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The continued development of amine solvents for post-combustion CO 2 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 (FeCO 3 ) crystal layers, reducing continued oxidation of Fe from the surface and therefore corrosion. [ABSTRACT FROM AUTHOR]

The reduction of capital cost in building post-combustion CO 2 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 (FeCO 3 ) 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 K 2 CO 3 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. [ABSTRACT FROM AUTHOR]

To mitigate CO 2 release, large-scale post-combustion capture with amine solvents is essential. To achieve capital cost savings, carbon steel infrastructure can replace stainless steel if corrosion by CO 2 -loaded amine solvents is controlled. A coating, to protect the carbon steel, formed using an amine (or additive) is beneficial because it can be regenerated. Siderite has been shown to form a protective crystalline product layer, created when Fe oxidised at the surface reacts with carbonate ions. Tertiary or sterically-hindered CO 2 -loaded amine solutions can form this layer. Herein siderite was prepared on carbon steel substrates from 5 M methyldiethanolamine (MDEA), 5 M 2-amino-2-methyl-1-propanol (AMP), and 1 M K 2 CO 3 at 40 and 80 °C. At 40 °C, K 2 CO 3 produced the most successful protective siderite layer; by contrast, the amine solutions developed layers with interlocking crystals at 80 °C. After siderite formation, these substrates were tested in 2.5 M MEA and AEPZ, both highly corrosive but with more desirable capture kinetics. At 80 °C, substrates pre-treated with MDEA or AMP showed good resistance against the corrosive actions of MEA and AEPZ for four weeks. The siderite layer reduced Fe oxidation at the surface and ingress of solution species thereby ceasing contact and corrosion. [ABSTRACT FROM AUTHOR]

Aqueous amine promoter blends have improved CO 2 absorption capacity and uptake. Tertiary (3°) and sterically-hindered (SH) amines are favoured for their molar absorption ratio, ( i . e . CO 2 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 CO 2 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. [ABSTRACT FROM AUTHOR]

Aqueous amine solutions loaded with CO 2 show a range of corrosion behaviour when in contact with carbon steels. Primary (1°) and secondary (2°) amines undergo corrosion, including the formation of iron oxide surface layers. By contrast, tertiary (3°) and sterically-hindered (SH) amines produce an excess of carbonate ions, leading to FeCO 3 formation, and thereby reducing corrosion. Four amines were tested under challenging conditions (1–5 M at 120 °C) to confirm these behaviors. Due to recent interest in blended amine solvents (1° or 2° with 3° or SH) for improved reaction kinetics, CO 2 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° or 2° 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° or 2° 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° or 2° amines alone, another benefit towards deployment. [ABSTRACT FROM AUTHOR]