Integrating Anode Recycle in a Solid Oxide Fuel Cell for Hybrid Applications: Design Considerations

Abstract

In Solid Oxide Fuel Cell (SOFC) hybrid systems, anode recycle allows us to reach high stack fuel utilization without causing anode re-oxidation, which is detrimental for the fuel cell. In addition, anode recycle also helps the system to mitigate the risk of carbon deposition within the fuel cell when employing fuel with high methane/CO content. This work incorporated anode recycle within a pre-existing fuel manifold model which is embedded in a larger real-time SOFC model. To optimize system performance, we considered fuel manifold design and anode recycle concurrently. The pre-existing manifold model contained a fuel valve, mixing volume, and pipe system for pressure losses. Because increasing anode recycle percentage increased fuel mass flow, pressure losses in the system also increased. Therefore, a sensitivity analysis on manifold pipe diameter and fuel composition was conducted with parametric variation in anode recycle percentage. This enabled both minimization of pressure loss to avoid damage to the SOFC, and minimization of manifold residence time to maintain acceptable control response. The updated model allowed for further investigation of the effects of anode recycle within the fuel cell and ultimately the entire hybrid system.