木材真空-浮压干燥特性的试验研究

以马尾松为试验材料 ,首先分别以过热蒸汽和空气作为干燥介质 ,在预热阶段通过对木材内部温度场和含水率变化的测定 ,探讨了木材真空 -浮压干燥预热阶段的特性 ;然后 ,通过对干燥介质条件与干燥速率之间影响关系的研究 ,总结出木材真空 -浮压干燥的特性。结果表明 :真空 -浮压干燥预热阶段进行得非常迅速 ,同时其表面水分的凝结量也较空气干燥大 ;木材的浮压干燥速率随着干燥介质温度的增加、绝对压力的减小和浮动频率的加大而增加。上述因素中对干燥速率影响程度从大到小的排列顺序为 :介质温度 (T) >压力浮动频率 (Hz) >绝对压力 (P)     

人工林落叶松髓心方材高频/真空干燥工艺研究

对人工林落叶松含髓心方材进行高频真空干燥试验,以确定高频真空干燥工艺参数。结果表明,适宜的高频真空干燥工艺,不但能保证落叶松髓心方材干燥质量,而且能大幅度提高干燥速度。试验得出较佳的干燥工艺条件为:电流0.4A,输入电压2kV;高频开启3min停1min,控制温度50℃;干燥初期真空度为13.33kPa,干燥后期真空度为6.67kPa。     

杨木真空干燥的临界尺寸研究

以不同横截面、长厚比的杨木试材,在干燥温度为45、65、85 ℃,绝对压力0.02 MPa的真空干燥条件下,通过未封面与侧面封闭试件的对比试验,对杨木真空干燥临界尺寸进行了研究.结果表明:木材的临界尺寸随干燥温度的升高而增大,随侧面积与体积比率的减小而减小.     

过热蒸汽预处理对落叶松方材高频/真空干燥质量的影响

对落叶松髓心方材采用不同温度的过热蒸汽预处理,再利用前期试验得出的高频/真空干燥参数进行试验。结果表明,采用常压105℃过热蒸汽预处理31 h,高频/真空干燥后试材的表裂明显减少,且终含水率分布更加均匀;过热蒸汽预处理工艺使高频/真空干燥周期有所延长,但综合考虑干燥周期和干燥质量,认为此工艺具有可行性。     

人工林落叶松髓心方材的高频真空干燥(英文)

对截面尺寸为100mm×100mm的人工林落叶松髓心方材进行系列高频真空干燥试验,分析研究不同高频真空干燥条件下干燥质量和干燥速度的变化规律,获得合理的高频真空干燥工艺基准;为了进一步减少试材表裂,干燥前对试材进行切口和过热蒸汽预处理。结果表明:沿试材长度方向的中心位置切口和过热蒸汽预处理都能有效减少试材表裂,提高干燥质量。     

沙棘鲜果渣真空干燥技术研究

为研究沙棘鲜果渣在真空干燥条件下的干燥特性,进而确定适宜的工艺参数,笔者选用了不同的干燥温度、真空度和物料厚度对沙棘鲜果渣进行脱水干燥试验,测定不同干燥工艺条件下沙棘果渣的干燥特性,并对干燥后沙棘果渣的总黄酮和原花青素含量进行测定。试验结果表明,适宜的沙棘鲜果渣真空干燥工艺条件为:干燥温度60℃,真空度80 k Pa,物料厚度1. 0 cm.干燥后的沙棘果渣总黄酮含量最高达4. 98 mg/g,原花青素含量最高达35. 67 mg/g.     

人工林杨木的高频真空干燥工艺

在人工林杨木的高频真空干燥系列试验中,通过不断改变干燥工艺参数并分析总结试验结果,从而确定杨木高频真空干燥适宜的工艺基准。结果表明,在本试验确定的高频真空干燥工艺下,初含水率较高的杨木不仅能保证干燥质量,而且干燥速度可比常规蒸汽干燥法和高温蒸汽干燥法提高数倍。     

木材真空-过热蒸汽干燥的预热特性

在真空状态下，分别对过热蒸汽和空气为干燥介质时木材干燥预热阶段进行对比试验，探讨了木材在真空－过热蒸汽干燥中预阶段的工艺特性。结果表明：过热蒸汽干燥的预热阶段进行得非常迅速，同时其表面水分的凝结量也较以空气为介质时表面水分的凝结量大。     

木材微波-真空干燥基本规律

对微波一真空干燥马尾松木材的干燥规律进行研究.结果表明:微波一真空干燥过程可分为加速、恒速和减速3个阶段,其中恒速干燥占整个干燥时间的50%以上;随着微波辐射时间和木材初含水率的增加,平均干燥速率显著增加;干燥室的真空度与木材的微波-真空干燥速率存在微弱正相关关系;木材厚度对干燥速率影响不显著.     

