EQUALIZATION OF MOISTURE IN PRE-DRIED PINEWOOD USING MICROWAVE POWER

Lena ANTTI
Prof.Dr. - Lulea University of Technology, Division of Wood Physics
Address: SE 931 87 Skelleftea, Sweden
E-mail: lena.antti@ltu.se

Lars HANSSON
Dr. - Lulea University of Technology, Division of Wood Physics
Address: SE 931 87 Skelleftea, Sweden
E-mail: lars.hansson@ltu.se

Abstract: Commonly, during air-circulation kiln drying moisture gradients within wood cross-sections are developed, i.e. the surfaces become drier than the interior. To minimize these gradients a conditioning step subsequent to the drying is needed. The aim with this study was to investigate the possibility to use microwave power for equalization of moisture within pinewood boards after air-circulation kiln drying to the average moisture content 0,14. Two dimensions of pinewood were tested; thickness 50 and 63 mm, in two different plants, generating 5 and 12 kW microwave power respectively. Results show that microwave energy give rise to a fast and advantageous moisture equalization within the wood. The higher microwave power density the faster heating and moisture redistribution in these wood dimensions. Required time for heating and redistribution of moisture was found to be as short as 3 minutes at the power density 500 kW/m3. In addition, split-tests indicate decreased or elimination of gap after microwave treatment in the investigated specimens.

Key words: wood drying, pine wood, equalisation, microwave power.

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