Experimental Investigation and Modeling of Direct Internal Reforming of Biogases in Tubular SOFC

Biogas-fed SOFC systems can be considered as interesting power systems in the framework of distributed generation plants. In particular, bio-methane (CH₄/CO₂ 60/40 vol.) and bio-hydrogen (H₂/CO₂ 50/50 vol.), produced from anaerobic digestion of wastes, represent renewable fuels for high efficiency electrochemical generators. This study investigates the behavior of an anode-supported (Ni-YSZ) tubular cell fed by the two fuels. The tubular geometry has been considered since it causes a complete separation of the electrodes reactants, allowing the analysis of the evolution of the fuel gas inside the tube, in terms of composition (consequence of electrochemical and heterogeneous chemical reactions) and temperature field. The experiments have been designed in order to analyse the behavior under different load and fuel utilization conditions. In particular, the fuel mixtures have been conditioned to avoid carbon build-up on the anode electrode. The experimental results have been then used to validate a 2D model (taking into account the cell axial symmetry) of the multi-physics phenomena occurring along the tubular cell. The model shows a good accordance with the experimental data, and has therefore been used to analyse the effects linked to the modification of some geometrical parameters of the tube in terms of performance of the cell.