Eliminating the freeze-dry bottleneck - Lyophilization Articles & Reports

Eliminating the freeze-dry bottleneck
9 April 2003
Laboratory Talk
CryoDry is an extension of Ilmvac's existing laboratory and production freeze drying business, which encompasses drying in flasks, vials, ampoules and bulk.
CryoDry is a technique that employs Liquid Nitrogen as a condenser in place of the traditional refrigeration system comprising compressor and expansion valve.
Using liquid nitrogen it is possible to condense much larger quantities of sublimed water vapour than with a refrigeration system, hence faster drying times can be achieved.
Condenser temperatures of -150C are achievable though a routine working pressure of -80C generally gives the best results.
The liquid nitrogen is circulated from a storage tank at 1bar pressure and a flow valve controls the flow through the condenser within the freeze dryer.
Re-directing the liquid nitrogen to pre-cool the product chamber, which in turn allows for easier loading without the risk of defrost of expensive product.
Using the CryoDry technique for condensing larger volumes of water vapour allows additional heat to be introduced to further accelerate the process.
This can be done either by heating the shelves in a bulk dryer by use of resistive plate heaters or re-circulated silicone fluid, or directly by positioning Infrared heater lamps above the product.
A further development of CryoDry is the innovative RGT rotary dryer for pellet material drying at very high process speeds.
Again, the drying chamber is pre-cooled allowing the product to be introduced in pellet form without concern of defrosting.
Pellet, as opposed to bulk tray drying, vastly increases the surface area of the product and makes for much more rapid sublimation.
In addition, Infrared heaters are used to accelerate the process and the whole drying chamber rotates to ensure that every pellet has equal exposure to heating, thus ensuring consistent results throughout the batch.
Only CryoDry liquid nitrogen condensers can cope with this rapidity of sublimation, says Ilmvac.
The result is a faster drying process.