A single cell model for pretreatment of wood by microwave explosion

A theoretical model was developed to better understand the process of microwave explosion treatment of wood cells. The cell expansion and critical conditions concerning pressure and temperature of ray parenchyma cells in Eucalyptus urophylla were simulated during microwave pretreatment. The results indicate that longitudinal and circumferential stresses were generated in the cell walls owing to the internal steam pressure during extensive microwave treatment. The circumferential stress is twice as high as the longitudinal stress. The pressure difference reaches its maximum value of 0.84 MPa when the extension ratio is 1.20 for the longitudinal direction and 1.62 for the circumferential direction. The maximum pressure difference at the theoretical yielding point is the critical pressure difference that can eventually rupture the ray cell. The critical pressure difference decreases with increasing cell radius and decreasing shear modulus in the cell wall. This simulated result provides useful information to modify wood at the level of ray parenchyma cells.