There are provided a solid oxide fuel
cell system comprising (a) a
solid oxide fuel
cell stack, (b) a preliminary reformer for removing hydrocarbons having two or more carbon atoms from a
hydrocarbon fuel by converting the hydrocarbons having two or more carbon atoms into
methane,
hydrogen, and
carbon monoxide, and (c) an integrated
heat exchanger for
catalytic combustion for heating either air or fuel, or both the air and fuel, to be guided to the
solid oxide fuel
cell stack, by use of a
combustion gas formed by combusting discharged fuel with the use of discharged air, wherein component equipment described above are disposed in an adiabatic vessel and the integrated
heat exchanger for
catalytic combustion for use in the
solid oxide fuel cell system. With the invention, an
advantage of the preliminary reformer in combination with that of the integrated
heat exchanger for
catalytic combustion can be obtained, and heat loss of the SOFC
system is eliminated or reduced as much as possible. In addition, with the integrated heat exchanger for catalytic
combustion according to the invention, since air and / or fuel, to be fed to the SOFC stack, can be heated by controlling the
maximum temperature achieved thereof, it is quite useful as an heat exchanger for an SOFC with
operation temperature on the order of 850° C. or lower, particularly, for a supported membrane type SOFC, and further, the same is quite useful in making up an SOFC system because an inexpensive material can be used as a constituent material of a component equipment of the system, the system in whole can be reduced in size, and so forth.