High temperature electrolyte supported Ni-GDC/YSZ/LSM SOFC operation on two-stage Viking gasifier product gas

This paper presents the results from a 150 h test of a commercial high temperature single planar solid oxide fuel cell (SOFC) operating on wood gas from the Viking two-stage fixed-bed downdraft gasifier, which produces an almost tar-free gas, that was further cleaned for particulates, sulphur and tar traces.

The chosen SOFC was electrolyte supported with a nickel/gadolinium-doped cerium oxide (Ni-GDC) anode, known for its carbon deposition resistance. Through humidification the steam to carbon ratio (S/C) was adjusted to 0.5, which results in a thermodynamically carbon free condition at the SOFC operating temperature T = 850 degrees C.

The cell operated with a fuel utilisation factor (U-f) around 30% and a current density of 260 mA cm(-2) resulting in an average power density of 207 mW cm(-2). Throughout the duration of the test, only a minor cell overpotential increase of 10 mV was observed. Nevertheless, the V-j (voltage-current density) curves on H-2/N-2 before and after the wood gas test proved identical.

Extensive SEM/EDS examination of the cell's anode showed that there was neither carbon deposition nor significant shifts in the anode microstructure or contamination when compared to an identical cell tested on H-2/N-2 only.