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1.
对40 mm厚杉木锯材制定两个高温干燥工艺并进行试验研究,检测和分析干燥周期、干燥速率、锯材干燥质量等指标。干燥工艺I采用高温湿空气进行干燥;干燥工艺II在干燥前期高含水率阶段采用过热蒸汽条件,干燥后期低含水率阶段采用高温湿空气进行干燥。结果显示:两个干燥工艺在各阶段的干燥速率差异明显,干燥前期工艺II的干燥速率为1.30%/h,较工艺I低约37.2%;但干燥后期工艺II的干燥速率为1.89%/h,较工艺I高约70.27%。干燥工艺II可以有效避免锯材内裂的发生,干燥质量满足GB/T 6491—2012《锯材干燥质量》二级材的指标要求,干燥效率提高。 相似文献
2.
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.
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Translated from Journal of Beijing Forestry University, 2008, 30(3): 96–100 [译自: 北京林业大学学报] 相似文献
3.
Sub-alpine fir (Abies lasiocarpa (Hook)) is characterized by its low permeability and that it is then hard-to-dry. Long drying time for the species causes kiln
capacity problems for numbers of spruce-pine-fir (SPF) lumber producers. A high-temperature drying schedule with a rapid rise
in dry-bulb temperature to a temperature above boiling point at the beginning is a potential approach to enhance the drying
productivity. Determinations in permeability of ten sub-alpine fir boards after slow heating and fast heating were carried
out in this study. The results indicated that a rapid rise in temperature increased the permeability of sub-alpine fir. By
statistical analysis, the permeability was increased significantly due to the fast heating in seven boards. The permeability
in other three boards was also increased, but not significantly. Using a scanning electron microscope (SEM), the impact of
heating speed on pit membrane of sub-alpine fir lumber was investigated. A small number of fine fractures were observed on
the pit membrane after slow heating, while in case of fast heating, the torus was partially ruptured and a separation occurred
in pit border and cell wall. By observing the SEM images, it was suggested that the force of vaporization and/or thermal stresses
due to the fast heating were able to open the aspirated pits and/or break the membranes in the wood cells, and therefore increase
the permeability, intensify the moisture transportability and improve the dry-ability of sub-alpine fir lumber. 相似文献
4.
Jianxiong Lü Zhiyuan Lin Jiali Jiang Youke Zhao Jinghui Jiang Ruiqing Gao Yafang Yin 《Frontiers of Forestry in China》2007,2(2):222-226
Chinese fir plantation sapwood and heartwood boards were treated by three drying methods: radio frequency-vacuum drying (RFVD),
conventional kiln drying (KD) and high temperature drying (HTD). The maximum amount of dyeing solution uptake by the capillary
rising method was used to evaluate the liquid penetration of the treated wood. The pit aspiration ratio was determined by
a semithin section method. Changes in wood microstructure were investigated using scanning electron microscopy. The results
show that liquid penetration of Chinese fir sapwood after RFVD is significantly higher than that after KD and HTD. Liquid
penetration of Chinese fir heartwood after RFVD is higher than that after HTD. Liquid penetration of Chinese fir sapwood is
significantly higher than that of heartwood after three drying treatments. Low pit aspiration ratio and cracks of some bordered
pits are the main reasons for the increase in liquid penetration after RFVD treatment.
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Translated from Scientia Silvae Sinicae, 2006, 42(10): 85–90 [译自: 林业科学] 相似文献
5.
To investigate the influence of heating and drying history on the microstructure of dry wood, in addition to the dynamic viscoelastic
properties, CO2 adsorption onto dry wood at ice.water temperature (273 K) was measured, and the micropore size distribution was obtained
using the Horvath-Kawazoe (HK) method. Micropores smaller than 0.6 nm exist in the microstructures of dry wood, and they decreased
with elevating out-gassing temperature and increased again after rewetting and drying. Dry wood subjected to higher temperatures
showed larger dynamic elastic modulus (E′) and smaller loss modulus (E″). This is interpreted as the result of the modification at higher temperature of the instability caused by drying. Drying
history influenced the number of micropores smaller than 0.6 nm in dry wood not subjected to high temperature, although the
difference in the number of micropores resulting from the drying history decreased with increasing out-gassing temperature.
A larger number of micropores smaller than 0.6 nm exist in the microstructure of dry wood in more unstable states, corresponding
to smaller E′ and larger E″ than in the stable state. Consequently, unstable states are considered to result from the existence of temporary micropores
in the microstructures of dry wood, probably in lignin.
Part of this report was presented at the 55th Annual Meeting of the Japan Wood Research Society, Kyoto, March 2005, and at
the 56th Annual Meeting of the Japan Wood Research Society, Akita, August 2006 相似文献
6.
