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Future large-scale fuel cell power plant applications will require the use of hydrocarbon feeds such as coal, heavy oils, and distillates containing sulfur. As a result, depending on the fuel conversion and cleanup processes used, varying amounts of sulfur will appear in the fuel cell feed. Because both the cost and complexity of the total plant increase as the removal levels increase, it is essential to identify the gas purity requirements of molten carbonate fuel cells. Therefore, the objectives of this study are: (1) to establish the performance and endurance characteristics of molten carbonate fuel cells as a function of sulfur contaminants in both fuel and oxidant feed gases; (2) to identify the sulfur tolerance of cell materials; and (3) to establish cell performance as a function of gas composition at 5 and 10-atm pressure. Cell tests using a variety of sulfur concentrations indicated that the sulfur tolerance of present molten carbonate fuel cells is below 10 ppM in the incoming feed gases. Both cell performance losses and endurance limitations were observed at these levels and they were shown to occur primarily on the anode side of the cell. The performance losses are due to a combination of structural changesmore » in the anode and reduced mass transfer characteristics of the carbonate melt caused by interactions between the carbonate melt and the sulfur species. The endurance limitations are due to corrosion of the current collector and other metallic components that were shown to be more severely corroded in the presence of the sulfur-containing gases. Potentially more sulfur-tolerant materials were identified in supplementary screening tests. (WHK)« less |
