Research On The Drying Characteristics Of Dahurian Larch Lumber From Russia

This paper researched the lumber's drying characteristic and drying technology, and the species of the samples was Larix gmelini of Russia. At first, four times drying experiences were carried, and the samples thickness are 30mm and 50mm. According to the analysis of wood temperature, moisture content, stress, shrinkage, and the temperature and humidity of drying medium etc., and combine with transfer rule of heat and medium in the course of drying, it summarized the rational drying technology and put forward the measure to improve the drying quality and production efficiency. It can offer theoretical foundation and technical assurance in order to establish the drying technology of Larix gmelini of Russia. The second, it determined the anatomical properties and physical properties of the sample, and compared them to Larix gmelini of China. Then, it discussed the causes that arose the drying defect. The third, it was measured the sample's physical and mechanical properties, which the samples were dried in different of drying technology. At the same time, it observed the microcosmic structure of dried samples by Scanning Electron Microscopy (SEM), and assessed the lumber drying quality. At last, according to the former results, it established the lumber's drying schedule, and put forward the effectual measure to improve the drying quality and production efficiency of Larix gmelini of Russia.According to the analysis of drying course, it put forward the 30mm and 50mm thickness-lumber drying schedule of Russia Larix gmelini. The ratio of finished product is over 98 percent by the new drying schedule. Thereinto, the first grade is over 90 percent. On the basis of the analysis of experience course, it offered some advices to drying course. The advices are described as follows. The condition of drying medium is not suitable to strong in the initial sates of drying. The time of metaphase process must be brought forward. It was feasible to decrease the temperature in drying technology, but the time to decrease the temperature must be appropriate.According to the analysis of anatomical properties and physical properties of Russian Larix gmelini, it showed that the cell wall of tracheid was thin, the ratio of cell wall to cavity was low, the density was lower, the deformation is smaller, the defect of craze is smaller, and the wood mechanical properties are higher than China Larix gmelini.According to the comparing study on physical and mechanical properties of Russian Larix gmelini, which the samples were dried in different of drying technology. It showed that air-seasoned lumber's density is larger, deformation degreee is smaller than kiln-dried lumber's. It was not obvious that the process of kiln-dried affected the wood physical and mechanical properties, it had obvious advantage at work efficiency from whole view.According to the observation by SEM, the cellular bordered pit in radial cellular wall is a lot, and most of them have pit membrane. Except for the resin canal, the resin exists in some tracheid and wood ray cell. The resin blocks the circulation of vapor, so the velocity of drying is reduced seriously, lumber's drying stress increased. The surface of pit border, pit membrane and cellular cavity in the heartwood of Russian Larix gmelini, are covered with a thin film, or non-cellulose film, or arabinogalactan film, it is one important factor of wood impregnation reducing. Under the observation of microcosmic structure of air-seasoned and kiln-dried lumber, it showed that pit membrane of air-seasoned lumber was not distinct change, and the pit membrane of kiln-dried lumber was rupture badly, but the rupture improved the circulating of moisture. The observation analysis of microcosmic structure provided basis for deciding former drying technology research and standard.