Mathematical modeling and analysis of microwave-assisted freeze-drying in biopharmaceutical applications

Freeze drying is an essential unit operation for the storage of biopharmaceuticals, with its main weakness being the very long primary drying times required to sublimate all of the ice formed in the initial freezing step. This study investigates the use of microwave irradiation to reduce drying times. Mechanistic models are derived in a proposed freeze-drying process in which two energy transfer mechanisms – microwave irradiation and heat conduction – occur simultaneously. For this design, a mechanistic model derived in this article predicts an 83% reduction in primary drying time compared to conventional freeze drying. The influence of microwave power and design parameters associated with heat conduction parameters on the primary drying time are investigated and discussed. The model is implemented as open-source software in Julia and is available for engineers to use for designing such equipment.