Computer Simulation of the Softwood Veneer-Drying Operation

A computer model simulating the drying of veneer in jet dryers was developed as a tool for studying the drying process under various circumstances at a reduced cost of experimenting and with a minimum disruption of the actual process in the mill. The model, written in FORTRAN IV, follows the “next event” simulation technique coupled with an enumeration technique for optimization of veneer flow through two jet dryers, a primary dryer for all green veneer and a secondary dryer to redry sheets that remained too wet in the primary drying stage. Input information is required regarding veneer parameters (specific gravity, thickness, heartwood percentage, and initial and desired final moisture contents), process parameters (air temperature and velocity, dryer design adjustment, and minimum time of passage), and cost parameters (operating cost and degrade from overdrying and redrying). Output variables are drying times in the primary and secondary dryers, the amounts of veneer falling in the “too wet,” “acceptable,” and “too dry” categories, and the associated drying cost. Examples calculated demonstrate the effects of veneer thickness, primary drying temperature, and presorting of green veneer on drying times and associated cost. The model can be tuned and run for specifically stated drying conditions to provide information for decision making by plant managers.

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