge, this is the first time ever that reports the changes in droplet Tg, T – Tg, solubility, and supersaturation based on actual experimental drying kinetics data as drying progressed.Using the history dependent approach, a close match between the predicted relative crystallinity and the experimentally measured crystallinity was achieved.On top of that, a new concept of critical crystallization period was validated. This finding also highlights the danger in using the final particle condition, hitherto, as a measure of partial crystallization in spray dried particles.Extended analysis using the nucleation-growth mechanism pointed to the same crystallization phenomenon analogous to the critical crystallization period concept.