ProLigno / ProLigno 2010 Issue 2  
     
 
 
   
 

 


 

 

 

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.

REFERENCES
NTTI, L. (1999). Heating and Drying Wood Using Microwave Power. Doctoral thesis. Lulea University of Technology; 1999:35.
EGNER, K. and JAGFELD, P. (1964). Versuche zur künstlichen Trocknung von Holz durch Mikrowellen. Holz-Zentralblatt Nr 129 Oktober 26, 297-300.
HANSSON, L. and ANTTI, L. (2008). Modeling Microwave Heating and Moisture Redistribution in Wood. Drying technology vol. 26, nr. 5, s. 552-559.
JOHANSSON, J., HAGMAN, O. and FJELLNER, B-A. (2003). Predicting Moisture Content and Density Distribution of Scots Pine by Microwave Scanning of Sawn Timber. Journal of Wood Science. 49:312-316.
STUDHALTER, B.; OZARSKA, B. and SIEMON, G. (2009). Temperature and Moisture Content Behaviour in Microwave Heated Wood Prior to Bending - Mountain Ash (Eucalyptus regnans). European Journal of Wood and Wood Products, Volume 67, Number 2 / May.
TORGOVNIKOV, G. and VINDEN, P. (2009). High-Intensity Microwave Wood Modification for Increasing Permeability. Forest Products Journal, April 01.



 

 

 
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