TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Process Details: The process comprises a primary conversion of the fuels into hydrogen (H2) and carbon monoxide (CO) by an endothermic reaction with water vapor, the water factor being 1.2-1.8 (the factor is the ratio of the flow rate of water vapor available to the stoichiometric value necessary for complete conversion to H2 and CO). The process also comprises a second conversion with water vapor of the methane and light hydrocarbons by an endothermic reaction in the presence of a catalyst specific to these hydrocarbons, and a stage of heating of the fuel and water vapor to a high temperature to establish an exothermic reaction of a fraction of the fuel with air. Other stages involve a cooling of the conversion products and recovery of the thermal energy, and stages of vaporization of water and preheating of fuel, air and water vapor .These stages are coupled by a recovery exchanger to enable continuous functioning of the process. Preferably the process also involves a mixing stage prior to or during the preheating of a fraction of the fuel and water to avoid cokefaction of the fuel during temperature rise and to start the conversion reaction during the preheating stage.Preferred Installation: The installation comprises a primary reactor (2) consisting of two zones. In the first zone (3) the fuel and water vapor are injected at high velocity (4) (25-200 m/s) to form a homogeneous mixture and initiate the reaction, and in the second zone (5) the reactants remain for a time sufficient for thermodynamic equilibrium and to achieve conversion of methane to H2 and CO. In a variant of the process, a second conversion reactor is included in the cooling zone (6) to effect the conversion of methane and light hydrocarbons in the presence of a specific catalyst. Preferably an exothermic reaction of a fraction of the fuel and water vapor with air is achieved in the first zone of the primary reactor. The installation also includes a mixer for the fuel and water vapor prior to or during the preheating stage. EXAMPLE - None given.