Energy-saving performance of the process modifications for carbon capture by diluted aqueous ammonia

Abstract

The regeneration energies of CO2-lean solvent and NH3-washing water comprise the main fractions of the total energy consumption in an NH3-based post-combustion carbon capture (PCC) process. However, the reconfiguration of the CO2 absorption process may significantly reduce the requirement for NH3-washing water to relieve the energy burden of regenerating it. Additionally, the utilization of a pressurized CO2 stripper to enhance the purity of CO2 in the overhead vapor is an alternative strategy for reducing the energy requirement for regenerating the CO2-lean solvent. Moreover, further energy reductions can be achieved by modifying the stripper configurations that have been reported in the literature. In this study, the energy-saving performance of the modified configurations, including the utilization of a two-stage absorber, a cold-split bypass (CSB) and an advanced flash stripper (AFS) for PCC by an NH3-based solvent is investigated. Our results indicate that the concentration of NH3 slip can be reduced to a quarter of the emission by the two-stage absorber. Moreover, this study also demonstrates that the configuration of AFS is a limiting case of the CSB modification. The energy requirement of AFS is higher than that of CSB because the heat recovery by the main heat exchanger in AFS must be sacrificed to avoid solid precipitation in the reflux.