Twenty Years Experience in Controlling Corrosion in Amine Unit, Badak LNG Plant

Abstract Controlling corrosion is the main reason for converting amine solutions in the CO2 Removal Unit of the LNG Plant. In twenty years of its operating experience, we have used three kinds of amine solutions; MEA, formulated MDEA Type-A, and formulated MDEA Type-B. Stress Corrosion Cracking (SCC) was the cause of vessel failure when operating with MEA solution in 1977-1989. SCC occurred in the Amine Regenerator and CO2 Absorber Columns. Prevention of further SCC and lost production due to unscheduled shutdowns for repairing corrosion damage were the main reasons for converting from MEA to an MDEA-based solution. The replacement of MEA with formulated MDEA Type-A eliminated SCC. Steam consumption to regenerate the rich amine solution was also reduced due to weaker bonding between CO2 and MDEA solution. Unfortunately, CO2 easily releases in low pressure regions, causing corrosion from carbonic acid. The corrosion product, iron carbonate scale, was always observed in hot areas. Operating conditions and equipment were modified but improvement was minimal. A one year test of an alternate solvent, formulated MDEA Type-B, in one train resulted in good CO2 absorption, low corrosion rate measured by coupon, and very low iron content in solution. Visual inspection of main equipment after a one year test revealed negligible corrosion attack. After another half year operation, there was still very low, stable iron content in solution. Other benefits of converting to formulated MDEA Type-B are lower solvent makeup and lower steam consumption for regeneration compared to formulated MDEA Type-A for the same CO2 pick up.