Chemical and physical systems for sour gas removal: An overview from reaction mechanisms to industrial implications

As global energy demand keeps rising, natural gas is meant to be the main protagonist of the clean energy transition, with increasingly importance in power generation and production of chemicals. However, the presence of contaminants in the raw gas, such as H₂S and CO₂, is the cause of several operational and technical issues ranging from equipment corrosion, fouling, catalyst deactivation, and environmental pollution. Therefore, it is necessary to remove contaminants from these gaseous mixtures for their efficient and safe use in multiple applications. The objective of this review is to explore different aspects of the acid gas removal (AGR) processes and technologies. The design of AGR unit and the main parameters affecting the process have been discussed. In the first part, the chemical absorption processes are summarised, including the chemical mechanisms involved and a screening of the main amine-based solvents currently used in such processes. In the second part, the physical absorption processes are presented, with properties, advantages and disadvantages of the typical absorbents. The comparison of various solvents, towards H₂S and CO₂ removal techniques, has been discussed and supported by simulation and experimental studies. Industrial applications of AGR processes have been included in the discussion. Finally, the future directions of research to improve the removal processes and materials have been indicated.