A study on pre-drying technology for Tectona grandis sawn timber in solar kiln

Abstract

The suitable pre-drying technological parameters for Tectona grandis plantation sawn timber in solar kiln were investigated after experimenting on the different drying gradients (U = 3.2; U = 3.6; U = 4.0). The results showed
that the percentage of wood checks and splits increased significantly when the drying gradient increased. This value was 0.53% at the softest drying schedule (U = 3.2), increased 3.3 times at the drying schedule U = 4.0. The degree of warping was only 0.02% at all the drying gradients. The shrinkage ratio was relatively high and had an insignificant difference between the drying schedules (3.316% in thickness and 4.328% in width on average). According to the cracking classification for dried wood in Australian Standard AS/NZ 4787:2000, dried timber was grade A at U = 3.2, the rest were grades C and D at U = 3.6 and U = 4.0, respectively. Drying time from 50% to 30% MC was very fast and different in three drying schedules, but the slowest drying time was only 12.38 days at U = 3.2. At the biggest drying gradient (U = 4.0), this lasted for nearly 6 days. At U = 3.2, drying quality of timbers was high and
drying time was suitable, and thus these parameters were selected as the predrying schedule for Tectona grandis sawn timber in solar kiln