Effect of Reformed Gas Components on the Operation of HT-PEMFC Stacks

Abstract

Due to still existing limitations in logistic and some risk in handling of compressed gases hydrogen is not a suitable fuel for all applications which can profit from the use of fuel cells. In such cases the use of a downstream reformer to generate hydrogen from another fuel is a viable option. Fuel cell which can tolerate the impurities contained in the reformed gas will avoid the need of sophisticated gas clean-up. Such tolerance is obtained by increasing the operation temperature. BASF has already shown that their Celtec® MEA can tolerated substantial CO and H2S concentration1 which was confirmed by us for MEA of other manufacturers2,3. Here, the effect of impurities on the operation of HT-PEMFC stacks is investigated.In this contribution investigations of the effect of impurities typically found in fuel gas obtained by auto thermal reforming of jet fuels is reported. Tests were conducted on Serenergy S165L-35 stacks with 35 cells of 165 cm2 geometric electrode area. Investigated were in detail the effect of dilution of hydrogen with nitrogen or CO2, the effect of fuel gas humidity and the effect of percent level CO and ppm level H2S impurities.It was found that the performance of the stack at an anode stoichiometry of 1.4 is strongly influenced by hydrogen dilution (cf. fig 1a and b). Thereby no difference is found between dilution with N2 or CO2 (cf. fig. 2) indicating that no relevant reversed water gas shift reaction does occur. High levels of humidification with anode feed dew point exceeding about 60 °C also reduce the stack performance (cf. fig 3). This effect can again be correlated to the dilution with hydrogen (cf. fig. 4). However, after longer test with high due points stack performance is irreversibly reduced (cf. fig 5). Adding CO or H2S to diluted hydrogen further reduces the performance as expected. Unexpectedly the impact of the addition of CO is higher than that of H2S (cf. fig 6). Finally adding CO and H2S has a combined effect (cf. fig 7) though not as strong a described by Schmidt and Baurmeister1.In the contribution further analysis of the different effects e.g, on cell voltage distribution will be given as well as the determination and validation of a suitable operating point for a jet fuel surrogate reformate.The work was financial supported by the European Defence Agency (EDA) through the Ad-Hoc project “IAPUNIT” Contract B 1490 GEM 3 GP, jointly financed by the Federal Republic of Austria, the Federal Republic of Germany, the Kingdom of the Netherlands, the Republic of Slovenia and the Kingdom of Sweden.References T. J. Schmidt and J. Baurmeister, ECS Trans., 3(1), 861 – 869 (2006)C. Cremers, M. S. Rau, A. Niedergesäß, K. Pinkwart, and J. Tübke, ECS Trans., 75(14), 919 – 929 (2016).M. Rau, A. Niedergesäß, C. Cremers, S. Alfaro, T. Steenberg, H.A, Hjuler, Fuel Cells, 16(5), 577 – 583 (2016). Figure 1