PASSAGE®/FreezeDrying

Passage®/FreezeDrying is a computer program designed for the simulation of freeze drying processes in vials and pans.  Passage®/FreezeDrying provides modeling of containers with axisymmetric boundary conditions with both primary and secondary drying simulation capabilities.  The software also handles containers with asymmetric boundary conditions, as in the case of vials placed in corners or near the walls of freeze-drying ovens.  The user-friendly, interactive preprocessor accepts externally generated meshes and support automatic entry of material properties, process conditions, and display of geometry. Passage®/FreezeDrying also has user-friendly, interactive post-processing modules which display the computed temperature, vapor concentration, water pressure, and glass transition distributions in the form of contour plots and x-y graphs.  Animation of sublimation front movements can also be obtained easily. Mathematical Models Solved Primary Drying Heat transfer in Dried and Frozen Layers   Mass Transfer in Dried Layer Water Concentration in Dried Layer Sublimation Front Between Dried and Frozen Layers Secondary Drying Heat transfer in Dried Layer Mass Transfer in Dried Layer Water Concentration in Dried Layer Objective Identify process conditions to: - Maximize drying rate and increase   production - Prevent chemical & structural   degradation - Provide uniform drying throughout the   material - Predict drying time for primary and   secondary stages to desired levels of   water concentration Results Time for primary and secondary drying of products Location for isolated islands of ice in pan drying Concentration contours Absorbed water concentration Interface position in time Sublimation frontal movement Temperature contours and history Water pressure contours Benefits Provide a tool to predict drying times and process conditions to alleviate "islands of ice" and glassing of product Results are used for FDA process approval Minimize cost of testing and shorten drying time to increase yield Provide detailed understanding of primary and secondary drying processes

Temperature Distribution after 8 Hours of Primary Drying in a Vial Analysis of Freeze Drying Sublimation Front Tracking Analysis of Freeze Drying Sorbed Water Concentration Pressure Distribution after 8 Hours of Primary Drying in a Vial Process Parameters Chamber pressure Higher chamber pressure increases water vapor flux Lower chamber pressure decreases material conductivity Rate of heating - Should provide uniform heating - Limited by thermal & structural stability   of material Performance Evaluations Optimum chamber pressure Uniform heating throughout the material Maximum temperature reached within material Pressure variations within material - Indicates isolated ice regions - Uniformity in drying