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An Approach For Longer Lifetime MCFCs

Masaru Matsumoto, Masahiko Tatsumi, Takuro Hayano, Hitoshi Takeya, Atsushi Miki MCFC Research Association 3-10-10, Minami-Ohtsuka, Toshima-ku, Tokyo, 170 JAPAN

For entering into commercialization of MCFC power plants in the beginning of the 21st century, we will devote to research for increasing lifetime as long as 40,000 hours with cell performance decay rate of 0.25 %/1000hrs as the target in FY 1999.

This paper will discuss on our approach for longer lifetime MCFCs through electrolyte-loss management and NiO precipitation management as well as micro-structural control of electrodes and matrix plates. Cell voltage decay rate will be estimated by simulation through series of experiments on accelerated conditions.

1. Introduction

MCFC power plants have the high potential for commercialization in competition with thermal power plants. From the technological viewpoint for commercialization, it will depend on cell voltage endurance for long term with appropriate current density under pressurized condition. From the economical viewpoint, it will depend on capital cost as well as system simplicity and reliability.

Several causes will contribute to voltage losses in a practical fuel cell. The cell performance is theoretically decreases from open circuit voltage by Nernst loss, the reaction polarization in anode and cathode, electronic polarization and ion conductive polarization. Open circuit voltage is also decreased by Ni precipitation amount and gas crossover. Each of them will cause output voltage decay during operation.

2. Investigation for Longer Endurance

MCFC stack components consist of porous materials such as anodes, cathodes and matrix plates as well as non-porous materials such as separators and current collectors. Every compartment in MCFC is, indeed, susceptible to suffer severe corrosion. It causes electrolyte loss from matrix, metallic Ni precipitation onto matrix plates and micro-structural degradation of porous materials. They have still limitation from several technical problems for 40,000 hour lifetime in operating conditions. Figure 1 shows major research efforts to be devoted corresponding to endurance time region.


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