What is the drying process of wood?

Technical parameters and procedures formulated according to tree species, size specifications and quality requirements when using the specified method to dry wood in the specified equipment. The dried wood must meet the water content and quality requirements.

Through production practice, people have created a variety of drying methods and processes, but the kiln drying method has been used for a long time and accumulated rich research data and practical experience (see wood kiln drying). In terms of equipment, this method must have a special building with good air tightness and heat preservation, equipped with heating and temperature adjustment equipment mainly based on heat exchangers, humidity control equipment mainly based on steam injection pipes and air intake and exhaust passages, and equipment driven by fans and forced air circulation through the pile in the form of turbulence. The process of this drying method is representative, and its procedures are as follows: ① If possible, air-dry or pre-dry the wet material until the water content is below 40%, creating conditions for ensuring quality and reducing drying cost. (2) In strict accordance with the process specification, pile the wood to be dried into a neat pile with pads to reduce the warping deformation of the wood. (3) When piling up wooden stakes, put in moisture content inspection boards and stress inspection boards, so as to keep abreast of the dryness of wood and the presence of stress and defects. (4) The kiln shell must be baked in advance to avoid condensation water in the kiln under high humidity. ⑤ Pile the materials into the kiln. ⑥ Preheat the wood at a temperature and humidity higher than the first drying stage until the internal temperature is slightly lower than the temperature of the medium, so as to avoid excluding external water absorption prematurely. ⑦ Reduce the temperature and humidity of the medium, start drying according to the standard corresponding to the tree species, size specifications and quality requirements of the wood to be dried, and adjust the standard in time according to the change of moisture content stage, so that the drying can be carried out rhythmically. (8) When the stress inspection board for wood shows signs of stress, stop the drying process according to the standard, and start the intermediate treatment aimed at eliminating stress, and soften the wood by increasing the temperature and relative humidity of the medium until the stress is eliminated; The intermediate treatment can be carried out many times according to the process requirements. Pet-name ruby before drying, the moisture content of wood is reduced to the predetermined final moisture content, that is, the final treatment. Its purpose is similar to that of intermediate treatment, which can make the distribution of moisture content in wood tend to be uniform. Attending the wood must be fully cooled in the kiln before it can be discharged from the kiln, so as to avoid cracking when it suddenly meets cold air. ? During the storage of dry wood in warehouse, measures should be taken to keep the final moisture content of wood basically unchanged.

The drying process of other methods is similar to kiln drying, but each has its own characteristics. The characteristics of high-frequency drying and microwave drying are that when the positive and negative poles of electricity alternate frequently, water molecules rub from wood to generate heat. The characteristics of vacuum (negative pressure) drying are: due to the decrease of atmospheric pressure, the boiling point of water in wood decreases; Under the condition of partial vacuum, the flow and diffusion of water in wood are accelerated.