Paper Board Microwave Dryer Equipment
Paper Board Microwave Dryer Equipment：
Microwave drying of wood flooring is a new technology, which is widely used in furniture and wood flooring industry. Because of the waste caused by deformation, cracking and mildew in conventional drying, microwave dryer has a series of advantages, such as uniform heating, fast drying speed, no distortion, no cracking, moth prevention and mildew prevention, good product quality, conducive to continuous and automated production. The distinctive feature of microwave drying of wood floors is that heat is not transmitted from the outside of the object, but directly heated through the moisture contained in the material and absorbed by the wood itself. Because of the evaporation of moisture on the surface of the material, the temperature inside the material is higher than that on the surface. The pressure difference inside the material is formed outward, and the surface migration of water is accelerated. So the speed of microwave drying wood is much higher than that of convective drying (natural drying, steam drying, infrared drying, etc.).
Characteristics of microwave dryer equipment: fast drying speed.
The drying time of reducing wood moisture content from 35% to 40% to 20% is about 10 to 15 minutes, which is 20 to 30 times as much as that of steam drying process. However, it must be noted that with the increase of microwave power, the drying speed will be faster. At the same time, the temperature inside the wood will rise sharply, which will cause wood cracking when the moisture vaporization and dehumidification are too fast. Even when the moisture content of wood is too low, it will cause local coking in the wood. Therefore, the processing speed should not be excessively pursued, and the larger microwave power should be used. 81
Generally speaking, the standard of water extraction rate is 1 kilowatt microwave power per hour to dry materials to remove 1 kilogram of moisture. The actual dehydration rate is about 0.8-1.0 kg per hour due to the difference of hardness between tree species and wood. But in the same tree species, wood along the direction of fiber, drying effect has obvious difference, the dehydration rate of short fiber length is higher, and vice versa is lower. The dehydration rate of soft wood is faster than that of hard wood. When the moisture content of wood falls below 15%, the water extraction rate will decrease. When the microwave power is estimated, the dehydration rate is about 0.8 kW per hour.
Because of the strong permeability and selectivity of heating in microwave drying of wood materials, the shrinkage rates of both ends of wood interior and exterior and intermediate fibers are basically the same during drying, so the cracking and deformation of wood are relatively small. However, the traditional drying methods will cause deformation, cracking, mildew, deterioration and other phenomena, seriously affecting the quality of wood, resulting in a large number of scrap. The utilization rate of wood and wood can be increased by about 5% by microwave drying, so a lot of wood can be saved. Microwave drying of wood is not affected by external climate conditions.When microwave drying wood equipment is used, it is not affected by the changes of external natural conditions. It takes up to one year or several years for conventional methods to adopt natural drying. It also occupies a large production base, spends more labor and increases production costs. Microwave drying wood to kill pests.When wood is dried by microwave, harmful borers in wood can be killed. This is due to the strong resonance effect between the energy of microwave electromagnetic field and water molecules in wood materials. The harmful borers, eggs and larvae inside the parasitic wood were killed together. When the treatment temperature was 70-80 degrees, it took only 2-3 minutes.