ABSTRACT
The use of small-scale freeze-dryers for process development is one of the most recent innovations in the field of freeze-drying processes: they allow saving raw materials and time in the phase of process design. The system presented and discussed in this chapter, the MicroFD® by Millrock Technology, Inc, allows attainment of uniform drying conditions in the batch through a metallic ring in the drying chamber: it surrounds the external row of vials of the batch, because it is in contact with them, and its temperature is adjusted on the basis of the mean temperature of the batch measured through thermocouples. The metallic ring mimics an additional row of vials. Results point out that by manipulating the temperature of the ring it is possible to get uniform drying conditions that enable a small-scale freeze-dryer to produce the product dynamics of a large-scale unit. Moreover, the system allows estimation of the heat and mass transfer coefficients and other critical process parameters, to be used with a one-dimensional model of the process for in silico process simulation and optimization.
