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

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.

Highlights

• Role of RM in catalytic lignite combustion under different O₂ contents is revealed.

• RM promotes volatiles release and improves ignition performance in coal combustion.

• Red mud exhibits good catalytic effect on the combustion of pyrolysis char.

• Red mud increases peak temperature of coal combustion and improves combustion rate.

• Red mud exhibits excellent sulfur fixation performance during coal combustion.

KEYWORDS:

• Combustion
• red mud
• lignite
• sulfur fixation

Acknowledgements

Thanks for the financial supporting of the National Natural Science Foundation of China (No. 21878044) and the Fundamental Research Funds for the Central Universities (No. DUT21TD103).

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Notes on contributors

Yu Cheng

Yu Cheng is a master of the School of Chemical Engineering, Dalian University of Technology. His research deals with the catalytic combustion of coal.

Guijin Wang

Guijin Wang is a postdoctor in the School of Chemical Engineering, Dalian University of Technology. He focuses on catalytic pyrolysis of coal.

Yiming Wang

Yiming Wang received his Ph.D from Dalian University of Technology. He mainly engages in research on coal pyrolysis.

Yanpeng Ban

Yanpeng Ban is a postdoctor in the School of Chemical Engineering, Dalian University of Technology. His research is mainly related with catalytic conversion of coal.

Yuanyuan Li

Yuanyuan Li is a master of the School of Chemical Engineering, Dalian University of Technology. Her research mainly deals with the mechanism of coal pyrolysis.

Yang Li

Yang Li is an associate professor of the School of Chemical Engineering, Dalian University of Technology. She earned her Ph.D from Huazhong University of Science and Technology. She is mainly engaged in the research work of pollutant formation and control in the process of energy utilization.

Haoquan Hu

Haoquan Hu is a professor of the School of Chemical Engineering, Dalian University of Technology. He received his Ph.D from Dalian University of Technology. He is mainly engaged in research on coal and oil shale conversion, supercritical fluid extraction, the preparation and application of porous materials.

Lijun Jin

Lijun Jin is a professor of the School of Chemical Engineering, Dalian University of Technology. He received his Ph.D from Dalian University of Technology. He mainly engages in research in thermal conversion of coal/biomass and hydrogen production from methane.