NO reduction by carbon-based gases based on coal gasification fractions: NO reduction intermediate identification and kinetic analysis

Highlights

	● The influencing factors of denitration of carbon-based gases were evaluated.
	● The kinetics of catalytic reactions of Coke, CaO, MgO and Fe2O3 were investigated.
	● The NCO• radical was essential for the NO reduction process.
	● Mixtures of alkaline metal oxides may have a synergistic effect on NO reduction.

Abstract

Combining pulverized coal gasifiers with cement kiln production is promising for application in low-cost and efficient NO reduction. This paper presents a pulverized coal gasifier catalytic denitration technique and investigates the homogeneous reduction (by CO and CH₄) and heterogeneous catalytic reduction (by coke, CaO, MgO, and Fe₂O₃) of NO. A combination of Chemkin simulations and fixed-bed experiments is used to elucidate the reaction pathways and key intermediates of NO reduction by carbon-based gases. In addition, the activation energies for different catalyst combinations were analyzed via reaction kinetics. The results demonstrate that the presence of small amounts of O₂ inhibits NO reduction by CO but promotes NO reduction by CH₄. The NCO• radical is essential for the NO reduction process, and the generation of this radical depends on the CH₄ cleavage intermediate and O• radical. CaO and Fe₂O₃ exhibit more significant catalytic effects on NO reduction by carbon-based gases than the other catalysts tested. The presence of a small amount of O₂ in the reacting gas mixtures facilitates the NO reduction reaction. The activation energy is reduced to 1.02 kJ/mol, and the NO conversion reaches 99.80% when the catalyst is C + CaO + MgO + Fe₂O₃ and the gas composition is CO + CH₄ + O₂. This work provides theoretical support and data recommendations for the use of pulverized coal gasifiers for the denitrification of cement kilns.

Graphical abstract

Keywords

Carbon-based gas / Catalytic denitration / Coke / Kinetic analysis / Reaction mechanism

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CRediT Authorship Contribution Statement

Xiang Zhang: Conceptualization, Methodology, Visualization, Writing-original draft, Writing-review and editing. Jian Tian: Methodology, Writing-review and editing, Supervision, Funding acquisition. Tanghui Hu: Methodology, Visualization, Guangyong Yue: Conceptualization, Xianlong Liu: Methodology, Supervision, Wen Zhou: Conceptualization, Methodology, Xiaohong Liu: Supervision, Visualization, Xinye Wang: Conceptualization, Writing-review and editing.

Acknowledgements

This work was supported by the Special Project for Innovation-driven Development in Guangxi, China (No. 2018AA21013). We are grateful to School of Energy and Environment, South-east University (China) for providing Chemkin software support.

Conflict of Interests

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Electronic Supplementary Material

Supplementary material is available in the online version of this article at https://doi.org/10.1007/s11783-025-1957-z and is accessible for authorized users.

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