Views: 9 Author: Site Editor Publish Time: 2020-04-17 Origin: Site
Veneer dryer is a continuous veneer drying equipment, is an indispensable plywood production equipment in the production of plywood. There are two main types commonly used, mesh belt and roller.
In the drying process of producing plywood, it is mainly divided into two stages, one is the drying stage and the other is the cooling stage.
The drying stage is mainly used to heat the veneer to evaporate moisture, and evaporate the water in the veneer through the circulation of hot air. According to the different output, the drying stage can be composed of several sub-chambers, and the structure of each sub-chamber is the same. The longer the drying section, the faster the speed of conveying the veneer, and the higher the production capacity of the equipment.
The role of the cooling stage is mainly to ventilate and cool the veneer during the transmission process. On the one hand, the stress in the veneer is eliminated to make the veneer flat. On the other hand, the temperature of the surface layer of the veneer is used to evaporate some of the water.
In the drying stage, it is mainly mesh belt type veneer dryer and roller type veneer dryer.
The mesh bag type veneer dryer uses upper and lower mesh bags to transport the veneer. The lower mesh belt is mainly used for support and transmission. The upper mesh belt is mainly compressed to prevent the veneer from being deformed during drying.
Roller veneer dryer is a pair of roller groups composed of upper and lower, relying on the rotation of the roller to drive the single board forward.
Since the distance between the front and rear rollers cannot be too small, this method of drying is suitable for veneers with a thickness of 0.5-1.0 mm or more. Because the conveying and pressing force of the roller is large, the flatness of the dried veneer is better than that of the mesh belt dryer.
Most veneer dryers use steam as a heat source. The cold air is heated by the heat exchanger into hot air as the drying medium, and then the heat is transferred to the veneer, and the cold air can also be directly heated by burning gas, fuel oil, wood, etc. The ventilation mode of the dryer is generally divided into horizontal and vertical. The same dryer uses different ventilation methods, and the drying effect will be different.
There are two types of dryers, vertical and horizontal. The direction of the board feed is the same as the fiber direction of the two and a half, we call it the longitudinal board feed. Generally, the mesh belt dryer and the roller dryer adopt this plate feeding method. If the board feed direction is perpendicular to the fiber direction of the board, it is called a transverse feed board.
Longitudinal feed into the board must be cut into single sheets after being cut into rolls before drying. In the horizontal direction, the rolled veneer can be unrolled and continuously dried.
After the veneer is dried, the reddish water content has a certain range of deviation. In order to reduce this deviation, a continuous water content tester can be installed at the rear of the dryer, so that the moisture content of the veneer after drying can be known as early as possible, and the dryer can be adjusted in time to make the veneer dry. Achieve the final moisture content that meets the requirements.
After the veneer is dried, it should be placed for a period of time to make the moisture content uniform, so as to reduce the deviation of the moisture content. In domestic factories, the dried veneer is usually placed for 24 hours before use.