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

An anode gas recycle (AGR) 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. 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 0.720-84, 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 AGR, 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.