Freeze-drying, or lyophilization, is the process of freezing a material then sublimating any frozen liquid directly from solid to gas. The method is often used to preserve food and pharmaceuticals, as it allows products to be easily stored and transported without requiring constant refrigeration.
Vacuum pumps are required for this process, and should be sized according to the freeze-dryer. If the pump’s flow rate is too high, then vapor will be pulled through the freeze-dryer’s condenser too quickly, reducing its efficiency. It is also important to clean the condenser after each run to prevent sublimation of frozen chemicals into the vacuum pump. Chemical resistance requirements for your freeze dryer vacuum pump depend upon the aggressiveness of your solvent. Freeze-dryer applications require an ultimate vacuum of below 0.1 mbar, which can be achieved with two-stage rotary vane pumps or ChemStar Dry.
Vacuum pump oil can be quickly compromised by the vapors from a freeze dryer. Once oil is chemically damaged, lubrication properties diminish and the vacuum pump quickly requires repair.