Recently, global warming and the depletion of fossil fuels are the problems in the world. As the solution to these problems, although fuel cells that makes hydrogen a fuel are highlighted because it does not exhaust CO2 during power generation, CO2 is exhausted in the hydrogen producing process. Therefore, we have been developing High Functional Direct Carbon Fuel Cell (HF-DCFC) composed of Molten Salts Gasification and Tubular Molten Carbonate Fuel Cell(T-MCFC), can use an organic waste as fuel directly. Molten Salts Gasification is able to produce H2 and CO for power generation of T-MCFC by functioning as a thermal catalyst. The previous study has established the manufacturing method of a T-MCFC single cell supported by a stainless tube of φ9. Aiming at commercialization of HF-DCFC, T-MCFC should be stacked to obtain a high power, and the support tube has to be changed from stainless to alumina to avoid short circuit. Therefore, we proposed that the socket type T-MCFC was composed of applying the cathode electrode to inside of the short alumina tube of φ8 and applying the anode electrode to outside of φ20, and the electrolyte thickness was thick 6mm because the alumina tube was used as an electrolyte. The T-MCFC stack was composed of connecting these socket type T-MCFC. However, because the crack was caused in both electrodes of this socket type, this socket type was able hardly to generate electricity by gas cross leakage through these cracks. We consider that these problems originated in the mismatching of a support tube diameter and each cell component thickness, and a presence of fine pores of the support tube. Therefore, these failure factors were confirmed by manufacturing the T-MCFC stack with a stainless support tube with the same diameter as the alumina support tube diameter. As a result, it was clarified that the relation between each cell component thickness and a support tube diameter in the stainless tube was not adaptable to the alumina tube, and the alumina tube was unsuitable to use as the matrix from the viewpoint of the high-resistivity and poor gas seal. Therefore, we confirmed the optimum thickness of each cell component using T-MCFC single cell supported by a stainless steel of φ19. Moreover, the T-MCFC stack was manufactured by connecting two single cells by alumina joint, and the fundamental performance was evaluated. As a result, when each cell component thickness of T-MCFC (φ19) was increased to about 1.5 times that of φ9, the crack of the electrode was hardly caused in the manufacturing process. Figure 1 shows the I-V performance of each T-MCFC. However, the I-V performance of T-MCFC single cell (φ19) was worse than that of others. Because the open circuit voltage of φ19 was lower than the theoretical OCV and the cell resistance was also larger, we judged that the crossover was surely caused. We consider that the oxidation expansion power of the cathode electrode exceeded the shrinkage force of the anode electrode by having increased the thickness of both electrodes by 1.5 times, and consequently the anode electrode and the matrix cracked by the expansion power of the cathode electrode. Therefore, we have to optimize the relation between thickness of each cell component and the diameter of the support tube further. Figure 1
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Mar 16, 2022
M Madhusudan + 3
Open Access