NOVELTY - Pre-reformer comprises electrically conducting member(s) arranged in a duct having inlet for receiving a hydrocarbon fuel and an outlet for supplying a pre-reformed hydrocarbon fuel, an electrical power supply connected to the conducting member, and a controller for controlling supply of electrical current through the conducting member to provide selective thermal decomposition of higher hydrocarbons in the hydrocarbon fuel.    USE - For use in fuel cell system (claimed), especially a solid oxide cell.    ADVANTAGE - The inventive pre-reformer is capable of reducing or preventing coking in the solid oxide fuel cells and other parts of the solid oxide fuel cell system. It operates the inlet pressure of the hydrocarbon fuel supply. It is simple and has no additional reactants required to react with the hydrocarbon fuel to remove the higher hydrocarbons. It can be easily maintained and replaced.    DETAILED DESCRIPTION - Pre-reformer (10) comprises a gas tight duct (12) and electrically conducting member(s) arranged in the duct. The conducting member is electrically isolated from the duct. The duct has an inlet (16) for receiving a hydrocarbon fuel at a first end (18) and an outlet (20) for supplying a pre-reformed hydrocarbon fuel at a second end (22). The inner surface (24) of the duct is chemically inert with respect to the hydrocarbon fuel. An electrical power supply (26) is electrically connected to the conducting member. A controller (28) controls the supply of electrical current through the conducting member to maintain the conducting member at a temperature to provide selective thermal decomposition of higher hydrocarbons in the hydrocarbon fuel. An INDEPENDENT CLAIM is also included for a fuel cell system comprising the above pre-reformer.    DESCRIPTION OF DRAWING(S) - The figure is a longitudinal cross-sectional view through a pre-reformer.    Pre-reformer (10)    Duct (12)    Inlet (16)    First end (18)    Outlet (20)    Second end (22)    Inner surface (24)    Electrical power supply (26)    Controller (28)    Seals (30, 32)