Cooperative Integration of SCR and CESAR-1, Focused on Mechanism and Performance

Limiting carbon dioxide (CO₂) emissions from large point sources such as thermoelectric plants is a central challenge for mitigating global warming. Among post-combustion capture methods, amine-based absorption using CESAR-1, a blended (AMP)/(PZ) solvent, has been widely used due to its higher CO₂ loading capacity and lower regeneration energy. However, the presence of nitrogen oxides (NO, NO₂) in flue gas imposes a critical limitation: during solvent regeneration, nitrogen oxides promote degradation of CESAR-1, leading to the formation of carcinogenic nitrosamines and nitramines, which are known to be toxic. This paper reviews the distinct characteristics of AMP and PZ, the two components of CESAR-1, as well as the reaction mechanism underlying CO₂ capture in CESAR-1 system. Also, it focuses on the solvent degradation pathway that occurs in the presence of nitrogen oxides, and the mechanism of selective catalytic reduction (SCR). Building on these concepts, we propose an integrated SCR-CESAR-1 system that combines SCR with CESAR-1, an amine-based solvent, to reduce CO₂ emissions while minimizing the risk of undesired byproduct formation. Furthermore, by optimizing the catalyst used in the SCR system, the suggested system aimed to minimize energy consumption across the system.

Since CO₂ is the greenhouse gas largely produced by human activity, measures to limit these emissions have often been described as an environmental imperative. Among the different types of carbon capture processes, post-combustion capture is widely used, as it can be retrofitted into existing industrial plants and processes. Amine-based absorption using CESAR-1, a blended (AMP)/(PZ) solvent widely applied in post-combustion CO₂ capture, has gained attention due to its higher CO₂ loading capacity and lower regeneration energy, since each amine compensates for the other's weakness. However, since CO₂ is not the sole constituent of the flue gas, the presence of other constituents, especially NOₓ (where x is mostly 1 or 2), in post-combustion CO₂ capture also poses potential problems, including (1) generation of MNPZ, a harmful byproduct to human health and the surrounding aqueous environment, and (2) solvent loss during regeneration. This can be addressed by installing an SCR system upstream of the CESAR-1 process to remove NOₓ from the flue stream before it passes through the CESAR-1 absorber. The SCR-CESAR-1 combined system includes the SCR reactor, CO₂ absorber, and stripper that comprises the CESAR-1. The system's advantages include a similar reaction temperature across all stages, which limits heat losses from heating and cooling. The proposed system also uses manganese-based ultra-low-temperature catalysts in the SCR, which are considered less harmful and more efficient for the integrated system.