赤桉半干材的窑干与调湿处理工艺

针对移行材和早材皱缩等主要气干缺陷,拟定出赤桉半干材的干燥工艺,窑干前进行回复皱缩和减小表面硬化的汽蒸处理,窑干至目标含水率时进行终了调湿处理.结果表明:汽蒸预处理可以有效地回复皱缩材和显著地减小表面硬化;5 d内将试材的平均含水率25.61%下降到11.72%;3 h的汽蒸处理和24 h的湿空气处理均可有效地减小含水率梯度和残余塑性变定,但后者效果更佳;板材干燥质量达到国家标准二级质量的要求.     

四种桉树人工林木材气干特性研究

本文对柠檬按、巨按、尾巨按和窿缘按4种按树人工林木材进行气干特性和干燥规律的研究，预测它们在不同季节和不同含水率阶段的气干速度，并对气干质量进行分析，为有效利用其气干特性和规律合理地组织气干-窑干联合干燥提供理论依据。     

人面子木材干燥特性及干燥工艺初探

采用百度试验法研究人面子木材的干燥特性,根据百度试验结果和企业的实际情况,拟定了相对偏软的24 mm和50 mm 2种厚度规格家具用材干燥工艺基准,进行了生产试验。24 mm厚人面子木材从初含水率85%干燥至12%,共用时506h,干燥质量良好,达到预期要求。针对50 mm厚毛边板材干燥速度慢,干燥不均匀,同一块板材内局部区域含水率异常偏高的现象,拟定了气干/窑干联合干燥工艺和相应的半波动窑干基准。     

杉木生材含水率分布及其对气干的影响

以人工林杉木为研究对象,研究生材状态下不同厚度锯材含水率的差异,比较含髓心、钝棱与其他类型等3类锯材的含水率差异,建立生长轮宽度与锯材含水率的关系,分析生材状态含水率对锯材气干周期的影响。研究结果显示,25mm和40 mm的锯材含水率差异极显著;含髓心锯材含水率最低,其次是其他类的,最大是含钝棱锯材;随着生长轮宽度减少,锯材含水率增大;生长轮宽度为4 mm时,是生材含水率分界线,即当生长轮平均宽度小于和不小于4.0 mm时,锯材含水率差异极显著;25 mm和40 mm厚不同含水率锯材各2组气干至含水率25%,低含水率锯材较高含水率的气干周期分别缩短57%和66%。     

电容式含水率测量仪在干燥室内测量准确性研究

室干过程中,测量木材的含水率是执行含水率基准和决定干燥终点的前提.木材易于产生弯曲,木材未干、板材含水率达不到标准若再次干燥,势必增加成本.监测干燥室内板材含水率有以下几种方法:用电阻和电容式水分仪测量;测量气流穿过材堆前后温度差,然后按经验公式推算含水率;用材堆的细     

低温冷等离子体对不同含水率杨木单板表面改性的初步研究

笔者采用低温等离子片材表面处理机处理气干、绝干、过干三种含水率条件下的杨木单板,测量其处理前后表面润湿性和胶合性能,结果表明:冷等离子体改性后,气干、绝干、过干三种含水率下的杨木单板表面接触角分别降低13.3%、22.8%、39.3%(甘油),16.2%、35.2%、64.3%(脲醛树脂胶),且降低幅度随含水率降低呈递增趋势;冷等离子体改性能有效提高杨木单板的胶合性能,其变化规律与润湿性基本一致。     

杨木实木地板坯料两种干燥工艺比较

采用产于江苏宿迁美洲黑杨25 mm厚的地板坯料湿材为研究对象,分别采用常规干燥工艺、气干窑干联合工艺对试材进行干燥质量对比。结果表明:采用气干与窑干联合干燥工艺,使杨木的含水率降低到25%左右时,再进行窑干,不仅没有降低干燥效率,还能克服杨木髓心板直接窑干带来的易端裂、皱缩、变形的现象。     

