The effect of CO2-loaded amine solvents on the corrosion of a carbon steel stripper

The corrosive behaviour of loaded amine solvents was evaluated under stripper operating conditions, for post-combustion carbon capture, to determine the feasibility of using carbon steel in plant construction. In addition to monoethanolamine, three alternative amine solvents: methyldiethanolamine (MDEA), 2-amino-2-methyl-1-propanol (AMP), 1-(2-aminoethyl)piperazine (AEPZ), and the common additive K2CO3 were studied when in contact with carbon steel (C1018) over a 28-day period. Corrosive behaviour was evaluated using carbon steel coupons: gravimetric method for weight change, surface imaging (SEM) and analytical techniques (EDX and XRD), and Fe ion concentration in solution (ICP–OES). The results demonstrated that MDEA and AMP as well as K2CO3 develop a significant siderite (FeCO3) layer on the carbon steel surface. The presence of this layer is attributed to the preferred reaction pathway with CO2 for tertiary and sterically hindered amines. The FeCO3 layer formed in the case of MDEA provides superior protection from continued corrosion of the carbon steel. By contrast, MEA and AEPZ show significant corrosion to the carbon steel surface. In conclusion, MDEA, AMP, and K2CO3 can preferentially produce sufficient surface FeCO3 layers to reduce corrosion levels in carbon steels for use under stripper conditions in post-combustion carbon capture plants

Carbon steel corrosion in piperazine-promoted blends under CO2 capture conditions

Aqueous amine promoter blends have improved CO2 absorption capacity and uptake. Tertiary (3°) and sterically-hindered (SH) amines are favoured for their molar absorption ratio, (i.e. CO2 absorption capacity). With a promoter, namely piperazine (PZ), the ordinarily slow reaction kinetics of a 3°/SH amine is accelerated. Amine blends of 30 and 50% by weight, MDEA + PZ and AMP + PZ, were tested using immersion corrosion techniques at 120 °C. In all cases, a siderite (FeCO3) product layer was formed on the surface of the carbon steel coupons. Aqueous PZ solutions produced thin layers with comparatively lower Fe ion concentrations than blended solutions. The fast CO2 capture kinetics of PZ, and therefore carbonate formation, makes the rapid reaction possible due to readily available Fe ions oxidised on the surface. The replacement of PZ content in a blend, by MDEA or AMP, resulted in slower formation of siderite and variably poorer corrosion protection. Critically, the use of AMP in the blend offers better protection against corrosion, shown by lower concentration of Fe ions in the bulk solution than parallel MDEA solutions. This can be attributed to the faster formation of carbonate species by AMP, as a SH amine, which also results in more imperfect crystals

Using pre-treated carbon steel for post-combustion carbon capture infrastructure

The reduction of capital cost in building post-combustion CO2 capture is necessary to realize its widespread use. Cheaper steels, e.g. carbon steel, are attractive but lack the necessary corrosion resistance. To protect from corrosion, one approach is to implement a protective coating on the surface. Particularly, a coating like siderite (FeCO3) is appealing because it can be formed by amines and therefore could be regenerated. This study investigates the formation, over seven days at 40 and 80 °C, of such siderite layers formed in methyldiethanolamine (MDEA), 2-amino-2-methyl-1-propanol (AMP), and a K2CO3 solution. When tested against 2.5 M monoethanolamine for 28 days, the coatings formed at 80 °C in MDEA and AMP appear the most resilient. There is a substantial siderite crystal layer remaining on the surface and only minimal weight loss

Investigating the corrosion due to high capacity and uptake promoter amine blends on carbon steel

The continued development of amine solvents for post-combustion CO2 capture is essential to the large-scale success of this technology, with particular interest in high capacity and uptake promoter blends. Some of these solutions also show reduced corrosive tendencies in the presence of carbon steel, a significantly cheaper alternative to the stainless steels generally employed. Optimization of the solution composition and reduced corrosion could yield both a decrease in capital and operating costs. Solutions (30% by weight) of monoethanolamine (MEA) or piperazine (PZ) were blended with either methyldiethanolamine (MDEA) or 2-amino-2-methyl-1-propanol (AMP). At 120 °C, Solutions containing PZ outperformed those with MEA showing the formation of good protective siderite (FeCO3) crystal layers, reducing continued oxidation of Fe from the surface and therefore corrosion