(654b) A Parametric Study of CO2 Absorption Into An Aqueous Potassium Carbonate Solution Promoted With Amines in a Packed Bed Column

Monoethanolamine (MEA) absorption processes are considered to be state-of-the-art for post-combustion CO₂ capture from coal combustion flue gas; however, they are energy intensive and thus expensive. It is important to develop new advanced CO₂ capture technologies in order to maintain the cost-effectiveness of coal-fired power generation. A novel hot carbonate absorption process with bicarbonate crystallization-enabled high pressure stripping (Hot-CAP) currently under development offers the potential to significantly reduce the energy penalty associated with CO₂ separation from the flue gas and work requirement for CO₂ compression.

In the Hot-CAP, CO₂ is absorbed into a concentrated potassium carbonate (PC) solution (about 40 wt%) at elevated temperatures (60-80^oC). Due to the low alkalinity of K₂CO₃, a technical issue to be considered is the low rate of CO₂ absorption into the PC solution compared with that into the MEA solution. Many promoters/catalysts have been studied to enhance the rate of absorption into carbonate solutions in the literatures. However, most of the studies have been limited to low temperatures (≤ 50°C) and low concentrations (<40 wt%) of carbonate solution. For this purpose, different inorganic and organic promoters were screened to enhance the CO₂ absorption rate in the concentrated PC solution at 70^oC in our previous work.

In this study, detailed parametric tests, including different dosage of promoter, L/G ratio, and CO₂ loading in solution, were conducted in a bench-scale packed-bed column to evaluate the CO₂ removal performance of the 40 wt% PC solution without and with the additions of three pre-screened amine promoters, diethanolamine (DEA), aminomethyl propanol (AMP), and piperazine (PZ). For the comparison purpose, the performance of CO₂ absorption into a benchmark 5M (30 wt%) MEA was also investigated. Results confirmed that the CO₂ removal efficiency increased with increasing L/G or promoter dosage, and decreased with increasing CO₂ loading. At the same dosage level of promoter, the CO₂ removal efficiency by the PC+PZ was higher than that by the PC+DEA or PC+AMP. Results also revealed that the CO₂ removal efficiency by the 40 wt% PC solution promoted with 1M DEA or 0.5M PZ, either for the CO₂ lean or rich solution, was higher than that of the 5M MEA counterpart solution under their typical operating conditions.

This presentation will provide a summary of results from the parametric study of CO₂ absorption into the concentrated PC solution promoted with three pre-screened amine promoters.