Vacuum drying of wood in drying chambers: technology, features and methods

The construction industry is currently experiencing an active stage of technological development, which is reflected in the tools used, and on the methodology of performing repair and installation operations, and, of course, on materials. At the same time, due to availability and low cost, traditional materials continue to be in demand, among them wood. Another thing is that it can not be used in its pure form, since even solid rocks no longer correspond to building standards in protective properties. Overcoming this barrier allows special preparation operations, including drying of wood in drying chambers - a technology that improves the whole range of technical and physical characteristics of the material.

Drying technology in the chambers

The principle of drying in vacuum chambers is based on the laws of evaporation and water circulation. That is, the main tasks of the method are to ensure the optimal rapid removal of moisture from the tree structure, but without negative consequences for performance. This technology is aimed at the implementation of this process. In practice, it is carried out with the help of special installations that ensure water circulation through the wood structure in the direction from the core to the outer part. Further, water is removed from the surface by evaporation. But it is important to understand that getting rid of moisture is not the only task that is realized by drying wood in drying chambers. Technology also allows you to eliminate physical defects, but for this, additional equipment like presses is used. As for the technical implementation of the process, it is usually performed by manually loading the material into the appropriate chamber. Further, due to the heating plates, the unit produces automatic heating against a background of intense evaporation.

Features of the vacuum drying method

Compared with traditional drying chambers, the new technologies of cylindrical vacuum drying allow achieving high process speed. This is due not so much to the principle of impact on the material as to the mechanics of loading and the arrangement of blanks with respect to functional plates. But the thermal effect has its own peculiarities. Since the wood material is compressed between the plates under pressure, a high intensity of the effect on the structure is provided - accordingly, more moisture is evaporated. In terms of energy consumption, also has its differences, vacuum drying of wood. The technology features in this parameter are determined by the increase in the plate temperature and optimization of the physical movement of the material inside the chamber. Therefore, in order to achieve the same results with alternative drying methods, such chambers consume less energy.

Stages of drying

Automated cameras allow the user to implement a standard set of technological steps without user intervention, which looks like this:

• Heating material. Primary heat treatment, during which the wood structure is prepared for the subsequent stages.
• Direct drying. At this stage, a combined moisturizing-drying operation is performed, allowing the material to soften as much as possible to further desiccate.
• Cooling. In fact, this is the stage of crystallization of the structure, due to which the wood that has become compliant due to heat treatment again acquires the optimum hardness characteristics.

As noted above, all stages of the drying process are monitored by the automation, and the operator monitors the indicators of safety indicators. But even before the start of the event, the user is required to set the optimum drying regime. In particular, it sets the pressure and temperature, focusing on the characteristics of the material. For example, for coniferous blanks 2.5 cm thick, a pressure of 500 kg / m2 is required. As for the temperature regime, in this case it can be 80 ° C.

The device of the drying chamber

Modern cameras are made in the form of a parallelepiped or cylinder. The output side of the structure is provided with a lid, through which the operations of loading / unloading the material are carried out. Moreover, the lid structure includes a rubber sheet fixed on a metal frame - this solution allows creating an almost perfect vacuum with increased sealing. Each layer of sawnwood is laid with heating plates, which are usually made of heat-conducting aluminum alloys. To carry out movements, the plates are provided with roller mechanisms. Due to the movement of the heaters, a balanced drying of the wood in the drying chambers is ensured. The technology of making chambers also provides the connection of circuits with circulating water. Boilers with liquid are placed separately and provide for their own heating. To maintain a stable vacuum inside the chamber, a special pump is placed.

Application of hydraulic press

It has already been said above that during the drying process, the structure of the wood softens and becomes pliable. This state is part of the drying process is a by-product and an excess. Actually, to eliminate these consequences, the final stage of cooling is envisaged. However, the softened structure of the material can be exposed to the hydraulic press, which will remove the workpiece from physical defects - at least ensure its straightening. Such presses are introduced into a common complex of capacities, where drying of wood in drying chambers is carried out. The pressing technology, in turn, also eliminates possible defects that were acquired by the material in the chamber. The final billet will be "correctly" deformed with those parameters that are needed for the working sawn timber.

Drying methods

At the moment, the development of technology is distinguished by three main methods of vacuum drying. The first two methods have already been considered - this is directly drying and press-vacuum preparation of the material. But there is also a method of steam processing in a vacuum chamber. Its relevance is due to the possibility of excluding heating plates from the chamber design, since hot steam covers the whole space, without requiring a special flow direction to separate parts of the blanks. This approach provides many advantages that provide steam heating methods for drying wood. Drying chambers, for example, allow loading not only in a labor-intensive manual manner, but also with forklifts.

What effect does drying provide?

By itself drying as a process of optimizing the hygroscopic property gives the wood a relatively high strength. This is enough for the material to meet the basic requirements of building regulations. But large wood processing plants use the above-described technologies and methods of drying wood only as a preparatory stage for further processing of the material. In particular, for impregnations, which additionally give the workpieces quality fireproofness, moisture resistance, frost resistance, etc.

Drying your own hands

For the manufacture of its own dryer available means in the first place will require a separate room. In size, it can correspond to a small utility room or a household block. The structure should preferably be made of brick or concrete, and the inner surfaces should be insulated and insulated with layers of foam with a foil coating. As a result, it turns out, though not a vacuum, but a pressurized dryer for boards. How to make elements of heat exposure? To do this, several convectors or radiators should be provided - their number will be determined by the design capabilities of the room and the requirements for drying itself. Heating equipment and will provide the effect of evaporation. For greater efficiency, it is possible to supplement the function of thermal action by fans.

Conclusion

During construction and repair operations, there is often a question of choosing between different materials. Limited financial opportunities often exclude metal alloys and high-strength plastics, leaving no alternative for wood. But this solution in many cases justifies itself by technical characteristics, if a drying chamber is used for sawn timber. With their hands without the cost of expensive radiators, such a camera, too, will not work, but in the long term, its use of investments will justify themselves. As the practice of operating structures on the basis of properly dried wood shows, the material can even serve in harsh conditions for years without losing its primary properties. Another thing is that much will depend on the type of tree that is planned to be used for such purposes.