杉木干燥过程中的有机挥发物释放

VOC Emission from Chinese Fir (Cunninghamia lanceolata) Drying

采用小型干燥机干燥木材,在冰浴中用酸化的2,4-二硝基苯肼溶液和去离子水分别对尾气中醛类和有机酸、醇类采样,用活性炭管对萜烯类采样,采用高效液相色谱仪和气相色谱仪对有机挥发物进行分析。结果表明:杉木干燥释放的主要物质是甲醇、乙酸和甲酸,其次是乙醛、甲醛、丙烯醛/丙酮;萜烯类挥发物主要有α-蒎烯、D-柠檬烯、莰烯、β-蒎烯、β-水芹烯。杉木高温干燥释放的醛类和酸、醇类挥发物远高于常规干燥,高温和常规干燥中挥发物总量分别为91.7g.m-3和29.9g.m-3,但萜烯类挥发物总量差异很小。木材干燥终含水率对醛类和有机酸、醇类释放量影响较大,对萜烯类释放量影响较小。甲醛高温干燥时随含水率降低释放速率增大,其他物质在高温和常规干燥时的释放速率随含水率减少呈下降趋势。

During Chinese Fir（ Cunninghamia lanceolata） drying at a pilot-scale kiln, aldehyde was trapped in 2,4-DNPH solution and polar compounds were trapped in deion water and then analyzed by HPLC. Terpene was trapped on active carbon tube and analyzed by GC-FID. The results showed that the total volatile organic compounds（VOC） volume were 91.7 g·m^-3 and 29.9 g·m^-3 at 120℃ and 90℃, respectively. During kiln drying the major components in VOC were methanol, acetic acid, formic acid, acetaldehyde, formaldehyde, acmlein/acetone. The major terpine were a-pinene, D-limonene, camphene, β-pinene and β-phellandrene. The volume of aldehydes, methanol, acetic acid and formic acid emitted from drying at 120 ℃ was much higher than that emitted from drying at 90 ℃. But the total amount of terpine was almost the same at 120 ℃ and 90 ℃. The final moisture content of wood had significant influence on emission amount of aldehydes and polar volatile compounds： However, the final moisture content on the emission amount of terpine was not significant. The rate of formaldehyde emission increased gradually with the decreasing of moisture content（MC） for high temperature drying at 120 ℃, and the rate of other components decreased with the decreasing of MC.