Coal gasification through microbial degradation in a low-pressure CO₂ and H₂ environment: An experimental study

Authors

JIAN Kuo, School of Safety and Emergency Management Engineering, Taiyuan University of Science and Technology, Taiyuan 030024, China; State Key Laboratory of Coal and Coalbed Methane Co-mining, Jincheng 048204, ChinaFollow
FU Xuehai, College of Resources and Earth Sciences, University of Mining and Technology, Xuzhou 221116, China
LIU Mingjie, State Key Laboratory of Coal and Coalbed Methane Co-mining, Jincheng 048204, China
LIU Jian, State Key Laboratory of Coal and Coalbed Methane Co-mining, Jincheng 048204, China
LI Jin, State Key Laboratory of Coal and Coalbed Methane Co-mining, Jincheng 048204, China
RU Zhongliang, School of Safety and Emergency Management Engineering, Taiyuan University of Science and Technology, Taiyuan 030024, China
JI Xiaofeng, School of Safety and Emergency Management Engineering, Taiyuan University of Science and Technology, Taiyuan 030024, China
WANG Qiang, National Coalbed Methane Quality Inspection Center, Jincheng 048026, China

Abstract

Objective and Methods This study aims to investigate the characteristics of CO₂ biomethanation and coal gasification through microbial degradation in a low-pressure environment. With low-rank bituminous coals (R_max = 0.67%) as fermentable substrates, this study conducted a 96-day gas production experiment through microbial fermentation in a low-pressure CO₂ and H₂ environment. Using techniques including gas chromatography, 16S rRNA gene sequencing, and low-temperature liquid nitrogen adsorption, this study delved into the intrinsic variation patterns of biogenic gas production, microbial communities, and coal structures. Results and Conclusions The results indicate that compared to conventional fermentation, the injection of low-pressure CO₂ inhibited CH₄ production, leading to a reduced CH₄ production efficiency. After the H₂ injection, the injected H₂ was consumed quickly, resulting in a rapid decrease in the H₂ concentration and contributing to CH₄ production. Meanwhile, the H₂ injection changed the production mode of biogenic gas, exerting a profound influence on the structure of microbial communities in fermentable liquids. Specifically, the relative abundance of Firmicutes and Bacteroidota increased. Notably, the S50_wastewater_sludge_group in Bacteroidota always predominated, trending upward together with the unclassified_W27 genus. This occurred due to the late-stage H₂ injection, which accelerated the growth and metabolism of both bacterial genera. Regarding the distribution of archaea at the genus level, Methanobacterium represented the highest proportion (47.66%‒83.05%), followed by Methanosarcina and Methanoculleus sequentially. Benefiting from the simultaneous consumption of H₂, CO₂, and substrates such as acetic acid, the relative abundance of Methanosarcina exhibited a significant upward trend. In contrast, Methanoculleus, which synthesizes methane via the hydrogenotrophic pathway, displayed a rapidly decreasing relative abundance due to a shortage of H₂ in the later stage. Compared to the raw coals, coals with injected low-pressure CO₂ exhibited a lower adsorption capacity, with the total pore volume and specific surface area decreasing. As more low-pressure CO₂ was injected, fractal dimensions D₁ and D₂ trended downward and upward, respectively, suggesting an increase in the surface roughness of coal pores and a decrease in the complexity/heterogeneity of pore structures. This is inferred to be associated with the dual effects of microbial degradation and carbonate precipitation. The results of this study enrich the fundamental theories on the microbial degradation of coals and the biological transformation and utilization of CO₂, especially providing a theoretical basis for the biological transformation and storage of CO₂ in coal seams.

Keywords

microbial transformation of coal, methane, low-pressure environment, CO2 and H2, microbial community, pore structure

DOI

10.12363/issn.1001-1986.24.03.0174

Recommended Citation

JIAN Kuo, FU Xuehai, LIU Mingjie, et al. (2024) "Coal gasification through microbial degradation in a low-pressure CO₂ and H₂ environment: An experimental study," Coal Geology & Exploration: Vol. 52: Iss. 12, Article 8.
DOI: 10.12363/issn.1001-1986.24.03.0174
Available at: https://cge.researchcommons.org/journal/vol52/iss12/8

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