| Summary: | 碩士 === 國立中央大學 === 機械工程學系 === 104 === This study applies an established high-pressure SOFC testing platform together with a button cell experimental setup, so that the impact of carbon deposition on the cell performance, electrochemical impedance spectroscopy (EIS), and stability tests of an anode-supported button full cell can be analyzed when using methane as a fuel. Fixed flow rates are used for all experiments (CH4 + N2: 50 +150 = 200 sccm in anode and air: 200 sccm in cathode) at two different cell loads (0.9V, 0.8V), temperatures (750, 800oC) and pressures (1, 3atm). Results show that cell power densities increase with increasing p and T. It found that the ohmic polarization resistance is independent of p, but it decreases with increasing T. The total polarizaiton resistances decrease with increasing T and p.
To investigate effects of operational parameters i.e. cell loading, temperature, and pressure on carbon deposition, we further conduct the stability test of the cell performance. Results suggest that increasing the cell loading can inhibit effectively carbon deposition. For example, when T = 800oC and p = 1 atm, the cell performance is stable at 0.8V for at least 120 minutes but degradation of performance is found at 0.9V. Though increasing T and p can promote methane cracking rate, cell performance can be also enhanced simultaneously resulting in higher concentrations of H2O and CO2 that remove carbon effectively. Therefore, the stability of cell performance depends on interactions of cell loading, temperature, and pressure. After the stability test of cell performance, we apply hydrogen for the reduction of carbon deposition. The result shows that carbon can be removed by using hydrogen but the original performance can not be fully recovered. The present study should be useful for understanding the carbon deposition phenomenon when using methane as the anode fuel. Generally, the power density increases due to pressurization. However, the effect of pressure must be combined with loading and temperature effects to determine whether cell performance can be stable. To the best knowledge of the authors, it is worth of noting that the aforesaid pressurization effect on carbon deposition is the first available experimental investigation in literatures, which should be useful in the development of pressurized SOFC integrating with micro gas turbines for hybrid power generation systems.
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