System model and performance analysis of a solid oxide fuel cell system self-humidified with anode off-gas recycling.

Recycling the anode off-gas of the solid oxide fuel cells can effectively improve the system fuel utilization (U f , s y s ) under a low stack fuel utilization (U f , 1 ), prolonging the service life and reducing the power generation cost. A compact self-humidified anode off-gas recycle (SAOR) system fueled by natural gas is proposed and analyzed. Clear mathematical relationships for key physical quantities in all system components are derived. Analytical expressions concerning the controllable parameters, U f , s y s and the recycling ratio (λ), and the controlling targets, U f , 1 and the oxygen to carbon ratio, are presented to facilitate the accurate system control for high efficiency and moderate U f , 1 and free of carbon deposition. The core system model is found to agree very well with multiple sets of available experimental data. The SAOR system performance for representative fuel flow rates and U f , 1 and for all λ are presented. The results show the SAOR system can achieve a DC efficiency similar to, but with U f , 1 10% lower than the best known non-SAOR system, demonstrating the presumed superiority of SAOR system. The SAOR system is a promising low cost design capable of achieving high efficiency and durability and should be pursuit for commercial development. • Explicit math model for novel self-humidified anode off-gas recycle system presented. • Validation of the core system model by multiple data sets of available experiments. • Analytical relationship expressions for control parameters and system targets derived. • Very high efficiency with moderate stack fuel utilization is proven for the system. • System performance for many combinations of operating parameters revealed & analyzed. [ABSTRACT FROM AUTHOR]