Study On Degradation Mechanism And Corrosion Characteristics Of New CO₂ Absorbent

Carbon capture,utilization and storage（CCUS）technology is currently the most effective technology to reduce carbon dioxide（CO₂）emissions.Among them,the absorption of CO₂ by organic amine method is the most widely used technology in industry.Diethylenetriamine（DETA）,which has a large absorption capacity（more than1 mol CO₂/mol DETA）,is significantly higher than the benchmark solvent monoethanolamine MEA（0.5 mol CO₂/mol MEA）,and has higher circulation capacity and low absorption heat,there is hope to replace MEA.In the CO₂ capture process,the degradation of the solvent and the corrosion of the equipment by the absorbent are issues that cannot be ignored.In this project,the degradation of the CO₂ benchmark absorbent MEA in fresh and dirty solutions containing NO₃^-and the corrosion behavior and mechanism of A106 steel.The oxidative degradation of DETA in the process of absorbing CO₂ was studied.The corrosion behavior and mechanism of A106 steel in DETA solution,and mixture solutions of DETA/2-amino-2-methyl-1-propanol（AMP）/methyldiethanolamine（MDEA）were studied in contrast.In this paper,the process of absorbing CO₂ by amine solution was simulated by glass reactor.The solution analysis method was used to study the degradation mechanism of the solution.The weight loss method,surface analysis technique and electrochemical method were used to study the corrosion behavior and mechanism of A106 steel.Among them,the weight loss method is used to calculate the average corrosion rate,the electrochemical method is used to study the corrosion mechanism,the ionization chromatography（IC）,fourier transform infrared spectroscopy（FTIR）,and nuclear magnetic resonance hydrogen spectroscopy（1HNMR）are used to study the degradation product composition,and the scanning electron microscope（SEM）,X-ray diffraction（XRD）and X-ray photoelectron spectroscopy（XPS）and other techniques to observe the morphological characteristics of corrosion products and analyze their composition.In fresh and dirty Na NO₃-MEA-CO₂-O₂ system,results showed that the presence of NO₃^-caused a higher corrosion rate at the initial stage,but had a minimal effect on the corrosion rate afterwards.The corrosion rate of A106 steel in dirty solution is lower than 0.01 mm/y,which may be caused by the degradation products of MEA adsorbed on the surface of carbon steel in dirty solution.Studies on the oxidative degradation of the DETA-CO₂-O₂ system show that the degradation products mainly include piperazine（PZ）,ethylenediamine（EDA）and various heat stable salts（HSSs）.Through the comparative study on the corrosion behavior of A106 steel in single DETA system and DETA/MDEA/AMP mixed amine system,it is found that the corrosion rate of A106 steel in different concentrations of DETA system is very serious,more than 2mm/y.Weight loss method showed that the corrosion rate of A106 steel in DETA-AMP system is lower than 1 mm/y.In the 0.5 mol/L DETA+2.5 mol/L AMP-CO₂-O₂ system,the corrosion rate of A106 steel decreases with time.After 360 h,there are not only corrosion product films composed of Fe₂O₃ and Fe₃O₄,but also ethylenediamine（EDA）films adsorbed on the surface of A106 steel.They both have a protective effect on the metal.