[Experimental study on CO2 absorption by aqueous ammonia-based blended absorbent].

Area of Science:

• Chemical Engineering
• Environmental Science
• Materials Science

Background:

• Aqueous ammonia (NH3) is a promising absorbent for CO2 capture.
• A major limitation of NH3-based absorbents is their slow CO2 absorption rate.
• Improving CO2 absorption kinetics is vital for efficient carbon capture.

Purpose of the Study:

• To investigate the effect of additives on the CO2 mass transfer coefficient (K(G)) in aqueous NH3 solutions.
• To evaluate the performance of monoethanolamine (MEA), piperazine (PZ), 1-methyl piperazine (1-MPZ), and 2-methyl piperazine (2-MPZ) as additives.
• To further study the optimal additive (PZ) under varying conditions and elucidate reaction mechanisms.

Main Methods:

• Utilized a wetted wall column facility to measure the mass transfer coefficient (K(G)) of CO2.
• Tested aqueous ammonia solutions with and without various amine additives (MEA, PZ, 1-MPZ, 2-MPZ).
• Investigated the impact of CO2 loading, temperature, and PZ concentration on absorption rates.

Main Results:

• All tested additives significantly increased the K(G) of CO2 in NH3 solutions.
• A 3 mol/L NH3 + 0.3 mol/L PZ blended solution showed a 1.9 to 2.2 fold increase in K(G) compared to pure NH3 across different CO2 loadings.
• Piperazine (PZ) demonstrated the best performance among the additives.
• The pseudo first order rate constant for the blended solution was calculated as 42.7 m3/(mol·s).

Conclusions:

• Piperazine (PZ) is an effective additive for enhancing CO2 absorption rates in aqueous ammonia solutions.
• The addition of PZ significantly improves the efficiency of NH3-based absorbents for CO2 capture.
• Further research into the reaction mechanism in NH3/PZ blended solutions is warranted for optimizing carbon capture processes.