生物质秸秆热重分析及几种动力学模型结果比较

利用热重分析在不同升温速率和氮气气氛下对两种生物质（玉米秸秆和稻秆）的热失重行为进行了研究。根据热重实验数据，采用四种利用热分析获取动力学参数的方法（Coats-Redfern法，Doyle法，最大速率法和分布活化能模型(DAEM)），计算生物质秸秆热分解反应活化能E、反应级数n及频率因子A，并进行比较。结果表明，采用不同的处理方法，得出的热分解动力学参数不同。利用Coats-Redfern法，玉米秸秆和稻秆在热解主要阶段（失重约5 w%～80 w%时）可由一段一级反应过程描述，升温速率10 K/min时活化能值分别为68.8 kJ/mol和70.0 kJ/mol。Doyle法和DAEM模型得到的结果较为接近，可以得到生物质热解过程中的活化能随失重率的变化曲线。生物质秸秆热解包含分子键能断裂的一系列复杂、连续反应过程。

BIOMASS PYROLYSIS AND ITS KINETIC PARAMETERS WITH DIFFERENT METHODS

Thermogravimetric analysis was used to study the pyrolysis characteristics of two biomass samples, corn straw and rice straw, at different heating rates of 5 K/min, 10 K/min, 20K/min, 40 K/min in a stream of N2. Four methods: Coats-Redfern，Doyle，Kissinger and DAEM, were used to determine the kinetic parameters, including reaction order, frequency factor and activation energies. The results indicated that the kinetic parameters were different with different methods. The pyrolysis process can be described by first-order global model for both corn straw and rice straw and their activation energy was 68.8 kJ/mol and 70.0 kJ/mol (weight loss from about 5 w% to 80 w%) at the heating rate of 10 K/min, respectively, with the method of Coats-Redfern. Almost the same results were obtained with Doyle and DAEM model. Pyrolysis of the two biomass samples was a complicated reaction and their activation energies varied with increasing weight loss. The model of Doyle and DAEM was efficient method to provide more information of pyrolysis of the biomass samples.