Study on Degreasing Drying Mechanism under the High Temperature and Pressure Steam for Larix
Author:Qi Hua Chun
Supervisor:liu yi xing cheng wan li
Larix is rich in resources,it’s accumulation is rich,there are many advantages with the other species,but there are many disadvantages of Larix,such as the wood is rich in resin,greatly influenced the use of Larix,but also bring a lot of negative in the processing and utilization.Because the resin exists in it,Larix still no place in the field of deep processing of wood products.So far,there was some study of pine,but also made a variety of technological methods and patented technologies,etc.but effectiveness and efficiency are limitation.The current problem to be solved is how to use less energy,and does not damage the pine itself has the advantage of rapid and efficient method to pine for degreasing,to chieve efficient use of pine.The investigate to receive and reference technologies from home and abroad,to exploring non-chemical treatment,no environmental pollution,high efficiency wood degreasing drying method.High temperature and pressure steam-vacuum degreasing methods,combined with the experience of previous exploration of Larix,study on degreasing the northeast of Larix,Explore the mechanism of degreasing of the Larix,and analysis testing of degreasing rate and performance of Larix board,it offer a science basis for Larix degreasing drying process.The main research contents were summarized as follows:(1)Design and customization of a multi-functional high temperature and pressure steam treatment device,the device to high temperature and pressure of saturated and superheated steam as drying medium on wood for heat treatment,the main control and steam saturation temperature of the medium and other parameters to ensure treatment effect on the drying process.Independent set of time,temperature,vacuum and keep the vacuum time.For high temperature and pressure steam treatment of wood and pine degreasing drying.(2)For the first time for different thicknesses,different initial moisture content of the Larix with high temperature and pressure steam-vacuum drying degreasing,by different processing temperature,time and vacuum times,It is degrease dry to the Larix respectively,then measure resin content and degreasing rate after treated Larix.Research shows that:with the increase of initial moisture content,processing temperature and processing time,the thickness of the smaller plates of degreasing rate increased significantly.The rosin content changed little in the board,and the rosin does not affect of the later use of Larix,and turpentine is remove of the radial is much larger than the tangential,therefore,the study of turpentine remove in the radial plate as a research priority.(3)Through the test,performance test to Larix after high temperature and pressure steam-vacuum drying degreasing:①Analysis of the physical and mechanical properties of treated Larix(compression strength stripes,compression strength parallel,bending strength,shear strength parallel,tensile strength parallel,moisture absorption and desorption characteristics).② Test the color parameter of the treated wood,then calculate brightness L*,saturation C*,hue angle Ag*and color difference △ E*.③ Test performance with paint after treated wood(glossiness of lacquer film,mass loss rate of lacquer film).(4)Study degreasing drying mechanism of high temperature and pressure steam-Vacuum of Larix.①High temperature and pressure steam treatment is easier than conventional treatment rapid warming within the wood,resin can rapid evaporation of the water channel,with the resin inside the resin canals move water into the wood surface,is conducive to the discharge of resin.②Wood by high temperature and pressure steam treatment,from the plate ultrastructure(SEM)can be observed in cell walls and pits and fissures with a certain degree of structural relaxation,which makes the permeability of the treated wood is improved.③High temperature and pressure treatment of wood,cellulose,hemi cellulose and lignin content of the molecular structure and a change in hemi cellulose degradation,so that the content of carboxyl groups by reducing the affinity of smaller timber of water,leading to the treatment sheet slightly lower wettability.④Fourier transform infrared spectroscopy(FTIR)of treated board of the peak change is further explained within the treated wood thermal decomposition of hemi cellulose and cellulose,hydroxyl content decreases,starch,sugar and other nutrients produced volatile,wood to form new chemical bonds within the re-integration.So that the efficiency of treatment of skim boards,color,bending strength,performance with paint,etc.,should be better than the previous board after the conventional heat treatment.