CO2 capture using piperazine-promoted, aqueous ammonia solution: Rate-based modelling and process simulation

Due to the fast reaction rate of piperazine (PZ) with CO2, it has the potential to act as a promoter in aqueous ammonia (NH3)-based CO2 capture processes. We have developed a rigorous, rate-based model for the NH3-PZ-CO2-H2O system using Aspen Plus r, and validated the model against experimental results. Absorption and desorption processes were simulated under real flue gas conditions to gain a practical understanding of the behaviour and characteristics of interactions between PZ-promoted NH3 solution and CO2. Adding PZ significantly increased the CO2 absorption rate in the NH3-based CO2 capture process via a fast reaction between PZ carbamate and CO2. The temperature along the column was higher than in the absence of PZ, and more free ammonia was released into the solution, which led to higher ammonia loss. Adding PZ also reduced the stripping heat, resulting in a smaller energy requirement for solvent regeneration.