Study on H2S Occurrence in Low Sulfur Coal Seams

Coal samples from the Shanxi Shaping coal mine were selected to investigate the occurrence of H2S in low sulfur coal seams. The adsorption mechanism of coal to H2S was explored, and an occurrence equation for H2S in coal seams was fitted through adsorption experiment results. The results showed that under ambient temperature and pressure conditions, the H2S adsorbed by coal reached equilibrium within 24 h. The increase in H2S concentrations and the moisture content of coal samples resulted in an increase in the adsorption capacity of H2S. Chemical adsorption of H2S by the coal also occurred. The total sulfur content in the coal increased, and water promoted the conversion from H2S to sulfur in coal. After adsorption, most of the H2S remains in the coal structure in the form of inorganic sulfur, such as sulfur hydride, iron sulfide sulfur, and monomeric sulfur, and a small proportion of H2S is bonded in the structure of the coal in the form of organic sulfur such as thiophene, C-S-C, and C-SH. Therefore, the higher the total sulfur content in coal, the greater the occurrence of H2S. The total amount of H2S increased exponentially with the concentration of free H2S and the moisture content of coal at equilibrium. This meant that the total amount of H2S in the coal seam could be estimated by fitting an equation according to the concentration of free H2S and the moisture content of coal seams. The concentration of free H2S decreased linearly with the increase in moisture content of the coal, therefore, the concentration of H2S in space could be reduced by injecting water into coal seams.