Selective H₂S removal (FLEXSORB™)

ExxonMobil’s FLEXSORB technology enables customers to process increasingly sour gas streams while helping to meet stringent emission regulations and sulfur recovery objectives. The highly selective H₂S removal process has been used in tail gas treating (TGT), acid gas enrichment (AGE) and high-pressure acid gas removal (AGR) units. The technology provides a cost-effective way to meet low H₂S specifications while minimizing CO₂ co-absorption.

The FLEXSORB SE technology is designed for the selective removal of H₂S in the presence of CO₂ and utilizes proprietary severely sterically hindered amines. The unique characteristics of the amine allow it to achieve high H₂S cleanup selectively at low solvent circulation rates. This gas treating technology has been proven in over 100 commercial units worldwide and is considered the best available technology in many regions, enabling facilities to meet stringent emissions standards. FLEXSORB SE Plus can help to meet or exceed the World Bank Standard (WBS) SO₂ emission limit of 150 mg/Nm³, equivalent to approximately 99.98% sulfur recovery efficiency (SRE).

Two variations:

In sulfur plant TGTU applications, FLEXSORB™ SE and SE Plus solvents require about half of the circulation rate and regeneration energy of other solvents based on methyldiethanolamine (MDEA). CO₂ rejection is very high, typically above 90%. Lower circulation rate translates into smaller heat exchangers and a smaller regenerator tower, thereby reducing investments for grassroots projects. For existing units, FLEXSORB SE and SE Plus solvents allow the unit to be debottlenecked with few or no equipment modifications.

In natural gas treating, selective H₂S removal from natural gas can be advantageous whenever a portion of the CO₂ can remain in the treated gas. In one natural gas treating facility, conversion to FLEXSORB SE solvent allowed the unit to increase gas production by 27% without modification of the existing hardware. At the same time, the circulation rate and reboiler duty was lowered to 65% and 78% of the design, respectively. FLEXSORB SE also improved the CO₂ slip and the operability of the unit by reducing the co-absorption of heavy hydrocarbons.

ExxonMobil’s FLEXSORB SE or SE Plus solvents are in use in a wide variety of Acid Gas Enrichment (AGE) designs around the world, enabling reserves that contain more CO₂ than H₂S to be economically developed. As the name implies, an AGE unit enriches the H₂S content of the acid gas stream, making it practical to recover sulfur in a conventional Claus unit. In applications where acid gas injection instead of Claus is used, FLEXSORB technology can be used to minimize the volume of acid gas for re-injection.

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