The use of alkanolamines is regarded as the most commonly used way in carbon capture and storage system (CCS) for carbon dioxide capture due to their best comprehensive effect compared with other methods. This work investigated the effect of monoethanolamine (MEA), diethanolamine (DEA) and Nmethyldiethanolamine (MDEA) on the corrosion behavior of N80 steel in water-saturated supercritical CO2 phase and supercritical CO2-saturated aqueous phase with impurities (SO2, NO2 and O2). The results by weight-loss measurements showed that all the tested alkanolamines inhibited corrosion, and the inhibition efficiency of the three alkanolamines at a concentration of 300 ppmv was between 55% and 67% in the aqueous phase, whereas the inhibition efficiencies were low in the water-saturated supercritical CO2 phase. The off-line pH measurements indicated that alkanolamines could increase the pH value of the solution. Scanning electron microscopy (SEM) was employed to investigate the surface morphology of the corroded specimens after corrosion for 24 h, and 3-dimensional profilometer was applied to measure the pitting rate of specimens after the removal of corrosion products. Chemical and phase compositions of corrosion products were tested by energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD), respectively.
Carbon capture and storage (CCS) can effectively reduce the amount of the carbon dioxide (CO2) produced by the combustion of fossil fuels. It can be divided into three parts: CO2 capture, CO2 transport and CO2 injection. For the CO2 capture, there are many ways to capture CO2, including the most commonly used aqueous solutions of alkanolamines. As the most commonly used alkanolamines, monoethanolamine (MEA), diethanolamine (DEA) and N-methyldiethanolamine (MDEA) have respective advantages.1, 2 The molecular structure of alkanolamines includes at least one hydroxyl group and one amino group. The role of the former is to reduce the vapor pressure of the compound and increase its water solubility, and the latter provides alkalinity to the aqueous solution to promote the absorption of the acidic gas component. The chemical reactions of CO2 in the flue gas with the alkanolamines in the absorber are as follows:3