TECHNOLOGY FOCUS - MECHANICAL ENGINEERING - Preferred Device: The roller (10) has at least one internal heat-transfer surface coated with an active catalyst and/or at least one zone containing a catalyst bed, over which is passed a fuel-air mixture. Suitable catalysts are precious metals (especially platinum, palladium or rhodium) or are based on non-precious metals (especially copper oxide). The roller is heated so that it provides a maximum specific evaporation capacity of about 120 kg/m2/h. It is a hollow roller coated with catalyst on the inside of the sleeve (12), which may be smooth or at least partly provided with ribs, non-woven fabric, laminations or a porous layer (all coated with catalyst), so that reaction takes place inside the roller sleeve. Sections of the catalyst surface or zone (viewed in the cross-machine direction), preferably sections of the catalyst-coated inside of the sleeve (12), may be exposed to different fuel concentrations and/or different amounts of air. The roller may have peripheral holes (20), preferably parallel to its axis, which are coated on the inside with catalyst or contain a catalyst bed as above; the inner surface of these holes may be smooth, porous with catalyst on the porous layer or lined with catalyst-coated non-woven fabric. The roller may comprise two coaxial roller tubes (10', 10") with catalyst-coated channels (22) in the outside of the inner tube (10"); these channels can be supplied with fuel and air and may be formed by milling, etching, stamping etc. Fuel supply is multi-stage or discontinuous. Preferred fuels are hydrogen, natural gas, biogas, methane, ethane, propane and the like. The catalyst may be preheated with a series-connected burner and/or the catalyst support may be electrically heated. Means are provided for switching to different fuels, and preferably controlled to enable switching from one fuel for start-up (preferably hydrogen) to other fuel(s) for further operation (other gases as listed above). The system includes inner and/or outer fuel sensor(s) and temperature sensor(s), plus alarms which are activated by the sensors. Catalyst-coated non-woven fabric (especially metal web) may also be fitted in leakage-critical areas such as rotary transmission lead-ins, especially to provide fuel-tight lead-throughs. The roller (10) may consist of sheet steel or a steel casting with a wall thickness of not more than 30 (preferably not more than 20) mm, or of material with a higher thermal conductivity than steel, especially a copper alloy. Rollers may also comprise several shells. With a heating surface formed by one roller, the roller diameter is in the range 800-1850 (preferably 800-1500) mm. Steaming-out is assisted by blast air, preferably from a blast box. Preferred Machines: Machines in which the heatable roller (10) is in a dry section, preferably in combination with a particularly temperature-resistant skeleton drum. Unburnt fuel from the roller (10) is passed to a downstream burner.