Characterization of Lyophilization of Frozen Bulky Solids

Abstract

Two methods to study the primary freeze-drying behavior of bulky solids are presented, namely, lyomicroscopy and neutron imaging. The applicability of both methods to visualize the evolution of the sublimation front is tested for maltodextrin particles with different sizes and solid concentrations. Exemplary results for both methods are reported and the applicability of both methods to study freeze-drying behavior of bulk solids is described. To estimate the impact of particle size and bed height for the freeze-drying of bulky solids, a modified Biot number is introduced to estimate the optimum particle size for a given bed height and formulation. The applicability of the two methods with regard to the modified Biot numbers is discussed.