(320b) Sub-Ambient CO2 Flux Measurements and Modeling Using Amino Acid Solvents

One of the main advantages of direct air capture (DAC) over point-source capture is the flexibility in plant siting anywhere around the world. In this study, aqueous amino acid solutions, specifically those of potassium sarcosinate (K-SAR), were used to capture CO₂ from air. Because plant siting involves areas where the temperature is occasionally below the freezing point of water, termed here as sub-ambient temperatures, there was a need to investigate the physical properties and performance of the solvent at such temperatures. The need for anti-freezing additives, such as triethylene glycol, was determined by comparing the freezing point, COâ‚‚ flux, and mass-transfer coefficient of K-SAR alone and K-SAR with glycol. The solvent viscosity and density were also measured for different temperatures and solvent concentrations. A reactor was set up to reliably measure the COâ‚‚ flux at different temperatures by ensuring a constant, measurable surface area and effective temperature control. The COâ‚‚ flux was measured between -20 and 45 °C for 1 and 3 M K-SAR, and the results were compared to theoretical estimations based on the solvent’s physical properties and operating conditions. For 1 M K-SAR at 25°C, the flux was experimentally determined at 5.9 × 10^-5 mol m^-2s^-1, while the theoretical flux was estimated at 5.4 × 10^-5 mol m^-2s^-1, showing good agreement between experimental data and theoretical results. The results of this study provide the fundamental basis for developing an effective carbon capture technology with amino acid solvents that can be used to effectively capture atmospheric COâ‚‚ at scale in different climates.