MOLTEN CARBONATE FUEL CELLS AS MEANS FOR POST-COMBUSTION CO_2 CAPTURE: RETROFITTING COAL-FIRED STEAM PLANTS AND NATURAL GAS-FIRED COMBINED CYCLES

摘要

The state-of-the-art conventional technology for post combustion capture of CO_2 from fossil-fuelled power plants is based on chemical solvents, which requires substantial energy consumption for regeneration. A promising alternative, available in the near future, is the application of Molten Carbonate Fuel Cells (MCFC) for CO_2 separation from post-combustion flue gases. Previous studies related to this technology showed both high efficiency and high carbon capture rates, especially when the fuel cell is thermally integrated in the flue gas path of a natural gas-fired combined cycle or an integrated gasification combined cycle plant. This work compares the application of MCFC based CO_2 separation process to pulverized coal fired steam cycles (PCC) and natural gas combined cycles (NGCC) as a 'retrofit' to the original power plant. Mass and energy balances are calculated through detailed models for both power plants, with fuel cell behaviour simulated using a 0D model calibrated against manufacturers' specifications and based on experimental measurements, specifically carried out to support this study. The resulting analysis includes a comparison of the energy efficiency and CO_2 separation efficiency as well as an economic comparison of the cost of CO_2 avoided under several economic scenarios. The proposed configurations reveal promising performance, exhibiting very competitive efficiency and economic metrics in comparison with conventional CO_2 capture technologies. Application as a MCFC retrofit yields a very limited (＜3%) decrease in efficiency for both power plants (PCC and NGCC), a strong reduction (＞80%) in CO_2 emission and a competitive cost for CO_2 avoided (25-40 €/ton).