Determination of diffusion coefficients for sub-alpine fir 总被引：5，自引：0，他引：5
Liping Cai 《Wood Science and Technology》2005,39(2):153-162
Estimates of the drying rate for sub-alpine fir lumber and the effect of process variables on final moisture contents are valuable information for kiln operators. The diffusion approach offers one generalized way to estimate the drying time required and the final moisture content distribution. The diffusion coefficients of normal wood and wet wood of sub-alpine fir lumber were determined by two types of approaches in this study: the traditional method and the inverse moisture diffusion algorithm. The results from both approaches indicate that the diffusion coefficient of normal wood is greater than that of wet wood for sub-alpine fir. 相似文献
7.
Mechanical behaviour of Eucalyptus wood modified by heat 总被引：4，自引：2，他引：2
J. A. Santos 《Wood Science and Technology》2000,34(1):39-43
Summary Eucalyptus wood (Blue gum) shows very high mechanical performances, presents very few knots and gives strong glued joints,
reasons that justify its interest for structural uses, carpentry and furniture components or even building construction. The
inconveniences of this species are its slow and difficult drying process and its low dimensional stability – with very high
swelling and shrinkage coefficients.
The drying process has been studied at INETI and the problem revealed to be solved with appropriate drying schedules and the
stresses released by a steam treatment. Heat treatment of Eucalyptus wood has been identified as one of the most promising
techniques to increase its dimensional stability. Studies in this area still proceed.
This paper presents some test results that show the influence of heat treatment in the strength properties of this wood, namely
the bending modulus of elasticity and tensile strength perpendicular to grain, in addition to the explanation of dimensional
stability evaluation and some results of dimensional stability treatments.
Received 15 June 1998 相似文献
8.
9.
10.
Summary A previous article presented the theoretical development of analytical indices to rate the severity of kiln schedules used to dry wood. These indices take into account the dry and wet bulb temperatures used during a kiln schedule together with the points of application and duration of application of each combination of temperature and humidity used. Experimental data for several such indices are presented for collapse development during the kiln drying of incense cedar pencil slats. While promising, the results were inconclusive as to the use of a severity integral for prediction of the effect of different schedules or schedule changes on drying degrade. A lack of homogeneity in the test material confounded the results.The assistance of the California Cedar Products Company, Stockton, California and, in particular, Charles Berolzheimer and John Rhemrev, is gratefully acknowledgedThe authors are, respectively, Research Associate and Project Leader, Forest Products Laboratory, University of California, Richmond 相似文献
11.
We studied seed storage behaviour of a multipurpose tree Calophyllum inophyllum (Clusiaseae). Seeds were collected at Roslyn bay (23°7′60″ S, 150°43’60″ E) Central Queensland. Seed drying and desiccation tolerance tests were carried out according to International Seed Testing Association (ISTA) rules. We found C. inophyllum seeds to be recalcitrant and vulnerable to chilling injury, hence, unsuited for cold storage. C. inophyllum seeds maintained their viability for an appreciable period (> 8 months) if stored in warmer environments. 相似文献
12.
以菲律宾桃花芯木为研究对象,探索30 mm厚菲律宾桃花芯木锯材干燥工艺。通过百度试验法得知其初期开裂为3级、内裂为2~3级、截面变形为1级;通过密度测定实验得知其气干密度为0.562 g/cm^3、全干密度为0.517 g/cm^3和基本密度为0.465 g/cm^3。根据该木材密度和干燥特性制定3种30 mm厚菲律宾桃花芯木锯材干燥基准并分别进行常规干燥工艺试验。通过对3次工艺试验结果的综合分析表明：在3次工艺实验所用执行基准均能满足2级干燥指标。其中,第一次工艺实验所用执行干燥基准为本研究中最佳干燥基准。第一次工艺实验的初始温度为60℃,末期温度为80℃、初含水率为66.97%、终含水率为7.79%的锯材干燥周期为185 h。 相似文献
13.
ZHOU Yongdong LI XiaolingResearch Institute of Wood Industry Chinese Academv of Forestry Beiijing P.R.China 《中国林业科技(英文版)》2004,3(4):72-75
The drying characteristic was studied for plantation wood of Chinese fir and poplar, which are typical plantation wood of southern and northern part of China, respectively. Through 100-degree-method the drying characteristic and basic drying condition were gotten, then drying schedule was developed for practical drying, the results showed that the drying schedule is suitable for Chinese fir and poplar plantation lumber, but shrinkage is large. The recommendation was made that enough dead weight is needed to decrease shrinkage in drying process. The drying quality of the two species of lumber is good in conventional drying method. 相似文献
14.
