Martin-christ Beta 2-8 LDplus User Manual download pdf (Page 17)

Operating Manual Freeze Dryer BETA 1-8 LDplus / BETA 2-8 LDplus General Information on Freeze-drying  17

2. General Information on

Freeze-drying

2.1. General Information on Freeze-drying

Freeze-drying is the most gentle process for drying products. It is

based on the physical phenomenon of sublimation i.e. the direct

conversion from solid to gaseous state. The frozen product is

placed in the vacuum drying chamber for drying. The ice

condenser can also be described as a vapour pump as the

moisture which evaporates under vacuum during drying freezes

onto the ice condenser. Consequently the vacuum pump is only

intended to remove the air from the drying chamber (=gas pump)

but not the vapour. In order to start the sublimation process,

energy must be supplied to the product. This takes place during

drying in round bottom flasks or wide-neck filter bottles etc. due to

the much warmer environment (direct heat contact), on unheated

shelves by means of heat radiation from the environment and

directly by means of the shelves when heatable. Once the “free

water” has been removed from the product, it is also possible to

remove the marginally contained adsorptively bound water by

means of very low vacuum. This part of the drying process is

referred to as final drying (desorption).

The main components of a freeze-dryer are :

 Vacuum drying chamber with heating device

a) heatable

and unheatable shelves for drying in

dishes

b) shelves with sealing device for drying in bottles

c) rubber valves for connecting round bottom flasks,

wide-neck filter bottles, etc.

d) manifold for connecting round bottom flasks, wide-,

neck filter bottles, etc.

 Pumps to evacuate air and water vapour

a) vacuum pump to evacuate the drying chamber

(= gas pump)

b) ice condenser with temperatures from -50°C to

-105°C (depending on type of unit) to remove the

water vapour from the chamber

(= vapour pump)

Heatable (controlled) shelves are only possible with an LSC control system.

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Martin-christ Beta 2-8 LDplus User Manual Page 17