Effects of high temperature kiln drying on the practical performances of Japanese cedar wood (Cryptomeria japonica) I: changes in hygroscopicity due to heating

The effect of heating on the hygroscopicity of Japanese cedar wood was investigated as a simple evaluation of thermal degradation in large-dimension timber being kiln-dried at high temperatures (>100°C). Small wood pieces were heated at 120°C in the absence of moisture (dry heating) and steamed at 60°, 90°, and 120°C with saturated water vapor over 2 weeks, and their equilibrium moisture contents (M) at 20°C and 60% relative humidity (RH) were compared with those of unheated samples. No significant change was induced by steaming at 60°C, while heating above 90°C caused loss in weight (WL) and reduction in M of wood. The effects of steaming were greater than those of dry heating at the same heating temperature. After extraction in water, the steamed wood showed additional WL and slight increase in M because of the loss of water-soluble decomposition residue. The M of heated wood decreased with increasing WL, and such a correlation became clearer after the extraction in water. On the basis of experimental correlation, the WL of local parts in large-dimension kiln-dried timber was evaluated from their M values. The results indicated that the thermal degradation of inner parts was greater than that of outer parts.     

Changes of decay and termite durabilities of Japanese larch (Larix leptolepis) wood due to high-temperature kiln drying processes

We investigated the effects of high-temperature drying schedules (120°–130°C) on decay and termite feeding of Japanese larch timbers. Thermogravimetric analysis was conducted to investigate changes of the wood components. Decay and termite feeding tests showed that specimens dried under high-temperature schedules were susceptible against a decaying fungus Fomitopsis palustris and attacks from termites Coptotermes formosanus and Reticulitermes speratus. These drying schedules changed chemical components, which were suggested by the thermal analytical result compared to the control sample. The results of this study indicated that the acceleration of termite feeding takes place even under temperatures that are comparatively lower than that used in our previous research in which 170°C steaming treatment was applied to Japanese larch wood. Decay durability against a brown rot fungus also decreased, possibly from production of low molecular weight fragments when hemicellulose decreased during the high-temperature drying processes.     

Hydration behavior and compressive strength of cement mixed with exploded wood fiber strand obtained by the water-vapor explosion process

Poor compatibility was found between exploded wood fiber strand (WFS) and cement due to the excessive presence of water-soluble degraded polysaccharides in extractives of exploded WFS obtained from weathered wood waste treated by the water-vapor explosion process (WVEP). This study presents some comparative results from a continuing investigation on the compressive strengths of exploded WFS–cement mixtures. Based on results previously obtained with the hydration test, the relation between hydration behavior and compressive strength of the mixture was explored. In addition, the effect of the curing age on compressive strength development of the mixture with selected additive chemicals was examined. The results supported the results of early studies with hydration tests indicating that adding MgCl₂ to the mixtures of exploded WFS mixed with quick-curing cement or ordinary Portland cement and a composite of MgCl₂ + CaO added to the mixture of exploded WFS and furnace-slag cement effectively improved the hydration behaviors; it greatly enhanced the compressive strengths of mixtures as well. Compressive strengths were strongly correlated to maximum hydration temperatures (T_max) of wood–cement mixtures influenced by the cement type, wood wastes (treated or not with WVEP), additive chemicals, and their content levels. The results also indicated that adding selected chemicals had no significant effect on compressive strength among the mixtures of exploded WFS mixed, respectively, with three types of cement at a curing age of 180 days. X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray spectroscopy were used to identify the hydration products and to probe the element distribution of the mixture in the wood–cement interface zone from a fractured surface.Part of this report was presented at the 52nd Annual Meeting of the Japan Wood Research Society, Gifu, April 2002     

对改进和完善常规木材干燥室设施的探讨

分析了我国当前木材干燥生产中常规干燥室存在的问题,探讨了干燥室的改进措施,提出了合理建议和意见。     

喷气式网带单板干燥机节能途径探讨

为了提高单板干燥过程中的能源利用效率,对单板干燥过程进行了分析并提出有效的节能措施与途径。提出利用单板干燥尾气余热回收系统,以减少尾气直接排入大气时的热量损失,对尾气余热回收利用;提出蒸汽梯级利用回收冷凝水的热量,达到对冷凝水余热回收利用的目的。     

不同干燥方法对苜蓿干草调制的影响

针对影响人工干燥苜蓿的水分、密度、摆放方式和人工辅助干燥方式4个因素进行人工鼓风干燥处理,设计L9(34)正交试验,监测高水分苜蓿草捆的湿度变化情况,比较不同处理营养物质、相对饲用价值和经济指标.对比分析结果可知:自然晾晒苜蓿干草时,营养物质损失严重;苜蓿高水分打捆后人工继续鼓风干燥处理有利于保存苜蓿干草的营养价值,其中水分为30％～35％、密度为120kg/m3、间隔20cm摆放、两台鼓风机每日鼓风干燥3h为最优组合,所得苜蓿草捆的品质较好.     

