Study on the Pyrolysis Characteristics and Mechanism of KCl-Pretreated Sunflower Stalk

Abstract

To study the influence of KCl pretreating on the pyrolysis kinetics of sunflower stalk, the pyrolysis of sunflower stalk pretreated by different concentration KCl solutions were performed by nonisothermal thermogravimetric analysis (TGA) at five different heating rates. The Ozawa and Kissinger methods were employed to calculate the activation energy and the Šatava method was used to obtain the kinetic mechanism model. The results showed that the pyrolysis process of the sunflower stalk pretreated by 3% and 10% KCl solution can be separated into four stages (water loss, depolymerization and vitrification, thermal decomposition, and carbonization). With the heating rate increasing, the main pyrolysis zone of the TG (thermogravimetric) and DTG curves move to the higher temperature direction, and the maximum pyrolysis rate and its corresponding temperature increase too. Adding a small amount of metal salts is conducive to the formation of volatile, and a certain amount of metal salts can improve the charcoal yield. More KCl additive makes the lower activation energy value, and the obtained activation energy value increases with the heating rate increasing. By means of the Šatava method, the kinetic mechanism model for the pyrolysis of KCl-pretreated sunflower stalk is Zhuralev-Lesakin-Tempelman equation, which is three-dimensional diffusion.