Performance analysis of a biogas-fueled SOFC/GT hybrid system integrated with anode-combustor exhaust gas recirculation loops

Abstract

This paper proposed a solid oxide fuel cell–gas turbine (SOFC-GT) hybrid system combined with anode and combustor exhaust recirculation loops. The ejector technology is introduced to perform the recirculation loops. And the hybrid system is fueled by a typical farm biogas. Furthermore, the interaction between these two recirculation is discussed. Results show that the anode recycle loop can rise the electrical efficiency of hybrid system and drop the SOFC temperature gradient. Meanwhile, the anode exhaust recirculation is beneficial to avoid the carbon deposition in reformer and prevent the fuel cell thermal crack, and the combustor exhaust recirculation can allow the system safety operated over a wider temperature range. The optimal recirculation ratio of 0.4 and 0.425 are determined in anode and combustor exhaust respectively to obtain the maximum power generation efficiency and ensure the safety operation of SOFC. The design efficiency of described system can reach to 62.21%. In addition, a parametric analysis is carried out to evaluate the coupling effect among multiple working parameters on the performance of SOFC-GT. Results indicated that the reasonable air flow rate, fuel flow rate, fuel utilization and steam to carbon ratio are the necessary prerequisite to safeguard the healthy operation of SOFC-GT.