Wood drying is an inevitable part of the production of all wood products. The quality of wood drying directly affects the later manufacture and use of wood products. If the drying is not complete, there will be residual stress in the wood. When the external air humidity changes, the wood will appear warping, cracking and other defects. In ancient times, when craftsmen used wood to make furniture or houses, they usually placed the wood in a cool place for a year and a half to allow it to fully eliminate internal stress and adapt to the local environment. This was later called atmospheric drying. However, in today's mechanization and modernization, accompanied by a huge consumer market, naturally the atmosphere is not feasible. Artificial drying methods, mainly steam drying, high frequency drying, and microwave drying, have become the choice of modern wood products enterprises.
Q1 Which drying method is used in the industry?
At present, most factories still use traditional convection drying methods to dry wood. This method has low cost and good quality. However, it can cause pollution to the atmosphere. For example, in the past few years, coal was burned, and that suddenly had a greater impact on the environment. It is now encouraging companies to use wood waste as fuel. There is a special factory that compresses the waste processed by these wooden products companies to make chalk-like biomass fuel. With the increasing attention to environmental protection issues, many places now require companies to use biomass materials. In Japan, environmental protection requirements are stricter and they use clean energy such as natural gas as fuel.
There are still a small number of wood products enterprises using high-frequency drying technology, including some redwood furniture companies in Fujian and Zhejiang have already used high-frequency drying equipment. The advantage of high-frequency drying is that it is fast, especially for some special materials such as wood with large end faces and precious wood.
Q2 What project did you cooperate with Zhongshan Taixing Furniture Co., Ltd.?
In Taixing, the research is mainly on improving the wood drying process. Before Taixing, it was also conventional drying, including several other drying centers in Dayong. Although conventional drying is low in cost, the drying cycle is relatively long, especially for the high density and dense structure of mahogany, the process requirements for conventional drying are relatively strict. High-frequency vacuum drying is to use the alternating electric field generated between the electrode plates, so that the dipoles such as moisture inside the wood will quickly flip in the high-frequency magnetic field and generate heat by friction, so the temperature inside the wood can rise quickly, forming internal high and external Low temperature and pressure gradients. In addition, under the condition of vacuum, the boiling point of water is reduced, and rapid drying at low temperature can be achieved.
Q3 said that this high-frequency drying speed is fast, can you give us a quantitative comparison?
According to the experiments I've done so far, thin sheets of rosewood rosewood, broadleaf rosewood, and barry rosewood can save 25% of the drying time. However, the advantages of high-frequency drying will be more obvious in thick plates or square materials. According to previous literature data, it can save 60% of time.