CO2 Capture from Flue Gas using Amino Acid Salt Solutions

The reversible absorption of CO2 into a chemical solvent is currently the leading CO2 capture technology. Available solvents are almost exclusively based on aqueous alkanolamine solutions, which entail both economic and environmental complications, making the commercialization of the technology difficult. Amino acid salt solutions have emerged as an alternative to the alkanolamine solutions. A number of advantages make amino acid salt solutions attractive solvents for CO2 capture from flue gas. In the present study CO2 absorption in aqueous solutions of 0.5 M potassium glycinate and 0.5 M monoethanolamine (MEA) were performed, using a stirred cell reactor experimental setup. The absorption of gas containing 10 mol % CO2 and 90 mol % N2 was followed by measuring the percentage of CO2 in the outlet gas. Also the temperature and pH in the solutions were measured during the absorption. The results showed that the CO2 absorption curves of potassium glycinate and MEA are very similar indicating a potential for potassium glycinate as replacement for MEA in chemical absorption of CO2 from flue gas. For both the potassium glycinate and the MEA solutions the CO2 loading capacity was 0.8 mol CO2/mol amine and the pH dropped between 2 and 3 units during the absorption process. In both types of solutions the temperature increased as a result of the CO2 absorption, which is expected due to the exothermic nature of the absorption reaction. The increase in temperature for the potassium glycinate was lower than for MEA indicating a lower heat of absorption/desorption.