大兴安岭针叶可燃物的热值和燃点与其超临界萃取物含量的相关性

Correlations between Supercritical Extracts of Coniferous Fuel and the Heat Yield Value and Ignition Point

【目的】研究大兴安岭林区主要针叶树种可燃物样品的超临界CO_2萃取物含量与热值和燃点的相关性,寻求简单、快速、准确获取可燃物抽提物含量的方法和技术,为林火管理提供理论和数据支撑。【方法】从兴安落叶松、樟子松、鱼鳞云杉、红皮云杉、偃松、兴安桧6个针叶树种中按针叶和小枝分别采集可燃物样品,风干后用植物粉碎机粉碎。利用优选法确定可获取最大萃取物含量的超临界萃取条件,采用美国PARR 6300全自动氧弹量热仪测定可燃物样品的热值,DW-2点着温度测定仪测定可燃物样品的燃点。【结果】可燃物样品超临界萃取物含量与热值显著相关,但与燃点相关性不显著。基于相关性分析,推断优选条件下获得的超临界萃取物主要为脂肪类抽提物。【结论】样品粒度40目、萃取釜温度45℃、萃取釜压力40 MPa、收集时间80 min、气体流速2.0 L·min^(-1),是获得可燃物样品中脂肪类抽提物的适宜条件。萃取物含量与热值密切相关,特别是针叶样品萃取物含量与热值相关系数达0.972 2。应用本研究方法,可快速测定可燃物样品中的脂肪类抽提物含量,与传统的索氏提取器方法相比,具有操作简单、耗时短、提取效率高等优点。

【Objective】Extracts,a very important component of fuel,can be divided into two categories： fatty acid extracts and volatile oil extracts. Traditional extraction methods have many shortcomings, including complicated operations,long procedure times,and low efficiency. To explore a simple,and fast technique for fuel extraction,the correlations between supercritical extracts of coniferous fuel,which were found on Daxing＇anling Mountain,and their heat yield value and ignition point were studied. 【Method】Fuel samples were collected from six conifer species,including Larix gmelinii,Pinus sylvestris var. mongolica,Picea jezoensis,Picea koraiensis,Pinus pumila,Sabina davurica. Samples of each tree species were divided into two categories： needles and twigs. After air drying,the samples were ground. By comparing extracts from different samples,the supercritical CO_2 extraction conditions were optimized. The heat yield values of the samples were determined using a PARR 6300 automatic oxygen bomb calorimeter. The ignition points of the samples were determined by a DW-2 ignition temperature sensor. 【Result】A correlation analysis showed that the heat yield values were closely correlated to the extract contents. However,there was no obvious correlation between the extract contents and the ignition point. Based on the correlation results,it can be inferred that the extracts in the experiment were mainly fatty acids.【Conclusion 】The supercritical fluid extraction conditions were established in the present study,i. e.,samples size 40 mesh,extraction temperature 45 ℃,extraction pressure 40 MPa,static extraction time 10 min,collectiontime 2 h,flow rate 2. 0 L·min^（-1）and is the suitable conditions for fatty acids extracts of forest fuels. Under these conditions,the needle extract contents were closely related to the heat yield values,as indicated by the high correlation coefficient（ 0. 972 2）. With the present methods,the fatty acid extracts contents of fuels can be determined quickly.Compared with the traditional Soxhlet extraction method,the present method has many advantages,including its simple operation,short procedure time,and high extraction efficiency.