Kinetics of sulfur dioxide- and oxygen-induced degradation of aqueous monoethanolamine solution during CO2 absorption from power plant flue gas streams

Studies of the kinetics of sulfur dioxide (SO2)- and oxygen (O-2) -induced degradation of aqueous monoethanolamine (MEA) during the absorption of carbon dioxide (CO2) from flue gases derived from coal- or natural gas-fired power plants were conducted as a function of temperature and the liquid phase concentrations of MEA, O-2, SO2 and CO2. The kinetic data were based on the initial rate which shows the propensity for amine degradation and obtained under a range of conditions typical of the CO2 absorption process (3-7 kmol/m(3) MEA, 6% O-2, 0-196 ppm SO2, 0-0.55 CO2 loading, and 328-393 K temperature). The results showed that an increase in temperature and the concentrations of MEA, O-2 and SO2 resulted in a higher MEA degradation rate. An increase in CO2 concentration gave the opposite effect. A semi-empirical model based on the initial rate, -gamma(MEA) = {6.74 x 10(9) e(-(29,403/RT))[MEA](0.02)([O](2.91) + [SO2](3.52))}/ {1 + 1.18[CO2](0-18)} was developed to fit the experimental data. With the higher order of reaction, SO2 has a higher propensity to cause MEA to degrade than O-2. Unlike previous models, this model shows an improvement in that any of the parameters (i.e. O-2, SO2, and CO2) can be removed without affecting the usability of the model. (C) 2008 Elsevier Ltd. All rights reserved.