Simulation of the performance for the direct internal reforming molten carbonate fuel cell. Part II: Comparative distributions of reaction rates and gas compositions

This study examined the distributions of the three reaction rates and the compositions of the gases at each point of the unit cell in DIR-MCFC using a numerical simulation. The electrochemical reaction rates at the anode gas entering position were almost two times faster than those at the anode gas outlet position and most of the feeding CH₄ reacted in the region from the position x = 0 to the position = 0.3. In addition, the water-gas shift reaction became faster from near the half position of the unit cell to the gas outlet position. Therefore, in the rear position of the unit cell, the steam reforming reaction played an important role as a supplementary reaction for providing the H₂ needed in the electrochemical reaction. The rates of the two catalytic reactions in the case without the electrochemical reaction were relatively slower than those in the DIR-MCFC. Unlike the distributions of temperature, the current density, gas compositions and the reactions rates at each point of the DIR-MCFC cell, the exit gas compositions from the simulation in particular could be comparative to those of the experimental results. Although there was an approximately 10% difference between both of them, the extent of the difference was considered to be reasonable for this simulation considering the experimental values that could be included in this simulation such as the lower conversion of the reactions, the lower current density and any other values.