Conversion mechanism of thermal plasma-enhanced CH4-CO2 reforming system to syngas under the non-catalytic conditions

Yang Zhou; Ruizhi Chu; Lulu Fan; Jianqiao Zhao; Weisong Li; Xiaofeng Jiang; Xianliang Meng; Yusai Li; Shi Yu; Yongzhou Wan

doi:10.1016/j.scitotenv.2023.161453

Conversion mechanism of thermal plasma-enhanced CH₄-CO₂ reforming system to syngas under the non-catalytic conditions

Sci Total Environ. 2023 Mar 25:866:161453. doi: 10.1016/j.scitotenv.2023.161453. Epub 2023 Jan 7.

Authors

Yang Zhou¹, Ruizhi Chu², Lulu Fan¹, Jianqiao Zhao¹, Weisong Li¹, Xiaofeng Jiang¹, Xianliang Meng³, Yusai Li¹, Shi Yu¹, Yongzhou Wan⁴

Affiliations

¹ School of Chemical Engineering and Technology, China University of Mining and Technology, Xuzhou 221116, Jiangsu, PR China.
² School of Chemical Engineering and Technology, China University of Mining and Technology, Xuzhou 221116, Jiangsu, PR China; Key Laboratory of Coal Processing and Efficient Utilization of Ministry of Education, Xuzhou 221116, Jiangsu, PR China.
³ School of Chemical Engineering and Technology, China University of Mining and Technology, Xuzhou 221116, Jiangsu, PR China; Key Laboratory of Coal Processing and Efficient Utilization of Ministry of Education, Xuzhou 221116, Jiangsu, PR China. Electronic address: meng27@cumt.edu.cn.
⁴ School of Chemical Engineering and Technology, China University of Mining and Technology, Xuzhou 221116, Jiangsu, PR China; Key Laboratory of Coal Processing and Efficient Utilization of Ministry of Education, Xuzhou 221116, Jiangsu, PR China. Electronic address: wyz212@163.com.

PMID: 36626987
DOI: 10.1016/j.scitotenv.2023.161453

Abstract

Thermal plasma activation of CH₄-CO₂ reforming (CRM) to syngas under non-catalytic conditions is an efficient and clean technology for the large-scale utilization of hydrocarbon resources and the conversion of greenhouse gases. This study investigates the equilibrium state and transformation mechanism of a CRM reaction system activated by thermal plasma through experimental, thermodynamic, and kinetic analyses. The experimental results illustrated that the CO₂ conversion rate and H₂ selectivity showed a downward trend with an increase in the CO₂/CH₄ molar ratio, whereas the CH₄ conversion rate and CO selectivity showed the opposite trend. When CO₂/CH₄ molar ratio was 6/4, the selectivity for CO and H₂ increased to 87.0 % and 80.8 %, respectively. Excess CO₂ promotes the partial oxidation of CH₄ to eliminate carbon deposition, resulting in an H₂/CO molar ratio value closer to 1. Thermodynamic results show that the thermal-plasma-initiated CRM reaction can reach thermodynamic equilibrium more easily than the conventional catalyzed reactions, achieving much higher feedstock gas conversion without carbon deposition. The kinetic results obtained from the PSR model revealed that CH₄ and CO₂ were cleaved to form free radicals at the instant of contact with the plasma flame. O, H, and other particles generated in the form of free radicals rapidly collided with each other and transformed into CO and H₂, accelerating the reaction process. The results presented in this study will help reveal the transformation mechanism of the CRM reaction activated by thermal plasma under non-catalytic conditions and provide a new perspective for studying CRM reactions.

Keywords: CH(4)-CO(2) reforming; Gas evolution; Non-catalytic; Syngas; Thermal plasma.