关键词: 林火, 可燃物, 超临界萃取, 热值, 燃点, 大兴安岭

Abstract: [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 CO₂ 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, collection time 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.

Key words: forest fire, fuel, supercritical extract, heat yield value, ignition point, Daxing’anling Mountain