Modeling and optimization of the supercritical wood impregnation process—Focus on pressure and temperature

The present paper deals with modelling and optimization of a supercritical wood impregnation process. In this process, the permeability of wood is a key factor that conditions the velocity of pressurization and depressurization. The variation of wood permeability with operating pressure was investigated at pressures ranging from 0.6 to 15.5MPa at 313K. The measurements reveal that the permeability of wood varies with pressure (at 15.0MPa, wood permeability is 260% higher than that at near atmospheric conditions), suggesting that wood is suffering physical or chemical alterations during the pressurization. The data obtained in the measurements was correlated and used has input for a dynamic model of the supercritical wood impregnation process. In the model, the cross section of a wood board is simulated. The wood is considered as a porous media and the flow of CO2 in the wood is described by a modified Darcy's Law. In the free space outside the board, the flow is governed by the weakly compressible Navier–Stokes equations.