(360b) Coupled Operation of a Diesel Steam Reformer and a PEFC

Coupled operation of a diesel steam reformer and a polymer electrolyte fuel cell (PEFC) offers a great potential for auxiliary power units (APU) in mobile applications such as caravans and yachts.  Considering its high energy density, diesel is a favourable fuel for early market introduction of mobile fuel cell systems. Furthermore, it is a broadly available fuel in the mobile sector. To generate the hydrogen required for fuel cell operation, on-board fuel processing is necessary.

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 is based on a diesel steam reformer and allows the operation of low-temperature (LT-) as well as high-temperature (HT-) PEFC. In preceding investigations of the author’s group, coupling of a steam reformer with an LT-PEFC was demonstrated using a sulfur-free surrogate fuel [1, 2]. Furthermore, the results of a fuel processor optimization regarding start-up, system integration, reformer geometry, and reformer catalyst performance have been reported [2-5].

The objective of this work is to demonstrate the coupled operation of the fuel processor and an LT-PEFC stack using logistic diesel from a gas station as a fuel. The main component of the fuel processor is a catalytically-coated microchannel heat exchanger with a channel height of 0.6 mm provided by BEHR GmbH & Co. KG. The heat exchanger thermally couples the endothermic steam reforming reaction with an exothermic catalytic combustion. The microchannels were alternatingly coated with HyProGen® reformer and burner catalysts, provided by Clariant International Ltd. The reformer catalyst has shown excellent performance with regards to fuel conversion for a sulfur-free diesel surrogate even at reformer temperatures as low as 700 °C. For this work, an LT-PEFC was selected due to its high energy density and excellent start-up performance. A single-stage preferential oxidation reactor was applied to achieve the CO concentration required by the LT-PEFC. Long-term coupled operation was carried out using both sulfur-free diesel surrogate (sulfur content < 2 wt. ppm) and logistic diesel from a German gas station (sulfur content < 10 wt. ppm). Hydrocarbon concentration in the reformate gas at the stack inlet was measured with a flame ionization detector (FID) to investigate the influence on stack voltage for both fuels. During operation with the diesel surrogate, no significant increase in hydrocarbon concentration was observed; the average cell voltage was stable at approximately 630 mV. For logistic diesel operation, an increase in hydrocarbon concentration was measured. Consequently, stack voltage decreased over operating time. With regards to the modular fuel cell system, a strategy for coupled system operation including cyclic catalyst regeneration is presented.

This research and development project is funded by the German Federal Ministry of Economics and Technology (BMWi, FKZ 03ET2052A).

References:

[1] P. Engelhardt, M. Maximini, F. Beckmann, M. Brenner, Int. J. of Hydrogen Energy, 37 (2012) 13470-13477

[2] P. Engelhardt, M. Maximini, F. Beckmann, M. Brenner, World Hydrogen Energy Conference 2012, Toronto, CAN

[3] M. Maximini, P. Engelhardt, M. Brenner, A. De Toni, H.-G. Anfang, World Hydrogen Energy Conference 2012, Toronto, CAN

[4] M. Maximini, P. Engelhardt, M. Grote, M. Brenner, Int. J. of Hydrogen Energy 37 (2012) 10125-10134

[5] M. Grote, M. Maximini, Z. Yang, P. Engelhardt, H. Köhne, K. Lucka, M. Brenner, J. of Power Sources 196 (2011) 9027– 9035