Abstract
Solvent degradation is a major factor in the cost associated with carbon capture using aqueous amine solutions. Heat stable salts (HSS) from oxidative amine degradation and acidic flue gas components, including SO2, NOx and HCl can accumulate in amine solvents and lead to corrosion, extra energy requirements and reduced capture efficiency. Accurate and reliable quantitation of HSS concentration is essential to monitor solvent degradation and corrosion potential inside the system. Two separate amine solvents were tested in a 0.1 MWth carbon capture pilot plant. 30% Monoethanolamine (MEA) was used as a baseline solvent and compared to a developed amine solvent, CAER-B2. Six HSS were identified in each solvent and the accumulation rates were determined. The observed HSS build-up was similar in magnitude to other published amine based CO2 capture plant data. The 30% MEA solvent accumulates HSS at a higher rate (48 ppm/hr vs. 22 ppm/hr) as the CAER-B2 which can be attributed to higher input SO2 levels during the solvent test campaign. Corrosion benchmark levels of HSS were exceeded for CAER-B2 and 30% MEA within a few days of normal operation.
Highlights
Solvent degradation is a major factor in the cost associated with carbon capture using amine solvents
The deployment of an accurate and reproducible ion Thompson et al, Aerosol and Air Quality Research, 14: 550–558, 2014 chromatography (IC) analysis method to quantify 10 potential Heat stable salts (HSS) that may be present in amine carbon capture solvents is reported. This method was evaluated during lab-scale solvent development used to analyze two separate amine solvents during test campaigns in a 0.1 MWth carbon capture pilot plant with coal-derived flue gas generator. 30% MEA was used as a baseline solvent and compared to a proprietary amine solvent, CAER-B2, developed at University of Kentucky
The precision was analyzed by completing all measurements in triplicate with relative standard deviation (RSD) of less than 10% for all calibration standards
Summary
Solvent degradation is a major factor in the cost associated with carbon capture using amine solvents. Amine solvents can degrade through oxidation, thermal degradation and through reactions with flue gas components to form heat stable salts (HSS) (Salizar et al, 2003). Amine oxidative degradation can yield other anion HSS species including acetate, formate, glycolate and oxalate. Corrosion is a problem at all amine carbon capture operations at locations including the absorber, stripper, reboiler and at pump and valve locations where temperature are high and acidic gases are present (Soosaipakaram and Veawab, 2008). Several HSS anion species have been directly related to increased corrosion in carbon steel in amine solvent systems. Other HSS from oxidative degradation of amines including oxalate, formate, glycolate and acetate contribute to higher carbon steel corrosion rates (Tanthapanichakoon and Veawab, 2006). The corrosion rates increase with higher concentrations of all of the HSS species
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