Oxidative Degradation of Aqueous Monoethanolamine in CO2 Capture Systems Under Absorber Conditions

Publisher Summary Alkanolamine systems are the current technology of choice for CO 2 capture from flue gas, with monoethanolamine (MEA) being the most widely used solvent. In this type of process, the flue gas is counter-currently contacted with the aqueous amine solution in an absorber column. The CO 2 reacts reversibly with MEA to form a MEA-carbamate. The rich amine solution, with a loading (α) of around 0.4 moles CO 2 /mole MEA, is then sent through a counter-current heat exchanger, where it is pre-heated by the lean amine solution, before being sent to the stripper column. The oxidative degradation of monoethanolamine (MEA) was quantified at conditions typical of an absorber to capture CO 2 from flue gas. Experiments were conducted in a heated, sparged reactor by bubbling air, containing varying concentrations of CO 2 , through the amine solution. Degradation rates were quantified by measuring the rate of evolution of ammonia from the MEA solution using Fourier–Transform infrared (FT-IR) spectroscopy. Solutions with lower CO 2 loadings degraded faster than those with high loadings. Additionally, (ethylenedinitrilo)-tetraacetic acid (EDTA) proved to be effective at inhibiting oxidative degradation; EDTA added at a ratio of as low as 1/1 with the dissolved metals resulted in decreasing the degradation rates by half.