Atmospheric Spray Freeze-Drying: Numerical Modeling and Comparison With Experimental Measurements.
Atmospheric spray freeze-drying (ASFD) represents a novel approach to dry thermosensitive solutions via sublimation. Tests conducted with a second-generation ASFD equipment, developed for pharmaceutical applications, have focused initially on producing a light, fine, high-grade powder consistently and reliably. To better understand the heat and mass transfer physics and drying dynamics taking place within the ASFD chamber, 3 analytical models describing the key processes are developed and validated. First, by coupling the dynamics and heat transfer of single droplets sprayed into the chamber, the velocity, temperature, and phase change evolutions of these droplets are estimated for actual operational conditions. This model reveals that, under typical operational conditions, the sprayed droplets require less than 100 ms to freeze. Second, because understanding the heat transfer throughout the entire freeze-drying process is so important, a theoretical model is proposed to predict the time evolution of the chamber gas temperature. Finally, a drying model, calibrated with hygrometer measurements, is used to estimate the total time required to achieve a predefined final moisture content. Results from these models are compared with experimental data.
School of Aeronautics and Astronautics, Purdue University, West Lafayette, Indiana 47907.
Israel
I
Borges Sebastião
Office of Research and Development, Aerosol Therapeutics, New York, New York 10128.
Thomas D
TD
Robinson
School of Aeronautics and Astronautics, Purdue University, West Lafayette, Indiana 47907. Electronic address: alexeenk@purdue.edu.
Alina
A
Alexeenko
D000465:Algorithms; D003890:Desiccation / Q000295:instrumentation / Q000379:methods; D004867:Equipment Design; D005612:Freeze Drying / Q000295:instrumentation / Q000379:methods*; D005740:Gases / Q000737:chemistry; D006358:Hot Temperature; D008956:Models, Chemical; D011208:Powders; D011506:Proteins / Q000737:chemistry; D018401:Sample Size; D013816:Thermodynamics
D005740:Gases; D011208:Powders; D011506:Proteins
freeze-drying/lyophilization; mathematical model; powder technology; proteins; simulations; spray freeze-drying; thermodynamics