Effect of operation conditions on soot formation in SOFC stacks

SOFCs can be operated with various fuel types which make them attractive to use for different applications. In many of these applications carbon containing gases are used as fuel that can cause soot formation in the cells especially during heating up - cooling down the SOFC stacks. Experiments have been performed in order to understand the effect of temperature, heating rate and gas composition for carbon containing fuel gas by simulating stack operation parameters. The soot formation phenomenon is studied on the pellets made from anode powders as well as on SOFC one cell stacks. The electrochemical behaviour evaluated by I-V-characteristics and impedance spectroscopy and microscopic analysis of the cells confirm soot formation when SOFC stack is fuelled under unfavourable temperature regions and heating rates. However, it is also found that stack can regenerate itself during operation after a small amount of coke has been deposited on the electrode.