Acid gas removal with membranes in natural gas processing

Acid gas cleaning is one of the natural gas processing steps where the acid gases are removed to satisfy the quality of the sweet gas. Conventionally, this is achieved by proc...cessing the sour gas through an acid gas removal (AGR) unit to produce the desired sweet gas while concentrating the H2S gas in the acid gas enrichment unit. Together with achieving the required high heating value of 930 BTU/SCF in the sweet gas, it is also desired from the process that the acid gases must contain 30–55% H2S content before feeding to the sulfur recovery unit. In addition, the waste gases sent to the thermal oxidizer must not contain more than 2000 ppmv H2S. However, these requirements put a constraint on the process operational flexibility especially when the feed gas has a high CO2 content. In this study, we propose the utilization of membrane units for the acid gas removal and acid gas enrichment in the natural gas processing instead of employing conventional amine solvents.