太阳能预干联合热压干燥对桉木单板质量的影响
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摘要
采用模拟太阳能加热(50℃)及太阳能预干联合热压法(温度140～200℃;时间2～3 min;压力0.5MPa)干燥桉木单板,研究太阳能干燥及热压联合干燥条件对单板质量产生的影响,并对单板的干燥质量、力学强度、粗糙度及接触角进行测定,采用近红外光谱及扫描电镜从微观层面分析变化原因。结果表明:太阳能预干干燥过程为等速干燥,单板热压干燥可快速降低含水率,联合干燥可有效提高干燥效率和干燥质量;随热压温度升高和热压时间的延长,单板力学强度不断增大,并在温度为180℃时达到最大值;在热压条件为200℃、3 min下,单板表面粗糙度最小为5.18μm,表面粗糙度与压缩率之间呈负相关关系,相关系数均在0.74以上;在热压条件为180℃、2 min下,接触角为107.63°,并在60 s后基本进入平衡状态。对单板微观结构进行分析可知,太阳能联合热压干燥过程中,单板主要成分会发生化学变化,半纤维素及木质素发生降解,内部成分及抽提物的迁移可增加单板表面的均一性,随着温度的升高,导管及纤维壁上出现褶皱。太阳能预干联合热压干燥在结合两种干燥方式优点的同时,可改善单板表面平整性,增加单板密实化程度,并能提高力学性能。
To explore the effect of solardrying and combined with hot-pressing on the drying quality of eucalyptus veneers,the drying quality,mechanical strength,roughness and contact angle of the veneer were measured by simulated solar drying( 50 ℃) and solar-predrying combined with hot pressing( Temperature: 140 ℃-200 ℃; Time: 2-3 min; Pressure: 0.5 MPa). Near infrared spectroscopy and scanning electron microscope were used to analyze from the micro level. The drying process of solar energy was isokinetic drying,hot pressing could rapidly reduce the moisture content. Combined drying effectively improved the drying efficiency and drying quality. With increasing of temperature and time,the mechanical strengthincreased continuously,and reaches the maximum at the temperature of 180 ℃; When the condition is at 200 ℃for 3 min,the minimum surface roughness of the veneer is 5.18 μm,the surface roughness and the compression ratio have a negative correlation,and the correlation coefficient is above 0.74; Under the condition of 180 ℃ for 2 min,the contact angle is 107.63°,and the contact angleis basically in the equilibrium state after 60 s. The analysis of the microstructure of the veneer showed that chemical changes in the main components of wood occurred during hot pressing. The migration of the internal components and extracts increased the uniformity of veneer surface,the wrinkles appeared on the tube and the fiber wall with increasing the temperature. Combined with the advantages of two kinds of drying methods,solar pre-drying combined with hot pressing can improve the surface roughnessand mechanical properties of the veneer,and increase the density.
To explore the effect of solardrying and combined with hot-pressing on the drying quality of eucalyptus veneers,the drying quality,mechanical strength,roughness and contact angle of the veneer were measured by simulated solar drying( 50 ℃) and solar-predrying combined with hot pressing( Temperature: 140 ℃-200 ℃; Time: 2-3 min; Pressure: 0.5 MPa). Near infrared spectroscopy and scanning electron microscope were used to analyze from the micro level. The drying process of solar energy was isokinetic drying,hot pressing could rapidly reduce the moisture content. Combined drying effectively improved the drying efficiency and drying quality. With increasing of temperature and time,the mechanical strengthincreased continuously,and reaches the maximum at the temperature of 180 ℃; When the condition is at 200 ℃for 3 min,the minimum surface roughness of the veneer is 5.18 μm,the surface roughness and the compression ratio have a negative correlation,and the correlation coefficient is above 0.74; Under the condition of 180 ℃ for 2 min,the contact angle is 107.63°,and the contact angleis basically in the equilibrium state after 60 s. The analysis of the microstructure of the veneer showed that chemical changes in the main components of wood occurred during hot pressing. The migration of the internal components and extracts increased the uniformity of veneer surface,the wrinkles appeared on the tube and the fiber wall with increasing the temperature. Combined with the advantages of two kinds of drying methods,solar pre-drying combined with hot pressing can improve the surface roughnessand mechanical properties of the veneer,and increase the density.
