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杉木人工林木材的高频真空干燥工艺 总被引：2，自引：0，他引：2
对人工林杉木25mm和50mm厚板材进行了系列高频真空干燥试验.结果表明:干燥后的板材变形小,表面平整,表芯层含水率差异较小.尽管试板的初始含水率差异较大,但根据高频真空干燥靠近正极板的木材比靠近负极板的干燥速度快的特点,试板的初始含水率由低至高在负极板至正极板之间进行顺序摆放码垛,干燥后的板材含水率可达到均匀一致. 相似文献
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小径级柞木干燥试验结果表明:在干燥初期干球温度为35℃、干燥末期干球温度为70℃、干燥周期中进行两次中间处理和末期终了处理、干燥周期为15 d的工艺条件下,板材干燥前总平均含水率41.6%,干燥结束后总平均含水率11.7%,板材厚度上含水率偏差<3%;干燥结束后伸长应力和压缩应力甚微,板材表面的颜色轻微变暗,除髓心材和水纹材有少数裂纹和轻微变形外,其余木材并没有发生翘曲、变形、开裂等干燥缺陷,干燥质量满足了GB6491—86《国家锯材干燥质量标准》二级以上的指标要求。本次试验确定的干燥工艺满足了小径级柞木板材的干燥工艺要求。 相似文献
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本文论述了板材在热压机加热加压下干燥的温度变化规律,分析了其内应力的变化,以及压力对板材内裂和收缩的影响。说明应用本方法干燥板材,不仅能缩短干燥周期,而且能保证干燥质量,提高木材的利用率。为正确应用这一技术和确定合理的工艺参数提供了理论依据。 相似文献
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采用高频真空干燥、常规窑干和高温干燥3种方法对杉木人工林木材的心、边板材进行干燥处理,用毛细管上升法评价干燥后试样的浸注性能,用半薄切片法测定干燥试样具缘纹孔的闭塞率,最后用扫描电子显微镜观察干燥试样微观构造的变化,比较分析3种干燥方法对杉木人工林木材浸注性的影响机理.结果表明:对于杉木边材,经高频真空干燥后试样的浸注性显著高于常规干燥和高温干燥后试样的浸注性,后2种干燥方法对试样浸注性影响的差异并不显著;对于杉木心材,高频真空干燥与高温干燥后试样的浸注性存在显著差异,而高频真空干燥与常规干燥之间、高温干燥与常规干燥之间对试样浸注性的影响差异均不显著;3种干燥方法处理后,杉木边材的浸注性均显著高于心材的浸注性;具缘纹孔的闭塞率较低以及部分具缘纹孔周缘破裂是高频真空干燥后木材浸注性提高的主要原因. 相似文献
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木材高频真空干燥及其应用前景 总被引：3，自引：0，他引：3
一、国内外发展概况及特点木材高频真空干燥是七十年代初首先在前苏联、美国、日本等国研究发展起来的一项先进的干燥技术,八十年代初开始应用于生产。美国的一家动力公司和日本的制造厂商,已推出高频真空干燥机的系列化产品,在欧、美及包括中国台湾在内的很多国家和地区推广应用。高频真空干燥的最大特点是木材干燥极为迅速。由于采用高频介电加热和在连续真空条件下作业,木材可在很短的时间内获得充分的热量,并在较低的温度下迅速干燥。一些用常规窑干法需要干燥数天乃至数十天的木料,采用高频真空干燥,仅需数小时或数十小时即可,干燥周期可缩短17 相似文献
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大果紫檀等3种红木薄板的高频真空干燥 总被引：1，自引：0，他引：1
《林业工程学报》2017,(1)
高频真空联合干燥具有高频快速加热及真空下水的沸点降低的双重优势,能够实现木材低温快速干燥,在大尺寸及名贵木材的干燥领域具有明显的优势。红木家具及工艺制品具有很高的经济和文化价值,但常规干燥由于温度高、周期长,容易导致红木变色、变脆及开裂等缺陷,严重影响了红木制品的质量。笔者在相同温度条件下对3种红木薄板进行高频真空干燥和常规干燥,对比分析了干燥后红木薄板的含水率分布、开裂、变色及干燥速度。试验结果表明:经过高频真空干燥的红木质量能达到国标二级,平均含水率达到家具及木制品生产工艺要求,颜色变化小,干燥速度快,尤其在高含水率范围内干燥速度更快。高频真空干燥能够提高红木薄板的干燥速度、干燥质量和效率,是红木材料干燥的优良方法。 相似文献
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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。 相似文献
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以35 mm厚柞木板材为对象,在常规干燥过程中的预热阶段分别对其进行不同条件(时间、温度)的处理,之后以相同工艺基准实施第一阶段干燥,检测试件干燥速度、含水率分布、残余应力指标及表面缺陷,通过对上述参数的对比分析,确定适宜预热处理条件,以及该条件对中间处理时机的影响。结果表明:预热时间是决定预热处理过程中含水率梯度的重要因素,预热温度对其没有影响;增加预热时间、提高预热温度,可以使干燥前期的干燥速度加快、含水率梯度和残余应力指标减小、中间处理时机滞后;对于35 mm厚柞木板材,温度70℃、湿度100%预热处理8 h为最佳条件,可以得到较好的干燥效果。 相似文献
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水分胁迫对栓皮栎幼苗生理特性及生长的影响 总被引：11，自引：0，他引：11
通过盆栽实验，研究了在不同的水分条件下栓皮栎幼苗生理特性的变化和苗木生长量的变化。研究表明，在水分胁迫初期，随土壤含水量的降低，栓皮栎叶片的净光合速率、蒸腾速率下降，而水分利用效率提高。在水分胁迫末期，由于长期的干旱胁迫，水分条件最差的一组苗木已干枯死亡，土壤含水量从38．123％下降到20．323％时，净光合速率和蒸腾速率均下降，水分利用效率也下降。随着土壤含水量的降低，苗高、地径和生物量均有下降的趋势，其中生物量下降的幅度最大。 相似文献
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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. 相似文献
