Using carbon steel in the stripper and reboiler for post-Combustion CO2 capture with aqueous amine blends

Aqueous amine solutions loaded with CO2 show a range of corrosion behaviour when in contact with carbon steels. Primary (1 degrees) and secondary (2 degrees) amines undergo corrosion, including the formation of iron oxide surface layers. By contrast, tertiary (3 degrees) and sterically-hindered (SH) amines produce an excess of carbonate ions, leading to FeCO3 formation, and thereby reducing corrosion. Four amines were tested under challenging conditions (1-5 M at 120 degrees C) to confirm these behaviors. Due to recent interest in blended amine solvents (1 degrees or 2 degrees with 3 degrees or SH) for improved reaction kinetics, CO2 absorption capacity and recoverability, four binary amine combinations (MEA + MDEA, MEA + AMP, AEPZ + MDEA, AEPZ + AMP) were tested in a range of compositions. Blends containing low concentrations of 1 degrees or 2 degrees amine show promise for use with carbon steel due to the formation of a siderite product layer and low corrosion levels. An increase in concentration of 1 degrees or 2 degrees amines, shows higher Fe ion concentrations initially as well as significant weight change to the coupon. However, the formation of more diverse product layers at longer time intervals reduces the Fe ion concentration in the bulk. Blends generally offer reduced corrosion compared to 1 degrees or 2 degrees amines alone, another benefit towards deployment. (C) 2016 Elsevier Ltd. All rights reserved.