kiln drying approach of solid wood flooring

Frequently used kiln drying approaches of solid wood flooring  and its

applicable conditions

Frequently used kiln drying approaches are: normal steam drying, furnace gas drying, hot

air drying, dehumilification drying, vacuum drying, and the popular hot water and high

temperature heating in recent years. We should choose suitable drying according to the

characteristics, requirements and the enterprise scale.

1　Normal steamed heating：

This approach use the saturated water vapor of pressure gauge P<=0.4Mpa. It dries the

wood by using heating machine. Its advantages are: the process parameters are easy to

control; the quality is good; temperature and humidity have a wide room to adjust; can dry

all kinds of wood and heat together. Therefore, this approach applies widely. However, we

have to use steamed boiler. The investment costs are high. As it mainly use steam,

condensate water is hard to recycle. Thus, we can not make full use them, wasting  and

increasing production cost. Therefore, this idea is only applicable to factories with a large

scale of production or enterprises with existing steam. It is especially applicable to

coniferous trees, broad-leaves trees and sheets which are easy to dry. As for small and

medium size enterprises, it is not suitable to them because of high cost steamed boiler.

2  Normal furnas gas drying

This is the approach which use waste wood to produce heat and dry the wood directly and

indirectly. Direct heating will lead to blackening the wood and causing fire. Therefore, it

would be no longer use. There are many ways of furnace gas heating indirectly.

①.simple fire pit type: stoves and furnace gas pipeline are arranged under the fire room

and the wood are laid in the fire room. It dries naturally by wet hot airflow. This is

primitive approach which would often baked the wood bad or cause fire. Thus, it is not

recommended.

②. Small stove oven type: this is a small drying machine that is the metal shell of a

container and it is loaded with waste wood combustion furnace,pipeline, and fans. It

could be filled with 2 to 5 CBM. It also has disadvantages. It can easily baked the wood

bad or cause fire, and also, due to unreasonable airflow, it can not dry evenly. Thus, it

is not recommended.

③. Modern indirect furnace heating drying kiln.

There is reasonable furnace gas heating gas tube in the kiln. Other configurations are the

same as the normals. If it is the kiln that is designed by experts, its security and reliability

can be ensured. The specilized furnace stove can put both outside and inside the kiln. The

former is safer, but the cost and heat loss are high.

Furnace gas heating drying does not need steamed boiler, use waste wood for energy

sources, and thus investment and cost are low. However, temperature and humidity are

difficult to control. We can not ensure the quality. If the drying kiln is not designed well, it

is easy to baked the wood bad and cause fire. We should be cautious to this method for the

medium or high grade hardwood flooring.

3  hot air heating

Hot heating stove is put outside the kiln. It is connected with air intake, air outtake

pipeling and drying kiln. Air drying medium heats by bringing the hot air into air intake

pipeline, then put into the kiln by aie blower. This is a normal air drying. But the heat

energy utilization rate is low; power consumption is big; temperature and humidity are

distributed unevenly. The process parameter is difficult to control; drying speed is slow

and uneven. Air intake pipeline and air blower are easy to decay. The volume is small and

cost of unit output are high. It is not recommended.

4  dehumilification drying

dehumidificating the air drying mediumin the kiln and add approriate heating to dry the

wood. Dehumidifier can only work and produce effects in a certain temperature. Normal

dehumidifier can work not exceed to 55C, medium drying machine can not exceed 65C. It

can prevent the electricity from polluting and easy to operate. The quality are good. But

the cost are high and the time is long. The production rate is low. Dehumidifier is easy to

malfunction and maintainance is high. Life span is short. It does not have adjustment and

can not eliminate the drying stress. As its impulse mainly reduce the humidity but not

 obvious. Low moisture content or wet tree species are not obvious. Nevertheless, dry tree

species or high moisture content are tired of dryness and slow speed. Sometimes, it will

lead to wood mold. It is recommended that enterprises do not adopt it, unless the

production are low or we have special environmental standards.

5  vacuum drying

Dry wood are put into tight container, pumping the air in the container after heating,

making the wood dry under certain negative pressure conditions. This method dries very

quickly, but we can not ensure the quality. The load is small; equipment are complex;

investment are high. As it use electricity, the cost are high.