Design and optimization of a combined fuel reforming and solid oxide fuel cell system with anode off-gas recycling

• Published in: Energy conversion and management 2011-09, Vol.52 (10), p.3214-3226
• Main Authors: Lee, Tae Seok, Chung, J.N., Chen, Yen-Cho
• Format: Article
• Language: English
• Subjects: Anode off-gas; Anodes; Applied sciences; Design engineering; Direct power generation; Dodecane; Energy; Exact sciences and technology; Fuel processor; Fuels; Optimization; Reforming; SOFC; Solid oxide fuel cells; Steam electric power generation; Steam reforming; System efficiency
• ISSN: 0196-8904; 1879-2227
• DOI: 10.1016/j.enconman.2011.05.009

► In this work, an analytical, parametric study is performed to evaluate the feasibility and performance of a combined fuel reforming and SOFC system. ► Specifically the effects of adding the anode off-gas recycling and recirculation components and the CO 2 absorbent unit are investigated. ► The AOG recycle ratio increases with increasing S/ C ratio and the addition of AOG recycle eliminates the need for external water consumption. ► The key finding is that for the SOFC operating at 900 °C with the steam to carbon ratio at 5 and no AOG recirculation, the system efficiency peaks. An energy conversion and management concept for a combined system of a solid oxide fuel cell coupled with a fuel reforming device is developed and analyzed by a thermodynamic and electrochemical model. The model is verified by an experiment and then used to evaluate the overall system performance and to further suggest an optimal design strategy. The unique feature of the system is the inclusion of the anode off-gas recycle that eliminates the need of external water consumption for practical applications. The system performance is evaluated as a function of the steam to carbon ratio, fuel cell temperature, anode off gas recycle ratio and CO 2 adsorption percentage. For most of the operating conditions investigated, the system efficiency starts at around 70% and then monotonically decreases to the average of 50% at the peak power density before dropping down to zero at the limiting current density point. From an engineering application point of view, the proposed combined fuel reforming and SOFC system with a range of efficiency between 50% and 70% is considered very attractive. It is suggested that the optimal system is the one where the SOFC operates around 900 °C with S/ C ratio higher than 3, maximum CO 2 capture, and minimum AOG recirculation.