Can a rich amine (MDEA) with 0.35 moles of H2S / mole of MDEA (40 wt %) carrying pipeline in offsite be operated at temperatures at or above 60 degc? It is usually observed that in offsite piping the rich amine is carried at around 40 degc. Kindly advise if there would be some adverse effect of higher temperature of rich amine at or above 60 degC carried through over 1 kilometer long pipe in offsite piping of carbon steel with NACE MR0103 compliant pipe class. Please advise me if there is any literature to support the decision.Sep-2021
Nathan Hatcher, Optimized Gas Treating, Inc., email@example.com
The answer depends upon whether the rich amine was produced in a high pressure or low pressure unit and the length of piping/pressure drop to the destination. Light-end hydrocarbons can flash and generate two-phase flow with velocities that can erode the protective iron sulfide passivation layer. In my former life, we had a rich amine line that ran considerably longer than 1 km. Loadings were managed to stay within targets from a site-specific risk assessment. Tools are available now to predict corrosion rates in this service. See, for example, "Is Amine System Corrosion Different from Sour Water System Corrosion", proceedings of the 2008 Brimstone Sulphur Symposium, Vail, CO. This model framework is incorporated into the OGT ProTreat® simulator.
Raj Dhamelia, HPCL, firstname.lastname@example.org
Process stream velocity will influence the amine corrosion rate and nature of attack. Corrosion is generally uniform however high velocities and turbulence will cause localized thickness losses. For carbon steel, common velocity limits are generally limited to 3 to 6 fps for rich amine and 20 fps for lean amine.
Corrosion rates increase with increasing temperature, particularly in rich amine service. Temperatures above about 220°F (104°C) can result in acid gas flashing and severe localized corrosion due to 2-phase flow, if the pressure drop is high enough.
Not sure whether rich amine temperature of 60 deg C can still result in flashing and 2-phase turbulent flow!