Method for heating a fuel cell system and fuel cell system

A method for heating a fuel cell system (1a;

• 1b;
• 1c;
• 1d) comprising at least one fuel cell stack (2) with an anode portion (3) and a cathode portion (4) as well as a reformer (5) upstream of the anode portion (3) for steam reforming using a fuel, the reformer (5) comprising a nickel-based catalyst, said method having the steps:
• starting a heating process for heating the fuel cell system (1a;
• 1b;
• 1c;
• 1d) with a heating device (6), and
• feeding a carbon-containing fluid in an anode gas supply line (8)
• upstream of a fluid delivery device (9) feeding steam from a steam supply line (10) into the anode gas supply line (8) for creating from the steam and the carbon-containing fluid a fuel/steam mixture in an anode gas supply line (8),
• conducting the fuel/steam mixture from the fluid delivery device (9), via the anode gas supply line (8), through the nickel-based catalyst of the reformer (5) during the heating process,
• wherein the fuel is used as carbon-containing fluid during the heating process in a fuel quantity of between 5% and 20% of the fuel quantity used during steam reforming in normal operation of the fuel cell system (1a;
• 1b;
• 1c;
• 1d).