Studies of SO₂- and O₂-Induced Degradation of Aqueous MEA during CO₂ Capture from Power Plant Flue Gas Streams

Abstract

A comprehensive study was conducted to evaluate the contributions of sulfur dioxide (SO2) and oxygen (O2) to the degradation of monoethanolamine (MEA) during CO2 capture from power-plant flue gas streams. The study was performed in a 600-mL semibatch autoclave reactor, using aqueous MEA concentrations in the range of 3−7 mol/L at temperatures in the range of 328−413 K and a constant gas pressure of 250 kPa. The aqueous MEA was contacted with SO2/O2/N2 gas mixtures that had SO2 concentrations in the range of 6−196 ppm and O2 concentrations in the range of 6−100 mol %. The effects of CO2 and a corrosion inhibitor (NaVO3) were also evaluated. The results showed that both SO2 and O2 were detrimental, because they accelerated the rate of MEA degradation. NaVO3 also accelerated the MEA degradation rate, whereas CO2 had the opposite effect. A new kinetic model was formulated to account for the presence of O2 and the option of the presence or absence of SO2 in the flue gas stream. This was of the form: