NOVELTY - The device (10) for the generation of hydrogen gas by dehydrogenation of hydrocarbon fuels, comprises a fuel reservoir (14) connected to a reactor (18) by a fuel inlet (16) to supply the fuel from the reservoir to the reactor, where the fuel is present in liquid phase in the reservoir and the reactor is connected with the reservoir over a return line, over which residual hydrocarbons generated during the dehydrogenation of the supplied fuels is recirculated to the reservoir, and a device for heating the fuels supplied to the reactor at a reaction temperature of greater than 400 degrees C.    USE - Device for the generation of hydrogen gas by dehydrogenation of hydrocarbon fuels, and useful in airplane, helicopter and motor vehicle, where the generated hydrogen gas is useful for the operation of auxiliary power units.    ADVANTAGE - The device can be compactly designed with light-weight and high energy efficiency.    DETAILED DESCRIPTION - The device (10) for the generation of hydrogen gas by dehydrogenation of hydrocarbon fuels, comprises a fuel reservoir (14) connected to a reactor (18) by a fuel inlet (16) to supply the fuel from the reservoir to the reactor, where the fuel is present in liquid phase in the reservoir and the reactor is connected with the reservoir over a return line, over which residual hydrocarbons generated during the dehydrogenation of the supplied fuels is recirculated to the reservoir, a device for heating the fuels supplied to the reactor at a reaction temperature of greater than 400 degrees C and a reaction pressure of 8 bar, and a heat exchanger (22) for transferring the heat from the return line to the inlet. The device allows to start the dehydrogenation in the supercritical phase of the fuel. The heating device comprises a burner, which is provided with generated residual hydrocarbons and/or impurities, which are separated from the generated hydrogen gas by a cleaning device. An INDEPENDENT CLAIM is included for a method for the generation of hydrogen gas by dehydrogenation of hydrocarbon fuels.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic representation of a device for the generation of hydrogen gas by dehydrogenation of hydrocarbon fuels.    Device (10)    Fuel reservoir (14)    Fuel inlet (16)    Reactor (18)    Heat exchanger. (22)