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 (O2)-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, O2, 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/m3 MEA, 6% O2, 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, O2 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, −rMEA = {6.74 × 109 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 O2. Unlike previous models, this model shows an improvement in that any of the parameters (i.e. O2, SO2, and CO2) can be removed without affecting the usability of the model.