Experimental investigation and computational analysis were performed to evaluate the influence of the ambient air parameters
during the drying process on the temperature, moisture and resulting deformations and stresses in wood samples. The numerical
procedure uses the Finite Volume Method to discretise the equations governing heat, mass and momentum balance and takes into
account the anisotropic nature of wood. The comparison of the numerical and experimental results shows very good agreements,
implying that the proposed numerical algorithm can be used as a useful tool in designing wood drying schedules.
Received 31 March 1999 相似文献
15.
The concentrations and seasonal dynamics of DOC in forest floors of monoculture plantations ofCastanopsis kawakamii and Chinese fir (Cunninghamia lanceolata) were assessed in Sanming, Fujian, China (26°11′30″N, 117°26′00″E). Forest floor samples were taken in January, April, July
and October in 2002 and divided into undecomposed material (horizon Oi), partially decomposed organic material (horizon Oe),
and fully decomposed organic material (horizon Oa). Upon collection, DOC concentrations of samples were analyzed by a High
Temperature TOC. The results showed that the annual average DOC concentration of Chinese fir (1341.7 mg·kg−1) in the forest floor was higher than that ofCastanopsis kawakamii (1178.9 mg·kg−1). Difference in DOC concentrations was observed among three horizons of the forest floor. DOC concentration of forest floor
in the two forests was the highest in horizon Oe. Seasonal trends of DOC concentrations in different horizons of forest floors
were similar and the maximal value occurred in autumn (or winter). The concentration and temporal change of DOC in studied
forests were probably related to the variation in moisture, temperature, biological activity and quantity of organic matter
in the forest floor.
Foundation item: This study was supported by the Teaching and Research Award program for MOE P.R.C. (TRAPOYT)
Biography: ZHANG Jiang-shan (1946-), male, Researcher in Fujian Normal University, Fuzhou 350007, P.R. China.
Responsible editor: Zhu Hong 相似文献
16.
该文使用 6 4kg·m-3 的CCA C木材防腐剂 ,在 11个后处理基准 (其温度为 5 0℃～ 70℃和 5个不同的相对湿度 )条件下 ,研究了固化干燥条件对处理北美红松和南洋松木材的固化速度和化学元素的流失的影响 .实验样品内的液体通过挤压方法被定期检测并分析其六价铬的含量 .调节固化后的样品按美国木材防腐协会E11 97标准进行流失实验 .一般情况下 ,对于大多数基准 ,红松固化比南洋松少、快 ,并且高温高湿的固化条件比低湿度的固化条件导致较快的固化速度和较少的铬和砷的流失 .对于2个材种在 11个固化干燥条件下 ,铜元素的流失没有很大的差异 .所有的CCA化学元素的流失情况 ,红松比南洋松更明显 .更进一步的工作需要CCA处理大尺寸样品 ,优化干湿球温度差 ,以便考察其固化干燥条件对流失的影响 相似文献
17.
M. Parvez Rana Sharif Ahmed Mukul M. Shawkat Islam Sohel Mohammad Shaheed Hossain Chowdhury Sayma Akhter M. Qumruzzaman Chowdhury Masao Koike 《Small-Scale Forestry》2010,9(1):41-51
An exploratory survey was carried out to assess economics and employment generation of the trade of bamboo and bamboo-based
secondary products in the eastern Bangladesh, to obtain reliable information about their status, socio-economic significance,
production and marketing. The study was undertaken over 30 bamboo-based enterprises in a suburban market of eastern Bangladesh,
to investigate regional product details, economic profitability and employment opportunities. The sample entrepreneurs, corresponding
to about 25% of the bamboo enterprise population were interviewed using a semi-structured questionnaire. About 202 full and
part-time workers were employed in the factories, under categories of artisan (who manufactured secondary products). The average number of worker’s in the large, medium and small factories were 9 (artisan
40%), 6.45 (artisan 35%) and 5 (artisan 25%) respectively. The study revealed that there was always a satisfied demand of
skilled artisans. Most of the workers were relatively newly employed (not more than 5 years). The daily wage rate varied between
70 and 130 Tk. ($US 1 equals approximately 70 Bangladeshi Taka (Tk.), as at December 2008). Bambusa balcooa was the most utilized species (39.96%) in terms of monetary value. The price of a single B. balcooa culm in the local market was Tk. 160–210. Nine sizes of articles under seven bamboo categories were identified, these being
bera (36″ × 120″ and 72″ × 96″), bookshelf (36″ × 24″), chaluni (12″ × 12″), chatai (48″ × 60″ and 36″ × 48″), jhuri, rickshaw hood and tukri. Net average profit per article was the highest for rickshaw hoods (Tk. 400 at the retailer stage). The total expected annual
income for an enterprises from all articles types sold was estimated to be Tk. 85,800. Three distinct marketing channels were
identified for selling bamboo and value-added secondary products. The study also generated policy implications for effective
management of bamboo-based enterprises. 相似文献
18.
