Model Predicted Effect of Process Variables on Kiln Drying of Pinus radiata Boards

Abstract

The effects of kiln-drying process variables on drying time and final moisture content (MC) variability were assessed using a mathematical drying model (a kiln-wide model) developed earlier. Drying time was predicted to decrease by using higher air velocities and temperatures and, to a less extent, by increasing fan reversal frequencies. The drying time extended as board thickness or stack width increased. Increase in air velocity from 5 to 8 m/s tended to minimize the final MC variability. At least three reversals in the early stages of drying were required to reduce final moisture contents variation. The final MC variability increased with increasing stack width and with increasing temperature.

Keywords:

• Drying schedule
• Moisture variation
• Quality
• Simulation
• Softwood processing

ACKNOWLEDGEMENTS

Thanks are due to Dr. Dave Cown and Dr. Rod Ball, Ensis Wood Quality Unit, New Zealand, and Mr. Richard Northway, Ensis Wood Quality Unit, Australia, for their comments during preparation of this article. Thanks are also due to Dr. Ruth Gadgil, Scion, New Zealand, for her substantial assistance in editing this manuscript.