Study On Steam Degreasing/High Temperature Drying Of Pinus Sylvestris Var.Mongolica

Containing rich resin content,Pinus sylvestris var.mongolica was limited the drying,and the resin content was easily to overflow the redundant resin in long-term use,affecting the quality and decorative effect of finishing and making it impossible to make full use of timber resources.In this study,artificial forest Pinus sylvestris var.mongolica timber as the research object by the steam degreasing and high-temperature drying treatment.Systematically studied the variation law of the internal temperature,moisture content,and resin content rate of Pinus sylvestris var.mongolica lumber during conventional drying,steam degreasing,and high-temperature drying and their relationship with each other.It is discussed the effect of steam degreasing and high temperature drying process of dried temperature on drying rate,measured the degreasing affection by surface resin overflow in preliminary,and used biological and optical microscope and scanning electron microscopy to observe the micro-structure such as resin canal for analyzing the main mechanism of pious wood for effective drying and degreasing.The results of the study are as follows:1.During the steam degreasing treatment of Pinus sylvestris var.mongolica timber at99.5°C.The process divided into rapid heating accelerated drying stage and constant temperature and constant drying stage about moisture content and temperature.The temperature difference between the surface and the core layer first increases and then decreases.Finally,the temperature of each layer of the wood maintained at about 88°C.With the extension of steaming time,the resin content decreased gradually,the degreasing rate increased.Considering the drying rate,the degreasing rate and the color of the board,the pre-treatment time of steaming should be 3 hours.2.In the steam degreasing and high temperature drying,it spent 18 h,the degreasing rate is 60.33%.The change trend of the resin content was roughly the same as that of the moisture content.That is,as the drying process progressed,the moisture content and resin content gradually decreased.Smaller speeds are getting slower and slower.The gradient of moisture content gradually decreases.At the end of drying,uniform the moisture content and resin content across the cross section.The degreasing effect was better.3.During the steam degreasing and high temperature drying process,the wood temperature changes significantly above and below the fiber saturation point.In the initial stage of drying,the average moisture content of the wood is always above the fiber saturation point,and the temperature of all layers of the wood tends to rise.Thetemperature of each layer of wood is on the rise,and it tends to be gentle when it reaches97°C.When the moisture content falls below the fiber saturation point,the temperature rapidly rises from 97°C to the temperature of the medium.4.The drying cycle is short with high temperature drying,which saves about 45% of the time compared with the conventional drying.The drying speed is 1.91 times the conventional drying speed.The degrease speed is about 2.67 times that of conventional drying.At the end of drying,the distribution of moisture content and resin content on the cross section of high-temperature drying is uniform,the degreasing effect is better.5.The structure remained intact of resin canals of Pinus sylvestris var.mongolica untreated wood,the resin canals are filled with liquid turpentine and other substances,and the tracheid around the resin canals are almost entirely filled with turpentine.There are more light-reflecting liquid turpentine in the resin canals and mixture of turpentine and liquid pine fat in the tracheid cells around the resin duct of conventional dried wood.The structure is complete of resin canals.The structural damaged of resin canals with steam degreasing and high temperature process,the associated parenchyma destroyed of the outer layer of the resin channel,and some of the tracheid damaged.There is a small amount of liquid pine fat and other substances in the resin canals,it causing a cavity.6.The rupture of pit membrane on the tracheid cell walls after steam degreasing and high temperature,and the occluded pit opened.Pit border is broken up,some were even out of the surface of the pit,some of the tracheid cell walls had larger cracks along the pit border;the intercellular layer showed a greater degree of cracking,and some of the cross-field pit opened,and some even form interconnecting channels.7.Drying destroyed associated parenchyma and pit membrane,the resulting crack widens the original passage in the wood or forms a new fluid passage.It increased the number of the effective pits,which made in more transport channels within wood,and improved the permeability effectively.The movement of turpentine and evaporation of water in wood during the treatment process were promoted,and it has important influence on the high efficiency drying and degreasing of Pinus sylvestris var.mongolica.