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Sadoth Sandoval-Torres Wahbi Jomaa Fran?oise Marc Jean-Rodolphe Puiggali 《Wood Science and Technology》2012,46(1-3):177-191
The formation of chromophore groups from a phenolic compound oxidized with air and the formation of dark materials from hydrolysable extractives are considered as causes of discoloration. In this work, the colour changes, antioxidant capacity, and Fourier Transform Infrared Spectra of dust-wood are investigated in European oak wood under different plain vacuum drying conditions. The conductive heat source is maintained at four temperatures (46, 61, 70 and 80°C), and vacuum in the chamber is controlled at three different intervals (60–100, 150–200, and 250–300?mbar). Drying kinetics and temperature profiles are presented. The results suggest that degradation of extractives allows yellowing in wood and temperature improves lightness under these special drying conditions (plain vacuum). Furthermore, the presence of carbonyl groups in surfaces is related to the loss in antioxidant potency. 相似文献
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The objective of this research was to analyze the cyclic vacuum drying curve within one cycle. Red oak specimens of two different groups, square in cross-section, were used. Group one was comprised of four different thicknesses (2.54, 3.81, 5.08, and 6.35 cm) with a length of 25.4 cm and group two was comprised of three different lengths (12.7, 25.4, and 38.1 cm) with the thickness of 2.54 cm. The specimens were heated to 60°C in the heating oven and then dried in the vacuum oven at 18 mm Hg. The vacuum oven was at room temperature (20°C). The vacuum pump was kept running for 140 min. It was found that the cyclic vacuum drying curve consisted of two distinct parts. The fast drying period lasted about 10 to 15 min. The slow drying period occurred when the pressure inside wood approached the ambient pressure. Most of the moisture was removed during the fast drying period. 相似文献
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Jaime Puértolas Marta Pardos María Dolores Jiménez Ismael Aranda José Alberto Pardos 《Annals of Forest Science》2008,65(6):611-611
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YiSonglin ZhangBiguang ChangJianmin DuChaogang 《中国林学(英文版)》2004,6(2):41-45
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 ℃. 相似文献
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对刨光后发生弯曲的厚度为３０ｍｍ的柞木刨光材进行回窑处理试验。试验结果表明，采用ＣＬＺ型侧风干燥窑在指接干球温度７０℃，平衡含水率１４．７％的干燥介质条件下，维持该干燥介质条件１７ｈ后，使弯曲的柞木刨光材基本恢复了平直。 相似文献
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以硬阔叶材柞木为研究对象，通过研究预热处理时间对锯材干燥质量和干燥速度的影响为制定节能预处理干燥工艺提供依据。结果表明：在相同条件下，25 mm厚的柞木锯材经常规预热处理（预热3.25 h）与预热2 h的干燥速度之间没有明显差异；预热2 h的锯材干燥质量能够达到GB/T 6491-2012《锯材干燥质量》规定的二级标准。 相似文献