Non-aqueous CO2 capture solvent corrosion results from testing at Technology Centre Mongstad

Abstract

RTI International demonstrated its non-aqueous CO2 capture solvent (NAS) at Technology Centre Mongstad in 2022. A corrosion study was conducted to determine appropriate materials of construction for NAS capture plants and generate an accurate techno-economic analysis. Stainless steel, carbon steel, resin, and elastomer corrosion coupons were installed in five process locations to investigate corrosion rates under different temperature, CO2 loading, flow velocity, and stream phase conditions. Following exposure, optical microscopy, scanning electron microscopy, dye penetrant testing, and shore hardness measurements were used to evaluate the material characteristics. Carbon steels had excellent corrosion resistance under cold solvent stream and stripper overhead conditions indicating lower alloy steel may be used in these process areas; stainless steels had excellent performance under all conditions. ULTEM 1000 resin and EPDM-60A elastomer were not suitable for use with NAS, however Gislaved Gummi’s proprietary EPDM-XH withstood exposure to NAS. NAS’ low water content was critical to minimizing the formation and transport of corrosion and solvent degradation inducing ions, resulting in low corrosivity. Dissolved metals and solvent conductivity were monitored as an indicator of system corrosion. NAS had significantly less dissolved metals content when compared to similar testing with 30 wt% MEA, which can be attributed to the low NAS corrosivity. Literature correlations between CO2 capture solvent conductivity and corrosion rates could not accurately predict the minimal NAS corrosion rates.