木材对流加热间歇真空干燥工艺研究

把木材堆放在密闭的容器内,在低于大气压力的条件下进行干燥的方法,称为木材真空干燥。一些常规窑干中易开裂、皱缩的木材,较难干燥的原锯材,采用真空干燥法,可在较低的温度下获得较快的干燥速度,干燥周期明显缩短,并可提高其干燥质量。     

木材真空干燥特点及国内研究现状

阐述了木材真空干燥的特点和国内研究现状,真空干燥可满足木材高品质、高效率、低成本的干燥目标,对推进行业节能减排工作、解决难干材和改性处理材干燥问题、提高干燥品质等均具有重要意义。对真空干燥木材的机理、研究进展、可能的研究方向进行评述,以期促进木材真空干燥科研工作和生产实践的共同发展。     

木材柔性真空干燥技术的发展与应用

介绍国内外木材柔性真空干燥技术的研究进展和应用现状,在分析现存问题的基础上,提出完善柔性真空干燥技术的建议,以期解决珍贵木材、大规格材、异型材等的干燥难题,实现这些木材的高质量、快速干燥。     

Dynamic viscoelastic behavior of wood under drying conditions

In this study heartwood from a Chinese fir [Cunninghamia lanceolata (Lamb.) Hook] plantation was treated using a high-temperature drying (HTD) method at 115°C, a low-temperature drying (LTD) method at 65°C, and freeze vacuum drying (FVD), respectively. The dynamic viscoelastic properties of dried wood specimens were investigated. The measurements were carried out at a temperature range of −120 to 250°C at four different frequencies (1, 2, 5, and 10 Hz) using dynamic mechanical analysis (DMA). We have drawn the following conclusions: 1) the storage modulus E′ and loss modulus E″ are the highest for HTD wood and the lowest for FVD wood; 2) three relaxation processes were detected in HTD and LTD wood, attributed to the micro-Brownian motion of cell wall polymers in the non-crystalline region, the oscillations of the torso of cell wall polymers, and the motions of the methyl groups of cell wall polymers in the non-crystalline region in a decreasing order of temperatures at which they occurred; and 3) in FVD wood, four relaxation processes were observed. A newly added relaxation is attributed to the micro-Brownian motions of lignin molecules. This study suggests that both the HTD and the LTD methods restrict the micro-Brownian motion of lignin molecules somewhat by the cross-linking of chains due to their heating history. __________ Translated from Journal of Beijing Forestry University, 2008, 30(3): 96–100 [译自: 北京林业大学学报]     

木材真空干燥设备及工艺参数

介绍了真空干燥的基本原理、干燥设备结构,以及间歇式真空干燥工艺和参数。     

Drying characteristics of wood under vacuum-superheated steam

This paper presents comparison and analysis of thermal-dynamic characteristics of air-drying and superheated steam drying under vacuum. The result reveals that for both convective heat transfer coefficient and resistance of mass transfer on the surface, superheated steam drying under vacuum is superior to air-drying under the same condition. With Masson pine as specimen,we found that the inversion temperature really exists through comparable experiments of air-drying and superheated steam drying under vacuum. When temperature is above inversion point of temperature, drying speed is faster than that of air-drying; however, if temperature is below the point, the result is opposite. The inversion temperature of experiment ranges from 80 to 85 ℃.     

木材改性、干燥一体设备

介绍一种木材改性、干燥一体设备,其可一次完成木材改性的前期真空处理、高压浸渍和干燥.这两个过程的有机结合可有效地减少木材干燥缺陷的产生,简化操作程序,降低劳动强度,实现整个过程的清洁生产和自动控制,提高了生产效率.     

Effect of compressive load on the dimensional changes of the Japanese larch dried in a radio-frequency/vacuum drier

This study investigated the effect of a compressive load of 0.092 MPa on the dimensional changes of Japanese larch in a humidity chamber after continuous radio-frequency/vacuum drying. The dimensional changes in the loading directions were significantly increased while those perpendicular to the loading directions were decreased. The shrinkages showed higher values in continuous drying than in intermittent drying. For the specimens loaded on their tangential sections, the radial shrinkages were even higher than the tangential shrinkages; thus, the tangential/radial shrinkage ratio was decreased by 0.27. The transverse hygroscopicity was reduced for the specimens loaded on their cross sections, but increased for the specimens loaded on their tangential sections.     

天然栀子黄色素的低温真空干燥研究

以加热板温度、干燥箱内真空度、料液的质量分数和料层厚度为影响因素,研究了天然栀子黄色素低温真空干燥制粉的优化工艺,设计了L9(34)的正交试验.当干燥产品达到一致的含水量时,对其色价(CV)、色差(CD)等指标以及干燥时间进行了分析.结果表明:加热板温度对产品的色价、色差以及干燥时间影响最大;料层厚度对栀予黄色素的色价...     

Factors affecting relative humidity during wood vacuum drying

Effects of pressure and temperature in the chamber during vacuum drying on the relative humidity and evaporation of wood surface were investigated by using the vacuum chamber. The setting temperature during vacuum drying included dry-bulb temperature td, the wet-bulb temperature tw and the temperature difference between the air in the vacuum chamber and the cooling water in the condenser. Results indicated that relative humidity during vacuum drying was affected by the dry-bulb temperature td, the wet-bulb temperature tw and the temperature difference between the air in the vacuum chamber and the water in the condenser. Relative humidity of wood decreased with the increase in temperature at the given temperature of the water in the condenser. The relative humidity was affected slightly by pressure in the vacuum chamber pA, and it decreased from 70% to 65% with pA increased from 50 kPa to 101 kPa. Moreover, there was nearly no evaporation under the vacuum without external heating.     

小径柞木真空干燥应力的试验研究

在真空干燥条件下,分析小径级柞木板材的应力与含水率、时间的关系,结果表明:在低温条件下,由于真空负压作用,水分蒸发速度得到了加快,干燥应力由于干燥前板材内的初始应力的差异,导致干燥过程中应力的发生、发展有所差异。根据应力表现的差异应当在干燥不同阶段及时进行调湿处理,预防板材开裂产生。