(360e) Optimization of the Start-Up Strategy for a Diesel Fuel Processor

Fuel cell systems based on liquid fuels are particularly suitable for auxiliary power generation. For mobile fuel cell systems, high energy density and easy storage of the fuel applied are important. To realize an easy market entry of fuel cell systems, the use of a broadly available fuel like diesel is favorable.

In the joint research project “MÖWE III” Oel-Waerme-Institut and industrial partners are developing a PEFC system based on diesel fuel to be applied as auxiliary power unit (APU) for caravans and yachts. The modular design allows an operation of the fuel processor with LT-PEFC and HT-PEFC providing a maximum power output of 3 kWe. The fuel processor includes a 10 kW microchannel steam reformer provided by Behr GmbH & Co. KG. It thermally couples the endothermic steam reforming reaction with a catalytic combustion using HyProGen® catalysts from Clariant International Ltd. In combination with HT-PEFC, the fuel processor can be coupled directly to the fuel cell. For LT-PEFC operation, a gas cleanup module is integrated.

The objective of the presented work is the optimization of the start-up procedure of the fuel processor. A novel start-up strategy is introduced and demonstrated. The new approach aims at reactive heating of water-gas shift (WGS) reactors and preferential oxidation (PROX) reactors by using reformate from oxidative steam reforming during the reformer heat-up, instead of sequential heating the reactors by large mass flows of hot gases.

The new strategy consists of a sequence of the following phases: preheating, start-up burner operation, reactive reformer heating, oxidative steam reforming, and steam reforming. A complete start-up procedure is demonstrated on a simplified test assembly including two multifunctional reactors for reactant conditioning that are capable to work as: start-up burners, Cool Flame reactors, and diesel-steam mixers. After preheating the 10 kW reformer by combustion gases, oxidative steam reforming is started at approx. 600°C and reformate is obtained from the reformer after 11:15 minutes. Steam reforming is performed after 14:30 minutes at equilibrium concentrations. Until steam reforming operation, 3.07 MJ of Diesel fuel is required. To assess the new procedure in terms of long term operation, soot formation is analysed after 10 of minutes steam reforming operation at 2 kW_th.

Eventually, the new procedure is successfully transferred to the complete fuel processor assembly. Concluding, the new start-up procedure is compared to sequential heating of the fuel processor by combustion gases.

Acknowledgement

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