Dynamic insights of carbon management and performance enhancement approaches in biogas-fueled solid oxide fuel cells: A computational exploration

Abstract

The solid oxide fuel cell (SOFC) is drastically affected by carbon deposition when exposed to hydrocarbon fuels such as biogas. Ensuring sustainable energy production requires long-term operation free from carbon formation. In this study, a transient computational fluid dynamics numerical model was developed to analyze the effects of carbon deposition when utilizing biogas as fuel. In addition to validating the model with experimental results, including polarization and stability curves and gas composition within the cell were also compared for the first time, revealing good agreement. Initially, a comparison was made between biogas and coal gasification fuel gas (CGFG) to study the impact of gas composition. Namely, biogas showed a higher power density than the CGFG but an unstable operation, decreasing the cell voltage by 43% at 750 °C and constant current density of 0.2 A cm−2 over 40 h. Additionally, while the rise in applied current density showed no significant impact on the carbon formation rate, increasing cell temperature and current density amplified the power reduction rate. Moreover, potential approaches for regulating the rate of carbon formation were investigated. Namely, N2 (mole fraction = 50%), CO2 (CO2:CH4 = 2), and steam injection (steam: CH4 = 1) led to a cell voltage decline of 12%, 1%, and 3%, respectively. In addition, an anode thickness growth could improve power generation and enhance the cell operation stability so that cell voltage degradation of 8% resulted in 0.8 mm thickness of the anode.