Effect of H2O on absorption performance of tetraethylenepentamine-ethanol-CO2 two-phase absorbent and its mechanism

There is about 10 vol% water vapor in coal-fired flue gas, and the existence of water has an effect on the phase separation performance of amine-alcohol two-phase absorbent. The effects of a small amount of water on the phase separation performance and mechanism of TEPA-ethanol-CO2 system in the range of 0.2 similar to 2.3M TEPA concentration were investigated. The influences of amine concentration and water content on the absorption rate, absorption loading, absorption capacity, mass fraction of CO2-rich phase and the proportion of CO2 enriched in the CO2-rich phase to total CO2 enriched were studied. The different mechanisms between aminealcohol-H2O-CO2 system and amine-H2O-CO(2 )or amine-alcohol-CO2 system were discussed. Fourier transform infrared spectroscopy (FTIR) analyses show that the 1308 cm(-1) absorption peak attributes to the superposition of angular vibration frequency of -CH2 and alkylcarbonate. The 1.6M-TEPA-ethanol-14%-H2O system shows the best comprehensive performance, 96.23 vol% CO2 is enriched in the CO2-rich phase, and the average CO2 absorption rate within the first 30 minutes is 2.4 times faster than 0.2M-TEPA-ethanol-14 %-H2O solution. The main products in CO2-rich phase of 1.6M-TEPA-ethanol-14%-H2O system are carbamate, protonated amine and a little alkylcarbonate. In FTIR spectrum, some unreacted ethanol is also found.

Automated summary

The study investigates the effects of water on the phase separation performance and mechanism of TEPA-ethanol-CO2 system, focusing on absorption rate, absorption capacity, and CO2 enrichment in CO2-rich phase. Experimental results and FTIR analysis show that the 1.6M-TEPA-ethanol-14%-H2O system exhibits the best comprehensive performance.