Design And Application Of A Multi-Functional High Temperature And Pressurized Steam Device For Wood Treatment

High-temperature and pressure superheated steam, which has tremendous heat emission coefficient and high heat transfer efficiency, can permeate into wood very well. The relative humidity and equilibrium moisturec content of superheated steam are higher than those of high-temperature air, therefore the drying condition is more gentle and the degrade is less. From the perspective of social development such as the improvement of timber quality and added value and environmental friendliness, people must increasingly pay attention to the utilization of superheated steam. As far as concerned, the study and application on the technology and mechanism of heat treatment is not much. The application of high temperature and pressure superheated steam in wood industry is still in its infancy now. There is no drying equipment met the demand of laboratory experiment and manufacturing in our country.The study attemped to design a multi-functional high temperature and pressurized device for wood treatment. The device treats wood with saturated or superheated steam, and controls the process by temperatures and saturation of steam. The temperature of drying medium is 120～250℃. And the saturation (Relative humidity) is 20～100%. Device work pressure is 1.2MPa and the vacuum is less than 1000 Pa. The device can be used in the study of high temperature and pressure superheated steam drying, pretreatment and pines degrease drying. In order to investigate the performance and feasibility of the equipment, experiments on the pretreatment and drying characteristics of Cyclobalanopsis glauca and the degrease processing of Larix gmelini were conducted.Research on the effect of pretreatment on drying properties of Cyclobalanopsis glauca were conducted in this study, water transfer in wood, variation of stresses and drying quality of Cyclobalanopsis glauca in high temperature and pressure superheated steam were also explored. Discuss the effect of pretreatment on drying properties by comparing the drying properties of pretreated wood with the kiln dried one and provide the theory basis for the study on pretreatment process. It was better to preheat the wood in low temperature with superheated steam. The treatment temperature should be less than 130℃. Relative humidity between 80%-100% is proper. The round-robin mode of steam effects on the moisture uniformity. It's better to make the steam horizontal passages the loads. High temperature and pressure superheated steam pretreatment can improve the properties of penetrability and decelerate drying time. In conventional drying process of Cyclobalanopsis lumber, low temperature preheating should be adopted and maintain some time. Dry-bulb temperature is not more than 40℃. Difference between dry-bulb and wet-bulb temperature is less than 1℃, and the circulation speed is 1.0～1.2 m/s or lower. In initial stage of drying, the moisture content decrease fast. High temperature is not appropriate. The drying speed can be controlled by temperature and circulation speed. For 30mm thick cyclobalanopsis lumber, a multi-stage drying schedule 3 can satisfy the request of second-class drying lumber. This schedule can be applied to floor-based material and furniture material.The study pretreated Larix gmelini with high temperature and pressure saturated steam as medium and analyzed the effect of temperature, treatment time, processing time with vacuum and initial moisture content of specimen on the efficient of degreasing by the comparing the resin content of treated specimen with untreated one. The reasonable degrease drying process was given at last. The treatment time in experiments is 1/3～1/5 to common vapor treatment. The ratio of degrease is 3 times than that of vapor drying.