高温热处理木材吸湿特性

doi:10.11707/j.1001-7488.20190713

摘要/Abstract

摘要： [目的]研究高温热处理对人工林樟子松、杉木、美洲黑杨木材平衡含水率和吸湿特性的影响，为科学评价热处理木材吸湿特性提供理论基础，为人工林木材高附加值利用和实际高温热处理木材生产提供参考。[方法]以水蒸气为保护介质，设定180、200和220℃3个温度进行高温热处理，采用双室温、湿度控制法，在25℃环境中以8种不同类型饱和盐溶液精确控制水蒸气相对湿度进行等温吸附试验，运用Hailwood-Horrobin模型拟合等温吸附曲线，分析高温热处理对木材水蒸气等温吸附曲线线形、平衡含水率、单层分子吸附水和多层分子吸附水的影响。[结果]180、200和220℃处理后，试样吸湿平衡含水率均值相当于素材含水率均值的80%、70%和50%左右；3个树种素材试样和高温热处理材试样均表现为第2类等温吸附曲线形态特征，Hailwood-Horrobin模型能够较好拟合不同树种素材和高温热处理材等温吸附曲线，不同热处理条件试样等温吸附曲线的拟合度均高于0.9800，处理温度越高，等温吸附曲线越接近直线；高温热处理后代表含有单位摩尔数吸附位的绝干木材质量参数（W）显著增加，不同相对湿度下高温热处理材的单层分子吸附水和多层分子吸附水含量也随之降低；180、200和220℃处理后，木材试样单层分子吸附水含量相较于素材下降20%、30%和50%左右，高温热处理对多层分子吸附水含量影响规律与之相近；高温热处理后单层分子吸附水、多层分子吸附水和吸附水总量的最大值相较于素材明显下降，且处理温度越高，下降幅度越大。[结论]高温热处理可明显降低3个树种试样的吸湿平衡含水率，且处理温度越高，平衡含水率下降幅度越大；高温热处理会一定程度影响木材等温吸附曲线线形，Hailwood-Horrobin模型可用于描述高温热处理材等温吸附曲线，且拟合度较高；高温热处理可明显降低3个树种试样等温吸附过程单层分子吸附水和多层分子吸附水含量，且处理温度越高影响越明显，单层分子吸附水和多层分子吸附水最大含量均明显降低，进而影响吸附水总量最大值。

关键词: 木材吸附特性, 高温热处理, Hailwood-Horrobin模型, 单层分子吸附, 多层分子吸附

Abstract: [Objective] The effects of high temperature heat treatment on the equilibrium moisture content and sorption isotherms characteristics of Pinus sylvestris var. mongolica,Cunninghamia lanceolata and Populus nigra were studied. The research result could be used in scientific evaluation of moisture adsorption characteristics of wood, and the relevant data could also be used as a reference in actual production.[Method] In this study water vapor was used as protective medium and three levels of heat treatment temperature were set, which was 180, 200 and 220℃, respectively. The sorption experiments were performed in the two-chamber setup, the relative humidity of air was controlled by eight kinds of salt solutions and the air temperature of sorption experiments were 25℃. The sorption isotherms of high temperature heat-treated wood was fitted by Hailwood-Horrobin equation, and the effects of high temperature heat treatment on the isothermal adsorption behavior, equilibrium moisture content, monolayer water and polylayer water were analyzed.[Result] The equilibrium moisture content of 180, 200, 220℃ treated samples were equivalent to 80%, 70% and 50% equilibrium moisture content of control samples, respectively. The Hailwood-Horrobin equation could be used to fit the isothermal adsorption curves of three species wood and their high temperature heat-treated wood, and their isothermal adsorption curves all belonged to typeⅡ, the fitting degree of isothermal adsorption curves were higher than 0.980 0 for all the conditions. The higher the treatment temperature was, the closer the isothermal adsorption curve is to the straight line. The parameter W which means the apparent molecular mass of the dry wood per sorption sites was significantly increased after heat treatment, meanwhile, the moisture content of monolayer and polylayer water in different relative humidity environment was significantly decreased after heat treatment. The monolayer water of samples reduced about 20%, 30% and 50% for 180, 200, 220℃ heat-treated wood comparing with those of control samples, respectively. The influence of high temperature heat treatment on polylayer water was similar. The maximum amount of monolayer water, polylayer water and the total amount of adsorbed water was significantly reduced compared with control samples after heat treatment, and the higher the treatment temperature, the greater degree of decline was found.[Conclusion] The equilibrium moisture content of wood could be significantly reduced by high temperature heat treatment, and the higher the treatment temperature, the greater the decreasing in the equilibrium moisture content was obtained. The Hailwood-Horrobin equation could be used to describe the isothermal adsorption curve of high temperature heat treatment wood, and the fitting degree is fairly high. The isothermal adsorption curve of wood could be significantly influenced by high temperature treatment. The amount of monolayer water, polylayer water and total adsorbed water could be significantly reduced by high temperature heat treatment, and the higher the treatment temperature, the more obvious of the influence was found. The maximum content of monolayer water, polylayer water was significantly reduced after heat treatment, which would affect the maximum amount of adsorbed water.

Key words: wood sorption isotherms characteristics, high temperature heat treatment, Hailwood-Horrobin model, monolayer water adsorption, polylayer water adsorption

中图分类号:

S781

高鑫, 周凡, 周永东. 高温热处理木材吸湿特性[J]. 林业科学, 2019, 55(7): 119-127.

Gao Xin, Zhou Fan, Zhou Yongdong. Sorption Isotherms Characteristics of High Temperature Heat-Treated Wood[J]. Scientia Silvae Sinicae, 2019, 55(7): 119-127.

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