A Simulation Tool for the Optimization of Lumber Drying Schedules

Abstract

A two-dimensional wood drying model based on the water potential concept is used to simulate the convection batch drying of lumber at conventional temperature. The model computes the average drying curve, the internal temperature and moisture content profiles, and the maximum effective moisture content gradient through board thickness. Various scenarios of conventional kiln-drying schedules are tested and their effects on drying time, maximum effective moisture content gradient, final moisture content distribution within and between boards, and energy consumption are analyzed. Simulations are performed for two softwood species, black spruce (Picea mariana (Mill.) B.S.P.) and balsam fir (Abies balsamea (L.) Mill.). The simulation results indicate that the predictive model can be a very useful tool to optimize kiln schedules in terms of drying time, energy consumption, and wood quality. Such a model could be readily combined with intelligent adaptive kiln controllers for on-line optimization of the drying schedules.

Keywords:

• Balsam fir
• Black spruce
• Drying quality
• Drying time
• Maximum effective moisture content gradient
• Energy consumption
• Surface checking
• Wood drying model

Acknowledgment

Authors would like to acknowledge financial help from the Natural Sciences and Engineering Council of Canada, the Canadian Forest Service, Forintek Canada Corp., and the Fonds de recherches sur la nature et les technologies, Gouvernement du Québec.