NOVELTY - A gas generator for converting a fuel into an oxygen-depleted gas and/or hydrogen-enriched gas, comprises the following units integrated within a reactor shell and arranged in series: a primary catalytic burner (8) or a catalytic partial oxidation zone, a secondary catalytic burner (14) for carrying out combustion or catalytic partial oxidation, cooling devices (9, 19), an oxygen absorber (22), and a shift converter or a methanator.    USE - The gas generator is useful for converting a fuel into an oxygen-depleted gas and/or hydrogen-enriched gas; used in a process for requiring oxygen-depleted gas and/or hydrogen-enriched gas; and for generating oxygen-depleted gas or hydrogen-enriched gas for start up, shut down or emergency shut down of a solid oxide fuel cell or a solid oxide electrolysis cell (claimed).    ADVANTAGE - The gas generator efficiently converts a fuel into an oxygen-depleted gas and/or hydrogen-enriched gas.    DETAILED DESCRIPTION - A gas generator for converting a fuel into an oxygen-depleted gas and/or hydrogen-enriched gas, comprises the following units integrated within a reactor shell and arranged in series: a primary catalytic burner or a catalytic partial oxidation zone, followed by a secondary catalytic burner for carrying out combustion or catalytic partial oxidation, cooling devices for cooling the flue gases from the primary and/or secondary catalytic burners or from the catalytic partial oxidation zone, an oxygen absorber for absorbing oxygen from the flue gas of the secondary catalytic burner followed by a shift converter or a methanator for converting carbon monoxide in the flue gas from the secondary catalytic burner to carbon dioxide or methane. An INDEPENDENT CLAIM is a process for the conversion of a fuel into an oxygen-depleted gas and/or a hydrogen-enriched gas, comprising: catalytically combusting a fuel in a primary catalytic burner with an oxygen-containing gas to produce a flue gas comprising oxygen, followed by combusting or partially oxidizing the flue gas comprising oxygen with excess fuel in a secondary catalytic burner to produce a gas comprising hydrogen and carbon monoxide, or a gas comprising traces of oxygen, and either reducing the trace amounts of oxygen from the gas comprising traces of oxygen and obtaining an oxygen-depleted gas, or reducing the amount of carbon monoxide present in the gas comprising hydrogen and carbon monoxide by catalytic conversion to carbon dioxide or methane to obtain a hydrogen-enriched gas.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of a gas generator.    Fuel (1)    Gas nozzle (2, 17)    Air distributor (3)    Oxygen-containing gas (4)    Igniting device (5)    Fuel combustion chamber (6)    Flame shield (7)    Primary catalytic burner (8)    Cooling device (9, 19)    Finned channels (10, 18)    Warmed-up cooling air (11)    Port (12)    Mixing zone (13)    Secondary catalytic burner (14)    Additional fuel (15)    Fuel injection channel (16)    Cooling air (20)    Outlet (21, 24)    Oxygen absorber (22)    Carbon monoxide converter (23)