竹材热解动力学的研究

INVESTIGATION ON KINETICS OF BAMBOO PYROLYSIS

利用热重分析(TG)仪,在氮气的氛围中,加热速率分别为5、10、20、30和40℃/min,热解温度40～500℃下,对竹材不同部位的外、中、内三层热解过程进行了研究.不同形状大小竹材的热解实验表明,传递现象对实验结果的影响很小.TG结果表明,竹材热解可认为是两步的反应过程.通过假设竹材热解反应的反应级数,对TG实验数据回归关联,根据回归线性相关度,筛选合理的反应级数,建立竹材热解动力学模型.计算结果发现,热解反应级数与加热速率有一定的关系,一般为1.5或2级;热解反应的表观活化能和频率因子呈现很强的规律性.

The kinetics of bamboo pyrolysis is essential to understand carbonization of bamboo and effective utilization of bamboo. In this paper, the study on pyrolysis kinetics of bamboo was based on thermogravimetry. Outer, middle and inner parts of bamboo were pyrolyzed in TG equipment (TGA/SDTA851 e) at heating rates of 5, 10, 20, 30 and 40 ℃/min under the temperature range of 40 - 500 ℃ and N_2 atmosphere, respectively. TG results demonstrated that the pyrolysis process of bamboo may be considered as a two-step reaction, one corresponds to the decomposition of hemicellulose and the other to the decomposition of cellulose and lignin. The experimental data were treated by supposing the reaction order of bamboo pyrolysis to be 0.5, 1, 1.5 and 2, respectively. The appropriate reaction order of 1.5 or 2 was obtained by minimizing the difference between the calculated and measured data and the orders of pyrolysis reaction for different bamboo parts are the same at heating rate of 5 to 40 ℃/min. The results showed that the heating rate of pyrolysis process influences the order of pyrolysis reaction, activation energy and frequency factor.