Hello!
I looked yours on your site. Beautiful and valuable work!
I can dry this tree so:
Vacuum drying technology is attractive, first and foremost because it presents a realistic opportunity to significantly decreasedrying time while preserving the quality of the wood, and often imroving it. It is known that in this regard, the capabilities of conventional drying are exhausted. More than one kind vacuum drying technology exists today. But first, a little bit about the vacuum drying process from physics' point of view.
Creating of vacuum in an environment where the drying process takes place, dramatically changes physical characteristics of heat and matter exchange processes that occur durin drying. The principal parameter that defines depth of the vacuum is the pressure in the drying environment; it is this parameter that determines the conditions and processes that occur there. The most important effect of lowering the pressure in the environment is lowering of the boiling point of water and temperature of saturated steam. The main processes that determine the kinetics of wood drying and connected with movement of moisture in liquid or steam from inside the material, and with diffusion of steam into the surrounding environment.
When part of steam/air mixture is removed and pressure is lowered, the number of molecules is decreases and their free movement increases. In a vacuum, it is significantly greater than the average microcapillary size, whose radius is less then 10-15cm. In this case, the character of molecular movement in the lumber pores changes fundamentally; effusion phenomenon occurs (Knudsen Flow). Density of the flow increases dozens of times. Additionally, with temperature of the lumber tissue being higher than boiling point with the given pressure, an excess steam pressure inside the material occurs, which significantly speeds up movement of moisture from the center to the surface of the wood. Lowering of pressure in the drying environment by 12 times speeds up the moisture movement by 4.7 times.
The above mentioned occurances during drying in a vacuum allow to achieve a certain effect when drying timber materials, compared to traditional drying. Energetic effectiveness of the process however, depends on supply of heat to the material and coducting the optimal drying mode. It is to these circumstances that we attribute creation of wide array of vacuum wood drying methods, vacuum technologies and equipment to implement them. Noteworthy is the fact that the advantages which this technology presents to the woodworking industry require complex and intricate equipment including: hermetically sealed and pressure resustant autoclave, heates which sometimes use High Frequency and Super (Ultra) High Frequency Current generators, vacuum pumps, circulation equipment, steam condensation and condensation removal systems. Practicability of using this drying system with high structural complexity is determined by a technoeconimical calculation. But simplification and lowering of equipment costs is relevant both to the producer and the consumer. For this very season we would like to call your attention to the results of an interesting development executed by the Russian company "Vacuum Plus". Developers of this kiln determined the following goals:
- Simplify constuction of the equipment and lumer drying technology.
- Achieve high quality of lumber drying.
The drying chamber consists of a cylindrical body (sizes depend on volume of the load) with an airlock. Length of the stack loaded into the chamber is 6300mm. The stack is located on a cart which is moved on guide tracks when loading and unloading the chamber. The lumber is placed on 25mm thick, 30-40mm wide with spacing, interliners calibrated according to thickness. Because of the curvilinear guides along the cart, the cross-section of the stack is not rectangular. Instead, it mimics the shape of the cylinder surface. Thus the most useful capacity possible is achieved.
Steaming, drying, heat and moisture treatment, and cooling modes are obtained emperically through the process of experimental refinement on an industrial installation. The result is a universal shedule for different breeds from initial moisture of 100% to final 5.0-6.0%, including oak of 75mm, 52mm, 32mm, walnut of 90mm thickness and others. Drying occurs on the set mode.
Developers note simplicity of maintenance of the equipment, which does not require constant presence of the operator. In the event of a power outage, the kiln automatically resumes the set operation mode when power is recoverd.
One of the advantages of this drying method, as mentioned above, is the high quality of the finished dry wood. When drying oak, moisture dispersion on the stack is 1.5%, differential for thickness of the lumber 0.5-1.0%. Drying times: hardwood leafed breeds 7-18 days, coniferous breeds 3-15 days, depending on thickness and initial moisture of 5-7%.
It seems strange at first glance to use natural circulation of the environment in the chamber, which of course lowers the intensity of the heat supply to the stack. Howeever, when treating slow-drying wood, the speed of moisture and heat exchange processes on the surface should correspond to the speed of internal moisture and heat movement. Our use of natural conductivity is one of the reasons for the high quality of drying oak and other lumber difficult in drying. The cost of this kiln is much lower than its counterparts abroad!
Additioanl dryer Information:
- Oak 60 mm thick from initial moisture of 65% dries to residual moisture of 4-5% in 18-20 days.
- Oak 60 mm thick from initial moisture of 35% dries to residual moisture of 4-5% in 10-12 days.
- Oak 25 mm thick from initial moisture of 65% dries to residual moisture of 4-5% in 9-10 days.
- Oak 25 mm thick from initial moisture of 35% dries to residual moisture of 4-5% in 7-8 days.
- Pine 55 mm thick from initial moisture of 65% dries to residual moisture of 5-6% in 8 days.
- Pine 55 mm thick from initial moisture of 35% dries to residual moisture of 5-6% in 6 days.
Our vacuum drying kiln provides 100% lumber drying of any breed (including exotic breeds) with moisture differential 0.5% for board thickness, no more than 0.9% for board length, and up to 1% for the stack.
E-mail:
info@vacuums.ruSergey
