杉木热解及燃烧特性热天平模拟试验研究

Study on the characteristics of fir pyrolysis and combustion in thermal balance for simulating typical fire condition

对南方森林主要树种-杉木的变工况热解行为进行了热重分析(TG)和差热分析(DTG)研究.将试样分别加热到200 ℃、300 ℃、400 ℃和500 ℃做空气变氮气、氮气变空气热天平试验,模拟实际火场由于火势发展产生的局部缺氧状态及由缺氧状态转变为富氧的状态;在空气气氛下将试样分别加热到250 ℃、300 ℃、350 ℃、400 ℃和450 ℃,然后冷却到50 ℃再继续加热直到700 ℃,模拟火场中可燃物不完全燃烧后的回燃情况.通过试验结果分析,深入研究了环境气氛变化对试样热解的影响.给出了杉木热解的两阶段一级反应模型,通过模型计算得出在233.3 ℃～369.9 ℃、369.9 ℃～490.8 ℃热解二阶段的活化能分别为77.85 kJ·mol-1、138.18 kJ·mol-1,频率因子分别为1.95×106、4.84×109.

TG and DTG experiments were carried out to study the pyrolysis kinetic behavior of the southern fir in various conditions. The atmosphere was changed from air to nitrogen or from nitrogen to air when the sample was heated to 200°C, 300°C, 400°C and 500°C respectively in a series of experiments. The aims of these experiments were to simulate the cases of local poor oxygen caused by fire and rich oxygen caused by the fresh airflow. The sample was first heated to 250°C, 300°C, 350°C, 400°C and 450°C respectively and then cooled to 50°C and reheated to 700°C in the atmosphere of air to simulate the repetitive burning after insufficient combustion in a fire. Through the experiments, the effects of pyrolysis conditions on the pyrolysis characteristics are understood. Based on the First Order Two-stage Model, the apparent activation energy and frequency factor of the samples in two temperature ranges of 233.3°C-369.9°C and 369.9°C-490.8°C were obtained, which are 77.85 kJ · mol-1 and 1.95 × 106 s-1, and 138.18 kJ · mol-1 and 4.84 × 109 s-1, respectively.