Development of Anode Gas Recycle System Using Ejector for 1 KW Solid Oxide Fuel Cell

An anode gas recycle system using an ejector for 1 kW solid oxide fuel cells (SOFCs) was developed to increase the electrical efficiency of combined power generation. We call this an AGR-SOFC (anode gas recycle-solid oxide fuel cell). The effects of recirculation ratio, externally steam feed rate, and fuel utilization were determined experimentally on the AGR-SOFC performance (i.e., output power, stack temperature and gas composition) using a variable flow ejector and a recirculation ratio of 0.55–0.62, overall fuel utilization of 0.72–0.84, and steam feed rate of 0–1.5 g/min. A quadrupole mass spectrometer was used to identify the recirculation ratio, the gas composition of reformed gas at the AGR-SOFC inlet, and that of the recycle gas at the outlet. Compared to one-path SOFC systems i.e. without an anode gas recycle, the AGR-SOFC was stable and generated about 15 W more electricity when the overall fuel utilization was 0.84 and the recirculation ratio was 0.622 with no steam supply. This improved performance was due to the reduced H₂O concentration in the anodic gas. In addition, although the recirculation ratio did not affect the AGR-SOFC performance, a high recirculation ratio can provide steam produced via the electrochemical reaction to the injected fuel for the steam reforming process.