STABILITY OF MATERIALS FOR MOLTEN CARBONATE FUEL CELLS

摘要

In order to obtain higher performance of MCFCs, especially for high-pressure operation, the stabilities of component materials have been studied experimentally as well as theoretically. In order to get lower solubility of Ni~(2+) ion in Li-Na eutectic carbonate melt, the effect of additives have been studied. Metal oxides were added to molten carbonate as well as solid NiO. The addition of Fe oxide and Mg oxide to NiO was effective to reduce the solubility of NiO. The addition of rare earth oxide (La_2O_3) to molten carbonate is more effective and can reduce the solubility of NiO one tenth of that in Li-K melt. Considering the solubility, MCFCs could operate over 40000 hours without Ni short even under high-pressure condition of 12 to 15 atm. Although the solubility of NiO decreases in the Li-Na carbonate melt, the severe corrosion of SUS316L took place during the initial period of the reaction at relatively low temperature. The corrosion was very severe below 550℃. The severe corrosion might be due to the instability of Fe oxide on the surface of the corrosion scale. Once a stainless steel was covered by stable Fe oxide, the stainless steel became very stable.