Combustion modeling and simulation of recycled anode-off-gas from solid oxide fuel cell

Abstract

A solid oxide fuel cell (SOFC) is popular amongst other fuel cell technologies due to fuel flexibility, low cost, and stability. Because of difficulties involved in the handling of hydrogen, onsite hydrogen production is considered for many small- and large-scale applications. It involves an integrated setup consisting of a reformer, combustor, and fuel cell stack. Being operated at high temperature, gases leaving SOFC contain a significant amount of thermal energy which can be utilized within the integrated reforming process. In addition, anode-off-gas (AOG) from SOFC contains unreacted hydrogen which can be utilized as fuel in an integrated combustor thereby increasing combustor efficiency. For effective integration of a combustor, reformer, and power generator, modeling and simulation is of great utility. In the present work, a 3D model of an integrated combustor unit is developed and implemented into the computational fluid dynamics (CFD) simulation package ANSYS FLUENT®. Main objective of this work is to prove the concept of enhancement in combustor performance by utilizing AOG from SOFC as a supplementary fuel in the combustor. Simulation results show a significant increase in combustor temperature and heat dissipated to the reformer side with AOG utilization. Up to an 18% saving in fuel (natural gas), used in combustor to supply heat to the reformer, is observed.