核桃壳热解特性及几种动力学模型结果比较

PYROLYSIS CHARACTERISTICS OF WALNUT SHELL AND ITS KINETIC PARAMETERS WITH DIFFERENT METHODS

利用热重分析在不同升温速率和氮气气氛下对核桃壳的热失重行为进行研究。根据热重实验数据,采用4种热分析动力学方法(Coats-Redfern法、Doyle法、Ozawa法和DAEM模型),计算核桃壳热解反应活化能E、反应级数n及频率因子A,并进行比较。结果表明:采用不同的动力学分析处理方法,得出的热解动力学参数不同。利用Coats-Redfern法,核桃壳在热解主要阶段(失重10%～95%)可由一段一级反应过程描述,升温速率20K/min时活化能为55.37kJ/mol。Doyle法和DAEM模型得到的结果较为接近,Ozawa法求得的活化能值最高。核桃壳热解包含分子键能断裂的一系列复杂、连续反应过程,并获得核桃壳的热解反应活化能随失重率的变化曲线。

The pyrolysis characteristics of walnut shell sample at different heating rates （5 -50K/min） in a stream of N2 were studied by using thermogravimetric analysis. Four methods ： Coats-Redfern, Doyle, Ozawa and DAEM, were used to determine the kinetic parameters, including activation energies, reaction order and frequency factor. The results showed that the kinetic parameters are different with different methods. The pyrolysis process can be described by first-order global model for walnut shell and its activation energy was 55.37kJ/mol （ weight loss from 10w% to 95w% ） at the heating rate of 20K/min with the method of Coats-Redfern. Almost the same results were obtained with Doyle and DAEM model. The activation energy is the highest with the method of Ozawa. Pyrolysis of the walnut shell sample is a complicated reaction and their activation energy varied with increasing weight loss.