Effect of red mud additive on the combustion performance of lignite and sulfur fixation behaviors

Abstract

ABSTRACT To reveal the role of red mud (RM) as the catalyst during the combustion behavior of lignite, two kinds of RM from Bayer red mud (SR) and sintering red mud (GR) were chosen to investigate the catalytic combustion behaviors of lignite under different oxygen contents, the action mechanism and the sulfur fixation performance by the thermogravimetric analysis (TGA) and fixed-bed reactor. Flynn–Wall–Ozawa (FWO) method was used to study the combustion kinetics. The results showed that RM can promote the release of pyrolysis volatiles and significantly improve the ignition performance of coal. Moreover, the improvement effect of RM becomes more noticeable with the increase of O2 content. RM decreased the ignition and burnout temperatures of the char combustion. The types of RM exert different catalytic properties owing to different compositions. Under oxygen-rich conditions, the apparent activation energy in the early stage of coal combustion can be significantly reduced by RM. In addition, RM enhances the peak temperature during constant combustion of coal, improves combustion rate, shortens the burnout time, and remarkably reduces SO2 emission in exhausted gas. About 83.7% SO2 in combustion gas produced at 700°C was reduced at the SR addition of 25 wt%, indicating RM is a potential and cheap catalyst for high-effective coal combustion.