The Research On Water Content Of Wood During High Temperature Treatment Process

In recent years, with the high temperature drying has been widely used and wood has been more applied under high temperature and humidity status in various fields, it is very necessary to discuss water-bearing condition and water adsorption mechanism in the high temperature area, it will be of great significance for revealing the physical mechanics properties of wood in high temperature and humidity, and especially for the rheological mechanics features and humidifying treatment during wood drying. This study use self-preparation equipment and method of directly reading, which contain wood-water adsorption experiments of Pinus massoniana, Cryptomeria fortunei Hooibrenk and Eucalyptus marginata Dehnh, temperature is 100℃～140℃and relative humidity is 10%～100%. The results of this study include five parts primarily:(1) The proper water-bath system can produce constant temperature and humidity workspace, and the vacuum system can eliminate interference of other gases, measuring exactly wood water adsorption.(2) The adsorption isotherms of wood show the same trend under above and below 100℃, EMC decreased with increasing temperature and rised with increasing relative humidity. However, when the relative humidity is over 95%, the EMC increased significantly with increasing temperature under high temperature condition. The type of adsorption isotherm is not of second type S curve, but transforming into the third type, and the adsorption isotherm has no large difference among three tree species, the difference is mainly caused by chemical components (cellulose, hemicellulose and lignin), crystallinity degree of cellulose and density of cell wall.(3) The corresponding experiments are carried out to validate BET and Haillwood-Horrobin models, thepredictive value of two models and measurement value are very anastomosis on monolayer adsorption, but it has large deviation on multilayer adsorption and capillary condensation, especially deviation is more serious with increasing temperature. In sum, Haillwood-Horrobin model is better than BET model, but two models are not suitable to as wood water adsorption model under high temperature.(4) According to relation between EMC, temperature and relative humidity, and the models of Pinus massoniana, Cryptomeria fortunei Hooibrenk and Eucalyptus marginata Dehnh are established respectively by means of MATLAB software, temperature is 100℃～140℃and relative humidity is 10%～100%. By testing to three models:thepredictive value of two models and measurement value are very anastomosis, it is better than BET and Haillwood-Horrobin model, and the model is best to Cryptomeria fortunei Hooibrenk, the second is Eucalyptus marginata Dehnh, the third is Pinus massoniana. When temperature are 105℃,115℃,125℃and 135℃, EMC thepredictive value of Cryptomeria fortunei Hooibrenk model and measurement value are very anastomosis. So it can obtain EMC of every tree species by experiment under certain temperature and relative humidity, and then according to experimental data establish mathematical model of every tree species, the mathematical model is carried out to get EMC of every tree species under certain temperature and relative humidity.(5) It can interpolation treatment to experiment data by using MATLAB software, thepredictive value of interpolation treatment and measurement value are very anastomosis by testing, so this thinking and method is correct and fessible. Thus, it can obtain EMC of every tree species by experiment under certain temperature and relative humidity, and then using MATLAB software interpolation treatment to experiment data, finally establishing a database, the database is carried out to get EMC of any tree species under certain temperature and relative humidity.