赤桉半干材的窑干与调湿处理工艺

Kiln Drying and Conditioning for Pre-air-dried Eucalyptus camaldulensis Lumber

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。

Collapse and huge moisture content（ MC） differences among boards are the main defects during Eucalypt lumber air drying. Therefore, a drying strategy, including pre-steaming before kiln drying and final conditioning after kiln drying, was developed by the authors with the intent to improve lumber drying quality. An experiment on Eucalyptus camaldulensis lumber with thickness of 30 mm showed the following： pre-steaming could help lumber collapse recover effectively and decrease casehardening significantly;mean MC decreased from 25.61% to 11.72% during a 5 day drying period ; both a 3-hour steaming and 24 hour wet-air conditioning could decrease MC gradient and release residual plastic set,while the effects of the latter were better;and the drying quality in this test met the demands of the second quality level in national standard GB/T 6491-1999.