A Study of the Compatibility of Carbon Steel for MEG Reclaiming Systems: Impact of pH Adjustment

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Mono-ethylene glycol (MEG) is often injected in offshore gas transport lines to prevent the formation of gas hydrates (crystalline solids comprised of water and gas that form at low temperatures). Glycol is one of the most effective products for this purpose and acts to further lower the temperature at which hydrates would normally form. As such, it is called a thermodynamic inhibitor.

Product Number: 51323-19467-SG

Author: J. Kittel, F. Grosjean, G.R. Joshi, G. Parer, F. Quinio, JC Brevot

Publication Date: 2023

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In this communication, we will describe an integrated monoethylene (MEG)-reclaiming process using carbon steels metallurgy for most of the lines and vessels that handle MEG slurry solutions. Due to the potentially highly corrosive conditions in this type of facility, corrosion resistant alloys such as duplex stainless steels often constitute the preferred option for this process. The aim of this work is to check if carbon steels represent a viable alternative. Corrosion tests were conducted on carbon steel (UNS K02100) and a duplex stainless steel (UNS S32205) at 120°C in MEG solutions saturated with salts and containing suspended solids. The main parameters that were investigated are oxygen contamination, pH level from acid (close to pH 4) to alkaline (pH above 10), and the type of chemical used for pH control (NaOH and Na2CO3). The results show that carbon steel could be used in reclaiming application operating under certain conditions, provided that pH control is properly applied.