5 kWe LPG hydrogen generator for PEFC

The determining step in PEFC (Polymer Electrolyte Fuel Cell) systems for power generation is the development of fuel flexible (fossil hydrocarbons and/or bio-alcohols) processor to provide hydrogen or hydrogen rich reformate gas. Low cost and efficient fuel processing system represents the transition bridge to the future commercialisation of this technology for stationary applications. This paper covers the activities performed at the CNR-ITAE aimed at developing a pre-commercial hydrogen generator unit, named HYGen 11, (now under assembling) for residential applications in a power range until 5 kWe. The prototype, based on our first HYGen 1 (2 kWe) system, successfully demonstrated and tested, is able to convert light hydrocarbons (methane, propane, LPG, butane). After the scale-up, the unit has been further optimized by redesign of the major components, emphasizing compactness, improved thermal and mass transfer and system efficiency. The processing unit is an integrated packed bed catalytic tubular reactor, filled with pellet catalysts, divided in two beds: the autothermal (ATR) and the intermediate water gas shift (ITS). The ATR catalyst is a proprietary CNR-ITAE catalyst, while the ITS catalyst is a commercial catalyst (NexTech Materials Ltd.). The system design incorporates, furthermore, heat exchanger, manual and automatic valves, pressure regulators and transducers, flow meters and ancillaries. Differently from our first prototype, the final step of CO clean-up is a PSA (Pressure Swing Adsorption) unit, able to obtain hydrogen with purity of 99,999%. The system design has been engineered to meet the requirements of small size and volume, quick start up, rapid response to change in hydrogen demand, high fuel conversion, stable performance for repeated start-up and shut-down cycles, heat management system optimized for different operating conditions. During the start-up, nitrogen is sent to the system, during the shut-down, air and propane are shut-off and nitrogen sent as a purge. The prototype includes a semi-automatic system to monitor operating conditions and control plant equipment, based on Field Point distribuited I/O hardware. In particular the alarm circuit includes an automatic cycle of shut-down for some different events: Pmax, Pmin, Thigh, Tlow, gas leakage. Besides the products are continuously analyzed. External heating is supplied only during the start-up; on regime operations the global heat balance is smoothly exothermic. The related efficiencies, ATR and prototype, (calculated as hydrogen higher heating value on propane higher heating value) reaches about 59 and 71 %, respectively.