铁木豆干燥基准的初步研究

研究了铁木豆的干燥特性,根据干燥缺陷等级试验确定出了适合铁木豆的干燥基准,结果表明：铁木豆的主要干燥缺陷为初期开裂、截面变形,此外,铁木豆的初期开裂、截面变形、内部开裂、扭曲变形的等级分别为5、3、1、2级,铁木豆属于难干木材。     

AHP-熵权法结合Box Behnken响应面法优化当归微波真空干燥工艺研究

为探究当归微波真空干燥的最佳工艺参数,以甘肃定西“岷归1号”为试验材料。运用HPLC法测定不同干燥温度、切片厚度、真空度条件下当归中藁本内酯（LA）、阿魏酸（FA）、洋川芎内酯H（SH）、洋川芎内酯I（SI）、绿原酸（CA）、丁烯基苯酞（BA）、抗氧化性（DPPH）、总酚（TPC）、总黄酮（TFC）、多糖（Pc）的含量,利用AHP-熵权法计算各有效活性成分的复合权重和综合评分;以综合评分为响应值,通过Box Behnken响应面法进行优化设计,确定当归微波真空干燥的最佳工艺参数。结果表明：AHP-熵权法计算得出LA、FA、SH、SI、CA、BA、DPPH、TPC、TFC、Pc、RR的Qj值分别为0.159、0.192、0.120、0.288、0.033、0.063、0.059、0.041、0.024、0.013、0.009;Box Behnken响应面法得到的当归微波真空干燥的最优工艺条件为干燥温度50 ℃、切片厚度5 mm、真空度-0.070 MPa,此时综合评分为84.95分;此外,微观电镜结果也表明在此工艺条件下,样品质构热稳定性最好且内部出现均匀规则的蜂窝状孔隙结构。因此AHP-熵权法可用于当归微波真空干燥工艺中多目标的优化。     

稻谷变温均质干燥装置工艺优化与性能试验

为研究装置干燥均匀性和稻谷干燥特性,通过多因素试验,以干燥温度、滚筒倾角、滚筒转速为影响因素,以干燥时间和干燥速率为评价指标,考察指标对稻谷干燥特性的影响,分析不同干燥工艺对稻谷爆腰率的影响。试验结果表明,影响稻谷干燥时间和干燥速率的主次因素顺序为：干燥温度、滚筒倾角、滚筒转速,最优干燥工艺为干燥温度55℃、滚筒倾角2°、滚筒转速40r/min。验证试验通过含水率均匀度K判定,最佳干燥工艺参数为干燥温度55℃、滚筒倾角2°、滚筒转速60r/min。在此条件下,稻谷干燥时间为191min,干燥速率为0.036％/min,稻谷含水率均匀度为99.6%,稻谷干燥效果最优。研究结果可以为稻谷变温均质干燥装置研制和工艺制定提供参考。     

干制对玫瑰花芳香品质的影响研究

玫瑰花是著名的药用、茶用材料,干制是其广泛采用的加工方式。为阐明玫瑰花朵干制过程中芳香物质的变化规律,以‘丰花’‘苦水’玫瑰为材料,采用烘箱干制不同时期的玫瑰花朵,并利用气相色谱质谱联用技术定量分析花朵烘干后芳香物质的含量情况。结果表明,采用50 ℃干燥条件,各品种开放花朵、花蕾分别需要烘干5.5、12 h达到质量恒定;玫瑰不同时期花朵干制后共检测出21种挥发成分,大蕾期、半开期检测到的挥发成分种类多于小蕾期与盛花期;定量分析干制后玫瑰花朵特征芳香成分,‘丰花’‘苦水’玫瑰中苯甲醇、苯乙醇、香茅醇等分别在大蕾期保存较多,盛花期保留最少。该研究的实施明确了玫瑰干制过程中芳香物质的保留规律,为进一步优化玫瑰干制技术体系,促进玫瑰产业健康发展提供了试验支持。