引文
[1] BEKHTA P,MAMONOVAM,SEDLIACIK J,et al. Anatomical study of short-term thermo-mechanically densified alder wood veneer with low moisture content[J]. European Journal of Wood&Wood Products,2016,74(5):643-652.
[2]周永东,孙锋,吕建雄,等.6种桉木单板干燥质量的比较[J].林业科学,2014,50(11):104-108.
[3]王硕.影响未来中国胶合板行业之关键词浅析[J].中国人造板,2010,17(9):3-6.
[4]吕欢,王贵富,何正斌,等.光电—光热联合木材太阳能预干燥设备性能探析[J].林业工程学报,2016,1(3):27-32.
[5]郝文刚,陆一锋,赖艳华,等.直接式太阳能干燥系统的热性能分析及应用[J].农业工程学报,2018,34(10):187-193.
[6] BELESSIOTIS V,DELYANNIS E. Solar drying[J]. Solar Energy,2011,85(8):1665-1691.
[7]邹淑萍,孟伊娜,张健,等.太阳能干燥装置对四种蔬菜干制效果的影响研究[J].新疆农业科学,2017,54(8):1505-1512.
[8]张璧光,伊松林.我国太阳能干燥现状及在热利用中应有的地位[J].干燥技术与设备,2012,10(1):32-37.
[9]王云峰,李明,王六玲,等.太阳能干燥装置性能及三七干燥效果[J].农业工程学报,2010,26(10):377-383.
[10] GERTZOS K P,CAOURIS Y G,PANIDIS T. Optimal den and placement of serpentine heat exchanges for indirect heat withdrawal,inside flat plate integrated collector storage solar water heaters(ICSSWH)[J]. Renewable Energy,2010,35(8):1741-1750.
[11] KOUKOUCH A,IDLIMAM A,ASBIK M,et al. Experimental determination of the effective moisture diffusivity and activation energy during convective solar drying of olive pomace waste[J].Renewable Energy,2017,101:565-574.
[12]史海舰,钱珊珠,淮守成,等.新型太阳能干燥系统的智能控制系统研究设计[J].农机化研究,2019,41(1):263-268.
[13]于海涛,高建民,陈瑶.储热技术在木材太阳能干燥中的应用与发展趋势[J].储能科学与技术,2015,4(4):382-387.
[14]陈琛,范祥林,邓玉和,等.密实化杨木单板的研究[J].浙江农林大学学报,2013,30(4):536-542.
[15] BEKHTA P,SEDLIACIK J,JONES D. Effect of short-term thermomechanical densification of wood veneers on the properties of birch plywood[J]. European Journal of Wood&Wood Products,2017,76(2):549-562.
[16] BEKHTA P,KRYSTOFIAK T. The influence of short-term thermo-mechanical densification on the surface wettability of wood veneers[J]. Maderas Ciencia Y Tecnologia,2016,18(1):79-90.
[17] FANG C H,MARIOTTI N,CLOUTIER A,et al. Densification of wood veneers by compression combined with heat and steam[J]. European Journal of Wood&Wood Products,2011,70(1/2/3):155-163.
[18]孙锋,周永东,李晓玲,等.桉木单板出材率的研究[J].北京林业大学学报,2013,35(4):128-133.
[19] ARRUDA L M,MENEZZI C H. Effect of thermomechanical treatment on physical properties of wood veneers[J]. International Wood Products Journal,2013,4(4):217-224.
[20] BEKHTA P,HIZIROGLU S,SHEPELYUK O. Properties of plywood manufactured from compressed veneer as building material[J]. Materials&Den,2009,30(4):947-953.
[21]龙传文.粗皮桉木材的干燥特性与干燥基准制定[J].中南林业科技大学学报,2012,32(1):48-50,60.
[22] BEKHTA P,PROSZYK S,KRYSTOFIAK T,et al. Effect of thermomechanical densification on surface roughness of wood veneers[J]. Wood Material Science&Engineering,2014,9(4):233-245.
[23] BEKHTA P,NIEMZ P,SEDLIACIK J. Effect of pre-pressing of veneer on the glueability and properties of veneer-based products[J]. European Journal of Wood&Wood Products,2010,70(1/2/3):99-106.
[24]徐信武,孙涛,杨刚,等.干燥处理对速生材单板表面特性的影响[J].材料热处理学报,2012,33(10):37-40.
