INSTRUCTION MANUAL-CoolSafe Freeze Dryersmodels
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7.3. Cleaning
If a sample is spilled in the concentrator chamber, it must be cleaned up immediately.
8. The Freeze-drying process
To understand the freeze-drying process, this section describes the theory for the process in short.
For more detailed information about freeze-drying please consult available literature e.g. “ An introduction
to freeze drying by James M. Flink & Henning Knudsen, ISBN 87-872-0084-8.
All material in free form will exist in one of
three states: Vapor, liquid or solid.
As shown in the diagram for water, the physical
state is dependent on the surrounding pressure
and the temperature. The point where all three
phases of water co-exist is called the triple
point.
Freeze-drying is basically a change in state and
properties of the material that is to be removed.
In principle the process is very simple, but in
reality it is can be very complex as the product
can consist of many components, which interact
with each other.
Moving from one state to another, requires the
supply or removal of energy to or from the product. This energy flux will have an impact on the structure of
the material being dried.
Freeze-drying is achieved using equipment that controls temperature and pressure in the environment of the
product and is a 3-step process.
In the first step, the product is frozen solid so that the water present in the material is converted to ice
(pre-freeze).
In the second step, the ice formed in pre-freezing is removed from the product by direct conversion
from solid to vapor. This process is called sublimation. In order to start removing moisture in the
sublimation process, the pressure surrounding the material has to be brought down to a value below
that of the triple point, whilst keeping the temperature of the product below its freezing point. The
condenser surface temperature must also be down to a temperature lower than the temperature of the
material handled. When the product is heated it will theoretically place itself somewhere on the
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