High frequency vacuum drying is a combined drying method of
high-frequency medium heating and vacuum low-temperature drying,
which is a fast and almost waste free drying method, especially
suitable for drying hardwood and heavy wood. High frequency heating: Also known as high-frequency medium heating, it converts a regular
380V AC power supply into a high-frequency electromagnetic field
after boosting and rectifying it. High frequency heating can be
achieved through related supporting equipment with anode and
cathode plates.High frequency heating is penetration heating, where the moisture
in the electric field is uniformly heated. The parts with more
moisture absorb more high-frequency electric fields, while the
parts with less moisture only absorb a small amount of
high-frequency electric fields. This effectively utilizes the
high-frequency output power. However, media such as wood or fiber,
due to their lack of polarity, do not absorb electric fields, and
high-frequency power is basically used without waste, saving energy
consumption and reducing drying costs.
Vacuum state mainly utilizes the lower boiling point of water in
vacuum state, which accelerates the evaporation rate and increases
the gradient of moisture content on the surface of wood. During the
drying process, on the one hand, surface moisture evaporates into
the surrounding air, and on the other hand, internal moisture
continuously moves towards the surface, thus accelerating the
drying rate at lower temperatures, ensuring the drying quality of
wood. The vacuum state is a negative pressure state that has a
certain water absorption effect, which is exactly similar to the
high-frequency pressure gradient and accelerates the discharge of
moisture from the wood core. In addition, under low pressure
conditions, the oxygen in the drying medium causes less
discoloration of the material due to thermal and oxidation effects,
which can basically maintain the natural color of precious wood.
Based on the above characteristics, the application of
high-frequency vacuum drying in wood drying has become a scientific
and environmentally friendly drying method, especially suitable for
drying hardwood with a large cross-section.