20mm厚尾赤桉锯材2种干燥工艺对比研究

分别采用常规窑干工艺和气干—窑干联合干燥工艺对20 mm厚尾赤桉锯材进行了干燥试验,并对2种工艺的干燥速度、干燥质量和能耗进行对比。结果表明:2种工艺的干燥质量均达到GB/T 6491-2012《锯材干燥质量》二级材标准;常规窑干工艺的周期为310 h,气干—窑干联合干燥工艺的周期为406 h,比常规窑干法多96 h;采用联合干燥法,可节约能源67.4%。     

毛白杨和沙兰杨木材气干过程和窑干工艺的研究

对毛白杨和沙兰杨木材分别进行气千,窑干及气干—窑千联合干燥试验,并对这二种木材的适宜干燥工艺进行了探讨。毛白杨生材窑干时易发生皱缩、内裂和湿心。采用气个—窑千联合干燥工艺可以有效地防止这些缺陷,还可以降低能耗和提高干燥窑生产能力。沙兰杨木材干燥速度较毛白杨快,窑干时一般不发生皱缩和内裂,可以采用高温基准对生材窑干。但采用气干—窑干联合干燥能够降低能耗和提高干燥窑生产能力,并且可以保持木材本色,因而更为合理。对北京地区和北方省份的气候条件及季节变化对气干预干期的影响进行了分析,提出了这些地区适宜的气干预干含水率范围。井提出了气干预干材的窑干基准。     

沙柳材物理力学特性测定与分析

为研究沙柳材物理力学特性,按照木材物理力学性能测试方法和沙生灌木相关标准,测定了沙柳气干材的含水率,得到沙柳气干材的含水率为10.41%;对沙柳气干材分别进行顺纹拉伸试验、压缩试验、三点弯曲试验。结果表明:沙柳气干材顺纹最大抗拉强度为133.28 MPa;轴向、弦向和径向的抗压强度分别为73.00、11.20 MPa和12.84 MPa;抗弯强度为106.31 MPa。研究可为沙柳锯切仿真提供数据支持。     

Drying of timber in progressive kilns: Simulation,quality, energy consumption and drying cost considerations

Abstract

Progressive (semi-continuous) kilns for softwood drying are very common in Finland and Sweden and are used in some other countries too. A simulation program has been developed that covers all three types of this kiln. The program calculates the climate in the length direction of the kiln and moisture content, moisture profile, wood temperature, slicing test gap and stress development. Energy consumption and drying costs may also be determined. The temperature level is the most important parameter regarding kiln efficiency. Two-zone progressive kilns are found to be more efficient than single-zone kilns. Progressive kilns have lower energy consumption and drying costs than batch kilns. Experimental full-scale tests show that the timber quality from a progressive kiln is comparable to, or in some cases even better than, timber dried in batch kilns.     

菲律宾桃花芯木锯材干燥工艺初探

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。     

Effect of drying method as a pretreatment on CUAZ preservative impregnation in Japanese cedar logs

Green Japanese cedar logs 2 m in length and 18 cm in diameter were dried to a mean moisture content of less than 30% by either air drying or kiln drying. Dried logs were impregnated with copper azole (CUAZ) solution according to Japanese Industrial Standard (JIS) A9002. Preservative absorption was calculated from the log weight before and after preservative impregnation. Impregnated logs were then dried in the air and cut at the center to determine preservative penetration. The penetration area was determined after visualizing the preservative with chrome azurol S. The visualized area indicated that the preservative solution penetrated into the sapwood portion of almost all the air-dried logs. However, the kiln-dried logs did not show full penetration into the sapwood portion. The visualized area of some kiln-dried sapwood showed a penetration value of less than 80%, which is the minimum requirement set by the Japanese Agricultural Standard (JAS) for sawn timber. Statistical analysis showed that penetration in the air-dried sapwood was significantly better than that in the kiln-dried sapwood. It was concluded that air drying is more favorable than kiln drying as the predrying method for CUAZ impregnation. On the other hand, preservative absorption was not affected by the drying method.     

