In freeze dryers, drying is accomplished indirectly under high vacuum and low temperatures (usually below 0 °C). This is done in special vacuum tray dryers. Freeze drying (also known as lyophilization), is frequently used for drying proteins vitamins and other heat sensitive products.
● Freeze Drying Procedure (Discrete)
The material balances are done based on the sublimation percentage of the solvent components. The specific power requirement (based on tray area or sublimation amount) is used to calculate the overall power requirement.
In Design Mode, the program calculates the sublimation capacity (in kg per cycle) based on the percentage of components that sublimate. If the calculated sublimation capacity exceeds the maximum, the program assumes multiple units operating in parallel with a total sublimation capacity equal to the calculated. The total tray area is calculated based on the number of entities processed per cycle and the entity specific area.
In Rating Mode, the user specifies the number of parallel units, their tray area and their sublimation capacity. If the sublimation or the area occupied by the entities exceeds the specified one then the program warns the user.
The drying time is either specified by the user or calculated based on the sublimation rate (in mm/h).
The interface of this operation has the following tabs:
● Oper. Cond’s, see Discrete Freeze Drying: Oper. Conds Tab
● Utility Data, see Drying Operations: Utility Data Tab
● Labor, etc, see Operations Dialog: Labor etc. Tab
● Description, see Operations Dialog: Description Tab
● Batch Sheet, see Operations Dialog: Batch Sheet Tab
● Scheduling, see Operations Dialog: Scheduling Tab