Studies on pre-treatment by compression for wood drying I: effects of compression ratio, compression direction and compression speed on the reduction of moisture content in wood

To remarkably reduce the moisture content (MC) in a short time, pre-treatment by compression for wood drying was systematically studied in terms of effects of compression ratio, compression direction and compression speed on the reduction of MC in Poplar and Chinese fir. The results showed (1) MC reduction was about 108 and 176 % after compression at a ratio of 60 % from water-saturated condition, and it was about 1.8 and 3.0 % every 1 % compression ratio for Poplar and Chinese fir, respectively. (2) Compressions in tangential, radial and 45° direction were very effective in MC reduction, suggesting that pre-treatment by compression is very effective on round wood and timbers of flat grain, vertical grain and in-between vertical and flat grain. Of all the compression directions, the tangential compression showed a maximum MC reduction. (3) For Poplar, when the compression speed was 0.5, 1 and 3 mm/min, MC reduction had no big change; while it became small when the compression speed was 5 and 10 mm/min. For Chinese fir, reduction of MC decreased with the increase in compression speed. After all, the pre-treatment by compression is very effective to reduce the MC for wood drying.