NOVELTY - A fuel cell system (10) has a fuel processor (12), conduit units (I,II), a water source (28) and a water feed unit. The fuel processor converts a hydrocarbon fuel into high-temperature reformed gas containing hydrogen, carbon dioxide and carbon monoxide. The water feed unit feeds water to the conduit unit(s) in a controlled manner to cool the reformed gas and/or gas stream to a desired temperature.    USE - For electricity production.    ADVANTAGE - The fuel cell system uses the water already present in the system to provide cooling for the reformed gas stream prior to feeding the reformed gas to the shift converter. The fuel cell system is compact. The temperature of gas streams is controlled and an optimum oxygen/carbon ratio is obtained. Water is fed in a controlled manner to ensure that the reformed gas stream entering the shift converter is at a desired temperature. The operation of the fuel cell is not affected by the presence of water in the feed to the fuel cell. Water may be recovered from the fuel cell and recycled to the water source for further uses. The need for large heat exchangers is eliminated. The size of the shift converter is reduced.    DETAILED DESCRIPTION - A fuel cell system (10) has a fuel processor (12), conduit units (I,II), a water source (28) and a water feed unit. The fuel processor converts a hydrocarbon fuel into a high-temperature reformed gas containing hydrogen, carbon dioxide and carbon monoxide. The first conduit unit (I) communicates the reformed gas to a shift converter (20) located downstream of the processor for further converting the reformed gas to primarily a hydrogen- and carbon-dioxide-containing gas stream. The second conduit unit (II) communicates the gas stream to the fuel cell (30) downstream of the shift converter for reacting the hydrogen in the gas stream. The water feed unit feeds water to the conduit unit(s) in a controlled manner to cool the reformed gas and/or gas stream, respectively, to a desired temperature.    An INDEPENDENT CLAIM is included for controlling the temperature in a fuel cell system, by providing a water source and injecting water from the water source into the reformed gas and/or gas stream, in a controlled manner to cool the reformed gas and/or gas stream to a desired temperature prior to feeding the reformed gas to a shift converter and the gas stream to the fuel cell.    DESCRIPTION OF DRAWING(S) - The figure shows a partial schematic illustration of a fuel cell power plant system.    Fuel cell system (10)    Fuel processor (12)    Shift converter (20)    Selective oxidizers (24, 26)    Water source (28)    Fuel cell (30)    Solenoid valve (46)