置换干燥原理及其在木材干燥中的应用

Principle and application prospect on wood drying of displacement drying

置换干燥是利用某种置换剂来置换湿物料中水分的一种非热力干燥方法。其干燥机理有两种形式 :“卷起 -浮升”机制和“颈缩”机制 ,主要特点为能量消耗低、干燥效率高、干燥时间短 ,且在被干燥物料表面不留水分斑迹。置换干燥在电子、航天、机械等方面已得到广泛应用。利用置换干燥方法干燥木材具有很强的吸引力和广阔的应用前景。为了降低木材干燥过程的能量消耗 ,提高出材率和产品质量 ,对不同的需干燥的木材应确定合理的干燥时间 ,选择合适的置换剂 ,并采取多级萃取的逆流结构。

One of the nonthermal methods of drying and dewatering is displacement drying where solvent is used to 'displace' liquid moisture from the wet material.Two alternative mechanisms have been proposed to explain displacement drying:'roll-up' mechanism and water-solvent interfacial tension lowering.Advantages of displacement drying include:reduced energy consumption compared to hot-air drying;higher drying rates and therefore shorter drying times;leaves no trace of moisture on the material surface.So the displacement drying has found application in the electronics,optics and mechanics.The displacement drying has strong magnetism and wider application prospect on wood drying.In order to reduce the energy consumption,improve the percentage of cut-turn and the product quality,the multistage extraction countercurrent configuration should be adopted,in addition the rational drying time and the appropriate solvent should be confirmed.