预处理棉花秆的热解动力学研究

Study on the Pyrolysis Kinetics of Pre-treated Cotton Stalk

为研究棉花秆4个样品(原生物质、盐酸酸洗、3%氯化钾加入及10%氯化钾加入)的热解动力学过程,采用热重法对其在不同升温速率下进行了热解实验。结果表明:4个样品的热解都可分为4个阶段,随着升温速率的提高,热解最大速率以及相对应的温度随之提高,主反应区热重曲线和微分热重曲线都向高温方向移动;盐酸酸洗有利于挥发成分的生成,氯化钾参与量达到一定程度可以提高炭产量。将Coats-Redfern积分法和Achar微分法相结合计算出20种常用机理函数的动力学参数与用Ozawa法计算出的动力学参数相比较,得出棉花秆原生物质热解最可能机理符合Zhuralev-Lesakin-Tempelman方程——三维扩散;盐酸酸洗和氯化钾参与的棉花秆热解最可能机理符合Avrami-Erofeev方程——随机成核和随后生长,反应级数n=2。

To investigate the pyrolysis kinetics process of four samples of biomass （untreated biomass, HCl-washed, 3% KCl-added and 10% KCl-added） of cotton stalks, the experiments were performed by thermogravimetric analysis （TGA） at different heating rates. The results showed the pyrolysis process of these samples could be separated into four stages. With the heating rate increasing, the maximum pyrolysis rate and its corresponding temperature were also increased, and the TG and DTG curves of those samples were shifted to the higher temperature scale. HCl- washed sample was easy to volatilize. For the certain amount of KCl-added biomass sample, the char yield during pyrolysis could be increased. A comparison of the kinetic parameters of 20 sorts of common mechanisms calculated by the methods of Coats-Redfern and Achar with that from the method of Ozawa was made and it inferred that the most possible mechanism functions of untreated biomass pyrolysis is Zhuralev-Lesakin-Tempelman equation, which is a three-dimension diffusion mechanism function; the Avrami-Erofeev equation is more proper for HCl- washed and KCl-added samples, which is a random nucleation and later growth mechanism function, whose reaction order is 2.