Characteristics of solid fuel oxidation in a molten carbonate fuel cell

Abstract

Oxidation behaviours of ash free coal (AFC), carbon, and H2 fuels were investigated with a coin type molten carbonate fuel cell. Because AFC has no electrical conductivity, its oxidation occurs via gasification to H2 and CO. An interesting behaviour of mass transfer resistance reduction at higher current density was observed. Since the anode reaction has the positive reaction order of H2, CO2 and H2O, the lack of CO2 and H2O from AFC results in a significant mass transfer resistance. However, the anode products of CO2 and H2O at higher current densities raise their partial pressure and mitigate the resistance. The addition of CO2 to AFC reduced the resistance sufficiently, thus the resistance reduction at higher current densities did not appear. Electrochemical impedance results also indicate that the addition of CO2 reduces mass transfer resistance. Carbon and H2 fuels without CO2 and H2O also show similar behaviour to AFC: mass transfer resistance is diminished by raising current density and adding CO2.