(690b) Direct Carbon Conversion in Carbon Dioxide as the Fuel for Solid-Oxide Fuel Cells

Fuel cells
efficiently convert chemical energy to electricity in a silent and
environmentally friendly way. They are believed to be a promising alternative
power source to traditional mobile and stationary sources, such as the internal
combustion engine and coal burning power plants. Among the various kinds of fuel
cells, solid-oxide fuel cell (SOFC) has the benefits of the high energy
efficiency and fuel flexibility because of their high operating temperature.
Therefore, they have received considerable attention in recent years. On the
other hand, the
remaining huge storage of available coal energy promotes the need for clean utilization of coal. Combining carbon gasification
technology and SOFC is a logical step as excess heat from the SOFC process can
be used for the coal gasifcation.

In this work, the carbon
was directly gasified in CO₂ to CO as the fuel for SOFC. There are
several benefits in combining SOFC and gasifier. The coal gasifier supply the
SOFC with CO as the fuel, while the SOFC provides heat for the gasifier from
the exothermal reactions and CO₂ for the gasification from the anode
exhaust. Fe_mO_y oxides were used as the catalysts in the
solid carbon conversion reactions. The maximum conversion efficiency of carbon
dioxide could be as high as 91 % at 800 ^oC compared to only ~60 %
without catalyst. An anode-supported fuel cell with the configration of Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-¦Ä/Sm_0.2Ce_0.8O_1.9/
Sm_0.2Ce_0.8O_1.9-Ni was used to test the feasibility
of the carbon gasification in CO₂. The power densities of 502, 368
and 216 mW/cm² were obtained at 850, 800 and 750 ^oC,
respectively. The preliminary study indicates that the direct carbon conversion
in CO₂ is a promising way to utilization of the solid coal as the
fuel for SOFC.

Keywords: Coal, Gasification, Solid-oxide fuel cells.

Acknowledgements

This work was supported by the National Natural
Science Foundation of China under contract Nos. 20646002 and 20676061, by National
863 program under contract No. 2007AA05Z133, and by National Basic Research Program of
China under contract No. 2007CB209704. Dr Zongping Shao also would like to acknowledge
the financial
support from Chinese Ministry of Education via the Program for Changjiang
Scholars and Innovative Research Team in University (No.IRT0732)