The Drying And Degreasing Characteristic Research On Micro-pressure And Automatic Release Superheated Steam With Pinus Massoniana Wood

As the most widely distributed in China,the largest number of pinus wood with rich resin content which limited the effective drying,and in long-term use,that was easily to overflow the redundant resin also restricted the improvement of the added value for their products.This research chosen Pinus massoniana Lamb.Plantation wood as research object,used micro-pressure and automatic release superheated steam as drying and degreasing modified medium,studied the change of temperature and the moisture content within wood under six different(110?160?)temperature superheated steam and two different thickness boards,discussed the effect of superheated steam temperature on drying rate,drying qualities,color and mechanical strength of dried and greased wood,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 pinus wood for effective drying and degreasing with superheated steam.Finally,in order to promote the academic achievement industrialization process,this study conducted a large capacity of pinus lumber for factory pilot research based on the selected optimum parameters in the laboratory.The main conclusions are as follows:1)According to the change of temperature and moisture content of pinus wood during the superheated steam drying and degreasing process,which could be divided into firstly rapid warming and accelerating drying period,then keeping the constant temperature drying period,and lately slow drying period three sections.Superheated steam temperature affected the drying rate significantly,and the thicknesses of boards showed little influence compared to the temperature;2)Compared with drying qualities of conventional dried wood,all of superheated steam dried wood achieved the standard about lumber drying qualities for second and above class with lower final moisture content,higher drying uniformity,less visible drying defects et al;while with higher superheated steam temperature,the more visible drying defects were showed,it must be mentioned that the medium temperature within treatment environment should be controlled within 140? when making the benchmark for drying and degreasing pinus wood,to ensure the higher drying rate with ideal drying qualities;3)The superheated steam dried pinus wood from 110 ? to 160 ? kept the primary colors after high temperature treatment,with the increase of temperature,the total color difference(?E*)showed the more obviously rising trend,compared with the conventional dried woodl,the change range of ?E*was 0.87?6.85;superheated steam temperature showed the significant effect on dimensional stability on pinus wood,when adjusting the temperature of superheated steam,which not only improved the permeability,but also reduced the absorption,and increased the ability to resist for deformation caused by the change of external environment;The lower temperature from 110? to 130? treatment had little affection on MOE,MOR of dried wood,while with the hiher temperature rose to and more than 140 ?,there was serious damage to the mechanical strength of wood,which MOR and MOE significantly reduced 37.71%and 42.78%respectively,compared to the conventional dried wood;4)After drying and degreasing through superheated steam,there was no resin overflow on the surface of treated boards,which achieved the class one for pinus wood in degreasing standard;and the micro-structure observation showed the damaged resin canals,which appeared the empty canal holes or contained solid colophony with ball and granular form inside;the superheated steam destroyed the pits membrane and the associated organizations closed to the thin-wall resin canals,and increased the number of the effective pits,which made in more transverse transport channels within wood,and improved the permeability effectively;5)The factory pilot research chosen 140 ? as drying temperature to realize the fast and effective industrialized drying for pinus wood;the drying time was shorten to 20 hours with 10m~3 lumber,and all of two batches kiln dried pinus wood reached the class 2 for drying qualities standard without visible defects,and some overflowed resin appeared on the dried surface,which accounted for the effective degreasing after superheated steam drying;there was little color change after wrot treatment,which achieved the integration for drying and degreasing with no color change in pinus wood;No air exchange from the outside in whole drying process,and the internal pressure could discharge from vapor form without emissions,which made the environment friendly work during the wood drying process.Because of the poor air circulation in the kiln drying process,there were big difference in drying uniformity,and in the later research,it is high time to develop the superheated steam kiln drier which support the better air circulation for fast-growing wood.