A technical and economic assessment of ammonia-based post-combustion CO2 capture at coal-fired power plants

An ammonia-based post-combustion CO2 capture system processing flue gas from a supercritical coal-fired power plant was modeled, and its estimated performance and cost were compared to an amine-based capture system. For the ammonia system the absorber CO2 capture efficiency, NH3 slip, and solids precipitation were evaluated for changes in lean solution NH3 concentration, NH3/CO2 ratio, and absorber temperature. Reductions in NH3 slip were also assessed for changes in absorber temperature and water wash flow rate. For 90% CO2 capture the levelized cost of electricity generation (annual revenue requirement) for the plant with ammonia-based capture was estimated at $US 105/MWh, which is comparable to the levelized cost of electricity generation for the plant with an amine-based capture system. The cost of the ammonia-based system was found to depend strongly on the fraction of CO2 captured as well as on key process design parameters such as lean solution NH3 concentration. Uncertainties in system performance and cost also were estimated probabistically. Assumptions about plant financing and utilization, as well as uncertainties in cooling costs and reaction rates that affect absorber cost were found in particular to produce a wide range of cost estimates for ammonia-based CO2 capture systems, and as a result the importance of reducing these uncertainties is emphasized.

► An ammonia-based post-combustion CO2 capture system was modeled.
► For 90% CO2 capture the power plant LCOE was estimated at $US 105.4/MWh.
► This cost depended strongly on key process variables and financial assumptions.
► Uncertainties in system performance and cost also were estimated probabistically.
► Uncertainties produced a wide range of cost estimates for ammonia capture.