Chinese Journal of Chemical Engineering, Vol.26, No.11, 2351-2360, 2018
The CO2 absorption and desorption performance of the triethylenetetramine plus N,N-diethylethanolamine + H-2 O system
Post-combustion CO2 capture (PCC) process faces significant challenge of high regeneration energy consumption. Biphasic absorbent is a promising alternative candidate which could significantly reduce the regeneration energy consumption because only the CO2 -concentrated phase should be regenerated. In this work, aqueous solutions of triethylenetetramine (TETA) and N,N-diethylethanolamine (DEEA) are found to be efficient biphasic absorbents of CO2 . The effects of the solvent composition, total amine concentration, and temperature on the absorption behavior, as well as the effect of temperature on the desorption behavior of TETA-DEEA-H2O system were investigated. An aqueous solution of 1 mol center dot L-1 TETA and 4 mol center dot L-1 DEEA spontaneously separates into two liquid phases after a certain amount of CO 2 is absorbed and it shows high CO2 absorption/desorption performance. About 99.4% of the absorbed CO2 is found in the lower phase, which corresponds to a CO2 absorption capacity of 3.44 mol center dot kg The appropriate absorption and desorption temperatures arc found to be 30 degrees C and 90 degrees C, respectively. The thermal analysis indicates that the heat of absorption of the 1 mol center dot L-1 TETA and 4 mol center dot L-1 DEEA solution is -84.38 kJ center dot (mol CO2) which is 6.92 kJ- (mol CO2) - less than that of aqueous MEA. The reaction heat, sensible heat, and the vaporization heat of the TETA-DEEA-H 2 0 system are lower than that of the aqueous MEA, while its CO2 capacity is higher. Thus the TETA-DEEA-H2O system is potentially a better absorbent for the post-combustion CO2 capture process. (C) 2018 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. All rights reserved.