Dual regulatory roles of CO ₂ on molecular sulfur dissolution in sour components of high-sulfur natural gas: insight from molecular dynamics simulations

Sulfur deposition is one of the major bottlenecks in the development of high-sulfur gas reservoirs, while carbon dioxide is one of the main industrial waste gases. Hydrogen sulfide, carbon dioxide, and methane are the primary solvents for elemental sulfur in sour natural gas. If carbon dioxide from industrial emissions could be utilized to enhance the solubility of elemental sulfur in natural gas, it would help suppress sulfur deposition and reduce greenhouse gas emission. Using molecular dynamics simulations, this study explored the feasibility of this concept from the perspective of the microscopic mechanisms of intermolecular interactions. The results show that CO₂ injection reduces the solubility of elemental sulfur in hydrogen sulfide but can increase its overall solubility in mixed gases by diluting and replacing methane. These two opposing effects cause the solubility of elemental sulfur in natural gas to vary with the amount of CO₂ injected. Overall, the solubility enhancement brought by CO₂ injection is limited in magnitude. This study reveals the molecular mechanism underlying the strategy against sulfur deposition by CO₂ injection, providing insights for further exploration of its feasibility, effectiveness, process complexity, and cost rationality.