Analysis of the Formation Mechanism of Hydrogen Sulfide in the 13# Coal Seam of Shaping Coal Mine

In order to accurately predict the law of occurrence and migration of hydrogen sulfide (H₂S) in the underground and effectively solve the problem of excessive concentration of H₂S gas, laboratory experiments on the content of various forms of sulfur in coal, sulfur isotopes, thermal evolution history, and coal seam water samples were carried out by applying the theories of coal mine geology, microbiology, and analytical chemistry, and based on the experimental results, the cause of H₂S gas was explored. Through the analysis of the geological conditions of the coal seam mined, it can be seen that the coal mine experienced the alternation of marine and continental phases in the process of coal formation and that there was no magma intrusion. The experimental results showed that iron sulfide in coal accounts for 73.25% of the total sulfur, indicating that the coal seam was rich in pyrite. The results of the isotope test showed that the sulfur isotopes in coal samples were all negative, indicating that the sulfur isotope fractionation in coal was large, the loss was serious, and the coal seam was greatly affected by seawater. According to the experimental results of vitrinite reflectance, it can be concluded that the highest temperature during the thermal evolution of the coal seam is 108.12 °C, which has not reached the temperature condition of sulfate thermochemical reduction. Comparing the concentration of acid ions in coal seam water and tap water, it was found that the concentration of SO₄^2- in coal seam water is low, while the concentration of HCO₃^- is high. According to the experimental results and theoretical analysis, the H₂S gas in the high-sulfur coal mine was caused by microbial sulfate reduction. Finally, the transformation path of sulfur in the coal seam was deduced and analyzed. The results showed that sulfur in coal is positively correlated with H₂S gas concentration.