A parametric investigation of the Chilled Ammonia Process from energy and economic perspectives

Abstract

As carbon dioxide anthropogenic generation and climate change appear to be correlated, carbon capture becomes advisable, in particular if applied to coal-fired power plants. The Chilled Ammonia Process (CAP) is a promising technology to be proved for the purpose. Continuing an ongoing study, this work examines the integration of Ultra Super Critical (USC) power plants with CAP, conducting a parametric investigation on the design parameters of the capture block in order to find the optimum from an energy perspective, analyzing then in details the power block and estimating ultimately the overall investment and annual costs. The commercial code Aspen Plus and the in-house research code GS are employed. The index SPECCA is adopted as preferred figure of merit of the global performance. With respect to a reference plant of 758MWe net electric production at 45.2% net electric efficiency, the carbon capture of 88.4% of the generated CO2 reduces the net electrical power by 19% and the net electrical efficiency by 8.6% points. The optimum SPECCA is 3.22MJ/kgCO2 and the corresponding specific heat duty to the reboiler is 2.46MJ/kgCO2. Finally, despite the investment cost of the capture block is about 15% of the power block, the cost of electricity increases from 59.9 to 82.4€/MWhe because of the net electric efficiency penalty, the additional operation and maintenance costs as well as the consumable costs. The resulting cost of avoided CO2 is 38.6€/tCO2. For comparison, the European Benchmark Task Force (EBTF) computes for conventional MEA a SPECCA of more than 4MJ/kgCO2, a cost of electricity of approximately 92€/MWhe and a cost of avoided CO2 of about 51€/tCO2.