Evaluation of solid oxide fuel cell performance with anode recirculation using variable flow ejector at rated conditions

Abstract

An anode gas recycle (AGR) system that uses an ejector for a 1 kW solid oxide fuel cell (SOFC) was developed to increase the electrical efficiency of combined power generation. The effects of anodic recirculation on the SOFC performance were determined experimentally with a variable flow ejector at a fuel utilization of 0.80 to 0.87 and a steam feed rate of 0 to 1.5 g/min. A quadrupole mass spectrometer was used to identify the recirculation ratio, the gas composition of reformed gas at the SOFC inlet, and that of the recycle gas at the recycle plenum located downstream of the SOFC. The recirculation ratio could be changed from 0.67 to 0.71 by moving the needle inside the ejector nozzle, and thus the SOFC showed stable performance with no steam supply, due to the large recirculation ratio of steam produced via the electrochemical reaction that was supplied to the injected fuel for the steam reforming process. The results indicate a slight decline in output power with an increase in the recirculation ratio. In addition, the fuel utilization limitation for SOFC operation is estimated to be as much as that for a one-path SOFC system without AGR to avoid a local lack of hydrogen as fuel.

Concentration Gradient of Reactants Extending from Reaction Sites Inward Inlet Periphery of Fuel Cells

“…In these forms, we can utmost enhance the inlet flow rates of the reactants for overcoming the mass transport limitation, which would then require recycling of the outflowing gas (off-gas) to achieve a high energy conversion efficiency. [26][27][28] To identify the impact of mass transport limitation on the performance of the microtubular SOFC, we initially measured spatial iV curves along the cell for different inlet flow rates and then derived the conventional (not spatial) iV curves according to 3…”