that depends on operating pressure and temperature, as well as on gas composition and reactants utilization [12].
Hence, the MCFC potential and its efficiency increase at increasing of carbon dioxide concentration at cathode
side with respect to anode side, while reduce at increasing of reactants utilization. The actual cell potential is lower
than the ideal value because of irreversible losses, mainly due to activation, ohmic and gas concentration
polarization phenomena.
The MCFC operating conditions are defined by setting
the current density and the polarization curve, that describes
the relationship between the cell potential and the current
density, for fixed values of temperature, pressure and
reactant stoichiometry [12]. A high current density allows a
high transfer rate of the carbonate ions and, consequently, a
more effective CO2 separation. However, the increase of
current density reduces the fuel cell potential and the
efficiency due to higher polarization losses. On the other
hand, for a fixed rated power, a low current density
improves the efficiency, but requires a larger cell area. In
this study, the MCFC stack operates at atmospheric pressure
and 625°C, with a current density of 1500 A/m2, offering a
good compromise between costs and efficiency.
ELECTROLYTE
ANODE
CATHODE
AIR AND CO2
O2
CO2
H2
INTERNAL REFORMING
ANODE ZONE
CO3--
2e- 2e-
2e-
2e-
2e-
2e-
CO
CO2 LEAN
CO2 RICH WITH STEAM
AND UNREACTED FUEL
GASES
CATHODE ZONE
METHANE AND STEAM