Development of a highly efficient solid oxide fuel cell system

The overall efficiency of a high-temperature fuel cell system can be enhanced by reuse of the unreacted fuel and the thermal energy from the system exhaust gas. Much of the steam in the anode off gas (AOG) can also be used for the methane steam reforming (MSR) reaction. In this study, a novel SOFC system has been developed. An ejector instead of a regenerative blower has been selected as a recirculation device for the AOG. The cathode air blower has been replaced with a turbocharger. To verify the efficiency enhancement of the proposed system, two other reference systems are presented, and their efficiencies are compared using Aspen Plus®. To estimate the system performance more accurately, a lumped electrochemical SOFC model and a one-dimensional ejector model are incorporated into the system model, using a Fortran® subroutine. To determine the optimal operating schemes for the presented system, its performance has been compared with that of two other reference systems by varying the operating parameters, such as the external reforming (ER) ratio, the fuel utilization, and the steam to carbon (S/C) ratio. Sensitivity analysis for the three systems has been conducted to determine the dominant operating parameters related to the system efficiency.