杨木太阳能干燥工艺特性

应用一种带有石蜡储热的新型太阳能干燥室干燥杨木,分析该干燥室的温、湿度变化对木材内外温度差和木材干燥速率的影响,并检测了杨木木材的干燥质量,结果表明:太阳能干燥室的温、湿度呈周期性变化规律,在一个温度变化周期内,干燥速度亦呈周期性.建议在升温段控制干燥速度,在降温段加快干燥速度.     

基于时延神经网络的木材干燥温湿度建模研究

利用神经网络建立了木材干燥的温湿度模型,给出了其时延神经网络辨识结构。分别提出温、湿度控制模型(控制信号与温、湿度之间的关系模型)和木材干燥基准模型(温、湿度与木材含水率之间的关系模型),并利用实验干燥窑得到的实际数据进行了仿真研究。仿真结果表明,利用此方法建模是可行的,所建模型是有效的。图10参16。     

木材干燥微机控制系统

木材干燥是决定木制品质量的重要工艺手段。为了提高木制品的产品质量，应该选择经济合理的木材干燥工艺方法。在木材干燥过程中，影响木材干燥质量及成材率的因素很多，如：材种、材型、木材含水率、窑内温、湿度及热风循环速度等。实践表明，目前大量使用的常规及半自动控制的木材干燥方法，很难获得理想的干燥效果，不能满足人们对木材干燥质量的要求。因此，有必要研究新的木材干燥控制方法。全自动木材干燥控制方法是较理想的干燥控制方法，它可对木材干燥全过程进行自动控制，这不但可以降低工人的劳动强度，而且还可以提高产品质量及…     

循环风速对木材干燥速度的影响

循环风速对木材干燥速度的影响刁秀明，王彦发，马秀华（黑龙江省林产工业研究所哈尔滨１５００４０）木材干燥的三个外部基本因子为温度、湿度和循环风速。温度和湿度随干燥过程的变化构成了木材的干燥基准，是木材干燥工艺的重要内容之一。关于温度和湿度对干燥速度和干...     

木材干燥过程中声发射信号分析北大核心

对木材在干燥过程中产生的声发射信号进行采集和特征分析,结果表明:木材干燥过程中主要采集到两种不同类型的声发射信号:一种信号来自木材内部自由水的蒸发,与木质部导管内水分空穴化过程的声发射信号一致;另一种信号与木材干燥过快时自身形变开裂相关。作为一种木材干燥质量的控制方法,测量和分析声发射信号,可为木材干燥温度和湿度的控制提供依据,实现防止木材干裂、提高木材干燥质量的目的。     

落叶松集成材木材干燥系统设计与控制分析

针对落叶松集成材中的木材干燥问题,阐述太阳能-热泵联合干燥系统,并对木材干燥室进行了设计研究,实现对木材干燥中温度、湿度、空气流动、加热时间等影响木材干燥的关键因素进行全程监测和精确控制。     

木材干燥过程中声发射信号分析

对木材在干燥过程中产生的声发射信号进行采集和特征分析,结果表明:木材干燥过程中主要采集到两种不同类型的声发射信号:一种信号来自木材内部自由水的蒸发,与木质部导管内水分空穴化过程的声发射信号一致;另一种信号与木材干燥过快时自身形变开裂相关.作为一种木材干燥质量的控制方法,测量和分析声发射信号,可为木材干燥温度和湿度的控制提供依据,实现防止木材干裂、提高木材干燥质量的目的.     

浅析木材干燥中的干燥梯度控制法

浅析木材干燥中的干燥梯度控制法张国宝，刘耀祥（吉林省露水河林业局福华地板公司）木材在干燥过程中，决定其干燥速度、干燥质量主要取决于所采用的干燥基准，而控制干燥基准的核心，一般来讲主要是控制干燥介质的温度、相对温度。对于干燥梯度控制法，在控制干燥介质温...     

