Reforming of diesel and jet fuel for fuel cells on a systems level: Steady-state and transient operation

Abstract

The operation of fuel cell systems using liquid fuels widens the application possibilities of this promising energy conversion technology. However, systems utilizing diesel and jet fuel reforming are fairly complex and suffer from poor stability and limited dynamics. To address these challenges, this paper investigates the steady-state and transient operation of a 28 kWth fuel processor on the systems level. With the help of experiments that make use of the developed prototype, suitable operating parameters are sought to maximize the simultaneous fuel conversion in the reformer and CO conversion in the shift reactor. Furthermore, a load change strategy is developed with the aim of keeping the CO concentration at the fuel cell anode inlet below the target concentration of 1% of the wet product gas at all times. The identified parameters enable very high conversions (>99.95%) and CO concentrations even lower than the target during steady-state operation using three commercial fuels under full load. The developed load change strategy was validated during 90 min tests, including 16 load change cycles with loads between 40% and 100%. As well as providing excess steam during load change, the selection and control of optimal O2/C and H2O/C ratios and temperature levels proved to be of key importance. In order to minimize the CO concentration, it is recommended to operate the reformer at the identified parameters for each fuel and keep the shift outlet temperature between 295 and 300 °C by adjusting the water feed. The proposed fuel processor concept and the experimentally-validated operating strategies in this work can enable the successful implementation of fuel cell technology in different application areas, including auxiliary power units, remote power systems and range extenders.