Effects of H2S on the performance of MCFC - I. Change of cell voltage and gas composition

Coal gas is expected to be a major fuel gas for molten carbonate fuel cells (MCFC). Usually, coal gas contains sulfur contaminants that may degrade the MCFC performance. In this study, to evaluate the effects H2S on the performance of MCFC, bench-scale cell tests were performed with fuel gas containing several levels of H2S. In the long term experiments, the poisoning by H2S causes the increase in the reaction resistance, the internal resistance and the decrease of the activity of Ni catalysis. In the early stages, the poisoning of H2S has large effect on cell voltage. but this effect shows a tendency to be lower with operating time. In the short term experiments, the poisoning by H2S causes the increase of the reaction resistance and the decrease of the activity of Ni catalysis. The higher the concentration of H2S in fuel gas and the current density are, the larger the reaction resistance is. In the case of CO rich gas, the causes of the cell voltage loss are not only the increase of reaction resistance, but also the decrease of the Nernst voltage. The decrease of the Nernst voltage is caused by the shortage of H-2 in fuel gas which is caused by the decrease of the water gas shirt reaction rate.