(374e) Optimal MEA/Dipa/Water Blending Ratio for Minimizing Regeneration Energy in Absorption Based Carbon Capture Process: Experimental Solubility and Thermodynamic Modeling

A new CO₂ absorption solution was developed by blending monoethanolamine (MEA) and diisopropanolamine (DIPA) in H₂O. The solubility of CO₂ in MEA/DIPA aqueous solutions with various blending ratios was measured at a temperature range of 323.15–383.15 K under CO₂ partial pressures of up to 400 kPa. The successive substitution method was introduced to calculate the molar fractions of all 12 species, and the electrolyte–UNIQUAC model was applied to consider non-idealities. Then, the optimal blending ratio was obtained for four different targets: 1) max Δ𝛼_{𝐶𝑂2} (total amine-based CO₂ cyclic capacity), 2) max Δ𝛽_{𝐶𝑂2} (total solution-based CO₂ cyclic capacity), 3) min −Δh_abs (heat of CO₂ absorption under stripping condition), and 4) min Q_regen (regeneration energy for the carbon capture process). Here, Δ𝛼_{𝐶𝑂2}, Δ𝛽_{𝐶𝑂2}, and −Δh_abs are the properties of solution, while Q_regen is a performance parameter of the process. The Q_regen, the sum of sensible heat, latent heat, and heat of reaction, was calculated according to the amine blending ratio using the “shortcut method” [1]. In the process, besides the cyclic capacity and heat of absorption, the effect of sensible heat and latent heat must be considered simultaneously. Therefore, the most reliable method to determine the amine blending ratio is Q_regen minimization. The obtained minimum Q_regen of the process was 3.44 GJ/t CO₂ using MEA/DIPA/H₂O solutions of 4.01/25.99/70 (w/w/w), which was 8.7% and 2.6% lower than those of the single MEA and DIPA aqueous solutions due to the synergistic effect of MEA and DIPA.