Molten carbonate fuel cell, operating method thereof, sintering furnace, and power generator

A molten carbonate fuel cell, operating method of the fuel cell, sintering furnace equipped with the fuel cell, and power generator, wherein a cathode gas with a high carbon dioxide concentration can be obtained without a process of increasing the carbon dioxide concentration, and the heat of furnace exhaust gas can be effectively reclaimed and the fuel consumption can be reduced. The cathode gas is a gas containing a furnace exhaust gas discharged from an industrial furnace for heating materials. Alternatively, the furnace exhaust gas can be used to pre-heat air to be fed to the cathode of the fuel cell. The carbon dioxide concentration of the cathode gas is 0.1-50 vol%.