Screening test of amino acid salts for CO₂ absorption at flue gas temperature in a membrane contactor

CO₂ absorption at the temperature of flue gas inlet could reduce the costs related to flue gas cooling systems and improve the economic feasibility of the postcombustion carbon capture processes. Amino acid salts are considered as promising absorbents to absorb CO₂ in a membrane contactor at elevated temperatures because of their advantages of lower volatility, less degradation, and higher surface tension. In this study, 24 common amino acids have been screened for their potential to absorb CO₂ at the temperature of flue gas inlet in a membrane contactor. These screening processes involved examination of the water solubility of amino acids, measurement of surface tension and viscosity of their potassium salts, CO₂ capacity, and CO₂ membrane absorption test. Taurine, sarcosine, and glycine were identified as performing well in all the screening tests and were further investigated for CO₂ membrane absorption at high temperatures up to 80 °C and various CO₂ loadings in a polypropylene hollow fiber membrane module. The results show that those amino acid salts are feasible to absorb CO₂ at high temperatures in a membrane contactor. Potassium sarcosinate is identified as the most promising absorbent for high-temperature CO₂ absorption with a better absorption performance than monoethanolamine and other amino acid salts.