CO2 capture results using EDA at different CO2 concentrations

https://doi.org/10.3390/en14206822

“Figure 3 shows the characteristic curves obtained during the CO₂ capture testing using EDA. Figure 3a depicts the drop in pressure as a function of time. The drop in pressure was proportional to the amine concentration. For the 20 wt.% amine solution, the gas consumption represented a pressure drop of ~50% from the initial pressure. Figure 3b shows the temperature profile in the first 5 min of the CO₂ capture process, where a “sudden” temperature increase was observed in the initial moments of the CO₂–liquid solution contact. The highest temperature points were reached approximately one minute after the CO₂ pressurization, being proportional to the amine concentration. The maximum value reached was ~324 K for the 20 wt.% amine solution, representing a ΔT=21 K. The temperature increments were related to the exothermic reaction between the CO₂ and the aqueous EDA solutions. Similar behavior was observed in the absorption processes of CO₂ [42] and other gases [43] in aqueous amine solutions. This exothermic phenomenon must be considered in the design of absorption towers for CO₂ capture using amines, since “one of the most important considerations involved in designing gas absorption towers is to determine whether temperatures will vary along with the height of the tower due to heat effects; note that the solubility usually depends strongly on temperature” [44]. A more detailed analysis of the exothermicity effect is presented in Section 3.3.”

“Figure 3c shows the CO₂ removed as a function of time. The amount of CO₂ captured was proportional to the concentration of the amine solution due to the EDA–CO₂ chemical affinity. Kumar et al. [22] proposed the use of EDA as an activator in the CO₂ capture process by increasing the solubility capacity of CO₂ in the amine aqueous solutions (chemical solvents). Snapshots of the aqueous amine solutions were taken at the end of the experiments (see Figure 3d). An increase in the intensity of a yellowish-brown color (amber color) could be observed with the naked eye in the aqueous amine solutions. The variability in the color intensity was proportional to the amine concentration, which correlates with the amount of CO₂ captured.