Corrosion in amine solvents used for the removal of acid gases

摘要

Processes using amine solvents for the removal of CO2 have long been usedrnfor the treatment of natural gas. More recently, developments in the field of postcombustionrnCO2 capture have gained considerable interest for greenhouse gasrnmitigation. Even though the nature of the amine is different for both applications, thernprocess flow diagrams are very similar. The raw gas is contacted with the aminernsolvent in an absorber column, and the CO2 is absorbed by the solvent. The richrnsolvent containing the CO2 then circulates to a regenerator, where the temperature isrnincreased to strip the CO2. The lean solvent then returns to the absorber for a newrncycle.rnFor these processes, corrosion is known to be a major issue. Usually, aminesrnare not corrosive but during operation of amine units, degradation of the solvent mayrnoccur due to the reaction with contaminants like oxygen. As a result, corrosivernspecies are formed including other amines and acids products like oxalates, formatesrnand acetates also known as Heat Stable Salts (HSS). Corrosion problems may alsorndepend on other parameters for instance type and concentration of the alkanolamine,rntemperature of the solvent or CO2 loading.rnIn order to extend the limits of gas treating processes, but also to develop thernnew processes for CO2 capture, a better understanding of corrosion in aminernsolvents is required. This paper presents the first results of a study where the impactrnof several parameters will be evaluated by electrochemical methods. The corrosivityrnof Monoethanolamine (MEA), Diethanolamine (DEA) and methyl-diethanolaminern(MDEA) was compared. Other parameters were studied, among which the impact ofrnCO2 loading and the concentration in HSS.