Analysis of influencing factors of biological methane production with coal slime by anaerobic fermentation

Coal slime is the tailings of coal preparation plant. It is difficult to dispose because of its huge amount, high moisture, ash and low calorific value. Coal slime is often dumped as a waste, resulting in a waste of land resource and environmental pollution. In order to increase the utilization of coal slime, realize an efficient utilization of resource and protect the environment, the factors influencing the conversion of coal slime into biomethane were explored. The coal slimes from the coal preparation plants of Xilinguole League Mine in Inner Mongolia, Yanzishan and Malan Mines in Shanxi and Zhaogu No.1 Mine in Henan were selected, and the domesticated bacterial liquid was used as the source of bacteria. The influence factors of gas production of different coal slimes were analyzed by biological gas production simulation experiment, infrared spectrum, fluorescence spectrum and 16S rRNA tests. The results show that the biogas production capacities of coal slimes are different, and the biogas production is controlled by the metamorphism grade of coal and the content of organic matter. The lower the coal rank of coal slime and the higher the organic matter content, the better the gas production effect of coal slime is, and vice versa. After the microbial degradation of low rank coal slimes, various groups such as aliphatic structure, hydroxyl and amino in coal are easier to fall off, and the aromatic compound are partly converted into small molecular-weight substances, which are easier to produce gas than high rank coal slime. The protein organic matter in low metamorphic coal slimes are decomposed more by microorganisms, and the gas production effect is better, while the high metamorphic coal slime contains more humus organic matter, which is not easy to degraded, and the gas production effect is poor. The diversity of bacteria is higher than that of archaea. The bacteria is mainly consisted of Pseudomonas and Macellibacteroides, whereas the archaea is mainly consisted of Methanocorpusculum and Methanothrix. The biogas from coal slime is affected by bacteria, and dominant bacteria plays a key role in the degradation of organic matter in the early stage. The biomethane mainly comes from the conversion and utilization of CO2 and H2 by methanogens. The results reveal the reasons for the difference in the gas production from different coal slimes, and provide a reference for the establishment of a potential evaluation method for coal slime to convert biomethane. © 2021 China Coal Society. All rights reserved.