PERFORMANCE ENHANCEMENT OF A MOLTEN CARBONATE FUEL CELL/MICRO GAS TURBINE HYBRID SYSTEM WITH CARBON CAPTURE BY OFF-GAS RECIRCULATION

摘要

The demand for clean energy continues to increase as the human society becomes more aware of environmental challenges such as global warming. Various power systems based on high-temperature fuel cells have been proposed, especially hybrid systems combining a fuel cell with a gas turbine, and research on carbon capture and storage technology to prevent the emission of greenhouse gases is already underway. This study suggests a new method to innovatively enhance the efficiency of a molten carbonate fuel cell/micro gas turbine hybrid system including carbon capture. The key technology adopted to improve the net cycle efficiency is off-gas recirculation. The hybrid system incorporating oxy-combustion capture was devised, and its performance was compared with that of a post-combustion system based on a hybrid system. A molten carbonate fuel cell system based on a commercial unit was modeled. Externally supplied water for reforming was not needed as a result of the presence of the water vapor in the recirculated anode off-gas. The analyses confirmed that the thermal efficiencies of all the systems (MCFC stand-alone, hybrid, hybrid with oxy-combustion capture, hybrid with post-combustion capture) were significantly improved by introducing the off-gas recirculation. In particular, the largest efficiency improvement was observed for the oxy-combustion hybrid system. Its efficiency is over 57% and is even higher than that of the post-combustion hybrid system.