Catalytic and Electrochemical Behaviour of Solid Oxide Fuel Cell Operated with Simulated-Biogas Mixtures

摘要

Being produced from organic matters of wastes (bio-wastes) through a fermentation process, biogas mainly composed of CH_4 and CO_2 and can be considered as a secondary energy carrier derived from solar energy. To generate electricity from biogas through the electrochemical process in fuel cells is a state-of-the-art technology possessing higher energy conversion efficiency without harmful emissions compared to combustion process in heat engines. Getting benefits from high operating temperature such as direct internal reforming ability and activation of electrochemical reactions to increase overall system efficiency, solid oxide fuel cell (SOFC) system operated with biogas becomes a promising candidate for distributed power generator for rural applications leading to reductions of environmental issues caused by greenhouse effects and bio-wastes. CO_2 reforming of CH_4 and electrochemical oxidation of the produced syngas (H_2-CO mixture) are two main reaction processes within porous anode material of SOFC. Here catalytic and electrochemical behavior of Ni-ScSZ (scandia stabilized-zirconia) anode in the feed of CH_4-CO_2 mixtures as simulated-biogas at 800 °C were evaluated. The results showed that CO_2 had strong influences on both reaction processes. The increase in CO_2 partial pressure resulted in the decrease in anode overvoltage, although open-circuit voltage was dropped. Besides that, the simulation result based on a power-law model for equimolar CH_4-CO_2 mixture revealed that coking hazard could be suppressed along the fuel flow channel in both open-circuit and closed-circuit conditions.