New narrow tube spray dryer for precise drying history control

ABSTRACT

Of all the operating conditions in a spray dryer, temperature of the drying medium holds the key parameter in affecting the degree of crystallinity in spray-dried particles. Previous experiments only focus on controlling the drying temperature at the inlet or outlet of drying chamber to delineate the drying history of particles, precluding any detailed studies on particle development throughout the drying duration. Hence, the objective of this work is to address the current limitation by introducing a modified narrow tube spray dryer which enables in situ control of drying history. Essentially, the drying chamber consists of 10 narrow copper tubes with an internal diameter of 1.7 cm. Each individual copper tube can be heated independently to create a unique controlled drying history. Scanning electron microscopy images demonstrate the significant impact of drying history on lactose morphology with possible crystallization by even slight variations in the drying history, which further accentuates the sensitivity of degree of crystallization to temperature. With this newly developed equipment, the detailed drying history conditions can be designed and manipulated to engineer the desired particle properties.

KEYWORDS:

• Crystallization
• drying history
• lactose
• pharmaceutics
• spray drying

Acknowledgment

M. G. Lee would like to thank Monash University for its support through Monash Graduate Scholarship and Monash Centre for Electron Microscopy (MCEM) for its facilities in obtaining SEM images.