Study on performance of $n-C_4H_10-driven$ solid oxide fuel cell

Abstract

The solid oxide fuel cell (SOFC), a type of high-temperature fuel cells, is an attractive energy conversion device due to its high electric efficiency and low pollution. A major advantage of SOFCs is their fuel flexibility, which comes from their high operating temperature. For the SOFC system, it is possible to design a compact reformer without a carbon monoxide removal process or internal reformation of various types of hydrocarbon fuels with steam on the anode. The operation type depends on the system size and the kind of fuel as well as on design of SOFC. Common problem for internal and external reforming is carbon deposition on anode. In this thesis, the practical problems in an SOFC coupled with an external reformer or fueled by internal reforming of $n-C_4H_10$ were individually analyzed by long-term operation of SOFC single cell and additional experiments, and then a newly designed SOFC single cell was developed as breakthrough for SOFC using $C_4$ level hydrocarbons for operation at maximum efficiency and carbon-free zone. First, as experiment for ER type SOFC, the performance deterioration of solid oxide fuel cells (SOFCs, Nickel-Yttria stabilized zirconia (Ni-YSZ) / YSZ / lanthanum doped strontium manganite-YSZ (LSM-YSZ)) coupled with $n-C_4H_10$ steam reformers (SR), autothermal reformers (ATR), or catalytic partial oxidation reformers (CPOX) was examined using an integrated system of a micro-reactor reformer and SOFC unit. When oxygen to carbon ratio of CPOX reformer was set to 0.5, the terminal voltage rapidly degraded in CPOX-driven SOFC. In contrast, it was fairly stable for SR-driven SOFC over 250h when steam to carbon ratio (SCR) was set to 2. For ATR-driven SOFC at near the thermoneutral point (OCR = 0.5 and SCR = 1.3), significant deterioration of the terminal voltage was observed in 100 h of operation. The main precursors of carbon deposition on the SOFC were identified by reformate gas analysis during the tests. In this part, it was identi...