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Direct Carbon Conversion in Carbon Dioxide as the Fuel for Solid-Oxide Fuel Cells

Zongpin Shao, Ran Ran, Rui Cai, and Xiaohua Lu. State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing University of Technology, Xinmofan Road 5#, Nanjing, China

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. FemOy 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 Ba0.5Sr0.5Co0.8Fe0.2O3-/Sm0.2Ce0.8O1.9/ Sm0.2Ce0.8O1.9-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)