[25]储德淼,母军,赖宗元,等.氮磷阻燃联合热处理杨木表面性能及热稳定性[J].建筑材料学报,2017,20(6):931-936.
[2]周永东,孙锋,吕建雄,等.6种桉木单板干燥质量的比较[J].林业科学,2014,50(11):104-108.
[3]王硕.影响未来中国胶合板行业之关键词浅析[J].中国人造板,2010,17(9):3-6.
[4]吕欢,王贵富,何正斌,等.光电—光热联合木材太阳能预干燥设备性能探析[J].林业工程学报,2016,1(3):27-32.
[5]郝文刚,陆一锋,赖艳华,等.直接式太阳能干燥系统的热性能分析及应用[J].农业工程学报,2018,34(10):187-193.
[6] BELESSIOTIS V,DELYANNIS E. Solar drying[J]. Solar Energy,2011,85(8):1665-1691.
[7]邹淑萍,孟伊娜,张健,等.太阳能干燥装置对四种蔬菜干制效果的影响研究[J].新疆农业科学,2017,54(8):1505-1512.
[8]张璧光,伊松林.我国太阳能干燥现状及在热利用中应有的地位[J].干燥技术与设备,2012,10(1):32-37.
[9]王云峰,李明,王六玲,等.太阳能干燥装置性能及三七干燥效果[J].农业工程学报,2010,26(10):377-383.
[10] GERTZOS K P,CAOURIS Y G,PANIDIS T. Optimal den and placement of serpentine heat exchanges for indirect heat withdrawal,inside flat plate integrated collector storage solar water heaters(ICSSWH)[J]. Renewable Energy,2010,35(8):1741-1750.
[11] KOUKOUCH A,IDLIMAM A,ASBIK M,et al. Experimental determination of the effective moisture diffusivity and activation energy during convective solar drying of olive pomace waste[J].Renewable Energy,2017,101:565-574.
[12]史海舰,钱珊珠,淮守成,等.新型太阳能干燥系统的智能控制系统研究设计[J].农机化研究,2019,41(1):263-268.
[13]于海涛,高建民,陈瑶.储热技术在木材太阳能干燥中的应用与发展趋势[J].储能科学与技术,2015,4(4):382-387.
[14]陈琛,范祥林,邓玉和,等.密实化杨木单板的研究[J].浙江农林大学学报,2013,30(4):536-542.
[15] BEKHTA P,SEDLIACIK J,JONES D. Effect of short-term thermomechanical densification of wood veneers on the properties of birch plywood[J]. European Journal of Wood&Wood Products,2017,76(2):549-562.
[16] BEKHTA P,KRYSTOFIAK T. The influence of short-term thermo-mechanical densification on the surface wettability of wood veneers[J]. Maderas Ciencia Y Tecnologia,2016,18(1):79-90.
[17] FANG C H,MARIOTTI N,CLOUTIER A,et al. Densification of wood veneers by compression combined with heat and steam[J]. European Journal of Wood&Wood Products,2011,70(1/2/3):155-163.
[18]孙锋,周永东,李晓玲,等.桉木单板出材率的研究[J].北京林业大学学报,2013,35(4):128-133.
[19] ARRUDA L M,MENEZZI C H. Effect of thermomechanical treatment on physical properties of wood veneers[J]. International Wood Products Journal,2013,4(4):217-224.
[20] BEKHTA P,HIZIROGLU S,SHEPELYUK O. Properties of plywood manufactured from compressed veneer as building material[J]. Materials&Den,2009,30(4):947-953.
[21]龙传文.粗皮桉木材的干燥特性与干燥基准制定[J].中南林业科技大学学报,2012,32(1):48-50,60.
[22] BEKHTA P,PROSZYK S,KRYSTOFIAK T,et al. Effect of thermomechanical densification on surface roughness of wood veneers[J]. Wood Material Science&Engineering,2014,9(4):233-245.
[23] BEKHTA P,NIEMZ P,SEDLIACIK J. Effect of pre-pressing of veneer on the glueability and properties of veneer-based products[J]. European Journal of Wood&Wood Products,2010,70(1/2/3):99-106.
[24]徐信武,孙涛,杨刚,等.干燥处理对速生材单板表面特性的影响[J].材料热处理学报,2012,33(10):37-40.
[25]储德淼,母军,赖宗元,等.氮磷阻燃联合热处理杨木表面性能及热稳定性[J].建筑材料学报,2017,20(6):931-936.