E. Kruszczak, H. Kierzkowska - Pawlak
Lodz University of Technology, Faculty of Process and Environmental Engineering, Łódź, PL


The absorption in aqueous alkanolamine solutions is the efficient technology of CO2 capture from the flue gases. The most popular absorbents are primary amines and secondary amines due to their high reactivity with CO2. However, the use of these chemicals is limited in the view of high costs of solvent regeneration and low CO2 loading capacity. Tertiary amines have a higher absorption capacity. Therefore, the current research is focused on studying absorption of acid gases in blended amine solutions which include the advantages of all components of a mixture. The blended amine solutions enhance the absorption rate of CO2 while maintaining a low energy demand for solvent regeneration. In this work, the CO2 absorption rate in activated aqueous solutions of N,N-diethylethanoloamine (DEEA) was studied in a stirred cell reactor with a plane gas - liquid interface, in the temperature range of 303 - 333 K. The total amine concentration was 2 kmol/m3. N-methyl-1,3-propane-diamine (MAPA) was used as a promoter. The molarities of the aqueous blends of (DEEA + MAPA) were (1.95 kmol/m3 + 0.05 kmol/m3), (1.90 kmol/m3 + 0.1 kmol/m3), (1.80 kmol/m3 + 0.2 kmol/m3). The CO2 absorption rates into mixed amine solvents were measured using the fall-in-pressure technique during a batch absorption of CO2 in the pressure range of (7-35 kPa). The determined absorption rates of CO2 in the blended solvents were much higher than those in a DEEA solution, whereas the increase in MAPA concentration resulted in the increase in the CO2 absorption rate. The obtained results for these absorbents were compared with different amine blends (DEEA + promoter) which were earlier studied by others. The activator MAPA was compared with N-ethylethanolamine (EEA), piperazine (PZ), N-(2-aminoethyl)ethanolamine (AEEA) and 1,6-hexamethyldiamine (HMDA). MAPA was found to act as a more effective activator of DEEA aqueous solution than other promoters.

Keywords: CO2 capture, N,N-diethylethanoloamine, N-methyl-1,3-propane-diamine, amine blends, CO2 absorption rate