WOOD RESEARCH Volume 69, Number 4, 2024
JINGE XIE, HONGHAI LIU, YU XIE, and XIAOKAI ZHANG

INFLUENCE OF TEMPERATURE AND PRESSURE ON SUPERCRITICAL CO2 DEWATERING OF BAMBOO STRIPS

In this study, therepressure (15, 22.5, 30 MPa) and two temperature (45, 60°C) of ScCO2dewatering were tested on Moso bamboo (Phyllostachys edulis) strips. The aim was to research the effects of these conditions on the dewatering rate, moisture distribution, and shrinkage of bamboo. The results showed that: 1)The first cycle discharges the most water of all drying conditions. The most effective dewatering time consisted of a 15 min depressurization period and a 5 min discharge period. 2)The ScCO2 dewatering rate of bamboo strips decreased with decreasing MC, with a maximum decrease of 78%.The maximum and minimum dewatering rates were 37.04%/h and 4.41%/h, respectively. The dewatering rate was synergistically affected by temperature and pressure, which increased significantly with pressure at 45°C, but was minimized at 60°C at 22.5 MPa. 3)After dewatering, the moisture distribution in the bamboo strips shows a trend of higher moisture content(MC) in the middle and lower MC on both sides in the tangential and radial directions. 4)Most of the bamboo strips produced shrinkage after the 1st cycle of dewatering, and the overall shrinkage in the tangential direction was greater than that in the radial direction. The maximum tangential and radial shrinkage rations are 3.06% (22.5 MPa/45°C) and 0.94% (15 MPa/60°C), respectively.

WOOD RESEARCH Volume 67, Number 6, 2022
HONGHAI LIU, XIAOKAI ZHANG, and Jingwen Zhang

Study of dewatering characteristics of eucalyptus wood by supercritical CO2

Wood collapse is a major defect for their applications in solid wood production. Supercritical CO2 (ScCO2) dewatering can quickly remove water in wood and effectively reduce the capillary tension leading to collapse of wood structure. In this study, Eucalyptus exserta F.V. Muell wood was dewatered using ScCO2 at 35, 45, 55°C and 15, 20, 25 MPa, separately. The dewatering characteristics and wood deformation were statistically analyzed and compared after dewatering. The results show that the dewatering rate of ScCO2 is affected by moisture content (MC) of wood, showing the higher the MC, the faster the dewatering. It is also affected significantly by pressure, indicating increased dewatering rate with the pressure. The effect of temperature on dewatering rate is not apparent as the pressure is less than 25 MPa, but it becomes significant at 25 MPa condition, showing an increased dewatering rate with temperature. In this experiment, the greatest dewatering rate was 19.8%·h-1 at 55°C and 25 MPa. The transversal shrinkage of all specimens after 5 cycles dewatering was lower than 1.5%, indicating the ScCO2 dewatering could effectively inhibit collapse of eucalyptus wood structure. The transversal shrinkage decreases with the pressure, and is not affected significantly by temperature.