Review on Experimental Plants for CO ₂ Removal Based on Ammonia

In the search for alternatives to conventional amine-based solvents for postcombustion CO2 capture, this study reviews ammonia-based processes and the experimental plants in which they have been tested. The available processes are (i) the Chilled Ammonia Process (CAP), which employs aqueous ammonia at low temperatures and can operate with or without solid formation; (ii) the Mixed Salts Process (MSP), which uses a novel solvent formulation based on potassium and ammonia; and (iii) the ECO2 process, which operates at around 20 °C with aqueous NH3 and integrates desulfurization by converting SOx into ammonium sulfates. Pilot and demonstration projects include: for the CAP, KIER (Korea), RIST (Korea), SRI and GE Växjö (Sweden), GE, EPRI, and WE Energies (Wisconsin, USA), EONCAP Karlshamn (Sweden), AEP Mountaineer (West Virginia, USA), TCM Mongstad (Norway), and Munmorah (Australia); for the MSP, SRI (California, USA), IHI (Japan), and Abbott power plant (Illinois, USA); and for the ECO2 process, a pilot at the Shadyside plant (Ohio, USA). To date, the CAP in its nonsolid-forming configuration is the most advanced in terms of industrial deployment. Key findings from testing indicate that under CO2 capture process conditions, NOx species are inert and do not degrade ammonia; ammonia slip in the CO2-depleted flue gas can be mitigated through water washing; the thermal energy required for solvent regeneration appears to be lower than in conventional amine-based processes, although further assessment is needed regarding the associated cooling duty.