Review on Experimental Plants for CO 2 Removal Based on Ammonia

In the search for alternatives to conventional amine-based solvents for postcombustion CO 2 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 ECO 2 process, which operates at around 20 °C with aqueous NH 3 and integrates desulfurization by converting SO x 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 ECO 2 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 CO 2 capture process conditions, NO x species are inert and do not degrade ammonia; ammonia slip in the CO 2 -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.