High temperature super-heated steam drying of boxed-heart timber from sugi [Cryptomeria japonica]
2005
Kobayashi, I.(Forestry and Forest Products Research Inst., Tsukuba, Ibaraki (Japan)) | Kuroda, N. | Ishikawa Honda, A.
The suitable drying schedules for the boxed-heart square timber of Sugi (Cryptomerfa japonica D. Don) were investigated in this study. Super-heated steam drying schedule "A" was examined comparing with the schedule "B" with the concept similar to the ordinary high-temperature drying schedule. In the schedule A, DBT was 130 deg C, and relative humidity was decreased from 100 to 60% in 48 hours at the early stage. On the other hand, in B, DBT was 115 deg C, and RH was dropped from 100 to 60% in 30 minutes at the initial stage. The results are summarized as follows; (1) Although both schedules of A and B were effective to reduce the surface checking. B was not effective to prevent the internal checking. (2) Although total drying time was not much different between A and B, surface moisture content in the schedule A was decreased more slowly and released surface strain at the early stage of drying was much smaller than in B. (3) The boxed-heart square Timber without kerf is possible to be dried with few internal checks and with accelerated drying speed by the appropriate control of RH even in higher temperature than 100 deg C.
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