Process Design of Aqueous Ammonia-based Post-combustion CO2 Capture

In the present work, the aqueous ammonia-based post-combustion CO2 capture (PCC) process is simulated using the rate-based model in Aspen Plus, by which the method of sizing column heights is revealed. The heights of the staged CO2 absorbers and the NH3 absorber are determined as 5 m, 6 m, and 6 m; in addition, the heights of the CO2 and NH3 strippers are 12 m and 6 m, respectively. It is well known that the pressurized CO2 stripper can reduce the energy burden for the solvent regeneration, effectively. However, since the staged CO2 absorbers are operated at atmosphere, the pressurized lean solvent needs to be relieved to atmosphere either in the absorber or before entering the absorber. In the present work, the electric power that is used to compress the depressurized vapor back into the CO2 stripper compares with the energy saving from the high pressure CO2 stripper in order to find the optimal operating conditions at which the minimal overall regeneration energy is posed. The minimum requirement can be found at 3.0 GJ/ton-CO2 under the operating conditions of the CO2 lean loading (mol-CO2/mol-NH3) at 0.13 and the CO2 stripper at 2 atm.