Drying of beech wood lumber with using high frequency-vacuum method

Wood materials, which are natural and renewable resources, contain a large amount of water when cut from the forest. This water in the wood material is unsuitable for its applications and must be removed (dried). In most drying methods, some pre-treatments (pre-drying, steaming, etc.) are applied to freshly cut wood materials to improve the drying quality. The aim of this study was to examine the efficiency of High Frequency-Vacuum (HF-V) for drying of wood without any pretreatments. Because the pre-treatments applied before drying cause time and economic losses to the enterprises. In this study, one of our domestic species, Eastern Beech (Fagus orientalis Lipsky) wood which is widely preferred in industry, was used. Drying process were performed in Sivrikaya Forest Products Company's facilities. A high frequency vacuum drying kiln with capacity of 8 m³ at maximum power of 50 kW, electrode voltage of 10 kV was used at frequency 6.75 MHz. The test specimens used in the study were prepared with dimensions of 4 x 16 x 90 cm and 6 x 16 x 90 cm and the average initial moisture content of samples were determined as 80%. During the drying process, the energy consumption and vacuum amount, wood temperature, the wood weight and water loss amounts were measured periodically. At the end of the drying process, the drying quality of the test specimens and the drying defects were evaluated according to the EDG (1992) standard. The wood moisture content was reduced from 80% to final moisture of 10% within 9 days. Very small surface checks occurred in the test samples and the pith checking and cupping was only observed for one sample. In addition, prong test showed no casehardening (residual stress) in the dried samples after drying. The drying quality of the dried samples without any pretreatments was in the class of "exclusive" according to EDG (1992). As a result, it can be concluded that beech wood can be dried without any pretreatments by HF-V drying method with satisfied quality. It is believed that the HF-V method can be also used for high quality drying of other wood species without any pretreatments.