H2S scavenging of produced gas using MEA-triazine: A mixed blessing

MEA-triazine is the most common scavenger in oil and gas industry for the removal of H2 S from sour gas. It is formulated as a basic aqueous solution (pH around 11), typically 30% to 60% by mass. Its success is due to high rates of H2 S removal, wide range of operational temperatures, easiness of the synthesis, and low cost. Major shortcomings are the fouling and scaling propensity of the wastewater containing spent and unspent scavengers (SUS) and the practical difficulties of operating the scavenging process at low stoichiometric excess. These aspects lead to large chemical consumption and high levels of unspent MEA-triazine in the discharged water in offshore operations.

Recent experimental research work carried out at Aalborg University (AAU) has been focused on physicochemical aspects of the gas-liquid reactions of MEA-triazine and H2 S, on the analytical characterization of the SUS by means of NMR and Raman Spectroscopy, and on the development of a membrane recovery process for the recovery of unspent MEA-triazine from the SUS. The membrane recovery technology is proposed as a viable way to reduce the consumption of MEA-triazine and the discharge into the sea of the unspent scavenger in offshore operations.

This work summarizes the recent findings regarding the gas-liquid reactions of MEA-triazine and H2 S. In addition, it presents preliminary and novel results obtained at AAU about the NMR characterization of the SUS, as well as about the development of quantitative Raman Spectroscopy (qRS) methods for the rapid quantitation of MEA-triazine in commercial products and of the key components of the SUS. Finally, the first results obtained on a novel membrane pilot unit for the recovery of MEA-triazine from the SUS are presented. The first results are confirmatory of previous research and indicate the possibility of recovering MEA-triazine with rejection factors above 80%, using commercially available nanofiltration membranes.