干燥过程中木材内部含水率检测的X射线扫描方法

以红橡和黑胡桃木材为研究对象,采用X射线扫描方法测量常规热风干燥过程中木材厚度方向含水率分布和平均含水率的可行性。结果表明:采用X射线扫描无损检测方法可以实现干燥过程中同一木材试件含水率分布和平均含水率的动态检测;与称重法含水率测量值相比,在8%～68%的较宽含水率范围内,不论是在高含水率阶段还是在低含水率阶段,采用X射线扫描法测量木材含水率时,都具有较高的测量精度,测量值偏差最大不超过3%;在热风干燥过程中,所有试件含水率的称重法测定值与X射线扫描法测定值之间相关系数的平方都在0.97以上;X射线扫描方法具有扫描速度快、设备费用较低、测量精度高的特点,为木材含水率的动态检测提供了一种很好的技术手段。     

竹材热压干燥过程中的水分迁移特性研究

研究了竹材热压干燥过程中的水分迁移特性.结果表明:在整个干燥过程中,前期含水率降低较快,后期含水率降低较慢.竹材平均干燥速度与次表层竹材的干燥速度相近;在含水率较高的干燥初期,水分迁移的阻力在竹材表面,水分迁移主要靠毛细管张力作用;在含水率较低的干燥后期,水分迁移的阻力在竹材内部,水分迁移主要以扩散方式进行,干燥速度取决于木材内部水分移动的速度.竹材热压干燥过程中的水分移动,主要受温度梯度和含水率梯度的共同作用.     

Determination and use of moisture diffusion coefficient to characterize drying of northern red oak (Quercus rubra)

Summary Diffusion analysis can be used to estimate the time required to dry lumber. However, more accurate calculations require additional information on the relationship between the diffusion coefficient as a function of moisture content and on the effects of temperature, equilibrium moisture content, board thickness, and air velocity on drying time and moisture gradients. The primary objectives of this study were (1) to determine the diffusion coefficient of northern red oak (Quercus rubra) as a function of moisture content and (2) to compare experimentally determined sorption times and moisture content gradients with those calculated by the diffusion model. The diffusion coefficient was found to increase approximately exponentially with moisture content over a range of 6 to 30 percent at 43°C. This relationship was similar in both adsorption and desorption tests. Experimental adsorption and desorption times and desorption moisture content gradients were compared with finite difference solutions to the diffusion equation. Practical uses of solutions to the diffusion equation are illustrated for kiln drying wood that has first been predried to below the fiber saturation point. Drying time is also related to variable kiln conditions and board thickness.This research was partially funded under the U. S. Department of Agriculture Competitive Grant programThe Forest Products Laboratory is maintained in cooperation with the University of Wisconsin. This article was written and prepared by U.S. Government employees on official time     

基于算术平均值和递推估计算法的木材含水率检测研究

试验采用电阻法测量木材干燥过程含水率,针对木材干燥窑中的传感器有数量多、测量的精确性受外界扰动较大等特点,文章提出采用算术平均值和递推估计算法对实时数据进行数据融合,从而得到精度更高的估计值.由于试验的被测量具有正态分布的特点,得到实时数据后首先剔除随机误差,再计算所采集数据的算术平均值作为原始检测结果,最后采用递推估计的计算方法得到较为精确的结果.通过对数据融合的仿真结果分析,验证该方法对于检测木材干燥过程含水率的可靠性.     

Lumber Quality Model: The theory

Abstract

A new model for predicting moisture content, distortion and shrinkage distribution after lumber drying has been designed, implemented and tested. The model was implemented using Monte Carlo simulation, and it involves three empirical equations that were developed on the basis of experimental data. The model is referred as the Lumber Quality Model, and it is designed to be calibrated by knowing the initial and final moisture content, distortion and shrinkage distribution for a reference drying run. After calibration, the model can be used to predict the same information for other hypothetical drying scenarios. The present study explains the theoretical aspects of the model and the methodology for implementation. The model was validated with experimental data measured in a laboratory kiln. A full-scale industrial validation will be reported in a future paper.     

不同干燥条件下小径桦木材性指标的研究

对小径桦木在大气及干燥室等不同条件下干燥后的材性进行了测试，结果表明：不同干燥条件对小径桦木的材性有影响。室干材的尺寸稳定性、变形程度及力学性能均优于气干材；采用软干燥基准时，可改善小径木的尺寸稳定性和力学性能，从而提高干燥质量。从总体材性指标可见，小径木更适合室内干燥。