Effects of NOx in the flue gas degradation of MEA

Abstract Post combustion CO 2 capture using amine absorbents is the most mature process and therefore the most relevant choice for realising full-scale capture within the next few years. The health and environmental impact of emissions to air is, however, a potential risk. Amines may react in the process or in the atmosphere post emission to form new substances that may be more harmful than the parent amine itself. The main objective of the current work was to investigate the flue gas degradation of monoethanolamine (MEA) in the process with special emphasis on the NOx induced chemical reactions. Degradation experiments have been carried out at absorber like conditions in the Aminox™ rig, followed by further degradation of the used solvent at higher temperature in a lab scale autoclave. Liquid samples were analysed by a range of methods to identify the formation of degradation by-products, with special focus on potential harmful compounds like nitrosamines and nitramines. On-line FT-IR and MS instruments were used for qualitative detection of volatile degradation products and to measure amine slip. MEA is a primary amine which in itself is unable to form a stable nitrosamine. However, experiments show that under the influence of NOx, MEA degrades to the secondary amine diethanolamine (DEA) which is then nitrosated. This work shows that some nitrosamine formation in the process must be expected from any amine. Based on data from real emission measurements, health and environmental risk assessment should be investigated in further studies.