A vacuum dryer is a method of drying wood by stacking it in a
closed container and drying it under conditions below atmospheric
pressure. Under vacuum conditions, the boiling point of water
decreases and the evaporation rate increases, thereby accelerating
the drying rate of wood at lower temperatures. During the drying
process of wood, on the one hand, surface moisture evaporates into
the surrounding air; On the other hand, the internal moisture
continuously moves towards the surface. So we need to accelerate
the drying speed and try to speed up the movement of moisture
inside the wood. In addition, under vacuum conditions, the boiling
point of water decreases, causing the evaporation rate of water
inside the wood to accelerate, and the moisture content gradient on
the wood surface to increase, preventing severe evaporation of
water on the wood surface and cracking of the wood surface. While
the moisture on the surface of wood evaporates violently, it also
absorbs a large amount of vaporization heat, causing the wood
surface to cool. These factors all accelerate the movement of
moisture inside the wood towards the surface.Under vacuum conditions, the air inside the drying device cannot be
heated using the usual methods. To solve the heating problem of
wood during vacuum drying, continuous heating is used to vacuum
dry. Vacuum drying can eliminate the surface hardening and cracking
phenomenon that is prone to occur under atmospheric pressure
drying. The pressure difference between the interior and surface of
vacuum dried wood is large, and under the pressure gradient, water
quickly moves to the surface. At the same time, it can improve the
drying rate, shorten the drying time, and reduce equipment
operating costs. In addition, under low pressure conditions, the
oxygen in the drying medium causes less discoloration of the
material due to thermal and oxidative effects, and can basically
maintain the natural color of the material.
Therefore, vacuum drying equipment is a fast drying equipment. It
is also an environmentally friendly drying equipment.
1, The wood vacuum dryer adopts continuous heating to quickly heat
up the wood and achieve fast drying time. 2, Automatic drainage,
automatic heating of wood both inside and outside, uniform heating,
good quality, and able to maintain the natural color of the wood.
3, Vacuum negative pressure water absorption reduces the
temperature of the wood drying process, causing the wood to
vaporize at low temperatures, making it less prone to cracking, and
improving the dehydration rate of the wood. 4, Environmentally
friendly and non polluting. 5, Vacuum drying has many
characteristics such as sterilization, insect killing, and
environmental protection, which can shorten the drying cycle and
further ensure the quality of wood drying. Especially suitable for
drying thick, hard, large section wood or square wood (conventional
drying methods require a long time), precious wood such as
rosewood, chicken wing wood, yellow pear, rosewood, etc. At the
same time, secondary drying of small batches and expedited wood
after moisture regain is also used. 