Red pine (Pinus resinosia Ait) and southern pine (Pinus spp.) sapwood blocks were pressure treated with CCA-C at retention of 6.4, 2.0, 1.5 kgm-3 followed by fixation using 11 post-treatment schedules ranging from 50–70 °C and 5 different relative humidity conditions.
The effect of these post-treatment schedules on fixation rate, chemical leachability and decay resistant once were evaluated
to better understand the effects of fixation/drying conditions on leachability and biodeterioration. Southern pine blocks
fixes slightly slower than red pine. Fixation of CCA at high temperature high humidity, essential initially fixation at high
humidity for fixation/drying schedules, resulted in lower leaching of chromium and arsenic elements than high temperature
low humidity or initially fixation at the high temperature low humidity conditions. Copper leaching was indicated no significant
difference under 11 fixation/drying conditions for both species. Weight losses for southern pine byChaetomium globosum was lower than red pine byGloeophyllom trabeum. There were some different capacities of decay resistance for both species under those post treatment conditions. 相似文献
19.
Zhongling Guo Qingkang Li Jinping Zheng Wande Liu Chunnan Fan Yuandan Ma Guirui Yu Shijie Han 《Frontiers of Forestry in China》2007,2(1):47-54
From 2001 to 2003, the litter decomposition dynamics of dominant tree species were conducted using a litterbag burying method
in the broadleaf-Korean pine forest, spruce-fir forest and Ermans birch forest, which represents three altitudinal belts in
Changbai Mountain, northeast China. The spatial and temporal dynamics of litter decomposition and the effects of litter properties
were examined. Furthermore, the decomposition trend of different species was simulated by the Olson model, and results showed
that annual mass loss rates increased over time, but was not significantly correlated. Leaf decomposition rates increased
after decomposing for 638 days (1.75 years), and the order of dry weight remaining rates of leaf litter for different species
is: Asian white birch (Betula platyphylla) (24.56%) < Amur linden (Tilia amurensis) (24.81%) < Korean pine (Pinus koraiensis) (38.48%) < spruce (Picea jezoensis var. microsperma) (41.15%) < Ermans birch (Betula ermanii) (41.53%) < fir (Abies nephrolepis) (42.62%). The dry weight remaining rates of twig litter was smaller than that of leaf litter, and followed the order of
Amur linden (44.98%) < fir (64.62%) < Korean pine (72.07%) < spruce (73.51%) < Asian white birch (77.37%) < Ermans birch (80.35%).
The simulation results by the Olson model showed that, in leaf, the 95%-decomposition rates ranged from 4.5 to 8.0 years,
and annual decomposition rate (k) followed the order of Amur linden (0.686) > Asian white birch (0.624) > Korean pine (0.441) > spruce (0.406) > fir (0.397)
> Ermans birch (0.385); in twig, it ranged from 7.8 to 29.3 years, and k follows the order: Amur linden (0.391) > fir (0.204) > Korean pine (0.176) > spruce (0.157) > Asian white birch (0.148) >
Ermans birch (0.102). In general, the differences of decomposition rate are evident between leaf and twig litter and among
species, and were higher in broad-leaved species compared with coniferous species at the same elevation, and decreased with
the ascending of elevation.
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Translated from Acta Ecologica Sinica, 2006, 26(4): 1,037–1,046 [译自: 生态学报] 相似文献
20.
Influence of heating history on dynamic viscoelastic properties and dimensions of dry wood 总被引：2，自引：2，他引：0
To obtain new information about the mechanical and physical properties of dry wood in unstable states, the influence of heating
history on viscoelastic properties and dimensional changes of dry wood in the radial, tangential, and longitudinal directions
was studied between 100° and 200°C. Unstable states of dry wood still existed after heating at 105°C for 30 min and were modified
by activated molecular motion in the first heating process to temperatures above 105°C. This phenomenon is thought to be caused
by the unstable states reappearing after wetting and drying again. Dry wood components did not completely approach the stable
state in the temperature range tested, because they did not entirely surpass the glass transition temperatures in most of
the temperature range. In constant temperature processes at 135° and 165°C, E′ increased and E″ decreased with time regardless of the direction. This indicated that the unstable states of dry wood components were gradually
modified with time at constant temperatures. On the other hand, anisotropy of dimensional change existed and dimension increased
in the longitudinal direction, was unchanged in the radial direction, and decreased in the tangential direction with time
at constant temperatures.
Part of this report was presented at the 13th Annual Meeting of the Chubu Branch of the Japan Wood Research Society, Shizuoka,
August 2003 相似文献