Thermodynamic and Emission Performance of SOFC-GT Hybrids with Dual Recirculation Strategies

Abstract

Solid oxide fuel cell–gas turbine (SOFC-GT) hybrid systems offer high efficiency and low emissions for sustainable power generation. This study compares two SOFC-GT configurations with different exhaust gas recirculation strategies: SOFC-GT-RAN (anode recirculation) and SOFC-GT-RAB (afterburner recirculation). Both systems were modeled in Aspen Plus using methane with 10% pre-reforming. Parametric analyses were conducted to examine the influence of fuel utilization, steam-to-carbon ratio, SOFC operating temperature, and recirculation ratio on system performance. The results show that SOFC-GT-RAN consistently outperforms SOFC-GT-RAB in terms of power output, efficiency, and CO₂ emissions. At optimal conditions (SOFC temperature = 1173 K, fuel utilization = 0.90, steam-to-carbon ratio = 2.0, anode recirculation ratio = 0.30, afterburner recirculation ratio = 0.10), SOFC-GT-RAN achieved SOFC and net powers of 208.51 kW and 207.47 kW, compared to 156.43 kW and 158.01 kW for SOFC-GT-RAB. Energy and exergy efficiencies were 93.18% and 89.81% for RAN, substantially higher than 70.96% and 68.40% for RAB. Moreover, CO₂ emissions were lower for RAN (205.98 kg/MWh) than for RAB (268.82 kg/MWh). These findings confirm that anode exhaust gas recirculation provides superior technical and environmental performance, highlighting SOFC-GT-RAN as a promising pathway for efficient and clean hybrid power generation.