Experimental Study on the Performance of a Single Sofc During Internal Reforming

Abstract

In the present work, a combined experimental and numerical investigation towards methane reforming using intermediate temperature solid oxide fuel cells (IT-SOFCs) with different gas compositions is presented. Steam methane reforming has been investigated from the perspective of methane conversion, hydrogen yield, power delivered, and cell stability. Different ratios between methane, steam, carbon dioxide, carbon monoxide and hydrogen were used in order to simulate different grades of methane internal reforming in the SOFC. Experimentally, it is reported an extensive characterization of these commercial anode-supported single cells by means of electrochemical impedance spectroscopy (EIS) and the distribution of relaxation times (DRT) method, polarization (I-V) curves and gas composition and temperature analyses for three different reformate compositions. Simultaneous gas and temperature analyses were carried out throughout the anode by means of an in-house built validated spot-sampling set-up. Additionally, in order to analyze the effect on the performance and stability of these planar IT-SOFC systems under internal reforming, a long-term test has been also carried out. Also, in this case, localized gas analyses and temperature measurements were frequently carried out, as well as EIS and I-V curves. The impedance spectra have been also analyzed through the DRT method and the cell study complemented with a post-mortem analysis. Furthermore, a comprehensive zero-dimensional (0D) model of the tested samples, incorporating thermodynamic equilibrium and some experimental parameters, has been also validated by confronting the simulated polarization curves with the experimental ones. Thermodynamic equilibrium modeling was employed to determine the concentrations of each gas species in the equilibrium state. Finally, an additional 2D model, based on finite differences and combined with some experimental results, has been also implemented for a mapping of the current density distribution over the anode.