• Energy Research

Abstract Together with the high-temperature polymer electrolyte fuel cell, the reactor for the autothermal reforming (ATR) of liquid hydrocarbons, such as diesel fuel or kerosene, is the key component of the Julich fuel cell system in the 5 kWe power class. This paper presents some of Julich’s most recent development in the field of ATR reactors, specifically the ATR 12. ATR 12 is characterized by a new concept for the internal generation of superheated steam as one of the ATR reactants using concentric shells instead of coiled tubing and particularly by the integration of an electric heating wire to enable fast and autonomous start-up. Three different experimental procedures for heating up the ATR 12 are presented and discussed, the most suitable of which enables the start-up of the ATR 12 within approximately 15 min. As a consequence, from the system perspective, the bulky start-up burner, which is also difficult to control, along with the corresponding heat exchanger unit, can be dispensed with. Additionally, comprehensive steady-state experiments identify suitable reaction conditions for the operation of the ATR 12.

Abstract This contribution deals with the development of suitable operating strategies for diesel/kerosene-fueled fuel cell APUs. The focus is on the autothermal reformer (ATR) and the water–gas shift (WGS) reactor. In the first part shutdown experiments under high-temperature shift (HTS) conditions were used to identify the possible detrimental effect of higher hydrocarbons on the activity and stability of two commercial WGS catalysts. The results indicated that 220 ppmv higher hydrocarbons had no negative effect on the catalyst activity/stability. The second part presents fuel processing system experiments, which revealed much higher concentrations of higher hydrocarbons during transients like startup/shutdown than the concentrations investigated in the first part. Through the development of new startup/shutdown strategies concentrations of higher hydrocarbons were lowered by a factor of up to 10 for startup and of up to 400 for shutdown. The results were reproduced using four different diesel and kerosene fuels. The newly developed strategies improve fuel conversion in the reformer and may possibly prevent catalyst deactivation in the water–gas shift reactor during transient conditions.

Abstract This paper describes the development and experimental evaluation of Juelich’s novel reactor type ATR AH2 for autothermal reforming of diesel fuel and kerosene. ATR AH2 overcomes the disadvantages of Juelich’s former reactor generations from the perspective of the fuel cell system by constructively integrating an additional pressure swirl nozzle for the injection of cold water and a steam generation chamber. As a consequence, ATR AH2 eliminates the need for external process configurations for steam supply. Additionally, the internal steam generator has been modified by increasing its cross-sectional area and by decreasing its length. This measure reduces the pressure drop of the steam generator from approx. 500 mbar to roughly a thirtieth. The experimental evaluation of ATR AH2 at steady state revealed that the novel concept for heat management applied in ATR AH2 is suitable for fuel cell systems at any reformer load point between 20% and 120% when the mass fractions of cold water to the newly integrated nozzle are set to values between 40% and 50%. The experimental evaluation of ATR AH2 during start-up and shut-down showed that slight modifications of the reaction conditions during these transient phases greatly reduced the concentrations of ethene, ethane, propene and benzene in the reformate. From the fuel cell system perspective, these improvements provide a very beneficial contribution to longer stabilities for the catalysts and adsorption materials.

AbstractHT-PEFC systems designed for operation with diesel and kerosene are currently being developed in Jülich. Fuel processing reactors consisting of an autothermal reformer, a two-stage water-gas shift reactor and a catalytic burner were designed with the aim of maximizing heat integration and minimizing system volume. The stack is designed for operation with reformate coming from fuel processing.This paper highlights the system architecture as well as experimental results in the 5 kWel power class. The integrated system concept was characterized via sub-system experiments. The stack performance was tested under system-relevant conditions. Finally, actual system performance was compared with APU targets.

Abstract This work deals with the theoretical and experimental analysis of fuel-cell-based auxiliary power units operated with reformate from diesel and kerosene reforming for trucks and aircraft. In the theoretical part, a PEFC and an HT-PEFC system were analyzed using process simulation software. In the experimental part, a fuel processor consisting of an autothermal reformer, a water-gas shift reactor and a catalytic burner with 28 kW thermal power was characterized using different diesel and kerosene fuels. These fuels included desulfurized Jet A-1 and Aral Ultimate diesel as petroleum-based fuels and GTL kerosene, GTL diesel (winter and summer grades) and BTL diesel as non-petroleum-based synthetic fuels. The PEFC system showed a calculated electrical net efficiency of 28.5%, whereas 22.3% was calculated for the HT-PEFC system. A high-quality reformate was produced using various diesel and kerosene fuel qualities in the reformer with a relevant technical power class for the APU application. Although a performance loss of the shift reactor was observed, it was kept at an acceptable level at the end of experiments.

Abstract A high-temperature PEFC system, developed with the aim of delivering 5 kW electrical power from the chemical energy stored in diesel and kerosene fuels for application as an auxiliary power unit, was simulated and tested. The key components of the system were an autothermal reformer, a water–gas shift reactor, a catalytic burner, and the HT-PEFC stack. The targeted power level of 5 kW was achieved using different fuels, namely GTL kerosene, BTL diesel and premium diesel. Using an integrated system approach, operation without external heat input was demonstrated. The overall analysis showed slight but non-continuous performance loss for 250 h operation time.

Abstract A diesel fuel processor for high temperature polymer electrolyte fuel cells in the 5 kWe power class was developed and tested. Emphasis was placed on a quick and sustainable start-up. Furthermore, operational conditions were identified that would achieve the desired reformate quality for the fuel cell anode. A thermal start-up strategy using a commercial diesel burner was developed and further optimized, resulting in a hybrid strategy with the help of a glow plug. With this strategy, self-sustaining operation of the fuel processor at full load was achieved in 27 min and the resulting reformate was of sufficient quality to operate the fuel cell in 31 min. The experimental plan includes operation periods of between 4 and 24 h with start/stop/regeneration cycles representing the daily operation of an auxiliary power unit at maximum load. With all fuels used, the target carbon monoxide concentration of 1% at the anode inlet (wet reformate) was achieved. Significant deviations from the design parameters were necessary to demonstrate a stable system performance with desulfurized Jet A-1 and to achieve the target carbon monoxide concentration with premium diesel. These results bring diesel fuel processing for auxiliary power units closer to real application, offering experimentally-validated solutions for start-up and stable operation under realistic conditions with different fuels on a systems level.