木材热压干燥研究现状与应用前景

文中综述了木材热压干燥理论及试验研究,分析了热压干燥工艺对干燥时间、干燥质量和物理力学性能的影响;为了对木材热压干燥过程进行预测和工艺控制,归纳了木材热压干燥传热传质规律以及数学模型构建与求解的研究现状,也为更好地建立和完善木材热压干燥数学模型与干燥工艺奠定了基础;指出木材热压干燥及传热传质模型研究中存在的主要问题,对完善木材热压干燥机理研究与传热传质数学模型构建提出建议,并对热压干燥在人工林木材中的应用进行了展望,可为人工林木材高效高附加值利用提供参考。     

木材干燥的自动控制

随着科技的发展，自动控制在木材干燥上用得越来越多。进口干燥设备几乎全部采用自动控制。国产干燥设备也在逐渐向自动控制过渡。由于木材干燥的特殊性，自动控制种类繁多，方式各异，令人有无所适从之感。本文旨在帮助使用者对木材干燥的自动控制有全面的、清晰的了解，以便更好地选择和使用适合自己情况的自动控制木材干燥设备。1自动控制的类型木材干燥过程实际上就是干燥介质作用于木材的过程。在这一过程中，木材的性质无法改变，因此也无法控制。人们能够控制的只是干燥介质的性质。所以，干燥过程的控制实际上只是对介质条件的控制…     

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.     

基于免疫算法的木材干燥窑PID控制系统

用神经网络方法对木材干燥窑PID控制系统进行系统辨识,并在此基础上用免疫PID算法取代传统PID算法进行PID参数的在线寻优,从而更加准确地控制干燥窑的温度和湿度的过程。仿真结果表明,新的控制系统在稳定性、动态性能等方面都有明显提高。     

高温高湿处理对落叶松锯材树脂脱除及分布影响分析

对落叶松锯材进行高温高湿处理是其木材干燥中一个重要过程。通过高温高湿处理,可使落叶松锯材中所含的树脂固体成分受热软化,粘度降低,流动性增强,在热力作用下向表面移动进而从木材中溢出。本研究通过对落叶松锯材进行不同时间高温高湿处理和不同后期处理条件的干燥试验,分析被处理的落叶松锯材树脂脱除和分布规律,为探讨合理落叶松脱脂工艺提供基础依据。通过试验分析,得出对落叶松锯材进行高温高湿处理的时间在8h以内时,木材中树脂从芯部向表层移动和从表面溢出明显。处理时间达到8h后,树脂分布变化和溢出变化不明显。     

New monitoring concept of moisture content distribution in wood during RF/vacuum drying

A new method for monitoring moisture content during radio-frequency (RF)/vacuum drying was developed by measurement of temperature and pressure in wood. Temperature and pressure inside the wood were measured simultaneously during RF/vacuum drying at the same point. The relative humidity (RH) and moisture content (MC) below the fiber saturation point (FSP) were calculated based on temperature and pressure, and the relationship between the temperature, RH, and equilibrium moisture content (EMC) at the measurement point. When the moisture content was below the FSP, the calculated MC was slightly greater than the value given by oven drying. The absolute error was within 0.8% near the open cross side, and was within 1.8% at another measurement point. Thus, we concluded that it was practicable to monitor the moisture content below the FSP according to the temperature and pressure inside the wood. Part of this study was presented at the 15th Annual Meeting of the Chugoku Shikoku Branch of the Japan Wood Research Society, Higashi-Hiroshima, Japan, September 2003     

白橡热压干燥材等温吸湿特性研究

以白橡热压干燥材为研究对象,利用动态水分吸附仪研究了不同热压温度干燥处理后白橡木材和未处理对照材的等温吸湿特性,并采用H-H模型拟合;分析热压干燥对木材吸湿特性的降低机理。结果表明:白橡木材等温吸湿线皆为IUPAC Ⅱ型等温吸湿线。在任意相对湿度下,热压干燥材平衡含水率均明显低于对照材,且热压温度越高,平衡含水率降低越明显。H-H模型对白橡木材等温吸湿数据表现出良好的拟合效果。单分子层和多分子层含水率降低共同作用使得热压干燥材吸湿性降低,且相对湿度越高,多分子层水的减少对吸湿性的降低作用越大。与对照材相比,热压干燥材(140、150 ℃和160 ℃)的纤维饱和点推测值分别降低8.89%、11.76%和13.62%。白橡热压干燥材吸湿性降低机理主要为游离羟基等亲水基团含量减少和细胞壁刚度增加等。     

