The Influence of Tar on the Performance of Solid Oxide Fuel Cells

The Influence of Tar on the Performance of Solid Oxide Fuel Cells

Van der Kleij, A.

Aravind, P.V. (mentor)
Boersma, B.J. (mentor)

Mechanical, Maritime and Materials Engineering

Process and Energy

Energy Technology (SPE)

2012-08-30

"As fossil fuels are depleting, polluting and an increasing source for global conflicts it has become important to find alternatives. It is essential to develop conversion chains that are able to compete with the non-renewable energy sources both technically and economically. Biomass is an upcoming flexible energy source, and has a close to carbon neutral life cycle. In case of combined heat and power production, high system efficiencies can be attained when biomass gasifiers are connected with solid oxide fuel cells. Contaminants form however a thread to successful performance and long-term operation. Tars are one of the main harmful contaminants as they cause carbon deposition, but can be made harmless and converted into heat and electricity using an SOFC. It was chosen to use a model tar (toluene) in combination with synthesized mixtures. Dry operation was compared with wet. The main variables were the temperature (973, 1073 and 1173K) and compositions. Open and closed circuit measurements were performed to evaluate the catalytic and electro-catalytic reactions. Ni/GDC cells were chosen for their resistance towards carbon deposition and placed in a single cell setup. Electrochemical impedance spectroscopy was used to evaluate material changes and polarisation losses. I-V curves were taken to evaluate the performance and degradation. Gas chromatography was used to analyse the anode-off gases and to give an indication of the mechanisms at stake. Syngas as well as biogas were successfully operated under dry and wet conditions, the voltage oscillated but the average remained constant. Power production was found to be possible, although within a voltage bandwidth. Dry syngas performed slightly better than wet syngas. During dry reforming of CH4 it was found that the closer to equimolar conditions the higher the produced power. Carbon deposition was suspected for all syngas conditions at all temperature levels, but it did not influence the short time operation (45 minutes). No degradation was found during a long term (24 hour) tar and syngas operation at 1073K.

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Student theses

master thesis

(c) 2012 Van der Kleij, A.