Study On The Occurrence Law Of Hydrogen Sulfide In No.13 Coal Seam Of Shaping Mine

Hydrogen sulfide（H₂S）is one of the common toxic and hazardous gases in coal mines.When the concentration of H₂S gas is too high,it not only poses a risk of explosion,but also leads to poisoning and death of people.The No.13 coal of Shanxi Shaping coal mine was used.The environment and origin of H₂S occurrence in coal seams was investigated by the vitrinite reflectivity and ion detection and morphological sulfur analysis.The adsorption mechanism of H₂S in coal and the occurrence equation of H₂S in coal seams were analyzed by adsorption experiments at room temperature and pressure and X-ray photoelectron spectroscopy（XPS）.The main research results were as follows.The results showed that the geological evolution and water distribution of the No.13 coal seam can provide a suitable environment for the generation of H₂S.Immediate roof and floor were dominated by mudstone with poor permeability,while the basic roof was dominated by medium-coarse sandstone with strong stability,whitch provided a sealed environment for the H₂S occurrence of the No.13 coal seam.The thermal evolution temperature range of SP coal seam were from 51.47 to 108.12°C,all of which were lower than 120°C,so it could exclude the origin as TSR.In water containing H₂S,the high bicarbonate concentration and low sulfate ion concentration indicated that the H₂S of the No.13 coal seam was due to BSR.The total sulfur content was also greater at locations with high H₂S concentrations and sulfate sulfur was also low,with a maximum of 0.06%,iron sulfide sulfur content was the highest,up to 4.5%,and organic sulfur content was the next highest,up to 0.73%.It was inferred that sulfate was converted to pyrite and organic sulfur by microorganisms,and there was a link between the occurrence of sulfur elements and H₂S.The state of H₂S in coal is mainly in the adsorbed state,there are also free and water-soluble states.The adsorption equilibrium time of H₂S in coal under normal temperature and pressure was24 h and the adsorption capacity increased with H₂S concentration and water content of coal samples.In addition to physical adsorption,chemical adsorption of H₂S also occurred in coal.After adsorption of H₂S,the total sulfur content of coal increased,and water can promote the conversion of H₂S to sulfides in coal.After adsorption of H₂S,the proportion of inorganic sulfur increased significantly.Most of H₂S were converted to inorganic sulfur such as hydrosulfides,ferric sulfide and elemental sulfur,a few H₂S were converted to organic sulfur such as thiophene,C-S-C and C-SH.Therefore,the higher the total sulfur content,the greater the amount of H₂S gas in coal.Organic sulfur and pyrite are coassigned with H₂S in coal with a certain companion relationship.H₂S was generated from sulfate in coal by BSR and reacted with organic matter and iron ions to form organic sulfur and pyrite,which was consistent with the actual assignment of morphological sulfur and H₂S at each sampling point in the No.13 coal seam of the Shaping Mine.Meanwhile,the total amount of H₂S occurrence in coal increased exponentially with the concentration of free H₂S and water content at equilibrium.According to the fitting equation,the average H₂S content was 0.92 m³/t in the No.13 coal seam by measuring the spatial free state H₂S concentration and the water content of the coal seam.When the total amount of H₂S is constant,the concentration of free H₂S decreased in a linear trend with the increase of water content of the coal samples.Therefore,the concentration of free H₂S can be reduced by injecting water into the coal seam.This paper explored the origin and occurrence law of H₂S in the No.13 coal seam of Shaping Mine through a series of experimental studies and theoretical analysis.It provides a theoretical basis for H₂S prevention and control in coal mines.