高压放电法、传导法及二者结合法干燥木材比较实验研究

采用高电压放电法干燥木材能实现木材整体加热,木材整体温度及湿度的均匀分布,在短时间内获得高质量的干燥木材.但高电压干燥法消耗的电能昂贵.热传导法干燥利用木材燃烧废料产生热能,能节约干燥成本.由于这两种方法的压力梯度与温度梯度方向相反,能实现相互抵消补偿,可达到降低沿截面压力梯度的目的,从而获得高质量的干燥木材,因此笔者分别利用高电压放电法、传导法及二者结合法进行了干燥木材比较实验研究.研究表明,利用高电压放电法结合传导加热法干燥木材,能以较少的消耗干燥成本及较短的干燥时间获得高质量的木材.     

Effect of EMC and air in wood on the new in-process moisture content monitoring concept under radiofrequency/vacuum (RF/V) drying

To improve the accuracy of the new in-process moisture content (MC) monitoring concept under radiofrequency/vacuum (RF/V) drying, equilibrium moisture content (EMC) tests were carried out under various ambient pressures, and pressure curves in wood were analyzed during chamber evacuation and heating phases. The results showed that EMC increased with a decrease in ambient pressure regardless of temperature, relative humidity (RH), and species. The accuracy of MC estimation for Hinoki under RF/V drying was improved from 1.5% maximum absolute errors to 0.6% after EMC modification. The pressure curves for Hinoki and Sugi under RF/V drying showed similar tendencies to an idealized process. Russian larch showed different curves, indicating that the pressure in the wood did not reach the ambient pressure because of its low permeability. Therefore, MC could not be estimated using this monitoring concept because of the presence of much air in the wood of Russian larch.     

Induced discoloration of buerger maple during drying process

Buerger maple (Liquidambarformosana Hance) is a kind of wood that is easily discolored. This paper tries to obtain satisfactory color and a broad prospect in the utilization of buerger maple by induced discoloration. The authors analyze the mechanism of induced discoloration of buerger maple based on the analysis of visual physical parameter, the infrared spectrum (IRS) and the scanning electron microscope (SEM) under different drying conditions. The result shows that it is feasible to induce discoloration during the drying process. The wood color tends to be red and fuscous during inducing discoloration of buerger maple.The induced discoloration mechanism is: 1) the high temperature and humidity accelerates the oxidation reaction of polyphenol,leuco-fancy pigment and tannin, which changes the wood color to red; 2) the hydroxy (-OH) is oxidized and the carbonyl (-C=0),carboxyl (-COOH), ester and ketone groups form during the high temperature steaming, which results in wood piece discoloration.     

Vapor phase reaction of wood with maleic anhydride (I): dimensional stability and durability of treated wood

Reaction between maleic anhydride (MA) and wood specimens was carried out in a vapor phase reaction system. Reaction conditions such as the ratio of supplied MA to wood, initial moisture content, and reaction temperature were optimized. The MA supplied to the reaction system was effectively absorbed by the wood, and a satisfactorily high dimensional stability was achieved even at a low MA/wood ratio. The dimensional stability increased with rising initial moisture content. When the reaction was conducted at an elevated temperature (180°C), high dimensional stability was attained without remarkable weight increase and bulking. The mechanism of dimensional stabilization was discussed on the basis of the dimensional changes at high humidity and during repeated water soaking and drying. It was shown that the dimensional stabilization arises mainly from a decrease of hygroscopicity. When the reaction was conducted at 180°C, the formation of cross-links in the cell wall was apparent. Following the MA treatment, the antifungal property was remarkably enhanced and met the Japanese Industrial Standard K1571. Therefore, MA treatment in the vapor phase is an effective method to attain antifungal properties as well as high dimensional stability with a small amount of nontoxic reagent.