Comparison of integrated fuel processing options for biogas-fed solid-oxide fuel cell plants

Abstract

The Solid-oxide fuel cell is a highly efficient prime mover for biogas conversion, but a part of biogas needs to be reformulated externally to facilitate the electrochemical conversion, easy control of reforming conditions, and thermal management of the stack. Carbon deposition and external mineralcarrying water should be avoided to ensure the durability of the fuel processor and stack catalysts. This paper investigates four plant layouts with different anode off-gas recirculation schemes and biogas reforming methods: (1) pre-reforming with hot recirculation (HR), (2) pre-reforming with cold recirculation (CR), (3) no pre-reforming and hot recirculation (NR), (4) partial oxidation with hot recirculation (PO). All the schemes feature an electrolyte supported SOFC working at 860°C and 0.23 A/cm2 current density. A sensitivity analysis of the plant efficiency as a function of the Recirculation Ratio (RR) and the Reformer Temperature (RT) is performed. The results show that HR and CR schemes achieve the highest efficiency (58-63%). The HR scheme benefits from the recirculated water and does not require external water for RR > 50% and RT > 600°C; the CR scheme achieves the same result for RR > 80% and RT > 700°C. The optimal RR is within 50 – 80% for the highest system efficiency, as a trade-off between the overall fuel utilization and electrochemistry performance. The RT should be between 600 and 700°C. The HR scheme is the overall best performing if the re-circulator and stack designs do not limit the flow rates at a high RR.

Design and Evaluation of a Metal-Supported Solid Oxide Fuel Cell Vehicle Power System with Bioethanol Onboard Reforming

“…Therefore, the carbon deposition risk of the SOFC entrance can be calculated with the C−H−O mole fraction of the gas mixture, and compared in the ternary diagram, determining whether the composition is outside the carbon deposition area. 40 25 The comparison between the prediction model and the experimental data at different current densities and temperature is shown in Figure 4, showing a good agreement with the experimental data.…”

“…The C–H–O ternary diagrams have been widely used to describe phase diagrams and carbon deposition boundary limits at various temperatures. Therefore, the carbon deposition risk of the SOFC entrance can be calculated with the C–H–O mole fraction of the gas mixture, and compared in the ternary diagram, determining whether the composition is outside the carbon deposition area …”

Waste to energy conversion for a sustainable future

“…They found landfills, urban solids, and farms to hold the potential of 116 PJ, 241 PT, and 1132 PT energy in the USA. They developed solid fuel cells to convert biogas into 16, 33, and 157 TWh energy reserves under waste 2 W (W2W) projects ( Ma et al., 2021 ; Wang et al., 2020 ). Elsevier launched the Journal of CO 2 utilization to convert GHG emissions into value-added products.…”