Physicochemical characteristics affecting biological coal gasification and coal pretreatment

Abstract:

Under the goals of carbon peaking and carbon neutrality, traditional fossil energy will be gradually replaced. China’s coal resources feature huge reserves and wide distribution. The biological gasification of untapped coal resources can provide additional natural gas resources. Therefore, it is of great theoretical and practical significance to study the mechanism of biological coalbed methane stimulation. Biological coal gasification is promising, but the difficulty lies in its slow dynamic characteristics. To reveal the generation potential and internal factors of biological coalbed methane, we discussed the influence of physicochemical characteristics of coal on biological gasification, the response of coal physicochemical properties to biological action, and the improvement of coal utilization by pretreatment. The internal factors and environmental conditions of biodegradable coal had been identified through indoor research. It was found that low-rank coal had a higher potential for biological coalbed methane production than high-rank coal. The biotransformation of coal by methanogenic microorganisms is bound to cause changes in the physicochemical properties of coal. It is a challenge to continuously provide available substrates for methanogens, which thus limits the biological coal gasification. Chemical pretreatment of coal is mostly used to improve the efficiency and methane yield of biological gasification, while supercritical CO₂ extraction physically dissolves small molecular organics in a macromolecule network for gasification. The production of biological coalbed methane can be further increased, but the in-situ increase needs to be further studied in light of the obvious differences between indoor experimental conditions and reservoir environments. The microbiological research on the biotransformation of organic matter in coal seams should be improved. The study of the main factors controlling the influence of different coal ranks and different reservoir environments on biological gasification is the key to the commercialization of biological gasification.