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The scaling-up of spray drying processes is an important and challenging step in commercializing specialty products with an ensured quality because it mandates a comprehensive understanding of several steps in the process such as atomization, efficient solvent removal, and particle segregation. The formation of needed particle sizes and shapes is impossible without appropriate atomization through spray dryer nozzles. Hence, research is discussed that investigates the atomization mechanism for a pilot scale externally-mixed, two-fluid nozzle spray dryer by using time resolved particle-image velocimetry to study the behavior of droplets in the near-field of the nozzle tip. Important near-field dynamics of droplets emanating from the nozzle are described, and particle formation characteristics are discussed for several formulations which are widely used in the pharmaceutical industry. Spray angle, droplet breakup length, and droplet sizes and velocity distributions are characterized. Understanding these parameters assists the interpretation of particle formation and enables the modeling of the spray drying process. |
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