Drying of boxed-heart timber from sugi [Cryptomeria japonica wood] using radio frequency/vacuum drying method in combination with superheated steam pre-treatment
2006
Kobayashi, I.(Forestry and Forest Products Research Inst., Tsukuba, Ibaraki (Japan)) | Kuroda, N. | Honda, A.
In the previous report, we showed that boxed-heart timber from Sugi (Cryptomeria Japonica D. Don) could be dried in 3 or 4 days with few surface and internal checks, but the degree of discoloration was pronounced. In this study, we examined a combination of superheated steam pre-treatment and radio frequency/vacuum drying (RF/V) to both reduce the discoloration and achieve high drying speed with few surface and internal checks. The results were as follows; 1) The degree of discoloration was pronounced when the timber was pre-treated for 48 hours with the superheated steam of 115 deg C, but it got closer to that of air dried timber when the pretreatment time was reduced to 12 hours. 2) Large internal and surface checks occurred in the test where the electric power put into the oscillator was 10 kW/m(3), and few surface and internal checks occurred in the test of 5 kW/m(3). The optimum power was estimated to be between 5 and 10 kW/m(3). 3) The boxed-heart timber of 83 % initial moisture content was able to be dried to 14 % in 94 hours.
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