Off-gas emission in CO2 capture process using aqueous monoethanolamine solution

Abstract A comprehensive study was conducted to evaluate roles of O 2 , SO 2 (i.e. H 2 SO 3 ), NO 2 (i.e. HNO 3 ), CO 2 and temperature to off-gas emissions using conditions normally encountered in the CO 2 capture process. Two possible pathways of radical induced oxidation of MEA in the presence/absence of H 2 SO 3 , HNO 3 , and CO 2 were proposed to explain the release of NH 3 as a major VOCs emission. In the presence of H 2 SO 3 , HNO 3 , and CO 2 , an increase of their concentrations decreased NH 3 concentration, while the rest of VOCs (i.e. acetaldehyde, acetone, diethylamine, 2-butanol, methyl dl-lactate, methanol and ethanol) were found to be insignificantly affected. An increase of temperature was found to increase the concentration of all VOCs detected in this study. Based on mechanism analysis, the roles of H 2 SO 3 , HNO 3 , and CO 2 were found to be that of cutting down the route to NH 3 formation and instead induced the formation of formate and acetate heat stable salts in MEA solution. Additional liquid MEA analysis revealed that most NH 3 was actually trapped and turned into NH 4 + salts in MEA solution before it could be emitted as NH 3 in the off-gas.