TECHNOLOGY FOCUS - CHEMICAL ENGINEERING - Preferred Components: In the gas generator, a thermal burner is located upstream the primary catalytic burner or the catalytic partial oxidation zone, where the thermal burner comprises a fuel igniting device. The primary and secondary catalytic burners comprise a noble metal catalyst. The noble metal catalyst comprises at least one of platinum, palladium, ruthenium, rhodium, osmium, gold and silver. The noble metal catalyst is in the form of a fixed bed catalyst, a net, a mesh, catalyzed hardware or a structured catalyst. Preferred Process: In the conversion of the fuel into the oxygen-depleted gas and/or the hydrogen-enriched gas, the primary and secondary catalytic burners are heated up to operation temperature by thermally igniting a fuel with an oxygen-containing gas under flame reactions. The flue gas comprising oxygen and/or the gas comprising hydrogen and carbon monoxide or the gas comprising traces of oxygen are cooled before the next step. The combustion in the primary catalytic burner is carried out with a super stoichiometric amount of air. Alternatively, the process for the conversion of the fuel into the oxygen-depleted gas and/or the hydrogen-enriched gas comprises: catalytically partially oxidizing a fuel in a primary catalytic burner with an oxygen-containing gas to produce a flue gas comprising carbon monoxide and hydrogen, followed by combusting the flue gas comprising carbon monoxide and hydrogen in a secondary catalytic burner to produce a gas consisting of traces of oxygen, carbon dioxide, steam and inerts or a gas comprising hydrogen and carbon monoxide, the amount of carbon monoxide present after combusting the flue gas in the secondary catalytic burner being reduced in comparison to the amount present before combusting the flue gas in the secondary catalytic burner, followed by either reducing the amount of oxygen in the gas consisting of traces of oxygen, carbon dioxide, steam and inerts, and obtaining an oxygen-depleted gas, or converting the carbon monoxide present in the gas comprising hydrogen and carbon monoxide to carbon dioxide or methane and obtaining a hydrogen-enriched gas. The primary and secondary catalytic burners are heated up to operation temperature by thermally igniting a fuel with an oxygen-containing gas under flame reactions. The combustion in the secondary catalytic burner is complete or is carried out with a substoichiometric amount of air.