Seong Ahn Hong

Studies of the effects of the reformer in an internal-reforming molten carbonate fuel cell by mathematical modeling

The effects of the reformer in an internal-reforming molten carbonate fuel cell (IR-MCFC) are studied by mathematical modeling. Temperature distributions, conversion of methane and compositions of gases are analyzed through mathematical modeling of the reformer and the cell. In the reformer, the methane-reforming reaction and the water-gas shift reaction occur simultaneously and the conversion of methane to hydrogen, calculated including the thermodynamic equilibrium of the reaction, reaches 99%. Additionally, the endothermic-reforming reaction contributes to a uniform temperature distribution. The voltage and the power of the IR-MCFC are similar to those of an external-reforming molten carbonate fuel cell (ER-MCFC), when the compositions at the inlet of the ER-MCFC are set as those at the outlet of the reformer in IR-MCFC. As the molar ratio of methane to water-gas decreases at a fixed total flow rate, the working voltage decreases.

Synthesis of ZSM-5 zeolite composite membranes for CO2 separation

ZSM-5 type zeolites were synthesized by the hydrothermal treatment of the reaction mixture of silica sol, aluminum nitrate, sodium hydroxide, and TPABr at the temperature range of 150–180 °C in the autoclave. The shape of the ZSM-5 zeolite calcined at 450 °C was spherical or polyhedral and its crystalline size was 0.5–3 μm. The synthetic ZSM-5 was found to be highly hydrophobic and active for CO2 adsorption. ZSM-5 zeolite composite membranes supported with porous α-alumina tubes have been synthesized by dip coating or pressurized coating of the reaction sol-mixture followed by hydrothermal treatment. The permeation mechanism of CO2 through ZSM-5 membranes was a surface diffusion and the membranes prepared by the pressurized-coating hydrothermal treatment showed a fairly high CO2/N2 separation factor of 9.0 and a permeability of 10−8–10−7 mol/m2 ·s·Pa at room temperature.

Effects of water-gas shift reaction on simulated performance of a molten carbonate fuel cell

A molten carbonate fuel cell (MCFC) is simulated. In order to determine the effects of the water-gas shift reaction, the calculated results such as temperature distribution, voltage distribution, conversion and performance, are compared with those calculated excluding the shift reaction. Uniformity in the temperature profile is deteriorated due to the shift reaction. At the entrance, hydrogen is consumed rapidly in order to reach the equilibrium state of the shift reaction. The conversion of hydrogen decreases along the direction of gas flow because of hydrogen generated by the shift reaction. Therefore, when the shift reaction is excluded, the conversion of hydrogen is higher than that in a practical cell. Additionally, at the same current density, the voltage calculated without the shift reaction would be higher than the real value. The effect of the shift reaction on the voltage distribution and cell performances is quite small.

Reinforcement of molten carbonate fuel cell matrixes by adding rod-shaped γ-LiAlO2 particles

Improvement in strength of γ-LiAlO2 matrixes for a molten carbonate fuel cell (MCFC) via addition of rod-shaped γ-LiAlO2 particles has been investigated. The rod-shaped γ-LiAlO2 particles with the aspect ratio of 9–15 were obtained by heat-treating rod-shaped β-LiAlO2 particles at 800 °C for 3 h, synthesized from the reaction mixture of LiOH-γ-Al2O3-NaOH. The γ-form was very stable for more than 700 h in a molten carbonate environment at 650 °C, while the β-form showed both a phase change from β- to γ-LiAlO2 and a morphology change from rod- to bipyramid-shapes. The average pore size and the porosity of the matrix (550 μm thickness) fabricated by tape-casting of the slurry with weight ratio 1.0 of rod-shaped γ-LiAlO2 particles to commercial γ-LiAlO2 powders (2.0 μm dia.) were about 0.12 μm and 54%, respectively, after being heat-treated at 650 °C for 2 h. The strength (197 gf/mm2) of the rod- shaped particle reinforced matrixes was enhanced more than twice as much as that of the non-reinforced γ-LiAlO2 matrixes (91 gf/mm2).