The environmental impact of post-combustion CO2 capture with MEA, with aqueous ammonia, and with an aqueous ammonia-ethanol mixture for a coal-fired power plant

In this paper the authors compare monoethanolamine (MEA) to aqueous ammonia (AA) and a solvent mixture of aqueous ammonia and ethanol (EAA) with respect to their post-combustion CO2 capture performance and their environmental impact. Simulation of all processes was carried out with Aspen Plus® and compared to experimental results for CO2 scrubbing with ammonia. Of special interest was the formation of stable salts, which could be observed in the experimental CO2 capture with both ammonia solvents. If CO2 can be captured in the form of ammonium salts, energy requirements are greatly reduced, since no energy is required for solvent regeneration and CO2 compression. The environmental impact of CO2 capture was investigated for a 500 MW pulverised coal power plant employing Life Cycle Assessment (LCA) using the software SimaPro®. For a comprehensive evaluation of this impact, influencing factors such as solvent production and solvent emissions were included. With kinetics taken into account, no salt formation could be observed in CO2 removal with aqueous ammonia. The necessary reduction of ammonia emissions leads to further energy requirements, and solvent production as well as the remaining ammonia losses to the environment have a more significant environmental impact than CO2 removal with MEA.