Microstructured reactors for diesel steam reforming, water-gas shift and preferential oxidation in the kiloWatt power range

The paper reports from development and testing of three microstructured reactors of the kW scale, namely an oxidative diesel steam reformer, a water-gas shift reactor and a preferential oxidation reactor as first prototypes of a future fuel processor system. The reformer (cubic shape, edge length 80 mm) had a co-current flow arrangement. While oxidative diesel steam reforming was performed in one flow path, the energy supply for this endothermic reaction originated from the combustion of hydrogen in an integrated afterburner. The reactor was operated in the temperature range between 850 degrees C and 900 degrees C at S/C ratios between 3.2 and 4.6 and O/C ratios of 0.15-0.2. Full conversion of the diesel fuel could be achieved under all test conditions, however, formation of light hydrocarbons started after some hours of operation at lower S/C ratios. At this stage of the development, the clean-up reactors were tested separately applying reformate surrogate as feed. The water-gas shift reactor was operated as a counter-current heat-exchanger, which utilized the cathode off-gas of the fuel cell as coolant. This further converted the CO towards the reactor outlet exceeding the equilibrium conversion achievable at the inlet. The reactor was operated at temperatures of up to 400 degrees C at the inlet and 250 degrees C at the outlet. Over 90% conversion could be achieved in this single stage water-gas shift reactor. The second clean-up stage, namely the preferential oxidation reactor, was designed as a co-current heat-exchanger. Water evaporation was chosen as the cooling source. The CO could be reduced under most operating conditions to levels below 100 ppm, which is sufficient to operate a CO-tolerant low temperature PEM fuel cell with the purified reformate. (C) 2009 Elsevier B.V. All rights reserved.