Coupled operation of a diesel steam reformer and an LT- and HT-PEFC

Abstract

Polymer electrolyte fuel cells (PEFC) combined with diesel fuel processors offer a great potential for auxiliary power units (APU) in mobile applications. In a joint research project with partners from industry, Oel-Waerme-Institut GmbH is developing an integrated modular fuel cell system for mobile power generation in caravans and yachts. The system includes a steam reforming fuel processor that allows the operation of low-temperature (LT-) as well as high-temperature (HT-) PEFC.In the presented work the coupled operation of the fuel processor and LT-PEFC and HT-PEFC stacks is demonstrated using logistic diesel from a gas station. For LT-PEFC operation, a single-stage preferential oxidation reactor (PROX) was applied to achieve the required CO concentration. Long-term coupled operation was carried out at a reformer temperature of 780 °C using both diesel surrogate (sulfur content <2 wt. ppm) and logistic diesel from a gas station (sulfur content <10 wt. ppm). In contrast to diesel surrogate, an increase in residual hydrocarbon concentration in the reformate was measured using logistic diesel, which is related to the catalyst deactivation from sulfur. Consequently, during LT-PEFC operation cell voltage remained stable using the diesel surrogate, but decreased over operating time using logistic diesel due to deactivation of both reformer and fuel cell catalyst. At a reformer temperature of 800 °C, residual hydrocarbon concentration and cell voltage of the LT-PEFC remained stable during operation with logistic diesel. It was concluded that residual hydrocarbons deactivate the LT-PEFC catalyst more severely than sulfuric compounds.During HT-PEFC operation, cell voltage remained stable in spite of an increasing hydrocarbon concentration. The HT-PEFC showed no indication of anode catalyst deactivation during operation with reformate from steam reforming of logistic diesel and therefore has great potential for coupling with the fuel processor without the need for a PROX reactor.