Drying of 32 mm oak-wood boards - comparison of the experimental and production kiln-dryng schedules

Drying properties of domestic wood species, especially oakwood, have prompted an analysis of 32 mm thick oakwood kiln-drying schedule. The schedule was applied in production conditions and was compared with the knowledge achieved through research and praxis in the world. Today drying schedules are just partially customized to different species und dimensions of dried wood, so that the drying process has to be conducted with respect to characteristics of wood in an area and drying-kiln conditions in question. The research was conducted in conventional drying kiln using a stack of 32 mm oakwood boards. At the beginning of the process the dry-bulb temperature (30°C) of the tested schedule was too low from the point of view of energy consumption, and the difference between the dry and the wet-bulb temperature was appropriate concerning the possibility of drying defect development. During later drying phases, approximately at the fiber saturation point, the dry-bulb temperature of 48°C and the difference between the dry and the wet-bulb temperuture of 5°C were low when compared to the values listed in references. Drying from 30% moisture content to the final moisture content took place at a lower dry-bulb temperature, except during the period from 30 % to 10% moisture content, but it became too high below 10 % moisture content. The kiln-schedule analysis suggests that the experimental kiln- schedules have to be fitted to real conditions before they are applied, and that even then careful operation and correction is needed throughout the drying process.